69,863 research outputs found

    Lubrication handbook

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    Information on lubricants from government reports, military specifications, qualified parts lists, and suppliers of commercial lubricants has been consolidated in one source. Handbook includes data on chemical and physical properties of solid, bonded solid, and liquid lubricants; dispersions and composites; and greases, oils, and hydraulic fluids

    Blood flow dynamics in patient specific arterial network in head and neck

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    This paper shows a steady simulation of blood flow in the major head and neck arteries as if they had rigid walls, using patient specific geometry and CFD software FLUENT R . The Artery geometry is obtained by CTā€“scan segmentation with the commercial software ScanIPTM. A cause and effect study with various Reynolds numbers, viscous models and blood fluid models is provided. Mesh independence is achieved through wall y+ and pressure gradient adaption. It was found, that a Newtonian fluid model is not appropriate for all geometry parts, therefore the nonā€“Newtonian properties of blood are required for small vessel diameters and low Reynolds numbers. The kā€“! turbulence model is suitable for the whole Reynolds numbe

    Field Effect Transistors on Rubrene Single Crystals with Parylene Gate Insulator

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    We report on fabrication and characterization of the organic field effect transistors (OFETs) on the surface of single crystals of rubrene. The parylene polymer film has been used as the gate insulator. At room temperature, these OFETs exhibit the p-type conductivity with the field effect mobility up to 1 cm^2/Vs and the on/off ratio ~ 10^4. The temperature dependence of the mobility is discussed.Comment: 3 page

    Frontier exploration and the North Atlantic Igneous Province : new insights from a 2.6ā€‰km offshore volcanic sequence in the NE Faroeā€“Shetland Basin

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    Acknowledgements and Funding This work was funded by Chevron. The authors would like to acknowledge the Chevron West of Shetlands team along with the Joint Venture partners OMV, Faroe Petroleum and Indemitsu for access to data along with permission to publish this study. PGS is thanked for access to the Corona Ridge Regional Geostreamer (CRRG) data and permission to publish the seismic line. The paper was improved thanks to insightful reviews by S. M. Jones and A. Saunders, which substantially improved an earlier draft. J. Still and F. Thompson gave invaluable technical support at the University of Aberdeen, and K. Wall helped with real-time cuttings analysis.Peer reviewedPostprin

    Transcriptome analysis of the synganglion from the honey bee mite, Varroa destructor and RNAi knockdown of neural peptide targets

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    Acknowledgements This work was funded by BBSRC-LINK grant # BB/J01009X/1 and Vita Europe Ltd. We are grateful to the Scottish Beekeepers Association, especially Mr Phil McAnespie in supporting this work at its inception. We acknowledge partial funding from a Genesis Faraday SPARK Award, part of a Scottish Government SEEKIT project for the early part of this work. We are grateful to Prof David Evans for his advice on Varroa destructor viruses.Peer reviewedPostprin

    Revisiting the 1954 Suspension Experiments of R. A.Bagnold

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    In 1954 R. A. Bagnold published his seminal findings on the rheological properties of a liquid-solid suspension. Although this work has been cited extensively over the last fifty years, there has not been a critical review of the experiments. The purpose of this study is to examine the work and to suggest an alternative reason for the experimental findings. The concentric cylinder rheometer was designed to measure simultaneously the shear and normal forces for a wide range of solid concentrations, fluid viscosities and shear rates. As presented by Bagnold, the analysis and experiments demonstrated that the shear and normal forces depended linearly on the shear rate in the 'macroviscous' regime; as the grain-to-grain interactions increased in the 'grain-inertia' regime, the stresses depended on the square of the shear rate and were independent of the fluid viscosity. These results, however, appear to be dictated by the design of the experimental facility. In Bagnold's experiments, the height (h) of the rheometer was relatively short compared to the spacing (t) between the rotating outer and stationary inner cylinder (h/t=4.6). Since the top and bottom end plates rotated with the outer cylinder, the flow contained two axisymmetric counter-rotating cells in which flow moved outward along the end plates and inward through the central region of the annulus. At higher Reynolds numbers, these cells contributed significantly to the measured torque, as demonstrated by comparing Bagnold's pure-fluid measurements with studies on laminar-to-turbulent transitions that pre-date the 1954 study. By accounting for the torque along the end walls, Bagnold's shear stress measurements can be estimated by modelling the liquid-solid mixture as a Newtonian fluid with a corrected viscosity that depends on the solids concentration. An analysis of the normal stress measurements was problematic because the gross measurements were not reported and could not be obtained

    Some neutron and gamma radiation characteristics of plutonium cermet fuel for isotopic power sources

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    Gamma and neutron measurements on various types of plutonium sources are presented in order to show the effects of O-17, O-18 F-19, Pu-236, age of the fuel, and size of the source on the gamma and neutron spectra. Analysis of the radiation measurements shows that fluorine is the main contributor to the neutron yields from present plutonium-molybdenum cermet fuel, while both fluorine and Pu-236 daughters contribute significantly to the gamma ray intensities

    The design, development, and flight test results of the Boeing 737 aircraft antennas for the ICAO demonstration of the TRSB microwave landing system

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    The Research Support Flight System, a modified Boeing 737, was used to evaluate the performance of several aircraft antennas and locations for the Time Reference Scanning Beam (TRSB) Microwave Landing System (MLS). These tests were conducted at the National Aviation Facilities Experimental Center (NAFEC), Atlantic City, New Jersey on December 18, 1975. The flight tests measured the signal strength and all pertinent MLS data during a straight-in approach, a racetrack approach, and ICAO approach profiles using the independent antenna-receiver combinations simultaneously on the aircraft. Signal drop-outs were experienced during the various approaches but only a small percentage could be attributed to antenna pattern effects

    Effects of Velocity-Dependent Dark Matter Annihilation on the Energy Spectrum of the Extragalactic Gamma-ray Background

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    We calculate the effects of velocity-dependent dark matter annihilation cross sections on the intensity of the extragalactic gamma-ray background. Our formalism does not assume a locally thermal distribution of dark matter particles in phase space, and is valid for arbitrary velocity-dependent annihilation. As concrete examples, we calculate the effects of p-wave annihilation (with the vv-weighted cross section of Ļƒv=a+bv2\sigma v=a+bv^2) on the mean intensity of extragalactic gamma rays produced in cosmological dark matter halos. This velocity variation makes the shape of the energy spectrum harder, but this change in the shape is too small to see unless b/a\agt 10^6. While we find no such models in the parameter space of the Minimal Supersymmetric Standard Model (MSSM), we show that it is possible to find b/a\agt 10^6 in the extension MSSMāŠ—U(1)Bāˆ’L\otimes U(1)_{B-L}. However, we find that the most dominant effect of the p-wave annihilation is the suppression of the amplitude of the gamma-ray background. A non-zero bb at the dark matter freeze-out epoch requires a smaller value of aa in order for the relic density constraint to be satisfied, suppressing the amplitude by a factor as low as 10āˆ’610^{-6} for a thermal relic. Non-thermal relics will have weaker amplitude suppression. As another velocity-dependent effect, we calculate the spectrum for s-wave annihilation into fermions enhanced by the attractive Sommerfeld effect. Resonances associated with this effect result in significantly enhanced intensities, with a slightly softer energy spectrum.Comment: 18 pages, 10 figure
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