1,720,982 research outputs found
A multi-utility and dynamic approach for the upgrade of an aged water distribution network
No full textWater Distribution Networks (WDNs) along with other utilities are among the most important assets in every industrialized society. The rehabilitation and upgrade of WDNs refer to a very complex and multi-criteria problem which needs a comprehensive decision support system providing optimal renewal plans for the asset managers. There is a multitude of real-world problems faced with such activities. In this regard, this study aims to propose a novel method to cope with three practical challenges in WDNs rehabilitation activities including 1-budget limitation, 2-hydraulic deficiency and 3-correlation of WDNs with other infrastructures bringing the risk of cascading failures to a multiplex network. This results in a multi-objective optimization problem with three objectives which are cost, hydraulic and decoupled reliabilities. The problem is solved dynamically with the contribution of a nature inspired optimization algorithm, the Non-Dominated Sorting Genetic Algorithm (NSGA-II). The method is applied to a deteriorated water pipe network, and the results are compared with the ones obtained only by the consideration of two objectives, costs and hydraulic reliability showing how much the objectives are conflicted with each other
Optimal rehabilitation planning for aged water distribution mains considering cascading failures of interdependent infrastructure systems
No full textWater distribution networks (WDNs) with other infrastructures constitute a complex and interdependent multi-utility system. Considering interdependencies between WDNs and other urban infrastructures, this work proposes WDN intervention planning using a dynamic multi-utility approach to tackle the challenges of pressure deficits and cascading failures by the decoupling of different infrastructure systems. For this purpose, the study develops reliability indices representing the hydraulic and decoupled statuses of WDNs with neighbor infrastructures; the hydraulic reliability represents the robustness of the network against the water pressure deficit, and decoupling reliability represents the extent to which WDN elements are decoupled from other assets elements. A multi-objective optimization algorithm is employed to develop rehabilitation strategies by introducing three approaches for WDN upgrade following a phased design and construction method. Evaluating intervention plans based on construction cost, reliability and cascade effects shows that, under budget limitation conditions, decoupling a WDN could significantly save the cascade cost such that 1% improvement in the decoupling reliability brings about 157.42 billion Rials cascade cost saving to asset managers. On the other hand, the decoupled network is weak against hydraulic reliability, which could make it by far less resilient network than the coupled network with around 75% hydraulic reliability difference
Multistep Approach for the Rehabilitation of a Deteriorated Water Distribution Network Operating Intermittently
No full textThis paper presents a multistep approach for the rehabilitation of the deteriorated and intermittently operated water distribution network (WDN) proposed by the organizers of the joint WDSA CCWI 2022 Conference as the case study for the battle. In the rehabilitation, various interventions are considered with the final objective to improve the operation of the WDN in terms of hours of service to users and total volume supplied to meet their demands, including pipe and device (pump/valve) replacements, leak repairs, and extended period optimization of device settings. The multistep approach is proposed to tame the extremely large space of decision variables and includes the following steps: (1) subdivision of the WDN into main chain and district metered areas (DMAs), rehabilitation of (2) the main chain and (3) the DMAs while looking at the final year of the rehabilitation, (4) sequencing of the interventions, and (5) optimization of device settings. Compared to other methodologies in the literature, the main novelty and merit of the present approach consist of the way the rehabilitation interventions are selected, i.e., by using engineering judgment and by maximizing the flow capacity of the main chain and the global resilience-failure index in the DMAs
Ensemble Evaluation and Member Selection of Regional Climate Models for Impact Models Assessment
No full textClimate change increasingly is affecting every aspect of human life on the earth. Many regional climate models (RCMs) have so far been developed to carefully assess this important phenomenon on specific regions. In this study, ten RCMs captured from the European Coordinated Downscaling Experiment (EURO CORDEX) platform are evaluated on the river Chiese catchment located in the northeast of Italy. The models’ ensembles are assessed in terms of the uncertainty and error calculated through different statistical and error indices. The uncertainties are investigated in terms of signal (increase, decrease, or neutral changes in the variables) and value uncertainties. Together with the spatial analysis of the data over the catchment, the weighted averaged values are used for the models’ evaluations and data projections. Using weighted catchment variables, climate change impacts are assessed on 10 different hydro-climatological variables showing the changes in the temperature, precipitation, rainfall events’ features, and the hydrological variables of the Chiese catchment between historical (1991–2000) and future (2071–2080) decades under RCP (Representative Concentration Path for increasing greenhouse gas emissions) scenario 4.5. The results show that, even though the multi-model ensemble mean (MMEM) could cover the outputs’ uncertainty of the models, it increases the error of the outputs. On the other hand, the RCM with the least error could cause high signal and value uncertainties for the results. Hence, different multi-model subsets of ensembles (MMEM-s) of 10 RCMs are obtained through a proposed algorithm for different impact models’ calculations and projections, making tradeoffs between two important shortcomings of model outputs, which are error and uncertainty. The single model (SM) and multi-model (MM) outputs imply that catchment warming is obvious in all cases and, therefore, evapotranspiration will be intensified in the future where there are about 1.28% and 6% value uncertainties for monthly temperature increase and the decadal relative balance of evapotranspiration, respectively. While rainfall events feature higher intensity and shorter duration in the SM, there are no significant differences for the mentioned features in the MM, showing high signal uncertainties in this regard. The unchanged catchment rainfall events’ depth can be observed in two SM and MM approaches, implying good signal certainty for the depth feature trend; there is still high uncertainty about the depth values. As a result of climate change, the percolation component change is negligible, with low signal and value uncertainties, while decadal evapotranspiration and discharge uncertainties show the same signal and value. While extreme events and their anomalous outcomes direct the uncertainties in rainfall events’ features’ values towards zero, they remain critical for yearly maximum catchment discharge in 2071–2080 as the highest value uncertainty is observed for this variable
Optimized phased planning for dynamic rehabilitation of integrated municipal infrastructure
No full textPhased planning for municipal infrastructure is based on the time-dependent status of multiple networks, which is in contrast to the traditional approach, where one-phase construction and a single status are considered for planning system activities. This study integrates and optimizes the corridor-wise intervention planning of water, sewer, and road networks where the number of equally long phases and intervention decisions are among the decision variables showing the extent to which phase number optimization can impact the cost and coordination of the interventions in interdependent systems. Optimizing the phase number for municipal infrastructure optimization within an evolutionary algorithm is a challenging task due to the evolutionary recombination between numerous planning solutions with different decision variable lengths. A multi-phase design and construction approach is developed for the rehabilitation of the system in a real case study in Montreal, Canada. The study involves 20 corridors in which a street section is co-located with water and sewer pipes. A metaheuristic single-objective optimization engine is employed to minimize the total net present value of intervention plan costs for the whole integrated system. The results show that phased optimization could bring about a 25% cost saving for the rehabilitation master plan and coordinated multi-systems intervention activities
Asset Management Perspective in Long-Term Rehabilitation of Aged Water Distribution Networks
No full textTraditionally, the rehabilitation and/or upgrade of water distribution networks (WDNs) are performed with only one perspective with the aim to bring a long-term reliable system to supply the consumers. On the contrary, such systems are not isolated but interdependent with other adjacent infrastructure and networks, including urban drainage and road networks. This means that the performance and rehabilitation schemes of different networks could have direct or indirect impacts on each other, requiring coordinated infrastructure management strategies to be adopted. For example, the pipe replacement in a WDN could interrupt a traffic flow on a co-located street, or a flood could prevent water utility staff from accessing the section of a WDN pipe, thus making maintenance infeasible. Furthermore, if different infrastructural activities (operation, maintenance, rehabilitation, and upgrading) are not planned in an integrated way, there will be a high risk of redundant activities in the same location, imposing unnecessary costs. This implies that in the decision-making process for the rehabilitation of a WDN, the status and plans of other correlated urban systems should be considered simultaneously. In this study, the single and multi-utility rehabilitation of a simplified real-world WDN are dynamically planned, as a part of asset management process, with the aid of a multiobjective optimization engine in which the objectives are utility practice cost and outcome reliability measures. Then the results are compared and discussed in terms of the pros and cons of the two mentioned approaches
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Stationary vs non-stationary modelling of flood frequency distribution across northwest England
Full text linkExtraordinary flood events occurred recently in northwest England, with several severe floods in Cumbria, Lancashire and the Manchester area in 2004, 2009 and 2015. These clustered extraordinary events have raised the question of whether any changes in the magnitude and frequency of river flows in the region can be detected. For this purpose, the annual maximum series of 39 river gauging stations in the study area are analysed. In particular, non-stationary models that include time, annual rainfall and annual temperature as predictors are investigated. Most records demonstrate a marked non-stationary behaviour and an increase of up to 75% in flood quantile estimates during the study period. Annual rainfall explains the largest proportion of variability in the peak flow series relative to other predictors considered in our study, providing practitioners with a useful framework for updating flood quantile estimates based on the dynamics of this highly accessible and informative climate indicator
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