基于螺杆启闭机的多段标定动态光电式扭矩传感器

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.     

城市已有应急物资储备库功能优化模型与实证研究——以石家庄市为例

实现城市区域内已有应急物资储备库应急服务的最优化、科学化,需要构建体现已有应急物资储备库功能优化本质的数学模型。构建的模型考虑了交通方式、需求点风险程度,优于前人的研究成果。联系石家庄应急管理的需要,该模型解决了石家庄市已有各应急物资储备库最优服务区、县(市)划定,最大服务半径取值,服务布局地图展示等现实问题。模型应用结果还表明:石家庄市应重点加强市区物资储备库一三五处的建设,应至少新增深泽县、辛集市、平山县3个应急物资储备库,并加强相关配套设施建设。     

男子古典式摔跤运动员膝关节肌力特征研究

采用文献资料法、专家访谈法以及等速肌力测试法,对不同水平的古典式摔跤运动员膝关节最大力量、快速力量、力量耐力及平均峰力矩等指标进行对比分析.结果发现:所选取一级运动员在膝关节伸、屈肌群最大力量、快速力量及力量耐力上均优于二级运动员;古典式摔跤运动员膝关节屈、伸肌群平均峰力矩之比均随速度加快而增大,且膝关节屈肌力量增长幅度高于其他项目运动员.建议在今后训练中应注重结合专项技术动作发展膝关节的快速蹬伸能力,努力提高膝关节伸、屈肌群的最大力量、快速力量及力量耐力水平,并注意膝关节伸、屈肌群力量的均衡发展.     

Criterion-related validity of the 20-m shuttle run test in youths aged 13–19 years

Abstract

We assessed the agreement between maximal oxygen consumption ([Vdot]O_2max) measured directly when performing the 20-m shuttle run test and estimated [Vdot]O_2max from five different equations (i.e. Barnett, equations a and b; Léger; Matsuzaka; and Ruiz) in youths. The 20-m shuttle run test was performed by 26 girls (mean age 14.6 years, s = 1.5; body mass 57.2 kg, s = 8.9; height 1.60 m, s = 0.06) and 22 boys (age 15.0 years, s = 1.6; body mass 63.5 kg, s = 11.5; height 1.70 m, s = 0.01). The participants wore a portable gas analyser (K4b2, Cosmed) to measure [Vdot]O₂ during the test. All the equations significantly underestimated directly measured [Vdot]O_2max, except Barnett's (b) equation. The mean difference ranged from 1.3 ml · kg^?1 · min^?1 (Barnett (b)) to 5.5 ml · kg^?1 · min^?1 (Léger). The standard error of the estimate ranged from 5.3 ml · kg^?1 · min^?1 (Ruiz) to 6.5 ml · kg^?1 · min^?1 (Léger), and the percentage error ranged from 21.2% (Ruiz) to 38.3% (Léger). The accuracy of the equations available to estimate [Vdot]O_2max from the 20-m shuttle run test is questionable at the individual level. Furthermore, special attention should be paid when comparisons are made between studies (e.g. population-based studies) using different equations. The results of the present study suggest that Barnett's (b) equation provides the closest agreement with directly measured [Vdot]O_2max (cardiorespiratory fitness) in youth.     

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

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.     

Critical velocity: A predictor of 2000-m rowing ergometer performance in NCAA D1 female collegiate rowers

Abstract

The aims of this study were to examine the use of the critical velocity test as a means of predicting 2000-m rowing ergometer performance in female collegiate rowers, and to study the relationship of selected physiological variables on performance times. Thirty-five female collegiate rowers (mean ± s: age 19.3 ± 1.3 years; height 1.70 ± 0.06 m; weight 69.5 ± 7.2 kg) volunteered to participate in the study. Rowers were divided into two categories based on rowing experience: varsity (more than 1 year collegiate experience) and novice (less than 1 year collegiate experience). All rowers performed two continuous graded maximal oxygen consumption tests (familiarization and baseline) to establish maximal oxygen uptake ([Vdot]O_2max), peak power output, and power output at ventilatory threshold. Rowers then completed a critical velocity test, consisting of four time-trials at various distances (400 m, 600 m, 800 m, and 1000 m) on two separate days, with 15 min rest between trials. Following the critical velocity test, rowers completed a 2000-m time-trial. Absolute [Vdot]O_2max was the strongest predictor of 2000-m performance (r = 0.923) in varsity rowers, with significant correlations also observed for peak power output and critical velocity (r = 0.866 and r = 0.856, respectively). In contrast, critical velocity was the strongest predictor of 2000-m performance in novice rowers (r = 0.733), explaining 54% of the variability in performance. These findings suggest the critical velocity test may be more appropriate for evaluating performance in novice rowers.     

Optimized and corrected peak power output during friction‐braked cycle ergometry

Assessments of maximal intensity exercise which determine peak power output on friction‐baked cycle ergometers have fallen into two categories: correction procedures which account for changes in momentum of the ergometer's flywheel and optimization procedures which attempt to satisfy muscle force‐velocity relationships. The aim of this study was to compare performance in each procedure and so investigate assumptions which underpin the tests. Nineteen males aged 20.9 ± 0.4 years and 18 females aged 22.2 ± 0.7 years (mean ± S.E.M.), who were fully accustomed to the procedures, participated in a single experimental protocol. After a 5 min warm‐up, the subjects performed four bouts of all‐out exercise on a Monark 814E cycle ergometer against randomly assigned loads. The loads were selected to produce peak pedalling rates in the range 100–200 rev min^?1 and each bout lasted 10 s. From the inverse linear relationship between applied load and peak pedalling rate, optimized peak power output (PP _opt) and the accompanying pedalling rate (RPM _opt) were calculated. One of the bouts used a loading equivalent to 7.5% of body weight and for this bout corrected peak power output (PP _corr) and its corresponding pedalling rate (RPM _corr) were calculated. The PP _opt was less than PP _corr in the males (915 ± 35 vs 1005 ± 32 W) and females (673 ± 33 vs 777 ± 39 W) (both P < 0.001). Similarly, RPM _opt was less than RPM _corr (111 ± 1 vs 128 ± 2 rev min^?1 and 101 ± 1 vs 111 ± 2 rev min^?1 in the males and females, respectively; P < 0.001). The results demonstrate that optimization and correction procedures produce different values of performance. These differences are probably attributable to the mechanical principles which underpin the tests.     

可调式液力变矩器导轮叶片转动轴位置的确定

本文对YBT900可调式液力变矩器导轮直列叶栅,在S_1流面上进行流场计算,以求得不同开启角时转动导轮叶片表面的压力分布情况及导轮叶片转动轴的位置。     

台阶试验的应用及研究进展

台阶试验是一项简单、方便、安全的评价心血管系统功能的运动负荷试验,已成为心血管功能现场测试的首选方法,在我国成年人体质监测和学生体质健康评价中都将台阶试验作为评价心血管系统功能的指标.文章总结了近十年来台阶试验在中国的应用,并对实践过程中发现的一些问题进行了初步的分析.     

电偶极子电场中的电场强度和电势

生物体所有的功能和活动，都以某种方式涉及到电。本讨论对于人体生物电有着重要意义的一种典型的电场——电偶极子的电场，并研究了心肌细胞的电学性质。