Construction of a new adaptive wavelet network and its learning algorithm

A new adaptive learning algorithm for constructing and training wavelet networks is proposed based on the time-frequency localization properties of wavelet frames and the adaptive projection algorithm. The exponential convergence of the adaptive projection algorithm in finite-dimensional Hilbert spaces is constructively proved, with exponential decay ratios given with high accuracy. The learning algorithm can sufficiently utilize the time-frequency information contained in the training data, iteratively determines the number of the hidden layer nodes and the weights of wavelet networks, and solves the problem of structure optimization of wavelet networks. The algorithm is simple and efficient, as illustrated by examples of signal representation and denoising.     

A two-dimensional warranty servicing strategy based on reduction in product failure intensity

The cost of servicing a warranty depends, amongst other factors, on the type of repair performed under warranty. Although “all minimal repair” and “all replacement” policies are easy to implement and analyze, they are not always feasible and/or practical. Having a combination of different types of repair often leads to lower warranty servicing costs. In this article, to reduce the warranty servicing cost, we study a servicing strategy that involves performing imperfect repairs in place of some of the minimal repairs of an “all minimal repair” strategy; the effect of an imperfect repair is characterized by a drop in the conditional intensity function of the failure process. We consider both fixed and random degrees of repair. For a given type of product, we partition the warranty region so that the expected total warranty servicing cost is minimized. We provide a numerical illustration and a comparison with previously-studied repair-replacement strategies.     

钢筋混凝土框架结构的性能化抗震设计指标及设计方法

层间位移角是钢筋混凝土框架结构抗震设计的性能指标,进行性能化抗震设计研究具有重要的理论和实践价值.综述了国内外规范对钢筋混凝土框架结构对性能目标的规定以及相关试验研究成果,建立了在不同性能水平时的量化指标.阐述了基于位移角的抗震性能评估方法,通过阻尼比折减法和R折减系数法,给出两个能力谱的实现路径,引用SAP2000完成了算例验算.研究表明：钢筋混凝土框架结构层间屈服最大位移角为1/300～1/150,顶点位移角为1/400～1/200;层间极限最大位移角为1/50～1/30,顶点极限位移角为1/100～1/50.阻尼比折减法和R折减系数法获得性能点基本一致,Vidic-Fajfar-Fischinger折减系数法比阻尼比折减法的计算结果略小,两种方法均可作为性能化抗震设计的实用技术.     

基于水平集方法的弱边界运动人体目标跟踪与轮廓提取

针对图像中目标和背景灰度偏差较小、目标边缘轮廓弱的特点,提出了一种快速收敛并具有较强捕获弱边缘能力的水平集曲线演化方法。该方法采用指数函数作为边缘指示函数,运用归一化的Gauss分布函数改进传统的正则化Dirac函数。在目标跟踪过程中,采用卡尔曼滤波获取视频相应帧图像的运动人体目标最小外接矩形框,对外接矩形框内运动人体进行水平集曲线演化,实现对人体目标的跟踪和轮廓提取。分别对可见光下的运动目标和红外运动视频序列进行仿真实验。结果表明,相对于传统方法,其在跟踪速度上有很大的提高,对于红外图像中的弱边界目标及凸凹度较大的区域,也具有快速准确的收敛效果。     

Buckling dynamics of imperfect Elastica subject to various loading conditions

Buckling dynamics of a pinned-pinned flexible imperfect beam attached to a sliding mass is investigated using nonlinear Elastica theory. Initially straight flexible buckling beam having pinned end boundary conditions loaded at one of its end with curved imperfection is considered. Large deflection analysis of flexible beam is studied using nonlinear Elastica theory. Imperfection analysis of the flexible beam is investigated considering the imperfection as an initial curvature. The governing differential equations are expressed in terms of nonlinear functions that are typical of flexible beams, generally leading to highly implicit relationships involving elliptic integrals and functions. Dynamic simulation of the flexible beam is studied using numerical simulation procedures with various types of loading (step, ramp, and sinusoidal) assuming this member buckles in its first mode. Dynamic response of the imperfect buckling Elastica has been obtained by using numerical Runge-Kutta methods. Load deflection characteristics of flexible beams are presented in polynomial curve fits. The polynomial curve fits obtained from nonlinear inextensible exact beam theory may then be used as the nonlinear lumped system stiffness. The buckling Elastica may find applications in compliant mechanism design. The motivation behind this research is not only to present the dynamic behavior of the buckling beam considering the magnitude of the imperfection but also to provide a tool to design new types of compliant mechanisms. Original compliant mechanism designs are presented demonstrating where the buckling dynamics of imperfect Elastica or flexible curved beams might be needed in mechanism design and synthesis.     

正交设计在钢框架梁柱连接性能分析中的应用

在钢结构框架中,梁柱腹板连接同翼缘连接一样普遍,而且设计和施工更为困难,因此对梁柱腹板连接的性能分析具有重要意义.在钢结构工程设计中,梁柱连接的承载力是反映连接性能的一项重要指标.本文通过在钢框架梁柱腹板连接承载力影响因素分析中引入正交设计方法,找出了主要因素和次要因素.结果表明:在梁柱腹板连接中,梁的高度对连接的承载力影响最大,柱翼缘宽度和柱翼缘厚度次之,而梁翼缘厚度的影响并不显著,对今后钢框架的设计有着一定的指导意义.     

多层住宅钢结构体系及其梁柱节点研究

对钢结构体系进行了分析,并以钢结构设计方法为依据,提出适用于多层住宅钢结构的节点型式。     

对几个小波基本概念的理解

讨论实际应用中经常涉及但容易产生误解的小波基本概念,以期提高电力系统小波应用研究水平。这些小波基本概念是:容许性条件;二进离散与二进小波;连续小波的离散条件;小波基;A=B=1的紧框架与正交小波;小波滤波器长度与时域分辨率;小波的滤波特性与不同尺度小波的频带交叠;线性相位小波与信号完全重构;双正交小波的小波包及小波包分解与1/2频程分解;整数倍伸缩小波变换与分数倍伸缩小波变换;小波的正则度与消失矩;Motlet函数与Morlet小波;小波变换模极大值(定义、与突变点位置的关系、与Lipschitz指数的关系、对小波的要求);时域、频域同时紧支小波;(时域)紧支正交线性相位小波;表征小波特性的基本指标与有价值的新小波。     

任意连接平面杆系结构自振特性分析的统一模型

基于基本假定和振动理论，通过严格的理论推导建立了具有任意连接刚度的半刚性连接平面系结构自振特性分析的统一模型，在该模型中只要选取适当的连接刚度因子即可分析经典桁架结构、平面刚架结构、混合结点及半刚性连接的任意平面杆系结构的自振特性，且给出了刚度矩阵的显式形式。算例与解析解进行了比较，结果相当吻合。     

谈新生如何适应大学生活

怎样适应大学生活是高校新生最为关注的话题.在此,笔者谈了如何在心理状态、生活方式、学习方法等方面适应大学生活,旨在帮助大学新生提高认识,尽快进入角色.