37,420 research outputs found
AI mass spectrometers for space shuttle health monitoring
The facility Hazardous Gas Detection System (HGDS) at Kennedy Space Center (KSC) is a mass spectrometer based gas analyzer. Two instruments make up the HGDS, which is installed in a prime/backup arrangement, with the option of using both analyzers on the same sample line, or on two different lines simultaneously. It is used for monitoring the Shuttle during fuel loading, countdown, and drainback, if necessary. The use of complex instruments, operated over many shifts, has caused problems in tracking the status of the ground support equipment (GSE) and the vehicle. A requirement for overall system reliability has been a major force in the development of Shuttle GSE, and is the ultimate driver in the choice to pursue artificial intelligence (AI) techniques for Shuttle and Advanced Launch System (ALS) mass spectrometer systems. Shuttle applications of AI are detailed
Heat-transfer characteristics of a water-to- cryogenic-hydrogen heat exchanger
Heat transfer characteristics of water/cryogenic hydrogen heat exchanger for nuclear rocket reacto
Creep of plasma sprayed zirconia
Specimens of plasma-sprayed zirconia thermal barrier coatings with three different porosities and different initial particle sizes were deformed in compression at initial loads of 1000, 2000, and 3500 psi and temperatures of 1100 C, 1250 C, and 1400 C. The coatings were stabilized with lime, magnesia, and two different concentrations of yttria. Creep began as soon as the load was applied and continued at a constantly decreasing rate until the load was removed. Temperature and stabilization had a pronounced effect on creep rate. The creep rate for 20% Y2O3-80% ZrO2 was 1/3 to 1/2 that of 8% Y2O3-92% ZrO2. Both magnesia and calcia stabilized ZrO2 crept at a rate 5 to 10 times that of the 20% Y2O3 material. A near proportionality between creep rate and applied stress was observed. The rate controlling process appeared to be thermally activated, with an activation energy of approximately 100 cal/gm mole K. Creep deformation was due to cracking and particle sliding
Evaluation of a stall-flutter spring-damper pushrod in the rotating control system of a CH-54B helicopter
Results of a design and flight test program conducted to define the effect of rotating pushrod damping on stall-flutter induced control loads are presented. The CH-54B helicopter was chosen as the test aircraft because it exhibited stall induced control loads. Damping was introduced into the CH-54B control system by replacing the standard pushrod with spring-damper assemblies. Design features of the spring-damper are described and the results of a dynamic analysis are shown which define the pushrod stiffness and damping requirements. Flight test measurements taken at 47,000 lb gross weight with and without the damper are presented. The results indicate that the spring-damper pushrods reduced high frequency, stall-induced rotating control loads by almost 50%. Fixed system control loads were reduced by 40%. Handling qualities in stall were unchanged, as expected
Coulomb Gap: How a Metal Film Becomes an Insulator
Electron tunneling measurements of the density of states (DOS) in ultra-thin
Be films reveal that a correlation gap mediates their insulating behavior. In
films with sheet resistance the correlation singularity appears
as the usual perturbative zero bias anomaly (ZBA) in the DOS. As R is
increased further, however, the ZBA grows and begins to dominate the DOS
spectrum. This evolution continues until a non-perturbative
Efros-Shklovskii Coulomb gap spectrum finally emerges in the highest R films.
Transport measurements of films which display this gap are well described by a
universal variable range hopping law .Comment: 4 figure
Analyses of composite structures
Stiffness and strength analyses on composite cross-ply and helical wound cylinders and flat laminate structure
Further experimental tests for simple relations between unpolarized and polarized quark parton distributions
Some simple relations between unpolarized and polarized quark parton
distributions have direct experimental consequences which will be presented
here. In particular, we will see that it is possible to relate the deep
inelastic structure functions and , both for proton and deuteron, in
fair agreement with experimental data.Comment: 5 pages, in Latex, 3 figure
Cohomological non-rigidity of generalized real Bott manifolds of height 2
We investigate when two generalized real Bott manifolds of height 2 have
isomorphic cohomology rings with Z/2 coefficients and also when they are
diffeomorphic. It turns out that cohomology rings with Z/2 coefficients do not
distinguish those manifolds up to diffeomorphism in general. This gives a
counterexample to the cohomological rigidity problem for real toric manifolds
posed in \cite{ka-ma08}. We also prove that generalized real Bott manifolds of
height 2 are diffeomorphic if they are homotopy equivalent
Multiple solutions of the quasirelativistic Choquard equation
We prove existence of multiple solutions to the quasirelativistic Choquard equation with a scalar potential
A principled approach to the measurement of situation awareness in commercial aviation
The issue of how to support situation awareness among crews of modern commercial aircraft is becoming especially important with the introduction of automation in the form of sophisticated flight management computers and expert systems designed to assist the crew. In this paper, cognitive theories are discussed that have relevance for the definition and measurement of situation awareness. These theories suggest that comprehension of the flow of events is an active process that is limited by the modularity of attention and memory constraints, but can be enhanced by expert knowledge and strategies. Three implications of this perspective for assessing and improving situation awareness are considered: (1) Scenario variations are proposed that tax awareness by placing demands on attention; (2) Experimental tasks and probes are described for assessing the cognitive processes that underlie situation awareness; and (3) The use of computer-based human performance models to augment the measures of situation awareness derived from performance data is explored. Finally, two potential example applications of the proposed assessment techniques are described, one concerning spatial awareness using wide field of view displays and the other emphasizing fault management in aircraft systems
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