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771.
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矩形截面抛物线楔形梁作为一种变截面杆件在平面框架结构中经常使用。本文通过求矩形截面抛物线楔形梁的单元柔度系数、刚度系数,提出了平面框架结构中矩形截面抛物线楔形梁的单元刚度矩阵。 相似文献
773.
A new watermarking algorithm of binary image is proposed.The complexity index of pixels is presented to reflect the change degree of pixels and to evaluate the modifiable degree of pixels.Firstly, in a small image block, the complexity index of"jumping-change"is calculated in vertical and horizontal direction.Secondly, the matrix of the complexity index is calculated by integrating the complexity index of pixels in two directions.Finally, the matrix of the complexity index is used to embed the watermark in binary images.Experimental results show that the proposed algorithm has a good performance. 相似文献
774.
Nie Wu 《船舶与海洋工程学报》2003,2(2):25-30
To find the difference in dynamic characteristics between conventional monohull ship and wave penetrating catamaran (WPC), a WPC was taken as an object; its dynamic characteristics were computed by transfer matrix method and finite element method respectively. According to the comparison of the nature frequency results and mode shape results, the fact that FEM method is more suitable to dynamic characteristics analysis of a WPC was pointed out, special features on dynamic characteristics of WPC were given, and some beneficial suggestions are proposed to optimize the strength of a WPC in design period. 相似文献
775.
776.
用影响矩阵考虑了桥梁在多点激振下的非线性地震响应,并利用Wilsom-θ法编制了相应的程序.该程序可用来计算非一致输入下的线性或非线性响应和一致输入下的线性或非线性响应.通过算例对以上四种情况进行了比较,结果表明多点激振效应和非线性作用对结构动力响应均有较大影响,不容忽视 相似文献
777.
为解决柴油发动机故障振动信号分析过程中的不稳定性和非线性,使用切片维格纳三谱来分析柴油机振动信号的时频分布,柴油机故障信号的切片维格纳三谱表明,每一种故障均具有各自的特征,从而为区分不同柴油机故障提供了信息依据. 相似文献
778.
Pei-Wei Lin Gang-Len Chang 《Transportation Research Part C: Emerging Technologies》2006,14(6):384-402
Most existing dynamic origin–destination (O–D) estimation approaches are grounded on the assumption that a reliable initial O–D set is available and traffic volume data from detectors are accurate. However, in most traffic systems, both types of critical information are either not available or subjected to some level of measurement errors such as traffic counts and speed measurement from sensors. To contend with those critical issues, this study presents two robust algorithms, one for estimation of an initial O–D set and the other for tackling the input measurement errors with an extended estimation algorithm. The core concept of the initial O–D estimation algorithm is to decompose the target network in a number of sub-networks based on proposed rules, and then execute the estimation of the initial O–D set iteratively with the observable information at the first time interval. To contend with the inevitable detector measurement error, this study proposes an interval-based estimation algorithm that converts each model input data as an interval with its boundaries being set based on some prior knowledge. The performance of both proposed algorithms has been tested with a simulated system, the I-95 freeway corridor between I-495 and I-695, and the results are quite promising. 相似文献
779.
4带正交小波系统的参数化和代数结构 总被引:1,自引:1,他引:0
给出了4带正交小波滤波器族对应多相矩阵完全分解形式,利用此结果,完成了一个滤波器设计程序,由此程序,不但可以给出一类4带小波滤波器族参数表示的形式,还可以用来刻划滤波器族代数结。 相似文献
780.
The simultaneous perturbation stochastic approximation (SPSA) algorithm has been used in the literature for the solution of the dynamic origin–destination (OD) estimation problem. Its main advantage is that it allows quite general formulations of the problem that can include a wide range of sensor measurements. While SPSA is relatively simple to implement, its performance depends on a set of parameters that need to be properly determined. As a result, especially in cases where the gradient of the objective function changes quickly, SPSA may not be as stable and even diverge. A modification of the SPSA algorithm, referred to as c-SPSA, is proposed which applies the simultaneous perturbation approximation of the gradient within a small number of carefully constructed “homogeneous” clusters one at a time, as opposed to all elements at once. The paper establishes the theoretical properties of the new algorithm with an upper bound for the bias of the gradient estimate and shows that it is lower than the corresponding SPSA bias. It also proposes a systematic approach, based on the k-means algorithm, to identify appropriate clusters. The performance of c-SPSA, with alternative implementation strategies, is evaluated in the context of estimating OD flows in an actual urban network. The results demonstrate the efficiency of the proposed c-SPSA algorithm in finding better OD estimates and achieve faster convergence and more robust performance compared to SPSA with fewer overall number of function evaluations. 相似文献