一个物理综合实验的设计与实践--弹簧振子加速度的红外遥测     

聂士忠 《实验室研究与探索》2006,25(1):31-33

介绍我们新开发的一个综合性实验,它主要包括拉力传感器、由LM331组成的V/F和F/V变换电路以及红外发射和接收装置等,以实现对弹簧振子加速度的红外遥测。利用计算机USB数据采集器进行数据采集和处理,包括计算弹簧振子的速度和位移、系统的弹性势能、重力势能、动能和总机械能,并绘制机械能变化曲线,由此验证了弹簧振子系统的机械能守恒。本实验项目在提高学生学习的主动性和创新能力方面取得了较好的效果。  相似文献   

基于 82C53 的重力加速度测量仪器的研制     

于复生  张涵  付学森  刘迎春 《实验室研究与探索》2003,22(6):102-103,115

主要介绍了一种低成本、高精度的重力加速度测量仪，该测量仪采用AT89C51单片机为核心处理器，采用82C53作为计数器，由89C51的P1．0管脚产生的脉冲信号输入到82C53作为计数脉冲和时间基准，由82C53的三个计数器作为时间记录器，记录小球依次通过三个位置的时间差，由这三个小球之间的距离差和小球依次通过的时间差计算出小球运动的加速度。本文介绍了该重力加速度测量系统的硬件设计和软件设计。该测量仪可应用于测量重力加速度的教学演示中，并可应用于测量其他运动物体的速度和加速度。  相似文献   

加速度共振现象及其特征   总被引：2，自引：0，他引：2  

孟振庭 《渭南师范学院学报》2001,16(6):88-91

在受迫振动中，振动加速度达到最大值时的共振现象，称为“加速度共振”，其共振条件为Ω=ω^2/√ω^2-2β^2,振幅比通常的位移共振的振幅小，初位相比通常的位移共振的初位相大，其共振特征明显，物理意义明确。  相似文献   

狭义相对论速度与加速度变换   总被引：1，自引：0，他引：1  

文军 《渭南师范学院学报》2009,24(5):17-20

文中给出了相对论速度变换与四维速度变换、加速度变换与四维加速度变换的联系.  相似文献   

Differences in hamstring activation characteristics between the acceleration and maximum-speed phases of sprinting     

Ayako Higashihara  Yasuharu Nagano  Takashi Ono  Toru Fukubayashi 《Journal of sports sciences》2018,36(12):1313-1318

This study aimed to investigate activation characteristics of the biceps femoris long head (BFlh) and semitendinosus (ST) muscles during the acceleration and maximum-speed phases of sprinting. Lower-extremity kinematics and electromyographic (EMG) activities of the BFlh and ST muscles were examined during the acceleration sprint and maximum-speed sprint in 13 male sprinters during an overground sprinting. Differences in hamstring activation during each divided phases and in the hip and knee joint angles and torques at each time point of the sprinting gait cycle were determined between two sprints. During the early stance of the acceleration sprint, the hip extension torque was significantly greater than during the maximum-speed sprint, and the relative EMG activation of the BFlh muscle was significantly higher than that of the ST muscle. During the late stance and terminal mid-swing of maximum-speed sprint, the knee was more extended and a higher knee flexion moment was observed compared to the acceleration sprint, and the ST muscle showed higher activation than that of the BFlh. These results indicate that the functional demands of the medial and lateral hamstring muscles differ between two different sprint performances.  相似文献   

An accurate estimation of the horizontal acceleration of a rower’s centre of mass using inertial sensors: a validation     

Lotte L. Lintmeijer  Gert S. Faber  Hessel R. Kruk  A. J. “Knoek” van Soest  Mathijs J. Hofmijster 《European Journal of Sport Science》2018,18(7):940-946

For a valid determination of a rower’s mechanical power output, the anterior–posterior (AP) acceleration of a rower’s centre of mass (CoM) is required. The current study was designed to evaluate the accuracy of the determination of this acceleration using a full-body inertial measurement units (IMUs) suit in combination with a mass distribution model. Three methods were evaluated. In the first two methods, IMU data were combined with either a subject-specific mass distribution or a standard mass distribution model for athletes. In the third method, a rower’s AP CoM acceleration was estimated using a single IMU placed at the pelvis.

Experienced rowers rowed on an ergometer that was placed on two force plates, while wearing a full-body IMUs suit. Correspondence values between AP CoM acceleration based on IMU data (the three methods) and AP CoM acceleration obtained from force plate data (reference) were calculated. Good correspondence was found between the reference AP CoM acceleration and the AP CoM accelerations determined using IMU data in combination with the subject-specific mass model and the standard mass model (intraclass correlation coefficients [ICC] >?0.988 and normalized root mean square errors [nRMSE]?3.81%). Correspondence was lower for the AP CoM accelerations determined using a single pelvis IMU (0.877?Based on these results, we recommend determining a rower’s AP CoM acceleration using IMUs in combination with the standard mass model. Finally, we conclude that accurate determination of a rower’s AP CoM acceleration is not possible on the basis of the pelvis acceleration only.  相似文献   

Use of probabilistic and deterministic measures to identify unfavorable earthquake records     

Abbas Moustafa  Izuru Takewaki 《浙江大学学报(A卷英文版)》2009,10(5):619-634

This study introduces measures to identify resonant （concentration of energy in a single or a few frequencies） or unfavorable earthquake ground motions. Probabilistic measures based on the entropy rate and the geometric properties of the power spectral density function （PSDF） of the ground acceleration are developed first. Subsequently, deterministic measures for the frequency content of the ground acceleration are also developed. These measures are then used for identifying resonance and criticality in stochastic earthquake models and 110 acceleration records measured at rock, stiff, medium and soft soil sites. The unfavorable earthquake record for a given structure is defined as the record having a narrow frequency content and dominant frequency close to the structure fundamental natural frequency. Accordingly, the measures developed in this study may provide a basis for selecting records that are capable of producing the highest structural response. Numerical verifications are provided on damage caused to structures by identified resonant records.  相似文献   

基于加速度传感器的上肢爆发力训练研究     

邢新阳  刘嘉嘉  张培  赵焕彬 《河北体育学院学报》2013,(4):83-86

利用＂三轴加速度传感器＂对运动员不同负荷下的卧推训练进行数据采集,分析得知：不同人爆发力水平不同,不同人在相同负荷下的爆发力也不同;同一人在不同负荷下的爆发力不同,且都存在极值点;同一人在保证卧推质量的前提下,在相同负荷中完成的五次卧推中所表现出来的爆发力基本相同;同一人的爆发力水平具有固定性和阶段性;速度对爆发力起关键作用;活体肌肉的力速关系符合希尔方程规律,但实验中最大爆发力值的负荷在1RM的41%-45%之间,对应的速度和力量约为50%-53%最大速度和52%-55%最大力量。并提出相关建议。  相似文献   

Velocity and acceleration before contact in the tackle during rugby union matches     

Sharief Hendricks  David Karpul  Fred Nicolls  Michael Lambert 《Journal of sports sciences》2013,31(12):1215-1224

Abstract

The velocity and acceleration at which the ball-carrier or tackler enters the tackle may contribute to winning the contest and prevailing injury free. Velocity and acceleration have been quantified in controlled settings, whereas in match-play it has been subjectively described. The purpose of this study was to determine the velocity and acceleration of the ball-carrier and tackler before contact during match-play in three competitions (Super 14, Varsity Cup, and Under-19 Currie Cup). Using a two-dimensional scaled version of the field, the velocity and acceleration of the ball-carrier and tackler were measured at every 0.1 s to contact for 0.5 s. For front-on tackles, a significant difference (P < 0.05) between the ball-carrier (4.6 ± 1 m · s^–1) and tackler (7.1 ± 3.5 m · s^–1) was found at the 0.5 s time to contact interval in the Varsity Cup. For side-on tackles, differences between the two opposing players were found at 0.5 s (ball-carrier: 4.6 ± 1.7 m · s^–1; tackler: 3.1 ± 1.2 m · s^–1) and 0.4 s (ball-carrier: 6.3 ± 2.3 m · s^–1; tackler: 3.7 ± 1.6 m · s^–1) at Under-19 level. After 0.4 s, no significant differences (P > 0.05) were evident. Also, the ball-carrier's velocity over the 0.5 s was relatively stable compared with that of the tackler. Results suggest that tacklers adjust their velocity to reach a suitable relative velocity before making contact with the ball-carrier.  相似文献   

Acceleration patterns in the lower and upper trunk during running     

Masahiro Kawabata  Kenta Goto  Ken Sasaki  Eiji Hihara  Takahiro Mizushina 《Journal of sports sciences》2013,31(16):1841-1853

Abstract

The purpose of the present study was to relate 3D acceleration patterns of the lower and upper trunk during running to running gait cycle, assess the validity of stride duration estimated from acceleration patterns, investigate speed-dependent changes in acceleration, and examine the test–retest reliability of these parameters. Thirteen healthy young men performed two running trials each on a treadmill and on land at three speeds (slow, preferred, and fast). The 3D accelerations were measured at the L3 spinous process (lower trunk) and the ensiform process (upper trunk) and synchronised with digital video data. The amplitude and root mean square of acceleration and stride duration were calculated and then analysed by three-way analysis of variance to test effects of running conditions, device location, and running speed. Bland-Altman analysis was used to evaluate the test–retest reliability. Marked changes in acceleration were observed in relation to foot strike during running. Stride durations calculated from the vertical accelerations were nearly equal to those estimated from video data. There were significant speed effects on all parameters, and the low test–retest reliability was confirmed in the anterior–posterior acceleration during treadmill running and the anterior–posterior acceleration at slow speed during treadmill and overground running.  相似文献