Search results for "Monte carlo method"

Finite-size scaling approach for critical wetting: rationalization in terms of a bulk transition with an order parameter exponent equal to zero.

2012

Clarification of critical wetting with short-range forces by simulations has been hampered by the lack of accurate methods to locate where the transition occurs. We solve this problem by developing an anisotropic finite-size scaling approach and show that then the wetting transition is a ``bulk'' critical phenomenon with order parameter exponent equal to zero. For the Ising model in two dimensions, known exact results are straightforwardly reproduced. In three dimensions, it is shown that previous estimates for the location of the transition need revision, but the conclusions about a slow crossover away from mean-field behavior remain unaltered.

Multicanonical Monte Carlo study and analysis of tails for the order-parameter distribution of the two-dimensional Ising model.

2003

The tails of the critical order-parameter distribution of the two-dimensional Ising model are investigated through extensive multicanonical Monte Carlo simulations. Results for fixed boundary conditions are reported here, and compared with known results for periodic boundary conditions. Clear numerical evidence for ‘‘fat’’ stretched exponential tails exists below the critical temperature, indicating the possible presence of fat tails at the critical temperature. Our work suggests that the true order-parameter distribution at the critical temperature must be considered to be unknown at present.

Initial state anisotropies in ultrarelativistic heavy-ion collisions from the Monte Carlo Glauber model

2012

In hydrodynamicalmodeling of heavy-ion collisions the initial state spatial anisotropies translate into momentum anisotropies of the final state particle distributions. Thus, understanding the origin of the initial anisotropies and quantifying their uncertainties is important for the extraction of specific QCD matter properties, such as viscosity, from the experimental data. In this work we study the wounded nucleon approach in the Monte Carlo Glauber model framework, focusing especially on the uncertainties which arise from the modeling of the nucleon-nucleon interactions between the colliding nucleon pairs and nucleon-nucleon correlations inside the colliding nuclei. We compare the black …

On the measurement of local gas hold-up and interfacial area in gas–liquid contactors via light sheet and image analysis

2010

Abstract Particle image velocimetry techniques coupled with advanced image processing tools are receiving an increasing interest for measuring flow quantities and local bubble-size distributions in gas–liquid contactors. Aim of this work is that of providing a numerical procedure able to reconstruct local gas hold-up and specific interfacial area from images obtained by laser sheet illumination. A correction for measured quantities accounting for laser sheet thickness is proposed and tested by means of Monte Carlo simulations. The algorithms proposed are robust and independent of any measured parameters of the actual bubble size distribution.

SU-F-T-13: Transit Dose Comparisons for Co-60 and Ir-192 HDR Sources

2016

Purpose: The purpose of this study is to compare the transit dose due to the movement of high dose rate (HDR) Ir-192 and Co-60 sources along the transfer tube. This is performed by evaluating air-kerma differences in the vicinity of the transfer tube when both sources are moved with the same velocity from a HDR brachytherapy afterloader into a patient. Methods: Monte Carlo simulations have been performed using PENELOPE2014. mHDR-v2 and Flexisource sources have been considered. Collisional kerma has been scored. The sources were simulated within a plastic catheter located in an infinite air phantom. The movement of the seed was included by displacing their positions along the connecting cath…

A Monte Carlo investigation of the dosimetric characteristics of the CSM11 137Cs source from CIS

2000

The purpose of this study is to calculate basic dosimetry data for a CSM11 low dose rate 137Cs source in water. This source is widely used in afterloadable dome cylinders designed to homogeneously irradiate the vaginal cuff alone or additional areas of the vagina in hysterectomized patients. In this study, the Monte Carlo simulation code GEANT, incorporating in detail source geometry, is used to investigate the dosimetric characteristics of the source. The calculated data were analyzed using a fitting procedure that is described in detail. Absolute dose rate distributions in water were calculated around this source and are presented as conventional 2D Cartesian lookup tables (classically al…

Dosimetric characteristics of the CDC-type miniature cylindrical 137Cs brachytherapy sources

2002

The low dose rate CDC-type miniature cylindrical 137 Cs sources are available, with one or three active beads, for use in source trains in automatic and manual afterloading systems for gynecological brachytherapy. Absolute dose rate distributions in water have been calculated around these sources using the Monte CarloGEANT3 code and they are presented as conventional two-dimensional Cartesian lookup tables. The AAPM Task Group 43 formalism for dose calculation has been also applied. The dose rate constant obtained for the one bead source is Λ=1.113±0.003 cGyh −1 U −1 , and the value for the three bead source is Λ=1.103±0.003 cGyh −1 U −1 . Finally, for the treatment planning systems based o…

Radiation dose distribution around a mobile linear accelerator Mobetron using Monte Carlo simulation

2016

The aim of this work is to analyze the scattered radiation produced by the mobile accelerator Mobetron. To do so detailed Monte Carlo simulation using two different codes, Penelope2011 and Geant4, were performed. Experimental measurements were also done to validate them. To quantify the attenuation of the internal structures present in the accelerator head on the scattered radiation produced, some of the main structural shielding in the Mobetron has been incorporated into the simulation. Results are compared with experimental measurements. Some discrepancies between the calculated and measured dose values were found. These differences can be traced back to the importance of the radiation co…

EP-1187: Measurements and Monte Carlo modeling of the back scatter from linac secondary collimator into beam monitor chamber

2013

Stochastic seismic analysis of structures with nonlinear viscous dampers

2007

Fluid damper devices inserted in buildings or bridges are commonly used as energy sinks for seismic protection. In the response analysis of structures with filled damper devices the main problem exists in the strong nonlinear behavior of such equipment, as a consequence the differential equation of motion remains nonlinear and the response spectrum analysis still cannot be applied. In this note, by using the concept of power spectral density function coherent with the elastic response spectrum and by using the statistical linearization technique, expressions for finding the equivalent linear damping have been found. Comparisons with results obtained by Monte Carlo simulations confirm that f…