分析比较中外短跑运动员途中跑技术的差异

通过文献资料、分析对比等方法,对短跑途中跑技术进行分析,发现我国运动员在途中跑“后蹬屈膝式”技术及放松、步幅、节奏等技术方面与国外优秀选手存在一定差距。     

Optimized versus corrected peak power during friction-braked cycle ergometry in males and females

Abstract

The aim of this study was to compare optimization and correction procedures for the determination of peak power output during friction-loaded cycle ergometry. Ten male and 10 female sports students each performed five 10-s sprints from a stationary start on a Monark 864 basket-loaded ergometer. Resistive loads of 5.0, 6.5, 8.0, 9.5, and 11.0% body weight were administered in a counterbalanced order, with a recovery period of 10 min between sprints. Peak power was greater and occurred earlier, with less work having been done before the attainment of peak power, when the data were corrected to account for the inertial and frictional characteristics of the ergometer. Corrected peak power was independent of resistive load (P > 0.05), whereas uncorrected peak power varied as a quadratic function of load (P < 0.001). For males and females, optimized peak power (971 ± 122 and 668 ± 37 W) was lower (P < 0.01) than either the highest (1074 ± 111 and 754 ± 56 W respectively) or the mean (1007 ± 125 and 701 ± 45 W respectively) of the five values for corrected peak power. Optimized and mean corrected peak power were highly correlated both in males (r = 0.97, P < 0.001) and females (r = 0.96, P < 0.001). The difference between optimized and mean corrected peak power was 37 ± 30 W in males and 33 ± 14 W in females, of which approximately 15 W was due to the correction for frictional losses. We conclude that corrected peak power is independent of resistive load in males and females.     

基于全寿命周期的软件项目投标风险规避研究

文章研究了将项目管理风险集成到投标风险,运用全寿命周期理论实施软件项目投标风险规避的问题。首先,介绍了软件项目全寿命周期流程和寿命周期各阶段的主要风险要素;其次,分析了软件项目投标风险对应的风险规避措施;最后,提出了软件项目投标风险规避的基本决策过程,并举例。     

无复位开关的单周控制新方法研究

采用积分复位的单周控制方法在变换器控制领域得到了广泛的研究。但是，由于它采用了积分复位开关，使其变成了一个十分复杂的非线性控制系统，建模和系统设计都非常困难。本文在分析单周控制方法基本原理的基础上，提出了无复位开关的单周控制新方法，以Buck变换器为例，建立了控制系统的小信号模型，通过理论分析和仿真结果证明了该方法的正确性。     

论企业成长与衰退的生命周期——以日本嘉娜宝公司为例

为了对我国的企业经营及决策能提供有益的帮助,剖析了日本知名百年大企业嘉娜宝公司的生长期、成熟期、衰退期和破产期等四个周期的发展和兴衰历程,从中找出百年企业经营成功的经验与失败的根源。并从经营战略、经营者的责任以及财务政策等方面进行失败的原因分析,最后得出对中国企业的启示。     

谐振子量子制冷循环性能的优化分析

基于量子主方程和半群逼近研究以谐振子系统为工质，由两个等温和两个等谐振子数过程组成的不可逆谐振子量子制冷循环的一般性能特性，导出了制冷循环的制冷系数、制冷率、输入功和熵产率等重要参数的一般表达式．并详细讨论了高温极限下谐振子量子制冷循环的优化性能，导出了最大制冷率和相应的制冷系数．所得结论可为非常规工质低温制冷循环的优化设计提供理论基础．     

国家重点学科生成期特征分析

本文基于对158个国家重点学科的问卷调查和对60个国家重点学科带头人及其团队成员的访谈,从学科研究方向、学位点、重点学科层级研究国家重点学科的生成周期;从学者数量和职称结构分析国家重点学科的组织规模;从学科发展的主导力量总结国家重点学科的生成路径;从学科生成所面临的问题归纳学科带头人和学科组织的主要工作领域.     

河南农民收入增长的波动周期

河南农民人均收入时间序列,服从二阶单整过程,期间存在结构性断点,适合建立H—P滤波模型。自改革开放以来可划分为三个增长周期,其在不同的历史阶段具有明显不同的波动特征。     

APL-based flexibility analysis of manufacturing grid

With the characteristics of diversity, randomness, concurrency and decomposability, tasks in manufacturing field are very complicated, and so manufacturing grid(MG)should have considerable flexibility to deal with this problem. With the definition of node and arc, MG structure is converted into a small-world network. Given construction cost constraint, the problem of shortest task waiting time is transformed into the constrained optimization problem, and a corresponding flexibility analysis model based on average path length(APL)is proposed, and the premise of arc-length and node-distance are defined. The results of application example show that the analysis model is effective.     

酒店服务业LCA清单分析及实证研究

运用生命周期评价的思想,对酒店服务业进行生命周期清单分析,旨在识别和评价酒店服务业的主要环境负载,为酒店服务业环境问题的解决和推进生命周期评价在酒店领域的应用提供有益参考.