THE DIGEST Official Publication of the National Aeronautics and Space Administration December 1994 Vol .18 No. 12 Software Of The Year Award Winners Tech Briefs OF NEW TECHNO L OGY Transferring Engineering Technology to Over 200,000 Qualified Readers Throughout Industry and Government https://ntrs.nasa.gov/search.jsp?R=20100030377 2019-08-30T11:09:24+00:00Z r I I I I I I L • National Instruments GPIB Cross-Platform Compatibility ;1 Maximum Performance Worldwide Technical Support AT-GPIBffNT brought you the 8 Mbytes/s HS488 protocol. This year, with the TNT4882C' single-chip interface, we I I I I Since 1976, National Instruments has set the standard for GPIB hardware and software for general-purpose computers. We also adhere to a continuous improve- ment and compatibility strategy for GPIB that is unmatched in the industry. Each new generation of our products delivers compatibility with increased functionality, I...~JJ were the first to deliver low-power products like the PCMClA-GPIB. reliability, and performance for the same low price. Cross-Platform Compatibility For the past 10 years, our industry-standard kfJ488.2~ software, included with every GPIB inter- face we sell, has guaranteed that you never have to rewrite your instrument control applications for new computer plat- forms or operating systems. Maximum Performance Worldwide Technical Support With our worldwide technical support team, we are committed to making you successful in your application, no matter when you bought our product. Free Brochure To learn more about our latest GPIB products, give us a call and we'll send you our new GPIB brochure. In 1987, we delivered the first inter- faces that surpassed the 1 Mbytes/s barrier. In 1990, with the NA T4882® chip, we brought the industry to IEEE 488.2 compatibility. In 1993, we Y NATIONAL ~ ~~~r!y~!~!~ f or your f REE GPIB brochure, call (800) 433-3488 (U.S. and Canada) 6504 Bridge Point Parkway · Austin, TX 78730-5039 • Tel: (512) 794-0100 ' 95 (800) 0100793 (Mexico) • Fax: (512) 794-8411 Branch Offices: A.ustroUa 03 879 9422 · Austria 0662 435986 · klglum 02 757 00 20 · Ccmodo 519 622 9310 · OenmCU'k 45 76 26 00 · Finland 90 5272321 • Frcmce I 48 14 24 24 · Germany 089741 31 30 Itoly 0248301892 . Japan 03 37881921 ' N ...... lonc/s 0348033466 · Norway 32848400 ' Spain 9 1 6400085 ' Sweden 08 73049 70 ' Swlturlond 056 205151 ' U.K. 0635523545 o Copyright 1994 NaiionaJ Instruments CorponutOn. All righlS reserved. Producc and company names Iisled are trademarks Of" lOIde names or their re..~poctive companies. For More Information Write In No. 501 For a FREE Trial Call today: 1·800·777·5151 DADiSP DADiSP offers more than 500 functions for collecting, displaying and analyzing your data with the power and flexibility of a spread- sheet. Load a new data series, matrix, signal, or image, alter a parameter, or select a new function, and all windows update au tomatically. • Data Acquisition • Data Reduction and Editing • Peak Analysis • Matrix Mathematics • Fourier Analysis • Plotting and Graphing • Statistics • Filter Design • Visual ization • Image Processing Construct sophisticated analysis chains in seconds. DADiSP's icons and menu-interface place signal processing analysis under your control. Justpoint and click and DADiSP displays your results immediately, with no programming. DADiSP runs under: DOS, Windows, UNIX, VMS. DSP Development Corporation One Kendall Square Cambridge, MA 02139 Phone 617·577·1133,FAX617·577· 211 For More Information Write In No. 500 , ... - .... - - .- -- ... . .- >e - .- .. - . - - - - ~ .............. . - . o-a.... .- J...o..oIo ~... ~ ... - OL.J _______ ---! TOJALaIV WED T __ rI .. ,rel.cIIIIIII .alctl, II •• 11111 10 .llIclDlle lid mid CIIIII ,rollct .ellP. D~"DDDD . ..... , ... ,"'I'J tlWltolJ1t1t ,.,.411111 J~ .... ~ .. -.. .. .. .. .. .. ... .. - SlIII-ol-Ul'-lrt graphici II. re,ortlng Clllhllnill .IU rolr '111 1111.r 101 •• lrallnd. 1l'Ick lid IUnl ..... ProdICUOI, Innnl.., lAd I .. ot 1IIIIrlIII II I •• JIIOI 10 ... 11.11111.11 ot IIDoc .ulpllenl and OIIIlr relD,reel. E Foundatron Deck -\Jt>f1ghIS Roof Shinglet ChlnlB prolecI ,1m 10 III OS or PElt C.lrtIIbOWlDI dlPeadl cy nnu, mllesloneslDd IIllul. I PERT Charts, was Structures And ComparatiVe S-Curves Get You All Excited, This Will Really Spin Your Hard Drive. Serious project managers need software that's as serious about the job as they are. And that software is CA-SuperProjecr. fOwerful yet flexible, SuperProject is sophisticated enough to reflect your work environment and is incredibly easy to use. 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New CA-SuperProiecr3.0 UIIX Windows OS/ 2 o ComPU1 1993 SWAGl'LOK Co .• ,II nOhlS reserved FS-I>(IIB WHITEY® PFA Valves Needle • Roddable, straight-through orifice for easy cleaning and high flow (Cv 's to 1.39) • 1/4", 3/8", and 1/2" SWAGELOK Tube Fitting end connections • Plug tip stem ensures leak-tight shut-off and offers flow control • Positive stem stop prevents accidental disassembly • Panel mountable • Patented stem seal eliminates leakage and requires less operating torque • Pressures to 180 psig • Temperatures to 300°F For More Information Write In No. 523 Plug Grooved PFA Tubing for leak-tight seal. No visible gap between nut and body hexes - with hexes aligned -ensures proper makeup. • 1/4 turn actuation • Easily cleaned or purged • Full flow design (Cv = 1.8) • Compact • 1/4" SWAGELOK Tube Fitting end connections • Pressure rating 60 psig • Temperatures to 200°F ~ACliib lM~e companies SWAGELOK Co. Solon, OH 44139 Excitation Circuits: Digital Signal- Processing Circuits • Filtering • Unearization • Temperature Compensation r---------------- Digital-to Analog Converters Microcontroller 1------'----------' Programmable Amplifier Galvanically Isolated To and From SAMS Controller A Universal Signal-Conditioning Amplifier is a rugged, versatile unit with self- and remote- programming capabilities. It is connected with a transducer and a tag RAM. RAM (see figure). A USCA can be installed in the field, is rugged, can pro- gram itself or be programmed by remote control, and supplies excitation (if need- ed) to the transducer. When the USCA is connected to a transducer with a tag RAM, it reads information from the tag RAM and programs itself with respect to excitation voltage or current, gain, out- put range, type of output (digital or ana- log), digital filter settings, and lineariza- tion (via curve fit by a polynomial of up to seventh order). A microcontroller and digital signal- processing circuitry in the USCA provide flexibility that enables the use of non- standard or unusual transducers in the otherwise standardized data-acquisition system. The USCA is contained in a special environmental housing. It mea- sures its internal temperature and cor- rects its gain and offset to prevent degradation of data by ambient-temper- ature effects from -25 to +60 cC. All parameters for calibration of the amplifier can be loaded electronically into an intemal nonvolatile RAM. The transducer inputs, digital and analog inputs and out- puts, and power input are galvanically isolated from each other to prevent ground loops and to minimize damage from lightning and other transients. The third development is that of a subsystem called the "self-aware measurement system (SAMS) con- troller." The SAMS controller resides in a centralized data-acquisition system and provides supervisory control, con- nect/disconnect status and time for all channels, and system information for all channels that contain tag RAMs alone or tag-RAM/USCA pairs. In a channel that contains only a tag RAM, the SAMS controller provides a host computer with the capability to identify and download all transducer-specific information locat- ed in the tag RAM. The system is also capable of putting any transducer into a remote-calibrate mode. The addition of a USCA expands the capabilities of the data channel. The cali- bration, setup, and other data contained in the tag RAM are then available to the USCA. With modifications, they are also available to the SAMS controller. The SAMS controller communicates bi-direc- tionally with the USCA, enabling remote control and monitoring of such USCA functions as new fi lter settings or modi- fied full -scale or offset ranges for special measurements with existing transduc- ers. The SAMS controller can read the automatic USCA setup parameter and enables the SAMS operator to override any parameters. This work was done by Mark A. Nurge and William E. Larson of Kennedy Space Center and Carl G. Hallberg, Steven W. Thayer, Jeffrey C. Ake, Stuart M. Gleman, David L. Thompson, Pedro J. Medelius, Wayne A. Crawford, Richard M. VanGilder, Johnny L. Kerce, and Joey S. Fairbanks of I-NET, Inc. For further information, write in 239 on the TSP Request Card. Versatile Controller for CCO's This circuit can control CCO's of various designs. Goddard Space Flight Center, Greenbelt, Maryland A general-purpose controller for a charge-coupled device (CCO) can be programmed to accommodate any of a variety of CCO designs. In the operation of the controller , software is used to specify the CCO-clock waveforms, which are thus available in great diversity. The controller includes a timing-signal gener- ator controlled by a microcomputer. The flexibili ty and speed of the controller make it a versat ile tool for laboratory testing and for a variety of applications. The controller can operate existing CCO's and will be able to operate most CCO's expected to be developed in the foreseeable future. For example, it can handle either a large CCO array or a mo- saic of smaller CCO's. It can operate in either an analog mode (long integration, slow readout) or in a photon-counting mode (fast, continuous readout). The capability of the controller for ad- justment of its speed, waveforms, and voltages via software is an important ad- vantage for evaluating CCO's in the labo- ratory. It is especially important in space applications in which CCO's can be de- graded by radiation but can be retuned to optimize their performances. The microcomputer in the controller is This invention is owned by NASA, and a patent application has been filed. Inquiries concerning nonexclusive or exclusive license for its commercial development should be addressed to the Patent Counsel, Kennedy Space Center {see page 20}, Refer to KSC- 11688. a single-chip integrated circuit that receives commands from a host com- pufer, issues instructions to the timing- signal generator, and loads CCO-clock waveforms into first - in/ first-out (FIFO) memories (see figure). The timing-signal generator produces the requisite number of pulses at the desired frequency to clock out data from the FIFO memories; it consists of five independent counter/ timers on a single chip; each counter/ timer can be programmed to generate a repetitive square wave at a particular frequency and duty cycle or to count to a preset number, stop, and o 1994 Hewlett-Packard Co. TMVXD4561NASA You can get IEEE 488 cards from a lot of places. But now that it's so easy to get them from HP, why would you go anywhere else? HP-IB card is best for you. We can also fax you specs or more infonna- tion on our entire line of HP-IB products right away. There is a better way. All you have to do is call us. You'll talk to an experienced engineer like Carol, who will help you determine which Prices start at just $395. So call 1-800-452-4844, Ext. 8909 today. And introduce yourself to HP quality. rli;' HEWLETT® ~~ PACKARD For More Information Write In No. 409 issue an interrupt to the microcomputer. Each FIFO memory stores waveform sequences that govem the operation of a CCO. The output of a FIFO memory is connected back to its input. As soon as a byte at the head of a queue of wave- form data has been clocked out of a FIFO memory by the timing-signal gen- erator, it goes back to the input and propagates through, joining the end of the queue. The FIFO memory is thus operated as a circular storage device, and any byte sequence can be used over and over again. One FIFO memory is used for parallel output, and two are used for serial out- put. The storage capacity of these FIFO memories is ample for currently available CCO's but can be expanded if neces- sary. The use of circuitry separate from the microcomputer to clock out the wave- forms ensures stability of the intervals between the readout of successive pix- els. It is also important for keeping noise low by use of double correlated sam- pling. The clock speed of both parallel and serial operations can be much high- er than that of the microcomputer. Several microcomputers can be con- Host Computer To ::: Parallel ::; Drivers To ..• Serial ::: Drivers CCD Waveforms and Timing Instructions travel from the host computer to the microcom- puter over a serial link. The microcomputer loads the commanded waveforms into the first- in/first-out memories and instructs the timing generator to clock out the waveform data. nected on a serial link to the host com- puter. The host can address a single mi- crocomputer, a subgroup of microcom- puters, or all microcomputers at once. A group of CCD's - each with its own mi- crocomputer, FIFO memories, and tim- ing generator - can therefore be con- trolled by the same host computer. A group of dissimilar CCO's each perform- ing a different function - e.g., tracking, image-motion compensation, image cor- rection, and scientific-data acquisition - can likewise be linked and controlled by a single host computer. This work was done by J. Novello of Goddard Space Flight Center and P. C. Chen of Computer Sciences Corp. For further information, write in 70 on the TSP Request Card. GSC-13269 Wavelength-Division Multiplexing of Bipolar Digital Signals Pulses at two different wavelengths signify opposite polarities. John F. Kennedy Space Center, Florida In the system shown in the figure, bi- polar digital data are transmitted by use of wavelength-division multiplexing on a single optical fiber. A bipolar digital signal can assume any of three levels: positive, zero, and negative. An electrical signal can be set at a corresponding positive, zero, or negative voltage, but the output of a light-emitting diode (LED) used to transmit digital data on an optical fiber can be set at only two levels: on and off. Accordingly, in this system, two LED's of different wavelengths are used. Turning on one LED, which radiates at a wavelength of 1,300 nm, signifies "posi- tive." Turning on the other LED, which radiates at 1,550 nm, signifies "nega- tive." Leaving both LED's turned off sig- nifies "zero." At the transmitter, the incoming electri- cal bipolar digital signal is first applied to analog circuits that separate it into its positive and negative component pulses. Each component is used to modulate the output of the LED assigned to it. The outputs of the LED's are combined by a wavelength-division multiplexer at the input end of the optical fiber. In the receiver, the signals coming out of the optical fiber at the two wave- 44 Two Different Wavelengths are used to transmit pulses that signify "positive" or "nega- tive" bipolar digital data. The simulta- neous absence of pulses at both wavelengths signi- fies digital "zero." --JlJL- Input Bipolar ElocttIcal Signal 0pIIcaI fiber Analog Input Circuits lengths are separated by a wavelength- division demultiplexer, and fed to sepa- rate photodetectors, which reconstruct the component positive and negative pulses. Analog output circuits combine these pulses, reconstructing the bipolar digital signal that was fed to the transmit- ter. This work was done by Ronnie D. Gibbons and John L. Ubele " of 'Positive' (1 .3OO-nm) 0pIIcaI SIgnal --I1JL ---uu- "Negative" (1 .55G-nm) 0pIIcaI Signal Lockheed Space Operations Co. for Kennedy Space Center. For further information, write in 22 on the TSP Request Card. Inquiries concerning rights for the commercial use of this invention should be addressed to the Kennedy Space Center [see page 20}, Refer to KSC- 11610. NASA Tech Briefs, December 1994 mallive amounts of multi __ riabIe data into Your Decisions Are Only as Good as Your Analysis Gathering data isn't so hard these days. Real- time information services, data acquisition systems, satellites, MRI scanners, and many other sources of information abound. All capable of generating more data than can be meaningfully interpreted. That's where PV-WAVE can help. complex data sets. PV-WAVE is built around a powerful and flexible 4GL designed specifically for interactively analyzing data and building custom data analysis environments. PV-WAVE'S concise language can reduce your coding by up to 80%, so you can generate results quickly. To do thiS, the PV-WAVE product family provides integrated mathematics and stati tics, advanced graphing and plotting, cust< GUI (Graphical User Interface) tools, real- data monitoring, direct interfaces to SOL 0 bases, connectivity to your existing application software, and even symbolic capabilities. PV-WAVE readily accepts al any data format, from rich HDF files, to r ASCII data, to TIFF or bit-mapped data, a even custom data formats. Making it a snap to turn even the most complicated data sets into practical know So call us today, and learn how technical financial customers the world over are us PV-WAVE to improve the speed and accur of their analyses and decision making. For additional informatian and a product demo, caD: 1-800-447-7147 Visual NumericS F'V-WA VE Products 6230 LaaIcout Rd •• Boulder. Colorado 80301 USA Tel: 303-530-9000 • FAX: 303-530-9329 CorporaIIt HeacIquartan 9990 Richmond A_. Suite .tOO • HousIDn. Tel: 713-784-3131 • FAX: 713-781-9260 wondows and Wondow. NT ... regi.o.ed Irodomorlu 01 MictoooIt ec.p PV-W4VE i. a rogi.o.ed trodemont 01 V ...... ~ OponVMS i. a ...,tIOfod trociomoIi< 01 tho IligiIaI ................................... Frequency-Shift Hearing Aid The voice spectrum would be mapped to frequencies where the ear remains sensitive. Langley Research Center, Hampton, Virginia A proposed hearing aid would map the spectrum of speech into a band of lower frequencies at which the ear remains sensitive. The frequency range of normal human hearing extends to about 15,000 Hz, but most speech is contained in the frequency range from 100 to 5,000 Hz. With increasing age, people often lose sensitivity to higher frequencies (often above about 1 ,500 Hz) . By redirecting normal speech fre- quencies into the frequency band from 100 to 1,500 Hz, the hearing aid would allow such people to understand normal conversation, including telephone calls, without excessive amplification. In con- trast, conventional hearing aids amplify all or selected parts of the speech spectrum: in cases of severe loss of hearing, the required amplification may become impractically high, and the con- tinued use of high amplification could damage the wearer's remaining hearing during the long term. Speech information is transferred by fairly slow amplitude modulation and slowly changing frequency modulation of an acoustic carrier wave. The carrier frequency must be high enough so that ears and eardrums can detect the carri- er wave effiCiently. The information is contained in words that are transmitted at a rate of about 2 per second and have a basic content of about 100 pieces of information per word . The basic information only conveys which word is being spoken, and this does not depend on the precise carrier frequen- cy. The word information can be trans- posed to a lower carrier frequency , much as a song can be sung in a lower pitch and still be understood. The frequency-shift hearing aid would separate the amplitude and frequency modulated information content of a message from the normal speech carri- er wave and use the information to modulate a carrier of lower frequency. The result would be a message at a lower carrier frequency but carrying information at the same rate. The carrier wave or the information modulation could be selectively clipped or filtered to suppress loud or distracting sounds. While the highest frequencies must be shifted down considerably, the low to middle frequencies do not have to be changed much. At the same time, the frequency modulation portion of the speech signa: must follow the same trends as the Original speech to convey the information in the clearest way. This is probably best done with nonlinear mapping. For example, fout = 23(fin)1 /2 - 130, where fout and fin are the output and input frequencies, respectively, in hertz. In this example, an input frequen- cy of 100 Hz would stay the same, while an input frequency of 5,000 Hz would be shifted down to just under 1,500 Hz. The principle of the operation of this hearing aid could be adapted to other uses as well. For example, it could be used to clear up noisy telephone or radio communication. In addition, loud- speakers could be more easily under- stood in the presence of high back- ground noise. This work was done by Leonard M. Weinstein of Langley Research Center. No further documentation is available. LAR-15056 Some prices must eventually obey the law of Gravity. VME + PC TIMING SOLUTIONS NOW UNDER $1,000 VMf Time & Frequency Processor bc336VMf + PC Real TIme Clock bc630AT - These mod- ules decode time code at real-time rates and offer excellent performance characteristics for many demanding time code processing requirements. PC Time Code Reader PC03XT - Always a strong performer, th s PC module is ideal for reading time code from tape recorders at non-real-time rates, in forward & reverse directions. Treat your budget to some down-to-earth prices from Datum! Call us toll-free today! I 800 348 0648 I Datum Inc BANCOMM DIVISION 6541 ViadeIOro, san]ose, CA 95119 USA • Te l4085784161 • Fax 408 5784165 NASA Tech Briefs, December 1994 For More Infonnatlon Write In No. 410 45 Physical Sciences Improvements in Optically Stimulated Electron Emission OSEE can reveal contamination in many situations in which other techniques do not work. Lang/ey Research Center, Hampton, Virginia Optically stimulated electron emission (OS EE) has been used by NASA in inspection for contamination of critical bonding surfaces in the solid rocket motors of the Space Shuttle prior to the formation of adhesive bonds on those surfaces during manufacture and refur- bishm ent. Th e fundamental OSEE inspection technique was described in "Surface-Contamination Inspection Tool for Field Use" (MFS-25581), NASA Tech Briefs, Vol. 6 , No. 2 (Summer 1981), page 190, and "Detecting Contamination With Photoelectron Emission " (MFS- 25619), NASA Tech Briefs, Vol. 6, NO. 3 (Fall / Winter 1981), page 307. This technique involves measurement of pho- toelectrons released from a substrate under ultraviolet irradiation. OSEE meas- urements have been shown to be sensitive to contaminants in amounts that, while large enough to weaken bonds, are too small to be visible to the naked eye. The OSEE technique is also applicable to roughened surfaces, for which many optical techniques cannot be used. The OSEE measurement head is easily port- able, and the measurement operation is convenient and rapid , making OSEE a useful inspection technique in the indus- trial environment. OSEE has proved use- ful enough that further development has been undertaken to increase the preci- sion and stability of the measurements. Work has also been done to extend the applicability of OSEE measurements to nonconducting substrates. Improvements being implemented in- clude a change in the geometry of the measurement volume so that the electric field lines are parallel within the illuminat- ed region, which itself is limited with both apertures and focusing optics. The pri- mary OSEE-generating spectral line of the ultraviolet lamp has been identified, and the radiation of that line from the lamp is independently measured and used to control lamp current to increase stability. The interfering effects associat- ed with oxygen and water vapor in the measurement region are being eliminat- ed from measurement by use of a purge gas. The lamp is further environmentally isolated and subjected to constant cool- ing to increase stability and optimize OSEE-producing radiation. Further improvements in the measure- ment have been identified . A laboratory prototype of a Kelvin Probe, capable of measuring surface work functions in me- tals, has been constructed and shown to be an appropriate complement to the basic OSEE apparatus for inspecting Fatigue-Crack-Tip Locator surfaces , the work functions of wh ich vary naturally. In addition , external con- trol of the collector bias voltage has made it possible to obtain reproducible OSEE measurements on nonconducting surfaces by using the measurement head to replace the electrons removed following a measurement. (The proce- dure is called "charge replacement. ") With these improvements and exten- sions, OSEE should become useful in a number of industrial processes in which inspection to detect contamination would be highly useful. In such process- es, no suitable contamination-inspection technique has been available. This work was done by William T Yost of Langley Res earch Center, Christopher S. Welch of the College of William and Mary, and Edmond J. Joe and Bill B. Hefner, Jr. , of Analytical Services and Materials, Inc., with coop- eration from Personnel from Marshall Space Flight Center. No further docu- mentation is available. This invention is owned by NASA, and a patent application has been filed. In- quiries concerning nonexclusive or ex- clusive license for its commercial devel- opment should be addressed to the Patent Counsel, Langley Research Cen- ter [see page 20j. Refer to LAR-J5063. Fatigue experiments can be run continuously under automated monitoring . Lang/ey Research Center, Hampton, Virginia Figu re 1 schematically illustrates part of a fatigue-testing system that includes an automated subsystem that continuously tracks the location of the fatigue-crack tip in a metal or other highly electrically conductive speci- men. The fat igue-crack-tip-Iocating subsystem can also search the speci- men to find the initial fatigue crack and its tip and to trace out hidden fatigue c racks and other flaws inside the specimen . The fatigue-crack-tip-Iocating sub- system operates under the overall 46 control of a personal computer, which also controls the load frame that applies the prescribed cyclic stresses to the specimen . An electromagnetic flaw detector based on the eddy-cur- rent prinCiple is scanned over a sur- face of the specimen by x- and y-axis stepping-motor drives controlled by the computer . [The electromagnetic flaw detector was described previously in "Electromagnetic Flaw Detector Is Easier To Use" (LAR-15046) , NASA Tech Briefs, Vol. 18, No. 7 (July 1994), page 36 . To recapitulate: the electro- magnetic flaw detector is a novel eddy-current probe that puts out a sing le , unambiguous ac voltage indicative of flaws in the specimen.] The automated search for the fatigue crack and its t ip is feasible because of the unambiguous flaw sig- nal provided by the probe . The top part of Figure 2 shows the output sig- nal of the probe as it is scanned across two fatigue cracks in an alu- minum-alloy specimen. The large peak in the output voltage of the probe occurs when the probe is centered NASA Tech Briefs, December 1994 massive amounts of multi-variable data inta easily interpreted images AD9434 Your Decisions Are PY'WAYE Only as Good as Your Analysis Gathering data isn't so hard these days. Rea l- time information services, data acquisition systems, satellites, MRI scanners, and many other sources of information abound. All capable of generating more data than can be meaningfully interpreted. That's where PV-WAVE can help. complex data sets. PV-WAVE is built around a powerful and flexible 4GL designed specifically for interactively analyzing data and building custom data ana lysis environments. PV-WAVE'S concise language can reduce your coding by up to 80%, so you can generate results quickly. To do this, the PV-WAVE product family provides integrated mathematics and statis- tics, advanced graphing and plotting, custom GUI (Graphica l User Interface) tools, real-time data monitoring, direct interfaces to SOL data- bases, connectivity to your existing application software, and even symbolic math capabi lities. PV-WAVE readily accepts almost any data format, from rich HDF files, to raw ASCII data, to TIFF or bit-mapped data, and even custom data formats. Making it a snap to turn even the most complicated data sets into practica l knowledge. So ca ll us today, and learn how technica l and financial customers the world over are using PV-WAVE to improve the speed and accuracy of their analyses and deciSion making. Perform analysis and display of multiple real-time data sources, such as data acquisition systems For additional information and a product demo, call: 1-800-447-7147 rJVisual Numerics' PV-WAVE Products 6230 Lookout Rd .• Boulder, Colorado 80301 USA Tel: 303-530-9000 • FAX: 303-530-9329 Corporate Headquarters 9990 Richmond Avenue, Suire 400 • Houston, Texas n042-4548 USA Tel: 713-784-3131 • FAX: 713-781 -9260 tindow~ and Windows NT ore registered trodemorks of Microsoft Corp. PY-WAVE is a registered trademark of Visual Numerics. OpenVMS is a registered trademark of the Digitol Equipment Corporation. For More IntonnatJon Write In No. 525 Physical Sciences Improvements in Optically Stimulated Electron Er OSEE can reveal contamination in many situations in which other techniques do nl Langley Research Center; Hampton, Virginia Optically stimulated electron emission (OSEE) has been used by NASA in inspection for contamination of critical bonding surfaces in the solid rocket motors of the Space Shuttle prior to the formation of adhesive bonds on those surfaces during manufacture and refur- bishment. The fundamental OSEE inspection technique was described in "Surface-Contamination Inspection Tool for Field Use" (MFS-25581), NASA Tech Briefs, Vol. 6, No.2 (Summer 1981), page 190, and "Detecting Contamination With Photoelectron Emission" (MFS- 25619), NASA Tech Briefs, Vol. 6, NO.3 (Fall/Winter 1981). page 307. This technique involves measurement of pho- toelectrons released from a substrate under ultraviolet irradiation. OSEE meas- urements have been shown to be sensitive to contaminants in amounts that, while large enough to weaken bonds, are too small to be visible to the naked eye. The OSEE technique is also applicable to roughened surfaces, for which many optical techniques cannot be used. The OSEE measurement head is easily port- able, and the measurement operation is convenient and rapid, making OSEE a useful inspection technique in the indus- trial environment. OSEE has proved use- ful enough that further development has been undertaken to increase the preci- sion and stability of the measurements. Work has also been done to extend the applicability of OSEE measurements to nonconducting substrates. Improvements being implemented in- clude a change in the geometry of the measurement volume so that the electric field lines are parallel within the illuminat- ed region, which itself is limited with both apertures and focusing optics. The pri- mary OSEE-generating spectral line of the ultraviolet lamp has been identified, and the radiation of that line from the lamp is independently measured and used to control lamp current to increase stability. The interfering effects associat- ed with oxygen and water vapor in the measurement region are being eliminat- ed from measurement by use of a purge gas. The lamp is further environmentally isolated and subjected to constant cool- ing to increase stability and optimize OSEE-producing radiation. Further improvements in the measure- ment have been identified. A laboratory prototype of a Kelvin Probe, capable of measuring surface work functions in me- tals, has been constructed and shown to be an appropriate complement to the basic OSEE apparatus for inspecting Fatigue-Crack-Tip Locator surfaces, the work vary naturally. In ad trol of the collect( made it possible to OSEE measuremen' surfaces by using head to replace thl following a measur dure is called "char~ With these imprc sions, OSEE shoulc number of industria inspection to del would be highly USE es, no suitable con technique has been This work was de of Lang ley RI Christopher S. w~ William and Mary, and Bill B. Hefn Services and Mat eration from Pers Space Flight Cen mentation is avaifaJj This invention is I a patent applicatio quiries concernin clusive license for opment should b Patent Counsel, Le ter [see page 20j. f Fatigue experiments can be run continuously under automated monitoring. Langley Research Center; Hampton, Virginia Figure 1 schematically illustrates part of a fatigue-testing system that includes an automated subsystem that continuously tracks the location of the fatigue-crack tip in a metal or other highly electrically conductive speci- men. The fatigue-crack-tip-Iocating subsystem can also search the speci- men to find the initial fatigue crack and its tip and to trace out hidden fatigue cracks and other flaws inside the specimen. The fatigue-crack-tip-Iocating sub- system operates under the overall 46 control of a personal computer, which also controls the load frame that applies the prescribed cyclic stresses to the specimen. An electromagnetic flaw detector based on the eddy-cur- rent principle is scanned over a sur- face of the specimen by x- and y-axis stepping-motor drives controlled by the computer. [The electromagnetic flaw detector was described previously in "Electromagnetic Flaw Detector Is Easier To Use" (LAR-15046). NASA Tech Briefs, Vol. 18, NO.7 (July 1994), page 36. To recapitulate: the electro- magnetic flaw I eddy-current pr single , unambl indicative of flaw~ The automat fatigue crack ar because of the u nal provided by part of Figure 2 ~ nal of the prot across two fatig minum-alloy spec in the output v occurs when th NASATE 48 x-axis Motor Drive y-axis Motor Drive Computer Load-Frame Controller Figure. 1. The Fatigue-Crack-TIp Locator is a subsystem of a fatigue-testing system. The probe IS scanned across the specimen to locate the tip of the fatigue crack. Hitachi's new KP-C571 Color Camera provides extraordinary performance in low light applications. The KP-C571 can automatically adjust for light levels from .05 lux to 100,000 lux using a combination of extended integra- tion and automatic gain. With a 768 x494 pixel CCD and a special noise reduction circuit, the camera provides 470 TV lines of resolution with a 48dB signal to noise ratio. In addition to low light microscopy and inspection applications, the camera has found extensive use in highway and bridge surveillance. Call for a demonstration. Hitachi Denshi , Ltd. Hitachi Denshi America, Ltd. HITACHI A New York 516-921-7200 A Atianta 404-242-3636 A Chicago 708-250-8050 A Los 31 0-328-6116 A Dallas 817-488-4528 A Canada 416-299-5900 For More Infonnatlon Write In No. 411 over the fatigue crack. When the probe is scanned along a crack, its output peaks at the crack tip. This is illustrated in the lower part of Figure 2, which is a plot of probe out- put as a function of position on an alu- minum-alloy plate speCimen with fatigue cracks emanating from a drilled central hole. The probe-output level rises sharply at the location of the hole and stays relatively constant around the circumference of the hole. The two fatigue cracks grown from the hole are easily detected as protrUSions from the otherwise circular pattem. In addition, the output level peaks at the outer tips of both fatigue cracks. Scanning outward along each crack, the output level falls sharply from the peak to the background level as the probe passes the crack tip. Thus, a computer peak-search rou- tine is used to locate the tip of a growing crack. Thereafter, the position of the probe is incremented in the direction of crack growth, as deter- mined by previous locations of the crack tip, and the scan is repeated until the new crack-tip location is found. After locating the new crack tip, the probe is moved a short distance back along the crack and the search repeat- ed. By continuously reevaluating the path of the crack near the crack tip , crack-tip-Iocation errors caused by noise and crack branching are avoided. During a typical fatigue experiment, a fatigue crack grows to predetermined lengths at which load levels and/or other parameters of operation of the load frame must be adjusted. Inasmuch as the computer has traced the growth of the crack from initiation it can automatically adjust the load ~ frame controls when the crack reaches these predetermined lengths. Thus, the fatigue-crack-tip locating system provides for automated control and monitOring of fatigue experiments, saving time for researchers and enabling experiments to run unattend- ed 24 hours a day. In addition, all infor- mation on crack-tip trajectories and rates of growth of cracks is recorded automatically, so that researchers have access to more information than is available from conventional, nonauto- mated monitOring. This work was done by Min Namkung and C. Gerald Clendenin of Langley Research Center, Buzz Wincheski, James P. Fulton, and Ronald G. Todhunter of Analytical Services and Materials, Inc., and John W. Simpson of Lockheed Engineering & Sciences Co. For further information write in 184 on the TSP Request Card. NASA Tech Briefs, December 1994 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.00 iJJ_iJJJJJf~___f. _ ___L_....:::L _ __'_ _ __'__ 0.0 0.6 1.3 1.9 2.5 3 .2 3.8 44 Posllioo Along Scan Una That Crosses Fatigue Crack, em ONE-DlMENSlONAL SCAN ACROSS CRACK IN PLATE Probe OUtput Relative Units TW().{)tMENSIONAL SCAN OVER PLATE WITH ORILLEO HOLE ANO CRACKS Figure 2. The Probe Output peaks as the probe is scanned across two fatigue cracks, and the peak is highest at the tip of the crack. This invention is owned by NASA, and a patent application has been filed. Inquiries concerning nonexclusive or exclusive license for its commercial development should be addressed to the Patent Counsel, Langley Research Center [see page 20]. Refer to LAR-15085. Preparation and Analysis of Specimens of Ablative Materials Inductively-coupled-plasma/atomic-emission spectroscopy is much faster than is atomic absorption spectroscopy. Marshall Space Flight Center, Alabama A procedure for chemical analysis of specimens of the silicone-based ablative thermal-insulation materials SLA-561 and MA25 involves acid digestion of the specimens to prepare them for analysis by inductively-coupled-plasma/atomic-emis- sion spectroscopy (ICP/AES) . In comparison with an older procedure in which atomic-absorption spectroscopy (AAS) was used, this procedure offers advantages including, primari- ly, that ICP/AES is faster and more accurate than AAS is. The results of such analyses can be stored in a data base, used to trace variations in concentrations of chemical elements in NASA Tech Briefs, December 1994 materials during long-term storage, and used in a timely manner in investiga- tions of failures. The acid-digestion por- tion of the procedure can be applied to other thermal-insulation materials that contain room-temperature-vulcanizing silicones and enables instrumental analysis of these materials. Super Ughtweight Ablator (SLA) is a composite of cured silicone resins highly filled with cork particles, small silica spheres, silica fibers, and phenolic microballoons. SLA is the primary abla- tive material on the extemal tank of the Space Shuttle. MA25 is similar to SLA- 561 but does not contain cork or pheno- lic microballoons. Previously, the prepa- ration of specimens of these materials for analysis included ashing in a muffle fumace, ovemight cooling, and 10 h of acid digestion. The high temperatures involved in the ashing process some- times caused loss of critical elements. The present acid-digestion process begins with the addition of 15 mL of fuming sulfuric acid to a 0.5-g specimen of SLA-561 or MA25 in a 125-mL polytetrafluoroethylene bottle. The bottle and the mixture of acid and specimen are heated for 2 h at 125°C; then the bottle is removed from the source of heat, and 5 mL of concentrated sulfuric acid are added. The bottle and mixture are then heated for approximately 1 h or until all solid particles are dissolved. The bottle is then removed from the source of heat and allowed to cool to ambient temperature. Five mL of concentrated nitric acid are added, and the bottle and its contents are heated again for 1 h at 125°C, then removed from the source of heat and allowed to cool to ambient temperature. Next, 2 mL of 48 percent hydrofluoric acid is carefully added, and the bottle and its contents are heated until the contents become translucent; this takes about 2 h. The contents are then transferred to a 100-mL polytetra- fluoroethylene volumetric flask and dilut- ed to volume with demineralized water. The diluted contents are then analyzed by ICP/AES. ICP/AES is orders of magnitude faster than is MS. In addition, ICP/AES offers simultaneous determination of the rela- tive concentrations of more than 40 ele- ments, whereas with MS, only a single element can be analyzed at a time. Also ICP/AES offers much lower detection limits, an analytical range of three orders of magnitude, and limited matrix effects in comparison with MS. A single speci- men of SLA-561 or MA25 can be ana- lyzed by ICP/AES for 15 elements in less than 5 minutes; such an analysis by MS would take 2 days. This work was done by William C. Solomon of Martin Marietta Corp. for Marshall Space Flight Center. No fur- ther documentation is available. MFS-28807 Apparatus Regulates Temperature Between -170 and 100 °C Temperature pulses are smoothed out by thermal mass and mixing. NASA's Jet Propulsion Laboratory, Pasadena, California Figure 1 illustrates schematically an apparatus that provides a flow of nitro- gen at a regulated temperature. It is deSigned to maintain the temperature of a laboratory instrument or a small envi- ronmental test chamber within ±2 °c of a set point that lies between -170 and 100 °C. In comparison with other cryo- genic apparatuses that regulate tem- peratures in the same range with similar precision, this one is relatively inexpen- sive, in large part because it is made of commercially available items, including temperature-control circuits, standard plumbing parts, and stock materials. The present apparatus was preceded by one in which hot gaseous nitrogen and cold liquid nitrogen were alternately pulsed into a feed line. Frequently, this predecessor apparatus produced over- cooling temperature excursions: even short pulses of liquid nitrogen often caused the temperature to fall below the set point by an unexpectedly large amount. The present apparatus also uses gaseous and liquid nitrogen, but incorporates several features that sup- press large temperature fluctuations. The apparatus is fed from liquid- and gaseous-nitrogen manifolds. Thermo- couples connected to the temperature- control circuits measure temperatures at selected locations along the flow path of the outflowing nitrogen mixture and in the instrument that is to be main- tained at the desired temperature. The 50 Shroud Vent ~p~h~ro~u~dJWWWWWTe~m~pe~ra~tu~re~Jc~o~n~tro~lI;vI;enI;t======~tl;I;I;A~.sphere psv Vent to ~m~p~v~v~e~nt~=========I;;;W;W;;;Nl~W;IA~tm~here Liquid-Nitrogen Manifold ~c=====*==~============~~~~ Gaseous- Nitrogen ==;=i======~=~==W=WWWWW=========~~~M.~lld I I Failsafe r.;;\J r.:;;-Ll... Overcooled Conlroller ~ ~ ~ JJJJJJJJ~J~ ~ i ~J~!!!h4!il~i~ Safe R I ~ Master TAHL I I I Cool Controller I I fJJJJJJJ"tJJJJJ~ I -L-_______ ~Jfi!>~i4 TAHL i I I I ___________ J JJJ~ I I I I Shroud Containing Instrument To Be Maintained at Set-Point Temperature Legend of Symbols: FE - Flowmeter TAHL- Alann For High or Low Temperature JC - Power Controller TS - Temperature Switch JS - Power Switch PSV - Pressure Safety Valve R - Red Light TE - Thennocouple VLN _ Liquid-Nitrogen Valve G - Green Light TIC - Temperature Indicater Control VGN _ Gaseous-Nitrogen Valve BL - Blue Light Figure 1. This Temperature-Control Apparatus mixes pulses of liquid nitrogen into smoothly flowing nitrogen gas to produce a flow of nitrogen gas at a controlled low temperature. NASA Tech Briefs, December 1994 Foam Insulation 3-in. Copper Pipe JJJ¥.f...I......~;WW~ Copper Wool --i+--Ne.! 24 in. Figure 2. The Mixing Chamber provides turbulence, thermal mass, and thermal con· ductance to promote thermal and mechani- cal mixing of the liquid and gaseous flows and thereby suppresses large transient deviations from the set-point temperature. flow of gaseous nitrogen is continuously measured and is manually adjustable. If the set-point temperature exceeds the ambient temperature, this gaseous flow is heated as necessary to raise the out- flow temperature. If the set-point tem- perature lies below the ambient temper- ature, then pulses of liquid nitrogen are added as needed to lower the outflow temperature. An important part of the apparatus is a mixing vessel (see Figure 2) that is specially designed to satisfy the follow- ing criteria: (1) It must be thermally mas- sive enough to suppress the tempera- ture excursions caused by pulsing the liquid nitrogen, but not so massive as to make the overall temperature-control feedback response unacceptably slug- gish; (2) the thermal mass must be con- figured for rapid transfer of heat from the gaseous to the liquid nitrogen; (3) the pressure drop in flow through the vessel must be acceptably small ; and (4) the vessel must be as simple and cheap as possible. The containment wall of the vessel is made from 3-in. (7.6-cm) copper pipe mounted in foam insulation. Flows of liq- uid and gaseous nitrogen enter the ves- sel through concentric copper tubes and first make contact with each other at the outlet of the inner concentric tube, part way down the outer concentric tube. The mixture emerges from the outer tube at the bottom of the vessel ; there, the mixture impinges on a bed of copper NASA Tech Briefs, December 1994 wool, which enhances mixing by provid- ing a combination of turbulence, thermal mass, and thermal conductivity. The mixture then flows back up, past a series of copper baffles, to an eccentric outlet at the top of the vessel. The baf- fles provide additional thermal mass , and the holes in the baffles are posi - tioned to enforce a weaving flow pattem that enhances the transfer of heat between the flowing nitrogen and the copper thermal masses. This invention is owned by NASA, and a patent application has been filed. Inquiries concerning nonexclusive or exclusive license for its commercial development should be addressed to the Patent Counsel, NASA Resident Office-JPL {see page 20]. Refer to NPO- 18995. This work was done by Kenneth R. Johnson of Caltech for NASA's Jet Propulsion Laboratory. For further information, write in 255 on the TSP Request Card. M author's name was omitted from a bnef appearing In the Physical Sciences section of the October 1994 issue. The brief entitled "Measurement of Crossflow Vortex Structure,' which appeared on page 75, should have credo ited both Navel K. Agarwal of Analytical Services and Materials, Inc. and Dal. V. Maddelon of Langley Research Center. IF YOU mINK YOU CAN'T SEAL IT, YOU HAVEN'T TRIED PI-tEUMArSFN ® Pneuma-Seal is an inflatable gasket that when pressurized with air, fills the gaps between surfaces, even hard-to-seal uneven surfaces. And when deflated, Pneuma-Seal quickly retracts to prevent interference when opening and dosing a door or cover. You can use Pneuma-Seal as an effective barrier against pressure differentials and to seal out water, dust, gas, chem- icals, noise and other contaminants. Pneuma-Seal is particularly suitable for: Large enclosures where it is uneconomical 10 machine the entire sealing surface Uneven fabrications where traditional compression gaskets or latches are ineliective Horizontal or vertical sliding doors or covers that would tend to drag on and abrade conventional seaJs Hinged doors where flush thresholds are required lYPical applications include: Processing equipment: chemical, food, textile, pharmaceu- ticals, dryers, ovens and where rapid sealing and unsealing are required PoUution control: sound attenuation, hopper seaJs Laboratory facUities: test equipment, clean rooms Transportation: military vebides, aircraft, shipboard, mass transit doors and hatches Construction: special purpose doors, IIood protection Pneuma-Seal is available in a wide range of profiles, with fabric reinfOrcing where applicable, and In a variety of rubber and silicone compounds 10 meet harsh environmental conditions. Pneuma-Seal is furnished complete, ready to install as continuous loops, strips, rectangles, or other shapes to your specified dimensional requirements. To obtain a complimentary copy of our designer's handbook, engineering assistance or to have a Presray representative contact you, please call us at any of the following telephone numbers: (914) 855-1220 Telex: 646720 FAX: (914) 855-1139 West Coast! (714) 751-2993 Presray Corporation 159 Charles Colman Boulevard, Pawling, NY 12564 YOU MAY ALSO CONTACf US BY CIRCLING THE RFSPONSE NUMBER INDICATED BELOW. For More Information Write In No. 413 51 Materials High-Performance Thermoelectric Semiconductors Figures of merit are almost double those of current state-of-the-art thermoelectric materials. NASA's Jet Propulsion Laboratory, Pasadena, California IrSb3 is a semiconductor that has been found to exhibit exceptional ther- moelectric properties . CoSb3 and RhSb3 have the same skutterudite crys- tallographic structure as that of IrSb3, and they exhibit exceptional transport properties that are expected to con- tribute to high thermoelectric perfor- mance. These three compounds form solid solutions (alloys with compositions of frl_u_yohpoypb~. This combination of properties offers potential for the development of new high-performance thermoelectric materials for more effi- cient thermoelectric power generators, coolers, and detectors. The dimensionless figure of merit for the thermoelectric performance of a material at a given temperature is called "zr and is given by S2T zr= -pI., where T is the absolute temperature, S is the Seebeck coefficient (the ratio between the electrical-potential and temperature gradients), p is the electrical resistivity, and A is the thermal conduc- tivity. A combination of theoretical and experimental efforts has resulted in opti- mization of p-type specimens of IrSb3. In particular, at a dopant concentration of 7xl018 cm-3, an experimental max- imum zr of nearly 1.8 was observed at a temperature of about 350 °C: This is about 80 percent higher than the zr val- ues of other p-type materials now in use (see figure). Even greater values of ZT are predicted for C01_x_yRhxlr ySb3 alloys 1.S 1.6 1.4 1.2 Bi2(Te, Seh Alloys r:f'I ~ frk~ ~ 1.0 O.S 0.6 0.4 < I I ~ / ;a'" / ~ IJl f( rf TAGS Alloys W~ ;f y~ t ~ / 1.4... vP' ~ ~ ~~ V- ..o-a-D" ~ o.t ~ (PB. Sn)(Te. Se) Alloys I ~ .~ Sio.aGeo.2 ~b. ,1 ~ ru,., , .....-u-o ~ /iJ 0.2 0.0 300 400 500 600 700 SOO 900 1000 1100 1200 1300 Temperature (K) The Dimensionless Figure of Merit, ZT, as a function of temperature is plotted for optimized p-type IrSb3 and for other state-of-the-art p-type thermoelectric materials. because the thermal conductivities of these alloys are less than that of IrSb3. In one potential application, p-type IrSb3 stages would be incorporated, along with n-type Sio.SGeO.2• into a radioisotope thermoelectric generator that would operate in the temperature range of 200 to 900 °c. The combined thermoelectric properties of IrSb3 and SiO.8GeO.2 would yield an energy-con- version efficiency of more than 13 per- cent - about 70 percent higher than that of an existing radioisotope thermo- electric generator that contains SiO.8GeO.2 (only). The increase in efficien- cy would increase specific power of the generator from the present value of 5.6 W/kg to more than lOW/kg. The enhanced thermoelectric performances of IrSb3 and the Ir1_x RhxCoySb3 alloys could also be utilized in other applica- tions such as waste heat recovery sys- tems. This work was done by Jean-Pierre Fleurial, Thierry Cail/at, and Alexander Borshchevsky of Caltech for NASA's Jet Propulsion Laboratory. For fur- ther information, write in 126 on the TSP Request Card. In accordance with Public Law 96- 517, the contractor has elected to retain title to this invention. Inquiries concem- ing rights for its commercial use should be addressed to William T. Callaghan, Manager Technology Commercialization JPL-301-350 4800 Oak Grove Drive Pasadena, CA 91109 Refer to NPO-19233, volume and num- ber of this NASA Tech Briefs issue, and the page number. Phenylethynyl-Terminated Polyimides Molecular weights can be selected to obtain desirable properties. Langley Research Center, Hampton, Virginia Phenylethynyl-terminated polyimides exhibit properties that are suitable for films, moldings, adhesives, and compos- ite-material matrices. These polyimides can be synthesized at various molecular weights, which can be selected to obtain 52 desirable properties for specific applica- tions. Polyimides are condensation polymers that can be synthesized by various routes. The most popular route involves the re- action of an aromatic dianhydride with an aromatic diamine to obtain a polyamide acid as an intermediate product. The polyamide acid is either thermally or chemically cyclodehydrated to form the polyimide, which has a repeat unit of the general type where Ar is a tetravalent NASA Tech Briefs. December 1994 Complete access to over 1500 pages of up-to-the- minute technical data is now available on-line on the Internet. Internet users worldwide can navigate within GE Plastics' WorldWideWeb address, www.ge.com.to access: Global Resources Guide. A quick reference to GE products, services, technical support and world- wide offices. Product Properties Guides. Individual properties and performance criteria for each GE engineering resin. Design Guides. Detailed design criteria and sugges- tions for over 10 resin families. Processing Guides. Parameters and procedures for molding and finishing processes. Application Information. The latest press announce- ments and customer application case studies and photographs. All available data can be downloaded or printed. For more information on GE Plastics'on-line interactive system and customized software for sim- plified access, call today, 1-800-845-0600. • GEPlastics For More Information Write In No. 514 Internet users can navigate through 1500 pages of engineering thermoplas- tics technical data by accessing the Gf system at www.ge.com c • .l..!JIl!tl!.. I . """,)' ""'"' , . .JJ......~ .... ) • ..... ( .... I--... ~ .. ... ).,., . .................. "" ........... .. - ... ~Eia.F W~ 6,000 g/mole) can form tough, creasible films. Furthermore, the cross-link densities of the cured phenylethynyl- terminated polyimides are chosen by selection of the molecular weights; low molecular weights lead to high cross-link densities. The advantage of phenylethynyl-terminated polyimides over ethynyl-terminated polyimides is the higher reaction temperature of the phenylethynyl group compared to the ethynyl group. The phenylethynyl group begins to react at a temperature about 350°C, compared to about 200°C for the ethynyl group. This higher reaction temperature provides a larger temperature range to melt-process these polymers, whereas ethynyl-terminated polymers begin to react and, therefore, are either not melt processible or have a very small temperature range for melt processing. Most polyimides have glass-transition temperatures greater than 200°C, so that there is virtually no or a very narrow temperature range of melt processibility for ethynyl-terminated polyimides. This work was done by Brian J. Jensen, Robert G. Bryant, and Paul M. Hergenrother of Langley Research Center. For further information, write in 58 on the TSP Request Card. LAR-15045 NASA Tech Briefs, December 1994 Aromatic Polyimides With Low Dielectric Constants These polyimides are also highly transparent. Langley Research Center, Hampton, Virginia An effort to develop improved dielectric film and coating materials has yielded linear aromatic polyimides that contain dimethylsilane linkages in the dian hydride portions of the mole- cules and at least one trifluoromethyl group in each of the diamine portions. Uke other polyimides, these offer advantages of thermal stability, low density, resistance to ionizing radiation, toughness, and flexibility. In comparison with other polyimides that are now commercially available, these polyimides exhibit lower dielectric constants, which are advantageous as dielectric films in electronic circuits. Also in comparison with commercial polyimides (which are generally bright yellow), these polyimides are nearly transparent and colorless - an advantage in protec- tive coating of solar photovoltaic celis, optical components, and antennas. ! Room Temperature Amide Solvent t7 ~ C~P ~ ~ t N-C Si C-N-Ar ~~W"©r Polyamic Acid HO-C 3 C-OH II II o 0 n ! Thermal Cure, 250 to 300 · C to~r~o t NyQ;C NNP~kJAr cf CH3 0 Polyimlde n Notes: 1. 5 S n S 100 2. Ar denotes -@-0-@-C(CF3h-@-0-@-, ©-0-@-C(CF3h-@-0-@ , CF3 -@-C(CF3h-@- , or A . A Linear Polylmlde With a Low Dielectric Constant is synthe- sized in reactions that incorporate dimethylsilane linkages in the dian hydride portions and at least one trifluoromethyl group in the diamine portions. The synthesis of a polyimide of this type (see figure) begins with a polymer-grade dianhydride that contains dimethylsilane (SiDA) and an equimolar quantity of a polymer-grade aromatic diamine that contains a trifluoromethyl group. These two ingre- dients are combined in an amide solvent, and the mixture is stirred at room temperature in a closed vessel until a high-mole- cular-weight polyamic acid is formed. The solution of polyamide acid in solvent is applied to a substrate to form a thin surface film, which is then thermally converted to the polyimide by heat- ing it to a temperature between 250 and 300 ae. The table shows some of the properties of representative NASA Tech Briefs, December 1994 VIDEO WINDOWS FOR6uVME SYSTEMS RGBIVIEW® 600 -SIMULATION _C 3 1 -SURVEILLANCE -INTERACTIVE VIDEO DISC TRAINING -ROBOTICS -INDUSTRIAL CONTROL -VIDEO TELECONFERENCING Six real time video windows Video windows scalable to full screen Optional inputs for FUR, radar, VGA and medical imagers X.TVTM program controls all video functions under X Windows Keyer overlays text and graphics on video No burden on host CPU or graphics controller 24-bit color processing of the video input Compatible with all high resolution graphics controllers Other models available SPECTRUM'" 950 Marina Village Parkway Alameda, CA 94501 Tel: (510) 814-7000 Fax: (510) 814-7026 For More Infonnatlon Write In No. 414 polymers of this type, along with the corresponding properties of the commer- cial polyimide film Kapton H®. The silicon and fluorine atoms incorporated into these polyimides yield significantly lower dielectric constants. These polyimides are also significantly clearer, as shown in spectroscopic measurements on film specimens 0.5 mil (about 13 ~mF thick at a wavelength of 500 nm. Each of the specimens of these polyimides was found to be at least 90 percent transpar- ent, while the Kapton® specimen was found to be only 30 percent transparent. This work was done by Anne K. St. Clair and Terry L. Sf. Clair of Langley Research Center and J. Richard Pratt of PRC Kentron. For further information, write in 271 on the TSP Request Card. This invention has been patented by NASA (U.S. Patent No. 5,093,453). Inquiries concerning nonexclusive or exclusive license for its commercial development should be addressed to the Patent Counsel, Langley Research Center [see page 20]. Refer to LAR- 14198. Abbreviated Diamine Physical Dielectric Name of Polymer Ar Appearance Constant (1 mil Thick) at 10GHz SiDA + 4, 4'-6F J@JCECc~2J@J Essentially 2.64 Colorless SiDA + 4-BDAF J@JlJ@JCECc~2J@JlJ@J Very Pale Yellow 2.56 SiDA + 3-BDAF J@JlJ@JCECc~2J@JlJ@J Pale Yellowl Colorless 2.66 CF3 SiDA+ DABTF h Pale Yellowl 2.75 Colorless Kaptonte Bright Yellow 3.20 Dielectric Constants of polyimides like those illustrated generically in Figure 1 tend to range approximately from 2.5 to about 2.8, whereas those of older commercial polyimides tend to range approximately from 3.2 to 4.0, exact values depending on moisture contents. Stable, Electroinactive Wetting Agent for Fuel Cells Perfluorooctanesulfonic acid can be used with gas-diffusion electrodes in liquid-feed fuel celis. NASA's Jet Propulsion Laboratory, Pasadena, California Straight-chain perfluorooctane- sulfonic acid (Ca acid) has been identi- fied as an innocuous and stable wetting agent for use with polytetrafluoroethyl- ene-containing electrodes in liquid-feed direct-oxidation fuel cells like those suggested for use in vehicles and portable power supplies. Ca acid in small concentrations (0.001 to 0.1 M) in aqueous liquid solutions of methanol, trimethoxymethane, dimethoxymeth- ane, and trioxane enables the oxidation of these substances by use of commer- cially available electrodes of the type designed originally for use with gases. This useful function is specific to the Ca acid molecule and is not achieved by other related perfluoroalkanesulfonic acids. Electrodes used in fuel cells usually include metal catalyst powders that are either unsupported or supported by carbon and are mixed with polytetraflu- oroethylene (which serves as a binder) and applied to polytetrafluoroethylene- containing carbon-paper substrates. Electrodes of this type that contain 15 to 50 percent of polytetrafluoroethylene are commercially available and are used in hydrogen/oxygen fuel cells in which the fuel and oxidant are supplied as gases. The large quantities of polytetra- 56 fluoroethylene in these cells are essen- tial to the creation of uniform thin layers of the electrocatalysts on the sub- strates. When aqueous solutions of methanol and other water-soluble oxy- genates are used in liquid-feed direct- oxidation fuel cells, the commercially available fuel-cell electrodes are unsuit- able because they are not wetted ade- quately by the fuel solutions. A wetting agent is necessary so that the elec- troactive materials will make the good contact with the electrode, as is neces- sary for oxidation of the fuels in the solutions. The wetting agent of choice must decrease the interfacial tension without hindering the desired oxidation reaction by being specifically adsorbed on the electrodes. The adsorption behavior of Ca acid has been studied by cyclic voltammetry in sulfuric acid aqueous solutions with platinum electrodes. The double-layer capacitance of the PVsulfuric acid inter- face, as determined from the slope of the current-scan-rate plot in the elec- tric-potential range of 0.4 to 0.6 V, is not affected by the presence of Ca acid, as can be seen in Figure 1. The absence of any new peaks in the cyclic voltammogram shows that Ca acid is not electroactive and that it is stable to TrJ~JJ~JJ~JJ~JJ__ ~ 6 PtlO.5 M Sulfuric Acid, 25 °C 5 o JN~~~~JJ~JJ~JJ~~ o 100 200 300 400 500 600 Scan Rate, mVls Figure 1. The Slopes of These Plots, which are derived from cyclic voltammo- grams, are proportional to the double-layer capacitance of the Ptlsulfuric acid interface. electro-oxidation in the potential range of 0.0 to -1.30 V vs. NHE. The cyclic voltammograms for PVsulfuric acid in methanolic solutions with and without Ca acid show that the kinetics of oxidation of methanol at the platinum electrode are unaffected by the pres- ence of Ca acid. The non adsorbing nature of the perfluorooctanesulfonic acid anion is due to its low nucleophilici- ty and the strong electron-withdrawing nature of the fluorine substituents. NASA Tech Briefs, December 1994 1.0 0.9 0.5 M Sulfuric Acid, 1 M Methanol, PtiSn 0.8 ~ 0.7 > - With 0.0001 M Ca Acid u.i 0.6 J: z ~ 0.5 ~ 0.4 c: * 0.3 Q. 0.2 0.1 0.0 0.001 0.01 The wetting action of Ca acid has been demonstrated in half-cell experi- ments in which polytetrafluoroethylene- containing, high-surface-area, carbon- supported platinum and platinum-alloy electrodes were used. Figure 2 shows the effect of the concentration of Ca acid on the kinetics of the oxidation of methanol at Pt/Sn electrodes in sulfuric acid electrolyte . The oxidation of methanol has also been carried out in 0.1 M pure Ca acid solutions (no sulfuric ~ With 0.01 M Ca Acid 0.1 10 Current Density, mAlcm2 acid), and the polarization curves indicate that the kinetics are unaffected by the presence of the perfluorooctane- sulfonate ion. This work was done by Surya G. Prakash, George A. Olah, Sekharipuram R. Narayanan, Subbarao Surampudi, and Gerald Halpert of Ca/tech for NASA's Jet Propulsion Laboratory. For further information, write in 262 on the TSP Request Card. In accordance with Public Law 96- 100 Figure 2. The Wetting Action of perfluorooctanesul- fonic acid is indi- cated by the reduc- tion of polarization during the electro- oxidation of methanol. 517, the contractor has elected to retain title to this invention. Inquiries concern- ing rights for its commercial use should be addressed to William T. Callaghan, Manager Technology Commercialization JPL-301-350 4800 Oak Grove Drive Pasadena, CA 91109 Refer to NPO-19227, volume and num- ber of this NASA Tech Briefs issue, and the page number. Uncommon Versatility in Imaging Boards & Software :------ 64 Mbyte Image Memory r---- On-Board DSP 50 MHZ A-D Call or fax for specifications! 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For More Infonnation Write In No. 415 Computer Programs COSMIC: Transferring NASA Software COSMIC, NASA'S Computer Software Management and Information Center, distributes soft- ware developed with NASA funding to industry, other govemment agencies and academia. COSMIC's inventory is updated regularly; new programs are reported in Tech Briefs.For addi- tional information on any of the programs described here, write in the appropriate TSP number. If you don't find a program in this issue that meets your needs, call COSMIC directly for a free review of programs in your area of Interest. You can also purchase the annual COSMIC Software Catalog, oontaining descriptions and ordering information for available software. COSMIC is part of NASA's Technology Transfer Network. Computer Programs These programs may be obtained at a very reasonable cost from COSMIC, a facility spon- sored by NASA to make computer programs available to the public. For information on pro- gram price, size, and availability, write in the reference number on the TSP and COSMIC Request card in this issue. Mathematics and Infonnation Sciences Decision-Tree Program INO offers capabilities useful to both nonexpert and expert users. A common approach to supervised classification and prediction in artificial intelligence and statistical pattern recog- nition involves the use of decision trees. A tree is "grown" from data by use of a recursive partitioning algorithm. The tree thus created yields good predictions of classes on new data. Standard algo- rithms are CART (by Breiman, Friedman, Olshen, and Stone) and 103 and its successor C4 (by Quinlan). In addition to reimplementing parts of these algorithms and offering experi- mental control suites, the INO computer program also introduces Bayesian and Markov/ maximum-likelihood (MML) methods and more-sophisticated meth- ods of searching in growing trees . These methods produce more-accurate class-probability estimates that are important in applications like diagnosis. INO is applicable to most sets of data that consist of independent instances, each described by a fixed-length vector of attribute values. An attribute value can be a number or one of a set of 58 attribute-specific symbols, or it can be omitted. One of the attributes is delegated the "target," and INO grows trees to predict the target. Prediction can then be done on new data, or the decision tree can be printed out for inspection. INO provides a range of features and styles with convenience for the casual user as well as fine-tuning for the advanced user or for those interested in research. INO can be operated in a CART-like mode (but without regression trees, surrogate splits, or multivariate splits) , and in a mode like that of the early version of C4. Advanced features enable more-extensive search, interac- tive control and display of growth of trees, and Bayesian and MML algorithms for pruning and smoothing of trees. These features often pro- duce more-accurate class-probability estimates at the leaves. INO also includes a comprehensive experimental control suite. INO consists of four basic kinds of routines: data-manipulation routines, tree-generation routines, tree-testing routines, and tree-display routines. The data-manipulation routines are used to partition a single large set of data into smaller training and test sets. The gener- ation routines are used to build classi- fiers. The test routines are used to evaluate classifiers and to classify data by use of classifiers. The display routines are used to display classifiers in various formats. INO is written in C language for Sun4- series computers. It consists of several programs with controlling shell scripts. Extensive UNIX man entries are includ- ed. INO is designed to be used on any UNIX system, although it has been tested thoroughly on Sun computers only. The standard distribution medium for INO is a O.25-in. (6.35-mm) stream- ing-magnetic-tape cartridge in UNIX tar COSMlc®- John A Gibson, Director Phone (706) 542-3265; FAA (706) 542-4807 The University of Georgia, 382 East Broad Street, Athens, Georgia 30602 format. An electronic copy of the docu- mentation in PostScript format is includ- ed on the distribution medium. INO was developed in 1992. This program was written by Wray Buntine of Ames Research Center. For further information, write in 28 on the TSP Request Card. ARC-13188 ~ Mechanics Conversion of Classical Orbital Elements OSMEAN converts mean to osculating elements or vice versa. OSMEAN is a sophisticated FORTRAN program that converts between osculat- ing and mean classical orbital elements. Mean orbital elements are advantageous for designing trajectories and planning maneuvers because they can be propa- gated very quickly. However, mean ele- ments cannot describe the exact orbit at any given time . Osculating elements enable an engineer to give an exact description of an orbit, but the cost of computational is significantly greater because of the numerical integration pro- cedure required for propagation. By calculating accurate conversions between osculating and mean orbital ele- ments, OSMEAN enables the engineer to exploit the advantages of each approach for the design and planning or orbital tra- jectories and maneuvers. OSMEAN can convert mean elements to osculating ele- ments or vice-versa. The conversion is based on mathematical modeling of all first-order aspherical terrestrial, lunar, and solar gravitational perturbations plus a second-order aspherical term based on the second-degree central-body NASA Tech Briefs, December 1994 HiPlole 7000 Series Our Competition is 1000/0 Behind Us. Hey, facts are facts! The HiPlot 7000 Series [).. and E-size pen plotters are the best in the world. • 100010 More Versatility. Our exclusive SCAN'(AD accessory allows the HiPlot to double as a wide format, 400dpi scanner - for under $2,7001 • 100% Faster. HiPlot combines 5.7g accelera-tion and 45ips velocity to produce ~ plots twice as fast as HP DrahPro ELN"Df~ • 3·Year Warranty. HiPlot's unique FlexLoopTli Plus. It even beats the DesignletTli ~ platen, HI" Grip drive system and Plotting-On-Air 650C on some drawings. Er. rOllUTlON ...... m design revolutionize the way pen plotters handle • 100% More Accurate. Even at these higher media. 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OSMEAN is written in FORTRAN 77 for HP 9000-series computers running HP-UX (NPO-18796) and DEC VAX-series computer running VMS (NPO-18741). The HP version requires 388K of random-access memory for execution, and the DEC VAX version requires 254K of random-access memo- ry for execution. Sample input and out- put are listed in the documentation. Sample input is also provided on the distribution medium. The standard distri- bution medium for the HP 90OD-series version is a 0.25-in. (6.35-mm) stream- ing-magnetic-tape cartridge in UNIX tar format. This version is also available on a 0.25-in. (6.35-mm) streaming-magnetic- tape cartridge in IOTAMAT format or on a 3.5-in. (8.89-cm) diskette in UNIX tar format. The standard distribution medium for the DEC VAX BACKUP for- mat. It is also available on a TK50 tape cartridge in DEC VAX BACKUP format. OSMEAN was developed on a VAX 6410 computer in 1989 and was ported to the HP 9000-series computers in 1991. It is a copyrighted work with all copyright vested in NASA. HP 9000 and HP-UX are trademarks of Hewlett-Packard Co. DEC VAX and VMS are trademarks of Digital Equipment Corp. UNIX is a trademark of AT&T. This program was written by Joseph R. Guinn, Ramachand S. Bhat, Mark A. Vincent, and Alexander S. Konop/iv of Ca/tech for NASA's Jet Propulsion Laboratory. For further information, write in 39 on the TSP Request Card. NPO-18741118796. Composite-Plate-Buckling Analysis Program High-order displacement functions are used instead of traditional finite-element analysis. The Composite-Plate-Buckling Analy- sis Program (COMPPAP) was written to help engineers determine buckling loads of orthotropic or isotropic irregularly shaped plates without need to perform manual calculations and without exten- sive finite-element mathematical model- ing. COMPPAP is a one-element finite- element program that utilizes high-order displacement functions to perform a plane-stress analysis of a general plate followed by a buckling calculation based on the stresses found in the plane-stress solution. The high order of the displace- ment functions enables the user to obtain results more accurate than those obtained by use of traditional h-version 60 finite elements. In the current version of COMPPAP, the plate is flat, of uniform thickness, and subject to a constant nor- mal or shear load on one or more edges. COMPPAP uses the power method to find the eigenvalues of the buckling prob- lem. The power method provides an effi- cient solution when only one eigenvalue is desired. Once the eigenvalue is found, the eigenvector, which corresponds to the shape of the plate buckling mode, is obtained as a by-product. A positive feature of the power method is that the dominant eigenvalue is the first one found; in this case, the dominant eigen- value is related to the lowest buckling load. COMPPAP is written in ANSI FOR- TRAN 77. Two machine versions are available from COSMIC: a version (MSC- 22428, this article) for computers of the IBM PC 386 and higher series and for compatible computers; and a UNIX ver- sion (MSC-22286). The distribution medi- um for both machine versions includes source code for both single- and double- precision versions. The PC version includes source code that has been opti- mized for implementation within DOS memory constraints as well as sample executable codes for both the single- and double-precision versions. The double- precision versions have been successfully implemented on an IBM PC 386- com- patible computer running MS-DOS, a Sun4-series computer running SunOS, an HP-9000 series computer running HP-UX, and a CRAY X-MP computer running UNICOS. COMPPAP requires 1 MB of random- access memory and the BLAS and UN- PACK math libraries, which are included on the distribution medium. The COMP- PAP documentation provides instructions for using the commercial post-processing package PATRAN for graphical inter- pretation of COMPPAP output. The UNIX version includes two electronic versions of the documentation: one in LATEX for- mat and one in PostScript format. The standard distribution medium for the PC version is a 5.25-in. (13.335-cm), 1.2MB MS-DOS-format diskette. The standard distribution medium for the UNIX version (MSC-22286) is a 0.25-in . (6.35-mm) streaming-magnetic-tape cartridge (Sun QIC-24) in UNIX tar format. For the UNIX version, alternate distribution media and formats are available upon request. COMPPAP was developed in 1992. This program was written by James P. Smith of Johnson Space Center. For further information on MSC-22428, write in 203 on the TSP Request Card. For further information on MSC-22286, write in 204 on the TSP Request Card. MSC-22428/MSC-22286 Computing Satellite Maneuvers for a Repeating Ground Track Mathematical models account for all significant perturbations of the trajectory. The TOPEX/POSEIDON Ground Track Maintenance Maneuver Targeting Program (GT ARG) was developed to assist in designing maneuvers to main- tain the orbit of the TOPEX/POSEIDON satellite. These maneuvers ensure that the ground track is kept within 1 km of a pattern that repeats exactly at intervals of approximately 9.9 days. Targeting strategies used by GTARG either maxi- mize the time between maneuvers (lon- gitude targeting) or force control band exit to occur at specified intervals (time targeting) . A runout mode allows for ground-track propagation without tar- geting. GT ARG incorporates an analytic mean-element propagation algorithm that accounts for all perturbations that are known to cause significant variations in the ground track. These perturbations include the oblateness of the Earth, luni- solar gravitation, drag, thrusts associat- ed with impulsive maneuvers, and unspecified fixed forces acting on the satellite in the direction along the trajec- tory. The geopotential field is computed in GTARG by use of Merson's extension of Grove's theory. Kaula's disturbing func- tion is used to include the luni-solar gravitational perturbations . GTARG includes a mathematical model of drag, unique to the satellite, that incorporates an approximate mean orbital Jacchia- Roberts atmosphere and a variable mean area model. Mathematical models of errors account for uncertainties in determination of orbits, errors in execu- tion of maneuvers, unpredictability of drag, and use of the knowledge of fixed forces along the trajectory. Changes in velocity during maneuvers are targeted to maintain precisely either the unbiased ground track or a comfortable (three- standard-deviation) error envelope about the unbiased ground track. GTARG is written in VAX-FORTRAN for DEC VAX computers running VMS. GTARG output is provided in two forms: an executive report summary in tabular form , and a plot file formatted as EZPLOT input namelists. Although the EZPLOT program and documentation are included with GTARG, EZPLOT requires PGPLOT, which was written by the Astronomy Department of the California Institute of Technology and is not available through COSMIC. GTARG users without access to PGPLOT may NASA Tech Briefs, December 1994 therefore want to use a standard spread- sheet program to produce plots of the tabular ground-track data stored in the executive report summary. Alternatively, with the help of information found in the GTARG User's Reference Manual, the user can write a graphical interpreter program of his or her choice. The stan- dard medium for distribution of GTARG is a 1,600-bitlin. (-=630-bitlcm), 9-track magnetic tape in DEC VAX BACKUP for- mat. It is also available on a TK50 tape cartridge in DEC VAX BACKUP format. GTARG was developed in 1993 and is a copyrighted work with all copyright vest- ed in NASA. This program was written by Bruce Shapiro of Caltech for NASA's Jet Propulsion Laboratory. For further information, write in 233 on the TSP Request Card. NPO-19257 • Materials Programs for Predicting Fatigue and Creep-Fatigue Resistances Software characterizes behavior and predicts life of metallic materials in high-tem- perature, long-life regime. TS-SRP/PACK is a set of computer programs for characterizing and predict- ing fatigue and creep-fatigue resistances of metallic materials under isothermal and non isothermal fatigue conditions in the high-temperature, long-life regime. The programs implement the total-strain version of the strainrange-partitioning (TS-SRP) method. The user should be thoroughly familiar with the TS-SRP method before attempting to use any of these pro- grams. The document for this program includes a theory manual as well as a detailed user's manual with a tutorial part to guide the user in the proper use ofTS-SRP. An extensive data base has also been developed in a parallel effort. This data base is an excellent source of high-tem- perature, creep-fatigue test data and can be used with other life-prediction computer codes as well. Five programs are included in TS- SRPI PACK along with the alloy data base. The TABLE program is used to print the sets of data (which are supplied in NAMELIST format), in a format that is easier to read. INDATA is used to create new sets of data or add to existing ones. NASA Tech Briefs, December 1994 The FAIL program is used to characterize the failure behavior of an alloy as given by the constants in the strain range-life relations used in the TS-SRP method and the inelastic-strain range-based ver- sion of the SRP method. The program FLOW is used to characterize the flow behavior (the constitutive response) of an alloy as given by the constants in the flow equations used in the TS-SRP method. Finally, LIFE predicts the life of a specified cycle, using the constants that characterize failure and flow behavior determined by FAIL and FLOW. LIFE is written in interpretive BASIC to avoid compiling and linking every time the con- stants in the equations are changed. Four out of five programs in this pack- age are written in FORTRAN 77 for IBM PC-series and compatible computers running MS-DOS and are designed to read data by use of the NAMELIST for- mat statement. The fifth is written in BASIC version 3.0 for IBM PC-series and compatible computers running MS-DOS version 3.10. The executable codes require at least 239K of memory and DOS 3.1 or higher. To compile the source code, a Lahey FORTRAN compil- er is required. Modifications of the source will be necessary if the compiler to be used does not support NAMELIST input. Probably the easiest revision to make is to use a list-directed READ statement. The standard distribution medium for this program is a set of two 5.25-in. (13.34- cm) 360K MS-DOS-format diskettes. The contents of the diskettes are com- pressed by use of the PKWARE archiv- ing software tools. The utility software to unarchive the files, PKUNZIP.EXE, is included. TS-SRPI PACK was developed in 1992. This program was written by J. F. Saltsman of Lewis Research Center. For further information, write in 97 on the TSP Request Card. LEW-15653 Program for Analysis of Metal-Matrix Composites METCAN simulates nonlinear behaviors of composites and their constituents. High-temperature metal-matrix com- posites offer great potential for use in advanced aerospace structures. The realization of this potential, however, requires concurrent developments in (1) technology for fabrication of high-tem- perature metal-matrix composite struc- tural components, (2) experimental "PuttingDesignto Work" Custom/Specialty Cases Custom designed for a wide range of environmental conditions to protect the most sensitive equipment. Superior reliability and engineering for the transportation environment. Deck Cases Shock-mounted aluminum deck provides superior protection for multiple types of fragile items. Standard sizes availablel 'I'C) IJ C. H, fll~fg~lllll~f~I IIfJlifllC)N1UJX II C) f~fF f~fF C~ll~f~~ Foam Cushion Cases Over 220 standard rotationally molded cases I Purchase them empty or with custom designed foam systems. 19" Rack-Mount Cases Strong shock mounted 19" EIA rack protects sensitive equipment from shock and vibration. Standard sizes available from 4 to 26 rack units in height. Tough rotationally molded shell stands up to severe environments. Interchange- able 2" deep front and rear lids (optional 5" depth available). ~.n§ Molded-in flange to support panel-mounted gear. Threaded inserts allow easy panel fastening. Standard sizes HARD/GG 393 North Main Street, SouthDeerfield,MA01373 A~ available! CASES TEL: 1-800-JHARDIGGor413-665-2163FAX:413-665-IDil For More Infonn. t lon Write In No. 4 18 61 techniques for measuring their thermal and mechanical characteristics, and (3) computational methods to predict their behavior. METCAN (METal matrix Composite ANalyzer) is a computer pro- gram developed to predict this behavior. METCAN can be used to simulate com- putationally the nonlinear behavior of high-temperature metal-matrix compos- ite structural components in specific applications, providing comprehensive analyses of thermal and mechanical per- formances. METCAN treats nonlinearity of a com- posite material at the constituent (fiber, matrix, and interphase) level, where the behavior of each constituent is modeled, accounting for the dependences among time, temperature, and stresses. The properties of the composite are synthe- sized from the instantaneous properties of the constituents by making use of composite micromechanics and macro- mechanics. Factors that affect the behavior of the properties of the com- posite include the variables of the fabri- cation process, the properties of the fiber and matrix, the bonding between the fibers and matrix, and/or the proper- ties of the interphase between the fiber and matrix. A METCAN simulation is performed as a pointwise analysis and produces com- posite properties that are readily incor- porated into a finite-element code to perform a global structural analysis. After one iteration of the global structural analysis has been performed, METCAN decomposes the properties of the com- posite back into the localized responses at the various levels of the simulation. Then the properties of the constituents are updated, and the next iteration in the analysis is initiated. This cyclic proce- dure is an instance of the integrated approach to analysis of metal-matrix composites. METCAN-PC is written in FORTRAN 77 for IBM PC-series and compatible computers running MS-DOS. An 80286 machine with an 80287 math coproces- sor is required for execution . The exe- cutable code requires at least 640K of random-access memory and DOS 3.1 or higher. The package includes sample executable codes that were compiled under Microsoft FORTRAN v. 5.1. The standard distribution medium for this program is one 5.25-in . (13.34-cm), 360K MS-DOS-format diskette . The contents of the diskette are compressed by use of the PKWARE archiving soft- ware tools. The utility software to unar- chive the files, PKUNZIP.EXE, is includ- ed. METCAN-PC was developed in 1992. This program was written by P. L. N. 62 Murthy of Lewis Research Center and S. K. Mital of the University of Toledo. For further information, write in 75 on the TSP Request Card. LEW-1571 1 Physical Sciences Program Computes Dendrite-Settling Velocities This program is based on empirical relationships among velocity, physical properties and shape. The motion and gravitational settling of free floating crystals and grain frag- ments can cause macrosegregation and can influence the structure of metal castings. An understanding of how the highly nonspherical shape of a metal crystal influences its positioning charac- teristics is needed to predict the struc- ture and segregation in castings. The empirical results of previous studies have been used to develop the DEN- DRIFT computer code, which calculates the settling velocities of metal-alloy crys- tals of various shapes. DEN DRIFT also calculates a number of other parame- ters of interest such as the volume and surface area of a dendrite. The program requires, as input, the physical proper- ties of the material system, and some geometric parameters of the dendrite under consideration, such as the aver- age radius of the primary arm. DEN DRIFT exploits the concept of an envelope around the dendrite to enable the calculation of an effective sphericity. In comparison with results of an experi- mental study of model dendrites, the settling velocities predicted by the code were found to be, on average, within 5 percent of measured values. The pre- dictions of the code were also found to be consistent and in good agreement with results of three other experimental investigations. Thus, incorporation into the code of the empirical relationships among velocity, sphericity, and enve- lope permeability appear valid , as do wall and inertial correction factors devel- oped for this code. In its current form, DENDRIFT does not account for gradi- ents in composition or density, interac- tions between particles, tertiary dendrite arms, or the possible influences of off- axis (tilted) dendrite settling. This program can also be used to est imate the settl ing veloc ities of spheres and cylinders with hemispheri- cal ends. The code can be useful as a subprogram in a comprehensive solidifi- cat ion/ cast ing code . The concepts demonstrated in DEN DRIFT may also be widely applicable in the chemical-pro- cessing industry by helping to describe the settling or floating of precipitates and flocs. DENDRIFT is written in FORTRAN 77 for IBM PC-series and compatible com- puters running MS-DOS 3.0 or later and has been successfu lly implemented using Lahey v5.01-EM32. For execution, it requires 80K of random-access mem- ory and an 80286, 80386, or 80486 processor. Sample input and output files and a sample DOS executable code are included with the distribution medium. The standard distribution medium for this program is one 5.25-in. (13.335- cm), 360K MS-DOS-format diskette. DEN DRIFT was developed in 1992. This program was written by Henry de Groh, III, of Lewis Research Center; Patrick Weidman and Riad Zakhem of the Univers ity of Colorado; and Christopher Beckerman and Sandeep Ahuja of the University of Iowa. For fur- ther information, write in 225 on the TSP Request Card. LEW-15751 Program Gives Data on Physical Properties of Hydrogen TAB II provides values of ther- modynamic and transport properties. The TAB II computer program pro- vides values of thermodynamic and transport properties of hydrogen in a useful format. In many problems, the properties have to be evaluated at numerous thermodynamic state points. TAB II provides these values for equilib- rium hydrogen and para-hydrogen. The program is fast, moderately accurate, and operates over wide ranges of input variables. For input, TAB II requires either one of two pairs of variables; (1) pressure and temperature or (2) pressure and enthalpy. The program covers (1) the pressure range from 1 to 5,000 pSia (about 7 kPa to about 34 MPa) and the temperature range from the triple point to 6,000 R (about 3,300 K) or (2) enthalpies from about -130 Btullb (-623 J/ mole) to about 25 ,000 Btu/lb (117 ,000 J/ mole) . Output variables include enthalpy or temperature, densi- ty, entropy, thermal conductivity, viscos- ity, speed of sound , heat capacity at constant pressure , heat capacity at constant volume, the ratio between the NASA Tech Briefs, December 1994 heat capacity at constant pressure and the heat capacity at constant volume, and a heat-transfer parameter. Values of properties on the liquid and vapor bound- aries are conveniently obtained through two small routines. TAB II achieves rapid output by use of linear interpolation in a grid of precomputed points that define the surface of values of the property to be interpolated. The maximum errors arising from the linear interpolation are shown on individual deviation plots for each combination of variables. Estimates of errors in the sources of data are similarty displayed. TAB II is written in FORTRAN 77 for IBM PC-series and compatible com- puters running MS-DOS. A sample executable code is included. The stan- dard distribution medium for this program is one 5 .25-in. (13.335-cm), 360K MS-DOS-format diskette. The contents of the diskette are compressed by use of the PKWARE archiving software tools. The utility software to unarchive the files, PKUNZIP.EXE, is included. TAB II was originally developed in FORTRAN IV for use on IBM 360-series computers. This updated version was created in 1992, and includes some updated data as well as code that has been rewritten in FORTRAN 77. This program was written by H. M. Roder, R. D. McCarty, and W J. Hall of the National Institute of Standards and Technology for Lewis Research Center. For further information, write in 224 on the TSP Request Card. LEW-15626 • Electronic Systems DET/MPS - The GSFC Energy Balance Programs DET IMPS determines and computes energy balance for DET and MPS-type space- craft power systems. The Direct Energy Transfer (DEl) and the MultiMission Spacecraft Modular Power System (MPS) computer pro- grams perform mathematical modeling and simulation to aid in both the design and analysis of DET and MPS space- craft power system performance in order to determine the energy balance of the subsystem. Typically, the DET spacecraft power system feeds the out- put of the solar photovoltaic array and the nickel cadmium batteries directly to the spacecraft bus. In a MPS system, NASA Tech Briefs. December 1994 the Standard Power Regulator Unit (SPRU) is utilized to operate the array at the array's peak power point. DET and MPS perform a minute-by-minute simu- lation of the performance of the power system as it responds to various orbital and operational parameters. The results of the simulation focus mainly on the out- put of the solar array and the character- istics of the batteries. While both software packages are limited in terms of orbital mechanics, they have sufficient capability to calculate data on eclipses and performance of arrays for circular or near-circular orbits. DET and MPS can be adjusted to run one orbit or a sequence of orbits as long as 1 week in simulated time. These pro- grams have been used on a wide variety of spacecraft projects in Goddard Space Flight Center. DET and MPS are written in FOR- TRAN-77 with some VAX FORTRAN- type extensions. Any FORTRAN compiler that includes VAX extensions should be able to compile and run the programs with little or no modification. The compil- er must at least support tab-delineated source format and "do do-while-end-do" control structures . DET and MPS are both available in three versions: GSC- 13374, for DEC VAX-series computers running VMS, is available in DEC VAX BACKUP format on a 9-track, 1600- bit/in. (630-bit/cm) magnetic tape (stan- dard distribution) or on a TK50 tape car- tridge; GSC-13443, for UNIX-based computers, is available on a 0.25-in. (6.35-mm) streaming-magnetic-tape car- tridge in UNIX tar format; and GSC- 13444, for Apple Macintosh computers running NUX with either the NKR FOR- TRAN for AbSoft MacFORTRAN II com- pilers, is available on a 3.5-in. (8.89-cm) 800K Macintosh format diskette. Source code and test data are supplied. The UNIX version of DET or MPS requires 90K of main memory for execution. DET and MPS were originally developed in 1990. "NUX" and "Macintosh" are registered trademarks of Apple Computer, Inc. "VMS: "DEC VAX," and "TK50" are trademarks of Digital Equipment Corp. "UNIX" is a registered trademark of AT&T Bell Laboratories. These programs were written by J. M. Jagielski of Goddard Space Flight Center. For further information on the DEC VAX version, write in 76 on the TSP Request Card. GSC-13374 For further information on the UNIX version, write in n on the TSP Request Card. GSC-13443 For further information on the A/UX version, write in 78 on the TSP Request Card. GSC-13444 Spend More Time Doing Science and Less Time Programming IDLe is the only software that allows you to program four to ten times faster* than FORTRAN or c. It seamlessly integrates all of your scientific computing needs in a single package - breathtaking 20, & 3D graphics, powerful number crunching, flexible data I/O and more. It even includes a complete GUI toolkit for creating pOint and click applications. And, because 10L runs on pes, Macs, Unix and VMS workstations you won't have to rewrite your code every time you change machines. Join the elite group of more than 20,000 scientists around the world who are saving time and money by using 10L. Call us for a free demo. JOJ- 78fi-9900 FAX JOJ- 78fi- 9909 Research Systems, Inc. 2995 Wilderness Place Boulder co 80301 ::: IDL 'based on , survey of lOl users For More Infonnatlon Write In No. 41 7 Mechanics Dual-Mode Adhesive Pad This device can be switched between sticking and peeling modes of operation. Lyndon B. Johnson Space Center, Houston, Texas A tool helps a worker grip and move along a large, smooth structure that offers no handgrips or footholds. The tool adheres to a surface but can be easily released from it by actuating a simple mechanism. The original version of the tool was conceived for use as a movable anchor on the outer surface of a spacecraft. Modified versions could be useful in such diverse operations as inspecting hulls of ships and scaling walls in rescue operations. The tool includes a handle and a seg- mented contact-adhesive pad (see fig- ure). The bulk of the pad is made of soft plastic foam that conforms to the sur- face of the structure. Each segment of the pad is reinforced with a rib. In the sticking mode, side catches engage the ends of the ribs, constrain- ing all the ribs to lie in the same plane. Thus, the ribs stiffen the pad and dis- tribute the load throughout the pad, which sticks firmly to the surface. When the user compresses an expansion spring, the side catches release the ribs. This relaxes the pad, so that the load is concentrated in the two outermost sticking segments. With the adhesive force thus weakened, the pad can easily be peeled away from the surface. The user sticks several such tools on Side catch End 01 Rib STICKING MODE PEEUNGMODE the surface and proceeds to move across the surface, hand over hand, by grasping the handles of the tools. By releasing tools and reapplying them, the user can traverse the surface indefinite- ly. The user can also string a tether between tools and move along the tether. This work was done by Leslie Hartz of Johnson Space Center. For further Handle Side catch In the Sticking Mode, ribs are braced by side catches. In the peeling mode, side catches are retracted, and the segmented adhesive pad loses its stiffness. information, write in 72 the TSP Request Card. This invention is owned by NASA, and a patent application has been filed. Inquiries concerning nonexclusive or ex- clusive license for its commercial devel- opment should be addressed to the Patent Counsel, Johnson Space Center [see page 20]. Refer to MSC-21955. Computing Response of a Structure to Random Transient Pressures A deterministic method yields more accurate prediction. John F. Kennedy Space Center, Florida An improved method of computing the vibrational response of a structure to transient random acoustic excitation at predominantly low frequencies has been devised. The method is called "deterministic" (1) to distinguish it from an older probabilistic method in which the acoustic excitation is approximated as stationary with spatial correlation of a theoretical white noise and (2) because it is based partly on the use, in 64 the equations of motion of the struc- ture, of deterministic excitations derived from measured pressure histories. The development of the deterministic method was motivated by the need to analyze more accurately the vibro/acoustic responses of structures at spacecraft-launching facilities and thereby determine whether there is need for reinforcement or redesign to withstand the launch environment. The deterministic method can also be used to study such phenomena as earth- quake motions, ocean waves, aircraft pressure gusts, responses of bridges to winds, and the effects of jet-engine noise on aircraft structures. The probabilistic method has been found to be overconservative from one perspective in that the use of a steady- state input excitation to approximate a transient excitation leads to prediction NASA Tech Briefs, December 1994 Photograph and FEA model provided counesy of Today's Kids. Dallas and ORO Corporal ion. Tulsa. WITH ANSYSfD FEA, IT'S EASY TO SOLVE EVEN THE HARDEST PROBLEMS. Complex design analysis will never be confused with childs' play. But with ANSYS FEA, it's easier ... faster. .. and more interactive than ever before. Not to mention more fun. New users navigate smoothly through ANSYS X-Windows Motif-based GUI, making the program's powerful capabilities easier to learn and apply. Experienced users simply work more efficiently. Underneath the inter- face is the same comprehensive code that makes ANSYS the industry's leading FEA program, with over 37,000 seats worldwide. Just ask Today's Kids which software worked best to optimize their play slide design. They 'll tell you there was no ques- tion. It's ANSYS. Call today for more details: 1-800-WE-R-FEA-l (1-800-937-3321). AN fD ANSYS, Inc. 20 1 Johnson Road Houston, PA 15342-1300 ANSYS FEA model c.,'onslrucledfrom a Pro/ENGINEER- assembly accurotl!ly showed thol/arge. nonlinear d~jNt!cJ lions tripled the maximum strrsses in Ihe slide handrail. 01994 ANSYS. Inc. ANSYS is. n:&is1ered ,"m.rt or SAS IP. ProIENGINEER i •• rellslered trademark of hnmelric TechnololY Corponllon. For More Information Write In No. 507 ,.0 g ~ ... r J ~ • • 7 If : il : 02 0., SlMPUAED terTb~ MODEL USED IN PROBABtUSTlC IIETHOD •• i 525. NM~a f N.I~Nt 18.6 1l zu. 50 ' 00 _ .Hz '50 CURVES D£RfVED FROM MEASUREMENTS OF LAUHCH-IHOUCED ACOUSTlC AELD USED IN DETEAIIIHISTIC IIE1liOO (ItORIZONTAI. OIRECT1OHJ g~ ... II ~ jf 0.' i l~ 02 EadI cw.. .. Di*o D ... -- 0.' .. 200 250 Some of the Complexity of the Transient Acoustic Field can be seen in the graph at the right, which is derived from measurements. 66 RAPID PROTOTYPING • REVERSE ENGINEERING • WrflI SAC's NEW GP-12 3-D DIGITIZER The most versatile, easy-to-use 3-D digitizer available. Capture 3-D data in real time from any solid object within an active volume of up to 8 ft. x 8 ft. x 8 ft. (512 cubic feet). It's easy to use, just unpack - plug it in - and type "install". Place the probe on the point(s) to be entered and you're capturing X, Y, Z Cartesian coordinates. SOFTWARE-HAROWARE COMPATIBILITY. The GP-12 works with all pop- ular CAD/CAM packages and PC platforms, and comes equipped with its own TSR (Terminate and Stay Resident) driver. Special packages are available for modeling/animation with HyperSpace TM software from Mira Imaging and CAM programs from Cutting Edge™. These pack- ages provide complete turnkey solutions to increase your productivity. THE MOST FLEXIBLE 3-0 DIGITIZER AVAILABLE • It's portable, works in any environment, digitizes any material, and has easy RS-232 interface. Ideal for reverse engineering ... acquiring 3-D data from prototypes ... defining tool paths ... generating data for 3-D graphics, plus applica- tions only limited by your imagination. SEE HOW THE GP-12 CAN PUT YOU INTO THE WORLD OF 3-0. CALL TODAY. _ SCIENCE ACCESSORIES CORPORATION 2 Research Drive, P.O. Box 825 phe~on I CT 06484 (203) 925-1661 Fax (203) 929-9636 For More Infonnation Write In No. 418 of unrealistically large vibrational stress and displacement responses and thus to overdesign and/or prediction of failures that do not occur. The probabilistic method is also potentially underconserv- ative from another perspective in that it yields only root-mean-square values of response, whereas the peak values needed for design are based on assumed (unverified) distributions. The deterministic method focuses on peak values. The deterministic method involves the concept of a response spectrum, in which the total response of the structure is the sum of responses in individual structural-vibration modes that are not coupled with each other. Therefore, the response in a given mode can be found by integrating the differential equation for that mode in the time domain. If the history of a generalized modal load is known, then such integration in time is possible, and it does not matter that the generalized modal load is a random transient. In the integration process, the input excitation is treated as a deter- ministic pressure history, but the defini- tion of a corresponding generalized modal load contains elements of a ran- dom-response analysis and is uniquely related to the power spectral density of the generalized modal load. A simple power spectral density alone is not sufficient to describe the acoustic field. To cope with the spatial and tem- poral complexity of the launch transient acoustic field, the deterministic method includes additional related spectral mea- sures: the normalized cross power spec- tral density (see figure). the correlated- pressure distribution (which provides a graphic illustration of vibro/acoustic coupling), and the pressure-correlation length. Both the deterministic and the proba- bilistic method provide solutions in matrix form, suitable for use in finite-ele- ment-method structural analyses. Within the low-frequency range (0 to 20 Hz) of resonances of launch-pad structures, the deterministic method is simpler and more accurate than the probabilistic method is . One disadvantage of the deterministic method is that the cor- rect prediction of peak generalized modal loads depends on correct placement of correlated pressure distrib- utions on structures to ensure that the predicted responses are, indeed, absolute maxima. This work was done by Valentin Sepcenko and Ravi Margasahayam of I-NET, Inc., for Kennedy Space Center. For further information, write in 36 on the TSP Request Card. KSC-11649 NASA Tech Briefs, December 1994 M A Could this be the end of 7th row center? 7b locate the best seat in the Muse, two heads are better than one. For Dick Campbell, world-class acoustics engineer, electrical engi-neering professor and ardent con- cert-goer with an "excellent ear" for music, where he sits in a concert hall can be as important as the program he sits through. "Not seventh row center. It's too close to the source. If you care more about watch- ing the musicians than hearing the music, it's fine. But the best seats start a quarter of the way back from the stage." And that's not just Dick's personal taste. It's a fact based on the unimpeachable impartiality of observations made by Fred (he's the one on the left, Dick's the one with a tie). Dick, a member of the Concert Hall Research Group, employs dummies like Fred to map the acoustics of concert halls around the world, including Symphony Hall in Boston and Washington's Kennedy Center. First, the dummy occupies various seats throughout the hall, each time listening MATHSoFT ON THE INTERNET Now you can reach us on the Internet. Simply connect to lip. moth.olt.com for anonymous FTP access to the /pub directory. If you're on the Web, try us at www.maffuoI.f.com. You'll find tips and techniques, applications from other Mathcad users, files for educators and students, and a lot more to help you get the most from using Mathcad. T H c A D to test sounds digitally recorded through microphones installed in its head. Then, the data is read into Mathcade PLUS 5.0 for interaural cross correlation analysis using the Signal Processing Function Pack. This involves octave filtering of the left and right impulse reponses and pick- ing out the maximum cross correlation of the octave· filtered pairs. It's a mildly contro- versial technique used for mathematical modeling of something otherwise ordained by still-quibbling critics, specifically, what makes a concert hall sound good. --- ". ........... ohdlO ...................... -.t!8 '10 _ (t)S. ............... JIPf._ .......... .;. ........... I ..... . " ........... "'''- .... .., .............. m_ t(a) ' •• - .... .... -<-en ... 0 .... ' . ~W..~!W=~~ _ .. ., :. 1.. LlDo(., :. L. ..... tIIdI .. ,..tD_ ........... .c:r- .... ~ .. . ................... 110 .... "' ... ____ ,., IDN~"D*D ......... ....;. I. • ...--. .............. 'Xtu 111",1 :5 D . . . Ilowl,", 0027Q,. ~ ... 005saQ72 ~Jn.v .. _ •• ~ .. 8 .. «m D(b) ·.,-+ ... (7).2"..,,2 .. ..,) But the importance of this work is not de- bated among his students. They study Dick's documents directly in Mathcad, revealing princi· pIes of acoustics in a way Dick calls "very much alive. They can manipulate the equa- tions and graphs right there in front of them. They can visualize what's going on, not just do math all day long. It lets them look at a problem like it's under a magnifying glass." Mathcad also lets Dick explore in a way that "might not be attempted otherwise." Like using a 20-term series expansion to find the first seven combined resonance frequencies for a coupled driver and standing wave tube. "You wouldn't even try this with a calculator. And the human factor of Mathcad makes it much faster than programming." Which leaves but one prObing question unan- swered. Are there any bargain seats in the great halls of the world? "No, not really. But don't ever sit under the balcony. That's the worst." Dick Campbell, EE, Professor, Worcester Polytechnic Institute, Worcester, MA. MaU\SoIl, In<. PO Box 1018. Cambridge. MA 02142-1519 USA · PIlon.: 1-800-823-4223 · Fax: 617·577-8829 . MathSoIl Europe. P.O. Box 58. LiviniSton, UK EH54 7M. · Phone: +44.506.460373 . Fax: +44.506.460374 C 1994 MathSon.. Inc. til and • signity manufacturer', trademark or registered trademark respectively. M A T H What makes calculating just like home remodeling? For Denzil Hellesen, it's lheJact that neilher one rrver seems to end. W hen mechanical engineer Denzil Hellesen takes on a project, you can bet it's going to be big. Big, like the design of a 10,000 PSI autoclave, up to 18 feet in diameter. Big, like the single Mathcad file (near- lya pound when printed) used to solve and document every calculation in the autoclave's spec. Or if you want to talk really big, let's talk about Denzil remodeling his home. By day, Denzil is a fierce and fearless number cruncher, building colossal programs in Mathcad, uniting hundreds of related calculations into single, seamless documents. "Typically, they run 75 to 100 pages," says Denzil, including all the live math, graphs and documentation. Already, he boasts 50 megabytes of such Mathcad documents, all devoted to calculations he used to do by hand. Like the standard flange design that required 1500 steps on a calculator and consumed half a day (not counting mistakes). The same calculation set takes five minutes in Mathcad (and there are no mistakes). Denzil will tell you it's not the math that's extra- ordinary ("mostly algebra and low level calculus"), but the way Mathcad lets him "go ahead and quickly produce results that people will understand. They stumble through calculations done with a computer language. But with Mathcad, they can actually see the math as you would write it." And that's just by day. At night, Mathcad fires up again, this time in aid of Denzil's continuing adventure remodeling his home. "It's a never-ending process. I've done kitchen cabinets, bathrooms, you name it. Mathcad calculates how much material is required for each project." At which point he jokingly concedes that among the 50 megabytes of Mathcad programs he's written, "okay, a meg or two are for remodeling." Denzil Hellesen, VP, ENMECO, Lebanon, MO c We want to continue responding to your need for the kind of spontaneous, interactive calculating power that's helping today's most productive engineers and scientists do their jobs better. Let us know how we can help you. o Send complete Mathcad product information, including Electronic Books and Function Packs o Send a free copy of The MathSojt Scratchpad, the quarterly Mathcad users' newsletter o I want to have my Mathcad experience featured in an upcoming The Way Math is Done Call today, or fax us at 617-577-8829, or e-mail us at salesinfo@mathsoft.com Name Tille Company Address Phone 12345678 State Zip e-mail 1·800·MATHCAD Available al Egghead and other software dealers. A D About Mathea" .1101'11 lerhlllcaJ professwnaJ.s me IfWhcad far caic'IIlatit)/ls than allY other sojt/l'are. And it's no lronder. Jfathcad helps them work faster. solve more problems, explore more possibilities. Jnth .IfaJhcad's relWU'lleil lire Document Interface, you do mallithe same u'ay yOll Ifamed it - on a scra/chprui Type equatwns ill reaimath lIolalion righl. on the screen Change L'(Jriables and instantly IIPdai.e ansuers. Numerk Cakulatioll Functiollll • Operators and builtJlNlfunclioD~llor /lumbers, vectors and matrices • ["IiL5 of mearurelllerll and dimenSIOn chRciNng • Si m ulta neous equation soh-er • Derivatil'es and integrals • Summa/wlls, products • Trigonometric, hyperbolic, exponential and Bessell U lIetions • Sta/u;ticalfunctwlls • CUrI'efilling • Fast Fourier and wavelet tranifonlls SgmboUc CalcuItUioIl FunctJolIII • "Lille" symbolic solutions • Symbolic in/egratwn and differentiatwn • Expand to series • Inverse, traNLIspo.~eI detennillant of a matrir • l,apIOl:e, z, Fourier Integral tranifrmlW'inverSfS Grap/Ik:.B FetJIun!s • X-Y. polar, contour; parametric suiface plots • Logarithmic and linpar ares • Annotate graphs l!l Dflfm!lItial Equatioll SoWers • 4th-Order Runge-KUlla me/lwd • 5th-Order Runge-Kut/a and adaptive step-size methods • BuUrsch-8toer methods lor stiff syslRms • Linear Shooting and relara/wn rnethodsfor bollndory value probll'rlls Admnced Matrix Functio/IB • .Ifatri.J: decampositio71 • Linear system soh'PT • Tootsfor row reduetwn, computing rank and finding matri.t nonns and condition numbers • EigPTIl'ai.weigPnl'ector capabilities Document PrepGmtio" Features • Wy'5'IWYG presentation.qualily output The Way Math is Done:" "Mighty Worm" Piezoelectric Actuator The piezoelectric element would be removed from the load path when not in use. NASA's Jet Propulsion Laboratory, Pasadena, California The figure illustrates schematically a piezoelectric actuator that was under construction when the information was submitted for this article. This actuator is designed to operate in three modes: 1. as an adjustable static structural member, the length of which can be changed slowly in a sequence of wormlike increments of motion; 2. as an active vibrator or vibration sup- pressor when operated in conjunction with a vibration sensor and a feed - back control system; or 3. as a simple inactive structural element. The "Mighty Worm" Piezoelectric Actuator can be used as an adjustable-length structural member, an active vibrator or vibration sup- pressor, and acts as a simple (fixed-length) structural member when inactive. The load force is not applied to the piezoelectric ele- ment in the simple-structural-member mode. The device is called a "mighty worm" actuator because in mode 3 it can with- stand a greater axial load force than can older piezoelectric devices called "inch- worm" actuators. This actuator includes two subassem- blies that move relative to each other. One subassembly includes a housing and clamps. The other subassembly includes the piezoelectric element (a stack of piezoelectric disks), clamping surfaces at the ends of the piezoelectric element, and a load (the lengthwise position of which is to be adjusted). Each clamp comprises a pair of cam- actuated spring-and-Iever mechanisms, and the cams can be driven by a rotary actuator to apply or release clamping force as commanded. The sequence of functions in the length-adjustment mode (mode 1) to move the load to the right is the follow- ing: 1. Clamp A, unclamp B, then energize the piezoelectric element. 2. Clamp B, unclamp A, then deenergize the piezoelectric element. 3. Repeat steps 1 and 2, as necesary, until the load has moved to the desired position. NASA Tech Briefs, December 1994 The sequence to move the load to the left is similar except that A and Bare interchanged . In the vibration-control mode (mode 2), A is clamped, B is unclamped, and the piezoelectric element is energized by the feedback control system. In the simple- structural-member mode (mode 3). A is unciamped , B is clamped , and the piezoelectric element is deenergized: the actuator can withstand a relatively high axial force in this mode because the piezoelectric element is removed from the load path. This work was done by Robert M. Bamford, Ben K. Wada, and Donald M. Moore of Caltech for NASA's Jet Propulsion Laboratory. For further information, write in 15 on the TSP Request Card. NPO-19046 Flowcharts Any Way You Want! Introducing Flow Charting"'4 for Windows! We've re-worked the basics to make flowcharting easier and more flexible than ever. We call it sensible technology. The end result is a flowcharting program that is incredibly powerful, yet remarkably quick to learn and use. And it's packed with everything f10wcharters want. Here's a sampling: SensibleLines'" are totally editable. You've never experienced anything like it. Experiment with the look of your charts! Get your point across thanks to distortion-free shape sizing with SensibleShapes"'. SensibleText'" - Word processing masterfully designed for flowcharts - it works the way you expect! • Job-specific shape templates let you create the perfect chart for the task at hand. Snapshor" your preferences. Your charts look great every time. And Flow Charting 4 is backed with a 90-day no-risk guarantee. Our legendary post-buy support includes free unlimited technical support, free subscription to The Flow Charter'" and access to valuable flowcharting re ources. For flowcharts exactly the way you want, you need Flow Charting 4 for Windows! See your local dealer today, or for a free interactive demo, call now: (800) 525-0082 ext. 284 International: (408) 778-6557 PATIDN&PATIDN •••• Pallon & Pallon Software Corporation 485 Cochrane Circle, Morgan Hill , CA 95037 All company and product names are trademarks or registered trademarks of their respective o .... 'ners. For More Infonnatlon Write In No. 419 Turbine-Driven Pipe-Cleaning Brush The flow of cleaning solution turns the turbine. John F. Kennedy Space Center; Florida A simple pipe-cleaning device includes a small turbine wheel axially connected, by a standoff, to a circular brush (see figure). The turbine wheel tums on a hub bearing attached to the end of an upstream cable. The turbine- and-brush assembly is inserted in a pipe with the cable trailing upstream and the brush facing downstream. The water or cleaning solution is then pumped through the pipe. The cable is held at its upstream end, so that it holds the turbine and brush in the pipe at the location to be cleaned. The flow in the pipe turns the turbine, which tums the wheel, producing the desired cleaning action. In addition to brushing action, the device provides even mixing of cleaning solution in the pipe. Of course, the turbine and brush must be sized to fit the inner diameter of the pipe to be cleaned, and the wire must be sufficiently long to enable the turbine-and -brush assembly to reach and traverse the part to be cleaned. The turbine-and-brush assem- bly can traverse long pipes and it can 70 travel around 90° bends and through pipe fittings. This work was done by Rudy J Werfink and David E Rowell of Kennedy Space Center. For further information, write in 270 on the TSP Request Card. This invention is owned by NASA, For More Infonnation Write In No. 420 The Turbine Wheel Turns in the flow in the pipe, rotati ng the wire brush to clean the inside of the pipe. The cable holds the turbine- and-brush assembly against the flow. and a patent application has been filed. Inquiries concerning nonexclusive or exclusive license for its commercial development should be addressed to the Patent Counsel, Kennedy Space Center [see page 20]. Refer to KSC- 11669. NASA Tech Briefs, December 1994 Geared Electromechanical Rotary Joint Springy planetary gears provide low-noise electrical contact. Goddard Space Flight Center; Greenbelt, Maryland The figure illustrates a geared rotary joint that provides low-noise ac or dc electrical contact between electrical subsys- tems that rotate relative to each other. This joint is designed to overcome some of the disadvantages of older electromechani- cal interfaces - especially the intermittency (and, consequently, the electrical noise) of sliding-contact and rolling-contact electromechanical joints. The first electrical subsystem is mounted on, or at least rotates with, the shaft and the two inner gears attached to the shaft. The inner gears are separated axially by an electrically insulating disk. Each inner gear constitutes one of two electrical terminals through which electrical power is fed to or from the first electrical subsystem. Outer (Ring) Gears Hollow, Springy Planetary Gears provide continuous, redundant, low-noise electrical contact between the inner and outer gears. NASA Tech Briefs, December 1994 The second electrical subsystem is mounted on, or at least rotates with, the outer (ring) gears. Similarly to the inner gears, the ring gears are separated axially by an electrically insulating annular disk, and they constitute the electrical terminals through which power is fed from or to the second electrical subsystem. Electrical contact between the inner and outer (ring) gears is provided by multiple, equally spaced, flexible planetary gears formed as hollow cylinders with thin, fluted walls. These gears mesh with the inner and outer (ring) gears. These gears are slightly oversize with respect to the gaps between the inner and outer gears, but their flexibility makes it possible to compress them slightly to install them in the gaps. After installation, mesh- ing of the gears maintains the even angular interval between the planetary gears at all rotational speeds. The planetary gears are made of beryllium copper, which is preferred for electrical contacts because it is a self-cleaning material that exhibits excellent current-carrying characteristics. A typical flexible planetary gear has 13 teeth, an axial length and an average diameter both "0.25 in. (6.35 mm), and a wall thick- ness of 0.004 in. (0.10 mm). Because each planetary gear is independently sprung into a cylinder-in-socket configuration with respect to the inner and outer gears, it maintains continu- ous electrical contact between them. The reliability and continu- ity of the electrical contact is further ensured by the redundancy of the multiple planetary gears. The multiplicity of the contacts also ensures low electrical resistance and large current -carrying capacity. • 61dBSNR • 30 MSPS on 2 ch. • Very Deep Buffers • Up to 32 ch. Systems Drivers in C. Pascal. BASIC. Windows DLL. LabVIEW. CompuScope 6012 LabWindows, DasyLab, HyperSignal .. . World's Fastest 12 Bit AID Card CSLlTE 8 bit 140 MSPS 1 16K $595 CS220 8 bit 1 40 MSPS 1256K $1,995 CS250 8 bit 1 100 MSPS 132K $3,500 CS1012 12 bit 120 MSPS 1512K $4,995 CS6012 12 bit/ 60 MSPS 151 2K $6,995 CALL 1-800-567-GAGE Gage Applied Sciences Inc. 5465 Vanden Abeele, Montreal, Quebec, Canada H45 151 GaGa From outside North America, call + 1-514-337-6893 Fax : (514) 337·8411 , BBS : (514) 3374317 For More Information Write In No. 421 71 SL-G S • ... for unprecedented performance Build precision, animated screens for visual display and interactive control of real-time applications. Since 1984 SL has offered rrue object- oriented graphics development tools and software components -the most advanced rW==Wil;;;gJ;;;;;;;;;J~D;;;;.J~WWiy available-to help build state-of-the-art, high performance dynamic graphical applica~ons. !her._ dramatically simplify the work needed to create interface screens of any complexity and animate them with your data. • Cape Canaveral CORE Program for control room • Facilities monitoring schematic Supported Platforms Nearly all varieties of UNIX (X Windows) on SUN, SGI, ill, IBM, MIPS, DEC (VAX/Alpha, Open VMS/OSF-I), Intel; Wmdows NT; OS/2; Chicago. For SGI, SL also generates display pipe-line code to reach real-time native speeds. Call: 415/927-1724 L S h errill-Lubinski SL Corporation Suite 110 Hunt Plaza 240 Tarnal Vista Boulevard Corte Madera ,CA 94925 C 1994 Sherrill·Lubinski Corporation For More Infonnation Write In No. 422 The springiness of the planetary gears automatically compensates for thermal expansion, thermal contraction, and wear; moreover, wear is expected to be minimal. Finally, the springiness of the planetary gears provides an anti backlash capability in a gear system that is sim- pler and more compact in comparison with conventional antibacklash gear sys- tems. This work was done by John M. Vranish of Goddard Space Flight Center. For further information, write in 31 on the TSP Request Card . This invention is owned by NASA, and a patent application has been filed. Inquiries concerning nonexclusive or exclusive license for its commercial development should be addressed to the Patent Counsel, Goddard Space Flight Center [see page 20). Refer to GSC-13540. Simulation of Probabilistic Wind Loads on a Building Results can be used to analyze tendencies toward sway, buckling, and/or overturning, Lewis Research Center, Cleveland, Ohio A method of simulating of probabilistic windloads on a building has been devel- oped. The numerical results of such a simulation can be used to assess the reliability of the building and the risk associated with tendencies of large gusts or high steady winds to cause the building to sway, buckle, and/or over- turn. USing of this method to analyze a proposed design in an iterative design cycle, a building can be designed for a specified reliability. Wind pressure or suction on an up- stream, downstream, or sidestream face of the building is approximated in this method by a mathematical model of the form P w = kS2, where k is a coefficient that depends on the direction of the wind with respect to the face and S is the speed of the wind. A semiempirical mathematical model , called the "multi- factor interactive equation" (MFIE), is used to compute S from constituent primitive variables that include atmos- pheric pressure (P) , temperature (T), and roughness height of terrain (R). The effect of gusts is included implicitly in the MFIE, which is S (Po P)8 (T. T)b s;;= ~~ P ;I~ T ( )c ~ )d( )e Rf - R f - W tf - t Rf - Ro f - W f tf - to where (j) is the frequency content of the gust, t is the time since the beginning of the gust, the subscript 0 denotes refer- ence conditions, the subscript f denotes the final condition of the variable to which it is appended, and the exponents a through e can either be determined through regression analysis of meas- ured values or estimated by expert opinion. The variables in the MFIE can be random with any distribution, but in this method, all are assumed to have normal distributions. The method was applied initially to the rectangular building shown at the top of the figure. In this application, the MFIE was incorporated into the CompOSite Load Spectra (CLS) computer program, which simulates probabilistic loads, f" LWard Q. WL Faces FOJ / , / , c~~ / ,r------ Right Y Windward 12ft ~~W~ BUILDING r l.oofJ J~_JJD - 400 CUMuunVE DlSTRIBUTlON FUNCTION OF WIND PRESSURE ON BUILDtNG SURFACES 0.00 -1 0 _"'In. CUMULAT1VE DlSTRIBUTlON FUNCTION OF SWAY AT TOP OF BUILDING Probabilistic Windloads on the rectangular building shown at the left were computed. Some of the numerical results are plotted. NASA Tech Briefs, December 1994 given the primitive variables, their statistical distributions, and the discrete probability intervals (histogram bins) required to discretize the input probability density functions. Then by use of Numerical Evaluation of Stochastic Structure Under Stress (NESSUS), which is a stochastic finite-element computer code, the simulated probabilistic wind loads were applied to the building to obtain cumulative distribution functions of sway displacements and reliability against overturning. Uncertainties in wind loads and stochastic deviations of dimensions and properties of components of the building from nominal values were incorporated into NESSUS. Sensitivities of responses to changes in structural parameters were also computed. In the particular case, the sway was found to be sensitive to the wind pressure, height of the building, and properties of the building materials. This work was done by Christos C. Chamis of Lewis Research Center and Ashwin R. Shah of Sverdrup Technology, Inc. For further information, write in 73 on the TSP Request Card. LEW-15685 Using a Digital X-Y Plotter as a Calibration Fixture Repetitive measurements that involve precise positioning can be automated fairly easily. Langley Research Center, Hampton, Virginia A digital x-y plotter can be used as a programmable calibra- tion fixture to make two-dimensional maps of the flux densities of small magnets. It could also be useful in other calibration procedures in which there is need for accurate two-axis posi- tioning of small parts. Accurate two-dimensional positioning of measurement devices is necessary for precise calibration. In the original application for which the use of a digital x-y plotter was con- ceived, there was a need for calibration of the flux densities of more than 100 small cylindrical permanent magnets. Inasmuch as the flux density of such a magnet is axisymmetric, it was necessary to map the flux densities in two dimensions only. However, the large number of magnets made it desirable to automate the measurement procedure. One approach to the solution of the automated-measure- ment problem could have involved mounting two programma- ble linear translation stages together at right angles to form a calibration fixture. This approach would have necessitated con- siderable hardware, long setup time, and extensive program- ming on a desktop computer. The use of a modified digital x-y plotter offered a much simpler solution. The probe of a gaussmeter was mounted at a fixed position to measure the flux density from the magnet under test. The magnet was attached to the pen holder of the plotter in the x-y plane of the plotter. Thus, by use of position commands of the type normally sent to the plotter from a personal computer, it was possible to position the magnet in x and y. A positioning resolution of ±0.001 in. (about ±0.03 mm) was achieved along both axes. This approach was easier, with respect to both implementation in hardware and program- ming the computer, than the other approach would have been. This work was done by Tom D. Finley of Langley Research Center. No further documentation is available. LAR-14666 NASA Tech Briefs, December 1994 For Simultaneous DTA/TGA, Trust The Compmy That Has stool The Test Of Time. For over 75 years. Harrop has been excel- ling' high temperature lab applications. And our innovative, simultaneous DTA/TGA combines two essential thermal analysis techniques into one. When easy-to-use, economical systems are important, consider Harrop. Our newest module for simultaneous DTA/TGA measure- ment offers a hi-resolution balance and integrated data acquisition software. Harrop's dedicated lab technicians and engineers are ready to put their experience to work for you. Harrop Industries, Inc., 3470 E. Fifth Ave., Columbus, OH 43219-1797. Phone: 614/231- 3621. Fax: 614/235-3699. eAooam ~~ _INDUSTAIEB.INC_ Fire OUf Imagination. For More Infonnatlon Write In No. 423 73 Machinery Dual-Actuator Active Vibration-Control System Feedback gains and filter parameters can be adjusted according to schedules. Lewis Research Center; Cleveland, Ohio The dual-actuator active vibration-con- trol (OM VC) system is a developmental system of the type described in the "Active Vibration Dampers for Rotating Machinery" (LEW-1S427). NASA Tech Briefs. Vol. 18. No.10 (October 1994). page 93. This system features sensors and actuators positioned and oriented at bearings to measure and counteract vibrations of a shaft along either of the two axes perpendicular to the axis of rotation. This system has been proven effective in damping vibrations of a heli- copter-engine test stand. thereby making it safer to operate the engine at speeds near and above the first resonance of the engine/test-stand system. In so doing. the DMVC system opens new opportuni- ties for engine designers to draw more power from this engine. and the concept should be applicable to other rotating machines as well. The DAAVC system (see figure) includes a hybrid analog/digital controller. Analog amplifiers and filters are used in the controller because they operate signif- icantly faster than competing digital circuits do. The amplifier gains and filter settings are adjustable; maximum versatil- ity is achieved by providing for download- ing the gains and filter settings from a microprocessor or desktop computer via Hybrid (Analog/Digital) 1-----, Controller t I Computer I Power Amplifier The Dual-Actuator Active Vibration-Control System is one in a continuing series of feed- back control systems that are being developed to suppress vibrations in rotating machinery. a digital-to-analog converter. The system is so capable that it even compensates for realistic misalignments of sensors and actuators. The gain and filter adjustments can be easily scheduled as in response to (that is. as functions o~ dc input signals that rep- resent speed. torque. or other operating parameters. The computer can be made to execute a grid-search algorithm to select feedback gains that minimize a vi- bration norm (a composite measure of absolute values of vibration amplitudes). These gains are then downloaded as active stiffnesses and rates of damping with a linear fit throughout the range of operating speeds. This work was done by Albert F. Kascak and Louis J. Kiraly of Lewis Re- search Center, Gerald T. Montague of Sverdrup Technology, Inc., and Alan B. Palazzolo and Daniel Manchala of Texas A&M University. For further information, write in 8 on the TSP Request Card. LEW-15765 Optimized Resolved-Rate Control of Telerobotic Manipulator In a simulation, this technique caused a robot hand to move as commanded in real time. Langley Research Center; Hampton, Virginia Velocity control is a popular way to control robot arms. The velocity of a robot hand is known. or commanded by an operator. and this velocity is resolved into rates of change of joint angles (resolved-rate control) to move the hand as commanded. Six indepen- dent jOints are all that are needed for general movement of the hand in its workspace. but the Laboratory Telerobotic Manipulator (L TM) has a seventh jOint. providing more choices for pint-angle rates to move the hand. The L TM (see figure) is a seven- degree-of-freedom robot arm built by the Oak Ridge National Laboratory for NASA for evaluation in ground-based 74 research to assess the role of redun- dant-degree-of-freedom arms in outer- space operations. Each arm has three pitch/yaw joints: one at the shoulder. another at the elbow. and a third at the wrist. The seventh degree of freedom is provided by a wrist-roll joint. The movement of the elbow plays an indispensable role in the use of a human hand; for example. in working on a car. Sometimes the position of the elbow must be changed to gain access for the hand or to provide leverage for wrenching . The extra joint in the LTM provides this type of flexibility. Of course. the extra joint complicates the control problem. making it more difficult to generate commands to move the hand in real time; i.e .• there is an increased computational burden. Optimized resolved-rate equations were developed for real-time control of the L TM. along with special resolved- rate equations to handle kinematic sin- gularities. These equations generate a least-squares solution for joint-angle rates. which are used to command the hand to move at a specified velocity. Optionally. the equations also represent a striving to configure the arm to satisfy a specified performance criterion with respect to the joint angles. The equations have been pro- grammed with application to a three- NASA Tech Briefs. December 1994 dimensional-graphics simulation. The graphical model of the L TM is driven by velocity commands from a six-axis hand controller to assess the equations thus developed. An operator deflects a six- axis hand controller to essentially "fly" the robot hand; the operator tells the hand to move in a desired direction by commanding a velocity in that direction. The commanded velocity is resolved into the motions cif the individual joints in the robot arm to move the hand. For the motions simulated thus far, the robot hand moves as commanded, and the special resolved-rate equations for kine- matic singularities appear reasonable. As redundant manipulators come into wider use, computationally efficient algo- rithms for inverse kinematics will become increasingly important. The approach tested on the L TM is practical for a class of manipulators. Because they offer the advantages of more effi- cient use of workspaces and the ability to reach around obstacles, redundant manipulators are expected to be used in mobile robots and teleoperators for haz- ardous environments, automotive assembly, welding, and spray painting. Practical resolved-motion control will be required in the implementation of such manipulators. The Laboratory Telerobotic Manipulator of the Oak Ridge National Laboratory is shown here with counterbalancings. Each arm has three pitch-and-yaw jOints and a wrist-roll joint. This work was done by L. Keith Barker and William S. McKinney, Jr., of Langley Research Center. Further information may be found in NASA TP- 2938 [N90-10618/TBj, "Optimized Resolved Rate Control of Seven-Degree- of-Freedom Laboratory Telerobotic Manipulator (L TM) with Application to 3-D Graphics Simulation. " Copies may be purchased [prepay- ment requiredj from the NASA Center, for AeroSpace Information, User Services Division, Linthicum Heights, Maryland, Telephone No. (301) 621- 0394. Rush orders may be placed for an extra fee by calling the same number. LAR-14261 Wetust solved one of the world's stickiest problems. It's called "stiction," but you won't find it in the dictionary. Stiction is that notorious affliction that causes air cylinders to stick at the start of a stroke - resulting in erratic, runaway motion. Introducing The Anti-Stiction Air Cylinder. The Airpel Air Cylinder effectively does away with stiction. And reduces running friction freely - without lubrication! to imperceptibly low levels. Since it contains no oil, it also runs cleaner This gives it the unique ability to impart than typical air cylinders. Without rubber or plastic super smooth motion. Even at very low pressures, seals to abrade, wear out, or harden with time. with very short strokes, at very slow speeds. And since its exposed surfaces are made of Yet it can also operate under extreme temp- stainless steel and nickel, Airpel is extremely clean eratures and very high speeds with no degradation and corrosion resistant. in performance. For information on models, prices and tech- How do you account for these remarkable nical specifications, write Airpel Division, capabilities? Airpot Corporation, 35 Lois Street, The Airpel is an instrument-quality air Norwalk, CT 06851. cylinder. Its graphite piston fits precisely Or call us at A . I TM inside a Pyrex® glass cylinder liner and slides 1-800-848-7681 I-me ~JJJJJJJJJJJJJJJJJJJJJJJJJJ T~e Anti-Stiction'::r rcylinder. ---1IIj n.tAirpe\ is a trademark of Airpol Corporarion. ® Pyrex is a regislered Irademark of Corning Glass Works. For More Information Write In No. 425 i!!I Fabrication Technology Rugged Preheaters for Vacuum Plasma Spraying Units preheat large parts effectively. Marshall Space Flight Center, Alabama Electric preheater units have been built to ensure that large workpieces to be coated with metals by vacuum plasma spraying are heated uniformly to the req- uisite high temperatures by the time the plasma torch arrives. For small work- pieces, heating by quartz lamps or by the plasma torch itself suffices to ensure the proper temperatures. However , for large workpieces, a more dependable source of heat is needed. Typically, a workpiece to be vacuum- plasma-sprayed should be at a tempera- ture between 800 and 2,000°F (430 and 1,100°C). On a large workpiece , the torch passes any given spot too infre- quently to maintain the needed constant high temperature. As a result, there can be large temperature gradients in the workpiece, and the quality of the coating is adversely affected. Quartz lamps are often used to maintain the proper tem- peratures, but they do not last long in the hot, low-pressure, metal-powder-Iaden environment. The present electric preheater units are similar to (but much larger than) the electrical-resistance ribbon heaters in toasters and in some small portable electric "space" heaters. Each unit includes an 801 20 nickellchromium resistance heater ribbon 1.5 in. (3.81 cm) wiGle by 0.1 in. (0.254 cm) thick, sup- ported and electrically insulated by oeramic spools (see figure). Each heater is designed to use power from a high- current (600-A), low-voltage power sup- ply, the low voltage being advantageous in that it minimizes arcing in the process vacuum. These heater units outgas hardly at all and are relatively unaffected by the buildup of metal powder from the process. Each unit is connected to the power supply by a thick, thermally and electrically insulated wire via vacuum feedthroughs. The ring preheater shown in the figure was used to heat cylindrical stainless- steel barrels 12 in. (about 30.5 cm) in di- ameter in a 40-torr (5.3-kPa) vacuum to a required temperature of 1 ,650°F (about 900°C). For this purpose, it was neces- sary to supply the heater with a current of 350 A at a potential of 53 V. The panel preheater shown in the figure was sup- plied at 180 A. 25 V to heat a valve 76 Nichrome Resistance·Heating Ribbons are wrapped around ceramic insulating spools on rings and on plates. A round workpiece is placed in the middle of the ring preheater. Plate preheaters can be stacked as needed near a workpiece. housing to 815°F (435°C), also in a 40- torr vacuum. Thereafter, the power was decreased to 130 A at 18 V to maintain a temperature of 925°F (496°C) during plasma spraying. Both the ring and the panel preheaters have proved durable. This work was done by William H. Woodford, Timothy N. McKechnie, Lewis D. Sander, Christopher A. Power, Heather L. Sander, and Dalton D. Nguyen of Rockwell International Corp. for Marshall Space Flight Center. For further information, write in 95 on the TSP Request Card. MFS-29983 NASA Tech Briefs, December 1994 Shear-Wave Ultrasonic Inspection With a Dry Couplant Liquid and gel couplants, which can contami- nate workpieces, are not needed. Marshall Space Flight Center, Alabama An automated ultrasonic inspection system includes a dry couplant pad attached to an ultrasonic transducer, so that there is no need for a liquid or gel to couple ultrasonic shear waves between the transducer and the workpiece under test. Heretofore, it has been common practice to use a liquid or gel to transfer acoustic energy efficiently between an ultrasonic transducer and the workpiece. However, a liquid or gel cou- plant must eventually be cleaned off a workpiece and is thus undesirable in a manufacturing environment. The present shear-wave ultrasonic inspection system with dry couplant is designed to be mounted on a robot arm in an automated manufacturing (robotic welding) work cell. Between, during, or after manufacturing operations, the robot can simply scan the ultrasonic transducer along the work- piece. The workpiece can be reworked in place, if necessary; there is no need to remove the workpiece from the work cell for testing and return it for further operations. In principle, the computer program that controls inspection can be overlaid on the computer program that controls the welding operations. The dry couplant pad is made of a compliant encapsulated A Dry Couplant Pad made of a compliant encapsulated epoxy material is attached to an ultrasonic-transducer wedge on the end of a robot arm. The robot arm presses the pad against a workpiece for ultrasonic-shear-wave inspection. NASA Tech Briefs, December 1994 New MINITEC® Modular Construction System for i....-__ • Machine Guards • Factory Furniture • Machine Bases • Automated Material Handling • Work Stations • Partitions & Enclosures Is A complete system including linear bearings, hinges, doors, feet etc. to design custom solutions from stock components. Get your FREE 148 page catalog today! 800 642-6446 FAX: 716 657-6153 In NYS: 716 657-6151 VELMEX NC ' East Bloomfield, N. Y. 14443 For More Information Write In No. 424 For More Information Write In No. 426 77 For More Information Write In No. 439 epoxy material and is attached as a facing to an ultrason ic-transducer wedge (see figure) . The transducer wedge and couplant pad are pressed against the workpiece; the surface of the compl iant pad conforms to the surface of the workpiece, ensuring transfer of acoustic energy with an effi- ciency lower than that of a liquid or 'gel couplant but nevertheless sufficient for the purpose. The contact surface of the pad can be made flat or curved to conform closely to the surface of the workpiece. The robot arm scans the transducer along the workpiece by alternately translating the transducer in small increments of position, then firmly seating the transducer and couplant pad on the workpiece at each position to apply approximately uniform contact pressure at the interface between the couplant pad and the workpiece. In an experiment, a couplant pad was tested for 10,000 inspection cycles without a detectable change in its char- acteristics . For a 0.375-in. (9.5-mm) transducer with 0 .125-in. (3 .2-mm) overlap, this corresponds to a minimum life expectancy of 2,500 in. (63.5 m) of distance along a weld seam or other linear workpiece feature. This work was done by James D. Wi/lenberg and Lisa Van Wyk of Rockwell International Corp. for Mar- shall Space Flight Center. For further information, write in 61 on the TSP Request Card. Inquiries concerning rights for the commercial use of this invention should be addressed to the Patent Counsel, Marshall Space Flight Center [see page 20]. Refer to MFS-29953. Making Ceramic Reference Specimens Containing Seeded Voids Small spheres are incorporated, then vaporized to produce the voids. Lewis Research Center, Cleveland, Ohio Internal and surface voids of known sizes can be incorporated into silicon carbide and silicon nitride ceramic reference specimens at prescribed locations. These specimens are used to demonstrate sensitivity and resolu- tion in nondestructive examination techniques like scanning laser acoustic microscopy (see Figure 1) and x-radi- ography, and to assist in establishing proper examination procedures. The raw material for the ceramic in a given case is silicon nitride or silicon carbide powder of appropriate purity Dynamic Ripple Gold Reflective Film Water (as Couplant) Incident Sound and particle size, prepared in a manner appropriate for dry pressing and with sintering aids and binder representative of the silicon carbide or silicon nitride ceramic object to be inspected by the applicable nondestructive tech- nique. Spheres of a solid material that vaporizes at a temperature lower than the sintering temperature of the ceram- ic are used to seed the voids in the ceramic; the material recommend- ed for this purpose is styrene divinyl benzene. The first step in fabricating a speci- Scanning Laser Translation Stage Piezoelectric Transducer Figure 1. The Scanning Laser Acoustic Microscope is used to detect voids in the ceramic specimen which, in this case, is a reference specimen seeded with surface voids as described in the text. NASA Tech Briefs, December 1994 men is to pour the ceramic powder into a die . The surface of the powder is leveled at the desired thickness, then the powder is pressed in the die at a pressure of 60 MPa. After pressing, the top surface of the powder is cleaned by a gentle stream of dry air to remove particles that are not flush with the sur- face. If voids embedded in the ceramic are desired, spheres to seed the voids are placed at known locations on the surface of the powder and pushed into ("green") specimen is placed in a thin- wall latex tube, which is then evacuated and sealed. The specimen thus encap- sulated is cold-isopressed at a pressure suitable for the specific material - nominally at 420 MPa. The isopressed specimen is removed from the tube , then heated in a vacuum to a tempera- ture of 550 °C for 45 min to decom- pose the styrene divinyl benzene spheres. Other temperatures and heat- ing times may be necessary for spheres Figure 2. A Seeded Void in the surface of a sintered specimen is shown in this electron micro- graph. Such voids tend to be ellipsoidal rather than spherical, and those in sintered silicon car- bide tend to be shallower than those in sintered silicon nitride. the surface at a pressure of 60 MPa. More powder is added to obtain the desired separation between layers of voids, and the sequence of leveling, pressing, cleaning , and pressing in of spheres is repeated. When the desired layers of spheres to form internal voids have been formed, a final layer of pow- der is added . If surface voids (see Figure 2) are desired, then the final layer is leveled , cleaned, and pressed at 60 MPa; the spheres to seed the voids are added as before ; and the sph- eres are pressed into the surface at 120 MPa . If no surface vo ids are desired, the final surface is pressed immediately at 120 MPa, this higher pressure being necessary to strengthen the compacted powder specimen suffi- ciently to withstand subsequent pro- cessing without breakage. The compacted but still unfired NASA Tech Briefs, December 1994 made of other materials, and a slightly lower temperature can be used if the specimen is to contain surface voids only. Finally, the specimen is sintered to achieve full densification. Silicon nitride should be sintered at a temperature of 2,140 °C for 2 h in a static nitrogen atmosphere at 5 MPa; silicon carbide should be sintered at 2,200 °C for 0.5 h in argon at 0.1 MPa. This work formed the basis for the ASTM Standard Practice C1212-92 entitled "Fabricating Ceramic Reference Specimens Containing Seeded Voids. " This work was done by George Y. Baaklini, Stanley J. Klima, and Don J. Roth of Lewis Research Center ' s Materials Division. For further informa- tion, write in 40 on the TSP Request Card. LEW-15739 Investigate a New Approach to Scientific Data Analysis Use Analysis Advisor™ Analysis Advisor is a free interactive analysis software tutorial that includes demonstrations of graphical and traditional programming methodologies for analysis. Using this interactive tutorial, you can investigate: • ai~tal signal processing • ai~tal filtering • Windowing • CUrve fitting • Signal averaging • Simulation • Interpolation • Descriptive statistics • Speed benchmarks Analysis Advisor requires Windows 3.1 and 8 MB of memay. Call for FREE Ana~sis Advisor Software (800) 433·3488 IU.S. and Canada) NATIONAL INSTRUMENTS· 6504 Bridge Point Parkway Austin, TX 78730-5039 Tel: 1512) 794{) 1 00 9518(0) 0100793 IMexico) fox: 1512)794·8411 IRANCH OFFICES AUSTIAUA 03 879 9422 • AUmJA 0662 435986 IElGIUM 02 75700 20 ' CANADA 5196229310 DENMARX 45 76 26 00 • FINlAND 90 527 2321 FRANCE 1 48 65 33 70 • GfIlMANY 089 7 14 50 93 ITAlY 02 48301892 ' JAPAN 03 37881921 NETHERlANDS 01720 45761 • NORWAY 03846866 SPAIN 91 6400085 • SwtDEN 087304970 SWITZERlAND 056 27 00 20 • U.I(, 0635 523545 CCgWpfD!iif99P~N""""""D~ .....,.,.j For More Infonnatlon Write In No. 441 Mathematics and Information Sciences Using Finite-Element Analysis in Estimating Reliability Probabilistic estimation and stress-analysis techniques are combined. Lewis Research Center, Cleveland, Ohio FINITE-ELEMENT MODEL For a designated probability of survival. the life of an elemental volume is given by c 11. L _, _ ('rREF) (VREF) n - '"REF tn -v,;- The life of the entire disk is given by ROTATING DISK Where Lis life t is stress Subscripts: V is stressed volume c Is stress·llfe exponent REF Is reference or gage life, stress or volume s is system life e Is Weibull slope (modulus) n is rf' life, stress or volume Figure 1. A Finite-Element Model is used in analyzing the reliability of a rotating disk that contains bolt holes. A method of estimating the design survivability of a structural component incorporates finite-element and proba- bilistic properties of materials. This method involves evaluation of design parameters through direct comparisons of the survivability of the component expressed in terms of percentages of like components that survive at various lifetimes. The probabilistic properties of materials, given in terms of Wei bull parameters, are coupled with the stress field computed by finite-element analy- sis to determine fatigue life based on initiation of cracks. A unique advantage of this approach is that fatigue testing of a coupon of material is the only mechanical testing needed to establish the fatigue parame- ters necessary for analysis of the life and survivability of a full-size compo- nent made of that material. Thus, the method can be used in the early stages of a design process to optimize life- based designs, thereby reducing the amount of testing of full-sized compo- nents needed to validate the designs. The method has been applied to a 80 rotating disk that contains bolt holes, representative of disks used in aero- space propulsion turbines . Figure 1 shows the disk and a finite-element model of a sector of the disk (the mod- els of the remaining sectors are identical by symmetry). The model was used in parametric computational studies of (1) the effect of the speed of rotation on the survivability of the disk and (2) the probabilistic effects of the properties of the disk material on the survivability of the disk. Figure 2 shows shear-stress and probability-of-survival contours in the vicinity of a bolt hole. One of the advantages of the method is that it takes account of the influence of the total state of stress in a compo- nent in calculations of the survivability of the component. Another advantage lies in identification of regions within the component that are critical, with respect to survivability, for purposes of optimiza- tion . Reliability can be enhanced in regions that would otherwise exhibit low survivability, whereas weight can be reduced in regions that would otherwise exhibit high survivability. This work was done by Erwin V. Zaretsky of Lewis Research Center and Richard August of Sverdrup Technology, Inc. Further information may be found in NASA TM-104400 [N91-23550ITB}, "Incorporating Finite Element Analysis Into Component Life and Reliability" and NASA TM-106022, [N93-23406ITB}, "Fatigue Criterion to System Design, Life and Reliability -....: A Primer." Copies may be purchased [prepay- ment required} from the NASA Center for AeroSpace Information, User Services Division, Linthicum Heights, Maryland, Telephone No. (301) 621- 0394. Rush orders may be placed for an extra fee by calling the same num- ber. LEW-15864 Shear Stress, MNlm2 138 152 SHEAR-STRESS CONTOURS Probability of Survival. Percent 99.9 PROBABILITY OF SURVIVAL Figure 2. These Contours Were Obtained With Finite-Element Analysis of detail A in Figure 1. The computation was per- formed with LREF = 10,000 cycles and a speed of rotation of 12,800 r/min. The survivability of the disk is computed as the product of survivabilities of all the finite elements. NASA Tech Briefs, December 1994 Stereoscopic, Force-Feedback Trainer for Telerobot Operators Operators can be trained on a simulator to prevent damage to real robots. NASA's Jet Propulsion Laboratory, Pasadena, California A computer-controlled simulator for training technicians to operate remote robots provides both visual and kines- thetic virtual reality . The simulator is used during the initial stage of training as a realistic substitute for a telerobot; it saves time and expense, increa- ses operational safety, and prevents damage to robots by inexperienced operators. The training simulator computes the virtual contact forces and torques of a compliant robot in real time, providing the operator with the feel of the forces experienced by the manipulator as well as a view of it in any of three modes: a single view, two split views, or a stereoscopic view. From a keyboard, the user can specify the force-reflection gain and the stiffness (compliance) of the manipulator hand for three trans- lational and three rotational axes. The system offers two simulated tele- robotic tasks. One of them is insertion of a peg in a hole in three dimensions. (See figure.) As the operator performs the insertion task, the simulator continu- ously shows an image of both peg and hole and feeds back manipulator contact forces through a force-reflect- MANIPULATOR WITH PEG APPROACHING HOLE IN WALL MANIPULATOR INSERTING PEG IN HOLE The Video Display of a Simulation shows a robotic manipulator inserting a peg in a hole. NASA Tech Briefs, December 1994 ing hand controller. The other sim- ulated task is removal and insertion of a drawer. The stereoscopic display is a modi- fied commercial apparatus in which left and right views are displayed alternately on the same video screen. The operator wears liquid-crystal-shutter goggles. A signal transmitted by an infrared emitter atop the stereoscopic video display synchronizes the shutters. When the left view is displayed, only the left shutter is open (clear), and the right shutter is opaque. When the right view is dis- played, only the right shutter is open. The video display is refreshed 120 times per second - frequently enough to appear not to flicker. Software for the stereoscopic display generates views for the two eyes from slightly different perspectives . Both views are obtained by projecting objects in the scene onto a plane called the "zero-disparity plane," which is par- allel to the plane of the display and is defined so that the points in the two images that represent the same points on the same object have the same hori- zontal coordinate in both images, regardless of the horizontal separation between the viewpoints (the locations of the simulated cameras). The views from the left and right viewpoints are obtained by simply translating the view- points right and left. The simulator is called a "high-fidelity" system for several reasons: - The simulation is based on accurate mathematical models of kinematics and dynamics of the manipulator and other objects. - The display is detailed and accurate. - Animated manipulator motions are smooth, with little or no perceptible lag between the operator's control actions and the corresponding simu- lated images and contact force feed- back via the hand controller. This work was done by Won S. Kim, Paul S. Schenker, and Antal K. Bejczy of Caltech for NASA's Jet Propulsion Laboratory. For further information, write in 266 on the TSP Request Card. NPO-18852 NEW OemI'vs VERSION 3! DERIVE is a powerful computer algebra system for dOing symbolic and numeric mathe- matics on your personal computer. DERIVE: • Performs numerical operations exactly with no round-off error • Approximates irrational expressions to thousands of digits of precision • Algebraically simplifies, expands, and factors expressions; and solves equations • Applies the rules of trigonometry, calculus, matrix algebra, and vector calculus • Plots explicitly and implicitly defined func- tions in 2D with looming and auto-scaling • Generates 3D wire-frame function plots using hidden-line removal • Displays and prints expressions using standard 2D mathematical notation DERIVE Requirements (regular memory version): A PC compatible running MS-DOS with 512K memory and a 3 1/2 inch (720K) diskette drive. List $125. DERIVE XM Requirements (extended memory version): A 386, 486 or Pentium- PC. MS-DOS, 2M extended memory and 31/2 inch (1.4M) diskette drive. List $250. DERIVE is a registered trademark of Soft Warehouse. Inc. rt:":l loft Watehou/e ~ Soft Warehouse, Inc. ' 3660 Waialae Avenue ~ Suite 304 • Honolulu, HI, USA 96816-3236 __ H 0 N 0 L U L U • HAW A I I Phone: (808) 734-5801 ' Fax: (808) 735-1105 For More Information Write In No. 427 81 Books& Reports These reports, studies, and handbooks are available from NASA as Technical Support Packages (TSPs) when a Request Card number is cited; otherwise they are available from the NASA Center for Aerospace Information. o Physical Sciences .~ Dynamics of Ions in a Radio-Frequency Quadrupole Trap A report describes a computer-simu- lation study of the motions of various numbers (up to 512) of ions in a Paul trap, which is an axisymmetric quadru- pole potential well created by imposition of a combination of dc and radio-fre- quency electric fields. This study is part of a continuing effort to understand the motions of trapped charged particles (which can be atoms, ions, molecules, or dust particles). The motions can be characterized in terms of heating by radio-frequency fields, the formation of crystallike structures in cold clouds of trapped particles, and other phenom- ena that are important in the operation of radio-frequency traps in frequency standards. This work was done by John D. Prestage, Angelyn P. Williams, and Lutfollah Maleki of Caltech for NASA's Jet Propulsion Laboratory. To obtain a copy of the report, "Dynamics of Charged Particles in a Paul Radio- Frequency Quadrupole Trap, n write In 178 on the TSP Request Card. NPO-18633 Comparison of Measurements of Atmospheric Water Vapor A report presents an experimental intercomparison among measurements by four spectrometric instruments for determining the concentration of atmos- pheric water vapor. Three of the instru- ments are ground-based and are need- ed to provide independent data to cali- brate and validate the measurements 82 taken by the fourth instrument, which is the airborne visible/infrared imaging spectrometer (AVIRIS). Heretofore, water-vapor data have been collected primarily by radiosondes carried aloft by balloons. Remote down-looking instru- ments like the AVIRIS can increase the accuracy and coverage of water-vapor measurements over those of radioson- des, but calibration and validation are needed. The experimental intercompari- son was performed to satisfy this need. This work was done by Carol J. Bruegge, James E. Conel, Jack S. Margolis, Robert O. Green, Geoffrey C. Toon, Veronique Carrere, Ronald G. Holm, and Gordon L. Hoover of Caltech for NASA's Jet Propulsion Laboratory. To obtain a copy of the report, 'In-situ water-vapor retrieval in support of AVIRIS validation,' write in 205 on the TSP Request Card. NPO-18431 Materials Reactive Melt Infiltration of Silicon Into Porous Carbon A recent report describes a study of the synthesis of silicon carbide and related ceramics by reactive melt infiltra- tion of silicon and silicon/molybdenum alloys into porous carbon preforms. Reactive melt infiltration has potential for making components in nearly net shape. In comparison with other processes, reactive melt infiltration can be performed in less time and at lower temperature. Ideally, reactive melt infiltration would convert the carbon to fully dense silicon carbide. In practice, the final material may contain some free carbon and sili- con or silicon alloy and may be slightly porous. The object of the study was to determine the effect of initial pore vol- ume fraction, pore size, and infiltration material on the quality of the resultant product. This work was done by Donald R. Behrendt of Lewis Research Center, and Mrityunjay Singh of the National Research Counsel. Further information may be found in NASA TM-105860 {N93-12398/TB}, "Studies of the Reactive Melt Infiltration of Silicon and Silicon-Molybdenum Alloys in Porous Carbon. n Copies may be purchased {prepay- ment required} from the NASA Center for AeroSpace Information, User Services Division, Linthicum Heights, Maryland, Telephone No. (301) 621- 0394. Rush orders may be placed for an extra fee by calling the same number. LEW-15861 Making Ceramic Fibers by Chemical Vapor Research and development of fabrica- tion techniques for the chemical vapor deposition (CVO) of ceramic fibers are presented in two new reports. The fibers of SiC, TiB2' TiC, B4C, and CrB2 are intended for use as reinforcements in metal-matrix composite materials. CVO offers important advantages over other processes: the fibers are purer and stronger and can be processed at tem- peratures below the melting points of the constituent materials. Fibers of the various ceramic materials were made by depositing the ceramic materials on car- bon-fiber tows and, in some cases, tungsten fibers from a variety of gaseous reactants. Processing sequences, pro- ceSSing conditions, and materials were selected for further development on the basis of thermodynamic analyses of a wide range of precursor materials, tem- peratures, pressures, and concentra- tions. Both continuous and batch processes were investigated. This work was done by Vithal V. S. Revankar and Vladimir Hlavacek of the State University of New York at Buffalo for Lewis Research Center. To obtain copies of the reports, "Synthesis of High Performance Silicon Carbide Fibers by Chemical Vapor Deposition" and 'Synthesis of High Performance Ceramic Fibers (Titanium diboride, TItanium car- bide, Boron carbide) by Chemical Vapor DepOSition for Advanced Meta/lics Reinforcing," write in 219 on the TSP Request Card. LEW-15415 Comparison of Models of . Metal-Matrix Composites A report presents a comparative review of four mathematical models of the micromechanical behaviors of fiber/metal-matrix composite materials. While the models differ in various details, all four are based on the properties of the fiber and matrix constituent materi- als, all involve square arrays of fibers that are continuous and parallel and all assume complete bonding between the constituents. Computer programs that implement the models are used to pre- dict the properties and stress-vs.-strain behaviors of unidirectional- and cross- ply laminated composites made of NASA Tech Briefs, December 1994 boron fibers in aluminum matrices and silicon carbide fibers in titanium matri- ces. The stresses in the fiber and matrix constituent materials are also predicted. This work was done by C. A. Bigelow and W. S. Johnson of Langley Research Center and R. A. Naik of Planning Research Corp. (Kentron). To obtain a copy of the report, 'A Comparison of Various Micromechanics Models for Metal Matrix Composites, ' write in 214 on the TSP Request Card. L4R-14463 ~ Mechanics Equations for Selected Fracture-Mechanics Parameters Equations that describe crack-mouth- opening displacements, stress-intensity factors, and related fracture-mechanics parameters of chevron-notched short bar and rod specimens are presented in a new report. The equations were devel- oped by fitting curves to previously avail- able data from compliance (crack opening and extension vs. load) tests of speci- mens from throughout the range of com- mon specimen geometries. The equations are in forms suitable for determining frac- ture toughnesses from maximum loads, for determining crack-extension-resis- tance curves ("R-curves"), and for setting sensitivities of testing instruments. The equations will be especially useful in facili- tating the testing and the interpretation of data from tests of brittle metals, ceramics, and glasses, which can be formed into chevron-notched specimens for fracture testing according to these concepts, but are difficult to fatigue-precrack to simulate natural flaws for fracture-toughness test- ing by older techniques. This work was done by Raymond T Bubsey, Thomas W. Orange, William S. Pierce, and John L. Shannon, Jr., of Lewis Research Center. Further information may be found in NASA TM- 83796 [N93-15369/TB], "Closed-Form Expressions for Crack-Mouth Displace- ments and Stress Intensity Factors for Chevron-Notched Short Bar and Short Rod Specimens Based on Experimental Compliance Measurements." Copies may be purchased [prepayment required] from the NASA Center for AeroSpace Information, Linthicum Heights, Maryland, Telephone No. (301) 621 -0390. Rush orders may be placed for an extra fee by calling the same number. LEW-15865 NASA Tech Briefs, December 1994 Computed Flow Through an Artificial Heart and Valve A NASA technical memorandum dis- cusses computations of the flow of blood through an artificial heart and through a tilting-disk artificial heart valve. The memorandum represents further progress in the research described in "Numerical Simulation of Flow Through an Artificial Heart" (ARC-12748), NASA Tech Briefs, Vol. 15, No. 12, (December, 1991), page 66. One of the purposes of this research is to exploit the advanced techniques of computational fluid dynamics and the capabilities of super- computers to gain an understanding of complicated internal flows of viscous, essentially incompressible fluids like blood. Another purpose is to use that understanding to design better artificial hearts and valves. This work was done by Stuart E. Rogers and Dochan Kwak of Ames Research Center, Cetin Kiris of MCAT Institute, and I-Dee Chang of Stanford University. Further information may be found in NASA TM-1 02270 [N93- 724711TBJ, "Numerical Simulation of Row Through Two Biofluid Devices. n Copies may be purchased [prepay- ment required] from the NASA Center for AeroSpace Information, User Services Division, Linthicum Heights, Maryland, Telephone No. (301) 621 - 0394. Rush orders may be placed for an extra fee by calling the same number. ARC-12983 Computed Flow Through an Artificial Heart Valve A report discusses computations of blood flow through a prosthetic tilting disk valve. The computational procedure developed in this simulation can be used to design better artificial hearts and valves by reducing or eliminating the fol- lowing adverse flow characteristics: (1) large pressure losses, which prevent hearts from working efficiently; (2) sepa- rated and secondary flows, which can cause clotting; and (3) high turbulent shear stresses, which can damage red blood cells. The report reiterates and expands upon part of the NASA technical memo- randum described in the previous brief "Computed Flow Through an Artificial Heart and Valve" (ARC-12983). It is also based partly on the research described in "Numerical Simulation of Flow Through an Artificial Heart " (ARC- 12478), NASA Tech Briefs, Vol. 15, No. 12, (December 1991), page 66. This work was done by S. Rogers and D. Kwak of Ames Research Center and C. Kiris and I. Chang of Stanford University. Further information may be found in AIAA paper A90-22243, Wumerical Simulation of the Incom- pressible Internal Row Through a Jilting Disk Valve. n Copies may be purchased [prepay- ment required] from AEROPLUS, Bur- lingame, CA 94010, Telephone No. (BOO) 622-2376, Fax No. (415) 259-5047. ARC-13123 Further Research on Helicopter Tail-Boom Strakes Two documents discuss the results of additional investigations of the con- cept introduced in ' Helicopter Tail - Boom Strakes ' (LAR-13233), NASA Tech Briefs, Vol. 10, No.2 (March/April 1986), page 132. The essence of the concept is that a strake or a pair of strakes on the side of the tail boom that faces the retreating side of the main rotor of a helicopter perturbs the flow (principally, downwash from the rotor) in such a way as to increase the aerody- namic pressure on that side, thereby contributing a force to the thrust from the tail rotor. Because of this force, the thrust required of the tail rotor for yaw control is reduced. This is an important advantage in low-speed flight, especial- ly in sideward (toward the side opposite that of the strakes) flight, in which the tail-rotor thrust in the absence of a strake is sometimes insufficient. One of the documents is a short, untitled dis- cussion of the concept in question-and- answer form. The other document is a report that describes an experimental study in which the effects of tail-boom strakes were investigated on an Army helicopter in flight. This work was done by Henry L. Kelley, Cynthia A. Crowell, and Kenneth R. Yenni of Langley Research Center and Michael B. Lance of Lockheed Engineering and Sciences Co. To obtain a copy of the untitled summary plus the report, 'Flight Investigation of the Effect of Tail Boom Strakes on Helicopter Directional Control, ' writer in 285 on the TSP Request card. This invention has been patented by NASA (U.S. Patent No. 5,209,430). Inquiries concerning nonexclusive or exclusive license for its commercial development should be addressed to the Patent Counsel, Langley Research Center [see page 20]. Refer to L4R- 14219. 83 Test of Digital Image Velocimetry A report describes an experiment to test digital image velocimetry, which Is being developed to measure velocities of flows seeded with light-reflecting parti- cles. Digital image velocimetry has been described previously in NASA Tech Briefs. To recapitulate: The flow in ques- tion is illuminated, and a sequence of video, photographic, or holographic images of the particles are recorded at known short intervals of time. The images are digitized and enhanced . Then the average velocity during the interval between two sequential images is computed by use of correlations between the images. This work was done by Y. C. Cho of Ames Research Center and H. Park of the University of California, Berkeley. Further information may be found in NASA TM-102875 [N93-72467ITB} "Instantaneous Velocity Field Meas- urement of Objects in Coaxial Rotation Using Digital Image Velocimetry." Copies may be purchased [prepay- ment required} from the NASA Center for AeroSpace Information, User Services Division, Linthicum Heights, Maryland, Telephone No. (301) 621-0394. Rush orders may be placed for an extra fee by calling the same number. ARC-13090. HEADHUNTERnI HEAD & EYE SLAVEn POINTING SYSTEM COMPLETE, NON-INVASIVE, REAL-TIME HARDWARE AND SOFTWARE INSTRUMEN- TATION TO COMPUTE AND ANAL VZE COMBINED HEAD AND EYE VECTORS FOR ADVANCED WEAPONS POINTING, SIMULATION fTRAINING & HUMAN FACTORS ASSESSMENT. 125 CAMBRIDGEPARK DR. CAMBRIDGE, MA 02140 TEL: 617-868-5353 FAX: 617-868-9231 For More Infonnatlon Write In No. 436 -0 Machinery Circular Scanning With RUM Actuators A technical paper discusses the use of rotating-unbalanced-mass (RUM) actua- tors to scan scientific instruments in cir- cular pattems centered on target points. It proposes reconfiguration of an existing experimental raster- and line-scanning RUM apparatus to enable experiments on circular scanning. It presents formulas for calculating the effects of a RUM mounted on the ends of a gimballed beam. Calculations for control gains of RUM and gimbal servos are also present- ed. The report describes a numerical sim- ulation that predicts that a representative circular-scanning RUM actuator would consume 1/33 the power of an equivalent gimbal torquer in normal Earth gravity and 1/688 times the power of the gimbal torquer in zero gravity. This work was done by M. E. Polites and D. C. Alhorn of Marshall Space Flight Center. Further information may be found in NASA TP-3282 [N92- 33601lTB}, "Reconfiguring the RUM Experiment To Test Circular Scanning With Rotating Unbalanced-Mass Devices on Gimballed Payloads. " Copies may be purchased [prepay- ment required} from the NASA Center for AeroSpace Information, User Services Division, Linthicum Heights, Maryland, Telephone No. (301) 621-0394. Rush orders may be placed for an extra fee by calling the same number. MFS-28919 Active Inertial Vibration Isolators and Dampers A report describes the development of active inertial vibration isolators and dampers in which the actuators are elec- tromagnet coils that move linearly within permanent magnetic fields in housings, somewhat as though they were massive, low-frequency voice coils in loudspeak- ers. Accelerometers detect the vibrations, and the outputs of the accelerometers are processed by digital electronic control circuits to generate currents in the coils such that the exchange of momentum between the coils and the housings gives rise to opposing vibrations and the result- ing overall level of vibrations is zero or very small. The report discusses the prin- ciple of operation, electrical and mechani- cal considerations in the design of actua- tors, characteristics of accelerometers, and frequency responses of control sys- tems. It describes the design and perfor- mance of a one- and a three-degree-of- freedom vibration-suppressing system based on this concept. This work was done by Darren Laughlin, John Blackburn, and Dennis Smith of Applied Technology Associates for Lewis Research Center. Further information may be found in NASA CR- 190798 [N93-15353ITB}, "Digital Active Material Processing Platform Effort (Damper), SBIR Phase II." Copies may be purchased [prepay- ment required} from the NASA Center for AeroSpace Information, Linthicum Heights, Maryland, Telephone No. (301) 621-0390. Rush orders may be placed for an extra fee by calling the same num- ber. LEW-15872 Tests of a Magnetic Bearing for Cryogenic Applications A report describes experiments per- formed in a test rig on a hybrid magnetic bearing for possible use in turbopumps at low temperature. The bearing includes a permanent magnet that provides bias magnetic flux, plus electromagnet wind- ings, shaft-position sensors, and associ- ated control circuitry that provide active control of position. The bearing support- ed a flexible rotor that served as a model of a rotor subject to bending. The rotor and bearing were placed in a test rig in which they were immersed in liquid nitrogen and driven by a motor to speeds up to 14,000 r/min. The results of the tests indicate that it is feasible to use the bearing in cryogenic environ- ments and that the bearing damps the bending-mode vibrations of the flexible rotor as the rotor accelerates or deceler- ates through speeds at which bending- mode oscillations are excited. The report concludes that further work should be done on the bearing controller to increase the effective bearing stiffness, and that improved displacement sensors should be developed to reduce temper- ature drift and electrical noise. This work was done by Biseo DiRusso and Gerald V. Brown of Lewis Research Center. Further information may be found in NASA TM-105627 ' [N92-20523ITB}, "Performance Tests of a Cryogenic Hybrid Magnetic Bearing for T urbopumps. " Copies may be purchased [prepay- ment required} from the NASA Center for AeroSpace Information, User Services Division, Linthicum Heights, Maryland, Telephone No. (301) 621-0394. Rush orders may be placed for an extra fee by calling the same number. LEW-15869 NASA Tech Briefs, December 1994 Multiple Pages Intentionally Left Blank NASA Tech Briefs LITERATURE SP TLIGHT Free catalogs and literature for NASA Tech Briefs' readers. To order, write in the corresponding number on the Readers Information Request Form (page 85). NUMERICAL ANALYSIS SOFTWARE Free HiQ numerical analy- sis and data visualization demonstration software for Macinrosh. The demon- srracion package includes the HiQ demo program and an 84 page Step-by-step demonsuation manual chat gives me user a comprehen- sive look at HiQ. Example problems include signal pro- cessing, ordinary differential equations. linear algebra. numerical integration, and 3Dvisualaation. Tel: 512-794- 0100.800-433-3488 (US and Canada); Fax: 512-794-8411. National Instruments For More Information Write In No. 300 IIRVI/. I//IOU ~ .... -. I~ < g ~._. :., ....... . . ~ .. .... .. -.. ~ HIGH VOLT- AGE CATALOG New 16-pg. catalog fea- tures Farnell Hivolt's stan- dard product range of lUgh voltage power supplies and test equipment. These units address such diverse applications as ion implan- tarion, x-ray equipment) CRT displays and analyti- cal instrumentarion. Tel: 216-349-0755; Fax: 216- 349-0142. Farnell Advance Power. 32111 Aurora Rd .• Solon, OH 44139. Farnell Advance Power For More Information Write In No. 303 LUMITEX ... CREATORS OF WOVEN LIGHT This eighr-page color cata- log describes new low- power. long-life light sources for use in portable and hand-held applica- tions. Also included are 6-'" new woven panel conS[ruc- L-______ --' cion options for use in high-volume, price sensi- tive backing areas. Ideal for LCD backlighting, machine ' vision. and switch, keypad, and control panel applica- tions. Lumitex, Inc .• 8443 Dow Circle. Strongsville. OH 44136. Tel: 800-969-5483; Fax: 216-243-8402. Lumitex, Inc. For More Information Write In No. 306 NASA Tech Briefs, December 1994 PRECISION COUPLING COMPONENTS Featuring a wide range of coupling devices in a vari- ery of materials. this 32 page brochure is the latest from Berg. Designed to complement the Inch and Merrie caralogs it contains Information Transmitting. Shock Absorbing. Misalignment Couplings. All designed and manufactured co meet the exacting demands of modern industry. W.M. Berg Inc. Tel: 516-596-1700; Fax: 516-599-3274. For More Information Write In No. 301 HIGH RESOLUTION DATA ACQUISITION FREE bookler shows many ways to automate data col- lection using your personal computer. it comes with a FREE Instatrend Real - Time Graphics Demo Disk. Dianacbart, Inc., 101 Round Hill Drive, Rockaway, NJ 07866. Tel: 201-625-2299. Dianachart, Inc. For More Wormation Write In No. 304 FOUR CHAN- NEL DSO COMBINES PERFOR- MANCE AND PORTABILITY Model DL1300A provides 21 waveform measuremem functions. 2-channel pass! fail testing, automatic sequence mode, TV trigger with line and field selection and GP1B interface. Optional fearures include built-in thermal printer. m~mory card storage and video output. Call Yokogawa Corporation of America at 800-258-2552 for a brochute. For More Information Write In No. 307 RAPIDSYN STEP MOTORS American Precision Indus- tries' 60 page product guide is a complete source for technical. application and product data for select- ing/applying Rapidsyn step motors. Seclions include: Construction and Technol- ogy. Formulas and General Motor Specifi.cations. Size 23, 34. and 42 Stop Motors, AC Synchronous and Specialty Motors. Conract American Precision Industries. Rapidsyn Division, 3229 Roymar Road. Oceanside. CA 92054. Tel: 619-439- 7500; Fax: 619-722-5428. American Precision Industries Rapidsyn Division For More Information Write In No. 302 PRECISION MOTION CONTROL API's 1995, 160 page step motor systems caralog. fearur- ing the new intelligent driver Wgffff~~".g series, is a complete source for modon control technical, applicacion and product data. L-______ -l Definitions. marker applica- tions, comparison chares, specificacions and diagrams. simplify the selection/applica- tion process. Contact American Precision Indusnies, Controls Division. 4401 Ge!lesee Street. Buffalo. NY 14225. Tel: 716-631-9800; Fax: 7 16-631-0152. American Precision Industries Controls Division For More Information Write In No. 305 SEALING ASSEMBLIES Conax Buffalo offers a 28-page catalog on Conax Buffalo Pressure and Vacuum Sealing Assem- blies with comprehensive information on soft sealed technology for wires and probes. Complete technical data and ratings for each product rype. from stan- dard sealing glands to complete assemblies, are included. as well as information on custom engineering and appli- cations. Caralog includes a postpaid reply card for techni- cal assistance. Conax Buffalo For More Wormation Write In No. 308 87 LITERATURE SPOTLIGHT --- ---,--- NEW PORTABLE OSCILLO- GRAPH Yokogawa's ORMI200 packs power in Iigh- filing. National Electrostatics Corp., 7540 Graber Road, P.O. Box 620310. Middleron. WI 53562-0310. Td: 608- 831-7600; Fax: 608-256-4103; Email: nec@wdU£ca.us National Electrostatics Corp. For More Information Write In No. 336 .., -- FILM INDICATES STRESS DISTRIBUTION p~ enables you 10 quickly and inapensivdy determine compression magnitude and distribution ~ between contact surfaces. ... _ Microcapsules within the film burst at specific pres- sure kvds causing an instanCllleoUS color change. and pro- ducing a permanent "topographical" intage of pressure vari- acion. p~ is a valuable aid in QC and R&D for such applications as laminating presses, nip impressions. and bolted joints. Td: 800-755-2201; Fax: 201-884-1699. Sensor Products Inc. For More Information W rill: In No. 339 EMCOR FEAT- URES EMVRFI ENCLOSURES FOR ALL TYPES OF REQUIRE- MENTS Emcor Products offers rwo lines of modular enclosures to control emissions: T he FCC Level Seties is used in commercial and industrial requirements and the TEM- PEST-style series is used when higber levels of attenua- tion are required Both have been ~ted to MIL-STD- 285 at a cc:rtified test facility. Emcor ProduCts, 1600 4th Avenue NW. Rochester. MN 55901. Tel: 507-289-3371. Emcor Products For More Information Write In No. 342 . CUSTOM MOLDED FOAM Polyetbelene, EVA and Polyurethane fOams, among o,hers. can be molded to create unique OEM parts or finished products. These custom designed products are being used in medical, sports and recreation. com- purer petipheral and aes- thetic packaging applica- tions. Fabric, film or narural finishes available. Call fOr free sample card llnd b rochure. Flatech. Inc.. New Hope. MN. Tel: 800-285-6660. Flextech, Inc. For More Information Write In No. 345 NASA Tech Briefs, December 1994 LITERATURE SPOTLIGHT HIGH REL HYBRID DC-DC CONVERTERS This new 32p catalog de- scribes a full line of hybrid and discrete DC-DC con- verters for Space. Military and lndusuial application; wide range of DC input voltages. output from 3 VDC. low output ripple. to 3 kilovol ts. multiple out- puts. full EMI filterslother systems type circuitry. Rad Hard versions specified. custom variations available. T eJ: 1-800-333-POWR; Fax: 516-345-3106. Modular Devices Inc. One Roned Road· Shirley. NY 11967. For More Information Write In No. 346 INTERPOW- ERTM EXPORT DESIGNER'S REFERENCE CATALOG New 224 page Reference Catalog #8 helps in design- ing primary power circuics of internat ional produc£s, Designer's Reference section shows world plug/-socket pancrns, voltages and frequencies, international safety agencies and important srandards pubHshed by IEC, UL and CSA. Tel: 515-673-5000; Fax: 515-673-5100. W<2f2 PANE L C COMPONENTS CORPORATION For More Information Write In No. 3 4 9 WAVE/COM- PRESSION SPRINGS JUSt updated. Catalog #WS-93 contains IiEW stock sizes of wave/com- pression springs available from stock. including spring design formulas. materials guide and typical applications. T he describes the many advantages of Smalley's exclusive edgewinding manufacturing process. Smalley springs. available from 3/8" to 84" in diameter. are produced by circle-coiling /lat wire to exaCt specifications involving no dies or special tooling ~. Tel: 708-537-7600; Fax: 708-537-7698. Smalley Steel Ring Co. For More Information Write In No. 352 " HANDS-ON" ADVANCED COMPOSITE WORKSHOPS- SINCE 1983 The brochure describes 13 different cchands~on" work- shops in advanced composite materials technology. These workshops cover fabrication, repair, manufacturing, tool- ing. bluep rint read ing. adhesive bondi ng. ultrason ic inspection of composites, and 4 engineering workshops. Emphasis is placed on prep reg carbon and aramid fiber materials and processes, utilizing vacuum bagging and high-temperature curing methods in the oven and auto- clave. Three workshops are Canadian DOT approved. REFRESHER WORKSHOPS OFFERED. For a free brochure. call 1-800-638-8441; Fax: 702-827-6599. Abaris Training Resources For More Information Write In No. 3 5 5 NASA Tech Briefs. December 1994 Free LiteraturerTo Advertise call (800) 944-NASA T he 1994 REM COR'" Catalog describes the new line of water Chillers and Recircularors. The easy to read tables and graphs make applications and Chiller identification sim- ple and convenient. Send for the complete Chiller Catalog today. Remcor Products Company. 500 Regency Drive. G lendale Heights. IL 60139. Tel: 708-980-6900; Fax: 708- 980-85 11. Remcor Products Company For More Information Write In No. 347 NEW MSC/NASTRAN BROCHURE 12-page brochure details latest features of lead ing FEA software. used world- wide to oprimize and pre- dict behavior of complex designs from aerospace and autOmotive to medical and consumer goods. Analysis types include static, normal modes. buckling, dynamic response. heat transfer. nonlin- ear, acoustic, and aeroelastic, using both h- and p-e1e- mems. Open architecture works with all modeHng/CAD systems. MacNeal-Schwendler Corp., Los Angeles. CA. Te!: 800-642-7437. ext. 500. MacNeal-Schwendler Corp. For More Information Write In No. 350 NON-STOP FROM PROIE® TO ANALYSIS & OPTIMIZATION COSMOS/M ENG I- NEER makes it easy and affordable to include analy- sis and Optimization on every design itinerary. lcs seamless interface to ProlE fully integrates the design. preprocess- ing and postptocessing featu res of ProlE with the analy- sis and optimization power of COSMOS/M: statics, buckling, frequency. heat transfer. optimization, nonlin- ear, advanced dynamics, a super fast solver and two meshing capabilities. Starting at $6500! Call 310-452- 2158 (west) or 412-635-5100 (east). COSMOS/M For More Information Write In No. 353 EQUIPMENT HOUSING HARDWARE Small quantities/immediate shipment. Design Stand- ards offers an international selection of opera tiona l hardware for control and access of equipment and mach ine ry. Ou r knobs. handles. levers. handwheels, spring pl ungers. levelers and wheels possess superior production. functional and aesthetic qualities. Design Standards: a division of Rogan Corporarion. 3455 Woodhead Dr .• Northbrook. IL 60062. Tel: 800-388-5656; Fax: 708-509-1705. Design Standards For More Information Write In No. 356 GPS- SYNCHRO- NIZED TIMING PRODUCTS TrueTime's Precision Timing Products catalog features GPS-Synchronized C locks in rackmo un t, portable, and board-level configu rations. Includ es illustrations and product specifi cations for our complete line of Synch ronized Clocks. Time Code ProductS. and Remote Displays to fit a variery of time and frequency applications. TrueTime, Inc. For More Information Write In No. 348 NEW AUTOMATED DISTILLATION SYSTEM Au toco l is auto mated, packed column still with Cost-saving applications for solvent recovery, concen- tration of wastes, and small scale batch production. With 15 theoretical plates for powerful fractionation of componenrs, AU[Qcol can automatically purify and recover individual solvents from complex mixtures. Tel: 414-251-9300; Fax: 414- 25 1-7387. Pope Scientific, Inc. For More Information Write In N o. 351 PRECISION STRIPIWIRE Elgiloy® is a combination strip and wire mill. We process a variery of alloys including Inconel®. Has- tetlo>,",. Monel'". MP35N". Titanium and Stain less. Our sales and engineering staff are quaHfied to handle your custom materia l re- quirements, and our on site testing lab assures you of prompt deliveries. Tel: 708-695-1900; Fax: 708-695-0169. Elgiloy® Limited Partnership For More Information Write In No. 354 FLEXIBLE BORESCOPES Visua l inspections can be made easy with the use of a flexib le borescope. Machida. Inc.'s new bro- chu re deta ils their co m- plete line of qualiry flexible borescopes designed fo r various industrial inspec- tions. Also highlighted are specialized turbine inspec- ,ion kits. blending borescopes. scopes with channels and working tools, video systems. light sources and borescope accessories. Tel: 800-431-5420. Machida, Inc. For More Information Write In No. 357 91 LITERATURE SPOTLIGHT 92 OXYGEN ANALYZERS A full-color brochur< introduces a complete line of oxygen analyzers for me labor-nory or process line. They are ideally suited for monitoring me oxygen lev- els in all types of gas Streams. Trace oxygen lev- els from ppb to 100% 21e accurately determined by [hese ruggedly construcced instruments. No periodic m.incen:mce or speci.1 operacor skills are required. Intrinsically-sa.fe and buttry-operated models are a.lso available. Illinois Instruments Inc. For More Information Write In o. 358 ELECTRO- MAGNETIC DESIGN SOFTWARE The legendary Vector Fields sui .. of software, including the TOSCA, ELEKTRA and OPERA IF VECTOR FIElDS packages, combines classical floi[t dement techniques wim user friendly interac- tive graphics for high accuracy 20 and 3D simulation a.nd design of all rypes of electromagnetic equipment. Vector Fields Inc. 1700 North Farnsworth Avenue Aurora, IL 60505 Tel : 708-851-1734 Fax: 708-851 -2106 For More Information Write In No. 309 _._--- JJ~.JJ -_..-.-.. .. -'- FREE CATA- LOG OF TOOL- ING COMPO- NENTS New reference catalog of over 18,000 items offers a full range of tooling com- ponents and equipment. Items include ha.ndwbeels, handles, knobs, spring & ball plungers, pads, clamps, set up accessories, locating devices, cutting tools, springs, mread inserts, a.nd metric items. All items are in stock for same day ship- ment with no minimum order requirement. Reid Tool Supply Company, 2265 Black Creek Rd., Muskegon, MI 49444. Tel: 1-800-253-1421; Fax: 1-800-438-1145. Reid Tool Supply Company For More Information Write In No. 363 TECLAB ESDWORK- STATION CATALOG Kalamazoo T ecbnical Fur- nitUre's 8-page 4/color brochure details me T edab line of stade protective workbenches, workstation systems, and ESD con- [rolled workstation acces- sories. Included are color options, product specifications, a.nd various levels of ESD protection available. T eclab also offers a Free Pla.nning a.nd Design Service. T eclab, me 'professional's bench: Tel: 1-800-832-5227. Fax: 616-372-6116. Kalamazoo Technical Furniture For More Information Write In No. 366 Free LiteraturefTo Advertise call (800) 944-NASA ULTRA-HARD MATERIALS FABRICATION Insaco's brochuce describes me CUStom ma.ouf.acture of components in sapphire, ruby, qua.nz. ceramics of all •• types including glass- ceramics, alumina, zirco- nia, carbides. a.nd nitrides. The company routinely fabricates mest materials for applications in optics, chem- istry, vacuum, bearings, decuonics, nuclear. space and medicine. Tolerances are measured in millionms of a.n inch wim surface finishes in angstroms and flatness <0 fractions of a waveleng

NASA Tech Briefs, December 1994

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