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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

An Empirical Analysis on the Transmission System Productivity and Efficiency of the Taiwan Power Company¡ÐThree Stage DEA

Huang, Chung-yi 02 September 2008 (has links)
This research use three phase stage- Data Envelopment Analysis to examine six power transmit organizations of Taipower Company from 2002 to 2006 regarding the statistical data of Taipower Company. In phase one, using SBM-DEA method analyses the management efficiency and the amount of input and output variable. Second, using SFA regression analysis probe into the environmental variable influencing degree to each power transmit organizations of Taipower Company. In addition, it take account of the environmental effect and the random interference effect to improve input and output variable. Finally, by way of DEA and Malmguist productivity index, it can measure the relative effects and the productivity change situation between each power transmit organization. The model result shows that SBM-DEA can weigh input difference and total output difference at the same time, by the way of using ratio adjustment, it can determine the really administration efficiency of every power transmit organization. According to phase one analysis results, Only 7 DMUs efficiency value are 1, it is 23% of all the DMUs efficiency value and shows that still have very big improvement space. By the regression analysis of phase 2, we know that the environmental parameter will exert an huge influence on input and output difference, in which the most influence is total asserts rate for working capital, asserts value, accident times, circuit lose and power supply. After adjustment every DMUs, there are 20 efficiency values getting higher, with 5 efficiency values unchanged, with 5 efficiency values decreasing. The amount of getting higher efficiency value is approximately 67% all of the DMUs. After adjustment environmental parameter, there is above 73% change in rank, with 9 DMUs advancement in rank ,13 DMUs degeneracy in rank, and only 8 DMUs unchanged. It shows that 9 DMUs work in unwell environment before adjustment, and 13 DMUs work in well environment before adjustment. It also shows that each power transmit organization still exist difference in working environment. Although the whole power transmit system efficiency represent is no bad ,but it still has large improvement space. Furthermore, according to Malmquist model efficiency index analysis from 2002 to 2006 data of power transmit system show that the total productivity element in Taipei, Hsintou, Chinan and Kaoping power transmit organization are higher than 1, it can attributes to the increasing of technology ,and Taizhong, Huitung, power transmit organization are lesser than 1, it can attributes to the decreasing of technology efficiency.
2

The Comparative Research between the Efficiencies of the Police Stations of the Police Bureau of the Kaohsiung City Government An Application of the Three-Stage DEA Approach

Chen, Tsung-min 25 June 2009 (has links)
This research use three phase stage- Data Envelopment Analysis to examine 49 police stations, 10 police precincts of Kaohsiung City Government Police Bureau(KCGPB) from 2003 to 2007 regarding the statistical data of KCGPB. In phase one, using SBM-DEA method analyses the management efficiency and the amount of input and output variable. In second phase, using SFA regression analyses to probe into the environmental variable influencing degree to each police station of KCGPB. In addition, it takes account of the environmental effect and the random interference effect to improve input and output variable. Finally, by way of DEA and Malmguist productivity index, it can measure the relative effects and the productivity change situations between each police station. The model result shows that SBM-DEA can weigh input difference and total output difference at the same time, by the way of using ratio adjustment, it can determine the really administration efficiency of every police station. According to phase one analysis results, 245 DMUs efficiency values are below 1, it is almost 100% of all the DMUs efficiency values and shows that still have very big improvement space. By the regression analysis of phase 2, we know that the environmental parameter will exert an huge influence on input and output difference, in which the most influence is the environmental parameters of violence crime on duty-costs, public services, and real-time solution of criminal cases. After adjustment every DMUs, there are 245 efficiency values getting higher. The amount of getting higher efficiency value is almost 100% of all the DMUs. After adjustment environmental parameter, about 96% change in rank, with 24 DMUs advancement in rank, 23 DMUs degeneracy in rank, and only 2 DMUs unchanged. It shows that 24 DMUs work in unwell environment before adjustment, and 23 DMUs work in well environment before adjustment. It also shows that each police station still exist difference in working environment. Although the whole efficiency of thw police stations represent is not bad, but it still has large improvement space. Furthermore, according to Malmquist model efficiency index analysis from 2003 to 2007 data of all police stations shows that the total productivity element in Sanming First Precinct, Sanming Second Precinct, Cianjhen Precinct, Gushan Precinct, Yancheng Precinct, Zuoying Precinct and Siaogang Precinct are higher than 1, it can attributes to the increasing of technology; Sinsing and Lingya Precincts are lesser than 1, it can attributes to the decreasing of technology efficiency.
3

Modeling of two & three phases bubble column / Modélisation d’une colonne à bulles biphasique et triphasique

Syed, Alizeb Hussain January 2017 (has links)
Abstract : The industrial partner of this project uses a slurry bubble reactor for the production of biogenic methanol. In the latter syngas is dispersed into the slurry continuous phase containing both liquid and solid phases. The rising bubbles containing a wide spectrum of the bubbles sizes, interact with the continuous phase due to the interface momentum transfer. The latter includes the drag, lift, wall lubrication and turbulent dispersion terms that require average bubble size, which needs to be calculated. One way to predict this average bubble size is by using population balance model (PBM), which can be coupled with the Eulerian framework. PBM also needs closure kernels for the bubble coalescence and bubble breakup. In this study, the influence of bubble coalescence and bubble breakup kernels have been studied in two- and three-phase system using eulerian approach, which solves momentum equation for each phase. The influence of the mesh sizes, number of bubble classes, numerical schemes, wall lubrication force and turbulent dispersion force are also included. In the two-phase system, results show that the Luo coalescence model needs to be tuned when used in combination with the Luo breakup kernel. The combination of the Luo coalescence and the Lehr breakup kernels (Luo-Lehr) show promising time-averaged radial profiles of gas holdup and axial liquid velocity as compared to empirical values. In the three-phase system, the combination of the Luo coalescence and the Lehr breakup kernels (Luo-Lehr) and the Luo coalescence and the Luo breakup kernels (Luo-Luo) predict convincing time-averaged radial profile of axial solid velocity as compared to experiments. However, at an elevated superficial gas velocity, a non-realistic behavior was predicted when compared to empirical observations. The sensitivity analysis results show that the 3 mm mesh size depicts a trend similar to the empirical values of the radial profiles of the gas holdup, axial liquid velocity, and solid axial velocity. The number of bubble classes influence the predicted bubble size distribution in the three-phase system while the numerical discretizing schemes have no influence on the results. The bench simulation results show that the inclusion of the turbulent dispersion term using a single porous tubular sparger influences the hydrodynamic behavior of the bubble column. / Le partenaire industriel de ce projet utilise un réacteur à suspension à trois phases pour la production de méthanol biogénique. Dans celui-ci, le gaz de synthèse est diffusé par barbotement dans la phase à suspension qui contient à la fois les phases liquide et solide. Les bulles en ascension présentent un large spectre de tailles et interagissent avec la phase à suspension en échangeant de la quantité de mouvement via leurs surfaces. Cet échange comprend les forces de trainé, de portance, de lubrification en proche parois et de dispersion par turbulence; lesquelles requièrent notamment le calcul de la taille moyenne des bulles. Une façon de prédire numériquement cette taille moyenne est de recourir à un modèle de bilan de population (PBM, de l’anglais Population Balance Model), qui peut être couplé avec un model multiphasique eulérien. Un tel PBM a requière des modèles de fermetures pour la coalescence et la rupture des bulles. Dans la présente étude, l'influence des modèles noyaux de coalescence et de rupture des bulles a été étudiée pour des systèmes à deux et à trois phases en utilisant l’approche eulérienne. L'influence de la taille du maillage, du nombre de classes de bulles, du schéma numérique, de la force de lubrification en proche parois et de la force de dispersion par turbulence sont également incluses. Dans un système bi-phasique, les résultats montrent que le modèle de coalescence Luo doit être ajusté lorsqu'il est utilisé en combinaison avec le noyau de rupture Luo. La combinaison des noyaux de coalescence Luo et de rupture Lehr (Luo-Lehr) montrent des profils radiaux moyennés dans le temps qui sont valides pour la concentration de gaz et la vitesse axiale du liquide par rapport aux mesures expérimentales. Dans le système triphasé, la combinaison des modèles noyaux de coalescence de Luo et de rupture de Lehr (Luo-Lehr) et de la coalescence de Luo et de rupture de Luo (Luo-Luo) prédisent des profils radiaux moyennés dans le temps qui sont valides pour la vitesse axiale moyenné dans le temps par rapport aux expériences. Cependant, à une vitesse de gaz superficielle élevée, ces profils prédisent un comportement non réaliste par rapport aux observations empiriques. Les résultats de l'analyse de sensibilité du maillage montrent qu’avec des cellules de 3 mm, le model prédit une tendance similaire aux valeurs empiriques pour les profils radiaux de concentration du gaz, de vitesse axiale du liquide et de vitesse axiale solide. Le nombre de classes de bulles influe sur les distributions prédites de taille de bulle dans le système triphasé alors que les schémas de discrétisation numériques n'ont aucune influence sur les résultats. Les résultats des simulations d’un banc d’essai avec diffuseur à bulles poreux montrent que tenir compte du terme de dispersion influence le comportement hydrodynamique de la colonne à bulles.
4

Desenvolvimento de um núcleo de simulador de eventos discretos para sistemas de manufatura com visualização 3D / Development of a discrete event simulation Kernel for manufacturing systems with 3D visualization

David Custódio de Sena 25 February 2010 (has links)
É crescente a necessidade de se conhecer e controlar o ambiente fabril. Ao longo do século passado e início deste, várias ferramentas e soluções foram desenvolvidas para suprir essa necessidade. Dentre elas, a simulação desempenha um suporte para o apoio da decisão amplamente utilizada principalmente na indústria manufatureira. A realidade virtual pode ser utilizada no ambiente de simulação como um canal de visualização e interação do usuário com o meio simulado. O objetivo deste trabalho é modelar uma biblioteca do núcleo de simulador de eventos discretos para sistemas de manufatura, com visualização tridimensional, que funcione em ambientes imersivos e não-imersivos. Para tal, as abordagens de três fases e orientada a objetos foram utilizadas com algumas alterações. Para a validação desse desenvolvimento, foram feitas duas simulações de um aplicativo que utiliza os elementos básicos de manufatura e foi feita a coleta de seus resultados que possibilitaram a verificação dos objetivos pretendidos. Por fim, foi feita a análise dos resultados e são apresentadas propostas de trabalhos futuros nesta área. / The need of knowledge and control of the manufacturing environment is continuously growing. Over the last century and the beginning of this, several tools and procedures were designed in order meet those necessities. Among them, simulation is a decision support tool widely used, mainly in the manufacturing industry. Virtual reality can be used in those simulations for user visualization and interaction with the simulated environment. The aim of this research was to model a library for a discrete event simulator core of a manufacturing system, with 3D visualization, that can be used in immersive and non-immersive environments. Two different approaches have been used: the three phases and the object-oriented one. To validate the software development, two simulations were carried out for an application that uses basic elements of manufacturing and production. Data was collected and analyzed in order to check the accomplishment of the research objectives. Finally, a conclusion about the results is presented along with some proposals for future work in this area.
5

Desenvolvimento de um núcleo de simulador de eventos discretos para sistemas de manufatura com visualização 3D / Development of a discrete event simulation Kernel for manufacturing systems with 3D visualization

Sena, David Custódio de 25 February 2010 (has links)
É crescente a necessidade de se conhecer e controlar o ambiente fabril. Ao longo do século passado e início deste, várias ferramentas e soluções foram desenvolvidas para suprir essa necessidade. Dentre elas, a simulação desempenha um suporte para o apoio da decisão amplamente utilizada principalmente na indústria manufatureira. A realidade virtual pode ser utilizada no ambiente de simulação como um canal de visualização e interação do usuário com o meio simulado. O objetivo deste trabalho é modelar uma biblioteca do núcleo de simulador de eventos discretos para sistemas de manufatura, com visualização tridimensional, que funcione em ambientes imersivos e não-imersivos. Para tal, as abordagens de três fases e orientada a objetos foram utilizadas com algumas alterações. Para a validação desse desenvolvimento, foram feitas duas simulações de um aplicativo que utiliza os elementos básicos de manufatura e foi feita a coleta de seus resultados que possibilitaram a verificação dos objetivos pretendidos. Por fim, foi feita a análise dos resultados e são apresentadas propostas de trabalhos futuros nesta área. / The need of knowledge and control of the manufacturing environment is continuously growing. Over the last century and the beginning of this, several tools and procedures were designed in order meet those necessities. Among them, simulation is a decision support tool widely used, mainly in the manufacturing industry. Virtual reality can be used in those simulations for user visualization and interaction with the simulated environment. The aim of this research was to model a library for a discrete event simulator core of a manufacturing system, with 3D visualization, that can be used in immersive and non-immersive environments. Two different approaches have been used: the three phases and the object-oriented one. To validate the software development, two simulations were carried out for an application that uses basic elements of manufacturing and production. Data was collected and analyzed in order to check the accomplishment of the research objectives. Finally, a conclusion about the results is presented along with some proposals for future work in this area.
6

Modélisation du comportement effectif du combustible MOX : par une analyse micro-mécanique en champs de transformation non uniformes

Largenton, Rodrigue 29 June 2012 (has links)
Parmi les combustibles nucléaires irradiés dans les Réacteurs à Eau Pressurisée d'Électricité de France, on trouve le combustible MOX, acronyme anglais de Mixed Oxide car il combine du dioxyde de plutonium et d'uranium. On y distingue trois phases, correspondant à des teneurs massiques en plutonium différentes. La teneur en matière fissile y étant différente, ces phases évoluent différemment sous irradiation, tant du point de vue mécanique que du point de vue chimique. Pour modéliser correctement le comportement macroscopique du combustible MOX dans un code de calcul industriel, les modèles ont besoin d'être alimentés de façon pertinente en propriétés effectives, mais il est aussi intéressant de disposer d'informations sur les champs locaux afin d'établir des couplages entre les mécanismes (couplage mécanique physico-chimie). L'objectif de la thèse fut donc de développer une modélisation par changement d'échelles, basée sur l'approche NTFA (Michel et Suquet 2003). Ces développements ont été réalisés sur des microstructures tridimensionnelles (3D) représentatives du combustible MOX et pour un comportement local visco-élastique vieillissant avec déformations libres. Dans un premier temps, pour représenter le combustible MOX en 3D nous avons utilisé des méthodes existantes pour traiter et segmenter les images expérimentales 2D, puis nous avons remonté les informations 2D indispensables (fuseau diamétral des inclusions et fractions surfaciques respectives) en 3D par la méthode stéréologique de Saltykov (Saltykov 1967) et enfin nous avons développé des outils pour représenter et discrétiser un composite multiphasé particulaire, type MOX. / Among the nuclear fuels irradiated in the Pressure Water Reactor of Électricité de France, MOX fuel is used, a Mixed OXide of plutonium and uranium. In this fuel, three phases with different plutonium content can be observed. The different fissile plutonium content in each phase leads different mechanical and physico-chemical evolutions under irradiation. To predict correctly the macroscopic behavior of MOX nuclear fuels in industrial nuclear fuel codes, models need to be fed in effective properties. But it's also interresting to obtain the local fields to establish coupling between mechanisms (mechanical and physico-chemical coupling). The aim of the PhD was to develop homogenisation method based on Non uniform Transformation Field Analysis (NTFA Michel and Suquet 2003}). These works were realised on three dimensions MOX microstructures and for local ageing visco-elastic behavior with free strains. The first work of the PhD was the numerical representation of the MOX microstructure in 3D. Three steps were realized. The first one consisted in the acquisition and the treatment of experimental pictures thanks to two soft-wares already developed. The second used the stereological model of textit{Saltykov} cite{R2S67} to go back up the two-dimensional statistical information in three-dimensional. And the last step was to develop tools which are able to build a numerical representation of the MOX microstructure. The second work of the PhD was to develop the NTFA model. Some theoretical (three dimensional, free strains and ageing hadn't ever studied) and numerical (choice and reduction of plastic modes, impact of the microstructures) studies were realised.

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