数字图像置乱技术及其Matlab实现

针对近年兴起的数字图像安全保密问题，本文探讨了几种数字置乱加密技术，包括基于几何变换、幻方变换、Hilber变换的置乱技术，基于采样技术的图像置乱技术，基于生命游戏的图像置乱技术等等，并给出了几个主要算法的Matlab实现代码。     

古希腊悲剧意识在《德伯家的苔丝》中的体现

英国著名作家托马斯·哈代的悲剧小说与古希腊悲剧有着较深的渊源,其作品中总能在许多方面体现其影响。《德伯家的苔丝》即是其中的典型代表。本文试图从悲剧角色及悲剧冲突这两个方面着重进行分析,从而探讨哈代的悲剧小说对古希腊悲剧意识的继承与发展。     

列车车辆轮对踏面故障动态诊断系统通过部级评审

一种用于检测列车车辆轮对踏面故障的高科技产品已由六○八研究所研制成功,近日在湖南株洲通过了铁道部“全路车辆专用设备管理委员会”主持的部级评审,获准进入铁路市场,将于今年起在全国铁路系统推广应用。目前六○八研究所通过代理商已签订了15台销售合同。     

Investigation on the Orientation Transition of Oriented Magnetostrictive TbDyFe Crystals

<110> and <112> TbDyFe magnetostrictive oriented crystals were prepared by the zone-melting unidirectional solidification method at 240 mm/h and 720 mm/h respectively. <112> oriented crystals were also obtained with <110> oriented seeds with the same technique as for growing the <112> oriented crystals. It is confirmed that this technique is stable for growing the oriented crystals in the TbDyFe alloys. Meanwhile, the variation of orientation, the solidification morphology and the magnetostriction were studied during the transition from <110> oriented seeds to the <112> oriented crystal growth. As the growth speeds up, the preferred orientation changed from <110> to <112>, and its morphology develops from of initial cellular to dendritic gradually. When an axial compressive pre-stress of 10 MPa is applied, the magnetostriction at the bottom, the middle and the top are 972×10-6, 918×10-6 and 900×10-6 at 100 mT respec-tively. The middle sections with mixed orientations have the same high magnetostriction performance as those with a single preferred orientation, which may be due to its celluar-dendritic morphology.     

基于最大熵原理与 MonteCarlo法的隧道衬砌结构可靠度计算

针对隧道衬砌结构参数统计特征难以推断的特点,运用信息熵概念和最大熵原理对隧道衬砌结构随机参数进行估计,得到了更加科学的参数估计值.同时,将该估计值用于 MATLAB环境下 MonteCarlo模拟法计算隧道衬砌结构可靠度,得到相应的破坏概率和可靠度,并对隧道衬砌结构安全稳定性进行了评价.研究结果表明:用最大熵原理所推断的隧道衬砌结构参数分布更加科学可靠,且在 MATLAB环境下进行 MonteCarlo模拟法计算隧道衬砌结构可靠度,其计算速度快,精度高,可供类似的结构参数估计和可靠度计算参考.     

基于量纲分析法对强夯加固深度的研究

影响强夯加固范围的主要因素有夯击能、夯锤面积、夯击次数、土体性质等,在分析这些影响因素的基础上,采取量纲分析的方法,建立了路基强夯加固的深度方程,并考虑土体的级配与含水量修正系数,建立了强夯加固深度的计算公式.最后和工程测试的有效加固深度进行对比,表明该公式与实际测试结果较为符合,证明该公式的有效性和可信性.     

数字媒体版权保护和信息保密的新途径--数字水印技术

数字水印技术作为数字媒体版权保护和信息保密的有效办法，近年来在国内外引起了人们极大的兴趣。本文大致介绍了数字水印技术本身的特点和典型算法，简要地介绍了利用Matlab语言进行的数字水印研究，并给出了一个利用Matlab语言实现数字水印的实例。     

渐变结构系统模糊可靠性灵敏度分析的矩方法(英文)

For a degradable structural system with fuzzy failure region, a moment method based on fuzzy reliability sensitivity algorithm is presented. According to the value assignment of performance function, the integral region for calculating the fuzzy failure probability is first split into a series of subregions in which the membership function values of the performance function within the fuzzy failure region can be approximated by a set of constants. The fuzzy failure probability is then transformed into a sum of products of the random failure probabilities and the approximate constants of the membership function in the subregions. Furthermore, the fuzzy reliability sensitivity analysis is transformed into a series of random reliability sensitivity analysis, and the random reliability sensitivity can be obtained by the constructed moment method. The primary advantages of the presented method include higher efficiency for implicit performance function with low and medium dimensionality and wide applicability to multiple failure modes and nonnormal basic random variables. The limitation is that the required computation effort grows exponentially with the increase of dimensionality of the basic random vari- able; hence, it is not suitable for high dimensionality problem. Compared with the available methods, the presented one is pretty competitive in the case that the dimensionality is lower than 10. The presented examples are used to verify the advantages and indicate the limitations.     

椭球形舞台壳体风荷载风洞实验研究

通过风洞模拟试验研究了椭球形舞台壳体 ,及其三种开启状态时的风荷载特性。结果表明就整体风荷载而言椭球体的阻力系数不是很大 ,但由于气流的分离和再附 ,椭球体的局部会出现很大的负压 ,系数可达 2 .0以上。另外 ,周围建筑对椭球形舞台壳体的风荷载影响很大。