摘要:

A review and evaluation of graph theory approaches for their applicability to reliability analysis of water distribution networks is made. The procedures are examined in both a general sense and with respect to the networks previously reported in the literature. State enumeration, filtering, and heuristic procedures are considered. Most of the procedures were found to have computational requirements that make them inappropriate for use in water distribution analysis. A general procedure of assessing how far a particular network deviates from its maximum reliability for a given expenditure is suggested. A distinction between undirected and directed graphs is made in terms of techniques that can exploit either situation and in how portions of water distribution networks can be approximated by either case. Network transformation and inversion are also considered as a means of defining reliability and finding networks with maximum reliability. Recommendations are made as to how to combine various parts of the networks into sections, which can then be analysed by using procedures that best exploit the common features of the network in each section.

ISSN:0263-0257    

DOI:10.1080/02630258808970505

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

This paper presents an account of a research project concerned with the application of artificial intelligence techniques to structural design in civil engineering. INDEX is a rule-based system for the design of industrial buildings that is being developed at the University of Edinburgh. It has a blackboard architecture and its knowledge base is organized into a hierarchy of two levels. The main focus of this paper is to summarize the implementation aspects of one of its knowledge modules, ALTSEL which is responsible for the preliminary design. The organization of knowledge inside the ALTSEL module is briefly outlined using a number of representative rules from its sub-modules. The use of the Edinburgh PROLOG Blackboard Shell in the development of INDEX is also described briefly.

ISSN:0263-0257    

DOI:10.1080/02630258808970506

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A successive fuzzification procedure has been developed by extending the 'fuzzifier' concept introduced by Zadeh. This technique provides an efficient fuzzification procedure for cases where an entity is influenced by human and system uncertainty originating from different sources. In such cases, each source of uncertainty is given an individual fuzzifier, and a composite fuzzifier is created for the entity from the individual ones. A specific application is cited in the area of transportation engineering where the technique has been used to improve pavement distress surveys. The distress condition of a pavement is conventionally expressed by the Pavement Condition Rating (PCR) derived from subjective ratings for different types of pavement distress. The human based uncertainty involved in the rating of distress severity and extent can be incorporated in the PCR by expressing it as a fuzzy number. The usefulness of the new fuzzification technique in forming the 'fuzzy PCR' is illustrated.

ISSN:0263-0257    

DOI:10.1080/02630258808970507

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The three-parameter lognormal distribution is widely used in hydrology to fit maximum annual flood events. The method most commonly used to estimate the parameters and 7”-year flood event is the method of maximum likelihood. In this paper, Bayes estimates of the parameters and of the 7”-yearflood and their posterior variances of estimates are obtained by using Lindley's Bayesian approximation procedure. These estimates are then compared to estimates obtained by the method of maximum likelihood. Twelve flood series from all over Canada that are shown to be well-fitted by the three-parameter lognormal distribution are used as numerical examples. In all cases the posterior variances of the Bayes estimates of the 7”-year flood events are less than the corresponding variances of their maximum likelihood counterparts.

ISSN:0263-0257    

DOI:10.1080/02630258808970508

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Many decisions require the application of subjective judgment. Two methods of modelling such decision behaviour by using fuzzy set theory are considered here. Yager (1 978) uses a method based on a maximin criterion, while Tsukamoto and Terano (1975) base their method on multivalued logic operations. In this paper sets of decision maker's evaluation of decision problems are compared with each of the two fuzzy set evaluations. The ability of the fuzzy set methods to replicate decision behaviour is measured by the rank correlation between orderings of alternatives obtained from the decision makers and those obtained from the. methods. Analysis of the experiment indicated that for the sample used, the methods generated very few correlations that were significantly greater than zero. These results appear to contradict claims for the methods made in the literature.

ISSN:0263-0257    

DOI:10.1080/02630258808970509

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The use of probability for structural engineering applications has fallen into disfavour in recent years because of continuing debates about the modelling of human cognition, the assessment of marginal and conditional probabilities, the computational intractability of Bayesianism, and the so-called closed-world assumption. In this paper the validity of these arguments is examined and the use of the causal or Bayes network in estimating the reliability index for existing structures is proposed. The Bayes network was introduced in the artificial intelligence community as a method for propagating uncertainty through an inference network. Specifically, it is postulated that a structure can be modelled as a causal network

ISSN:0263-0257    

DOI:10.1080/02630258808970510

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

This paper demonstrates the use of a rule-based weighted rating system (RWRS) developed for improving the rating of concrete culverts. RWRS combines the qualitative rating based on a guideline commonly used by the Department of Transportation, the quantitative rating based on a regression model, and the inspector's own judgment on the culvert's rating. Weight on each rating is provided by the supervisor. A case study is presented to demonstrate the use of RWRS.

ISSN:0263-0257    

DOI:10.1080/02630258808970511

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A method of grey-level histogram threshold selection using fuzzy probability is reported. An image is treated as a set composed of two fuzzy subsets: ‘object’ and ‘background’. The grades of membership of grey levels in the ‘object’ subset are found with an experimentally determined membership function. The fuzzy probability that the ‘object’ points appear in an image is calculated from the membership function, and the frequency of occurrence of each grey level. This probability is equal to the area fraction of the objects in the image. Once the area fraction has been determined, the appropriate threshold can be selected. This method mimics the human process of locating boundaries of objects, and is especially useful for quantitative image analysis. It produces consistent thresholding with different users even when an image's histogram contains a broad. flat valley between its peaks.

ISSN:0263-0257    

DOI:10.1080/02630258808970512

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

ISSN:0263-0257    

DOI:10.1080/02630258808970513

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

ISSN:0263-0257    

DOI:10.1080/02630258808970515

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor