结构抗震设计的凸面模型

1 前言 不同研究者已提出了各种估算结构系统对地震激励的最大反应的方法。Drenik(1970,1973)提出过一种想法,可以利用表征地面运动的,变化范围很大但个数有限的确定性信息,来求取结构系统对地震的最不利反应。利用地震在结构位置上可能输入的总能量,在使结构反应最大的可能的动力集合范围内,寻求一个“临界激励”,然而,由于只限制了总能量,因此结构相当保守。Shinozuka(1970)建议通过限定傅氏幅值谱的包络来表示地震激励。由于这一方法中所包含的信息大大地限制了可能的激励集合,因此由之得到的结果的保守程度比Drenick的要小得多,因此结构最大反应值也减小了。Admadi(1986)求出了水平、竖向组合地震地面运动作用下,弹性结构最大反应的几个里耶普诺夫限值。然而,该法需要了解最大地面加速度的合适的有效持时。除上述估算地震中结构最大反应的方法外,还提出了统计方法(Biot, 1941; Housner, 1959; Newmark,1973)和概率方法(Crandall, 1966; Vanmarcke, 1972)。 由于与破裂过程有关的震源效应。

Secure planar convex hull protocol for large-scaled point sets in semi-honest model

Efficiency and scalability are still the bottleneck for secure multi-party computation geometry （SMCG）. In this work a secure planar convex hull （SPCH） protocol for large-scaled point sets in semi-honest model has been proposed efficiently to solve the above problems. Firstly, a novel priva- cy-preserving point-inclusion （PPPI） protocol is designed based on the classic homomorphic encryp- tion and secure cross product protocol, and it is demonstrated that the complexity of PPPI protocol is independent of the vertex size of the input convex hull. And then on the basis of the novel PPPI pro- tocol, an effective SPCH protocol is presented. Analysis shows that this SPCH protocol has a good performance for large-scaled point sets compared with previous solutions. Moreover, analysis finds that the complexity of our SPCH protocol relies on the size of the points on the outermost layer of the input point sets only.

Fractal model of thermal elasto-plastic contact of rough surfaces

Without considering the influence of heat,existing fractal contact models are not applicable to analyze the contacts when the temperature changes.For this problem,the normal load model and the normal stiffness model of thermal elasto-plastic contact of rough surfaces are developed respectively in this paper.The proposed model is based on the normal contact mechanics model of fractal theory of anisotropic and thermal elasto-plastic contact theory which can be used to characterize the rough surface thermodynamic properties.Then the validity of the model is verified.Finally,the influence of main parameters on the total normal load and the whole normal stiffness of thermal elasto-plastic contact at the interface is analyzed by contact simulation.The results show that the total normal load of thermal elasto-plastic contact increases with the increases of temperature.The whole normal stiffness of thermal elasto-plastic contact increases with increasing coefficient of linear expansion,scale factor,temperature difference or fractal dimension,but decreases with increasing fractal roughness.This model expands basic theory and applications of traditional models,and can be used to calculate and analyze the contacts when the temperature changes.

基于多尺度分割的对象级影像平滑算法

提出了一种对象级的保边缘影像平滑算法。该算法利用空间聚类对影像进行多尺度分割,在分割过程中,提取出不同尺度下的符合凸面模型(convexity model)的影像对象(image object);依据对象的统计参数对影像对象进行筛选,符合要求的影像对象内部进行平滑处理,其余对象不受影响。利用该方法可以有效地去除噪声和无用小目标,在不破坏指定目标边缘的同时,实现影像的平滑处理。