基于组稀疏残差去噪的磁共振图像重构     

袁小君  李杨  杨晓城  蒋明峰 《教育技术导刊》2021,20(1):209-213

为了克服磁共振图像重构精度低的问题,方便医生诊断与治疗,提出一种将组稀疏残差去噪和近似消息传递相结合的磁共振图像重构算法.在基于迭代软阈值的去噪近似消息传递(D-AMP)重构算法中,滤波的去噪算法将使用基于组稀疏残差约束(GSRC)的图像去噪实现.实验结果表明,基于组稀疏残差去噪的磁共振图像重建算法可有效缓解重建图像局...  相似文献   

Biomechanical analysis of the sidearm throwing motion for distance of a flying disc: A comparison of skilled and unskilled Ultimate players     

Kei Sasakawa  Shinji Sakurai 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(3):311-321

Joint angles of the throwing limb were examined from the acceleration phase up until release for the sidearm throwing motion when using a flying disc. 17 individuals (ten skilled, seven unskilled) threw a disc as far as possible ten times. Throwing motions were recorded using three-dimensional high-speed videography. The initial condition of disc release and joint angle kinematics of the upper limb during the throwing motion were obtained. Mean ( ± standard deviation) throwing distance and disc spin rate were significantly greater for skilled throwers (51.4 ± 6.6 m, 12.9 ± 1.3 rps) than for unskilled throwers (29.5 ± 7.6 m, 9.4 ± 1.3 rps), although there was no significant difference in initial velocity of the disc between the two groups (skilled: 21.7 ± 1.7 m/s; unskilled: 20.7 ± 2.5 m/s). A marked difference in motion of supination/pronation of the forearm before disc release was identified, with the forearm supinated in the final acceleration phase leading up to disc release for the unskilled participants, while the forearm was pronated in the same phase for the skilled participants. These differences in joint kinematics could be related to differences in disc spin rate, and thus led to the substantial differences in throwing distance.  相似文献   

Informational constraints on the emergence of passing direction in the team sport of futsal     

《European Journal of Sport Science》2013,13(2):169-176

Abstract

This study investigated compound spatial and temporal measures of interpersonal interactions purported to constrain the emergence of affordances for passing direction in the team sport of futsal. For this purpose, attacker–defender interactions in 37 sequences of play from a futsal competition in which 24 male professional players participated (M=30.04 years, SD=4.10) were filmed and analysed using TACTO software. Relative angle data were used as measures to study coordination tendencies that emerged between players during performance. Results showed that the direction for a pass emerged from relative angles between: (1) the vector from a ball carrier to ball receiver and the vector from the ball carrier to the nearest defender (70°) (p<0.01) and (2) the vector from a ball carrier to ball receiver and the vector from the ball carrier to a ball receiver's nearest defender (31°) (p < 0.01). Furthermore, passing direction was also constrained by temporal information from the emergence of both angles, since the pass was performed to attacker–defender dyads with the highest velocities of these angles (p < 0.05). Results suggested that decisions on selecting the direction of a pass in the team sport of futsal emerged at critical values of these key compound motion measures.  相似文献   

Brachial artery characteristics and micro-vascular filtration capacity in rock climbers     

《European Journal of Sport Science》2013,13(4):296-304

Abstract

Rock climbers perform repeated isometric forearm muscle contractions subjecting the vasculature to repeated ischaemia and distorted haemodynamic signals. This study investigated forearm vascular characteristics in rock climbers compared to healthy untrained controls. Eight climbers (CLIMB) (BMI; 22.3, s = 2.0 kg/m², isometric handgrip strength; 46, s = 8 kg) were compared against eight untrained controls (CON) (BMI; 23.8, s = 2.6 kg/m², isometric handgrip strength; 37, s = 9 kg). Brachial artery diameter and blood flow were measured, using Doppler ultrasound, at rest and following 5-mins ischaemia (peak diameter) and ischaemic exercise (maximal dilation) to calculate flow mediated dilation (FMD) and dilatory capacity (DC). Capillary filtration capacity was assessed using venous occlusion plethysmography. Resting (4.30, s = 0.26 vs. 3.79, s = 0.39 mm), peak (4.67, s = 0.31 vs. 4.12, s = 0.45 mm) and maximal (5.14, s = 0.42 vs. 4.35, s = 0.47 mm) diameters were greater (P < 0.05) in CLIMB than CON, respectively, despite no difference in FMD (9.2, s = 2.6 vs. 8.7, s = 2.9%). Peak reactive hyperaemic blood flow (1136, s = 504 vs. 651, s = 221 ml/min) and capillary filtration capacity (3.8, s = 0.9 vs. 5.2, s = 0.7 ml.min^?1.mmHg^?1.100 ml tissue^?1 × 10^?3) were greater (P < 0.05) in CLIMB compared to CON, respectively. Rock climbers exhibit structural vascular adaptation compared to untrained control participants but have similar vascular function. This may contribute to the enhanced ability of climbers to perform repeated isometric contractions.  相似文献   

Reliability and validity of two tests of soccer skill     

Ajmol Ali  Clyde Williams  Mark Hulse  Anthony Strudwick    Lee Howarth 《Journal of sports sciences》2013,31(13):1461-1470

Abstract

Twenty-four players from the 1st/2nd (elite) and 24 players from the 3rd/4th (non-elite) university football teams were recruited to evaluate the Loughborough Soccer Passing Test (LSPT) and Loughborough Soccer Shooting Test (LSST) as tools to assess soccer skill. The LSPT requires players to complete 16 passes as quickly as possible. The LSST requires players to pass, control, and shoot the ball to targets on a full-sized goal. Participants completed two main trials each separated by at least one day. During both trials, the participants were given practice efforts before recording the mean of the next two (LSPT) or 10 (LSST) attempts as the performance score. For the LSPT, the mean time taken, added penalty time, and overall performance time were less in the elite players (elite: 43.6 s, s = 3.8; non-elite: 52.5 s, s = 7.4; P = 0.0001). For the LSST, there was no difference in the mean points scored per shot between groups (elite: 1.34, s = 0.46; non-elite: 1.28, s = 0.53). However, the elite players had higher mean shot speed (elite: 80 km · h^?1, s = 4.5; non-elite: 74 km · h^?1, s = 4.2; P < 0.0001) and performed each shot sequence faster (elite: 7.87 s, s = 0.29; non-elite: 8.07 s, s = 0.35; P = 0.037) than the non-elite players. Performance on both tests was more repeatable in elite players. In conclusion, the LSPT and LSST are valid and reliable protocols to assess differences in soccer skill performance.  相似文献   

室内五人制足球比赛传球方式特征研究     

任定猛 《北京体育大学学报》2013,36(1):123-126+139

现代五人制足球是对已有的传统足球运动形式进行改造而产生的,它与十一人制足球是同一运动的不同表现形式。五人制足球与十一人制足球训练竞赛过程的差异,是五人制足球运动理论研究的实践基础。鉴于现代五人制足球项目的研究现状和发展所需,对五人制足球运动的传球特征进行分析,结果显示:1)五人制足球比赛中运用最多的传球距离是小于10 m的短传球;2)停—传球是五人制足球比赛组织进攻过程中最为常用的传球组合方式;3)横传球是五人制足球比赛中运用最多的传球方向;4)中场是五人制足球比赛中传球次数运用最多的区域,这个区域也是组织进攻的主要区域。研究为提高我国五人制足球运动训练以及竞赛水平提供有益的理论支持。  相似文献   

PROFIBUS总线系统TTR的计算     

甄丽平  司绍伟 《中国科技信息》2011,(16):87-87,93

从分析PROFIBUS-DP的各种数据通信入手,分别详细分析了数据交换和令牌传的时间行为,给出了满足每个主站持有足够的令牌时间时,TTR的选取方法。  相似文献   

论传球成功率在足球比赛中的重要性及实现     

曹磊 《军事体育进修学院学报》2011,30(1):69-71

运用文献资料法、数理统计法对意大利足球甲级联赛参赛球队的比赛技术统计指标与联赛结果的相关性进行比较分析,并对照第18届足球世界杯参赛球队各项比赛技术统计指标,从中得出传球成功率与比赛胜负高度相关,并对传球成功率的提高进行了研究,旨在进一步提高技战术水平.  相似文献   

个体灵魂的自我拯救——试论“过客”行走的终极意义     

孙海军 《石家庄学院学报》2013,15(2):80-83

《过客》是《野草》重要的篇章之一,它不仅暴露了当时鲁迅自我认同和价值信仰的严重危机,更展现了作为生命个体的鲁迅全力自救的心理历程。过客的自省意识和实践精神激励起危机中的鲁迅,使得鲁迅通过自我拷问、自我调整,最终走出人生的第二次危机,重新建立起新的身份和信仰认同,由此凸现出"行走"这一生命情态在鲁迅个体灵魂自我拯救中的终极性意义。  相似文献   

软式排球教学脚步移动与垫球成功率的线性分析   总被引：1，自引：0，他引：1  

张玉英 《河北体育学院学报》2002,16(2):45-46

运用教学实验文献资料、数理统计等方法 ,对软式排球教学中脚步移动与双手正面垫球效果的线性关系进行了研究 ,结果表明 :与硬式排球相比 ,脚步移动动作亦是影响双手正面垫球效果的直接因素。  相似文献