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  • 1
    Publication Date: 2011-08-24
    Description: This paper describes the development of a gas collection and analysis system that is to be installed in the Eight-Foot High Temperature Tunnel (8' HTT) at NASA's Langley Research Center. This system will be used to analyze the test gas medium that results after burning a methane-air mixture to achieve the proper tunnel test parameters. The system consists of a sampling rake, a gas sample storage array, and a gas chromatographic system. Gas samples will be analyzed after each run to assure that proper combustion takes place in the tunnel resulting in a correctly balanced composition of the test gas medium. The proper ratio of gas species is critically necessary in order for the proper operation and testing of scramjet engines in the tunnel. After a variety of methane-air burn conditions have been analyzed, additional oxygen will be introduced into the combusted gas and the enriched test gas medium analyzed. The pre/post enrichment sets of data will be compared to verify that the gas species of the test gas medium is correctly balanced for testing of air-breathing engines.
    Keywords: RESEARCH AND SUPPORT FACILITIES (AIR)
    Type: In: International Instrumentation Symposium, 38th, Las Vegas, NV, Apr. 26-30, 1992, Proceedings (A93-37851 15-35); p. 581-596.
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  • 2
    Publication Date: 2011-08-24
    Description: Surface acoustic wave (SAW) piezoelectric devices are finding widespread applications in many arenas, particularly in the area of chemical sensing. We have developed an oxygen pressure sensor based on coating a SAW device with an oxygen binding agent which can be tailored to provide variable sensitivity. The coating is prepared by dissolving an oxygen binding agent in a toluene solution of a copolymer which is then sprayed onto the surface of the SAW device. Experimental data shows the feasibility of tailoring sensors to measure the partial pressure of oxygen from 2.6 to 67 KPa (20 to 500 torr). Potential applications of this technology are discussed.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: International Instrumentation Symposium, 39th, Albuquerque, NM, May 2-6, 1993, Proceedings (A93-54351 24-35); p. 161-176.
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  • 3
    Publication Date: 2011-08-24
    Description: BACKGROUND: Temporary shunt placement can quickly restore perfusion after extremity arterial injury. This study examined the adequacy of limb blood flow with shunt use, non-heparin-bonded shunt patency over prolonged periods, and the safety of this technique. METHODS: Common iliac arteries were divided and 4.0-mm Silastic Sundt shunts placed in 16 anesthetized pigs. Eight (group I) had shunts placed immediately; eight others (group II) were shunted after an hour of limb ischemia and hemorrhagic shock. Physiologic parameters and femoral artery blood flow in both hindlimbs were continuously monitored. Limb lactic acid generation, oxygen utilization, and hematologic and metabolic effects were serially evaluated for 24 hours. RESULTS: Shunts remained patent in 13 of 16 pigs. Shunts thrombosed in two group I animals because of technical errors, but functioned well after thrombectomy and repositioning. Patency could not be maintained in one animal that died from shock. Flow in group I shunted limbs was 57 (+/-11 SD) % of control. For group II animals in shock, shunted limb flow initially averaged 46 +/- 15% of control, but 4 hours after shunt placement, the mean limb blood flow was the same as in group I. Increased oxygen extraction compensated for the lower flow. Lactic acid production was not increased in comparison to control limbs. CONCLUSION: Shunts provided adequate flow in this model of extremity trauma. Correctly placed shunts stayed patent for 24 hours, without anticoagulation, if shunt placement followed resuscitation.
    Keywords: Life Sciences (General)
    Type: The Journal of trauma (ISSN 0022-5282); Volume 47; 1; 64-71
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  • 4
    Publication Date: 2011-08-19
    Description: A synchronous, strobed laser light sheet has been developed for use in flow visualization of a helicopter rotor model. The light sheet strobe circuit included selectable blade position, strobe duration, and multiple pulses per revolution for rotors having 2 to 9 blades. The flow was seeded with propylene glycol. Between runs, a calibration grid board was placed in the plane of the laser sheet and recorded with the video camera at the position used to record the flow field. A slip-sync mode permitted slow motion visualization of the flow field over complete rotations of the rotor. The system was used to make two-dimensional flow field cuts of a four-bladed rotor operating at advance ratio of 0.37 at wind tunnel speeds up to 79.25 meters per second (260 feet per second).
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: ISA Proceedings (ISSN 0227-7576); 9-22
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  • 5
    Publication Date: 2011-08-18
    Description: The spectral reflectance characteristics of vegetation have been studied with the objective to learn how to extract useful information about the state of surface vegetation from space-borne observing systems, with emphasis on agricultural applications. Results of simulation studies based on high-resolution airborne spectrometer data indicate that changes in biomass, plant pigment, and leaf water content can be independently tracked by monitoring the reflective properties of vegetation with an appropriate selection of bands.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
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  • 6
    Publication Date: 2013-08-29
    Description: A detailed comparison between optical and electrical interconnections is presented, with emphasis on advantages and drawbacks of optical link utilization. The impact of attenuation, dispersive degradation, and fan out on signal integrity is discussed. Reflections from discontinuities are taken into account in the section on fan out. According to our results, there is no obvious advantage of using optical interconnections for the distribution of digital signals containing significant frequency components in excess of 10 GHz, unless substantial distances are involved, for which low dispersion optical waveguides could provide a solution. The implementation of a polyimide optical waveguide in the MCNC package is discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Solid State Technology Branch of NASA Lewis Research Center; p 83-92
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  • 7
    Publication Date: 2013-08-31
    Description: How late Archean tectonics could be seen to have operated in the Slave Province is illustrated. Lithospheric thinning and stretching, with the formation of rifted margins (to continental or island arc fragments), and lithospheric flexural loading of the kind familiar in arcs and mountain belts could be discerned.
    Keywords: GEOPHYSICS
    Type: Lunar and Planetary Inst., Workshop on the Deep Continental Crust of South India; p 79-80
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  • 8
    Publication Date: 2018-06-05
    Description: Temperature sensitive paints (TSP s) have recently been used to detect small temperature differences on aerodynamic model surfaces. These types of applications impose stringent performance requirements on a paint system. The TSP s must operate over a broad temperature range, must be physically robust (cannot chip or peel), must be polishable to at least the smoothness of the model surface, and must have sufficient sensitivity to detect small temperature differences. TSP coatings based on the use of metal complexes in polymer binders were developed at NASA Langley Research Center which meet most of the requirements for detection of small temperature differences under severe environmental conditions.
    Keywords: Spacecraft Propulsion and Power
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  • 9
    Publication Date: 2019-06-28
    Description: With traditional event list techniques, evaluating a detailed discrete event simulation model can often require hours or even days of computation time. Parallel simulation mimics the interacting servers and queues of a real system by assigning each simulated entity to a processor. By eliminating the event list and maintaining only sufficient synchronization to insure causality, parallel simulation can potentially provide speedups that are linear in the number of processors. A set of shared memory experiments is presented using the Chandy-Misra distributed simulation algorithm to simulate networks of queues. Parameters include queueing network topology and routing probabilities, number of processors, and assignment of network nodes to processors. These experiments show that Chandy-Misra distributed simulation is a questionable alternative to sequential simulation of most queueing network models.
    Keywords: COMPUTER SYSTEMS
    Type: NASA-CR-180616 , NAS 1.26:180616
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  • 10
    Publication Date: 2016-06-07
    Description: The task was to evaluate the ability of a set of timing/synchronization subsystem features to provide a set of desirable characteristics for the evolving Defense Communications System digital communications network. The set of features related to the approaches by which timing/synchronization information could be disseminated throughout the network and the manner in which this information could be utilized to provide a synchronized network. These features, which could be utilized in a large number of different combinations, included mutual control, directed control, double ended reference links, independence of clock error measurement and correction, phase reference combining, and self organizing.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Goddard Space Flight Center Proc. of the Tenth Ann. Precise Time and Time Interval (PTTI) Appl. and Planning Meeting; p 437-461
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