43,854 research outputs found
Finite element analysis of aerodynamic heating in three dimensional viscous high speed compressible flow: An assessment
The current capability of the finite element method for solving problems of viscous flow is reviewed. Much work has been directed to the simulation of incompressible flows and the relevant features are described. The methods available for, and the problems associated with, the finite element solution of high speed viscous compressible flows are analyzed. A plan for developing finite element research in this area with experimental support is presented
Condition sensor system and method
The condition sensor system comprises a condition detector which produces a pulse when a parameter of the monitored condition exceeds a desired threshold. A resettable condition counter counts each pulse. A resettable timer is preset to produce a particular time frame. The counter produces a condition signal when the accumulated number of pulses within the time frame is equal to or greater than a preset count. Control means responsive to the incoming pulses and to the condition signal produce control signals that control utilization devices. After a suitable delay, the last detected pulse simultaneously resets the pulse counter and the timer, and prepares them for sensing another condition occurrence within the time frame. The invention has particular utility in the process of detecting rocking motions of blind people. A controlled, audible, bio-feedback signal is provided which constitutes a warning to the blind person that he is rocking
A characterisation of weakly locally projective amalgams related to and the sporadic simple groups and
A simple undirected graph is weakly -locally projective, for a group of
automorphisms , if for each vertex , the stabiliser induces on the
set of vertices adjacent to a doubly transitive action with socle the
projective group for an integer and a prime power .
It is -locally projective if in addition is vertex transitive. A theorem
of Trofimov reduces the classification of the -locally projective graphs to
the case where the distance factors are as in one of the known examples.
Although an analogue of Trofimov's result is not yet available for weakly
locally projective graphs, we would like to begin a program of characterising
some of the remarkable examples. We show that if a graph is weakly locally
projective with each and or , and if the distance factors
are as in the examples arising from the rank 3 tilde geometries of the groups
and , then up to isomorphism there are exactly two possible
amalgams. Moreover, we consider an infinite family of amalgams of type
(where each and ) and prove that if
there is a unique amalgam of type and it is
unfaithful, whereas if then there are exactly four amalgams of type
, precisely two of which are faithful, namely the ones related
to and , and one other which has faithful completion
Effects of practice and work load on the performance of a code transformation task /COTRAN/
Practice and operator work load effects on acquisition and performance of code transformation /COTRAN/ tas
Performance measurement of nonverbal mediation Semiannual status report, 1 Oct. 1968 - 31 Mar. 1969
Operator training effects on performance measurement of nonverbal mediatio
Production of Millisecond Dips in Sco X-1 Count Rates by Dead Time Effects
Chang et al. (2006) reported millisecond duration dips in the X-ray intensity
of Sco X-1 and attributed them to occultations of the source by small
trans-Neptunian objects (TNOs). We have found multiple lines of evidence that
these dips are not astronomical in origin, but rather the result of high-energy
charged particle events in the RXTE PCA detectors. Our analysis of the RXTE
data indicates that at most 10% of the observed dips in Sco X-1 could be due to
occultations by TNOs, and, furthermore, we find no positive or supporting
evidence for any of them being due to TNOs. We therefore believe that it is a
mistake to conclude that any TNOs have been detected via occultation of Sco
X-1.Comment: Submitted to ApJ; uses emulateapj.cls, 8 pages with 8 figure
Radioisotope thermal photovoltaic application of the GaSb solar cell
An examination of a RTVP (radioisotopic thermophotovoltaic) conceptual design has shown a high potential for power densities well above those achievable with radioisotopic thermoelectric generator (RTG) systems. An efficiency of 14.4 percent and system specific power of 9.25 watts/kg were predicted for a system with sixteen GPHS (general purpose heat source) sources operating at 1100 C. The models also showed a 500 watt system power by the strontium-90 isotope at 1200 C at an efficiency of 17.0 percent and a system specific power of 11.8 watts/kg. The key to this level of performance is a high-quality photovoltaic cell with narrow bandgap and a reflective rear contact. Recent work at Boeing on GaSb cells and transparent back GaAs cells indicate that such a cell is well within reach
- …