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Ceramics Made From Wood

Properties can be tailored in many different ways. The term “ecoceramics” (a contraction of “environment-conscious ceramics”) denotes a class of ceramics made partly from wood-based products, which can include natural wood, sawdust, cardboard, and/ or paper. In addition to the environmental advantage of renewability of the carbonaceous ingredients, the concept of ecoceramics offers an advantage of tailorability of the properties of the ceramic end products.

Posted in: Materials, Briefs

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Annealing for Tailoring Au/GaN Schottky-Barrier Height

It should be possible to make metal/semiconductor contacts more reproducible. Annealing has been found to be an effective means of tailoring the height of a Schottky barrier between gold and gallium nitride. This finding offers promise for the development of improved metal contacts on GaN semiconductors. Heretofore, the commercialization of GaN semiconductor devices has been impeded by difficulties of fabrication and by nonreproducibility of the Schottky-barrier heights and other properties of the metal/GaN interfaces. Now it appears that annealing may be the key to making GaN devices with smaller unit-tounit variations of contact properties and, in particular, tailorability of Schottky-barrier heights over a wide energy range.

Posted in: Materials, Briefs

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Ex — Software for Numerical Computation in Native Oberon

“Ex” is the name of a library of software modules from which one can rapidly develop prototype or production versions of efficient numerical-computation application programs in the Native Oberon programming environment. Mathematical constructs that can be represented and processed by use of Ex modules include both integer and non-integer rational, real, and complex numbers; vectors; matrices; and the arithmetic, algebra, and calculus of the aforementioned quantities.

Posted in: Information Sciences, Briefs

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Program Computes Pointing Corrections for a Radiotelescope

TLC is a computer program that determines corrections for radiotelescopepointing errors associated with tilts and elastic deformations. These errors occur because for rotation in azimuth, a radiotelescope is mounted on wheels that move on a circular track that deviates from perfect flatness. TLC processes radiotelescope field data through smoothing, filtering, segment-fitting, trend-removal, Fourier-transform, and high-passfiltering algorithms to generate a lookup table that contains the pointing corrections. The field data in question are readouts from four inclinometers, the relative positions of the inclinometers, and readouts from an azimuth-angle encoder. Written in the Matlab software system, TLC is a user-friendly program that provides a graphical user interface that enables even an unfamiliar user to proceed, step by step, to the final result.

Posted in: Mechanics, Mechanical Components, Briefs

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Improved Lifetime for Stirling Cryogenic Coolers

Core-technology advances extend maintenance-free operating life of coolers to more than 50,000 hours. A Stirling cooler is a mechanical system that approximates the ideal gas cycle. Often associated with airborne or portable cooling applications that require compact design and low input power, Stirling coolers are suitable for such applications because of their high efficiency. Compared to Gifford-McMahon and Joule-Thomson cycles, Stirling offers more than twice the cooling performance in the capacity range from 1-100 W. The coolers have a variety of military and commercial applications in infrared receivers and thermal imaging equipment.

Posted in: Mechanical Components, Briefs

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Software for Analyzing Root Causes of Process Anomalies

Root Cause Analysis (RoCA) is a computer program that assists analysts in understanding the root causes of process anomalies. As used here, “process anomalies” includes incidents that have caused, or that can potentially cause, injuries to personnel, damage to facilities, abnormal costs, or delays in processing. RoCA could be used, for example, in industry to investigate anomalies in production and by government agencies and airlines in investigating airplane accidents. Older software developed to aid such investigations offers limited capabilities for mapping the contribution of each root cause to a given process anomaly. Unlike the prior software, RoCA not only identifies root causes of process anomalies but also supports the identification of trends over multiple anomalies.

Posted in: Information Sciences, Briefs

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Oscillating-Flow Heat-Transfer and Pressure-Drop Test Rig

Test specimens are plugs of material representative of regenerator matrices of Stirling engines. The figure illustrates an apparatus for measuring heat-transfer and pressure-drop characteristics of porous plug specimens in oscillating flows. The apparatus is built around an oscillating-flow test rig that was originally designed for pressure-drop (but not heat-transfer) measurements and has since been modified and refined. The flows and specimens are chosen to be representative of those encountered in the regenerators of Stirling engines.

Posted in: Physical Sciences, Briefs

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