Based on the existing component models in the Pspice software package, a combined model for Insulat- ed the Bipolar Transistor (IGBT) is established, in which a non - linear is introduced to represent the parasitic ...Based on the existing component models in the Pspice software package, a combined model for Insulat- ed the Bipolar Transistor (IGBT) is established, in which a non - linear is introduced to represent the parasitic capacitance. Using this model, computerized simulation is conducted for the FB - ZVZCS - PWM soft - ewitching converter,the switching and energy-transferring characteristics of the components are analyzed.The simulation results are testified by experiments.It is proved that by abopting appropriate models,computerized simulation becomes an effective tool for investigation of arc welding inverter power source.展开更多
The structure and properties of molten salt solution o J Li,K|F,Cl system have been investiged by computerized simulation of molecular dynamic method.The partial RDF,the partial molar energy of mixing and the diffusio...The structure and properties of molten salt solution o J Li,K|F,Cl system have been investiged by computerized simulation of molecular dynamic method.The partial RDF,the partial molar energy of mixing and the diffusion coeffients of Li^+,K^+,F^- and Cl^- have been calculated. The results are in agreement with the experimental values.The regularities of the distribution of ions and mieroscopic holes are discussed based on the results of computerized simulation.展开更多
Whereas theπ-πstacking interactions at oil/water interfaces can affect interfacial structures hence the interfacial properties,the underlying microscopic mechanism remains largely unknown.We reported an all-atom mol...Whereas theπ-πstacking interactions at oil/water interfaces can affect interfacial structures hence the interfacial properties,the underlying microscopic mechanism remains largely unknown.We reported an all-atom molecular dynamics(MD)simulation study to demonstrate how the Gemini surfactants with pyrenyl groups affect the interracial properties,structural conformations,and the motion of molecules in the water/n-octane/surfactant ternary systems.It is found that the pyrenyl groups tend to be vertical to the interface owing to theπ-πstacking interaction.Besides,a synergistic effect between theπ-πinteraction and steric hindrance is found,which jointly affects the coalescence of liquid droplets.Therefore,the existence of aromatic groups and a moderate number of surfactants helps to form microemulsion.This work provides a molecular understanding of Gemini surfactants with aromatic groups in microemulsion preparation and applications.展开更多
The structure and behaviour of LiF-KF solution,as a typical common-anion system,has been simulated by Monte Carlo method.The calculation of partial radial distribution function of ions,heat of mixing and potential ene...The structure and behaviour of LiF-KF solution,as a typical common-anion system,has been simulated by Monte Carlo method.The calculation of partial radial distribution function of ions,heat of mixing and potential energy distribution shows that the average distance be- tween Li^+ and F^- ions will significantly narrow after mixing of molten LiF and KF.This is very similar to the lean-on-one-side effect in molten LiF-KCl solution.The calculated heat of mixing is in fair agreement with the measured one.The dominant source of the energy of mixing may be that the decrease of the repulsion energy between cations,the decrease of the attraction energy between cations and anions,and the decrease of the repulsion energy be- tween anions.展开更多
The structure of molten DyF_3-LiF system has been simulated by Monte Carlo method.The radial distribution functions(RDFs)and the local structure have been obtained.It is concluded that F^- ions distribute closely arou...The structure of molten DyF_3-LiF system has been simulated by Monte Carlo method.The radial distribution functions(RDFs)and the local structure have been obtained.It is concluded that F^- ions distribute closely around Dy^(3+) ions.There exist some fissures and holes between F^- ions and Li^+ ions. There are mainly two kinds of ionic types:the complex ions like DyF_n^(3-n) clusters with the central Dy^(3+) ions (the main ionic clusters are octahedral complex ions like DyF_6^(3-))and the“free”Li^+ ions.Moreover,some complex ions like DyF_n^(3-n) clusters are connected to one another by flourine-bridge,forming more compli- cated ionic clusters like Dy_m^(3m-n) F_n.By calculating the potential energies of all types of ions,it is concluded that Li^+ ions have the highest potential energy in the molten system,which are current-carrying ions in the electrolytic conductance.展开更多
The structure of NaAlO_2 melt has been studied by computerized simulation using Monte Carlo method.The radial distribution functions and Local structure of this melt are calculated.It has been found that NaAlO_2 melt ...The structure of NaAlO_2 melt has been studied by computerized simulation using Monte Carlo method.The radial distribution functions and Local structure of this melt are calculated.It has been found that NaAlO_2 melt contains ionic clusters formed by corner-sharing AlO_4 tetrahedra,sodium ions and xNa^+.yO^(2-) ionic clusters.展开更多
Computer simulation researches on Direct Torque Control System (DTC) are to be done. That fact is demonstrated:at high speed,the operating property of an induction motor is very good,almost the same as fieldoriented c...Computer simulation researches on Direct Torque Control System (DTC) are to be done. That fact is demonstrated:at high speed,the operating property of an induction motor is very good,almost the same as fieldoriented control system fat low speed (for example: below 2-3Hz), the operating property of a motor is getting worse,and the stator resistance R1 of the motor must be compensated. If compensation precision gets 5 %,the operating property of the motor will be greatly improved.展开更多
Log centering accuracy depends on the computerized simulative level of its three-dimension outline. In this paper, the basic methods about distinguishing three dimensions outline of log by means of computerized simula...Log centering accuracy depends on the computerized simulative level of its three-dimension outline. In this paper, the basic methods about distinguishing three dimensions outline of log by means of computerized simulation are discussed. It is suggested that straight lines or certain curves should be introduced to connect the separated points along some log generatrices. Taking bent logs for example verify the accuracy of computerized simulative method.展开更多
Transition metal dichalcogenides are nowadays appealing to researchers for their excellent electronic properties.Vertical stacked nanosheet FET(NSFET)based on MoS_(2)are proposed and studied by Poisson equation solver...Transition metal dichalcogenides are nowadays appealing to researchers for their excellent electronic properties.Vertical stacked nanosheet FET(NSFET)based on MoS_(2)are proposed and studied by Poisson equation solver coupled with semiclassical quantum correction model implemented in Sentaurus workbench.It is found that,the 2D stacked NSFET can largely suppress short channel effects with improved subthreshold swing and drain induced barrier lowering,due to the excellent electrostatics of 2D MoS_(2).In addition,small-signal capacitance is extracted and analyzed.The MoS_(2)based NSFET shows great potential to enable next generation electronics.展开更多
Describes a new computer program (Regress-3D) to simulate the regression of complex 3D grain cavity and calculate the burning surface area. It has a large region of applicability in solid rocket motor design and has...Describes a new computer program (Regress-3D) to simulate the regression of complex 3D grain cavity and calculate the burning surface area. It has a large region of applicability in solid rocket motor design and has made new improvements compared with other available codes. User can easily and rapidly build his initial grain shapes and then obtain geometric information of his design. Considering with the calclulting results, redesigning can be performed as desire until reaching at the satisfied result. Advantages and disadvantages of this method are also discussed.展开更多
Fuel consumption has always been a matter of concern for ships propulsion. In this research we aim to develop computer models of several containership cargo stacking configurations and discuss an optimal configuration...Fuel consumption has always been a matter of concern for ships propulsion. In this research we aim to develop computer models of several containership cargo stacking configurations and discuss an optimal configuration at a constant front wind speed. The paper presents the simulation results by using ANSYS CFX for a 1:4 scale PostPanamax 9000 TEU containership. The ship is modelled in a cubic domain that contains unstructured mesh with details, in such a way that can demonstrate the influence of the container configuration on wind force. Also the numerical results are verified versus wind tunnel test data. An optimal stack configuration led to about 25%reduction in air resistance. It is proposed that in order to reduce the wind drag force and consequently reduce the fuel consumption and pollutant emissions, empty spaces between the cargo containers and unbalanced cargo distribution over the deck should be inhibited. Also, it is advised to make the cargo distribution on the most forward and aftward deck areas more streamlined.展开更多
The effects of applied tensile strain on the coherent α_2→O-phase transformation in Ti-Al-Nb alloys are explored bycomputer simulation using a phase-field method. The focus is on the influence of the applied strain ...The effects of applied tensile strain on the coherent α_2→O-phase transformation in Ti-Al-Nb alloys are explored bycomputer simulation using a phase-field method. The focus is on the influence of the applied strain direction onthe microstructure and volume fraction of the O-phase precipitates. It is found that altering applied strain directioncan modify microstructure of Ti-25Al-10～12Nb (at. pct) alloy during α_2→O-phase transformation effectively andfull laminate microstructure in the Ti-25Al-10Nb (at. pct) alloy can be realized by an applied strain only along thedirection 30°away from the α_2 phase <1010> in magnitude equivalent to the stress-free transformation strain. Thesimulation also shows that not only the magnitude of applied strain but also the applied strain direction influencesthe O-phase volume fraction and the effect of strain direction on the volume fraction is up to 25%.展开更多
The effects of twin spacing and temperature on the deformation behavior of nanotwinned Al under tensile loading are investigated using a molecular dynamic（MD） simulation method.The result shows that the yield streng...The effects of twin spacing and temperature on the deformation behavior of nanotwinned Al under tensile loading are investigated using a molecular dynamic（MD） simulation method.The result shows that the yield strength of nanotwinned Al decreases with the increase of twin spacing,which is related to the repulsive force between twin boundary and the dislocation.The result also shows that there is no strain-hardening at the yield point.On the contrary,the stress is raised by strain hardening in the plastic stage.In addition,we also investigate the effects of stacking fault thickness and temperature on the yield strength of the Al nanowire.The simulation results indicate that the stacking fault may strengthen the Al nanowire when the thickness of the stacking fault is below a critical value.展开更多
Molecular simulations were performed to investigate the molecular structural effects on needle coke mesophase stacking.The simulation results showed that the stacking states of anthracene trimer and tetramer accumulat...Molecular simulations were performed to investigate the molecular structural effects on needle coke mesophase stacking.The simulation results showed that the stacking states of anthracene trimer and tetramer accumulations were orderly,while the stacking states of anthracene dimer,pentamer,and hexamer accumulations were disorderly.Anthracene trimer and tetramer in the model compounds were two of the most ideal needle coke mesophase constituents.It was also found that the introduction of methyl side chains in anthracene trimer derivatives was not conducive to the formation of a mesophase crystal.To sum up,the molecules which had similar structures to anthracene trimer or tetramer with no alkyl chains are ideal constituents of needle coke mesophase.展开更多
The geometry of joints has a significant influence on the mechanical properties of rocks.To simplify the curved joint shapes in rocks,the joint shape is usually treated as straight lines or planes in most laboratory e...The geometry of joints has a significant influence on the mechanical properties of rocks.To simplify the curved joint shapes in rocks,the joint shape is usually treated as straight lines or planes in most laboratory experiments and numerical simulations.In this study,the computerized tomography (CT) scanning and photogrammetry were employed to obtain the internal and surface joint structures of a limestone sample,respectively.To describe the joint geometry,the edge detection algorithms and a three-dimensional (3D) matrix mapping method were applied to reconstruct CT-based and photogrammetry-based jointed rock models.For comparison tests,the numerical uniaxial compression tests were conducted on an intact rock sample and a sample with a joint simplified to a plane using the parallel computing method.The results indicate that the mechanical characteristics and failure process of jointed rocks are significantly affected by the geometry of joints.The presence of joints reduces the uniaxial compressive strength (UCS),elastic modulus,and released acoustic emission (AE) energy of rocks by 37%–67%,21%–24%,and 52%–90%,respectively.Compared to the simplified joint sample,the proposed photogrammetry-based numerical model makes the most of the limited geometry information of joints.The UCS,accumulative released AE energy,and elastic modulus of the photogrammetry-based sample were found to be very close to those of the CT-based sample.The UCS value of the simplified joint sample (i.e.38.5 MPa) is much lower than that of the CT-based sample (i.e.72.3 MPa).Additionally,the accumulative released AE energy observed in the simplified joint sample is 3.899 times lower than that observed in the CT-based sample.CT scanning provides a reliable means to visualize the joints in rocks,which can be used to verify the reliability of photogrammetry techniques.The application of the photogrammetry-based sample enables detailed analysis for estimating the mechanical properties of jointed rocks.展开更多
The structure and transport properties in molten NaF have been studied using the method of molecular dynamics simulation. The calculations are based on two models of interionic potentials, which are Fumi-Tosi potentia...The structure and transport properties in molten NaF have been studied using the method of molecular dynamics simulation. The calculations are based on two models of interionic potentials, which are Fumi-Tosi potential (FT) and the Fumi-Tosi potential without Van der Waals attractive item (FT). The radial distribution function (RDF) and the Na^+ and F^- self-diffusion coefficients have been calculated. The calculated results are in good agreement with the experimental ones. The calculation shows that the two models give nearly identical radial distribution function and self-diffusion coefficient, but the results of FTpotential are a little better than those of FT potential.展开更多
文摘Based on the existing component models in the Pspice software package, a combined model for Insulat- ed the Bipolar Transistor (IGBT) is established, in which a non - linear is introduced to represent the parasitic capacitance. Using this model, computerized simulation is conducted for the FB - ZVZCS - PWM soft - ewitching converter,the switching and energy-transferring characteristics of the components are analyzed.The simulation results are testified by experiments.It is proved that by abopting appropriate models,computerized simulation becomes an effective tool for investigation of arc welding inverter power source.
文摘The structure and properties of molten salt solution o J Li,K|F,Cl system have been investiged by computerized simulation of molecular dynamic method.The partial RDF,the partial molar energy of mixing and the diffusion coeffients of Li^+,K^+,F^- and Cl^- have been calculated. The results are in agreement with the experimental values.The regularities of the distribution of ions and mieroscopic holes are discussed based on the results of computerized simulation.
基金supported by National Natural Science Foundation of China(21878078,22108022)PetroChina Scientific Research and Technology Development Project(2018A-0907)。
文摘Whereas theπ-πstacking interactions at oil/water interfaces can affect interfacial structures hence the interfacial properties,the underlying microscopic mechanism remains largely unknown.We reported an all-atom molecular dynamics(MD)simulation study to demonstrate how the Gemini surfactants with pyrenyl groups affect the interracial properties,structural conformations,and the motion of molecules in the water/n-octane/surfactant ternary systems.It is found that the pyrenyl groups tend to be vertical to the interface owing to theπ-πstacking interaction.Besides,a synergistic effect between theπ-πinteraction and steric hindrance is found,which jointly affects the coalescence of liquid droplets.Therefore,the existence of aromatic groups and a moderate number of surfactants helps to form microemulsion.This work provides a molecular understanding of Gemini surfactants with aromatic groups in microemulsion preparation and applications.
文摘The structure and behaviour of LiF-KF solution,as a typical common-anion system,has been simulated by Monte Carlo method.The calculation of partial radial distribution function of ions,heat of mixing and potential energy distribution shows that the average distance be- tween Li^+ and F^- ions will significantly narrow after mixing of molten LiF and KF.This is very similar to the lean-on-one-side effect in molten LiF-KCl solution.The calculated heat of mixing is in fair agreement with the measured one.The dominant source of the energy of mixing may be that the decrease of the repulsion energy between cations,the decrease of the attraction energy between cations and anions,and the decrease of the repulsion energy be- tween anions.
基金The project supported by Laboratory of Rare-Earth Chemistry and Physics,Changchun Institute of Applied Chemistry,Academia Sinica
文摘The structure of molten DyF_3-LiF system has been simulated by Monte Carlo method.The radial distribution functions(RDFs)and the local structure have been obtained.It is concluded that F^- ions distribute closely around Dy^(3+) ions.There exist some fissures and holes between F^- ions and Li^+ ions. There are mainly two kinds of ionic types:the complex ions like DyF_n^(3-n) clusters with the central Dy^(3+) ions (the main ionic clusters are octahedral complex ions like DyF_6^(3-))and the“free”Li^+ ions.Moreover,some complex ions like DyF_n^(3-n) clusters are connected to one another by flourine-bridge,forming more compli- cated ionic clusters like Dy_m^(3m-n) F_n.By calculating the potential energies of all types of ions,it is concluded that Li^+ ions have the highest potential energy in the molten system,which are current-carrying ions in the electrolytic conductance.
文摘The structure of NaAlO_2 melt has been studied by computerized simulation using Monte Carlo method.The radial distribution functions and Local structure of this melt are calculated.It has been found that NaAlO_2 melt contains ionic clusters formed by corner-sharing AlO_4 tetrahedra,sodium ions and xNa^+.yO^(2-) ionic clusters.
文摘Computer simulation researches on Direct Torque Control System (DTC) are to be done. That fact is demonstrated:at high speed,the operating property of an induction motor is very good,almost the same as fieldoriented control system fat low speed (for example: below 2-3Hz), the operating property of a motor is getting worse,and the stator resistance R1 of the motor must be compensated. If compensation precision gets 5 %,the operating property of the motor will be greatly improved.
文摘Log centering accuracy depends on the computerized simulative level of its three-dimension outline. In this paper, the basic methods about distinguishing three dimensions outline of log by means of computerized simulation are discussed. It is suggested that straight lines or certain curves should be introduced to connect the separated points along some log generatrices. Taking bent logs for example verify the accuracy of computerized simulative method.
基金supported in part by National Natural Science Foundation of China under Grant 62022047,Grant 61874065,Grant U20A20168 and Grant 51861145202in part by the National Key R&D Program under Grant 2021YFC3002200 and Grant 2020YFA0709800+7 种基金in part by Fok Ying-Tong Education Foundation under Grant 171051in part by Beijing Natural Science Foundation(M22020)in part by Beijing National Research Center for Information Science and Technology Youth Innovation Fund(BNR2021RC01007)in part by State Key Laboratory of New Ceramic and Fine Processing Tsinghua University(No.KF202109)in part by Tsinghua-Foshan Innovation Special Fund(TFISF)(2021THFS0217)in part by the Research Fund from Beijing Innovation Center for Future Chipthe Independent Research Program of Tsinghua University under Grant 20193080047supported by the Opening Project of Key Laboratory of Microelectronic Devices&Integrated Technology,Institute of Microelectronics,Chinese Academy of Sciences.
文摘Transition metal dichalcogenides are nowadays appealing to researchers for their excellent electronic properties.Vertical stacked nanosheet FET(NSFET)based on MoS_(2)are proposed and studied by Poisson equation solver coupled with semiclassical quantum correction model implemented in Sentaurus workbench.It is found that,the 2D stacked NSFET can largely suppress short channel effects with improved subthreshold swing and drain induced barrier lowering,due to the excellent electrostatics of 2D MoS_(2).In addition,small-signal capacitance is extracted and analyzed.The MoS_(2)based NSFET shows great potential to enable next generation electronics.
文摘Describes a new computer program (Regress-3D) to simulate the regression of complex 3D grain cavity and calculate the burning surface area. It has a large region of applicability in solid rocket motor design and has made new improvements compared with other available codes. User can easily and rapidly build his initial grain shapes and then obtain geometric information of his design. Considering with the calclulting results, redesigning can be performed as desire until reaching at the satisfied result. Advantages and disadvantages of this method are also discussed.
文摘Fuel consumption has always been a matter of concern for ships propulsion. In this research we aim to develop computer models of several containership cargo stacking configurations and discuss an optimal configuration at a constant front wind speed. The paper presents the simulation results by using ANSYS CFX for a 1:4 scale PostPanamax 9000 TEU containership. The ship is modelled in a cubic domain that contains unstructured mesh with details, in such a way that can demonstrate the influence of the container configuration on wind force. Also the numerical results are verified versus wind tunnel test data. An optimal stack configuration led to about 25%reduction in air resistance. It is proposed that in order to reduce the wind drag force and consequently reduce the fuel consumption and pollutant emissions, empty spaces between the cargo containers and unbalanced cargo distribution over the deck should be inhibited. Also, it is advised to make the cargo distribution on the most forward and aftward deck areas more streamlined.
文摘The effects of applied tensile strain on the coherent α_2→O-phase transformation in Ti-Al-Nb alloys are explored bycomputer simulation using a phase-field method. The focus is on the influence of the applied strain direction onthe microstructure and volume fraction of the O-phase precipitates. It is found that altering applied strain directioncan modify microstructure of Ti-25Al-10～12Nb (at. pct) alloy during α_2→O-phase transformation effectively andfull laminate microstructure in the Ti-25Al-10Nb (at. pct) alloy can be realized by an applied strain only along thedirection 30°away from the α_2 phase <1010> in magnitude equivalent to the stress-free transformation strain. Thesimulation also shows that not only the magnitude of applied strain but also the applied strain direction influencesthe O-phase volume fraction and the effect of strain direction on the volume fraction is up to 25%.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10902083)the Program for New Scientific and Technological Star of Shaanxi Province,China (Grant No. 2012KJXX-39)
文摘The effects of twin spacing and temperature on the deformation behavior of nanotwinned Al under tensile loading are investigated using a molecular dynamic（MD） simulation method.The result shows that the yield strength of nanotwinned Al decreases with the increase of twin spacing,which is related to the repulsive force between twin boundary and the dislocation.The result also shows that there is no strain-hardening at the yield point.On the contrary,the stress is raised by strain hardening in the plastic stage.In addition,we also investigate the effects of stacking fault thickness and temperature on the yield strength of the Al nanowire.The simulation results indicate that the stacking fault may strengthen the Al nanowire when the thickness of the stacking fault is below a critical value.
基金Funding provided by the Molecular Simulation Key Laboratory at SINOPEC Research Institute of Petroleum Processing is gratefully acknowledged.
文摘Molecular simulations were performed to investigate the molecular structural effects on needle coke mesophase stacking.The simulation results showed that the stacking states of anthracene trimer and tetramer accumulations were orderly,while the stacking states of anthracene dimer,pentamer,and hexamer accumulations were disorderly.Anthracene trimer and tetramer in the model compounds were two of the most ideal needle coke mesophase constituents.It was also found that the introduction of methyl side chains in anthracene trimer derivatives was not conducive to the formation of a mesophase crystal.To sum up,the molecules which had similar structures to anthracene trimer or tetramer with no alkyl chains are ideal constituents of needle coke mesophase.
基金supported by the National Natural Science Foundation of China(Grant Nos.42277150,41977219)Henan Provincial Science and Technology Research Project(Grant No.222102320271).
文摘The geometry of joints has a significant influence on the mechanical properties of rocks.To simplify the curved joint shapes in rocks,the joint shape is usually treated as straight lines or planes in most laboratory experiments and numerical simulations.In this study,the computerized tomography (CT) scanning and photogrammetry were employed to obtain the internal and surface joint structures of a limestone sample,respectively.To describe the joint geometry,the edge detection algorithms and a three-dimensional (3D) matrix mapping method were applied to reconstruct CT-based and photogrammetry-based jointed rock models.For comparison tests,the numerical uniaxial compression tests were conducted on an intact rock sample and a sample with a joint simplified to a plane using the parallel computing method.The results indicate that the mechanical characteristics and failure process of jointed rocks are significantly affected by the geometry of joints.The presence of joints reduces the uniaxial compressive strength (UCS),elastic modulus,and released acoustic emission (AE) energy of rocks by 37%–67%,21%–24%,and 52%–90%,respectively.Compared to the simplified joint sample,the proposed photogrammetry-based numerical model makes the most of the limited geometry information of joints.The UCS,accumulative released AE energy,and elastic modulus of the photogrammetry-based sample were found to be very close to those of the CT-based sample.The UCS value of the simplified joint sample (i.e.38.5 MPa) is much lower than that of the CT-based sample (i.e.72.3 MPa).Additionally,the accumulative released AE energy observed in the simplified joint sample is 3.899 times lower than that observed in the CT-based sample.CT scanning provides a reliable means to visualize the joints in rocks,which can be used to verify the reliability of photogrammetry techniques.The application of the photogrammetry-based sample enables detailed analysis for estimating the mechanical properties of jointed rocks.
文摘The structure and transport properties in molten NaF have been studied using the method of molecular dynamics simulation. The calculations are based on two models of interionic potentials, which are Fumi-Tosi potential (FT) and the Fumi-Tosi potential without Van der Waals attractive item (FT). The radial distribution function (RDF) and the Na^+ and F^- self-diffusion coefficients have been calculated. The calculated results are in good agreement with the experimental ones. The calculation shows that the two models give nearly identical radial distribution function and self-diffusion coefficient, but the results of FTpotential are a little better than those of FT potential.
