May 2000

Briefs : Test & Measurement
Instrument Measures Fluorescence From Chlorophyll in Plants

An optoelectronic instrument, known as a plant fluorescence sensor, is being developed for use as a working tool in agricultural settings. This instrument is a remote, passive monitor that provides a means of discerning plant stress at very early stages. With sufficient warning, the...

Briefs : Electronics & Computers
On-Chip Correction for Defective Pixels in an Image Sensor

A method of correcting for defective pixels in an integrated-circuit image sensor of the active-pixel sensor (APS) type has been proposed. The corrections would be made by additional readout circuitry on the image-sensor chips. By making it unnecessary to discard sensor chips that...

Briefs : Mechanical & Fluid Systems
Surface Micromachined Silicon Carbide Accelerometers

Surface micromachined silicon carbide accelerometers are undergoing development for eventual use in high-temperature environments like those inside turbines, internal-combustion engines, and other machines. These accelerometers would be used to measure vibrations indicative of deterioration of...

Briefs : Physical Sciences
Software for Predicting Behavior of a Pyrotechnic Actuator

A theoretical model that predicts the time-dependent behavior of a pyrotechnically actuated mechanism and a computer program that implements the model have been developed. The model and program are especially applicable to a pyrotechnic device known as the NASA Standard Initiator (NSI)....

Briefs : Physical Sciences
Dither Sensing for Controlling a Segmented-Mirror Telescope

Image-plane multidither sensing has been found to be suitable for adaptive wavefront correction in a large telescope in which the main optic is a precise reflector divided into lightweight, controllably actuated segments. In image-plane multidither sensing, the telescope is aimed at a...

Briefs : Physical Sciences
Self-Temperature-Compensated Ceramic Strain Gauges

Ceramic static-strain gauges capable of generating mechanical-strain signals much larger than spurious thermal signals have been invented. These gauges are intended for use at temperatures from room temperature to 1,250 °C. Heretofore, external circuits have been used to provide temperature...

Briefs : Physical Sciences
"Set and Hold With Power Off" Cryogenic Actuators

Magnetostrictive actuators that would hold their displacements with power turned off have been proposed for use at temperatures from about 10 to about 77 K. Such "set and hold with power off" actuators are attractive for effecting fine position adjustments in cryogenic scientific instruments,...

Briefs : Electronics & Computers
Electrobiotic Toxic-Agent Sensors

Electrobiotic sensors have been proposed for detecting toxic substances in a variety of environments. Electrobiotic sensors would be inexpensive, compact units that would be easy to use and could be deployed either singly or in large numbers, depending on the size of an environment to be monitored and/or the...

Briefs : Electronics & Computers
Magnetoelectric Sensors and Electric Generators

Electric generators and magnetic-field sensors of a proposed type would be based on the magnetoelectric effect. A simple device of this type (see figure) would consist mainly of an inner layer of a magnetoelectric material sandwiched between two outer layers of a ferromagnetic material. Electrical...

Briefs : Electronics & Computers
Submillimeter-Sized Bi2–xSbxTe3 Thermoelectric Devices

Submillimeter-sized thermoelectric devices based on thick films of Bi2–xSbxTe3 are undergoing development. As electronic circuits are designed with ever greater packaging densities and power densities, there is an increasing need for small thermoelectric...

Briefs : Electronics & Computers
High-Speed Complex-Amplitude Liquid-Crystal SLMs

High-speed complex-amplitude spatial light modulators (SLMs) containing liquid crystals with pixel electronic circuitry on single-crystal-silicon backplanes are undergoing development. The basic approach taken in this project is to use fast-switching liquid-crystal materials and...

Briefs : Test & Measurement
Laser Heating for Testing Rocket-Engine Insulating Phenolic

A continuous-wave CO2 laser has been selected as a source of heat for testing the thermal response of carbon-cloth phenolic like that used as insulating material in a reusable solid-fuel rocket motor (RSRM). The particular thermal response of interest, observed during...

Briefs : Software
SIMON — School Internet Manager Over Networks

School Internet Manager Over Networks (SIMON) is a software tool, exclusively for use on Macintosh computers, that is designed to provide access to, and management of, Internet information for teachers and students in kindergarten through twelfth grade. By eliminating the requirement for advanced...

Briefs : Materials
RTM-Processable Resins Containing Thermosetting Plasticizers

A number of matrix resins that contain thermosetting plasticizers have been developed for use in the resin-transfer molding (RTM) of composite-material (fiber/matrix) parts. These resins and composites are candidates for use in manufacturing lightweight components of aircraft engines...

Briefs : Mechanical & Fluid Systems
Molded Plastic Simulated Landscapes

Simulated landscapes of Mars have been made of thermoplastic sheets molded to shapes derived from images of the Martian terrain. These simulated landscapes can be used to advantage in scientific experiments, simulations, educational displays, and other applications, in which unitary molded plastic sheets...

Briefs : Materials
Burn-Resistant, Strong Nickel Alloys

Investigators at the Johnson Space Center White Sands Test Facility (WSTF) have developed specifications of the amounts of alloying elements needed to increase the specific strengths of nickel alloys while consistently maintaining their burn resistance. The issue of burn resistance versus strength arises...

Briefs : Materials
Aerogels With Gradients of Density

Aerogels with gradients in density have been produced in experiments, as part of an effort to develop materials that will be used in outer space to capture particles traveling at high speeds for the STARDUST mission.

Briefs : Photonics/Optics
Bleaching by Laser for Marking Black Anodized Aluminum

Irradiation by the beam from a CO2laser has been found to be an effective means of marking a black anodized aluminum surface. In general, this process works on any dark anodized surface. The beam is scanned over the surface to form a desired pattern. Depending on the...

Briefs : Photonics/Optics
Three-Color Focal-Plane Array of Infrared QWIPs

A proposed focal-plane array (FPA) of quantum-well infrared photodetectors (QWIPs) would sense images in three different infrared wavelength bands simultaneously. These and other QWIP infrared image sensors are undergoing development for use in measuring temperature distributions in images;...

Briefs : Photonics/Optics
Update on Fuzzy-Logic-Enhanced Digital-PIV Software

Two reports present additional information on the subject matter of "Software for Processing Data in Particle-Image Velocimetry" (LEW-16857),NASA Tech Briefs, Vol. 24, No. 1 (January 2000), page 26a. Like the cited prior article, both reports discuss the principles and the practical aspects of...

Briefs : Photonics/Optics
Two-Color Random Reflectors for QWIPs

Random reflectors of a proposed type would be fabricated on the back surfaces of quantum-well infrared photodetectors (QWIPs) to increase the coupling efficiency of infrared light into the QWIPs in two wavelength bands. A reflective surface according to this proposal would comprise an array of square cells,...

Briefs : Photonics/Optics
Tridirectional Gratings as Improved Couplers for QWIPs

Tridirectional diffraction gratings have been proposed to provide optical coupling to quantum-well infrared photodetectors (QWIPs) in focal-plane arrays. The tridirectional gratings would be improved versions of the bidirectional (rectangular-pattern) gratings described in "Cross-Grating...

Briefs : Photonics/Optics
Optical Filters Based on Dense Arrays of Microscopic Pillars

A proposal for development of a class of high-transmission and antireflection optical filters is derived from the observation that the eyes of moths reflect almost no light, regardless of the wavelength or the angle of incidence of illumination. The low-reflection property of moth...

Briefs : Photonics/Optics
Organic Light-Emitting Diodes (OLED) Have Many Potential Uses

Organic light-emitting diodes (OLEDs) are grounded in a self-luminous display technology based on thin organic films as the light emitter. Like conventional inorganic light-emitting diodes (LEDs), OLEDs require a low drive voltage to produce bright visible light. But unlike discrete...

Briefs : Photonics/Optics
Simplified Radiometer for Quantifying Aircraft Icing Hazard

A simplified microwave radiometric apparatus has been proposed for use in quantifying the potential danger of accretion of ice onto an aircraft flying through a cloud. The quantity of interest, called the "icing hazard potential" (IHP), is the product of (1) the liquid-water content...

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