• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 748
  • 339
  • 172
  • 67
  • 47
  • 44
  • 32
  • 15
  • 12
  • 12
  • 11
  • 10
  • 7
  • 6
  • 5
  • Tagged with
  • 1760
  • 1760
  • 344
  • 310
  • 304
  • 204
  • 184
  • 172
  • 155
  • 151
  • 143
  • 139
  • 132
  • 126
  • 125
  • 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.
601

A chip multiprocessor for a large-scale neural simulator

Painkras, Eustace January 2013 (has links)
A Chip Multiprocessor for a Large-scale Neural SimulatorEustace PainkrasA thesis submitted to The University of Manchesterfor the degree of Doctor of Philosophy, 17 December 2012The modelling and simulation of large-scale spiking neural networks in biologicalreal-time places very high demands on computational processing capabilities andcommunications infrastructure. These demands are difficult to satisfy even with powerfulgeneral-purpose high-performance computers. Taking advantage of the remarkableprogress in semiconductor technologies it is now possible to design and buildan application-driven platform to support large-scale spiking neural network simulations.This research investigates the design and implementation of a power-efficientchip multiprocessor (CMP) which constitutes the basic building block of a spikingneural network modelling and simulation platform. The neural modelling requirementsof many processing elements, high-fanout communications and local memoryare addressed in the design and implementation of the low-level modules in the designhierarchy as well as in the CMP. By focusing on a power-efficient design, the energyconsumption and related cost of SpiNNaker, the massively-parallel computation engine,are kept low compared with other state-of-the-art hardware neural simulators.The SpiNNaker CMP is composed of many simple power-efficient processors withsmall local memories, asynchronous networks-on-chip and numerous bespoke modulesspecifically designed to serve the demands of neural computation with a globallyasynchronous, locally synchronous (GALS) architecture.The SpiNNaker CMP, realised as part of this research, fulfills the demands of neuralsimulation in a power-efficient and scalable manner, with added fault-tolerancefeatures. The CMPs have, to date, been incorporated into three versions of SpiNNakersystem PCBs with up to 48 chips onboard. All chips on the PCBs are performing successfully, during both functional testing and their targeted role of neural simulation.
602

Uplatňování principů udržitelného rozvoje cestovního ruchu v oblasti hotelnictví / Application of sustainable practices of tourism development in hotel industry

Gerlová, Martina January 2012 (has links)
This thesis concentrates on sustainable development of tourism and application of these sustainable practices in hotel industry. The aim of this thesis is analysis of concrete practices of the biggest hotel groups in the world and outline appropriate trend in this field. The theoretical part of this thesis concentrates on the definition of sustainable development of tourism as well as on its history. Furthermore, the thesis focuses on certification of sustainable development in hotels. In the analytical part there are already analyzed concrete practices and approaches of the biggest hotel groups sustainability reports. The practices focus on energy efficiency, waste production, water conservation and production of carbon emissions. At the end of this analytical part there is sum up of these concrete practices and approaches and outline appropriate trend.
603

System Effects of Improved Energy Efficiency in Swedish District-Heated Buildings

Åberg, Magnus January 2014 (has links)
To alleviate global warming, European-Union member states must reduce primary energy use, emit less carbon dioxide (CO2), and increase renewable energy use. Buildings constitute a great potential for energy savings, but saving energy in district-heated buildings influences combined heat and power (CHP) production, other electricity generation, and global CO2 emissions.   This thesis investigates the system effects from Swedish district heating production caused by district heating demand changes due to energy conservation in buildings. The cost-optimising linear programming modelling tools MODEST and FMS, the latter developed in the context of this thesis, are used to describe present district heating production and to investigate the impact of heat-demand reductions in twelve Swedish district heating systems, four of them representing all Swedish district heating.   Energy savings in district-heated, multi-family residential buildings yield a lower, more seasonally levelled district heating demand. These demand changes mainly reduce use of fossil-fuel and biomass for heat production. CHP production is significantly reduced if it supplies intermediate or peak district heating load. The αsystem value (ratio between generated CHP electricity and produced district heating) increases by demand reductions if CHP mainly supplies base district heating load. CO2 emissions due to district heat production depend on the approach used for CO2 assessment of electricity, and are generally reduced with heat demand reductions, unless the share of CHP production is large and the reduced fuel use yields smaller emission reductions than the emission increase from power production that replaces reduced CHP generation.   In total, heat demand reductions reduce CO2 emissions due to Swedish district heating, and the district heating systems even constitute a carbon sink at certain energy conservation levels. If saved biomass replaces fossil fuels elsewhere, a lower heat demand reduces CO2 emissions for every studied district heating system.
604

Earth Integration and Thermal Mass (for Global Energy Use Reduction)

Wright, Jim Allen, Wright, Jim Allen January 2016 (has links)
As the rest of the world under development catches up economically with the developed nations, adoption of western tastes is projected to lead to enormous increases in energy use. Specifically, air conditioning use within countries with low saturation rates and high cooling degree rates (India and China) have a potential demand of up to 5 times that of the U.S. market. This growth in HVAC (Heating Ventilation&Air Conditioning) means billions of tons of increased carbon dioxide emissions and trillions of dollars in investment in electricity generation and transmission infrastructure.If there is adoption of Earth sheltering and integration design within these geographical areas, then it might be possible to mitigate the need for such high increase in electricity demand.Ultimately, an estimate of how much quantifiable impact wide adoption of earth integration can have in the regions in question needs to be calculated and compared to projected energy demand if things continue as they are. To do so, parameters need to be determined to see how much of the future air conditioning demand can be met through thermal mass/earth integration. That is, how much future energy demand can be avoided through earth sheltering? To do so:1-Determine what areas account for the greatest projected demand in future air conditioning use.2-See how much of the projected demand can be met through Thermal Mass and Earth Integration (T.M./E.I.) within these areas.3-A design/energy modeling exercise showing proper use and implementation of Earth sheltering within our local climate will be carried out to prove effectiveness of varied strategic thermal mass applications.4-Compare the relative savings of different levels of Earth Integration to arrive at an average overall savings if universal adoption takes place.Top-down approach to energy savings (HVAC efficiency) is not enough to offset projected adoption and its impact on the local and global environments. Energy efficient design is necessary to deal with as much of the increase in projected demand as possible. The use of earth as a building material can be a powerful tool in the fight against increasing energy demands and accompanied destructive environmental effects and needs greater consideration and adoption.
605

Integrated dynamic simulation of large thermal systems

Arndt, D C 05 July 2006 (has links)
Studies concluded that more that 10% of all energy consumed in the world is expended by building air-conditioning systems. Energy efficiency in building and HVAC (Heating, Ventilating and Air-conditioning) design is therefore exceptionally important. A cost¬-effective way to improve the energy efficiency of a HV AC system, without compromising indoor comfort, is by implementing better control. System energy cost savings of up to 50% can be realised by optimising the system operating control strategies with direct payback periods of less than a year. However, when changing the operating strategy of a system it is often difficult to predict the resulting changes in system energy consumption and indoor comfort. To achieve these predictions, a dynamic simulation tool, which can efficiently and accurately simulate the building with the HV AC and control system in an integrated fashion, is required. Extensions to the integrated tool QUICKcontrol is therefore proposed to suite the needs of the energy service contractor. QUICKcontrol still has many shortcomings in the availability of component models for certain equipment commonly used in building systems today. New dynamic component models were therefore derived in this study. The accuracy and applicability of integrated building and natural ventilation modelling is illustrated in animal housing facilities. The predicted results obtained during this study were satisfactory to use these models with confidence in this type of building applications. The applicability of building, HV AC system and control simulations was illustrated in conference facilities. The results obtained show the value of integrated building and system simulation in the evaluation of energy cost saving inventions in commercial buildings. The mining and industrial sectors in South Africa consume about 40% of ESKOM's total electrical energy production. Mines alone use nearly 20% of the electricity provided by ESKOM. Ventilation and cooling (VC) systems are responsible for approximately 25% or R750 million of this energy. It will therefore be beneficial if the mines can be more energy clever in order to reduce their VC operating costs. The use of an extended integrated building and system simulation tool was therefore realised to investigate the potential for energy cost savings in mine VC applications. To extend QUICKcontrol for the simulation of other large thermal systems found in mining and industrial applications, new component models and simulations procedures were developed. Two case studies were performed with the extended tool to illustrate its applicability in thermal systems other than building systems. The potential for Demand Side Management (DSM) on a surface cooling plant and an underground clear water-pumping system was investigated. Satisfactory results were obtained during the two investigations to utilise this extended tool with confidence in practice. With more extensions to the tool it should be possible to investigate the potential for energy cost saving on any other thermal industrial applications. / Thesis (PhD (Mechanical Engineering))--University of Pretoria, 2007. / Mechanical and Aeronautical Engineering / unrestricted
606

Household energy use in South Africa : a systemic study of an individual intervention

Du Preez, Mathilda January 2015 (has links)
The world-wide problem of increasing greenhouse gas emissions has received considerable attention in recent decades. In South Africa, several factors necessitate residential energy efficiency research. These include the high levels of pollution caused by the generation of electricity with low quality coal, which is fairly readily available, the increasing consumer base since 1994, and electricity price increases of 20% per annum since 2008. This study investigates qualitative and quantitative aspects of energy efficiency strategies employed in 41 South African households from diverse socio-economic backgrounds, within the Pretoria region. Field work was conducted during 2010 and 2011. This research was conducted using a multi-phased combined experimental and ex post facto mixed methodology. Actual electricity consumption levels were recorded in all participating households, which were divided into two experimental groups, but only participants in the first experimental group participated in an interview and intervention to reduce electricity consumption. Measurements were followed by focus group sessions open to all participants. Thematic analysis was used to identify participants’ main strategies for energy efficiency, and the effectiveness of these strategies was quantified. The qualitative and quantitative findings are discussed both separately from and in conjunction with one another. Feedback was shown to be a key factor in enabling behaviour change. Needs not only for information but for guidance in its interpretation are highlighted, particularly where literacy levels are lower. Erroneous beliefs about the functioning of appliances were identified and quantified. Winter was identified as the best time to introduce an intervention and improve energy savings due to the ‘normal’ steep increase during that time. Popular and effective strategies employed in households to reduce electricity consumption were also identified. This study culminates in a theoretical model, placing the micro, meso and exo implications of residential energy efficiency in a cyclical empowerment model of environmental concern, the need for information, behaviour change and the resulting need for feedback. Suggestions for policy development and future research are made focussing specifically on the role of females in designing energy efficiency measures, measuring quality of life and not just kWhs and emphasising the importance of real-time feedback on consumption. / Thesis (PhD)--University of Pretoria, 2015. / Psychology / Unrestricted
607

Plataforma automatizada e normatizada de monitoração, verificação e gestão de índices de energia

Castro, Renato Ely January 2014 (has links)
Este trabalho descreve os requisitos para definição, implantação, manutenção e melhoria de sistemas de gestão de energia no ambiente industrial com um enfoque sistemático no que se refere às rotinas de melhoria contínua para eficiência energética. Para tanto, propôs-se a estruturação de uma plataforma automatizada visando o monitoramento, verificação e gerenciamento de recursos energéticos compatível com um sistema de gestão de energia normatizado, incluindo os requisitos de uso e consumo de energia, além do monitoramento, documentação, comunicação, melhores práticas de projeto, aquisição de equipamentos, sistemas, processos e recursos humanos envolvidos no desempenho energético. A estratégia de análise do uso da energia proposta neste trabalho baseou-se na metodologia de monitoramento e gestão de índices que consiste em uma abordagem sistemática na utilização de recursos energéticos objetivando alcançar o melhor resultado econômico através da gestão permanente do consumo de energia. Além disso, propôs-se a inclusão dessa metodologia como um procedimento na fase de planejamento da norma ISO50001, a qual estabelece os conceitos para a implantação de sistemas de gestão de energia. Visando integrar as ferramentas associadas a este cenário, esta plataforma contempla o uso de um sistema de supervisão associado a um aplicativo (Soft-PLC) que executa a aplicação de controle do uso de energia em um ambiente industrial com automação distribuída compatível com a norma IEC61131. O projeto do aplicativo de controle do uso de energia foi conduzido adotando-se diferentes linguagens de programação definidas na IEC para executar todos os procedimentos de medição, monitoração e gestão exigidos pelo sistema, incluindo análise comparativa com as “melhores práticas”, uso de tecnologias inovadoras, abordagem de produto e serviço, auditoria energética e conformidade com marcos regulatórios. Os resultados decorrentes da adoção de uma plataforma baseada em automação para o gerenciamento energético incluem elevada flexibilidade, adaptabilidade e usabilidade do sistema. Além disso, um projeto de automação neste cenário de plataforma aberta tende a apresentar menores custos de desenvolvimento e implantação. / This work describes the requirements for the definition, implementation, maintenance and improvement of energy management systems in the industrial environment with a systematic approach concerning continuous improvement routines for energy efficiency. For this purpose, it was proposed the establishment of a framework based on automation to implement monitoring, verification and management of energy resources compatible with a standardized energy management system, including requirements for energy use and consumption, in addition to monitoring, documentation, communication, project best practices, equipment acquisition, systems, processes and human resources involved in energy performance. The strategy of energy use analysis proposed in this work is based on the methodology of monitoring and targeting that consists of a systematic approach in the use of energy resources in order to achieve the best economic result through the permanent management of energy consumption. Furthermore, this work includes that system as a procedure in the planning phase of ISO50001 standard which establishes the concepts for energy management systems implementation. In order to aggregate all tools associated to this scenario, this paper proposes the use of a supervisory tool integrated to a real-time software (Soft-PLC) that runs the control application and a factory floor distributed system automation hardware in an IEC61131 compatible environment. The project of the control application of energy use was conducted using different programming languages defined in IEC to perform all the procedures of measurement, monitoring and management required by the system, including comparative analysis with the "best practices", use of innovative technologies, product and service approach, energy audit and compliance with regulatory milestones. The expected results of adopting an automation-based platform for energetic management include system flexibility, adaptability and usability. Besides, a project of automation in this scenario of open platform tends to introduce lower development and deployment costs.
608

Energy and speed exploration in digital CMOS circuits in the near-threshold regime for very-wide voltage-frequency scaling

Stangherlin, Kleber Hugo January 2013 (has links)
Esta tese avalia os benefícios e desafios associados com a operação em uma ampla faixa de frequências e tensões próximas ao limiar do transistor. A diminuição da tensão de alimentação em circuitos digitais CMOS apresenta grandes vantagens em termos de potência consumida pelo circuito. Esta diminuição da potência é acompanhada por uma redução da performance, reflexo da diminuição na tensão de alimentação. A operação de circuitos digitais no ponto de energia mínima é comumente associada ao regime de operação abaixo do limiar do transistor, trazendo enormes penalidades em performance e variabilidade. Esta dissertação mostra que é possível obter 8X mais eficiência energética com uma ampla faixa dinâmica de tensão e frequência, da tensão nominal até o limite inferior da operação próximo ao limiar do transistor. Como parte deste estudo, uma biblioteca de células digitais CMOS para esta ampla faixa de frequências foi desenvolvida. A biblioteca de células lógicas foi exercitada em um PDK comercial de 65nm para operação próximo ao limiar do transistor, reduzindo os efeitos da variabilidade sem comprometer o projeto em termos de área e energia quando operando em inversão forte. Para operar próximo e abaixo do limiar do transistor as células devem ser desenvolvidas com um número limitado de transistores em série. Nosso estudo mostra que uma performance aceitável em termos de margens de ruído estático é obtida para um conjunto restrito de células, onde são empregados no máximo dois transistores em série. Reportamos resultados para projetos de média complexidade que incluem um filtro notch de 25kgates, um microcontrolador 8051 de 20kgates, e 4 circuitos combinacionais/ sequenciais do conjunto de avaliação ISCAS. Neste trabalho, é estudada a máxima frequência atingida em cada tensão de alimentação, desde 0.15V até 1.2V. O ponto de mínima energia é demonstrado em operação abaixo do limiar do transistor, aproximadamente 0.29V, oque representa um ganho de 2X em eficiência energética comparado ao regime de operação próximo ao limiar do transistor. Embora o pico de eficiência energética ocorra abaixo do limiar do transistor para os circuitos estudados, nós também demonstramos que nesta tensão de alimentação ultra-baixa o atraso e a potência sofrem um impacto substancial devido ao aumento na variabilidade, atigindo uma degradação em performance de 30X, com respeito à operação próxima ao limiar do transistor. / This thesis assesses the benefits and drawbacks associated with a very wide range of frequency when operation at near-threshold is considered. Scaling down the supply voltage in digital CMOS circuits presents great benefits in terms of power reduction. Such scaling comes with a performance penalty, hence in digital synchronous circuits the reduction in frequency of operation follows, for a given circuit layout, the VDD reduction. Minimum-energy operation of digital CMOS circuits is commonly associated to the sub-VT regime, carrying huge performance and variability penalties. This thesis shows that it is possible to achieve 8X higher energy-efficiency with a very-wide range of dynamic voltage-frequency scaling, from nominal voltages down to the lower boundary of near-VT operation. As part of this study, a CMOS digital cell-library for such wide range of frequencies was developed. The cell-library is exercised in a 65nm commercial PDK and targets near-VT operation, mitigating the variability effects without compromising the design in terms of area and energy at strong inversion. For near-VT or sub-VT operation the cells have to be designed with few stacked transistors. Our study shows that acceptable performance in terms of static-noise margins is obtained for a constrained set of cells, for which a maximum of 2-stacked transistors are allowed. In this set we include master-slave registers. We report results for medium complexity designs which include a 25kgates notch filter, a 20kgates 8051 compatible core, and 4-combinational/4-sequential ISCAS benchmark circuits. In this work the maximum frequency attainable at each supply for a wide variation of voltage is studied from 150mV up to nominal voltage (1.2V). The sub-VT operation is shown to hold the minimum energy-point at roughly 0.29V, which represents a 2X energy-saving compared to the near-VT regime. Although energy-efficiency peaks in sub-VT for the circuits studied, we also show that in this ultra-low VDD the circuit timing and power suffer from substantially increased variability impact and a 30X performance drawback, with respect to near-VT.
609

Utilização do fator de potência como indicador da eficiência energética no torneamento da liga de alumínio 2011F (Al-Cu) / Power factor use as an indicator of energy efficiency in turning aluminium alloy 2011F (Al-Cu)

Silveira, Neimar Sousa, 1974- 12 September 2014 (has links)
Orientador: Amauri Hassui / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-26T12:36:15Z (GMT). No. of bitstreams: 1 Silveira_NeimarSousa_M.pdf: 2291885 bytes, checksum: f93cbac8489b6ba667cbeac32fd40f84 (MD5) Previous issue date: 2014 / Resumo: Processos de fabricação são responsáveis por cerca de metade do consumo global de energia primária, muito do que é consumido por máquinas de produção de peças discretas. O tema da eficiência energética é impulsionado por usuários de máquinas-ferramenta que exigem baixos custos operacionais, bem como pelo impulso social e legislativo que requer produção ambientalmente mais amigável. O uso do alumínio em componentes e estruturas, principalmente na indústria automotiva e aeronáutica, vem crescendo a demanda de manufatura desse tipo de material. Entretanto, o aumento do consumo de energia cresce e com isso a preocupação para se criar meios e métodos para serem aplicados para melhoria da eficiência energética. Nesse estudo, é possível considerar a aplicação do fator potência como fator de análise da eficiência no processo de torneamento da liga alumínio 2011F, aplicado aos parâmetros de profundidade de corte, da rotação do torno, das classes da ferramenta e do raio de ponta. O planejamento experimental foi realizado de forma aleatória usando o método da ANOVA, com os parâmetros de entrada: profundidade de usinagem, raio de ponta, classe da ferramenta e rotação, e como respostas foram consideradas: a potência ativa, potência reativa e fator de potência. Os resultados obtidos mostram que as avaliações da eficiência energética são satisfatórias pela análise do fator de potência e pela potência reativa em termos de baixa profundidade de usinagem e pela modificação da classe da ferramenta com ou sem revestimento / Abstract: Manufacturing processes are responsible for about half of global consumption of primary energy, much of which is consumed by discrete parts manufacturing machines. The topic of energy efficiency is driven by machine tool users that require low operating costs, as well as by social and legislative boost which requires environmentally friendlier production. The use of aluminium in components and structures, mainly in automotive and aeronautics, has been growing demand for manufactures of this type of material. However, the increase of energy consumption grows and with it the concern to create means and methods to be applied to improving energy efficiency. In this study, it is possible to consider the application of power factor as a factor in efficiency analysis in the process of turning aluminium alloy 2011F, applied to parameters of depth of cut, spin around, of the classes of the tool and the nose RADIUS. The experimental planning was conducted at random using the ANOVA method with the input parameters: machining depth, radius, edge class of tool and rotation, and how responses were considered: the active power, reactive power and power factor. The results obtained show that energy efficiency assessments are satisfactory for the analysis of the power factor and reactive power in terms of low machining depth and by modifying the tool class with or without coating / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica
610

Análise da eficiência de geradores de energia com biodiesel obtido de óleos de fritura usados / Analysis of power generators efficiency with biodiesel used frying oils

Silva, Thadeu Alfredo Farias, 1961- 12 December 2014 (has links)
Orientador: Elias Basile Tambourgi / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-26T11:34:50Z (GMT). No. of bitstreams: 1 Silva_ThadeuAlfredoFarias_D.pdf: 3309858 bytes, checksum: 91c6bd469e2d60cb979c09c7afa27066 (MD5) Previous issue date: 2014 / Resumo: Neste trabalho se analisou os índices de eficiência de consumo de combustível e emissões de gases poluentes de um gerador de energia elétrica de 6 KW operando com 50% da carga nominal. Os equipamentos operaram com biodiesel obtido de óleos de fritura usados e comparou-se nos experimentos o consumo do combustível de misturas de óleo mineral fóssil com 6% de concentração, comercializado nos postos de combustíveis, com biodiesel de óleos fritura usados nas concentrações 10%, 20%, 30%, 40%, 50%, 75% e 100% (biocombustível puro), observando-se com resultados o aumento de consumo. Relativo a emissão de gases observou-se índices de emissão de monóxido de carbono (CO) favoráveis para as misturas com baixas concentrações, sendo consideradas menos poluentes. No que tange a emissão de dióxido de carbono (CO2), o gerador de energia apresentou índices razoáveis de queima de combustível, considerada esta opção de biodiesel factível para sua utilização. Verificou-se ainda durante o experimento que para as concentrações de mistura de biodiesel, não ocorrem variações de potência elétrica na saída dos geradores, bem como variações significativas da intensidade sonora que alterem características mecânicas ou elétricas do gerador de energia / Abstract: This paper analyzed the fuel consumption efficiency rates and gas emissions of an electric power generator 6 KW, operating at 50% of rated load. The equipment operated with biodiesel obtained from used frying oils and compared in the experiments the consumption of fossil fuel mineral oil mixtures with 6% concentration, sold at gas stations with biodiesel oils frying used in concentrations of 10%, 20%, 30%, 40%, 50%, 75% and 100% (pure biodiesel), observing results with increasing consumption. On the emission of gases was observed carbon monoxide emission rates (CO) favorable for mixtures with low concentrations and is considered less polluting. With regard to carbon dioxide (CO2), the power generator had reasonable rates of burning fuel, biodiesel considered this feasible option to use. It was also found during the experiment that for biodiesel blend concentrations, there were no variations in the electrical power output of the generator, as well as significant variations in sound intensity which change electrical or mechanical characteristics of the power generator / Doutorado / Sistemas de Processos Quimicos e Informatica / Doutor em Engenharia Química

Page generated in 0.0549 seconds