The Yangtze finless porpoise(YFP)is an endemic freshwater cetacean species that exclusively inhabits the middle and lower reaches of the Yangtze River basin.Since the late 1970s,the YFP has experienced a drastic popul...The Yangtze finless porpoise(YFP)is an endemic freshwater cetacean species that exclusively inhabits the middle and lower reaches of the Yangtze River basin.Since the late 1970s,the YFP has experienced a drastic population decline and was classified as critically endangered by the IUCN in 2013.To save this unique species,a range of integrated conservation measures have been implemented,including strengthening natural habitat protection(in-situ),enhancing insurance populations(ex-situ),and advancing captive breeding and research initiatives.These efforts have yielded significant progress in the conservation of the YFP.The natural population has been starting to increase after a sharp decline,and the establishment of three insurance populations has provided a solid foundation for recovery.Additionally,advancement in captive breeding and research has delivered crucial technical support for population conservation.As a flagship species of Yangtze River biodiversity and an indicator of the river’s ecosystem health,the YFP’s integrated conservation strategy not only benefits its own population but also offers valuable insights for the protection of other endangered aquatic species in the Yangtze River and other threatened small cetaceans worldwide.展开更多
The paper analyzed the opportunities and challenges faced by the urban heritage protection of Dashilanr historical district based on the concept of the integrated conservation of the urban heritage of Beijing old city...The paper analyzed the opportunities and challenges faced by the urban heritage protection of Dashilanr historical district based on the concept of the integrated conservation of the urban heritage of Beijing old city at present.Then,the paper put forward the protection of urban heritage to lead the revitalization of Dashilanr historical district,and then the paper analyzed the historical and cultural value carrier of the Dashilanr urban heritage.Finally,the paper proposed that integrated conservation of the Dashilanr urban heritage needed the protection method of historic urban landscape.展开更多
Several factors overlap in making urban heritage conservation vulnerable in terms of long-term sustainability.The purpose of this study is to offer insights into the dynamic role that heritage governance plays in the ...Several factors overlap in making urban heritage conservation vulnerable in terms of long-term sustainability.The purpose of this study is to offer insights into the dynamic role that heritage governance plays in the current sustainability debate.This purpose is achieved by investigating the shift from a‘governing for culture’approach to a‘governing through culture’approach in heritage conservation.Subsequently,a case is built for a circularity-based conservation strategy applicable to the governance of historic cities.Different indicators of the circular governance approach are considered,and useful data are collected in comparative form.The cross-matching relationship between the factors is then evaluated by employing the analytic hierarchy process(AHP)on the collected data.As a test case,the conservation strategy of the Medina of Tunis is presented.For a more general conservation model,case-specific data are acquired.Finally,the same framework is applied to compare the case-dependent and case-independent data to define an integrated conservation framework.The obtained results show that the knowledge and data exchange factor,carries the highest significance.This result translates into heritage-led urban regeneration through knowledge sharing and the effective redistribution of cultural activities in historic city centres.展开更多
In the realities of the modern world, when the natural habitat is rapidly disappearing and the number of imperiled plants is constantly growing, ex situ conservation is gaining importance. To meet this challenge, bota...In the realities of the modern world, when the natural habitat is rapidly disappearing and the number of imperiled plants is constantly growing, ex situ conservation is gaining importance. To meet this challenge, botanic gardens need to revise both their strategic goals and their methodologies to achieve the new goals. This paper proposes a strategy for the management of threatened plants in living collections,which includes setting regional conservation priorities for the species, creation of genetically representative collections for the high priority species, and usage of these collections in in situ actions. In this strategy, the value of existing and future species living collections for conservation is determined by the species' conservation status and how well the accessions represent their natural genetic variation.展开更多
Carbon storage serves as a key indicator of ecosystem services and plays a vital role in maintaining the global carbon balance.Land use and cover change(LUCC)is one of the primary drivers influencing carbon storage va...Carbon storage serves as a key indicator of ecosystem services and plays a vital role in maintaining the global carbon balance.Land use and cover change(LUCC)is one of the primary drivers influencing carbon storage variations in terrestrial ecosystems.Therefore,evaluating the impacts of LUCC on carbon storage is crucial for achieving strategic goals such as the China’s dual carbon goals(including carbon peaking and carbon neutrality).This study focuses on the Aral Irrigation Area in Xinjiang Uygur Autonomous Region,China,to assess the impacts of LUCC on regional carbon storage and their spatiotemporal dynamics.A comprehensive LUCC database from 2000 to 2020 was developed using Landsat satellite imagery and the random forest classification algorithm.The integrated valuation of ecosystem services and trade-offs(InVEST)model was applied to quantify carbon storage and analyze its response to LUCC.Additionally,future LUCC patterns for 2030 were projected under multiple development scenarios using the patch-generating land use simulation(PLUS)model.These future LUCC scenarios were integrated with the InVEST model to simulate carbon storage trends under different land management pathways.Between 2000 and 2020,the dominant land use types in the study area were cropland(area proportion of 35.52%),unused land(34.80%),and orchard land(12.19%).The conversion of unused land and orchard land significantly expanded the area of cropland,which increased by 115,742.55 hm^(2).During this period,total carbon storage and carbon density increased by 7.87×10^(6) Mg C and 20.19 Mg C/hm^(2),respectively.The primary driver of this increase was the conversion of unused land into cropland,accounting for 49.28%of the total carbon storage gain.Carbon storage was notably lower along the northeastern and southeastern edges.By 2030,the projected carbon storage is expected to increase by 0.99×10^(6),1.55×10^(6),and 1.71×10^(6) Mg C under the natural development,cropland protection,and ecological conservation scenarios,respectively.In contrast,under the urban development scenario,carbon storage is projected to decline by 0.40×10^(6) Mg C.In line with China’s dual carbon goals,the ecological conservation scenario emerges as the most effective strategy for enhancing carbon storage.Accordingly,strict enforcement of the cropland red line is recommended.This study provides a valuable scientific foundation for regional ecosystem restoration and sustainable development in arid regions.展开更多
Aim To extend several fundamental theorems of conventional elasticity theory to quasicrystalelasticity theory. Methods The basic governing equations of quasicrystal elasticity theory and Gauss's theorem were appli...Aim To extend several fundamental theorems of conventional elasticity theory to quasicrystalelasticity theory. Methods The basic governing equations of quasicrystal elasticity theory and Gauss's theorem were applied in the derivation. Results and Conclusion The principle of virtual work, Betti's reciprocal theorem and the uniqueness theorem of quasicrystal elasticity theory are proud, and some conservative integrals in quasicrystal elasticty theory are obtained.展开更多
In this paper, we study the classical Allen-Cahn equations and investigate the maximum- principle-preserving (MPP) techniques. The Allen-Cahn equation has been widely used in mathematical models for problems in materi...In this paper, we study the classical Allen-Cahn equations and investigate the maximum- principle-preserving (MPP) techniques. The Allen-Cahn equation has been widely used in mathematical models for problems in materials science and fluid dynamics. It enjoys the energy stability and the maximum-principle. Moreover, it is well known that the Allen- Cahn equation may yield thin interface layer, and nonuniform meshes might be useful in the numerical solutions. Therefore, we apply the local discontinuous Galerkin (LDG) method due to its flexibility on h-p adaptivity and complex geometry. However, the MPP LDG methods require slope limiters, then the energy stability may not be easy to obtain. In this paper, we only discuss the MPP technique and use numerical experiments to dem-onstrate the energy decay property. Moreover, due to the stiff source given in the equation, we use the conservative modified exponential Runge-Kutta methods and thus can use rela-tively large time step sizes. Thanks to the conservative time integration, the bounds of the unknown function will not decay. Numerical experiments will be given to demonstrate the good performance of the MPP LDG scheme.展开更多
This paper presents a high order symplectic con- servative perturbation method for linear time-varying Hamil- tonian system. Firstly, the dynamic equation of Hamilto- nian system is gradually changed into a high order...This paper presents a high order symplectic con- servative perturbation method for linear time-varying Hamil- tonian system. Firstly, the dynamic equation of Hamilto- nian system is gradually changed into a high order pertur- bation equation, which is solved approximately by resolv- ing the Hamiltonian coefficient matrix into a ＂major compo- nent＂ and a ＂high order small quantity＂ and using perturba- tion transformation technique, then the solution to the orig- inal equation of Hamiltonian system is determined through a series of inverse transform. Because the transfer matrix determined by the method in this paper is the product of a series of exponential matrixes, the transfer matrix is a sym- plectic matrix; furthermore, the exponential matrices can be calculated accurately by the precise time integration method, so the method presented in this paper has fine accuracy, ef- ficiency and stability. The examples show that the proposed method can also give good results even though a large time step is selected, and with the increase of the perturbation or- der, the perturbation solutions tend to exact solutions rapidly.展开更多
In this paper, a new spectral problem is proposed and the corresponding soliton equations hierarchy are also obtained. Under a constraint between the potentials and the eigenfunctions, the eigenvalue problem is nonlin...In this paper, a new spectral problem is proposed and the corresponding soliton equations hierarchy are also obtained. Under a constraint between the potentials and the eigenfunctions, the eigenvalue problem is nonlinearized so as to be a new finite-dimensional Hamiltonian system. By resotring to the generating function approach, we obtain conserved integrals and the involutivity of the conserved integrals. The finite-dimensional Hamiltonian system is further proved to be completely integrable in the Liouville sense. Finally, we show the decomposition of the soliton equations.展开更多
Finite-dimensional integrable Hamiltonian systems, obtained through the non- linearization of the 3×3 spectral problems associated with the Manakov and the derivative Manakov equations, are investigated. A genera...Finite-dimensional integrable Hamiltonian systems, obtained through the non- linearization of the 3×3 spectral problems associated with the Manakov and the derivative Manakov equations, are investigated. A generating function method is used to give a simple and effective way to prove the involutivity of integrals. Finite-parameter solutions of the Manakov and the derivative Manakov equations are calculated based on the commutative systems of ordinary differential equations with these integrals as Hamiltonians.展开更多
Finite-dimensional integrable Hamiltonian system, obtained through the nonlinearization of the 3 × 3 spectral problem associated with the Boussinesq equation, is investigated. A generating function method startin...Finite-dimensional integrable Hamiltonian system, obtained through the nonlinearization of the 3 × 3 spectral problem associated with the Boussinesq equation, is investigated. A generating function method starting from the Lax-Moser matrix is used to give an effective way to prove the involutivity of integrals. Finite-parameter solution of the Boussinesq equation is calculated based on the commutative system of ordinary differential equations with these integrals as Hamiltonians. The problem of the third order differential operator associated with the Boussinesq Neumann system put forward by H. Flaschka in 1983 is solved.展开更多
文摘The Yangtze finless porpoise(YFP)is an endemic freshwater cetacean species that exclusively inhabits the middle and lower reaches of the Yangtze River basin.Since the late 1970s,the YFP has experienced a drastic population decline and was classified as critically endangered by the IUCN in 2013.To save this unique species,a range of integrated conservation measures have been implemented,including strengthening natural habitat protection(in-situ),enhancing insurance populations(ex-situ),and advancing captive breeding and research initiatives.These efforts have yielded significant progress in the conservation of the YFP.The natural population has been starting to increase after a sharp decline,and the establishment of three insurance populations has provided a solid foundation for recovery.Additionally,advancement in captive breeding and research has delivered crucial technical support for population conservation.As a flagship species of Yangtze River biodiversity and an indicator of the river’s ecosystem health,the YFP’s integrated conservation strategy not only benefits its own population but also offers valuable insights for the protection of other endangered aquatic species in the Yangtze River and other threatened small cetaceans worldwide.
文摘The paper analyzed the opportunities and challenges faced by the urban heritage protection of Dashilanr historical district based on the concept of the integrated conservation of the urban heritage of Beijing old city at present.Then,the paper put forward the protection of urban heritage to lead the revitalization of Dashilanr historical district,and then the paper analyzed the historical and cultural value carrier of the Dashilanr urban heritage.Finally,the paper proposed that integrated conservation of the Dashilanr urban heritage needed the protection method of historic urban landscape.
文摘Several factors overlap in making urban heritage conservation vulnerable in terms of long-term sustainability.The purpose of this study is to offer insights into the dynamic role that heritage governance plays in the current sustainability debate.This purpose is achieved by investigating the shift from a‘governing for culture’approach to a‘governing through culture’approach in heritage conservation.Subsequently,a case is built for a circularity-based conservation strategy applicable to the governance of historic cities.Different indicators of the circular governance approach are considered,and useful data are collected in comparative form.The cross-matching relationship between the factors is then evaluated by employing the analytic hierarchy process(AHP)on the collected data.As a test case,the conservation strategy of the Medina of Tunis is presented.For a more general conservation model,case-specific data are acquired.Finally,the same framework is applied to compare the case-dependent and case-independent data to define an integrated conservation framework.The obtained results show that the knowledge and data exchange factor,carries the highest significance.This result translates into heritage-led urban regeneration through knowledge sharing and the effective redistribution of cultural activities in historic city centres.
文摘In the realities of the modern world, when the natural habitat is rapidly disappearing and the number of imperiled plants is constantly growing, ex situ conservation is gaining importance. To meet this challenge, botanic gardens need to revise both their strategic goals and their methodologies to achieve the new goals. This paper proposes a strategy for the management of threatened plants in living collections,which includes setting regional conservation priorities for the species, creation of genetically representative collections for the high priority species, and usage of these collections in in situ actions. In this strategy, the value of existing and future species living collections for conservation is determined by the species' conservation status and how well the accessions represent their natural genetic variation.
基金supported by the National Key R&D Program of China(2022YFD1900503).
文摘Carbon storage serves as a key indicator of ecosystem services and plays a vital role in maintaining the global carbon balance.Land use and cover change(LUCC)is one of the primary drivers influencing carbon storage variations in terrestrial ecosystems.Therefore,evaluating the impacts of LUCC on carbon storage is crucial for achieving strategic goals such as the China’s dual carbon goals(including carbon peaking and carbon neutrality).This study focuses on the Aral Irrigation Area in Xinjiang Uygur Autonomous Region,China,to assess the impacts of LUCC on regional carbon storage and their spatiotemporal dynamics.A comprehensive LUCC database from 2000 to 2020 was developed using Landsat satellite imagery and the random forest classification algorithm.The integrated valuation of ecosystem services and trade-offs(InVEST)model was applied to quantify carbon storage and analyze its response to LUCC.Additionally,future LUCC patterns for 2030 were projected under multiple development scenarios using the patch-generating land use simulation(PLUS)model.These future LUCC scenarios were integrated with the InVEST model to simulate carbon storage trends under different land management pathways.Between 2000 and 2020,the dominant land use types in the study area were cropland(area proportion of 35.52%),unused land(34.80%),and orchard land(12.19%).The conversion of unused land and orchard land significantly expanded the area of cropland,which increased by 115,742.55 hm^(2).During this period,total carbon storage and carbon density increased by 7.87×10^(6) Mg C and 20.19 Mg C/hm^(2),respectively.The primary driver of this increase was the conversion of unused land into cropland,accounting for 49.28%of the total carbon storage gain.Carbon storage was notably lower along the northeastern and southeastern edges.By 2030,the projected carbon storage is expected to increase by 0.99×10^(6),1.55×10^(6),and 1.71×10^(6) Mg C under the natural development,cropland protection,and ecological conservation scenarios,respectively.In contrast,under the urban development scenario,carbon storage is projected to decline by 0.40×10^(6) Mg C.In line with China’s dual carbon goals,the ecological conservation scenario emerges as the most effective strategy for enhancing carbon storage.Accordingly,strict enforcement of the cropland red line is recommended.This study provides a valuable scientific foundation for regional ecosystem restoration and sustainable development in arid regions.
文摘Aim To extend several fundamental theorems of conventional elasticity theory to quasicrystalelasticity theory. Methods The basic governing equations of quasicrystal elasticity theory and Gauss's theorem were applied in the derivation. Results and Conclusion The principle of virtual work, Betti's reciprocal theorem and the uniqueness theorem of quasicrystal elasticity theory are proud, and some conservative integrals in quasicrystal elasticty theory are obtained.
基金Jie Du is supported by the National Natural Science Foundation of China under Grant Number NSFC 11801302Tsinghua University Initiative Scientific Research Program+1 种基金Eric Chung is supported by Hong Kong RGC General Research Fund(Projects 14304217 and 14302018)The third author is supported by the NSF grant DMS-1818467.
文摘In this paper, we study the classical Allen-Cahn equations and investigate the maximum- principle-preserving (MPP) techniques. The Allen-Cahn equation has been widely used in mathematical models for problems in materials science and fluid dynamics. It enjoys the energy stability and the maximum-principle. Moreover, it is well known that the Allen- Cahn equation may yield thin interface layer, and nonuniform meshes might be useful in the numerical solutions. Therefore, we apply the local discontinuous Galerkin (LDG) method due to its flexibility on h-p adaptivity and complex geometry. However, the MPP LDG methods require slope limiters, then the energy stability may not be easy to obtain. In this paper, we only discuss the MPP technique and use numerical experiments to dem-onstrate the energy decay property. Moreover, due to the stiff source given in the equation, we use the conservative modified exponential Runge-Kutta methods and thus can use rela-tively large time step sizes. Thanks to the conservative time integration, the bounds of the unknown function will not decay. Numerical experiments will be given to demonstrate the good performance of the MPP LDG scheme.
基金supported by the National Natural Science Foun-dation of China (11172334)
文摘This paper presents a high order symplectic con- servative perturbation method for linear time-varying Hamil- tonian system. Firstly, the dynamic equation of Hamilto- nian system is gradually changed into a high order pertur- bation equation, which is solved approximately by resolv- ing the Hamiltonian coefficient matrix into a ＂major compo- nent＂ and a ＂high order small quantity＂ and using perturba- tion transformation technique, then the solution to the orig- inal equation of Hamiltonian system is determined through a series of inverse transform. Because the transfer matrix determined by the method in this paper is the product of a series of exponential matrixes, the transfer matrix is a sym- plectic matrix; furthermore, the exponential matrices can be calculated accurately by the precise time integration method, so the method presented in this paper has fine accuracy, ef- ficiency and stability. The examples show that the proposed method can also give good results even though a large time step is selected, and with the increase of the perturbation or- der, the perturbation solutions tend to exact solutions rapidly.
基金Supported by the National Natural Science Foundation of China(1127100861072147+2 种基金11447220)Supported by the First-class Discipline of Universities in ShanghaiSupported by the Science and Technology Department of Henan Province(152300410230)
文摘In this paper, a new spectral problem is proposed and the corresponding soliton equations hierarchy are also obtained. Under a constraint between the potentials and the eigenfunctions, the eigenvalue problem is nonlinearized so as to be a new finite-dimensional Hamiltonian system. By resotring to the generating function approach, we obtain conserved integrals and the involutivity of the conserved integrals. The finite-dimensional Hamiltonian system is further proved to be completely integrable in the Liouville sense. Finally, we show the decomposition of the soliton equations.
基金Supported by the Special Funds for Major State Basic Research Project of China(G20000077301)
文摘Finite-dimensional integrable Hamiltonian systems, obtained through the non- linearization of the 3×3 spectral problems associated with the Manakov and the derivative Manakov equations, are investigated. A generating function method is used to give a simple and effective way to prove the involutivity of integrals. Finite-parameter solutions of the Manakov and the derivative Manakov equations are calculated based on the commutative systems of ordinary differential equations with these integrals as Hamiltonians.
文摘Finite-dimensional integrable Hamiltonian system, obtained through the nonlinearization of the 3 × 3 spectral problem associated with the Boussinesq equation, is investigated. A generating function method starting from the Lax-Moser matrix is used to give an effective way to prove the involutivity of integrals. Finite-parameter solution of the Boussinesq equation is calculated based on the commutative system of ordinary differential equations with these integrals as Hamiltonians. The problem of the third order differential operator associated with the Boussinesq Neumann system put forward by H. Flaschka in 1983 is solved.
