Multiloop Rapid-Rise/Rapid Fall High-Voltage Power Supply

A proposed multiloop power supply would generate a potential as high as 1.25 kV with rise and fall times <100 μs. This power supply would, moreover, be programmable to generate output potentials from 20 to 1,250 V and would be capable of supplying a current of at least 300 μA at 1,250 V. This power supply is intended to be a means of electronic shuttering of a microchannel plate that would be used to intensify the output of a charge-coupled-device imager to obtain exposure times as short as 1 ms. The basic design of this power supply could also be adapted to other applications in which high voltages and high slew rates are needed. At the time of reporting the information for this article, there was no commercially available power supply capable of satisfying the stated combination of voltage, rise-time, and fall-time requirements.

Posted in: Briefs, Electronics & Computers, High voltage systems, High voltage systems

Applications for Subvocal Speech

research and development effort now underway is directed toward the use of subvocal speech for communication in settings in which (1) acoustic noise could interfere excessively with ordinary vocal communication and/or (2) acoustic silence or secrecy of communication is required. By “subvocal speech” is meant sub-audible electromyographic (EMG) signals, associated with speech, that are acquired from the surface of the larynx and lingual areas of the throat. Topics addressed in this effort include recognition of the sub-vocal EMG signals that represent specific original words or phrases; transformation (including encoding and/or enciphering) of the signals into forms that are less vulnerable to distortion, degradation, and/or interception; and reconstruction of the original words or phrases at the receiving end of a communication link. Potential applications include ordinary verbal communications among hazardous- material-cleanup workers in protective suits, workers in noisy environments, divers, and firefighters, and secret communications among law enforcement officers and military personnel in combat and other confrontational situations.

Posted in: Briefs, Electronics & Computers, Acoustics, Acoustics

A 640 x 512-Pixel Portable Long-Wavelength Infrared Camera

This hand-held camera shows promise for imaging at high thermal resolution.

A portable long-wavelength infrared electronic camera having a cutoff wavelength of 9 μm has been built around an image sensor in the form of a 640 × 512- pixel array of AlxGa1–xAs/GaAs quantum well infrared photodetectors (QWIPs). This camera is an intermediate product of a continuing program to develop high-resolution, high-sensitivity infrared cameras.

Posted in: Briefs, TSP, Electronics & Computers, Imaging, Imaging and visualization, Imaging, Imaging and visualization

An Array of Optical Receivers for Deep-Space Communications

This array would be considerably simpler and less expensive to implement.

An array of small optical receivers is proposed as an alternative to a single large optical receiver for high-data-rate communications in NASA’s Deep Space Network (DSN). Because the telescope for a single receiver capable of satisfying DSN requirements must be greater than 10 m in diameter, the design, building, and testing of the telescope would be very difficult and expensive. The proposed array would utilize commercially available telescopes of 1- m or smaller diameter and, therefore, could be developed and verified with considerably less difficulty and expense.

Posted in: Briefs, TSP, Electronics & Computers, Optics, Optics, Test equipment and instrumentation

Composite Elastic Skins for Shape-Changing Structures

Anisotropic stiffness properties can be tailored for specific applications.

Composite elastic skins having tailorable mechanical properties have been invented for covering shape-changing (“morphable”) structures. These skins are intended especially for use on advanced aircraft that change shapes in order to assume different aerodynamic properties.

Posted in: Briefs, TSP, Materials, Composite materials, Elastomers, Aircraft

Glass/Ceramic Composites for Sealing Solid Oxide Fuel Cells

Ceramic fillers in a glass contribute to strength and fracture toughness.

A family of glass/ceramic composite materials has been investigated for use as sealants in planar solid oxide fuel cells. These materials are modified versions of a barium calcium aluminosilicate glass developed previously for the same purpose. The composition of the glass in mole percentages is 35BaO + 15CaO + 5Al2O3 + 10B2O3 + 35SiO2. The glass seal was found to be susceptible to cracking during thermal cycling of the fuel cells.

Posted in: Briefs, TSP, Materials, Fuel cells, Ceramics, Composite materials, Glass

Manufacturing Large Membrane Mirrors at Low Cost

Shapes are determined by edge retention fixtures rather than by precise molds.

Relatively inexpensive processes have been developed for manufacturing lightweight, wide-aperture mirrors that consist mainly of reflectively coated, edge-supported polyimide membranes. The polyimide and other materials in these mirrors can withstand the environment of outer space, and the mirrors have other characteristics that make them attractive for use on Earth as well as in outer space:

Posted in: Briefs, Manufacturing & Prototyping, Mirrors, Manufacturing processes

Double-Vacuum-Bag Process for Making Resin-Matrix Composites

To prevent formation of voids, volatiles are removed before applying consolidation pressure.

A double-vacuum-bag process has been devised as a superior alternative to a single-vacuum-bag process used heretofore in making laminated fiber-reinforced resin-matrix composite-material structural components. This process is applicable to broad classes of high-performance matrix resins — including polyimides and phenolics — that emit volatile compounds (solvents and volatile by-products of resin-curing chemical reactions) during processing. The superiority of the double-vacuum-bag process lies in enhanced management of the volatile compounds. Proper management of volatiles is necessary for making composite material components of high quality: if not removed and otherwise properly managed, volatiles can accumulate in interior pockets as resins cure, thereby forming undesired voids in the finished products.

Posted in: Briefs, Manufacturing & Prototyping, Composite materials, Resins

Surface Bacterial-Spore Assay Using Tb3+/DPA Luminescence

A total spore count could be obtained in minutes.

Equipment and a method for rapidly assaying solid surfaces for contamination by bacterial spores are undergoing development. The method would yield a total (nonviable plus viable) spore count of a surface within minutes and a viable-spore count in about one hour. In this method, spores would be collected from a surface by use of a transparent polymeric tape coated on one side with a polymeric adhesive that would be permeated with one or more reagent(s) for detection of spores by use of visible luminescence. The sticky side of the tape would be pressed against a surface to be assayed, then the tape with captured spores would be placed in a reader that illuminates the sample with ultraviolet light and counts the green luminescence spots under a microscope to quantify the number of bacterial spores per unit area. The visible luminescence spots seen through the microscope would be counted to determine the concentration of spores on the surface.

Posted in: Briefs, TSP, Bio-Medical, Medical, Medical equipment and supplies, Test procedures

Simplified Microarray Technique for Identifying mRNA in Rare Samples

This method can be implemented by use of portable equipment.

Two simplified methods of identifying messenger ribonucleic acid (mRNA), and compact, low-power apparatuses to implement the methods, are at the proof-of-concept stage of development. These methods are related to traditional methods based on hybridization of nucleic acid, but whereas the traditional methods must be practiced in laboratory settings, these methods could be practiced in field settings.

Posted in: Briefs, TSP, Bio-Medical, Medical, Biological sciences, Medical, health, and wellness

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