7,367 research outputs found

    Development of flexible rotor balancing criteria

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    Several studies in which analytical procedures were used to obtain balancing criteria for flexible rotors are described. General response data for a uniform rotor in damped flexible supports were first obtained for plain cylindrical bearings, tilting pad bearings, axial groove bearings, and partial arc bearings. These data formed the basis for the flexible rotor balance criteria presented. A procedure by which a practical rotor in bearings could be reduced to an equivalent uniform rotor was developed and tested. It was found that the equivalent rotor response always exceeded to practical rotor response by more than sixty percent for the cases tested. The equivalent rotor procedure was then tested against six practical rotor configurations for which data was available. It was found that the equivalent rotor method offered a procedure by which balance criteria could be selected for practical flexible rotors, using the charts given for the uniform rotor

    First results of the CERN Resonant WISP Search (CROWS)

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    The CERN Resonant WISP Search (CROWS) probes the existence of Weakly Interacting Sub-eV Particles (WISPs) like axions or hidden sector photons. It is based on the principle of an optical light shining through the wall experiment, adapted to microwaves. Critical aspects of the experiment are electromagnetic shielding, design and operation of low loss cavity resonators and the detection of weak sinusoidal microwave signals. Lower bounds were set on the coupling constant g=4.5108g = 4.5 \cdot 10^{-8} GeV1^{-1} for axion like particles with a mass of ma=7.2μm_a = 7.2 \mueV. For hidden sector photons, lower bounds were set for the coupling constant χ=4.1109\chi = 4.1 \cdot 10^{-9} at a mass of mγ=10.8μm_{\gamma'} = 10.8 \mueV. For the latter we were probing a previously unexplored region in the parameter space

    Multi-wavelength Observations of LS I +61 303 with VERITAS, Swift and RXT E: 2006-2008

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    A long term, multi-wavelength monitoring campaign on the TeV binary LS I +61 303 has been performed utilizing >300 GeV observations with VERITAS along with monitoring in the 0.2-10 keV band by RXTE and Swift between September 2006 and February 2008. The source was detected by VERITAS as a variable TeV source with flux values ranging from 5-20% of the Crab Nebula flux with the strongest flux levels appearing around apastron. X-ray observations by RXTE and Swift show the source as a highly variable hard X-ray source with flux values varying in the range of 0.5-3*10^-11 ergs cm^-2 s^-1 over a single orbital cycle. The 2007-2008 RXTE data set also shows the presence of several extremely large flaring episodes presenting a flux of up to 7.2*10^-11 ergs cm^-2 s^-1, the largest such flare recorded from this source. Comparison of the contemporaneous TeV and X-ray data does not show a correlation at this time, however, the sparsity of data sets do not preclude the existence of such a correlation.Comment: Submitted to Proceedings of "4th Heidelberg International Symposium on High Energy Gamma-Ray Astronomy 2008

    Continuous loading of an electrostatic trap for polar molecules

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    A continuously operated electrostatic trap for polar molecules is demonstrated. The trap has a volume of ~0.6 cm^3 and holds molecules with a positive Stark shift. With deuterated ammonia from a quadrupole velocity filter, a trap density of ~10^8/cm^3 is achieved with an average lifetime of 130 ms and a motional temperature of ~300 mK. The trap offers good starting conditions for high-precision measurements, and can be used as a first stage in cooling schemes for molecules and as a "reaction vessel" in cold chemistry.Comment: 4 pages, 3 figures v2: several small improvements, new intr

    Very-High Energy Gamma-Ray Flux Limits for Nearby Active Galactic Nuclei

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    Combining the results of targeted observations, H.E.S.S. has accumulated a large amount of extra-galactic exposure at TeV energies. Due to its large field of view a considerable part of the sky (0.6 sr) has been observed with high sensitivity outside the targeted observation positions. Since this exposure region contains little inherent bias, it is well suited for studies of extra-galactic source populations. Given the correlation between ultra-high energy cosmic rays and nearby extra-galactic objects recently claimed by the Auger collaboration, this unbiased sky sample by H.E.S.S. is of interest since it includes (besides the targeted sources) 63 AGN within 100 Mpc, for which very-high energy gamma-ray flux limits are derived.Comment: 4 pages, 5 figures, Submitted to Proceedings of "4th International Symposium on High Energy Gamma-Ray Astronomy 2008

    A computational procedure for the solution of the single-stage production sequencing problem with deadline and earliest start time constraints

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    A computational procedure for the solution of the single stage facility with deadline and earliest start time constraints is presented. The procedure is a modification to the Pierce and Hatfield algorithm for the solution of this type of problem. The aim of the procedure is to reduce the number of nodes that will require evaluation for an optimal solution and thus reduce the total processor running time required to produce this optimal solution
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