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91.
集约化农区耕地利用变化及其驱动机制分析 总被引:26,自引:3,他引:26
以河北省曲周县为集约化农区的典型样区,利用统计资料和典型调查数据,对曲周县1973年到2000年耕地利用变化进行了分析;在此基础上探讨了县域耕地利用变化的驱动机制。分析表明,曲周县耕地面积年均递减率为0.026%,但高产田面积、水浇地面积、粮食播种面积单产分别增加了4.91倍、2.15倍和7.26倍;耕地内部种植结构表现为小麦播种面积稳定,玉米和棉花面积变化起伏大,蔬菜面积不断上升。耕地减少的直接原因是建设占用,耕地质量的提高主要是中低产田改造的结果,粮食产量提高的直接驱动因子是科学技术进步、间接驱动因素是农用土地政策的改革。 相似文献
92.
在全面建设小康社会和构建社会主义和谐社会的进程中,要坚持和完善公有制为主体的基本经济制度,必须使公有资本不断地保值增值,需要充分发挥公有资本人格化的道德力量。如何实现公有资本人格化,这是国有企业摆脱目前困境的根本途径之一,也是我国当前构建社会主义和谐社会的伦理道德基础。 相似文献
93.
利用TiAlN涂层刀具对718模具钢进行高速铣削试验研究,获得铣削速度v、背吃刀量αp、进给速度vf和径向铣削深度αe对铣削力的影响规律,为合理选择铣削参数提供可靠的依据。同时,在正交试验结果的基础上, 应用多元线性回归分析方法,建立铣削力的回归数学模型,并用R检验和F检验法验证模型的显著性。 相似文献
94.
以唯物史观和唯物主义辩证法两大锐利思想武器作为马克思主义生产力理论方法论基础的确立,是马克思主义生产力理论成为科学的理论以及与西方经济学理论相区别的最本质的特征;马克思主义生产力理论方法论基础、所揭示的基本原理(生产力发展规律)与其科学的分析框架之间的内在逻辑一致性,是马克思主义生产力理论科学性的本质体现;邓小平关于“科学技术是第一生产力”的思想,是马克思主义生产力理论在当代中国的创造性发展。 相似文献
95.
近年来,脑卒中和交通事故造成上肢损伤的人数逐年上升,医疗领域对康复器械的需求越来越大。为满足实际需求,开发以气动人工肌肉为驱动器的4自由度(肩关节外收/内展(被动)、前驱/后伸、肘关节屈曲、腕关节屈曲)可穿戴上肢康复机器人。首先设计上肢康复机器人的结构,并采用气动人工肌肉作为肘关节与腕关节的驱动器。然后针对该上肢康复机器人,研究主动康复训练控制策略,设计两种控制策略。通过穿戴实验验证控制策略的有效性和实际应用价值。 相似文献
96.
Dorota Sadowska Justyna Krzepota Andrzej Klusiewicz 《Journal of sports sciences》2019,37(16):1892-1898
The aim of the study was to evaluate the effect of maximal specific physical effort on postural balance and rifle stability in biathletes in a standing shooting position. The study included 10 junior elite biathletes. The measurements were taken with the Vicon system and AMTI force platform. Postural balance and rifle stability characteristics were determined at rest as well as 1 and 5 min post maximal specific physical effort which was performed on a ski ergometer and continued until exhaustion. Maximal physical effort exerted a significant effect on all examined postural sway and rifle sway characteristics. The duration of the post-exercise changes was longer than 5 minutes. Higher post-effort rifle sway was observed in the vertical direction than in the across the shooting line direction. Post-effort postural balance impairment in the shooting line was much greater than in the across the shooting line direction. Moreover, a strong correlation was found between postural balance and rifle stability. Maximal physical effort influenced postural balance and rifle stability during aiming. Rifle sway during aiming in a standing shooting position seems to be coordinated with the postural sway of the biathlete’s body. Thus, an increase in postural sway contributes to greater sway and lesser stability of the rifle. 相似文献
97.
贾谊 《河北体育学院学报》2017,31(5):64-70
目的:研究男子排球运动员扣球起跳蹬地动作过程中,人体下肢的相关力学参数特征.对象:男子大学生排球运动员10名.方法:使用高速人体动作捕捉系统及三维测力台,对相关运动学和动力学参数进行采集.结果:①起跳过程中,地面反作用力峰值和均值均为优势腿大于非优势腿;②非优势腿地面反作用力峰值与重心最大高度呈高度负相关(r=-0.961,P=0.002<0.05);③双脚同时着地过程中,优势腿地面反作用力冲量明显大于非优势腿,两脚地面反作用力冲量差与重心最大高度呈显著负相关(r=-0.531,P=0.034<0.05).结论:①在后排起跳过程中,优势腿与非优势腿表现出不同的用力形式;②应当通过适当控制非优势腿在着地初期的制动作用,并在双脚最后用力阶段有意识地提高非优势腿的参与程度,以提高人体的起跳高度;③排球运动员髌腱炎的发病可能与踝关节绕矢状轴力矩和膝关节绕垂直轴力矩较大有关. 相似文献
98.
Amador García-Ramos Belén Feriche Alejandro Pérez-Castilla Paulino Padial Slobodan Jaric 《European Journal of Sport Science》2017,17(6):690-698
This study aimed to explore the strength of the force–velocity (F–V) relationship of lower limb muscles and the reliability of its parameters (maximum force [F0], slope [a], maximum velocity [V0], and maximum power [P0]). Twenty-three men were tested in two different jump types (squat and countermovement jump: SJ and CMJ), performed under two different loading conditions (free weight and Smith machine: Free and Smith) with 0, 17, 30, 45, 60, and 75?kg loads. The maximum and averaged values of F and V were obtained for the F–V relationship modelling. All F–V relationships were strong and linear independently whether observed from the averaged across the participants (r?≥?0.98) or individual data (r?=?0.94–0.98), while their parameters were generally highly reliable (F0 [CV: 4.85%, ICC: 0.87], V0 [CV: 6.10%, ICC: 0.82], a [CV: 10.5%, ICC: 0.81], and P0 [CV: 3.5%, ICC: 0.93]). Both the strength of the F–V relationships and the reliability of their parameters were significantly higher for (1) the CMJ over the SJ, (2) the Free over the Smith loading type, and (3) the maximum over the averaged F and V variables. In conclusion, although the F–V relationships obtained from all the jumps tested were linear and generally highly reliable, the less appropriate choice for testing the F–V relationship could be through the averaged F and V data obtained from the SJ performed either in a Free weight or in a Smith machine. Insubstantial differences exist among the other combinations tested. 相似文献
99.
Recurve archery is an Olympic sport that requires extreme precision, upper body strength and endurance. The purpose of this research was to quantify how postural stability variables both pre- and post-arrow release, draw force, flight time, arrow length and clicker reaction time, collectively, impacted on the performance or scoring outcomes in elite recurve archery athletes. Thirty-nine elite-level recurve archers (23 male and 16 female; mean age?=?24.7?±?7.3 years) from four different countries volunteered to participate in this study prior to competing at a World Cup event. An AMTI force platform (1000Hz) was used to obtain centre of pressure (COP) measurements 1s prior to arrow release and 0.5s post-arrow release. High-speed footage (200Hz) allowed for calculation of arrow flight time and score. Results identified clicker reaction time, draw force and maximum sway speed as the variables that best predicted shot performance. Specifically, reduced clicker reaction time, greater bow draw force and reduced postural sway speed post-arrow release were predictors of higher scoring shots. It is suggested that future research should focus on investigating shoulder muscle tremors at full draw in relation to clicker reaction time, and the effect of upper body strength interventions (specifically targeting the musculature around the shoulder girdle) on performance in recurve archers. 相似文献
100.
Yoichi Ohta 《Journal of sports sciences》2017,35(23):2304-2312
The present study aimed to clarify the effects of oncoming target velocities on the ability of rapid force production and accuracy and variability of simultaneous control of both force production intensity and timing. Twenty male participants (age: 21.0 ± 1.4 years) performed rapid gripping with a handgrip dynamometer to coincide with the arrival of an oncoming target by using a horizontal electronic trackway. The oncoming target velocities were 4, 8, and 12 m · s?1, which were randomly produced. The grip force required was 30% of the maximal voluntary contraction. Although the peak force (Pf) and rate of force development (RFD) increased with increasing target velocity, the value of the RFD to Pf ratio was constant across the 3 target velocities. The accuracy of both force production intensity and timing decreased at higher target velocities. Moreover, the intrapersonal variability in temporal parameters was lower in the fast target velocity condition, but constant variability in 3 target velocities was observed in force intensity parameters. These results suggest that oncoming target velocity does not intrinsically affect the ability for rapid force production. However, the oncoming target velocity affects accuracy and variability of force production intensity and timing during rapid force production. 相似文献