滑模控制在抑制大望远镜驱动系统非线性干扰中的应用研究

针对当代大型天文望远镜驱动伺服系统中存在的非线性干扰,分析了非线性干扰的类型。在此基础上建立了大型望远镜驱动控制系统的数学模型,提出了高阶滑模控制方案,将系统中存在的不连续性拓展到状态控制的最高阶,抑制系统的高频振动现象,克服了普通滑模控制的缺点数值仿真证明了该方案的可行性和有效性。     

A new controller for the seni-active suspension system with magnetor heological dampers

A new sliding mode controller for semi-active suspension system with magnetorheological (MR) damper is presented in this paper. In the proposed sliding mode controller, a semi-active suspension based on the skyhook damper system is chosen as the reference model to be followed, and the control law is so determined that the asymptotically stable error dynamics occurs between the controlled state and the reference model state. Numerical simulations are carried out to study the performance of the new sliding mode controller. The results show that the proposed controller yields almost perfect tracking to the reference model and has a high robustness against model parameter uncertainties and disturbances.     

基于Delphi开发计算机考试模拟系统

在计算机考试模拟系统开发中,采用Delph i作为开发工具,使用数据库技术和ADO、OLE自动化技术,并应用数据压缩技术和顶层窗体设计技术,提高了系统的仿真性和针对性。     

DISCUSSION ON KARMARKAR''''S METHOD FOR SOLVING UNSTANDARD MODEL.

In this paper,a discussion on the new polynomial-time algorithm for linearprogramming as proposed by Karmarkar.N.is presented.The problem is solved when aninitial feasible solution is unknown.For the case where the optimum value of the objectivefunction is unknown,the reasonableness and feasibility of the sliding objective functionmethod are proved.And a method of modifying the parameters is put forward.     

科学合作与论文影响力之间的相关性研究

[目的/意义]随着科学研究综合性逐步加强，合作日渐成为主流的科研方式。通过对科学合作和论文影响力之间相关性进行研究，以探究科学合作是否对论文影响力存在着提升作用。[方法/过程]本文基于JCR的期刊数据，在Web of Science核心合集中选取了复合材料、图书情报和科学史与科学哲学领域2009-2012年的发文和被引数据，借助多元统计软件SPSS21.0和社会网络分析软件等从作者、机构、国家等3个层次研究科学合作和论文影响力之间的相关关系，进而以高被引论文为研究对象探寻最佳的合作规模。[结果/结论]在不同的学科中，作者合作、机构合作和国家合作均与论文影响力呈显著的正相关关系，但科学合作的边际效益不同。科学合作的规模不可能无限扩大，最佳的作者合作规模为2~4人，最佳的机构合作规模为1~3个，最佳的国家合作数目为1~2个。     

一种基于TCP网络流量的多协议快速仿真方法

提出了一种新的网络仿真方法———基于TCP网络流量的多协议快速仿真方法。可以根据不同网络的差异模拟网络环境,来测试该网络的拓扑及频宽,以及测试网络协议的性能。提出了一些对TCP流量控制的算法,由实验证明可有效避免网络拥塞,并在仿真中加入新的功能,比较各种不同起始窗口大小对TCP效能的影响,发现在数据包丢失较少时,增大起始窗口大小对效能有正面的影响。     

A comparison among citation-based journal indicators and their relative changes with time

This study compares the two-year impact factor (JIF2), JIF2 without journal self-citation (JIF2_noJSC), five-year impact factor (JIF5), eigenfactor score and article influence score (AIS) and investigates their relative changes with time. JIF2 increased faster than JIF5 overall. The relative change between JIF2 and JIF_noJSC shows that the control of JCR over journal self-citation is effective to some extent. JIF5 is more discriminative than JIF2. The correlation between JIF5 and AIS is stronger than that between JIF5 and the eigenfactor score. The relative change in journal rank according to different indicators varies with the ratio of the indicators and can be up to 60 % of the number of journals in a subject category. There is subject category discrepancy in the average AIS and its change over time. Through the screening of journals according to variations in the ratio of JIF2 to JIF5 for journals in individual subject categories, we found that journals in the same subject categories can have considerably different citation patterns. To provide a fair comparison of journals in individual subject categories, we argue that it is better to replace JIF2 with the ready-made JIF5 when ranking journals.     

Improving the reliability of short-term citation impact indicators by taking into account the correlation between short- and long-term citation impact

The normalized citation indicator may not be sufficiently reliable when a short citation time window is used, because the citation counts for recently published papers are not as reliable as those for papers published many years ago. In a limited time period, recent publications usually have insufficient time to accumulate citations and the citation counts of these publications are not sufficiently reliable to be used in the citation impact indicators. However, normalization methods themselves cannot solve this problem. To solve this problem, we introduce a weighting factor to the commonly used normalization indicator Category Normalized Citation Impact (CNCI) at the paper level. The weighting factor, which is calculated as the correlation coefficient between citation counts of papers in the given short citation window and those in the fixed long citation window, reflects the degree of reliability of the CNCI value of one paper. To verify the effect of the proposed weighted CNCI indicator, we compared the CNCI score and CNCI ranking of 500 universities before and after introducing the weighting factor. The results showed that although there was a strong positive correlation before and after the introduction of the weighting factor, some universities’ performance and rankings changed dramatically.     

一类永磁同步电动机的TSM控制器设计

基于永磁同步电动机精确的数学模型,针对永磁同步电动机绕组相电流和转速强耦合特性,依据中继切换控制机制和有限时间收敛的终端滑动模态控制机制,考虑了永磁同步电动机的有限时间跟踪问题。给出了其终端滑模控制器的设计方案。在所设计的控制作用下,闭环系统将在有限时间内达到平衡状态。并且保证了闭环系统所有信号的有界性和平衡点的全局稳定性,以及系统在有限时间内精确地跟踪给定的参考信号。最后对一具体的永磁同步电动机模型进行了数值仿真,仿真结果表明在所设计的终端滑模控制器作用下,系统的跟踪误差在有限时间内达到零,验证了所提算法的正确有效性。     

基于视窗分析模型的我国高校科研效率评价

本文分别取窗宽为1-5,应用视窗分析模型对我国各省市高校在2003-2007年的科研效率进行动态分析。通过比较不同窗宽的分析结果,发现随着窗宽的增加,我国各省市高校的TE和PE呈递减变化,SE呈无规律变化;科研效率在不同年份对窗宽的敏感程度不同;选择不同的窗宽会使得研究者对科研效率的长期变化趋势得出大相径庭的结论。对于"如何确定理想的窗宽",从理论上提出新的分析方法,研究确定理想的窗宽,建立适合于我国高校科研效率动态分析的更合理的视窗分析模型。与传统DEA模型的分析结果进行对比,发现两者之间存在很大的偏差。这进一步说明了建立理想窗宽的视窗分析模型,对我国高校科研效率进行动态分析是很有必要的,此视窗模型的分析结果更符合科研工作的实际情况。