25,395 research outputs found
Heat dissipation of high rate Li-SOCl sub 2 primary cells
The heat dissipation problem occurring in the lithium thionyl chloride cells discharged at relatively high rates under normal discharge conditions is examined. Four heat flow paths were identified, and the thermal resistances of the relating cell components along each flow path were accordingly calculated. From the thermal resistance network analysis, it was demonstrated that about 90 percent of the total heat produced within the cell should be dissipated along the radial direction in a spirally wound cell. In addition, the threshold value of the heat generation rate at which cell internal temperature could be maintained below 100 C, was calculated from total thermal resistance and found to be 2.9 W. However, these calculations were made only at the cell components' level, and the transient nature of the heat accumulation and dissipation was not considered. A simple transient model based on the lumped-heat-capacity concept was developed to predict the time-dependent cell temperature at different discharge rates. The overall objective was to examine the influence of cell design variable from the heat removal point of view under normal discharge conditions and to make recommendations to build more efficient lithium cells
Monopoles and Knots in Skyrme Theory
We show that the Skyrme theory actually is a theory of monopoles which allows
a new type of solitons, the topological knots made of monopole-anti-monopole
pair,which is different from the well-known skyrmions. Furthermore, we derive a
generalized Skyrme action from the Yang-Mills action of QCD, which we propose
to be an effective action of QCD in the infra-red limit. We discuss the
physical implications of our results.Comment: 4 pages. Phys. Rev. Lett. in pres
Warped brane-world compactification with Gauss-Bonnet term
In the Randall-Sundrum (RS) brane-world model a singular delta-function
source is matched by the second derivative of the warp factor. So one should
take possible curvature corrections in the effective action of the RS models in
a Gauss-Bonnet (GB) form. We present a linearized treatment of gravity in the
RS brane-world with the Gauss-Bonnet modification to Einstein gravity. We give
explicit expressions for the Neumann propagator in arbitrary D dimensions and
show that a bulk GB term gives, along with a tower of Kaluza-Klein modes in the
bulk, a massless graviton on the brane, as in the standard RS model. Moreover,
a non-trivial GB coupling can allow a new branch of solutions with finite
Planck scale and no naked bulk singularity, which might be useful to avoid some
of the previously known ``no--go theorems'' for RS brane-world
compactifications.Comment: 23 pages, typos in Secs. 5 & 6 corrected, expanded/published version
(IJMPA
Fundamental study of flow field generated by rotorcraft blades using wide-field shadowgraph
The vortex trajectory and vortex wake generated by helicopter rotors are visualized using a wide-field shadowgraph technique. Use of a retro-reflective Scotchlite screen makes it possible to investigate the flow field generated by full-scale rotors. Tip vortex trajectories are visible in shadowgraphs for a range of tip Mach number of 0.38 to 0.60. The effect of the angle of attack is substantial. At an angle of attack greater than 8 degrees, the visibility of the vortex core is significant even at relatively low tip Mach numbers. The theoretical analysis of the sensitivity is carried out for a rotating blade. This analysis demonstrates that the sensitivity decreases with increasing dimensionless core radius and increases with increasing tip Mach number. The threshold value of the sensitivity is found to be 0.0015, below which the vortex core is not visible and above which it is visible. The effect of the optical path length is also discussed. Based on this investigation, it is concluded that the application of this wide-field shadowgraph technique to a large wind tunnel test should be feasible. In addition, two simultaneous shadowgraph views would allow three-dimensional reconstruction of vortex trajectories
Geometrization of the Gauge Connection within a Kaluza-Klein Theory
Within the framework of a Kaluza-Klein theory, we provide the geometrization
of a generic (Abelian and non-Abelian) gauge coupling, which comes out by
choosing a suitable matter fields dependence on the extra-coordinates.
We start by the extension of the Nother theorem to a multidimensional
spacetime being the direct sum of a 4-dimensional Minkowski space and of a
compact homogeneous manifold (whose isometries reflect the gauge symmetry); we
show, how on such a ``vacuum'' configuration, the extra-dimensional components
of the field momentum correspond to the gauge charges. Then we analyze the
structure of a Dirac algebra as referred to a spacetime with the Kaluza-Klein
restrictions and, by splitting the corresponding free-field Lagrangian, we show
how the gauge coupling terms outcome.Comment: 10 pages, no figure, to appear on Int. Journ. Theor. Phy
Charged particle display
An optical shutter based on charged particles is presented. The output light
intensity of the proposed device has an intrinsic dependence on the
interparticle spacing between charged particles, which can be controlled by
varying voltages applied to the control electrodes. The interparticle spacing
between charged particles can be varied continuously and this opens up the
possibility of particle based displays with continuous grayscale.Comment: typographic errors corrected in Eqs (37) and (39); published in
Journal of Applied Physics; doi:10.1063/1.317648
Effective Lagrangian from Higher Curvature Terms: Absence of vDVZ Discontinuity in AdS Space
We argue that the van Dam-Veltman-Zakharov discontinuity arising in the limit of the massive graviton through an explicit Pauli-Fierz mass term
could be absent in anti de Sitter space. This is possible if the graviton can
acquire mass spontaneously from the higher curvature terms or/and the massless
limit is attained faster than the cosmological constant . We discuss the effects of higher-curvature couplings and of an explicit
cosmological term () on stability of such continuity and of massive
excitations.Comment: 23 pages, Latex, the version to appear in Class. Quant. Gra
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