Bulletin of the American Physical Society
2005 TSAPS/AAPT/SPS Joint Fall Meeting
Thursday–Saturday, October 20–22, 2005; Houston, TX
Session D3: Theory III |
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Room: Waldorf Astoria D 210D |
Friday, October 21, 2005 4:00PM - 4:12PM |
D3.00001: Geometrical aspects of isoscaling Alan Davila, Christian Escudero, Jorge Lopez, Claudio Dorso The property of isoscaling in nuclear fragmentation is studied using a simple bond percolation model with ``isospin'' added as an extra degree of freedom. It is shown analytically,first, that isoscaling is expected to exist in such a simple model with the only assumption of fair sampling with homogeneous probabilities. Second, numerical percolations of hundreds of thousands of grids of diferent sizes and with diferent N to Z ratios confirm this prediction with remarkable agreement. It is thus concluded that isoscaling emerges from the simple assumption of fair sampling with homogeneous probabilities, a requirement which, if put in the nomenclature of the minimum information theory, translates simply into the existence of equiprobable configurations in maximum entropy states. [Preview Abstract] |
Friday, October 21, 2005 4:12PM - 4:24PM |
D3.00002: Dynamical aspects of isoscaling Claudio Dorso, Christian Escudero, M. Ison, Jorge Lopez The origin and dynamical evolution of isoscaling was studied using classical molecular dynamics simulations of 40Ca + 40Ca, 48Ca + 48Ca, and 52Ca + 52Ca, at beam energies ranging from 20 MeV/A to 85 MeV/A. The analysis included a study of the time evolution of this effect. Isoscaling was observed to exist in these reactions from the very early primary isotope distributions (produced by highly non-equilibrated systems) all the way to asymptotic times. This indicates that isoscaling is independent of quantum effects and thermodynamical equilibrium. In summary, collision-produced isoscaling appears to be due more to the mere partitioning of the proton-neutron content of the participant nuclei, than to specific details of the reaction dynamics. [Preview Abstract] |
Friday, October 21, 2005 4:24PM - 4:36PM |
D3.00003: Sub-natural resonances in M\"ossbauer spectroscopy Petr Anisimov |
Friday, October 21, 2005 4:36PM - 4:48PM |
D3.00004: Triple and quadruple junctions thermophotovoltaic devices using short-period strain-balanced GaAs$_{1-x}$N$_{x}$ / InAs$_{1-x}$N$_{x }$ superlattices lattice-matched to InP(001) L. Bhusal, A. Freundlich Power conversion in thermophotovoltaic (TPV) or any other photovoltaic device can be increased by implementing monolithically series connected multi-bandgap structure. The main concern for the optimal operation of the multiband gap device is the availability of different band gaps and lattice matching to the available substrat. Based on the recent work, GaAsN/InAsN superlattice (SL) lattice matched to InP has shown the potential of achieving band gaps in the range of 0.7-0.4eV, which is technologically important range for the TPV structure due to the availability of the photon energies in this range from the heat source. In this work, we will present the calculation details and results to find the maximum power generated by the multi-bandgap monolithically series connected devices utilizing the appropriate bandgaps of the SL. Optimized band gaps for well-behaved $p-i$(SL)-$n$ junction subcells were estimated by finding the optimal current to provide the maximum power through the series-connected multi junction cells for given blackbody radiation as an incident flux. [Preview Abstract] |
Friday, October 21, 2005 4:48PM - 5:00PM |
D3.00005: Strain analysis and electronic structure of short-period strain-balanced GaAs$_{1-x}$N$_{x}$/InAs$_{1-x}$N$_{x }$ superlattices lattice-matched to InP(001) L. Bhusal, A. Alemu, A. Freundlich A theoretical strain analysis and investigation of the electronic band structure in the vicinity of the $\Gamma $-point of GaAs$_{1-x}$N$_{x}$/InAs$_{1-x}$N$_{x}$ short period superlattices strain-balanced to (001) InP is performed. Conditions for strain balancing to create nearly zero strained superlattice on InP is developed by minimizing the total strain energy of the system. A six-band Kane Hamiltonian and a band anti-crossing model, modified for the strain effects are used to describe the electronic states of the highly strained zincblend GaAs$_{1-x}$N$_{x}$ and InAs$_{1-x}$N$_{x}$ ternaries. The evolution of the conduction band minima and valence subbands maxima of GaAs$_{1-x}$N$_{x}$ and InAs$_{1-x}$N$_{x}$ as a function of the nitrogen composition (x$<$0.05) indicate the occurrence of a type I band alignment for the superlattice involving the $m_{j}=\pm $3/2 valence subbands and a type II band alignment for the one that involves the $m_{j}=\pm $1/2 valence subbands. Room temperature operating wavelengths, as characterized by the energy gap between the first electron miniband and hole minibands,of these short period superlattices are predicted to extend beyond 3 $\mu $m for x =0.05. [Preview Abstract] |
Friday, October 21, 2005 5:00PM - 5:12PM |
D3.00006: Positron Lifetime Studies on Thermal Aging of Natural Rubber V.O. Jobando |
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