Influence of static pre-loading on the dynamic bending strength of concrete with particle element modeling

Experimental tests show that static pre-loading has a significant effect on the dynamic strength of concrete.Based on meso-scale particle element model,numerical simulations of dynamic bending tests with pre-loading are performed.Complete stress–strain relationships are then obtained.Significant increase in dynamic strength is found when the pre-loadings are imposed within the elastic limit of concrete.However,when the imposition of pre-loadings reaches the plastic or softening range,dynamic strengths may gradually decrease along with the increase in pre-loadings.The distribution of energy components and the failure modes are discussed to explain the mechanisms of the phenomena.     

Evaluation research on applicability of rapid iodide migration test

The applicability of the rapid iodide migration test was systematically studied. Comparative experimental tests of different test conditions, including several external voltages, test durations, concrete ages and mixing proportions, were carried out to make clear the transport behaviors of iodide under parallel electric fields. Numerical simulations were also done using the finite element method to found the correlation between chloride and iodide transport behaviors. The test and numerical results show that the chloride transport behaviors of RIM and RCM tests have a good correlation under the several conditions used in the present paper. Moreover, the influence of external conditions （external voltages, test durations） on the test results is small. Thus, it can be concluded that the RIM method is available to determine the chloride penetration resistance of the chloride-eroded structural concrete.     

校园网资源整合与校园云服务模式研究

云计算应用正以势如破竹的态势进入到教育领域,云计算的推广有利于教育资源的共建共享,方便师生快捷地获取所需资源和服务,更高效地开展学习和科研工作.分析了现有网络资源的具体实际情况,利用云计算技术,探究资源整合的有效方式,整合校园网资源,探索适合于教师教学与科研、学生学习与成长,以及学校提升社会服务能力的校园私有云服务模式.     

基于模糊决策的风力发电产业评价研究

根据风力发电技术产业的特点,构建改进层次分析与模糊一致矩阵相结合的方案决策数学模型,该模型既可以减少确定判断矩阵的盲目性,又可以避开评价体系中各等级间的隶属度确定问题,使评价结果更加可靠,适合于信息尚不完整、受主观因素影响较强的评价。实例验证了这一模型的合理性、可行性和有效性,具有实用价值。     

基于机器视觉的微片状物厚度检测

针对片状颗粒厚度检测的实际需求,结合机器视觉、图像处理和嵌入式技术,设计与实现了一套基于高性能ARM11的微片状颗粒厚度检测系统。该系统以QT和S3C6410为软硬件平台,提出了利用轮廓提取和最小矩形边界框相结合的方法计算片状颗粒厚度。结果表明,该检测系统具有处理速度快,测量精度高和成本低廉等优点,满足了对颗粒厚度测量的需求。     

The optimized copyright protection system with genetic watermarking

Applications for robust watermarking is one of the major branches in digital rights management (DRM) systems and related researches. Based on existing experiences to evaluate the applicability of robust watermarking, it is generally agreed that three parameters or requirements, including the quality of watermarked contents, the survivability of extracted watermark after deliberate or unintentional attacks, and the number of bits embedded, need to be considered. However, performances relating to these three parameters conflict with each other, and the trade off must be searched for. In this paper, we take all the three requirements into consideration, and add the flexibility to meet the specific design in implementation. With the aid of genetic algorithm, we design an applicable system that would obtain the good quality, acceptable survivability, and reasonable capacity after watermarking. Simulation results present the effectiveness in practical implementation and possible application of the proposed algorithm.     

Content-based image authentication: current status, issues, and challenges

With today’s global digital environment, the Internet is readily accessible anytime from everywhere, so does the digital image manipulation software; thus, digital data is easy to be tampered without notice. Under this circumstance, integrity verification has become an important issue in the digital world. The aim of this paper is to present an in-depth review and analysis on the methods of detecting image tampering. We introduce the notion of content-based image authentication and the features required to design an effective authentication scheme. We review major algorithms and frequently used security mechanisms found in the open literature. We also analyze and discuss the performance trade-offs and related security issues among existing technologies.     

基于LDA模型的新闻话题的演化

新闻话题及演化的研究可以帮助人们快速了解和获取新闻内容。提出了一种挖掘新闻话题随时间变化的方法,通过话题抽取和话题关联实现话题的演化。首先应用LDA(Latent Dirichlet Allocation Model)对不同时间段的文集进行话题的自动抽取,话题数目在不同时间段是可变的;计算相邻时间段中任意两个话题的分布距离实现话题的关联。实验结果证明该方法不但可以描述同一个话题随时间的演化过程,还可以描述话题内容随时间的变化,反映了话题(或子话题)之间多对多的演化关系。     

A general formulation of monotonically convergent algorithms in the control of quantum dynamics beyond the linear dipole interaction

This paper presents a general method to formulate monotonically convergent algorithms for identifying optimal control fields to manipulate quantum dynamics phenomena beyond the linear dipole interaction. The method, facilitated by a field-dependent dipole moment operator, is based on an integral equation of the first kind arising from the Heisenberg equation of motion for tracking a time-dependent, dynamical invariant observable associated with a reference control field.     

An improved closed-loop stability related measure forfinite-precision digital controller realizations

The pole-sensitivity approach is employed to investigate the stability issue of the discrete-time control system, where a digital controller implemented with finite word length (FWL), is used. A stability related measure is derived, which is more accurate in estimating the closed-loop stability robustness of an FWL implemented controller than some existing measures for the pole-sensitivity analysis. This improved stability measure thus provides a better criterion to find the optimal realizations for a generic controller structure that includes output-feedback and observer-based controllers. A numerical example is used to verify the theoretical analysis and to illustrate the design procedure