Special Coverage

Distributed Propulsion Concepts and Superparamagnetic Energy Harvesting Hummingbird Engine
Aerofoam
Wet Active Chevron Nozzle for Controllable Jet Noise Reduction
Magnetic Relief Valve
Locking Mechanism for a Flexible Composite Hinge
Active Aircraft Pylon Noise Control System
Unmanned Aerial Systems Traffic Management
Method of Bonding Dissimilar Materials
Sonar Inspection Robot System
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Nano-Multiplication-Region Avalanche Photodiodes and Arrays

Oxide embedding structures and nanoscale multiplication regions would afford improvements in performance. Nano- multiplication- region avalanche photodiodes (NAPDs), and imaging arrays of NAPDs integrated with complementary metal oxide/semiconductor (CMOS) active-pixel-sensor integrated circuitry, are being developed for applications in which there are requirements for high-sensitivity (including photoncounting) detection and imaging at wavelengths from about 250 to 950 nm. With respect to sensitivity and to such other characteristics as speed, geometric array format, radiation hardness, power demand of associated circuitry, size, weight, and robustness, NAPDs and arrays thereof are expected to be superior to prior photodetectors and arrays including CMOS active-pixel sensors (APSs), charge-coupled devices (CCDs), traditional APDs, and microchannelplate/ CCD combinations.

Posted in: Briefs, TSP, Electronics & Computers

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Disabling CNT Electronic Devices by Use of Electron Beams

Selected CNTs would be burned out. Bombardment with tightly focused electron beams has been suggested as a means of electrically disabling selected individual carbon-nanotubes (CNTs) in electronic devices. Evidence in support of the suggestion was obtained in an experiment in which a CNT field-effect transistor was disabled (see figure) by focusing a 1-keV electron beam on a CNT that served as the active channel of a field-effect transistor (FET).

Posted in: Briefs, TSP, Electronics & Computers

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Tailored Asymmetry for Enhanced Coupling to WGM Resonators

Surfaces are made to have optimum combinations of curvatures in orthogonal planes. Coupling of light into and out of whispering- gallery-mode (WGM) optical resonators can be enhanced by designing and fabricating the resonators to have certain non- axisymmetric shapes (see figure). Such WGM resonators also exhibit the same ultrahigh values of the resonance quality factor (Q) as do prior WGM resonators. These WGM resonators are potentially useful as tunable narrow-band optical filters having throughput levels near unity, high-speed optical switches, and low-threshold laser resonators. These WGM resonators could also be used in experiments to investigate coupling between high-Q and chaotic modes within the resonators.

Posted in: Briefs, TSP, Electronics & Computers

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Ski Binding Prototype Designed and Tested with FEA Software

Weight and strength of plastic and metal components were optimized with finite-element analysis. G3 Genuine Guide Gear (G3) of North Vancouver, British Columbia, Canada, is a specialized manufacturer of backcountry ski and safety equipment — including telemark bindings and accessories, climbing skins, and shovels and saws — designed for guides and avalanche professionals.

Posted in: Briefs, Manufacturing & Prototyping

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LiCoPO4 Cathode Layers for Thin-Film Batteries

Highest voltage thin-film batteries ever reported are demonstrated at low current densities. LiCoPO4 has been found to be a promising active cathode material for high-energy-density, thin-film, rechargeable electrochemical power cells. The potential of the charge/discharge plateau of a cell containing an LiCoPO4 cathode is 4.8 V — a value that compares favorably with the corresponding value of 3.8 V of a state-of-the art cell containing an LiCoO2 cathode.

Posted in: Briefs, TSP, Materials

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High-Temperature SMAs for Actuator Applications

Work output is comparable to conventional SMA alloys but with transition temperatures significantly exceeding those of conventional materials. Compositions and production processes have been developed for making NiTi-based shape-memory alloys (SMAs) that can be tailored for use as actuator materials at temperatures exceeding those of conventional alloys. Whereas conventional shape-memory alloys are limited to use at temperatures well below 100 °C due to low transformation temperatures, these high-temperature shape-memory alloys (HTSMAs) have transformation temperatures exceeding 300 °C while maintaining many of the other attributes associated with NiTi alloys, most importantly high work output (see Figure 1). Other attractive properties of this family of NiTiPt HTSMAs include usefully high values of tensile ductility, relatively narrow hysteresis, good oxidation resistance up to 600 °C, and excellent thermal and dimensional stability. Just as important, these alloys can be readily processed into various structural forms such as thin rod and fine-diameter wire by conventional processes (see Figure 2). These materials hold promise for expanding the variety of applications in which SMAbased actuators could be used.

Posted in: Briefs, TSP, Materials

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Integrated Force Method for Indeterminate Structures

Indeterminate structural-mechanics problems can now be solved systematically. Two methods of solving indeterminate structural-mechanics problems have been developed as products of research on the theory of strain compatibility. In these methods, stresses are considered to be the primary unknowns (in contrast to strains and displacements being considered as the primary unknowns in some prior methods). One of these methods, denoted the integrated force method (IFM), makes it possible to compute stresses, strains, and displacements with high fidelity by use of modest finite-element models that entail relatively small amounts of computation. The other method, denoted the completed Beltrami Mitchell formulation (CBMF), enables direct determination of stresses in an elastic continuum with general boundary conditions, without the need to first calculate displacements as in traditional methods.

Posted in: Briefs, TSP, Mechanical Components, Mechanics

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