惠斯通电桥测量杨氏模量的实验探究

通过惠斯通电桥测量杨氏模量的引入和误差分析,把测量所得的结果与传统的静态拉伸法进行比较,得出用惠斯通电桥法测量杨氏模量的精确度更高,更接近理论值.     

大型拉伸缸试压工装的开发

大型拉伸缸是拉伸机的关键装置,为了检验拉伸缸装配后的密封性能,需要进行压力试验。通过对试压工装的受力状况进行分析计算、方案对比,结合拉伸缸的结构特征,开发设计了一种满足试验压力为36MPa的安全、可靠、经济的大型拉伸缸试压工装。     

Investigation of low-cycle fatigue behavior of austenitic stainless steel for cold-stretched pressure vessels

Cold-stretched pressure vessels from austenitic stainless steels(ASS) are widely used for storage and transportation of liquefied gases,and have such advantages as thin wall and light weight.Fatigue is an important concern in these pressure vessels,which are subjected to alternative loads.Even though several codes and standards have guidelines on these pressure vessels,there are no relevant design methods on fatigue failure.To understand the fatigue properties of ASS 1.4301(equivalents include UNS S30400 and AISI 304) in solution-annealed(SA) and cold-stretched conditions(9% strain level) and the response of fatigue properties to cold stretching(CS),low-cycle fatigue(LCF) tests were performed at room temperature,with total strain amplitudes ranging from -.4% to -.8%.Martensite transformations were measured during the tests.Comparisons on cyclic stress response,cyclic stress-strain behavior,and fatigue life were carried out between SA and CS materials.Results show that CS reduces the initial hardening stage,but prolongs the softening period in the cyclic stress response.Martensite transformation helps form a stable regime and subsequent secondary hardening.The stresses of monotonic and cyclic stress-strain curves are improved by CS,which leads to a lower plastic strain and a much higher elastic strain.The fatigue resistance of the CS material is better than that of the SA material,which is approximately 1?03 to 2?04 cycles.The S-N curve of the ASME standard for ASS is compared with the fatigue data and is justified to be suitable for the fatigue design of cold-stretched pressure vessels.However,considering the CS material has a better fatigue resistance,the S-N curve will be more conservative.The present study would be helpful in making full use of the advantages of CS to develop a new S-N curve for fatigue design of cold-stretched pressure vessels.     

The sports performance application of vibration exercise for warm-up,flexibility and sprint speed

Abstract

Since the turn of the 21st century, there has been a resurgence of vibration technology to enhance sport science especially for power and force development. However, vibration exercise has been trialled in other areas that are central to athlete performance such as warm-up, flexibility and sprint speed. Therefore, the aim of this review was to attempt to gain a better understanding of how acute and short-term vibration exercise may impact on warm-up, flexibility and sprint speed. The importance of warming up for sporting performance has been well documented and vibration exercise has the capability to be included or used as a standalone warm-up modality to increase intramuscular temperature at a faster rate compared to other conventional warm-up modalities. However, vibration exercise does not provide any additional neurogenic benefits compared to conventional dynamic and passive warm-up interventions. Vibration exercise appears to be a safe modality that does not produce any adverse affects causing injury or harm and could be used during interval and substitution breaks, as it would incur a low metabolic cost and be time-efficient compared to conventional warm-up modalities. Acute or short-term vibration exercise can enhance flexibility and range of motion without having a detrimental effect on muscle power, however it is less clear which mechanisms may be responsible for this enhancement. It appears that vibration exercise is not capable of improving sprint speed performance; this could be due to the complex and dynamic nature of sprinting where the purported increase in muscle power from vibration exercise is probably lost on repeated actions of high force generation. Vibration exercise is a safe modality that produces no adverse side effects for injury or harm. It has the time-efficient capability of providing coaches, trainers, and exercise specialists with an alternative modality that can be implemented for warm-up and flexibility either in isolation or in conjunction with other conventional training methods.     

运动后静力牵张对大鼠骨骼肌的生物力学影响

对大鼠进行连续跑台训练,并在每次运动后进行静力牵张练习,目的是探讨运动后静力牵张对骨骼肌的长期影响,为科学训练和科学地指导全民健身活动提供理论依据.成功制作了大鼠运动后静力牵张模型.通过跑台运动使大鼠骨骼肌抗拉伸能力略有增强,但变形能力有降低的趋势,使柔韧性降低,增大了运动损伤的发生机率.运动后静力牵张使骨骼肌变形能力增加,提高了机体的柔韧性,可有效减小运动损伤的发生率.     

对跳远起跳中髋关节角度变化及其作用的研究

用高速摄影机和影片解析仪对六名二级以上跳远运动员进行测试、分析和研究了髋关节在跳远起跳中角度的变化及其作用。结果表明：在踏板、缓冲、蹬伸三个不同阶段髋关节角度的变化对跳远起跳都有很大的影响。     

排球运动员上步纵跳的运动学分析

采用运动录象和解析法，对沈阳体育学院男排和沈阳工业大学男排上步跳的起跳动作进行研究分析，结果表明运动员膝关节的缓冲能力、踝关节的蹬伸能力及髋、膝、踝关节合理的用力顺序与上步纵跳成绩密切相关．     

历史与文化绵延向度中的教育审察

过往《中国教育史》著作的叙述具有形式上的多人共撰性、内容上的教育专属性、维度上西方史学观念主导性三个特点。高校专业设置和课程教学的改革、时代的迅猛发展和高校学生身心特点的变化、教育史学科自身的建设和发展完善等,都需要对《中国教育史》的叙述做出部分变更。《中国教育史》的编撰应当采取如下三种言说方式来进行,即:明线应强调历时维度的政治性、暗线应强调共时维度的文化性、主线应强调内容维度的两分性。依中国文化历史演进的基本理路来阐述先秦至新中国成立后的教育历史演进通貌。     

蛙泳伸臂阶段上体下沉过深现象分析研究

上体下沉过深,口鼻难于出水,吸气困难,游速慢,是蛙泳学习阶段遇到的普遍问题。对蛙泳伸臂阶段上体下沉过深现象进行分析,认为下沉时上体升力不足是上体下沉的力学根本原因;吸气时上体出水偏高,外划手掌划水过肩,伸臂阻力大,换气时头手配合节奏不当,伸臂偏迟,水性未达学习进程要求,划臂升力不足等是导致蛙泳上体下沉过深动的运动技术学原因。     

影响棒球投手投球速度的关键因素研究

综合运用摄像法、运动学测试法、动力学测试法、比较分析法和运动解剖学分析法,对影响棒球投手投球速度的关键因素进行研究.结果表明:投手伸踏脚落地与球出手最快时的地面反弹力最大,支撑脚的冲量最大;投手的肩关节、肘关节、腕关节、髋关节和膝关节在投手投球伸踏脚落地球出手最快阶段角加速度最大;影响投手投球速度的关键因素是投手伸踏脚的地面反弹力、支撑脚蹬伸冲量,以及各关节的角加速度;具体可通过增加投手肩肘外展外旋柔韧度、背弓幅度、主要关节肌群力量、肌力伸长度和收缩速度等训练来提高投球速度.