This letter presents a theoretical model of the normal （head-on） collisions between two soft spheres for predicting the experimental characteristic of the coefficient of restitution dependent on impact velocity. Aft...This letter presents a theoretical model of the normal （head-on） collisions between two soft spheres for predicting the experimental characteristic of the coefficient of restitution dependent on impact velocity. After the contact force law between the contacted spheres during a collision is phenomenologically formulated in terms of the compression or overlap displacement under considera- tion of an elastic-plastic loading and a plastic unloading subprocesses, the coefficient of restitution is gained by the dynamic equation of the contact process once an initial impact velocity is input. It is found that the theoretical predictions of the coefficient of restitution varying with the impact velocity are well in agreement with the existing experimental characteristics which are fitted by the explicit formula.展开更多
This paper presents a theoretical model on the normal(head-on) collision between soft-spheres on the basis of elastic loading of the Hertz contact for compression process and a nonlinear plastic unloading for restitut...This paper presents a theoretical model on the normal(head-on) collision between soft-spheres on the basis of elastic loading of the Hertz contact for compression process and a nonlinear plastic unloading for restitution one,in which the parameters all are determined in terms of the material and geometric ones of the spheres,and the behaviors of perfect elastic,inelastic,and perfect plastic collisions appeared in the classical mechanics are fully described once a value of coefficient of restitution is specified in the region of 0 ≤ ε ≤ 1.After an empirical formula of the coefficient of restitution dependent on the impact velocity is suggested to fit the existing experimental measurements by means of the least square method,the predictions of the dependency and the collision duration are in well quantitative agreement with their experimental measurements.It is found that the measurable quantities are dependent on both the impact velocity and the parameters of spheres.Following this model,finally,an approach to determine the spring coefficient in the linear viscoelastic model of the collision is also displayed.These results obtained here will be significantly beneficial for the applications where a collision model is requested in the simulations of relevant grain flows and impact dynamics etc..展开更多
An improved list sphere decoder （ILSD） is proposed based on the conventional list sphere decoder （LSD） and the reduced- complexity maximum likelihood sphere-decoding algorithm. Unlike the conventional LSD with fix...An improved list sphere decoder （ILSD） is proposed based on the conventional list sphere decoder （LSD） and the reduced- complexity maximum likelihood sphere-decoding algorithm. Unlike the conventional LSD with fixed initial radius, the ILSD adopts an adaptive radius to accelerate the list cdnstruction. Characterized by low-complexity and radius-insensitivity, the proposed algorithm makes iterative joint detection and decoding more realizable in multiple-antenna systems. Simulation results show that computational savings of ILSD over LSD are more apparent with more transmit antennas or larger constellations, and with no performance degradation. Because the complexity of the ILSD algorithm almost keeps invariant with the increasing of initial radius, the BER performance can be improved by selecting a sufficiently large radius.展开更多
本文采用 DEM（Discrete Element Method）软球模型来研究颗粒间的碰撞过程,用金属球代替流场中的颗粒,研究这些金属球在平面上的运动。运用DEM软球模型求出碰撞过程中小球所受的瞬时接触力以及碰撞时间,并分析这些参数随颗粒物性以及...本文采用 DEM（Discrete Element Method）软球模型来研究颗粒间的碰撞过程,用金属球代替流场中的颗粒,研究这些金属球在平面上的运动。运用DEM软球模型求出碰撞过程中小球所受的瞬时接触力以及碰撞时间,并分析这些参数随颗粒物性以及运动参数的变化规律。计算得出:颗粒间的接触力以及碰撞时间与颗粒的相对速度、碰撞角度以及杨氏模量等参数有关。展开更多
基金supported by the Innovation Team Fund of the National Natural Science Foundation of China(11121202)
文摘This letter presents a theoretical model of the normal （head-on） collisions between two soft spheres for predicting the experimental characteristic of the coefficient of restitution dependent on impact velocity. After the contact force law between the contacted spheres during a collision is phenomenologically formulated in terms of the compression or overlap displacement under considera- tion of an elastic-plastic loading and a plastic unloading subprocesses, the coefficient of restitution is gained by the dynamic equation of the contact process once an initial impact velocity is input. It is found that the theoretical predictions of the coefficient of restitution varying with the impact velocity are well in agreement with the existing experimental characteristics which are fitted by the explicit formula.
基金supported by the Key Fund of the National Natural Science Foundation of China (11032006)
文摘This paper presents a theoretical model on the normal(head-on) collision between soft-spheres on the basis of elastic loading of the Hertz contact for compression process and a nonlinear plastic unloading for restitution one,in which the parameters all are determined in terms of the material and geometric ones of the spheres,and the behaviors of perfect elastic,inelastic,and perfect plastic collisions appeared in the classical mechanics are fully described once a value of coefficient of restitution is specified in the region of 0 ≤ ε ≤ 1.After an empirical formula of the coefficient of restitution dependent on the impact velocity is suggested to fit the existing experimental measurements by means of the least square method,the predictions of the dependency and the collision duration are in well quantitative agreement with their experimental measurements.It is found that the measurable quantities are dependent on both the impact velocity and the parameters of spheres.Following this model,finally,an approach to determine the spring coefficient in the linear viscoelastic model of the collision is also displayed.These results obtained here will be significantly beneficial for the applications where a collision model is requested in the simulations of relevant grain flows and impact dynamics etc..
基金The National Natural Science Founda-tion of China ( No 60496316)the National Hi-Tech Re-search and Development Program (863) of China (No2006-AA01Z270)
文摘An improved list sphere decoder （ILSD） is proposed based on the conventional list sphere decoder （LSD） and the reduced- complexity maximum likelihood sphere-decoding algorithm. Unlike the conventional LSD with fixed initial radius, the ILSD adopts an adaptive radius to accelerate the list cdnstruction. Characterized by low-complexity and radius-insensitivity, the proposed algorithm makes iterative joint detection and decoding more realizable in multiple-antenna systems. Simulation results show that computational savings of ILSD over LSD are more apparent with more transmit antennas or larger constellations, and with no performance degradation. Because the complexity of the ILSD algorithm almost keeps invariant with the increasing of initial radius, the BER performance can be improved by selecting a sufficiently large radius.
文摘本文采用 DEM（Discrete Element Method）软球模型来研究颗粒间的碰撞过程,用金属球代替流场中的颗粒,研究这些金属球在平面上的运动。运用DEM软球模型求出碰撞过程中小球所受的瞬时接触力以及碰撞时间,并分析这些参数随颗粒物性以及运动参数的变化规律。计算得出:颗粒间的接触力以及碰撞时间与颗粒的相对速度、碰撞角度以及杨氏模量等参数有关。
