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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.
31

Proposta de um controlador difuso Takagi-Sugeno com desempenho H \'INFINITO\' para regulagem da marcha lenta em motores de ciclo Otto / Otto cicle engine idle speed H \'INFINITE\' Takagi-Sugeno fuzzy control

Carlos Eduardo Milhor 22 February 2008 (has links)
Propõe-se um controlador difuso Takagi-Sugeno com índice de desempenho H \'INFINITO\' para regulagem da marcha lenta em motores de ciclo Otto. Obtém-se uma representação difusa do motor de ciclo Otto operando em marcha lenta. Esse modelo é utilizado para a síntese do controlador. O controlador difuso com desempenho H \'INFINITO\' é projetado para rejeitar o efeito de distúrbios de cargas externas sobre a rotação do motor em regime de marcha lenta. As ações de controle, posição da borboleta de aceleração e ponto de ignição, são limitadas a uma faixa de operação específica para a marcha lenta. O controlador projetado apresenta ação de controle por realimentação de estados. Os ganhos de realimentação para cada regra do controlador difuso são obtidos a partir de um problema de otimização formulado através de LMIs. / It is proposed an Otto cicle engine idle speed H \'INFINITE\' Takagi-Sugeno fuzzy control. It is presented an Otto cicle engine idle speed fuzzy model. This model is then used to control design. The H \'INFINITE\' fuzzy control is designed to reject external load disturbance effect at idle speed engine rotation. A specifc idle speed operation range is defined to both actions control, throttle plate position and spark advance. A state feedback control is designed. A LMI optmization problem is used to find the state feedback gains at each fuzzy control rule.
32

Optimalizace procesu soustružení zohledňující mechanické a vykonove vlastnosti stroje / Optimization of turning regarding mechanical and power machine characteristics

Holík, David January 2011 (has links)
Manufacturing companies are increasingly compelled to optimize their machining processes for various reasons, such as improved cost effectiveness, tighter regulations and marketing advantages. Increasing energy costs in particular shift the reduction of energy consumption and the cost effectiveness of the production method more into the focus of corporate strategy. This is done by using the example of a turning process for the production of a tapered roller bearing. The main goal of this thesis can be identified as a detailed investigation of the energy consumption of certain turning machine. Further, different optimization approaches regarding energy efficiency are introduced taking under consideration tooling costs and machining time.
33

ATT SPELA RIKTIGA SPEL : Vad spelare tycker om att spela incremental-spel / PLAYING REAL GAMES : What players like about playing incremental games

Olsson, Måns January 2023 (has links)
Incremental-spel är en spelgenre som innehåller spel med mycket enkla spelmekaniker (Cutting, Gundry & Cairns 2019). De har utvecklats som satir av trender på spelmarknaden (Bogost 2010; Deterding 2016), och har anklagats för att inte vara riktiga spel (Cutting, Gundry & Cairns 2019; Deterding 2016; Purkiss& Khaliq 2015). Trots detta har de blivit mycket populära. Följande arbete har med hjälp av grundad teori (Glaser & Strauss 1967) på ett utforskande sätt undersökt vad spelare tycker om med att spela incremental-spel. Spelare har intervjuats under semistrukturerade intervjuer om deras åsikter. Intervjuerna spelades in, transkriberades och analyserades. Analysen bestod av iterativ kodning för att hitta koncept som kunde utvecklas till beskrivande teman. Arbetet visar att progression, problemlösning, tillgänglighet och speltid är viktiga för incremental-spel. I framtida forskning kan dessa teman undersökas med större grupper och andra typer av spel, för att utöka förståelsen för hur spel påverkar spelare.
34

Rapid Prototyping Job Scheduling Optimization

Wu, Yingxiang 29 November 2001 (has links)
Today's commercial rapid prototyping systems (i.e., solid freeform fabrication, layered manufacturing) rely on human intervention to load and unload build jobs. Hence, jobs are processed subject to both the machine's and the operator's schedules. In particular, first-in-first-out (FIFO) queuing of such systems will result in machine idle time whenever a build job has been completed and an operator is not available to unload that build job and start up the next one. These machine idle times can significantly affect the system throughput, and, hence, the effective cost rate. This thesis addresses this problem by rearranging the job queue to minimizing the machine idle time, subject to the machine's and operator's schedules. This is achieved by employing a general branch-and-bound search method, that, for efficiency, reduces the search space by identifying contiguous sequences and avoiding reshuffling of those sequences during the branching procedure. The effectiveness of this job scheduling optimization has been demonstrated using a sequence of 30 jobs extracted from the usage log for the FDM 1600 rapid prototyping system in the Department of Mechanical Engineering at Virginia Tech. / Master of Science
35

政策終結與課責:以我國閒置公共設施之活化再利用為例 / Policy Termination and Accountability: Using the Activation of Idle Public Facilities in Taiwan as an Example

郭韶莛, Kuo, Shao-Ting Unknown Date (has links)
公共設施的設立雖被視為公共利益的增進,但我國公共設施閒置的現象卻也十分普遍,因而引發許多關注、爭議與批評,使閒置公共設施活化的議題,成為近年行政管理的重要目標。對此,本文的研究目標有二:首先透過政策終結的理論觀點,探討我國閒置公共設施進行活化的決定因素;其次,在確保活化目標的基礎上,更進一步探討活化過程的課責機制,以行政、法律、政治、專業等四種面向進行分析。試圖對未來的活化策略以及課責機制的精進,提供實務上之政策建議。 依據上述目標,本研究以行政院公共工程委員會104年第三季的113個列管案件為分析對象,透過系統性的文獻分析與整理,以及利害關係人的深度訪談進行實證研究。由研究結果可知,法律障礙、經濟成本與心理抗拒等三項因素,是誘發我國閒置公共設施選擇進行全面活化的主要因素;而若從活化執行過程的課責機制面向來看,行政課責與政治課責是亟待改進之處。 最後,依據研究成果,本文提出之研究建議包含:(一)強化機關的政策評估能力:在公共建設計畫的編審作業階段嚴格要求成本效益分析、環境影響評估的執行,以強化計畫與人民需求之間的連結;(二)納入公民參與機制:透過公聽會、座談會的舉行,瞭解人民需求,確保政府決策的公開透明,並強化政府與人民間的信任關係;(三)建立適當的退場機制:針對區位不佳或活化成本過高的列管案件,給予適度的法規鬆綁,以避免閒置公共設施的再次閒置。 / Although public facilities are built to promote public interest, idle public facilities are everywhere in Taiwan. This so-called “mosquito houses” phenomena have gotten public attention to cast doubts on government effectiveness. In response, government activates a new program to reinventing idle public facilities. This research is design to explore the factors through which government implements the reinventing program. Under the guidance of policy termination and accountability theories, this study explores the mechanism of accountability behind the reinventing program in four dimensions, included political accountability, bureaucratic accountability, legal accountability and professional accountability. This research is expected to provide theoretical answers and practical suggestion to enhance the reinventing program as well as the mechanism of accountability behind public facilities construction decisions. This research utilizes government documents to analyze 113 “mosquito house” cases monitored by Public Construction Commission, Executive Yuan as well as literature review and in-depth interviews. The results indicate that, the legal obstacles, economic costs and the psychological reluctance, were the decisive factors to lead to the activation of reinventing program. As for the accountability, it would be urgent to improve the mechanism of administrative accountability and political accountability. Lastly, this study could provide three main practical suggestions as follows: (1) Strengthening the capacity of policy assessment in government, (2) bringing in the citizen participation (3) Building a mechanism of public facility termination.
36

Le Mali et les biocarburants : une analyse à partir d'un modèle d'équilibre général calculable dynamique

Yamba, Emmanuel Magloire January 2015 (has links)
Résumé : Les résultats alarmants du Groupe d’Experts Intergouvernemental sur l’Évolution du Climat (GIEC) et la tenue des sommets chaque année sur le réchauffement climatique poussent de nombreux pays à prendre la chose au sérieux (notre-planète.info, 2015). C’est ainsi que le Mali, pays enclavé et importateur net de produits pétroliers, cherche des moyens non seulement pour emboiter le pas à la communauté internationale sur la protection de l’environnement mais aussi à mieux gérer sa politique énergétique. Cette volonté repose sur le développement des biocarburants grâce au jatropha qui se cultive aussi bien sur des sols semi-arides que fertiles. Depuis plusieurs décennies les biocarburants font l’objet de recherches. Certaines études permettent de conclure que leur utilisation réduirait les émissions de GES tandis que d’autres vont plus loin au-delà du cadre écologique et trouvent que c’est une source de rentabilité économique. Pour mieux illustrer ses effets, nous avons utilisé un modèle d’équilibre général calculable dynamique (MEGCD) qui permet de voir les interactions des variables structurelles de l’économie malienne sur une durée de 4 ans. Les résultats montrent qu’une politique protectionniste du secteur des biocarburants jumelée à une politique d’exploitation accrue du jatropha à partir des terres non occupées au Mali, génèrent plus d’activité dans le pays et permet de réduire les importations de carburant. De même, la croissance dans le secteur de l’énergie permet d’augmenter la production en électricité dans le pays. / Abstract : The alarming results of the Intergovernmental Panel on Climate Change (IPCC) and the summits annually on global warming are pushing many countries to take it seriously (notre-planète.info, 2015). In this way Mali, landlocked and importing country of fuel, take measure to join in international community on protection of environment also to manage better his energetic policy. This determination is based on the development of biofuels through jatropha which both grown on semi-arid soils fertile. Many searchers are worked on the advantages and disadvantages to Jatropha compared to diesel and fund that his useful reduced greenhouse gas emission while others go further beyond the ecological environment and find it a source of economic profitability. We use a dynamic calculable general equilibrium model (DCGEM) to illustrate relations between all structural variables of economy Malian on four years. We find that a biofuel protectionist policy combined with an increased operating policy jatropha from idle land in Mali, generate more activity and reduces fuel imports. Similarly, growth in the energy sector can increase electricity production in the country.
37

Utilizing Valvetrain Flexibility to Influence Gas Exchange and Reduce Reliance on Exhaust Manifold Pressure Control for Efficient Diesel Engine Operation

Kalen Vos (6787271) 02 August 2019 (has links)
Environmental health awareness has elevated in recent years alongside the evidence that supports the need to mitigate harmful greenhouse gas (GHG) emissions from non-renewable energy resources. The transportation sector alone significantly contributes to the pollutants on a global scale. Although it is commonly used for its superior energy-density and fuel efficiency, diesel engines are a significant portion of the transportation sector that contributes to these pollutants. As a result, this motivates novel research to simultaneously drive fuel efficiency improvements and emissions reductions. <div><br></div><div>The aftertreatment system for a diesel engine is critical in reducing the amount of harmful tailpipe emissions. Efficient operation of these aftertreatment systems generally requires elevated temperatures of 250◦C or above. In this effort, a flexible valvetrain will be utilized to demonstrate fuel-efficient strategies via intake valve closure (IVC) modulation at elevated speeds and loads. In addition, thermal management strategies will be demonstrated at low-to-moderate loads via cylinder deactivation (CDA), cylinder cutout, exhaust valve opening (EVO) modulation, and high-speed idle operation.</div><div><br></div><div>At elevated engine speeds, late intake valve closure (LIVC) enables improved cylinder filling via a dynamic charging effect. It is experimentally and analytically demonstrated that LIVC at 2200 RPM and 7.6 bar to 12.7 bar BMEP can be used to increase the volumetric efficiency and enable higher exhaust gas recirculation fractions without penalizing the air-to-fuel ratio. As a result, efficiency improving injection advances are implemented to achieve 1.2% and 1.9% fuel savings without sacrificing NOx penalties. In order to implement the LIVC benefits on a cammed engine, production-viable valve profile solutions were investigated. It is demonstrated that lost-motion-enabled and/or added-motion-enabled boot shape profiles are capable of improving volumetric efficiency at elevated engine speeds and loads. These profiles were also considered for one (of two) -valve modulation and two-valve modulation. Nearly 95% of the volumetric efficiency benefits are possible using production-viable boot or phase profiles, while 80% of the benefits are possible for single-valve modulation. </div><div><br></div><div>At curb idle, CDA and cylinder cutout operation realize stay-warm aftertreatment thermal management improvements by leveraging their impact on the gas exchange process. Specifically, cylinder cutout demonstrates 17% fuel savings, while CDA demonstrates 40% fuel savings, over the conventional six-cylinder thermal calibration. Additionally, the performance of cylinder cutout is subject to the geometry of the exhaust manifold, location of the EGR loop, and ability to control the exhaust manifold pressure. </div><div><br></div><div>Elevating the idle speed, while maintaining the same idle load, enables improved aftertreatment warm-up performance with engine-out NOx and PM levels no higher than a state-of-the-art thermal calibration at conventional idle operation. Elevated idle speeds of 1000RPM and 1200 RPM, compared to conventional idle at 800 RPM, realized 31% to 51% increase in exhaust flow and 25◦C to 40◦C increase in engine-out temperature, respectively. Additional engine-out temperature benefits are experimentally demonstrated at all three idle speeds considered (800, 1000, and 1200 RPM), without compromising the exhaust flow rates or emissions, by modulating the EVO timing. </div><div><br></div><div>At low-to-moderate loads modern diesel engines manipulate exhaust manifold pressures to drive EGR and thermally manage the aftertreatment. In these engines exhaust manifold pressure control is typically achieved via either a valve after the turbine, a variable geometry turbine, or wastegating. It is experimentally demonstrated that valvetrain flexibility enables efficient engine and aftertreatment operation without requiring exhaust manifold pressure control. Specifically, IVC modulation and CDA at elevated engine speeds, along with EVO modulation, CDA, and internal EGR at low engine speeds can match, or improve, efficiency and thermal management performance compared to a stock thermal calibration that requires exhaust manifold pressure control.<br></div>
38

Beam Search e inserção de ociosidade no problema de programação de uma máquina em ambiente do tipo JIT. / Beam Search and idle time insertion in the single-machine scheduling problem in a JIT environment.

Colin, Emerson Carlos 14 October 1997 (has links)
Este trabalho apresenta procedimentos que podem ser utilizados na programação da produção em um ambiente JIT. Esses procedimentos deveriam ser utilizados em sistemas clássicos de programação, onde a utilização do sistema kanban é inviável. O caso estudado se baseia em uma única máquina, com datas de entrega múltiplas e com penalidades distintas de adiantamento e de atraso para cada ordem. O objetivo a ser alcançado é a minimização do custo total. Para isso, é utilizado um procedimento de busca denominado beam search, para gerar as seqüências, e um algoritmo de inserção de ociosidade, para definir os programas. O algoritmo utilizado é uma generalização do algoritmo de GAREY et al. (1988) onde as penalidades são distintas para adiantamento e para atraso. O procedimento e o algoritmo são testados em várias condições sendo comparados com regras de despacho e com a função EXP-ET. Quando a função EXP-ET é utilizada com a possibilidade de inserção de ociosidade, o período de ociosidade ótimo é determinado. Assume-se que a dificuldade de solução do problema é dependente de dois parâmetros clássicos: fator de atraso médio e amplitude relativa das datas de entrega. Testes empíricos comparativos são realizados através de simulação computacional, onde se mede o tempo de solução e o valor alcançado pela função objetivo. Os resultados indicam que o desempenho dos vários procedimentos testados é altamente dependente dos dois parâmetros, mostrando que para a escolha de um procedimento apropriado, deve-se primeiramente conhecer o valor dos parâmetros. São fornecidos os resultados encontrados e os códigos computacionais utilizados no estudo. / This work presents some procedures which can be used in production scheduling problems in JIT environments. These procedures may be used in cases of classical production scheduling where the use of the kanban system is infeasible. The case studied is based on a single machine, with multiple due dates, and distinct earliness and tardiness penalties for each job. The objective function is to minimize total cost. A heuristic search procedure known as beam search is used to construct sequences of jobs, and an idleness insertion algorithm is used to obtain schedules. The algorithm used is a generalization of the GAREY et al. (1988) algorithm, where penalties are distinct for earliness and tardiness. The procedure and algorithm are tested in many conditions involving comparisons with dispatching rules and the EXP-ET function. When EXP-ET function is applied with possibility of idleness insertion, the optimal idleness period is provided. It was assumed that problem hardness is dependent on two classical parameters: average tardiness factor and relative range of due dates. Empirical comparative tests are conducted with computational simulation, where computational solution time and objective function value are evaluated. Results indicate that procedures performance is highly dependent on both parameters, showing that is necessary to know parameters values before choosing an appropriate procedure. The detailed results and computational code used in this study are also provided.
39

A interpretação de Ignácio Rangel e o Brasil do \"milagre\" e \"antimilagre\" econômico / Ignácio Rangel\'s interpretation and the Brazil of the economic \"miracle\" and \"antimiracle\"

Nogueira, Leandro Mendes 08 December 2017 (has links)
Essa dissertação tem como propósito compreender a interpretação de Ignácio Rangel sobre o Brasil, destacando sua análise acerca da transferência de recursos ociosos (presentes no âmbito dos bens de produção, o chamado Departamento I) para as áreas estranguladas da economia (os serviços de utilidade pública), que ocorreria através da concessão de serviços públicos à iniciativa privada. Essa transferência provocaria uma expansão dos serviços de utilidade pública e a consequente expansão da demanda global, e criaria um vigoroso capitalismo financeiro nacional. Essa seria a alternativa rangeliana para a saída da crise dos anos 1980, o período do \"antimilagre\" econômico. Para compreendermos a proposta das concessões, se faz necessário apresentarmos algumas de suas teses: dualidade básica, o eixo estruturador do seu pensamento; dialética da capacidade ociosa; e o papel do Estado e do setor privado. A abordagem do pensamento rangeliano, além do mergulho em sua própria obra, será apoiada na análise da trajetória política e profissional do autor, das relações com seus interlocutores e, também, do diálogo que estabelece, nem sempre explícito, com Caio Prado Jr., Celso Furtado e Florestan Fernandes, intérpretes brasileiros contemporâneos a Rangel, que refletiram sobre a natureza e as especificidades do desenvolvimento brasileiro. Essa análise tem por intuito, afinal, situar as contribuições de Rangel como interpretações relevantes da realidade brasileira. / This dissertation aims to understand Ignácio Rangel\'s interpretation of Brazil, highlighting his analysis of the transfer of idle resources (present among production goods, the so-called Department I) to strangled areas of the economy (such as public services), which would occur through the concession of public services to private initiative. This transfer would promote an expansion of public services and a consequent expansion of global demand, and would also create a vigorous national financial capitalism. This would be the Rangelian alternative to face the crisis of the 1980s, the period of Brazil\'s economic \"antimiracle\". In order to understand the concessions proposal, it is necessary to present some of Rangel\'s thesis: the basic duality, the structural axis of his thought; the dialectics of idle capacity dialectics; and the role of the State and the private sector. This approach of the Rangelian thought, besides delving into his writings, is also going to be supported by an analysis of his own political and professional trajectory and by the not always explicit dialogues he establishes with other Brazilian authors such as Caio Prado Jr., Celso Furtado and Florestan Fernandes, who also reflected upon the nature and the specific features of Brazilian development. Finally, this analysis intends to situate Rangel\'s contributions as relevant interpretations of the Brazilian reality
40

A interpretação de Ignácio Rangel e o Brasil do \"milagre\" e \"antimilagre\" econômico / Ignácio Rangel\'s interpretation and the Brazil of the economic \"miracle\" and \"antimiracle\"

Leandro Mendes Nogueira 08 December 2017 (has links)
Essa dissertação tem como propósito compreender a interpretação de Ignácio Rangel sobre o Brasil, destacando sua análise acerca da transferência de recursos ociosos (presentes no âmbito dos bens de produção, o chamado Departamento I) para as áreas estranguladas da economia (os serviços de utilidade pública), que ocorreria através da concessão de serviços públicos à iniciativa privada. Essa transferência provocaria uma expansão dos serviços de utilidade pública e a consequente expansão da demanda global, e criaria um vigoroso capitalismo financeiro nacional. Essa seria a alternativa rangeliana para a saída da crise dos anos 1980, o período do \"antimilagre\" econômico. Para compreendermos a proposta das concessões, se faz necessário apresentarmos algumas de suas teses: dualidade básica, o eixo estruturador do seu pensamento; dialética da capacidade ociosa; e o papel do Estado e do setor privado. A abordagem do pensamento rangeliano, além do mergulho em sua própria obra, será apoiada na análise da trajetória política e profissional do autor, das relações com seus interlocutores e, também, do diálogo que estabelece, nem sempre explícito, com Caio Prado Jr., Celso Furtado e Florestan Fernandes, intérpretes brasileiros contemporâneos a Rangel, que refletiram sobre a natureza e as especificidades do desenvolvimento brasileiro. Essa análise tem por intuito, afinal, situar as contribuições de Rangel como interpretações relevantes da realidade brasileira. / This dissertation aims to understand Ignácio Rangel\'s interpretation of Brazil, highlighting his analysis of the transfer of idle resources (present among production goods, the so-called Department I) to strangled areas of the economy (such as public services), which would occur through the concession of public services to private initiative. This transfer would promote an expansion of public services and a consequent expansion of global demand, and would also create a vigorous national financial capitalism. This would be the Rangelian alternative to face the crisis of the 1980s, the period of Brazil\'s economic \"antimiracle\". In order to understand the concessions proposal, it is necessary to present some of Rangel\'s thesis: the basic duality, the structural axis of his thought; the dialectics of idle capacity dialectics; and the role of the State and the private sector. This approach of the Rangelian thought, besides delving into his writings, is also going to be supported by an analysis of his own political and professional trajectory and by the not always explicit dialogues he establishes with other Brazilian authors such as Caio Prado Jr., Celso Furtado and Florestan Fernandes, who also reflected upon the nature and the specific features of Brazilian development. Finally, this analysis intends to situate Rangel\'s contributions as relevant interpretations of the Brazilian reality

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