景观动态及其驱动因素和效应分析——以江西省泰和县灌溪乡千烟洲为例

本文运用土地利用的ＤＬＵ（ＤｉｆｅｒｅｎｔｉａｔｅｄＬａｎｄＵｓｅ）战略理论和景观动态分析模型，分析了江西省泰和县灌溪乡千烟洲的土地利用时间动态，并对其产生的效应和它们的驱动因素进行了概括和总结。     

False-performance feedback does not affect punching forces and pacing of elite boxers

Prior research indicates that providing participants with positive augmented feedback tends to enhance motor learning and performance, whereas the opposite occurs with negative feedback. However, the majority of studies were conducted with untrained participants performing unfamiliar motor tasks and so it remains unclear if elite athletes completing familiar tasks respond in a similar fashion. Thus, this study investigated the effects of three different versions of false-performance feedback on punching force (N), pacing (force over time) and ratings of perceived exertion (RPE) in 15 elite amateur male boxers. Athletes completed a simulated boxing bout consisting of three rounds with 84 maximal effort punches delivered to a punching integrator on four separate days. Day one was a familiarisation session in which no feedback was provided. In the following three days athletes randomly received false-positive, false-negative and false-neutral feedback on their punching performance between each round. No statistical or meaningful differences were observed in punching forces, pacing or RPE between conditions (P > 0.05; ≤ 2%). These null results could stem from the elite status of the athletes involved, the focus on performance rather than learning, or they may indicate that false feedback has a less potent effect on performance than previously thought.     

Specific tackling situations affect the biomechanical demands experienced by rugby union players

Tackling in Rugby Union is an open skill which can involve high-speed collisions and is the match event associated with the greatest proportion of injuries. This study aimed to analyse the biomechanics of rugby tackling under three conditions: from a stationary position, with dominant and non-dominant shoulder, and moving forward, with dominant shoulder. A specially devised contact simulator, a 50-kg punch bag instrumented with pressure sensors, was translated towards the tackler (n = 15) to evaluate the effect of laterality and tackling approach on the external loads absorbed by the tackler, on head and trunk motion, and on trunk muscle activities. Peak impact force was substantially higher in the stationary dominant (2.84 ± 0.74 kN) than in the stationary non-dominant condition (2.44 ± 0.64 kN), but lower than in the moving condition (3.40 ± 0.86 kN). Muscle activation started on average 300 ms before impact, with higher activation for impact-side trapezius and non-impact-side erector spinae and gluteus maximus muscles. Players’ technique for non-dominant-side tackles was less compliant with current coaching recommendations in terms of cervical motion (more neck flexion and lateral bending in the stationary non-dominant condition) and players could benefit from specific coaching focus on non-dominant-side tackles.     

老工业基地区域经济差异时空演变及驱动机制研究——以吉林省中部地区为例

以吉林省中部地区为例,运用区域经济差异的测度方法以及GIS的空间分析方法,分析1995—2010年吉林省中部地区经济差异的时空演变特征及驱动机制. 结果表明：1995—2010年吉林省中部地区总体差异呈“上升-下降”的倒“U”型的变化趋势. 1995年以来长-吉两市一直是经济的快速发展地区,并逐渐向长-吉地区和松原市区集聚的趋势显著. 经济发展基础、区域政策推动、市场经济促进、产业集聚与扩散带动和人才技术支撑5个方面是吉林省中部地区经济差异时空演变的驱动机制.     

辽宁省排球后备力量选拔、训练及比赛的现状分析与对策研究

运用文献资料法、访谈法、问卷调查法,对辽宁省排球后备力量的选拔、训练及比赛等方面现状做了详实的调查分析。结果显示,辽宁在排球后备力量的选拔、训练及比赛方面还存在问题,具体表现为:科学选材工作还不到位,运动员整体身体素质一般,基本功不够扎实,青少年运动员参赛机会偏少。根据调查,提出了相应的对策。     

太极拳运动单脚支撑姿势持续时间与地面反作用力特征的分析

运用摄影测量法和Novel Pedar-X足底压力测试系统采集了16名太极拳练习者在太极拳运动和正常步行中足底压力和运动影像信息,并对两种运动方式的单脚支撑姿势持续时间指标进行对比分析。研究表明:与正常步行相比,在太极拳运动中单脚支撑姿势总的持续时间所占比例(标准化值)较少(P<0.05);单次单脚支撑姿势平均持续时间较长(P<0.01);认为太极拳运动可以提高人体单脚平衡能力。另外还发现太极拳运动和正常步行中地面反作用力都在不断变化;太极拳运动中地面反作用力小于其正常步行值。     

2008年北京奥运会我国竞技游泳后备人才的培养对策

从社会学、运动训练学、体育管理学、人才学等视角,针对我国竞技游泳下滑现状和影响发展的因素,以及2008年北京奥运会我国竞技游泳后备力量的培养形式等问题,采用文献资料法、问卷调查法、走访调查法、专家咨询法,比较分析法、数理统计法以及趋势研究法等综合研究方法对我国部分地区(北京、上海、广州、辽宁等)、不同水平的游泳运动员以及他们的教练员、领队进行调查研究,全面分析我国竞技游泳的滑坡原因及存在的问题,旨在延长高水平游泳运动员的运动寿命,提出培养北京奥运会我国竞技游泳后备力量的可行性措施。     

简论推动现代排球运动发展的主要动力

本文对排球运动发展的历史过程进行分析、探讨,并从哲学角度运用自然辩证法进行论证,发现以寻求攻防平衡为目的的规则改变不断地改进和完善排球运动,使排球运动更加激烈、精彩;另外不同时期人们对排球各种功能的需求也有效地推动了排球运动的发展。它们是推动排球运动发展的主要因素。更好地把握和利用排球运动发展的动因能更好地促进排球运动的发展。     

Responses to Forces Influencing Cohesion As a Function of Player Status and Level of Male Varsity Basketball Competition

Abstract

This exploratory study determined if the responses of male varsity basketball players to six factors influencing cohesion were a function of level of competitive intensity and/or the importance of the players to their team. Players on intact teams from five levels of competition – elementary school, junior high school, senior high school, small college and large college–responded to a cohesion questionnaire at the end of the season. Coaches designated five players with the most game playing time as “starters” and five players with the least game playing time as “reserves.” A team factor score for Team Performance Satisfaction, Self Performance Satisfaction, Task Cohesion, Affiliation Cohesion, Desire for Recognition and Value of Membership was calculated. Each team factor score served as the dependent variable in a 2 (player status) × 5 (level of competition) analysis ofcovariance design, with teams nested in the second factor. The won-loss record served as the covariate. Results indicated that “starters” were more satisfied with their own performance, were more task conscious, had a greater affiliation desire, and valued their membership on the team to a greater degree than the “reserves.” The elementary and junior high school team members were significantly more satisfied with the team's performance, were more satisfied with their own self performance, were more affiliation conscious, and valued their team membership to a greater degree than did college team members. The interaction between player status and level of competition was not significant for any of the factor scores.     

Effect of chainring ovality on joint power during cycling at different workloads and cadences

Non-circular chainrings theoretically enhance cycling performance by increasing effective chainring diameter and varying crank velocity, but research has failed to consistently reproduce the benefits in cycling trials. The aim of this study was (1) to investigate the effect of different chainring shapes on sagittal knee joint moment and sagittal lower limb joint powers and (2) to investigate whether alterations are affected by cadence and workload. Fourteen elite cyclists cycled in six conditions (70, 90 and 110 rpm, each at 180 and 300 W), for 2 min each, using three chainrings of different ovalities (1.0–1.215). Kinematic data and pedal forces were collected. For most conditions, only the chainring with the highest ovality (1.215) was characterised by smaller sagittal knee joint moments, smaller relative sagittal knee joint power contribution and larger relative sagittal hip joint power contribution, which suggests a change from maximising efficiency to maximising power production. Effect sizes increased with higher cadences, but not with higher workload. This study has application for athletes, clinicians and sports equipment industry as a non-circular chainring can change joint-specific power generation and decrease knee joint moment, but certain ovality seems to be necessary to provoke this effect.