Global urbanization is exerting severe stress and having far-reaching impacts on the eco-environment, and yet there exists a complex non-linear coupling relationship between the two. Research on the interactive coupli...Global urbanization is exerting severe stress and having far-reaching impacts on the eco-environment, and yet there exists a complex non-linear coupling relationship between the two. Research on the interactive coupling effect between urbanization and the eco-environment will be a popular area of study and frontier in international earth system science and sustainability science in the next 10 years, while also being a high-priority research topic of particular interest to international organizations. This paper systematically collates and summarizes the international progress made in research on interactive coupling theory, coupling relationships, coupling mechanisms, coupling laws, coupling thresholds, coupling models and coupling optimization decision support systems. The research shows that urbanization and eco-environment interactive coupling theories include the Kuznets curve theory, telecoupling theory, planetary boundaries theory, footprint family theory and urban metabolism theory; most research on interactive coupling relationships is concerned with single- element coupling relationships, such as those between urbanization and water, land, atmosphere, climate change, ecosystems and biodiversity; the majority of research on interactive coupling mechanisms and laws focuses on five research paradigms, including coupled human and nature systems, complex social-ecological systems, urban ecosystems, social-economic-natural complex ecosystems, and urbanization development and eco-environment constraint ring; the majority of interactive coupling simulations use STIRPAT models, coupling degree models, multi-agent system models and big data urban computer models; and research has been carried out on urbanization and eco-environment coupling thresholds, coercing risk and optimal decision support systems. An objective evaluation of progress in international research on interactive coupling between urbanization and the eco-environment suggests that there are six main research focal points and six areas lacking research： a lot of research exists on macroscopic coupling effects, with little research on urban agglomeration and scale coupling effects; considerable research exists on sin-gle-dimension coupling effects, with little on multiple-dimension coupling effects; a great deal exists on ＂one-to-one＂ dual- element coupling effects, with little on ＂many-to-many＂ multiple-element coupling effects; a lot exists on positive feedback coupling effects, and little on negative feedback coupling effects; a great deal exists on empirical coupling effects, and little on theoretical coupling effects; a great deal exists on the use of simple quantitative methods, and little on using integrated simulation methods. Future studies should focus on coupling effects between urbanization in urban agglomerations and the eco-environment, spatial scale coupling effects, multi-dimensional coupling effects, telecoupling effects, ＂one-to-many＂ and ＂many-to-many＂ element coupling effects, and positive and negative feedback coupling effects. There is also a need to strengthen the development and application of dynamic models for multi-element,-scale,-scenario,-module and-agent integrated spatiotemporal coupling systems and further improve theoretical innovations in coupling effect research and integrate and form complete and diverse coupling theoretical systems.展开更多
Understanding the photon number statistics of a quantum emitter(QE)interacting with complex photonic environments is fundamental to advances in quantum optics and nanophotonics.We introduce a general theoretical frame...Understanding the photon number statistics of a quantum emitter(QE)interacting with complex photonic environments is fundamental to advances in quantum optics and nanophotonics.We introduce a general theoretical framework for calculating the modal photon number density spectrum(MPNDS)in arbitrary dielectric structures with an embedded two-level QE.We validate our approach by investigating a system composed of a two-level QE and a photonic crystal(PhC)slab with an L3 cavity and a waveguide,finding that the MPNDS exhibits significant changes in both waveguide and background radiative channels as the interaction between the QE and modal field transitions from weak coupling to strong coupling.We observe that the number of photons guided along the waveguide shows a strong dependence on the QE’s transition frequency and transition dipole moment,but demonstrates robustness to the transition dipole moment when the transition frequency approaches the waveguide cutoff frequency.Our work allows for the determination and tailoring of light emission characteristics across diverse radiative channels in complex photonic environments.展开更多
Mega-urban agglomerations are strategic core areas for national economic development and the main regions of new urbanization. They also have important roles in shifting the global economic center of gravity to China....Mega-urban agglomerations are strategic core areas for national economic development and the main regions of new urbanization. They also have important roles in shifting the global economic center of gravity to China. However, the development of mega-urban agglomerations has triggered the interactive coercion between resources and the eco-envi- ronment. The interactive coupled effects between urbanization and the eco-environment in mega-urban agglomerations represent frontier and high-priority research topics in the field of Earth system science over the next decade. In this paper, we carried out systematic theo- retical analysis of the interactive coupling mechanisms and coercing effects between ur- banization and the eco-environment in mega-urban agglomerations. In detail, we analyzed the nonlinear-coupled relationships and the coupling characteristics between natural and human elements in mega-urban agglomerations. We also investigated the interactive coercion intensities between internal and external elements, and the mechanisms and patterns of local couplings and telecouplings in mega-urban agglomeration systems, which are affected by key internal and external control elements. In addition, we proposed the interactive coupling theory on urbanization and the eco-environment in mega-urban agglomerations. Furthermore we established a spatiotemporal dynamic coupling model with multi-element, multi-scale, multi-scenario, multi-module and multi-agent integrations, which can be used to develop an intelligent decision support system for sustainable development of mega-urban agglomera- tions. In general, our research may provide theoretical guidance and method support to solve problems related to mega-urban agglomerations and maintain their sustainable development.展开更多
The process of contaminant transport is a problem of multicomponent and multiphase flow in unsaturated zone. Under the presupposition that gas existence affects water transport, a coupled mathematical model of contami...The process of contaminant transport is a problem of multicomponent and multiphase flow in unsaturated zone. Under the presupposition that gas existence affects water transport, a coupled mathematical model of contaminant transport in unsaturated zone has been established based on fluid_solid interaction mechanics theory. The asymptotical solutions to the nonlinear coupling mathematical model were accomplished by the perturbation and integral transformation method. The distribution law of pore pressure, pore water velocity and contaminant concentration in unsaturated zone has been presented under the conditions of with coupling and without coupling gas phase. An example problem was used to provide a quantitative verification and validation of the model. The asymptotical solution was compared with Faust model solution. The comparison results show reasonable agreement between asymptotical solution and Faust solution, and the gas effect and media deformation has a large impact on the contaminant transport. The theoretical basis is provided for forecasting contaminant transport and the determination of the relationship among pressure_saturation_permeability in laboratory.展开更多
The influence of annealing time on the magnetic properties and microstructure of nanocomposite Pr7.5Dy1Fe71Co15Nb1B4.5 ribbons was systematically investigated by the methods of vibrating sample magnetometer （VSM）, ...The influence of annealing time on the magnetic properties and microstructure of nanocomposite Pr7.5Dy1Fe71Co15Nb1B4.5 ribbons was systematically investigated by the methods of vibrating sample magnetometer （VSM）, X-ray diffraction （XRD） and high resolution transmission electron microscopy （HRTEM）. Interaction domains derived from strong exchange coupling interactions between hard and soft magnetic grains were imaged using magnetic force microscopy （MFM）. Maximum remanence, intrinsic coercivity, and maximum energy product values were obtained in the ribbons annealed at 700℃ for 15 min, which were composed of Pr2（Fe, Co）14B, α-（Fe, Co）, and slight Pr2（Fe, CO）17 phases. Although Jr, Hci, and （Bn）max decreased gradually with further increase of annealing time, it is emphasized that comparatively high Jr and Hci and （BH）max were obtained in a wide annealing time period of 15 to 360 min. The shape of initial magnetization curves and hysteresis loops change as a function of annealing time, indicating different magnetization reversal routes, which can be fully explained by the corresponding microstructure.展开更多
The coupling interaction between an individual optical emitter and the propagating surface plasmon polaritons in a graphene microribbon （GMR） waveguide is investigated by numerical calculations, where the emitter is...The coupling interaction between an individual optical emitter and the propagating surface plasmon polaritons in a graphene microribbon （GMR） waveguide is investigated by numerical calculations, where the emitter is situated above the GMR or in the same plane of the GMR, The results reveal a multimode coupling mechanism for the strong interaction between the emitter and the propagating plasmonic waves in graphene. When the emitter is situated in the same plane of the GMR, the decay rate from the emitter to the surface plasmon polaritons increases more than 10 times compared with that in the case with the emitter above the GMR.展开更多
In a three-sphere system, the middle sphere is acted upon by two opposite depletion forces from the other two spheres. It is found that, in this system, the two depletion forces are coupled with each other and result ...In a three-sphere system, the middle sphere is acted upon by two opposite depletion forces from the other two spheres. It is found that, in this system, the two depletion forces are coupled with each other and result in a strengthened depletion force. So the difference of the depletion forces of the three-sphere system and its corresponding two two-sphere systems is introduced to describe the coupling effect of the depletion interactions. The numerical results obtained by Monte- Carlo simulations show that this coupling effect is affected by both the concentration of small spheres and the geometrical confinement. Meanwhile, it is also found that the mechanisms of the coupling effect and the effect on the depletion force from the ~eometry factor are the same.展开更多
It is shown that the fine structure constant at Planck times tends to one as well as those of the weak and strong interactions. This results by constraining them at the Planck force. That seems to provide interesting ...It is shown that the fine structure constant at Planck times tends to one as well as those of the weak and strong interactions. This results by constraining them at the Planck force. That seems to provide interesting new results which confirm that at the beginning of space time (Planck scale) all fundamental forces converge to the same unit value.展开更多
The existence of strings has not yet been proven, but if a fermion is considered as being made up of two coupled strings, then the coupling between these two strings creates tension in the strings, and this tension is...The existence of strings has not yet been proven, but if a fermion is considered as being made up of two coupled strings, then the coupling between these two strings creates tension in the strings, and this tension is proportional to the coupling force via the Planck constant. This provides an explanation for the origin of the Planck constant.展开更多
The influence of power-low long-range interactions （LRI） and helicoidal coupling （HC） on the properties of localized solitons in a DNA molecule when a ribonucleic acid polymerase （RNAP） binds to it at the physio...The influence of power-low long-range interactions （LRI） and helicoidal coupling （HC） on the properties of localized solitons in a DNA molecule when a ribonucleic acid polymerase （RNAP） binds to it at the physiological temperature is analytically and numerically investigated in this paper. We have made an analogy with the Heisenberg model Hamiltonian of an anisotropic spin ladder with ferromagnetic legs and anti-ferromagnetic rung coupling. When we limit ourselves to the second-order terms in the Taylor expansion, the DNA dynamics is found to be governed by a completely integrable nonlinear Schr？dinger （NLS） equation. In this case, results show that increasing the value of HC force or LRI parameter enhances the bubble height and reduces the number of base pairs which form the bubble. For the fourth-order terms in a Taylor expansion, results are closely resembling those of second-order terms, and are confirmed by numerical investigation. These results match with some experimental data and thus provide a better representation of the base pairs opening in DNA which is essential for the transcription process.展开更多
The authors analyze a piezoelectric energy harvester as an electro-mechanically coupled system. The energy harvester consists of a piezoelectric bimorph with a concentrated mass attached at one end, called the harvest...The authors analyze a piezoelectric energy harvester as an electro-mechanically coupled system. The energy harvester consists of a piezoelectric bimorph with a concentrated mass attached at one end, called the harvesting structure, an electric circuit for energy storage, and a rectifier that converts the AC output of the harvesting structure into a DC input for the storage circuit. The piezoelectric bimorph is assumed to be driven into flexural vibration by an ambient acoustic source to convert the mechanical energies into electric energies. The analysis indicates that the performance of this harvester, measured by the power density, is characterized by three important non-dimensional parameters, i.e., the non-dimensional inductance of the storage circuit, the non-dimensional aspect ratio （length/thickness） and the non-dimensional end mass of the harvesting structure. The numerical results show that： （1） the power density can be optimized by varying the non-dimensional inductance for each fixed non-dimensional aspect ratio with a fixed non-dimensional end mass; and （2） for a fixed non-dimensional inductance, the power density is maximized if the non-dimensional aspect ratio and the non-dimensional end mass are so chosen that the harvesting structure, consisting of both the piezoelectric bimorph and the end mass attached, resonates at the frequency of the ambient acoustic source.展开更多
The northern South China Sea(SCS) is frequently affected by typhoons. During severe storm events, wave-current interactions produce storm surges causing enormous damage in the path of the typhoon. To evaluate the infl...The northern South China Sea(SCS) is frequently affected by typhoons. During severe storm events, wave-current interactions produce storm surges causing enormous damage in the path of the typhoon. To evaluate the influence of wave-current interactions on storm surge, we used a coupled ocean-atmospherewave-sediment transport(COAWST) modeling system with radiation-stress and vortex-force formulations to simulate two typically intense tropical storms that invaded the SCS, namely Typhoons Nuri(2008) and Hagupit(2008), and compared results with observations from the Hong Kong Observatory. Both radiationstress and vortex-force formulations significantly improved the accuracy of the simulation. Depending on which typhoon and the topography encountered, the influence of surface waves on the oceanic circulation showed different characteristics, including the differences of range and intensity of storm surge between vortex-force and radiation-stress experiments. During typhoon landing, strong sea-surface elevation in concert with wave set-up/set-down caused the adjustment of the momentum balance. In the direction perpendicular to the current, but especially in the cross-shore direction, the pressure gradient and wave effects on the current dominated the momentum balance.展开更多
The fatigue flexural performance of RC beams attacked by salt spray was studied. A testing method involving electro osmosis, electrical accelerated corrosion and salt spray was proposed. This corrosion process method ...The fatigue flexural performance of RC beams attacked by salt spray was studied. A testing method involving electro osmosis, electrical accelerated corrosion and salt spray was proposed. This corrosion process method effectively simulates real-world salt spray and fatigue loading exerted by RC components on sea bridges. Four RC beams that have different stress amplitudes were tested. It is found that deterioration by corrosion and fatigue loading reduces the fatigue life of the RC and decreases the ability of deformation. The fatigue life and deflection ability could be reduced by increasing the stress amplitude and the corrosion duration time. The test result demonstrates that this experimental method can couple corrosion deterioration and fatigue loading reasonably. This procedure may be applied to evaluate the fatigue life and concrete durability of RC components located in a natural salt spray environment.展开更多
Inducing ferromagnetism into graphene is vital today because it has a wide range of applications such as spintronics devices and magnetic memory devices. In this paper, we will report a new method to synthesize ferrom...Inducing ferromagnetism into graphene is vital today because it has a wide range of applications such as spintronics devices and magnetic memory devices. In this paper, we will report a new method to synthesize ferromagnetic graphene by nitrogen doping. X-ray photoelectron spectroscopy(XPS) and Raman spectroscopy were utilized to testify the N-doped material and further discuss the N-doped process.The superconducting quantum interference device(SQUID) was put in and used to analyze the magnetic properties of the N-doped graphene sheets. It shows that the material exhibits ferromagnetism at both 3 K and 300 K and the ferromagnetic saturation moment is 0.412 emu/g and 0.051 emu/g, respectively.The mechanism of the origin of the ferromagnetism in N-doped graphene sheets will also be discussed in this paper. It shows that, when the amount graphitic N reached the threshold, the origin of the ferromagnetism will change from defects induced by nitrogen atoms to the transition in energy band caused by graphitic N.展开更多
Background:Afforestation is a common and effective approach used for the restoration of degraded ecosystems worldwide.In China,Robinia pseudoacacia(RP)is among the main non-native tree species and has been widely plan...Background:Afforestation is a common and effective approach used for the restoration of degraded ecosystems worldwide.In China,Robinia pseudoacacia(RP)is among the main non-native tree species and has been widely planted in revegetation of the Loess Plateau.However,owing to uncertainties regarding soil water consumption and carbon sequestration,it is necessary to assess the suitability and sustainability of R.pseudoacacia in restoration.In this study,we aimed to analyse the dynamic effects of R.pseudoacacia forest on soil carbon storage(SCS)and soil water storage(SWS).Specifically,we investigated the association between soil water content(SWC)and soil organic carbon(SOC)and underlying factors in the 0-500-cm profile of a 10-to 50-year-old chronosequence.Results:The results obtained indicated that the dynamics of SWS and SCS on this time scale could be divided into an initial reduction phase(the initial 20 years after afforestation)and subsequent recovery(20-50 years after afforestation).Compared with in the abandoned land(AL),the net accumulation of SCS in R.pseudoacacia forest was 2.51 Mg·ha^(-1)at 50 years after afforestation,whereas there was a 398.76-mm deficit in SWS.Additionally,the natural succession of R.pseudoacacia forest has contributed to the continuous change in stand structure(e.g.vegetation cover(VC),understory vegetation coverage(UVC),and litter biomass(LB)).Conclusions:These findings indicate that vegetation restoration increases carbon sequestration while causing soil water deficit.Furthermore,stand density(SD)was established to make a predominant contribution to the dynamics of SWS and SCS via its effects in altering vegetation,soil,and litter characteristics.Therefore,high-density plantation forests in the Loess Plateau area should be appropriately thinned to reduce the density of forest stands on the basis of soil erosion control and wind and sand fixation,so as to increase carbon sink with lower water consumption,thus realizing the synergistic development of soil carbon sequestration and water connotation.展开更多
In light of the characteristics of the interactions between flexible structure and wind in three directions, and based on the rational mechanical section-model of structure, a new aerodynamic force model is accepted, ...In light of the characteristics of the interactions between flexible structure and wind in three directions, and based on the rational mechanical section-model of structure, a new aerodynamic force model is accepted, i.e, the coefficients of three component forces are the functions of the instantaneous attack angle and rotational speed C-t = C-t (beta(t), 0). (i = D, L, M). So, a new method to formulate the linear and nonlinear aerodynamic items of wind and structure interacting has been put forward in accordance with 'strip theory' and modified 'quasi-static theory', and then the linear and nonlinear coupled theory of super-slender structure for civil engineering analyzing are converged in one model, For the linear aerodynamic-force parts, the semi-analytical expressions of the items so-called 'flutter derivatives' corresponding to the one in the classic equations have been given here, and so have the nonlinear parts. The study of the stability of nonlinear aerodynamic-coupled torsional vibration of the old Tacoma bridge shows that the form and results of the nonlinear control equation in rotational direction are in agreement with that of V. F. Bohm's.展开更多
Experimental and theoretical researches on nanostructured exchange coupled magnets have been carried out since about 1988. Here, we review the structure and magnetic properties of the anisotropic nanocomposite soft/ha...Experimental and theoretical researches on nanostructured exchange coupled magnets have been carried out since about 1988. Here, we review the structure and magnetic properties of the anisotropic nanocomposite soft/hard multilayer magnets including some new results and phenomena from an experimental point of view. According to the different component of the oriented hard phase in the nanocomposite soft/hard multilayer magnets, three types of magnets will be discussed：1） anisotropic Nd2Fe（14）B based nanocomposite multilayer magnets, 2） anisotropic SmCo5 based nanocomposite multilayer magnets, and 3） anisotropic rare-earth free based nanocomposite multilayer magnets. For each of them, the formation of the oriented hard phase, exchange coupling, coercivity mechanism, and magnetic properties of the corresponding anisotropic nanocomposite multilayer magnets are briefly reviewed, and then the prospect of realization of bulk magnets on new results of anisotropic nanocomposite multilayer magnets will be carried out.展开更多
The single photon scattering properties in a pair of waveguides coupled by a whispering-gallery resonator in- teracting with a semiconductor quantum dot are investigated theoretically. The two waveguides support four ...The single photon scattering properties in a pair of waveguides coupled by a whispering-gallery resonator in- teracting with a semiconductor quantum dot are investigated theoretically. The two waveguides support four possible ports for an incident single photon. The quantum dot is considered a V-type system. The incident direction-dependent single photon scattering properties are studied and equal-output probability from the four ports for a single photon incident is discussed. The influences of backscattering between the two modes of the whispering-gallery resonator for incident direction-dependent single photon scattering properties are also pre- sented.展开更多
Spin glass system is a complex disordered system with a number of local minima separated by entropic barriers.Therefore,parallel tempering Monte Carlo simulation was used in order to get fast thermalisation(to minimiz...Spin glass system is a complex disordered system with a number of local minima separated by entropic barriers.Therefore,parallel tempering Monte Carlo simulation was used in order to get fast thermalisation(to minimize the relaxation time).Distance dependent interaction coupling in 2D is studied in order to show how a spin glass phase transition occurs when couplings between far away spins are permitted by considering Edwards-Anderson Ising spin glass model.The interaction coupling is a quenched random variable whose probability of being non-zero decays with distance between two spin sites rij=|i-j|mod(L/2).The interaction coupling is random and its probability distribution is decaying with the distance between the spins(p(Jij)αrij^-ρ).The model is studied by changing p among three different regimes(p〉2D,4/3 D〈p〈2D,p〈4/3D).A phase transition temperature for p=2,3,4 is obtained.展开更多
As a results of magnetoelastic interaction, the mechanical behavior of current-carrying coil structures, such as deformation and instability, is a key problem in the design of strong held magnets. In this paper, a non...As a results of magnetoelastic interaction, the mechanical behavior of current-carrying coil structures, such as deformation and instability, is a key problem in the design of strong held magnets. In this paper, a nonlinear mathematical model is presented to describe the deformation and buckling of D-type current-carrying coils, based on the Biot-Savart law and the bending theory of curved beams. The bending deformation, the critical value of current for the magnetoelastic buckling of the current-carrying coil, and the effects of the type and number of supports at middle part of the bending coil on the critical value are quantitatively investigated by a semi-analytical and semi-numerical method. The numerical results are shown to be in good agreement with the experimental data.展开更多
基金Major Program of the National Natural Science Foundation of China,No.41590840,No.41590842
文摘Global urbanization is exerting severe stress and having far-reaching impacts on the eco-environment, and yet there exists a complex non-linear coupling relationship between the two. Research on the interactive coupling effect between urbanization and the eco-environment will be a popular area of study and frontier in international earth system science and sustainability science in the next 10 years, while also being a high-priority research topic of particular interest to international organizations. This paper systematically collates and summarizes the international progress made in research on interactive coupling theory, coupling relationships, coupling mechanisms, coupling laws, coupling thresholds, coupling models and coupling optimization decision support systems. The research shows that urbanization and eco-environment interactive coupling theories include the Kuznets curve theory, telecoupling theory, planetary boundaries theory, footprint family theory and urban metabolism theory; most research on interactive coupling relationships is concerned with single- element coupling relationships, such as those between urbanization and water, land, atmosphere, climate change, ecosystems and biodiversity; the majority of research on interactive coupling mechanisms and laws focuses on five research paradigms, including coupled human and nature systems, complex social-ecological systems, urban ecosystems, social-economic-natural complex ecosystems, and urbanization development and eco-environment constraint ring; the majority of interactive coupling simulations use STIRPAT models, coupling degree models, multi-agent system models and big data urban computer models; and research has been carried out on urbanization and eco-environment coupling thresholds, coercing risk and optimal decision support systems. An objective evaluation of progress in international research on interactive coupling between urbanization and the eco-environment suggests that there are six main research focal points and six areas lacking research： a lot of research exists on macroscopic coupling effects, with little research on urban agglomeration and scale coupling effects; considerable research exists on sin-gle-dimension coupling effects, with little on multiple-dimension coupling effects; a great deal exists on ＂one-to-one＂ dual- element coupling effects, with little on ＂many-to-many＂ multiple-element coupling effects; a lot exists on positive feedback coupling effects, and little on negative feedback coupling effects; a great deal exists on empirical coupling effects, and little on theoretical coupling effects; a great deal exists on the use of simple quantitative methods, and little on using integrated simulation methods. Future studies should focus on coupling effects between urbanization in urban agglomerations and the eco-environment, spatial scale coupling effects, multi-dimensional coupling effects, telecoupling effects, ＂one-to-many＂ and ＂many-to-many＂ element coupling effects, and positive and negative feedback coupling effects. There is also a need to strengthen the development and application of dynamic models for multi-element,-scale,-scenario,-module and-agent integrated spatiotemporal coupling systems and further improve theoretical innovations in coupling effect research and integrate and form complete and diverse coupling theoretical systems.
基金Project supported by the Basic and Applied Basic Research Project,Guangzhou Basic Research Plan(Grant No.202201011444).
文摘Understanding the photon number statistics of a quantum emitter(QE)interacting with complex photonic environments is fundamental to advances in quantum optics and nanophotonics.We introduce a general theoretical framework for calculating the modal photon number density spectrum(MPNDS)in arbitrary dielectric structures with an embedded two-level QE.We validate our approach by investigating a system composed of a two-level QE and a photonic crystal(PhC)slab with an L3 cavity and a waveguide,finding that the MPNDS exhibits significant changes in both waveguide and background radiative channels as the interaction between the QE and modal field transitions from weak coupling to strong coupling.We observe that the number of photons guided along the waveguide shows a strong dependence on the QE’s transition frequency and transition dipole moment,but demonstrates robustness to the transition dipole moment when the transition frequency approaches the waveguide cutoff frequency.Our work allows for the determination and tailoring of light emission characteristics across diverse radiative channels in complex photonic environments.
基金The Major Program of National Natural Science Foundation of China, No.41590840, No.41590842
文摘Mega-urban agglomerations are strategic core areas for national economic development and the main regions of new urbanization. They also have important roles in shifting the global economic center of gravity to China. However, the development of mega-urban agglomerations has triggered the interactive coercion between resources and the eco-envi- ronment. The interactive coupled effects between urbanization and the eco-environment in mega-urban agglomerations represent frontier and high-priority research topics in the field of Earth system science over the next decade. In this paper, we carried out systematic theo- retical analysis of the interactive coupling mechanisms and coercing effects between ur- banization and the eco-environment in mega-urban agglomerations. In detail, we analyzed the nonlinear-coupled relationships and the coupling characteristics between natural and human elements in mega-urban agglomerations. We also investigated the interactive coercion intensities between internal and external elements, and the mechanisms and patterns of local couplings and telecouplings in mega-urban agglomeration systems, which are affected by key internal and external control elements. In addition, we proposed the interactive coupling theory on urbanization and the eco-environment in mega-urban agglomerations. Furthermore we established a spatiotemporal dynamic coupling model with multi-element, multi-scale, multi-scenario, multi-module and multi-agent integrations, which can be used to develop an intelligent decision support system for sustainable development of mega-urban agglomera- tions. In general, our research may provide theoretical guidance and method support to solve problems related to mega-urban agglomerations and maintain their sustainable development.
文摘The process of contaminant transport is a problem of multicomponent and multiphase flow in unsaturated zone. Under the presupposition that gas existence affects water transport, a coupled mathematical model of contaminant transport in unsaturated zone has been established based on fluid_solid interaction mechanics theory. The asymptotical solutions to the nonlinear coupling mathematical model were accomplished by the perturbation and integral transformation method. The distribution law of pore pressure, pore water velocity and contaminant concentration in unsaturated zone has been presented under the conditions of with coupling and without coupling gas phase. An example problem was used to provide a quantitative verification and validation of the model. The asymptotical solution was compared with Faust model solution. The comparison results show reasonable agreement between asymptotical solution and Faust solution, and the gas effect and media deformation has a large impact on the contaminant transport. The theoretical basis is provided for forecasting contaminant transport and the determination of the relationship among pressure_saturation_permeability in laboratory.
基金This work was financially supported by the National Natural Science Foundation of China (No.10074005)
文摘The influence of annealing time on the magnetic properties and microstructure of nanocomposite Pr7.5Dy1Fe71Co15Nb1B4.5 ribbons was systematically investigated by the methods of vibrating sample magnetometer （VSM）, X-ray diffraction （XRD） and high resolution transmission electron microscopy （HRTEM）. Interaction domains derived from strong exchange coupling interactions between hard and soft magnetic grains were imaged using magnetic force microscopy （MFM）. Maximum remanence, intrinsic coercivity, and maximum energy product values were obtained in the ribbons annealed at 700℃ for 15 min, which were composed of Pr2（Fe, Co）14B, α-（Fe, Co）, and slight Pr2（Fe, CO）17 phases. Although Jr, Hci, and （Bn）max decreased gradually with further increase of annealing time, it is emphasized that comparatively high Jr and Hci and （BH）max were obtained in a wide annealing time period of 15 to 360 min. The shape of initial magnetization curves and hysteresis loops change as a function of annealing time, indicating different magnetization reversal routes, which can be fully explained by the corresponding microstructure.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51172030,11274052,51102019,51172208,and 61274015)the National Basic Research Program of China(Grant No.2010CB923200)
文摘The coupling interaction between an individual optical emitter and the propagating surface plasmon polaritons in a graphene microribbon （GMR） waveguide is investigated by numerical calculations, where the emitter is situated above the GMR or in the same plane of the GMR, The results reveal a multimode coupling mechanism for the strong interaction between the emitter and the propagating plasmonic waves in graphene. When the emitter is situated in the same plane of the GMR, the decay rate from the emitter to the surface plasmon polaritons increases more than 10 times compared with that in the case with the emitter above the GMR.
基金Project supported by the Scientific Research Fund of Hunan Provincial Education Department, China (Grant Nos. 08B028 and 10A075)the Natural Science Foundation of Hunan Province, China (Grant No. 08jj6043)
文摘In a three-sphere system, the middle sphere is acted upon by two opposite depletion forces from the other two spheres. It is found that, in this system, the two depletion forces are coupled with each other and result in a strengthened depletion force. So the difference of the depletion forces of the three-sphere system and its corresponding two two-sphere systems is introduced to describe the coupling effect of the depletion interactions. The numerical results obtained by Monte- Carlo simulations show that this coupling effect is affected by both the concentration of small spheres and the geometrical confinement. Meanwhile, it is also found that the mechanisms of the coupling effect and the effect on the depletion force from the ~eometry factor are the same.
文摘It is shown that the fine structure constant at Planck times tends to one as well as those of the weak and strong interactions. This results by constraining them at the Planck force. That seems to provide interesting new results which confirm that at the beginning of space time (Planck scale) all fundamental forces converge to the same unit value.
文摘The existence of strings has not yet been proven, but if a fermion is considered as being made up of two coupled strings, then the coupling between these two strings creates tension in the strings, and this tension is proportional to the coupling force via the Planck constant. This provides an explanation for the origin of the Planck constant.
文摘The influence of power-low long-range interactions （LRI） and helicoidal coupling （HC） on the properties of localized solitons in a DNA molecule when a ribonucleic acid polymerase （RNAP） binds to it at the physiological temperature is analytically and numerically investigated in this paper. We have made an analogy with the Heisenberg model Hamiltonian of an anisotropic spin ladder with ferromagnetic legs and anti-ferromagnetic rung coupling. When we limit ourselves to the second-order terms in the Taylor expansion, the DNA dynamics is found to be governed by a completely integrable nonlinear Schr？dinger （NLS） equation. In this case, results show that increasing the value of HC force or LRI parameter enhances the bubble height and reduces the number of base pairs which form the bubble. For the fourth-order terms in a Taylor expansion, results are closely resembling those of second-order terms, and are confirmed by numerical investigation. These results match with some experimental data and thus provide a better representation of the base pairs opening in DNA which is essential for the transcription process.
基金Project supported by the U.S.Navy's Metrology R&D Program,the US Naval Surface Warfare Center's Measurement Science Department,AEPTEC Microsystems Inc.,and the University of California,MICRO Program.
文摘The authors analyze a piezoelectric energy harvester as an electro-mechanically coupled system. The energy harvester consists of a piezoelectric bimorph with a concentrated mass attached at one end, called the harvesting structure, an electric circuit for energy storage, and a rectifier that converts the AC output of the harvesting structure into a DC input for the storage circuit. The piezoelectric bimorph is assumed to be driven into flexural vibration by an ambient acoustic source to convert the mechanical energies into electric energies. The analysis indicates that the performance of this harvester, measured by the power density, is characterized by three important non-dimensional parameters, i.e., the non-dimensional inductance of the storage circuit, the non-dimensional aspect ratio （length/thickness） and the non-dimensional end mass of the harvesting structure. The numerical results show that： （1） the power density can be optimized by varying the non-dimensional inductance for each fixed non-dimensional aspect ratio with a fixed non-dimensional end mass; and （2） for a fixed non-dimensional inductance, the power density is maximized if the non-dimensional aspect ratio and the non-dimensional end mass are so chosen that the harvesting structure, consisting of both the piezoelectric bimorph and the end mass attached, resonates at the frequency of the ambient acoustic source.
基金Supported by the National Key Research and Development Program of China(No.2016YFC1402000)the National Natural Science Foundation of China(Nos.41376027,U1133001,41606024)+3 种基金the National Program on Global Change and Air-Sea Interaction(No.GASI-IPOVAI-01-06)the NSFC-Shandong Joint Fund for Marine Science Research Centers(No.U1406401)the NSFC Innovative Group Grant Project(No.41421005)the High Performance Computing Environment Qingdao Branch of Chinese Academy of Science(CAS)
文摘The northern South China Sea(SCS) is frequently affected by typhoons. During severe storm events, wave-current interactions produce storm surges causing enormous damage in the path of the typhoon. To evaluate the influence of wave-current interactions on storm surge, we used a coupled ocean-atmospherewave-sediment transport(COAWST) modeling system with radiation-stress and vortex-force formulations to simulate two typically intense tropical storms that invaded the SCS, namely Typhoons Nuri(2008) and Hagupit(2008), and compared results with observations from the Hong Kong Observatory. Both radiationstress and vortex-force formulations significantly improved the accuracy of the simulation. Depending on which typhoon and the topography encountered, the influence of surface waves on the oceanic circulation showed different characteristics, including the differences of range and intensity of storm surge between vortex-force and radiation-stress experiments. During typhoon landing, strong sea-surface elevation in concert with wave set-up/set-down caused the adjustment of the momentum balance. In the direction perpendicular to the current, but especially in the cross-shore direction, the pressure gradient and wave effects on the current dominated the momentum balance.
文摘The fatigue flexural performance of RC beams attacked by salt spray was studied. A testing method involving electro osmosis, electrical accelerated corrosion and salt spray was proposed. This corrosion process method effectively simulates real-world salt spray and fatigue loading exerted by RC components on sea bridges. Four RC beams that have different stress amplitudes were tested. It is found that deterioration by corrosion and fatigue loading reduces the fatigue life of the RC and decreases the ability of deformation. The fatigue life and deflection ability could be reduced by increasing the stress amplitude and the corrosion duration time. The test result demonstrates that this experimental method can couple corrosion deterioration and fatigue loading reasonably. This procedure may be applied to evaluate the fatigue life and concrete durability of RC components located in a natural salt spray environment.
基金supported by National Natural Science Foundation of China (Nos. 21271082 and 21371068)。
文摘Inducing ferromagnetism into graphene is vital today because it has a wide range of applications such as spintronics devices and magnetic memory devices. In this paper, we will report a new method to synthesize ferromagnetic graphene by nitrogen doping. X-ray photoelectron spectroscopy(XPS) and Raman spectroscopy were utilized to testify the N-doped material and further discuss the N-doped process.The superconducting quantum interference device(SQUID) was put in and used to analyze the magnetic properties of the N-doped graphene sheets. It shows that the material exhibits ferromagnetism at both 3 K and 300 K and the ferromagnetic saturation moment is 0.412 emu/g and 0.051 emu/g, respectively.The mechanism of the origin of the ferromagnetism in N-doped graphene sheets will also be discussed in this paper. It shows that, when the amount graphitic N reached the threshold, the origin of the ferromagnetism will change from defects induced by nitrogen atoms to the transition in energy band caused by graphitic N.
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB40020000)the National Natural Science Foundation of China(No.41807011)。
文摘Background:Afforestation is a common and effective approach used for the restoration of degraded ecosystems worldwide.In China,Robinia pseudoacacia(RP)is among the main non-native tree species and has been widely planted in revegetation of the Loess Plateau.However,owing to uncertainties regarding soil water consumption and carbon sequestration,it is necessary to assess the suitability and sustainability of R.pseudoacacia in restoration.In this study,we aimed to analyse the dynamic effects of R.pseudoacacia forest on soil carbon storage(SCS)and soil water storage(SWS).Specifically,we investigated the association between soil water content(SWC)and soil organic carbon(SOC)and underlying factors in the 0-500-cm profile of a 10-to 50-year-old chronosequence.Results:The results obtained indicated that the dynamics of SWS and SCS on this time scale could be divided into an initial reduction phase(the initial 20 years after afforestation)and subsequent recovery(20-50 years after afforestation).Compared with in the abandoned land(AL),the net accumulation of SCS in R.pseudoacacia forest was 2.51 Mg·ha^(-1)at 50 years after afforestation,whereas there was a 398.76-mm deficit in SWS.Additionally,the natural succession of R.pseudoacacia forest has contributed to the continuous change in stand structure(e.g.vegetation cover(VC),understory vegetation coverage(UVC),and litter biomass(LB)).Conclusions:These findings indicate that vegetation restoration increases carbon sequestration while causing soil water deficit.Furthermore,stand density(SD)was established to make a predominant contribution to the dynamics of SWS and SCS via its effects in altering vegetation,soil,and litter characteristics.Therefore,high-density plantation forests in the Loess Plateau area should be appropriately thinned to reduce the density of forest stands on the basis of soil erosion control and wind and sand fixation,so as to increase carbon sink with lower water consumption,thus realizing the synergistic development of soil carbon sequestration and water connotation.
文摘In light of the characteristics of the interactions between flexible structure and wind in three directions, and based on the rational mechanical section-model of structure, a new aerodynamic force model is accepted, i.e, the coefficients of three component forces are the functions of the instantaneous attack angle and rotational speed C-t = C-t (beta(t), 0). (i = D, L, M). So, a new method to formulate the linear and nonlinear aerodynamic items of wind and structure interacting has been put forward in accordance with 'strip theory' and modified 'quasi-static theory', and then the linear and nonlinear coupled theory of super-slender structure for civil engineering analyzing are converged in one model, For the linear aerodynamic-force parts, the semi-analytical expressions of the items so-called 'flutter derivatives' corresponding to the one in the classic equations have been given here, and so have the nonlinear parts. The study of the stability of nonlinear aerodynamic-coupled torsional vibration of the old Tacoma bridge shows that the form and results of the nonlinear control equation in rotational direction are in agreement with that of V. F. Bohm's.
基金Project supported by the State Key Project of Research and Development of China(Grant No.2017YFA0206302)the National Nature Science Foundation of China(Grant Nos.51590883,51331006,and 51471167)the Chinese Academy of Sciences(Grant No.KJZD-EW-M05-3)
文摘Experimental and theoretical researches on nanostructured exchange coupled magnets have been carried out since about 1988. Here, we review the structure and magnetic properties of the anisotropic nanocomposite soft/hard multilayer magnets including some new results and phenomena from an experimental point of view. According to the different component of the oriented hard phase in the nanocomposite soft/hard multilayer magnets, three types of magnets will be discussed：1） anisotropic Nd2Fe（14）B based nanocomposite multilayer magnets, 2） anisotropic SmCo5 based nanocomposite multilayer magnets, and 3） anisotropic rare-earth free based nanocomposite multilayer magnets. For each of them, the formation of the oriented hard phase, exchange coupling, coercivity mechanism, and magnetic properties of the corresponding anisotropic nanocomposite multilayer magnets are briefly reviewed, and then the prospect of realization of bulk magnets on new results of anisotropic nanocomposite multilayer magnets will be carried out.
基金Supported by the National Natural Science Foundation of China under Grant No 11105001the Anhui Provincial Natural Science Foundation under Grant Nos 1408085QA22 and 1608085MA09
文摘The single photon scattering properties in a pair of waveguides coupled by a whispering-gallery resonator in- teracting with a semiconductor quantum dot are investigated theoretically. The two waveguides support four possible ports for an incident single photon. The quantum dot is considered a V-type system. The incident direction-dependent single photon scattering properties are studied and equal-output probability from the four ports for a single photon incident is discussed. The influences of backscattering between the two modes of the whispering-gallery resonator for incident direction-dependent single photon scattering properties are also pre- sented.
文摘Spin glass system is a complex disordered system with a number of local minima separated by entropic barriers.Therefore,parallel tempering Monte Carlo simulation was used in order to get fast thermalisation(to minimize the relaxation time).Distance dependent interaction coupling in 2D is studied in order to show how a spin glass phase transition occurs when couplings between far away spins are permitted by considering Edwards-Anderson Ising spin glass model.The interaction coupling is a quenched random variable whose probability of being non-zero decays with distance between two spin sites rij=|i-j|mod(L/2).The interaction coupling is random and its probability distribution is decaying with the distance between the spins(p(Jij)αrij^-ρ).The model is studied by changing p among three different regimes(p〉2D,4/3 D〈p〈2D,p〈4/3D).A phase transition temperature for p=2,3,4 is obtained.
基金The project supported by the National Natural Science Foundation of Chinathe Science Foundation of the State Education Committee of China for Outstanding Teacher in Universities the Natural Science Foundation of Gansu Province of China
文摘As a results of magnetoelastic interaction, the mechanical behavior of current-carrying coil structures, such as deformation and instability, is a key problem in the design of strong held magnets. In this paper, a nonlinear mathematical model is presented to describe the deformation and buckling of D-type current-carrying coils, based on the Biot-Savart law and the bending theory of curved beams. The bending deformation, the critical value of current for the magnetoelastic buckling of the current-carrying coil, and the effects of the type and number of supports at middle part of the bending coil on the critical value are quantitatively investigated by a semi-analytical and semi-numerical method. The numerical results are shown to be in good agreement with the experimental data.
