In this paper,we review the development of a phase theory for systems and networks in its first five years,represented by a trilogy:Matrix phases and their properties;The MIMO LTI system phase response,its physical in...In this paper,we review the development of a phase theory for systems and networks in its first five years,represented by a trilogy:Matrix phases and their properties;The MIMO LTI system phase response,its physical interpretations,the small phase theorem,and the sectored real lemma;The synchronization of a multi-agent network using phase alignment.Towards the end,we also summarize a list of ongoing research on the phase theory and speculate what will happen in the next five years.展开更多
Lithium metal anode is one of the most important anode materials for next-generation high-specificenergy secondary batteries.Structured lithium metal anodes have received extensive attention in the development of prac...Lithium metal anode is one of the most important anode materials for next-generation high-specificenergy secondary batteries.Structured lithium metal anodes have received extensive attention in the development of practical lithium metal batteries.Methods of driving lithium metal to deposit inside the pores of structured lithium metal anodes have always been one of the most concerned issues,especially for highly conductive frameworks.An electrochemical phase field theory with galvanostatic lithium plating process is employed in this work,the mechanism that illustrates the preference of lithium metal to deposit at the top of the framework structure has been revealed,and through the simulation analysis of various regulating strategies,the strategies that can efficiently drive lithium to deposit inside structured pores are summarized.This work presents the theoretical calculation and analysis methods that can be used for the rational design of lithium metal batteries.展开更多
On basis of the Burgers model, a new model consisting of modified dashpot and Van Der Poel model was derived from rheological and viscoelastic theory. Subsequently, triaxial repeated load permanent deformation tests o...On basis of the Burgers model, a new model consisting of modified dashpot and Van Der Poel model was derived from rheological and viscoelastic theory. Subsequently, triaxial repeated load permanent deformation tests of AC16 asphalt mixtures were conducted to validate this new developed model. Parameters of new developed model were obtained by a nonlinear regression analysis of test data, and then permanent strains and flow number of each mixture were calculated. The experimental results prove that the new developed model can well describe three phases permanent deformation of asphalt mixture under repeated load and it can be used for pavement mechanical analysis and rutting prediction.展开更多
The structural and elastic properties of the recently-discovered wⅡ- and δ-Si3N4 are investigated through the plane-wave pseudo-potential method within ultrasoft pseudopotentials.The elastic constants show that wⅡ-...The structural and elastic properties of the recently-discovered wⅡ- and δ-Si3N4 are investigated through the plane-wave pseudo-potential method within ultrasoft pseudopotentials.The elastic constants show that wⅡ- and δ-Si3N4 are mechanically stable in the pressure ranges of 0-50 GPa and 40-50 GPa,respectively.The α→wⅡ phase transition can be observed at 18.6 GPa and 300 K.The β→δ phase transformation occurs at pressures of 29.6,32.1,35.9,39.6,41.8,and 44.1 GPa when the temperatures are100,200,300,400,500,and 600 K,respectively.The results show that the interactions among the N-2s,Si-3s,3p bands(lower valence band) and the Si-3p,N-2p bands(upper valence band) play an important role in the stabilities of the wⅡ and S phases.Moreover,several thermodynamic parameters(thermal expansion,free energy,bulk modulus and heat capacity) of δ-Si3N4 are also obtained.Some interesting features are found in these properties.δ-Si3N4 is predicted to be a negative thermal expansion material.The adiabatic bulk modulus decreases with applied pressure,but a majority of materials show the opposite trend.Further experimental investigations with higher precisions may be required to determine the fundamental properties of wⅡ- andδ-Si3N4.展开更多
The atomic geometry, structure stability, electronic and magnetic properties of VSe2 were systematically investigated based on the density functional theory(DFT). Varying from 3D to 2D four VSe2 structures, bulk 2H-...The atomic geometry, structure stability, electronic and magnetic properties of VSe2 were systematically investigated based on the density functional theory(DFT). Varying from 3D to 2D four VSe2 structures, bulk 2H-VSe2 and 1T-VSe2, monolayer H-VSe2 and T-VSe2 are all demonstrated as thermodynamically stable by lattice dynamic calculations. More interestingly, the phase transition temperature is dramatically different due to the lattice size. Finally, owing to different crystal structures, H-VSe2 is semimetallic whereas T-VSe2 is totally metallic and also they have different magnetic moments. Our main argument is that being exfoliated from bulk to monolayer, 2H-VSe2 transforms to T-VSe2, accompanied by both semimetallic-metallic transition and dramatic magnetic moment variation. Our calculations provide a novel structure phase transition and an efficient way to modulate the electronic structure and magnetic moment of layered VSe2, which suggests potential applications as high-performance functional nanomaterial.展开更多
With the developing of the computer, the network is more and more liked by the users. It has become an indispensable part of the living and production. However, with the expanding of network scale, there have been som...With the developing of the computer, the network is more and more liked by the users. It has become an indispensable part of the living and production. However, with the expanding of network scale, there have been some problems in the operation of the network system. Most of people lack of understanding on these issues, so they couldn' t handle them well. Some people use the theory of phase transitions to explain the power law phenomena in computer network. But it only start from the theory, but ignores the correlation of network nodes. The lack of holistic thinking mode, make the development of computer network get into a stray area. This paper started from the phase transition theory, elaborated the connotations of phase transformation and the overall correlation, and described the problems about them.展开更多
Based on Presnel-Kirchhoff diffraction theory, we set up a diffraction model of nonlinear optical media to Gaussian beam, which can interpret the Z-scan phenomenon from a new way. This theory is not only well consiste...Based on Presnel-Kirchhoff diffraction theory, we set up a diffraction model of nonlinear optical media to Gaussian beam, which can interpret the Z-scan phenomenon from a new way. This theory is not only well consistent with the conventional Z-scan theory in the case of small nonlinear phase shift, but also can fit for the lager nonlinear phase shift. Numeric computations indicate the shape of the Z-scan curve is greatly affected by the value of the nonlinear phase shift. The symmetric dispersion-like Z-scan curve is only valid for small nonlinear phase shift (|Δφ0| < π), but with increasing the nonlinear phase shift, the valley of the transmittance is severely suppressed and the peak is greatly enhanced. Further calculations show some new interesting results.展开更多
The research reviewed the development trend of vertical greening industry and divided it into four stages as follows: demand exploring phase, theory and technology development and application phases, and ripening pha...The research reviewed the development trend of vertical greening industry and divided it into four stages as follows: demand exploring phase, theory and technology development and application phases, and ripening phase of vertical greening system. The characteristics in different phases were detailed, providing ref- erences for development of vertical greening industry in future.展开更多
The constitutive equation for a semiconcentrated fibre suspension in the Oldroyd-B fluid has been derived from a statistical model of such a suspension by employing the molecular theory for polymeric liquids.To circum...The constitutive equation for a semiconcentrated fibre suspension in the Oldroyd-B fluid has been derived from a statistical model of such a suspension by employing the molecular theory for polymeric liquids.To circumvent theoretical difficulties in viscoelastic fluid mechanics,several simplified models are used to account for the interactions of fibres and polymer molecules.Some of material functions are calculated in terms of the constitutive equation.展开更多
Based on the phase field theory, the phase precipitation sequence of Ni75A110Cr15 alloy and the free energy of each phase were studied. Moreover, the interatomic potentials of Llo phase, L12 phase and DO22 phase chang...Based on the phase field theory, the phase precipitation sequence of Ni75A110Cr15 alloy and the free energy of each phase were studied. Moreover, the interatomic potentials of Llo phase, L12 phase and DO22 phase changing with temperature and concen- trations were computed through utilizing the interatomic potentials equations induced by Khachaturyan's relational equations between the interatomic potentials and the long-range order (LRO) parameters. Results match preceding work and demonstrate that the phase precipitation sequence of Ni75AlloCr15 alloy is the disordered phase -L10 pre-precipitation phase -L12 equilibrium phase -L12+DO22 equilibrium phase. Free energies of Llo pre-precipitation phase are higher and interatomic potentials are smaller than those of L12 equilibrium phase; therefore, it is concluded that Llo phase is unstable, and phase transformation would occur to L12 which is more stable; L12 phase precipitates earlier than DO22 phase because L12's interaction potentials are larger than DO22's.展开更多
OBJECTIVE:To study the Chinese ancient five-element theory,one of the philosophical foundations of Traditional Chinese Medicine(TCM)theory construction,from the perspective of comtemporary cognitive science,and to rev...OBJECTIVE:To study the Chinese ancient five-element theory,one of the philosophical foundations of Traditional Chinese Medicine(TCM)theory construction,from the perspective of comtemporary cognitive science,and to reveal the important functions of five-element theory in the construction of TCM theory.METHODS:The basic effects of five-element theory in the construction of TCM theory are intensively expounded and proved from the following aspects:embodiment of five-element theory in cognizing the world,quasi axiom of five-element theory in essence,classification thery of family resemblance and deductive inference pattern of five-element theory,and the openness and expansibility of five-element theory.RESULTS:If five-element theory is considered acognitive pattern or cognitive system related to culture,then there should be features of cognitive embodiment in the cognitive system.If five-element theory is regarded as a symbolic system,however,then there should be a quasi-axiom for the system,and inferential deduction.If,however,five-element theory is taken as a theoretical constructive metaphor,then there should be features of opening and expansibility for the metaphor.CONCLUSION:Based on five-element theory,this study provides a cognitive frame for the construction of TCM(a medicine that originated in China,and is characterized by holism and treatment based on pattern identification differentiation)theory with the function of constructing a concept base,thereby implying further research strategies.Useful information may be produced from the creative inferences obtained from the incorporation of five-element theory.展开更多
We apply the derivative coupling model with ZM and ZM3 parameters to investigate the longitudinal response function in quasielastic electron scattering in the relativistic random phase approximation. The non-spectral ...We apply the derivative coupling model with ZM and ZM3 parameters to investigate the longitudinal response function in quasielastic electron scattering in the relativistic random phase approximation. The non-spectral method is chosen to describe the nucleon Green's function in a finite nucleus. Some remarks have been made in conclusion.展开更多
Environmental impact assessment(EIA)system has been established in China since 1973.In present EIA cases,there are four participants in general:governments,enterprises,EIA organizations and the public.The public has h...Environmental impact assessment(EIA)system has been established in China since 1973.In present EIA cases,there are four participants in general:governments,enterprises,EIA organizations and the public.The public has held responsible for both social costs and social duties.The public supervises social costs produced by enterprises discharging pollutant in EIA.However public participation is mostly deputized by governments,which severely weaken the independence of the public as one participant in EIA.In this paper,EIA refers to the different attitudes of the par-ticipants whose optional strategies may be described by a proper game model.According to disfigurements in EIA,three sides(governments,enterprises,and EIA organizations)dynamic iterative game theory of many phases is established referring to iterative game theory,dynamic game theory of incomplete information,and perfect Bayesian equilibrium theory to analyze the reciprocity relation among governments,EIA organizations and enterprises.The results show that in a short period,economic benefit is preponderant over social benefit.Governments and enterprises both do not want to take EIA to reveal social costs.EIA organizations’income comes from enterprises and the collusions are built between them to vindicate economic benefit.In a long run,social benefit loss caused by environmental pollution must be recuperated sooner or later and environmental deterioration will influence the achievements of economic benefit,so both governments and enterprises are certain to pursue high social benefit and willing to take EIA,helpful to increase private benefit.EIA organizations will make fair assessment when their economic benefit are ensured.At present,the public as silent victims can not take actual part in EIA.The EIA system must be improved to break the present equilibrium of three sides,bringing the public to the equilibrium to exert public supervision.展开更多
As a single-phase multiferroic material, Fe3O4 exhibits spontaneous ferroelectric polarization below 38 K. However, the nature of the ferroelectricity in Fe3O4and effect of external disturbances such as strain on it r...As a single-phase multiferroic material, Fe3O4 exhibits spontaneous ferroelectric polarization below 38 K. However, the nature of the ferroelectricity in Fe3O4and effect of external disturbances such as strain on it remains ambiguous. Here, the spontaneous ferroelectric polarization of low-temperature mon- oclinic Fe3O4 was investigated by first-principles calculations. The pseudo-centrosymmetric FeB42- FEB43 pair has a different valence state. The noncentrosymmetric charge distribution results in fer- roelectric polarization. The initial ferroelectric polarization direction is in the -x and -z directions. The ferroelectricity along the y axis is limited owing to the symmetry of the Cc space group. Both the ionic displacement and charge separation at the FeB42-FeB43 pair are affected by strain, which further influences the spontaneous ferroelectric polarization of monoclinic Fe3O4. The ferroelectric polarization along the z axis exhibits an increase of 45.3% as the strain changes from 6% to -6%.展开更多
Today, large quantities of vehicle data(FCD:floating car data) are widely used by traffic service providers to create and broadcast traffic states in road networks. As a first processing step, all raw position data re...Today, large quantities of vehicle data(FCD:floating car data) are widely used by traffic service providers to create and broadcast traffic states in road networks. As a first processing step, all raw position data received from Global Positioning Systems(GPS) have to be map matched in a digital road map. The technical aspects of such a matching process for GPS data are described in this report. After the matching process, spacetime-diagrams are created of the probe data showing traffic situation details over space and time. Various examples illustrate how traffic service quality depends on the number of matched GPS raw data; it will be stated that when 2% of connected vehicles in the total traffic flow are sending their GPS data in shorter time intervals, a high quality and precise reconstruction of the current traffic phases is achieved. Traffic reconstruction is followed by a translation into traffic information messages, which can be sent and used in vehicle navigation systems for driver information and dynamic route guidance.展开更多
基金supported in part by the National Natural Science Foundation of China(62073003,72131001)Hong Hong Research Grants Council under GRF grants(16200619,16201120,16205421,1620-3922)Shenzhen-Hong Kong-Macao Science and Technology Innovation Fund(SGDX20201103094600006)。
文摘In this paper,we review the development of a phase theory for systems and networks in its first five years,represented by a trilogy:Matrix phases and their properties;The MIMO LTI system phase response,its physical interpretations,the small phase theorem,and the sectored real lemma;The synchronization of a multi-agent network using phase alignment.Towards the end,we also summarize a list of ongoing research on the phase theory and speculate what will happen in the next five years.
基金supported by Beijing Natural Science Foundation(JQ20004)National Key Research and Development Program(2021YFB2400300)+1 种基金National Natural Scientific Foundation of China(22109011)the China Postdoctoral Science Foundation(BX20200047,2021M690380)。
文摘Lithium metal anode is one of the most important anode materials for next-generation high-specificenergy secondary batteries.Structured lithium metal anodes have received extensive attention in the development of practical lithium metal batteries.Methods of driving lithium metal to deposit inside the pores of structured lithium metal anodes have always been one of the most concerned issues,especially for highly conductive frameworks.An electrochemical phase field theory with galvanostatic lithium plating process is employed in this work,the mechanism that illustrates the preference of lithium metal to deposit at the top of the framework structure has been revealed,and through the simulation analysis of various regulating strategies,the strategies that can efficiently drive lithium to deposit inside structured pores are summarized.This work presents the theoretical calculation and analysis methods that can be used for the rational design of lithium metal batteries.
基金Funded by the National Natural Science Foundation of China (No.50878054)
文摘On basis of the Burgers model, a new model consisting of modified dashpot and Van Der Poel model was derived from rheological and viscoelastic theory. Subsequently, triaxial repeated load permanent deformation tests of AC16 asphalt mixtures were conducted to validate this new developed model. Parameters of new developed model were obtained by a nonlinear regression analysis of test data, and then permanent strains and flow number of each mixture were calculated. The experimental results prove that the new developed model can well describe three phases permanent deformation of asphalt mixture under repeated load and it can be used for pavement mechanical analysis and rutting prediction.
基金Funded by National Natural Science Foundation of China(Nos.61475132,61501392,11475143,11304141)the National Training Programs of Innovation and Entrepreneurship for Undergraduates(No.201510477001)
文摘The structural and elastic properties of the recently-discovered wⅡ- and δ-Si3N4 are investigated through the plane-wave pseudo-potential method within ultrasoft pseudopotentials.The elastic constants show that wⅡ- and δ-Si3N4 are mechanically stable in the pressure ranges of 0-50 GPa and 40-50 GPa,respectively.The α→wⅡ phase transition can be observed at 18.6 GPa and 300 K.The β→δ phase transformation occurs at pressures of 29.6,32.1,35.9,39.6,41.8,and 44.1 GPa when the temperatures are100,200,300,400,500,and 600 K,respectively.The results show that the interactions among the N-2s,Si-3s,3p bands(lower valence band) and the Si-3p,N-2p bands(upper valence band) play an important role in the stabilities of the wⅡ and S phases.Moreover,several thermodynamic parameters(thermal expansion,free energy,bulk modulus and heat capacity) of δ-Si3N4 are also obtained.Some interesting features are found in these properties.δ-Si3N4 is predicted to be a negative thermal expansion material.The adiabatic bulk modulus decreases with applied pressure,but a majority of materials show the opposite trend.Further experimental investigations with higher precisions may be required to determine the fundamental properties of wⅡ- andδ-Si3N4.
基金Funded by the National Natural Science Foundation of China(No.11547115)the Science Research Foundation for Ph D of Liaoning Province(No.201501091)
文摘The atomic geometry, structure stability, electronic and magnetic properties of VSe2 were systematically investigated based on the density functional theory(DFT). Varying from 3D to 2D four VSe2 structures, bulk 2H-VSe2 and 1T-VSe2, monolayer H-VSe2 and T-VSe2 are all demonstrated as thermodynamically stable by lattice dynamic calculations. More interestingly, the phase transition temperature is dramatically different due to the lattice size. Finally, owing to different crystal structures, H-VSe2 is semimetallic whereas T-VSe2 is totally metallic and also they have different magnetic moments. Our main argument is that being exfoliated from bulk to monolayer, 2H-VSe2 transforms to T-VSe2, accompanied by both semimetallic-metallic transition and dramatic magnetic moment variation. Our calculations provide a novel structure phase transition and an efficient way to modulate the electronic structure and magnetic moment of layered VSe2, which suggests potential applications as high-performance functional nanomaterial.
文摘With the developing of the computer, the network is more and more liked by the users. It has become an indispensable part of the living and production. However, with the expanding of network scale, there have been some problems in the operation of the network system. Most of people lack of understanding on these issues, so they couldn' t handle them well. Some people use the theory of phase transitions to explain the power law phenomena in computer network. But it only start from the theory, but ignores the correlation of network nodes. The lack of holistic thinking mode, make the development of computer network get into a stray area. This paper started from the phase transition theory, elaborated the connotations of phase transformation and the overall correlation, and described the problems about them.
基金This work was supported by the National Natural Science Foundation of China under Grant No. 60007009 the President Foundation of Chinese Academy of Sciences under Grant No. 40007059.
文摘Based on Presnel-Kirchhoff diffraction theory, we set up a diffraction model of nonlinear optical media to Gaussian beam, which can interpret the Z-scan phenomenon from a new way. This theory is not only well consistent with the conventional Z-scan theory in the case of small nonlinear phase shift, but also can fit for the lager nonlinear phase shift. Numeric computations indicate the shape of the Z-scan curve is greatly affected by the value of the nonlinear phase shift. The symmetric dispersion-like Z-scan curve is only valid for small nonlinear phase shift (|Δφ0| < π), but with increasing the nonlinear phase shift, the valley of the transmittance is severely suppressed and the peak is greatly enhanced. Further calculations show some new interesting results.
基金Supported by Shenzhen Urban Management Science Research Fund(201208-1)~~
文摘The research reviewed the development trend of vertical greening industry and divided it into four stages as follows: demand exploring phase, theory and technology development and application phases, and ripening phase of vertical greening system. The characteristics in different phases were detailed, providing ref- erences for development of vertical greening industry in future.
基金The project Supported by the University of Melbourne of Australia,the National Natural Scicnce Foundation of China and Zhejiang Province
文摘The constitutive equation for a semiconcentrated fibre suspension in the Oldroyd-B fluid has been derived from a statistical model of such a suspension by employing the molecular theory for polymeric liquids.To circumvent theoretical difficulties in viscoelastic fluid mechanics,several simplified models are used to account for the interactions of fibres and polymer molecules.Some of material functions are calculated in terms of the constitutive equation.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10902086, 51075335 and 50875217)the Basic Re-search Fund of the Northwestern Polytechnical University (Grant No. JC201005)the Doctoral Foundation of Northwestern Polytechnical University (Grant No. CX201103)
文摘Based on the phase field theory, the phase precipitation sequence of Ni75A110Cr15 alloy and the free energy of each phase were studied. Moreover, the interatomic potentials of Llo phase, L12 phase and DO22 phase changing with temperature and concen- trations were computed through utilizing the interatomic potentials equations induced by Khachaturyan's relational equations between the interatomic potentials and the long-range order (LRO) parameters. Results match preceding work and demonstrate that the phase precipitation sequence of Ni75AlloCr15 alloy is the disordered phase -L10 pre-precipitation phase -L12 equilibrium phase -L12+DO22 equilibrium phase. Free energies of Llo pre-precipitation phase are higher and interatomic potentials are smaller than those of L12 equilibrium phase; therefore, it is concluded that Llo phase is unstable, and phase transformation would occur to L12 which is more stable; L12 phase precipitates earlier than DO22 phase because L12's interaction potentials are larger than DO22's.
基金Supported by the Natural Science Foundation of China(No.30973971,No.81173464)Doctoral Fund of the Ministry of Education of China(No.20090013110012)
文摘OBJECTIVE:To study the Chinese ancient five-element theory,one of the philosophical foundations of Traditional Chinese Medicine(TCM)theory construction,from the perspective of comtemporary cognitive science,and to reveal the important functions of five-element theory in the construction of TCM theory.METHODS:The basic effects of five-element theory in the construction of TCM theory are intensively expounded and proved from the following aspects:embodiment of five-element theory in cognizing the world,quasi axiom of five-element theory in essence,classification thery of family resemblance and deductive inference pattern of five-element theory,and the openness and expansibility of five-element theory.RESULTS:If five-element theory is considered acognitive pattern or cognitive system related to culture,then there should be features of cognitive embodiment in the cognitive system.If five-element theory is regarded as a symbolic system,however,then there should be a quasi-axiom for the system,and inferential deduction.If,however,five-element theory is taken as a theoretical constructive metaphor,then there should be features of opening and expansibility for the metaphor.CONCLUSION:Based on five-element theory,this study provides a cognitive frame for the construction of TCM(a medicine that originated in China,and is characterized by holism and treatment based on pattern identification differentiation)theory with the function of constructing a concept base,thereby implying further research strategies.Useful information may be produced from the creative inferences obtained from the incorporation of five-element theory.
基金Supported by National Basic Research Program of China (2009CB824800)National Natural Science Foundation of China (11103001)+1 种基金Hunan Provincial Natural Science Foundation of China (11JJ3006)Research Grants of Changsha University of Science and Technology,the Construct Program of the Key Discipline in Hunan Province and Aid Program for Science and Technology Innovative Research Team in Higher Educational Institute of Hunan Province
文摘We apply the derivative coupling model with ZM and ZM3 parameters to investigate the longitudinal response function in quasielastic electron scattering in the relativistic random phase approximation. The non-spectral method is chosen to describe the nucleon Green's function in a finite nucleus. Some remarks have been made in conclusion.
文摘Environmental impact assessment(EIA)system has been established in China since 1973.In present EIA cases,there are four participants in general:governments,enterprises,EIA organizations and the public.The public has held responsible for both social costs and social duties.The public supervises social costs produced by enterprises discharging pollutant in EIA.However public participation is mostly deputized by governments,which severely weaken the independence of the public as one participant in EIA.In this paper,EIA refers to the different attitudes of the par-ticipants whose optional strategies may be described by a proper game model.According to disfigurements in EIA,three sides(governments,enterprises,and EIA organizations)dynamic iterative game theory of many phases is established referring to iterative game theory,dynamic game theory of incomplete information,and perfect Bayesian equilibrium theory to analyze the reciprocity relation among governments,EIA organizations and enterprises.The results show that in a short period,economic benefit is preponderant over social benefit.Governments and enterprises both do not want to take EIA to reveal social costs.EIA organizations’income comes from enterprises and the collusions are built between them to vindicate economic benefit.In a long run,social benefit loss caused by environmental pollution must be recuperated sooner or later and environmental deterioration will influence the achievements of economic benefit,so both governments and enterprises are certain to pursue high social benefit and willing to take EIA,helpful to increase private benefit.EIA organizations will make fair assessment when their economic benefit are ensured.At present,the public as silent victims can not take actual part in EIA.The EIA system must be improved to break the present equilibrium of three sides,bringing the public to the equilibrium to exert public supervision.
基金This work was supported by the National Natural Science Foundation of China (Grant Nos. 51671142 and U1632152) and the Key Project of the Natural Science Foundation of Tianjin City (Grant No. 16JCZDJC37300).
文摘As a single-phase multiferroic material, Fe3O4 exhibits spontaneous ferroelectric polarization below 38 K. However, the nature of the ferroelectricity in Fe3O4and effect of external disturbances such as strain on it remains ambiguous. Here, the spontaneous ferroelectric polarization of low-temperature mon- oclinic Fe3O4 was investigated by first-principles calculations. The pseudo-centrosymmetric FeB42- FEB43 pair has a different valence state. The noncentrosymmetric charge distribution results in fer- roelectric polarization. The initial ferroelectric polarization direction is in the -x and -z directions. The ferroelectricity along the y axis is limited owing to the symmetry of the Cc space group. Both the ionic displacement and charge separation at the FeB42-FeB43 pair are affected by strain, which further influences the spontaneous ferroelectric polarization of monoclinic Fe3O4. The ferroelectric polarization along the z axis exhibits an increase of 45.3% as the strain changes from 6% to -6%.
文摘Today, large quantities of vehicle data(FCD:floating car data) are widely used by traffic service providers to create and broadcast traffic states in road networks. As a first processing step, all raw position data received from Global Positioning Systems(GPS) have to be map matched in a digital road map. The technical aspects of such a matching process for GPS data are described in this report. After the matching process, spacetime-diagrams are created of the probe data showing traffic situation details over space and time. Various examples illustrate how traffic service quality depends on the number of matched GPS raw data; it will be stated that when 2% of connected vehicles in the total traffic flow are sending their GPS data in shorter time intervals, a high quality and precise reconstruction of the current traffic phases is achieved. Traffic reconstruction is followed by a translation into traffic information messages, which can be sent and used in vehicle navigation systems for driver information and dynamic route guidance.