4,577 research outputs found

    Properties of air and combustion products of fuels with air

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    Thermodynamic and transport properties include ratio of specific heats, molecular weight, viscosity, heat capacity, thermal conductivity, and Prandtl number. Properties are calculated from 300 to 2500 degrees K and for pressures of three and ten atmospheres

    Loop constraints: A habitat and their algebra

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    This work introduces a new space \T'_* of `vertex-smooth' states for use in the loop approach to quantum gravity. Such states provide a natural domain for Euclidean Hamiltonian constraint operators of the type introduced by Thiemann (and using certain ideas of Rovelli and Smolin). In particular, such operators map \T'_* into itself, and so are actual operators in this space. Their commutator can be computed on \T'_* and compared with the classical hypersurface deformation algebra. Although the classical Poisson bracket of Hamiltonian constraints yields an inverse metric times an infinitesimal diffeomorphism generator, and despite the fact that the diffeomorphism generator has a well-defined non-trivial action on \T'_*, the commutator of quantum constraints vanishes identically for a large class of proposals.Comment: 30 pages RevTex, 2 figures include

    Gigahertz-peaked spectra pulsars and thermal absorption model

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    We present the results of our radio interferometric observations of pulsars at 325 MHz and 610 MHz using the Giant Metrewave Radio Telescope (GMRT). We used the imaging method to estimate the flux densities of several pulsars at these radio frequencies. The analysis of the shapes of the pulsar spectra allowed us to identify five new gigahertz-peaked spectra (GPS) pulsars. Using the hypothesis that the spectral turnovers are caused by thermal free-free absorption in the interstellar medium, we modeled the spectra of all known objects of this kind. Using the model, we were able to put some observational constrains on the physical parameters of the absorbing matter, which allows us to distinguish between the possible sources of absorption. We also discuss the possible effects of the existence of GPS pulsars on future search surveys, showing that the optimal frequency range for finding such objects would be from a few GHz (for regular GPS sources) to possibly 10 GHz for pulsars and radio-magnetars exhibiting very strong absorption.Comment: Accepted for publication in ApJ, 28 pages, 8 figure

    Multi-frequency observations and spectral analysis of two gigahertz-peaked spectra pulsars

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    We report the multi-frequency observations of two pulsars: J1740+1000 and B1800-21, using the Giant Metrewave Radio Telescope and the Green Bank Telescope. The main aim of these observations was to estimate the flux density spectrum of these pulsars, as both of them were previously reported to exhibit gigahertz-peaked spectra. J1740+1000 is a young pulsar far from the Galactic plane and the interpretation of its spectrum was inconclusive in the light of the recent flux density measurements. Our result supports the gigahertz-peaked interpretation of the PSR J1740+1000 spectrum. B1800-21 is a Vela-like pulsar near the W30 complex, whose spectrum exhibit a significant change between 2012 and 2014 year. Our analysis shows that the current shape of the spectrum is similar to that observed before 2009 and confirms that the observed spectral change happen in a time-scale of a few years.Comment: 9 pages, 7 figure

    Modelling of the radio spectrum evolution in the binary pulsar B1259−-63

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    In this paper we give the first attempt to model the evolution of the spectrum of PSR B1259−-63 radio emission while the pulsar orbits the companion Be star. As suggested by Kijak et al. (Mon. Not. R. Astron. Soc. 418:L114, 2011a) this binary system can be useful in understanding the origin of the gigahertz-peaked spectrum of pulsars. The model explains, at least qualitatively, the observed alterations of the spectral shape depending on the orbital phases of this pulsar. Thus, our results support the hypothesis that the external factors have a significant impact on the observed radio emission of a pulsar. The model can also contribute to our understanding of the origin of some non-typical spectral shapes(e.g. flat or broken spectra).Comment: 9 pages, 2 tables, 3 figure

    Completeness of Wilson loop functionals on the moduli space of SL(2,C)SL(2,C) and SU(1,1)SU(1,1)-connections

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    The structure of the moduli spaces \M := \A/\G of (all, not just flat) SL(2,C)SL(2,C) and SU(1,1)SU(1,1) connections on a n-manifold is analysed. For any topology on the corresponding spaces \A of all connections which satisfies the weak requirement of compatibility with the affine structure of \A, the moduli space \M is shown to be non-Hausdorff. It is then shown that the Wilson loop functionals --i.e., the traces of holonomies of connections around closed loops-- are complete in the sense that they suffice to separate all separable points of \M. The methods are general enough to allow the underlying n-manifold to be topologically non-trivial and for connections to be defined on non-trivial bundles. The results have implications for canonical quantum general relativity in 4 and 3 dimensions.Comment: Plain TeX, 7 pages, SU-GP-93/4-

    A project of universal computing platform - cluster of floating point DSP processors (Projekt uniwersalnej platformy obliczeniowej - klastra zmiennoprzecinkowych procesorów DSP)

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    In this paper, a project of DSP processors cluster is presented. This project is realized as an extension board for PC computers. A block diagram of the board is described. A DSP processor properties for cluster computation was described. The aim is to use a number of such boards for building a cluster of DSP clusters. Such architecture will be used for High Energy Physics Experiments results calculations with such data as CMS, ILC and E-XFEL

    Cold Molecule Spectroscopy for Constraining the Evolution of the Fine Structure Constant

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    We report precise measurements of ground-state, λ\lambda-doublet microwave transitions in the hydroxyl radical molecule (OH). Utilizing slow, cold molecules produced by a Stark decelerator we have improved over the precision of the previous best measurement by twenty-five-fold for the F' = 2 →\to F = 2 transition, yielding (1 667 358 996 ±\pm 4) Hz, and by ten-fold for the F' = 1 →\to F = 1 transition, yielding (1 665 401 803 ±\pm 12) Hz. Comparing these laboratory frequencies to those from OH megamasers in interstellar space will allow a sensitivity of 1 ppm for Δα/α\Delta\alpha/\alpha over ∼\sim101010^{10} years.Comment: This version corrects minor typos in the Zeeman shift discussio

    Normal-superfluid interaction dynamics in a spinor Bose gas

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    Coherent behavior of spinor Bose-Einstein condensates is studied in the presence of a significant uncondensed (normal) component. Normal-superfluid exchange scattering leads to a near-perfect local alignment between the spin fields of the two components. Through this spin locking, spin-domain formation in the condensate is vastly accelerated as the spin populations in the condensate are entrained by large-amplitude spin waves in the normal component. We present data evincing the normal-superfluid spin dynamics in this regime of complicated interdependent behavior.Comment: 5 pages, 4 fig
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