In this study, the rapidity distribution, collective flows, and nuclear stopping power in ^(197)Au+^(197)Au collisions at intermediate energies were investigated using the ultrarelativistic quantum molecular dynamics(...In this study, the rapidity distribution, collective flows, and nuclear stopping power in ^(197)Au+^(197)Au collisions at intermediate energies were investigated using the ultrarelativistic quantum molecular dynamics(UrQMD) model with GEMINI++ code. The UrQMD model was adopted to simulate the dynamic evolution of heavy-ion collisions, whereas the GEMINI++ code was used to simulate the decay of primary fragments produced by UrQMD. The calculated results were compared with the INDRA and FOPI experimental data. It was found that the rapidity distribution, collective flows, and nuclear stopping power were affected to a certain extent by the decay of primary fragments, especially at lower beam energies. Furthermore, the experimental data of the collective flows and nuclear stopping power at the investigated beam energies were better reproduced when the sequential decay effect was included.展开更多
Branched flow is an interesting phenomenon that can occur in diverse systems.It is usually linear in the sense that the flow does not alter the properties of the medium.Branched flow of light on thin films has recentl...Branched flow is an interesting phenomenon that can occur in diverse systems.It is usually linear in the sense that the flow does not alter the properties of the medium.Branched flow of light on thin films has recently been discovered.It is therefore of interest to know whether nonlinear light branching can also occur.Here,using particle-in-cell simulations,we find that in the case of an intense laser propagating through a randomly uneven medium,cascading local photoionization by the incident laser,together with the response of freed electrons in the strong laser fields,triggers space–time-dependent optical unevenness.The resulting branching pattern depends dramatically on the laser intensity.That is,the branching here is distinct from the existing linear ones.The observed branching properties agree well with theoretical analyses based on the Helmholtz equation.Nonlinear branched propagation of intense lasers potentially opens up a new area for laser–matter interaction and may be relevant to other branching phenomena of a nonlinear nature.展开更多
A method for measuring the intensity of focused high-power laser pulses based on numerical simulation of high-harmonic generation in the laser peeler regime is proposed.The dependence of the efficiency of high-harmoni...A method for measuring the intensity of focused high-power laser pulses based on numerical simulation of high-harmonic generation in the laser peeler regime is proposed.The dependence of the efficiency of high-harmonic generation on the laser pulse intensity and the spatial parameters during interaction with solid targets is studied numerically.The simulation clearly shows that the amplitude of the generated harmonics depends on the laser pulse parameters.The proposed method is simpler than similar intensity measurement techniques and does not require complex preparation.展开更多
We review several recent theoretical and experimental results in the study of exciton condensates. This includes the present experimental advances in the study of exciton condensates both using layers and coupled bila...We review several recent theoretical and experimental results in the study of exciton condensates. This includes the present experimental advances in the study of exciton condensates both using layers and coupled bilayers. We will shortly illustrate the different phases of exciton condensates. We focus especially on the Bardeen-Cooper-Schrieffer-like phase and illustrate the similarities to superconductors. Afterwards, we want to illustrate several recent advances and proposals for measuring the different phases of superconductors. In the remainder of this short review, we will provide an outlook for the possibilities and complications for future technical applications of exciton condensates.展开更多
We describe a scheme for universal quantum computation with Majorana fermions. We investigate two possible dissipative couplings of Majorana fermions to external systems, including metallic leads and local phonons. Wh...We describe a scheme for universal quantum computation with Majorana fermions. We investigate two possible dissipative couplings of Majorana fermions to external systems, including metallic leads and local phonons. While the dissipation when coupling to metallic leads to uninteresting states for the Majorana fermions, we show that coupling the Majorana fermions to local phonons allows to generate arbitrary dissipations and therefore universal quantum operations on a single QuBit that can be enhanced by additional two-QuBit operations.展开更多
Spin-wave excitation plays important roles in the investigation of the magnetic phases. In this paper, we study the spin-wave excitation spectra of two-component Bose gases with spin–orbit coupling in a deep square o...Spin-wave excitation plays important roles in the investigation of the magnetic phases. In this paper, we study the spin-wave excitation spectra of two-component Bose gases with spin–orbit coupling in a deep square optical lattice using the spin-wave theory. We find that, while the excitation spectrum of the vortex crystal phase is gapless with a linear dispersion in the vicinity of the minimum point, the spectra of the commensurate spiral spin phase and the skyrmion crystal phase are gapped. Significantly, the spin fluctuations strongly destabilize the classical ground state of the skyrmion phase with the appearance of an imaginary part in the eigenfrequencies of spin excitations. Such features of the spin excitation spectra provide further insights into the exotic spin phases.展开更多
We present modeling work on three young stellar objects that are promising targets for future high-resolution observations to investigate circumstellar disk evolution. The currently available data comprise the spectra...We present modeling work on three young stellar objects that are promising targets for future high-resolution observations to investigate circumstellar disk evolution. The currently available data comprise the spectral energy distribution from optical to millimeter wavelengths which allow constraining the structure of the circumstellar disk using self-consistent radiative transfer models. The results suggest that the assumption of well-mixed dust and gas leads to overestimation of flux in the far-infrared. Observational and theoretical arguments suggest that an overall decrease in far-infrared excess can be explained by dust settling towards the midplane. A new disk model is hence employed to take the effect of dust sedimentation into account. The extended model satisfactorily reproduces all existing observations. The three targets studied here therefore deserve follow-up observations to reveal the evolutionary state of their protoplanetary disks.展开更多
Time evolution of ionospheric D-region plasmas including the perturbations of electronsand charged aerosol particles is investigated under the conditions of polar mesosphere summerechoes (PMSE).It is shown that the ti...Time evolution of ionospheric D-region plasmas including the perturbations of electronsand charged aerosol particles is investigated under the conditions of polar mesosphere summerechoes (PMSE).It is shown that the time scale of decay of the electron density is in the orderof an hour under typical PMSE conditions,in the majority of cases,the electron density is anticorrelatedto the ion density,except that the radius of aerosol particles is greater than 50 nm.Also,the evolutions under varied parameters,such as the amplitude and width of perturbation,theaerosol particle radius,and the altitude of the PMSE occurrence are investigated.The obtainedresults are useful for interpreting the experimental observations.展开更多
In this brief communication we present a new integral transform, so far unknown, which is applicable, for instance, to studying the kinetic theory of natural eigenmodes or transport excited in plasmas with bounded dis...In this brief communication we present a new integral transform, so far unknown, which is applicable, for instance, to studying the kinetic theory of natural eigenmodes or transport excited in plasmas with bounded distribution functions such as in Q machines/plasma diodes or in the scrap-off layer of Tokamak fusion plasmas. The results are valid for functions of function spaces—Lebesgue spaces, which are defined using a natural generalization of the p-norm for finite-dimensional vector spaces, where is the real set, σs is the σ-algebra of Lebesgue measurable sets, and the μ Lebesgue measure. , so that . Note that, using a simpler notation, more natural/known to engineers, f could be considered any piecewise continuous function, that is: Here is a Euclidian space with the usual norm (inner product: ) given by: [1].展开更多
<正> The properties of nuclei belonging to the newly observed α-decay chain starting from ~(265)Bh have beenstudied.The axially deformed relativistic mean-field calculation with the force NL-Z2 has been perform...<正> The properties of nuclei belonging to the newly observed α-decay chain starting from ~(265)Bh have beenstudied.The axially deformed relativistic mean-field calculation with the force NL-Z2 has been performed in the blockedBCS approximation.Some ground state properties such as binding energies,deformations,spins,and parities,as well asQ-values of the α-decay for this decay chain have been calculated and compared with known experimental data.Goodagreement is found.The single-particle spectrum of the nucleus ~(265)Bh is studied and some new magic numbers are found,while the magnitudes of the shell gaps in superheavy nuclei are much smaller than those of nuclei before the actiniumregion,and the Fermi surfaces are close to the continuum.Thus the superheavy nuclei are usually not stable.Theα-decay lifetimes in the ~(265)Bh decay chain are evaluated by different formulae,and compared with experimental dáta.The methods which give good agreement with the data are selected.展开更多
The multiplicity difference correlators between two well-separated bins are studied in second-order quark-gluon plasma(QGP)phase transition within the Ginzburg-Landau model.For the case with very low mean multipliciti...The multiplicity difference correlators between two well-separated bins are studied in second-order quark-gluon plasma(QGP)phase transition within the Ginzburg-Landau model.For the case with very low mean multiplicities,an exponentγis found,which has very weak dependence on the parameters of the model and can be used as a signal for the formation of QGP in ultra-relativistic heavy-ion collisions.展开更多
Considered here is a plasma grating generated by two counterpropagating short laser pulses. Because of the shortness of the laser pulses, theplasma dynamics are determined by only electrons, which respond to the ponde...Considered here is a plasma grating generated by two counterpropagating short laser pulses. Because of the shortness of the laser pulses, theplasma dynamics are determined by only electrons, which respond to the ponderomotive pressure generated by the interacting laser fields.An electron grating cannot exist for longer than the inverse ion plasma frequency, and so because of the limited time of the ponderomotivepressure, both the life time and spatial extent of an electron grating are finite. When one of the short laser pulses is circularly polarized(propagating in the x direction with electric field vectors in the yz plane) and the other is linearly y-polarized, the electron grating is producedby the y components. Meanwhile, the z component is partially reflected, and only a fraction of it is transmitted. Thus, the finite plasmagrating can either alter the polarization of the yz-polarized pulse or act as a pulse splitter. The present paper is focused on the reflection andtransmission rates. The action of the density grating on the z component cannot be explained by the Bloch wave theory for infinite crystals,and instead a theory is developed based on four-wave mixing, which explains the transmission and reflection of the z component wheninteracting with a grating of finite extent.展开更多
We consider the solution of matching problems with a convex cost function via a network flow algorithm. We review the general mapping between matching problems and flow problems on skew symmetric networks and revisit ...We consider the solution of matching problems with a convex cost function via a network flow algorithm. We review the general mapping between matching problems and flow problems on skew symmetric networks and revisit several results on optimality of network flows. We use these results to derive a balanced capacity scaling algorithm for matching problems with a linear cost function. The latter is later generalized to a balanced capacity scaling algorithm also for a convex cost function. We prove the correctness and discuss the complexity of our solution.展开更多
In recent years, modelling crowd and evacuation dynamics has become very important, with increasing huge numbers of people gathering around the world for many reasons and events. The fact that our global population gr...In recent years, modelling crowd and evacuation dynamics has become very important, with increasing huge numbers of people gathering around the world for many reasons and events. The fact that our global population grows dramatically every year and the current public transport systems are able to transport large amounts of people heightens the risk of crowd panic or crush. Pedestrian models are based on macroscopic or microscopic behaviour. In this paper, we are interested in developing models that can be used for evacuation control strategies. This model will be based on microscopic pedestrian simulation models, and its evolution and design requires a lot of information and data. The people stream will be simulated, based on mathematical models derived from empirical data about pedestrian flows. This model is developed from image data bases, so called empirical data, taken from a video camera or data obtained using human detectors. We consider the individuals as autonomous particles interacting through social and physical forces, which is an approach that has been used to simulate crowd behaviour. The target of this work is to describe a comprehensive approach to model a huge number of pedestrians and to simulate high density crowd behaviour in overcrowding places, e.g. sport, concert and pilgrimage places, and to assist engineering in the resolution of complicated problems through integrating a number of models from different research domains.展开更多
We study the quantum theory of the mass-less vector fields on the Rindler space. We evaluate the Bogoliubov coefficients by means of a new technique based upon the use of light-front coordinates and Mellin transform. ...We study the quantum theory of the mass-less vector fields on the Rindler space. We evaluate the Bogoliubov coefficients by means of a new technique based upon the use of light-front coordinates and Mellin transform. We briefly comment about the ensuing Unruh effect and its consequences.展开更多
The pattern of isentropes in the vicinity of a first-order phase transition is proposed as a key for a sub-classification. While the confinement-deconfinement transition, conjectured to set in beyond a critical end po...The pattern of isentropes in the vicinity of a first-order phase transition is proposed as a key for a sub-classification. While the confinement-deconfinement transition, conjectured to set in beyond a critical end point in the QCD phase diagram, is often related to an entropic transition and the apparently settled gas-liquid transition in nuclear matter is an enthalphic transition, the conceivable local isentropes w.r.t. “incoming” or “outgoing” serve as another useful guide for discussing possible implications, both in the presumed hydrodynamical expansion stage of heavy-ion collisions and the core-collapse of supernova explosions. Examples, such as the quark-meson model and two-phase models, are shown to distinguish concisely the different transitions.展开更多
Using classical density functional theory (DFT) in a modified mean-field approximation we investigate the fluid phase behavior of quasi-two dimensional dipolar fluids confined to a plane. The particles carry three-dim...Using classical density functional theory (DFT) in a modified mean-field approximation we investigate the fluid phase behavior of quasi-two dimensional dipolar fluids confined to a plane. The particles carry three-dimensional dipole moments and interact via a combination of hard-sphere, van-der-Waals, and dipolar interactions. The DFT predicts complex phase behavior involving first- and second-order isotropic-to-ferroelectric transitions, where the ferroelectric ordering is characterized by global polarization within the plane. We compare this phase behavior, particularly the onset of ferroelectric ordering and the related tri-critical points, with corresponding three-dimensional systems, slab-like systems (with finite extension into the third direction), and true two-dimensional systems with two-dimensional dipole moments.展开更多
We analyse the proximity effect in hybrid nanoscale junctions involving superconducting leads. We develop a general framework for the analysis of the proximity effect using the same theoretical methods typically emplo...We analyse the proximity effect in hybrid nanoscale junctions involving superconducting leads. We develop a general framework for the analysis of the proximity effect using the same theoretical methods typically employed for the analysis of conductance properties. We apply our method to a normal-superconductor tunnel contact and compare our results to previous results.展开更多
We have coupled an upright HG mode into a fiber-optic waveguide and used the application of stress to generate a Laguerre-Gaussian laser mode. We have generalized previous results by McGloin et al. by using a polarize...We have coupled an upright HG mode into a fiber-optic waveguide and used the application of stress to generate a Laguerre-Gaussian laser mode. We have generalized previous results by McGloin et al. by using a polarized input beam, a true 3-mode fiber and by applying the stress on a stripped piece of the optical waveguide. These generalizations are necessary in order to perform quantum information experiments and obtain reliable information on the stress imposed on the optical fiber.展开更多
基金partly supported by the National Natural Science Foundation of China (Nos. U2032145 and 11875125)the National Key Research and Development Program of China (No. 2020YFE0202002)。
文摘In this study, the rapidity distribution, collective flows, and nuclear stopping power in ^(197)Au+^(197)Au collisions at intermediate energies were investigated using the ultrarelativistic quantum molecular dynamics(UrQMD) model with GEMINI++ code. The UrQMD model was adopted to simulate the dynamic evolution of heavy-ion collisions, whereas the GEMINI++ code was used to simulate the decay of primary fragments produced by UrQMD. The calculated results were compared with the INDRA and FOPI experimental data. It was found that the rapidity distribution, collective flows, and nuclear stopping power were affected to a certain extent by the decay of primary fragments, especially at lower beam energies. Furthermore, the experimental data of the collective flows and nuclear stopping power at the investigated beam energies were better reproduced when the sequential decay effect was included.
基金supported by the National Natural Science Foundation of China(Grant Nos.12205201,12175154,11875092,and 12005149)the Natural Science Foundation of Top Talent of SZTU(Grant Nos.2019010801001 and 2019020801001)+1 种基金GCS Jülich(Project No.QED20)in GermanyThe EPOCH code is used under a UK EPSRC contract(Grant Nos.EP/G055165/1 and EP/G056803/1).
文摘Branched flow is an interesting phenomenon that can occur in diverse systems.It is usually linear in the sense that the flow does not alter the properties of the medium.Branched flow of light on thin films has recently been discovered.It is therefore of interest to know whether nonlinear light branching can also occur.Here,using particle-in-cell simulations,we find that in the case of an intense laser propagating through a randomly uneven medium,cascading local photoionization by the incident laser,together with the response of freed electrons in the strong laser fields,triggers space–time-dependent optical unevenness.The resulting branching pattern depends dramatically on the laser intensity.That is,the branching here is distinct from the existing linear ones.The observed branching properties agree well with theoretical analyses based on the Helmholtz equation.Nonlinear branched propagation of intense lasers potentially opens up a new area for laser–matter interaction and may be relevant to other branching phenomena of a nonlinear nature.
基金This work was supported by the Russian Science Foundation within the framework of Project No.20-62-46050.
文摘A method for measuring the intensity of focused high-power laser pulses based on numerical simulation of high-harmonic generation in the laser peeler regime is proposed.The dependence of the efficiency of high-harmonic generation on the laser pulse intensity and the spatial parameters during interaction with solid targets is studied numerically.The simulation clearly shows that the amplitude of the generated harmonics depends on the laser pulse parameters.The proposed method is simpler than similar intensity measurement techniques and does not require complex preparation.
文摘We review several recent theoretical and experimental results in the study of exciton condensates. This includes the present experimental advances in the study of exciton condensates both using layers and coupled bilayers. We will shortly illustrate the different phases of exciton condensates. We focus especially on the Bardeen-Cooper-Schrieffer-like phase and illustrate the similarities to superconductors. Afterwards, we want to illustrate several recent advances and proposals for measuring the different phases of superconductors. In the remainder of this short review, we will provide an outlook for the possibilities and complications for future technical applications of exciton condensates.
文摘We describe a scheme for universal quantum computation with Majorana fermions. We investigate two possible dissipative couplings of Majorana fermions to external systems, including metallic leads and local phonons. While the dissipation when coupling to metallic leads to uninteresting states for the Majorana fermions, we show that coupling the Majorana fermions to local phonons allows to generate arbitrary dissipations and therefore universal quantum operations on a single QuBit that can be enhanced by additional two-QuBit operations.
基金supported by the National Natural Science Foundation of China(Grant Nos.11347197,11404225,and 11474205)
文摘Spin-wave excitation plays important roles in the investigation of the magnetic phases. In this paper, we study the spin-wave excitation spectra of two-component Bose gases with spin–orbit coupling in a deep square optical lattice using the spin-wave theory. We find that, while the excitation spectrum of the vortex crystal phase is gapless with a linear dispersion in the vicinity of the minimum point, the spectra of the commensurate spiral spin phase and the skyrmion crystal phase are gapped. Significantly, the spin fluctuations strongly destabilize the classical ground state of the skyrmion phase with the appearance of an imaginary part in the eigenfrequencies of spin excitations. Such features of the spin excitation spectra provide further insights into the exotic spin phases.
基金Supported by the National Natural Science Foundation of China(Grant Nos.10733030,10921063 and 11173060)
文摘We present modeling work on three young stellar objects that are promising targets for future high-resolution observations to investigate circumstellar disk evolution. The currently available data comprise the spectral energy distribution from optical to millimeter wavelengths which allow constraining the structure of the circumstellar disk using self-consistent radiative transfer models. The results suggest that the assumption of well-mixed dust and gas leads to overestimation of flux in the far-infrared. Observational and theoretical arguments suggest that an overall decrease in far-infrared excess can be explained by dust settling towards the midplane. A new disk model is hence employed to take the effect of dust sedimentation into account. The extended model satisfactorily reproduces all existing observations. The three targets studied here therefore deserve follow-up observations to reveal the evolutionary state of their protoplanetary disks.
基金supported by National Natural Science Foundation of China (Nos. 40831062, 10775134)partially supported by CAS Knowledge Innovation Program (No. kjcx2-yw-n28)National Basic Research Program of China (Nos. 2008CB717800, 2009GB105001)
文摘Time evolution of ionospheric D-region plasmas including the perturbations of electronsand charged aerosol particles is investigated under the conditions of polar mesosphere summerechoes (PMSE).It is shown that the time scale of decay of the electron density is in the orderof an hour under typical PMSE conditions,in the majority of cases,the electron density is anticorrelatedto the ion density,except that the radius of aerosol particles is greater than 50 nm.Also,the evolutions under varied parameters,such as the amplitude and width of perturbation,theaerosol particle radius,and the altitude of the PMSE occurrence are investigated.The obtainedresults are useful for interpreting the experimental observations.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10674125 and 10475070, and the National Basic Research Programme of China under Grant No 2007CB925200.
文摘In this brief communication we present a new integral transform, so far unknown, which is applicable, for instance, to studying the kinetic theory of natural eigenmodes or transport excited in plasmas with bounded distribution functions such as in Q machines/plasma diodes or in the scrap-off layer of Tokamak fusion plasmas. The results are valid for functions of function spaces—Lebesgue spaces, which are defined using a natural generalization of the p-norm for finite-dimensional vector spaces, where is the real set, σs is the σ-algebra of Lebesgue measurable sets, and the μ Lebesgue measure. , so that . Note that, using a simpler notation, more natural/known to engineers, f could be considered any piecewise continuous function, that is: Here is a Euclidian space with the usual norm (inner product: ) given by: [1].
基金The project supported by National Natural Science Foundation of China under Grant Nos. 10175082, 10235020, 10375001, 10275094, and 10075080, the Major Basic Research Development Program under Grant Nos. G2000-0774-07 and G2000-0774-00, the Knowledge Innovation Project of the Chinese Academy of Sciences under Grant No. KJCX2-SW-N02, 0ne Hundred＂ Person Project of CAS, the State Key Basic Research Program of the Ministry of Science and Technology under Grant Nos. 2001CCB01200 and 2002CCB00200
文摘<正> The properties of nuclei belonging to the newly observed α-decay chain starting from ~(265)Bh have beenstudied.The axially deformed relativistic mean-field calculation with the force NL-Z2 has been performed in the blockedBCS approximation.Some ground state properties such as binding energies,deformations,spins,and parities,as well asQ-values of the α-decay for this decay chain have been calculated and compared with known experimental data.Goodagreement is found.The single-particle spectrum of the nucleus ~(265)Bh is studied and some new magic numbers are found,while the magnitudes of the shell gaps in superheavy nuclei are much smaller than those of nuclei before the actiniumregion,and the Fermi surfaces are close to the continuum.Thus the superheavy nuclei are usually not stable.Theα-decay lifetimes in the ~(265)Bh decay chain are evaluated by different formulae,and compared with experimental dáta.The methods which give good agreement with the data are selected.
基金Supported in part by the National Natural Science Foundation of China under Grant No.19875019the Natural Science Foundation of Hubei Province,and the Die Deutsche Forschungsgemeinschaft in Germany.
文摘The multiplicity difference correlators between two well-separated bins are studied in second-order quark-gluon plasma(QGP)phase transition within the Ginzburg-Landau model.For the case with very low mean multiplicities,an exponentγis found,which has very weak dependence on the parameters of the model and can be used as a signal for the formation of QGP in ultra-relativistic heavy-ion collisions.
基金Computational support and infrastructure were provided by the Centre for Information and Media Technology(ZIM)at the University of Düsseldorf(Germany).Development of the EPOCH PIC code used in this work was funded in part by the Engineering and Physical Sciences Research Council(UK)(Grant Nos.EP/G054950/1,EP/G056803/1,EP/G055165/1,and EP/M022463/1).
文摘Considered here is a plasma grating generated by two counterpropagating short laser pulses. Because of the shortness of the laser pulses, theplasma dynamics are determined by only electrons, which respond to the ponderomotive pressure generated by the interacting laser fields.An electron grating cannot exist for longer than the inverse ion plasma frequency, and so because of the limited time of the ponderomotivepressure, both the life time and spatial extent of an electron grating are finite. When one of the short laser pulses is circularly polarized(propagating in the x direction with electric field vectors in the yz plane) and the other is linearly y-polarized, the electron grating is producedby the y components. Meanwhile, the z component is partially reflected, and only a fraction of it is transmitted. Thus, the finite plasmagrating can either alter the polarization of the yz-polarized pulse or act as a pulse splitter. The present paper is focused on the reflection andtransmission rates. The action of the density grating on the z component cannot be explained by the Bloch wave theory for infinite crystals,and instead a theory is developed based on four-wave mixing, which explains the transmission and reflection of the z component wheninteracting with a grating of finite extent.
文摘We consider the solution of matching problems with a convex cost function via a network flow algorithm. We review the general mapping between matching problems and flow problems on skew symmetric networks and revisit several results on optimality of network flows. We use these results to derive a balanced capacity scaling algorithm for matching problems with a linear cost function. The latter is later generalized to a balanced capacity scaling algorithm also for a convex cost function. We prove the correctness and discuss the complexity of our solution.
文摘In recent years, modelling crowd and evacuation dynamics has become very important, with increasing huge numbers of people gathering around the world for many reasons and events. The fact that our global population grows dramatically every year and the current public transport systems are able to transport large amounts of people heightens the risk of crowd panic or crush. Pedestrian models are based on macroscopic or microscopic behaviour. In this paper, we are interested in developing models that can be used for evacuation control strategies. This model will be based on microscopic pedestrian simulation models, and its evolution and design requires a lot of information and data. The people stream will be simulated, based on mathematical models derived from empirical data about pedestrian flows. This model is developed from image data bases, so called empirical data, taken from a video camera or data obtained using human detectors. We consider the individuals as autonomous particles interacting through social and physical forces, which is an approach that has been used to simulate crowd behaviour. The target of this work is to describe a comprehensive approach to model a huge number of pedestrians and to simulate high density crowd behaviour in overcrowding places, e.g. sport, concert and pilgrimage places, and to assist engineering in the resolution of complicated problems through integrating a number of models from different research domains.
文摘We study the quantum theory of the mass-less vector fields on the Rindler space. We evaluate the Bogoliubov coefficients by means of a new technique based upon the use of light-front coordinates and Mellin transform. We briefly comment about the ensuing Unruh effect and its consequences.
文摘The pattern of isentropes in the vicinity of a first-order phase transition is proposed as a key for a sub-classification. While the confinement-deconfinement transition, conjectured to set in beyond a critical end point in the QCD phase diagram, is often related to an entropic transition and the apparently settled gas-liquid transition in nuclear matter is an enthalphic transition, the conceivable local isentropes w.r.t. “incoming” or “outgoing” serve as another useful guide for discussing possible implications, both in the presumed hydrodynamical expansion stage of heavy-ion collisions and the core-collapse of supernova explosions. Examples, such as the quark-meson model and two-phase models, are shown to distinguish concisely the different transitions.
文摘Using classical density functional theory (DFT) in a modified mean-field approximation we investigate the fluid phase behavior of quasi-two dimensional dipolar fluids confined to a plane. The particles carry three-dimensional dipole moments and interact via a combination of hard-sphere, van-der-Waals, and dipolar interactions. The DFT predicts complex phase behavior involving first- and second-order isotropic-to-ferroelectric transitions, where the ferroelectric ordering is characterized by global polarization within the plane. We compare this phase behavior, particularly the onset of ferroelectric ordering and the related tri-critical points, with corresponding three-dimensional systems, slab-like systems (with finite extension into the third direction), and true two-dimensional systems with two-dimensional dipole moments.
文摘We analyse the proximity effect in hybrid nanoscale junctions involving superconducting leads. We develop a general framework for the analysis of the proximity effect using the same theoretical methods typically employed for the analysis of conductance properties. We apply our method to a normal-superconductor tunnel contact and compare our results to previous results.
文摘We have coupled an upright HG mode into a fiber-optic waveguide and used the application of stress to generate a Laguerre-Gaussian laser mode. We have generalized previous results by McGloin et al. by using a polarized input beam, a true 3-mode fiber and by applying the stress on a stripped piece of the optical waveguide. These generalizations are necessary in order to perform quantum information experiments and obtain reliable information on the stress imposed on the optical fiber.
