Temporal and kinetic analysis of unilateral jumping in the vertical,horizontal, and lateral directions

Abstract

The aims of this study were to: (1) assess the reliability of various kinetic and temporal variables for unilateral vertical, horizontal, and lateral countermovement jumps; (2) determine whether there are differences in vertical ground reaction force production between the three types of jumps; (3) quantify the magnitude of asymmetry between limbs for variables that were established as reliable in a healthy population and whether asymmetries were consistent across jumps of different direction; and (4) establish the best kinetic predictor(s) of jump performance in the vertical, horizontal, and lateral planes of motion. Thirty team sport athletes performed three trials of the various countermovement jumps on both legs on two separate occasions. Eccentric and concentric peak force and concentric peak power were the only variables with acceptable reliability (coefficient of variation = 3.3–15.1%; intra-class correlation coefficient = 0.70–0.96). Eccentric and concentric peak vertical ground reaction force (14–16%) and concentric peak power (45–51%) were significantly (P < 0.01) greater in the vertical countermovement jump than in the horizontal countermovement jump and lateral countermovement jump, but no significant difference was found between the latter two jumps. No significant leg asymmetries (–2.1% to 9.3%) were found in any of the kinetic variables but significant differences were observed in jump height and distance. The best single predictors of vertical countermovement jump, horizontal countermovement jump, and lateral countermovement jump performance were concentric peak vertical power/body weight (79%), horizontal concentric peak power/body weight (42.6%), and eccentric peak vertical ground reaction force/body weight (14.9%) respectively. These findings are discussed in relation to monitoring and developing direction-specific jump performance.     

Effects of stance angle on postural stability and performance with national-standard air pistol competitors

Abstract

The effects of stance angle on postural stability and shooting processes were studied using eight national-standard male air-pistol shooters. Each shooter performed 60 shots each in four stance angles (0°, 15°, 30° and 45° from the line of fire). Postural stability was determined by measuring change in centre of pressure with a dual-force platform system assessing centre-of-pressure (COP) excursion (average difference of the centre of pressure from the mean) and COP speed (total COP path divided by time). Shooting process measures were determined by using a NOPTEL ST-2000 optoelectronic system. Score was assessed with a Sius Ascor S10 electronic scoring system. The results revealed no significant difference among the various stance angles; COP excursion or COP speed, p>0.05. Results indicated a significant stance angle effect with the shooting process measure, hit fine (percentage of hold within an area the size of the 10-ring when centred over the actual shot; p = 0.025) and the shooting performance measure adjusted score (raw score adjusted for true zero; p=0.008). Moreover, best overall performance was with a stance angle of 15°. These findings suggest that stance angle may affect pistol stability and performance in air-pistol athletes.     

测井法探测剩余油方法研究

本文简单介绍了探测剩余油饱和度和分布的方法,对比各自方法的优缺点,最终选择测井方法探测剩余油。从理论出发建立了基于瞬变电磁法的三层柱状介质模型,通过对模型理论的推导及求解,计算出了地层的感应电动势。并通过软件的仿真,直观地说明了发射电流、发射线圈匝数、收发距对感应电动势的影响,验证了此方法探测剩余油的可行性。     

淮河流域中游湿地景观格局演变的驱动力分析

淮河流域中游河湖湿地水空间巨大。解放后50年来,淮河流域中游地区湿地萎缩,大量的湿地转变成水田和非湿地,大量的天然湿地演变成人工湿地和非湿地,其中又以作为天然湿地主体的河湖湿地损失最多,并存在河湖湿地-滩地-非湿地的演变过程。通过分析得知,在这50年里,影响淮河流域中游湿地景观格局演变的主要驱动力是土地利用和河流调控两大因素。     

论中亚宗教极端势力的基本特征

"中亚宗教极端势力"是中亚研究领域中的一个独特、重要的问题.独特性在于,宗教极端主义进入中亚后,与该地区的政治、宗教、民族、文化等因素相结合,形成了独特的复杂性、顽固性和普遍性;重要性在于,宗教极端势力对中亚的影响广泛而纵深:给地区安全和社会稳定带来威胁;是影响中亚政局和中亚国家调整内外政策的因素之一;在人文领域,宗教极端思想影响着新一代中亚人;与"东突"分子相勾结,给中国西北安全带来影响:是中亚地区大国博弈的一个变量因素.     

改制射钉枪的检验鉴定方法

文章讨论了射钉器的分类、结构与击发机理,指导我们检验改制射钉枪,辨析原射钉器的结构检验和改制部位的检验的方法及重点,最后通过试射实验,判明了改制射钉枪的致伤力。     

液压叠加式力标准机力值重复性、示值误差和长期稳定性观测与思考

文章以500k N液压方式叠加机作为验证机和研究平台,根据其力值重复性、示值误差和长期稳定性指标优于0.0086%(突破规程0.03级的极限,挑战现有理论模式)的检测数据,评估其不确定度,指出现检定规程存在的问题,坚持以0.01%精度为深入研究的切入点,寻找减小不确定度分量的方法,提出完善高精度叠加机计量传递链的部分改进思路。     

国家重点实验室运行驱动力及对策研究

运用主成分分析及专家评分法,围绕四个方面分析国家重点实验室运行驱动力,设计运行驱动力影响因子并计算了其权重.研究发现,现阶段推动国家重点实验室运行发展的驱动力主要以政府推动力和创新带动力为主,科学家及市场的带动作用还没有完全发挥.最后,提出了针对国家重点实验室运行发展的政策建议.     

对当前我国高校马克思主义宗教观教育的新思考

随着宗教升温现象在大学校园的蔓延,高校必须重视和加强马克思主义宗教观教育。通过坚持科学的教育原则、确定科学的教育内容及实施科学的教育手段,高校构建起马克思主义宗教观教育的科学体系。在整合多方教育资源的基础上,形成“以学校为主导,以家庭为基础,以社会为保障”的教育合力,共同引导大学生树立科学思想信仰。