Research on structure adaptive multi-atoms matching pursuit algorithm of image sparse representation

图像内容的有效表示是图像处理领域的基本问题。图像的稀疏表示是指用相对较少的数据来表示出目标图像的主要信息。稀疏表示能够更有效地对图像建模，已成为带动压缩感知与图像处理、信号处理、通信等领域发展的核心技术之一，是当前图像处理领域的研究热点与难点，受到国内外学者的广泛关注。本文主要围绕图像稀疏表示理论中过完备字典设计和快速稀疏分解算法两个方面进行了详细和深入的研究，取得的主要研究成果及创新点如下： 1)根据图像的几何结构特性，参考哺乳类动物的视觉系统感知特性，选取二维Gabor函数作为过完备字典的生成函数，建立了可以匹配多种图像结构的Gabor多成分过完备字典。该字典包含平滑、边缘轮廓与纹理三种...Efficient representation of image is the basic problem in digital image processing. Image sparse representation can capture significant information of the original image with relatively less data. Because sparse representation model can effectively represent the image, it becomes one of the core technologies which drive the development of many subjects, such as Compressed Sensing, Signal Processin...学位：工程硕士院系专业：信息科学与技术学院计算机科学系_计算机技术学号：2302009115270

SNS use in teaching and learning in China

Social Network Sites (SNSs) are increasingly influencing the academic and industry researchers intrigued by their affordances and settings. Although SNS has been claimed that it occupied too much of peoples’ daily lives by many researchers and scientists, the fact also demonstrates the growing use of SNS in education area, which proved that SNS has its unique pedagogical significance and potential to foster students’ learning experience. Used and promoted in many countries around the world, SNS is now not only serving as a social network environment (SNE) for people to communicate, but also a platform for academic information exchange and sharing in various contexts. This study aimed at exploring the differences between western and Chinese localised SNS, evaluating the practicability of SNS use in China’s education, and identifying certain problems in the implementation. Referenced by the literature on SNS experiment in teaching, cultural influence and pedagogy value, Chinese SNS would be analysed from comprehensive perspectives. This study combined two parts, one was the comparison study for four selected SNSs from China and foreign countries, the other was the research experiment conducted with a class of 17 students enrolling in an English educational institution in Chinese mainland, where the students took a spoken English course which lasted for one and a half month. The selected SNSs used in the experiment were implemented to facilitate the teaching and support designed learning process that requires students to explore the use of SNS and motivate them to interact more with peers and teacher off-class while completing the course objectives. Date collection and analysis conducted mixed methods in this research, the data of this research were collected by different levels of participants’ interviews, observations, recordings and questionnaires that covers the perceptions for research topic, everyday use of SNSs, taken-forgranted interactions and communication among teacher and students in the learning and teaching process. This research not only justify the practicability of SNS use in China’s education, it also revealed various functions that SNSs could provide in China’s education. In terms of functionality, it could serves as a platform for (a) facilitating presentation and demonstration, (b) developing personal learning record and portfolios, (c) distributing and sharing resources, (d) promoting student-teacher offline interaction, (e) enabling free comment and feedbacks. Theoretical research would be conducted and practical implementation would also be introduced. Through the experiment, the research would make the best of SNSs in education, which further discuss the special characteristics of Chinese localised SNSs and broaden the understanding of using SNS in education. Pedagogical principles are also discussed.published_or_final_versionEducationMasterMaster of Educatio

弓网接触力在线测试方法研究

弓网接触力是评估弓网受流质量和弓头滑板磨损寿命、诊断接触网局部缺陷的直接依据,其在线监测是未来电气化铁路发展亟待解决的关键问题之一。针对现有测试方法存在的问题,本文提出了在弓头簧片背面安装应变传感器的可行方案,避免了滑板更换对传感器带来的影响;同时,实现了加载过程中任一时刻接触点位置的直接测量,结合测点应变值,可直接反推出接触力,无需对滑板实体结构进行简化

高速受电弓下框架等效阻尼的实验研究

良好的弓网关系要求满足弓网接触力平均值的前提下,其标准差尽可能小。已有研究结果表明下框架等效阻尼增大可以有效降低接触力标准差。以DSA380型高速受电弓为研究对象,本文设计了悬挂弹簧法,结合文献中提出的下置弹簧法,实现了将各部件对下框架阻尼贡献的解耦测量分析,提出了采用双阻尼器这一可行的优化设计方案

基于模态实验的单滑板受电弓全柔模型修正方法

动车组通过受电弓从接触网上获取电能,良好的弓网接触是列车受流的重要保障.随着列车速度的提高,弓网动态特性问题日益突出.受电弓在高速或更高速运行时,接触网不平顺、气动效应等高频激励,将激发受电弓的高频弹性模态及富有高频成分的弓网相互作用力.只考虑受电弓3个垂向自由度的三质量块模型不再适用于高频弓网动力学分析,为进行更高速下的受电弓动力学参数设计和弓网受流质量评估,需建立反映结构弹性模态的受电弓全柔模型.文章提出基于模态实验的受电弓全柔模型的修正方法.首先,开展一款新型单滑板高速受电弓的模态实验,获得260 Hz以内的两阶垂向耦合振动模态参数和6阶垂向弹性模态参数.然后,进行受电弓模态频率对材料参数的灵敏度分析,研究得到弓头、上臂和下臂的弹性模量和密度及弓头弹簧刚度,对受电弓的8阶垂向模态频率的影响显著,确定了模型修正的参数.最后,利用粒子群优化算法,获得与模态实验结果吻合度较高的修正全柔模型,其与实验结果的误差仅为5.2%.此外,提出基于模态置信度的振型识别方法,实现了迭代寻优过程中正确率为100%的模态自动识别