In this article, by using theory of linear evolution system and Schauder fixed point theorem, we establish a sufficient result of exact null controllability for a non-autonomous functional evolution system with nonloc...In this article, by using theory of linear evolution system and Schauder fixed point theorem, we establish a sufficient result of exact null controllability for a non-autonomous functional evolution system with nonlocal conditions. In particular, the compactness condition or Lipschitz condition for the function g in the nonlocal conditions appearing in various literatures is not required here. An example is also provided to show an application of the obtained result.展开更多
A new algorithm for symbolic computation of polynomial-type conserved densities for nonlinear evolution systems is presented. The algorithm is implemented in Maple. The improved algorithm is more efficient not only in...A new algorithm for symbolic computation of polynomial-type conserved densities for nonlinear evolution systems is presented. The algorithm is implemented in Maple. The improved algorithm is more efficient not only in removing the redundant terms of the genera/form of the conserved densities but also in solving the conserved densities with the associated flux synchronously without using Euler operator. Furthermore, the program conslaw.mpl can be used to determine the preferences for a given parameterized nonlinear evolution systems. The code is tested on several well-known nonlinear evolution equations from the soliton theory.展开更多
This paper first develops a Lyapunov-type theorem to study global well-posedness(existence and uniqueness of the strong variational solution)and asymptotic stability in probability of nonlinear stochastic evolution sy...This paper first develops a Lyapunov-type theorem to study global well-posedness(existence and uniqueness of the strong variational solution)and asymptotic stability in probability of nonlinear stochastic evolution systems(SESs)driven by a special class of Levy processes,which consist of Wiener and compensated Poisson processes.This theorem is then utilized to develop an approach to solve an inverse optimal stabilization problem for SESs driven by Levy processes.The inverse optimal control design achieves global well-posedness and global asymptotic stability of the closed-loop system,and minimizes a meaningful cost functional that penalizes both states and control.The approach does not require to solve a Hamilton-Jacobi-Bellman equation(HJBE).An optimal stabilization of the evolution of the frequency of a certain genetic character from the population is included to illustrate the theoretical developments.展开更多
This paper is concerned with the existence and the nonlinear asymptotic stabil- ity of traveling wave solutions to the Cauchy problem for a system of dissipative evolution equations {θt=vζx＋（ζθ）x＋aθxx,ζt=-θ...This paper is concerned with the existence and the nonlinear asymptotic stabil- ity of traveling wave solutions to the Cauchy problem for a system of dissipative evolution equations {θt=vζx＋（ζθ）x＋aθxx,ζt=-θx＋βζxx;with initial data and end states （ζθ）（x,0）=（ζ0,θ0）（x）→（ζ±,θ±）as x→∞.We obtain the existence of traveling wave solutions by phase plane analysis and show the asymptotic nonlinear stability of traveling wave solutions without restrictions on the coeffi- cients a and v by the method of energy estimates.展开更多
An optimal(practical) stabilization problem is formulated in an inverse approach and solved for nonlinear evolution systems in Hilbert spaces. The optimal control design ensures global well-posedness and global practi...An optimal(practical) stabilization problem is formulated in an inverse approach and solved for nonlinear evolution systems in Hilbert spaces. The optimal control design ensures global well-posedness and global practical K∞-exponential stability of the closed-loop system, minimizes a cost functional,which appropriately penalizes both state and control in the sense that it is positive definite(and radially unbounded) in the state and control, without having to solve a Hamilton-Jacobi-Belman equation(HJBE). The Lyapunov functional used in the control design explicitly solves a family of HJBEs. The results are applied to design inverse optimal boundary stabilization control laws for extensible and shearable slender beams governed by fully nonlinear partial differential equations.展开更多
A complex system is inherently high-dimensional.Recent studies indicate that,even without complete knowledge of its evolutionary dynamics,the future behavior of such a system can be predicted using time-series data(da...A complex system is inherently high-dimensional.Recent studies indicate that,even without complete knowledge of its evolutionary dynamics,the future behavior of such a system can be predicted using time-series data(data-driven prediction).This suggests that the essential dynamics of a complex system can be captured through a low-dimensional representation.Virus evolution and climate change are two examples of complex,time-varying systems.In this article,we show that mutations in the spike protein provide valuable data for predicting SARS-CoV-2 variants,forecasting the possible emergence of the new macro-lineage Q in the near future.Our analysis also demonstrates that carbon dioxide concentration is a reliable indicator for predicting the evolution of the climate system,extending global surface air temperature(GSAT)forecasts through 2500.展开更多
Amid ongoing global environmental change and the critical pursuit of sustainable development,human-environment systems are exhibiting increasingly complex dynamic evolutions and spatial relationships,underscoring an u...Amid ongoing global environmental change and the critical pursuit of sustainable development,human-environment systems are exhibiting increasingly complex dynamic evolutions and spatial relationships,underscoring an urgent need for innovative research frameworks.Integrated geography synthesizes physical geography,human geography,and geographic information science,providing key frameworks for understanding complex human-environment systems.This editorial proposes an emerging research framework for integrated geography—“Composite driving-System evolution-Coupling mechanism-Synergistic regulation(CSCS)”—based on key issues such as climate change,biodiversity loss,resource scarcity,and social-ecological interactions,which have been highlighted in both recent critical literature on human-environment systems and UN assessment reports.The framework starts with diverse composite driving forces,extends to the evolution of human-environment system structures,processes,and functions that these drivers induce,explores couplings within human-environment systems,and calls for regulation aimed at sustainable development in synergies.Major research frontiers include understanding the cascading“evolution-coupling”effects of shocks;measuring system resilience,thresholds,and safe and just operating space boundaries;clarifying linkage mechanisms across scales;and achieving synergistic outcomes for multi-objective sustainability.This framework will help promote the interdisciplinary integration and development of integrated geography,and provide geographical solutions for the global sustainable development agenda.展开更多
The Longmenshan structural belt on the eastern edge of the Tibetan Plateau experienced the impactful Mw7.92008 Wenchuan Earthquake,causing a 350 km surface rupture.Traditional models attribute this to the Beichuan and...The Longmenshan structural belt on the eastern edge of the Tibetan Plateau experienced the impactful Mw7.92008 Wenchuan Earthquake,causing a 350 km surface rupture.Traditional models attribute this to the Beichuan and Pengguan faults,but our research reveals a complex fault system at the northern end,with inconsistencies in surface rupture,aftershock distribution,and focal mechanisms.We integrate shallow geology,active source seismic reflection,and magnetotelluric profiling to establish a deep structural model for the northern end of the Longmenshan structural belt.This area exhibits dominant reverse thrust nappe tectonics,and analyzing the tectonic evolution history provides insights into deformation propagation from the orogenic belt toward the Sichuan Basin.Focal mechanism analysis and relocated aftershock data reveals two distinct types of seismogenic structures in the northern end of the Longmenshan structural belt.In the middle to northern segments,the reverse fault type is attributed to reactivated pre-existing faults.Conversely,at the northern end,the strike-slip fault type originates from high-angle co-seismic rupture cutting through pre-existing reverse faults.This study enhances our understanding of fault complexity and seismic mechanisms in the northeastern Longmenshan structural belt,providing new insights into regional tectonics.展开更多
High-performance 24CrNiMo steel was fabricated using Laser Powder Bed Fusion (LPBF). Subsequent quenching treatment was applied and the influence of quenching temperatures on micro-structure evolution and properties w...High-performance 24CrNiMo steel was fabricated using Laser Powder Bed Fusion (LPBF). Subsequent quenching treatment was applied and the influence of quenching temperatures on micro-structure evolution and properties was systematically characterised and analysed. The micro-structure of the as-built steel consisted of two parts. The first part comprised martensite with twins combined with ω-Fe nano-particles, and the second part consisted of lower bainite in the molten pool, as well as upper bainite, granular bainite and tempered martensite in the heat-affected zone. With the quenching temperatures varying from 800℃ to 950℃, the micro-structure gradually transformed from acicular ferrite + martensite to tempered martensite +θ-Fe3C carbides, and the grain size exhibited noticeable growth. Moreover, quenching treatments could eliminate the anisotropy and inhomogeneity of the micro-structure. The rod-shaped nanosized η-Fe2C and θ-Fe3C precipitates were clearly observed, which were converted from ω-Fe and distributed at multiple angles in the lath. The size and number of nano-precipitates, triggered by the high self-tempering degree of martensite, gradually increased. The relationships among grain size, the twins, dislocation density and nano-precipitation and the dramatically improved performance of quenched samples were analysed using strengthening mechanisms. After quenching at 850℃, the as-built 24CrNiMo steel attained ultra-high mechanical properties including hardness, Ultimate Tensile Strength (UTS), Elongation (El) and impact energy with values of 480.9 HV_(1), 1611.4 MPa, 9.8% and 42.8 J, respectively. Meanwhile, both the wear and thermal fatigue resistance increased by approximately 40%. This study demonstrated that LPBF-fabricated 24CrNiMo steel, with matching good performances, can be achieved using a subsequent one-step quenching process.展开更多
The protection system for traditional Chinese medicine(TCM)varieties,as an important policy tool to promote the development of TCM,has a long history of over 30 years,from the promulgation of the“Regulations on the P...The protection system for traditional Chinese medicine(TCM)varieties,as an important policy tool to promote the development of TCM,has a long history of over 30 years,from the promulgation of the“Regulations on the Protection of Traditional Chinese Medicine Varieties”in 1992 to the comprehensive revision of the draft for soliciting opinions in 2022.The TCM protection system evolves to meet the needs of innovative development of TCM.This paper reviews the policy developments in TCM varieties protection,collates protection data(1993 to 2024),and analyzes enterprises application strategies amid impending regulatory changes.展开更多
Spark plasma sintering method （SPS） was used to consolidate mixed W-5.6Ni-1.4Fe （mass fraction, %） powders from commercial fine elemental powders, and both the densification behavior and microstructure evolution i...Spark plasma sintering method （SPS） was used to consolidate mixed W-5.6Ni-1.4Fe （mass fraction, %） powders from commercial fine elemental powders, and both the densification behavior and microstructure evolution in sintering were investigated at different heating rates. The results show that the SPS densification process can be divided into three stages. At the initial unshrinking stage, fast heating generates instantaneous discharge and locally inhomogeneous temperature distribution in solid-state powder particles, enhancing later densification; during the intermediate solid state sintering stage, diffusion is more sufficient in the slow-heated SPS process; at the final transient liquid-phase sintering stage, tungsten grains become sphered and coarsen rapidly, but fast heating helps maintain rather small grain sizes.展开更多
The metabolic evolution model of transportation demand for comprehensive transportation systems is put forward on the basis of a metabolic theory of ecology. In the model, the growth rates or changing rates of transpo...The metabolic evolution model of transportation demand for comprehensive transportation systems is put forward on the basis of a metabolic theory of ecology. In the model, the growth rates or changing rates of transportation volumes for the various transportation modes of a city are determined not only by the GDP per capita which reflects the size of the city itself, but also by the relationship of competition and cooperation among transportation modes. The results of empirical analysis for Chinese cities show that the allometric growth exponent in the equation for the variation rate of passenger demand volume on rail is greater than the predicted value of 1/4 in metabolic ecology, whereas the allometric growth relationship is not so evident in the equation for the variation rate of passenger demand volume on road. The changing rate of road transportation is thus mainly affected by the relationship of competition and cooperation among transportation modes for Chinese cities.展开更多
The limiting behavior of stochastic evolution processes with small noise intensityεis investigated in distribution-based approaches.Letμεbe a stationary measure for stochastic process Xεwith smallεand X0 be a sem...The limiting behavior of stochastic evolution processes with small noise intensityεis investigated in distribution-based approaches.Letμεbe a stationary measure for stochastic process Xεwith smallεand X0 be a semiflow on a Polish space.Assume that{με:0<ε≤ε0}is tight.Then all their limits in the weak sense are X0-invariant and their supports are contained in the Birkhoff center of X0.Applications are made to various stochastic evolution systems,including stochastic ordinary differential equations,stochastic partial differential equations,and stochastic functional differential equations driven by Brownian motion or Levy processes.展开更多
Impulse observability and impulse controllability of regular degenerate evolution systems are discussed by using functional analysis and operator theory in Banach space. Necessary and sufficient conditions for the imp...Impulse observability and impulse controllability of regular degenerate evolution systems are discussed by using functional analysis and operator theory in Banach space. Necessary and sufficient conditions for the impulse observability and impulse controllability of the system are obtained. This research is theoretically important for studying the design of the degenerate evolution system.展开更多
The existence and uniqueness of a strong periodic solution of the evolution system describing geophysical flow in bounded domains of RN (N = 3, 4) are proven if external forces are periodic in time and sufficiently sm...The existence and uniqueness of a strong periodic solution of the evolution system describing geophysical flow in bounded domains of RN (N = 3, 4) are proven if external forces are periodic in time and sufficiently small.展开更多
In this paper, firstly, we study the local existence and uniqueness of mild solutions for fractional evolution systems with nonlocal in time nonlinearity. Then, we claim that such a mild solution is weak solution of t...In this paper, firstly, we study the local existence and uniqueness of mild solutions for fractional evolution systems with nonlocal in time nonlinearity. Then, we claim that such a mild solution is weak solution of this system. Finally, we prove a blow-up result under some conditions.展开更多
The phylogenetic relationships of four species,Bufo melanostictus,Hyla chinensis,Rana limnocharis and Rana guentheri,which belong to three differrent families of Anura,were detected with RAPD technique.The genomic DNA...The phylogenetic relationships of four species,Bufo melanostictus,Hyla chinensis,Rana limnocharis and Rana guentheri,which belong to three differrent families of Anura,were detected with RAPD technique.The genomic DNA of each species was amplified with 19 random primers.16 primers given clear amplified bands were used for analysis and the genetic distances between four species were calculated.The results show that RAPD bands obtained by all 16 primers evinced different degree polymorphisms.The genetic distance between R.limnocharis and R.guentheri is the nearest,that between B.melanostictus and H.chinensis is the second nearest,and that between B.melanostictus and R.guentheri is the furthest.The different distances also indicated that the relationship between Bufoidae and Hylidae is closer than that between Bufonidae and Ranidae at genomic DNA level.In concordant with the conclusion of the morphology,chromosomal and mitochondrial DNA studies,our results provide a new evidence of the systematic evolution of the three families of Anura at DNA molecular level.展开更多
Due to the immaturity of practice and the increasing complexity of system of system (SoS). It is necessary to develop systematic methodologies that enable evolution of such systems. This paper presents a prototype d...Due to the immaturity of practice and the increasing complexity of system of system (SoS). It is necessary to develop systematic methodologies that enable evolution of such systems. This paper presents a prototype design for a synthetic system evolution environment (SEE). It outlines the purpose of the environment, describes its concept of operations, details its main functions and processes in utilizing the system architecture knowledge for systems evolution, and introduces its initial high level architecture design.In addition, it also documents the approach for developing the environment.展开更多
In this paper,the long time behaviors of non-autonomous evolution system describing geophysical flow within the earth are studied.The uniqueness and existence of the solution to the evolution system and the existence ...In this paper,the long time behaviors of non-autonomous evolution system describing geophysical flow within the earth are studied.The uniqueness and existence of the solution to the evolution system and the existence of uniform attractor are proven.Moreover,the upper bounds of the uniform attractor's hausdorff and Fractal dimensions are obtained.展开更多
基金supported by NSF of China (11171110)Shanghai Leading Academic Discipline Project (B407)
文摘In this article, by using theory of linear evolution system and Schauder fixed point theorem, we establish a sufficient result of exact null controllability for a non-autonomous functional evolution system with nonlocal conditions. In particular, the compactness condition or Lipschitz condition for the function g in the nonlocal conditions appearing in various literatures is not required here. An example is also provided to show an application of the obtained result.
文摘A new algorithm for symbolic computation of polynomial-type conserved densities for nonlinear evolution systems is presented. The algorithm is implemented in Maple. The improved algorithm is more efficient not only in removing the redundant terms of the genera/form of the conserved densities but also in solving the conserved densities with the associated flux synchronously without using Euler operator. Furthermore, the program conslaw.mpl can be used to determine the preferences for a given parameterized nonlinear evolution systems. The code is tested on several well-known nonlinear evolution equations from the soliton theory.
文摘This paper first develops a Lyapunov-type theorem to study global well-posedness(existence and uniqueness of the strong variational solution)and asymptotic stability in probability of nonlinear stochastic evolution systems(SESs)driven by a special class of Levy processes,which consist of Wiener and compensated Poisson processes.This theorem is then utilized to develop an approach to solve an inverse optimal stabilization problem for SESs driven by Levy processes.The inverse optimal control design achieves global well-posedness and global asymptotic stability of the closed-loop system,and minimizes a meaningful cost functional that penalizes both states and control.The approach does not require to solve a Hamilton-Jacobi-Bellman equation(HJBE).An optimal stabilization of the evolution of the frequency of a certain genetic character from the population is included to illustrate the theoretical developments.
基金supported by the Natural Science Foundation of China(11001095)the Ph.D.specialized grant of the Ministry of Education of China(20100144110001)+2 种基金the Special Fund for Basic Scientific Research of Central Colleges(CCNU12C01001)supported by the Fundamental Research Funds for the Central Universities(2015IA009)the Natural Science Foundation of China(61573012)
文摘This paper is concerned with the existence and the nonlinear asymptotic stabil- ity of traveling wave solutions to the Cauchy problem for a system of dissipative evolution equations {θt=vζx＋（ζθ）x＋aθxx,ζt=-θx＋βζxx;with initial data and end states （ζθ）（x,0）=（ζ0,θ0）（x）→（ζ±,θ±）as x→∞.We obtain the existence of traveling wave solutions by phase plane analysis and show the asymptotic nonlinear stability of traveling wave solutions without restrictions on the coeffi- cients a and v by the method of energy estimates.
文摘An optimal(practical) stabilization problem is formulated in an inverse approach and solved for nonlinear evolution systems in Hilbert spaces. The optimal control design ensures global well-posedness and global practical K∞-exponential stability of the closed-loop system, minimizes a cost functional,which appropriately penalizes both state and control in the sense that it is positive definite(and radially unbounded) in the state and control, without having to solve a Hamilton-Jacobi-Belman equation(HJBE). The Lyapunov functional used in the control design explicitly solves a family of HJBEs. The results are applied to design inverse optimal boundary stabilization control laws for extensible and shearable slender beams governed by fully nonlinear partial differential equations.
基金Natural science foundation of Inner Mongolia(2024LHMS06018)The basic scientific research funding for directly affiliated universities in the Inner Mongolia(JY20250094)。
文摘A complex system is inherently high-dimensional.Recent studies indicate that,even without complete knowledge of its evolutionary dynamics,the future behavior of such a system can be predicted using time-series data(data-driven prediction).This suggests that the essential dynamics of a complex system can be captured through a low-dimensional representation.Virus evolution and climate change are two examples of complex,time-varying systems.In this article,we show that mutations in the spike protein provide valuable data for predicting SARS-CoV-2 variants,forecasting the possible emergence of the new macro-lineage Q in the near future.Our analysis also demonstrates that carbon dioxide concentration is a reliable indicator for predicting the evolution of the climate system,extending global surface air temperature(GSAT)forecasts through 2500.
基金supported by the National Natural Science Foundation of China(Grants No.W2412144,42271292)the 111 project,and the Fundamental Research Funds for the Central Universities of China.
文摘Amid ongoing global environmental change and the critical pursuit of sustainable development,human-environment systems are exhibiting increasingly complex dynamic evolutions and spatial relationships,underscoring an urgent need for innovative research frameworks.Integrated geography synthesizes physical geography,human geography,and geographic information science,providing key frameworks for understanding complex human-environment systems.This editorial proposes an emerging research framework for integrated geography—“Composite driving-System evolution-Coupling mechanism-Synergistic regulation(CSCS)”—based on key issues such as climate change,biodiversity loss,resource scarcity,and social-ecological interactions,which have been highlighted in both recent critical literature on human-environment systems and UN assessment reports.The framework starts with diverse composite driving forces,extends to the evolution of human-environment system structures,processes,and functions that these drivers induce,explores couplings within human-environment systems,and calls for regulation aimed at sustainable development in synergies.Major research frontiers include understanding the cascading“evolution-coupling”effects of shocks;measuring system resilience,thresholds,and safe and just operating space boundaries;clarifying linkage mechanisms across scales;and achieving synergistic outcomes for multi-objective sustainability.This framework will help promote the interdisciplinary integration and development of integrated geography,and provide geographical solutions for the global sustainable development agenda.
基金supported by the National Key Research and Development Project of China(No.2021YFC3000600)。
文摘The Longmenshan structural belt on the eastern edge of the Tibetan Plateau experienced the impactful Mw7.92008 Wenchuan Earthquake,causing a 350 km surface rupture.Traditional models attribute this to the Beichuan and Pengguan faults,but our research reveals a complex fault system at the northern end,with inconsistencies in surface rupture,aftershock distribution,and focal mechanisms.We integrate shallow geology,active source seismic reflection,and magnetotelluric profiling to establish a deep structural model for the northern end of the Longmenshan structural belt.This area exhibits dominant reverse thrust nappe tectonics,and analyzing the tectonic evolution history provides insights into deformation propagation from the orogenic belt toward the Sichuan Basin.Focal mechanism analysis and relocated aftershock data reveals two distinct types of seismogenic structures in the northern end of the Longmenshan structural belt.In the middle to northern segments,the reverse fault type is attributed to reactivated pre-existing faults.Conversely,at the northern end,the strike-slip fault type originates from high-angle co-seismic rupture cutting through pre-existing reverse faults.This study enhances our understanding of fault complexity and seismic mechanisms in the northeastern Longmenshan structural belt,providing new insights into regional tectonics.
基金co-supported by the National Key Research and Development Program of China (No. 2022YFB4600500)the National Natural Science Foundation of China (No. 52235006)
文摘High-performance 24CrNiMo steel was fabricated using Laser Powder Bed Fusion (LPBF). Subsequent quenching treatment was applied and the influence of quenching temperatures on micro-structure evolution and properties was systematically characterised and analysed. The micro-structure of the as-built steel consisted of two parts. The first part comprised martensite with twins combined with ω-Fe nano-particles, and the second part consisted of lower bainite in the molten pool, as well as upper bainite, granular bainite and tempered martensite in the heat-affected zone. With the quenching temperatures varying from 800℃ to 950℃, the micro-structure gradually transformed from acicular ferrite + martensite to tempered martensite +θ-Fe3C carbides, and the grain size exhibited noticeable growth. Moreover, quenching treatments could eliminate the anisotropy and inhomogeneity of the micro-structure. The rod-shaped nanosized η-Fe2C and θ-Fe3C precipitates were clearly observed, which were converted from ω-Fe and distributed at multiple angles in the lath. The size and number of nano-precipitates, triggered by the high self-tempering degree of martensite, gradually increased. The relationships among grain size, the twins, dislocation density and nano-precipitation and the dramatically improved performance of quenched samples were analysed using strengthening mechanisms. After quenching at 850℃, the as-built 24CrNiMo steel attained ultra-high mechanical properties including hardness, Ultimate Tensile Strength (UTS), Elongation (El) and impact energy with values of 480.9 HV_(1), 1611.4 MPa, 9.8% and 42.8 J, respectively. Meanwhile, both the wear and thermal fatigue resistance increased by approximately 40%. This study demonstrated that LPBF-fabricated 24CrNiMo steel, with matching good performances, can be achieved using a subsequent one-step quenching process.
文摘The protection system for traditional Chinese medicine(TCM)varieties,as an important policy tool to promote the development of TCM,has a long history of over 30 years,from the promulgation of the“Regulations on the Protection of Traditional Chinese Medicine Varieties”in 1992 to the comprehensive revision of the draft for soliciting opinions in 2022.The TCM protection system evolves to meet the needs of innovative development of TCM.This paper reviews the policy developments in TCM varieties protection,collates protection data(1993 to 2024),and analyzes enterprises application strategies amid impending regulatory changes.
基金Project (2010CB635104) supported by the National Basic Research Program of ChinaProject (2007AA03Z112) supported by the National High-Tech Research and Development Program of China+2 种基金Project (9140A18040709JW1601) supported by the Advanced Research Fund of DOD, ChinaProject (2009ZZ0019) supported by the Fundamental Research Funds for the Central Universities, ChinaProject (NCET-10-0364) supported by the Program for New Century Excellent Talents in University, China
文摘Spark plasma sintering method （SPS） was used to consolidate mixed W-5.6Ni-1.4Fe （mass fraction, %） powders from commercial fine elemental powders, and both the densification behavior and microstructure evolution in sintering were investigated at different heating rates. The results show that the SPS densification process can be divided into three stages. At the initial unshrinking stage, fast heating generates instantaneous discharge and locally inhomogeneous temperature distribution in solid-state powder particles, enhancing later densification; during the intermediate solid state sintering stage, diffusion is more sufficient in the slow-heated SPS process; at the final transient liquid-phase sintering stage, tungsten grains become sphered and coarsen rapidly, but fast heating helps maintain rather small grain sizes.
基金The Ph.D.Programs Foundation of Ministry of Education of China(No.20060286005)China Postdoctoral Science Foundation(No.20070411018)
文摘The metabolic evolution model of transportation demand for comprehensive transportation systems is put forward on the basis of a metabolic theory of ecology. In the model, the growth rates or changing rates of transportation volumes for the various transportation modes of a city are determined not only by the GDP per capita which reflects the size of the city itself, but also by the relationship of competition and cooperation among transportation modes. The results of empirical analysis for Chinese cities show that the allometric growth exponent in the equation for the variation rate of passenger demand volume on rail is greater than the predicted value of 1/4 in metabolic ecology, whereas the allometric growth relationship is not so evident in the equation for the variation rate of passenger demand volume on road. The changing rate of road transportation is thus mainly affected by the relationship of competition and cooperation among transportation modes for Chinese cities.
基金supported by National Natural Science Foundation of China(Grant Nos.11771295,11271356,11371041,11431014 and 11401557)Key Laboratory of Random Complex Structures and Data Science,Academy of Mathematics and Systems Science,Chinese Academy of Sciences,and the Fundamental Research Funds for the Central Universities(Grant No.WK0010000048)。
文摘The limiting behavior of stochastic evolution processes with small noise intensityεis investigated in distribution-based approaches.Letμεbe a stationary measure for stochastic process Xεwith smallεand X0 be a semiflow on a Polish space.Assume that{με:0<ε≤ε0}is tight.Then all their limits in the weak sense are X0-invariant and their supports are contained in the Birkhoff center of X0.Applications are made to various stochastic evolution systems,including stochastic ordinary differential equations,stochastic partial differential equations,and stochastic functional differential equations driven by Brownian motion or Levy processes.
基金supported by the National Natural Science Foundation of China under Grant No.61174081
文摘Impulse observability and impulse controllability of regular degenerate evolution systems are discussed by using functional analysis and operator theory in Banach space. Necessary and sufficient conditions for the impulse observability and impulse controllability of the system are obtained. This research is theoretically important for studying the design of the degenerate evolution system.
基金the Special Funds for Major State Basic Research Projects of China(No.G1999032801) and the National Natural Science Foundation
文摘The existence and uniqueness of a strong periodic solution of the evolution system describing geophysical flow in bounded domains of RN (N = 3, 4) are proven if external forces are periodic in time and sufficiently small.
基金Supported by National Natural Science Foundation of China-NSAF(Grant No.10976026)
文摘In this paper, firstly, we study the local existence and uniqueness of mild solutions for fractional evolution systems with nonlocal in time nonlinearity. Then, we claim that such a mild solution is weak solution of this system. Finally, we prove a blow-up result under some conditions.
文摘The phylogenetic relationships of four species,Bufo melanostictus,Hyla chinensis,Rana limnocharis and Rana guentheri,which belong to three differrent families of Anura,were detected with RAPD technique.The genomic DNA of each species was amplified with 19 random primers.16 primers given clear amplified bands were used for analysis and the genetic distances between four species were calculated.The results show that RAPD bands obtained by all 16 primers evinced different degree polymorphisms.The genetic distance between R.limnocharis and R.guentheri is the nearest,that between B.melanostictus and H.chinensis is the second nearest,and that between B.melanostictus and R.guentheri is the furthest.The different distances also indicated that the relationship between Bufoidae and Hylidae is closer than that between Bufonidae and Ranidae at genomic DNA level.In concordant with the conclusion of the morphology,chromosomal and mitochondrial DNA studies,our results provide a new evidence of the systematic evolution of the three families of Anura at DNA molecular level.
文摘Due to the immaturity of practice and the increasing complexity of system of system (SoS). It is necessary to develop systematic methodologies that enable evolution of such systems. This paper presents a prototype design for a synthetic system evolution environment (SEE). It outlines the purpose of the environment, describes its concept of operations, details its main functions and processes in utilizing the system architecture knowledge for systems evolution, and introduces its initial high level architecture design.In addition, it also documents the approach for developing the environment.
基金This research is supported by the Special Funds for Major State Basic Research Projects(G1999032801) by the Natural Science Foundation of China with Grant No.19671067 and 10001028.
文摘In this paper,the long time behaviors of non-autonomous evolution system describing geophysical flow within the earth are studied.The uniqueness and existence of the solution to the evolution system and the existence of uniform attractor are proven.Moreover,the upper bounds of the uniform attractor's hausdorff and Fractal dimensions are obtained.
