10,559 research outputs found
Modal analysis of wave propagation in dispersive media
Surveys on wave propagation in dispersive media have been limited since the
pioneering work of Sommerfeld [Ann. Phys. 349, 177 (1914)] by the presence of
branches in the integral expression of the wave function. In this article, a
method is proposed to eliminate these critical branches and hence to establish
a modal expansion of the time-dependent wave function. The different components
of the transient waves are physically interpreted as the contributions of
distinct sets of modes and characterized accordingly. Then, the modal expansion
is used to derive a modified analytical expression of the Sommerfeld precursor
improving significantly the description of the amplitude and the oscillating
period up to the arrival of the Brillouin precursor. The proposed method and
results apply to all waves governed by the Helmholtz equations.Comment: 10 pages, 9 figure
An Exactly Solvable Supersymmetric Model of Semimagic Nuclei
A simple model of nucleons coupled to angular momentum zero (s-pairs)
occupying the valance shell of a semi-magic nuclei is considered. The model has
a separable, orbit dependent pairing interaction which dominates over the
kinetic term. It is shown that such an interaction leads to an exactly solvable
model whose (0+) eigenstates and energies can be computed very easily with the
help of the algebraic Bethe ansatz method. It is also shown that the model has
a supersymmetry which connects the spectra of some semimagic nuclei. The
results obtained from this model for the semimagic Ni isotopes from 58Ni to
68Ni are given. In addition, a new and easier technique for calculating the
energy eigenvalues from the Bethe ansatz equations is also presented.Comment: Talk given at the International Conference on Nuclear Physics and
Astrophysics: From Stable Beams to Exotic Nuclei, Cappadocia, June 200
Surgical treatment of giant cardiac aneurysm with pseudoaneurysm in a colon carcinoma patient
Left ventricular pseudoaneurysm is a rare and lethal condition associated with a high risk of rapid enlargement and rupture. It develops after transmural myocardial infarction (MI), cardiac surgery, trauma, or infection. When a left ventricular pseudoaneurysm is detected, surgical repair is recommended due to the high possibility of rupture. In this report, we present surgical treatment of a giant cardiac pseudoaneurysm that occurred after MI in a colon carcinoma patient
Experimental and numerical investigations of free convection heat transfer in solar oven
The use of solar energy for baking, heating or drying represents a sustainable way of solar energy
applications with negligible negative effects. Solar oven is an alternative to conventional oven that rely
heavily on coal and wood or Electric oven that uses the power from the National grid of which the end
users have little or no control. Since the Solar oven uses no fuel and it cost nothing to run, it use are
widely promoted especially in situations where minimum fuel consumption or fire risks are considered
highly important. As useful as the Solar Oven proved, it major setback in the area of applications has
been its future sustainability. For the use of Solar Oven/Cookers to be sustained in the future, the design
and development of solar oven must rely on sound analytical tools. Therefore, this work focused on the
design and development of the solar oven. To test the performance of the Small Solar Oven a 5000cm3
beaker of water was put into the Oven and the temperature of the water was found to reach 810C after
about 3hrs under an average ambient temperature of 300C. On no load test, the oven reached a
maximum temperature of 112oC in 6hrs. In order to carry out the parametric studies and improve the
performance of the Solar Oven, Mathematical models were developed and solved by using
Characteristics-Based Split (CBS) Finite Element Method. The Model results were compared with the
Experimental results and a good agreement ware found between the two results
Classical Strongly Coupled QGP: VII. Energy Loss
We use linear response analysis and the fluctuation-dissipation theorem to
derive the energy loss of a heavy quark in the SU(2) classical Coulomb plasma
in terms of the monopole and non-static structure factor. The result is
valid for all Coulomb couplings , the ratio of the mean potential
to kinetic energy. We use the Liouville equation in the collisionless limit to
assess the SU(2) non-static structure factor. We find the energy loss to be
strongly dependent on . In the liquid phase with , the
energy loss is mostly metallic and soundless with neither a Cerenkov nor a Mach
cone. Our analytical results compare favorably with the SU(2) molecular
dynamics simulations at large momentum and for heavy quark masses.Comment: 18 pages, 15 figures. v2: added references, changed title, replaced
figures for Fig. 7, corrected typo
Self-force and synchrotron radiation in odd space-time dimensions
Classical electrodynamics in flat 3+1 space-time has a very special retarded
propagator delta(x^2) localized on the light cone, so that a particle does not
interact with its past field. However, this is an exception, and in flat
odd-dimensional space-times as well as generic curved spaces this is not so. In
this work we show that the so called self-force is not only non-zero, but it
matches (in 2+1 dimensions) the radiation reaction force derived from the
radiation intensity.Comment: 9 pages, 1 figur
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