24,305 research outputs found
Simulating Male Selfish Strategy in Reproduction Dispute
We introduce into the Penna Model for biological ageing one of the possible
male mechanisms used to maximize the ability of their sperm to compete with
sperm from other males. Such a selfish mechanism increases the male
reproduction success but may decrease the survival probability of the whole
female population, depending on how it acts. We also find a dynamic phase
transition induced by the existence of an absorbing state where no selfish
males survive.Comment: 7 pages, latex including 2 eps figure
Towards a knowledge-based system to assist the Brazilian data-collecting system operation
A study is reported which was carried out to show how a knowledge-based approach would lead to a flexible tool to assist the operation task in a satellite-based environmental data collection system. Some characteristics of a hypothesized system comprised of a satellite and a network of Interrogable Data Collecting Platforms (IDCPs) are pointed out. The Knowledge-Based Planning Assistant System (KBPAS) and some aspects about how knowledge is organized in the IDCP's domain are briefly described
Nematic liquid crystal dynamics under applied electric fields
In this paper we investigate the dynamics of liquid crystal textures in a
two-dimensional nematic under applied electric fields, using numerical
simulations performed using a publicly available LIquid CRystal Algorithm
(LICRA) developed by the authors. We consider both positive and negative
dielectric anisotropies and two different possibilities for the orientation of
the electric field (parallel and perpendicular to the two-dimensional lattice).
We determine the effect of an applied electric field pulse on the evolution of
the characteristic length scale and other properties of the liquid crystal
texture network. In particular, we show that different types of defects are
produced after the electric field is switched on, depending on the orientation
of the electric field and the sign of the dielectric anisotropy.Comment: 7 pages, 12 figure
FINITE SIZE SCALING FOR FIRST ORDER TRANSITIONS: POTTS MODEL
The finite-size scaling algorithm based on bulk and surface renormalization
of de Oliveira (1992) is tested on q-state Potts models in dimensions D = 2 and
3. Our Monte Carlo data clearly distinguish between first- and second-order
phase transitions. Continuous-q analytic calculations performed for small
lattices show a clear tendency of the magnetic exponent Y = D - beta/nu to
reach a plateau for increasing values of q, which is consistent with the
first-order transition value Y = D. Monte Carlo data confirm this trend.Comment: 5 pages, plain tex, 5 EPS figures, in file POTTS.UU (uufiles
Broad histogram relation for the bond number and its applications
We discuss Monte Carlo methods based on the cluster (graph) representation
for spin models. We derive a rigorous broad histogram relation (BHR) for the
bond number; a counterpart for the energy was derived by Oliveira previously. A
Monte Carlo dynamics based on the number of potential moves for the bond number
is proposed. We show the efficiency of the BHR for the bond number in
calculating the density of states and other physical quantities.Comment: 7 pages, 7 figure
The viscosity of R32 and R125 at saturation
This paper reports new measurements of the viscosity of R32 and R125, in both the liquid and the vapor phase, over the temperature range 220 to 343 K near the saturation line. The measurements in both liquid and vapor phases have been carried out with a vibrating-wire viscometer calibrated with respect to standard reference values of viscosity. It is estimated that the uncertainty of the
present viscosity data is one of 0.5-1%, being limited partly by the accuracy of
the available density data. The experimental data have been represented by polynomial functions of temperature for the purposes of interpolation
Combination of improved multibondic method and the Wang-Landau method
We propose a method for Monte Carlo simulation of statistical physical models
with discretized energy. The method is based on several ideas including the
cluster algorithm, the multicanonical Monte Carlo method and its acceleration
proposed recently by Wang and Landau. As in the multibondic ensemble method
proposed by Janke and Kappler, the present algorithm performs a random walk in
the space of the bond population to yield the state density as a function of
the bond number. A test on the Ising model shows that the number of Monte Carlo
sweeps required of the present method for obtaining the density of state with a
given accuracy is proportional to the system size, whereas it is proportional
to the system size squared for other conventional methods. In addition, the new
method shows a better performance than the original Wang-Landau method in
measurement of physical quantities.Comment: 12 pages, 3 figure
Simulation of VUV electroluminescence in micropattern gaseous detectors: the case of GEM and MHSP
Electroluminescence produced during avalanche development in gaseous
avalanche detectors is an useful information for triggering, calorimetry and
tracking in gaseous detectors. Noble gases present high electroluminescence
yields, emitting mainly in the VUV region. The photons can provide signal
readout if appropriate photosensors are used. Micropattern gaseous detectors
are good candidates for signal amplification in high background and/or low rate
experiments due to their high electroluminescence yields and radiopurity. In
this work, the VUV light responses of the Gas Electron Multiplier and of the
Micro-Hole Strip Plate, working with pure xenon, are simulated and studied in
detail using a new and versatile C++ toolkit. It is shown that the solid angle
subtended by a photosensor placed below the microstructures depends on the
operating conditions. The obtained absolute EL yields, determined for different
gas pressures and as functions of the applied voltage, are compared with those
determined experimentally.Comment: Accepted for publication in Journal of Instrumentatio
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