Traditional biomechanical analyses of human movement are generally derived from linear mathematics.While these methods can be useful in many situations,they do not describe behaviors in human systems that are predomin...Traditional biomechanical analyses of human movement are generally derived from linear mathematics.While these methods can be useful in many situations,they do not describe behaviors in human systems that are predominately nonlinear.For this reason,nonlinear analysis methods based on a dynamical systems approach have become more prevalent in recent literature.These analysis techniques have provided new insights into how systems(1) maintain pattern stability,(2) transition into new states,and(3) are governed by short-and long-term(fractal) correlational processes at different spatio-temporal scales.These different aspects of system dynamics are typically investigated using concepts related to variability,stability,complexity,and adaptability.The purpose of this paper is to compare and contrast these different concepts and demonstrate that,although related,these terms represent fundamentally different aspects of system dynamics.In particular,we argue that variability should not uniformly be equated with stability or complexity of movement.In addition,current dynamic stability measures based on nonlinear analysis methods(such as the finite maximal Lyapunov exponent) can reveal local instabilities in movement dynamics,but the degree to which these local instabilities relate to global postural and gait stability and the ability to resist external perturbations remains to be explored.Finally,systematic studies are needed to relate observed reductions in complexity with aging and disease to the adaptive capabilities of the movement system and how complexity changes as a function of different task constraints.展开更多
Stone structures with dry joints, that is, without mortar, have shown a surprising behavior when earthquakes occur. An example of this behavior is the perennially of the so-called Inca wall in Peru, which despite havi...Stone structures with dry joints, that is, without mortar, have shown a surprising behavior when earthquakes occur. An example of this behavior is the perennially of the so-called Inca wall in Peru, which despite having suffered several earthquakes over time has remained stable without collapsing. This article presents the research carried out on stone masonry wails with dry joint, without mortar, subject to a seismic action. In order to understand the behavior of the masonry without mortar, it designs a Grid mode/ of Finite Elements. From the results, it is concluded that these walls with a certain thickness have ductility that allows them to withstand high displacement and rotation values, thus accommodating the movement of the earth subject to an earthquake. The individual stone blocks move relative to each other through rotations and displacements, which are processed in the free joints of any mortar. The joints work as energy sinks. The free movements in the joints dissipate the energy transmitted by the earthquake, not causing in this way the rupture of the stone blocks. The goal of this article is to understand the p importance of lack of mortar in the seismic behavior of the mansonry.展开更多
The interactive effects of natural and human factors on ecosystems have been well studied, and the quantitative assessment of large-scale ecological vulnerability caused by natural and human factors is now one of the ...The interactive effects of natural and human factors on ecosystems have been well studied, and the quantitative assessment of large-scale ecological vulnerability caused by natural and human factors is now one of the most active topics in the ifeld. Taking the Guangxi Xijiang River Economic Belt in southwest China （GXEB） as a case study, we assess ecological vulnerability based on the Vulnerability Scoping Diagram （VSD） model. The indices system is decomposed into three sub objects, ten elements and 25 indicators layer by layer, which included factors from both natural and human ifelds. Results indicate that zones with lower, middle-lower, middle, middle-higher and higher vulnerability account for 11.31%, 22.63%, 27.60%, 24.39%, and 14.07%, respectively. The western and eastern parts of GXEB are more vulnerable than the central part and the mountain and urban areas are of higher vulnerability than the basins and river valleys. Compared with a vulnerability assessment based on natural factors only, it is concluded that human activities indeed cause the transition from naturally stable zones to vulnerable zones. The nature-dominated vulnerable zones are different with human-dominated ones in size and distribution, the latter being smaller, more scattered and distributed in urban areas and their surroundings. About 53%of total construction land is distributed in zones with middle and middle-higher ecological vulnerability;less vulnerable zones should attract construction in the future. Relevant suggestions are proposed on how to reduce vulnerability according to inducing factors. The VSD model has a signiifcant advantage in the quantitative evaluation of ecological vulnerability, but is insufficient to distinguish nature- or human-dominated vulnerability quantitatively.展开更多
文摘Traditional biomechanical analyses of human movement are generally derived from linear mathematics.While these methods can be useful in many situations,they do not describe behaviors in human systems that are predominately nonlinear.For this reason,nonlinear analysis methods based on a dynamical systems approach have become more prevalent in recent literature.These analysis techniques have provided new insights into how systems(1) maintain pattern stability,(2) transition into new states,and(3) are governed by short-and long-term(fractal) correlational processes at different spatio-temporal scales.These different aspects of system dynamics are typically investigated using concepts related to variability,stability,complexity,and adaptability.The purpose of this paper is to compare and contrast these different concepts and demonstrate that,although related,these terms represent fundamentally different aspects of system dynamics.In particular,we argue that variability should not uniformly be equated with stability or complexity of movement.In addition,current dynamic stability measures based on nonlinear analysis methods(such as the finite maximal Lyapunov exponent) can reveal local instabilities in movement dynamics,but the degree to which these local instabilities relate to global postural and gait stability and the ability to resist external perturbations remains to be explored.Finally,systematic studies are needed to relate observed reductions in complexity with aging and disease to the adaptive capabilities of the movement system and how complexity changes as a function of different task constraints.
文摘Stone structures with dry joints, that is, without mortar, have shown a surprising behavior when earthquakes occur. An example of this behavior is the perennially of the so-called Inca wall in Peru, which despite having suffered several earthquakes over time has remained stable without collapsing. This article presents the research carried out on stone masonry wails with dry joint, without mortar, subject to a seismic action. In order to understand the behavior of the masonry without mortar, it designs a Grid mode/ of Finite Elements. From the results, it is concluded that these walls with a certain thickness have ductility that allows them to withstand high displacement and rotation values, thus accommodating the movement of the earth subject to an earthquake. The individual stone blocks move relative to each other through rotations and displacements, which are processed in the free joints of any mortar. The joints work as energy sinks. The free movements in the joints dissipate the energy transmitted by the earthquake, not causing in this way the rupture of the stone blocks. The goal of this article is to understand the p importance of lack of mortar in the seismic behavior of the mansonry.
基金National Natural Science Foundation of China(41201110)Young Talents Foundation of Nanjing Institute of Geography and Limnology of CAS(NIGLAS2011QD03)
文摘The interactive effects of natural and human factors on ecosystems have been well studied, and the quantitative assessment of large-scale ecological vulnerability caused by natural and human factors is now one of the most active topics in the ifeld. Taking the Guangxi Xijiang River Economic Belt in southwest China （GXEB） as a case study, we assess ecological vulnerability based on the Vulnerability Scoping Diagram （VSD） model. The indices system is decomposed into three sub objects, ten elements and 25 indicators layer by layer, which included factors from both natural and human ifelds. Results indicate that zones with lower, middle-lower, middle, middle-higher and higher vulnerability account for 11.31%, 22.63%, 27.60%, 24.39%, and 14.07%, respectively. The western and eastern parts of GXEB are more vulnerable than the central part and the mountain and urban areas are of higher vulnerability than the basins and river valleys. Compared with a vulnerability assessment based on natural factors only, it is concluded that human activities indeed cause the transition from naturally stable zones to vulnerable zones. The nature-dominated vulnerable zones are different with human-dominated ones in size and distribution, the latter being smaller, more scattered and distributed in urban areas and their surroundings. About 53%of total construction land is distributed in zones with middle and middle-higher ecological vulnerability;less vulnerable zones should attract construction in the future. Relevant suggestions are proposed on how to reduce vulnerability according to inducing factors. The VSD model has a signiifcant advantage in the quantitative evaluation of ecological vulnerability, but is insufficient to distinguish nature- or human-dominated vulnerability quantitatively.
