The reflection of light ions, such as H+,3He+ and 4He+, with energies of 0.1- 10 keV, from Cu and Ni surface has been studied by Monte Carlo simulation and transport theory. The Monte Carlo simulation gives the detail...The reflection of light ions, such as H+,3He+ and 4He+, with energies of 0.1- 10 keV, from Cu and Ni surface has been studied by Monte Carlo simulation and transport theory. The Monte Carlo simulation gives the detail energy spectra for the reflected particles and their angular distribution for different incident angles. It shows that the reflected particle energy spectra can be approximately described by an analytical formula for the whole energy range, all the incident angles and different ion- target combination studied here. The reflected particle energy vs its average reflection angle to the surface normal can almost be expressed by a universal curve for all cases studied here. The reflection energy spectra are used for the calculation of the reflection coefficient by transport theory including the realistic surface correction. The present work is compared with both experimental measurement and other simulation codes.展开更多
When multiphysics coupling calculations contain time-dependent Monte Carlo particle transport simulations, these simulations often account for the largest part of the calculation time, which is insufferable in certain...When multiphysics coupling calculations contain time-dependent Monte Carlo particle transport simulations, these simulations often account for the largest part of the calculation time, which is insufferable in certain important cases. This study proposes an adaptive strategy for automatically adjusting the sample size to fulfil more reasonable simulations. This is realized based on an extension of the Shannon entropy concept and is essentially different from the popular methods in timeindependent Monte Carlo particle transport simulations, such as controlling the sample size according to the relative error of a target tally or by experience. The results of the two models show that this strategy can yield almost similar results while significantly reducing the calculation time. Considering the efficiency, the sample size should not be increased blindly if the efficiency cannot be enhanced further. The strategy proposed herein satisfies this requirement.展开更多
A Monte Carlo simulation method with an instantaneous density dependent meanfree-path of the ablated particles and the Ar gas is developed for investigating the transport dynamics of the laser-ablated particles in a l...A Monte Carlo simulation method with an instantaneous density dependent meanfree-path of the ablated particles and the Ar gas is developed for investigating the transport dynamics of the laser-ablated particles in a low pressure inert gas.The ablated-particle density and velocity distributions are analyzed.The force distributions acting on the ablated particles are investigated.The influence of the substrate on the ablated-particle velocity distribution and the force distribution acting on the ablated particles are discussed.The Monte Carlo simulation results approximately agree with the experimental data at the pressure of 8 Pa to 17 Pa.This is helpful to investigate the gas phase nucleation and growth mechanism of nanoparticles.展开更多
In this paper, the integrated software system named PRDII(Project Range Distribution of Ion Implantation), which is based on the transport theory and Monte Carlo method and is developed by ourselves for range distribu...In this paper, the integrated software system named PRDII(Project Range Distribution of Ion Implantation), which is based on the transport theory and Monte Carlo method and is developed by ourselves for range distribution of ion implantation, is introduced. The system generally possess versatility., efficiency and practicality. As for versatility, the system can build and utilize the parameter bank of various ions and material bank of various parts, can calculate the range distributions of implanted ions in the target for various conditions, such as for different incident ions, for different compositions and shapes of targets, for different energies.. doses and angles of incidence; As for efficiency, the computations are accelerated greatly by using some numerical simulating formulae instead of numerical iterative solutions in key procedure and using fixed fly path instead of random fly path; As for practicality, the preassumptions of the simulation are more close to the reality and the simulating results are more accurate in that the sputtering and the dynamic changes of target composition during penetration are considered and the advanced Monte Carlo method is used. Compared to other similar software, such as famous TRIM[1] and SASAMAL[2], it is more beautiful for interface, more convenient for operation, It can call, compute.. compare.. comment, copy and print all curves needed, and the simulating results consist with the experiments very well.展开更多
Understanding the excluded volume of anisotropic particle is of great importance in the evaluation of continuum percolation and random packing behaviors of soft/hard particle systems in heterogeneous disordered media....Understanding the excluded volume of anisotropic particle is of great importance in the evaluation of continuum percolation and random packing behaviors of soft/hard particle systems in heterogeneous disordered media.In this work,we obtain the excluded volumes of several anisotropic convex particles including prolate spheroids,oblate spheroids,spherocylinders,and Platonic particles,using theoretical and numerical approaches.According to the second virial coefficient,we first present a theoretical scheme for determining the excluded volumes of anisotropic particles.Also,the mean tangent diameters of anisotropic convex particles are formulated by the quantitative stereology.Subsequently,Monte Carlo simulations are demonstrated to numerically evaluate the excluded volumes.The theoretical results of the dimensionless excluded volume are thereafter compared with that of the numerical results to verify the validity of the theoretical scheme.We further investigate the dependence of the dimensionless excluded volume on the geometric characteristics of anisotropic particles based on the proposed theoretical and numerical schemes.Results show that the dimensionless excluded volume mainly relies on the shape and surface information of anisotropic particles.The developed theoretical and numerical schemes can provide theoretical insights into the percolation threshold and packing density of soft/hard anisotropic particle systems in heterogeneous materials,physics,and chemistry fields.展开更多
在核测井领域,蒙特卡罗方法应用于仪器开发设计到数据解释的各个环节。通用型多粒子输运程序(Monte Carlo N-Particle Transport Code,MCNP)作为领域内开展研究和解决问题的首要选择,其使用一直以来都受到许可限制,令研究人员面临挑战...在核测井领域,蒙特卡罗方法应用于仪器开发设计到数据解释的各个环节。通用型多粒子输运程序(Monte Carlo N-Particle Transport Code,MCNP)作为领域内开展研究和解决问题的首要选择,其使用一直以来都受到许可限制,令研究人员面临挑战。因此,FLUktuierende KAskade(FLUKA)具有开放使用权限的优势,利用FLUKA开展核测井基准模拟,对比分析FLUKA作为MCNP替代方案的可行性。利用FLUKA和MCNP分别构建具有代表性的核测井基准模型,涵盖伽马射线输运、中子输运以及伽马-中子耦合输运过程,获取了伽马能谱和密度、孔隙度等测井响应,用以评估FLUKA在低能辐射传输模拟中的表现。研究结果显示,对于低能伽马辐射输运,FLUKA获取的地层散射伽马能谱和MCNP响应之间的最大相对误差为5.37%,密度响应相对误差在3.75%以内。对于低能中子输运,二者孔隙度响应的相对误差不超过1%,并且中子诱发伽马射线能谱基本吻合。该研究通过对基准核测井问题的模拟分析,证明了可以使用FLUKA代替MCNP在核测井领域分析解决问题。展开更多
In gamma spectrometry of voluminous samples, inhomogeneous distribution of radioactivity caused by the presence of hot particles can create significant Bias in the results of activity determinations. We developed a no...In gamma spectrometry of voluminous samples, inhomogeneous distribution of radioactivity caused by the presence of hot particles can create significant Bias in the results of activity determinations. We developed a novel method to reduce this Bias using the gamma-peak ratio. We show that the peak area ratio of two gamma peaks of different energies, emitted by the same radionuclide, is a sensitive measure of emitting source location and thus the inhomogeneity. A new calibration formula was then derived for true gamma efficiency <em>p<sub>i</sub></em> as a function of efficiency ratio <em>p<sub>i</sub></em>/<em>p<sub>j</sub></em> of two peaks. This approach was verified by Monte Carlo simulations for a sample of 1-L volume containing from 1 up to 2048 of hot particles randomly distributed in a soil matrix. A <sup>152</sup>Eu radionuclide was selected for calculations and we used various combinations of two gamma spectral peaks selected from three gamma energies of 121.8, 344.3, and 1408.0 keV. This new method is shown to reduce the Bias range and Bias standard deviation by several times when compared with the traditional homogeneous calibration applied to measuring hot particles. The method is independent of the number, location, and distribution of hot particles in the samples, and can be applied to a mixture of radionuclides. It complements our previous calibration model based on the peak-to-total ratio.展开更多
基金The Project Supported by the National Natural Science Foundation of China
文摘The reflection of light ions, such as H+,3He+ and 4He+, with energies of 0.1- 10 keV, from Cu and Ni surface has been studied by Monte Carlo simulation and transport theory. The Monte Carlo simulation gives the detail energy spectra for the reflected particles and their angular distribution for different incident angles. It shows that the reflected particle energy spectra can be approximately described by an analytical formula for the whole energy range, all the incident angles and different ion- target combination studied here. The reflected particle energy vs its average reflection angle to the surface normal can almost be expressed by a universal curve for all cases studied here. The reflection energy spectra are used for the calculation of the reflection coefficient by transport theory including the realistic surface correction. The present work is compared with both experimental measurement and other simulation codes.
基金supported by the CAEP Found (No.CX20200028)Youth Program of National Natural Science Foundation of China (No.11705011).
文摘When multiphysics coupling calculations contain time-dependent Monte Carlo particle transport simulations, these simulations often account for the largest part of the calculation time, which is insufferable in certain important cases. This study proposes an adaptive strategy for automatically adjusting the sample size to fulfil more reasonable simulations. This is realized based on an extension of the Shannon entropy concept and is essentially different from the popular methods in timeindependent Monte Carlo particle transport simulations, such as controlling the sample size according to the relative error of a target tally or by experience. The results of the two models show that this strategy can yield almost similar results while significantly reducing the calculation time. Considering the efficiency, the sample size should not be increased blindly if the efficiency cannot be enhanced further. The strategy proposed herein satisfies this requirement.
基金supported by the Natural Science Foundation of Hebei Province,China(No.A2015201166)the Natural Science Foundation of Hebei University,China(No.2013-252)
文摘A Monte Carlo simulation method with an instantaneous density dependent meanfree-path of the ablated particles and the Ar gas is developed for investigating the transport dynamics of the laser-ablated particles in a low pressure inert gas.The ablated-particle density and velocity distributions are analyzed.The force distributions acting on the ablated particles are investigated.The influence of the substrate on the ablated-particle velocity distribution and the force distribution acting on the ablated particles are discussed.The Monte Carlo simulation results approximately agree with the experimental data at the pressure of 8 Pa to 17 Pa.This is helpful to investigate the gas phase nucleation and growth mechanism of nanoparticles.
文摘In this paper, the integrated software system named PRDII(Project Range Distribution of Ion Implantation), which is based on the transport theory and Monte Carlo method and is developed by ourselves for range distribution of ion implantation, is introduced. The system generally possess versatility., efficiency and practicality. As for versatility, the system can build and utilize the parameter bank of various ions and material bank of various parts, can calculate the range distributions of implanted ions in the target for various conditions, such as for different incident ions, for different compositions and shapes of targets, for different energies.. doses and angles of incidence; As for efficiency, the computations are accelerated greatly by using some numerical simulating formulae instead of numerical iterative solutions in key procedure and using fixed fly path instead of random fly path; As for practicality, the preassumptions of the simulation are more close to the reality and the simulating results are more accurate in that the sputtering and the dynamic changes of target composition during penetration are considered and the advanced Monte Carlo method is used. Compared to other similar software, such as famous TRIM[1] and SASAMAL[2], it is more beautiful for interface, more convenient for operation, It can call, compute.. compare.. comment, copy and print all curves needed, and the simulating results consist with the experiments very well.
基金The authors acknowledge financial supports from National Natural Science Foundation Project of China(Grant No.11402076)Natural Science Foundation Project for Jiangsu Province(Grant No.BK20130841)+5 种基金China Postdoctoral Science Foundation Funded Project(Grant Nos.2014M560385 and 2015T80493)the Open Research Fund of State Key Laboratory of Structural Analysis for Industrial Equipment(Grant No.GZ1405)the Open Research Fund of State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin(Grant No.IWHR-SKL-201511)the Open Research Fund of Jiangsu Key Laboratory of Construction Materials(Grant No.CM2014-03)Jiangsu Postdoctoral Science Foundation Project(Grant No.1402053C)Research Special of the China Institute of Water Resources and Hydropower Research(Grant No.KY1640).
文摘Understanding the excluded volume of anisotropic particle is of great importance in the evaluation of continuum percolation and random packing behaviors of soft/hard particle systems in heterogeneous disordered media.In this work,we obtain the excluded volumes of several anisotropic convex particles including prolate spheroids,oblate spheroids,spherocylinders,and Platonic particles,using theoretical and numerical approaches.According to the second virial coefficient,we first present a theoretical scheme for determining the excluded volumes of anisotropic particles.Also,the mean tangent diameters of anisotropic convex particles are formulated by the quantitative stereology.Subsequently,Monte Carlo simulations are demonstrated to numerically evaluate the excluded volumes.The theoretical results of the dimensionless excluded volume are thereafter compared with that of the numerical results to verify the validity of the theoretical scheme.We further investigate the dependence of the dimensionless excluded volume on the geometric characteristics of anisotropic particles based on the proposed theoretical and numerical schemes.Results show that the dimensionless excluded volume mainly relies on the shape and surface information of anisotropic particles.The developed theoretical and numerical schemes can provide theoretical insights into the percolation threshold and packing density of soft/hard anisotropic particle systems in heterogeneous materials,physics,and chemistry fields.
文摘在核测井领域,蒙特卡罗方法应用于仪器开发设计到数据解释的各个环节。通用型多粒子输运程序(Monte Carlo N-Particle Transport Code,MCNP)作为领域内开展研究和解决问题的首要选择,其使用一直以来都受到许可限制,令研究人员面临挑战。因此,FLUktuierende KAskade(FLUKA)具有开放使用权限的优势,利用FLUKA开展核测井基准模拟,对比分析FLUKA作为MCNP替代方案的可行性。利用FLUKA和MCNP分别构建具有代表性的核测井基准模型,涵盖伽马射线输运、中子输运以及伽马-中子耦合输运过程,获取了伽马能谱和密度、孔隙度等测井响应,用以评估FLUKA在低能辐射传输模拟中的表现。研究结果显示,对于低能伽马辐射输运,FLUKA获取的地层散射伽马能谱和MCNP响应之间的最大相对误差为5.37%,密度响应相对误差在3.75%以内。对于低能中子输运,二者孔隙度响应的相对误差不超过1%,并且中子诱发伽马射线能谱基本吻合。该研究通过对基准核测井问题的模拟分析,证明了可以使用FLUKA代替MCNP在核测井领域分析解决问题。
文摘In gamma spectrometry of voluminous samples, inhomogeneous distribution of radioactivity caused by the presence of hot particles can create significant Bias in the results of activity determinations. We developed a novel method to reduce this Bias using the gamma-peak ratio. We show that the peak area ratio of two gamma peaks of different energies, emitted by the same radionuclide, is a sensitive measure of emitting source location and thus the inhomogeneity. A new calibration formula was then derived for true gamma efficiency <em>p<sub>i</sub></em> as a function of efficiency ratio <em>p<sub>i</sub></em>/<em>p<sub>j</sub></em> of two peaks. This approach was verified by Monte Carlo simulations for a sample of 1-L volume containing from 1 up to 2048 of hot particles randomly distributed in a soil matrix. A <sup>152</sup>Eu radionuclide was selected for calculations and we used various combinations of two gamma spectral peaks selected from three gamma energies of 121.8, 344.3, and 1408.0 keV. This new method is shown to reduce the Bias range and Bias standard deviation by several times when compared with the traditional homogeneous calibration applied to measuring hot particles. The method is independent of the number, location, and distribution of hot particles in the samples, and can be applied to a mixture of radionuclides. It complements our previous calibration model based on the peak-to-total ratio.
