4,577 research outputs found
Properties of air and combustion products of fuels with air
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
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
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
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 B125963
In this paper we give the first attempt to model the evolution of the
spectrum of PSR B125963 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 and -connections
The structure of the moduli spaces \M := \A/\G of (all, not just flat)
and 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)
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
We report precise measurements of ground-state, -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 F = 2
transition, yielding (1 667 358 996 4) Hz, and by ten-fold for the F' = 1
F = 1 transition, yielding (1 665 401 803 12) Hz. Comparing these
laboratory frequencies to those from OH megamasers in interstellar space will
allow a sensitivity of 1 ppm for over
years.Comment: This version corrects minor typos in the Zeeman shift discussio
Normal-superfluid interaction dynamics in a spinor Bose gas
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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