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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.
81

Stereo visual servoing from straight lines

Alkhalil, Fadi 24 September 2012 (has links) (PDF)
Closing the control loop of a manipulator robot with vision feedback is widelyknown. It concerns nowadays all areas of robotics. Such a return can make a comparison between a desired state and current state, using visual measurements. The main objective of this doctoral thesis is to design several types of kinematic control laws for stereo visual servoing. It strongly involves the formalism of the task function which is a well-known and useful mathematical tool to express the visual error as a function of state vectors.We have investigated the decoupling between the rotational and translational velocities control laws together with the epipolar constraint with a stereo visual feedback.That is why, the visual measurements and features used in this thesis are the 3Dstraight lines.The interests of this type of visual features rely on the robustness against the noise, and the possibility to represent straight lines or other features like points or planes pairs by the Plücker coordinates, as a 3D straight line can be represented as well by two points or the intersection of two planes. This makes all the control laws designed in this thesis valid for another visual features like points
82

Control of an ultrahigh speed centrifugal compressor for the air management of fuel cell systems

Zhao, Dongdong 10 December 2013 (has links) (PDF)
Air compressor supplying the oxygen to the stack is an important component in the fuel cell systems. The compressor can consumes up to 20 % of the generated power in the most severe cases. The selecting of the compressor and corresponding control are directly related to the performance of the fuel cell. The size and weight of the air compressor has to be reduced to make them more feasible for automotive applications. Moreover, the control of the air compression system is also an important issue, which affects the efficiency and the safety of the fuel cell. To avoid oxygen starvation of the stack, the mass flow of the supplied air has to be controlled appropriately according to the load demand. Meanwhile, the pressure should not have large deviations or ripples which may damage the stack membrane.A recently proposed disturbance decoupling control (DDC) is used for the centrifugal compression system. DDC treats the internal interactions as a disturbance and then eliminates them in the control. The performance of the DDC is compared with a decentralized sliding mode controller. Through the comparison of those two controllers, the results show that the proposed DDC performs better in both the steady state and dynamic conditions, making the centrifugal compressor is capable of applying to the fuel cell in automotive applications. On a hardware-in-the-loop (HIL) testbench, the proposed controller is validated with a 10 kW fuel cell model under varied load demands. Moreover, a surge avoidance method, namely reference limiter, is proposed to prevent the compressor from surging. The experimental results show that the operation is restricted to the right of the surge line.
83

La répartition optimale de la puissance réactive pour le contrôle des tensions de barre d'un réseau électrique par simplex LP /

Diarra, Adama D., January 1984 (has links)
Mémoire (M. Sc. A.)-- Université du Québec à Chicoutimi, 1984. / bibliographie: f. 102-104. Document électronique également accessible en format PDF. CaQCU
84

2D coordinate space Hartree-Fock-Bogoliubov calculations for neutron-rich nuclei in the A [approximately equal to] 100 mass region

Blazkiewicz, Artur Robert. January 2005 (has links)
Thesis (Ph. D. in Physics)--Vanderbilt University, Dec. 2005. / Title from title screen. Includes bibliographical references.
85

Σχεδίαση παρατηρητή και ελεγκτή μη γραμμικού συστήματος με εφαρμογή στο σύστημα των τριών δεξαμενών

Γιαννοπούλου, Παναγιώτα 03 October 2011 (has links)
Στην παρούσα διπλωματική εργασία, στόχος είναι η μελέτη του προβλήματος αποσύζευξης τόσο σαν γενική προσέγγιση για την αποσύζευξη εισόδων-εξόδων και διαταραχών, όσο και η εφαρμογή των μεθόδων αποσύζευξης στο σύστημα των τριών διασυνδεδεμένων δεξαμενών. Πιο συγκεκριμένα, χωρίζουμε τη διπλωματική σε τρία κεφάλαια. Στο πρώτο κεφάλαιο, παρουσιάζουμε το μοντέλο των τριών διασυνδεδεμένων δεξαμενών που υπάρχουν στο χώρο του εργαστηρίου και συνδέουμε τη φυσική διάταξη με την ύπαρξη του προβλήματος της σύζευξης στο σύστημα που μελετάμε. Στο δεύτερο κεφάλαιο, μελετάμε τις μεθόδους αποσύζευξης που παρουσιάζονται σε συγκεκριμένα άρθρα που αφορούν τα μη γραμμικά συστήματα και τις σχέσεις εισόδου-εξόδου και αποσύζευξης διαταραχών. Τέλος, στο τρίτο κεφάλαιο, με βάση τα αποτελέσματα που έχουμε αποκομίσει από το δεύτερο κεφάλαιο, εφαρμόζουμε μεθόδους αποσύζευξης εισόδου-εξόδου για το σύστημά των τριών διασυνδεδεμένων δεξαμενών και βγάζουμε τα συμπεράσματά μας για το αν εφαρμόζεται η κάθε μέθοδος και τι αποτελέσματα θα μας επιφέρει. / -
86

O viés de tarifa fixa e seu impacto na renúncia de consumo do serviço de telefonia

Nunes, Marcelo de Oliveira January 2015 (has links)
O viés da tarifa fixa ocorre quando um consumidor contrata um determinado nível de serviço e, em média, consome menos do que ele/ela tem direito a consumir. Tal comportamento é documentado em variados setores, em especial no de telecomunicações. Nesta dissertação, espera-se que o tipo de tarifa que uma pessoa tem seja a causa de determinados comportamentos. Assim, este estudo se baseia nas teorias da contabilidade mental e da dissociação da transação, para medir o impacto de tipos diferentes de tarifas no comportamento de consumo de telefonia móvel. Em uma sequência de três experimentos, foi descoberto que usuários de tarifa fixa são mais dispostos a abrir mão do consumo e se sentem menos frustrados e menos arrependidos do que usuários de tarifa por uso. Este comportamento é condizente com os efeitos dos custos irrecuperáveis que, conforme hipotetizado, também são observados em serviços por assinatura, e não apenas transacionais. Adicionalmente, foi observado que na medida em que aumenta a quantidade de pessoas consumindo o mesmo plano, a disposição a renunciar o consumo permanece a mesma. Por fim, foi observado que o viés da tarifa fixa não compromete comportamentos futuros, como a intenção de migrar ou permanecer com o mesmo plano. Estes resultados apoiam tanto implicações gerenciais quanto teóricas, e oferecem novos caminhos de estudos em mercados menos típicos, porém promissores, de serviços por assinatura. / The flat-rate bias takes place whenever a consumer contracts a given service level and, in average, consumes only a fraction of what s/he is entitled. Such behavior is documented in a number of different sectors, specially the telecommunications sector. In this thesis, the type of tariff an individual has is expected to be the cause of particular behaviors. Therefore, this study draws on mental accounting and transaction decoupling theories, to measure the impact of different types of tariffs on mobile phone consumer behavior. In a series of three experiments, it was found that flat-rate consumers are more willing to forgo consumption and they feel less frustrated and less regretful than users of a pay-per-use plan. This behavior is consistent with the sunk cost effects which, as hypothesed, can also be seen in contract services, and not only in transactional ones. Additionally, it was noted that as the amount of people consuming the same plan increases, the willingness to forgo consumption remains unaltered. Finally, it was observed that the flat-rate bias does not commit future behavior, such as the intention to either change or stay with the same plan. These results support both managerial and theoretical implications, and offer new avenues of studies on the less typical, yet promising, markets of subscription services.
87

Desacoplamento de sistemas de controle multivariáveis por ICA com modificação do branqueamento.

CRUZ, Fábio George Nogueira. 16 October 2018 (has links)
Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-10-16T14:50:15Z No. of bitstreams: 1 FÁBIO GEORGE NOGUEIRA CRUZ - DISSERTAÇÃO (PPGEQ) 2017.pdf: 3691156 bytes, checksum: 5b1dfe0077677e8425fa32fdbb895e39 (MD5) / Made available in DSpace on 2018-10-16T14:50:15Z (GMT). No. of bitstreams: 1 FÁBIO GEORGE NOGUEIRA CRUZ - DISSERTAÇÃO (PPGEQ) 2017.pdf: 3691156 bytes, checksum: 5b1dfe0077677e8425fa32fdbb895e39 (MD5) Previous issue date: 2017-03-27 / A utilização de sensores em sistemas de controle de processos é de vital importância para o monitoramento e operação adequada das plantas industriais. Por sua vez, os sinais podem apresentar interferências de outras fontes, além de que em certos casos, não é possível observar diretamente os sinais individuais das fontes. Diante disso, as técnicas de processamento e separação de sinais são utilizadas no intuito de extrair as informações das fontes contidas nos sinais misturados. As principais técnicas de separação de sinais estão associadas a técnica ICA (Independent Component Analysis), que sofreu significativa evolução desde sua criação nos anos 80. Tal evolução teve contribuição também da técnica PCA (Principal Component Analysis) e do desenvolvimento da capacidade de processamento computacional. No entanto, essas técnicas apresentam dois problemas básicos, a saber: desvio de amplitude e mudança de fase, sendo tais problemas limitantes quanto a sua utilização em sistemas de controle. Sendo assim, esse trabalho tem como objetivo apresentar uma solução do problema de amplitude das técnicas ICA’s para utilização na redução do acoplamento de sistemas multivariáveis. A correção proposta, baseada na correção da etapa de branqueamento dos algoritmos ICA, gerando a técnica MOD-ICA, foi utilizada como alternativa para a quebra da correlação entre variáveis dos sistemas multivariados. Essa técnica foi utilizada para o projeto e obtenção dos pares de controle de uma planta de produção de etanol anidro modelada na plataforma Aspen Dynamics. No estudo de caso proposto, foi observada uma redução significativa no número condicional dos pares de controle propostos, e a matriz de separação foi utilizada como parâmetro de desacoplamento do sistema de controle. Dessa forma, a técnica proposta MOD-ICA apresentada pode ser utilizada como ferramenta de geração de projeto de sistemas de controle, podendo a matriz de separação ser considerada como modelo de redução de acoplamento, resultando assim na obtenção de um sistema de controle mais robusto às variações inerentes do processo. / The use of sensors in process control systems is of vital importance for the proper operation and monitoring of industrial plants. In turn, process signals may have interference from other sources and, in some cases, it is not possible to observe directly the individual signals of the sources. In view of this, signal processing and separation techniques are used in order to extract the information from the sources contained in mixed signals. The main signal separation techniques are associated with the Independent Component Analysis (ICA), which has undergone significant evolution since its creation in the 1980s. Such evolution also had the contribution of the Principal Component Analysis (PCA) and the development of computational processing power. However, these techniques have two basic glitches: deviation of amplitude and phase change, which limit their use in control systems. Therefore, this research aims to present a solution to the problem of amplitude in ICA techniques for use in decoupling reduction in multivariate systems. The proposed correction, based on the stage of whitening ICA algorithms, which generated the technique MOD-ICA, was used as an alternative to breaking the correlation between variables in multivariate systems. Such technique was used for projecting and obtaining controlling pairs in an industrial plant of anhydrous ethanol production modeled on the Aspen Dynamics platform. In the case study proposed in this research, a significant reduction in the conditional numbers of the proposed controlling pairs was observed, and the separating matrix was used as a parameter of decoupling for the control system. As a result, the proposed MOD-ICA technique can be used as a tool for generating control systems, and its separating matrix can be considered as a model for decoupling reduction, which results in a more robust control system for process variation.
88

Intégration de capacités verticales débouchantes au sein d'un interposeur silicium / Through silicon capacitor integration on silicon interposer

Guiller, Olivier 02 April 2015 (has links)
La densité des circuits intégrés n’a pas cessé d’augmenter depuis la découverte du transistor en 1947, à travers la réduction de la taille de leurs composants. Cependant, cette miniaturisation se heurte aujourd’hui à certaines barrières et la réduction de la longueur de grille des transistors ne permet plus à elle seule l’augmentation des performances globales des circuits intégrés. L’industrie de la microélectronique s’est donc tournée vers de nouvelles solutions d’intégrations hétérogènes visant à développer la diversification des fonctionnalités proposées par les circuits. Parmi ces solutions, l’intégration 3D consistant à empiler plusieurs puces de silicium les unes sur les autres à l’aide de « Through Silicon Vias » (TSV) apparait très prometteuse. Toutefois, de telles structures mettront du temps à atteindre leur maturité puisqu’elles requièrent l’évolution de tout l’écosystème industriel. Une solution intermédiaire en termes de maturité technologique réside dans l’utilisation de l’interposeur : un substrat aminci placé entre les puces haute densité et le « Ball Grid Array » faisant office de plateforme d’intégration permettant le placement côte à côte de puces hétérogènes ainsi que la réalisation d’une forte densité d’interconnexions. Cependant, l’ajout de l’interposeur dans le système a pour effet l’augmentation de l’impédance du réseau de distribution de puissance. L’intégration d’une capacité de découplage au sein de l’interposeur répond à cette problématique en assurant l’intégrité de l’alimentation dans des structures tridimensionnelles.L’objectif de cette thèse de doctorat consiste en l’étude de l’intégration d’un nouveau type de capacité intégrée au sein de l’interposeur silicium. Cette capacité basée sur un empilement Métal-Isolant-Métal (MIM) tridimensionnelle a pour particularité de traverser l’intégralité de l’épaisseur de l’interposeur et d’être co-intégrée avec les TSV.La première étape de l’étude de ce nouveau composant intégré a été la définition d’une architecture performante, réalisée à travers une étude de modélisation permettant l’évaluation de l’influence des nombreux paramètres géométriques et matériaux entrant en jeu. Cette étude a permis de mettre en avant les faibles valeurs d’ESR et d’ESL atteignable par la structure (de l’ordre du m et fH respectivement). Ensuite, la réalisation de la capacité a nécessité le développement de procédés de fabrication innovants permettant le dépôt d’un empilement MIM dans des matrices de vias profonds ainsi que sa co-intégration avec les TSV. Enfin, les performances du composant ont été évaluées à travers la réalisation et la caractérisation d’un démonstrateur de test ainsi qu’une campagne de simulations électromagnétiques par éléments finis. Une densité de capacité de 20 nF.mm-2 a été atteinte sur ce démonstrateur, offrant un gain d’un facteur supérieur à 6 par rapport à une structure planaire. / Integrated circuits density never stopped rising since the discovery of the transistor in 1947, through components size shrinking. However, this miniaturization now encounters barriers and reduction of transistor’s gate size alone no longer allows integrated circuits overall performances increase. Therefore, microelectronic industry turned to new heterogeneous integration solutions aiming to develop the diversification of functionalities offered by the circuits. Among these solutions, 3D integration involving stacking several silicon dies on top of each other with the help of Through Silicon Vias (TSV) appears to be promising. Nevertheless, such structures will take times to reach maturity since they require the evolution of the whole industrial ecosystem. A transitional solution in term of technological maturity lies in the use of the interposer: a thinned substrate placed between the high density silicon dies and the Ball Grid Array acting as an integration platform allowing side by side placement of heterogeneous dies as well as high density interconnections. However, the addition of the interposer in the system leads to the increase of the Power Delivery Network impedance. The integration of a decoupling capacitor on the interposer resolves this issue by ensuring power integrity within 3D structures.The objective of this PhD thesis consists in the study of different aspects of a new kind of integrated capacitor within the silicon interposer. This 3D Metal-Insulator-Metal (MIM) capacitor has the particularity to cross over the whole silicon interposer’s thickness and to be co-integrated with TSV.The first step of this new integrated component study has been the definition of an efficient architecture, achieved through a modeling study allowing the influence evaluation of the numerous geometrical and material parameters coming into play. This modeling study pointed out the low ESR and ESL values achievable by the structure (in the m and fH range respectively). Then, the fabrication of the capacitor required the development of innovative process steps allowing the deposition of a MIM stack in deep vias matrices as well as co-integration with TSV. Finally, component performances have been evaluated through the fabrication of a test demonstrator as well as a finites elements electromagnetic simulation campaign. A capacitance density of 20 nF.mm-2 has been reached on this demonstrator, showing an increase up to a factor 6 compared to a planar structure.
89

Semla eller inte semla? : Motivera personal med icke-monetära belöningar som en del i ett kulturskapande / Swedish cream bun or not? : Motivate personnel with non-monetary rewards as a part of culture building

Axelsson, Sofie, Berglund, Julia January 2018 (has links)
Icke-monetära belöningar har på senare tid uppmärksammats mer och mer och börjat användas av företag i allt större utsträckning. Syftet med uppsatsen är därför att undersöka hur just icke-monetära belöningar upplevs av anställda och effekten de har på motivation. Är ökningen av icke-monetära belöningar verkligen berättigad? Tidigare studier har ofta kommit fram till att icke-monetära belöningar har en positiv påverkan på motivation men inte varför de har det och det är här vår studie har sitt bidrag. Studien genomfördes med hjälp av kvalitativa semistrukturerade intervjuer på en bank som i princip endast använder icke-monetära belöningar. För att ha en god grund att diskutera fallstudiens resultat, har tre teorier använts; teorin om frikoppling, Maslows behovstrappa samt Herzbergs tvåfaktorteori. Med hjälp av teorin om frikoppling har en diskussion förts kring den frikoppling som setts mellan de olika hierarkiska nivåerna. Motivationsteorierna har gett sitt bidrag i att stödja inre och yttre motivationskrafter. Både Maslow och Herzberg förespråkar vikten av icke-monetära belöningar men att de först uppskattas då grundläggande behov är uppfyllda. I intervjuerna nämndes ofta monetära belöningar i ett första skede som bra motivationsfaktorer men vidare sågs den betydelse de icke-monetära belöningarna verkligen har. Studien har bekräftat innebörden av icke-monetära belöningar där främst utvecklingsmöjligheter uppskattas. Varför dessa icke-monetära belöningarna fungerar är för att de kan bidra till att skapa en kultur som på ett indirekt sätt motiverar de anställda. Utifrån studiens resultat kan slutsatsen dras att en god företagskultur där det exempelvis erbjuds goda utvecklingsmöjligheter, olika förmåner och en semla på semmeldagen skapar en trivsel vilket leder till att de anställda motiveras i det långa loppet och blir lojala till sina arbetsgivare. / Recently non-monetary rewards have been receiving more and more attention which have led to an increase in the usage of them by multiple companies. The purpose of this paper is therefore to investigate how non-monetary rewards are perceived by the employees and consequently how it affects the motivation of the employees. Is the increase justified or is it only a trend passing by? Prior research has identified that non-monetary rewards have a positive effect on the motivation of the employees. Why it has a positive effect is, however, uncertain and that is how our study will contribute to the field of study. The study was conducted through a series of qualitative semi-structured interviews on a single bank which basically only use non-monetary rewards. In order to be able to discuss the result of the case study, three theories have been used, decoupling theory, Maslow’s hierarchy of needs and Herzberg’s two-factor theory. By using the decoupling theory, a discussion about decoupling between the different levels of hierarchy has been held. Both motivation theories used in the study have contributed with support to both the internal and external forces of motivation. Maslow and Herzberg both describe the importance of non-monetary rewards and how they only can be fully appreciated once the basic needs are fulfilled. Monetary rewards were often mentioned in the beginning of the interviews as important first motivating factors but later in (in the interviews) the meaning of non-monetary rewards was emphasized. The study has also confirmed the appreciation of non-monetary rewards and especially developing opportunities within the company. A reason why these non-monetary rewards work in practice are because they can create a culture that indirectly motivate the employees. Based on the result of the study a conclusion can be made. By creating a good corporate culture that promote developing opportunities, benefits and by offering a Swedish cream bun on a special day, it results in a well-being which eventually leads to motivated and long-term committed employees.
90

O viés de tarifa fixa e seu impacto na renúncia de consumo do serviço de telefonia

Nunes, Marcelo de Oliveira January 2015 (has links)
O viés da tarifa fixa ocorre quando um consumidor contrata um determinado nível de serviço e, em média, consome menos do que ele/ela tem direito a consumir. Tal comportamento é documentado em variados setores, em especial no de telecomunicações. Nesta dissertação, espera-se que o tipo de tarifa que uma pessoa tem seja a causa de determinados comportamentos. Assim, este estudo se baseia nas teorias da contabilidade mental e da dissociação da transação, para medir o impacto de tipos diferentes de tarifas no comportamento de consumo de telefonia móvel. Em uma sequência de três experimentos, foi descoberto que usuários de tarifa fixa são mais dispostos a abrir mão do consumo e se sentem menos frustrados e menos arrependidos do que usuários de tarifa por uso. Este comportamento é condizente com os efeitos dos custos irrecuperáveis que, conforme hipotetizado, também são observados em serviços por assinatura, e não apenas transacionais. Adicionalmente, foi observado que na medida em que aumenta a quantidade de pessoas consumindo o mesmo plano, a disposição a renunciar o consumo permanece a mesma. Por fim, foi observado que o viés da tarifa fixa não compromete comportamentos futuros, como a intenção de migrar ou permanecer com o mesmo plano. Estes resultados apoiam tanto implicações gerenciais quanto teóricas, e oferecem novos caminhos de estudos em mercados menos típicos, porém promissores, de serviços por assinatura. / The flat-rate bias takes place whenever a consumer contracts a given service level and, in average, consumes only a fraction of what s/he is entitled. Such behavior is documented in a number of different sectors, specially the telecommunications sector. In this thesis, the type of tariff an individual has is expected to be the cause of particular behaviors. Therefore, this study draws on mental accounting and transaction decoupling theories, to measure the impact of different types of tariffs on mobile phone consumer behavior. In a series of three experiments, it was found that flat-rate consumers are more willing to forgo consumption and they feel less frustrated and less regretful than users of a pay-per-use plan. This behavior is consistent with the sunk cost effects which, as hypothesed, can also be seen in contract services, and not only in transactional ones. Additionally, it was noted that as the amount of people consuming the same plan increases, the willingness to forgo consumption remains unaltered. Finally, it was observed that the flat-rate bias does not commit future behavior, such as the intention to either change or stay with the same plan. These results support both managerial and theoretical implications, and offer new avenues of studies on the less typical, yet promising, markets of subscription services.

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