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Abstract The mechanical responses (i.e. external contact forces and external power) of 25 elite rowers to a race-pace rowing protocol were investigated on the traditional fixed stretcher mechanism and the more recently introduced free-floating stretcher mechanism rowing ergometers. Using a Rowperfect rowing ergometer for both conditions, external contact forces at the handle, stretcher and sliding seat, as well as the displacements of the handle and stretcher, were recorded. The external power was calculated as the product of the force and velocity data from both the handle and stretcher. Significant differences (P < 0.05) between the two conditions for each mechanical parameter were observed. The fixed condition showed larger maximum values for forces and external power and average power throughout the rowing cycle. Moreover, rowing with the fixed mechanism generated higher inertial forces during the transition between the propulsion and recovery phases, especially at the catch of the cycle. The results suggest that: (i) muscular coordination may differ according to the stretcher mechanism used, which could have an impact on the physiological adaptations of muscles; and (ii) the free-floating mechanism may induce lower catch and maximum values for net joint forces and net joint moments that could decrease the risk of injury. 相似文献
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本实验采用原子吸收分光光度法对凤阳地区 6类植物性食品中锌的含量进行了分析测定。结果表明 ,凤阳地区谷类含锌量平均为 5 .0 2 1 3mg/kg ;豆类平均为 2 3.0 82 2mg/kg ;咸菜类为 1 6.5 4 65mg/kg ;根茎类为 2 1 .331 6mg/kg ;瓜茄类为 2 4 .470 3mg/kg ;叶嫩茎类为 35 .5 80 8mg/kg。这为本地区调配平衡膳食提供了参考。 相似文献
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模糊理论在人才招聘中的应用研究 总被引：16，自引：0，他引：16
本文采用模糊优先评价模型以及层次分析法设置评价指标的权重,将应聘者与待聘岗位有关的各项特性进行合理、全面的评判,以实现主观向客观、定性向定量的转变,为招聘者提供科学、直观的决策思路与方法。 相似文献
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Yoann Blache Thomas Creveaux Raphaël Dumas Laurence Chèze Isabelle Rogowski 《Sports biomechanics / International Society of Biomechanics in Sports》2017,16(1):127-142
The primary role of the shoulder joint in tennis forehand drive is at the expense of the loadings undergone by this joint. Nevertheless, few studies investigated glenohumeral (GH) contact forces during forehand drives. The aim of this study was to investigate GH compressive and shearing forces during the flat and topspin forehand drives in advanced tennis players. 3D kinematics of flat and topspin forehand drives of 11 advanced tennis players were recorded. The Delft Shoulder and Elbow musculoskeletal model was implemented to assess the magnitude and orientation of GH contact forces during the forehand drives. The results showed no differences in magnitude and orientation of GH contact forces between the flat and topspin forehand drives. The estimated maximal GH contact force during the forward swing phase was 3573 ± 1383 N, which was on average 1.25 times greater than during the follow-through phase, and 5.8 times greater than during the backswing phase. Regardless the phase of the forehand drive, GH contact forces pointed towards the anterior-superior part of the glenoid therefore standing for shearing forces. Knowledge of GH contact forces during real sport tasks performed at high velocity may improve the understanding of various sport-specific adaptations and causative factors for shoulder problems. 相似文献
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林广泽 《内江师范学院学报》2000,(3)
本文立足于人类文化的本质、发展的基本倾向和终极使命等三大基点上 ,对人类文化在 2 1世纪将可能具有的功能与特性作了预测性的展望 ,认为在新世纪里人类文化将具有更能激励人类面对现实与未来的挑战 ;更具有全球意识和整体人类观 ;更具有文化—科技一体化 ;更具有文化的民主等功能与特 相似文献
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Isabelle Rogowski Thomas Creveaux Laurence Chèze Raphaël Dumas 《Sports biomechanics / International Society of Biomechanics in Sports》2014,13(2):166-175
Scapular dyskinesis is recognized as an abnormality in the kinetic chain; yet, there has been little research quantifying scapular motion during sport tasks. Tennis forehand drives of eight highly skilled tennis players were studied to assess the scapulothoracic kinematics and evaluate repeatability using video-based motion analysis. Scapulothoracic downward/upward rotation, posterior/anterior tilt, and internal/external rotation were computed using an acromial marker cluster. On average, the upward rotation, anterior tilt, and internal rotation varied from 1° to 26°, from 7° to 32°, and from 42° to 100°, respectively, during the tennis forehand drive. During the backswing and forward swing phases of the forehand stroke, small changes were observed for the three scapular angle values, while all angles increased rapidly during the follow-through phase. This suggests that the tennis forehand drive may contribute to scapula dyskinesis, mainly due to the great amplitude in scapulothoracic anterior tilt and internal rotation observed during the follow-through phase. Knowledge of normal scapula motion during sport tasks performed at high velocity could improve the understanding of various sport-specific adaptations and pathologies. 相似文献
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Thomas Creveaux Violaine Sevrez Raphaël Dumas Laurence Chèze 《Sports biomechanics / International Society of Biomechanics in Sports》2018,17(1):131-141
The aim of this study was to examine the respective aptitudes of three rotation sequences (YtXf′Yh′′, ZtXf′Yh′′, and XtZf′Yh′′) to effectively describe the orientation of the humerus relative to the thorax during a movement involving a large horizontal abduction/adduction component: the tennis forehand drive. An optoelectronic system was used to record the movements of eight elite male players, each performing ten forehand drives. The occurrences of gimbal lock, phase angle discontinuity and incoherency in the time course of the three angles defining humerothoracic rotation were examined for each rotation sequence. Our results demonstrated that no single sequence effectively describes humerothoracic motion without discontinuities throughout the forehand motion. The humerothoracic joint angles can nevertheless be described without singularities when considering the backswing/forward-swing and the follow-through phases separately. Our findings stress that the sequence choice may have implications for the report and interpretation of 3D joint kinematics during large shoulder range of motion. Consequently, the use of Euler/Cardan angles to represent 3D orientation of the humerothoracic joint in sport tasks requires the evaluation of the rotation sequence regarding singularity occurrence before analysing the kinematic data, especially when the task involves a large shoulder range of motion in the horizontal plane. 相似文献
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马云泽 《辽宁师范大学学报(社会科学版)》2001,24(4):106-109
在西方近代国家学说史上，霍布斯是第一个在国家问题上自觉反对神学国家学说的人，他的国家学说建立在人性论的理论基础之上，并认为君主专制是最好的国家政体形式。尽管霍布斯的国家学说具有历史局限性，但同时它还具有反对宗教神权、反对封建割据、主张国家主权来自人民的进步意义，霍布斯的国家学说在西方近代国家学说史上具有十分重要的地位。 相似文献