摘要:

Comparing transportation facilities (i.e., intersections and road sections) in terms of traffic accident occurrences is among the interests of most traffic safety analysts. This paper uses statistical techniques as appropriate tools for performing such analyses. Traditionally, traffic accidents are represented as occurrences of events per certain unit, such as time and vehicle miles; this representation is consistent with Poisson nature. In this paper, Poisson distribution is used to describe the distribution of traffic accident occurrences. The objective is to develop a test statistic in order to enable traffic analysts to compare traffic accident rates in various transportation facilities. The obtained test statistic is simple and requires minimal data to perform the comparison analysis.

ISSN:0263-0257    

DOI:10.1080/02630259308970122

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Explicit algorithms have been developed for use in water quality studies and management of distribution networks with sources of dissimilar quality. The proposed algorithms can be effectively used for directly determining a variety of blended water quality parameters for a given set of network loading and operational conditions. The parameters include the spatial distribution of constituent concentrations, the flow influence characteristics of supply sources, and the water age distribution throughout the system. The developed algorithms are formulated analytically from mass balance relationships as contingent linear boundary value problems in conjunction with a topological sorting methodology. The resulting formulations yield coefficient matrices, of order equal to the number of junction nodes, that are triangular and positive definite. The parameter solutions sought are, thus, derived through a direct application of a one step substitution process. The proposed algorithms are both robust and efficient, and guaranteed to yield mathematically consistent solutions. Moreover, the algorithms are simple to understand and implement, and are well suited to the needs of those practicing engineers who wish to write and run their own programs. Two example applications are presented. Enhancement of distribution system water quality management is a principal benefit of the algorithms.

ISSN:0263-0257    

DOI:10.1080/02630259308970123

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Secondary sedimentation plays a fundamental role in biological wastewater treatment processes where activated sludges are used. In addition to water clarification and sludge compaction, the secondary settler is used as a dynamic storage for the biomass in the system. This role is important for process control since displacing sludge from the settler to the oxidation tank is the main way to adjust process conditions in the short time-scale. The scope of this paper is to present a model for the time-varying behaviour of the total activated mass, taking into account the coupling between the aeration tank and the secondary settler. Numerical simulations show that the model can reproduce any relevant feature of the real system and can be used in control strategy design for sludge management.

ISSN:0263-0257    

DOI:10.1080/02630259308970124

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The preliminary design of a query system for the computer simulation of physical processes is presented. Most engineering simulations produce vast amounts of quantitative data. It often requires special training to interpret the data and many of them may not be directly relevant to a particular decision. Human beings usually find qualitative explanations easier to absorb than large quantities of detail. The query system described in the paper is a preliminary to the production of an interrogation system which can provide both qualitative answers and explanations. In the first part of the system, natural language queries are transformed into standard query types using a neural net. In the second part qualitative replies are formed from neural nets which are trained by data from the simulation. An object oriented hierarchy which facilitates the mappings of quantitative data into qualitative attributes is presented. The development of a more detailed and sophisticated explanation system is also discussed.

ISSN:0263-0257    

DOI:10.1080/02630259308970125

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A method for designing flexible water distribution networks is presented. Flexibility is the extent to and ease with which a distribution network can cope with eventualities for which it was not specifically designed. This paper shows that some flexibility can be achieved by maximizing the entropy of the flows. A sample network is considered and designs for various levels of entropy are examined. Several indices including energy and head loss are used to compare the designs. The results suggest that an entropy constraint can reduce the tendency towards implicitly branched configurations characteristic of cost minimization models. A striking feature of the proposed methodology is its apparent ability to produce resilient designs without a substantial increase in cost. The results further highlight some implications for connectivity-based reliability measures and core tree approaches to layout optimization.

ISSN:0263-0257    

DOI:10.1080/02630259308970126

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A method for calculating the probability of very low pressures at nodes within a pressurised pipe network subject to a set of independent nodal demands with known probability distributions is presented. The method is applicable to tree networks, and has been verified by checking against a Monte-Carlo simulation.

ISSN:0263-0257    

DOI:10.1080/02630259308970127

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:0263-0257    

DOI:10.1080/02630259308970128

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor