This paper examines the interface development between a single crystalline Ag matrix and core-shell AgnCom nanoclusters that have been deposited with energies varying between 0.25 eV and 1.5 eV per atom using computer...This paper examines the interface development between a single crystalline Ag matrix and core-shell AgnCom nanoclusters that have been deposited with energies varying between 0.25 eV and 1.5 eV per atom using computer modeling techniques. Clusters undergo deformation as a result of the slowing down;they may also become epitaxial with the substrate and maintain their core-shell structure. A detailed analysis of the effects of the cluster-surface interaction is conducted over a realistic size and energy range, and a model is created to show how clusters accumulate. It is discovered that both the silver shells and the cobalt cluster cores exhibit limited epitaxy with the substrate, and that the contact produced is only a few atomic layers thick. The effect is higher for Ag shells than for Co cores, and it is not very energy dependent.展开更多
Stochastic perturbations and periodic excitations are generally regarded as sources to induce critical transitions in complex systems. However, we find that they are also able to slow down an imminent critical transit...Stochastic perturbations and periodic excitations are generally regarded as sources to induce critical transitions in complex systems. However, we find that they are also able to slow down an imminent critical transition. To illustrate this phenomenon, a periodically driven bistable eutrophication model with Gaussian white noise is introduced as a prototype class of real systems.The residence probability(RP) is presented to measure the possibility that the given system stays in the oligotrophic state versus Gaussian white noise and periodic force. Variations in the mean first passage time(MFPT) and the mean velocity(MV) of the first right-crossing process are also calculated respectively. We show that the frequency of the periodic force can increase the MFPT while reduce the MV under different control parameters. Nevertheless, the noise intensity or the amplitude may result in an increase of the RP only in the case of control parameters approaching the critical values. Furthermore, for an impending critical transition, an increase of the RP appears with the interaction between the amplitude and noise intensity or the combination of the noise intensity and frequency, while the interaction of the frequency and amplitude leads to an extension of the MFPT or a decrease of the MV. As a result, an increase of the RP and MFPT, and a decrease of the MVobtained from our results claim that it is possible to slow down an imminent critical transition via Gaussian white noise and periodic force.展开更多
Fusion-born alpha particles in burning plasmas are usually regarded as have a slowing-down distribution,which differs significantly from the Maxwellian distribution of thermal particles in velocity space.A generalized...Fusion-born alpha particles in burning plasmas are usually regarded as have a slowing-down distribution,which differs significantly from the Maxwellian distribution of thermal particles in velocity space.A generalized multi-point average method has been developed for gyrokinetic Poisson equation with slowing-down equilibrium distribution using optimization in Fourier space.Its accuracy is verified in both long and short wavelength limits.The influence of changing equilibrium distribution from Maxwellian to slowing-down on gyrokinetic Poisson equation is analyzed to illustrate the significance of the new method.The effect of critical speed in the slowingdown distribution on the field solver is also presented.This method forms an important basis for global gyrokinetic simulation of low-frequency drift Alfvénic turbulence in burning plasmas.展开更多
Objective:To optimize targeted beta therapy for liver lesions in adult male phantom by comparing the efficacy and safety profiles of five different beta-emitting radionuclides:90Y,166Ho,153Sm,47Sc,and 177Lu.Methods:Th...Objective:To optimize targeted beta therapy for liver lesions in adult male phantom by comparing the efficacy and safety profiles of five different beta-emitting radionuclides:90Y,166Ho,153Sm,47Sc,and 177Lu.Methods:This study includes Monte Carlo simulations of the behavioral characteristics of five different beta emitters that have current or potential use in targeted beta therapy.The energy loss of beta particles moving within the material through ionization or chemical processes,the energy transferred to the material,the energy lost by beta particles along the distance traveled within the tissue,and consequently,the stopping power are calculated using the Bethe-Bloch formula.The CSDA(continuous slowing-down approximation)range of beta particles within the tissue is examined using ESTAR and GEANT codes,while the stopping power of the tissue is investigated using FLUKA,ESTAR,and GEANT codes.Tissue dose calculations for the target organ are obtained using the IDAC-Dose2.1 and MIRDcalc simulation programs,using parameters such as absorbed dose per accumulated activity(S-factor)and specific absorbed fraction(SAF).Additionally,dose and flux values are obtained using the PHITS program.Results:The behaviors and dose contribution of beta particles in liver tissue have been addressed in various ways.90Y,which has the highest average beta energy,was observed to provide a higher absorbed dose value in the liver compared to other beta-emitting isotopes,while the lowest absorbed dose was observed with 177Lu.In other organs,it has been observed that 90Y and 47Sc contribute to a higher absorbed dose compared to other betaemitting isotopes.Conclusions:This study emphasizes the complexity and significance of targeted beta therapy optimization.展开更多
In the paper, related research and progress of molecular clock hypothesis were summarized, including definition of molecular clock, supporting proofs, contro- versy, significance and perfection, application and accomp...In the paper, related research and progress of molecular clock hypothesis were summarized, including definition of molecular clock, supporting proofs, contro- versy, significance and perfection, application and accompanying challenges.展开更多
The investigation is generalized to clusters with sizes up to 3000 atoms, covering this way the range of sizes experimentally available for low energy cluster beam deposition. The atomic scale modeling is carried on b...The investigation is generalized to clusters with sizes up to 3000 atoms, covering this way the range of sizes experimentally available for low energy cluster beam deposition. The atomic scale modeling is carried on by both Molecular Dynamics and Metropolis Monte Carlo. This represents a huge series of simulations (175 cases) to which further calculations are added by spot when finer tuning of the parameters is necessary. Analyzing the results is a major task which is still in progress. This way, not only a realistic range of sizes is covered, but also the whole range of compositions and the temperature range relevant to the solid and the liquid states.展开更多
This paper uses the implicit Monte–Carlo full-orbit-following parallel program ISSDE to calculate the prompt loss and slowing down process of neutral beam injection(NBI)-generated fast ions due to Coulomb collisions ...This paper uses the implicit Monte–Carlo full-orbit-following parallel program ISSDE to calculate the prompt loss and slowing down process of neutral beam injection(NBI)-generated fast ions due to Coulomb collisions in the equilibrium configuration of Experimental Advanced Superconducting Tokamak(EAST).This program is based on the weak equivalence of the Fokker–Planck equation under Rosenbluth Mac Donald Judd(RMJ)potential and Stratonovich stochastic differential equation(SDE).The prompt loss with the LCFS boundary and the first wall(FW)boundary of the two co-current neutral injection beams are studied.Simulation results indicate that the loss behavior of fast ions using the FW boundary is very different from that of the LCFS boundary,especially for fast ions with a large gyration radius.According to our calculations,about 5.11%of fast ions generated by perpendicular injection drift out of the LCFS and then return inside the LCFS to be captured by the magnetic field.The prompt loss ratio of fast ions and the ratio of orbital types depend on the initial distribution of fast ions in the Pζ–Λspace.Under the effect of Coulomb collisions,the pitch-angle scattering and stochastic diffusion happens,which will cause more fast ion loss.For short time scales,among the particles lost due to collisions,the fraction of banana ions reaches 92.31%in the perpendicular beam and 58.65%in the tangential beam when the fraction of banana ions in the tangential beam is 3.4%of the total ions,which means that the effect of Coulomb collisions on banana fast ions is more significant.For long time scales,the additional fast ion loss caused by Coulomb collisions of tangential and perpendicular beams accounted for 16.21%and 25.05%of the total particles,respectively.We have also investigated the slowing down process of NBI fast ions.展开更多
A slower pace of life has become fashionable to more urbanites Life was almost all work and no play for Shi Ming,a 40-something worker at a research institute in Beijing,before a heart attack two years ago.
A Monte Carlo implicit simulation program,Implicit Stratonovich Stochastic Differential Equations(ISSDE),is developed for solving stochastic differential equations(SDEs)that describe plasmas with Coulomb collision.The...A Monte Carlo implicit simulation program,Implicit Stratonovich Stochastic Differential Equations(ISSDE),is developed for solving stochastic differential equations(SDEs)that describe plasmas with Coulomb collision.The basic idea of the program is the stochastic equivalence between the Fokker-Planck equation and the Stratonovich SDEs.The splitting method is used to increase the numerical stability of the algorithm for dynamics of charged particles with Coulomb collision.The cases of Lorentzian plasma,Maxwellian plasma and arbitrary distribution function of background plasma have been considered.The adoption of the implicit midpoint method guarantees exactly the energy conservation for the diffusion term and thus improves the numerical stability compared with conventional Runge-Kutta methods.ISSDE is built with C++and has standard interfaces and extensible modules.The slowing down processes of electron beams in unmagnetized plasma and relaxation process in magnetized plasma are studied using the ISSDE,which shows its correctness and reliability.展开更多
We solve the equilibrium meanfield equation of state of Ising ferromagnet （obtained from Bragg-Williams theory） by Newton-Raphson method. The number of iterations required to get a convergent solution （within a spe...We solve the equilibrium meanfield equation of state of Ising ferromagnet （obtained from Bragg-Williams theory） by Newton-Raphson method. The number of iterations required to get a convergent solution （within a specified accuracy） of equilibrium magnetisation, at any particular temperature, is observed to diverge in a power law fashion as the temperature approaches the critical value. This is identified as the critical slowing down. The exponent is also estimated. This value of the exponent is compared with that obtained from analytic solution. Besides this, the numerical results are also compared with some experimental results exhibiting satisfactory degree of agreement. It is observed from this study that the information of the invariance of time scale at the critical point is present in the meanfield equilibrium equation of state of Ising ferromagnet.展开更多
We study the critical slowing down phenomenon in deformation and groundwater observations before the Nilka-Gongliu MS6. 0 earthquake on November 1, 2011 and Xinyuan-Hejing M S6. 6 earthquake on June 30,2012. Firstly,w...We study the critical slowing down phenomenon in deformation and groundwater observations before the Nilka-Gongliu MS6. 0 earthquake on November 1, 2011 and Xinyuan-Hejing M S6. 6 earthquake on June 30,2012. Firstly,we remove the annual variation and tendency change of basic data by means of wavelet transform analysis.Secondly,we calculate the autocorrelation coefficients and variance of the critical slowing down phenomenon. Lastly,we try to verify the critical slowing down phenomenon before an earthquake. The result indicates that there was obvious critical slowing down of the records at different stations before earthquakes.展开更多
文摘This paper examines the interface development between a single crystalline Ag matrix and core-shell AgnCom nanoclusters that have been deposited with energies varying between 0.25 eV and 1.5 eV per atom using computer modeling techniques. Clusters undergo deformation as a result of the slowing down;they may also become epitaxial with the substrate and maintain their core-shell structure. A detailed analysis of the effects of the cluster-surface interaction is conducted over a realistic size and energy range, and a model is created to show how clusters accumulate. It is discovered that both the silver shells and the cobalt cluster cores exhibit limited epitaxy with the substrate, and that the contact produced is only a few atomic layers thick. The effect is higher for Ag shells than for Co cores, and it is not very energy dependent.
基金supported by the National Natural Science Foundation of China(Grant Nos.11772255&11872305)the Fundamental Research Funds for the Central Universities+2 种基金Shaanxi Province Project for Distinguished Young ScholarsInnovation Foundation for Doctor Dissertation of Northwestern Polytechnical Universitythe China Postdoctoral Science Foundation
文摘Stochastic perturbations and periodic excitations are generally regarded as sources to induce critical transitions in complex systems. However, we find that they are also able to slow down an imminent critical transition. To illustrate this phenomenon, a periodically driven bistable eutrophication model with Gaussian white noise is introduced as a prototype class of real systems.The residence probability(RP) is presented to measure the possibility that the given system stays in the oligotrophic state versus Gaussian white noise and periodic force. Variations in the mean first passage time(MFPT) and the mean velocity(MV) of the first right-crossing process are also calculated respectively. We show that the frequency of the periodic force can increase the MFPT while reduce the MV under different control parameters. Nevertheless, the noise intensity or the amplitude may result in an increase of the RP only in the case of control parameters approaching the critical values. Furthermore, for an impending critical transition, an increase of the RP appears with the interaction between the amplitude and noise intensity or the combination of the noise intensity and frequency, while the interaction of the frequency and amplitude leads to an extension of the MFPT or a decrease of the MV. As a result, an increase of the RP and MFPT, and a decrease of the MVobtained from our results claim that it is possible to slow down an imminent critical transition via Gaussian white noise and periodic force.
基金the National Magnetic Confinement Fusion Program of China(No.2015GB110000)National Natural Science Foundation of China(No.11975201).
文摘Fusion-born alpha particles in burning plasmas are usually regarded as have a slowing-down distribution,which differs significantly from the Maxwellian distribution of thermal particles in velocity space.A generalized multi-point average method has been developed for gyrokinetic Poisson equation with slowing-down equilibrium distribution using optimization in Fourier space.Its accuracy is verified in both long and short wavelength limits.The influence of changing equilibrium distribution from Maxwellian to slowing-down on gyrokinetic Poisson equation is analyzed to illustrate the significance of the new method.The effect of critical speed in the slowingdown distribution on the field solver is also presented.This method forms an important basis for global gyrokinetic simulation of low-frequency drift Alfvénic turbulence in burning plasmas.
文摘Objective:To optimize targeted beta therapy for liver lesions in adult male phantom by comparing the efficacy and safety profiles of five different beta-emitting radionuclides:90Y,166Ho,153Sm,47Sc,and 177Lu.Methods:This study includes Monte Carlo simulations of the behavioral characteristics of five different beta emitters that have current or potential use in targeted beta therapy.The energy loss of beta particles moving within the material through ionization or chemical processes,the energy transferred to the material,the energy lost by beta particles along the distance traveled within the tissue,and consequently,the stopping power are calculated using the Bethe-Bloch formula.The CSDA(continuous slowing-down approximation)range of beta particles within the tissue is examined using ESTAR and GEANT codes,while the stopping power of the tissue is investigated using FLUKA,ESTAR,and GEANT codes.Tissue dose calculations for the target organ are obtained using the IDAC-Dose2.1 and MIRDcalc simulation programs,using parameters such as absorbed dose per accumulated activity(S-factor)and specific absorbed fraction(SAF).Additionally,dose and flux values are obtained using the PHITS program.Results:The behaviors and dose contribution of beta particles in liver tissue have been addressed in various ways.90Y,which has the highest average beta energy,was observed to provide a higher absorbed dose value in the liver compared to other beta-emitting isotopes,while the lowest absorbed dose was observed with 177Lu.In other organs,it has been observed that 90Y and 47Sc contribute to a higher absorbed dose compared to other betaemitting isotopes.Conclusions:This study emphasizes the complexity and significance of targeted beta therapy optimization.
基金Supported by Hunan Education Reform ProjectEducation Reform Project of Hunan University of Humanities,Science and Technology(RKJGY1101)~~
文摘In the paper, related research and progress of molecular clock hypothesis were summarized, including definition of molecular clock, supporting proofs, contro- versy, significance and perfection, application and accompanying challenges.
文摘The investigation is generalized to clusters with sizes up to 3000 atoms, covering this way the range of sizes experimentally available for low energy cluster beam deposition. The atomic scale modeling is carried on by both Molecular Dynamics and Metropolis Monte Carlo. This represents a huge series of simulations (175 cases) to which further calculations are added by spot when finer tuning of the parameters is necessary. Analyzing the results is a major task which is still in progress. This way, not only a realistic range of sizes is covered, but also the whole range of compositions and the temperature range relevant to the solid and the liquid states.
基金the National MCF Energy Research and Development Program(Grant No.2018YFE0304100)the National Key Research and Development Program of China(Grant Nos.2016YFA0400600,2016YFA0400601,2016YFA0400602,and 2019YFE0302004)the National Natural Science Foundation of China(Grant Nos.11805273 and 11905220)。
文摘This paper uses the implicit Monte–Carlo full-orbit-following parallel program ISSDE to calculate the prompt loss and slowing down process of neutral beam injection(NBI)-generated fast ions due to Coulomb collisions in the equilibrium configuration of Experimental Advanced Superconducting Tokamak(EAST).This program is based on the weak equivalence of the Fokker–Planck equation under Rosenbluth Mac Donald Judd(RMJ)potential and Stratonovich stochastic differential equation(SDE).The prompt loss with the LCFS boundary and the first wall(FW)boundary of the two co-current neutral injection beams are studied.Simulation results indicate that the loss behavior of fast ions using the FW boundary is very different from that of the LCFS boundary,especially for fast ions with a large gyration radius.According to our calculations,about 5.11%of fast ions generated by perpendicular injection drift out of the LCFS and then return inside the LCFS to be captured by the magnetic field.The prompt loss ratio of fast ions and the ratio of orbital types depend on the initial distribution of fast ions in the Pζ–Λspace.Under the effect of Coulomb collisions,the pitch-angle scattering and stochastic diffusion happens,which will cause more fast ion loss.For short time scales,among the particles lost due to collisions,the fraction of banana ions reaches 92.31%in the perpendicular beam and 58.65%in the tangential beam when the fraction of banana ions in the tangential beam is 3.4%of the total ions,which means that the effect of Coulomb collisions on banana fast ions is more significant.For long time scales,the additional fast ion loss caused by Coulomb collisions of tangential and perpendicular beams accounted for 16.21%and 25.05%of the total particles,respectively.We have also investigated the slowing down process of NBI fast ions.
文摘A slower pace of life has become fashionable to more urbanites Life was almost all work and no play for Shi Ming,a 40-something worker at a research institute in Beijing,before a heart attack two years ago.
基金Project supported by the National MCF Energy R&D Program of China(Grant No.2018YFE0304100)the National Key Research and Development Program of China(Grant Nos.2016YFA0400600,2016YFA0400601,and 2016YFA0400602)the National Natural Science Foundation of China(Grant Nos.NSFC-11805273 and NSFC-11905220).
文摘A Monte Carlo implicit simulation program,Implicit Stratonovich Stochastic Differential Equations(ISSDE),is developed for solving stochastic differential equations(SDEs)that describe plasmas with Coulomb collision.The basic idea of the program is the stochastic equivalence between the Fokker-Planck equation and the Stratonovich SDEs.The splitting method is used to increase the numerical stability of the algorithm for dynamics of charged particles with Coulomb collision.The cases of Lorentzian plasma,Maxwellian plasma and arbitrary distribution function of background plasma have been considered.The adoption of the implicit midpoint method guarantees exactly the energy conservation for the diffusion term and thus improves the numerical stability compared with conventional Runge-Kutta methods.ISSDE is built with C++and has standard interfaces and extensible modules.The slowing down processes of electron beams in unmagnetized plasma and relaxation process in magnetized plasma are studied using the ISSDE,which shows its correctness and reliability.
文摘We solve the equilibrium meanfield equation of state of Ising ferromagnet （obtained from Bragg-Williams theory） by Newton-Raphson method. The number of iterations required to get a convergent solution （within a specified accuracy） of equilibrium magnetisation, at any particular temperature, is observed to diverge in a power law fashion as the temperature approaches the critical value. This is identified as the critical slowing down. The exponent is also estimated. This value of the exponent is compared with that obtained from analytic solution. Besides this, the numerical results are also compared with some experimental results exhibiting satisfactory degree of agreement. It is observed from this study that the information of the invariance of time scale at the critical point is present in the meanfield equilibrium equation of state of Ising ferromagnet.
基金sponsored by the Earthquake Science Foundation of Xinjiang,China(201105)
文摘We study the critical slowing down phenomenon in deformation and groundwater observations before the Nilka-Gongliu MS6. 0 earthquake on November 1, 2011 and Xinyuan-Hejing M S6. 6 earthquake on June 30,2012. Firstly,we remove the annual variation and tendency change of basic data by means of wavelet transform analysis.Secondly,we calculate the autocorrelation coefficients and variance of the critical slowing down phenomenon. Lastly,we try to verify the critical slowing down phenomenon before an earthquake. The result indicates that there was obvious critical slowing down of the records at different stations before earthquakes.
