Search results for "Computer simulation"

Influence of the simultaneous calibration of multiple ring dosimeters on the individual absorbed dose

2021

Abstract Ring dosimeters for personal dosimetry are calibrated in accredited laboratories following ISO 4037-3 guidelines. The simultaneous irradiation of multiple dosimeters would save time, but has to be carefully studied, since the scattering conditions could change and influence the absorbed dose in nearby dosimeters. Monte Carlo simulations using PENELOPE-2014 were performed to explore the need to increase the uncertainty of H p 0 .07 in the simultaneous irradiation of three and five DXT-RAD 707H-2 (Thermo Scientific) ring dosimeters with beam qualities: N-30, N-80 and N-300. Results show that the absorbed dose in each dosimeter is compatible with each of the others and with the refere…

Numerical Simulation as a Tool for Design Optimization of Two-Phase Swirl Flow Atomizers

2021

This study aims to analyze the hydrodynamics in two-phase swirl flow conical atomizers. The Euler-Euler model was used for the calculations. Numerical simulations were performed to provide information about the fluid velocity distribution and the atomizer’s internal flow. The numerical calculations confirmed the experimental data. This data was found based on the consistency of the spray angles obtained by both methods. Assuming the correctness of the numerical simulations performed, they can be treated as a tool for further analysis of mass and energy exchange along with the atomizer and optimizing the atomizer’s design depending on the requirements. The influence of the swirl chamber geom…

A two steps Lagrangian–Eulerian numerical model for the simulation of explosive welding of three dissimilar materials joints

2021

Abstract Explosion welding (EXW) is a solid-state joining process used to produce lap joints out of metal plates of dissimilar materials. During the process, a controlled explosive detonation results in a pressure wave pushing one of the plates to be welded, called flyer, against the other with high velocity. The high pressure and temperature generated, because of the impact energy decaying into heat, create the conditions for solid bonding phenomenon to take place. Due to the complexity of experimental tests, numerical simulation is considered a fundamental design tool for the process. Different approaches are found in literature to simulate the process. In this paper, a dual step Lagrangi…

Numerical simulation of heat transfer problem for layered gypsum products exposed to fire

2018

Ion conduction in the KcsA potassium channel analyzed with a minimal kinetic model.

2004

We use a model by Nelson to study the current-voltage and conductance-concentration curves of bacterial potassium channel KcsA without assuming rapid ion translocation. Ion association to the channel filter is rate controlling at low concentrations, but dissociation and transport in the filter can limit conduction at high concentration for ions other than ${\mathrm{K}}^{+}$. The absolute values of the effective rate constants are tentative but the relative changes in these constants needed to qualitatively explain the experiments should be of significance.

Features of randomized electric-field assisted domain inversion in lithium tantalate

2011

We report on bulk and guided-wave second-harmonic generation via random Quasi-Phase-Matching in Lithium Tantalate. By acquiring the far-field profiles at several wavelengths, we extract statistical information on the distribution of the quadratic nonlinearity as well as its average period, both at the surface and in the bulk of the sample. By investigating the distribution in the two regions we demonstrate a non-invasive approach to the study of poling dynamics.

Crystallization in suspensions of hard spheres: a Monte Carlo and molecular dynamics simulation study

2011

The crystallization of a metastable melt is one of the most important non-equilibrium phenomena in condensed matter physics, and hard sphere colloidal model systems have been used for several decades to investigate this process by experimental observation and computer simulation. Nevertheless, there is still an unexplained discrepancy between the simulation data and experimental nucleation rate densities. In this paper we examine the nucleation process in hard spheres using molecular dynamics and Monte Carlo simulation. We show that the crystallization process is mediated by precursors of low orientational bond-order and that our simulation data fairly match the experimental data sets.

A Numerical Study on Interlaminar Defects Characterization in Fibre Metal Laminates with Flying Laser Spot Thermography

2018

This work describes a numerical study on non-destructive evaluation of interlayer disbond defects in aerospace grade Fibre Metal Laminate sheets (FMLs). A recently proposed infrared non-destructive testing setup is considered, where a continuous laser is moved over the material surface, while the thermal footprint of the moving heat source is acquired, e.g. by an infrared thermal camera. Interlayer disbonds are then detected by analysing the features of the acquired thermograms. The experimental feasibility of this approach has been recently proved. The present work proposes a numerical simulation of the NDT approach, where the material thermal response is analysed and correlated to defects…

Octave-spanning ultraflat supercontinuum with soft-glass photonic crystal fibers

2009

We theoretically identify some photonic-crystal-fiber structures, made up of soft glass, that generate ultrawide (over an octave) and very smooth supercontinuum spectra when illuminated with femtosecond pulsed light. The design of the fiber geometry in order to reach a nearly ultraflattened normal dispersion behavior is crucial to accomplish the above goal. Our numerical simulations reveal that these supercontinuum sources show high stability and no significant changes are detected even for fairly large variations of the incident pulse. Ministerio de Ciencia e Innovación (TEC2008-05490) and Generalitat Valenciana (GV/2007/043).

Study of the glow curves of TLD exposed to thermal neutrons.

2007

The glow curves of thermoluminescent dosimeters (TLD600, TLD700 and MCP), exposed to a mixed field of thermal neutrons and gamma photons are analysed. The fluence values of thermal neutrons used, comparable with those used in radiotherapy, allow one to define the reliability of the TLDs, in particular the most sensitive MCP, in this radiation field and to get information on the dose absorbed values. The glow curves obtained have been deconvoluted using general order kinetics and the observed differences for the different LET components have been analysed. In particular, the ratio of the n(0) parameter of two different peaks seems to allow to discriminate the different contributions of neutr…