Search results for "monte carlo simulation"
showing 10 items of 104 documents
Dosimetric perturbations of a lead shield for surface and interstitial high-dose-rate brachytherapy.
2014
In surface and interstitial high-dose-rate brachytherapy with either (60)Co, (192)Ir, or (169)Yb sources, some radiosensitive organs near the surface may be exposed to high absorbed doses. This may be reduced by covering the implants with a lead shield on the body surface, which results in dosimetric perturbations. Monte Carlo simulations in Geant4 were performed for the three radionuclides placed at a single dwell position. Four different shield thicknesses (0, 3, 6, and 10 mm) and three different source depths (0, 5, and 10 mm) in water were considered, with the lead shield placed at the phantom surface. Backscatter dose enhancement and transmission data were obtained for the lead shields…
RELAXATION OF ELECTRON SPIN DURING FIELD TRANSPORT IN GaAs BULKS
2011
The spin depolarization of drifting electrons in a n-type doped GaAs bulk semiconductor is studied, in a wide range of lattice temperature (40 K < TL < 300 K) and doping density (10^{13} cm^{−3} < n < 10^{16} cm^{−3}), by adopting a semiclassical Monte Carlo approach. The effect of the mechanism of Dyakonov-Perel (DP) on the spin depolarization of the conduction electrons is analyzed as a function of the amplitude of a static electric field, ranging between 0.1 and 6 kV cm^{−1}, by considering the spin dynamics of electrons in both the Γ-valley and the upper L-valleys of the semiconductor. Moreover, the role of the electron-electron scattering mechanism in the suppression of DP spin relaxat…
Micropollutants throughout an integrated urban drainage model: Sensitivity and uncertainty analysis
2017
Abstract The paper presents the sensitivity and uncertainty analysis of an integrated urban drainage model which includes micropollutants. Specifically, a bespoke integrated model developed in previous studies has been modified in order to include the micropollutant assessment (namely, sulfamethoxazole – SMX). The model takes into account also the interactions between the three components of the system: sewer system (SS), wastewater treatment plant (WWTP) and receiving water body (RWB). The analysis has been applied to an experimental catchment nearby Palermo (Italy): the Nocella catchment. Overall, five scenarios, each characterized by different uncertainty combinations of sub-systems (i.e…
An experience of elicited inquiry elucidating the electron transport in semiconductor crystals
2016
In this study we report the results of an inquiry-driven learning path experienced by a sample of 10 electronic engineering students, engaged to investigate the electron transport in semiconductors. The undergraduates were first instructed by following a lecture-based class on condensed matter physics and then involved into an inquiry based path of simulative explorations. The students were invited by two instructors to explore the electron dynamics in a semiconductor bulk by means of Monte Carlo simulations. The students, working in group, had to design their own procedure of exploration, as expected in a traditional guided inquiry. But they experienced several difficulties on planning and…
Monte Carlo simulation in phylogenies: an application to test the constancy of evolutionary rates.
1994
Monte Carlo simulation has commonly been used in phylogenetic studies to test different tree-reconstruction methods, and consequently, its application for testing evolutionary models can be considered as a natural extension of this usage. Repetitive simulation of a given evolutionary process, under the restrictions imposed by the model to be tested, along a determinate tree topology allow the estimate of probability distributions for the desired parameters. Next, the phylogenetic tree can be reconstructed again without the constraints of the model, and the parameter of interest, derived from this tree, can be compared to the corresponding probability distribution derived from the restricted…
Uncertainty analysis of life cycle assessment of asphalt surfacings
2023
The Life Cycle Assessment (LCA) of asphalt pavements are associated with significant uncertainty resulting from variability in the quantity and impact of individual components, the quality of data for each component, and variability of asphalt durability. This study presents a framework to quantify and incorporate the uncertainty of LCA and asphalt durability data into LCA of asphalt surfacings. The suggested framework includes: estimating the uncertainty of asphalt production processes by the pedigree matrix method, conducting a deterministic LCA, applying Monte Carlo Simulation (MCS) to estimate the probability density functions (PDFs) of the considered impacts using the uncertainty data,…
A new OLS-based procedure for clusterwise linear regression
2009
Data heterogeneity, within a (linear) regression framework, often suggests the use of a Clusterwise Linear Regression (CLR) procedure, which implies, among other things, the estimate of the appropriate number of clusters as well as the cluster membership of each unit. The approaches to the estimation of a CLR model are essentially based on the Ordinary Least Square (OLS) criterion or the likelihood criterion. In this paper, in a context of OLS approach, we propose an estimation of the model making use of an algorithm based on a threshold criterion for the determination coefficient of each cluster, to identify the appropriate number of clusters, and of a modified Spath's algorithm, to estima…
High-temperature X-ray absorption spectroscopy study of thermochromic copper molybdate
2019
Financial support provided by Scientific Research Project for Students and Young Researchers Nr. SJZ/2017/5 and SJZ/2018/1 realized at the Institute of Solid State Physics, University of Latvia is greatly acknowledged. The work was also supported by philanthropist MikroTik and administrated by the University of Latvia Foundation . The experiment at the Elettra synchrotron was performed within the project No. 20150303 .
Thermal disorder and correlation effects in anti-perovskite-type copper nitride
2017
This work has been supported by the Latvian National Research Program IMIS2. The EXAFS experiment has been financed from the European Community's Seventh Framework Programme under grant agreement No. 226716 (Project I-20100098 EC). J.T. also gratefully acknowledges support from the National Science Foundation under the DMREF program Grant No. CHE-1534184.
Monte Carlo analysis of polymer translocation with deterministic and noisy electric fields
2012
AbstractPolymer translocation through the nanochannel is studied by means of a Monte Carlo approach, in the presence of a static or oscillating external electric voltage. The polymer is described as a chain molecule according to the two-dimensional “bond fluctuation model”. It moves through a piecewise linear channel, which mimics a nanopore in a biological membrane. The monomers of the chain interact with the walls of the channel, modelled as a reflecting barrier. We analyze the polymer dynamics, concentrating on the translocation time through the channel, when an external electric field is applied. By introducing a source of coloured noise, we analyze the effect of correlated random fluct…