Rock burst is a kind of severe engineering disaster resulted from dynamic fracture process of rocks.The macrofailure behaviors of rocks are primarily formed after experiencing the initiation,propagation,and coalescenc...Rock burst is a kind of severe engineering disaster resulted from dynamic fracture process of rocks.The macrofailure behaviors of rocks are primarily formed after experiencing the initiation,propagation,and coalescenceof micro-cracks.In this paper,the grain-based discretized virtual internal bond model is employed to investigatethe fracturing process of unloaded rock under high in-situ stresses from the micro-fracture perspective.Thesimulated micro-fracturing process reveals that the longitudinal stress waves induced by unloading lead to thevisible unloading effect.The influences of in-situ stresses,mineral grain sizes,and grain heterogeneity on rockmacro and micro fracture are investigated.Micro-crack areas of tensile and shear cracks and micro-crack anglesare statistically analyzed to reveal the rock micro-fracture characteristics.The simulated results indicate thatthe combined effect of the stress state transition and the unloading effect dominates the rock unloading failure.The vertical and horizontal in-situ stresses determine the stress state of surrounding rock after unloading andthe unloading effect,respectively.As the vertical stress increases,the stress level after unloading is higher,andthe shear failure characteristics become more obvious.As the horizontal stress increases,the unloading effectincreases,leading to the intensification of tensile failure.The mineral grain size and grain heterogeneity alsohave nonnegligible influences on rock unloading failure.The micro-fracture perspective provides further insightinto the unloading failure mechanism of deep rock excavation.展开更多
The desire to increase spatial and temporal resolution in modeling groundwater system has led to the requirement for intensive computational ability and large memory space. In the course of satisfying such requirement...The desire to increase spatial and temporal resolution in modeling groundwater system has led to the requirement for intensive computational ability and large memory space. In the course of satisfying such requirement, parallel computing has played a core role over the past several decades. This paper reviews the parallel algebraic linear solution methods and the parallel implementation technologies for groundwater simulation. This work is carried out to provide guidance to enable modelers of groundwater systems to make sensible choices when developing solution methods based upon the current state of knowledge in parallel computing.展开更多
Metallic amorphous/crystalline(A/C)nanolaminates exhibit excellent ductility while retaining their high strength.However,the underlying physical mechanisms and the resultant structural changes during plastic deformati...Metallic amorphous/crystalline(A/C)nanolaminates exhibit excellent ductility while retaining their high strength.However,the underlying physical mechanisms and the resultant structural changes during plastic deformation still remain unclear.In the present work,the structure-property relationship of CuZr/Cu A/C nanolaminates is established through integrated high-throughput micro-compression tests and molecular dynamics simulations together with high-resolution transmission electron microcopy.The serrated flow of nanolaminates results from the formation of hexagonal-close-packed(HCP)-type stacking faults and twins inside the face-centered-cubic(FCC)Cu nano-grains,the body-centered-cubic(BCC)-type ordering at their grain boundaries,and the crystallization of the amorphous CuZr layers.The serration behavior of CuZr/Cu A/C nanolaminates is determined by several factors,including the formation of dense dislocation networks from the multiplication of initial dislocations that formed after yielding,weak-spots-related configurational-transitions and shear-transition-zone activities,and deformation-induced devitrification.The present work provides an insight into the heterogeneous deformation mechanism of A/C nanolaminates at the atomic scale,and mechanistic base for the microstructural design of self-toughening metallic-glass(MG)-based composites and A/C nanolaminates.展开更多
In response to the demand for rapid geometric modeling in Monte Carlo radiation transportation calculations for large-scale and complex geometric scenes,functional improvements,and algorithm optimizations were perform...In response to the demand for rapid geometric modeling in Monte Carlo radiation transportation calculations for large-scale and complex geometric scenes,functional improvements,and algorithm optimizations were performed using CAD-to-Monte Carlo geometry conversion(CMGC)code.Boundary representation(BRep)to constructive solid geometry(CSG)conversion and visual CSG modeling were combined to address the problem of non-convertible geometries such as spline surfaces.The splitting surface assessment method in BRep-to-CSG conversion was optimized to reduce the number of Boolean operations using an Open Cascade.This,in turn,reduced the probability of CMGC conversion failure.The auxiliary surface generation algorithm was optimized to prevent the generation of redundant auxiliary surfaces that cause an excessive decomposition of CAD geometry solids.These optimizations enhanced the usability and stability of the CMGC model conversion.CMGC was applied successfully to the JMCT transportation calculations for the conceptual designs of five China Fusion Engineering Test Reactor(CFETR)blankets.The rapid replacement of different blanket schemes was achieved based on the baseline CFETR model.The geometric solid number of blankets ranged from hundreds to tens of thousands.The correctness of the converted CFETR models using CMGC was verified through comparisons with the MCNP calculation results.The CMGC supported radiation field evaluations for a large urban scene and detailed ship scene.This enabled the rapid conversion of CAD models with thousands of geometric solids into Monte Carlo CSG models.An analysis of the JMCT transportation simulation results further demonstrated the accuracy and effectiveness of the CMGC.展开更多
The analysis of the fuel depletion behavior is critical for maintaining the safety of accelerator-driven subcritical systems(ADSs). The code COUPLE2.0 coupling 3-D neutron transport and point burnup calculation was de...The analysis of the fuel depletion behavior is critical for maintaining the safety of accelerator-driven subcritical systems(ADSs). The code COUPLE2.0 coupling 3-D neutron transport and point burnup calculation was developed by Tsinghua University. A Monte Carlo method is used for the neutron transport analysis, and the burnup calculation is based on a deterministic method. The code can be used for the analysis of targets coupled with a reactor in ADSs. In response to additional ADS analysis requirements at the Institute of Modern Physics at the Chinese Academy of Sciences, the COUPLE3.0 version was developed to include the new functions of(1) a module for the calculation of proton irradiation for the analysis of cumulative behavior using the residual radionuclide operating history,(2) a fixed-flux radiation module for hazard assessment and analysis of the burnable poison, and(3) a module for multi-kernel parallel calculation, which improves the radionuclide replacement for the burnup analysis to balance the precision level and computational efficiency of the program. This paper introduces thevalidation of the COUPLE3.0 code using a fast reactor benchmark and ADS benchmark calculations. Moreover,the proton irradiation module was verified by a comparison with the analytic method of calculating the210 Po accumulation results. The results demonstrate that COUPLE3.0 is suitable for the analysis of neutron transport and the burnup of nuclides for ADSs.展开更多
Numerical modeling is of crucial importance in understanding the behavior of regional groundwater system. However, the demand on modeling capability is intensive when performing high-resolution simulation over long ti...Numerical modeling is of crucial importance in understanding the behavior of regional groundwater system. However, the demand on modeling capability is intensive when performing high-resolution simulation over long time span. This paper presents the application of a parallel program to speed up the detailed modeling of the groundwater flow system in the North China Plain. The parallel program is implemented by rebuilding the well-known MODFLOW program on our parallelcomputing framework, which is achieved by designing patch-based parallel data structures and algorithms but maintaining the compute flow and functionalities of MODFLOW. The detailed model with more than one million grids and a decade of time has been solved. The parallel simulation results were examined against the field observed data and these two data are generally in good agreement. For the comparison on solution time, the parallel program running on 32 cores is 6 times faster than the fastest MICCG-based MODFLOW program and 11 times faster than the GMG-based MODFLOW program. Therefore, remarkable computational time can be saved when using the parallel program, which facilitates the rapid modeling and prediction of the groundwater flow system in the North China Plain.展开更多
A multi-phase-field model is implemented to investigate the peritectic solidification of Fe-C alloy. The nucleation mode of austenite is based on the local driving force, and two different thicknesses of the primary a...A multi-phase-field model is implemented to investigate the peritectic solidification of Fe-C alloy. The nucleation mode of austenite is based on the local driving force, and two different thicknesses of the primary austenite on the surface of the ferrite equiaxed crystal grain are used as the initial conditions. The simulation shows the multiple interactions of ferrite, austenite, and liquid phases, and the effects of carbon diffusion, which presents the non-equilibrium dynamic process during Fe-C peritectic solidification at the mesoscopic scale. This work not only reveals the influence of the austenite nucleation position, but also clarifies the formation mechanism of liquid phase channels and molten pools. Therefore, the present study contributes to the understanding of the micro-morphology and micro-segregation evolution mechanisms of Fe-C alloy during peritectic solidification.展开更多
A geometrically exact Kirchhoff beam formulation(GEKBF)established on the Lie group SO(3)for simulating the dynamics of a slender beam is proposed.The kinematic description,dynamic equilibrium equations and their line...A geometrically exact Kirchhoff beam formulation(GEKBF)established on the Lie group SO(3)for simulating the dynamics of a slender beam is proposed.The kinematic description,dynamic equilibrium equations and their linearization are derived in this framework.Then,a second-order interpolation function for the torsion angle is introduced to improve the convergence of the element.Next,the rotation vector parameterization is developed to reduce the geometric nonlinearity caused by the rotation of the rigid body.In addition,the influence of the reference frame is considered,and the derivation of the elastic force and Jacobian matrix is simplified using the spatial-parallel transport.The semi-discrete equations of motion are in the form of a second-order ordinary differential equation on Lie group,which are solved using the Lie group generalizedα-method.Finally,the accuracy of the proposed formulation is verified using several numerical examples.展开更多
The amount of water withdrawn by wells is one of the quantitative variables that can be applied to estimate groundwater resources and further evaluate the human influence on groundwater systems. The accuracy for the c...The amount of water withdrawn by wells is one of the quantitative variables that can be applied to estimate groundwater resources and further evaluate the human influence on groundwater systems. The accuracy for the calculation of the amount of water withdrawal significantly influences the regional groundwater resource evaluation and management. However, the decentralized groundwater pumping, inefficient management, measurement errors and uncertainties have resulted in considerable errors in the groundwater withdrawal estimation. In this study, to improve the estimation of the groundwater withdrawal, an innovative approach was proposed using an inversion method based on a regional groundwater flow numerical model, and this method was then applied in the North China Plain. The principle of the method was matching the simulated water levels with the observation ones by adjusting the amount of groundwater withdrawal. In addition, uncertainty analysis of hydraulic conductivity and specific yield for the estimation of the groundwater withdrawal was conducted. By using the proposed inversion method, the estimated annual average groundwater withdrawal was approximately 24.92×10^9 m^3 in the North China Plain from 2002 to 2008. The inversion method also significantly improved the simulation results for both hydrograph and the flow field. Results of the uncertainty analysis showed that the hydraulic conductivity was more sensitive to the inversion results than the specific yield.展开更多
A data identifier(DID)is an essential tag or label in all kinds of databases—particularly those related to integrated computational materials engineering(ICME),inheritable integrated intelligent manufacturing(I3M),an...A data identifier(DID)is an essential tag or label in all kinds of databases—particularly those related to integrated computational materials engineering(ICME),inheritable integrated intelligent manufacturing(I3M),and the Industrial Internet ofThings.With the guidance and quick acceleration of the developme nt of advanced materials,as envisioned by official documents worldwide,more investigations are required to construct relative numerical standards for material informatics.This work proposes a universal DID format consisting of a set of build chains,which aligns with the classical form of identifier in both international and national standards,such as ISO/IEC 29168-1:2000,GB/T 27766-2011,GA/T 543.2-2011,GM/T 0006-2012,GJB 7365-2011,SL 325-2014,SL 607-201&WS 363.2-2011,and QX/T 39-2005.Each build chain is made up of capital letters and numbers,with no symbols.Moreover,the total length of each build chain is not restricted,which follows the formation of the Universal Coded Character Set in the international standard of ISO/IEC 10646.Based on these rules,the proposed DID is flexible and convenient for extendi ng and sharing in and between various cloud-based platforms.Accordingly,classical two-dimensional(2D)codes,including the Hanxin Code,Lots Perception Matrix(LP)Code,Quick Response(Q.R)code,Grid Matrix(GM)code,and Data Matrix(DM)Code,can be constructed and precisely recognized and/or decoded by either smart phones or specific machines.By utilizing these 2D codes as the fingerprints of a set of data linked with cloud-based platforms,progress and updates in the composition-processing-structure-property-performance workflow process can be tracked spontaneously,paving a path to accelerate the discovery and manufacture of advanced materials and enhance research productivity,performance,and collaboration.展开更多
Automatic conversion from a computer-aided design(CAD) model to Monte Carlo geometry is one of the most effective methods for large-scale and detailed Monte Carlo modeling. The CAD to Monte Carlo geometry converter(CM...Automatic conversion from a computer-aided design(CAD) model to Monte Carlo geometry is one of the most effective methods for large-scale and detailed Monte Carlo modeling. The CAD to Monte Carlo geometry converter(CMGC) is a newly developed conversion code based on the boundary representation to constructive solid geometry(BRep→CSG) conversion method. The goal of the conversion process in the CMGC is to generate an appropriate CSG representation to achieve highly efficient Monte Carlo simulations. We designed a complete solid decomposition scheme to split a complex solid into as few nonoverlapping simple sub-solids as possible. In the complete solid decomposition scheme, the complex solid is successively split by so-called direct, indirect, and auxiliary splitting surfaces. We defined the splitting edge and designed a method for determining the direct splitting surface based on the splitting edge, then provided a method for determining indirect and auxiliary splitting surfaces based on solid vertices. Only the sub-solids that contain concave boundary faces need to be supplemented with auxiliary surfaces because the solid is completely decomposed, which will reduce the redundancy in the CSG expression. After decomposition, these sub-solids are located on only one side of their natural and auxiliary surfaces;thus, each sub-solid can be described by the intersections of a series of half-spaces or geometrical primitives. The CMGC has a friendly graphical user interface and can convert a CAD model into geometry input files for several Monte Carlo codes. The reliability of the CMGC was evaluated by converting several complex models and calculating the relative volume errors. Moreover, JMCT was used to test the efficiency of the Monte Carlo simulation. The results showed that the converted models performed well in particle transport calculations.展开更多
The detection technology of concealed bulk explosives is related to social security and national defense construction and has important research significance. In this paper, an element analysis method of concealed exp...The detection technology of concealed bulk explosives is related to social security and national defense construction and has important research significance. In this paper, an element analysis method of concealed explosives based on thermal neutron analysis is proposed.This method could provide better reconstruction precision for hydrogen, carbon, and nitrogen ratios, making it possible to discriminate explosives from other compounds with the same elements but different proportions, as well as to identify the types of concealed bulk explosives. In this paper, the basic principles and mathematical model of this method are first introduced, and the calculation formula of the element number ratio(the ratio between the nucleus numbers of two different elements) of the concealed explosive is deduced. Second, a numerical simulation platform of this method was established based on the Monte Carlo JMCT code. By calibrating the absorption efficiencies of the explosive device to c rays, the element number ratios of a concealed explosive model under the irradiation of thermal neutrons were reconstructed from the neutron capture prompt c-ray spectrum. The reconstruction values were in good agreement with the actual values,which shows that this method has a high reconstruction precision of the element number ratio for concealed explosives. Lastly, it was demonstrated using the simulation study that this method can discriminate explosives,drugs, and common materials, with the capability of determining the existence of concealed bulk explosives and identifying explosive types.展开更多
Determining the mass of plutonium metal is an important research objective in the field of nuclear material accounting and control.Based on the 3D neutron and photon transport code JMCT(Jointed Monte Carlo Transport),...Determining the mass of plutonium metal is an important research objective in the field of nuclear material accounting and control.Based on the 3D neutron and photon transport code JMCT(Jointed Monte Carlo Transport),the gamma ray multiplicity of ^(240)Pu was simulated in this study,and the average number of gamma rays leaking from ^(240)Pu solid spheres with different masses was also obtained.The simulation results show that there is a oneto-one correspondence between the average number of gamma rays and the mass of ^(240)Pu solid spheres in the range of 0.50–3.00 kg.This result provides a basis for using the average number of gamma rays to account for the mass of ^(240)Pu.展开更多
Spectral and directional control of thermal emission based on excitation of confined electromagnetic resonant modes paves a viable way for the design and construction of microscale thermal emitters/absorbers. In this ...Spectral and directional control of thermal emission based on excitation of confined electromagnetic resonant modes paves a viable way for the design and construction of microscale thermal emitters/absorbers. In this paper, we present numerical simulation results of the thermal radiative properties of a silicon carbide（Si C） thermal emitter/absorber composed of periodic microstructures. We illustrate different electromagnetic resonant modes which can be excited with the structure,such as surface phonon polaritons, magnetic polaritons and photonic crystal modes, and the process of radiation spectrum optimization based on a non-linear optimization algorithm. We show that the spectral and directional control of thermal emission/absorption can be efficiently achieved by adjusting the geometrical parameters of the structure. Moreover, the optimized spectrum is insensitive to 3% dimension modification.展开更多
Entropy-stabilized multi-component alloys have been considered to be prospective structural materials attributing to their impressive mechanical and functional properties.The local chemical complexions,microstates and...Entropy-stabilized multi-component alloys have been considered to be prospective structural materials attributing to their impressive mechanical and functional properties.The local chemical complexions,microstates and configurational transformations are essential to reveal the structure–property relationship,thus,to promote the development of advanced multicomponent alloys.In the present work,effects of local lattice distortion(LLD)and microstates of various configurations on the equilibrium volume(V0),total energy,Fermi energy,magnetic moment(μMag)and electron work function(Φ)and bonding structures of the Fe–Mn–Al medium entropy alloy(MEA)have been investigated comprehensively by first-principles calculations.It is found that theΦandμMag of those MEA are proportional to the V 0,which is dominated by lattice distortion.In terms of bonding charge density,both the strengthened clusters or the so-called short-range order structures and the weakly bonded spots or weak spots are characterized.While the presence of weakly bonded Al atoms implies a large LLD/mismatch,the Fe–Mn bonding pairs result in the formation of strengthened clusters,which dominate the local microstates and the configurational transitions.The variations ofμMag are associated with the enhancement of the nearest neighbor magnetic Fe and Mn atoms,attributing to the LLD caused by Al atoms,the local changes in the electronic structures.This work provides an atomic and electronic insight into the microstate-dominated solid-solution strengthening mechanism of Fe–Mn–Al MEA.展开更多
Using an extended slave-boson method,we draw a global phase diagram summarizing both magnetic phases and paramagnetic（PM） topological insulators（TIs） in a three-dimensional topological Kondo insulator（TKI）. By i...Using an extended slave-boson method,we draw a global phase diagram summarizing both magnetic phases and paramagnetic（PM） topological insulators（TIs） in a three-dimensional topological Kondo insulator（TKI）. By including electron hopping（EH） up to the third neighbors, we identify four strong TI（STI） phases and two weak TI（WTI） phases. Then, the PM phase diagrams characterizing topological transitions between these TIs are depicted as functions of EH,f-electron energy level,and hybridization constant. We also find an insulator-metal transition from an STI phase that has surface Fermi rings and spin textures in qualitative agreement with the TKI candidate SmBs. In the weak hybridization regime, antiferromagnetic（AF） order naturally arises in the phase diagrams. Depending on how the magnetic boundary crosses the PM topological transition lines,AF phases are classified into the AF topological insulator（AFTI） and the non-topological AF insulator, according to their Z2 indices. In two small regions of parameter space, two distinct topological transition processes between AF phases occur, leading to two types of AFTIs showing distinguishable surface dispersions around their Dirac points.展开更多
In order to calculate the electronic structure of correlated materials, we propose implementation of the LDA＋Gutzwiller method with Newton＇s method. The self-consistence process, efficiency and convergence of calcul...In order to calculate the electronic structure of correlated materials, we propose implementation of the LDA＋Gutzwiller method with Newton＇s method. The self-consistence process, efficiency and convergence of calculation are improved dramatically by using Newton＇s method with golden section search and other improvement approaches.We compare the calculated results by applying the previous linear mix method and Newton＇s method. We have applied our code to study the electronic structure of several typical strong correlated materials, including SrVO3, LaCoO3, and La2O3Fe2Se2. Our results fit quite well with the previous studies.展开更多
We have systematically studied the behaviors of the resistivity and magnetization of CeSb2 single crystals as a function of temperature and external field. Four anomalies in the resistivity/magnetization-versus-temper...We have systematically studied the behaviors of the resistivity and magnetization of CeSb2 single crystals as a function of temperature and external field. Four anomalies in the resistivity/magnetization-versus-temperature curves are observed at low magnetic field. They are located at 15.5 K, 11.5 K, 9.5 K, and 6.5 K, corresponding to the paramagnetic–magnetically ordered state（MO）, MO-antiferromagnetic（AFM）, AFM–AFM, and AFM–ferromagnetic（FM） transitions, respectively.The anomaly at 9.5 K is only visible with H‖[010] by magnetic susceptibility measurements, indicating that the AFM–AFM transition only happens along [010] direction in ab-plane. The four magnetic transitions are strongly suppressed by high external field. Finally, the field-temperature phase diagrams of CeSb2 with different orientations of the applied field in ab-plane are constructed and indicate the highly anisotropic nature of the magnetization of CeSb2.展开更多
Fe-based metallic glasses(MGs)have been extensively investigated due to their unique properties,especially the outstanding soft-magnetic properties.However,conventional design of soft-magnetic Fe-based MGs is heavily ...Fe-based metallic glasses(MGs)have been extensively investigated due to their unique properties,especially the outstanding soft-magnetic properties.However,conventional design of soft-magnetic Fe-based MGs is heavily relied on“trial and error”experiments,and thus difficult to balance the saturation flux density(Bs)and thermal stability due to the strong interplay between the glass formation and magnetic interaction.Herein,we report an eXtreme Gradient Boosting(XGBoost)machine-learning(ML)model for developing advanced Fe-based MGs with a decent combination of Bs and thermal stability.展开更多
W is considered a potential candidate as a plasma facing ma- terial for future nuclear fusion devices because of its high melting point, low sputtering rate, and low H or He solubility [1-3]. In a fusion environment, ...W is considered a potential candidate as a plasma facing ma- terial for future nuclear fusion devices because of its high melting point, low sputtering rate, and low H or He solubility [1-3]. In a fusion environment, W will be in direct contact with heat flux, H/He particle fluxes, and the irradiation of high-energy neutrons, causing several defects to be generated, which decrease the service life of W materials. The grain boundary （GB）, which is an important type of defect, affects the various physical and mechanical properties of ma- terials. In the nuclear environment, the GB can act as a sink for the defects when the material is under irradiation.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.12302501)the China Postdoctoral Science Foun-dation(Grant No.2023MD744236)+4 种基金the Natural Science Basic Research Program of Shaanxi(Grant No.2024JC-YBQN-0061)the Postdoctoral Research Project of Shaanxi Province(Grant No.2023BSHEDZZ270)the Special Scientific Research Plan Project of Education Department of Shaanxi Provincial Government(Grant No.23JK0509)the Scientific Research Foundation for Excellent Returned Overseas Chinese Schol-ars funded by Shaanxi Provincial Government(Grant No.2023-021)the Innovation and Entrepreneurship Projects for College Students(Grant No.S202310703047).
文摘Rock burst is a kind of severe engineering disaster resulted from dynamic fracture process of rocks.The macrofailure behaviors of rocks are primarily formed after experiencing the initiation,propagation,and coalescenceof micro-cracks.In this paper,the grain-based discretized virtual internal bond model is employed to investigatethe fracturing process of unloaded rock under high in-situ stresses from the micro-fracture perspective.Thesimulated micro-fracturing process reveals that the longitudinal stress waves induced by unloading lead to thevisible unloading effect.The influences of in-situ stresses,mineral grain sizes,and grain heterogeneity on rockmacro and micro fracture are investigated.Micro-crack areas of tensile and shear cracks and micro-crack anglesare statistically analyzed to reveal the rock micro-fracture characteristics.The simulated results indicate thatthe combined effect of the stress state transition and the unloading effect dominates the rock unloading failure.The vertical and horizontal in-situ stresses determine the stress state of surrounding rock after unloading andthe unloading effect,respectively.As the vertical stress increases,the stress level after unloading is higher,andthe shear failure characteristics become more obvious.As the horizontal stress increases,the unloading effectincreases,leading to the intensification of tensile failure.The mineral grain size and grain heterogeneity alsohave nonnegligible influences on rock unloading failure.The micro-fracture perspective provides further insightinto the unloading failure mechanism of deep rock excavation.
基金supported by the National Basic Research Program (973 Program) of China under Grant No.2010CB428804 and 2011CB 309702
文摘The desire to increase spatial and temporal resolution in modeling groundwater system has led to the requirement for intensive computational ability and large memory space. In the course of satisfying such requirement, parallel computing has played a core role over the past several decades. This paper reviews the parallel algebraic linear solution methods and the parallel implementation technologies for groundwater simulation. This work is carried out to provide guidance to enable modelers of groundwater systems to make sensible choices when developing solution methods based upon the current state of knowledge in parallel computing.
基金financially supported by the National Natural Science Foundation of China(Nos.51690163 and 51601147)the Science Challenge Project(No.TZZT2019-D1.5)+4 种基金the Ministry of Science and Technology of China(No.2017YFA0700700)the United States National Science Foundation(Nos.DMR-1006557,1611180,and 1809640)the Fundamental Research Funds for the Central Universities in China(No.G2016KY0302)the CyberStar cluster funded by NSF through grant No.OCI-0821527the XSEDE clusters supported by NSF through Grant No.ACI-1053575。
文摘Metallic amorphous/crystalline(A/C)nanolaminates exhibit excellent ductility while retaining their high strength.However,the underlying physical mechanisms and the resultant structural changes during plastic deformation still remain unclear.In the present work,the structure-property relationship of CuZr/Cu A/C nanolaminates is established through integrated high-throughput micro-compression tests and molecular dynamics simulations together with high-resolution transmission electron microcopy.The serrated flow of nanolaminates results from the formation of hexagonal-close-packed(HCP)-type stacking faults and twins inside the face-centered-cubic(FCC)Cu nano-grains,the body-centered-cubic(BCC)-type ordering at their grain boundaries,and the crystallization of the amorphous CuZr layers.The serration behavior of CuZr/Cu A/C nanolaminates is determined by several factors,including the formation of dense dislocation networks from the multiplication of initial dislocations that formed after yielding,weak-spots-related configurational-transitions and shear-transition-zone activities,and deformation-induced devitrification.The present work provides an insight into the heterogeneous deformation mechanism of A/C nanolaminates at the atomic scale,and mechanistic base for the microstructural design of self-toughening metallic-glass(MG)-based composites and A/C nanolaminates.
基金supported by the National Natural Science Foundation of China(No.U23B2067)Innovation Program of CAEP(No.CX20210045)。
文摘In response to the demand for rapid geometric modeling in Monte Carlo radiation transportation calculations for large-scale and complex geometric scenes,functional improvements,and algorithm optimizations were performed using CAD-to-Monte Carlo geometry conversion(CMGC)code.Boundary representation(BRep)to constructive solid geometry(CSG)conversion and visual CSG modeling were combined to address the problem of non-convertible geometries such as spline surfaces.The splitting surface assessment method in BRep-to-CSG conversion was optimized to reduce the number of Boolean operations using an Open Cascade.This,in turn,reduced the probability of CMGC conversion failure.The auxiliary surface generation algorithm was optimized to prevent the generation of redundant auxiliary surfaces that cause an excessive decomposition of CAD geometry solids.These optimizations enhanced the usability and stability of the CMGC model conversion.CMGC was applied successfully to the JMCT transportation calculations for the conceptual designs of five China Fusion Engineering Test Reactor(CFETR)blankets.The rapid replacement of different blanket schemes was achieved based on the baseline CFETR model.The geometric solid number of blankets ranged from hundreds to tens of thousands.The correctness of the converted CFETR models using CMGC was verified through comparisons with the MCNP calculation results.The CMGC supported radiation field evaluations for a large urban scene and detailed ship scene.This enabled the rapid conversion of CAD models with thousands of geometric solids into Monte Carlo CSG models.An analysis of the JMCT transportation simulation results further demonstrated the accuracy and effectiveness of the CMGC.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA03030102)
文摘The analysis of the fuel depletion behavior is critical for maintaining the safety of accelerator-driven subcritical systems(ADSs). The code COUPLE2.0 coupling 3-D neutron transport and point burnup calculation was developed by Tsinghua University. A Monte Carlo method is used for the neutron transport analysis, and the burnup calculation is based on a deterministic method. The code can be used for the analysis of targets coupled with a reactor in ADSs. In response to additional ADS analysis requirements at the Institute of Modern Physics at the Chinese Academy of Sciences, the COUPLE3.0 version was developed to include the new functions of(1) a module for the calculation of proton irradiation for the analysis of cumulative behavior using the residual radionuclide operating history,(2) a fixed-flux radiation module for hazard assessment and analysis of the burnable poison, and(3) a module for multi-kernel parallel calculation, which improves the radionuclide replacement for the burnup analysis to balance the precision level and computational efficiency of the program. This paper introduces thevalidation of the COUPLE3.0 code using a fast reactor benchmark and ADS benchmark calculations. Moreover,the proton irradiation module was verified by a comparison with the analytic method of calculating the210 Po accumulation results. The results demonstrate that COUPLE3.0 is suitable for the analysis of neutron transport and the burnup of nuclides for ADSs.
基金supported by the National Basic Research Program (973 Program) of China (Nos. 2010CB428804 and 2011CB309702)the Key Projects of National Natural Science Foundation of China (No. 61033009)
文摘Numerical modeling is of crucial importance in understanding the behavior of regional groundwater system. However, the demand on modeling capability is intensive when performing high-resolution simulation over long time span. This paper presents the application of a parallel program to speed up the detailed modeling of the groundwater flow system in the North China Plain. The parallel program is implemented by rebuilding the well-known MODFLOW program on our parallelcomputing framework, which is achieved by designing patch-based parallel data structures and algorithms but maintaining the compute flow and functionalities of MODFLOW. The detailed model with more than one million grids and a decade of time has been solved. The parallel simulation results were examined against the field observed data and these two data are generally in good agreement. For the comparison on solution time, the parallel program running on 32 cores is 6 times faster than the fastest MICCG-based MODFLOW program and 11 times faster than the GMG-based MODFLOW program. Therefore, remarkable computational time can be saved when using the parallel program, which facilitates the rapid modeling and prediction of the groundwater flow system in the North China Plain.
基金Project supported by the Science Challenge Project,China(Grant No.TZZT2019-D1-03)the National Natural Science Foundation of China(Grant No.51972028)the National Key Research and Development Program of China(Grant No.2019YFA0307900)。
文摘A multi-phase-field model is implemented to investigate the peritectic solidification of Fe-C alloy. The nucleation mode of austenite is based on the local driving force, and two different thicknesses of the primary austenite on the surface of the ferrite equiaxed crystal grain are used as the initial conditions. The simulation shows the multiple interactions of ferrite, austenite, and liquid phases, and the effects of carbon diffusion, which presents the non-equilibrium dynamic process during Fe-C peritectic solidification at the mesoscopic scale. This work not only reveals the influence of the austenite nucleation position, but also clarifies the formation mechanism of liquid phase channels and molten pools. Therefore, the present study contributes to the understanding of the micro-morphology and micro-segregation evolution mechanisms of Fe-C alloy during peritectic solidification.
基金the National Natural Science Foundation of China(Grant Nos.12102033,12072026,and 11832005).
文摘A geometrically exact Kirchhoff beam formulation(GEKBF)established on the Lie group SO(3)for simulating the dynamics of a slender beam is proposed.The kinematic description,dynamic equilibrium equations and their linearization are derived in this framework.Then,a second-order interpolation function for the torsion angle is introduced to improve the convergence of the element.Next,the rotation vector parameterization is developed to reduce the geometric nonlinearity caused by the rotation of the rigid body.In addition,the influence of the reference frame is considered,and the derivation of the elastic force and Jacobian matrix is simplified using the spatial-parallel transport.The semi-discrete equations of motion are in the form of a second-order ordinary differential equation on Lie group,which are solved using the Lie group generalizedα-method.Finally,the accuracy of the proposed formulation is verified using several numerical examples.
基金supported by the National Basic Research Program of China (No. 2010CB428804)the Public Welfare Industry Special Funds for Scientific Research from Ministry of Land and Resources of China (No. 201211079-4).
文摘The amount of water withdrawn by wells is one of the quantitative variables that can be applied to estimate groundwater resources and further evaluate the human influence on groundwater systems. The accuracy for the calculation of the amount of water withdrawal significantly influences the regional groundwater resource evaluation and management. However, the decentralized groundwater pumping, inefficient management, measurement errors and uncertainties have resulted in considerable errors in the groundwater withdrawal estimation. In this study, to improve the estimation of the groundwater withdrawal, an innovative approach was proposed using an inversion method based on a regional groundwater flow numerical model, and this method was then applied in the North China Plain. The principle of the method was matching the simulated water levels with the observation ones by adjusting the amount of groundwater withdrawal. In addition, uncertainty analysis of hydraulic conductivity and specific yield for the estimation of the groundwater withdrawal was conducted. By using the proposed inversion method, the estimated annual average groundwater withdrawal was approximately 24.92×10^9 m^3 in the North China Plain from 2002 to 2008. The inversion method also significantly improved the simulation results for both hydrograph and the flow field. Results of the uncertainty analysis showed that the hydraulic conductivity was more sensitive to the inversion results than the specific yield.
基金This work was financially supported by the National Key Research and Development Program of China(2018YFB0703801,2018YFB0703802,2016YFB0701303,and 2016YFB0701304)CRRC Tangshan Co.,Ltd.(201750463031).Special thanks to Professor Hong Wang at Shanghai Jiao Tong University for the fruitful discussions and the constructive suggestions/comments.
文摘A data identifier(DID)is an essential tag or label in all kinds of databases—particularly those related to integrated computational materials engineering(ICME),inheritable integrated intelligent manufacturing(I3M),and the Industrial Internet ofThings.With the guidance and quick acceleration of the developme nt of advanced materials,as envisioned by official documents worldwide,more investigations are required to construct relative numerical standards for material informatics.This work proposes a universal DID format consisting of a set of build chains,which aligns with the classical form of identifier in both international and national standards,such as ISO/IEC 29168-1:2000,GB/T 27766-2011,GA/T 543.2-2011,GM/T 0006-2012,GJB 7365-2011,SL 325-2014,SL 607-201&WS 363.2-2011,and QX/T 39-2005.Each build chain is made up of capital letters and numbers,with no symbols.Moreover,the total length of each build chain is not restricted,which follows the formation of the Universal Coded Character Set in the international standard of ISO/IEC 10646.Based on these rules,the proposed DID is flexible and convenient for extendi ng and sharing in and between various cloud-based platforms.Accordingly,classical two-dimensional(2D)codes,including the Hanxin Code,Lots Perception Matrix(LP)Code,Quick Response(Q.R)code,Grid Matrix(GM)code,and Data Matrix(DM)Code,can be constructed and precisely recognized and/or decoded by either smart phones or specific machines.By utilizing these 2D codes as the fingerprints of a set of data linked with cloud-based platforms,progress and updates in the composition-processing-structure-property-performance workflow process can be tracked spontaneously,paving a path to accelerate the discovery and manufacture of advanced materials and enhance research productivity,performance,and collaboration.
基金the National Natural Science Foundation of China(No.11805017)。
文摘Automatic conversion from a computer-aided design(CAD) model to Monte Carlo geometry is one of the most effective methods for large-scale and detailed Monte Carlo modeling. The CAD to Monte Carlo geometry converter(CMGC) is a newly developed conversion code based on the boundary representation to constructive solid geometry(BRep→CSG) conversion method. The goal of the conversion process in the CMGC is to generate an appropriate CSG representation to achieve highly efficient Monte Carlo simulations. We designed a complete solid decomposition scheme to split a complex solid into as few nonoverlapping simple sub-solids as possible. In the complete solid decomposition scheme, the complex solid is successively split by so-called direct, indirect, and auxiliary splitting surfaces. We defined the splitting edge and designed a method for determining the direct splitting surface based on the splitting edge, then provided a method for determining indirect and auxiliary splitting surfaces based on solid vertices. Only the sub-solids that contain concave boundary faces need to be supplemented with auxiliary surfaces because the solid is completely decomposed, which will reduce the redundancy in the CSG expression. After decomposition, these sub-solids are located on only one side of their natural and auxiliary surfaces;thus, each sub-solid can be described by the intersections of a series of half-spaces or geometrical primitives. The CMGC has a friendly graphical user interface and can convert a CAD model into geometry input files for several Monte Carlo codes. The reliability of the CMGC was evaluated by converting several complex models and calculating the relative volume errors. Moreover, JMCT was used to test the efficiency of the Monte Carlo simulation. The results showed that the converted models performed well in particle transport calculations.
文摘The detection technology of concealed bulk explosives is related to social security and national defense construction and has important research significance. In this paper, an element analysis method of concealed explosives based on thermal neutron analysis is proposed.This method could provide better reconstruction precision for hydrogen, carbon, and nitrogen ratios, making it possible to discriminate explosives from other compounds with the same elements but different proportions, as well as to identify the types of concealed bulk explosives. In this paper, the basic principles and mathematical model of this method are first introduced, and the calculation formula of the element number ratio(the ratio between the nucleus numbers of two different elements) of the concealed explosive is deduced. Second, a numerical simulation platform of this method was established based on the Monte Carlo JMCT code. By calibrating the absorption efficiencies of the explosive device to c rays, the element number ratios of a concealed explosive model under the irradiation of thermal neutrons were reconstructed from the neutron capture prompt c-ray spectrum. The reconstruction values were in good agreement with the actual values,which shows that this method has a high reconstruction precision of the element number ratio for concealed explosives. Lastly, it was demonstrated using the simulation study that this method can discriminate explosives,drugs, and common materials, with the capability of determining the existence of concealed bulk explosives and identifying explosive types.
基金supported by the National Natural Science Foundation of China(No.12005199)the fund project of the China Academy of Engineering Physics(Nos.TP03201601 and CX20210009)。
文摘Determining the mass of plutonium metal is an important research objective in the field of nuclear material accounting and control.Based on the 3D neutron and photon transport code JMCT(Jointed Monte Carlo Transport),the gamma ray multiplicity of ^(240)Pu was simulated in this study,and the average number of gamma rays leaking from ^(240)Pu solid spheres with different masses was also obtained.The simulation results show that there is a oneto-one correspondence between the average number of gamma rays and the mass of ^(240)Pu solid spheres in the range of 0.50–3.00 kg.This result provides a basis for using the average number of gamma rays to account for the mass of ^(240)Pu.
基金Project supported by the National Natural Science Foundation of China(Grant No.51076002)the National Basis Research Program of China(Grant No.2013CA328900)the Key Project of Complicated Electromagnetic Environment Laboratory of CAEP,China(Grant No.2015E0-01-1)
文摘Spectral and directional control of thermal emission based on excitation of confined electromagnetic resonant modes paves a viable way for the design and construction of microscale thermal emitters/absorbers. In this paper, we present numerical simulation results of the thermal radiative properties of a silicon carbide（Si C） thermal emitter/absorber composed of periodic microstructures. We illustrate different electromagnetic resonant modes which can be excited with the structure,such as surface phonon polaritons, magnetic polaritons and photonic crystal modes, and the process of radiation spectrum optimization based on a non-linear optimization algorithm. We show that the spectral and directional control of thermal emission/absorption can be efficiently achieved by adjusting the geometrical parameters of the structure. Moreover, the optimized spectrum is insensitive to 3% dimension modification.
基金financially supported by the Key Project of the Equipment Pre-Research Field Fund of China(No.6140922010302)the National Natural Science Foundation of China(No.51690164)。
文摘Entropy-stabilized multi-component alloys have been considered to be prospective structural materials attributing to their impressive mechanical and functional properties.The local chemical complexions,microstates and configurational transformations are essential to reveal the structure–property relationship,thus,to promote the development of advanced multicomponent alloys.In the present work,effects of local lattice distortion(LLD)and microstates of various configurations on the equilibrium volume(V0),total energy,Fermi energy,magnetic moment(μMag)and electron work function(Φ)and bonding structures of the Fe–Mn–Al medium entropy alloy(MEA)have been investigated comprehensively by first-principles calculations.It is found that theΦandμMag of those MEA are proportional to the V 0,which is dominated by lattice distortion.In terms of bonding charge density,both the strengthened clusters or the so-called short-range order structures and the weakly bonded spots or weak spots are characterized.While the presence of weakly bonded Al atoms implies a large LLD/mismatch,the Fe–Mn bonding pairs result in the formation of strengthened clusters,which dominate the local microstates and the configurational transitions.The variations ofμMag are associated with the enhancement of the nearest neighbor magnetic Fe and Mn atoms,attributing to the LLD caused by Al atoms,the local changes in the electronic structures.This work provides an atomic and electronic insight into the microstate-dominated solid-solution strengthening mechanism of Fe–Mn–Al MEA.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11764010,11504061,11564008,11704084,and 11704166the Natural Science Foundation of Guangxi Province under Grant Nos 2017GXNSFAA198169 and 2017GXNSFBA198115the SPC-Lab Research Fund under Grant No XKFZ201605
文摘Using an extended slave-boson method,we draw a global phase diagram summarizing both magnetic phases and paramagnetic（PM） topological insulators（TIs） in a three-dimensional topological Kondo insulator（TKI）. By including electron hopping（EH） up to the third neighbors, we identify four strong TI（STI） phases and two weak TI（WTI） phases. Then, the PM phase diagrams characterizing topological transitions between these TIs are depicted as functions of EH,f-electron energy level,and hybridization constant. We also find an insulator-metal transition from an STI phase that has surface Fermi rings and spin textures in qualitative agreement with the TKI candidate SmBs. In the weak hybridization regime, antiferromagnetic（AF） order naturally arises in the phase diagrams. Depending on how the magnetic boundary crosses the PM topological transition lines,AF phases are classified into the AF topological insulator（AFTI） and the non-topological AF insulator, according to their Z2 indices. In two small regions of parameter space, two distinct topological transition processes between AF phases occur, leading to two types of AFTIs showing distinguishable surface dispersions around their Dirac points.
基金supported by the National Natural Science Foundation of China(Grant No.2011CBA00108)the National Basic Research Program of China(Grant No.2013CB921700)the Foundation of LCP
文摘In order to calculate the electronic structure of correlated materials, we propose implementation of the LDA＋Gutzwiller method with Newton＇s method. The self-consistence process, efficiency and convergence of calculation are improved dramatically by using Newton＇s method with golden section search and other improvement approaches.We compare the calculated results by applying the previous linear mix method and Newton＇s method. We have applied our code to study the electronic structure of several typical strong correlated materials, including SrVO3, LaCoO3, and La2O3Fe2Se2. Our results fit quite well with the previous studies.
基金supported by the Science Challenge Project(Grant No.TZ2016004)the Dean Foundation of China Academy of Engineering Physics(Grant No.201501040)the National Basic Research Program of China(Grant No.2015CB921303)
文摘We have systematically studied the behaviors of the resistivity and magnetization of CeSb2 single crystals as a function of temperature and external field. Four anomalies in the resistivity/magnetization-versus-temperature curves are observed at low magnetic field. They are located at 15.5 K, 11.5 K, 9.5 K, and 6.5 K, corresponding to the paramagnetic–magnetically ordered state（MO）, MO-antiferromagnetic（AFM）, AFM–AFM, and AFM–ferromagnetic（FM） transitions, respectively.The anomaly at 9.5 K is only visible with H‖[010] by magnetic susceptibility measurements, indicating that the AFM–AFM transition only happens along [010] direction in ab-plane. The four magnetic transitions are strongly suppressed by high external field. Finally, the field-temperature phase diagrams of CeSb2 with different orientations of the applied field in ab-plane are constructed and indicate the highly anisotropic nature of the magnetization of CeSb2.
基金This research was supported by National Natural Science Foundation of China(Nos.51671018,51671021,51531001,11790923,and 51961160729)the Funds for Creative Research Groups of China(No.51921001),Program for Changjiang Scholars and Innovative Research Team in University of China(No.IRT_14R05)+3 种基金National Key Basic Research Program China(No.2016YFB0300502)the Fundamental Research Fund for the Central Universities(Nos.FRF-GF-19-011A and FRF-BD-19-002B)X.J.L.is grateful to the financial support from the Projects of SKLAMM-USTB(2018Z-19)HXL appreciates the financial support from the Natural Science Foundation of Beijing,China(Grant No.2202033).
文摘Fe-based metallic glasses(MGs)have been extensively investigated due to their unique properties,especially the outstanding soft-magnetic properties.However,conventional design of soft-magnetic Fe-based MGs is heavily relied on“trial and error”experiments,and thus difficult to balance the saturation flux density(Bs)and thermal stability due to the strong interplay between the glass formation and magnetic interaction.Herein,we report an eXtreme Gradient Boosting(XGBoost)machine-learning(ML)model for developing advanced Fe-based MGs with a decent combination of Bs and thermal stability.
基金supported by the National Magnetic Confinement Fusion Program(Grant No.2013GB109002)the National Natural Science Foundation of China(Grant Nos.51171008,and 51325103)
文摘W is considered a potential candidate as a plasma facing ma- terial for future nuclear fusion devices because of its high melting point, low sputtering rate, and low H or He solubility [1-3]. In a fusion environment, W will be in direct contact with heat flux, H/He particle fluxes, and the irradiation of high-energy neutrons, causing several defects to be generated, which decrease the service life of W materials. The grain boundary （GB）, which is an important type of defect, affects the various physical and mechanical properties of ma- terials. In the nuclear environment, the GB can act as a sink for the defects when the material is under irradiation.
