Dissertations / Theses: 'Electric energy losses'

1

Gantt, Lynn Rupert. "Energy Losses for Propelling and Braking Conditions of an Electric Vehicle." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/32879.

Full text

Abstract:

The market segment of hybrid-electric and full function electric vehicles is growing within the automotive transportation sector. While many papers exist concerning fuel economy or fuel consumption and the limitations of conventional powertrains, little published work is available for vehicles which use grid electricity as an energy source for propulsion. Generally, the emphasis is put solely on the average drive cycle efficiency for the vehicle with very little thought given to propelling and braking powertrain losses for individual components. The modeling section of this paper will take basic energy loss equations for vehicle speed and acceleration, along with component efficiency information to predict the grid energy consumption in AC Wh/km for a given drive cycle. This paper explains how to calculate the forces experienced by a vehicle while completing a drive cycle in three different ways: using vehicle characteristics, United States Environmental Protection Agencyâ s (EPA) Dynamometer â targetâ coefficients, and an adaptation of the Sovran parameters. Once the vehicle forces are determined, power and energy demands at the wheels are determined. The vehicle power demands are split into propelling, braking, and idle to aide in the understanding of what it takes to move a vehicle and to identify possible areas for improvement. Then, using component efficiency data for various parameters of interest, the energy consumption of the vehicle as a pure EV is supplied in both DC (at the battery terminals) and AC (from the electric grid) Wh/km. The energy that flows into and out of each component while the vehicle is driving along with the losses at each step along the way of the energy path are detailed and explained. The final goal is to make the results of the model match the vehicle for any driving schedule. Validation work is performed in order to take the model estimates for efficiencies and correlate them against real world data. By using the Virginia Tech Range Extended Crossover (VTREX) and collecting data from testing, the parameters that the model is based on will be correlated with real world test data. The paper presents a propelling, braking, and net energy weighted drive cycle averaged efficiency that can be used to calculate the losses for a given cycle. In understanding the losses at each component, not just the individual efficiency, areas for future vehicle improvement can be identified to reduce petroleum energy use and greenhouse gases. The electric range of the vehicle factors heavily into the Utility Weighted fuel economy of a plug-in hybrid electric vehicle, which will also be addressed.
Master of Science

APA, Harvard, Vancouver, ISO, and other styles

2

Alley, Robert Jesse. "VTool: A Method for Predicting and Understanding the Energy Flow and Losses in Advanced Vehicle Powertrains." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/33697.

Full text

Abstract:

As the global demand for energy increases, the people of the United States are increasingly subject to high and ever-rising oil prices. Additionally, the U.S. transportation sector accounts for 27% of total nationwide Greenhouse Gas (GHG) emissions. In the U.S. transportation sector, light-duty passenger vehicles account for about 58% of energy use. Therefore incremental improvements in light-duty vehicle efficiency and energy use will significantly impact the overall landscape of energy use in America. A crucial step to designing and building more efficient vehicles is modeling powertrain energy consumption. While accurate modeling is indeed key to effective and efficient design, a fundamental understanding of the powertrain and auxiliary systems that contribute to energy consumption for a vehicle is equally as important if not more important. This thesis presents a methodology that has been packaged into a tool, called VTool, that can be used to estimate the energy consumption of a vehicle powertrain. The method is intrinsically designed to foster understanding of the vehicle powertrain as it relates to energy consumption while still providing reasonably accurate results. VTool explicitly calculates the energy required at the wheels of the vehicle to complete a prescribed drive cycle and then explicitly applies component efficiencies to find component losses and the overall energy consumption for the drive cycle. In calculating component efficiencies and losses, VTool offers several tunable parameters that can be used to calibrate the tool for a particular vehicle, compare powertrain architectures, or simply explore the tradeoffs and sensitivities of certain parameters. In this paper, the method is fully and explicitly developed to model Electric Vehicles (EVs), Series Hybrid Electric Vehicles (HEVs) and Parallel HEVs for various different drive cycles. VTool has also been validated for use in UDDS and HwFET cycles using on-road test results from the 2011 EcoCAR competition. By extension, the method could easily be extended for use in other cycles. The end result is a tool that can predict fuel consumption to a reasonable degree of accuracy for a variety of powertrains, calculate J1711 Utility Factor weighted energy consumption for Extended Range Electric Vehicles (EREVs) and determine the Well-to-Wheel impact of a given powertrain or fuel. VTool does all of this while performing all calculations explicitly and calculating all component losses to allow the user maximum access which promotes understanding and comprehension of the fundamental dynamics of automotive fuel economy and the powertrain as a system.
Master of Science

APA, Harvard, Vancouver, ISO, and other styles

3

Jin, Lebing. "Integrated Compact Drives for Electric and Hybrid Electric Vehicles." Doctoral thesis, KTH, Elkraftteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-196732.

Full text

Abstract:

To develop more competitive solutions, one of the trends in the development of drive systems for electric and hybrid electric vehicles (EVs/HEVs) is to integrate the power electronic converter and the electric motor. This thesis aims to investigate the performance and the operation of modular converters in integrated motor drive systems for EVs/HEVs. In the first part, the concept of integrated modular motor drive systems for EVs/HEVs is introduced. Three suitable modular converter topologies, namely, the stacked polyphase bridges (SPB) converter, the parallel-connected polyphase bridges (PPB) converter and the modular high frequency (MHF) converter, are evaluated and compared with conventional electric drives in terms of power losses, energy storage requirements, and semiconductor costs. In the second part of the thesis, the harmonic content of the dc-link current of the SPB converter is analyzed. By adopting an interleaving modulation the size of the dc-link capacitor can be reduced without increasing the switching frequency, which is beneficial for achieving a compact integrated system. This method allows for around 80% reduction of the dc-link capacitance for vehicle drives, resulting in a significant size reduction of the power converter and improved integration. Finally, a communication-based distributed control system for the SPB converter is presented. The communication delay arising from the serial communication is inevitable, thus a timing analysis is also presented. It has been found that stability is maintained even when the baud rate of the SPI communication is lower than 1 Mbps, indicating that other communication protocols with lower bandwidths can also be adopted for this topology. The analytical investigations provided in this thesis are validated by experiments on a four-submodule laboratory prototype. Experimental results verify the correctness of the theoretical analysis, as well as the dynamic performance of the distributed control system.

QC 20161121

APA, Harvard, Vancouver, ISO, and other styles

4

VIEIRA, RODRIGO SANTOS. "ASSESSMENT OF ENERGY LOSSES AND CHARACTERIZATION OF THE RESALE AND MAINTENANCE MARKET OF REFURBISHED ELECTRIC MOTORS IN BRAZIL." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2018. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=37028@1.

Full text

Abstract:

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO
PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTITUIÇÕES COMUNITÁRIAS DE ENSINO PARTICULARES
Os motores elétricos no Brasil são responsáveis pelo consumo de cerca de 25 porcento de toda a energia elétrica no país e, em sua grande parte, estão presentes na indústria. Estes equipamentos são fabricados para uso em bombas hidráulicas, compressores de ar, elevadores etc., podendo ser comercializados se atenderem aos índices de eficiência mínimos definidos pela Portaria INMETRO/MDIC N488 de 2010, garantindo o seu perfeito funcionamento e o consumo energético adequado. Contudo, alguns estabelecimentos estão comercializando produtos usados recondicionados, não atendendo à regulamentação desta Portaria, além de reformarem motores sem condições de uso. O objetivo desta dissertação é dimensionar e caracterizar o mercado de revenda e manutenção de motores elétricos de indução recondicionados no Brasil, estimando a perda de energia decorrente do recondicionamento incorreto. A metodologia do trabalho pode ser dividida em cinco etapas: estudo do estado da arte de recondicionamento de motores; quantificação de empresas e funcionários por meio de consultas às bases de dados governamentais; pesquisa de campo em amostras de empresas que fazem recondicionamento; extrapolação do estudo conduzido nas amostras para a população de empresas pesquisadas durante a pesquisa de campo; comparação dos resultados com estudos anteriores e dimensionamento das perdas elétricas do Brasil. Como resultado foi caracterizado e dimensionado o mercado de motores recondicionados, contendo: 6.503 empresas; 24,4 mil funcionários; 45 porcento das empresas realizando revenda de recondicionados; 6,9 milhões de motores recondicionados por ano, totalizando 7,46 porcento de perda, equivalentes a 2,9 Terawatt-hora. Além disso, dos 20 milhões de motores existentes no Brasil em 2016 há uma perda de 8,4 Terawatt-hora por uso de motores recondicionados e um grande aumento da venda de motores importados de baixa qualidade. Foram, assim, atingidos todos os objetivos propostos nesta pesquisa, sendo identificadas as novas tendências do mercado de motores brasileiro e gerando subsídios para o desenvolvimento de novas políticas de eficiência energética no país.
Electric motors in Brazil are responsible for the consumption of about 25 percent of all electricity in the country and, being mostly presented in the industry. These equipments are manufactured for being used in hydraulic pumps, air compressors, elevators, etc., and can be commercialized in compliance with the energy efficiency levels defined by INMETRO/MDIC Ordinance N488 of 2010, ensuring adequate energy consumption. However, some establishments are commercializing refurbished motors, not complying with the regulation considered by the Ordinance, including reforming motors without a minimum condition of use. The aim of this dissertation is to evaluate the Brazilian market of refurbished motors, including resale market and maintenance market, estimating the energy losses due to incorrect reconditioning. The methodology of the work can be divided in five steps: state of the art of refurbished motors; quantifying companies and employees by querying the database come from the government; survey on samples of companies that are doing the refurbishing service; extrapolation of the study conducted in the surveyed samples of companies to the population of companies; comparison of results with previous studies and estimating of energy losses in Brazil. As a result, the market for refurbished motors was characterized and dimensioned, containing: 6 503 companies; 24.400 employees; 45 percent of companies performing resale of refurbished motors; 6.9 million motors being refurbished per year, totaling 7.46 percent of energy losses, equivalent to 2.9 TW h. In addition, of the 20 million motors remaining in Brazil in 2016, there is a loss of 8.4 TW h per use of refurbished motors, and a large increase of the sale of low quality imported motors. Thus, all the proposed objectives in this dissertation were achieved, having been identified the new trends in the Brazilian electric motor market and generating subsidies for energy efficiency policies in the country.

APA, Harvard, Vancouver, ISO, and other styles

5

Han, Xue. "Quantitative Analysis of Distributed Energy Resources in Future Distribution Networks." Thesis, KTH, Industriella informations- och styrsystem, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-98484.

Full text

Abstract:

There has been a large body of statements claiming that the large scale deployment of Distributed Energy Resources (DERs) will eventually reshape the future distribution grid operation in numerous ways. However, there is a lack of evidence specifying to what extent the power system operation will be alternated. In this project, quantitative results in terms of how the future distribution grid will be changed by the deployment of distributed generation, active demand and electric vehicles, are presented. The quantitative analysis is based on the conditions for both a radial and a meshed distribution network. The input parameters are on the basis of the current and envisioned DER deployment scenarios proposed for Sweden. The simulation results indicate that the deployment of DERs can significantly reduce the power losses and voltage drops by compensating power from the local energy resources, and limiting the power transmitted from the external grid. However, it is notable that the opposite results (e.g., severe voltage uctuations, larger power losses) can be obtained due to the intermittent characteristics of DERs and the irrational management of different types of DERs in the DNs. Subsequently, this will lead to challenges for the Distribution System Operator (DSO).

APA, Harvard, Vancouver, ISO, and other styles

6

Penin, Carlos Alexandre de Sousa. "Combate, prevenção e otimização das perdas comerciais de energia elétrica." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/3/3143/tde-14082008-092248/.

Full text

Abstract:

As perdas de energia elétrica devidas a furtos e fraudes, também chamadas de Perdas Não-Técnicas (PNT) ou Perdas Comerciais, têm sido matéria prioritária das empresas concessionárias de distribuição de energia elétrica, bem como dos órgãos reguladores, tanto pelo seu crescimento nos últimos anos quanto pelo seu impacto no sistema elétrico brasileiro. As formas de fraude são as mais variadas possíveis, o que gera enormes dificuldades para as concessionárias. Este trabalho tem como objetivo o estudo do problema das PNT utilizando-se de uma abordagem multidisciplinar, que analisa a experiência tanto de concessionárias no Brasil como no exterior. O trabalho discute as melhores práticas para mitigação das mesmas e propõe melhorias nos processos de combate e de prevenção, e nos procedimentos legais para recuperação de receitas, apoiados sobre uma cuidadosa contextualização regulatória. Chamase a atenção para a diversidade sócio-econômica nacional, compara-se com diversos exemplos internacionais, e propõe-se identificar os aspectos mais relevantes a serem considerados na regulação sobre o tema, discutindo procedimentos e metodologias para o equacionamento do montante de recursos a serem aplicados pelas companhias distribuidoras para a adequada redução dessas perdas de energia. Observa-se que grande parte das PNT tem origem em questões de cunho social. O Estado pode e deve estabelecer políticas para resolver tais questões, possibilitando a universalização do acesso e subsidiando o fornecimento de energia elétrica. Não fez parte dessa pesquisa discutir se estes instrumentos são suficientes ou devem ser aprimorados, mas sim analisar amplamente a questão das PNT com base nos condicionantes regulatórios atuais, que obrigam as concessionárias a reduzir estas perdas visando entre outros a modicidade tarifária dos consumidores regulares.
The electric power losses due to thefts and frauds, also called Non technical Losses (NTL), have been priority matter for concessionary companies of electric power distribution, as well as for government regulatory agencies, not only due to rapid growth over the past years but also due to its impact on Brazilian electrical system. There is a wide range of possible types and methods of frauds, causing enormous difficulties to licensed companies. The objective of this work is to study the problem of NTL using a wide approach, analyze the experience of dealerships in Brazil and abroad, discuss the best practices for mitigation of those losses and propose improvements in the combat and prevention processes, and the legal procedures for recovery of incomes, leaning on a careful regulatory context. This study draws attention to Brazil\'s socioeconomic diversity, comparing it to various international examples, and intends to identify the most relevant aspects that must be considered on the theme, discussing procedures and methodologies for the equation of the amount of resources to be applied by distributing companies to achieve the appropriate reduction of NTL. A large part of the commercial losses has its origin in issues of social stamp. The State owes and can establish policies to solve such issues, making possible the access to electric power supply for all consumers. It was not part of this research to discuss if these instruments are enough, but to analyze the issue of the commercial losses thoroughly based in the regulatory policies that push dealerships to reduce NTL objecting reasonable regular consumers\' tariff.

APA, Harvard, Vancouver, ISO, and other styles

7

Beckman, Mathias, and Gerald Volden Alex Christy. "Performance Assessment of Electrical Motor for Electric Aircraft Propulsion Applications : Evaluation of the Permanent Magnet Motor and its Limitations in Aircraft Propulsion." Thesis, Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-45157.

Full text

Abstract:

This thesis project will evaluate which kind of electrical motor is best suited for aircraft propulsion and which parameters effect the efficiency. An economic analysis was conducted, comparing the fuel price (Jet A1) for a gas turbine and the electricity price for an electric motor of 1MW. The study was conducted by using analytical methods in MATLAB. Excel was used to compile and present the data. The data used in this thesis project were assumed with regards to similar studies or pre-determined values. The main losses for the Permanent Magnet Synchronous Motor (PMSM) were calculated to achieve a deeper understanding of the most important parameters and how these parameters need to improve to allow for future electric propulsion systems. The crucial parameters for the losses were concluded to be the temperature, voltage level, electrical frequency, magnetic flux density, size of the rotor and rotational speed. The three main losses of a PMSM was illustrated through the analytical equations used in MATLAB. The calculations present how the ohmic losses depend on the temperature (0-230°C) at different voltages (700V and 1000V), how the core losses depend on frequency (0-1000Hz) at different magnetic flux densities and how the windage losses depend on rotational speed (7000-10000 rpm). It could be concluded that at 8500 rpm an efficiency of 91,26% could be achieved at 700V, 1.5T and 90.4% at 1000V, 1.65T. The decrease in efficiency is a result of the increase in magnetic flux density. When looking at the economic viability of electrical integration the power to weight ratio and energy price was compared for the gas turbine and electrical motor including an inverter and battery. This resulted in a conclusion that a pure electrical system may not compete with a gas turbine in 30 years of time due to the low energy density of the battery. It was also concluded that the emissions during cruise could be lowered significantly. If the batteries were charged in Sweden the emissions would decrease from ~937 kg CO2 to ~31 kg CO2. If the batteries were charged in the Nordic region the emissions would decrease to ~119kg CO2. However, if the batteries were to be charged in the US the carbon dioxide emission would be ~1084 kg CO2, which is an increase in CO2 emission compared to the gas turbine.

APA, Harvard, Vancouver, ISO, and other styles

8

Мандрика, Анатолій Семенович, Анатолий Семенович Мандрыка, Anatolii Semenovych Mandryka, and О. М. Молошний. "Потенційні можливості енергозбереження в системах електропостачання." Thesis, Сумський державний університет, 2014. http://essuir.sumdu.edu.ua/handle/123456789/40529.

Full text

Abstract:

Значним джерел економії палива є зниження втрат в електричних мережах. В Україні ці втрати обумовлюється великими об’ємами крадіжок електричної енергії, відсутністю дієвої систем обліку, застарілим і зношеним обладнанням електромереж.

APA, Harvard, Vancouver, ISO, and other styles

9

Paulino, Clóvis Aparecido. "Estudo de tecnologias aplicáveis à automação da medição de energia elétrica residencial visando à minimização de perdas." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/3/3143/tde-13122006-151957/.

Full text

Abstract:

Atualmente a medição de energia elétrica para residências em centros urbanos é realizada por meio de medidores eletromecânicos lidos de forma manual. Neste processo uma série de problemas foram observados, dos quais se destacam: erros de leitura, dificuldade de acesso ao ponto de medição, bancos de dados sem atualização, dentre outros. A automação do processo de medição e da leitura, com base nos medidores existentes ou com o uso de medidores eletrônicos da energia elétrica, além de resolver os problemas citados, tem potencialmente uma série de vantagens, que incluem: combate a fraudes e furto de energia, implementação de tarifas diferenciadas em função da hora de consumo (tarifa amarela), corte e religamento remoto de energia, implementação de programas de energia pré-paga, levantamento de curvas de carga e eliminação de erros e custos do processo de leitura manual. Por outro lado observa-se que existem no Brasil cerca de 43 milhões de medidores residenciais instalados, sendo relativamente baixos os custos dos medidores eletromecânicos e do sistema de leitura manual. Desta forma, somente será possível implementar sistemas de automação da medição de energia elétrica residencial se os sistemas ora propostos forem ao mesmo tempo de custo reduzido e altamente confiáveis. O sistema de automação em estudo irá considerar inclusive o aproveitamento dos medidores eletromecânicos existentes, com a instalação de sistemas eletrônicos de coleta dos dados de consumo comunicando-se com concentradores locais, que por sua vez são interligados a sistemas computacionais instalados dentro da concessionária. Os resultados do estudo mostram que hoje existe uma concreta possibilidade de se obter sistemas de automação da medição de energia elétrica residencial seguros e de custos reduzidos. O trabalho ora proposto será desenvolver um sistema automatizado para a medição de energia residencial em centros urbanos, constituído por um módulo concentrador para oito residências, com comunicação deste para um centro de operação da concessionária. Será apresentada a metodologia para a implementação do sistema e considerado um estudo de caso.
In these days, the energy measurement system for residences in urban areas is carried out by eletromechanical meters, which are read manually. Several problems have been observed in this process, which we can emphasize: reading errors, difficulty to access the measurement place, outdated databases, etc. The reading and the measurement automation processes, based in the current eletromechanical meters or with the electronic version of these equipment, besides solving the mentioned problems, have several advantages, such as: minimization of fraud and robbery of energy, implementation of differentiated rates depending on the time of the day (ex:yellow rate), remote energy switch-off and switch-on, implementation of a prepaid system, possibility to get the load curve of each consumer and elimination of error and costs embedded in the manually reading process. On the other hand, we can observe that in Brazil there are an estimated 43 millions residential meters already installed, and the costs for the current measurement system, and also of the meters, are very low. In this scenario, the implementation of a automated system for residential energy measurement is that the proposed system has a very low cost at the same time provides a high reliability. The proposed automation system will consider the reutilization of the current mechanical meters, with the installation of an electronic systems for the consumption data collection, communicating with local concentrators, which in their turn are linked to a computing systems in the energy company. The results of the present work show that, nowadays, there is a real possibility to get, a trustable and cheap automated measurement system for energy in residential urban area. The proposed work is the development of an automated system, for residential energy measurement in urban area. It's composed of a concentrator module for eight residences, with communication from this point to the energy company's operation center. It will be presented a methodology to implement such a system and also a case study.

APA, Harvard, Vancouver, ISO, and other styles

10

Петровський, Михайло Васильович, Михаил Васильевич Петровский, Mykhailo Vasylovych Petrovskyi, А. В. Титаренко, С. В. Федірка, and Р. С. Вольвач. "Визначення втрат на нагрів дефектних з'єднань розподільчих пристроїв на основі даних тепловізійної діагностики обладнання." Thesis, Видавництво СумДУ, 2012. http://essuir.sumdu.edu.ua/handle/123456789/27710.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Bruch, Rafael. "Estudo das perdas térmicas de panelas entre o vazamento no forno elétrico à arco e o transporte para o forno-panela." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2012. http://hdl.handle.net/10183/60805.

Full text

Abstract:

A busca de melhoria de produtos siderúrgicos leva uma atenção especial para a área de aciarias. A introdução da metalurgia da panela, e portanto no refino secundário, contribuiu fundamentalmente para o aumento da qualidade do aço produzido. Um dos efeitos foi o aumento do tempo de residência do aço na panela, o que obrigou a utilização de materiais refratários de melhor qualidade. O controle da temperatura do aço líquido ao longo do processo de produção é de fundamental importância para se atingir os requisitos de qualidade e produtividade exigidos atualmente. Com o desenvolvimento de tecnologias siderúrgicas e a busca pela eficiência energética, torna-se necessário o conhecimento e redução das perdas térmicas do aço durante todo o ciclo produtivo. Neste trabalho foram estudadas, em uma aciaria elétrica a arco, as correlações entre as perdas térmicas das panelas através do conhecimento dos tempos de espera e do tempo de transporte das panelas do forno elétrico a arco até o forno-panela, além de comparar a temperatura do revestimento refratário de panelas com e sem isolante refratário. Melhorias no ciclo de panelas foram propostas visando diminuir as perdas térmicas das panelas, otimizar o ciclo de panelas e, consequentemente, reduzir o consumo de energia elétrica do forno-panela, diminuindo os custos envolvidos durante o processo de fabricação do aço. Os resultados apresentaram significância estatística entre o consumo de energia elétrica do fornopanela e as perdas térmicas das panelas. Através dos resultados obtidos observou-se que a minimização do tempo de espera da panela antes de iniciar o vazamento e a diminuição do tempo de transporte da panela até o forno-panela são fundamentais para diminuir as perdas térmicas nas panelas.
The search for improved steel products takes special attention to the melthops. The introduction of ladle metallurgy, and therefore the secondary refining, contributed essentially to increase the quality of steel produced. One effect was to increase the residence time of the steel in the ladle, forcing the use of refractory materials of better quality. Temperature control of liquid steel during the process is of fundamental importance for achieving the requirements of quality and productivity currently required. With the development of technologies and the reach of energetic efficiency, it becomes necessary to reduce the thermal losses during the steel production cycle. In this study the correlations between the thermal losses in the ladles through the knowledge of waiting times and transport times of the ladles to the of the electric arc furnace to the ladle furnace were determined as well as a comparison between temperatures of ladle refractory lining with and without refractory insulation. Improvements in the ladle cycle were proposed to reduce the thermal losses in the ladles and to optimize the ladle cycle and, consequently, to reduce the electric energy in the ladle furnace, reducing the costs involved during the manufacturing process of steel. The results showed statistical significance between the energy consumption in the ladle furnace and heat losses in the ladles. The results obtained showed that minimizing the waiting time of the ladle before the tap and reducing transportation time of the ladle to the ladle furnace are essential to reduce the heat losses in the ladles.

APA, Harvard, Vancouver, ISO, and other styles

12

Taran, Narges. "Optimum Design of Axial Flux PM Machines based on Electromagnetic 3D FEA." UKnowledge, 2019. https://uknowledge.uky.edu/ece_etds/145.

Full text

Abstract:

Axial flux permanent magnet (AFPM) machines have recently attracted significant attention due to several reasons, such as their specific form factor, potentially higher torque density and lower losses, feasibility of increasing the number of poles, and facilitating innovative machine structures for emerging applications. One such machine design, which has promising, high efficiency particularly at higher speeds, is of the coreless AFPM type and has been studied in the dissertation together with more conventional AFPM topologies that employ a ferromagnetic core. A challenge in designing coreless AFPM machines is estimating the eddy current losses. This work proposes a new hybrid analytical and numerical finite element (FE) based method for calculating ac eddy current losses in windings and demonstrates its applicability for axial flux electric machines. The method takes into account 3D field effects in order to achieve accurate results and yet greatly reduce computational efforts. It is also shown that hybrid methods based on 2D FE models, which require semi-empirical correction factors, may over-estimate the eddy current losses. The new 3D FE-based method is advantageous as it employs minimum simplifications and considers the end turns in the eddy current path, the magnetic flux density variation along the effective length of coils, and the field fringing and leakage, which ultimately increases the accuracy of simulations. After exemplifying the practice and benefits of employing a combined design of experiments and response surface methodology for the comparative design of coreless and conventional AFPM machines with cores, an innovative approach is proposed for integrated design, prototyping, and testing efforts. It is shown that extensive sensitivity analysis can be utilized to systematically study the manufacturing tolerances and identify whether the causes for out of specification performance are detectable. The electromagnetic flux path in AFPM machines is substantially 3D and cannot be satisfactorily analyzed through simplified 2D simulations, requiring laborious 3D models for performance prediction. The use of computationally expensive 3D models becomes even more challenging for optimal design studies, in which case, thousands of candidate design evaluations are required, making the conventional approaches impractical. In this dissertation a new two-level surrogate assisted differential evolution multi-objective optimization algorithm (SAMODE) is developed in order to optimally and accurately design the electric machine with a minimum number of expensive 3D design evaluations. The developed surrogate assisted optimization algorithm is used to comparatively and systematically design several AFPM machines. The studies include exploring the effects of pole count on the machine performance and cost limits, and the systematic comparison of optimally designed single-sided and double-sided AFPM machines. For the case studies, the new optimization algorithm reduced the required number of FEA design evaluations from thousands to less than two hundred. The new methods, developed and presented in the dissertation, maybe directly applicable or extended to a wide class of electrical machines and in particular to those of the PM-excited synchronous type. The benefits of the new eddy current loss calculation and of the optimization method are mostly relevant and significant for electrical machines with a rather complicated magnetic flux path, such is the case of axial flux and of transvers flux topologies, which are a main subject of current research in the field worldwide.

APA, Harvard, Vancouver, ISO, and other styles

13

Claesson, Gabriel. "Evaluation of Energy Losses in a Wind Farm." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-293053.

Full text

Abstract:

In recent years, the power production from wind power and other renewable energy sources has increased significantly. Arguably, this is due to the greenhouse effect and the economic benefit of generating power from the wind. Wind power has the potential to replace other non-renewable power sources. Thus, it is of interest to maximize the efficiency of the wind farms, to produce the most power to the grid. This implies that the power losses within the wind farms needs to be minimized. Evidently, there are expected and unavoidable power losses within the wind farm. However, when there are unexpected power losses or the power losses exceed what is expected, the question arises as to what the reason for this is and if it is possible to avoid or decrease these power losses. In this thesis, a case study is conducted in collaboration with Skellefteå Kraft. An existing wind farm is studied, as the case company noted inconsistencies in power losses. One section has a larger share of power losses than the other section in the wind farm. Thus, it is of interest to the case company to find out why this is, to find the source to these power losses, as unnecessary power losses mean a loss of profit as well as loss of useful power produced from renewable energy sources. This suggests that if the sources of the power losses are identified and the power losses are deemed unnecessary for the operation of the wind farm, the case company can take actions accordingly. Hence, this thesis aims to identify the sources of the power losses and to create basis to whether these power losses are justified and necessary for the operation of the existing wind farm or not. To study the power losses in the existing wind farm, a model is developed utilizing load flow analysis. The load flow analysis is based on real hour power production data of the year of 2019. Thus, several load flow calculations are carried out to modify the system parameters to optimize the accuracy, and to verify the model. The model is then used to estimate and evaluate the power losses within the wind farm, and for identification of the sources of the power losses. The results of the case study prove that a rather accurate model was successfully developed. The model indicates that, for the year of 2019, the difference in power losses between the two sections of the wind farm was primarily due to the de-icing systems. The de-icing system of one section constituted for a significantly larger share of the power losses in that section than what the de-icing system of the other section constituted for the power losses in the other section. This suggests that the de-icing system needs to be evaluated further. Due to the design of the wind farm, there is an additional transformer in one of the sections. Through utilizing the model, the power losses of the additional transformer were estimated. For the year of 2019, the model indicated that the power losses of the additional transformer contributed rather insignificantly to the difference in power losses between the two sections.
Under de senaste åren har kraftproduktionen från vindkraft och andra förnybara energikällor ökat avsevärt. Det beror bland annat på växthus- effekten och de ekonomiska fördelarna med att generera el från vindkraft. Vindkraften har potential att ersätta andra icke förnybara energikällor. Därför är det av intresse att maximera vindkraftparkernas effektivitet och maximera den genererade effekten ut på elnätet. Detta innebär att effektförlusterna inom vindkraftsparkerna bör minimeras. Det finns förväntade och oundvikliga kraftförluster inom vindkraftsparken. När det uppstår oväntade effektförluster eller effektförlusterna överstiger det som förväntas, blir frågan om vad orsaken är och om det är möjligt att undvika alternativt minska på dessa effektförluster. I detta arbete genomförs en fallstudie i samarbete med Skellefteå Kraft. En befintlig vindkraftspark studeras, eftersom företaget har noterat oväntade effektförluster. En sektion har större andel effektförluster jämfört med den andra delen av vindkraftsparken. Därför är det av intresse för företaget att ta reda på anledningen till detta, eftersom onödiga effektförluster innebär ekonomiska och effektmässiga förluster. Det betyder att om källorna till effektförlusterna identifieras och är onödiga för driften av vindkraftsparken kan företaget vidta åtgärder därefter. Syftet med detta arbete är därför att identifiera källorna av effektförlusterna och identifiera om dessa effektförluster är nödvändiga för driften av vindkraftsparken eller inte. För att studera effektförlusterna i den befintliga vindkraftsparken utvecklas en modell med hjälp av lastflödesanalys. Lastflödesanalysen är baserad på realtidsdata för kraftproduktion under år 2019. Således utförs flera lastflödesberäkningar för att modifiera modellens systemparametrar, för att öka noggrannheten och för att verifiera modellen. Modellen används sedan för att uppskatta och utvärdera effektförlusterna inom vindkraftsparken och för identifiering av källorna till effektförlusterna. Resultaten från studien visar att en noggrann modell kunde utvecklas. Modellen indikerar att skillnaden i effektförluster mellan de två sektionerna i vindkraftparken för år 2019 främst berodde främst på avisningssystemen. Avisningssystemet i den ena sektionen utgjorde en betydligt större andel av effektförlusterna än i den andra sektionen. Detta tyder på att avisningssystemet bör utvärderas ytterligare. På grund av vindkraftsparkens utformning finns det en extra transformator i en av sektionerna. För år 2019 indikerade modellen att effektförlusterna för den extra transformatorn knappt bidrog till skillnaderna i effektförluster mellan de två sektionerna.

APA, Harvard, Vancouver, ISO, and other styles

14

Склярук, В. М. "Вплив малих гідроелектростанцій на режими роботи розподільних електромереж." Thesis, ВНТУ, 2016. http://conferences.vntu.edu.ua/index.php/all-feeem/all-feeem-2016/paper/view/531.

Full text

Abstract:

Робота присвячена аналізу впливу малих гідроелектростанцій,зокрема з асинхронним генераторами, на режими роботи розподільних електричних мереж та втрати електроенергії в них. Запропоновано шляхи зменшення адресних втрат електроенергії
The work is dedicated to analyze the impact of small hydropower plants, including asynchronous generators, the modes of distribution electrical grids and power losses in them. Ways to reduce targeted power losses prompted.

APA, Harvard, Vancouver, ISO, and other styles

15

Гапон, Дмитро Анатолійович. "Методи та засоби аналізу якості електропостачання та електромагнітної сумісності електротехнічних комплексів та систем." Thesis, Національний технічний університет "Харківський політехнічний інститут", 2020. http://repository.kpi.kharkov.ua/handle/KhPI-Press/48409.

Full text

Abstract:

Дисертація на здобуття наукового ступеня доктора технічних наук за спеціальністю 05.09.03 – Електротехнічні комплекси та системи. – Національний технічний університет "Харківський політехнічний інститут", Харків, 2019. У роботі міститься вирішення актуальної наукової проблеми аналізу якості електропостачання та електромагнітної сумісності електротехнічних комплексів та систем. Ця проблема полягає у відсутності математичної бази та, відповідно, нормативної бази оцінювання впливу окремого електротехнічного комплексу або системи споживача на якість електроенергії. Діючи норми покладають усю відповідальність за низьку якість електропостачання на безпосередньо постачальну організацію у вигляді штрафів, що, як показує досвід, не сприяє побудові оптимальних систем електропостачання. В роботі запропоновано оцінку якості електропостачання шляхом порівняння режиму електроспоживання діючого електротехнічного комплексу з еталонним споживачем у вигляді числових коефіцієнтів потужності та втрат. Отримані розрахункові формули для однофазних, трифазних трипровідних та чотирьохпровідних систем електропостачання. Запропоновано розподіл загальних втрат на втрати від несиметрії, не лінійності, реактивності та нестаціонарності. Запропоновано та досліджено концепції еталонного реактивного споживача та усередненого реактивного споживача. Запропоновано методику врахування якості електроспоживання при розрахунках за спожиту електроенергію, яка створює економічний стимул для підвищення ефективності енергорежимів споживача. Запропоновано методику оцінки порушення споживачем норм споживання за величиною потужності і гармонійних складових, що потенційно здатні викликати вихід показників якості електричної енергії за допустимі межі. Надано основи методики побудови штрафних санкцій щодо споживача у разі перевищення допустимих параметрів електроспоживання, а також штрафних санкцій щодо постачальника електричної енергії у разі низької якості електричної енергії та відсутності порушень з боку споживача.
The dissertation on achieving the scientific degree Doctor of Technical Sciences by specialty 05.09.03 – "Electrotechnical complexes and systems" - National Technical University "Kharkiv Polytechnic Institute", Kharkiv, 2020. The paper contains the solution of the actual scientific problem of the analysis of quality of power supply and electromagnetic compatibility of electrotechnical complexes and systems. This problem is the lack of a mathematical basis and, accordingly, a regulatory framework for assessing the impact of a particular electrical complex or consumer system on the quality of electricity. The current regulations place all responsibility for the low quality of electricity supply directly on the supply organization in the form of fines, which, as experience shows, does not contribute to the construction of optimal power supply systems. The paper analyzes the compatibility of the existing regulatory framework (including IEEE519, EN50160) and evaluates the effectiveness of the proposed methods of determining responsibility using computer simulations. The analysis showed that the existing methods have significant limitations, as a result of which they are not suitable for practical application. The paper proposes an assessment of the quality of power supply by comparing the mode of power consumption of the existing electrical complex with the reference consumer in the form of numerical coefficients of power and losses. Calculation formulas for single-phase, three-phase three-wire and four-wire power supply systems are obtained. Three-phase three-wire system the reference consumer, regardless of the voltage parameters, is a symmetrical triangle of constant active resistance is shown. Three-phase four-wire system the reference consumer, regardless of voltage parameters, is a combination of a symmetric triangle of constant active resistances and a symmetrical star, the resistance in the branches of which is as many times more than the resistance of the triangle is shown. It is noted that the general assessment of the loss ratio is not informative enough about the reasons for the deterioration of electricity quality. To solve this problem, the division of total losses into losses from asymmetry, nonlinearity, reactivity and nonstationarity is proposed. The concept of the reference reactive consumer is offered, and conclusions concerning possibility and expediency of its use are made. A method for determining the reactivity coefficient by volumes of energy flowing in the forward and reverse directions is proposed. The concept of the average reactive consumer is offered. The paper proposes to build an assessment of the contribution of a separate electrical complex or consumer system in the deterioration of power supply on the basis of power values specified in the contract and the establishment of normalized resistance of the power supply system. Based on these values, a mathematical apparatus is proposed, which allows not only to determine the fact of violation of the limits of electromagnetic compatibility but also to quantify the amount of electricity that has been damaged. It is proposed to determine the coefficient of losses from asymmetry using a reference consumer. This coefficient is calculated as the ratio between the power loss of three independent single-phase reference consumers to the losses of the reference three-phase consumer. This solution avoids the influence of such factors as nonlinearity and reactivity. In addition, the device of symmetrical components is not used, which is inconvenient in the case of non-sinusoidal voltages and currents. It is proposed to select individual coefficients of losses from reactivity and nonlinearity, which are calculated by dividing the harmonic components of the distortion current by the power direction. The method of calculation of losses from nonstationarity is calculated, which is calculated as the ratio of total losses of reference consumers on several "short" intervals, and losses of the reference consumer on a long interval that includes all "short". The analysis of character of complex resistance of an electric network depending on parameters of its elements for typical cases of connection of consumers of various character on voltage of 10 KV is carried out. The obtained dependence allows us to talk about the possible use of normalized values to estimate network bandwidth. An empirical method for calculating the normalized resistance is proposed. A method for measuring the parameters of the electrical network mode is proposed, which allows to implement algorithms for assessing the quality of power consumption, the advantages of which are self-synchronization, calculation of values strictly for one period of the main voltage harmonic, absence of gaps and overlays of observation intervals. A method for measuring the current values of currents and voltages on their discrete images is proposed, taking into account the discrepancy between the moments of the initial and final readings of the digital image of the signal with the moments of the beginning and end of the measurement period. A method of taking into account the quality of electricity consumption in the calculations for the consumed electricity is proposed, which creates an economic incentive to increase the efficiency of energy regimes of the consumer. The method of estimation of infringement by the consumer of norms of consumption on size of power and harmonic components which are potentially capable to cause an exit of indicators of quality of electric energy beyond admissible limits is offered. The basics of the method of construction of penalties against the consumer in case of exceeding the allowable parameters of electricity consumption, as well as penalties against the supplier of electricity in case of low quality of electricity and the absence of violations by the consumer. In the experimental part of the work the application of the offered mathematical devices on the examples of test mathematical models and oscillograms obtained on real objects is tested. The experiment allowed to confirm the effectiveness of the proposed methods, in addition to the method of comparison with the reference medium-reactive consumer, which has not proved to be an effective tool for analysis and does not seem promising. Also in the work the hardware realization in the form of the electric energy meter taking into account its quality is offered.

APA, Harvard, Vancouver, ISO, and other styles

16

Muellejans, Harald. "Secondary electron emission in coincidence with primary energy losses." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240071.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

Самойлов, Дмитро Юрійович, and Dmytro Samoilov. "Зменшення втрат електричної енергії в мережі електропостачання олійноекстракційного заводу." Master's thesis, ТНТУ імені Івана Пулюя, 2019. http://elartu.tntu.edu.ua/handle/lib/29567.

Full text

Abstract:

У дипломній роботі проведено аналіз, та здійснено розробку заходів для зменшення втрат електричної енергії в мережі електропостачання олійноекстракційного заводу. Проведено дослідження системи електропостачання олійноекстракційного заводу в цілому, та одного з його цехів, а саме здійснено вибір комутаційно-захисної апаратури та провідників цехової і заводської мереж, вибір та місце розташування цехових трансформаторних підстанцій грануляційного цеху. Розроблена система електропостачання на основі аналізу електричних навантажень.
An analysis is conducted in diploma work, and development of measures is carried out for reduction of losses of electric energy in the network of power supply of oil extraction plant. A study of the system of power supply of oil extraction plant is undertaken on the whole, and one of his workshops, the choice of switchgears-protection apparatus and explorers of workshop and plant networks, choice and place of location of workshop transformer substations of granulation workshop, is namely carried out. The worked out system of power supply is on the basis of analysis of the electric loading.
ВСТУП 7 1 АНАЛІТИЧНА ЧАСТИНА 10 1.1 Загальні відомості про підприємство 10 1.2 Інформація про потужності підприємства 13 1.3 Короткий опис технологічного процесу 14 1.4 Відомості про джерела живлення 16 1.5 Оцінка категорії з надійності електропостачання 16 1.6 Відомості про споживання електроенергії на підприємстві 17 1.7 Особливості розрахунків електропостачальних систем 17 1.8 Вимоги до електричних мереж. Надійність електропостачання 20 1.9 Класифікація заходів по зниженню втрат електроенергії 20 2 НАУКОВО-ДОСЛІДНА ЧАСТИНА 24 2.1 Заходи із забезпечення надійності роботи електротехнічних пристроїв 24 2.2 Ефективність функціонування енергетики 28 2.3 Забезпечення системної надійності якості електроенергії на підприємствах з безперервними технологічними процесами 31 3 ТЕХНОЛОГІЧНА ЧАСТИНА 40 3.1 Вибір схеми електропостачання грануляційного цеху 40 3.2 Розрахунок навантаження грануляційного цеху 40 3.3 Розрахунок електричних навантажень підприємства 44 3.4 Побудова картограми навантажень 50 3.5 Вибір комутаційно-захисної апаратури та провідників цехової мережі 53 3.6 Вибір схем та основних елементів заводської мережі 57 4 ПРОЕКТНО-КОНСТРУКТОРСЬКА ЧАСТИНА 63 4.1 Структура існуючої схеми та характеристика обладнання 63 5 СПЕЦІАЛЬНА ЧАСТИНА 81 5.1 Визначення втрат в лініях і мережах 81 5.2 Заходи зі зменшення втрат в розподільчих мережах 81 5.2.1 Економія електроенергії в трифазних мережах напругою до 1000 В з несиметричним навантаженням 85 6 ОБГРУНТУВАННЯ ЕКОНОМІЧНОЇ ЕФЕКТИВНОСТІ 88 6.1 Визначення техніко–економічного аналізу 88 6.2 Техніко-економічне обґрунтування вибраного заходу по зменшенню втрат в лініях електропостачання 90 7 ОХОРОНА ПРАЦІ ТА БЕЗПЕКА В НАДЗВИЧАЙНИХ СИТУАЦІЯХ 95 7.1 Технічні рішення з безпечної експлуатації об'єкту 95 7.2 Технічні рішення з гігієни праці і виробничої санітарії 99 7.3 Ліквідація наслідків надзвичайних ситуацій 102 8 ЕКОЛОГІЯ 106 8.1 Актуальність охорони навколишнього середовища 106 8.2 Вплив олійноекстракційного заводу на екологію 107 ЗАГАЛЬНІ ВИСНОВКИ ДО ДИПЛОМНОЇ РОБОТИ 109 ПЕРЕЛІК ПОСИЛАНЬ 110

APA, Harvard, Vancouver, ISO, and other styles

18

Rafferty, Brian Edward. "Probing electronic structure near the bandgap region using electron energy loss spectroscopy." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627334.

Full text

APA, Harvard, Vancouver, ISO, and other styles

19

Roth, Friedrich. "Electronic structure of selected aromatic hydrocarbon systems investigated with electron energy-loss spectroscopy." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-106800.

Full text

Abstract:

Organic materials with fascinating/intriguing electronic properties have been the driving force for many research activities in the past, and in particular for important progress in materials science covering both new functional materials as well as theoretical developments. In addition, charge transfer, i. e., the addition or removal of charges to or from molecules in organic solids is one route to modify and control their electronic properties. Recently, the discovery of superconductivity in several alkali metal intercalated hydrocarbon systems (picene, phenanthrene, coronene and 1,2;8,9-dibenzopentacene) with rather high transition temperatures has opened a new chapter in organic material science as well as solid-state physics. The search for a microscopic understanding of the mechanism that drives materials superconducting always has initiated a large number of scientific activities, and there are numerous examples where these activities have provided major advancement. A basic foundation of this understanding is the knowledge of the electronic properties of the material under investigation. In this context, this thesis reports first, very detailed insight into the electronic structure of both undoped as well as potassium doped picene, coronene and 1,2;8,9-dibenzopentacene using electron energy-loss spectroscopy (EELS) as main experimental method. Additionally, also photoemission spectroscopy experiments have been performed to investigate the occupied electronic density of states close to the chemical potential. In order to learn more about the electronic structure we have compared the results we obtained from EELS and photoemission spectroscopy with theoretical calculations based on Density functional theory (DFT) using the local-density approximation (LDA). We identify the peculiar case of very close lying conduction bands that upon doping harbour the electrons that form the Cooper-pairs in the superconducting state. Moreover, the presented data display substantial changes in the electronic excitation spectrum upon doping, whereas in the doped case the appearance of one new peak (for picene) and several new peaks (for coronene and 1,2;8,9-dibenzopentacene) in the former optical gap is reported. By using a Kramers–Kronig analysis (KKA) it is possible to gain information about the nature of this doping introduced excitations. In particular, in case of picene, the new low energy feature can be assigned to a charge carrier plasmon. Interestingly, this plasmon disperses negatively upon increasing momentum transfer, which deviates significantly from the traditional picture of metals based on the homogeneous electron gas. The comparison with calculations of the loss function of potassium intercalated picene shows how this finding is the result of the competition between metallicity and electronic localization on the molecular units. Furthermore, core level excitation measurements show the reduction of the lowest lying C 1s excitation feature, which clearly demonstrates that potassium intercalation leads to a filling of the conduction bands with electrons. Additionally, the measurements of potassium intercalated 1,2;8,9-dibenzopentacene clearly indicate the formation of particular doped phases with compositions K_xdibenzopentacene (x = 1, 2, 3), whereas the data suggest that K_1dibenzopentacene has an insulating ground state with an energy gap of about 0.9 eV, while K_2dibenzopentacene and K_3dibenzopentacene might well be metallic, because of the absent of an energy gap in the electronic excitation spectra. Interestingly, a comparison of the photoemission as well as EELS spectra of undoped 1,2;8,9-dibenzopentacene and pentacene reveal that the electronic states close to the Fermi level and the electronic excitation spectra of the two materials are extremely similar, which is due to the fact, that the additional two benzene rings in 1,2;8,9-dibenzopentacene virtually do not contribute to the delocalized pi molecular orbitals close to the Fermi level. This close electronic similarity is in contrast to the behavior upon potassium doping, where evidence for a Mott state has been reported in the case of pentacene. A comparison of the low energy excitation spectra of chrysene with picene (phenacenes) as well as tetracene with pentacene (acenes) crystals reveal a significant difference between the former and the latter two materials. While for the phenacenes (zigzag arrangement) the excitation onset is characterized by up to five weak excitation features with only small anisotropy and without visible Davydov splitting within the a*, b*-planes, the acene (linear arrangement) spectra are dominated by a large excitation close to the onset and a sizable Davydov splitting. The presented data show further that the spectral shape of the pentacene excitation spectrum provides clear evidence for a large admixture of molecular Frenkel-type excitons with charge-transfer excitations resulting in excited states with a significantly mixed character. This conclusion is in good agreement with recent advanced calculations which predicted a charge-transfer admixture to the lowest singlet excitation which is significantly dependent upon the length of the acene molecules. Moreover, also for picene and chrysene we observe differences which point towards an increased charge-transfer contribution to the singlet excitation spectrum in the former. Finally, investigations of the electronic properties of undoped and potassium doped chrysene, a close relative of picene, show that the doping introduced changes are in a similar range such as observed in case of picene. Interestingly, due to the analogy between the observed changes in the electronic structure upon potassium doping between chrysene and picene and further similarity in the crystal structure we speculate that chrysene is a promising candidate for another aromatic hydrocabon superconductor.

APA, Harvard, Vancouver, ISO, and other styles

20

ASEVEDO, FRANCIS ROCHA DE. "GENERALIZED LINEAR APPROACH TO ESTIMATE NON-TECHNICAL LOSSES OF ELECTRICAL ENERGY." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2011. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=18163@1.

Full text

Abstract:

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
A necessidade de simular um ambiente de mercado competitivo para incentivar ganhos de eficiência fez a Agência Nacional de Energia Elétrica (ANEEL) estipular metas para indicadores gerenciáveis, dentre eles o nível de perdas não técnicas (PNT’s) das distribuidoras de energia elétrica. Os prejuízos causados pelas perdas não técnicas de energia chegam à ordem de oito bilhões de reais anuais e impactam diretamente nos valores tarifários em exercício. É nesse contexto que a ANEEL, inspirada nas práticas de regulação por incentivo, estabeleceu um modelo econométrico que relaciona o nível aceitável de perdas não técnicas com a complexidade social das áreas de concessão das distribuidoras brasileiras. Entretanto, entidades do setor enxergam no modelo espaços para melhoria nos resultados e na robustez teórica do modelo, com isso, surge a idéia de propor uma abordagem de estimação diferenciada. É importante ressaltar que além da previsão, tem-se por objetivo testar novas variáveis potencialmente relevantes nesta análise, baseadas na recente literatura acerca do tema. O presente estudo demonstra que a variável de interesse, perdas não técnicas, não segue a distribuição normal, sendo assim, buscou-se a verdadeira distribuição dos dados e a modelagem se deu seguindo os arcabouços da abordagem linear generalizada. Os resultados corroboraram a aderência de uma distribuição que pertence a família exponencial (condição para a aplicação da abordagem linear generalizada). Além disso, o modelo proposto obteve boas estimativas, trazendo inclusive novas variáveis importantes para explicar as perdas não técnicas não utilizadas antes em outros estudos sobre estas perdas. O modelo proposto pode ser visto como uma alternativa viável ao modelo praticado pela ANEEL, sendo assim, sua discussão fundamental para o próximo ciclo de revisão tarifária.
The need of simulating a competitive market environment in order to encourage efficiency gains made the National Electrical Energy Agency (ANEEL) fixes targets for manageable indicators, including the level of non-technical losses (NTL s) of electricity distributors. The financial damage caused by losses not techniques reach the order of eight billion reais per year and directly impacts on the electricity tariffs. In this context, ANEEL inspired by the practice of regulation by incentives, established an econometric model that relates the acceptable level non-technical losses to the social complexity in concession areas of each Brazilian distributor. However, entities in the sector find gaps in the model and improvement in the results and robustness of the model should be done, this brings idea of proposing a different approach to the estimation. It is important to emphasize that in addition to forecasting, there is the willing of testing new variables potentially relevant in this analysis, based on recent literature on the subject. This study proves that the variable of interest, nontechnical losses, does not follow the Gaussian distribution, thus, we sought the true distribution of data and modeling took place in the frameworks of general linear approach. The results confirm adherence to a distribution that belongs to the exponential family (condition for applying the generalized linear approach model), in addition, the proposed model obtained good estimates, including the use of new important variables to explain the non-technical losses not used in other studies. The proposed model can be seen as possible alternative to the model used by ANEEL, so, its discussion is really important to the next review cycle of electricity rates.

APA, Harvard, Vancouver, ISO, and other styles

21

CALILI, RODRIGO FLORA. "SYSTEM DEVELOPMENT TO DETECT COMMERCIAL LOSSES IN ELECTRICAL ENERGY DISTRIBUTION NETWORK." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2005. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=7629@1.

Full text

Abstract:

COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
Os modelos matemáticos comumente usados na identificação de irregularidades na medição se baseiam na análise da redução percentual do consumo do mês (normalmente de 20% a 30%) em relação aos meses anteriores. Este método tem gerado resultados imprecisos uma vez que considera o valor do consumo como um valor rígido e, portanto, não incorpora o efeito da sazonalidade na tipologia das cargas das unidades consumidoras. Este trabalho tem o intuito de melhorar a identificação de clientes fraudulentos utilizando métodos de inteligência artificial, tais como Redes Neurais e Lógica Fuzzy, implementados a um banco de dados de cadastro da Distribuidora de Energia ELEKTRO e a uma Pesquisa de Posses e Hábitos de Consumo (PPH) feita nesta mesma empresa. Nesta dissertação, o objetivo foi classificar um grupo de consumidores como normal (adimplente), inadimplente e fraudulento. Para tanto, foi feita inicialmente uma clusterização utilizando uma Rede Neural, mais especificamente uma Rede de Kohonen, para o banco de dados de cadastro disponibilizado pela distribuidora. Tomando os grupos desta classificação prévia feita pela Rede identificaram-se quais e quantos destes tiveram PPH´s realizadas. Para se ter a classificação de um grupo quanto a incidência de consumidores normais, inadimplentes e fraudulentos utilizou-se um processo de Análise Fuzzy, o qual identifica os clusters com os consumidores de cada um dos segmentos. É feita uma análise de desempenho do modelo proposto com dados reais fornecidos pela empresa, na qual os resultados apontaram para uma robustez do método.
Mathematical models commonly used to identify irregularities in measurement are based on percentile reduction analysis of the monthly consumption (normally from 20% to 30%) in relation to the previous months. This method tends to generate imprecise results, since it considers the value of the consumption as a rigid value and, therefore, it does not incorporate the seasonal effect in the loads topology of the consumer units. This work has intention to improve the identification of fraudulent customers using artificial intelligence methods, such as Neural Networks and Fuzzy Logic, implemented to a database of consumers of ELEKTRO a distributing utility of São Paulo State, Brazil. It also uses information on appliances ownership obtained via market research in ELEKTRO area, named PPH (Portuguese for this particular type of market research). In this dissertation, the main objective was to classify a group of consumers as solvent, insolvent and fraudulent. In order to achieve this task, a clustering was initially made using a Neural Network framework, more specifically a Kohonen Network, for the database available. It was then checked which of the groups had a minimum number of clients interviewed in the PPH. In order to have the classification of the clients in the three categories it was used Fuzzy Analysis. Selected data is also presented, considering the available database of the Company as well as the research environment, which had been taken from the PPH. Finally, it was checked the performance of the method against real data obtained from the utility and the results were very satisfactory.

APA, Harvard, Vancouver, ISO, and other styles

22

Menon, Nanda. "A study of electronic structure anisotropy by spatially resolved electron energy loss spectroscopy." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624123.

Full text

APA, Harvard, Vancouver, ISO, and other styles

23

Pickard, Christopher James. "Ab initio electron energy loss spectroscopy." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627420.

Full text

APA, Harvard, Vancouver, ISO, and other styles

24

Barr, Kenneth C. (Kenneth Charles) 1978. "Energy aware lossless data compression." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/87316.

Full text

APA, Harvard, Vancouver, ISO, and other styles

25

Neurouth, Adrien. "Etude de la performance énergetique d’une transmission de puissance haute vitesse." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI017/document.

Full text

Abstract:

Une des voies d’amélioration des véhicules hybrides et électriques est l’utilisation de moteurs tournant plus vite, jusqu’à plus de 42.000tr/min. Le but est d’augmenter la densité de puissance et le rendement des groupes motopropulseurs. Pour utiliser ces moteurs de nouveaux réducteurs mécaniques doivent être développés. Cela doit se faire sans générer de surcoût important face aux solutions utilisées à basse vitesse et en assurant un niveau de performance énergétique élevé. Cette thèse se situe en amont de la phase de conception d’un réducteur haute vitesse lubrifié par barbotage. Elle a pour but d’identifier les problèmes d’échauffement et de pertes de puissance ainsi que de proposer des pistes d’amélioration énergétique. Ce travaille propose la modélisation thermomécanique de l’étage grande vitesse (GV) du réducteur, réalisée à l’aide de la méthode des réseaux thermiques. Ce modèle couple les pertes de puissance avec les températures. Une attention particulière est portée sur la modélisation des roulements de l’arbre GV. Un nouveau modèle thermomécanique de roulement est développé. Les pertes par barbotage deviennent importantes à grande vitesse. Une méthode permettant de fortement les réduire est caractérisée
A way to improve both electric and hybrid vehicles is to use high speed motors, operating over than 42.000rpm. The goal is to increase the power density and the efficiency of powertrains. Using these new motors, new gearboxes should be developed. This must be done without generating significant additional cost regarding already mastered low speed solutions. High energy performance level also has to be maintained. This PhD comes before the design phase of a high-speed oil bath lubricated gearbox. It aims to identify the warm-up and power loss problems, and propose ways to improve efficiency. This work proposes a thermomechanical modelling of the gearbox’s first stage, using the thermal network method. This model links power losses with temperatures. Particular attention is paid to high speed bearing modelling. A new thermomechanical model of rolling element bearing is developed. As churning losses being significant at high speeds, a method to greatly reduce this power loss is characterized

APA, Harvard, Vancouver, ISO, and other styles

26

Eljarrat, Ascunce Alberto. "Quantitative methods for electron energy loss spectroscopy." Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/349214.

Full text

Abstract:

This thesis explores the analytical capabilities of low-loss electron energy loss spectroscopy (EELS), applied to disentangle the intimate configuration of advanced semiconductor heterostructures. Modern aberration corrected scanning transmission electron microscopy (STEM) allows extracting spectroscopic information from extremely constrained areas, down to atomic resolution. Because of this, EELS is becoming increasingly popular for the examination of novel semiconductor devices, as the characteristic size of their constituent structures shrinks. Energy-loss spectra contain a high amount of information, and since the electron beam undergoes well-known inelastic scattering processes, we can trace the features in these spectra down to elementary excitations in the atomic electronic configuration. In Chapter 1, the general theoretical framework for low-loss EELS is described. This formulation, the dielectric model of inelastic scattering, takes into account the electrodynamic properties of the fast electron beam and the quantum mechanical description of the materials. Low-loss EELS features are originated both from collective mode (plasmons) and single electron excitations (e.g. band gap), that contain relevant chemical and structural information. The nature of these excitations and the inelastic processes involved has to be taken into account in order to analyze experimental data or to perform simulations. The computational tools required to perform these tasks are presented in Chapter 2. Among them, calibration, deconvolution and Kramers-Kronig analysis (KKA) of the spectrum constitute the most relevant procedures, that ultimately help obtain the dielectric information in the form of a complex dielectric function (CDF). This information may be then compared to the one obtained by optical techniques or with the results from simulations. Additional techniques are explained, focusing first on multivariate analysis (MVA) algorithms that exploit the hyperspectral acquisition of EELS, i.e. spectrum imaging (SI) modes. Finally, an introduction to the density functional theory (DFT) simulations of the energy-loss spectrum is given. In Chapter 3, DFT simulations concerning (Al, Ga, In)N binary and ternary compounds are introduced. The prediction of properties observed in low-loss EELS of these semiconductor materials, such as the band gap energy, is improved in these calculations. Moreover, a super-cell approach allows to obtain the composition dependence of both band gap and plasmon energies from the theoretical dielectric response coefficients of ternary alloys. These results are exploited in the two following chapters, in which we experimentally probe structures based on group-III nitride binary and ternary compounds. In Chapter 4, two distributed Bragg reflector structures are examined (based upon AlN/GaN and InAlN/GaN multilayers, respectively) through different strategies for the characterization of composition from plasmon energy shift. Moreover; HAADF image simulation is used to corroborate he obtained results; plasmon width, band gap energy and other features are measured; and, KKA is performed to obtain the CDF of GaN. In Chapter 5, a multiple InGaN quantum well (QW) structure is examined. In these QWs (indium rich layers of a few nanometers in width), we carry out an analysis of the energy-loss spectrum taking into account delocalization and quantum confinement effects. We propose useful alternatives complementary to the study of plasmon energy, using KKA of the spectrum. Chapters 6 and 7 deal with the analysis of structures that present pure silicon-nanocrystals (Si-NCs) embedded in silicon-based dielectric matrices. Our aim is to study the properties of these nanoparticles individually, but the measured low-loss spectrum always contains mixed signatures from the embedding matrix as well. In this scenario, Chapter 6 proposes the most straightforward solution; using a model-based fit that contains two peaks. Using this strategy, the Si-NCs embedded in an Er-doped SiO2 layer are characterized. Another strategy, presented in Chapter 7, uses computer-vision tools and MVA algorithms in low-loss EELS-SIs to separate the signature spectra of the Si-NCs. The advantages and drawbacks of this technique are revealed through its application to three different matrices (SiO2, Si3N4 and SiC). Moreover, the application of KKA to the MVA results is demonstrated, which allows to extract CDFs for the Si-NCs and surrounding matrices.
Este trabajo explora las posibilidades analíticas que ofrece la técnica de espectroscopia electrónica de bajas pérdidas (low-loss EELS), capaces de revelar la configuración estructural de los más avanzados dispositivos semiconductores. El uso de modernos microscopios electrónicos de transmisión-barrido (STEM) nos permite obtener información espectroscópica a partir de volúmenes reducidos, hasta llegar a resolución atómica. Por ello, EELS es cada vez mas popular para la observación de los dispositivos semiconductores, a medida que los tamaños característicos de sus estructuras constituyentes se miniaturiza. Los espectros de pérdida de energía contienen mucha información: dado que el haz de electrones sufre unos bien conocidos procesos de dispersión inelástica, podemos trazar relaciones entre estos espectros y excitaciones elementales en la configuración atómica de los elementos y compuestos constituyentes de cada material. Se describe un marco teórico para el estudio del low-loss EELS: el modelo dieléctrico de dispersión inelástica, que toma en consideración las propiedades electrodinámicas del haz de electrones y la descripción mecano-cuántica de los materiales. Adicionalmente, se describen en detalle las herramientas utilizadas en el análisis de datos experimentales o la simulación teórica de espectros. Monitorizando las energías de band gap y plasmon en los datos experimentales de low-loss EELS se obtiene información directa sobre propiedades electrónicas de los materiales. Además, usando análisis Kramers-Kronig en los espectros se obtiene información dieléctrica que puede ser comparada con las simulaciones o con otras técnicas (ópticas). Se demuestra el uso de estas herramientas con una serie de estudios sobre estructuras basadas en nitruros del grupo-III. Por otro lado, el uso de algoritmos para el análisis multivariante permite separar las contribuciones individuales que se miden mezcladas en espectros de estructuras complicadas. Hemos utilizado estas avanzadas herramientas para el análisis de estructuras basadas en silicio que contienen nano-cristales embebidos en matrices dieléctricas.

APA, Harvard, Vancouver, ISO, and other styles

27

Nicholls, Rebecca Jane. "Electron energy loss spectroscopy of fullerene materials." Thesis, University of Oxford, 2006. http://ora.ox.ac.uk/objects/uuid:2fd55ddf-ca30-4b9a-a37f-61b024a3f22f.

Full text

Abstract:

This thesis is comprised of two closely related studies of fullerenes. The first part is an investigation of C60 and C70 nanocrystals using both experimental and simulated electron energy loss (EEL) spectra. Through a detailed comparison of particular features in EEL spectra collected from these materials in a transmission electron microscope, with simulated spectra, it is established that differences in spectra from different materials can be linked to particular aspects of the structural models. For example, in the case of C60 differences in experimental spectra from different samples can be linked to differences in the bond lengths within the molecules of different samples. In the case of C70, it is found that features within the spectrum which have previously been attributed to the ten equatorial atoms do not have this origin in a crystal. The second part is an experimental investigation of endohedral fullerenes Nd@C82 and Sc3N@C80. The effect of temperature on the EEL spectrum is investigated and, in the case of Nd@C82, the effect of the presence of different isomers is also investigated. Spectra are successfully obtained from the encapsulated atoms, and the importance of careful experiments in terms of avoiding contamination is highlighted.

APA, Harvard, Vancouver, ISO, and other styles

28

Natusch, Michael Kurt Heinrich. "Detection limits in electron energy-loss spectroscopy." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624128.

Full text

APA, Harvard, Vancouver, ISO, and other styles

29

Fu, Jian. "Prototypage virtuel incrémental des actionneurs électromécanique pour la synchronisation en position." Thesis, Toulouse, INSA, 2016. http://www.theses.fr/2016ISAT0008/document.

Full text

Abstract:

Dans le domaine de l'aéronautique, les concepts basés sur l’usage étendu de l'électricité dans les aéronefs plus électriques (MEA) et même tout électriques (AEA) font appel à des actionneurs électromécaniques (EMA) en replacement des actionneurs servo-hydrauliques conventionnels (HSA). Lorsque les EMA sont utilisés pour des applications d'actionnement critique comme les commandes de vol, certains problèmes spécifiques liés à l’équilibre thermique, l'inertie réfléchie, le mouvement parasite dû aux élasticités structurelles, la réponse aux fautes (grippage et rupture) et la synchronisation d’EMA actifs sur charges indépendantes ne peuvent être ignorés. La simulation apporte un support indéniable à la conception pour l’évaluation et la validation des concepts. A cet effet, il est nécessaire de développer des prototypes virtuels des EMA avec une vision système et de façon structurée pour répondre aux besoins des ingénieurs. Malheureusement, les phénomènes physiques qui apparaissent dans les EMA sont multidisciplinaires, couplés et fortement non linéaires. De nombreux logiciels commerciaux de simulation système multi-domaines sont désormais disponibles. Cependant, le processus de modélisation et les besoins des ingénieurs sont rarement pris en compte selon une vision globale, en raison du manque d'approches scientifiques pour la définition d’architectures, la modélisation incrémentale et l’amélioration de l’implémentation numérique des modèles. Dans cette thèse, le prototypage virtuel de l'EMA est adressé en utilisant le formalisme Bond-Graph. De nouvelles approches sont proposées pour permettre la modélisation incrémentale de l'EMA en vue de fournir des modèles pour la synthèse de la commande, l’évaluation de la consommation d'énergie, l'analyse thermique, le calcul des forces de réaction, la simulation de la pollution du réseau d'alimentation électrique, la réponse aux fautes et l'influence de la température. L’intérêt des modèles proposés est illustré sur l’exemple de la synchronisation de position de deux EMA actionnant des charges indépendantes
In the aerospace field, the concepts based on extended use of electricity in “More Electric Aircraft” (MEA) and even “All Electric Aircraft” (AEA), involve electromechanical actuators (EMAs) to replace conventional hydraulic servo actuators (HSAs). When EMAs are used for safety-critical actuation applications like flight controls, some specific issues related to thermal balance, reflected inertia, parasitic motion due to compliance, response to failure (jamming and free-run) and synchronization of EMAs driving independent loads cannot be ignored. The simulation-aided design process can efficiently support the assessment and validation of the concepts fixing these issues. For that, virtual prototypes of EMAs at system-level have to be developed in a structured way that meets the engineers’ needs. Unfortunately, the physical effects governing the EMAs behavior are multidisciplinary, coupled and highly nonlinear. Although numerous multi-domain and system-level simulation packages are now available in the market of simulation software, the modelling process and the engineers’ needs are rarely addressed as a whole because of lack of scientific approaches for model-based architecting, multi-purpose incremental modelling and model implementation for efficient numerical simulation. In this thesis, the virtual prototyping of EMAs is addressed using the Bond-Graph formalism. New approaches are proposed to enable incremental modelling of EMAs that provides models supporting control design, energy consumption and thermal analysis, calculation of reaction forces, power network pollution simulation, prediction of response to faults and influence of temperature. The case of preliminary design of EMAs position synchronization is used to highlight the interests and advantages of the proposed process and models of EMAs

APA, Harvard, Vancouver, ISO, and other styles

30

Maclean, Ewan Douglas William. "Valence losses at interfaces in aluminium alloys." Thesis, Connect to e-thesis, 2002. http://theses.gla.ac.uk/917/.

Full text

Abstract:

Thesis (Ph.D.) -- University of Glasgow, 2002.
Ph.D. thesis submitted to the Department of Physics and Astronomy and the Department of Chemistry, University of Glasgow, 2002. Includes bibliographical references. Print version also available.

APA, Harvard, Vancouver, ISO, and other styles

31

Peña, Manchón Francisco Javier de la. "Advanced methods for Electron Energy Loss Spectroscopy core-loss analysis." Paris 11, 2010. http://www.theses.fr/2010PA112379.

Full text

Abstract:

Les microscopes électroniques en transmission modernes sont capables de fournir une grande quantité d'informations sous la forme de jeux de données multi-dimensionnelles. Bien que les procédures développées pour l'analyse des spectres uniques soient utilisables pour le traitement de ces données, le développement de techniques plus avancées est indispensable pour une exploitation optimale de ces informations hautement redondantes. Dans ce contexte, nous avons exploré des alternatives aux méthodes standard de quantification, et cherché à optimiser les acquisitions expérimentales afin d'améliorer la précision des analyses. Cela constitue une réponse aux défis actuels de la spectroscopie de perte d'énergie d'électrons (EELS) dont les facteurs limitants sont souvent liés aux dégâts d'irradiation et à la contamination. La quantification élémentaire par la méthode standard d'intégration est limitée aux cas simples. Nous avons montré que l'utilisation d'une méthode basée sur l'ajustement des courbes expérimentales peut surmonter la plupart des limitations de la méthode standard. Cette nouvelle méthode nous a non seulement permis d'obtenir des cartographies élémentaires mais aussi les premières cartographies des liaisons chimiques à l'échelle nanométrique. Les méthodes quantitatives exigent de connaître à priori la composition de l'échantillon, ce qui constitue une difficulté majeur lors de l'analyse d'échantillons inconnus. Nous avons montré que les méthodes de séparation aveugle des sources permettent une analyse rapide et efficace des données multi-dimensionnelles, sans nécessiter la définition d'un modèle. En conditions optimales, il est ainsi possible d'extraire à partir des données expérimentales les signaux correspondants aux différents constituants chimiques ainsi que leur distribution dans l'échantillon
Modern analytical transmission electron microscopes are able to gather a large amount of information from the sample in the form of multi-dimensional datasets. Although the analytical procedures developed for single spectra can be extended to the analysis of multi-dimensional datasets, for an optimal use of this highly redundant information, more advanced techniques must be deployed. In this context, we investigate alternatives to the standard quantification methods and seek to optimise the experimental acquisition for accurate analysis. This addresses the current challenges facing the electron energy-loss spectroscopy (EELS) community, for whom beam damage and contamination are often the limiting factors. EELS elemental quantification by the standard integration method is limited to well-behaved cases. As an alternative we use curve fitting which, as we show, can overcome most of the limitations of the standard method. Furthermore, we extend the method to obtain, in addition to elemental maps, the first bonding maps at the nanoscale. A major difficulty when analysing multi-dimensional datasets of samples of unknown composition is that the quantitative methods require as an input the composition of the sample. We show that blind source separation methods enable fast and accurate analysis of multi-dimensional datasets without defining a model. In optimal conditions these methods are capable of extracting signals from the dataset corresponding to the different chemical compounds in the sample and their distribution

APA, Harvard, Vancouver, ISO, and other styles

32

Gass, Mhairi Hope. "Low-loss electron energy loss spectroscopy in a scanning transmission electron microscope of GaInNAs." Thesis, University of Liverpool, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415656.

Full text

APA, Harvard, Vancouver, ISO, and other styles

33

Murooka, Yoshie. "Parallel electron energy loss spectroscopy of electron hole drilling in calcite." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361611.

Full text

APA, Harvard, Vancouver, ISO, and other styles

34

Queiroz, Altamira de Souza. "Algoritmos de inteligência computacional utilizados na detecção de fraudes nas redes de distribuição de energia elétrica." Universidade Estadual do Oeste do Paraná, 2016. http://tede.unioeste.br:8080/tede/handle/tede/1030.

Full text

Abstract:

Made available in DSpace on 2017-07-10T16:41:32Z (GMT). No. of bitstreams: 1 Dissertacao Altamira Queiroz2.pdf: 2299194 bytes, checksum: 07ecb127ebc11ad21a0cb551e23c2f1b (MD5) Previous issue date: 2016-02-19
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
One of the main problems currently faced by electric utilities is the occurrence of energy losses in the distribution network caused by fraud and electricity theft. Because of the financial losses and risks to public safety, the development of solutions to detect and combat fraud in the distribution networks is of the utmost importance. This work presents an analysis of computational intelligence algorithms to extract knowledge in databases with information from monthly energy consumption to identify consumption patterns with anomalies which could represent fraud. The algorithms Artificial Neural Networks and Support Vector Machines were tested to see which one perform better on the identification consumption patterns with abnormalities. Tests have shown that the algorithms used are able to detect patterns in electricity consumption curves, including special situations of fraud that manual techniques did not detect.
Um dos principais problemas que enfrentam atualmente as empresas concessionárias de energia elétrica é a ocorrência de perdas de energia na rede de distribuição, causadas por fraudes e furtos de energia elétrica. Sendo que tais problemas provocam prejuízos financeiros e também colocam em risco a segurança pública, é de grande interesse das concessionárias encontrar soluções para detectar e combater fraudes nas redes de distribuição de energia elétrica. Neste conceito, o presente trabalho apresenta uma análise dos algoritmos de Inteligência Computacional para extrair conhecimento de bases de dados de informações de consumo mensal de energia elétricas de usuários de uma determinada concessionária, a fim de identificar padrões de consumo com anomalias que representem possíveis fraudes nas redes de distribuição de energia elétrica. Para detectar padrões nas curvas de consumo, foram utilizados algoritmos de Redes Neurais Artificiais e Máquinas de Vetores de Suporte. Após a criação dos modelos, estes foram testados para verificar qual seria o melhor algoritmo para a detecção de padrões de consumo com anomalias, e os resultados obtidos, foram então, comparados com uma base de dados fornecida pela concessionária com a verificação manual dos usuários. Os testes demonstraram que os algoritmos utilizados são capazes de detectar padrões nas curvas de consumo de energia elétrica, inclusive detectando situações especiais de fraudes que técnicas manuais não detectaram.

APA, Harvard, Vancouver, ISO, and other styles

35

Eriksson, Daniel, and Axel Persson. "Energy Optimization of Scheduling and Packet Loss in Wireless Sensor Networks." Thesis, KTH, Skolan för elektro- och systemteknik (EES), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-214699.

Full text

Abstract:

We study the data aggregation of Wireless SensorNetworks (WSN). This is done by considering two problemformulations. The problems examine two different parts of thenetworks and their impact on its energy consumption. The firstproblem looks at the impact of packet loss and the secondproblem on the impact of network scheduling. The reason behindthis is that WSN usually operate on battery power and may beplaced in locations where they are hard to replace. Thus if itis possible to reduce the energy consumption of a WSN, thetotal lifespan of it will be increased. This led to the formulationof a NP-hard deadline constraint problem that is solved bysimulation. For simulation purposes a fixed tree topology wasused to investigate the impact of packet loss rate. The simulationsof the seven different scheduling policies use the same tree. Itcould be concluded from this that an increase in packet lossby only 12% percent leads to two times as long transmissiontime and therefore also twice the energy consumption. For thesecond problem the scheduling policies are evaluated by theirspeed, reliability and evenness and assigned an index based onthese parameters. Here we could see that clear improvementscould be done to a system depending on which parameters wereprioritized.

APA, Harvard, Vancouver, ISO, and other styles

36

Drummond-Brydson, Richard. "Electron energy loss spectroscopy in solid-state chemistry." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.237906.

Full text

APA, Harvard, Vancouver, ISO, and other styles

37

Wilkins, A. C. R. "Translational energy loss studies of electron capture reactions." Thesis, Swansea University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636601.

Full text

Abstract:

Translational energy spectroscopy is an invaluable tool in the study of ion-neutral processes. By measuring the change in energy of the projectile ion information can be obtained about the initial and final states of the projectile and the final states of the target (presuming that the target possesses only thermal energy and is initially in its ground state) for a wide range of collisional processes. One such process is that of electron capture where the multiply-charged ion will capture one or more electrons from the target. The Wigner spin-conservation rule has previously been studied for binary collision processes, however the applicability to electron capture reactions has not been studied extensively. Over eighty reaction channels for the single-electron capture by N²⁺, O²⁺, C²⁺ and Ar⁴⁺ have been identified, all of which conform with the rule. Of equal significance the spin non-conserved channels which lie in the same energy range are conspicuously absent. With the O²⁺ and Ar⁴⁺ collision systems a rare quintet state is also identified in the primary ion beam. The spin rule appears less stringent for double-electron capture reactions where many spin forbidden reaction channels have been identified. These are explained as being allowed through two consecutive spin-conserved single electron capture channels. The importance of the design of the collision cell is often overlooked in a spectrometer. Two novel collision cells have been constructed; the first, a thin collision cell, was utilised to assess and reduce the collisional broadening aberration in a translational energy loss spectrum. A second larger cell was designed to attenuate the ion beam to a high degree so that the metastable content of an ion beam can be measured using the ion beam attenuation method. Metastable ions play a substantial part in many collisional phenomena and these measurements are used to quantify the previously obtained electron-capture spectra.

APA, Harvard, Vancouver, ISO, and other styles

38

Eustace, David Andrew. "Spin polarisation effects in electron energy loss spectroscopy." Thesis, University of Glasgow, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438978.

Full text

APA, Harvard, Vancouver, ISO, and other styles

39

Yuan, Jun. "Electron energy loss and cathodoluminescence of rare earths." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.256453.

Full text

APA, Harvard, Vancouver, ISO, and other styles

40

Walls, Michael Gerard. "Electron energy-loss spectroscopy of surfaces and interfaces." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254503.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

Protheroe, A. R. "Electron energy loss spectroscopy of some alkaline earth oxides." Thesis, University of York, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377302.

Full text

APA, Harvard, Vancouver, ISO, and other styles

42

McComb, David William. "An electron energy-loss spectroscopy investigation of zeolite dealumination." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359404.

Full text

APA, Harvard, Vancouver, ISO, and other styles

43

Pališaitis, Justinas. "Valence Electron Energy Loss Spectroscopy of III-Nitride Semiconductors." Doctoral thesis, Linköpings universitet, Tunnfilmsfysik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-85907.

Full text

Abstract:

This doctorate thesis covers both experimental and theoretical investigations of the optical responses of the group III-nitrides (AlN, GaN, InN) and their ternary alloys. The goal of this research has been to explore the usefulness of valence electron energy loss spectroscopy (VEELS) for materials characterization of group III-nitride semiconductors at the nanoscale. The experiments are based on the evaluation of the bulk plasmon characteristics in the low energy loss part of the EEL spectrum since it is highly dependent on the material’s composition and strain. This method offers advantages as being fast, reliable, and sensitive. VEELS characterization results were corroborated with other experimental methods like X-ray diffraction and Rutherford backscattering spectrometry as well as full-potential calculations (Wien2k). Investigated III-nitride structures were grown using magnetron sputtering epitaxy and metal organic chemical vapor deposition techniques. Initially, it was demonstrated that EELS in the valence region is a powerful method for a fast compositional analysis of the Al1-xInxN (0≤x≤1) system. The bulk plasmon energy follows a linear relation with respect to the lattice parameter and composition in Al1-xInxN layers. Furthermore, the effect of strain on valence EELS was investigated. It was experimentally determined that the AlN bulk plasmon peak experiences a shift of 0.156 eV per 1% volume change at constant composition. The experimental results were corroborated by full-potential calculations, which showed that the bulk plasmon peak position varies nearly linearly with the unit-cell volume, at least up to 3% volume change. Employing the bulk plasmon energy loss, compositional characterization was also applied to confined structures, such as nanorods and quantum wells (QWs). Compositional profiling of spontaneously formed AlInN nanorods with varying In concentration was realized in cross-sectional and plan-view geometries. It was established that the structures exhibit a core-shell structure, where the In concentration in the core is higher than in the shell. The growth of InGaN/GaN multiple QWs with respect to composition and interface homogeneities was investigated. It was found that at certain compositions and thicknesses of QWs, where phase separation does not occur due to spinodal decomposition. Instead, QWs develop quantum dot like features inside the well as a consequence of Stranski-Krastanov-type growth mode, and delayed In incorporation into the structure. The thermal stability and degradation mechanisms of Al1-xInxN (0≤x≤1) films with different In contents, stacked in a multilayer sample, and different periodicity Al1-xInxN/AlN multilayer films, was investigated by performing a thermal annealing in combination with VEELS mapping in-situ. It was concluded that the In content in the Al1-xInxN layer determines the thermal stability and decomposition path. Finally, the phase separation by spinodal decomposition of different periodicity AlInN/AlN layers, with a starting composition inside the miscibility gap, was explored.

APA, Harvard, Vancouver, ISO, and other styles

44

Ureh, Henry Chigozie. "IMPACTS OF PLUG-IN ELECTRIC VEHICLE ON RESIDENTIAL ELECTRIC DISTRIBUTION SYSTEM USING STOCHASTIC AND SENSITIVITY APPROACH." DigitalCommons@CalPoly, 2011. https://digitalcommons.calpoly.edu/theses/642.

Full text

Abstract:

Plug-in Electric Vehicles (PEVs) are projected to become a viable means of transportation due to advances in technology and advocates for green and eco-friendly energy solutions. These vehicles are powered partially, or in some cases, solely by the energy stored in their battery packs. The large sizes of these battery packs require large amount of energy to charge, and as the demand for PEV increases, the increase in energy demand needed to recharge these PEV batteries could pose problems to the present electric distribution system. This study examines the potential impacts of PEV on a residential electric distribution system at various penetration levels. An existing residential distribution network is modeled up to each household service point and various sensitivity scenarios and stochastic patterns of PEV loads are simulated. Impact studies that include voltage drop, service transformers overload, energy loss, and transformer thermal loss-of-life expectancy are analyzed. Results from the study are reported and recommendations to mitigate the impacts are presented.

APA, Harvard, Vancouver, ISO, and other styles

45

Кузнецов, Валерій Геннадійович, Валерий Геннадиевич Кузнецов, Valeriy G. Kuznetsov, Walery G. Kuzniecov, and Valerii H. Kuznetsov. "Розвиток теоретичних основ енергозбереження в системах електропостачання тяги поїздів постійного струму." Thesis, Видавництво Дніпропетровського національного університету залізничного транспорту імені академіка В. Лазаряна, 2012. http://eadnurt.diit.edu.ua:82/jspui/handle/123456789/1335.

Full text

Abstract:

Кузнецов , В. Г. Розвиток теоретичних основ енергозбереження в системах електропостачання тяги поїздів постійного струму : авт. дис. д-ра т. н.: 05.22.09 / В. Г. Кузнецов ; Днепропетр. нац. ун-т ж.-д. тр-та им. акад. В. Лазаряна. - Д. : Вид-во Днiпропетр. нац. ун-ту залізн. трансп. iм. акад. В. Лазаряна, 2012. УДК 629.423.3:621.331.024 ГРНТИ 55.41.29 Захист - 6 грудня 2012 р.
UK: Дисертація присвячена розвитку теоретичних основ енергозбереження в системах електропостачання тяги поїздів постійного струму для підвищення енергетичної та економічної ефективності процесу перевезень. У даній роботі проблема енергозбереження в системах тяги поїздів постійного струму розглядається як комплексна, багаторівнева й багатофакторна проблема. Створено методологічні підходи до вибору енергозберігаючих заходів у системах електропостачання тяги поїздів постійного струму. Удосконалено метод розрахунку систем тягового електропостачання на основі потоків відновлення для визначення втрат потужності та електроенергії в елементах тягових підстанцій. Розроблено метод визначення раціональних режимів систем тягового електропостачання постійного струму на основі генетичного алгоритму, визначено раціональні регламенти перемикань. Розроблено науково обґрунтовані методи визначення норм витрат електроенергії на потреби стаціонарних споживачів та на власні потреби тягових підстанцій, постів секціонування й пунктів паралельного з'єднання. Надано науково обґрунтовані рекомендації зі зниження небалансів електроенергії. Розроблені моделі й методи в сукупності складають теоретичні основи вирішення комплексних завдань енергозбереження, що виникають під час експлуатації систем електропостачання тяги поїздів постійного струму.
RU: Диссертация посвящена развитию теоретических основ энергосбережения в системах электроснабжения тяги поездов постоянного тока для повышения энергетической и экономической эффективности процесса перевозок. В данной работе проблема энергосбережения в системах тяги поездов постоянного тока рассматривается как комплексная, многоуровневая и многофакторная проблема. В работе созданы методологические основы выбора энергосберегающих мероприятий в системах тягового электроснабжения на основе определения потенциала энергосбережения с учетом системного эффекта, выбора альтернатив на предложенной графовой модели, инвариантно-согласованного метода анализа иерархий. На основе разработанных методологических основ предложены научные подходы к модернизации тяговых подстанций с учетом возможности перевода тяги поездов на высший класс напряжения. Разработаны новые научные подходы к определению условий рациональных режимов систем тягового электроснабжения. Показано, что при принятии решений необходимо учитывать возможность расчетов за потребленную электроэнергию по переменным в течение дня тарифам за электроэнергию. Также необходимо учитывать надежность силового оборудования, участвующего в регулировании. Составлена структурно-логическая схема для расчета показателей потока отказов при осуществлении регулирования режимов. На основе информации о величине потока отказов и типовых калькуляций работ определены величины экономического ущерба от возможных отказов при осуществлении регулирования. Усовершенствован метод расчета систем тягового электроснабжения на базе потоков восстановления в части дополнения его расчетными выражениями для определения потерь мощности и электроэнергии в элементах тяговых подстанций с учетом регулировочных воздействий. Разработан генетический алгоритм для решения задачи определения рациональных режимов системы электроснабжения тяги поездов постоянного тока. Разработан метод расчета регламента переключений оборудования фидерного участка, в котором учитываются современные возможности оплаты за электроэнергию по двух, трехзонным тарифам и оптовым ценам, потери надежности оборудования при переключениях, а также соответствующее программное обеспечение. Установлена зависимость величины потерь мощности в тяговой сети от дислокации поездов и расстояния между ними. Показано, что имеется существенный резерв по снижению потерь в контактной сети за счет подбора рациональной дислокации поездов. Вариация потерь мощности в зависимости от дислокации и расстояния между поездами достигает 3,5 раза на одной из межподстанционных зон постоянного тока. Разработаны усовершенствованные методологические основы и создана нормативная документация по определению норм расхода электроэнергии на нужды стационарных потребителей железных дорог Украины. При этом нормы расхода электроэнергии определяются по регрессионным зависимостям. Предложенная методология легла в основу методических указаний ЦЕ-0015. Созданы научные подходы и нормативная документация по определению норм расходов электроэнергии на собственные нужды тяговых подстанций, постов секционирования и пунктов параллельного соединения. Показано, что расход электроэнергии на собственные нужды распределительных устройств 3,3 кВ целесообразно определять по установленной мощности и продолжительности работы оборудования. На основе предложенных подходов создана инструкция ЦЕ-0018. Установлено, что причиной сверхнормативных небалансов электроэнергии является низкая загрузка измерительных трансформаторов тока и напряжения. Для подтверждения нормируемых метрологических характеристик трансформаторов напряжения согласно их классам точности 0,5 при действительных значениях мощностей и коэффициентов мощности их вторичной нагрузки было предложено мощность вторичной нагрузки обмоток и коэффициенты мощности вторичной нагрузки трансформатора напряжения привести в соответствие с требованиями ГОСТ-1983 и ГОСТ-7746 соответственно. Для этой цели предложено подключать к вторичной обмотке трансформатора напряжения добавочное сопротивление. Разработанные модели и методы в совокупности составляют теоретические основы по решению комплексных задач энергосбережения, возникающих при эксплуатации систем электроснабжения тяги поездов постоянного тока.
EN: The thesis is dedicated to the development of theoretical bases of DC traction power supply systems to increase energy and economic efficiency of the transport. In this paper the energy saving problem in DC traction systems is considered as a complex, multilevel and multifactorial problem. It’s created a methodological approach to the selection of energy saving measures in the DC traction power supply systems. It’s improved the method for calculating the traction power supply systems based on the restoration flows for estimating the power and energy losses in the elements of traction substations. It’s developed the method for determination of rational modes of DC traction power supply systems based on genetic algorithm, defined the rational switching rules. The author developed scientific justified methods for determining norms of electricity needs for stationary consumers and for self needs of traction substations, sectioning posts and points of parallel connection. Provided scientific and reasonable guidelines for reducing power unbalances. The developed models and methods together form the theoretical basis for solving complex energy saving problems during exploitation of electrical DC traction systems.

APA, Harvard, Vancouver, ISO, and other styles

46

Pierce, William Renton. "High-resolution transmission electron microscopy and electron energy loss spectroscopy of doped nanocarbons." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/highresolution-transmission-electron-microscopy-and-electron-energy-loss-spectroscopy-of-doped-nanocarbons(dd1340ba-4a31-49e5-a421-9dd47ea35256).html.

Full text

Abstract:

Graphene, a one-atom thick sheet of carbon, is the thinnest, strongest and most electrically conductive material ever discovered. Alongside carbon nanotubes it is part of the group of nanocarbons whose unique properties have sparked huge interest in possible applications, including electronic devices, solar cells and biosensors. Doping of these materials allows for the modification of their optical and electronic properties,which is crucial to realising these applications. Studying the properties of these doped materials at atomic resolution and finding controllable and industrially scalable routes to doping, such as low energy ion implantation, are thus essential if they are to becomethe materials of the future. In this thesis, highly localised optical enhancements in metal doped graphene are studied using energy-filtered transmission electron microscopy in a monochromated and aberration corrected electron microscope. The ideal conditions for imaging the low energy loss region of graphene using EFTEM are discussed and new methods to compensate for image artifacts when using this technique at high resolution are presented. Density functional theory is used to reveal new visible spectrum plasmon excitations in the electron energy loss spectra of boron and nitrogen doped nanocarbons. Atomic resolution scanning transmission electron microscopy and nanoscale electron energy loss spectroscopy are used to investigate controllable and defect-free substitutional doping of suspended graphene films through low energy ion implantation. Computational methods for filtering high angle annular dark field images are shown and software for the automated processing and spectroscopic analysis of these images is developed.

APA, Harvard, Vancouver, ISO, and other styles

47

Currie, Michael James. "Fabrication of a luminescent solar concentrator that minimizes self-absorption losses using inter-chromophore energy transfer." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40516.

Full text

Abstract:

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.
Includes bibliographical references (p. 57-59).
The projected need for carbon-free power during this century is immense. Solar power offers the largest resource base to supply this need, but in light of recent silicon shortages, it is an open question whether silicon photovoltaics can keep pace with demand. The development of economical concentrators could relieve this resource pressure. The luminescent solar concentrator (LSC) is an architecture that collects and concentrates light using the luminescent properties of chromophores embedded in a waveguide. This method of concentration alleviates the need for expensive tracking equipment necessary for optical concentration. Combined with the low cost and flexible fabrication of organic materials, this technology is inherently scalable. A major limitation to LSC efficiency is self-absorption between different chromophores within the waveguide. Finding inspiration from the architecture of phycobilisome antenna complexes, a system of chromophores is developed that minimizes self-absorption through Firster energy transfer. Precise control of intermolecular spacing is achieved through thermal evaporation of small molecule organics. A LSC with a geometric gain of 25 is fabricated that employs this optimized system. External quantum efficiencies of 32% are achieved across nearly half the visible spectrum, with a total power conversion efficiency of 1.6%. Additionally, modeling and theory are presented to highlight places for device improvement. It is shown that a simple path integral successfully captures the dynamics of the LSC.
by Michael James Currie.
S.M.

APA, Harvard, Vancouver, ISO, and other styles

48

Rao, Shodhan. "Energy methods for lossless systems using quadratic differential forms." Thesis, University of Southampton, 2008. https://eprints.soton.ac.uk/65886/.

Full text

Abstract:

In this thesis, we study the properties of lossless systems using the concept of quadratic differential forms (QDFs). Based on observation of physical linear lossless systems, we define a lossless system as one for which there exists a QDF known as an energy function that is positive along nonzero trajectories of the system and whose derivative along the trajectories of the system is zero if inputs to the system are made equal to zero. Using this deffnition, we prove that if a lossless system is autonomous, then it is oscillatory. We also give an algorithm whose output is a two-variable polynomial that induces an energy function of a lossless system and we describe a suitable way of splitting a given energy function into its potential and kinetic energy components. We further study the space of QDFs for an autonomous linear lossless system, and note that this space can be decomposed into the spaces of conserved and zero-mean quantities. We then show that there is a link between zero-mean quantities and generalized Lagrangians of an autonomous linear lossless system. Finally, we study various methods of synthesis of lossless electric networks like Cauer and Foster methods, and come up with an abstract deffnition of synthesis of a positive QDF that represents the total energy of the network to be synthesized. We show that Cauer and Foster method of synthesis can be cast in the framework of our deffnition. We show that our deffnition has applications in stability tests for linear systems, and we also give a new Routh-Hurwitz like stability test.

APA, Harvard, Vancouver, ISO, and other styles

49

Muto, Shunsuke, and Kazuyoshi Tatsumi. "Local electronic structure analysis by site-selective ELNES using electron channeling and first-principles calculations." IOP Publishing, 2009. http://hdl.handle.net/2237/20788.

Full text

APA, Harvard, Vancouver, ISO, and other styles

50

Wachsmuth, Philipp [Verfasser]. "Momentum-resolved electron energy-loss spectroscopy of graphene / Philipp Wachsmuth." Ulm : Universität Ulm. Fakultät für Naturwissenschaften, 2014. http://d-nb.info/1054045453/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'Electric energy losses'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles