The structural, electronic and mechanical properties of transition metal hydrides （TMH, TM=Mo, Tc, Ru） are investigated by means of first principles calculation based on density fimctional theory with generalized gr...The structural, electronic and mechanical properties of transition metal hydrides （TMH, TM=Mo, Tc, Ru） are investigated by means of first principles calculation based on density fimctional theory with generalized gradient approximation. Among the five crystallographic structures that have been investigated, the cubic phase is found to be more stable than the hexagonal ones. A structural phase transition from ZB to WC in Moll, NaC1 to NiAs in TcH and NaCI to ZB to NiAs in RuH is also predicted under high pressure. The calculated elastic constants indicate that all the three hydrides are mechanically stable at ambient pressure.展开更多
The cubic-quintic nonlinear Schroedinger equation （CQNLS） plays important parts in the optical fiber and the nuclear hydrodynamics. By using the homogeneous balance principle, the bell type, kink type, algebraic sol...The cubic-quintic nonlinear Schroedinger equation （CQNLS） plays important parts in the optical fiber and the nuclear hydrodynamics. By using the homogeneous balance principle, the bell type, kink type, algebraic solitary waves, and trigonometric traveling waves for the cubic-quintic nonlinear Schroedinger equation with variable coefficients （vCQNLS） are derived with the aid of a set of subsidiary high-order ordinary differential equations （sub-equations for short）. The method used in this paper might help one to derive the exact solutions for the other high-order nonlinear evolution equations, and shows the new application of the homogeneous balance principle.展开更多
Using the most recent phase shift data for pp,nn,and np elastic scattering for different states (l=0,1,...) in the energy range of i MeV to 350 MeV,the charge dependency of the strong nuclear force is investigated.Our...Using the most recent phase shift data for pp,nn,and np elastic scattering for different states (l=0,1,...) in the energy range of i MeV to 350 MeV,the charge dependency of the strong nuclear force is investigated.Our results indicate that although the charge independency holds in most of the energy range,such charge independency is broken in the particular energy range of 120 MeV to 200 MeV for all partial wave states considered here.展开更多
In this paper,a microscopic phase-field model was used to investigate the effect of the oriented diffusion channel and the phases' effect mechanism for the Ni75Al6.0V19.0 alloy during a phase transformation proces...In this paper,a microscopic phase-field model was used to investigate the effect of the oriented diffusion channel and the phases' effect mechanism for the Ni75Al6.0V19.0 alloy during a phase transformation process.A diffusion channel of V was formed in the [100] direction.The oriented growth of DO22 in this direction,when an elastic misfit stress field existed,forced Al to form a diffusion channel next to DO22,resulting in L12-oriented growth.With an increase in stress,the oriented growth increased initially and then decreased.At a higher stress,the average values of the occupation probability for V atoms became constant later while Al atoms earlier.展开更多
Ramping a physical parameter is one of the most common experimental protocols in studying a quantum system, and ramping dynamics has been widely used in preparing a quantum state and probing physical properties. Here,...Ramping a physical parameter is one of the most common experimental protocols in studying a quantum system, and ramping dynamics has been widely used in preparing a quantum state and probing physical properties. Here, we present a novel method of probing quantum many-body correlation by ramping dynamics. We ramp a Hamiltonian parameter to the same target value from different initial values and with different velocities, and we show that the first-order correction on the finite ramping velocity is universal and path-independent, revealing a novel quantum many-body correlation function of the equilibrium phases at the target values. We term this method as the non-adiabatic linear response since this is the leading order correction beyond the adiabatic limit. We demonstrate this method experimentally by studying the Bose-Hubbard model with ultracold atoms in three-dimensional optical lattices.Unlike the conventional linear response that reveals whether the quasi-particle dispersion of a quantum phase is gapped or gapless, this probe is more sensitive to whether the quasi-particle lifetime is long enough such that the quantum phase possesses a well-defined quasi-particle description. In the BoseHubbard model, this non-adiabatic linear response is significant in the quantum critical regime where well-defined quasi-particles are absent. And in contrast, this response is vanishingly small in both superfluid and Mott insulators which possess well-defined quasi-particles. Because our proposal uses the most common experimental protocol, we envision that our method can find broad applications in probing various quantum systems.展开更多
Symmetries play important roles in modern theories of physical laws. In this paper, we review several experimental tests of important symmetries associated with the gravitational interaction, including the universalit...Symmetries play important roles in modern theories of physical laws. In this paper, we review several experimental tests of important symmetries associated with the gravitational interaction, including the universality of free fall for self-gravitating bodies,time-shift symmetry in the gravitational constant, local position invariance and local Lorentz invariance of gravity, and spacetime translational symmetries. Recent experimental explorations for post-Newtonian gravity are discussed, of which, those from pulsar astronomy are highlighted. All of these tests, of very different aspects of gravity theories, at very different length scales, favor to very high precision the predictions of the strong equivalence principle(SEP) and, in particular, general relativity which embodies SEP completely. As the founding principles of gravity, these symmetries are motivated to be promoted to even stricter tests in future.展开更多
This work is concerned about multiscale models of compact bone. We focus on the lacuna-canalicular system. The interstitial fluid and the ions in it are regarded as sol- vent and others are treated as solute. The syst...This work is concerned about multiscale models of compact bone. We focus on the lacuna-canalicular system. The interstitial fluid and the ions in it are regarded as sol- vent and others are treated as solute. The system has the characteristic of solvation process as well as non-equilibrium dynamics. The differential geometry theory of sur- faces is adopted. We use this theory to separate the macroscopic domain of solvent from the microscopic domain of solute. We also use it to couple continuum and discrete descriptions. The energy functionals are constructed and then the variational principle is applied to the energy functionals so as to derive desirable governing equations. We consider both long-range polar interactions and short-range nonpolar interactions. The solution of governing equations leads to the minimization of the total energy.展开更多
Based on a general variational principle, Einstein–Hilbert action and sound facts from geometry, it is shown that the long existing pseudotensor, non-localizability problem of gravitational energy-momentum is a resul...Based on a general variational principle, Einstein–Hilbert action and sound facts from geometry, it is shown that the long existing pseudotensor, non-localizability problem of gravitational energy-momentum is a result of mistaking different geometrical, physical ob jects as one and the same. It is also pointed out that in a curved spacetime, the sum vector of matter energy-momentum over a finite hyper-surface can not be defined. In curvilinear coordinate systems conservation of matter energy-momentum is not the continuity equations for its components. Conservation of matter energy-momentum is the vanishing of the covariant divergence of its density-flux tensor field. Introducing gravitational energy-momentum to save the law of conservation of energy-momentum is unnecessary and improper. After reasonably defining "change of a particle's energy-momentum", we show that gravitational field does not exchange energy-momentum with particles. And it does not exchange energy-momentum with matter fields either. Therefore, the gravitational field does not carry energy-momentum, it is not a force field and gravity is not a natural force.展开更多
Using the particle swarm optimization algorithm on crystal structure prediction,we first predict that Mg Y alloy undergoes a first-order phase transition from Cs Cl phase to P4/NMM phase at about 55 GPa with a small v...Using the particle swarm optimization algorithm on crystal structure prediction,we first predict that Mg Y alloy undergoes a first-order phase transition from Cs Cl phase to P4/NMM phase at about 55 GPa with a small volume collapse of 2.63%.The dynamical stability of P4/NMM phase at 55 GPa is evaluated by the phonon spectrum calculation and the electronic structure is discussed.The elastic constants are calculated,after which the bulk moduli,shear moduli,Young's modui,and Debye temperature are derived.The brittleness/ductile behavior,and anisotropy of two phases under pressure are discussed in details.Our results show that external pressure can change the brittle behavior to ductile at10 GPa for Cs Cl phase and improve the ductility of Mg Y alloy.As pressure increases,the elastic anisotropy in shear of Cs Cl phase decreases,while that of P4/NMM phase remains nearly constant.The elastic anisotropic constructions of the directional dependences of reciprocals of bulk modulus and Young's modulus are also calculated and discussed.展开更多
A method to generate Airy beam by combining the Fresnel holographic lens and the cubic phase of Airy beam is proposed. The detailed theoretical derivation to express the optical transform principle of the proposed met...A method to generate Airy beam by combining the Fresnel holographic lens and the cubic phase of Airy beam is proposed. The detailed theoretical derivation to express the optical transform principle of the proposed method is presented. And excellent experimental results are demonstrated. It is shown that this approach works well and simplifies the experimental facility effectively, especially reducing the optical system length to half of that of the conventional method. In addition, the proposed method can realize the beam propagation trajectory control of Airy beam and generate Airy beam array.展开更多
文摘The structural, electronic and mechanical properties of transition metal hydrides （TMH, TM=Mo, Tc, Ru） are investigated by means of first principles calculation based on density fimctional theory with generalized gradient approximation. Among the five crystallographic structures that have been investigated, the cubic phase is found to be more stable than the hexagonal ones. A structural phase transition from ZB to WC in Moll, NaC1 to NiAs in TcH and NaCI to ZB to NiAs in RuH is also predicted under high pressure. The calculated elastic constants indicate that all the three hydrides are mechanically stable at ambient pressure.
基金The project supported in part by Natural Science Foundation of Henan Province of China under Grant No. 2006110002 and the Science Foundation of Henan University of Science and Technology under Grant No. 2004ZD002
文摘The cubic-quintic nonlinear Schroedinger equation （CQNLS） plays important parts in the optical fiber and the nuclear hydrodynamics. By using the homogeneous balance principle, the bell type, kink type, algebraic solitary waves, and trigonometric traveling waves for the cubic-quintic nonlinear Schroedinger equation with variable coefficients （vCQNLS） are derived with the aid of a set of subsidiary high-order ordinary differential equations （sub-equations for short）. The method used in this paper might help one to derive the exact solutions for the other high-order nonlinear evolution equations, and shows the new application of the homogeneous balance principle.
文摘Using the most recent phase shift data for pp,nn,and np elastic scattering for different states (l=0,1,...) in the energy range of i MeV to 350 MeV,the charge dependency of the strong nuclear force is investigated.Our results indicate that although the charge independency holds in most of the energy range,such charge independency is broken in the particular energy range of 120 MeV to 200 MeV for all partial wave states considered here.
基金supported by the National Natural Science Foundation of China (Grant Nos. 51075335, 10902086, 50875217)the NPU Foundation for Fundamental Research (Grant No. JC201005)the Doctorate Foundation of Northwestern Polytechnical University (Grant No.CX201007)
文摘In this paper,a microscopic phase-field model was used to investigate the effect of the oriented diffusion channel and the phases' effect mechanism for the Ni75Al6.0V19.0 alloy during a phase transformation process.A diffusion channel of V was formed in the [100] direction.The oriented growth of DO22 in this direction,when an elastic misfit stress field existed,forced Al to form a diffusion channel next to DO22,resulting in L12-oriented growth.With an increase in stress,the oriented growth increased initially and then decreased.At a higher stress,the average values of the occupation probability for V atoms became constant later while Al atoms earlier.
基金supported by Beijing Outstanding Young Scholar Programthe National Key Research and Development Program of China (2021YFA0718303, 2021YFA1400904, and 2016YFA0301501)+1 种基金the National Natural Science Foundation of China (91736208, 11974202, 61975092, 11920101004,61727819, 11934002, 11734010, and 92165203)the XPLORER Prize。
文摘Ramping a physical parameter is one of the most common experimental protocols in studying a quantum system, and ramping dynamics has been widely used in preparing a quantum state and probing physical properties. Here, we present a novel method of probing quantum many-body correlation by ramping dynamics. We ramp a Hamiltonian parameter to the same target value from different initial values and with different velocities, and we show that the first-order correction on the finite ramping velocity is universal and path-independent, revealing a novel quantum many-body correlation function of the equilibrium phases at the target values. We term this method as the non-adiabatic linear response since this is the leading order correction beyond the adiabatic limit. We demonstrate this method experimentally by studying the Bose-Hubbard model with ultracold atoms in three-dimensional optical lattices.Unlike the conventional linear response that reveals whether the quasi-particle dispersion of a quantum phase is gapped or gapless, this probe is more sensitive to whether the quasi-particle lifetime is long enough such that the quantum phase possesses a well-defined quasi-particle description. In the BoseHubbard model, this non-adiabatic linear response is significant in the quantum critical regime where well-defined quasi-particles are absent. And in contrast, this response is vanishingly small in both superfluid and Mott insulators which possess well-defined quasi-particles. Because our proposal uses the most common experimental protocol, we envision that our method can find broad applications in probing various quantum systems.
文摘Symmetries play important roles in modern theories of physical laws. In this paper, we review several experimental tests of important symmetries associated with the gravitational interaction, including the universality of free fall for self-gravitating bodies,time-shift symmetry in the gravitational constant, local position invariance and local Lorentz invariance of gravity, and spacetime translational symmetries. Recent experimental explorations for post-Newtonian gravity are discussed, of which, those from pulsar astronomy are highlighted. All of these tests, of very different aspects of gravity theories, at very different length scales, favor to very high precision the predictions of the strong equivalence principle(SEP) and, in particular, general relativity which embodies SEP completely. As the founding principles of gravity, these symmetries are motivated to be promoted to even stricter tests in future.
文摘This work is concerned about multiscale models of compact bone. We focus on the lacuna-canalicular system. The interstitial fluid and the ions in it are regarded as sol- vent and others are treated as solute. The system has the characteristic of solvation process as well as non-equilibrium dynamics. The differential geometry theory of sur- faces is adopted. We use this theory to separate the macroscopic domain of solvent from the microscopic domain of solute. We also use it to couple continuum and discrete descriptions. The energy functionals are constructed and then the variational principle is applied to the energy functionals so as to derive desirable governing equations. We consider both long-range polar interactions and short-range nonpolar interactions. The solution of governing equations leads to the minimization of the total energy.
文摘Based on a general variational principle, Einstein–Hilbert action and sound facts from geometry, it is shown that the long existing pseudotensor, non-localizability problem of gravitational energy-momentum is a result of mistaking different geometrical, physical ob jects as one and the same. It is also pointed out that in a curved spacetime, the sum vector of matter energy-momentum over a finite hyper-surface can not be defined. In curvilinear coordinate systems conservation of matter energy-momentum is not the continuity equations for its components. Conservation of matter energy-momentum is the vanishing of the covariant divergence of its density-flux tensor field. Introducing gravitational energy-momentum to save the law of conservation of energy-momentum is unnecessary and improper. After reasonably defining "change of a particle's energy-momentum", we show that gravitational field does not exchange energy-momentum with particles. And it does not exchange energy-momentum with matter fields either. Therefore, the gravitational field does not carry energy-momentum, it is not a force field and gravity is not a natural force.
基金Supported by the Henan Joint Funds of the National Natural Science Foundation of China under Grant Nos.U1304612,U1404608the National Natural Science Foundation of China under Grant Nos.51501093,51374132+2 种基金the Special Fund of the Theoretical Physics of China under Grant No.11247222Postdoctoral Science Foundation of China under Grant No.2015M581767Young Core Instructor Foundation of Henan Province under Grant No.2015GGJS-122
文摘Using the particle swarm optimization algorithm on crystal structure prediction,we first predict that Mg Y alloy undergoes a first-order phase transition from Cs Cl phase to P4/NMM phase at about 55 GPa with a small volume collapse of 2.63%.The dynamical stability of P4/NMM phase at 55 GPa is evaluated by the phonon spectrum calculation and the electronic structure is discussed.The elastic constants are calculated,after which the bulk moduli,shear moduli,Young's modui,and Debye temperature are derived.The brittleness/ductile behavior,and anisotropy of two phases under pressure are discussed in details.Our results show that external pressure can change the brittle behavior to ductile at10 GPa for Cs Cl phase and improve the ductility of Mg Y alloy.As pressure increases,the elastic anisotropy in shear of Cs Cl phase decreases,while that of P4/NMM phase remains nearly constant.The elastic anisotropic constructions of the directional dependences of reciprocals of bulk modulus and Young's modulus are also calculated and discussed.
文摘A method to generate Airy beam by combining the Fresnel holographic lens and the cubic phase of Airy beam is proposed. The detailed theoretical derivation to express the optical transform principle of the proposed method is presented. And excellent experimental results are demonstrated. It is shown that this approach works well and simplifies the experimental facility effectively, especially reducing the optical system length to half of that of the conventional method. In addition, the proposed method can realize the beam propagation trajectory control of Airy beam and generate Airy beam array.
