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1.
Gas flow has fractional order dynamics; therefore, it is reasonable to assume that the pneumatic systems with a proportional valve to regulate gas flow have fractional order dynamics as well. There is a hypothesis that the fractional order control has better control performance for this inherent fractional order system, although the model used for fractional controller design is integer order. To test this hypothesis, a fractional order sliding mode controller is proposed to control the pneumatic position servo system, which is based on the exponential reaching law. In this method, the fractional order derivative is introduced into the sliding mode surface. The stability of the controller is proven using Lyapunov theorem. Since the pressure sensor is not required, the control system configuration is simple and inexpensive. The experimental results presented indicate the proposed method has better control performance than the fractional order proportional integral derivative (FPID) controller and some conventional integral order control methods. Points to be noticed here are that the fractional order sliding mode control is superior to the integral order sliding mode counterpart, and the FPID is superior to the corresponding integral order PID, both with optimal parameters. Among all the methods compared, the proposed method achieves the highest tracking accuracy. Moreover, the proposed controller has less chattering in the manipulated variable, the energy consumption of the controller is therefore substantially reduced.  相似文献   
2.
This paper investigates a stability problem for linear systems with time-varying delays. By constructing suitable augmented Lyapunov–Krasovskii functionals, improved stability criteria under various conditions of time-varying delays are derived within the framework of linear matrix inequalities (LMIs). Moreover, to reduce the computational burden caused by the non-convex term including h2(t), how to deal with it is applied by estimating it to the convex term including h(t). Finally, three illustrative examples are given to show the effectiveness of the proposed criteria.  相似文献   
3.
To achieve the frequency restoration (FR) and accurate reactive power sharing (RPS) in islanded microgrids (MGs), an improved P-f droop control is proposed. Firstly, the inverter impedance, whose value is set by the virtual impedance method, is used to minimize the impact of line resistance on powers coupling and RPS. Then, in order to restore the frequency of distributed generations (DGs) to the rated value, the reference is changed for compensating the frequency deviation (FD) caused by loads change. And the fast FR rate is achieved under a large constant k. Besides, in order to eliminate the inaccuracy of RPS caused by voltages difference (VD), the line voltage drop (LVD) is used to compensate the voltage droop characteristics. The use of voltage feedback ensures that the obtained voltage is desired after the LVD compensation. Finally, the simulation in RT-LAB indicates the effectiveness of proposed method in an islanded MG model.  相似文献   
4.
近代诗词作者辈出,目前学界对他们生卒年岁的研究成果卓然。然而笔者在拜读前贤诸著之余,仍发现不少词人的生卒年存在着各种各样的歧异与缺失。故不揣愚钝,谨据词人别集及相关史料,就陈祖善、廷奭、周茂榕等若干知名词人的生卒年岁作进一步考辨,以期于近代诗词研究提供些许助益。  相似文献   
5.
This paper investigates the passivity and synchronization problems for two classes of multiple weighted coupled neural networks (MWCNNs) with or without time delays. Firstly, by utilizing an impulsive control strategy and some inequality techniques, several passivity criteria for MWCNNs with diverse dimensions of output and input are established. Then, based on the Lyapunov functional, some sufficient conditions to ensure the synchronization of MWCNNs via impulsive control are derived. In addition, combined with the comparison principle and the impulsive delay differential inequality, the global exponential synchronization of MWCNNs with time-varying delays is considered under impulsive control. Finally, two numerical examples illustrate the effectiveness of the obtained results.  相似文献   
6.
摘 要 【目的】比较并分析SCI收录的综合性化学通讯类期刊,为不断提升中国科技期刊国际影响力做积极探索。【方法】 检索Web of Science查询5种化学综合性通讯类期刊的基本情况,分析2009-2013年期刊的影响因子、总被引频次、载文量、文献类型和稿源分布以及中国作者的论文对这5种科技期刊的贡献。【结果】 影响因子、总被引频次和载文量最高的是Chem Commun,其次是Org Lett, Chin Chem Lett影响因子和总被引频次提升最大。Chem Commun和Org Lett稿源主要集中在中国、美国、日本、英国、德国等,而Chem Lett和Chin Chem Lett则具有明显的地域性。从引用角度看,中国作者的论文质量普遍高于期刊的平均质量。【结论】要提升期刊的质量和影响力,除发表研究论文外,还可以发表高质量的综述类文章和述评;不仅要追求稿源国际化,还要发表国内高质量的文章,建设国际有影响力的期刊出版集团,建立集群化发展模式。  相似文献   
7.
在贵州高原上土生土长的苗族作家万胜昌、欧阳克俭、李文明、李再春等在田野调查的基础上以民族志的方式呈现苗族社会奇特的社会文化现象,用富于民族色彩的叙事来探寻根本性的个性文学表述.由于他们的民族志书写以深入的观察和切身的体验为基础,因而他们的作品自始至终流贯着强烈的民族尊严感、认同感和忧患意识.  相似文献   
8.
为了深入了解国内外在索引领域的研究进展,本文应用文献计量法和内容分析法,对2005-2009年间国内外研究索引的文献进行统计分析,包括期刊分布、作者分布、主题分布三个方面,总结当前国内外索引研究的热点,并预测未来研究中的发展趋势。结果表明,国外索引领域的核心期刊已基本形成,而国内索引领域的核心期刊群尚未稳定;国内外目前都尚未形成稳定的核心作者群;在研究热点方面,国内外情况有所差异,但发展趋势趋于一致。  相似文献   
9.
高校学报编辑与作者对话是推进稿件运转的关键环节。文章从编辑的角度探讨高校学报编辑与作者对话的有效性,强调编辑与作者对话前应熟知文稿内容,及时查阅资料,弥补知识缺漏;尽可能多地了解作者的背景信息,确定对话内容的重点、详略;与任何作者对话,语气皆宜谦和委婉;提出的书面意见具有不可变更性,务必准确、稳妥、清晰且理据充分。  相似文献   
10.
增强服务意识,构建稳定的作者队伍   总被引:1,自引:0,他引:1  
质量是学报的生命线,构建一支稳定的高层次的作者队伍,是学报可持续发展的基石。通过对学报现状的分析,提出了构建作者队伍的设想和措施,强调了学报编辑要增强服务意识,要尊重、关爱作者,为学报的可持续发展创造良好的条件。  相似文献   
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