• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 2060
  • 1555
  • 210
  • 50
  • 20
  • 19
  • 19
  • 9
  • 9
  • 8
  • 6
  • 6
  • 5
  • 3
  • 3
  • Tagged with
  • 4426
  • 1634
  • 752
  • 752
  • 561
  • 498
  • 445
  • 423
  • 393
  • 324
  • 318
  • 291
  • 290
  • 275
  • 275
  • 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.
151

Prédiction de la structure de contrôle de bactéries par optimisation sous incertitude

Ait El Faqir, Marouane 22 November 2016 (has links)
L'approche de la biologie des systèmes vise à intégrer les méthodologies appliquées dans la conception et l'analyse des systèmes technologiques complexes, au sein de la biologie afin de comprendre les principes de fonctionnement globaux des systèmes biologiques. La thèse s'inscrit dans le cadre de la biologie des systèmes et en particulier dans la prolongation d'une méthode issue de ce cadre : la méthode Resource Blance Analysis (RBA). Nous visons dans cette thèse à augmenter le pouvoir prédictif de la méthode via un travail de modélisation tout en gardant un bon compromis entre représentativité des modèles issus de ce cadre et leur résolution numérique efficace. La thèse se décompose en deux grandes parties : la première vise à intégrer les aspects thermodynamiques et cinétiques inhérents aux réseaux métaboliques. La deuxième vise à comprendre l'impact de l'aspect stochastique de la production des enzymes sur le croissance de la bactérie. Des méthodes numériques ont été élaborées pour la résolution des modèles ainsi établis dans les deux cas déterministe et stochastique. / In order to understand the global functioning principals of biological systems, system bio- logy approach aims to integrate the methodologies used in the conception and the analysis of complex technological systems, within the biology. This PhD thesis fits into the system biology framework and in particular the extension of the already existing method Resource Balance Analysis (RBA). We aim in this PhD thesis to improve the predictive power of this method by introducing more complex model. However, this new model should respect a good trade-off between the representativity of the model and its efficient numerical computation. This PhD thesis is decomposed into two major parts. The first part aims the integration of the metabolic network inherent thermodynamical and kinetic aspects. The second part aims the comprehension of the impact of enzyme production stochastic aspect on the bacteria growth. Numerical methods are elaborated to solve the obtained models in both deterministic and stochastic cases.
152

Application of Multidisciplinary Design Optimisation to Engine Calibration Optimisation.

Yin, Xuefei January 2012 (has links)
Automotive engines are becoming increasingly technically complex and associated legal emissions standards more restrictive, making the task of identifying optimum actuator settings to use significantly more difficult. Given these challenges, this research aims to develop a process for engine calibration optimisation by exploiting advanced mathematical methods. Validation of this work is based upon a case study describing a steady-state Diesel engine calibration problem. The calibration optimisation problem seeks an optimal combination of actuator settings that minimises fuel consumption, while simultaneously meeting or exceeding the legal emissions constraints over a specified drive cycle. As another engineering target, the engine control maps are required as smooth as possible. The Multidisciplinary Design Optimisation (MDO) Frameworks have been studied to develop the optimisation process for the steady state Diesel engine calibration optimisation problem. Two MDO strategies are proposed for formulating and addressing this optimisation problem, which are All At Once (AAO), Collaborative Optimisation. An innovative MDO formulation has been developed based on the Collaborative Optimisation application for Diesel engine calibration. Form the MDO implementations, the fuel consumption have been significantly improved, while keep the emission at same level compare with the bench mark solution provided by sponsoring company. More importantly, this research has shown the ability of MDO methodologies that manage and organize the Diesel engine calibration optimisation problem more effectively. / Jaguar Land Rover
153

Optimisation of both energy use and pumping costs in water distribution networks with several water sources using the setpoint curve

León Celi, Christian Fernando 10 September 2018 (has links)
La optimización de los sistemas de bombeo se suele realizar a través de las curvas características de la red (asociadas con las curvas resistentes). Estas curvas están sujetas a la resistencia generada por el usuario en función de las necesidades de caudal y presión en cada punto de consumo. Dicha resistencia es muy variable y difícil de determinar lo que hace que el cálculo de las curvas sea poco práctico. El problema radica en que al no definirse adecuadamente las curvas resistentes, no se conocen las necesidades reales de caudal y presión de la red. Por lo tanto no se puede estimar el exceso de energía aportado por las bombas ni el aumento de costos de operación que esto representa. Sin embargo, existe otro tipo de curva denominada curva de consigna (CC). Dicha curva ha sido poco estudiada hasta ahora y su cálculo es relativamente fácil. De ahí que el presente trabajo tiene como objetivo la optimización de la energía y de los costes de bombeo mediante el uso de la CC. Para cumplir con el objetivo, primero se estudia el cálculo de la CC en redes de agua con múltiples estaciones de bombeo, consumos no dependientes y dependientes de la presión, y sin tanques de almacenamiento. Posteriormente, se lleva a cabo la optimización sólo desde la perspectiva energética (caudal y altura de bombeo). Para ello se realiza la búsqueda de la distribución de caudales óptima entre las estaciones de bombeo que conlleve a las CC óptimas. Se proponen dos métodos: uno discreto (M-D) y otro continuo (M-C). El M-D considera la distribución de caudales como una variable discreta. La distribución óptima se obtiene de un conjunto de soluciones previamente definidas. En el M-C la distribución de caudales se asume como variable continua. La solución óptima viene dada por el uso de un algoritmo de optimización. Se han usado los algoritmos: Hooke-Jeeves y Nelder-Mead. El siguiente paso es la optimización de costos de operación (costos de bombeo y costos de producción de agua). Para ello se parte del M-C y se incluyen además las tarifas de energía, las tarifas de producción de agua y un criterio sobre el rendimiento mínimo esperado en las estaciones de bombeo. El último paso consiste en la optimización energética y de costos en redes con tanques. La inclusión de tanques implica la modificación del cálculo de la CC y por ende la metodología de optimización. En la función de costes se incluyen además de los costes de bombeo y de producción, costes de penalización por incumplimiento de presiones y de volúmenes de reserva. Al incluirse los tanques, incrementa el número de variables de decisión. Por lo que, es necesario el uso de algoritmos más potentes. Se han usado el Differential Evolution y el Hybrid Algorithm. Este último es un aporte añadido de este trabajo. La metodología de optimización se aplica a cinco redes de distribución: TF, Catinen, Coplaca, Anytown y Richmond. Los tanques sólo se consideran en las dos últimas redes. En el caso de la red TF se realiza una demostración sin entrar en profundidad de la selección de bombas a través del uso de las CC óptimas. Sin embargo, este paso está fuera de los límites de este trabajo. Tampoco se consideran condiciones de operación múltiples de la red, ni la fiabilidad en el caso de la remoción de tanques o sistemas de bombeo. No obstante, los resultados obtenidos evidencian que los sistemas de bombeo operados usando la CC pueden mejorar sus costos operativos hasta en un 12%. La metodología proporciona información sobre las estaciones de bombeo que representan mayores ahorros frente a aquellas que son menos importantes o innecesarias. Además, el método ha permitido demostrar que mejores condiciones de bombeo (bajas tarifas de energía y altos rendimientos) no siempre significan menores costos de operación. Finalmente, algunos resultados muestran la posible utilidad del método para optimizar tanto el uso como la ubicación de los tanqu / Usually, pumping optimisation in water distribution networks is carried out by means of the system head curves (SHCs), also known as the resistance curves (RCs). These curves are subjected to the resistance generated by the users, according with the flow and pressure head needs at the final points of demand. Such resistance is highly variable and hard to determine. Thus the calculation of the RCs and all the points that define them results impractical. As a RCs suitable calculation is not possible, real flow and pressure needs of the network are not known. Therefore, neither energy excess of the pumping regarding the real requirements nor the raising operating costs due to such excess, are estimated. However, there is another type of SHC defined as the setpoint curve (SC). It can be easily calculated, but has been poorly studied so far. Thus, this work aims the optimisation of the energy use and operating costs in pumping systems by using the SCs. To achieve the objective, first of all the SC calculation is studied for networks with several pumping stations, non-pressure driven demands, pressure-driven demands, and without tanks. Next, the optimisation is performed only from the energy point of view (i.e. flow and pumping head required). For that, a search of the optimum flow distribution among pumping stations to find the optimum SCs is performed. Two methods are proposed: the discrete (D-M) and the continuous (C-M). The D-M considers the flow distribution as a discrete variable. The optimum flow distribution is obtained from a set of solutions defined previously. In the C-M, the flow distribution is assumed as a continuous variable. The optimum solution comes from using optimisation algorithms. Two algorithms have been applied: Hooke-Jeeves and Nelder-Mead. Then, the cost optimisation (pumping cost and water production cost) is developed. For that purpose, the M-C is used as starting point. Then, energy tariffs, water production fares and the minimum expected efficiency at the pumping stations, are included. The last step consists in the energy and cost optimisation in networks with tanks. When tanks are included the SC calculation methodology changes. Hence, the optimisation process also does. In that sense, besides the costs of pumping and water production, the cost function also considers penalty costs for unaccomplished minimum pressures and minimum storage leves. Moreover, tanks inclusion also rises the number of decision variables. Thus, the use of more powerful algorithms is required. In that context, the Differential Evolution and the Hybrid Algorithm have been applied. The last one is an additional contribution of this work. The optimisation methodology is applied to five distribution networks: TF, Catinen, Coplaca, Anytown and Richmond. Tanks are only considered in the last two networks. In the case of TF network, demonstrative pumps selection (without going into great depth) by the optimum SCs application is done. However pumps sizing and selection study is out of the scope of this research. Neither multiple operation conditions nor reliability (i.e. in the case that tanks or pumping stations are removed), are considered. Nevertheless, the results obtained evidence that pumping systems operated by mean of the optimum SCs could reduce their operating costs up 12%. The methodology also gives information about which pumping stations represent major savings and which are less important or not needed. Besides, the method demonstrates that better pumping conditions (i.e. low energy tariffs and high efficiencies) not always mean lower operating costs. Finally, some results show that the method could be useful for the optimisation of both placement and use of storage tanks. / L'optimització dels sistemes de bombament se sol realitzar a través de les corbes característiques de la xarxa (associades amb les corbes resistents). Aquestes corbes estan subjectes a la resistència generada per l'usuari en funció de les necessitats de cabal i pressió en cada punt de consum. Aquesta resistència és molt variable i difícil de determinar el que fa que el càlcul de les corbes siga poc pràctic. El problema radica que al no definir-se adequadament les corbes resistents, no es coneixen les necessitats reals de cabal i pressió de la xarxa. Per tant no es pot estimar l'excés d'energia aportat per les bombes ni l'augment de costos d'operació que açò representa. No obstant açò, existeix un altre tipus de corba denominada corba de consigna (CC). Aquesta corba ha sigut poc estudiada fins ara i el seu càlcul és relativament fàcil. Per aquest motiu el present treball té com a objectiu l'optimització de l'energia i dels costos de bombament mitjançant l'ús de la CC. Per a complir amb l'objectiu, primer s'estudia el càlcul de la CC en xarxes d'aigua amb múltiples estacions de bombament, consums no depenents i dependents de la pressió, i sense tancs d'emmagatzematge. Posteriorment, es duu a terme l'optimització només des de la perspectiva energètica (cabal i altura de bombament). Per a açò es realitza la cerca de la distribució de cabals òptima entre les estacions de bombament que comporte a les CC òptimes. Es proposen dos mètodes: un de discret (M-D) i un altre continu (M-C). El M-D considera la distribució de cabals com una variable discreta. La distribució òptima s'obté d'un conjunt de solucions prèviament definides. En el M-C la distribució de cabals s'assumeix com a variable contínua. La solució òptima ve donada per l'ús d'un algorisme d'optimització. S'han usat els algorismes: Hooke-Jeeves i Nelder-Mead. El següent pas és l'optimització de costos d'operació (costos de bombament i costos de producció d'aigua). Per a açò es parteix del M-C i s'inclouen a més les tarifes d'energia, les tarifes de producció d'aigua i un criteri sobre el rendiment mínim esperat en les estacions de bombament. L'últim pas consisteix en l'optimització energètica i de costos en xarxes amb tancs. La inclusió de tancs implica la modificació del càlcul de la CC i per tant la metodologia d'optimització. En la funció de costos s'inclouen a més dels costos de bombament i de producció, costos de penalització per incompliment de pressions i de volums de reserva. En incloure's els tancs, incrementa el nombre de variables de decisió. Pel que, és necessari l'ús d'algorismes més potents. S'han usat el Differential Evolution i el Hybrid Algorithm. Aquest últim és una aportació afegida d'aquest treball. La metodologia d'optimització s'aplica a cinc xarxes de distribució: TF, Catinen, Coplaca, Anytown i Richmond. Els tancs només es consideren en les dues últimes xarxes. En el cas de la xarxa TF es realitza una demostració sense entrar en profunditat de la selecció de bombes a través de l'ús de les CC òptimes. No obstant açò, aquest pas està fora dels límits d'aquest treball. Tampoc es consideren condicions d'operació múltiples de la xarxa, ni la fiabilitat en el cas de la remoció de tancs o sistemes de bombament. No obstant açò, els resultats obtinguts evidencien que els sistemes de bombament operats usant la CC poden millorar els seus costos operatius fins a en un 12%. La metodologia proporciona informació sobre les estacions de bombament que representen majors estalvis enfront d'aquelles que són menys importants o innecessàries. A més, el mètode ha permès demostrar que millors condicions de bombament (baixes tarifes d'energia i alts rendiments) no sempre signifiquen menors costos d'operació. Finalment, alguns resultats mostren la possible utilitat del mètode per a optimitzar tant l'ús com la ubicació dels tancs d'emmagatzematge. / León Celi, CF. (2018). Optimisation of both energy use and pumping costs in water distribution networks with several water sources using the setpoint curve [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/107956
154

An integrated control system for an Automatic Guided Vehicle (AGV)

Boje, E.P., Kotze, B.J. January 2008 (has links)
Published Article / An immense amount of research is currently, being done on the development and use of Automatic Guided Vehicles (AGVs) in industry. An important component of this research often involves navigation and route-optimization of such AGVs. In this paper the design and control of an AGV, using a stationary control system and a GPS-like navigational system, is discussed. Substantial provision has also been made for the display of operational characteristics of the AGV on the stationary control unit.
155

Simulateur de billard réaliste

Ploquin, Julien January 2012 (has links)
Aujourd'hui, il n'existe aucun simulateur de jeu de billard qui puisse bénéficier d'une validation scientifique. Les approximations physiques et les limitations dans la liberté des joueurs sont les principales responsables des problèmes de réalisme qu'il est possible d'observer dans les simulateurs existants. L'objectif de cette maîtrise est donc de créer un simulateur qui soit le plus réaliste possible, justification à l'appui. Pour cela, des formules analytiques de physique mécanique combinées à une simulation par événements seront utilisées pour mettre à jour les positions et vélocités des billes. La vitesse de calcul et de résolution de coup ne devant pas devenir trop encombrante, des techniques pour accélérer le traitement seront utilisées. Parmi celles-ci, notons un résolveur d'équation quartique s'appuyant sur une méthode non-itérative. Des outils d'optimisation de problèmes de complémentarité linéaire seront également utilisés pour pallier à certains cas problématiques introduits par la liberté d'action dans l'axe z. Le simulateur répond finalement à la majorité des coups réels, sauf certains utilisant des aspects physiques non-traités tels que la déformation des bandes qui devront être traités dans des travaux futurs. Une analyse qualitative de certains coups filmés viendra confirmer la validité des modèles utilisés pour la simulation. Il est aussi montré que la sensibilité d'un joueur est grandement affectée par la liberté et la fidélité physique proposée grâce à une comparaison avec un simulateur reconnu se limitant à un modèle physique comprenant de nombreuses approximations.
156

Conception d'un système de propulsion omnidirectionnel pour les bateaux sport

Foley, David January 2010 (has links)
Les bateaux sport sont conçus pour performer à haute vitesse, mais au détriment de la maniabilité à basse vitesse. Un système de propulsion omnidirectionnel et contrôlé par un joystick trois axes est présenté pour améliorer la maniabilité du bateau à basse vitesse. Le bateau est équipé de deux pompes à jet. La propulsion s'effectue en redirigeant l'écoulement des pompes dans un ensemble de jets d'eau autour de la coque. Chaque jet est équipé d'une valve et est fixé selon une position et un angle qui optimise la maniabilité, tel qu'évalué par un index basé sur l'omnidirectionnalité. Afin d'exécuter une commande de force en provenance du joystick, on contrôle les valves et le régime des pompes à jet pour moduler le débit et donc, la poussée à chaque jet. L'optimisation du système de propulsion et la conception de la loi de contrôle s'appuient sur un modèle de propulsion qui calcule la force des jets au centre de masse pour une configuration de valves et de régimes moteurs. L'inversion du modèle de propulsion est l'étape principale pour la conception de la loi de contrôle. Un outil de simulation en 3D permet de valider différents paramètres de conception. Le simulateur sert aussi de plateforme pour le développement d'algorithmes de contrôle plus sophistiqués.Les résultats expérimentaux démontrent l'atteinte des critères de conception pour la propulsion omnidirectionnelle.
157

Calibration of water distribution system hydraulic models

Kapelan, Zoran January 2002 (has links)
A number of mathematical models are used nowadays to describe behaviour of the reallife water distribution system (WDS). It is a well known fact that, to have any meaningful use, any WDS mathematical model must be calibrated first. Here, calibration is defined as process in which a number of WDS model parameters are adjusted until the model mimics behaviour of the real WDS as closely as possible. In this thesis, WDS mathematical models that are used to model water quantity aspect only are analysed. Three hydraulic models considered here are: (1) steady-state flow model, (2) quasi-steady flow (extended period simulation) model and (3) unsteady flow model. The calibration problem analysed here is formulated as a constrained optimisation problem of weighted least square type with the objective defined in a way that enables effective incorporation of prior information on calibration parameters. WDS calibration problem is then analysed in detail, including special issues of identifiability, uniqueness and stability of the problem solution. A list of diagnostic and other statistics and analysis is presented to improve existing calibration approaches by providing partial insight into the calibration process. Calibration of WDS hydraulic models is further improved by the development of new hybrid optimisation method. Being closely related to calibration, the problem of sampling design for calibration of WDS hydraulic models is also addressed here. First, sampling design is formulated as a constrained two-objective optimisation problem. Then, two novel models are developed to solve it. The first model is based on standard, single-objective Genetic Algorithms (SOGA). The second model is based on multi-objective Genetic Algorithms (MOGA). Finally, all novel methodologies presented here are verified successfully on multiple case studies that involve both artificial and real-life WDS. At the end, relevant conclusions are drawn and suggestions for further research work are made.
158

Mathematical optimization and signal processing techniques for cooperative wireless networks

Bournaka, Georgia January 2013 (has links)
The rapid growth of mobile users and emergence of high data rate multimedia and interactive services have resulted in a shortage of the radio spectrum. Novel solutions are therefore required for future generations of wireless networks to enhance capacity and coverage. This thesis aims at addressing this issue through the design and analysis of signal processing algorithms. In particular various resource allocation and spatial diversity techniques have been proposed within the context of wireless peer-to-peer relays and coordinated base station (BS) processing. In order to enhance coverage while providing improvement in capacity, peer-to-peer relays that share the same frequency band have been considered and various techniques for designing relay coefficients and allocating powers optimally are proposed. Both one-way and two-way amplify and forward (AF) relays have been investigated. In order to maintain fairness, a signal-to-interference plus noise ratio (SINR) balancing criterion has been adopted. In order to improve the spectrum utilization further, the relays within the context of cognitive radio network are also considered. In this case, a cognitive peer-to-peer relay network is required to achieve SINR balancing while maintaining the interference leakage to primary receiver below a certain threshold. As the spatial diversity techniques in the form of multiple-input-multipleoutput (MIMO) systems have the potential to enhance capacity significantly, the above work has been extended to peer-to-peer MIMO relay networks. Transceiver and relay beamforming design based on minimum mean-square error (MSE) criterion has been proposed. Establishing uplink downlink MSE duality, an alternating algorithm has been developed. A scenario where multiple users are served by both the BS and a MIMO relay is considered and a joint beamforming technique for the BS and the MIMO relay is proposed. With the motivation of optimising the transmission power at both the BS and the relay, an interference precoding design is presented that takes into account the knowledge of the interference caused by the relay to the users served by the BS. Recognizing joint beamformer design for multiple BSs has the ability to reduce interference in the network significantly, cooperative multi-cell beamforming design is proposed. The aim is to design multi-cell beamformers to maximize the minimum SINR of users subject to individual BS power constraints. In contrast to all works available in the literature that aimed at balancing SINR of all users in all cells to the same level, the SINRs of users in each cell is balanced and maximized at different values. This new technique takes advantage of the fact that BSs may have different available transmission powers and/or channel conditions for their users.
159

Linkage Synthesis and Optimisation Techniques with Skiboard Product Design Case Study

Kauke, Lisa Marie January 2010 (has links)
This thesis explores the design development and experimental testing of a planar linkage for the Skiboard, a novel snowsports equipment device. The Skiboard, similar to a skateboard in appearance and style of use, combines two short skis with a bindingless board. Its aim is to fill a gap in the snowsports market for a product that offers a wide range of freestyle and trick riding possibilities, beyond those of a snowboard, while being as stable and easy to ride as a pair of skis. While the concept of the Skiboard in itself is simple, the task of designing a mechanism to link the skis to the board is complex. To translate a gradual lean of the rider into a gradual and equal tilting of the skis requires a multi-loop linkage mechanism. The synthesis and analysis of a mechanism for this application was the inspiration for the development of the synthesis-related design tools presented in this thesis. Design methodologies and design software concepts have been developed for use by designers faced with under-defined, “black-box” linkage synthesis problems similar to the Skiboard mechanism synthesis task. A software-based design of experiments setup, called SMAC, is introduced in this thesis and was used throughout the linkage synthesis process for the Skiboard. One promising candidate mechanism, developed and chosen using SMAC, is followed through to the pre-prototyping phase of the design process. PSEO, another, more advanced, software tool for complex and multi-loop linkage synthesis is also presented in the concept stage of development. This type of program has the potential to automate some of the most time-consuming portions of the synthesis and analysis process with the use of a genetic algorithm and curve-matching algorithm. Additionally, it keeps much of the user’s interaction with the design process and the design itself intact, which is something not offered by existing tools incorporating similar levels of automation. Overall, this thesis is an exploration into the field of linkage design, a topic with little crossover between theory and practical design helps. It includes a review of existing synthesis tools and the development of new tools to suit complex applications such as the Skiboard. The design process for the Skiboard linkage mechanism is also presented and illustrates the way in which the creative design process is iterative, progressively informing the designer’s understanding of the functional requirements of the linkage and how to best satisfy them.
160

Optimisation of Final Product Composition

Burnett, Hayley Rose January 2014 (has links)
The composition of dairy products can have a significant impact on a dairy manufacturer’s revenue. By including more of the low-value components (water and lactose) and less of the higher value components (fat and protein) in their products, within customer specifications, higher yields and therefore higher revenue can be attained. The purpose of this project was to optimise product composition at Westland Milk Products, and develop procedures for the maintenance of yield reporting.

Page generated in 0.0926 seconds