29,521 research outputs found
Electromechanical rotary actuator operates over wide temperature range
Electromechanical rotary actuator, which operates over wide temperature range, contains a spring stop which has been calculated to limit internal deceleration loads to a magnitude equal to stall torque. Cryogenic capability is obtained by using dry lubricant on the gears and no lubrication on the bearings
Study of early nausea and vomiting response of swine to ionizing radiation Final technical progress report, 15 Sep. - 12 Dec. 1969
Early nausea and vomiting response of swine to ionizing radiation related to radiation dosage and effect on humans in space mission
An evaluation of the total quality management implementation strategy for the advanced solid rocket motor project at NASA's Marshall Space Flight Center
An evaluation of the NASA's Marshall Space Flight Center (MSFC) strategy to implement Total Quality Management (TQM) in the Advanced Solid Rocket Motor (ASRM) Project is presented. The evaluation of the implementation strategy reflected the Civil Service personnel perspective at the project level. The external and internal environments at MSFC were analyzed for their effects on the ASRM TQM strategy. Organizational forms, cultures, management systems, problem solving techniques, and training were assessed for their influence on the implementation strategy. The influence of ASRM's effort was assessed relative to its impact on mature projects as well as future projects at MSFC
Advanced fiber-composite hybrids--A new structural material
Introduction of metal foil as part of matrix and fiber composite, or ""sandwich'', improves strength and stiffness for multidirectional loading, improves resistance to cyclic loading, and improves impact and erosion resistance of resultant fiber-composite hybrid structure
Perfect Andreev Reflection of Helical Edge Modes in InAs/GaSb Quantum Wells
We present an experimental study of inverted InAs/GaSb composite quantum
wells in the hybridization regime and contacted by superconducting electrodes.
A front gate is used to vary the Fermi level into the mini-gap, where recent
experiments indicate existence of helical edge modes [arXiv:1105.0137]. Zero
bias dips in differential resistance are observed across the mini-gap,
suggesting transport dominated by Andreev reflection processes. Evolution of
the mini-gap differential resistance with applied bias as well as measured
mini-gap excess current of 150 nA are in good agreement with the prediction of
perfect Andreev reflection of the helical edge modes, which is necessitated by
the absence of back-scattering channels. The perfect Andreev reflection occurs
in spite of a finite barrier at the interface and shows strong sensitivity to
time-reversal breaking - hallmarks of the helical nature of quantum spin Hall
edges
Magnetic properties of microtektites Semiannual status report, 1 Jan. - 31 Jun. 1969
Magnetic susceptibility, magnetization, and Curie constants for normal and bottle-green microtektites found in deep-sea sediment core
Test evaluation of fuel cell catalysts Quarterly report, 15 Feb. - 15 May 1967
Catalytic activity of iron compounds for fuel cell catalyst
Efficient diagnosis of multiprocessor systems under probabilistic models
The problem of fault diagnosis in multiprocessor systems is considered under a probabilistic fault model. The focus is on minimizing the number of tests that must be conducted in order to correctly diagnose the state of every processor in the system with high probability. A diagnosis algorithm that can correctly diagnose the state of every processor with probability approaching one in a class of systems performing slightly greater than a linear number of tests is presented. A nearly matching lower bound on the number of tests required to achieve correct diagnosis in arbitrary systems is also proven. Lower and upper bounds on the number of tests required for regular systems are also presented. A class of regular systems which includes hypercubes is shown to be correctly diagnosable with high probability. In all cases, the number of tests required under this probabilistic model is shown to be significantly less than under a bounded-size fault set model. Because the number of tests that must be conducted is a measure of the diagnosis overhead, these results represent a dramatic improvement in the performance of system-level diagnosis techniques
Boron/aluminum graphite/resin advanced fiber composite hybrids
Fabrication feasibility and potential of an adhesively bonded metal and resin matrix fiber-composite hybrid are determined as an advanced material for aerospace and other structural applications. The results show that using this hybrid concept makes possible a composite design which, when compared with nonhybrid composites, has greater transverse strength, transverse stiffness, and impact resistance with only a small penalty on density and longitudinal properties. The results also show that laminate theory is suitable for predicting the structural response of such hybrids. The sequence of fracture modes indicates that these types of hybrids can be readily designed to meet fail-safe requirements
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