In this paper, we conduct an investigation into two-dimensional squeezed magnetopolarons. The Hamiltonian of magnetopolarons is dealt with two-mode squeezed states transformation, which is based on the Lee-Low-Pines a...In this paper, we conduct an investigation into two-dimensional squeezed magnetopolarons. The Hamiltonian of magnetopolarons is dealt with two-mode squeezed states transformation, which is based on the Lee-Low-Pines and Huybrechts (LLP-H) canonical transformations. This method makes it possible to take account of the linear terms, bilinear ones of phonon operators, and the correlation between two longitudinal optical (LO) phonon modes. The energies of the ground state and excited states are evaluated by variational approach, and accurate results are obtained. Furthermore, the renormalized cyclotron masses for some possible transitions are discussed in detail.展开更多
The stability and collective excitation of Bose-Einstein condensates with both two- and three-body interactions in a two-dimensional anhaxmonic trap (i.e., harmonic plus quartic trap) are investigated. By using the ...The stability and collective excitation of Bose-Einstein condensates with both two- and three-body interactions in a two-dimensional anhaxmonic trap (i.e., harmonic plus quartic trap) are investigated. By using the variational method, the influence of the three-body interaction and the anharmonicity on the stability axe discussed in detail. It is found that the anhaxmonicity of the trap and the three-body interaction have significant effect on the stability and collective excitations of the system.展开更多
The fully consistent relativistic continuum random phase approximation (RCRPA) has been constructed in the momentum representation in the first part of this paper. In this part we describe the numerical details for ...The fully consistent relativistic continuum random phase approximation (RCRPA) has been constructed in the momentum representation in the first part of this paper. In this part we describe the numerical details for solving the Bethe-Salpeter equation. The numerical results are checked by the inverse energy weighted sum rules in the isoscalar giant monopole resonance, which are obtained from the constraint relativistic mean field theory and also calculated with the integration of the RCRPA strengths. Good agreement between them is achieved. We study the effects of the self-consistency violation, particularly the currents and Coulomb interaction to various collective multipole excitations. Using the fully consistent RCRPA method, we investigate the properties of isoscalar and isovector collective multipole excitations for some stable and exotic from light to heavy nuclei. The properties of the resonances, such as the centroid energies and strength distributions are compared with the experimental data as well as with results calculated in other models.展开更多
Drama is a motivational, powerful, and feasible technique and tool for language learning. Interactions in the class play an important role. Thus, teachers exploit a number of opportunities to give chance to participan...Drama is a motivational, powerful, and feasible technique and tool for language learning. Interactions in the class play an important role. Thus, teachers exploit a number of opportunities to give chance to participants for communication. Writing drama and enacting it can be a good space for generating discussion to develop language skills. Analysis of language interaction in drama focuses on negotiations of language. Co-generative dialogues help participants to focus on the social aspects of life. The interaction and communication to environment play a vital role as it conveys a positive message through performance and fulfills the socio effective requirement. As English Language teaching teachers, we always look for innovative and motivational ideas for language learning and thus, “Drama for language learning through co-generative dialogues” helped me to expand the repertoire of dynamics in the classroom. Drama included co-generative dialogues stage production and performance. It is a powerful and innovative medium for exploring and learning language. It communicated response, moods, and information to the audience. The research explored the effect of drama for language learning through co-generative dialogues, to build cultural awareness, create bondage, meet people, and solve problems.展开更多
Normal vibrations of ethylbenzene in the first excited state have been studied using resonant two-photon ionization spectroscopy. The band origin of ethylbenzene of S1-S0 transition appeared at 37586 cm-1. A vibration...Normal vibrations of ethylbenzene in the first excited state have been studied using resonant two-photon ionization spectroscopy. The band origin of ethylbenzene of S1-S0 transition appeared at 37586 cm-1. A vibrational spectrum of 2000 cm-1 above the band origin in the first excited state has been obtained. Several chain torsions and normal vibrations are obtained in the spectrum. The energies of the first excited state are calculated by the time- dependent density function theory and configuration interaction singles (CIS) methods with various basis sets. The optimized structures and vibrational frequencies of the So and S1 states are calculated using Hartree-Fock and CIS methods with 6-311++G(2d,2p) basis set. The calculated geometric structures in the So and $1 states are gauche conformations that the symmetric plane of ethyl group is perpendicular to the ring plane. All the observed spectral bands have been successfully assigned with the help of our calculations.展开更多
Offshore platforms in seismically active areas should be designed to service severe earthquake excitations with no global structural failure. This paper summarizes the dynamic analysis of a typical fixed platform unde...Offshore platforms in seismically active areas should be designed to service severe earthquake excitations with no global structural failure. This paper summarizes the dynamic analysis of a typical fixed platform under the earthquake loading in the seismically active area. The dynamic analysis includes interpretation of dynamic design parameters based on the available site-specific data,together with foundation design recommendations for earthquake loading conditions,which include free-field site response analyses,liquefaction analyses and soil-pile interaction analyses.展开更多
in geotechnical engineering, numerical simulation of problems is of great importance. This work proposes a new formulation of coupled finite-infinite elements which can be used in numerical simulation ofgeotechnical p...in geotechnical engineering, numerical simulation of problems is of great importance. This work proposes a new formulation of coupled finite-infinite elements which can be used in numerical simulation ofgeotechnical problems in both static and dynamic conditions. Formulation and various implementation aspects of the proposed coupled finite-infinite elements are carefully discussed. To the authors' knowledge, this approach that considers coupled finite-infinite elements is more efficient in the sense that appropriate and accurate results are obtained by using less elements. The accuracy and efficiency of the proposed approach is considered by comparing the obtained results with analytical and numerical results. In a static case, the problem of circular domain ol infinite length is considered. In a dynamic case, one dimensional wave propagation problems arising from the Heaviside step fimction and impulse functions are considered. In order to get a more complete picture, two dimensional wave propagation in a circular qtmrter space is considered and the results are presented. Finally, a soil-structure interaction system subjected to seismic excitation is analyzed. In the analysis of soil-structure interaction phenomenon, frames with different number of storeys and soil media with various stiffness characteristics have been taken into consideration. In the analysis, the finite element software ANSYS has been used. For the newly developed infinite element, the programming has been done by the help of the User Programmable Features of the ANSYS software, which enable creating new elements in the ANSYS software.展开更多
Characteristics of wheel-rail dynamic interaction due to the rail corrugation in a high-speed railway are analyzed based on the theory of vehicle-track coupled dynamics in this paper.Influences of the corrugation wave...Characteristics of wheel-rail dynamic interaction due to the rail corrugation in a high-speed railway are analyzed based on the theory of vehicle-track coupled dynamics in this paper.Influences of the corrugation wavelength and depth on the wheel-rail dynamic performance are investigated.The results show that,under the excitation of a measured rail corrugation,the wheel-rail dynamic interaction of high-speed railway is enhanced obviously,and the high-frequency dynamic force between wheel and rail is generated,which has an obvious impact on the vibrations of the wheelset and rail,and little effect on the vibration of the frame and carbody.If the corrugation wavelength is shorter than the sensitive wavelength,the wheel-rail vertical force will increase with the growth of the corrugation wavelength,otherwise,it will decrease.However,the wheel-rail vertical force keeps increasing with the growth of corrugation depth.Furthermore,if the corrugation wavelength is shorter than the sensitive wavelength,the wheel-rail vertical force will increase with the decrease of the running speed,otherwise,it will decrease.It is also found that the critical wavelength of corrugation increases with the growth of the corrugation depth and the running speed,and the critical depth of corrugation is nonlinearly related to the sensitive wavelength.展开更多
Nanocrystal coalescence has attracted paramount attention in nanostructure fabrication in the past decades. Tremendous endeavor and progress have been made in understanding its mechanisms, benefiting from the developm...Nanocrystal coalescence has attracted paramount attention in nanostructure fabrication in the past decades. Tremendous endeavor and progress have been made in understanding its mechanisms, benefiting from the development of transmission electron microscopy. However, many mechanisms still remain unclear, especially for nanocrystals that lack a permanent dipole moment standing on a solid substrate. Here, we report an in situ coalescence of Pt nanocrystals on an amorphous carbon substrate induced by electron-excitation- enhanced van der Waals interactions studied by transmission electron microscopy and first principles calculations. It is found that the electron-beam-induced excitation can significantly enhance the van der Waals interaction between Pt nanocrystals and reduce the binding energy between Pt nanocrystals and the carbon substrate, both of which promote the coalescence. This work extends our understanding of the nanocrystal coalescence observed in a transmission electron microscope and sheds light on a potential pathway toward practical electron- beam-controlled nanofabrication.展开更多
We study spontaneous excitation of both a static detector (modelled by a two-level atom) immersed in a thermal bath and a uniformly accelerated one in the Minkowski vacuum interacting with a real massive scalar fiel...We study spontaneous excitation of both a static detector (modelled by a two-level atom) immersed in a thermal bath and a uniformly accelerated one in the Minkowski vacuum interacting with a real massive scalar field. Our results show that the mass of the scalar field manifests itself in the spontaneous excitation rate of the static detector in a thermal bath (and in vacuum) in the form of a selection rule for transitions among states of the detector. However, this selection rule disappears for the accelerated ones, demonstrating that an accelerated detector does not necessarily behave the same as an inertial one in a thermal bath. We lind the imprint left by the mass is the appearance of a grey-body factor in the spontaneous excitation and de-excitation rates, which maintains the detailed balance condition between them and thus ensures a thermal equilibrium at the Unruh temperature the same as that of the massless case. We also analyze quantitatively the effect of the mass on the rate of change of the detector's energy and find that when the mass is very small, it only induces a small negative correction. However, when it is very large, it then exponentially damps the rate, thus essentially forbidding any transitions among states of the detector.展开更多
The single particle energies obtained in a Kohn-Sham density functional theory(DFT) calculation are generally known to be poor approximations to electron excitation energies that are measured in transport,tunneling an...The single particle energies obtained in a Kohn-Sham density functional theory(DFT) calculation are generally known to be poor approximations to electron excitation energies that are measured in transport,tunneling and spectroscopic experiments such as photo-emission spectroscopy. The correction to these energies can be obtained from the poles of a single particle Green's function derived from a many-body perturbation theory. From a computational perspective, the accuracy and efficiency of such an approach depends on how a self energy term that properly accounts for dynamic screening of electrons is approximated. The G_0W_0 approximation is a widely used technique in which the self energy is expressed as the convolution of a noninteracting Green's function(G_0) and a screened Coulomb interaction(W_0) in the frequency domain. The computational cost associated with such a convolution is high due to the high complexity of evaluating W_0 at multiple frequencies. In this paper, we discuss how the cost of G_0W_0 calculation can be reduced by constructing a low rank approximation to the frequency dependent part of W_0. In particular, we examine the effect of such a low rank approximation on the accuracy of the G_0W_0 approximation. We also discuss how the numerical convolution of G_0 and W_0 can be evaluated efficiently and accurately by using a contour deformation technique with an appropriate choice of the contour.展开更多
基金The project supported by National Natural Science Foundation of China under Grant Nos. 10174024 and 10474025
文摘In this paper, we conduct an investigation into two-dimensional squeezed magnetopolarons. The Hamiltonian of magnetopolarons is dealt with two-mode squeezed states transformation, which is based on the Lee-Low-Pines and Huybrechts (LLP-H) canonical transformations. This method makes it possible to take account of the linear terms, bilinear ones of phonon operators, and the correlation between two longitudinal optical (LO) phonon modes. The energies of the ground state and excited states are evaluated by variational approach, and accurate results are obtained. Furthermore, the renormalized cyclotron masses for some possible transitions are discussed in detail.
基金The project by the National Natural Science Foundation of China under Grant No.10774120by the Natural Science Foundation of Gansu Province,China under Grant No.3ZS051-A25-013by Creation of Science and Technology of Northwest Normal University,China under Grant No.NWNU-KJCXGC-03-17
文摘The stability and collective excitation of Bose-Einstein condensates with both two- and three-body interactions in a two-dimensional anhaxmonic trap (i.e., harmonic plus quartic trap) are investigated. By using the variational method, the influence of the three-body interaction and the anharmonicity on the stability axe discussed in detail. It is found that the anhaxmonicity of the trap and the three-body interaction have significant effect on the stability and collective excitations of the system.
基金Supported by the National Natural Science Foundation of China under Grant Nos. 10875150, 10775183, 10535010Major State Basic Research Development Programme of China Under Contract Number 2007CB815000
文摘The fully consistent relativistic continuum random phase approximation (RCRPA) has been constructed in the momentum representation in the first part of this paper. In this part we describe the numerical details for solving the Bethe-Salpeter equation. The numerical results are checked by the inverse energy weighted sum rules in the isoscalar giant monopole resonance, which are obtained from the constraint relativistic mean field theory and also calculated with the integration of the RCRPA strengths. Good agreement between them is achieved. We study the effects of the self-consistency violation, particularly the currents and Coulomb interaction to various collective multipole excitations. Using the fully consistent RCRPA method, we investigate the properties of isoscalar and isovector collective multipole excitations for some stable and exotic from light to heavy nuclei. The properties of the resonances, such as the centroid energies and strength distributions are compared with the experimental data as well as with results calculated in other models.
文摘Drama is a motivational, powerful, and feasible technique and tool for language learning. Interactions in the class play an important role. Thus, teachers exploit a number of opportunities to give chance to participants for communication. Writing drama and enacting it can be a good space for generating discussion to develop language skills. Analysis of language interaction in drama focuses on negotiations of language. Co-generative dialogues help participants to focus on the social aspects of life. The interaction and communication to environment play a vital role as it conveys a positive message through performance and fulfills the socio effective requirement. As English Language teaching teachers, we always look for innovative and motivational ideas for language learning and thus, “Drama for language learning through co-generative dialogues” helped me to expand the repertoire of dynamics in the classroom. Drama included co-generative dialogues stage production and performance. It is a powerful and innovative medium for exploring and learning language. It communicated response, moods, and information to the audience. The research explored the effect of drama for language learning through co-generative dialogues, to build cultural awareness, create bondage, meet people, and solve problems.
文摘Normal vibrations of ethylbenzene in the first excited state have been studied using resonant two-photon ionization spectroscopy. The band origin of ethylbenzene of S1-S0 transition appeared at 37586 cm-1. A vibrational spectrum of 2000 cm-1 above the band origin in the first excited state has been obtained. Several chain torsions and normal vibrations are obtained in the spectrum. The energies of the first excited state are calculated by the time- dependent density function theory and configuration interaction singles (CIS) methods with various basis sets. The optimized structures and vibrational frequencies of the So and S1 states are calculated using Hartree-Fock and CIS methods with 6-311++G(2d,2p) basis set. The calculated geometric structures in the So and $1 states are gauche conformations that the symmetric plane of ethyl group is perpendicular to the ring plane. All the observed spectral bands have been successfully assigned with the help of our calculations.
文摘Offshore platforms in seismically active areas should be designed to service severe earthquake excitations with no global structural failure. This paper summarizes the dynamic analysis of a typical fixed platform under the earthquake loading in the seismically active area. The dynamic analysis includes interpretation of dynamic design parameters based on the available site-specific data,together with foundation design recommendations for earthquake loading conditions,which include free-field site response analyses,liquefaction analyses and soil-pile interaction analyses.
文摘in geotechnical engineering, numerical simulation of problems is of great importance. This work proposes a new formulation of coupled finite-infinite elements which can be used in numerical simulation ofgeotechnical problems in both static and dynamic conditions. Formulation and various implementation aspects of the proposed coupled finite-infinite elements are carefully discussed. To the authors' knowledge, this approach that considers coupled finite-infinite elements is more efficient in the sense that appropriate and accurate results are obtained by using less elements. The accuracy and efficiency of the proposed approach is considered by comparing the obtained results with analytical and numerical results. In a static case, the problem of circular domain ol infinite length is considered. In a dynamic case, one dimensional wave propagation problems arising from the Heaviside step fimction and impulse functions are considered. In order to get a more complete picture, two dimensional wave propagation in a circular qtmrter space is considered and the results are presented. Finally, a soil-structure interaction system subjected to seismic excitation is analyzed. In the analysis of soil-structure interaction phenomenon, frames with different number of storeys and soil media with various stiffness characteristics have been taken into consideration. In the analysis, the finite element software ANSYS has been used. For the newly developed infinite element, the programming has been done by the help of the User Programmable Features of the ANSYS software, which enable creating new elements in the ANSYS software.
基金supported by the National Basic Research Program of China("973"Project)(Grant Nos.2013CB036206,2013CB036205)the National Natural Science Foundation of China(Grant No.61134002)
文摘Characteristics of wheel-rail dynamic interaction due to the rail corrugation in a high-speed railway are analyzed based on the theory of vehicle-track coupled dynamics in this paper.Influences of the corrugation wavelength and depth on the wheel-rail dynamic performance are investigated.The results show that,under the excitation of a measured rail corrugation,the wheel-rail dynamic interaction of high-speed railway is enhanced obviously,and the high-frequency dynamic force between wheel and rail is generated,which has an obvious impact on the vibrations of the wheelset and rail,and little effect on the vibration of the frame and carbody.If the corrugation wavelength is shorter than the sensitive wavelength,the wheel-rail vertical force will increase with the growth of the corrugation wavelength,otherwise,it will decrease.However,the wheel-rail vertical force keeps increasing with the growth of corrugation depth.Furthermore,if the corrugation wavelength is shorter than the sensitive wavelength,the wheel-rail vertical force will increase with the decrease of the running speed,otherwise,it will decrease.It is also found that the critical wavelength of corrugation increases with the growth of the corrugation depth and the running speed,and the critical depth of corrugation is nonlinearly related to the sensitive wavelength.
文摘Nanocrystal coalescence has attracted paramount attention in nanostructure fabrication in the past decades. Tremendous endeavor and progress have been made in understanding its mechanisms, benefiting from the development of transmission electron microscopy. However, many mechanisms still remain unclear, especially for nanocrystals that lack a permanent dipole moment standing on a solid substrate. Here, we report an in situ coalescence of Pt nanocrystals on an amorphous carbon substrate induced by electron-excitation- enhanced van der Waals interactions studied by transmission electron microscopy and first principles calculations. It is found that the electron-beam-induced excitation can significantly enhance the van der Waals interaction between Pt nanocrystals and reduce the binding energy between Pt nanocrystals and the carbon substrate, both of which promote the coalescence. This work extends our understanding of the nanocrystal coalescence observed in a transmission electron microscope and sheds light on a potential pathway toward practical electron- beam-controlled nanofabrication.
基金Supported in part by the National Natural Science Foundation of China under Grant Nos. 11075083,10935013 and 11005013the Zhejiang Provincial Natural Science Foundation of China under Grant No. Z6100077+3 种基金the National Basic Research Program of China under Grant No. 2010CB832803the PCSIRT under Grant No. IRT0964the Research Foundation of Education Bureau of Hunan Province under Grant No. 10C0377Provincial Natural Science Foundation of China under Grant No. 11JJ700
文摘We study spontaneous excitation of both a static detector (modelled by a two-level atom) immersed in a thermal bath and a uniformly accelerated one in the Minkowski vacuum interacting with a real massive scalar field. Our results show that the mass of the scalar field manifests itself in the spontaneous excitation rate of the static detector in a thermal bath (and in vacuum) in the form of a selection rule for transitions among states of the detector. However, this selection rule disappears for the accelerated ones, demonstrating that an accelerated detector does not necessarily behave the same as an inertial one in a thermal bath. We lind the imprint left by the mass is the appearance of a grey-body factor in the spontaneous excitation and de-excitation rates, which maintains the detailed balance condition between them and thus ensures a thermal equilibrium at the Unruh temperature the same as that of the massless case. We also analyze quantitatively the effect of the mass on the rate of change of the detector's energy and find that when the mass is very small, it only induces a small negative correction. However, when it is very large, it then exponentially damps the rate, thus essentially forbidding any transitions among states of the detector.
基金supported by the SciD AC Program on Excited State Phenomena in Energy Materials funded by the US Department of Energy,Office of Basic Energy Sciences and of Advanced Scientific Computing Research at Lawrence Berkeley National Laboratory(Grant No.DE-AC02-05CH11231)the Center for Applied Mathematics for Energy Research Applications funded by US Department of Energy,Office of Science,Advanced Scientific Computing Research and Basic Energy Sciences,the Alfred P.Sloan FellowshipNational Natural Science Foundation of China(Grant No.11171232)
文摘The single particle energies obtained in a Kohn-Sham density functional theory(DFT) calculation are generally known to be poor approximations to electron excitation energies that are measured in transport,tunneling and spectroscopic experiments such as photo-emission spectroscopy. The correction to these energies can be obtained from the poles of a single particle Green's function derived from a many-body perturbation theory. From a computational perspective, the accuracy and efficiency of such an approach depends on how a self energy term that properly accounts for dynamic screening of electrons is approximated. The G_0W_0 approximation is a widely used technique in which the self energy is expressed as the convolution of a noninteracting Green's function(G_0) and a screened Coulomb interaction(W_0) in the frequency domain. The computational cost associated with such a convolution is high due to the high complexity of evaluating W_0 at multiple frequencies. In this paper, we discuss how the cost of G_0W_0 calculation can be reduced by constructing a low rank approximation to the frequency dependent part of W_0. In particular, we examine the effect of such a low rank approximation on the accuracy of the G_0W_0 approximation. We also discuss how the numerical convolution of G_0 and W_0 can be evaluated efficiently and accurately by using a contour deformation technique with an appropriate choice of the contour.