Adaptive radial importance sampling under directional stratification

We establish radial importance sampling under directional stratification and construct its easy-to-implement algorithm for estimating the probability of failure in structural reliability analysis. The proposed algorithm is expected to run in a fully adaptive manner for averaging the increasing realizations towards the unknown stratum probability of failure, along with updating parameterized importance sampling and adjusting the allocation of computing budget only occasionally yet effectively, fully considering the decreasing stratum variances, all on a single set of replications. The formulation does not require a monotonicity condition on the radial distance in the polar coordinate system to justify a deterministic numerical procedure, such as the root finding of directional simulation in its standard form. A wide variety of numerical results were provided for illustrating the applicability and effectiveness of the proposed framework and algorithm.     

基于边重要度的矩阵分解链路预测算法

基于矩阵分解的链路预测方法的领域适应性较好.然而在已有基于矩阵分解的链路预测方法中,0-1矩阵的网络数据表示对网络中未知连边的假设较强,同时对网络中已知连边的重要度无区分性.为此,文中放松0-1矩阵的网络数据表示假设,对未知节点对连边不做任何假设,并提出边重要度度量方法,对网络中已知连边进行重要度度量,最终建立基于网络权重矩阵分解的链路预测模型.在8个公开网络数据集上对比基于度量的链路预测方法和已有矩阵分解方法,文中方法链路预测结果更好.     

一种改进的粒子滤波算法及其在GPS/DR组合定位中的应用

针对粒子滤波的重要性密度函数选择问题,提出一种基于集合卡尔曼滤波(Ensemble Kalman Filter,EnKF)的改进粒子滤波算法。该方法利用集合卡尔曼滤波产生粒子滤波在每一时刻各粒子的重要性密度函数,在融合最新观测信息的同时,使重要性密度函数更加符合状态的真实后验概率分布。为消除样本枯竭现象,对重采样后的粒子进行马尔科夫链蒙特卡洛处理。在仿真实验中,将新算法用于GPS/DR组合定位系统,与粒子滤波、扩展卡尔曼粒子滤波以及无迹粒子滤波进行比较。仿真结果表明,该算法的估计精度高于传统粒子滤波算法,同时其能够有效控制计算量,并且在粒子数目较少时仍能保证较好的估计性能。     

An efficient reliability-based optimization scheme for uncertain linear systems subject to general Gaussian excitation

A very efficient methodology to carry out reliability-based optimization of linear systems with random structural parameters and random excitation is presented. The reliability-based optimization problem is formulated as the minimization of an objective function for a specified reliability. The probability that design conditions are satisfied within a given time interval is used as a measure of the system reliability. Approximation concepts are used to construct high quality approximations of dynamic responses in terms of the design variables and uncertain structural parameters during the design process. The approximations are combined with an efficient simulation technique to generate explicit approximations of the reliability measures with respect to the design variables. In particular, an efficient importance sampling technique is used to estimate the failure probabilities. The number of dynamic analyses as well as reliability estimations required during the optimization process are reduced dramatically. Several example problems are presented to illustrate the effectiveness and feasibility of the suggested approach.     

故障树分析法在石化装置可靠性分析中的应用

石化装置具有大型化、复杂化、高速化和连续化生产的特点，一旦发生故障将造成巨大的经济损失，甚至造成人员伤亡，污染环境，因此保证装置安全可靠地工作尤为重要。这里在底事件分布类型、参数和发生概率已知的条件下，以应用广泛的锅炉为例，利用故障树分析法对系统进行定性分析和定量计算，求出系统的最小割集、重要度，发现系统的最薄弱环节，以及确定了预防性维修的时间。     

A simple method for detecting salient regions

A simple method for detecting salient regions in images is proposed. It requires only edge detection, threshold decomposition, the distance transform, and thresholding. Moreover, it avoids the need for setting any parameter values. Experiments show that the resulting regions are relatively coarse, but overall the method is surprisingly effective, and has the benefit of easy implementation. Quantitative tests were carried out on Liu et al.'s dataset of 5000 images. Although the ratings of our simple method were not as good as their approach which involved an extensive training stage, they were comparable to several other popular methods from the literature. Further tests on Kootstra and Schomaker's dataset of 99 images also showed promising results.     

基于空间句法的空间拓扑区域中心评判研究

该文以遗传算法基本原理做理论基础，结合空间句法分析中的构形的概念，并以连接值、控制值为空间重要性特征设计出符合要求的适应度函数。以此值最大值作为区域中心的评判标准。     

Estimation of failure probabilities by local approximation of the limit state function

For failure probability estimates of large structural systems, the numerical expensive evaluations of the limit state function have to be replaced by suitable approximations. Most of the methods proposed in the literature so far construct global approximations of the failure hypersurface. Rather than concentrating on the construction of the failure hypersurface, an adaptive local approximation scheme for the limit state function that is based on the moving least squares method is proposed in this study. It integrates well with existing importance sampling schemes and yields both efficient and robust estimates of the failure probability.     

谈中国对外贸易的现状及其科技创新的重要性

改革开放以来,中国在国际经济舞台上的地位不断攀升,取得的成就有目共睹,已成为真正的贸易大国。本文针对中国对外贸易的发展过程和现状以及存在的问题进行了客观地阐述,指出了科技在中国对外贸易由大向强发展过程中的重要性。     

Integrating service quality evaluation model to improve employees' satisfaction for high‐tech iindustry

This study addresses the deficiency research of service quality by integrating the importance–satisfaction model (I‐S model) and the performance control matrix to provide a more comprehensive assessment model for improving specific quality attributes. The study applies this integrated measuring instrument in a Taiwanese high‐tech industry by using a questionnaire survey of production‐line employees to assess importance and satisfaction in their capacity as internal customers of the company. The study thus identifies and prioritizes quality attributes that require improvement. The findings are significant for service providers because they take into account: (i) the relative importance of quality attributes; (ii) the relative satisfaction level of these attributes; and (iii) the resources available for improvement. The study demonstrates that the I‐S model and the performance control matrix, taken together, provide an excellent measuring instrument for assessing priorities for quality improvement. © 2011 Wiley Periodicals, Inc.