165,777 research outputs found
Investigation of Micro Porosity Sintered wick in Vapor Chamber for Fan Less Design
Micro Porosity Sintered wick is made from metal injection molding processes,
which provides a wick density with micro scale. It can keep more than 53 %
working fluid inside the wick structure, and presents good pumping ability on
working fluid transmission by fine infiltrated effect. Capillary pumping
ability is the important factor in heat pipe design, and those general
applications on wick structure are manufactured with groove type or screen
type. Gravity affects capillary of these two types more than a sintered wick
structure does, and mass heat transfer through vaporized working fluid
determines the thermal performance of a vapor chamber. First of all, high
density of porous wick supports high transmission ability of working fluid. The
wick porosity is sintered in micro scale, which limits the bubble size while
working fluid vaporizing on vapor section. Maximum heat transfer capacity
increases dramatically as thermal resistance of wick decreases. This study on
permeability design of wick structure is 0.5 - 0.7, especially permeability (R)
= 0.5 can have the best performance, and its heat conductivity is 20 times to a
heat pipe with diameter (Phi) = 10mm. Test data of this vapor chamber shows
thermal performance increases over 33 %.Comment: Submitted on behalf of TIMA Editions
(http://irevues.inist.fr/tima-editions
On two- and three-body descriptions of hybrid mesons
Hybrid mesons are exotic mesons in which the color field is not in its ground
state. Their understanding deserves interest from a theoretical point of view,
because it is intimately related to nonperturbative aspects of QCD. In this
work, we analyze and compare two different descriptions of hybrid mesons,
namely a two-body system with an excited string, or a three-body
system. In particular, we show that the constituent gluon approach
is equivalent to an effective excited string in the heavy hybrid sector.
Instead of a numerical resolution, we use the auxiliary field technique. It
allows to find simplified analytical mass spectra and wave functions, and still
leads to reliable qualitative predictions. We also investigate the light hybrid
sector, and found a mass for the lightest hybrid meson which is in satisfactory
agreement with lattice QCD and other effective models.Comment: 2 figure
On bosonic limits of two recent supersymmetric extensions of the Harry Dym hierarchy
Two generalized Harry Dym equations, recently found by Brunelli, Das and
Popowicz in the bosonic limit of new supersymmetric extensions of the Harry Dym
hierarchy [J. Math. Phys. 44:4756--4767 (2003)], are transformed into
previously known integrable systems: one--into a pair of decoupled KdV
equations, the other one--into a pair of coupled mKdV equations from a
bi-Hamiltonian hierarchy of Kupershmidt.Comment: 7 page
Topological phase transition in wire medium enables high Purcell factor at infrared frequencies
In this paper, we study topological phase transition in a wire medium
operating at infrared frequencies. This transition occurs in the reciprocal
space between the indefinite (open-surface) regime of the metamaterial to its
dielectric (closed-surface) regime. Due to the spatial dispersion inherent to
wire medium, a hybrid regime turns out to be possible at the transition
frequency. Both such surfaces exist at the same frequency and touch one
another. At this frequency, all values of the axial wavevector correspond to
propagating spatial harmonics. The implication of this regime is the
overwhelming radiation enhancement. We numerically investigated the gain in
radiated power for a sub-wavelength dipole source submerged into such the
medium. In contrast to all previous works, this gain (called the Purcell
factor) turns out to be higher for an axial dipole than for a transversal one
Slow cross-symmetry phase relaxation in complex collisions
We discuss the effect of slow phase relaxation and the spin off-diagonal
-matrix correlations on the cross section energy oscillations and the time
evolution of the highly excited intermediate systems formed in complex
collisions. Such deformed intermediate complexes with strongly overlapping
resonances can be formed in heavy ion collisions, bimolecular chemical
reactions and atomic cluster collisions. The effects of quasiperiodic energy
dependence of the cross sections, coherent rotation of the hyperdeformed
intermediate complex, Schr\"odinger cat states and
quantum-classical transition are studied for Mg+Si heavy ion
scattering.Comment: 10 pages including 2 color ps figures. To be published in Physics of
Atomic Nuclei (Yadernaya fizika
A possible source of spin-polarized electrons: The inert graphene/Ni(111) system
We report on an investigation of spin-polarized secondary electron emission
from the chemically inert system: graphene/Ni(111). An ordered passivated
graphene layer (monolayer of graphite, MG) was formed on Ni(111) surface via
cracking of propylene gas. The spin-polarization of the secondary electrons
obtained from this system upon photoemission is only slightly lower than the
one from the clean Ni surface, but does not change upon large oxygen exposure.
These results suggest to use such passivated Ni(111) surface as a source of
spin-polarized electrons stable against adsorption of reactive gases.Comment: 11 pages, 3 figure
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