Special Coverage

Transducer-Actuator Systems for On-Machine Measurements and Automatic Part Alignment
Wide-Area Surveillance Using HD LWIR Uncooled Sensors
Heavy Lift Wing in Ground (WIG) Cargo Flying Boat
Technique Provides Security for Multi-Robot Systems
Bringing New Vision to Laser Material Processing Systems
NASA Tests Lasers’ Ability to Transmit Data from Space
Converting from Hydraulic Cylinders to Electric Actuators
Automating Optimization and Design Tasks Across Disciplines
Vibration Tables Shake Up Aerospace and Car Testing
Supercomputer Cooling System Uses Refrigerant to Replace Water

RS Forward Error Correction for Variable-Length Frames

Method accommodates dynamically varying frame length.

A method of forward error correction by Reed-Solomon (RS) coding has been devised to increase the link margins of data-communication systems that must handle variable-length frames or packets of data. Heretofore, RS coding has involved fixed-length blocks: In order to encode variable-length frames, it has been necessary to (a) choose a fixed block length equal to a multiple of some given block length and greater than or equal to the length of the longest variable-length frame and (b) in the case of a frame shorter than the fixed block length, pad or fill the remainder of the block with extra bytes. This is very inefficient because the fill conveys no useful information, and any errors in the fill diminish the overall coding gain by using up some or all of the available error-correction capacity.

Posted in: Briefs, Information Sciences, Communication protocols, Data exchange, Communication protocols, Data exchange

Fast NRZLM Encoding and Decoding Algorithm

Byte-oriented algorithms save time.

A recently developed algorithm saves encoding and decoding time in the operation of data-communication systems that utilize the NRZM code, which is derived from the better-known non-return-to-zero-level (NRZL) code. This algorithm utilizes lookup tables that contain the results of routine encoding and decoding computations that would otherwise have to be performed repeatedly.

Posted in: Briefs, TSP, Information Sciences, Mathematical models, Communication protocols, Cryptography, Communication protocols, Cryptography

Polyaniline Compounds for Protection Against Corrosion

Protective surface layers can be formulated and applied in various ways.

Corrosion of iron and steel substrates can be inhibited by coating them with any of the wide variety of compounds denoted generally as polyanilines. A polyaniline suitable for this type of application can be in either an electrically conductive salt (doped) form or an electrically nonconductive base form. Typically, polyaniline is dissolved in an organic solvent and the resulting solution is applied to a substrate by spraying, dipping, or brushing. The solvent is then allowed to evaporate leaving the substrate coated with a solid film of polyaniline, typically 1 to 200µm thick.

Posted in: Briefs, TSP, Materials, Coatings Colorants and Finishes, Coatings, colorants, and finishes, Corrosion resistant alloys, Iron, Polymers, Steel

Program Predicts Jet Noise

MGBK is a computer program that predicts the mixing noise and the shock noise generated by a subsonic or low-supersonic jet, given input data on the mean flow and turbulence fields as predicted by a suitable state-of-the-art computational fluid dynamics (CFD) program. More specifically, MGBK can be regarded as a post-processing program for use with a CFD program that computes a Reynolds-averaged Navier-Stokes solution with turbulence represented by a mathematical model of a type known in the art as "k — e" [in which k denotes the time-averaged kinetic-energy density associated with the local fluctuating (turbulent) component of flow, while e denotes the time-averaged rate of dissipation of this turbulent-kinetic-energy density]. The predictions generated by MGBK are in the forms of sound-pressure levels and frequency spectra on arcs or sidelines.

Posted in: Briefs, Software, Computational fluid dynamics, Noise, Noise, Jet engines, Hypersonic and supersonic aircraft

Program for Analyzing Static Transmission Error of Helical Gears

The computer program HeliStat performs finite-element analysis to simulate meshing of helical gears. This program is a logical extension of the program DANST, which applies to spur gears. [DANST was described in "Computing Stresses in Spur Gears (LEW-15420), NASA Tech Briefs, Vol. 19, No. 12 (December 1995), page 73 and "Updated Program for Computing Stresses in Spur Gears (LEW-16575) NASA Tech Briefs, Vol. 22, No. 8 (August 1998), page 59.]

Posted in: Briefs, Software, Finite element analysis, Computer software / hardware, Computer software and hardware, Computer software / hardware, Computer software and hardware, Gears

Software for Multidisciplinary Analysis of Optical Systems

Integrated Modeling of Optical Systems (IMOS) is a MATLAB™ computer program that provides many functions for analysis of a system represented by mathematical models of its thermal, structural, control, and/or optical aspects. For example, IMOS can be used to study thermal distortion of structural components of an optical instrument and the resulting degradation of optical performance. Heretofore, such an analysis would have entailed the use of separate programs to perform thermal, structural, control, and optical sub-analyses. The uniqueness of IMOS lies in the possibility of performing the entire analysis in one program. The common MATLAB!" software environment offers several advantages, including capabilities for optimizing the design of a system on the basis of multidisciplinary (e.g., thermal and optical) criteria and a capability for optimizing the designing of the control subsystem. IMOS provides interfaces between itself and several other programs, including NASTRAN to IMOS, IMOS to SINDA, IMOS to TSS, and IMOS to MACOS. Both MATLAB and IMOS have plotting capabilities that assist in visualization of results.

Posted in: Briefs, Software, Analysis methodologies, Computer software / hardware, Computer software and hardware, Optics, Computer software / hardware, Computer software and hardware, Optics

Software for Multidisciplinary Analysis of Graded Composites

The Coupled Structural/Thermal/Electromagnetic (CSTEM) computer program implements an integrated multidisciplinary approach to analysis and optimization of the designs of graded composite-material structures. The name of the program reflects recognition of the coupling among thermal, electromagnetic, mechanical, and other phenomena in such structures. The integrated multidisciplinary approach is necessary because the coupling among the phenomena gives rise to complexity and contributes to nonlinearity in the characteristics and responses of the structures, such that separate analyses of a structure according to traditionally separate disciplines (e.g., acoustics, structural vibrations, structural loads, thermal effects, and electromagnetic properties taken by themselves) could lead to erroneous conclusions.

Posted in: Briefs, Software, Analysis methodologies, Computer software / hardware, Computer software and hardware, Computer software / hardware, Computer software and hardware, Composite materials

Electrically Isolating, Thermally Coupling Devices

Digital signals would be coupled thermally instead of electrically or optically.

Integrated signaling devices of a proposed type would utilize thermal coupling to transfer digital signals between electronic circuits that are required to be kept electrically isolated from each other. The proposed devices would be implemented as silicon-on-insulator complementary metal oxide/semiconductor (SOI CMOS) integrated circuits and could therefore be readily integrated with other SOI CMOS devices. For some applications, the proposed devices could be an attractive alternative to conventional optocouplers, which have not been amenable to integration with CMOS devices because of a lack of silicon-based integrated sources of light.

Posted in: Briefs, TSP, Electronics & Computers, Integrated circuits, Integrated circuits

Improved Coatings for Flexible Insulating Blankets

These materials offer increased resistance to erosion.

"ACE" (for "advanced ceramic engineered") denotes a type of coating mate-rial that increases the ability of flexible thermal-insulation blankets to resist erosion. Developed for use on the insulating blankets on the space shuttle orbiters, these coating materials could also be used on similar terrestrial insulating blankets on aircraft, engine, and furnace components.

Posted in: Briefs, Materials, Coatings Colorants and Finishes, Coatings, colorants, and finishes, Insulation

Improved Ignitor and Keeper Power Supplies for Hall Thruster

The key to reliable operation of a cold cathode is correct power-supply waveforms.

Ignitor and keeper power supplies have been developed specifically for a Hall-effect thruster with a cold cathode. Prior to the development of these power supplies, difficulties had been observed in the operation of cold-cathode Hall thrusters; in particular, they did not start reliably upon turn-on of power. Many specialists in Hall thrusters had attributed the difficulties to the characteristics of cold cathodes as distinguished from those of hot cathodes.

Posted in: Briefs, Electronics & Computers

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