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本文介绍了一款窄带矩形腔双模滤波器的设计方法,相对带宽只有0.272%,并且利用电容加载技术,使腔体体积缩小。采用螺钉耦合实现两个模式之间的扰动,耦合缝实现腔体间的耦合。首先利用自编程序得到满足指标要求的耦合系数矩阵,然后运用HFSS仿真软件得到耦合螺钉的长度与耦合缝的尺寸,最后通过调试得到窄带双模滤波器。 相似文献
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留法勤工俭学运动是我国近代史上的一件大事,也是中国共产党历史上的重要一页,对中国革命的胜利及教育事业的长远发展产生了不可估量的巨大作用。同样,留法勤工俭学运动对中西文化的交流与发展、中国革命的历史进程以及战后欧洲经济重建也产生了深远的影响。 相似文献
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利用潍坊地区某医学院大学生2003-2012的体质指数作为样本,构建灰色预测GM(1,1)模型,对该地区大学生2013的体质指数进行预测、分析研究,掌握该地区青少年的身体健康状况,有针对性地提出合理化建议。 相似文献
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ABSTRACTReading success has a significant impact on social, academic and vocational engagement. While there have been many advances in Brazilian educational policy, and a reduction in rates of absolute illiteracy, low levels of literacy continue to be a significant area of concern. We aimed to scope the literature to identify the types of intervention researched in Brazil for people with developmental dyslexia; map the findings to international theories of dyslexia and draw on these findings to inform future clinical practice and research. Four databases were searched and a total of 13 studies met eligibility criteria. Four key themes were identified: (1) phonological-based intervention, reading and writing; (2) intervention using computerised technology; (3) auditory processing training and (4) training of visuomotor skills. Whilst most interventions were in keeping with current international theory, a number of methodological issues were identified which, if addressed, would strengthen future research and inform clinical practice in Brazil. 相似文献
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Leitao Gao Guangshe Zhao Guoqi Li Lei Deng Fei Zeng 《Journal of The Franklin Institute》2018,355(16):8141-8157
Determining an input matrix, i.e., locating predefined number of nodes (named “key nodes”) connected to external control sources that provide control signals, so as to minimize the cost of controlling a preselected subset of nodes (named “target nodes”) in directed networks is an outstanding issue. This problem arises especially in large natural and technological networks. To address this issue, we focus on directed networks with linear dynamics and propose an iterative method, termed as “L0-norm constraint based projected gradient method” (LPGM) in which the input matrix B is involved as a matrix variable. By introducing a chain rule for matrix differentiation, the gradient of the cost function with respect to B can be derived. This allows us to search B by applying probabilistic projection operator between two spaces, i.e., a real valued matrix space RN?×?M and a L0 norm matrix space by restricting the L0 norm of B as a fixed value of M. Then, the nodes that correspond to the M nonzero elements of the obtained input matrix (denoted as ) are selected as M key nodes, and each external control source is connected to a single key node. Simulation examples in real-life networks are presented to verify the potential of the proposed method. An interesting phenomenon we uncovered is that generally the control cost of scale free (SF) networks is higher than Erdos-Renyi (ER) networks using the same number of external control sources to control the same size of target nodes of networks with the same network size and mean degree. This work will deepen the understanding of optimal target control problems and provide new insights to locate key nodes for achieving minimum-cost control of target nodes in directed networks. 相似文献
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本文在分析DC／DC开关变换器滑模控制方法的基础上，针对以往开关变换器滑模控制器抖振现象严重的不足，通过引入趋近律的方法，以Buck变换器为例，给出了一种适合PWM控制方式的时不变滑模控制器的设计方法，并易于推广到其他类型变换器上。仿真结果表明，该控制方案可以减少系统超调，动、静态特性较好，并能有效削弱滑模运动的抖振现象。 相似文献
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