AFTER ten years of silence since his Blue Kite of 1992, earlier this year Tian Zhuangzhuang, one of the most respected of China’s fifth-generation directors, made his version of Spring in a Small Town. A classic fil...AFTER ten years of silence since his Blue Kite of 1992, earlier this year Tian Zhuangzhuang, one of the most respected of China’s fifth-generation directors, made his version of Spring in a Small Town. A classic film originally directed by Fei Mu in 1948, it is Tian’s favorite. He has watched the film at least once a year for the past decade, each time with fresh anticipation.展开更多
【目的】探究在不同减氮水平下,绿肥联合麦秸还田对春小麦(Triticum aestivum L.)籽粒产量及叶片光合特性的影响,为构建春小麦复种绿肥节氮高效型生产模式提供理论依据和技术支撑。【方法】试验于2022和2023两个年度在甘肃农业大学武威...【目的】探究在不同减氮水平下,绿肥联合麦秸还田对春小麦(Triticum aestivum L.)籽粒产量及叶片光合特性的影响,为构建春小麦复种绿肥节氮高效型生产模式提供理论依据和技术支撑。【方法】试验于2022和2023两个年度在甘肃农业大学武威绿洲农业试验站进行。采用裂区试验设计,主区为不同还田物料处理,设绿肥联合麦秸还田(W-GS)、绿肥单独还田(W-G)和麦后休闲(W-F)3个水平;副区为施氮量,设地方常规施氮量(N1,225 kg N·hm^(-2))、减氮约15%(N2,190 kg N·hm^(-2))、减氮约30%(N3,155 kg N·hm^(-2))和减氮约45%(N4,120 kg N·hm^(-2))4个水平。测定春小麦顶端展开叶片的叶绿素值(SPAD值)、光合特性和籽粒产量。【结果】减量施氮对春小麦籽粒产量呈负效应,而绿肥联合麦秸还田能补偿这种效应,甚至增加春小麦籽粒产量。同一施氮量下,W-GS、W-G处理的春小麦较W-F分别增产15.3%和9.4%,W-GS较W-G增产5.4%;W-F的春小麦籽粒产量随施氮量的减少呈降低趋势,而W-GS的春小麦籽粒产量N3与N1处理间无显著差异;W-GSN3较W-GSN1和W-FN1均未减产。绿肥联合麦秸还田能改善减量施氮春小麦的叶片光合特性。与同一施氮量下W-G和W-F相比,W-GS的春小麦叶片SPAD值、净光合速率(P_(n))、气孔导度(G_(s))、蒸腾速率(T_(r))和叶片水分利用效率(LWUE)均显著提高;随施氮量的减少,W-F的春小麦叶片SPAD值、P_(n)、G_(s)、T_(r)、LWUE均显著降低,而W-GS的春小麦相关指标在N3与N1之间无显著差异;组合处理之间相比较,W-GSN3与W-GSN1和W-FN1的春小麦光合特性指标之间无显著差异。W-GS较W-F使春小麦光能利用率(LUE)提高了5.2%;W-F的春小麦LUE随施氮量的减少呈降低趋势,而W-GS的春小麦LUE在N3与N1之间差异不显著;W-GSN3的春小麦LUE与W-GSN1和W-FN1相比未显著降低。通径分析结果表明,本研究条件下春小麦的叶片气孔导度对其净光合速率、蒸腾速率的调控作用较大,进而影响千粒重而决定籽粒产量。【结论】绿肥联合麦秸还田主要通过改善春小麦叶片光合特性而提高春小麦千粒重,最终使减氮约30%处理的春小麦不减产。因此,绿肥联合麦秸还田结合施氮155 kg·hm^(-2)可推荐为干旱绿洲灌区春小麦复种绿肥节氮高效型生产模式。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
文摘AFTER ten years of silence since his Blue Kite of 1992, earlier this year Tian Zhuangzhuang, one of the most respected of China’s fifth-generation directors, made his version of Spring in a Small Town. A classic film originally directed by Fei Mu in 1948, it is Tian’s favorite. He has watched the film at least once a year for the past decade, each time with fresh anticipation.
文摘【目的】探究在不同减氮水平下,绿肥联合麦秸还田对春小麦(Triticum aestivum L.)籽粒产量及叶片光合特性的影响,为构建春小麦复种绿肥节氮高效型生产模式提供理论依据和技术支撑。【方法】试验于2022和2023两个年度在甘肃农业大学武威绿洲农业试验站进行。采用裂区试验设计,主区为不同还田物料处理,设绿肥联合麦秸还田(W-GS)、绿肥单独还田(W-G)和麦后休闲(W-F)3个水平;副区为施氮量,设地方常规施氮量(N1,225 kg N·hm^(-2))、减氮约15%(N2,190 kg N·hm^(-2))、减氮约30%(N3,155 kg N·hm^(-2))和减氮约45%(N4,120 kg N·hm^(-2))4个水平。测定春小麦顶端展开叶片的叶绿素值(SPAD值)、光合特性和籽粒产量。【结果】减量施氮对春小麦籽粒产量呈负效应,而绿肥联合麦秸还田能补偿这种效应,甚至增加春小麦籽粒产量。同一施氮量下,W-GS、W-G处理的春小麦较W-F分别增产15.3%和9.4%,W-GS较W-G增产5.4%;W-F的春小麦籽粒产量随施氮量的减少呈降低趋势,而W-GS的春小麦籽粒产量N3与N1处理间无显著差异;W-GSN3较W-GSN1和W-FN1均未减产。绿肥联合麦秸还田能改善减量施氮春小麦的叶片光合特性。与同一施氮量下W-G和W-F相比,W-GS的春小麦叶片SPAD值、净光合速率(P_(n))、气孔导度(G_(s))、蒸腾速率(T_(r))和叶片水分利用效率(LWUE)均显著提高;随施氮量的减少,W-F的春小麦叶片SPAD值、P_(n)、G_(s)、T_(r)、LWUE均显著降低,而W-GS的春小麦相关指标在N3与N1之间无显著差异;组合处理之间相比较,W-GSN3与W-GSN1和W-FN1的春小麦光合特性指标之间无显著差异。W-GS较W-F使春小麦光能利用率(LUE)提高了5.2%;W-F的春小麦LUE随施氮量的减少呈降低趋势,而W-GS的春小麦LUE在N3与N1之间差异不显著;W-GSN3的春小麦LUE与W-GSN1和W-FN1相比未显著降低。通径分析结果表明,本研究条件下春小麦的叶片气孔导度对其净光合速率、蒸腾速率的调控作用较大,进而影响千粒重而决定籽粒产量。【结论】绿肥联合麦秸还田主要通过改善春小麦叶片光合特性而提高春小麦千粒重,最终使减氮约30%处理的春小麦不减产。因此,绿肥联合麦秸还田结合施氮155 kg·hm^(-2)可推荐为干旱绿洲灌区春小麦复种绿肥节氮高效型生产模式。
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.
