205,750 research outputs found

    Computer program TRACK performs transient and/or steady state thermal analysis with coupled fluid flow and heat conduction

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    Computer program called TRACK was developed by combining a transient fluid flow computer code and the existing modified TOSS heat conduction code to perform the computation

    Vibroacoustic study of the NASA Goddard Space Flight Center OSS-1 payload

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    A comparative evaluation of shuttle liftoff and ground test random response data obtained from the Office of Space Science-1 (OSS-1) pallet payload flown in the cargo bay of STS-3 is presented. The study was initiated to evaluate the possibility that the payload flight vibration response can exceed that occurred during ground test when the ground test acoustic excitation is normalized to the flight acoustic environment. In addition, the analytically derived response from the Vibroacoustic Payload Environment Prediction System (VAPEPS) is compared with OSS-1 ground test results

    Design of photonic crystal optical waveguides with single-mode propagation in the photonic bandgap

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    The authors present a systematic method for designing dielectric-core photonic crystal optical waveguides that support only one mode in the photonic bandgap (PBG). It is shown that by changing the sizes of thc air columns (without perturbing the positions of the centres of the air column) in the two rows that are adjacent to the middle slab, the higher order mode(s) can be pushed out of the photonic bandgap, resulting in single-mode wave propagation in the bandgap

    A MEMS electrostatic particle transportation system

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    We demonstrate here an electrostatic MEMS system capable of transporting particles 5-10μm in diameter in air. This system consists of 3-phase electrode arrays covered by insulators (Figs. 1, 2). Extensive testing of this system has been done using a variety of insulation materials (silicon nitride, photoresist, and Teflon), thickness (0- 12μm), particle sizes (1-10μm), particle materials (metal, glass, polystyrene, spores, etc), waveforms, frequencies, and voltages. Although previous literature [1-2] claimed it impractical to electrostatically transport particles with sizes 5-10μm due to complex surface forces, this effort actually shows it feasible (as high as 90% efficiency) with the optimal combination of insulation thickness, electrode geometry, and insulation material. Moreover, we suggest a qualitative theory for our particle transportation system which is consistent with our data and finite-element electrostatic simulations

    An application of cluster detection to scene analysis

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    Certain arrangements of local features in a scene tend to group together and to be seen as units. It is suggested that in some instances, this phenomenon might be interpretable as a process of cluster detection in a graph-structured space derived from the scene. This idea is illustrated using a class of scenes that contain only horizontal and vertical line segments
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