Briefs: Physical Sciences
Simulations of Evolving Transitional Mixing Layers

A report describes direct numerical simulations of single- and two-phase, temporally developing transitional mixing layers at Reynolds numbers (based on the initial vorticity thickness and mean velocity difference) from 200 to 600. As many as 300 × 332 ×180 grid points were used to discretize...

Briefs: Physical Sciences
Simulations of a Transitional Droplet-Laden Mixing Layer

A report describes direct numerical simulations of a droplet-laden mixing layer (e.g., evaporating droplets of a hydrocarbon fuel in air) undergoing a transition to mixing turbulence. The governing equations are those of Lagrangian transport of discrete droplets through a flowing gas,...

Briefs: Physical Sciences
Thermodynamic Instability of InxGa1–xAs/GaAs Quantum Dots

A report describes experiments that generated evidence of thermodynamic instability of nanometer-size islands (quantum dots) in InxGa1–xAs grown on GaAs. InxGa1–xAs/GaAs specimens were grown by metal-organic chemical vapor deposition,...

Briefs: Manufacturing & Prototyping
Maskless Gray-Scale X-Ray Lithography

In a proposed technique of maskless gray-scale x-ray lithography, a photoresist to be patterned would be exposed to a parallel beam of hard x-rays. As explained below, the photoresist would be translated across the beam at a varying rate to effect one-dimensional spatial variations in the radiation dose...

Briefs: Photonics/Optics
Nonsaturating Electronic Image Sensors

Focal-plane electronic image sensors that would not saturate when exposed to intense illumination have been proposed. These sensors could be used to acquire accurate, scientific-quality data on images (including spectral images), even when the images contain both very bright and very dark areas. The...

Briefs: Photonics/Optics

A methodology for designing highly accurate readout circuits for infrared (IR) image detectors that have large pixel detector capacitances (of the order of tens of picofarads) and...

Briefs: Photonics/Optics

Efforts are under way to develop a technique of noncontact acousto-ultrasonic testing in which (1) a pulsed laser beam excites ultrasonic waves in a plate specimen and (2) the...

Briefs: Test & Measurement

A lightweight, low-power-consumption power supply has been developed to generate a combination of radio-frequency (RF) and dc voltages needed for the operation of a miniature quadrupole...

Briefs: Physical Sciences

A computer program (see figure) has been developed to serve as a time- and cost-effective means of automating thermal analyses of such hypersonic flight systems as the space shuttle orbiter, the...

Briefs: Physical Sciences

A computer program written within the Mathematica software system automatically generates FORTRAN computer codes that numerically simulate, with high accuracy, the acoustical...

Briefs: Physical Sciences

Dryden Flight Research Center has developed a computer program that performs signal management for analysis in real time (SMART). This program, called "SMART," has been effectively used since 1991...

Briefs: Mechanical & Fluid Systems
Comprehensive Micromechanics-Analysis Code (MAC/GMC)

Micromechanics Analysis Code With Generalized Method of Cells (MAC/GMC) is a comprehensive, user-friendly, efficient computer program that predicts the elastic and inelastic thermomechanical responses of continuous and discontinuous composite materials with arbitrary internal microstructures...

Briefs: Information Technology

Forth Source Code Analysis Tool Set (FSCATS) is a computer program that provides a wide range of capabilities for documenting, analyzing, and reverse-engineering computer programs written in the Forth...

Briefs: Electronics & Computers

Planar arrays of cadmium zinc telluride photodetectors with readout electronic circuitry have been developed for use as hard-x-ray and y-ray image sensors. When a coded,...

Briefs: Materials

Ceramics Analysis and Reliability Evaluation of Structures/Creep (CARES/CREEP) is a computer program that predicts the creep lives of ceramic structural components. [CARES/CREEP should not...

Briefs: Physical Sciences

The presence of corrosives in the Earth's atmosphere is of global concern. From acid rains that are destroying forests and disfiguring monuments like the Parthenon and the pyramids, to atmospheric pollutants that produce...

Briefs: Physical Sciences
Controlling Crystal-Growth Habit in Directional Freezing

A method of controlling the crystal-growth habit in directional freezing has been devised. A substance can be purified by directional-freeze crystallization, wherein (1) the liquid phase of the substance is partially frozen, causing impurities to become preferentially concentrated in the...

Briefs: Electronics & Computers

A transceiver has been developed to serve as a data-communication link between (1) the RS-232-standard serial communication port of a personal computer (PC) running the Windows 95 or Windows NT operating system...

Briefs: Electronics & Computers

Special-purpose, "intelligent," computer-controlled, highly miniaturized radio transceivers have been proposed for use in monitoring critical and/or valuable pieces of equipment....

Briefs: Electronics & Computers

A method of designing fault-tolerant networks of computers and other electronic circuits has been conceived with a view toward minimizing costs by utilizing commercial off-the-shelf (COTS)...

Briefs: Electronics & Computers

Innovative optoelectronic encoders for measuring absolute, linear or angular position with super-high resolution have been invented. The new encoders rely on a combination of high-accuracy...

Briefs: Motion Control

The figure illustrates an improved electronic circuit that generates a signal proportional to either the instantaneous vibrational velocity or the instantaneous position...

Briefs: Materials
Carbon Nanotubes as Anodes in Rechargeable Lithium-Ion Cells

Carbon nanotubes (also known as "bucky tubes") have shown promise for use as anode materials in rechargeable lithium-ion power cells. In comparison with graphite and other forms of carbon used under identical conditions, bucky tubes exhibit greater specific discharge capacity and...

Briefs: Motion Control
Pulse-Mode Reaction Control System Thruster

A spacecraft reaction-control-system (RCS) thruster now undergoing development generates a thrust of 870 lbf (3,870 N) by burning ethanol and liquid oxygen (LOX), which are nontoxic. The performance of the thruster has been tested in operation in multiple pulse modes with pulses as short as 160 ms;...

Briefs: Motion Control

The figure illustrates an improved electronic circuit that excites constant-magnitude vibrations in an electrostatically actuated, capacitively sensed mechanical resonator. The circuit...

Briefs: Motion Control

Single crystals of Tb-Dy alloys exhibit magnetostrictive strains approaching 1 percent and can generate forces sufficiently large to make them useful as actuators in cryogenic...

Briefs: Motion Control

This is the first of four articles that address various issues concerning the generation and utilization of electronic signals in the operation of micromachined planar vibratory...

Briefs: Electronics & Computers

Fatigue cracks and plastic deformation of parts in jet aircraft engines could be detected, even during engine operation, by use of proposed in situ monitoring devices called "wireless...

Briefs: Motion Control

Electronic circuitry has been devised to compensate for variations in the resonance quality factor (Q) of a planar vibratory microgyroscope like that described in the first of the...

Trending Stories

Briefs: Mechanical & Fluid Systems

Finned Carbon-Carbon Heat Pipe With Potassium Working Fluid

Articles: Manufacturing & Prototyping

What Does Resolution Mean in 3D Printing?

NASA Spinoff: Materials

Nanotechnology Repairs Engine Damage in Cars

Technology Leaders: Energy

Supercapacitors Go Hybrid for Increased Performance and Efficiency

Briefs: Sensors/Data Acquisition

Gas Biosensors “See” Through Soil to Analyze Microbial Interactions

NASA Spinoff: Manufacturing & Prototyping

Conducting the Heat

Videos