Low mean level sustained and intermittent grip exertions: Influence of age on fatigue and recovery

The goal of this study was to quantify localised muscle fatigue resulting from low mean levels of exertion in younger (< 40 years) and older (>50 years) adults. Fatigue, elicited in the finger flexor muscles by intermittent (10% mean maximum voluntary contraction (MVC)) and sustained (8% MVC) handgrip exercises, was quantified by a muscle twitch force response before, immediately after and during 3 h following exercise. Despite greater mean loads, recovery time was shorter following intermittent than sustained contractions, which suggests that recovery from fatigue is more sensitive to rest within the work cycle than mean work. The more pronounced effects for younger than older individuals following the sustained exertion indicate that changes in muscle fibre type composition might predispose older individuals to be more resistant to fatigue resulting from sustained contractions of low level. Performing hand exertion tasks requiring low mean force levels contributes to similar long-lasting fatigue effects regardless of gender and age. Intermittent periods of complete rest reduce muscle fatigue. Since fatigue was not perceived during recovery from the tested sustained and intermittent contractions, subjective evaluations may not be a reliable indicator of localised muscle fatigue.     

Using Tabulated Information

Abstract

Different tabulation formats for currency conversion tables wore examined. It was found that most formats could be used equally well to make conversions bi-directionally, i.e. from A to B and from 13 to A. A fully redundant table, one that required no additional arithmetic operations, could be used more quickly than a schematic table, and in schematic tables it was more important to have each of the major units given directly rather than each of the minor units. A matrix, although fully redundant, was much more difficult to use than the corresponding table of lists. Many subjects clearly did not understand the principles of matrix format. Measures of incidental learning suggested that practice at using a table resulted in only slight knowledge of the content of the table, even though much of each table could be generated from a single rule     

最小生成树算法在旅行商问题中的应用

如何在n个顶点之间的1/2(n-1)!巡回路径中选择距离最短的,这是一个典型的组合优化问题,也是解决旅行商问题的根本。在最小生成树的基本思想上进行了改进,成功地解决了旅行商问题。     

高功率因数双开关升压整流器的单周期控制方法

研究了一种高功率因数的双开关升压整流器的单周期控制方法。在该整流器中。二极管整流电路和功率因数校正环节结合在一起。减少了导通损耗。具有效率高，结构简单等特点。但是由于升压电感在交流侧，电流和电压检测不是很方便。为此，引进单周期控制技术。它不需要检测交流输入电压。而且对输入电流的检测也相对简单。同时单周期控制电路具有简单可靠、响应快、成本低、易于实现等特点。文中较为详细地分析了单周期控制双开关升压整流器的工作原理和实现方式，最后在PSpice中进行了仿真验证。     

次件开发中面向对象的方法

在分析传统的软件工程不足的基础上，介绍了软件开发中面向对象的方法的主要内容。对应于软件的生存周期各个阶段具体分析了软件工程开发中面向对象的方法。     

统一软件开发过程的研究

简要分析了当前软件开发对软件工程方法的要求;详细介绍了统一软件开发过程（以下简称“统一过程”）的3个突出特点;结合实际信息系统的开发过程,深入讨论了统一过程的生命周期,并对支持统一过程的相关产品及应用进行了相应地描述;最后展望了统一过程的应用前景.     

矿用汽车发动机润滑系统保养周期的研究

分析了矿用汽车润滑系统保养周期制定的影响因素，提出了科学合理的制定矿用汽车润滑系统保养周期的方法。在此基础上，提出了科学运用矿用汽车、增加汽车润滑系统保养周期间隔、减少润滑油消耗的途径，以达到矿山企业降低运输成本，提高经济效益的目地。     

从电解铝工业生命周期评价看能源、环境对产业结构的制约

以货币量化为手段计算了电解铝工业生命周期内的主要污染排放造成的环境成本，并综合电解铝工业的生产成本、整个生命周期内能源耗费、环境成本衡量了电解铝厂的经济发展状况，进一步探讨了能源、环境对产业结构的制约。     

Fatigue life calculation by means of the cycle counting and spectral methods under multiaxial random loading

The paper contains a new algorithm for estimation of fatigue life in HCF regime under multiaxial random loading using spectral methods. Loading of Gaussian distribution and narrow‐ and broad‐band frequency spectra were assumed. Various characteristic states of multiaxial loading were considered. The equivalent stress history was determined with use of the failure criteria of multiaxial fatigue based on the critical plane. For determination of the critical plane position, the method of variance was applied. During simulation, the authors compared the results obtained by a spectral method in the frequency domain with those from the rain‐flow algorithm in the time domain. The paper also contains the results of fatigue tests for 18G2A structural steel subjected to bending and combined bending with torsion. The tests were performed in order to verify the proposed algorithms for determination of fatigue life. It has been shown that under multiaxial random loading results of fatigue life calculated according to the considered algorithms in frequency and time domains are well correlated with the results of experiments.     

江西有色金属工业发展循环经济的思考

根据江西有色金属工业发展的形势，着重分析了江西有色金属工业发展循环经济的必要性，并从体制、政策、法律、法规等方面提出了发展江西有色金属工业循环经济的思路，为引导江西有色金属工业循环经济的发展提供政策参考。