The physically-based internal state variable (ISV) models were used to describe the changes of dislocation density, grain size, and flow stress in the high temperature deformation of titanium alloys in this study. T...The physically-based internal state variable (ISV) models were used to describe the changes of dislocation density, grain size, and flow stress in the high temperature deformation of titanium alloys in this study. The constants of the present models could be identified based on experimental results, which were conducted at deformation temperatures ranging from 1093 K to 1303 K, height reductions ranging from 20% to 60%, and the strain rates of 0.001, 0.01, 0.1, 1.0, and 10.0 s-1. The physically-based internal state variable models were implemented into the commercial finite element (FE) code. Then, a three-dimensional (3D) FE simulation system coupling of deformation, heat transfer, and microstructure evolution was developed for the blade forging of Ti-6Al-4V alloy. FE analysis was carried out to simulate the microstructure evolution in the blade forging of Ti-6Al-4V alloy. Finally, the blade forging tests of Ti-6Al-4V alloy were performed to validate the results of FE simulation. According to the tensile tests, it is seen that the mechanical properties, such as tensile strength and elongation, satisfy the application requirements well. The maximum and minimum differences between the calculated and experimental grain size of primary α phase are 11.71% and 4.23%, respectively. Thus, the industrial trials show a good agreement with FE simulation of blade forging.展开更多
We study how can an angular momentum coherent state |τ> keeps its form-invariant during time evolution governed by the Hamiltonian H = f(t)J++ f^*(t)J-+ g(t)Jz. We discuss this topic in the context of boson realiz...We study how can an angular momentum coherent state |τ> keeps its form-invariant during time evolution governed by the Hamiltonian H = f(t)J++ f^*(t)J-+ g(t)Jz. We discuss this topic in the context of boson realization of |τ>. By employing the entangled state representation |ζ> and deriving a new binomial theorem involving two-subscript Hermite polynomials, we derive the wave function <ζ|τ>, which turns out to be a single-subscript Hermite polynomial. Based on this result the maintenance of angular momentum coherent state during time evolution is examined, and the value of τ(t) is totally determined by the parameters involved in the Hamiltonian.展开更多
Understanding the intrinsic activity of oxygen evolution reaction(OER) is crucial for catalyst design.To date,different metal-doping strategies have been developed to achieve this,but the involving mechanisms remain u...Understanding the intrinsic activity of oxygen evolution reaction(OER) is crucial for catalyst design.To date,different metal-doping strategies have been developed to achieve this,but the involving mechanisms remain unclear.Here,the electronic structure of the transition metal-doped NiFe_(2)O_(4)(001) surface is scrutinized for OER intrinsic activity using density functional theory calculations.Five 3d-orbital filling metals(Ti,V,Cr,Mn,and Co) are introduced as dopants onto A-and B-layers of the NiFe_(2)O_(4)(001) surface,and variation of oxidation states over Fe sites is observed on B-layer.Analyzing the magnetic moment and charge transfer of surface cation sites reveals that the variation of Fe oxidation states originates from the super-exchange effect and is influenced by the t2g-electron configuration of 3d metal dopants.This trend governs the generation of highly-active Fe3+sites on the B-layer,the adsorption strength of OER intermediates,i.e.,*O and*OH,and therefore the intrinsic activity.The finding of super-exchange mechanism induced by 3d early metal doping offers insights into electronic structure tailoring strategies for improving the intrinsic activity of OER electrocatalysts.展开更多
In this paper, a unified internal state variable(ISV) model for predicting microstructure evolution during hot working process of AZ80 magnesium alloy was developed. A novel aspect of the proposed model is that the in...In this paper, a unified internal state variable(ISV) model for predicting microstructure evolution during hot working process of AZ80 magnesium alloy was developed. A novel aspect of the proposed model is that the interactive effects of material hardening, recovery and dynamic recrystallization(DRX) on the characteristic deformation behavior were considered by incorporating the evolution laws of viscoplastic flow, dislocation activities, DRX nucleation and boundary migration in a coupled manner. The model parameters were calibrated based on the experimental data analysis and genetic algorithm(GA) based objective optimization. The predicted flow stress, DRX fraction and average grain size match well with experimental results. The proposed model was embedded in the finite element(FE) software DEFORM-3 D via user defined subroutine to simulate the hot compression and equal channel angular extrusion(ECAE) processes. The heterogeneous microstructure distributions at different deformation zones and the dislocation density evolution with competitive deformation mechanisms were captured.This study can provide a theoretical solution for the hot working problems of magnesium alloy.展开更多
We analyze the multipartite entanglement evolution of three-qubit mixed states composed of a GHZ state and a W state. For a composite system consisting of three cavities interacting with independent reservoirs, it is ...We analyze the multipartite entanglement evolution of three-qubit mixed states composed of a GHZ state and a W state. For a composite system consisting of three cavities interacting with independent reservoirs, it is shown that the entanglement evolution is restricted by a set of monogamy relations. Furthermore, as quantified by the negativity, the entanglement dynamical property of the mixed entangled state of cavity photons is investigated. It is found that the three cavity photons can exhibit the phenomenon of entanglement sudden death (ESD). However, compared with the evolution of a generalized three-qubit GHZ state which has the equal initial entanglement, the ESD time of mixed states is later than that of the pure state. Finally, we discuss the entanglement distribution in the multipartite system, and point out the intrinsic relation between the ESD of cavity photons and the entanglement sudden birth of reservoirs.展开更多
We investigate how an optical squeezed chaotic field(SCF) evolves in an amplitude dissipation channel. We have used the integration within ordered product of operators technique to derive its evolution law. We also ...We investigate how an optical squeezed chaotic field(SCF) evolves in an amplitude dissipation channel. We have used the integration within ordered product of operators technique to derive its evolution law. We also show that the density operator of SCF can be viewed as a generating field of the squeezed number state.展开更多
Semisolid rheoforming(SSR)is a promising technology for the production of Mg wrought alloy in foundry settings.In order to realize SSR,it is necessary to characterize the grain structure evolution during slurry prepar...Semisolid rheoforming(SSR)is a promising technology for the production of Mg wrought alloy in foundry settings.In order to realize SSR,it is necessary to characterize the grain structure evolution during slurry preparation.In this paper,slurry of AZ31 alloy was produced by a novel rheocast process known as self-inoculation method(SIM).Interrupted quenching technology was applied to investigate the primaryα-Mg evolution during continuous cooling and isothermal holding.Results indicate that the initial microstructure of slurry produced by SIM is a mixture of irregular grains,which becomes ideally globular when the slurry slowly cools to 620℃and isothermally held for at least 30 s.The local solute diffusion leads to dendritic fragmentation and forms separated particles.During prolonged holding,the particle surface gradually becomes smooth because of protuberance melting and groove advancement.Coarsening ofα-Mg grains in isothermal holding was analyzed using Lifshitz-Slyozov-Wagner theory.Results suggest that coalescence is most likely the dominant coarsening mechanism in the early stage while Ostwald ripening tends to be the principal one later.The EDS results indicate that a longer holding time leads to Al solute element segregation at the grain boundaries,but Zn distribution within liquid matrix has no obvious change.展开更多
The two one-state-variable, rate- and state-dependent friction laws, i.e., the slip and slowness laws, are com- pared on the basis of dynamical behavior of a one-degree-of-freedom spring-slider model through numerical...The two one-state-variable, rate- and state-dependent friction laws, i.e., the slip and slowness laws, are com- pared on the basis of dynamical behavior of a one-degree-of-freedom spring-slider model through numerical simulations. Results show that two (normalized) model parameters, i.e., A (the normalized characteristic slip distance) and β-α (the difference in two normalized parameters of friction laws), control the solutions. From given values of △, β, and α, for the slowness laws, the solution exists and the unique non-zero fixed point is stable when △〉(β-α), yet not when △ 〈(β-α). For the slip law, the solution exists for large ranges of model parameters and the number and stability of the non-zero fixed points change from one case to another. Results suggest that the slip law is more appropriate for controlling earthquake dynamics than the slowness law.展开更多
To conveniently calculate the Wigner function of the optical cumulant operator and its dissipation evolution in a thermal environment, in this paper, the thermo-entangled state representation is introduced to derive t...To conveniently calculate the Wigner function of the optical cumulant operator and its dissipation evolution in a thermal environment, in this paper, the thermo-entangled state representation is introduced to derive the general evolution formula of the Wigner function, and its relation to Weyl correspondence is also discussed. The method of integration within the ordered product of operators is essential to our discussion.展开更多
Using the thermal-entangled state representation and the operator-ordering method, we investigate Wigner function(WF) for the squeezed negative binomial state(SNBS) and the analytical evolution law of density operator...Using the thermal-entangled state representation and the operator-ordering method, we investigate Wigner function(WF) for the squeezed negative binomial state(SNBS) and the analytical evolution law of density operator in the amplitude decay channel.The results show that the analytical WF is related to the square of the module of single-variable Hermite polynomials, which leads to a new two-variable special function and its generating function, and the parameters s and γplay opposite roles in the WF distributions.Besides, after undergoing this channel, the initial pure SNBS evolves into a new mixed state related to two operator Hermite polynomials within normal ordering, and fully loses its nonclassicality and decays to vacuum at long decay time.展开更多
The Earth is the only body in the solar system for which significant observational constraints are accessible to such a degree that they can be used to discriminate between competing models of Earth's tectonic evo...The Earth is the only body in the solar system for which significant observational constraints are accessible to such a degree that they can be used to discriminate between competing models of Earth's tectonic evolution.It is a natural tendency to use observations of the Earth to inform more general models of planetary evolution.However,our understating of Earth's evolution is far from complete.In recent years,there has been growing geodynamic and geochemical evidence that suggests that plate tectonics may not have operated on the early Earth,with both the timing of its onset and the length of its activity far from certain.Recently,the potential of tectonic bi-stability(multiple stable,energetically allowed solutions)has been shown to be dynamically viable,both from analytical analysis and through numeric experiments in two and three dimensions.This indicates that multiple tectonic modes may operate on a single planetary body at different times within its temporal evolution.It also allows for the potential that feedback mechanisms between the internal dynamics and surface processes(e.g.,surface temperature changes driven by long term climate evolution),acting at different thermal evolution times,can cause terrestrial worlds to alternate between multiple tectonic states over giga-year timescales.The implication within this framework is that terrestrial planets have the potential to migrate through tectonic regimes at similar‘thermal evolution times'(e.g.,points were they have a similar bulk mantle temperature and energies),but at very different'temporal times'(time since planetary formation).It can be further shown that identical planets at similar stages of their evolution may exhibit different tectonic regimes due to random variations.Here,we will discuss constraints on the tectonic evolution of the Earth and present a novel framework of planetary evolution that moves toward probabilistic arguments based on general physical principals,as opposed to particular rheologies,and incorporates the potential of tectonic regime transitions and multiple tectonics states being viable at equivalent physical and chemical conditions.展开更多
We study thc time evolution of a state vector in a square tight-binding lattice, focusing on its evolution localized over the system surfaces. In this tight-binding lattice, the energy of atomic orbital centred at sur...We study thc time evolution of a state vector in a square tight-binding lattice, focusing on its evolution localized over the system surfaces. In this tight-binding lattice, the energy of atomic orbital centred at surface site is different from that at the interior (bulky) site by an energy shift U. It is shown that for the state vector initially localized on a surface, there exists an exponential law (y = ae^x/b + Y0) determined by the absolute value of the energy shift, |U|, which describes the transition of the state evolving on the square tight-binding lattice, from delocalized over the whole lattice to localized over the surfaces.展开更多
Based on the idea of adiabatic evolution, we propose two probabilistic but simple schemes for generating maximally entangled states for two distant atoms and concentrating unknown atomic entangled states. Taking advan...Based on the idea of adiabatic evolution, we propose two probabilistic but simple schemes for generating maximally entangled states for two distant atoms and concentrating unknown atomic entangled states. Taking advantage of adiabatic passage, the atoms have no probability of being excited and thus the atomic spontaneous emission is suppressed. Furthermore, in the two schemes accurate adjustment of the interaction time is not required.展开更多
This paper investigates the dynamical instability and adiabatic evolution of the atom homonuclear-trimer dark state of a condensate system in a stimulated Raman adiabatic passage aided by Feshbach resonance. It obtain...This paper investigates the dynamical instability and adiabatic evolution of the atom homonuclear-trimer dark state of a condensate system in a stimulated Raman adiabatic passage aided by Feshbach resonance. It obtains analytically the regions for the appearance of dynamical instability caused by the interparticle interactions. Moreover, the adiabatic property of the dark state is also studied in terms of a newly defined adiabatic fidelity. It shows that the nonlinear collisions have a negative effect on the adiabaticity of the dark state and hence reduce the conversion efficiency.展开更多
Discrete element method (DEM) is used in the present paper to simulate the microstructural evolution of a planar layer of copper particles during sintering. Formation of agglomerates and the effect of their rearrang...Discrete element method (DEM) is used in the present paper to simulate the microstructural evolution of a planar layer of copper particles during sintering. Formation of agglomerates and the effect of their rearrangement on densification are mainly focused on. Comparing to the existing experimental observations, we find that agglomerate can form spontaneously in sintering and its rearrangement could accelerate the densification of compacts. Snapshots of numerical simulations agree qualitatively well with experimental observations. The method could be readily extended to investigate the effect of agglomerate on sintering in a three- dimensional model, which should be very useful for understanding the evolution of microstructure of sintering systems.展开更多
In this paper, swarm optimization hybridized with differential evolution (PSO-DE) technique is proposed to solve static state estimation (SE) problem as a minimization problem. The proposed hybrid method is tested on ...In this paper, swarm optimization hybridized with differential evolution (PSO-DE) technique is proposed to solve static state estimation (SE) problem as a minimization problem. The proposed hybrid method is tested on IEEE 5-bus, 14-bus, 30-bus, 57-bus and 118-bus standard test systems along with 11-bus and 13-bus ill-conditioned test systems under different simulated conditions and the results are compared with the same, obtained using standard weighted least square state estimation (WLS-SE) technique and general particle swarm optimization (GPSO) based technique. The performance of the proposed optimization technique for SE, in terms of minimum value of the objective function and standard deviations of minimum values obtained in 100 runs, is found better as compared to the GPSO based technique. The statistical error analysis also shows the superiority of the proposed PSO-DE based technique over the other two techniques.展开更多
This paper presents an evolution strategy to induce fuzzy finite-state automata from examples of fuzzy languages. The coding, fitness function of a generated automaton and corresponding mutation operators are given re...This paper presents an evolution strategy to induce fuzzy finite-state automata from examples of fuzzy languages. The coding, fitness function of a generated automaton and corresponding mutation operators are given respectively. The application example given at last shows the effectiveness of the proposed evolution strategy for automata induction.展开更多
The European Union,which is at the beginning of its term of office for all Member States in the European Parliament,the European Commission,its governing body and the Member States,is concerned with finalizing directi...The European Union,which is at the beginning of its term of office for all Member States in the European Parliament,the European Commission,its governing body and the Member States,is concerned with finalizing directives and future development strategies.Of course,the fundamental objective of the European Union would be to establish strategies to ensure economic growth in all the Member States of the European Union and,on the other hand,to establish how each Member State seeks to implement the European directives aimed at this end desideratum.There are a number of areas in which some countries,especially those that have joined European Union in recent waves,still have difficulty responding to the European Union’s desires and concerns to ensure economic growth,with a tendency to level the playing field trains in the next period.It aims at establishing a minimum wage in the European Union,divides a number of other issues in the field of environment,in the field of economic development,being important challenges for all Member States.Of course,it should be noted that these Member States have different possibilities to respond to these challenges,through strategies that correlate,on the one hand,the individual interests of each of the Member States,but at the same time,in close coordination(correlation)with the major objectives set by the European Union.All these aspects are important,but must be reconsidered,in the context of the global effect of the pandemic and financial-economic crisis.The European Union is now considering a program to support all states,but especially those most affected by the above-mentioned crisis.展开更多
We carry out detailed momentum-dependent and temperature-dependent measurements on Bi_2Sr_2CaCu_2O_(8+δ)(Bi2212) superconductor in the superconducting and pseudogap states by super-high resolution laser-based an...We carry out detailed momentum-dependent and temperature-dependent measurements on Bi_2Sr_2CaCu_2O_(8+δ)(Bi2212) superconductor in the superconducting and pseudogap states by super-high resolution laser-based angleresolved photoemission spectroscopy. The precise determination of the superconducting gap for the nearly optimally doped Bi2212(T_c= 91 K) at low temperature indicates that the momentum-dependence of the superconducting gap deviates from the standard d-wave form(cos(2Φ)). It can be alternatively fitted by including a high-order term(cos(6Φ)) in which the next nearest-neighbor interaction is considered. We find that the band structure near the antinodal region smoothly evolves across the pseudogap temperature without a signature of band reorganization which is distinct from that found in Bi_2Sr_2CuO_(6+δ) superconductors. This indicates that the band reorganization across the pseudogap temperature is not a universal behavior in cuprate superconductors.These results provide new insights in understanding the nature of the superconducting gap and pseudogap in high-temperature cuprate superconductors.展开更多
The system of the Hamiltonian involving a driving part,a single mode part,and a two-mode squeezedone and a two-mode coupled one is discussed using the Lewis-Riesenfeld invariant theory.The time evolution operatoris ob...The system of the Hamiltonian involving a driving part,a single mode part,and a two-mode squeezedone and a two-mode coupled one is discussed using the Lewis-Riesenfeld invariant theory.The time evolution operatoris obtained.When the initial state is a coherent state,the quantum fluctuation of the system is calculated,and it isdependent on the squeezed part and the two-mode coupled part,but not dependent on the driving one.展开更多
基金supported by the National Natural Science Foundation of China (No.50975234)China Postdoctoral Science Foundation (No.20110491685)
文摘The physically-based internal state variable (ISV) models were used to describe the changes of dislocation density, grain size, and flow stress in the high temperature deformation of titanium alloys in this study. The constants of the present models could be identified based on experimental results, which were conducted at deformation temperatures ranging from 1093 K to 1303 K, height reductions ranging from 20% to 60%, and the strain rates of 0.001, 0.01, 0.1, 1.0, and 10.0 s-1. The physically-based internal state variable models were implemented into the commercial finite element (FE) code. Then, a three-dimensional (3D) FE simulation system coupling of deformation, heat transfer, and microstructure evolution was developed for the blade forging of Ti-6Al-4V alloy. FE analysis was carried out to simulate the microstructure evolution in the blade forging of Ti-6Al-4V alloy. Finally, the blade forging tests of Ti-6Al-4V alloy were performed to validate the results of FE simulation. According to the tensile tests, it is seen that the mechanical properties, such as tensile strength and elongation, satisfy the application requirements well. The maximum and minimum differences between the calculated and experimental grain size of primary α phase are 11.71% and 4.23%, respectively. Thus, the industrial trials show a good agreement with FE simulation of blade forging.
基金Project supported by the National Natural Science Foundation of China(Grant No.11347026)the Natural Science Foundation of Shandong Province,China(Grant Nos.ZR2016AM03 and ZR2017MA011)
文摘We study how can an angular momentum coherent state |τ> keeps its form-invariant during time evolution governed by the Hamiltonian H = f(t)J++ f^*(t)J-+ g(t)Jz. We discuss this topic in the context of boson realization of |τ>. By employing the entangled state representation |ζ> and deriving a new binomial theorem involving two-subscript Hermite polynomials, we derive the wave function <ζ|τ>, which turns out to be a single-subscript Hermite polynomial. Based on this result the maintenance of angular momentum coherent state during time evolution is examined, and the value of τ(t) is totally determined by the parameters involved in the Hamiltonian.
基金supported by the Australian Research Council(FT170100224,DP210103892,IC200100023)support from Tsinghua National Laboratory for Information Science and Technology for theoretical simulations。
文摘Understanding the intrinsic activity of oxygen evolution reaction(OER) is crucial for catalyst design.To date,different metal-doping strategies have been developed to achieve this,but the involving mechanisms remain unclear.Here,the electronic structure of the transition metal-doped NiFe_(2)O_(4)(001) surface is scrutinized for OER intrinsic activity using density functional theory calculations.Five 3d-orbital filling metals(Ti,V,Cr,Mn,and Co) are introduced as dopants onto A-and B-layers of the NiFe_(2)O_(4)(001) surface,and variation of oxidation states over Fe sites is observed on B-layer.Analyzing the magnetic moment and charge transfer of surface cation sites reveals that the variation of Fe oxidation states originates from the super-exchange effect and is influenced by the t2g-electron configuration of 3d metal dopants.This trend governs the generation of highly-active Fe3+sites on the B-layer,the adsorption strength of OER intermediates,i.e.,*O and*OH,and therefore the intrinsic activity.The finding of super-exchange mechanism induced by 3d early metal doping offers insights into electronic structure tailoring strategies for improving the intrinsic activity of OER electrocatalysts.
基金funding supported by National Natural Science Foundation of China(No.52175285)Beijing Municipal Natural Science Foundation(No.3182025)+1 种基金National Defense Science and Technology Rapid support Project(No.61409230113)Scientific and Technological Innovation Foundation of Shunde Graduate School,USTB and Fundamental Research Funds for the Central Universities(No.FRFBD-20-08A,FRF-TP-20-009A2)。
文摘In this paper, a unified internal state variable(ISV) model for predicting microstructure evolution during hot working process of AZ80 magnesium alloy was developed. A novel aspect of the proposed model is that the interactive effects of material hardening, recovery and dynamic recrystallization(DRX) on the characteristic deformation behavior were considered by incorporating the evolution laws of viscoplastic flow, dislocation activities, DRX nucleation and boundary migration in a coupled manner. The model parameters were calibrated based on the experimental data analysis and genetic algorithm(GA) based objective optimization. The predicted flow stress, DRX fraction and average grain size match well with experimental results. The proposed model was embedded in the finite element(FE) software DEFORM-3 D via user defined subroutine to simulate the hot compression and equal channel angular extrusion(ECAE) processes. The heterogeneous microstructure distributions at different deformation zones and the dislocation density evolution with competitive deformation mechanisms were captured.This study can provide a theoretical solution for the hot working problems of magnesium alloy.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10905016 and 10971247)the Natural Science Foundation of Hebei Province of China (Grant Nos. A2012205062,A2012205013,and A2010000344)the Fund of Hebei Normal niversity
文摘We analyze the multipartite entanglement evolution of three-qubit mixed states composed of a GHZ state and a W state. For a composite system consisting of three cavities interacting with independent reservoirs, it is shown that the entanglement evolution is restricted by a set of monogamy relations. Furthermore, as quantified by the negativity, the entanglement dynamical property of the mixed entangled state of cavity photons is investigated. It is found that the three cavity photons can exhibit the phenomenon of entanglement sudden death (ESD). However, compared with the evolution of a generalized three-qubit GHZ state which has the equal initial entanglement, the ESD time of mixed states is later than that of the pure state. Finally, we discuss the entanglement distribution in the multipartite system, and point out the intrinsic relation between the ESD of cavity photons and the entanglement sudden birth of reservoirs.
基金Project supported by the National Natural Science Foundation of China(Grant No.10574647)the Natural Science Foundation of Shandong Province,China(Grant No.Y2008A16)the University Experimental Technology Foundation of Shandong Province of China(Grant No.S04W138)
文摘We investigate how an optical squeezed chaotic field(SCF) evolves in an amplitude dissipation channel. We have used the integration within ordered product of operators technique to derive its evolution law. We also show that the density operator of SCF can be viewed as a generating field of the squeezed number state.
基金supported by the National Natural Science Foundation of China(50964010)
文摘Semisolid rheoforming(SSR)is a promising technology for the production of Mg wrought alloy in foundry settings.In order to realize SSR,it is necessary to characterize the grain structure evolution during slurry preparation.In this paper,slurry of AZ31 alloy was produced by a novel rheocast process known as self-inoculation method(SIM).Interrupted quenching technology was applied to investigate the primaryα-Mg evolution during continuous cooling and isothermal holding.Results indicate that the initial microstructure of slurry produced by SIM is a mixture of irregular grains,which becomes ideally globular when the slurry slowly cools to 620℃and isothermally held for at least 30 s.The local solute diffusion leads to dendritic fragmentation and forms separated particles.During prolonged holding,the particle surface gradually becomes smooth because of protuberance melting and groove advancement.Coarsening ofα-Mg grains in isothermal holding was analyzed using Lifshitz-Slyozov-Wagner theory.Results suggest that coalescence is most likely the dominant coarsening mechanism in the early stage while Ostwald ripening tends to be the principal one later.The EDS results indicate that a longer holding time leads to Al solute element segregation at the grain boundaries,but Zn distribution within liquid matrix has no obvious change.
基金supported by Academia Sinica (Taipei) and Science Council (Grant NSC96-2116-M-001-012-MY3).
文摘The two one-state-variable, rate- and state-dependent friction laws, i.e., the slip and slowness laws, are com- pared on the basis of dynamical behavior of a one-degree-of-freedom spring-slider model through numerical simulations. Results show that two (normalized) model parameters, i.e., A (the normalized characteristic slip distance) and β-α (the difference in two normalized parameters of friction laws), control the solutions. From given values of △, β, and α, for the slowness laws, the solution exists and the unique non-zero fixed point is stable when △〉(β-α), yet not when △ 〈(β-α). For the slip law, the solution exists for large ranges of model parameters and the number and stability of the non-zero fixed points change from one case to another. Results suggest that the slip law is more appropriate for controlling earthquake dynamics than the slowness law.
基金Project supported by the Foundation for Young Talents in College of Anhui Province, China (Grant Nos. gxyq2021210 and gxyq2019077)the Natural Science Foundation of the Anhui Higher Education Institutions, China (Grant Nos. 2022AH051580 and 2022AH051586)。
文摘To conveniently calculate the Wigner function of the optical cumulant operator and its dissipation evolution in a thermal environment, in this paper, the thermo-entangled state representation is introduced to derive the general evolution formula of the Wigner function, and its relation to Weyl correspondence is also discussed. The method of integration within the ordered product of operators is essential to our discussion.
基金Project supported by the National Natural Science Foundation of China(Grant No.11347026)the Natural Science Foundation of Shandong Province,China(Grant Nos.ZR2016AM03 and ZR2017MA011)
文摘Using the thermal-entangled state representation and the operator-ordering method, we investigate Wigner function(WF) for the squeezed negative binomial state(SNBS) and the analytical evolution law of density operator in the amplitude decay channel.The results show that the analytical WF is related to the square of the module of single-variable Hermite polynomials, which leads to a new two-variable special function and its generating function, and the parameters s and γplay opposite roles in the WF distributions.Besides, after undergoing this channel, the initial pure SNBS evolves into a new mixed state related to two operator Hermite polynomials within normal ordering, and fully loses its nonclassicality and decays to vacuum at long decay time.
基金supported in part by the Cyberinfrastructure for Computational Research funded by NSF under Grant CNS-0821727the Data Analysis and Visualization Cyberinfrastructure funded by NSF under grant OCI-0959097Rice University
文摘The Earth is the only body in the solar system for which significant observational constraints are accessible to such a degree that they can be used to discriminate between competing models of Earth's tectonic evolution.It is a natural tendency to use observations of the Earth to inform more general models of planetary evolution.However,our understating of Earth's evolution is far from complete.In recent years,there has been growing geodynamic and geochemical evidence that suggests that plate tectonics may not have operated on the early Earth,with both the timing of its onset and the length of its activity far from certain.Recently,the potential of tectonic bi-stability(multiple stable,energetically allowed solutions)has been shown to be dynamically viable,both from analytical analysis and through numeric experiments in two and three dimensions.This indicates that multiple tectonic modes may operate on a single planetary body at different times within its temporal evolution.It also allows for the potential that feedback mechanisms between the internal dynamics and surface processes(e.g.,surface temperature changes driven by long term climate evolution),acting at different thermal evolution times,can cause terrestrial worlds to alternate between multiple tectonic states over giga-year timescales.The implication within this framework is that terrestrial planets have the potential to migrate through tectonic regimes at similar‘thermal evolution times'(e.g.,points were they have a similar bulk mantle temperature and energies),but at very different'temporal times'(time since planetary formation).It can be further shown that identical planets at similar stages of their evolution may exhibit different tectonic regimes due to random variations.Here,we will discuss constraints on the tectonic evolution of the Earth and present a novel framework of planetary evolution that moves toward probabilistic arguments based on general physical principals,as opposed to particular rheologies,and incorporates the potential of tectonic regime transitions and multiple tectonics states being viable at equivalent physical and chemical conditions.
文摘We study thc time evolution of a state vector in a square tight-binding lattice, focusing on its evolution localized over the system surfaces. In this tight-binding lattice, the energy of atomic orbital centred at surface site is different from that at the interior (bulky) site by an energy shift U. It is shown that for the state vector initially localized on a surface, there exists an exponential law (y = ae^x/b + Y0) determined by the absolute value of the energy shift, |U|, which describes the transition of the state evolving on the square tight-binding lattice, from delocalized over the whole lattice to localized over the surfaces.
文摘Based on the idea of adiabatic evolution, we propose two probabilistic but simple schemes for generating maximally entangled states for two distant atoms and concentrating unknown atomic entangled states. Taking advantage of adiabatic passage, the atoms have no probability of being excited and thus the atomic spontaneous emission is suppressed. Furthermore, in the two schemes accurate adjustment of the interaction time is not required.
基金supported by the National Natural Science Foundation of China (Grant Nos 10674174,10604009 and 10725521)the National Fundamental Research Programme of China (Grant No 2006CB921400 and 2007CB814800)Natural Science Foundation of Liaoning Province of China (Grant No 20072054)
文摘This paper investigates the dynamical instability and adiabatic evolution of the atom homonuclear-trimer dark state of a condensate system in a stimulated Raman adiabatic passage aided by Feshbach resonance. It obtains analytically the regions for the appearance of dynamical instability caused by the interparticle interactions. Moreover, the adiabatic property of the dark state is also studied in terms of a newly defined adiabatic fidelity. It shows that the nonlinear collisions have a negative effect on the adiabaticity of the dark state and hence reduce the conversion efficiency.
基金supported by the National Natural Science Foundation of China (10972220, 11125211 and 11021262)973 Project(2012CB937500)
文摘Discrete element method (DEM) is used in the present paper to simulate the microstructural evolution of a planar layer of copper particles during sintering. Formation of agglomerates and the effect of their rearrangement on densification are mainly focused on. Comparing to the existing experimental observations, we find that agglomerate can form spontaneously in sintering and its rearrangement could accelerate the densification of compacts. Snapshots of numerical simulations agree qualitatively well with experimental observations. The method could be readily extended to investigate the effect of agglomerate on sintering in a three- dimensional model, which should be very useful for understanding the evolution of microstructure of sintering systems.
文摘In this paper, swarm optimization hybridized with differential evolution (PSO-DE) technique is proposed to solve static state estimation (SE) problem as a minimization problem. The proposed hybrid method is tested on IEEE 5-bus, 14-bus, 30-bus, 57-bus and 118-bus standard test systems along with 11-bus and 13-bus ill-conditioned test systems under different simulated conditions and the results are compared with the same, obtained using standard weighted least square state estimation (WLS-SE) technique and general particle swarm optimization (GPSO) based technique. The performance of the proposed optimization technique for SE, in terms of minimum value of the objective function and standard deviations of minimum values obtained in 100 runs, is found better as compared to the GPSO based technique. The statistical error analysis also shows the superiority of the proposed PSO-DE based technique over the other two techniques.
文摘This paper presents an evolution strategy to induce fuzzy finite-state automata from examples of fuzzy languages. The coding, fitness function of a generated automaton and corresponding mutation operators are given respectively. The application example given at last shows the effectiveness of the proposed evolution strategy for automata induction.
文摘The European Union,which is at the beginning of its term of office for all Member States in the European Parliament,the European Commission,its governing body and the Member States,is concerned with finalizing directives and future development strategies.Of course,the fundamental objective of the European Union would be to establish strategies to ensure economic growth in all the Member States of the European Union and,on the other hand,to establish how each Member State seeks to implement the European directives aimed at this end desideratum.There are a number of areas in which some countries,especially those that have joined European Union in recent waves,still have difficulty responding to the European Union’s desires and concerns to ensure economic growth,with a tendency to level the playing field trains in the next period.It aims at establishing a minimum wage in the European Union,divides a number of other issues in the field of environment,in the field of economic development,being important challenges for all Member States.Of course,it should be noted that these Member States have different possibilities to respond to these challenges,through strategies that correlate,on the one hand,the individual interests of each of the Member States,but at the same time,in close coordination(correlation)with the major objectives set by the European Union.All these aspects are important,but must be reconsidered,in the context of the global effect of the pandemic and financial-economic crisis.The European Union is now considering a program to support all states,but especially those most affected by the above-mentioned crisis.
基金Supported by the National Key Research and Development Program of China under Grant No 2016YFA0300300the National Natural Science Foundation of China under Grant No 11334010+1 种基金the National Basic Research Program of China under Grant No2015CB921300the Strategic Priority Research Program(B)of the Chinese Academy of Sciences under Grant No XDB07020300
文摘We carry out detailed momentum-dependent and temperature-dependent measurements on Bi_2Sr_2CaCu_2O_(8+δ)(Bi2212) superconductor in the superconducting and pseudogap states by super-high resolution laser-based angleresolved photoemission spectroscopy. The precise determination of the superconducting gap for the nearly optimally doped Bi2212(T_c= 91 K) at low temperature indicates that the momentum-dependence of the superconducting gap deviates from the standard d-wave form(cos(2Φ)). It can be alternatively fitted by including a high-order term(cos(6Φ)) in which the next nearest-neighbor interaction is considered. We find that the band structure near the antinodal region smoothly evolves across the pseudogap temperature without a signature of band reorganization which is distinct from that found in Bi_2Sr_2CuO_(6+δ) superconductors. This indicates that the band reorganization across the pseudogap temperature is not a universal behavior in cuprate superconductors.These results provide new insights in understanding the nature of the superconducting gap and pseudogap in high-temperature cuprate superconductors.
基金National Natural Science Foundation of China under Grant Nos.10405006 and 10547106
文摘The system of the Hamiltonian involving a driving part,a single mode part,and a two-mode squeezedone and a two-mode coupled one is discussed using the Lewis-Riesenfeld invariant theory.The time evolution operatoris obtained.When the initial state is a coherent state,the quantum fluctuation of the system is calculated,and it isdependent on the squeezed part and the two-mode coupled part,but not dependent on the driving one.