How neuronal spike trains encode external information is a hot topic in neurodynamics studies. In this paper, we investigate the dynamical states of the Hodgkin-Huxley neuron under periodic forcing. Depending on the p...How neuronal spike trains encode external information is a hot topic in neurodynamics studies. In this paper, we investigate the dynamical states of the Hodgkin-Huxley neuron under periodic forcing. Depending on the parameters of the stimulus, the neuron exhibits periodic, quasiperiodic and chaotic spike trains. In order to analyze these spike trains quantitatively, we use the phase return map to describe the dynamical behavior on a one-dimensional （1D） map. According to the monotonicity or discontinuous point of the 1D map, the spike trains are transformed into symbolic sequences by implementing a coarse-grained algorithm -- symbolic dynamics. Based on the ordering rules of symbolic dynamics, the parameters of the external stimulus can be measured in high resolution with finite length symbolic sequences. A reasonable explanation for why the nervous system can discriminate or cognize the small change of the external signals in a short time is also presented.展开更多
秸秆还田是一种更有效的秸秆处理措施,引起国际相关研究领域的关注。利用CiteSpace和VOSviewer可视化软件对Web of Science(891篇)和CNKI(3213篇)核心数据库文献进行分析。结果表明:(1)发文量总体呈上升趋势,其中《农业工程学报》和《...秸秆还田是一种更有效的秸秆处理措施,引起国际相关研究领域的关注。利用CiteSpace和VOSviewer可视化软件对Web of Science(891篇)和CNKI(3213篇)核心数据库文献进行分析。结果表明:(1)发文量总体呈上升趋势,其中《农业工程学报》和《印度农业科学杂志》分别是国内外载文量最多的期刊,而农业基础科学和农艺学是最受欢迎的学科类别。(2)发文量前3位的国家有中国(593篇)、印度(130篇)、美国(103篇),研究力量主要集中在高等教育机构,而中国科学院在国际上影响力深远,以鲁剑巍、Ping H E等为代表的团队合作呈现出总体分散、局部集中的特点。(3)关键词经历了机械化农业—土壤肥力—温室气体排放—秸秆还田技术4个研究阶段。(4)关键词密度共现分析表明,秸秆还田领域研究热点可归纳为秸秆还田培肥土壤与作物产量、长期施肥与秸秆联合效益及保护性耕作与土壤理化性质3个方面,未来可能聚焦于因地制宜的秸秆还田技术与经济效益的研究。展开更多
基于Lemaitre and Chaboche非线性随动强化理论、等向强化和Mises屈服准则,建立了复杂加载模式下非线性混合强化材料模型的弹塑性应力应变本构关系,并采用Backward Euler切向预测径向返回算法计算应力应变增量.基于ABAQUS开发式程序接口...基于Lemaitre and Chaboche非线性随动强化理论、等向强化和Mises屈服准则,建立了复杂加载模式下非线性混合强化材料模型的弹塑性应力应变本构关系,并采用Backward Euler切向预测径向返回算法计算应力应变增量.基于ABAQUS开发式程序接口,编写了非线性混合强化材料模型用户子程序.以Numisheet’93板料U型弯曲考题为例,分析了不同材料强化模型对板料回弹量的影响.结果表明,线性随动强化因模拟板料成形后的应力最小而低估了回弹量,各向同性强化因模拟成形后的应力最大而使预测的回弹量偏大.与Numisheet’93实验值的比较可知,对于复杂加载问题,采用非线性混合强化材料模型预测板料回弹量的精度最高.展开更多
The spring-loaded inverted pendulum(SLIP) has been widely studied in both animals and robots.Generally,the majority of the relevant theoretical studies deal with elastic leg,the linear leg length-force relationship of...The spring-loaded inverted pendulum(SLIP) has been widely studied in both animals and robots.Generally,the majority of the relevant theoretical studies deal with elastic leg,the linear leg length-force relationship of which is obviously conflict with the biological observations.A planar spring-mass model with a nonlinear spring leg is presented to explore the intrinsic mechanism of legged locomotion with elastic component.The leg model is formulated via decoupling the stiffness coefficient and exponent of the leg compression in order that the unified stiffness can be scaled as convex,concave as well as linear profile.The apex return map of the SLIP runner is established to investigate dynamical behavior of the fixed point.The basin of attraction and Floquet Multiplier are introduced to evaluate the self-stability and initial state sensitivity of the SLIP model with different stiffness profiles.The numerical results show that larger stiffness exponent can increase top speed of stable running and also can enlarge the size of attraction domain of the fixed point.In addition,the parameter variation is conducted to detect the effect of parameter dependency,and demonstrates that on the fixed energy level and stiffness profile,the faster running speed with larger convergence rate of the stable fixed point under small local perturbation can be achieved via decreasing the angle of attack and increasing the stiffness coefficient.The perturbation recovery test is implemented to judge the ability of the model resisting large external disturbance.The result shows that the convex stiffness performs best in enhancing the robustness of SLIP runner negotiating irregular terrain.This research sheds light on the running performance of the SLIP runner with nonlinear leg spring from a theoretical perspective,and also guides the design and control of the bio-inspired legged robot.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No.60871085)the Natural Science Foundation of Zhejiang Province,China (Grant No.Y1100119)
文摘How neuronal spike trains encode external information is a hot topic in neurodynamics studies. In this paper, we investigate the dynamical states of the Hodgkin-Huxley neuron under periodic forcing. Depending on the parameters of the stimulus, the neuron exhibits periodic, quasiperiodic and chaotic spike trains. In order to analyze these spike trains quantitatively, we use the phase return map to describe the dynamical behavior on a one-dimensional （1D） map. According to the monotonicity or discontinuous point of the 1D map, the spike trains are transformed into symbolic sequences by implementing a coarse-grained algorithm -- symbolic dynamics. Based on the ordering rules of symbolic dynamics, the parameters of the external stimulus can be measured in high resolution with finite length symbolic sequences. A reasonable explanation for why the nervous system can discriminate or cognize the small change of the external signals in a short time is also presented.
文摘秸秆还田是一种更有效的秸秆处理措施,引起国际相关研究领域的关注。利用CiteSpace和VOSviewer可视化软件对Web of Science(891篇)和CNKI(3213篇)核心数据库文献进行分析。结果表明:(1)发文量总体呈上升趋势,其中《农业工程学报》和《印度农业科学杂志》分别是国内外载文量最多的期刊,而农业基础科学和农艺学是最受欢迎的学科类别。(2)发文量前3位的国家有中国(593篇)、印度(130篇)、美国(103篇),研究力量主要集中在高等教育机构,而中国科学院在国际上影响力深远,以鲁剑巍、Ping H E等为代表的团队合作呈现出总体分散、局部集中的特点。(3)关键词经历了机械化农业—土壤肥力—温室气体排放—秸秆还田技术4个研究阶段。(4)关键词密度共现分析表明,秸秆还田领域研究热点可归纳为秸秆还田培肥土壤与作物产量、长期施肥与秸秆联合效益及保护性耕作与土壤理化性质3个方面,未来可能聚焦于因地制宜的秸秆还田技术与经济效益的研究。
文摘基于Lemaitre and Chaboche非线性随动强化理论、等向强化和Mises屈服准则,建立了复杂加载模式下非线性混合强化材料模型的弹塑性应力应变本构关系,并采用Backward Euler切向预测径向返回算法计算应力应变增量.基于ABAQUS开发式程序接口,编写了非线性混合强化材料模型用户子程序.以Numisheet’93板料U型弯曲考题为例,分析了不同材料强化模型对板料回弹量的影响.结果表明,线性随动强化因模拟板料成形后的应力最小而低估了回弹量,各向同性强化因模拟成形后的应力最大而使预测的回弹量偏大.与Numisheet’93实验值的比较可知,对于复杂加载问题,采用非线性混合强化材料模型预测板料回弹量的精度最高.
基金supported by National Natural Science Foundation of China(Grant No.61175107)National Hi-tech Research and Development Program of China(863 Program+3 种基金Grant No.2011AA0403837002)Self-Planned Task of State Key Laboratory of Robotics and SystemHarbin Institute of TechnologyChina(Grant No.SKLRS201006B)
文摘The spring-loaded inverted pendulum(SLIP) has been widely studied in both animals and robots.Generally,the majority of the relevant theoretical studies deal with elastic leg,the linear leg length-force relationship of which is obviously conflict with the biological observations.A planar spring-mass model with a nonlinear spring leg is presented to explore the intrinsic mechanism of legged locomotion with elastic component.The leg model is formulated via decoupling the stiffness coefficient and exponent of the leg compression in order that the unified stiffness can be scaled as convex,concave as well as linear profile.The apex return map of the SLIP runner is established to investigate dynamical behavior of the fixed point.The basin of attraction and Floquet Multiplier are introduced to evaluate the self-stability and initial state sensitivity of the SLIP model with different stiffness profiles.The numerical results show that larger stiffness exponent can increase top speed of stable running and also can enlarge the size of attraction domain of the fixed point.In addition,the parameter variation is conducted to detect the effect of parameter dependency,and demonstrates that on the fixed energy level and stiffness profile,the faster running speed with larger convergence rate of the stable fixed point under small local perturbation can be achieved via decreasing the angle of attack and increasing the stiffness coefficient.The perturbation recovery test is implemented to judge the ability of the model resisting large external disturbance.The result shows that the convex stiffness performs best in enhancing the robustness of SLIP runner negotiating irregular terrain.This research sheds light on the running performance of the SLIP runner with nonlinear leg spring from a theoretical perspective,and also guides the design and control of the bio-inspired legged robot.
