| publications-4131 |
article |
2009 |
Irwin, Elena G. and Irwin, Elena G. and Jayaprakash, C. and Jayaprakash, Ciriyam and Munroe, Darla K. and Munroe, Darla K. |
Towards a comprehensive framework for modeling urban spatial dynamics |
Landscape Ecology |
10.1007/s10980-009-9353-9 |
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The increasing availability of spatial micro data offers new potential for understanding the micro foundations of urban spatial dynamics. However, because urban systems are complex, induction alone is insufficient. Nonlinearities and path dependence imply that qualitatively new dynamics can emerge due to stochastic shocks or threshold effects. Given the policy needs for managing urban growth and decline and the growing desire for sustainable urban forms, models must be able not only to explain empirical regularities, but also characterize system-level dynamics and assess the plausible range of outcomes under alternative scenarios. Towards this end, we discuss a comprehensive modeling approach that is comprised of bottom-up and top-down models in which both inductive and deductive approaches are used to describe and explain urban spatial dynamics. We propose that this comprehensive modeling approach consists of three iterative tasks: (1) identify empirical regularities in the spatial pattern dynamics of key meso and macro variables; (2) explain these regularities with process-based micro models that link individual behavior to the emergence of meso and macro dynamics; and (3) determine the systems dynamical equations that characterize the relationships between micro processes and meso and macro pattern dynamics. Along the way, we also clarify types of complexity (input and output) and discuss dimensions of complexity (spatial, temporal, and behavioral). While no one to date has achieved this kind of comprehensive modeling, meaningful progress has been made in characterizing and explaining urban spatial dynamics. We highlight examples of this work from the recent literature and conclude with a discussion of key challenges. |
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| publications-4132 |
article |
2013 |
Diao, Kegong and Rauch, Wolfgang |
Controllability analysis as a pre-selection method for sensor placement in water distribution systems |
Water Research |
10.1016/j.watres.2013.07.026 |
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| publications-4133 |
article |
2012 |
Aisopou, Angeliki and Aisopou, Angeliki and Stoianov, Ivan and Stoianov, Ivan and Graham, Nigel and Graham, Nigel |
In-pipe water quality monitoring in water supply systems under steady and unsteady state flow conditions: A quantitative assessment |
Water Research |
10.1016/j.watres.2011.10.058 |
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| publications-4134 |
article |
2014 |
Yang, Xueyao and Boccelli, Dominic L. |
Bayesian Approach for Real-Time Probabilistic Contamination Source Identification |
Journal of Water Resources Planning and Management |
10.1061/(asce)wr.1943-5452.0000381 |
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AbstractDrinking water distribution system models have been increasingly utilized in the development and implementation of contaminant warning systems. This study proposes a Bayesian approach for probabilistic contamination source identification using a beta-binomial conjugate pair framework to identify contaminant source locations and times and compares the performance of this algorithm to previous work based on a Bayes’ rule approach. The proposed algorithm is capable of directly assigning a probability to a potential source location and updating the probability through the use of a backtracking algorithm and Bayesian statistics. The evaluation of the performance associated with the two algorithms was conducted by a simple comparison, as well as a simulation study in terms of a conservative chemical intrusion event through both a small skeletonized network and a large all-pipe distribution system network. Results from the simple comparison showed that the beta-binomial approach was more responsive to ch... |
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| publications-4135 |
article |
2009 |
Ho, Cheng-I and Ho, Cheng-I and Lin, Minβ€Der and Lin, Min-Der and Lin, Min-Der and Lo, Shangβ€Lien and Lo, Shang-Lien and Lo, Shang-Lien |
Prioritizing pipe replacement in a water distribution system using a seismic-based artificial neural network model. |
Environmental Engineering Science |
10.1089/ees.2008.0057 |
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Abstract This work focused on developing an approach for prioritizing the order of pipe replacement in a water distribution system (WDS) using a seismic-based artificial neural network (ANN). The qualified earthquake data obtained from the Taiwan Water Corporation Leakage Repair Management System (TWC-LRMS) were classified to build the model that was analyzed by both backward propagation network (BPN) and radial basis function network (RBFN). Pipe diameter, pipe material, and the number of monthly magnitude-3+ earthquakes provide the input parameters of the seismic-based ANN model for anticipating the priority of pipe replacement. The WDS of Yilan County, which frequently suffers from earthquakes in northeastern Taiwan, was used as the object of the case study. A comparison of the accuracy and reliability of the prediction model between BPN and RBFN demonstrated that RBFN outperformed BPN. The seismic-based ANN model developed in this work is streamlined for establishing a priority project of pipe replace... |
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| publications-4136 |
article |
2001 |
Danon-Schaffer, Monica N. and Danon-Schaffer, Monica N. |
Walkerton's Contaminated Water Supply System: A Forensic Approach to Identifying the Source |
Environmental Forensics |
10.1006/enfo.2001.0054 |
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In May 2000 an investigation of a contaminated water distribution system in the town of Walkerton, Ontario, was performed by the Bruce-Grey-Owen Sound Health Unit (BGOSHU), with the assistance of Health Canada and the Ontario Ministry of Health and Long-Term Care. The purpose of the investigation was to determine the scope, likely cause and contributing factors of an Escherichia coli 0157:H7 outbreak. This investigation-represented the first documented outbreak of E. coli 0157:H7 associated with a treated municipal water supply in Canada and the largest multi-bacterial waterborne outbreak in Canada. The investigation proceeded on an expedited basis to determine the extent of damages to the water supply system. Environmental forensic techniques were incorporated into hydrogeological studies, environmental transport assessment, genetic characterization, and fate and transport of contaminants. The probable sources of bacteria contamination included the use of cast-iron pipes, the thickness and concentration of bio-film sediment and mineral, the infiltration of contaminated surface runoff due to heavy rain or flooding, flow velocity related to the diameter of the pipe, and/or surface water. |
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| publications-4137 |
article |
2014 |
Oliker, Nurit and Oliker, Nurit and Ostfeld, Avi and Ostfeld, Avi |
Minimum volume ellipsoid classification model for contamination event detection in water distribution systems |
Environmental Modelling and Software |
10.1016/j.envsoft.2014.03.011 |
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| publications-4138 |
article |
2010 |
Weickgenannt, Martin and Kapelan, Zoran and Blokker, Mirjam and Savic, Dragan |
Risk-Based Sensor Placement for Contaminant Detection in Water Distribution Systems |
Journal of Water Resources Planning and Management |
10.1061/(asce)wr.1943-5452.0000073 |
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A method for optimizing sensor locations to effectively and efficiently detect contamination in a water distribution network is presented here. The problem is formulated and solved as a twin-objective optimization problem with the objectives being the minimization of the number of sensors and minimization of the risk of contamination. Unlike past approaches, the risk of contamination is explicitly evaluated as the product of the likelihood that a set of sensors fails to detect contaminant intrusion and the consequence of that failure (expressed as volume of polluted water consumed prior to detection). A novel importance-based sampling method is developed and used to effectively determine the relative importance of contamination events, thus reducing the overall computation time. The above problem is solved by using the nondominated sorting genetic algorithm II. The methodology is tested on a case study involving the water distribution system of Almelo (The Netherlands) and the potential intrusion of E. co... |
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| publications-4139 |
article |
2001 |
Bourgeois, Wilfrid and Bourgeois, W. and Burgess, J.E. and Burgess, J.E. and Stuetz, Richard M. and Stuetz, Richard M. |
Onβ€line monitoring of wastewater quality: a review |
Journal of Chemical Technology & Biotechnology |
10.1002/jctb.393 |
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Real-time monitoring of wastewater quality remains an unresolved problem to the wastewater treatment industry. In order to comply with increasingly stringent environmental regulations, plant operators as well as instrument manufacturers have expressed the need for new standards and improved comparability and reliability of existing techniques. A review of currently available methods for monitoring global organic parameters (BOD, COD, TOC) is given. The study reviews both existing standard techniques and new innovative technologies with the focus on the sensors' potential for on-line and real-time monitoring and control. Current developments of biosensors, optical sensors and sensor arrays as well as virtual sensors for the monitoring of wastewater organic load are presented and the interests and limitations of these techniques with respect to their application to the wastewater monitoring are discussed. Β© 2001 Society of Chemical Industry |
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| publications-4140 |
article |
2000 |
Sakarya, A. Burcu Altan and Mays, Larry W. |
Optimal Operation of Water Distribution Pumps Considering Water Quality |
Journal of Water Resources Planning and Management |
10.1061/(asce)0733-9496(2000)126:4(210) |
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A new methodology has been developed for determining the optimal operation of water distribution system pumps with water quality considerations. The methodology is based upon describing the operation as a discrete time optimal scheduling problem that can be used to determine the optimal operation schedules of the pumps in distribution systems. The solution methodology is based upon a mathematical programming approach resulting in a large-scale nonlinear programming problem that cannot be solved using existing nonlinear codes. The solution of the optimization problem is obtained by interfacing a hydraulic and water quality simulation code, EPANET, with a nonlinear optimization code, GRG2. Bound constraints on the state variables are incorporated into the objective function using the augmented Lagrangian penalty method. Three objective functions were used in the model to minimize (1) the deviations of actual substance concentrations from desired concentration values; (2) the total pump duration times; or (3... |
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