Strength of the DTM RapidSteel 1.0 Material

This paper reports the results of a study into the strength of the DTM RapidSteel 1.0 material. Elastic modulus and strength of the metal/copper composite material was investigated as a function of the distance from the point of copper infiltration, the furnace cycle duration, and the furnace type. The microstructure of the RapidSteel material was also examined in an attempt to understand the science behind the infiltration process. The results have implications for the design of tools to be made using the RapidTool process in situations where the tool will be used as a production tool, rather than a prototype tool.Mechanical Engineerin

A Study of Effects of Viscosity on Flow over Slender Inclined Bodies of Revolution

The observed flow field about slender inclined bodies of revolution is compared with the calculated characteristics based upon potential theory. The comparison is instructive in indicating the manner in which the effects of viscosity are manifest. Based on this and other studies, a method is developed to allow for viscous effects on the force and moment characteristics of bodies. The calculated force and moment characteristics of two bodies of high fineness ratio are shown to be in good agreement, for most engineering purposes, with experiment. (author

Investigation of Some Wake Vortex Characteristics of an Inclined Ogive-Cylinder Body at Mach Number 2

For a body consisting of a fineness-ratio-3 ogival nose tangent to a cylindrical afterbody 7.3 diameters long, pitot-pressure distributions in the flow field, pressure distributions over the body, and downwash distributions along a line through the vortex centers have been measured for angles of attack to 20 degrees. The Reynolds numbers, based on body diameter, were 0.15 x 10 to the 6th power and 0.44 x 10 to the 6th power. Comparisons of computed and measured vortex paths and downwash distributions are made. (author

Material Properties Measurements for Selected Materials

Hugoniot equation of state measurements were made on Coconino sandstone, Vacaville basalt, Kaibab limestone, Mono Crater, pumice and Zelux (a polycarbonate resin) for pressures to 2 Mb. A single data point was obtained for fused quartz at 1.6 Mb. In addition to the hugoniot studies, the uniaxial compressive stress behavior of Vacaville basalt and Zelux was investigated at strain rates from about 10(exp -5)/sec to 10(exp 3)/second. The data presented include the stress - strain relations as a function of strain rate for these two materials

Investigation of the Drag of Various Axially Symmetric Nose Shapes of Fineness Ratio 3 for Mach Numbers from 1.24 to 7.4

Experimental drag measurements at zero angle of attack for various theoretical minimum drag nose shapes, hemispherically blunted cones, and other more common profiles of fineness ratios of about 3 are compared with theoretical results for a Mach number and Reynolds number range of 1.24 to 7.4 and 1.0 x 10 to the 6th power to 7.5 x 10 to the 6th power (based on body length), respectively. The results of experimental pressure-distribution measurements are used for the development of an empirical expression for predicting the pressure drag of hemispherically blunted cones

Unzipping of DNA with correlated base-sequence

We consider force-induced unzipping transition for a heterogeneous DNA model with a correlated base-sequence. Both finite-range and long-range correlated situations are considered. It is shown that finite-range correlations increase stability of DNA with respect to the external unzipping force. Due to long-range correlations the number of unzipped base-pairs displays two widely different scenarios depending on the details of the base-sequence: either there is no unzipping phase-transition at all, or the transition is realized via a sequence of jumps with magnitude comparable to the size of the system. Both scenarios are different from the behavior of the average number of unzipped base-pairs (non-self-averaging). The results can be relevant for explaining the biological purpose of correlated structures in DNA.Comment: 22 pages, revtex4, 14 eps figures; reprinted in the June 15, 2004 issue of Virtual Journal of Biological Physics Researc

Multiple shutters for a stereoscopic camera

Focal plane shutter assembly composed of three mechanically separate rotary shutters permits exposure of three separated photographic films simultaneously with exposure time of 0.08 second. Exposure time is repeatable within 2 percent, uniformity of exposure over all three films is within 5 percent