竞技体育中的力学     

张超平  张帆  王立宪 《漯河职业技术学院学报》2008,7(2):49-50

分析体操、跳水、技巧、花样滑冰、举重、跳高、短跑等项目在运动员选材、动作技能训练及创新、裁判员执法标准尺度等方面中力学知识的应用,说明在竞技体育运动中力学知识的应用无处不在。  相似文献   

彩色玻屏旋转移载机驱动系统设计     

邢春芳  刘万兵 《安阳工学院学报》2008,(2):30-34

在生产实际中,通常根据经验来选用较大规格的驱动设备以满足生产需要,不仅增大了一次投资的成本,也造成设备和能源的浪费。通过对安彩集团玻屏生产线销钉区旋转驱动系统的分析和计算,指出了经验选型之中存在的问题,提出了用变频器替代原伺服系统进行定位的方案,并在实践中获得成功。对类似的系统设计具有一定的参考意义。  相似文献   

运用统计学原理评价城市道路通行能力     

周文强  李伶洋  王洁 《台州学院学报》2014,(6):10-14

运用人工计数法、数据统计分析、以及概率论与数理统计等统计学原理,通过SPSS、EXCEL等工具首先对城市道路通行能力的三参数：流量、密度、速度进行分析。再根据道路通行理论修正自由流速度、实际道路通行能力。最后以V/C饱和度作为评价服务水平的主要指标,结合大中型车的混入比对实际道路通行能力的影响程度,把所研究的时段划分为发生车祸、驾驶员检测与响应、平稳过渡、严重拥堵四个阶段并给出其服务水平（LOS）为C级。  相似文献   

Association between non-alcoholic fatty liver disease and arterial stiffness in the non-obese,non-hypertensive,and non-diabetic young and middle-aged Chinese population     

Xin-yan Yu  Yi Zhao  Xiao-xiao Song  Zhen-ya Song 《Journal of Zhejiang University. Science. B》2014,15(10):879-887

Background and objective: Non-alcoholic fatty liver disease (NAFLD) is associated with arterial stiffness in the general population. Age, obesity, hypertension, and diabetics are risk factors for arterial stiffness. In this study, we aimed to investigate the association between NAFLD and arterial stiffness as measured by brachial-ankle pulse wave velocity (baPWV) in the non-obese, non-hypertensive, and non-diabetic young and middle-aged Chinese population. Methods: A cross-sectional study with 1296 non-obese, non-hypertensive, and non-diabetic young and middle-aged (20–65 years) subjects undergoing routine medical check-ups in the International Health Care Center of the Second Affiliated Hospital of School of Medicine of Zhejiang University was carried out. Fatty liver was diagnosed by ultrasonography, and baPWV was measured using an automatic waveform analyzer. The subjects were classified into two groups according to the presence of NAFLD, and divided into a further two groups according to their baPWV. Results: The overall incidence of NAFLD was 19.0%, and NAFLD patients had a significantly higher level of baPWV than the controls ((1321±158) cm/s vs. (1244±154) cm/s; P<0.001). The incidence of NAFLD was clearly higher in the increased baPWV group than in the normal baPWV group (29.3% vs. 16.9%; P<0.001), and the incidence increased in line with the increase of baPWV quartiles in the normal range as well as with the severity of arterial stiffness (both P for trend <0.001). Multiple linear logistic regression analysis showed that the presence of NAFLD was positively and independently associated with baPWV. Conclusions: Our results suggest that the presence of NAFLD is associated with arterial stiffness as measured by baPWV in the non-obese, non-hypertensive, and non-diabetic young and middle-aged Chinese population.  相似文献   

Effects of isometric quadriceps strength training at different muscle lengths on dynamic torque production     

Marika Noorkõiv  Kazunori Nosaka  Anthony J. Blazevich 《Journal of sports sciences》2015,33(18):1952-1961

This study aims to (1) determine whether isometric training at a short vs. long quadriceps muscle length affects concentric torque production; (2) examine the relationship between muscle hypertrophy and concentric torque; and (3) determine whether changes in fascicle length are associated with changes in concentric torque.

Sixteen men performed isometric training at a short (SL, n = 8) or a long muscle length (LL, n = 8). Changes in maximal concentric torque were measured at 30, 60, 90, 120, 180, 240 and 300 rad · s^?1. The relationships between the changes in concentric torque, cross-sectional area, volume and fascicle length were tested.

Concentric torque increased significantly after training only in LL and at angular velocities of 30 and 120 rad · s^?1 by 12–13% (P < 0.05). Muscle size increased in LL only, the changes were correlated (r = 0.73–0.93, P < 0.05) with the changes in concentric torque. Vastus lateralis (VL) fascicle length increased in both groups (5.4 ± 4.9%, P = 0.001) but the change was not correlated with changes in concentric torque in either group.

Isometric training-induced increases in muscle size and concentric torque were best elicited by training at long muscle lengths. These results highlight a clear muscle length dependence of isometric training on dynamic torque production.  相似文献   

一种测量风传种子沉降速度系统的设计与实现     

王学进  李鑫  戴梅 《常熟理工学院学报》2014,(4):95-99

介绍了一种测量风传种子沉降速度系统的设计.系统采用MC9S12XS128单片机为主控芯片,利用两个线性CCD传感器分别采集种子下落过程中的视频信号,通过图像边缘检测算法精确捕捉种子下落过程中的始末两个时刻,利用加权算术平均法计算出种子沉降速度值,同时拟合出沉降高度与速度的曲线.实际测试表明,本系统具有测量精度高、抗干扰能力强、检测效率高、操作简单等优点.  相似文献   

自动扶梯控制柜检测台的设计与实现     

陈洁 《常熟理工学院学报》2014,(2):79-83

根据GB16899-2011《自动扶梯和自动人行道的制造与安装安全规范》的要求,分析了扶梯控制系统的组成结构,提出了一种检测自动扶梯控制柜功能的方案,给出了电路原理、产生速度脉冲的方法,并列出了材料清单。  相似文献   

Relative Age Effect,Biological Maturation,and Coaches’ Efficacy Expectations in Young Male Soccer Players     

Iván Peña-González  Jaime Fernández-Fernández  Manuel Moya-Ramón  Eduardo Cervelló 《Research quarterly for exercise and sport》2018,89(3):373-379

Purpose: The talent identification and selection process in young male soccer players is mainly focused on anthropometrics and physical performance, but social factors are also considered in this process. The purpose of this study was to test the existence of the relative age effect and its possible influence on anthropometrics and physical performance and to analyze coaches’ efficacy expectations. Method: Data for 564 young male soccer players (M_age = 13.7 ± 1.5 years; M_weight = 53.7 ± 11.6 kg; M_height = 160.2 ± 11.6 cm) included their birth quartile, maturity status, anthropometrics, a physical test battery, and coaches’ efficacy expectations. Results: Early-born players were overrepresented (p < .05). Early-born players were not statistically taller, heavier, or better at physical performance (p > .05) when maturation and chronological age were controlled as confounding factors. However, coaches expected more from early-born players (p < .05), and the inferential analysis showed likely to very likely worthwhile differences between the coaches’ expectations for players born in the first quartile of the year and those born in the fourth quartile of the year. Conclusions: Anthropometrical and physical performance variables were not affected by birth quartile, and coaches’ efficacy expectations were related to the relative age effect.  相似文献   

煤气洗涤水的治理研究   总被引：1，自引：0，他引：1  

陶静 《鞍山师范学院学报》1999,(3)

采用氧化 絮凝方法对煤气洗涤水进行了研究 .通过实验选择二氧化氯为氧化剂 ,聚丙烯酰胺和石灰为混凝剂 ,并综合考虑处理效果和药剂费用等各方面因素 ,通过正交实验确定了主要技术参数 .  相似文献   

短跑支撑阶段运动生物力学分析          下载免费PDF全文

施宝兴 《体育科研》2010,31(6):40-43

采用测力、高速录像及特殊的数据平滑处理方法研究短跑运动员途中跑技术的运动学和动力学特征,进行田径技术原理的探索。结果表明,支撑时期可以分为着地阶段和蹬伸阶段,蹬伸阶段可分前蹬,后蹬前段,后蹬后段。途中跑前蹬段是人体重心垂直方向向上加速的重要时刻,前蹬时下肢一定程度的垂直加速用力虽影响水平速度,但对提高垂直速度有积极意义,前蹬和后蹬前段是身体重心垂直向上加速运动的阶段。着地缓冲后的前蹬用力也是实现良好成绩的技术之一。途中跑着地和前蹬阶段失去的水平速度损失完全可以从后蹬中得到补充。着地点过近对前支撑阶段获得重要的垂直速度不利,支撑阶段离地前的20ms身体重心速度已经开始下降。  相似文献