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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Analysis, modelling and optimal control of water supply and distribution systems

Chen, Yue-Chun January 1989 (has links)
This thesis is concerned with the developments of analysis, modelling and optimization techniques and computer program algorithms, with the ultimate aim of control of water supply and distribution systems to lead to overall optimal operation. Typical system features and operational conditions are analyzed, and the requirements for the overall objective are examined, to determine an overall control strategy which is subsequently developed and tested on real systems throughout this thesis. As a prerequisite, short-term water demand forecasting is extensively studied by employing time series analysis. Special consideration is given to improving the forecasting accuracy of the method and its on-line implementation. In order to speed up the solution time of optimal system operation, simplified system models -- namely, piecewise macroscopic model and equivalent network model -- are developed respectively. Then by employing the piecewise macroscopic model, a nonlinear programming method is developed to cater for the optimal operation of a class of multi-source systems without significant storage. The optimal operation policy obtained by this method is realized at two levels: the first level calculates the optimized apportioning of water to be delivered by different sources; the second level decides the least cost pump schedules to supply the optimized apportioning of water. Based on the equivalent network model, a linear programming method is developed for optimization of a class of multi-source, multi-reservoir systems with a mixture of fixed speed pumps and variable speed and/or variable throttle pumps. This method yields directly optimized pump schedules and reservoir trajectories in terms of least cost system operation. The integration of the developments results in a scheme which can be applied to give overall dynamic control of a wide range of water supply and distribution systems. The application results presented in this thesis justify the theoretical developments and show that benefits can be obtained from these developments.
2

A comparison of flow cytometry and conventional microbiology in the study of biofilms

Jian, Xiangrong January 2002 (has links)
A comprehensive study on the application of flow cytometry (FCM) for the analysis of biofilms has been undertaken and the results presented in this thesis have shown that flow cytometry can been successfully used to enumerate, sort and image the bacteria and amoebae in biofilms and water distribution systems as a rapid and sensitive semiautomated technique compared with conventional microbiology. It has been shown that the results of flow cytometric analysis of total Legionella pneumophila cells have a strong statistical correlation with the numbers of Legionella cfu by BCYE plate counting (BCYE PC) methods for biofilms and planktonic phases. There are also strong statistical correlations between flow cytometric analysis and epifluorescent microscopic (EFM) analysis (direct counting) for determination of bacteria, including Legionella, Escherichia coli, Salmonella, Pseudomonas and amoebae, and total and viable cells in pure cultures, water distribution systems and biofilms. The flow cytometric protocols have been set up and optimised for the analysis of environmental microorganisms. The novel fluorescent dyes and immunofluorescence antibodies from the most current commercial dyes also have been screened and the staining protocols have been optimised and adopted for flow cytometric analysis and direct counting by epifluorescent microscopy. The tap water biofilms and river water biofilms were analysed by the flow cytometer and direct counting methods as well as by conventional microbiological methods (plate counting). The bacterial populations in real water distribution systems have been fully investigated and the total, viable bacteria were determined by the above methods. The findings of this work have practical implications with respect to the rapid and automatic detection and predictions of Legionella spp. and the risk assessment from biofilms and water environments.
3

Hybrid optimisation algorithms for two-objective design of water distribution systems

Wang, Qi January 2014 (has links)
Multi-objective design or extended design of Water Distribution Systems (WDSs) has received more attention in recent years. It is of particular interest for obtaining the trade-offs between cost and hydraulic benefit to support the decision-making process. The design problem is usually formulated as a multi-objective optimisation problem, featuring a huge search space associated with a great number of constraints. Multi-objective evolutionary algorithms (MOEAs) are popular tools for addressing this kind of problem because they are capable of approximating the Pareto-optimal front effectively in a single run. However, these methods are often held by the “No Free Lunch” theorem (Wolpert and Macready 1997) that there is no guarantee that they can perform well on a wide range of cases. To overcome this drawback, many hybrid optimisation methods have been proposed to take advantage of multiple search mechanisms which can synergistically facilitate optimisation. In this thesis, a novel hybrid algorithm, called Genetically Adaptive Leaping Algorithm for approXimation and diversitY (GALAXY), is proposed. It is a dedicated optimiser for solving the discrete two-objective design or extended design of WDSs, minimising the total cost and maximising the network resilience, which is a surrogate indicator of hydraulic benefit. GALAXY is developed using the general framework of MOEAs with substantial improvements and modifications tailored for WDS design. It features a generational framework, a hybrid use of the traditional Pareto-dominance and the epsilon-dominance concepts, an integer coding scheme, and six search operators organised in a high-level teamwork hybrid paradigm. In addition, several important strategies are implemented within GALAXY, including the genetically adaptive strategy, the global information sharing strategy, the duplicates handling strategy and the hybrid replacement strategy. One great advantage of GALAXY over other state-of-the-art MOEAs lies in the fact that it eliminates all the individual parameters of search operators, thus providing an effective and efficient tool to researchers and practitioners alike for dealing with real-world cases. To verify the capability of GALAXY, an archive of benchmark problems of WDS design collected from the literature is first established, ranging from small to large cases. GALAXY has been applied to solve these benchmark design problems and its achievements in terms of both ultimate and dynamic performances are compared with those obtained by two state-of-the-art hybrid algorithms and two baseline MOEAs. GALAXY generally outperforms these MOEAs according to various numerical indicators and a graphical comparison tool. For the largest problem considered in this thesis, GALAXY does not perform as well as its competitors due to the limited computational budget in terms of number of function evaluations. All the algorithms have also been applied to solve the challenging Anytown rehabilitation problem, which considers both the design and operation of a system from the extended period simulation perspective. The performance of each algorithm is sensitive to the quality of the initial population and the random seed used. GALAXY and the Pareto-dominance based MOEAs are superior to the epsilon-dominance based methods; however, there is a tie between GALAXY and the Pareto-dominance based approaches. At the end, a summary of this thesis is provided and relevant conclusions are drawn. Recommendations for future research work are also made.
4

Rule(s) over regulation : the making of water reforms and regulatory cultures in Maharashtra, India

Srivastava, Shilpi January 2015 (has links)
This research focuses on how water sector reforms are unfolding in the state of Maharashtra, India. In 2005, Maharashtra launched an ambitious reform programme with support from the World Bank to establish an independent water regulator and make water user associations mandatory for water delivery in the state. The establishment of the regulator, the first of its kind in the Indian water sector, invited much attention from policy makers and civil society organisations after which several Indian states followed Maharashtra's footsteps. Celebrated for its ‘independent' and ‘apolitical' virtues, this model of regulation was designed to provide answers to inefficiency and political opportunism in the water sector. What gained immense traction in the regulatory discourse was the concept of entitlements and the possibility of introducing water markets for ‘efficient' pricing and distribution of water. To date, however, this reform project has faced reversals, limitations and subversions which have been described as ‘evolution' by pro-reformers and ‘failures' by the resisting groups. This thesis shows how a seemingly ‘apolitical' initiative aimed to dilute the authority of the State in the water sector is subverted to shape and reinforce its control. Though the idea of independent water regulator is increasingly getting mainstreamed into water policy discourses in India, divergent framings and rationales have made regulation a deeply contested political process. In Maharashtra, the turf war between politicians, the water resources department and the water regulator coupled with cases of corporate water grab lie at the heart of rule-making for regulation. This has made the authority of the water regulator and the meaning of regulation ambiguous and blurred. This ambiguity in turn shapes the distribution of water entitlements. In the sugarcane belt of Western Maharashtra where farmers access water from different sources, entitlements are shaped by persistent inequities in water distribution. They take on different meanings as they are subsumed into struggles over water control between the irrigation officials and the farmers on one hand, and amongst different groups of the farmers on the other. This struggle over meanings and practices across the reform process constitutes what I call “regulatory cultures” in this thesis. Using anthropological methods to study policy processes, this work shows how water regulation is discursively shaped and becomes a deeply political practice embedded in networks of power. These networks are formed at the intersection of donors, different layers of irrigation bureaucracy, water user associations and prosperous sugarcane farmers. I argue that the architecture of the Indian State, embedded in these very networks, is central to understanding the politics and practice of water regulation in Maharashtra.
5

Electricity cost optimisation of a surface potable water pump system / M.P. Slade

Slade, Michael Peter January 2007 (has links)
South Africa is fast approaching an era where its electrical energy demand will surpass the generating capacity of it's primary utility. The reason for this is due to the fact that over the past 10 years, the economic growth in South Africa has increased considerably and has become very energy intensive. South African electrical energy consumption is currently estimated to be growing at a rate of around 1 000 MW per year. Due to the electrical energy demand being the greatest during peak-times, Eskom has introduced various "time of use" tariff structures, such as Megaflex and Ruraflex. These two tariff structures differentiate between standard, peak and off-peak periods of the day, as well as different seasons of the year. The tariffs for these different scenarios are adjusted such that the consumers are persuaded into avoiding unnecessary electrical energy consumption during peak periods. It has been identified that electrical energy consumption can be split into two categories. One of the categories considers sectors where there are a large number of electrical energy consumers, each utilising a negligible amount of power. The other category considers sectors where there are few electrical energy consumers, each utilising large amounts of power. This therefore means that the consumers in the latter category have a great potential in implementing more efficient ways of consuming power. In order to try and control the electrical energy demand problem in South Africa, Eskom has implemented a DSM (Demand Side Management) programme in order to help the larger energy consumers in shifting their peak-time loads to off-peak periods. If the client wishes to shift their load to off-peak periods, Eskom will assist by funding all costs to carry out such a project. According to Eskom's monitoring and verification team, Eskom's DSM initiative has proven to be highly successful. Since the inception of Eskom's DSM programme in 2003, up until the end of 2005, an accumulated total load reduction of 296.3 MW has successfully been realised. At present, most water distribution schemes have been developed without making use of Eskom's DSM initiative. As these schemes consume considerable amounts of electrical energy, they are prime candidates for an initiative such as Eskom's DSM initiative. It had previously been identified that the Vaal Gamagara Water Scheme, situated in Delportshoop, was a prime candidate for Eskom's DSM initiative. Presented in this dissertation are the findings of the DSM investigation. Although the project has yet to be implemented, the proposed intervention methodology was manually tested, where a 3 MW load shift in the evening peak and a 3.6 MW load shift in the morning peak was achieved. If the current intervention methodology is maintained, the annual savings will be in the region of R 830,000.00. / Thesis (M.Ing. (Electrical Engineering))--North-West University, Potchefstroom Campus, 2008.
6

Electricity cost optimisation of a surface potable water pump system / M.P. Slade

Slade, Michael Peter January 2007 (has links)
South Africa is fast approaching an era where its electrical energy demand will surpass the generating capacity of it's primary utility. The reason for this is due to the fact that over the past 10 years, the economic growth in South Africa has increased considerably and has become very energy intensive. South African electrical energy consumption is currently estimated to be growing at a rate of around 1 000 MW per year. Due to the electrical energy demand being the greatest during peak-times, Eskom has introduced various "time of use" tariff structures, such as Megaflex and Ruraflex. These two tariff structures differentiate between standard, peak and off-peak periods of the day, as well as different seasons of the year. The tariffs for these different scenarios are adjusted such that the consumers are persuaded into avoiding unnecessary electrical energy consumption during peak periods. It has been identified that electrical energy consumption can be split into two categories. One of the categories considers sectors where there are a large number of electrical energy consumers, each utilising a negligible amount of power. The other category considers sectors where there are few electrical energy consumers, each utilising large amounts of power. This therefore means that the consumers in the latter category have a great potential in implementing more efficient ways of consuming power. In order to try and control the electrical energy demand problem in South Africa, Eskom has implemented a DSM (Demand Side Management) programme in order to help the larger energy consumers in shifting their peak-time loads to off-peak periods. If the client wishes to shift their load to off-peak periods, Eskom will assist by funding all costs to carry out such a project. According to Eskom's monitoring and verification team, Eskom's DSM initiative has proven to be highly successful. Since the inception of Eskom's DSM programme in 2003, up until the end of 2005, an accumulated total load reduction of 296.3 MW has successfully been realised. At present, most water distribution schemes have been developed without making use of Eskom's DSM initiative. As these schemes consume considerable amounts of electrical energy, they are prime candidates for an initiative such as Eskom's DSM initiative. It had previously been identified that the Vaal Gamagara Water Scheme, situated in Delportshoop, was a prime candidate for Eskom's DSM initiative. Presented in this dissertation are the findings of the DSM investigation. Although the project has yet to be implemented, the proposed intervention methodology was manually tested, where a 3 MW load shift in the evening peak and a 3.6 MW load shift in the morning peak was achieved. If the current intervention methodology is maintained, the annual savings will be in the region of R 830,000.00. / Thesis (M.Ing. (Electrical Engineering))--North-West University, Potchefstroom Campus, 2008.
7

Performance Measurement of Water Distribution Systems (WDS). A Critical and Constructive Appraisal of the State-of-the-art

Moradi Jalal, Mahdi 24 February 2009 (has links)
Water supply and distribution infrastructures are vital for current life. They have a significant role in public health, providing safe water for drinking and human consumption as well as for essential non-potable uses such as fire fighting. These diverse objectives create challenges for everyone who must address in some way the actual performance of the system. This research critically evaluates all common objectives of conventional design approaches and evaluates the advantages and drawbacks of various performance measures. New ideas for a more realistic and comprehensive approach to the design, operation assessment of WDS are proposed. A new approach, called a Risk-based Performance Assessment, for hydraulic performance evaluation is tentatively proposed. It is based on integration of reliability, resiliency, and vulnerability as three basic operational indices in the operation of WDS. Furthermore, the Total Life-cycle Cost evaluation approach is tentatively proposed based on considering all major costs of a WDS.
8

Performance Measurement of Water Distribution Systems (WDS). A Critical and Constructive Appraisal of the State-of-the-art

Moradi Jalal, Mahdi 24 February 2009 (has links)
Water supply and distribution infrastructures are vital for current life. They have a significant role in public health, providing safe water for drinking and human consumption as well as for essential non-potable uses such as fire fighting. These diverse objectives create challenges for everyone who must address in some way the actual performance of the system. This research critically evaluates all common objectives of conventional design approaches and evaluates the advantages and drawbacks of various performance measures. New ideas for a more realistic and comprehensive approach to the design, operation assessment of WDS are proposed. A new approach, called a Risk-based Performance Assessment, for hydraulic performance evaluation is tentatively proposed. It is based on integration of reliability, resiliency, and vulnerability as three basic operational indices in the operation of WDS. Furthermore, the Total Life-cycle Cost evaluation approach is tentatively proposed based on considering all major costs of a WDS.
9

Performance assessment of leak detection failure sensors used in a water distribution system

Khan, Asar, Widdop, Peter D., Day, Andrew J., Wood, Alastair S., Mounce, Steve R., Machell, James January 2005 (has links)
No
10

Advanced modelling and simulation of water distribution systems with discontinuous control elements

Paluszczyszyn, Daniel January 2015 (has links)
Water distribution systems are large and complex structures. Hence, their construction, management and improvements are time consuming and expensive. But nearly all the optimisation methods, whether aimed at design or operation, suffer from the need for simulation models necessary to evaluate the performance of solutions to the problem. These simulation models, however, are increasing in size and complexity, and especially for operational control purposes, where there is a need to regularly update the control strategy to account for the fluctuations in demands, the combination of a hydraulic simulation model and optimisation is likely to be computationally excessive for all but the simplest of networks. The work presented in this thesis has been motivated by the need for reduced, whilst at the same time appropriately accurate, models to replicate the complex and nonlinear nature of water distribution systems in order to optimise their operation. This thesis attempts to establish the ground rules to form an underpinning basis for the formulation and subsequent evaluation of such models. Part I of this thesis introduces some of the modelling, simulation and optimisation problems currently faced by water industry. A case study is given to emphasise one particular subject, namely reduction of water distribution system models. A systematic research resulted in development of a new methodology which encapsulate not only the system mass balance but also the system energy distribution within the model reduction process. The methodology incorporates the energy audits concepts into the model reduction algorithm allowing the preservation of the original model energy distribution by imposing new pressure constraints in the reduced model. The appropriateness of the new methodology is illustrated on the theoretical and industrial case studies. Outcomes from these studies demonstrate that the new extension to the model reduction technique can simplify the inherent complexity of water networks while preserving the completeness of original information. An underlying premise which forms a common thread running through the thesis, linking Parts I and II, is in recognition of the need for the more efficient paradigm to model and simulate water networks; effectively accounting for the discontinuous behaviour exhibited by water network components. Motivated largely by the potential of contemplating a new paradigm to water distribution system modelling and simulation, a further major research area, which forms the basis of Part II, leads to a study of the discrete event specification formalism and quantised state systems to formulate a framework within which water distribution systems can be modelled and simulated. In contrast to the classic time-slicing simulators, depending on the numerical integration algorithms, the quantisation of system states would allow accounting for the discontinuities exhibited by control elements in a more efficient manner, and thereby, offer a significant increase in speed of the simulation of water network models. The proposed approach is evaluated on a number of case studies and compared with results obtained from the Epanet2 simulator and OpenModelica. Although the current state-of-art of the simulation tools utilising the quantised state systems do not allow to fully exploit their potential, the results from comparison demonstrate that, if the second or third order quantised-based integrations are used, the quantised state systems approach can outperform the conventional water network simulation methods in terms of simulation accuracy and run-time.

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