着地缓冲对我国男子短跑途中跑技术的影响

通过运用运动生物力学原理分析中外男子百米运动员途中跑着地缓冲技术特点的差异以及这些差异产生的原因和对途中跑整体技术的影响。得出结论:我国短跑传统技术原理和长期采用的技术专门练习是造成中外短跑运动员途中跑着地缓冲技术差异的原因;也是影响我国短跑途中跑整体技术水平提高的主要原因。     

一种防止堆缓冲区溢出的新方法

缓冲区溢出是当今计算机安全所面临的重大威胁.首先分析了堆缓冲区溢出的原理,然后提出了一种新的内存管理机制,这种机制可以根据缓冲区的大小,自我进行内存管理,从而有效地防止堆缓冲区溢出的发生.     

Shock and impact reduction in moderate and strenuous landing activities

Shock reduction has been well studied in moderate activities such as walking and running. However, there is a clear lack of research concerning shock wave transmission and reduction in more strenuous landing activities. In this study, we examined the impact of shock transmission and reduction in landing activities with varied mechanical demands. Ten active males were recruited for the study. They performed five successful step-off landing trials from each of five heights: 30, 45, 60, 75, and 90 cm. Right sagittal kinematics, ground reaction forces, and acceleration were recorded simultaneously. Impact frequencies were analysed using a discrete Fast Fourier Transform and power spectral density was computed. Increased range of motion for the ankle, knee, and hip joints was observed at higher landing heights. The peaks of the vertical ground reaction force, forehead and tibial accelerations, and eccentric muscle work by lower extremity joints were increased with increased landing heights. The peak head power spectral density was severely attenuated at higher frequencies but the peak tibia power spectral density did not demonstrate this trend. Shock reduction showed increased reduction at higher frequencies, but minimal changes across five landing heights. Unlike the responses observed for walking and running, the shock reduction did not show significant improvement with elevated mechanical demands.     

Vertical Ground Reaction Forces of Children during One- and Two-Leg Rope Jumping

Abstract

Sport offers opportunities for children to identify and resolve moral issues. Moral issues in sport have primarily been studied from the researcher's perspective, with the child's perspective relatively ignored. Thus, the purpose of this study was to explore the nature and content of the issues children experienced in sport. Interview participants consisted of 7 boys and 8 girls ranging in age from 10 to 12 years (M = 11.6 years, SD = 1.7) who had competitive youth sport experience. An inductive content analysis revealed that children identified issues surrounding three overall dimensions concerning fairness of adult's actions, negative game behaviors, and negative team behaviors. Specific examples of issues included unfair actions by coaches, disrespecting opponents, and selfish behavior in practice. The self-identified issues both confirmed and expanded upon the content found in hypothetical moral dilemmas in sport.     

人体重心与投掷标枪技术的关系

采用技术图片解析法、应用所学有关运动的基础理论知识、结合专业理论和实践,对掷标枪最后用力阶段的人体重心变化进行运动学分析,经过专项运动训练实践、观察分析并与国内外优秀标枪运动员相关运动学参数进行比较,促进标枪运动成绩的提高.     

试论跑的支撑时期着地缓冲与后蹬阶段的止、起点的划分

我国主要田径教材关于跑的周期阶段的划分存在着多种理论,其中对支撑时期着地缓冲与后蹬起、止点的划分也存在较大分歧.为解决该问题,运用信息技术为主的方法,对当今世界男子100 m记录保持者博尔特的有关技术参数进行分析,提出了着地缓冲与后蹬止、起点的新划分方法,指出划分应具体量化,以期为短跑技术分析的实际运用提供理论依据.     

应用于无线局域网802.11a高中频下变频器的设计(英文)

给出了一个应用于无线局域网WLAN802.11a的中低噪声、高增益的下变频器.该下变频器采用高中频的结构,输入的射频频率(RF)、本振(LO)频率和输出的中频频率(IF)分别为5.15 ～5.35,4.15 ～4.35和1GHz.为了提高混频器的线性度,电路采用了伪差分的吉尔伯特结构和源极电阻负反馈技术;为了获得低的噪声系数,混频器采用电流源注入技术和LC谐振电路作为负载.此外,采用了一种改进的源极跟随器输出缓冲电路,在不恶化其他性能的情况下混频器可以达到较高的增益.该芯片采用0.18μm RF CMOS工艺制作,包含所有焊盘在内的芯片尺寸为580μm×1 185μm.测试结果表明:在1.8V电源电压下,消耗电流为3.8mA,转换增益为10.1dB,输入1dB压缩点为-3.5dBm,输入三阶截点为5.3dBm,单边带(SSB)噪声系数(NF)为8.65dB.     

男子三级跳远运动员跨步跳踏跳技术的生物力学分析

运用SAFMS-T型六维测力平台测量与平面定点录像解析相结合的研究方法，从冲击阶段、积极缓冲阶段、反射蹬伸阶段、动力蹬伸阶段等，对男子三级跳远运动员跨步跳技术进行分析。结果显示：踏跳着地技术的优劣表现在以髋关节为轴的大腿积极剪绞速度和幅度；踏跳缓冲技术中，形成以膝、踝关节主动缓冲的积极缓冲阶段和以屈踝缓冲为主的反射蹬伸阶段；踏跳蹬伸技术中，反射蹬伸阶段获得垂直速度，动力蹬伸阶段获得水平速度。     

渡海登陆作战军人体能需求与针对性训练

针对渡海登陆作战的特点，结合部队的作战任务，分析未来渡海登陆作战对军人体能的基本需求；探索、运用正确的训练手段和训练方法，使体能训练最大程度地同未来渡海登陆实战相适应，以达到有针对性地指导部队的体能教学训练，提高部队战斗力。     

高、低帮篮球鞋对落地时踝关节稳定及肌肉功能影响的研究

目的:探讨高、低帮篮球鞋对落地时踝关节内翻的运动学、地面反作用力及下肢主要肌群活动的影响,尝试理解高、低帮篮球鞋与踝关节落地稳定之间的关系;方法:13名受试者分别穿着高、低帮篮球鞋,手抓杠悬于空中,从40 cm高度分别垂直下落至内翻15°、内翻30°、内翻25°伴随跖屈10°(25°+10°)、内翻25°伴随跖屈20°(25°+20°)的倾斜面上,分析其踝关节运动学、地面反作用力及小腿主要外翻和背屈肌群(胫骨前肌、腓骨长肌和腓骨短肌)的肌电活动;结果:高、低帮鞋对内翻角度的变化、最大内翻角速度和地面垂直及水平冲击力没有显著影响;在15°倾斜面时,穿着高帮鞋出现预激活时间比低帮鞋晚(P<0.05),同时,在15°和25°+20°下腓骨长肌和腓骨短肌落地前50 ms的平均振幅更小(P<0.05);结论:选取的高帮鞋对踝关节的运动学和冲击力的改变不显著,但却在一定程度上影响了周围肌肉的预激活,对限制踝关节活动起到了积极的作用.