JANTX1N2989B zener diode
Report evaluates effects of power and temperature overstress on General Semiconductor and Siemens devices. Mechanical disruption is prominent failure mode. Other failures are described.
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Results for “Effectiveness evaluation”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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JANTX1N3016B zener diode
Report evaluates effects of power and temperature overstress on Motorola and Siemens devices. Reverse bias leakage maximum limit failure and Zener-breakdown maximum limit failure were common. Other failures are described.
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JANTX2N2605 transistor
Report evaluates effects of power and temperature overstress on Raytheon and National Semiconductor devices. Breakdown voltage hysteresis, possibly due to contamination of semiconductor by gold from leads, was prominent.
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JANTX2N2905A transistor
Report evaluates effects of power and temperature overstress on Motorola and Texas Instruments devices. A variety of failure modes are described.
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JANTX2N3811 dual transistor
Report evaluates effects of power and temperature overstress on Motorola and National Semiconductor devices. National Semiconductor devices exceeded 50 percent failure after 160 hours at 225 deg C. Motorola suffered more rejects but failures occurred at 300 deg C. Difference in lead bonding technique may explain performance.
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JANTX2N4150 transistor
Report evaluates effects of power and temperature overstress on General Semiconductor and Transitron devices. General Semiconductor lot exceeded 50 percent failure 500 hours into 125 percent maximum rated power test. Catastrophic failure rates differed between manufacturers. Modes of failure are analyzed.
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Selecting optimum algorithms for image processing
Collection of registration, compression, and classification algorithms allows users to evaluate approaches and select best one for particular application. Program includes six registration algorithms, six compression algorithms, and two classification algorithms. Package also includes routines for evaluating effects of processing on image data. Collection is written in FORTRAN IV for batch execution.
Jaroe, R. R.↗
NASCAP modelling of environmental-charging-induced discharges in satellites
A study of the charging and discharging characteristics of a typical geosynchronous satellite experiencing time-varying geomagnetic substorms, in sunlight, is conducted. The NASA Charging Analyzer Program (NASCAP) is used. An electric field criteria of 1.5 x 10 to the 5th volts/cm to initiate discharges and transfer of 67% of the stored charge is used in this study, based on ground test results. The substorm characteristics are arbitrarily chosen to evaluate effects of electron temperature and particle density (which is equivalent to current density). It has been found that while there is a minimum electron temperature for discharges to occur, the rate of discharges is dependent on particle density and duration times of the encounter. Hence, it is important to define the temporal variations in the substorm environments.
Stevens, N. J.↗
Hybrid composites that retain graphite fibers on burning
A laboratory scale program was conducted to determine fiber release tendencies of graphite reinforced/resinous matrix composites currently used or projected for use in civil aircraft. In the event of an aircraft crash and burn situation, there is concern that graphite fibers will be released from the composites once the resin matrix is thermally decomposed. Hybridizing concepts aimed at preventing fiber release on burning were postulated and their effectiveness evaluated under fire, impact, and air flow during an aircraft crash.
House, E. E.↗
Analyzing Multirate-Sampled Systems
New method available for monitoring stability of system on basis of data sampled at multiple rates--in particular, at two rates, one of which is twice frequency of other. Method is called Multirate Matrix Frequency Response (MMFR) analysis. MMFR was used in Space Shuttle to evaluate effect of decreasing sample rate of error loop in ascent-phase digital autopilot. Should also be useful to designers of other control systems and to structural, civil, and mechanical engineers for structure and vibration analysis.
Hendrix, N.↗
Report of subpanel on inter-image matching
Research needs in the area inter-image matching for remote Earth observation systems are defined. Correlation considerations include types of correlation algorithms, preprocessing techniques, limits on subpixed accuracy, relief and atmospheric refraction effects, evaluation of success rate, and evaluation of accuracy. Also recommended are investigations of the interaction of inter-image matching procedures and selection of ground control points for a given sensor; global multisensor control point library feasibility; multiple control point considerations; centralized processing systems; and user systems.
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Design study of Software-Implemented Fault-Tolerance (SIFT) computer
Software-implemented fault tolerant (SIFT) computer design for commercial aviation is reported. A SIFT design concept is addressed. Alternate strategies for physical implementation are considered. Hardware and software design correctness is addressed. System modeling and effectiveness evaluation are considered from a fault-tolerant point of view.
Wensley, J. H.↗
Large-area sheet task advanced dendritic web growth development
The "discrete shield' temperature model was completed and verified. Modifications to the J419 low stress configuration were tested experimentally to evaluate effects on growth speed. A composite lid and shield configuration combining the low stress features of the J419 with the width limiting characteristics of the J98M3 was fabricated and tested in the N-furnace. Several long crystals were grown with width limited to about 3.3 cm and with melt replenishment, although the configuration is not yet optimized for steady state growth.
Duncan, C. S.↗
Streaming-Potential Studies
Apparatus and experimental technique based on measurements of streaming potentials evaluates effects of surface coatings for reducing or eliminating electro-osmotic flow.
Gregonis, D.↗
Dynamics of early planetary gear trains
A method to analyze the static and dynamic loads in a planetary gear train was developed. A variable-variable mesh stiffness (VVMS) model was used to simulate the external and internal spur gear mesh behavior, and an equivalent conventional gear train concept was adapted for the dynamic studies. The analysis can be applied either involute or noninvolute spur gearing. By utilizing the equivalent gear train concept, the developed method may be extended for use for all types of epicyclic gearing. The method is incorporated into a computer program so that the static and dynamic behavior of individual components can be examined. Items considered in the analysis are: (1) static and dynamic load sharing among the planets; (2) floating or fixed Sun gear; (3) actual tooth geometry, including errors and modifications; (4) positioning errors of the planet gears; (5) torque variations due to noninvolute gear action. A mathematical model comprised of power source, load, and planetary transmission is used to determine the instantaneous loads to which the components are subjected. It considers fluctuating output torque, elastic behavior in the system, and loss of contact between gear teeth. The dynamic model has nine degrees of freedom resulting in a set of simultaneous second order differential equations with time varying coefficients, which are solved numerically. The computer program was used to determine the effect of manufacturing errors, damping and component stiffness, and transmitted load on dynamic behavior. It is indicated that this methodology offers the designer/analyst a comprehensive tool with which planetary drives may be quickly and effectively evaluated.
August, R.↗
Water-Thickness Gage
Gage for determining depth of water buildup on outside of aircraft relatively simple to operate and yields result independent of conductivity of water. Gage used to evaluate effects of water on lift and detect water weight excesses. Dual-sensor gage eliminates effects of water conductivity, providing direct correlation between resistivity and water thickness.
Weinstein, L. M.↗
Preliminary investigations of protein crystal growth using the Space Shuttle
Four preliminary Shuttle experiments are described which have been used to develop prototype hardware for a more advanced system that will evaluate effects of gravity on protein crystal growth. The first phase of these experiments has centered on the development of micromethods for protein crystal growth by vapor-diffusion techniques (using a space version of the hanging-drop method) and on dialysis using microdialysis cells. Results suggest that the elimination of density-driven sedimentation can effect crystal morphology. In the dialysis experiment, space-grown crystals of concanavalin B were three times longer and 1/3 the thickness of earth-grown crystals.
Delucas, L. J.↗
Survey of computer programs for heat transfer analysis
An overview is given of the current capabilities of thirty-three computer programs that are used to solve heat transfer problems. The programs considered range from large general-purpose codes with broad spectrum of capabilities, large user community, and comprehensive user support (e.g., ABAQUS, ANSYS, EAL, MARC, MITAS II, MSC/NASTRAN, and SAMCEF) to the small, special-purpose codes with limited user community such as ANDES, NTEMP, TAC2D, TAC3D, TEPSA and TRUMP. The majority of the programs use either finite elements or finite differences for the spatial discretization. The capabilities of the programs are listed in tabular form followed by a summary of the major features of each program. The information presented herein is based on a questionnaire sent to the developers of each program. This information is preceded by a brief background material needed for effective evaluation and use of computer programs for heat transfer analysis. The present survey is useful in the initial selection of the programs which are most suitable for a particular application. The final selection of the program to be used should, however, be based on a detailed examination of the documentation and the literature about the program.
Noor, Ahmed K.↗