Browsing by Author "Zhou, Y."

Now showing 1 - 8 of 8
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    Automated Creation of District Metered Area Boundaries in Water Distribution Systems
    (American Society of Civil Engineers, 2012-04-03) Diao, Kegong; Zhou, Y.; Rauch, W.
    Accounting for water in a distribution system can be improved by dividing systems into smaller, metered zones. This paper proposes an approach that could create boundaries for district metered areas (DMA) automatically on the basis of the community structure of water distribution systems. Community structure—the gathering of vertices into communities such that there is a higher density of edges within communities than between them—is a common property of many complex systems. For verification, the method was tested on a real-world distribution system, and the result was compared with a manually designed DMA layout. Although further improvements are necessary, because the achieved community structure is in excellent agreement with the zoning plan in reality, this approach is a new addition to the number of automated methods aimed at complementing and eventually substituting the empirical trial-and-error approach.
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    Battle of the Water Calibration Networks
    (American Society of Civil Engineers, 2011) Ostfeld, A.; Salomons, E.; Ormsbee, L.; Uber, J.; Bros, C.; Kalungi, P.; Burd, R.; Zazula-Coetzee, B.; Belrain, T.; Kang, D.; Lansey, K.; Shen, H.; McBean, E.; Yi Wu, Z.; Walski, T.; Alvisi, S.; Franchini, M.; Johnson, J.; Ghimire, S.; Barkdoll, B.; Koppel, T.; Vassiljev, A.; Kim, J.; Chung, G.; Yoo, D.; Diao, Kegong; Zhou, Y.; Li, J.; Liu, Z.; Chang, K.; Gao, J.; Qu, S.; Yuan, Y.; Prasad, T.; Laucelli, D.; Vamvakeridou Lyroudia, L.; Kapelan, Z.; Savic, D.; Berardi, L.; Barbaro, G.; Giustolisi, O.; Asadzadeh, M.; Tolson, B.; McKillop, R.
    Calibration is a process of comparing model results with field data and making the appropriate adjustments so that both results agree. Calibration methods can involve formal optimization methods or manual methods in which the modeler informally examines alternative model parameters. The development of a calibration framework typically involves the following: (1) definition of the model variables, coefficients, and equations; (2) selection of an objective function to measure the quality of the calibration; (3) selection of the set of data to be used for the calibration process; and (4) selection of an optimization/manual scheme for altering the coefficient values in the direction of reducing the objective function. Hydraulic calibration usually involves the modification of system demands, fine-tuning the roughness values of pipes, altering pump operation characteristics, and adjusting other model attributes that affect simulation results, in particular those that have significant uncertainty associated with their values. From the previous steps, it is clear that model calibration is neither unique nor a straightforward technical task. The success of a calibration process depends on the modeler’s experience and intuition, as well as on the mathematical model and procedures adopted for the calibration process. This paper provides a summary of the Battle of the Water Calibration Networks (BWCN), the goal of which was to objectively compare the solutions of different approaches to the calibration of water distribution systems through application to a real water distribution system. Fourteen teams from academia, water utilities, and private consultants participated. The BWCN outcomes were presented and assessed at the 12th Water Distribution Systems Analysis conference in Tucson, Arizona, in September 2010. This manuscript summarizes the BWCN exercise and suggests future research directions for the calibration of water distribution systems.
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    Battle of the Water Calibration Networks (BWCN): A Component Status Changes Oriented Calibration Method for Zonal Management Water Distribution Networks
    (American Society of Civil Engineers, 2010) Diao, Kegong; Zhou, Y.; Li, J.; Liu, Z.
    Calibration is the prerequisite for a hydraulic model of water distribution system to be utilized in practice. Given the case-specific feature of model calibration, this paper introduces a method that is oriented by component status changes in zonal management water distribution systems. This method is specified for zonal systems in which the operation of every zone could be framed to a stable periodical performance based on control routines, which would not be affected substantially by condition variation in other zones or the effects could be deduced. The principle of this methodology is to identify scenarios with status changes of several crucial components in water distribution networks which give rise to significant effects on hydraulic performance at least in a certain region of the water distribution system. After, those scenarios could be used for calibration of both pipe roughness and demand pattern multipliers with measured data (e.g. SCADA data) as constraints. For verification, this methodology is applied to the case study of "The Battle of the Water Calibration Networks (BWCN)" based on understanding of the system features and behaviors according to available data and corresponding statistical analysis. The final outcomes demonstrate that this approach could reach acceptable results more efficiently if characteristics of the studied system could be well identified.
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    Case Study of Urban Water Distribution Networks Districting Management Based on Water Leakage Control
    (American Society of Civil Engineers, 2009) Wu, S.; Li, Xiaohong; Tang, S.; Zhou, Y.; Diao, Kegong
    Globally, water demand is rising and resources are diminishing. Most of the world's water systems have been highly successful in delivering high-quality water to large populations. However, most of these systems also incur a notable amount of loss in their operations. Water loss from the water supply system has long been a feature of operations management, even in the countries with a well-developed infrastructure and good operating practices. There is no doubt that the sustainable management of water supply system is a challenge for the whole world. Water leakage cannot be completely avoided, but they can be managed so that they remain within economic limits. Some new models of water loss management have been developed recently. As the technical and economic levels varied in different cities, the best practice using in their water supply systems leakage control should be taken suited to local conditions. In this case study a water loss management strategy for a large city in north China was suggested and the technological means for the optimized its managing were provided. The basic principles for structuring district meter areas in this water supply system according its features were developed. The GIS as the tool was used during the study. Based on the field test, the water balance calculations of three DMAs were carried out, and using the fuzzy appraisal method to evaluated their degree of water losses.
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    Genetic approaches to sustainable pest management in sugar beet (Beta vulgaris).
    (Association of Applied Biologists, 2008) Zhang, C. L.; Xu, D.-C.; Jiang, X-C; Zhou, Y.; Zhang, C-X; Cui, J.; Chen, D. F.; Fowler, Mark R.; Elliott, Malcolm C.; Scott, Nigel W.; Dewar, A. M.; Slater, A.
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    Multiobjective Sparse Ensemble Learning by Means of Evolutionary Algorithms
    (Elsevier, 2018-05-31) Zhao, Jiaqi; Jiao, Licheng; Xia, Shixong; Basto-Fernandes, V.; Yevseyeva, Iryna; Zhou, Y.; Emmerich, Michael T. M.
    Ensemble learning can improve the performance of individual classifiers by combining their decisions. The sparseness of ensemble learning has attracted much attention in recent years. In this paper, a novel multiobjective sparse ensemble learning (MOSEL) model is proposed. Firstly, to describe the ensemble classifiers more precisely the detection error trade-off (DET) curve is taken into consideration. The sparsity ratio (sr) is treated as the third objective to be minimized, in addition to false positive rate (fpr) and false negative rate (fnr) minimization. The MOSEL turns out to be augmented DET (ADET) convex hull maximization problem. Secondly, several evolutionary multiobjective algorithms are exploited to find sparse ensemble classifiers with strong performance. The relationship between the sparsity and the performance of ensemble classifiers on the ADET space is explained. Thirdly, an adaptive MOSEL classifiers selection method is designed to select the most suitable ensemble classifiers for a given dataset. The proposed MOSEL method is applied to well-known MNIST datasets and a real-world remote sensing image change detection problem, and several datasets are used to test the performance of the method on this problem. Experimental results based on both MNIST datasets and remote sensing image change detection show that MOSEL performs significantly better than conventional ensemble learning methods.
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    Software Evolution for Evolving China
    (Springer Nature, 2008) Yang, Hongji; Chen, Feng; Zhou, Y.; Zhao, M.; Wang, Y.; Guo, H.
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    Speedup of water distribution simulation by domain decomposition
    (Elsevier, 2013-10-24) Diao, Kegong; Wang, Z.; Burger, G.; Chen, C.; Rauch, W.; Zhou, Y.
    The Schur complement domain decomposition method is used for solution of large linear systems. The algorithm is based on the subdivision of the domain into smaller ones and the solution of those sub-domains independently. Regarding water distribution systems modeling, the hydraulic simulation could be formulated as a sequence of systems of linear equations. Therefore, this paper utilizes the domain decomposition method to accelerate the simulation process further. The method is evaluated using a large scale real-world system with 63,616 junctions and 64,200 pipes as case study. The case study shows that the methodology could improve the performance of hydraulic simulation app. by a factor of 8 without losing accuracy at a suitable level of domain decomposition. Although the optimal level of decomposition is case specific, considerable speedup might still be achievable by decomposing a large system into only a few subsystems.