Based on the fact that a static problem has an equivalent wave speed of infinity and a dynamic problem has a wave speed of finite value, an effective loading algorithm associated with the explicit dynamic relaxation m...Based on the fact that a static problem has an equivalent wave speed of infinity and a dynamic problem has a wave speed of finite value, an effective loading algorithm associated with the explicit dynamic relaxation method was presented to produce meaningful numerical solutions for static problems. The central part of the explicit dynamic relaxation method is to turn a time-independent static problem into an artificial time-dependent dynamic problem. The related numerical testing results demonstrate that: (1) the proposed effective loading algorithm is capable of enabling an applied load in a static problem to be propagated throughout the whole system within a given loading increment, so that the time-independent solution of the static problem can be obtained; (2) the proposed effective loading algorithm can be straightforwardly applied to the particle simulation method for solving a wide range of static problems.展开更多
在Web服务器市场,尽管Apache Web Server和Microsoft IIS占据了全球绝大部分互联网网站,但是仍然有很多颇受欢迎的轻量级Web Server,例如lighttpd,litespeed,nginx,thttpd,boa,TUX等等,它们向你展示了一个多姿多彩的Web服务器世界,能够...在Web服务器市场,尽管Apache Web Server和Microsoft IIS占据了全球绝大部分互联网网站,但是仍然有很多颇受欢迎的轻量级Web Server,例如lighttpd,litespeed,nginx,thttpd,boa,TUX等等,它们向你展示了一个多姿多彩的Web服务器世界,能够给你带来Apache/IIS所无法带来的功能和魅力。本期"工具"栏目将为您介绍几种常用轻量级Web服务器,并对它们的性能及使用范围进行横向比较与分析,希望能够帮助读者朋友在众多的轻量级Web服务器中,挑选出最适合的。展开更多
In order to fulfill the goal of autonomous walking on rough terrain,a distributed gait planningmethod applied to hexapod biomimetic robot locomotion is proposed based on the research effort of gait co-ordination mecha...In order to fulfill the goal of autonomous walking on rough terrain,a distributed gait planningmethod applied to hexapod biomimetic robot locomotion is proposed based on the research effort of gait co-ordination mechanism of stick insect.The mathematical relation of walking velocity and gait pattern wasdepicted,a set of local rules operating between adjacent legs were put forward,and a distributed networkof local rules for gait control was constructed.With the interaction of adjacent legs,adaptive adjustmentof phase sequence fluctuation of walking legs resulting from change of terrain conditions or variety of walk-ing speed was implemented to generate statically stable gait.In the simulation experiments,adaptive ad-justment of inter-leg phase sequence and smooth transition of velocity and gait pattern were realized,andstatic stableness was ensured simultaneously,which provided the hexapod robot with the capability ofwalking on rough terrain stably and expeditiously.展开更多
Many analytical methods have been adopted to estimate the slope stability by providing various stability numbers,e.g.static safety of factor(static FoS)or the critical seismic acceleration coefficient,while little att...Many analytical methods have been adopted to estimate the slope stability by providing various stability numbers,e.g.static safety of factor(static FoS)or the critical seismic acceleration coefficient,while little attention has been given to the relationship between the slope stability numbers and the critical seismic acceleration coefficient.This study aims to investigate the relationship between the static FoS and the critical seismic acceleration coefficient of soil slopes in the framework of the upper-bound limit analysis.Based on the 3D rotational failure mechanism,the critical seismic acceleration coefficient using the pseudo-static method and the static FoS using the strength reduction technique are first determined.Then,the relationship between the static FoS and the critical seismic acceleration coefficient is presented under considering the slope angleβ,the frictional angleφ,and the dimensionless coefficients B/H and c/γH.Finally,a fitting formula between the static FoS and the critical seismic acceleration coefficient is proposed and validated by analytical and numerical results.展开更多
Analytical equations are presented herein to predict the penetration of semi-infinite metallic targets struck normally by long rods at high velocities for Yp<S where Yp is the rod strength and S is the static targe...Analytical equations are presented herein to predict the penetration of semi-infinite metallic targets struck normally by long rods at high velocities for Yp<S where Yp is the rod strength and S is the static target resistance.The equations are derived based on energy balance method.It is assumed that the kinetic energy loss of a long rod is related to the energy dissipated by the plastic deformations in the target,the energy consumed by the long-rod penetrator itself and the energy carried by the eroded rod debris.Secondary penetration is also examined in the present paper due to the fact that the eroded rod debris forms a tube which can penetrate the target further if the density of the rod is greater than that of the target and the impact velocity is high enough.The present analytical equation is found to be in good agreement with the experimental data for a wide range of impact velocities.展开更多
基金Projects(10872219 10672190) supported by the National Natural Science Foundation of China
文摘Based on the fact that a static problem has an equivalent wave speed of infinity and a dynamic problem has a wave speed of finite value, an effective loading algorithm associated with the explicit dynamic relaxation method was presented to produce meaningful numerical solutions for static problems. The central part of the explicit dynamic relaxation method is to turn a time-independent static problem into an artificial time-dependent dynamic problem. The related numerical testing results demonstrate that: (1) the proposed effective loading algorithm is capable of enabling an applied load in a static problem to be propagated throughout the whole system within a given loading increment, so that the time-independent solution of the static problem can be obtained; (2) the proposed effective loading algorithm can be straightforwardly applied to the particle simulation method for solving a wide range of static problems.
文摘在Web服务器市场,尽管Apache Web Server和Microsoft IIS占据了全球绝大部分互联网网站,但是仍然有很多颇受欢迎的轻量级Web Server,例如lighttpd,litespeed,nginx,thttpd,boa,TUX等等,它们向你展示了一个多姿多彩的Web服务器世界,能够给你带来Apache/IIS所无法带来的功能和魅力。本期"工具"栏目将为您介绍几种常用轻量级Web服务器,并对它们的性能及使用范围进行横向比较与分析,希望能够帮助读者朋友在众多的轻量级Web服务器中,挑选出最适合的。
基金Supported by the National High Technology Research and Development Programme of China (No. 2006AA04Z245)by the Progran for Changjiang Scholars and Innovative Research Team in University of China (PCSIRT) (IRT0423)
文摘In order to fulfill the goal of autonomous walking on rough terrain,a distributed gait planningmethod applied to hexapod biomimetic robot locomotion is proposed based on the research effort of gait co-ordination mechanism of stick insect.The mathematical relation of walking velocity and gait pattern wasdepicted,a set of local rules operating between adjacent legs were put forward,and a distributed networkof local rules for gait control was constructed.With the interaction of adjacent legs,adaptive adjustmentof phase sequence fluctuation of walking legs resulting from change of terrain conditions or variety of walk-ing speed was implemented to generate statically stable gait.In the simulation experiments,adaptive ad-justment of inter-leg phase sequence and smooth transition of velocity and gait pattern were realized,andstatic stableness was ensured simultaneously,which provided the hexapod robot with the capability ofwalking on rough terrain stably and expeditiously.
基金Project(2017YFB1201204)supported by the National Key R&D Program of ChinaProject(1053320190957)supported by the Fundamental Research Funds for the Central Universities,China。
文摘Many analytical methods have been adopted to estimate the slope stability by providing various stability numbers,e.g.static safety of factor(static FoS)or the critical seismic acceleration coefficient,while little attention has been given to the relationship between the slope stability numbers and the critical seismic acceleration coefficient.This study aims to investigate the relationship between the static FoS and the critical seismic acceleration coefficient of soil slopes in the framework of the upper-bound limit analysis.Based on the 3D rotational failure mechanism,the critical seismic acceleration coefficient using the pseudo-static method and the static FoS using the strength reduction technique are first determined.Then,the relationship between the static FoS and the critical seismic acceleration coefficient is presented under considering the slope angleβ,the frictional angleφ,and the dimensionless coefficients B/H and c/γH.Finally,a fitting formula between the static FoS and the critical seismic acceleration coefficient is proposed and validated by analytical and numerical results.
基金supported by the National Natural Science Foundation of China(Grant No.11172298)
文摘Analytical equations are presented herein to predict the penetration of semi-infinite metallic targets struck normally by long rods at high velocities for Yp<S where Yp is the rod strength and S is the static target resistance.The equations are derived based on energy balance method.It is assumed that the kinetic energy loss of a long rod is related to the energy dissipated by the plastic deformations in the target,the energy consumed by the long-rod penetrator itself and the energy carried by the eroded rod debris.Secondary penetration is also examined in the present paper due to the fact that the eroded rod debris forms a tube which can penetrate the target further if the density of the rod is greater than that of the target and the impact velocity is high enough.The present analytical equation is found to be in good agreement with the experimental data for a wide range of impact velocities.
