认知负荷对乒乓球运动员注意空间的影响*     

杨〓义  岳珍珠 《广州体育学院学报》2019,(2):99-101

目的 同时注意空间中多个目标刺激对于乒乓球运动员非常重要。考察认知负荷对青少年乒乓球运动员注意分布的影响。方法：实验中采用计算机行为实验，控制认知负荷（同时注意的目标数量为2、4或6个），并且在不同注意范围（离中央注视点3°、6°和9°视角）的位置上同时呈现刺激，要求被试对刺激的亮度变化做辨别反应。结果：:认知负荷对于乒乓球运动员的注意范围有显著调节。当刺激个数为2时，在3°和6°视角条件下呈现的刺激反应时均显著快于9°视角条件下的刺激。当刺激个数为4时，视角为3°条件下的反应时快于视角为6°和9°时的反应时，而视角为6°时又比视角为9°时的反应时显著要快。当刺激个数为6时，视角为3°时的反应时均快于视角为6°和9°时的反应时。结论：当前研究证明随着认知负荷增加，乒乓球运动员注意焦点范围显著缩小。可以通过测量运动员在高负荷条件下注意焦点的范围来进行运动员的选拔。  相似文献   

Does an interactive table of contents promote learning from videos? A study of consultation strategies and learning outcomes     

Salomé Cojean  Eric Jamet 《British journal of educational technology : journal of the Council for Educational Technology》2022,53(2):269-285

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乒乓球运动员膝关节损伤机制研究——对3种常用步法的膝关节负荷特征分析     

周星栋  肖丹丹  郭文霞  黄习梅  张晓栋 《中国体育科技》2020,(6):62-67

目的:了解不同性别乒乓球运动员完成并步、跳步、跨步3种常用步法时膝关节的负荷特征,并探析乒乓球运动员膝关节的损伤机制。方法:对乒乓球男、女各10名运动员完成3种常用步法动作时的下肢运动学、动力学数据进行采集和处理,并运用方差分析法比较不同性别、不同技术之间的差异。结果:受试者在完成3种步法过程中,膝关节屈角大致范围在20°~60°。当地面反作用力最大时,女运动员比男运动员表现出更小的外展角(P<0.05),跳步比并步和跨步表现出更小的外展角(P<0.05);在三维受力方面,膝关节受到垂直方向上的力最大,水平向后和向左的力次之,未表现出显著的性别差异和技术差异;在三维力矩方面,膝关节受到的伸膝力矩较大,也未表现出显著的性别差异和技术差异。结论:膝关节屈曲状态下,较大的地面反作用力和膝关节外展角易导致乒乓球运动员前交叉韧带损伤,女运动员的损伤风险小于男运动员,跳步的损伤风险小于并步和跨步;水平向后和向左的力易造成乒乓球运动员软骨和半月板损伤;过大的伸膝力矩易导致乒乓球运动员髌腱末端病和髌骨软化。  相似文献   

国际乒联频繁修改规则的批判性反思     

王翾  梁勤超  李林 《武汉体育学院学报》2020,54(10):88-94

采用文献资料等方法，梳理国际乒联21世纪以来的规则改革，反思其存在的问题。21世纪以来，国际乒联在器材、技术和赛制等方面进行了一系列的改革。一系列规则改革在技术上使得运动员技术选择和使用随意性增大，比赛胜负的偶然性增大；在国际乒坛秩序上产生了正、反两方面影响，一方面改变了中国队"一家独大"的局面，国际大赛的奖牌分布趋于多元化，另一方面，使得运动员打法逐渐呈现单一化趋势。同时国际乒联频繁修改规则还存在规则修改程序正义性、规则相对稳定性，以及权力行使过于随意等问题。要维系国际乒坛秩序的良性发展，国际乒联还需出台具体的规则改革制度，保证竞赛规则的相对稳定性，并合理行使规则修改的权力。  相似文献   

A coaches’ perspective on the contribution of anthropometry,physical performance,and motor coordination in racquet sports     

Kamasha Robertson  Johan Pion  Mireille Mostaert  Mohd Rozilee Wazir Norjali Wazir  Tamara Kramer  Irene Renate Faber 《Journal of sports sciences》2018,36(23):2706-2715

ABSTRACT

Differences and similarities between table tennis and other racquet sports exist, but are not well documented in the literature, in spite of the relevance for talent identification. In this study we aimed at identifying the key characteristics of table tennis in comparison with tennis and badminton based upon a survey in coaches. A total of 177 licensed coaches from all across the world and with diverse professional backgrounds completed a survey on anthropometric measures, physical performance, and motor coordination skills. On a scale from 1 to 10, coaches indicated to what extent a talent characteristic was important for their sport. MANOVA identified key differences as well as similarities between all three racquet sports and a subsequent discriminant analysis allocated coaches correctly for table tennis, tennis, and badminton 81.01%, 55.6%, and 71.4% respectively. Our results show that table tennis and other racquet sport coaches are well aware of differences between the racquet sports and also the importance and value of testing and assortment of skill components. These findings can assist coaches in future talent orientation and transfer in racquet sports.  相似文献   

Utilization of cues in action anticipation in table tennis players     

Qi Zhao  Kyle J. Jaquess  Chenglin Zhou 《Journal of sports sciences》2018,36(23):2699-2705

ABSTRACT

By manipulating the congruency between body kinematics and subsequent ball trajectory, this study investigated the anticipation capabilities of regional-level, college-level, and novice table tennis players using a full video simulation occluder paradigm. Participants watched footage containing congruent, incongruent, or no ball trajectory information, to predict the landing point of the ball. They were required to choose between two potential locations to make their prediction. Percent accuracy and relevant indexes (d-prime, criterion, effect size) were calculated for each condition. Results indicated that experienced table tennis players (both regional and college players) were superior to novices in the ability to anticipate ball trajectory using kinematic information, but no difference was found between regional-level and college-level players. The findings of this study further demonstrate the superior anticipation ability of experienced table tennis players. Furthermore, the present result suggests that there may be a certain “baseline” level of motor experience in racquet sports for effective action anticipation, while the addition of further motor experience does not appear to assist direction anticipation.  相似文献   

搜索技术的现状及发展前景   总被引：4，自引：0，他引：4  

李子臣 《情报科学》2006,24(3):468-474

对搜索引擎的排序规则、语义理解能力、双字节处理水平和个性化搜索的技术局限和发展现状进行了分析，对桌面搜索、视频搜索和搜索引擎的细化、全能化发展趋势进行了研究。  相似文献   

Mixed control of uncertain jumping time-delay systems     

Magdi S. Mahmoud  Fouad M. AL-Sunni  Yan Shi   《Journal of The Franklin Institute》2008,345(5):536-552

In this paper, we investigate a class of linear continuous-time systems with Markovian jump parameters. An integral part of the system dynamics is a delayed state with time-varying and bounded delays. The jumping parameters are modeled as a continuous-time, discrete-state Markov process. Employing norm-bounded parametric uncertainties and utilizing the second-method of Lyapunov, we examine the problem of designing a mixed controller which minimizes a quadratic performance measure while satisfying a prescribed -norm bound on the closed-loop system. It is established that sufficient conditions for the existence of the mixed controller and the associated performance upper bound could be cast in the form of linear matrix inequalities.  相似文献   

巴山水青冈叶面积表的编制     

李勇威  胡进耀  吴庆贵  杨冬生  李国辉 《绵阳师范学院学报》2007,26(8):83-86

叶片是植物进行光合作用的主要器官。为了便于测定叶面积系数和生产率,编制了有使用价值的叶面积表。从8个回归方程中筛选出叶宽与叶面积相关密切的方程Y=aXb(相关系数达0.95以上),编制出叶面积表。该表应用方法简单,实用性强。通过对叶面积的统计分析,初步探讨了三种不同样地条件下巴山水青冈叶面积的差异。  相似文献   

札剌亦儿部显贵"国王"爵位封授与承袭     

谢咏梅 《内蒙古师范大学学报(哲学社会科学版)》2003,32(4)

札剌亦儿部木华黎是最早受封国王位号的功臣。1217年木华黎受封国王讫元终,子孙承袭,世世无绝。但嗣封者往往受蒙、汉礼制的双重影响以及对蒙廷的亲疏等因素的作用。国王最初代朝廷全权经营中原。随着大汗亲历戎行及蒙古重心的南移,尤其中原统治机构的构建,国王的军权、政权渐渐被削弱,日渐偏远。其职责也转为充当畿辅藩屏或充任朝廷"藩大臣"。元中后期,由于驸马及部分著有拥戴之功的异姓功臣频繁封王拜爵而势力日涨,国王在异姓功臣中的地位也日渐暗淡了。  相似文献