小波分解求取含噪混沌时间序列的关联维数

关联维数是一个混沌时间序列分析中很重要的参数,在分析了噪声对关联维数求取的影响后,提出了一种应用小波分解求取含噪混沌时间序列关联维数的方法,数值试验证实了我们这种方法的正确性与可行性.     

A graphical approach to obtaining confidence limits of Cpk

The process capability index C_pk has been widely used as a process performance measure. In practice this index is estimated using sample data. Hence it is of great interest to obtain confidence limits for the actual index given a sample estimate. In this paper we depict graphically the relationship between process potential index (C_p), process shift index (k) and percentage non-conforming (p). Based on the monotone properties of the relationship, we derive two-sided confidence limits for k and C_pk under two different scenarios. These two limits are combined using the Bonferroni inequality to generate a third type of confidence limit. The performance of these limits of C_pk in terms of their coverage probability and average width is evaluated by simulation. The most suitable type of confidence limit for each specific range of k is then determined. The usage of these confidence limits is illustrated via examples. Finally a performance comparison is done between the proposed confidence limits and three non-parametric bootstrap confidence limits. The results show that the proposed method consistently gives the smallest width and yet provides the intended coverage probability. © 1997 John Wiley & Sons, Ltd.     

一种新的通用概念层次编码方法

概念层次是目前数据挖掘和知识发现的前沿性方法。为了把概念层次用于数据挖掘,需要解决如何从现有数据集自动生成概念层次,如何存储和处理网状概念层次结构及如何提高概念层次结构的搜索效率等问题。文章提出适用于任何数据挖掘功能的通用编码方法——基于层次域的概念层次实数编码法,该方法有效地解决了概念层次的存储和检索问题,并在微机电系统领域进行了与典型算法的对比分析。     

A theoretical study of fault coupling

Fault coupling is the phenomenon whereby a test set is able to detect faults when they occur in isolation, but fails to do so when they occur in combination. It is widely regarded as a nuisance in fault‐based approaches to software testing, which focus on the detection of single faults and normally neglect multiple faults. This paper presents a theoretical study of fault coupling, based on a simple model of fault‐based testing. This provides for the presence of two faults that interact with each other and thus includes the possibility of fault coupling between them. The model is analysed mathematically, the conclusion reached being that fault coupling only occurs infrequently. This result provides support for current approaches to fault‐based testing, but it is not quite enough to conclude that they are thereby validated. In effect, the paper generalizes the results of a previous paper that dealt with the restricted case where the functions underlying programs are bijective as well as finite. The restriction that functions be bijective is lifted here, but they are still required to be finite. Though the same theoretical framework is used in both cases, and more or less the same results are obtained, the techniques employed to arrive at the results in the general case are quite different. Copyright © 2000 John Wiley & Sons, Ltd.     

Secret and public key image watermarking schemes for imageauthentication and ownership verification

We describe a watermarking scheme for ownership verification and authentication. Depending on the desire of the user, the watermark can be either visible or invisible. The scheme can detect any modification made to the image and indicate the specific locations that have been modified. If the correct key is specified in the watermark extraction procedure, then an output image is returned showing a proper watermark, indicating the image is authentic and has not been changed since the insertion of the watermark. Any modification would be reflected in a corresponding error in the watermark. If the key is incorrect, or if the image was not watermarked, or if the watermarked image is cropped, the watermark extraction algorithm will return an image that resembles random noise. Since it requires a user key during both the insertion and the extraction procedures, it is not possible for an unauthorized user to insert a new watermark or alter the existing watermark so that the resulting image will pass the test. We present secret key and public key versions of the technique.     

Path entropy method for multiple-source water distribution networks

Over the past decade, one of the key research areas for water distribution networks has been the quantification of network reliability. An interesting approach in this research topic is the use of informational entropy as a surrogate measure for the reliability of water distribution network. Research on water distribution network entropy has progressed to the stage where practical applications are possible, but the actual meaning of the network entropy has never been fully elucidated. Recently, an alternative approach to calculate network entropy was proposed, which was termed the path entropy method (PEM). This alternative method was shown to be useful for the case of single-source water distribution networks. The purpose of this article is to explore the use of the PEM on multiple-source networks. A two-source and two-demand water distribution network is analysed to gain insight into the differences between single-source and multiple-source networks in terms of maximum-entropy flow distribution. This leads to the formal proof of the principle governing maximum-entropy flow ratios in multiple-source water distribution networks.