March 1999

Briefs : Robotics, Automation & Control
Engines for Remotely Piloted Atmospheric-Science Airplanes

A spark-ignited reciprocating gasoline engine, intake-pressurized with three cascaded stages of turbocharging, was selected by NASA's Environmental Research Aircraft and Sensor Technology (ERAST) Program, managed at the Dryden Flight Research Center, to propel the next generation of...

Briefs : Mechanical & Fluid Systems
Stable, Soft-Opening/Soft-Closing Pressure-Relief Valves

Improved pressure-relief valves have been developed for systems that contain gases and liquids in a variety of pneumatic, hydraulic, and cryogenic applications. These valves could prove especially beneficial in both cryogenic and noncryogenic systems that contain oxygen. The improved...

Briefs : Physical Sciences
Inflatable Fresnel Lenses as Concentrators for Solar Power

Inflatable Fresnel lenses are being developed for use as optical concentrators in solar power systems. These lenses are of two types: dome (point-focus) lenses and cylindrical (line-focus) lenses (see Figure 1). Originally intended for supplying power to spacecraft, these lenses might...

Briefs : Physical Sciences
Hybrid Acoustic/Electrostatic Levitation Apparatus

The figure schematically illustrates a developmental automated hybrid acoustic/electrostatic apparatus for levitating both electrically charged and electrically neutral liquid drops with sizes up to about 1 mm. The apparatus is particularly suitable for experiments on the growth of protein...

Briefs : Physical Sciences
Low-Distortion Imaging Spectrometers

"Pushbroom" imaging spectrometers of a proposed type would exhibit little or no distortion in either the spectral or spatial direction. These spectrometers would feature modified Offner optics, which afford a desirable combination of compactness and a high degree of optical correction. Although Offner optics...

Briefs : Photonics/Optics
Highly Stable Lateral-Transfer Retroreflectors

Lateral-transfer optical retroreflectors can now be made extremely stable to both external and internal fluctuations and gradients of temperature. As explained in more detail in the fourth paragraph, this high stability is achieved through improvements in design and fabrication.

Briefs : Information Technology
Improvements in Generating and Using Unstructured CFD Grids

Some recent and continuing efforts to develop a software system for simulations of flows in gas-turbine combustors by Computational Fluid Dynamics (CFD) have addressed such major issues as the integration of CAD (Computer Aided Design) data for grid generation purposes. The generation...

Briefs : Manufacturing & Prototyping
Mounting Heater Wires on Glass Capillary-Heat-Transfer Tubes

Two mounting schemes were devised for attaching heater wires to special-purpose glass tubing used in a capillary-heat-transfer experiment. Not only were the wires required to supply heat needed for the experiment; in addition, it was required that the liquid and vapor enclosed by the...

Briefs : Mechanical & Fluid Systems
Noise-Reducing Fairings for Flush-Mounted Microphones

Streamlined fairings have been invented for housing single or multiple microphones to measure noise in flowing gases and liquids. Each fairing of this type is designed to minimize the spurious (background) component of noise generated by local flow disturbances caused by the fairing itself....

Briefs : Information Technology
ParVox - a Parallel-Processing Software for Volume Rendering of Data

ParVox is a distributed visualization system consisting of a rendering core running on a parallel computer and a graphic user interface program (GUI) running on a Unix workstation. The ParVox system is designed for interactive, distributed visualization of large multiple time...

Briefs : Physical Sciences
Properties of Ni/Zr Melts Related to Formability of Glasses

A report describes a study of the relationships between (1) the viscosities and specific volumes of Ni/Zr melts and (2) the formability of Ni/Zr-alloy metallic glasses. Experiments were performed on electrostatically levitated, radiantly heated molten specimens of two compound-forming...

Briefs : Photonics/Optics
Optical Diagnostics of High-Pressure Liquid Fuel Sprays

A report describes experiments in which nonintrusive optical diagnostic techniques were applied to high-pressure fuel sprays in simulated advanced turbine-engine combustor environments. The experiments involved three different fuel injectors in two unique optically accessible combustors: a...

Briefs : Software
Software Detects Small Satellites in Spacecraft Imagery

A computer program processes images acquired at different times by instrumentation aboard a spacecraft to detect small satellites of asteroids and other planetary bodies. The program coregisters the images, removes instrument artifacts and images of background stars, and performs a...

Briefs : Physical Sciences
The Lewis Number Under Supercritical Conditions

An effective Lewis number has been defined for two-fluid mixtures under conditions of (1) supercritical temperature and pressure and (2) large gradients of temperature and composition. The Lewis number is a measure of the ratio between characteristic lengths for diffusion of heat and diffusion of...

Briefs : Materials
Room-Temperature, Ultraviolet Curing of Polyimides

Polyimides have been used widely in fiber-reinforced composite materials for aerospace components and in thin films for packaging of electronic circuitry. Typically, the synthesis of a material of this type involves the condensation of a diamine with a dianhydride. This synthesis also produces...

Briefs : Photonics/Optics
Wide-Angle, Open-Faced Retroreflectors for Optical Metrology

Wide-angle, open-faced retroreflectors of a proposed type would be constructed by use of traditional corner-cube reflectors as building blocks. Wide-angle retroreflectors are needed in optical stellar interferometry, and in other branches of highly precise laser metrology; in...

Briefs : Mechanical & Fluid Systems
Push/Pull Four-Point-Bending Apparatus

The figure depicts an improved apparatus for three- or four-point bending tests of stripe specimens. In a bending test, the specimen is subjected to tension along its top surface and compression along its bottom surface, or vice versa. A three- or four-point bending fixture of older design is capable of...

Briefs : Physical Sciences
Model of Interacting O₂ Drops Surrounded by H₂ at High Pressure

A mathematical model has been developed to predict the behavior of mutually interacting drops of a first fluid surrounded by a second fluid, under quiescent conditions at supercritical temperature. The model has been specialized to represent the behavior of drops of liquid...

Briefs : Physical Sciences
On the Validity of Using Assumed PDFs in Modeling Two-Phase Mixing

A report describes an investigation of the validity of using statistical methods based on single-point probability density functions (PDFs) in mathematical modeling of mixing between a turbulently flowing carrier gas and the vapor from liquid drops suspended in the gas. The...

Briefs : Photonics/Optics
Composing Flow-Streak Images From Colorized Particle Images

A method for making a flow visible in a plane and determining in-plane velocities involves the digitization and digital processing of a sequence of monochrome video images of particles entrained in the flow. The particle-laden flow passes through a sheet of laser or lamp light in the...

Briefs : Software
Easy-to-Use Software for Planning and Scheduling

The Automated Planning and Scheduling Environment (ASPEN) version 2 computer program comprises a modular, reconfigurable software framework and collection of software components that can be used for automated planning and scheduling in a variety of applications. ASPEN can automatically generate...

Briefs : Mechanical & Fluid Systems
Using Genetic Algorithms in Spacecraft Vibration Control

Three software products are being developed to help satisfy the needs of NASA and of private industry for reconfigurable active control systems to suppress vibrations in Reusable Launch Vehicles (RLVs) and other structures. These potentially highly marketable products are the...

Briefs : Software
Recursive and Adjacency Algorithms for Ranking Hypotheses

A library of computer programs has been developed to solve the problem of parametric ranking of a set of hypotheses on the basis of incomplete and/or uncertain information. In general, the ranking must be learned by use of training examples in which one observes the values of random...

Briefs : Materials
Diffusing Hf and Si Into Aluminide Bond Coats for TBCs

A process for making superior diffusion platinum-aluminide bond coats for plasma-sprayed or physical-vapor-deposited thermal-barrier coats (TBCs) on superalloy substrates has been devised. The novel aspect of the process lies in the use of several relatively inexpensive pack diffusion steps...

Briefs : Electronics & Computers
Study of Mixed-Norm Controllers for Suppressing Vibrations

A report describes a study of nominal-performance (H2), robust-performance (μ-synthesis), and mixed H2/μ methods for designing fixed-order controllers applied to an active-tendon control system for suppressing seismic vibrations in a structure. The study involves...

Briefs : Mechanical & Fluid Systems
Two Techniques for Controlling Altitudes of Lifting Balloons

Two techniques have been proposed (see figure) for controlling the buoyancies and thus the altitudes of robotic lifting balloons (aerobots) that would carry scientific instruments for exploration of Mars. Buoyancy-control techniques other than these have been, variously, used on Earth...

Briefs : Physical Sciences
Mathematical Model of Vortex Pyrolysis of Biomass

A mathematical model has been developed for analyzing the steady-state performances of vortex pyrolysis reactors used to convert particles of raw biomass materials (usually small wood chips) into char, tar, and gas. Optimal designs are usually considered to be those that maximize the production...

Briefs : Electronics & Computers
Algorithm for Equalizing Rectangular Signal Constellations

A rectangular-constellation-based blind-equalization (RECBEQ) technique implemented by a real-time, recursive algorithm has been developed to improve the performances of radio receivers in recovering unknown signals that are modulated with digital information and that have been distorted...

Briefs : Physical Sciences
Model of a Drop of O₂ Surrounded by H₂ at High Pressure

A mathematical model has been developed to predict the behavior of an isolated drop of a first fluid surrounded by a second fluid, under quiescent conditions at supercritical temperature and pressure. The model has been specialized to represent the behavior of a drop of liquid oxygen...

Briefs : Physical Sciences
Ultrasonic Profiling of an Object

A computer-controlled ultrasonic C-scan instrumentation system that was developed primarily for use in finding defects inside solid material specimens can also be used to obtain three-dimensional profiles of the top surfaces of such specimens. In some applications, ultrasonic profiling by use of this system...

Briefs : Electronics & Computers
Microwave Heating With Uniform Temperature History

Several microwave-cavity devices at various stages of development are designed for heating material samples or process streams with uniform temperature-versus-time histories. These devices could satisfy needs for heating according to well-regulated temperature-vs.-time schedules for batch and...

Briefs : Materials
Improved Synthesis of SnO Powder for Lithium-Ion Power Cells

An improved method of synthesis of crystalline tin monoxide (SnO) powder for use in anodes of lithium-ion electrochemical power cells has been developed. The carbon used in anodes of Li-ion cells is relatively expensive and difficult to produce, and SnO has been found potentially...

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