Hybrid nematic films have been studied by Monte Carlo simulations using a lattice spin model, in which the pair potential is spatially anisotropic and dependent on elastic constants of liquid crystals. We confirm in t...Hybrid nematic films have been studied by Monte Carlo simulations using a lattice spin model, in which the pair potential is spatially anisotropic and dependent on elastic constants of liquid crystals. We confirm in the thin hybrid nematic film the existence of a biaxially nonbent structure and the structure transition from the biaxial to the bent-director structure, which is similar to the result obtained using the Lebwoh-Lasher model. However, the step-like director＇s profile, characteristic for the biaxial structure, is spatially asymmetric in the film because the pair potential leads to K1 ≠ K3. We estimate the upper cell thickness to be 69 spin layers, in which the biaxial structure can be found.展开更多
The deep sea holds vital resources and spatial potential for future human survival and development,reflecting the common interests and concerns of all mankind.Amidst unprecedented global transformations in a hundred y...The deep sea holds vital resources and spatial potential for future human survival and development,reflecting the common interests and concerns of all mankind.Amidst unprecedented global transformations in a hundred years,the deep sea has emerged as a critical area of international competition and serves as a new frontier for resource extraction,a strategic space for military competition,and a contested space for great power rivalry and rule-making.展开更多
The Natural Forest Protection Project(NFPP),initiated by the Chinese government in 2000,is a crucial ecological construction project that has played a significant role in forest restoration in China.Forests in the Qin...The Natural Forest Protection Project(NFPP),initiated by the Chinese government in 2000,is a crucial ecological construction project that has played a significant role in forest restoration in China.Forests in the Qinghai-Tibet Plateau(QTP)serve as important habitats for many rare and endemic birds.Understanding the conservation efficiency of NFPP implementation on these birds holds significant practical significance.In this study,we utilized land use change matrices to analyze the forest changes in the QTP before and after NFPP implementation,predicted the potential spatial distribution of 16 nationally protected birds using Species Distribution Models(SDMs),and compared the impacts of this project on bird habitats under different carbon emission scenarios.Mann-Whitney U tests were employed to analyze the adaptation of different birds to forest changes during NFPP implementation.Our results showed that NFPP protected 172,398 km^(2) of primary forests and added 6379 km^(2) of secondary forests in our study area.The potential spatial distribution and sympatric species richness of the 16 protected birds slightly increased after NFPP implementation under different climate change scenarios,and NFPP implementation contributed to improving the potential spatial distribution of birds.Compared to newly established secondary forests,protected primary forests exhibited enhanced conservation for forest birds(Z-value>0 for six bird species,P<0.1),while being less suitable for non-forest birds(significantly unsuitable for three non-forest bird species,Z-value<0,P<0.05;non-significantly unsuitable for four non-forest bird species,Zvalue<0,P>0.1).This indicates that the protection of primary forests during NFPP implementation benefits forest bird conservation while the addition of secondary forests is beneficial to non-forest birds.To enhance the role of NFPP in avian conservation in the QTP,it is suggested to increase the landscape heterogeneity of forest,particularly in newly established secondary forests.展开更多
We propose a hierarchy of novel absorbing boundary conditions for the onedimensional stationary Schr¨odinger equation with general(linear and nonlinear)potential.The accuracy of the new absorbing boundary conditi...We propose a hierarchy of novel absorbing boundary conditions for the onedimensional stationary Schr¨odinger equation with general(linear and nonlinear)potential.The accuracy of the new absorbing boundary conditions is investigated numerically for the computation of energies and ground-states for linear and nonlinear Schr¨odinger equations.It turns out that these absorbing boundary conditions and their variants lead to a higher accuracy than the usual Dirichlet boundary condition.Finally,we give the extension of these ABCs to N-dimensional stationary Schr¨odinger equations.展开更多
基金Project supported by the National Natural Science Foundation of China (Grants Nos 60736042 and 60878047)the Key Subject Construction Project of Hebei Province University
文摘Hybrid nematic films have been studied by Monte Carlo simulations using a lattice spin model, in which the pair potential is spatially anisotropic and dependent on elastic constants of liquid crystals. We confirm in the thin hybrid nematic film the existence of a biaxially nonbent structure and the structure transition from the biaxial to the bent-director structure, which is similar to the result obtained using the Lebwoh-Lasher model. However, the step-like director＇s profile, characteristic for the biaxial structure, is spatially asymmetric in the film because the pair potential leads to K1 ≠ K3. We estimate the upper cell thickness to be 69 spin layers, in which the biaxial structure can be found.
文摘The deep sea holds vital resources and spatial potential for future human survival and development,reflecting the common interests and concerns of all mankind.Amidst unprecedented global transformations in a hundred years,the deep sea has emerged as a critical area of international competition and serves as a new frontier for resource extraction,a strategic space for military competition,and a contested space for great power rivalry and rule-making.
基金funded by Central Fiscal Forestry and Grassland Ecological Protection and Restoration Fund in 2022(grant number:HYGJ22069P(2022zfcg03469)-HT01)National Natural Science Foundation of China(grant number:3152010390332070452)。
文摘The Natural Forest Protection Project(NFPP),initiated by the Chinese government in 2000,is a crucial ecological construction project that has played a significant role in forest restoration in China.Forests in the Qinghai-Tibet Plateau(QTP)serve as important habitats for many rare and endemic birds.Understanding the conservation efficiency of NFPP implementation on these birds holds significant practical significance.In this study,we utilized land use change matrices to analyze the forest changes in the QTP before and after NFPP implementation,predicted the potential spatial distribution of 16 nationally protected birds using Species Distribution Models(SDMs),and compared the impacts of this project on bird habitats under different carbon emission scenarios.Mann-Whitney U tests were employed to analyze the adaptation of different birds to forest changes during NFPP implementation.Our results showed that NFPP protected 172,398 km^(2) of primary forests and added 6379 km^(2) of secondary forests in our study area.The potential spatial distribution and sympatric species richness of the 16 protected birds slightly increased after NFPP implementation under different climate change scenarios,and NFPP implementation contributed to improving the potential spatial distribution of birds.Compared to newly established secondary forests,protected primary forests exhibited enhanced conservation for forest birds(Z-value>0 for six bird species,P<0.1),while being less suitable for non-forest birds(significantly unsuitable for three non-forest bird species,Z-value<0,P<0.05;non-significantly unsuitable for four non-forest bird species,Zvalue<0,P>0.1).This indicates that the protection of primary forests during NFPP implementation benefits forest bird conservation while the addition of secondary forests is beneficial to non-forest birds.To enhance the role of NFPP in avian conservation in the QTP,it is suggested to increase the landscape heterogeneity of forest,particularly in newly established secondary forests.
基金supported by the French ANR fundings under the project MicroWave NT09_460489.
文摘We propose a hierarchy of novel absorbing boundary conditions for the onedimensional stationary Schr¨odinger equation with general(linear and nonlinear)potential.The accuracy of the new absorbing boundary conditions is investigated numerically for the computation of energies and ground-states for linear and nonlinear Schr¨odinger equations.It turns out that these absorbing boundary conditions and their variants lead to a higher accuracy than the usual Dirichlet boundary condition.Finally,we give the extension of these ABCs to N-dimensional stationary Schr¨odinger equations.
