车轴端面孔专用双头数控镗床的研制

在探讨国内外车轴端面孔加工方法优缺点的基础上,结合机床柔性化设计理念,提出了车轴端面孔加工专用数控镗床的设计思路.文中介绍了适用不同规格车轴端面孔的镗削加工工艺,提出了卧式双头配置的专用镗床总体结构方案,并给出机床的工作方式和主要技术参数,分析了专用夹具工作方式,阐述了三菱E60L数控系统配置及调试,设计出机床关键部件——数控滑台和滚珠丝杆副.     

基于改进节约法的物流配送路径优化研究

物流配送中路径的选择是否合理影响着公司配送的速度、客户满意度、成本以及效益.在传统节约法的基础上,提出了考虑时间窗的配送路径的选择,这样既验证了节约法的可行性,又得出了车辆的可行发车时间范围,最后结合具体事例,对该方法进行了实际验证.     

斜面下滑滑块机械能守恒问题新解

重新解答了斜面上自由下滑滑块的机械能守恒问题,得出了在地面上和相对于地面做匀速运动的小车上观察,自由下滑滑块的机械能都守恒的新结论.     

The problem of citation impact assessments for recent publication years in institutional evaluations

Bibliometrics has become an indispensable tool in the evaluation of institutions (in the natural and life sciences). An evaluation report without bibliometric data has become a rarity. However, evaluations are often required to measure the citation impact of publications in very recent years in particular. As a citation analysis is only meaningful for publications for which a citation window of at least three years is guaranteed, very recent years cannot (should not) be included in the analysis. This study presents various options for dealing with this problem in statistical analysis. The publications from two universities from 2000 to 2011 are used as a sample dataset (n = 2652, univ 1 = 1484 and univ 2 = 1168). One option is to show the citation impact data (percentiles) in a graphic and to use a line for percentiles regressed on ‘distant’ publication years (with confidence interval) showing the trend for the ‘very recent’ publication years. Another way of dealing with the problem is to work with the concept of samples and populations. The third option (very related to the second) is the application of the counterfactual concept of causality.     

An intelligent self-repairing control for nonlinear MIMO systems via adaptive sliding mode control technology

In this paper, an intelligent self-repairing control scheme is proposed for a class of nonlinear MIMO system. A direct self-repairing controller of a nonlinear SISO system is firstly designed, and then the control scheme is promoted to a nonlinear MIMO system. The error signals are replaced by the state variables to deal with the high derivate problems of the desired signals and a nonlinear regulating function is brought in to improve the performances of the sliding mode. The self-repairing controller is made up of four parts: the nonlinear regulator, the equal controller, the compensator I and the compensator II. The control method is applied to a helicopter flight control system with loss-in-effectiveness faults. Some simulation results illustrate the effectiveness and feasibility of the proposed control scheme in the paper.     

基于直线型滑移索单元的输电线路结构张力分析

为了研究高压架空输电线索结构与塔架等其他杆件连接处的滑移特性,定义了一组滑移索单元,由一个通过滑动节点连接的三节点活动滑移索单元和多个两节点非活动滑移索单元组成．基于更新拉格朗日格式推导了三节点直线型滑索单元几何非线性刚度矩阵,并通过两跨和三跨等高连续索结构的有限元数值算例验证了空间直线型滑移索单元的有效性．研究结果表明,推导的直线型滑移索单元张力与已有计算结果相比,误差在1％以内．考虑滑移的索结构初始平衡状态内力与不考虑滑移的情况比较相差较大,因而在实际工程中应该考虑索的滑移．     

8mm大功率输出窗的模拟分析

输出窗是高功率回旋管的关键部件之一。它的好坏直接影响回旋管的性能,甚至整管研制的成败。如果窗片的反射升高,在高功率情况下返回到高频系统的功率将显著上升,引起在高频系统中自激振荡,从而降低回旋管的高频输出功率和模式纯度,乃至于使回旋管不能正常稳定工作。由于窗片介质损耗因子的存在,当微波通过输出窗时会在窗片中产生高频介质损...     

中国电子信息行业上市公司绩效评价研究——基于面板数据的DEA分析

电子信息产业在促进经济增长、推动节能减排等方面发挥着重要作用,已成为引领国家发展的战略性主导产业。电子信息行业上市公司是带动电子信息产业发展的中坚力量,客观评价其经营绩效,有助于提升公司竞争力。选择国内19家电子信息行业上市公司,运用2005-2010年面板数据和BBC模型及视窗分析方法对其进行经营绩效评价。结果显示,目前我国该行业经营绩效稳定,但内生增长能力低下,在未来发展中实现结构升级和技术创新势在必行。     

通用的多模式SAR处理算法

标准条带成像处理算法不适用于新的合成孔径雷达成像模式.基于方位频率去斜原理,对多模式回波进行处理,使其具有一致的时频历程,从而实现通用的成像处理过程.对多模式SAR仿真回波数据的处理结果表明,采用这种算法能够实现各种模式的精确成像.     

基于时间窗和关键链的多项目资源分配的研究

随着企业内部和外部环境的不断变化,大多数企业都处于多项目环境。传统基于关键链技术的多项目管理方法,在一定程度上解决了资源分配的问题,但仍然存在一定的缺陷。在分析和总结国内外多项目环境下资源分配方法的基础上,研究基于时间窗的多项目资源分配问题,提出增加时间窗参数以及惩罚因子建立的多项目管理资源分配模型,并分析模型求解问题,最后结合实际案例进行分析得出各个项目的完成时间分布图。