Null controllability of some degenerate wave equations

This paper is devoted to a study of the null controllability problems for one-dimensional linear degenerate wave equations through a boundary controller. First, the well-posedness of linear degenerate wave equations is discussed. Then the null controllability of some degenerate wave equations is established, when a control acts on the non-degenerate boundary. Different from the known controllability results in the case that a control acts on the degenerate boundary, any initial value in state space is controllable in this case. Also, an explicit expression for the controllability time is given. Furthermore, a counterexample on the controllability is given for some other degenerate wave equations.     

城中村的人居环境分析及改造思考

概括城中村的现状并结合太原市现阶段的改造情况,提出要正确把握城中村的定位,并从制度和形式上提出改造措施。     

我国地震预测成绩的回顾与统计

地震预测预报的难度大，但并非了无痕迹或不可知，我国每次较大的地震都有案例总结。统计表明，近４０ 年来，有７７ 次地震在发生前均有中期、短期甚至临震预测，不能因为汶川地震预测的失败，就全面抹杀中国的地震预报成绩，即我国的地震预测成绩是应予肯定的，汶川地震也并非是无前兆的“怪震”。     

浅谈电力系统继电保护的意义、维护及前景

继电保护对电力系统的安全有效运行影响重大,要确实保证电力系统的正常使用,就要在保护措施上做好工作,而继电保护是其中最主要,最有效的方式.因此,为保障电力系统的安全运行,必须对继电保护有一定的了解,才能有效使用.本文将对继电保护的作用意义和装置使用及维护,以及其技术发展前景进行分析.     

高校家庭经济困难学生认定机制探析

家庭经济困难学生认定工作是各高校资助工作的基础性工作,也是资助工作中的难点工作.贫困生认定的准确性直接影响到高校资助工作的效率和效果,本文通过分析目前贫困生认定工作存在的问题,提出了相应的改进措施,对保证助困资源的合理配置和效益最大化,实现教育公平具有重要意义.     

试析走出去企业的社会责任

关于企业社会责任仁者见仁智者见智。借鉴国内外专家的观点,走出去企业尤其需要注意的社会责任包括经济责任、法律责任、安全责任、道义责任、文化责任等。     

Weighted symbol-flipping decoding algorithm for nonbinary LDPC codes with flipping patterns

A novel low-complexity weighted symbol-flipping algorithm with flipping patterns to decode nonbinary low-density parity-check codes is proposed.The proposed decoding procedure updates the hard-decision received symbol vector iteratively in search of a valid codeword in the symbol vector space.Only one symbol is flipped in each iteration,and symbol flipping function,which is employed as the symbol flipping metric,combines the number of failed checks and the reliabilities of the received bits and calculated symbols.A scheme to avoid infinite loops and select one symbol to flip in high order Galois field search is also proposed.The design of flipping pattern’s order and depth,which is dependent of the computational requirement and error performance,is also proposed and exemplified.Simulation results show that the algorithm achieves an appealing tradeoff between performance and computational requirement over relatively low Galois field for short to medium code length.     

Sample average approximation method for a class of stochastic variational inequality problems

This paper considers a class of stochastic variational inequality problems. As proposed by Jiang and Xu (2008), by using the so-called regularized gap function, the authors formulate the problems as constrained optimization problems and then propose a sample average approximation method for solving the problems. Under some moderate conditions, the authors investigate the limiting behavior of the optimal values and the optimal solutions of the approximation problems. Finally, some numerical results are reported to show efficiency of the proposed method.     

论桥梁抗震模型建立分析的目的

文章论述了桥梁抗震评估的建立模型和分析手段,其目的是用结构位移、构件受力及变形对桥梁地震反应进行定量化分析.