Ground reaction forces and kinematics of plant leg position during instep kicking in male and female collegiate soccer players

The players' ability to achieve the greatest distance in kicking is determined by their efficiency in transferring kinetic energy from the body to the ball. The purpose of this study was to compare the kinetics and kinematics of the plant leg position between male and female collegiate soccer players during instep kicking. Twenty-three soccer players (11 males and 12 females) were filmed in both the sagittal and posterior views while performing a maximal instep kick. Plant leg kinetic data were also collected using an AMTI 1000 force platform. There were no significant differences between the sexes in plant leg position, but females had significantly greater trunk lean, plant leg angle, and medial-lateral ground reaction force than the males. Males showed higher vertical ground reaction forces at ball contact, but there were no significant differences in ball speed at take-off between the sexes. Ball speed at take-off was inversely related to peak anterior–posterior ground reaction force ( ? 0.65). The anatomical differences between the sexes were reflected in greater trunk lean and lower leg angle in the females.     

Surface settlement caused by twin-parallel shield tunnelling in sandy cobble strata

City metro tunnels are usually constructed as twin-parallel tunnels and their adjacent construction may lead to surface deformation, affecting the surface environment and the safety of the tunnels. Due to its strong dispersion, sandy cobble strata can be easily disturbed by shield tunneling. Based on the project of the Chengdu Metro Line 1, field and model tests were carried out to study the surface settlement caused by shield tunneling in sandy cobble strata by measuring surface settlement curves, ground loss ratios and construction influence zones. The discrete element method (DEM) was used to study the factors affecting the formation of ground arches in sandy cobble strata at the microscopic level. Results show that the shape of the surface settlement curve in sandy cobble strata is different from that in soft soil. The buried depth and clear spacing of the two tunnels had a significant impact on the formation of ground arches.     

多雷达综合:航迹合成(英文)

目前多雷达跟踪空中交通管制系统的雷达数据处理有两种方法,其中之一是航迹合成法。本文讨论把来自不同雷达站的同一目标的当地航迹合成唯一的一条系统航迹的方法和主要问题,并具体讨论了其中座标变换的问题,分析了由于变换公式的近似引起的实际变换误差。     

浅谈降低接地装置接地电阻的几种措施

根据通信电力网中接地引起的电网事故,就降低接地装置的接地电阻进行了探讨,并提出了建设性意见.     

足球运动专项有氧耐力训练设计实证研究

目的:旨在结合足球运动项目专项特征的基础上,探索不同形式有球训练方法与手段设计是否能够有效提高足球运动员专项有氧耐力的训练水平. 方法:以12名北京体育大学男子足球代表队队员为实验对象,利用Polar Team2团队心率监控系统,对所设计的结合球有氧训练方法与手段进行科学验证和监控分析. 结果:(1)在4v2移动传控练习中50% -80%强度占总负荷的98. 65%;(2)6v6击垒得分练习中60% -90%强度占总负荷强度的99. 48%;(3)在4v4无方向传抢练习与小场地比赛练习中70%以上强度分别占总负荷的98. 44%与96. 96%,其中90% -100%强度百分比分别占总负荷的74. 69%与69%. 结论:不同负荷强度与训练控制要素下的结合球训练设计能够满足足球运动专项有氧耐力训练的基本要求.     

The Christian Doctrines of Salvation in John Bunyan’s"Doubting Castle"and"Enchanted Ground"

John Bunyan’s The Pilgrim’s Progress has been written to preach the glad tidings of salvation.Therefore its allegorical protagonists have gradually gone through many tests and trials on the path to salvation.This paper is focused on the doctrinal instruction of the later two episodes,Doubting Castle and Enchanted Ground.     

汉语网语的焦点／背景解析

语言注意是目前认知语言学研究的热点问题之一。焦点／背景理论是研究语言注意有效的切入点①。从焦点／背景理论的视角,对网语中含谐音词和英汉混合词的语句进行了详细的认知解析,发现网语在句法上的凸显,与传统语言规律相同;而在词法上,网语词汇的焦点／背景凸显更加复杂,即在词典词义的显性的、正向的一次凸显的基础上,往往需要（由词典义向网络义）隐性的、逆向的二次凸显。焦点的凸显具有主观性。当说话人（或作者）的凸显瞬间被听话人（或读者）接收,凸显成功;否则当听话人（或读者）对说话人（或作者）言语中所含的（网络义）不了解时,凸显失败。焦点凸显的正向或逆向、成功与失败往往与人的认知能力相关。     

自动检测系统中的接地抗干扰技术

为了消除自动检测系统中的一些无用信号，需采取相应的措施抑制干扰。本文主要介绍抑制干扰的最常用的、行之有效的接地抗干扰技术。     

PROTEL99在PCB中的应用探讨

在Protel系列电路设计软件变成EDA(电路设计自动化)领域中举足轻重的领导软件的今天,学好和用好Protel系列电路设计软件变得十分必要。本文主要介绍Protel 99 PCB的制作要点及着重要注意的几个地方。     

Analytical solution for electromagnetic scattering from a sphere of uniaxial left-handed material

INTRODUCTION The concept of left-handed materials (LHM for short, also called negative index materials) was in- troduced by Veselago (1968). An LHM has both negative permittivity and negative permeability, which makes the wave vector, the electric-field vector, and the magnetic-field vector in the LHM obey the left-hand rule. Experimental verifications for the existence of an LHM were made and its use as a perfect lens was suggested (Pendry, 2000; Shelby et al., 2001a; 2001b; Smith …