基于螺杆启闭机的多段标定动态光电式扭矩传感器     

陈超  魏兴  陈荣娜  黄振东 《六安师专学报》2013,(5):46-48

螺杆启闭机在水电站、水库、河道渠坝等水利工程的启闭运行中起着重要的控制作用.扭矩传感器是检测螺杆启闭机荷载的关键部件.目前采用的静态扭矩式传感器,只有通过转化,才能实时检测出螺杆启闭机在运转状态下的实际负载.通过试验比较不同方案扭矩传感器的工作性能,研究采用光电滑环和多段标定技术,基于螺杆启闭机的动态光电式扭矩传感器,较好地解决了摩阻力随着启闭荷载变化时传感器无法直观显示实际荷载的关键问题,能够实时、真实、高精度地检测螺杆启闭机的运行负载,很好地满足了工程需要.  相似文献   

Lack of association of the ACE genotype with the muscle strength response to resistance training     

《European Journal of Sport Science》2013,13(4):331-337

Abstract

Introduction: Previous studies have attempted to link the insertion/deletion (I/D) polymorphism in the angiotensin-converting enzyme (ACE) gene with the variability in muscle strength responses to resistance training (RT); however, the literature is inconclusive. The purpose of the present study was to investigate the association between the ACE I/D genotype and muscle strength response to a RT program in young men.

Methods: 124 men (22±2.6 years; 174.8±6.5cm; 71.5±13.8 kg) without resistance training experience were tested before and after 11 weeks of five whole-body RT exercises (bench press, seated row, knee extension, knee flexion and sit ups). The bench press 1RM test was used to assess upper-body muscle strength and the isokinetic knee extensor peak torque (PT) was used as a measure of lower-body strength.

Results: At baseline, there were no differences among ACE genotype for 1RM load (54±11.7 kg for II, 58.5±8.9 kg for ID and 52.3±12.2 kg for DD) or knee extensor peak torque (PT) (220.1±36.8 N·m for II, 209.4 ±44.4 N·m for ID and 199.7±32.4 N·m for DD). Moreover, ACE genotype was not associated with lower-body (7.1±10.5%, 15.7±10.4% and 14.1±22.7% for II, ID and DD, respectively) or upper-body strength gains (16.2±8.9%, 14.5±11.3% and 21.9±17.1% for II, ID and DD, respectively) in response to RT.

Conclusion: The ACE I/D genotype was not associated with the muscle strength responses to RT.  相似文献   

Trunk rotation torques through the hip joints during the one- and two-handed backhand tennis strokes     

Susumu Akutagawa  Takeji Kojima 《Journal of sports sciences》2013,31(8):781-793

The aim of the present study was to compare kinetically the roles of the lower extremities in generating trunk rotation in the tennis one-handed and two-handed backhand strokes. Fourteen male collegiate tennis players, seven with a preference for the one- and seven with a preference for the two-handed technique, were recruited as participants. The motion of each backhand stroke was filmed using two high-speed cine-cameras, and the ground reaction forces on the feet were measured separately using two force platforms to determine the joint moments and joint reaction forces at the hip, knee and ankle joints. A significant difference in hip joint moments between the two types of stroke was found in the phase from the start of forward rotation of the pelvis to the start of racket forward movement. For trunk rotation, the one-handed backhand players exerted a large joint moment in the front leg, whereas the two-handed backhand players exerted a large joint moment in the back leg. The exertion of a large hip joint moment in the latter stroke was comparable with the exertion in a forehand stroke reported previously.  相似文献   

Determinants of countermovement jump performance: a kinetic and kinematic analysis     

Stuart McErlain-Naylor  Mark King  Matthew Thomas Gerard Pain 《Journal of sports sciences》2013,31(19):1805-1812

Abstract

This study aimed to investigate the contributions of kinetic and kinematic parameters to inter-individual variation in countermovement jump (CMJ) performance. Two-dimensional kinematic data and ground reaction forces during a CMJ were recorded for 18 males of varying jumping experience. Ten kinetic and eight kinematic parameters were determined for each performance, describing peak lower-limb joint torques and powers, concentric knee extension rate of torque development and CMJ technique. Participants also completed a series of isometric knee extensions to measure the rate of torque development and peak torque. CMJ height ranged from 0.38 to 0.73 m (mean 0.55 ± 0.09 m). CMJ peak knee power, peak ankle power and take-off shoulder angle explained 74% of this observed variation. CMJ kinematic (58%) and CMJ kinetic (57%) parameters explained a much larger proportion of the jump height variation than the isometric parameters (18%), suggesting that coachable technique factors and the joint kinetics during the jump are important determinants of CMJ performance. Technique, specifically greater ankle plantar-flexion and shoulder flexion at take-off (together explaining 58% of the CMJ height variation), likely influences the extent to which maximal muscle capabilities can be utilised during the jump.  相似文献   

The influence of golf shaft torque on clubhead kinematics and ball flight     

Sasho James Mackenzie  Erik Matthew Henrikson  Heidi Lynette Macdonald  Troy William Hillier 《Journal of sports sciences》2013,31(24):2849-2855

ABSTRACT

The purpose of this study was to investigate the influence of shaft torque (torsional rigidity) on clubhead kinematics and the resulting flight of the ball. Two driver shafts with disparate levels of torque, but otherwise very similar properties, were tested by 40 right-handed golfers representing a range of abilities. Shaft deflection data as well as grip and clubhead kinematics were collected from 14 swings, with each shaft, for each golfer using an optical motion capture system. Ball flight and additional clubhead kinematics were collected using a Doppler radar launch monitor. At impact, the high torque shaft (HT) was associated with increased delivered loft (P = .028) and a more open face (P < .001) relative to the low torque shaft (LT). This resulted in the HT shaft being associated with a ball finishing position that was further right (P = .002). At the individual level, the change in face angle due solely to shaft deformation was significantly higher for the HT shaft for 25/40 participants. Although shaft twist was not directly measured, it was logically deduced using the collected data that these outcomes were the result of the HT being twisted more open relative to the LT shaft at impact.  相似文献   

Kinetic analysis of the lower limbs in baseball tee batting     

Kazumichi Ae  Sekiya Koike  Norihisa Fujii  Michiyoshi Ae  Takashi Kawamura 《Sports biomechanics / International Society of Biomechanics in Sports》2017,16(3):283-296

The purpose of this study was to investigate effects of the ground reaction forces on the rotation of the body as a whole and on the joint torques of the lower limbs associated with trunk and pelvic rotation in baseball tee batting. A total of 22 male collegiate baseball players participated in this study. Three-dimensional coordinate data were acquired by a motion capture system (250 Hz), and ground reaction forces of both legs were measured with three force platforms (1,000 Hz). Kinetic data were used to calculate the moment about the vertical axis through the body’s centre of mass resulting from ground reaction forces, as well as to calculate the torque and mechanical work in the lower limb joints. The lateral/medial ground reaction force generated by both legs resulted in the large whole body moment about its vertical axis. The joint torques of flexion/extension of both hips, adduction of the stride hip and extension of the stride knee produced significantly larger mechanical work than did the other joint torques. To obtain high bat-head speed, the batter should push both legs in the lateral/medial direction by utilising both hips and stride knee torques so as to increase the whole body rotation.  相似文献   

Analysis of elbow muscle strength parameters in Brazilian jiu-jitsu practitioners     

Bruno Follmer  Rodolfo André Dellagrana  Luis Antonio Pereira de Lima  Walter Herzog 《Journal of sports sciences》2017,35(23):2373-2379

Upper-body dynamic and isometric maximum strength are essential components for success in Brazilian jiu-jitsu (BJJ). This study was aimed at analysing strength parameters in the elbow flexor and extensor muscles of BJJ practitioners. Participants (n = 28) performed maximum isometric contractions of elbow flexors and extensors to determine peak torque (PT), rate of force development (RFD), and the torque–angle (T–A) relationship at elbow angles of 45°, 60°, 75°, 90°, 105°, and 120°. Additionally, concentric and eccentric PTs were measured at 1.04 rad·s^-1. Student t-test and ANOVA were performed using α = 0.05. Elbow flexors were stronger isometrically (P < 0.001, ES = 1.23) but weaker concentrically (P < 0.05, ES = 0.54) than extensor muscles, possibly because of the extensive grip disputes and pushing of opponents in BJJ. The T–A relationship had an inverted “U”-shape. Torque differences across elbow angles were moderate (ES = 0.62) for the extensor and large (ES = 0.92) for the flexor muscles. Isometric torque was greatest for elbow angles of 105° and 75° and smallest for 45° and 120° for extensor and flexor muscles, respectively. Elbow flexors had a greater RFD than extensors, regardless of elbow angle. The present study provides comprehensive results for elbow muscle strength in BJJ practitioners.  相似文献   

基于多体动力学的发动机稳态工况动态转矩计算     

符升平  王君 《鹭江职业大学学报》2014,(5):6-11

理论分析发动机转矩波动产生机理,通过有限元分析得到离散化曲轴模型,建立了滑动轴承动态接触数学模型;协同各子部件间动力学关系,考虑燃气压力、变惯性力等激励载荷,在ADAMS中建立发动机曲轴连杆机构多体动力学模型,仿真计算发动机不同稳态工况下动态转矩,研究曲轴弹性、滑动轴承弹性支承、输出转速等对发动机输出动态转矩的影响。通过试验对比和简谐分析,表明了仿真方法的可行性和准确性,为车辆动力传动系统的扭振分析提供激励条件。  相似文献   

腘绳肌拉伤可变危险因素的筛选及对策研究     

李东河  宋磊刚  李增明  母春雷 《河北体育学院学报》2014,28(6):70-72

目的:对腘绳肌拉伤可变危险因素进行分析和筛选,确定主要危险因素,为损伤预防指明方向。方法:以河北省体育运动学校28名学生为研究对象,依据是否发生过单侧腘绳肌拉伤将其分为未受伤组(18人)和受伤组(10人);用Biodex System-3型等速肌力测试系统,对两组学生两膝关节进行屈伸测试,得到两组学生的腘绳肌峰力矩、腘绳肌最佳力矩角度、股四头肌峰力矩、股四头肌最佳力矩角度、股四头肌峰力矩与腘绳肌峰力矩比值(Q/H),并对所得数据进行统计分析。结果:受伤组伤侧腘绳肌峰力矩明显小于健侧(P0.05),伤侧Q/H显著大于健侧和未受伤组(P0.05)。伤侧腘绳肌最佳力矩角度大于健侧,有非常显著性差异(P0.01)。结论及建议:腘绳肌最佳力矩角度、腘绳肌峰力矩、Q/H可以作为腘绳肌拉伤的预测指标,建议选择适当的力量练习以预防腘绳肌拉伤。  相似文献   

给纸机分离头扭矩分析及实验研究     

蒋新萍  王仪明 《科技通报》2014,(9)

针对给纸机输纸稳定性问题,对分离头凸轮分配轴扭矩分布特性进行了理论及试验研究。通过对国内典型飞达子机构进行运动学和动力学分析,得到飞达各子机构对于凸轮分配主轴的作用力及作用于分离头墙板上的反力,得到了分离头扭矩分布特性。利用开发的分离头扭矩试验平台,对分离头的扭矩波动进行了试验研究。结果表明:理论分析的扭矩分布与试验研究基本一致,从而为给纸机分离头的设计与应用提供必要的数据和优化的解决方案。  相似文献