关于一类二阶发展方程的反周期解

本研究了在Hilbert空间中与极大单调算子族相联系的抽象的二阶发展方程的反周期问题．给出了关于算子族{A(t)：0≤t≤T}的新的假设，并在此假设下证明了反周期解的存在性与惟一性，推广了已有的结果．最后给出一个例子说明抽象的反周期问题在非线性偏微分方程中的简单应用．     

The exercise intensity at maximal oxygen uptake (i⩒O2max): Methodological issues and repeatability

The minimum exercise intensity that elicits ?O_2max (i?O_2max) is an important variable associated with endurance exercise performance. i?O_2max is usually determined during a maximal incremental exercise test; however, the magnitude and duration of the increments used influence the i?O_2max value produced by a given test. The aims of this study were twofold. The first was to investigate whether the i?O_2max value produced by a single cycle ergometer test (i?O_2max(S)) was repeatable. The second was to determine if i?O_2max(S) represents the minimum intensity at which ?O_2max is elicited when compared to a refined i?O_2max value (i?O_2max(R)) derived from repeated tests. Seventeen male cyclists (age 33.9?±?7.7 years, body mass 80.9?±?10.2?kg, height 1.82?±?0.05?m; VO_2max 4.27?±?0.62 L?min^?1) performed four maximal incremental tests for the determination of i?O_2max(S) and i?O_2max(R) (3 min stages; 20?W increments). Trials 1 and 2 were identical and used for assessing the repeatability of i?O_2max(S), trials 3 and 4 began at different intensities and were used to determine i?O_2max(R). i?O_2max(S) showed good test–retest repeatability for i?O_2max (CV?=?4.1%; ICC?=?0.93), VO_2max (CV?=?6.3%; ICC?=?0.88) and test duration (CV?=?6.7%; ICC?=?0.89). There was no significant difference between i?O_2max(S) and i?O_2max(R) (303?±?40?W vs. 301?±?42?W) (P?2max determined directly during a maximal incremental test is repeatable and provides a very good estimate of the minimum exercise intensity that elicits ?O_2max.     

二元函数的导数在经济分析中的应用浅析

运用二元函数的导数及导数的意义，对经济活动分析，即边际、需求交叉价格偏弹性、经济最优等问题进行初探。     

(?)(X)中含零元的极大逆子半群的结构特征

本文运用全变换半群(?)(X)的格林等价理论和(?)(X)中逆子半群的性质,找出了(?)(X)中含各零的极大逆子半群在结构上的某些重要特征,为全面研究(?)(X)的极大逆子半群奠定了理论基础.     

Letter to the editor

Santos-Concejero and Tucker argued in their letter to the editor that in our study the running economy in achieving superior performance was overlooked due to some methodological aspects. Having given the remarks of Santos-Concejero and Tucker appropriate consideration, in this letter to the editor, we argue that our paper does not downplay the influence of running economy on the determinants of the East African running phenomenon, but rather adds novel insights into the interaction between running economy, maximal oxygen uptake and performance.     

Mechanical energy generation and transfer in the racket arm during table tennis topspin backhands

The ability to generate a high racket speed and a large amount of racket kinetic energy on impact is important for table tennis players. The purpose of this study was to understand how mechanical energy is generated and transferred in the racket arm during table tennis backhands. Ten male advanced right-handed table tennis players hit topspin backhands against pre-impact topspin and backspin balls. The joint kinetics at the shoulder, elbow and wrist of the racket arm was determined using inverse dynamics. A majority of the mechanical energy of the racket arm acquired during forward swing (65 and 77% against topspin and backspin, respectively) was due to energy transfer from the trunk. Energy transfer by the shoulder joint force in the vertical direction was the largest contributor to the mechanical energy of the racket arm against both spins and was greater against backspin than against topspin (34 and 28%, respectively). The shoulder joint force directed to the right, which peaked just before impact, transferred additional energy to the racket. Our results suggest that the upward thrust of the shoulder and the late timing of the axial rotation of the upper trunk are important for an effective topspin backhand.     

智能化电机测功机实验装置的研制

对他励式电机测功机进行研究，研制出电机测功机实验装置，并设计出单片机数据采集系统对电机转矩进行智能化测量，为学生电机实验提供了良好的条件。     

Stein极大算子的加权模不等式

利用分解球面测度的方法，对Stein球面极大算子M进行研究，得到了该算子的一系列加权模不等式。     

D_l(F)在B_l(F)中的扩群及其泛正规性

域 F上 Dl(l≥ 4)型 Chevalley群 Dl(F)可自然地嵌入到 Bl(F)中去。当 Char F≠ 2 ,且 F=F2 时 ,本文定出了 Dl(F)在 (Bl(F)中的所有扩群 ,由此获得了 Bl(F)的一类极大子群。进而证明了 Dl(F)是 Bl(F)的泛正规子群     

极大平坦模与极大平坦维数

给出极大平坦模的定义，研究极大平坦模的性质，得到极大平坦模与平坦模、极大内射模之间的关系，并利用极大平坦维数刻画环。