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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

Rationalised protection for embedded generation

Alshamali, M. A. M. January 2001 (has links)
No description available.
2

How does servitization impact inter-organisational structure and relationships of a truck manufacturer's network?

Cakkol, Mehmet January 2013 (has links)
Network relationships play a significant role in the provision of servitized offerings. To date, little empirical research has been conducted to investigate the link between servitization and inter-organisational relationships. The objective of this doctoral thesis is to explore the implications of servitization on a manufacturer’s network. Particular emphasis is placed on the impact on the network structure and relationship attributes. An exploratory in-depth case study was conducted within the truck manufacturing industry using a multi-organisational perspective. An abductive research approach was adopted which was underlined by pragmatism. As part of this approach, 43 interviews were conducted in a total of 11 companies. The findings of the study suggest that managers need to be aware of the different customer needs, related offerings and resultant implications on the network structure and relationships. To this end, the findings show that as the offerings move towards advanced servitized offerings the network becomes more complex in terms of its structure and relationships. The research contributes to the literature by providing a more nuanced description of what actually occurs in a network when a manufacturer provides servitized offerings in conjunction with other product-based offerings. In particular, it identifies the relationship attributes that need to be managed in order to drive the right behaviour for the provision of each of these offerings. Moreover, it is the first known study to uncover triadic as well as tetradic network structures in a servitization context. Equally important, it provides a framework that captures the interplay between the different offerings and the resultant network structure and relationship attributes. In all of these capacities, this research is one of the first known studies to uncover some of the complexities surrounding the way in which inter-organisational relationships are enacted in a servitization context.
3

How does servitization impact inter-organisational structure and relationships of a truck manufacturer's network?

Cakkol, Mehmet 06 1900 (has links)
© Cranfield University 2013. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright owner. / Network relationships play a significant role in the provision of servitized offerings. To date, little empirical research has been conducted to investigate the link between servitization and inter-organisational relationships. The objective of this doctoral thesis is to explore the implications of servitization on a manufacturer’s network. Particular emphasis is placed on the impact on the network structure and relationship attributes. An exploratory in-depth case study was conducted within the truck manufacturing industry using a multi-organisational perspective. An abductive research approach was adopted which was underlined by pragmatism. As part of this approach, 43 interviews were conducted in a total of 11 companies. The findings of the study suggest that managers need to be aware of the different customer needs, related offerings and resultant implications on the network structure and relationships. To this end, the findings show that as the offerings move towards advanced servitized offerings the network becomes more complex in terms of its structure and relationships. The research contributes to the literature by providing a more nuanced description of what actually occurs in a network when a manufacturer provides servitized offerings in conjunction with other product-based offerings. In particular, it identifies the relationship attributes that need to be managed in order to drive the right behaviour for the provision of each of these offerings. Moreover, it is the first known study to uncover triadic as well as tetradic network structures in a servitization context. Equally important, it provides a framework that captures the interplay between the different offerings and the resultant network structure and relationship attributes. In all of these capacities, this research is one of the first known studies to uncover some of the complexities surrounding the way in which inter-organisational relationships are enacted in a servitization context.
4

La capacidad hidráulica en las redes de agua potable y su influencia en el proceso de sectorización

Martins Alves, Carlos 21 January 2021 (has links)
[ES] La sectorización en sectores hidrométricos de las redes de abastecimiento de agua potable ha sido, a lo largo de los últimos años, una de las técnicas más empleadas para ubicar y controlar las fugas. Esto es de vital importancia ante un recurso, el agua potable, cada vez más escaso y valioso. Sin embargo, el empleo de esta técnica, algunas veces, es llevada a cabo por ensayo y error, o sin una estrategia previamente establecida. La capacidad hidráulica de la red, o caudal máximo que puede aportar cumpliendo los requisitos mínimos de servicio, puede afectarse cuando se lleva a cabo un proceso de sectorización. Esto es debido a que el cierre de tramos de la red cambia las condiciones de servicio, pudiendo generar afectaciones graves desde el punto de vista de presiones y de calidad de agua. Algunas veces, también, es aplicado el proceso de sectorización sin una evaluación previa de las características de la red y de las condiciones operativas. Partiendo de estas situaciones, se planteó indagar acerca de cómo las condiciones iniciales de operación de la red pudiesen afectar la formación de los sectores hidrométricos desde el punto de vista de su configuración. En los procesos de sectorización pueden emplearse algoritmos de clústering debido a la analogía existente entre los agrupamientos de los diferentes elementos de los sistemas de abastecimiento de agua y los principios aplicados en las técnicas de agrupamiento de datos. Así, se decidió aplicar diversas técnicas basadas en la detección de comunidades en redes, ya que poseen la ventaja de agrupar en función de la información en las conexiones, y no solo en la información almacenada en los nodos, lo cual resulta favorable para el tema en estudio en este trabajo, debido a que pudiera tomarse en cuenta cómo la variación de los niveles de exigencia en las tuberías, ocasionados por la variación en la demanda, afectaría la formación de sectores. Para ello se planteó trabajar con dos redes de prueba conocidas en la literatura, a las cuales se les simuló bajo distintas capacidades de carga de trabajo y a través del empleo de varios algoritmos de agrupamiento, tales como Infomap, Walktrap, Fast gready, Edge betweeness, Luovain y Leiden. La metodología desarrollada fue, finalmente, aplicada a una red real de gran tamaño, lo que valida dicha metodología para un problema del mundo real. Como parámetros para ponderar las conexiones se probaron cuatro opciones: caudal circulante con la red trabajando a la capacidad deseada; energía disipada en cada tramo con la red trabajando a la capacidad deseada; relación entre el caudal circulante en el tramo y el caudal circulante a capacidad máxima teórica de la red; y relación entre la energía disipada trabajando a la capacidad deseada y la disipación de la energía en los tramos con la red trabajando a capacidad máxima. Obtenida la partición por cualquiera de los métodos anteriormente expuestos, se optimizaron las entradas y salidas de los sectores por medio de la implementación de un algoritmo de enjambre de partículas; adicionalmente, se hace una comparación del resultado con otro obtenido a partir de un algoritmo de colonia de hormigas, lo que permite dar robustez a la metodología desarrollada. / [CA] La partició o sectorització de les xarxes d'abastiment d'aigua potable a les anomenades districtes hidromètrics ha estat, durant els darrers anys, una de les tècniques més utilitzades per localitzar i controlar les pèrdues d'aigua. La sectorització és crucial quan es tracta d'un recurs cada vegada més escàs i valuós com es l'aigua. Tanmateix, l'ús d'aquesta tècnica de vegades es duu a terme mitjançant proves i errors, o sense una estratègia prèviament establerta. La capacitat hidràulica d'una xarxa o el cabal màxim que pot proporcionar mentre compleix els requisits mínims de servei es pot veure afectat quan es realitza un procés de sectorització. Això es deu al fet que el tancament de seccions de la xarxa modifica les condicions del servei, la qual cosa pot generar greus efectes des del punt de vista de la pressió i la qualitat de l'aigua. A més, de vegades s'apliquen processos de sectorització sense una avaluació prèvia de les característiques de la xarxa i de les condicions de funcionament. Partint d'aquestes situacions, ens vam preguntar sobre com les condicions inicials de funcionament de la xarxa podrien afectar la construcció dels sectors hidromètrics des del punt de vista de la seva configuració. Els algoritmes de clusterització es poden utilitzar en processos de sectorització a causa de l'analogia entre l'agrupació dels diferents elements dels sistemes d'abastiment d'aigua i els principis aplicats en les tècniques d'agrupament de dades. Així, vam decidir aplicar diverses tècniques basades en la detecció de comunitats a les xarxes, ja que tenen l'avantatge de realitzar agrupacions basades en la informació de les unions i no només en la informació emmagatzemada als nodes. Això és favorable per al tema en estudi en aquest treball, perquè es pot considerar com la variació dels nivells de demanda a les canonades, causada per la variació de la demanda, pot afectar la construcció de sectors. Amb aquesta finalitat, es va proposar treballar amb dues xarxes de proves conegudes a la literatura, que es van simular sota diferents capacitats de càrrega i mitjançant l'ús de diversos algorismes de clusterització, com Infomap, Walktrap, Fast gready, Edge betweeness, Luovain i Leiden. La metodologia desenvolupada es va aplicar, finalment, a una gran xarxa real, que valida la metodologia per a una xarxa de subministrament d'aigua del món real. Com a paràmetres per ponderar les unions, es van provar quatre opcions: cabal circulant amb la xarxa treballant a la capacitat desitjada; energia dissipada a cada secció amb la xarxa treballant a la capacitat desitjada; relació entre el cabal circulant a la secció i el cabal circulant a la capacitat màxima teòrica de la xarxa; i la relació entre l'energia dissipada que treballa a la capacitat desitjada i la dissipació d'energia a les seccions amb la xarxa que treballa a la màxima capacitat. Un cop obtinguda la partició per qualsevol dels mètodes esmentats anteriorment, les entrades i sortides dels sectors s'optimitzen mitjançant un algorisme d'optimització d'eixam de partícules; a més, es fa una comparació del resultat amb un altre algoritme d'optimització, és a dir, un algoritme d'optimització de colònies de formigues, que permet proporcionar robustesa a la metodologia desenvolupada. / [EN] Partitioning or sectorization of drinking water supply networks into so-called district metered areas has been, over the last years, one of the most used techniques to locate and control leaks. Sectorization is crucial when dealing with an increasingly scarce and valuable resource as water. However, the use of this technique is sometimes carried out by trial and error, or without a previously established strategy. The hydraulic capacity of a network, or the maximum flow it can provide while meeting the minimum service requirements, can be affected when a sectorization process is carried out. This is due to the fact that the closure of sections of the network changes the service conditions, which could generate serious effects from the point of view of pressure and water quality. Also, sometimes sectorization processes are applied without a prior evaluation of the characteristics of the network and of the operating conditions. Starting from these situations, we inquired about how the initial operating conditions of the network could affect the construction of the hydrometric sectors or district metered areas from the point of view of their configuration. Clustering algorithms can be used in sectorization processes due to the analogy between the grouping of the different elements of water supply systems and the principles applied in data grouping techniques. Thus, we decided to apply various techniques based on the detection of communities in networks, since they have the advantage of performing grouping based on the information at the junctions, and not only on the information stored at the nodes. This is favourable for the subject under study in this work, because one may consider how the variation of the demand levels in the pipes, caused by the demand variation, can affect the construction of sectors. To this end, it was proposed to work with two test networks known in the literature, which were simulated under different load capacities and through the use of various clustering algorithms, namely Infomap, Walktrap, Fast gready, Edge betweeness, Luovain and Leiden. The methodology developed was, finally, applied to a large real network, which validates the methodology for a real-world water supply network. As parameters to weight the junctions, four options were tested: circulating flow with the network working at the desired capacity; energy dissipated in each section with the network working at the desired capacity; relationship between the circulating flow in the section and the circulating flow at the theoretical maximum capacity of the network; and the relationship between the energy dissipated working at the desired capacity and the dissipation of energy in the sections with the network working at maximum capacity. Once the partition is obtained by any of the previously said methods, the inputs and outputs of the sectors are optimized by using a particle swarm optimization algorithm; additionally, a comparison of the result is made with another optimization algorithm, namely, an ant colony optimization algorithm, which allows to provide robustness to the developed methodology. / Martins Alves, C. (2020). La capacidad hidráulica en las redes de agua potable y su influencia en el proceso de sectorización [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/159938
5

Detecção de vazamentos em redes sob pressão baseada na análise dos sinais de pressão e vazão com um sistema de reconhecimento de padrões / Leak detection in water networks based on the analysis of flow and pressure signals by a pattern recognition system

Gamboa Medina, Maria Mercedes 29 July 2013 (has links)
O controle de perdas em sistemas de distribuição de água para abastecimento é uma preocupação constante, e uma tarefa fundamental para a solução do problema é a detecção rápida e confiável dos vazamentos que frequentemente iniciam em qualquer ponto da rede. Uma abordagem promissória é a detecção de vazamentos baseada na análise de sinais adquiridos pelo monitoramento das redes durante sua operação, e dentro dela se enquadra este trabalho. É desenvolvido um sistema de reconhecimento de padrões para análise de sinais de pressão e vazão que permite identificar se durante a aquisição do sinal aconteceu um vazamento ou não. Para a conformação desse sistema diversas técnicas são exploradas, incluindo a extração de características no domínio do tempo (energia, entropia, número de cruzamentos por zero) e na decomposição wavelet (distribuição da energia nas componentes). Também é explorado o uso de algoritmos para classificação de diferentes tipos (vizinhos mais próximos, árvore de decisão, regra de decisão, Naive Bayes, máquina de vetor suporte e rede neural artificial com funções de base radial). Sinais são adquiridos junto ao circuito hidráulico experimental, que permitiu a simulação da ocorrência de um vazamento na rede, para constituir uma amplia base de dados com sinais de exemplo. Além da revisão bibliográfica e os conceitos relativos às metodologias exploradas, são apresentadas neste documento as análises que conduzem à criação do sistema de reconhecimento de padrões mais apropriado para o problema. Das análises dos diferentes métodos considerados é definido o sistema de reconhecimento de padrões, em suas etapas de segmentação e padronização, extração de características e classificação. A avaliação do sistema proposto mostra um desempenho totalmente satisfatório, com reconhecimento acertado de sinais vinculados ou não a um vazamento em mais de 95% dos testes. / Control of losses in water supply systems is a constant concern, and a key to the solution of this problem is the rapid and reliable detection of leaks that often begin anywhere on the network. A promising approach to solve the problem is the leak detection based on the analysis of signals acquired by monitoring the network in operation, and this research fits with that approach. Its developed a pattern recognition system for the analysis of pressure and flow signals, which identifies whether a leak happened during signal acquisition. Several techniques are exploited for forming this system, including the feature extraction in the time domain (energy, entropy, zero crossings count) and in the wavelet decomposition (energy distribution in the components). Also, the use of different types of algorithms for classification (nearest neighbors, decision tree, decision rule, Naive Bayes, support vector machine and artificial neural network with radial basis functions) is explored. Signals are acquired from the experimental hydraulic circuit, allowing the simulation of the onset of a leak in the network, to form a big database of example signals. Besides the literature review and the concepts relating to the considered methods, in this document are shown the analyses leading to the creation of the pattern recognition system most appropriate for the problem. The analysis of the methods considered allows defining the pattern recognition system, which is composed by segmentation and standardization, feature extraction and classification. The evaluation of the proposed system shows a completely satisfactory performance, recognizing rightly the signals as linked or not to a leak in more than 95% of the tests.
6

Risk and Visibility in Global Supply Chains: An Empirical Study

Nguyen, Hung V 14 December 2011 (has links)
Working with international suppliers in global supply chains, manufacturing firms now are faced with substantial supplier risks which could be triggered by disruptions in either their suppliers or the supplier’s market. Reactive actions to the risks, however, have usually been shown to be inefficient and sometimes ineffective. In this dissertation, therefore, I develop a theoretical framework linking some key relationship-specific capabilities to supplier risk. My contention is that the capabilities, when developed, can help proactively mitigate the risk. Thus, the model in this study is grounded in the resource-based and the relational views. In this study, the survey method has been employed to collect data from 66 manufacturing firms in the United State who are sourcing from international suppliers. Procedural and statistical methods have been employed to guard against typical empirical issues including non-response bias, common method bias, and problems in validity and reliability of measurement instruments. Structural equation modeling with partial least squares was employed to test the model with bootstrapping to estimate t-values for the paths. The analysis results showed support for the model. A conclusion from the study is that visibility is the critical relationship-specific capability that needs to develop for buying firms to mitigate supplier risk proactively. This is because it may not be substitutable by other mechanisms like goodwill trust, and other capabilities, including absorptive capacity and IT integration, will only operate via visibility to influence risk performance. Moreover, visibility is a significant capability that helps mitigate risk regardless of the relationship duration between the buyer and the supplier and of the market conditions under which the supplier is working. This study thus adds to the risk literature with discussions of supplier risks. Nuances have also been added to the resource-based and relational views by developing the theoretical relationships among the identified capabilities and by examining the contextual conditions under which the relationships are working to mitigate supplier risk. Managers from both sides of a dyadic relationship may benefit from the study by utilizing the tools and the study results to monitor and mitigate supplier risk.
7

Lietuvos geriamojo vandens suvartojimo ir jo pokyčių įvertinimas didžiuosiuose miestuose / The drinking water consumption and assessment of its alteration in major Lithuanian cities

Sirtautas, Danius 17 June 2014 (has links)
Magistrantūros studijų baigiamajame darbe nagrinėjamos geriamojo vandens suvartojimo ir jo pokyčių tendencijos 1996–2012 m. laikotarpyje. Tyrimo objektu pasirinkti didieji Lietuvos miestai – Vilnius, Kaunas, Klaipėda. Tyrimo tikslas – išanalizuoti statistikos departamento duomenis apie vandens suvartojimą ir jo pokyčių tendencijas bei atlikti įvairių veiksnių, lemiančių vandens suvartojimą, analizę. Šiame darbe analizuojami veiksniai, kurie galėtų daryti įtaką išgaunamo ir sunaudojamo požeminio vandens kiekiui. Šie veiksniai gali būti įvardijami kaip – gyventojų skaičiaus mažėjimas, vandens tiekimo ir nuotekų surinkimo kainos, sumažėjusi pramonės gamyba, BVP kitimas, elektros kainos, būsto vartojimo išlaidos. Požeminio vandens gavyba nuo 1996 m. iki 2012 m. sumažėjo 45 %, todėl galima teigti, kad suprojektuotos vandenvietes ir vandentiekio tinklai dirba sumažintu pajėgumu, kas gali bloginti vandens kokybę dėl užsistovinčio vandens vamzdžiuose. Analizuojant statistikos departamento duomenis buvo ieškomas ryšys tarp suvartoto vandens kiekio ir gyventojų skaičiaus kitimo, elektros kainos, pinigų skiriamų būsto vartojimo išlaidoms vienam asmeniu bei BVP kitimo. Remiantis duomenimis paaiškėjo, kad laikotarpyje nuo 1996 m. iki 2012 m. Lietuvoje vienas žmogus per parą suvartojo apie 106 l vandens. Analizuojant statistinį ryšį tarp vandens suvartojimo ir pinigų sumos skiriamos vartojimo išlaidoms, Kaune, gautas aukštas determinacijos koeficientas R2=0,79, Vilniuje – 0,86, Klaipėdoje... [toliau žr. visą tekstą] / The tendencies of changes in water consumption are discussed in this final master’s studies research in 1996–2012 time periods. As research objects are chosen large Lithuanian cities - Vilnius, Kaunas, Klaipėda. The aim of research is to collect and analyze data on water consumption as well as the changes in trends and perform analysis of factors influencing water consumption. This research shows the factors that could affect the extracted and consumed amount of underground water. These factors can be identified as population, GDP changes, housing consumption expenditure. Groundwater extraction from 1996 to 2012 decreased by 45%, suggesting that the designed water supplies and water-supply system operates at a reduced capacity, which can lead to deterioration in water quality due to standing water in pipes. The analysis of the statistical data of the Department has been requested for the relationship between water consumption and population changes, electricity prices, the money allocated for housing consumption expenditure per capita and GDP changes. The statistical data showed that during the period from 1996 to 2012 one person consumed on average 106 liters of water per day in Lithuania. The analysis of the statistical relationship between the rate of water consumption and the amount of money allocated to consumer spending in Kaunas received a high coefficient of determination R2 = 0.79, Vilnius – 0,86, in Klaipėda much lower – 0,45.
8

Friends of My Enemies: A Longitudinal Investigation into Supply Base Management

January 2016 (has links)
abstract: In this dissertation research, I expand the definition of the supply network to include the buying firm’s competitors. Just as one buyer-supplier relationship impacts all other relationships within the network, the presence of competitor-supplier relationships must also impact the focal buying firm. Therefore, the concept of a “competitive network” made up of a focal firm, its competitors and all of their combined suppliers is introduced. Utilizing a unique longitudinal dataset, this research explores how the organic structural changes within the new, many-to-many supply network impact firm performance. The investigation begins by studying the change in number of suppliers used by global auto manufacturers between 2004 and 2013. Following the Great Recession of 2008-09, firms have been growing the number of suppliers at more than twice the rate they had been reducing suppliers just a few years prior. The second phase of research explores the structural changes to the network resulting from this explosive growth in the number of suppliers. The final investigation explores a different flow – financial flow -- and evaluates its association with firm performance. Overall, this dissertation research demonstrates the value of aggregating individual supply networks into a macro-network defined as the competitive network. From this view, no one firm is able to control the structure of the network and the change in structure directly impacts firm performance. A new metric is introduced which addresses the subtle changes in buyer-supplier relationships and relates significantly to firm performance. The analyses expand the body of knowledge through the use of longitudinal datasets and uncovers otherwise overlooked dynamics existing within supply networks over the past decade. / Dissertation/Thesis / Doctoral Dissertation Business Administration 2016
9

CalibraÃÃo do coeficiente de decaimento do cloro (Kw) em redes de abastecimento de Ãgua utilizando o mÃtodo iterativo do gradiente hidrÃulico alternativo (MIGHA) / Calibration of the coefficient of decline of chlorine (Kw) in nets of water supply using the iterative method of the alternative hydraulical gradient (MIGHA)

Rejane Felix Pereira 02 September 2009 (has links)
Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / Um dos maiores desafios das companhias brasileiras de saneamento à a disponibilizaÃÃo de Ãgua potÃvel dentro dos padrÃes de qualidade preconizados pela Portaria n 518/2004 do MinistÃrio da SaÃde. Para obtenÃÃo dessa qualidade, à prÃtica comum a utilizaÃÃo de cloro nas estaÃÃes de tratamento de Ãgua, porÃm, este participa de diversas reaÃÃes com os compostos de natureza orgÃnica e inorgÃnica presentes no interior das tubulaÃÃes, reagindo tanto no seio do lÃquido, quanto nas paredes dos tubos, ocasionando o decaimento do cloro ao longo da rede de distribuiÃÃo. Diante do exposto, para tornar mais eficiente o gerenciamento do cloro residual em sistemas distribuiÃÃo de Ãgua, a literatura expÃe a utilizaÃÃo da modelagem, assumindo que os efeitos do decaimento do cloro podem ser representados pelos coeficientes kbulk e kwall. Contudo, o cÃlculo dos valores desses parÃmetros à uma tarefa complexa, em virtude dos sistemas apresentarem diversos tipos de materiais das tubulaÃÃes, variaÃÃo da idade dos tubos que os compÃem e os tipos de mananciais (superficiais e subterrÃneos) inseridos no sistema. Neste trabalho, à desenvolvida uma rotina computacional a fim de determinar o parÃmetro de decaimento do cloro nas paredes das tubulaÃÃes (kwall) em redes de distribuiÃÃo de Ãgua potÃvel, utilizando o MÃtodo Iterativo do Gradiente HidrÃulico Alternativo (MIGHA) como mÃtodo de otimizaÃÃo. O modelo de calibraÃÃo proposto foi aplicado em uma rede modelo, com resultados avaliados de acordo com a quantidade de nÃs com concentraÃÃes do residual de cloro conhecidas. Com o objetivo de comparaÃÃo dos resultados, o modelo proposto, tambÃm foi aplicado em uma rede modelo estudada em outros trabalhos cuja determinaÃÃo do parÃmetro em questÃo foi realizada atravÃs do mÃtodo dos algoritmos genÃticos / One of the biggest challenges of the Brazilian companies to sanitation is the provision of drinking water within the quality standards recommended by the Ordinance No 518/2004 of the Ministry of Health. To obtain this quality, it is common practice to use chlorine in water treatment plants. However, it participates in various reactions with the compounds of organic and inorganic nature on the inside of pipes, reacting both within the liquid, as the walls of the pipes, causing the decay of chlorine throughout the distribution network. Considering the above, to make more efficient the management of residual chlorine in water distribution systems, the literature describes the use of modeling, assuming that the effects of the decay of chlorine can be represented by the coefficients kbulk and kwall. However, the calculation of these parameters is a complex task, because the systems have different types of piping materials, variation of age of the pipes that make up and the types of springs (surface and underground) entered in the system. In this work, it developed a computational routine to determine the parameter of decay of chlorine in the walls of the pipes (kwall) in distribution networks for drinking water, using the Iterative Method of Hydraulic Gradient Alternative (MIGHA) as a method of optimization. The proposed calibration model was applied to a network model, with results evaluated according to the number of nodes with residual chlorine concentrations of the known. In order to compare the results, the proposed model was also applied to a hypothetical network studied in other works whose determination of the parameter in question was performed by the method of genetic algorithms
10

Detecção de vazamentos em redes sob pressão baseada na análise dos sinais de pressão e vazão com um sistema de reconhecimento de padrões / Leak detection in water networks based on the analysis of flow and pressure signals by a pattern recognition system

Maria Mercedes Gamboa Medina 29 July 2013 (has links)
O controle de perdas em sistemas de distribuição de água para abastecimento é uma preocupação constante, e uma tarefa fundamental para a solução do problema é a detecção rápida e confiável dos vazamentos que frequentemente iniciam em qualquer ponto da rede. Uma abordagem promissória é a detecção de vazamentos baseada na análise de sinais adquiridos pelo monitoramento das redes durante sua operação, e dentro dela se enquadra este trabalho. É desenvolvido um sistema de reconhecimento de padrões para análise de sinais de pressão e vazão que permite identificar se durante a aquisição do sinal aconteceu um vazamento ou não. Para a conformação desse sistema diversas técnicas são exploradas, incluindo a extração de características no domínio do tempo (energia, entropia, número de cruzamentos por zero) e na decomposição wavelet (distribuição da energia nas componentes). Também é explorado o uso de algoritmos para classificação de diferentes tipos (vizinhos mais próximos, árvore de decisão, regra de decisão, Naive Bayes, máquina de vetor suporte e rede neural artificial com funções de base radial). Sinais são adquiridos junto ao circuito hidráulico experimental, que permitiu a simulação da ocorrência de um vazamento na rede, para constituir uma amplia base de dados com sinais de exemplo. Além da revisão bibliográfica e os conceitos relativos às metodologias exploradas, são apresentadas neste documento as análises que conduzem à criação do sistema de reconhecimento de padrões mais apropriado para o problema. Das análises dos diferentes métodos considerados é definido o sistema de reconhecimento de padrões, em suas etapas de segmentação e padronização, extração de características e classificação. A avaliação do sistema proposto mostra um desempenho totalmente satisfatório, com reconhecimento acertado de sinais vinculados ou não a um vazamento em mais de 95% dos testes. / Control of losses in water supply systems is a constant concern, and a key to the solution of this problem is the rapid and reliable detection of leaks that often begin anywhere on the network. A promising approach to solve the problem is the leak detection based on the analysis of signals acquired by monitoring the network in operation, and this research fits with that approach. Its developed a pattern recognition system for the analysis of pressure and flow signals, which identifies whether a leak happened during signal acquisition. Several techniques are exploited for forming this system, including the feature extraction in the time domain (energy, entropy, zero crossings count) and in the wavelet decomposition (energy distribution in the components). Also, the use of different types of algorithms for classification (nearest neighbors, decision tree, decision rule, Naive Bayes, support vector machine and artificial neural network with radial basis functions) is explored. Signals are acquired from the experimental hydraulic circuit, allowing the simulation of the onset of a leak in the network, to form a big database of example signals. Besides the literature review and the concepts relating to the considered methods, in this document are shown the analyses leading to the creation of the pattern recognition system most appropriate for the problem. The analysis of the methods considered allows defining the pattern recognition system, which is composed by segmentation and standardization, feature extraction and classification. The evaluation of the proposed system shows a completely satisfactory performance, recognizing rightly the signals as linked or not to a leak in more than 95% of the tests.

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