The singularly perturbed initial boudary value problem for the nonlocal reaction diffusion systems was considered. Using iteration method the comparison theorem was obtained. Introducing stretched variable the formal ...The singularly perturbed initial boudary value problem for the nonlocal reaction diffusion systems was considered. Using iteration method the comparison theorem was obtained. Introducing stretched variable the formal asymptotic solution was constructed. And the existence and its asymptotic behavior of solution for the problem were studied by using the method of the upper and lower solution.展开更多
By the subsuper solutions method, the explosive supersolutions and explosive subsol utions are obtained and the exsistence of explosive solutions is proved on a bounded domain for a class of nonlinear elliptic problem...By the subsuper solutions method, the explosive supersolutions and explosive subsol utions are obtained and the exsistence of explosive solutions is proved on a bounded domain for a class of nonlinear elliptic problems.Then, the exsitence of an entire large solution is proved by the perturbed method.展开更多
The article describes the activity of two Italian photographers： Carlo Bavagnoli （1932） and Mario Dondero （1928） In particular, it focuses on their debuts in the world of photojournalism in Italy since the early ...The article describes the activity of two Italian photographers： Carlo Bavagnoli （1932） and Mario Dondero （1928） In particular, it focuses on their debuts in the world of photojournalism in Italy since the early 1950s. First, it offers an overview of the national photographic research in the post-Second World War, underlining a significant evolution compared with the past and the complexity of the directions undertaken. Then, in the outlined context, it studies the work of the two photographers and their approach to a socially active photography, dwelling mainly on the relationships interwoven with the ruling publishing system. It also underlines the elements characterizing the nature of their reportages and the distance from an idea of image exploitation, derived from an always increasing interference of the political control over the images destined to mass communication. Both Dondero and Bavagnoli avoid any tendency to spectacularization and to the representative models typical of the common neorealist orientation, proposing an information founded on the effectiveness of narration, on the concreteness and immediacy of evidence; the first collaborations with the most progressive magazines testify the peculiarity of a method that both will coherently develop in the experiences matured outside the Italian context.展开更多
In this paper,a new matrix decomposition called the weighted polar decomposition is considered.Two uniqueness theorems of weighted polar decomposition are presented,and the best approximation property of weighted unit...In this paper,a new matrix decomposition called the weighted polar decomposition is considered.Two uniqueness theorems of weighted polar decomposition are presented,and the best approximation property of weighted unitary polar factor and perturbation bounds for weighted polar decomposition are also studied.展开更多
Surface vortex behavior in front of the tunnel intake was investigated in this paper.The critical submergence of vortex was discussed based on the concept of 'critical spherical sink surface'(CSSS).The vortex ...Surface vortex behavior in front of the tunnel intake was investigated in this paper.The critical submergence of vortex was discussed based on the concept of 'critical spherical sink surface'(CSSS).The vortex formation and evolution at the tunnel intake were analyzed based on the theory of CSSS considering the effect of circulation.A theory was proposed to explain the surface vortex.The theoretical development was verified by the physical model experiments of Xiluodu hydropower station.The radial velocity and vortex circulation were considered as the main factors that influence the formation and evolution of surface vortex.Finally,an anti-vortex intake configuration was proposed to weaken the air-core vortex in front of the tunnel intakes of the hydraulic structures.展开更多
Analysis of forest canopy hemisphere images is one of the most important methods for measuring forest canopy structure parameters. In this study, our main focus was on using circular image region segmentation, which i...Analysis of forest canopy hemisphere images is one of the most important methods for measuring forest canopy structure parameters. In this study, our main focus was on using circular image region segmentation, which is the basis of forest canopy hemispherical photography. The boundary of a forest canopy hemisphere image was analyzed via histogram, rectangle, and Fourier descriptors. The image boundary characteristics were defined and obtained based on the following：（1） an edge model that contains three parts, i.e., step, ramp, and roof;（2） boundary points of discontinuity;（3） an edge that has a linear distribution of scattering points. On this basis, we proposed a segmentation method for the circular region in a forest canopy hemisphere image, fitting the circular boundary and computing the center and radius by the least squares method. The method was unrelated to the parameters of the image acquisition device. Hence, this study lays a foundation for automatically adjusting the parameters of high-performance image acquisition devices used in forest canopy hemispherical photography.展开更多
文摘The singularly perturbed initial boudary value problem for the nonlocal reaction diffusion systems was considered. Using iteration method the comparison theorem was obtained. Introducing stretched variable the formal asymptotic solution was constructed. And the existence and its asymptotic behavior of solution for the problem were studied by using the method of the upper and lower solution.
基金National Natural Science Foundation of China (No.10131050)
文摘By the subsuper solutions method, the explosive supersolutions and explosive subsol utions are obtained and the exsistence of explosive solutions is proved on a bounded domain for a class of nonlinear elliptic problems.Then, the exsitence of an entire large solution is proved by the perturbed method.
文摘The article describes the activity of two Italian photographers： Carlo Bavagnoli （1932） and Mario Dondero （1928） In particular, it focuses on their debuts in the world of photojournalism in Italy since the early 1950s. First, it offers an overview of the national photographic research in the post-Second World War, underlining a significant evolution compared with the past and the complexity of the directions undertaken. Then, in the outlined context, it studies the work of the two photographers and their approach to a socially active photography, dwelling mainly on the relationships interwoven with the ruling publishing system. It also underlines the elements characterizing the nature of their reportages and the distance from an idea of image exploitation, derived from an always increasing interference of the political control over the images destined to mass communication. Both Dondero and Bavagnoli avoid any tendency to spectacularization and to the representative models typical of the common neorealist orientation, proposing an information founded on the effectiveness of narration, on the concreteness and immediacy of evidence; the first collaborations with the most progressive magazines testify the peculiarity of a method that both will coherently develop in the experiences matured outside the Italian context.
文摘In this paper,a new matrix decomposition called the weighted polar decomposition is considered.Two uniqueness theorems of weighted polar decomposition are presented,and the best approximation property of weighted unitary polar factor and perturbation bounds for weighted polar decomposition are also studied.
基金supported by Tsinghua University Initiative Scientific Research Program (Grant No. 2009THZ07060)the State Key Laboratory of Hydroscience and Engineering of Tsinghua University (Grant No. 2010-TC-2,2009-TC-2)
文摘Surface vortex behavior in front of the tunnel intake was investigated in this paper.The critical submergence of vortex was discussed based on the concept of 'critical spherical sink surface'(CSSS).The vortex formation and evolution at the tunnel intake were analyzed based on the theory of CSSS considering the effect of circulation.A theory was proposed to explain the surface vortex.The theoretical development was verified by the physical model experiments of Xiluodu hydropower station.The radial velocity and vortex circulation were considered as the main factors that influence the formation and evolution of surface vortex.Finally,an anti-vortex intake configuration was proposed to weaken the air-core vortex in front of the tunnel intakes of the hydraulic structures.
基金Project supported by the Fundamental Research Funds for the Central Universities,China（No.2572014BB04） the National Natural Science Foundation of China（No.31370710） the Specialized Research Fund for the Doctoral Program of Higher Education of China（No.20110062110002）
文摘Analysis of forest canopy hemisphere images is one of the most important methods for measuring forest canopy structure parameters. In this study, our main focus was on using circular image region segmentation, which is the basis of forest canopy hemispherical photography. The boundary of a forest canopy hemisphere image was analyzed via histogram, rectangle, and Fourier descriptors. The image boundary characteristics were defined and obtained based on the following：（1） an edge model that contains three parts, i.e., step, ramp, and roof;（2） boundary points of discontinuity;（3） an edge that has a linear distribution of scattering points. On this basis, we proposed a segmentation method for the circular region in a forest canopy hemisphere image, fitting the circular boundary and computing the center and radius by the least squares method. The method was unrelated to the parameters of the image acquisition device. Hence, this study lays a foundation for automatically adjusting the parameters of high-performance image acquisition devices used in forest canopy hemispherical photography.
