35,185 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
Magnetic Helicity Conservation and Inverse Energy Cascade in Electron Magnetohydrodynamic Wave Packets
Electron magnetohydrodynamics (EMHD) provides a fluid-like description of
small-scale magnetized plasmas. An EMHD wave (also known as whistler wave)
propagates along magnetic field lines. The direction of propagation can be
either parallel or anti-parallel to the magnetic field lines. We numerically
study propagation of 3-dimensional (3D) EMHD wave packets moving in one
direction. We obtain two major results: 1. Unlike its magnetohydrodynamic (MHD)
counterpart, an EMHD wave packet is dispersive. Because of this, EMHD wave
packets traveling in one direction create opposite traveling wave packets via
self-interaction and cascade energy to smaller scales. 2. EMHD wave packets
traveling in one direction clearly exhibit inverse energy cascade. We find that
the latter is due to conservation of magnetic helicity. We compare inverse
energy cascade in 3D EMHD turbulence and 2-dimensional (2D) hydrodynamic
turbulence.Comment: Phys. Rev. Lett., accepted (4pages, 4 figures
Heavy Baryons and electromagnetic decays
In this talk I review the theory of electromagnetic decays of the ground
state baryon multiplets with oneheavy quark, calculated using Heavy Hadron
Chiral Perturbation Theory. The M1 and E2 amplitudes for (S^{*}-> S gamma),
(S^{*} -> T gamma) and (S -> T gamma)are separately analyzed. All M1
transitions are calculated up to O(1/\Lambda_\chi^2). The E2 amplitudes
contribute at the same order for (S^{*}-> S gamma), while for (S^{*} -> T
gamma) they first appear at O(1/(m_Q \Lambda_\chi^2))and for (S -> T gamma) are
completely negligible. Once the loop contributions is considered, relations
among different decay amplitudes are derived. Furthermore, one can obtain an
absolute prediction for the widths of Xi^{0'(*)}_c-> Xi^{0}_c gamma and
Xi^{-'(*)}_b-> Xi^{-}_b gamma.Comment: Talk presented at 4^{th} International Conference Hyperons, Charm and
Beauty Hadrons Conference, Valencia June 200
Casimir Force for Arbitrary Objects Using the Argument Principle and Boundary Element Methods
Recent progress in the simulation of Casimir forces between various objects
has allowed traditional computational electromagnetic solvers to be used to
find Casimir forces in arbitrary three-dimensional objects. The underlying
theory to these approaches requires knowledge and manipulation of quantum field
theory and statistical physics. We present a calculation of the Casimir force
using the method of moments via the argument principle. This simplified
derivation allows greater freedom in the moment matrix where the argument
principle can be used to calculate Casimir forces for arbitrary geometries and
materials with the use of various computational electromagnetic techniques.Comment: 6 pages, 2 figure
Scalar field fluctuations in Schwarzschild-de Sitter space-time
We calculate quantum fluctuations of a free scalar field in the
Schwarzschild-de Sitter space-time, adopting the planar coordinates that is
pertinent to the presence of a black hole in an inflationary universe. In a
perturbation approach, doing expansion in powers of a small black hole event
horizon compared to the de Sitter cosmological horizon, we obtain time
evolution of the quantum fluctuations and then derive the scalar power
spectrum.Comment: 16 pages and 4 figures, accepted by Classical and Quantum Gravit
Stability of the Magnetic Monopole Condensate in three- and four-colour QCD
It is argued that the ground state of three- and four-colour QCD contains a
monopole condensate, necessary for the dual Meissner effect to be the mechanism
of confinement, and support its stability on the grounds that it gives the
off-diagonal gluons an effective mass sufficient to remove the unstable ground
state mode.Comment: jhep.cls, typos corrected, references added, some content delete
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
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
Stability of inflating branes in a texture
We investigate the stability of inflating branes embedded in an O(2) texture
formed in one extra dimension. The model contains two 3-branes of nonzero
tension, and the extra dimension is compact. When the gravitational
perturbation is applied, the vacuum energy which is responsible for inflation
on the branes stabilizes the branes if the symmetry-breaking scale of the
texture is smaller than some critical value. This critical value is determined
by the particle-hierarchy scale between the two branes, and is smaller than the
5D Planck-mass scale. The scale of the vacuum energy can be considerably low in
providing the stability. This stability story is very different from the
flat-brane case which always suffers from the instability due to the
gravitational perturbation.Comment: 16 pages, 5 eps figures, revte
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