17,451 research outputs found
Performance tests of a gas blending system based on mass-flow controllers
The system provides many of the gas mixtures required for calibrating analytical instruments used in engine exhaust gas analysis and is capable of blending from one to four additive gases with either of two carrier gases in concentrations from 20 ppm to 50%. Two mixtures can be flowing simultaneously. Performance tests were made to determine the stability accuracy of the system while it was in limited use for a period of 2 years. The accuracy of the blender was measured by comparing binary mixtures from the blender with National Bureau of Standards standard reference materials. Analytical instruments were used to make these comparisons. The expected accuracy of 2% was obtained in some of the tests, by the majority showed a systematic biAs of -5%. Although these tests revealed subtle instabilities in the flow controllers that contributed to the random scatter of data, the accuracy of wet test meters and bubble flowmeters used for calibration is marginal for this purpose. A simple procedure is recommended that should enable the full potential of the system to be realized
Evaluation of two gas-dilution methods for instrument calibration
Two gas dilution methods were evaluated for use in the calibration of analytical instruments used in air pollution studies. A dual isotope fluorescence carbon monoxide analyzer was used as the transfer standard. The methods are not new but some modifications are described. The rotary injection gas dilution method was found to be more accurate than the closed loop method. Results by the two methods differed by 5 percent. This could not be accounted for by the random errors in the measurements. The methods avoid the problems associated with pressurized cylinders. Both methods have merit and have found a place in instrument calibration work
Stability of some epoxy-encapsulated diode thermometers
The stability upon thermal cycling and handling of ten small, epoxy-encapsulated silicon diode thermometers at six temperatures in the range from liquid nitrogen temperatures to about 60 C. The nominal temperatures of measurement were -196, -78, 0, 20, 40, and 60 C, as measured on the International Practical Temperature Scale of 1968. Diodes were to be thermally cycled 15 to 20 times. Since NASA anticipates that the uncertainty in their temperature measurements will be + or - 50 mK, uncertainties as large as + or - 10 mK in the measurements of the evaluaton can be accommodated without deleteriously affecting the value of the results of the investigation
High voltage planar multijunction solar cell
A high voltage multijunction solar cell is provided wherein a plurality of discrete voltage generating regions or unit cells are formed in a single generally planar semiconductor body. The unit cells are comprised of doped regions of opposite conductivity type separated by a gap or undiffused region. Metal contacts connect adjacent cells together in series so that the output voltages of the individual cells are additive. In some embodiments, doped field regions separated by a overlie the unit cells but the cells may be formed in both faces of the wafer
Method of making a high voltage V-groove solar cell
A method is provided for making a high voltage multijunction solar cell. The cell comprises a plurality of discrete voltage generating regions, or unit cells, which are formed in a single semiconductor wafer and are connected together so that the voltages of the individual cells are additive. The unit cells comprise doped regions of opposite conductivity types separated by a gap. The method includes forming V-shaped grooves in the wafer and thereafter orienting the wafer so that ions of one conductivity type can be implanted in one face of the groove while the other face is shielded. A metallization layer is applied and selectively etched away to provide connections between the unit cells
High voltage v-groove solar cell
A high voltage multijunction solar cell comprises a number of discrete voltage generating regions, or unit cells, which are formed in a single semiconductor wafer and are connected together so that the voltages of the individual cells are additive. The unit cells comprise doped regions of opposite conductivity types separated by a gap. The method includes forming V-shaped grooves in the wafer and orienting the wafer so that ions of one conductivity type can be implanted in one face of the groove while the other face is shielded. A metallization layer is applied and selectively etched away to provide connections between the unit cells
Planar multijunction high voltage solar cells
Technical considerations, preliminary results, and fabrication details are discussed for a family of high-voltage planar multi-junction (PMJ) solar cells which combine the attractive features of planar cells with conventional or interdigitated back contacts and the vertical multijunction (VMJ) solar cell. The PMJ solar cell is internally divided into many voltage-generating regions, called unit cells, which are internally connected in series. The key to obtaining reasonable performance from this device was the separation of top surface field regions over each active unit cell. Using existing solar cell fabricating methods, output voltages in excess of 20 volts per linear centimeter are possible. Analysis of the new device is complex, and numerous geometries are being studied which should provide substantial benefits in both normal sunlight usage as well as with concentrators
Amplitude analysis of four-body decays using a massively-parallel fitting framework
The GooFit Framework is designed to perform maximum-likelihood fits for
arbitrary functions on various parallel back ends, for example a GPU. We
present an extension to GooFit which adds the functionality to perform
time-dependent amplitude analyses of pseudoscalar mesons decaying into four
pseudoscalar final states. Benchmarks of this functionality show a significant
performance increase when utilizing a GPU compared to a CPU. Furthermore, this
extension is employed to study the sensitivity on the mixing
parameters and in a time-dependent amplitude analysis of the decay . Studying a sample of 50 000 events and setting
the central values to the world average of and , the statistical sensitivities of and are determined
to be and .Comment: Proceedings of the 22nd International Conference on Computing in High
Energy and Nuclear Physics, CHEP 201
The Nature of the Compact/Symmetric Near-IR Continuum Source in 4C 40.36
Using NICMOS on HST, we have imaged the emission-line nebulae and the
line-free continuum in 4C 40.36, a ultra-steep spectrum FR II radio galaxy at
z=2.269. The line-free continuum was found to be extremely compact and
symmetric while the emission-line nebulae seen in H-alpha+[N II] show very
clumpy structures spreading almost linearly over 16 kpc. However, this linear
structure is clearly misaligned from the radio axis. The SED of the line-free
continuum is very flat, suggesting that if the continuum emission is produced
by a single source, it is likely to be a young bursting stellar population or
scattered AGN light. However, because of the lack of a line-free optical image
with a comparable spatial resolution, we cannot exclude the possibility that
the observed SED is a composite of a young blue population and an old red
population.Comment: 4 pages, 2 figures; to appear in the proceedings of "The Hy-Redshift
Universe: Galaxy Formation and Evolution at High Redshift", eds. A.J.Bunker
and W. J. M. van Breuge
A Pilot Study of Brief Group Therapies for Preschool Children: Parent Training vs Group Play Therapy vs Project Group
The optimum modality for treating preschool age children with behavioral and emotional problems is uncertain. One study showed that children with good ego strength respond to psychotherapy independent of whether it is group or individual psychotherapy, provided that a minimum period of psychotherapy occurs (ovick, 1965). The literature has demonstrated that parent training, individual play therapy, and group therapy are all effective modes of treatment with children (Axline, 1969; Moreland, et ai, 1983; Pesco solido & Petrella, 1986). Due to the limited psychiatric resources in the military setting and increasing demand for service, the option for individual therapy may be restricted to specific neurotic clinical diagnoses. We studied the efficacy of short term group treatment applicable to behavior ally and emotionally disordered children, ages 4 through 6 years. In a review of various group treatments, the number of sessions ranged from 10 to 15 (Abramowitz, 1976). In another study, the mean n umber of hours needed to produce therapeutic benefits in parent training was 9.5 (Forehand, et al, 1979). All of the treatments to be considered are structured around a group principal to allow more patients to be treated for the same clinician time expenditure. Our study compared parent training, to group play therapy, and a project group on a population of behaviorally or emotionally disordered children, ages 4 to 6. The groups themselves ran for eight weeks, 75 minutes each week, along with 50-minute pre and post sessions with each set of parents. Total clinical time was approximately 24 hours per group for both therapists
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