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Shaping Diffraction-Grating Grooves To Optimize Efficiency

Spectral response of a grating could be tailored to complement responses of other components. A method of shaping diffraction-grating grooves to optimize the spectral efficiency, spectral range, and image quality of a spectral imaging instrument is under development. The method is based on the use of an advanced design algorithm to determine the possibly complex shape of grooves needed to obtain a desired efficiency- versus- wavelength response (see figure). Then electron- beam fabrication techniques are used to realize the required groove shape. The method could be used, for example, to make the spectral efficiency of the grating in a given wavelength range proportional to the inverse of the spectral efficiency of a photodetector array so that the overall spectral efficiency of the combination of the grating and the photodetector array would be flat. The method has thus far been applied to one-dimensional gratings only, but in principle, it is also applicable to two-dimensional gratings.

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Conical Bearingless Motor/Generators

Advantages include high-speed, long-life operation in a compact form factor. Motor/generators based on conical magnetic bearings have been invented as an improved alternative to prior such machines based, variously, on radial and/or axial magnetic bearings. Both the present and prior machines are members of the class of so-called “bearingless” or “self bearing” (in the sense of not containing mechanical bearings) rotary machines. Each motor/generator provides both a torque and force allowing it to either function as a motor and magnetic bearing or a generator and magnetic bearing concurrently. Because they are not subject to mechanical bearing wear, these machines have potentially long operational lives and can function without lubrication and over wide ranges of speed and temperature that include conditions under which lubricants would become depleted, degraded, or ineffective and mechanical bearings would fail.

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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.

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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.

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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: Materials, Briefs, TSP

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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.

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Split-Block Waveguide Polarization Twist for 220 to 325 GHz

This device is superior to conventional twisted rectangular waveguides for submillimeter wavelengths. Figure 1. A Channel Having Asymmetric Steps is cut into the lower block.An identical channel is cut into the upper block. Then with the help ofalignment pins, the blocks are assembled so that the two channels mergeinto one channel that makes a transition between two orthogonal orientationsof a WR-3 waveguide.A split-block waveguide circuit that rotates polarization by 90° has been designed with WR-3 input and output waveguides, which are rectangular waveguides used for a nominal frequency range of 220 to 325 GHz. Heretofore, twisted rectangular waveguides equipped with flanges at the input and output have been the standard means of rotating the polarizations of guided microwave signals. However, the fabrication and assembly of such components become difficult at high frequency due to decreasing wavelength, such that twisted rectangular waveguides become impractical at frequencies above a few hundred gigahertz. Conventional twisted rectangular waveguides are also not amenable to integration into highly miniaturized subassemblies of advanced millimeter- and submillimeter- wave detector arrays now undergoing development. In contrast, the present polarization-rotating waveguide can readily be incorporated into complex integrated waveguide circuits such as miniaturized detector arrays fabricated by either conventional end milling of metal blocks or by deep reactive ion etching of silicon blocks. Moreover, the present splitblock design can be scaled up in frequency to at least 5 THz.

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