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Transient monte carlo simulation of phonon transport in silicon nanofilms with the local heat source

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Science China(Technological Sciences) 2024年第7期67卷 2087-2098页

作者： LI JiaQi CAI JiuQing LI Rui LIU ZhiChun LIU Wei School of Energy and Power Engineering Huazhong University of Science and TechnologyWuhan 430074China Wuhan Second Ship Design and Research Institute Wuhan 430205China

Accurate prediction of junction temperature is crucial for the efficient thermal design of silicon nano-devices. In nano-scale semiconductor devices, significant ballistic effects occur due to the mean free path of phonons comparable to the heat source size and device scale. We employ a three-dimensional non-gray monte carlo simulation to investigate the transient heat conduction of silicon nanofilms with both single and multiple heat sources. The accuracy of the present method is first verified in the ballistic and diffusion limits. When a single local heat source is present, the width of the heat source has a significant impact on heat conduction in the domain. Notably, there is a substantial temperature jump at the boundary when the heat source width is 10 *** increasing heat source width, the boundary temperature jump weakens. Furthermore, we observe that the temperature excitation rate is independent of the heat source width, while the temperature influence range expands simultaneously with the increase in heat source width. Around 500 ps, the temperature and heat flux distribution in the domain stabilize. In the case of dual heat sources, the hot zone is broader than that of a single heat source, and the temperature of the hot spot decreases as the heat source spacing increases. However, the mean heat flux remains unaffected. Upon reaching a spacing of 200 nm between the heat sources, the peak temperature in the domain remains unchanged once a steady state is reached. These findings hold significant implications for the thermal design of silicon nano-devices with local heat sources.

关键词： phonon transport monte carlo simulation transient heat conduction silicon nanofilms local heat source

Health risk assessment of trace metal(loid)s in agricultural soils based on monte carlo simulation coupled with positive matrix factorization model in Chongqing, southwest China

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Journal of Mountain Science 2024年第1期21卷 100-112页

作者： MA Jie CHU Lijuan SUN Jing WANG Shenglan GE Miao DENG Li Chongqing Ecological and Environmental Monitoring Center Chongqing 401147China Key Laboratory of Organic Pollutants in Environmental Chemical Behavior and Ecological Toxicology of Chongqing Chongqing 401147China Department of Pediatrics Chongqing Health Center for Women and ChildrenChongqing 401147China Department of Pediatrics Women and Children’s Hospital of Chongqing Medical UniversityChongqing 401147China

This study aimed to investigate the pollution characteristics, source apportionment, and health risks associated with trace metal(loid)s(TMs) in the major agricultural producing areas in Chongqing, China. We analyzed the source apportionment and assessed the health risk of TMs in agricultural soils by using positive matrix factorization(PMF) model and health risk assessment(HRA) model based on monte carlo simulation. Meanwhile, we combined PMF and HRA models to explore the health risks of TMs in agricultural soils by different pollution sources to determine the priority control factors. Results showed that the average contents of cadmium(Cd), arsenic (As), lead(Pb), chromium(Cr), copper(Cu), nickel(Ni), and zinc(Zn) in the soil were found to be 0.26, 5.93, 27.14, 61.32, 23.81, 32.45, and 78.65 mg/kg, respectively. Spatial analysis and source apportionment analysis revealed that urban and industrial sources, agricultural sources, and natural sources accounted for 33.0%, 27.7%, and 39.3% of TM accumulation in the soil, respectively. In the HRA model based on monte carlo simulation, noncarcinogenic risks were deemed negligible(hazard index <1), the carcinogenic risks were at acceptable level(10^(-6)

关键词： monte carlo simulation Health risk assessment Trace metal(loid)s Positive matrix factorization Agricultural soils

Optimization of the Use of Spherical Targets for Point Cloud Registration Using monte carlo simulation

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Journal of Geodesy and Geoinformation Science 2024年第2期7卷 18-36页

作者： CHAN Ting On XIAO Hang XIA Linyuan LICHTI Derek D LI Ming Ho DU Guoming School of Geography and Planning Sun Yat-sen UniversityGuangzhou 510275China Guangdong Provincial Key Laboratory of Urbanization and Geo-simulation Sun Yat-sen UniversityGuangzhou 510275China Guangdong Provincial Engineering Research Center for Public Security and Disasters Sun Yat-sen UniversityGuangzhou 510275China Department of Geomatics Engineering Schulich School of EngineeringUniversity of CalgaryCalgary AB T2N 1N4Canada

Registrations based on the manual placement of spherical targets are still being employed by many professionals in the ***,the placement of those targets usually relies solely on personal experience without scientific evidence supported by numerical *** paper presents a comprehensive investigation,based on monte carlo simulation,into determining the optimal number and positions for efficient target placement in typical scenes consisting of a pair of *** demonstrates new check-up statistical rules and geometrical constraints that can effectively extract and analyze massive simulations of unregistered point clouds and their corresponding *** than 6×10^(7) sets of the registrations were simulated,whereas more than IOO registrations with real data were used to verify the results of *** results indicated that using five spherical targets is the best choice for the registration of a large typical registration site consisting of two vertical facades and a ground,when there is only a box set of spherical targets *** a result,the users can avoid placing extra targets to achieve insignificant improvements in registration *** results also suggest that the higher registration accuracy can be obtained when the ratio between the facade-to-target distance and target-to-scanner distance is approximately 3:***,the targets should be placed closer to the scanner rather than in the middle between the facades and the scanner,contradicting to the traditional thought. Besides,the results reveal that the accuracy can be increased by setting the largest projected triangular area of the targets to be large.

关键词： point cloud registration monte carlo simulation optimalization spherical target

monte carlo simulation of reflection effects of multi-element materials on gamma rays

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Nuclear Science and Techniques 2021年第1期32卷 85-94页

作者： Ying-Hong Zuo Jin-Hui Zhu Peng Shang Northwest Institute of Nuclear Technology Xi’an 710024China

To study the effects of the gamma reflection of multi-element materials,gamma ray transport models of single-element materials,such as iron and lead,and multielement materials,such as polyethylene and ordinary concrete,were established in this *** among the albedo factors of the gamma photons and energies and average energy of the reflected gamma rays by material type,material thickness,incident gamma energy,and incidence angle of gamma rays were obtained by monte carlo *** results show that the albedo factors of single-element and multi-element materials increase rapidly with an increase in the material *** the thickness of the material increases to a certain value,the albedo factors do not increase further but rather tend to the saturation *** saturation values for the albedo factors of the gamma photons,and energies and the reflection thickness are related not only to the type of material but also to the incident gamma energy and incidence angle of the gamma *** a given incident gamma energy,which is between 0.2 and 2.5 MeV,the smaller the effective atomic number of the multi-element material is,the higher the saturation values of the albedo factors *** larger the incidence angle of the gamma ray is,the greater the saturation value of the gamma albedo factor,saturation reflection thickness,and average saturation energy of the reflected gamma photons are.

关键词： Multi-element materials Gamma albedo factor Effective atomic number monte carlo simulation

monte carlo simulation of the Structure of Mono-and Bidisperse Polyethylene Nanocomposites

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Chinese Journal of Polymer Science 2015年第2期33卷 275-283页

作者： Adisak Takhulee Rahmi Ozisik Visit Vao-soongnern Laboratory of Computational and Applied Polymer Science School of Chemistry Institute of Science Suranaree University of Technology Department of Materials Science and Engineering Rensselaer Polytechnic Institute

The structure of bidisperse polyethylene（PE） nanocomposite mixtures of 50：50（by mole） of long and short chains of C160H322/C80H162 and C160H322/C40H82 filled with spherical nanoparticles were investigated by a coarse-grained, on lattice monte carlo method using rotational isomeric state theory for short-range and Lennard-Jones for long-range energetic interactions. simulations were performed to evaluate the effect of wall-to-wall distance between fillers（D）, polymer-filler interaction（w） and polydispersity（number of short chains in the mixture） on the behavior of the long PE chains. The results indicate that long chain conformation statistics remain Gaussian regardless of the effects of confinement, interaction strength and polydispersity. The various long PE subchain structures（bridges, dangling ends, trains, and loops） are influenced strongly by confinement whereas monomer-filler interaction and polydispersity did not have any impact. In addition, the average number of subchain segments per filler in bidisperse PE nanocomposites decreased by about 50% compared to the nanocomposite system with monodisperse PE chains. The presence of short PE chains in the polymer matrix leads to a reduction of the repeat unit density of long PE chains at the interface suggesting that the interface is preferentially populated by short chains.

关键词： monte carlo simulation Polymer nanocomposites Bidisperse

monte carlo simulation of neutron sensitivity of microfission chamber in neutron flux measurement

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Nuclear Science and Techniques 2022年第6期33卷 128-138页

作者： Ze-Peng Wu Xin-Biao Jiang Wen-Shou Zhang Chun-Lei Su Yong-Gang Zhang-Sun Li-Hong Bao State Key Laboratory of simulation and Effect for Intense Pulse Radiation Northwest Institute of Nuclear TechnologyXi’an 710024China

Microfission chambers loaded with highly enriched fissile materials are widely used for measuring power in reactors. The neutron sensitivity of the microfission chamber is a key parameter that determines the accuracy of the power measurement. To evaluate the performance of the FC4A microfission chamber, in this work, we introduced an accurate and validated model of the microfission chamber, a performed monte carlo simulation of the neutron sensitivity of the microfission chamber with GEANT4 code, and conducted an irradiation experiment on the neutron irradiation effect platform #3 of the Xi’an Pulsed Reactor. We compared the simulated sensitivity with the experimental results, which showed that the sensitivity obtained from the simulation was in good agreement with the experimental results. In addition, we studied the impact of the design parameters of the fission chamber on the calculated neutron sensitivity of the microfission chamber.

关键词： Microfission chamber Neutron sensitivity monte carlo simulation GEANT4

monte carlo simulation of the exposure factor

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Chinese Physics B 2009年第6期18卷 2217-2222页

作者：张涛刘义保杨波吴和喜顾金虎 Key Laboratory of Nuclear Resources and Environment (East China Institute of Technology) Ministry of Education School of Nuclear Engineering and Technology East China Institute of Technology

In this paper, we simulate the exposure factor by a simple model of a flee-air ionization chamber with the monte carlo programme Geant4. Special emphasis is placed on the discussion of the exposure factor related to parameters of the chamber model. The reason for the variation in exposure factor with incident ray energy is also analysed in terms of reaction cross section for different types of reactions. The obtained results indicate that our simulation is accurate in the calculation of the exposure factor and can serve as a reference in designing air ionization chambers.

关键词： exposure factor Geant4 monte carlo simulation free-air ionization chamber

monte carlo simulation of ramified aggregates on hetero-substrates

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Chinese Physics B 2009年第5期18卷 1947-1954页

作者：钱昌吉李洪钟瑞罗孟波叶高翔 Department of Physics Wenzhou University Department of Physics Zhejiang University

We have studied the aggregation of particles on a hetero-substrate consisting of two different substrates A and B with finite surface barriers EAB and EBA between the AB and BA boundaries, respectively. With the diffusion energy limited aggregation （DELA） model, we find that the number of clusters and the mean radius of gyration of the clusters are dependent on the surface barriers EAB and EBA. For the case with a constant of EBA, a series of minima are summarized as EAB ：（E0 - kBAEBA）/kAB with kAB and kBA being two integers, for main minima （kBA = kAB = 1） and two local minima （kBA = kAB and kBA = kAB ＋ 1） between two neighbouring main minima.

关键词： diffusion energy limited aggregation hetero-substrate monte carlo simulation cluster

monte carlo simulation of Laser-Ablated Particle Splitting Dynamic in a Low Pressure Inert Gas

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Plasma Science and Technology 2016年第6期18卷 641-646页

作者：丁学成张子才梁伟华褚立志邓泽超王英龙 College of Physics Science and Technology Hebei University

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 *** ablated-particle density and velocity distributions are *** force distributions acting on the ablated particles are *** influence of the substrate on the ablated-particle velocity distribution and the force distribution acting on the ablated particles are *** monte carlo simulation results approximately agree with the experimental data at the pressure of 8 Pa to 17 *** is helpful to investigate the gas phase nucleation and growth mechanism of nanoparticles.

关键词： ablated particles monte carlo simulation transport dynamic instantaneous mean-free-path low pressure