37 research outputs found

    The Algorithm for Langevin Equation and Phonon Transport in Low Dimensional Systems

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    本文第一章介绍了用双色根树图数值求解随机微分方程的方法,并将该方法应用到Langevin方程的情形下,提出了精度为o(7,4.5)的Langevin方程数值算法,从而提高了数值积分求解Langevin方程的精度。为了验证我们这套算法的可行性和普适性,我们给出了四个实例。第一、二个例子使用我们的算法计算了双势阱中的能量驰豫和倾斜Smoluchowski-Feynman棘轮中的粒子流和外力的关系,第三、四个例子我们数值积分了含时Langevin方程和多Langevin方程。我们将我们的算法与Euler算法、Heun算法分别进行了比较,发现在保证计算精度的前提下,这两套算法的最大积分步幅分别为0.0...Chapter 1 of this thesis introduces the numerical algorithm for stochastic differential equation by Bicolour Rooted Tree method, and then applies this method to Langevin equation. We propose an algorithm for Langevin equation and improve the accuracy to order o(7,4.5). To demonstrate the validity and universality of our algorithm, we give four examples. In the first and second examples, we c...学位:理学硕士院系专业:物理与机电工程学院物理学系_理论物理学号:1982007115232

    像素矩阵法获取整体式立铣刀容屑槽端截形的研究

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    以螺旋运动包络法和数学形态学二值图像的处理算法为基础,本文提出了一种方便快捷准确求取整体铣刀容屑槽端截形的像素矩阵法。该方法首先将砂轮回转面离散成点云后在刀具坐标系下进行包络运动,截取砂轮回转面离散点包络运动在刀具端面上留下轨迹的点云数据,然后转化成像素点,利用数学形态学对该二值像素点图像进行膨胀和腐蚀算法提取截形边界,最后对所提取边界进行平滑处理和插值,得到高精度的容屑槽端截形。该方法无需解析法求解非线性方程获取接触线的过程,避免了解析法的缺点(计算复杂,有异常解),且提取边界的廓形能满足计算精度要求且直观,是理论上获取刀具容屑槽端截形,分析刀具相关参数的新方法,尤其适用于分析成型刀具包络加工螺旋面。2018年智能制造新模式应用资助项目(工信部联装[2018]265号

    像素矩阵法获取整体式立铣刀容屑槽端截形的研究

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    以螺旋运动包络法和数学形态学二值图像的处理算法为基础,提出了一种方便快捷准确求取整体铣刀容屑槽端截形的像素矩阵法。该方法首先将砂轮回转面离散成点云后在刀具坐标系下进行包络运动,截取砂轮回转面离散点包络运动在刀具端面上留下轨迹的点云数据,将其转化成像素点,利用数学形态学对该二值像素点图像进行膨胀和腐蚀算法提取截形边界,对所提取边界进行平滑处理和插值,得到高精度的容屑槽端截形。该方法无需解析法求解非线性方程获取接触线的过程,避免了解析法的缺点(计算复杂和有异常解),且提取边界的廓形能满足计算精度要求又直观,是理论上获取刀具容屑槽端截形、分析刀具相关参数的新方法,尤其适用于分析成型刀具包络加工螺旋面。工信部2018年智能制造新模式应用资助项目(工信部联装[2018]265号

    Design of Ultra-wideband Printed Rectangular Monopole Antenna

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    针对超宽带通信应用,研究影响印制单极天线阻抗带宽的主要因素,设计基于微带馈电的小型化印制矩形单极天线。按照等效性原理,采用黄金分割比设计矩形振子体;通过接地面上端引入渐变梯形或凹形结构,同时调整馈入端接地面间隙,可实现印制矩形单极天线的超宽带特性。对具有渐变梯形或凹形接地面结构的微带馈电矩形印制单极天线结构进行优化,仿真结果表明,前者的阻抗带宽为2.96~17.94gHz,后者的阻抗带宽为2.9~13.3gHz,而两者的辐射方向基本保持不变。实测结果与仿真结果基本一致,达到了超宽带通信应用的要求。To achieve ultra-wideband(UWB)radio applications,the microstrip-fed printed rectangular monopole antenna is analyzed and devised.Using golden section ratio the rectangular monopole is of layout based on equivalent principle.To maximize the impedance bandwidth,it is necessary introducing the taper or concave ground plane and feed gap of microstrip line.The simulated results of the optimized-size antennas show that the impedance bandwidth defined by return loss less than-10dB is from 2.96GHz to 17.94GHz with a ratio of about 6.06∶1 for taper ground antenna and from 2.9GHz to 13.3GHz with a ratio of about 4.59∶1 for concave ground antenna.At the same time a nearly omnidirectional radiation pattern is exhibited.These results are confirmed by the experimental test and these compact size antennas are suitable for various wideband applications.福建省科技计划重点资助项目(2007H0036

    表面电性可控磁珠微流控芯片在DNA提取中的应用

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    制备了表面电性可控的氨基化SiO2@Fe3O4磁性复合微球,采用激光刻蚀和热压键合的方法制作了聚甲基丙烯酸甲酯(PMMA)材质的DNA固相萃取芯片,将磁珠灌注于芯片通道中,借助永磁铁固定并控制磁珠,将磁珠芯片应用于人类全血中的基因组DNA提取,优化了提取实验条件,并对提取产物进行凝胶电泳和PCR分析。实验结果表明,磁珠微流控芯片成功地从全血中提取出纯度较高的基因组DNA,提取效率约35%,提取液的凝胶电泳条带与商品化试剂盒提取的基因组DNA一致,提取液可用于进一步的PCR反应。国家星火计划项目(No.2015GA721002);;黄土与第四纪地质国家重点实验室开放基金(No.SKLLQG1607);;福建省中青年教师科技计划项目(No.JAT170817)资助~

    Distribution Automation Communication System and IEC60870-5-104 Communication Protocol Software Design and Implementation

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    作为配电网自动化系统的基础,FTU(终端馈线单元)的实现很大程度上取决于选取合适的远动通信协议。远动通信规约种类较多,针对各自特点和实际情况而被应用于不同的现场环境。但是,协议之间的转换才能促使用户的设备正常地通信,因此,标准化的通信规约出现之后,如何解决这个兼容性的问题,而且又要保证实现通信的高效、快捷,易于维护,成为FTU选取合适通信协议的依据。 本文的研究方向就是实现采集数据后的FTU之间正常地进行通信及传输数据。因此,经过多种远动协议的比较分析,从中选取了IEC60870-5-104规约作为FTU传输数据的通信协议。接下来,本文首先对配电自动化通信系统进行相关研究介绍,如层次结构、通...As the basis of distribution automation system, the FTU (terminal feeder unit) implementation depends largely on selecting the appropriate remote communication protocol. So many categories of remote communication protocol, according for their own characteristics and the actual situation, are used in different field. However, the conversion between protocols makes it communicate normally among the...学位:工学硕士院系专业:信息科学与技术学院_通信与信息系统学号:2332010115314

    Synthesis and Properties of Branched PET Copolyesters

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    基于IEC60870-5-104远动规约的软件设计

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    该文关于IEC60870-5-104规约的介绍,主要包括104规约的产生及应用的概述,104规约结构的简要说明,如104传输报文所定义的格式。然后针对104规约的实施过程,给出一套在VISuAl C++6.0上运行的软件设计方案。最后,对其应用现状及其发展分析作了一定的分析与展望

    Information Transparency and the Efficiency of Corporate Governance——Evidence from CEO Turnover in China's Listed Companies

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    本文以中国上市公司为研究对象,从会计信息系统和组织结构复杂性两个维度,建立了一套客观反映上市公司信息透明度水平的评价指标体系,并以此考察信息透明度对总经理变更与公司业绩之间敏感程度的影响。实证结果表明,公司信息透明度越高,总经理因业绩下降而被更换的可能性越大。这表明,公司信息透明度的提高不仅有助于投资者甄别管理者经营水平的高低,而且可以强化董事会对总经理的监管机制,从而增进了公司治理制度安排的效率。Based on the Chinese stock market,this paper analyzes the effect of information transparency on the sensitivity of CEO turnover to firm performance.The paper firstly develops a set of information transparency index from two dimensions,namely,ac-counting information system and organizational structure complex-ity.And based on the above-mentioned two dimentions,the paper examines the impacts the information transparency imposes on the sensitivity of top management turnover to firm performance.The empirical result shows that information transparency signifi-cantly enhances the association between CEO turnover and poor performance,which suggests that the improvement in information transparency will help investors distinguish between good and bad managers,strengthen the boards'control mechanism over CEO,and thus improve the effectiveness of the governance mechanism of cor-porations.This research not only develops the corporate transpar-ency research,but also presents the direct evidence which supports the argument that better information transparency helps promote the efficient governance of corporations.国家自然科学基金重点项目(70632001)资

    The Effect of Landscape Pattern on Soil Erosion in Loess Plateau Catchment——Take Huangjia Ercha Catchment as an Example

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    以黄家二岔流域为例,分析该区的景观格局,选取斑块大小、斑块破碎度、等高连通度、顺坡连通度和斑块相对位置指数5个指标对景观格局进行量化,再结合地形,将该流域分为阴坡和阳坡分别计算它们的景观格局,并分析它们与土壤侵蚀的关系.最后得到,黄家二岔流域主要土地利用类型为耕地和人工草地,其中阳坡以人工草地为主,其斑块较完整,等高连通度大,斑块排列顺序也利于保持水土;而阴坡以耕地为主,斑块完整,顺坡连通度大,斑块排列顺序不利于水土保持.因此阳坡景观格局利于保持水土,而阴坡景观格局利于土壤侵蚀
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