| publications-4541 |
article |
2002 |
Mounce, S. R. and Mounce, Steve R. and Day, Andrew J. and Day, Andrew J. and Wood, Alastair S. and Wood, Alastair S. and Khan, Asar and Khan, Asar and Widdop, Peter D. and Widdop, Peter D. and Machell, John and Machell, James |
A neural network approach to burst detection. |
Water Science and Technology |
10.2166/wst.2002.0595 |
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This paper describes how hydraulic and water quality data from a distribution network may be used to provide a more efficient leakage management capability for the water industry. The research presented concerns the application of artificial neural networks to the issue of detection and location of leakage in treated water distribution systems. An architecture for an Artificial Neural Network (ANN) based system is outlined. The neural network uses time series data produced by sensors to directly construct an empirical model for predication and classification of leaks. Results are presented using data from an experimental site in Yorkshire Water's Keighley distribution system. |
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| publications-4542 |
article |
1955 |
Simon, Herbert A. and Simon, Herbert A. |
A Behavioral Model of Rational Choice |
Quarterly Journal of Economics |
10.2307/1884852 |
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Introduction, 99. β€” I. Some general features of rational choice, 100.β€” II. The essential simplifications, 103. β€” III. Existence and uniqueness of solutions, 111. β€” IV. Further comments on dynamics, 113. β€” V. Conclusion, 114. β€” Appendix, 115. |
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| publications-4543 |
article |
1978 |
Nemhauser, George L. and Wolsey, Laurence A. and Fisher, Marshall L. |
An analysis of approximations for maximizing submodular set functions--I |
Mathematical Programming |
10.1007/bf01588971 |
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LetN be a finite set andz be a real-valued function defined on the set of subsets ofN that satisfies z(S)+z(T)źz(SźT)+z(SźT) for allS, T inN. Such a function is called submodular. We consider the problem maxSźN{a(S):|S|≤K,z(S) submodular}. Several hard combinatorial optimization problems can be posed in this framework. For example, the problem of finding a maximum weight independent set in a matroid, when the elements of the matroid are colored and the elements of the independent set can have no more thanK colors, is in this class. The uncapacitated location problem is a special case of this matroid optimization problem. We analyze greedy and local improvement heuristics and a linear programming relaxation for this problem. Our results are worst case bounds on the quality of the approximations. For example, whenz(S) is nondecreasing andz(0) = 0, we show that a "greedy" heuristic always produces a solution whose value is at least 1 ź[(K ź 1)/K]K times the optimal value. This bound can be achieved for eachK and has a limiting value of (e ź 1)/e, where e is the base of the natural logarithm. |
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| publications-4544 |
article |
1984 |
Jones, C. Vaughan and Jones, C. Vaughan and Morris, John R. and Morris, John R. |
Instrumental Price Estimates and Residential Water Demand |
Water Resources Research |
10.1029/wr020i002p00197 |
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Instrumental estimates of two price specifications, one motivated by the consumer decision problem given full information about rates and charges and the other an average price formulation, are developed to correct for measurement error when residential water sales are made at a schedule of rates, rather than at uniform prices. Annual water purchases of single-family residences are regressed on these instrumental price estimates, family income, and household size by ordinary least squares, based on a sample of 326 observations from metropolitan Denver, Colorado, for 1976. The resulting demand estimates are robust to the price concept specified, given proportional variation in all rates and charges, and are consistent with findings in the literature. The overall price elasticity estimates range between β’0.14 in a linear model to β’0.44 in a log-log model, while the estimated income elasticity varies between 0.40 and 0.55. |
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| publications-4545 |
article |
1992 |
Jadas-HΓ©cart, Alain and Jadas-Hecart, A. and Morer, A. El and Morer, A. El and Stitou, Mostafa and Stitou, M. and Bouillot, P. and Bouillot, P. and LΓ©gube, B. and Legube, Bernard |
Modelisation de la demande en chlore d'une eau traitee |
Water Research |
10.1016/0043-1354(92)90143-r |
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| publications-4546 |
article |
1994 |
Mackenzie, W R and Wr, Mac Kenzie and Hoxie, N J and Proctor, M E and Gradus and Blair, K. A. and Blair, K A and Peterson, Dan E. and Peterson, D E and Rose, J B and Jj, Kazmierczak and Addiss, David G. and Kr, Fox and Rose, Joan B. and Jb, Rose |
A Massive Outbreak in Milwaukee of Cryptosporidium Infection Transmitted through the Public Water Supply |
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10.1056/nejm199407213310304 |
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Early in the spring of 1993 there was a widespread outbreak of acute watery diarrhea among the residents of Milwaukee. |
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| publications-4547 |
article |
1996 |
Gupta, Rajesh and Gupta, Rajesh and Gupta, Rajesh and Bhave, Pramod R. and Bhave, Pramod R. |
Comparison of Methods for Predicting Deficient-Network Performance |
Journal of Water Resources Planning and Management |
10.1061/(asce)0733-9496(1996)122:3(214) |
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When a nodal demand is excessive as in a fire-flow condition or when a pump fails or a pipe breaks, a water distribution system (WDS) may temporarily become deficient and unable to satisfy all nodal demands. However, the prediction of the performance of a WDS under a temporarily-deficient condition is necessary for simulation-based reliability analysis and design of WDSs. Available methods for such prediction are reviewed herein. When the actual outlets are considered as demand nodes the methods which simultaneously consider the nodal flows and heads give fairly accurate and similar results. However, when the demands of secondary networks are assumed concentrated at the nodes of the primary WDSs, the prediction of the deficient-condition performance of a primary WDS is rather approximate. For reliability purposes, however, the method using parabolic head-discharge relationship (no flow at minimum head to required flow at desirable head), is the best for prediction of deficient-network performance. |
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| publications-4548 |
article |
1998 |
Xu, Chengchao and Xu, Chengchao and Goulter, I. C. and Goulter, Ian C. |
Probabilistic Model for Water Distribution Reliability |
Journal of Water Resources Planning and Management |
10.1061/(asce)0733-9496(1998)124:4(218) |
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A two-stage methodology for assessment of reliability of water distribution networks recognizing uncertainties in nodal demands, pipe capacity, reservoir/tank levels, and availability of system components is proposed. In the first stage, the probability distribution functions for nodal heads are derived from a linearized hydraulic model on the basis of known probability distribution functions of the nodal demands, pipe roughnesses, and reservoir/tank levels. The effects of nonlinearity in the network hydraulic model are accounted for in this step by partitioning the nodal demands into a number of categories or intervals. The probability of supply failure calculated in this first stage assumes that the system state or configuration is fixed, e.g., certain pipes and pumps are specified as being out of operation; that the pipe capacity varies randomly; and that demands vary around a specified level. The second step involves combining this probability with the probabilities of different system configurations and demand levels to generate the overall reliability measures for the whole system or a particular area of the system. |
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| publications-4549 |
article |
1999 |
Faloutsos, Michalis and Faloutsos, Michalis and Faloutsos, Petros and Faloutsos, Petros and Faloutsos, Christos and Faloutsos, Christos |
On power-law relationships of the Internet topology |
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10.1145/316188.316229 |
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Despite the apparent randomness of the Internet, we discover some surprisingly simple power-laws of the Internet topology. These power-laws hold for three snapshots of the Internet, between November 1997 and December 1998, despite a 45\% growth of its size during that period. We show that our power-laws fit the real data very well resulting in correlation coefficients of 96\% or higher.Our observations provide a novel perspective of the structure of the Internet. The power-laws describe concisely skewed distributions of graph properties such as the node outdegree. In addition, these power-laws can be used to estimate important parameters such as the average neighborhood size, and facilitate the design and the performance analysis of protocols. Furthermore, we can use them to generate and select realistic topologies for simulation purposes. |
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| publications-4550 |
article |
2003 |
Corral-Verdugo, VΔ±Μctor and Corral-Verdugo, Victor and Corral-Verdugo, Victor and Corral-Verdugo, Victor and Bechtel, Robert B. and Bechtel, Robert B. and Fraijo-Sing, Blanca and Fraijo-Sing, Blanca |
Environmental beliefs and water conservation: An empirical study |
Journal of Environmental Psychology |
10.1016/s0272-4944(02)00086-5 |
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