• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 190
  • 69
  • 43
  • 18
  • 9
  • 5
  • 4
  • 3
  • 3
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 374
  • 94
  • 85
  • 54
  • 50
  • 47
  • 41
  • 40
  • 40
  • 37
  • 37
  • 36
  • 36
  • 30
  • 29
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
341

Translation of Technical terms : a study of translation strategies when translating terminology in the field of hydropower generation

Marklund, Åsa January 2011 (has links)
Abstract   This study analyses the translation of a technical guidebook in the subject field of hydropower generation. The aim is to identify and apply functional translation theories when translating general technical terms, industry terms and contract terms. The theoretical basis for the study consists of Eugene Nida’s and Vinay & Darbelnet’s models for translation as well as theories on terminology by Rune Ingo and Therésa Cabré. During the translation process, technical terms were identified and subsequently translated using one or more of the theories described. The result was then analysed and discussed. Although the study is not comprehensive enough to draw significant conclusions, the result indicates that in order to render the best possible translation of technical terms, a combination of theories and methods are best applied; direct translation regarding systematized terminology similar to general technical terms and oblique translation, or dynamic equivalence, regarding industry terms and contract terms. The results further suggest that structural analysis is of great value in order to determine the correct level of the term. In addition, the translator’s experience and knowledge of the subject field as well as readiness to consult parallel texts seem to be vital to the outcome of the translation.
342

Déficit da geração hídrica e a repactuação do risco hidrológico no setor elétrico brasileiro: uma análise sob a perspectiva da teoria dos grupos de interesse / Hydropower Shortage and Hydrologic Risk Renegotiation in the Brazilian Power Sector: An Analysis based on the Economic Theory of Regulation

Darwiche, Talita Jamil 04 October 2016 (has links)
O setor elétrico brasileiro é composto, majoritariamente, por usinas hidrelétricas, cuja operação é realizada de forma centralizada pelo Operador Nacional do Sistema (ONS). Devido às características do setor, foi criado durante a década de 1990 o Mecanismo de Realocação de Energia (MRE) com o intuito de compartilhar o risco hidrológico entre as usinas participantes deste mecanismo, o qual é medido pelo Generation Scaling Factor (GSF). Entre os anos de 2014 e 2015, o Brasil enfrentou um período de escassez hídrica que impactou negativamente o caixa dos geradores hídricos. Estes, insatisfeitos com o cenário, articularam-se junto à Agência Nacional de Energia Elétrica (ANEEL) e ao Ministério de Minas e Energia (MME) para que o risco hidrológico fosse transferido para os consumidores. A agência reguladora posicionou-se contrária ao pleito dos geradores na primeira fase da Audiência Pública 32/2015, que tratou do tema em questão, entretanto o governo editou a Medida Provisória 688/2015 que possibilitou a repactuação do risco hidrológico mediante um pagamento de prêmio de risco pelos geradores hídricos. Neste contexto, esta dissertação foi desenvolvida com o objetivo principal de avaliar o processo de repactuação do risco hidrológico, a partir dos estudos sobre a evolução da Teoria da Regulação, com foco na atuação dos grupos de interesse. Os resultados indicam possibilidade em aplicar os pressupostos da Teoria dos Grupos de Interesse, principalmente a abordagem de Pelztman (1976), no processo de repactuação do risco hidrológico, demonstrando que: (i) a regulação surge como demanda dos grupos de interesse; (ii) a regulação tende a beneficiar os grupos de interesse que forem mais ativos politicamente; (iii) os agentes envolvidos no processo de regulação atuam para maximizar sua própria utilidade; e (iv) a regulação tende a beneficiar grupos de interesse cujo benefício per capita seja maior. / The Brazilian Power sector consists of hydroelectric plants, whose operation is performed centrally by the mainly National System Operator. Due to the system characteristics, during the 1990s, was created the Energy Reallocation Mechanism in order to share hydrological risk among mechanism\'s participating, which is measured by the Generation Scaling Factor (GSF). Between 2014 and 2015, Brazil faced a water scarcity period that negatively affected the hydropower generators revenue. The generators unsatisfied with this situation have started seek to influence the electricity regulatory agency and the Ministry of Mines and Energy in order to transferred the hydrologic risk to consumers. The regulatory agency has positioned itself against the claim of the generators in the first phase of the Public Hearing 32/2015, but the government has published Interim Measure 688/2015 which allowed the renegotiation of the hydrological risk through a premium risk payment by hydropower generators. In this context, this work was developed with the main objective of analysing the renegotiation process of hydrological risk, such analysis was based on the evolution of regulation theory studies, focusing on the role of interest groups. The results indicate the possibility of applying the assumptions of Theory of Economics Regulation, mainly the Pelztman (1976) approach, on the renegotiation of the hydrological risk process demonstrating that: (i) regulation is supplied in reponse to the interest groups demand for regulation; (ii) regulation is most likely to benefit the interest groups that are more active politically; (iii) agents involved in the regulatory process act to maximize their own utility; and (iv) regulation trends to benefit interest groups which highest per capita benefit.
343

Posouzení vlivu jednotlivých druhů OZE na elektrizační soustavu / Assessment of the impact of different types of RES in the power system

Zmeškal, Pavel January 2011 (has links)
This thesis deals with usage of each kind of RES under conditions of Czech republic and their usage at areas placed in. Consequently supplied RES output power at time and its influence on reliability of supply in EPS CZ. Way of operation of RES from point of view of requirement on regulation and control of operation of EPS is more studied on operation of different kinds of wind power plants, which due to its variable output power affects not only EPS CZ. At final caption, economic influence of RES to EPS is reviewed as a unit, increasingly claims on regulation, increasingly benefit on support of RES. All these influences increase price of electricity for end user.
344

Projekt malé vodní elektrárny pro konkrétní lokalitu. / Design of small hydropower plant for specific location.

Paštěka, František January 2009 (has links)
This master's thesis is specialised in designing of small hydropower plant for specific location. In work should be designed suitable turbine for parameters found on the site, then created a basic project documentation of small hydropower plant with all devices and used principles, so that the plant would be capable of operation. In the next part of thesis should be extented the calculation of flow in the turbine delivery and assessed effect of geometry of turbine delivery on the flow.
345

[en] VALIDATION OF SYSTEMIC DYNAMIC SIMULATIONS USING SYNCHROPHASOR DATA / [pt] VALIDAÇÃO DE SIMULAÇÕES DINÂMICAS SISTÊMICAS UTILIZANDO REGISTROS SINCROFASORIAIS

03 November 2020 (has links)
[pt] Os Sistemas de Energia Elétrica (SEE) operam de acordo com limites de segurança definidos pelo planejamento da operação através de simulações computacionais. Portanto, os componentes da rede elétrica devem ser devidamente modelados para garantir uma operação segura e econômica. A tecnologia dos sistemas de medição fasorial sincronizada permite a obtenção de registros de distúrbios reais, que podem ser comparados com simulações para verificar sua aderência. Tem-se verificado nos atuais SEE diferenças entre os registros e as simulações computacionais dos eventos observados. Tais diferenças têm ocorrido também no Sistema Interligado Nacional (SIN), principalmente em relação ao desvio de frequência, sendo a resposta simulada menos severa quando comparada ao comportamento observado, podendo levar o SIN a operar em um ponto inseguro com risco de atuação de esquemas regionais de alívio de carga. Nesta dissertação são avaliados os modelos de usinas hidráulicas e termoelétricas e os parâmetros que podem influenciar significativamente a resposta das simulações, com ênfase no desempenho da frequência. Distúrbios que ocorreram no SIN são reproduzidos utilizando casos de tempo real, construídos a partir dos dados de estimadores de estado, em conjunto com uma base de modelos dinâmicos. Os resultados das simulações são comparados com os registros reais obtidos pelas PMUs (Phasor Measurement Unit) instaladas no SIN. Parâmetros como altura de queda, resposta dos reguladores de velocidade e modelagem dinâmica e estática das cargas são investigados. Impactos e simulações do fenômeno multi-infeed são apresentados. Os resultados obtidos mostram a necessidade de melhorias nos modelos e nos parâmetros de entrada das simulações de transitórios eletromecânicos do SIN. Ressalta-se a importância da contínua validação sistêmica e específica dos modelos para o planejamento da operação do SIN. / [en] Electric power systems (EPS) operate according to safety limits defined by the operation planning assessed through computer simulations. Therefore, the components of the electrical grid must be properly represented to ensure secure and economical operation. The technology of synchronized phasor measurement systems allows to obtain records of actual faults, which can be compared to simulation results to check their accuracy. Differences between records and computer simulations of the observed events have been verified in the current EPS. Such differences have also occurred in the Brazilian interconnected system (BIS), mainly related to frequency deviations, with the simulated response being less severe when compared to the observed performance. This may lead the BIS to operate under unsafe conditions, with risk of activating regional protection schemes for load shedding; a possible hasty and undesirable action. In this dissertation, the models of hydraulic and thermoelectric power plants and other parameters that can significantly influence the response of simulations are evaluated, with an emphasis on frequency performance. Disturbances that occurred in the BIS are reproduced using real-time cases, built from state estimator data, together with a collection of dynamic models. The simulation results are compared with the actual records obtained by PMUs (Phasor Measurement Units) installed in the BIS. Parameters such as hydropower head, response of speed regulators and dynamic and static modeling of loads are explored. Impacts and simulations of the multi-infeed phenomenon are also presented. The results show the need for improvements in the models and simulation input parameters of electromechanical transient studies of the BIS. There is a continuous need to observe the systemic and specific validation of models for planning and operation of the BIS.
346

Tribology of newly developed EAL versus water in hydropower turbine bearings

Dhakal, Nayan January 2019 (has links)
The increasing demand for more readily bio-degradable, renewable and non-toxic environmentally adaptive lubricants with a lower degree of bioaccumulation has escalated the investigation of water-based lubricants as the potential alternatives for conventional mineral-based oils. Water is an excellent environmentally adapted lubricant; however, it is a low viscous fluid and holds downsides of having corrosive nature and extremely low pressure-viscosity coefficient leading to insufficient load-carrying capacity. These shortcomings make pure water a poor choice for operations involving high load and low speed, for instance, within hydropower applications. Therefore, the choice of appropriate modifiers and additives is crucial to improve the viscosity, friction-reducing performance and anti-wear properties of water as a base lubricant. Appropriate selection and combination of bearing materials also significantly improve the tribological performance of the lubricants. In the presented work, tribological behavior of polyvinylpyrrolidone (PVP) and poly(sodium 4-styrenesulfonate) (PSS) thickening agents with water as a base fluid in the lubrication of pure UHMWPE and SCF reinforced UHMWPE bearing materials has been investigated individually under reciprocating tribometer. The results showed that both PVP and PSS are excellent viscosity modifiers. PVP exhibited excellent friction-reducing and anti-wear performance, while PSS revealed increased wear rates with an insignificant reduction of friction coefficients. This study aims to explore the potential for using newly developed water-based lubricants in the replacement of traditional mineral-based lubricants for hydropower turbine bearings.
347

Visionen om elintensiva industrier i Norrbottens län : Hur påverkade Porjus vattenkraftverk den industriella utvecklingen i Norrbottens län mellan år 1915–1938?

Wiss, Emma January 2022 (has links)
Studien undersöker hur Porjus vattenkraftverk påverkade den industriella utvecklingen i Norrbottens län mellan 1915–1938. Syftet med uppsatsen var att undersöka om elintensiva industrier etablerades efter vattenkraftverkets invigning samt hur industristrukturen i Norrbottens län påverkades under perioden 1915–1938. För att svara på frågorna blev undersökningen en fallstudie som utredde hur och om elektriciteten från Porjus vattenkraftverk bidrog till ekonomisk utveckling i Norrbottens län. Att utvecklingen av elektricitet och elinfrastruktur ska gynna den ekonomiska utvecklingen genom en ökad etableringstakt av industrier samt att industrierna blir mer elintensiva har visats i tidigare forskning. Samtidigt som andra studier demonstrerat hur elektrifiering inte nödvändigtvis leder till ekonomisk utveckling om inte priserna är lönsamma. Slutsatsen av undersökningen är att Porjus vattenkraftverk gav upphov till ökad industrietablering i Norrbottens län, där de elintensiva industrigrupperna gynnades till störst del. Slutligen drogs slutsatsen att industristrukturen i Norrbotten primärt stärktes snarare än ändrades efter att vattenkraftverket invigdes år 1915. / This thesis analyzes how Porjus hydropower plant affected the industrial development in Norrbotten county between 1915-1938. The purpose of the study was to investigate if electricity-intensive industries arose after the inauguration of the hydropower plant, and how the industrial structure in Norrbotten county was influenced during the period 1915-1938. To answer those questions a case study was performed to investigate if and/or how the electricity from Porjus hydropower plant contributed to economic development in Norrbotten county. Previous studies have shown that the development of electricity and electricity infrastructures will benefit economic development through an increased number of industries and that the industries will become more electricity-intensive. At the same time, other studies have demonstrated how electrification does not necessarily lead to economic development unless prices are profitable. The conclusion of the thesis is that an increase of industrial establishments in Norrbotten county appeared after the inauguration of Porjus hydropower plant. At the same time the electricity-intensive industrial groups where the ones that benefited the most from the increased electricity the hydropower plant generated. Finally, it was concluded that the industrial structure in Norrbotten primarily was strengthened rather than changed after the hydropower plant was inaugurated in 1915.
348

Modeling, Control and Optimization Of Cascade Hydroelectric-Irrigation Plants : Operation and Planning / Optimisation fonctionnelle des stations hydrauliques pour la génération électrique et pour l’irrigation

Bou-Fakhreddine, Bassam 15 May 2018 (has links)
Ce travail de recherche vise à optimiser la procédure opérationnelle des centrales hydroélectriques en cascade afin de les utiliser efficacement pour la production d’électricité et l’irrigation. Le défi consistait à trouver le modèle le plus réaliste basé sur la caractéristique stochastique des ressources en eau, sur la demande en énergie et sur le profil d'irrigation. Tous ces aspects sont affectés à court et à long terme par un large éventail de conditions différentes (hydrologique, météorologique et hydraulique). Au cours de ce projet, une étude bibliographique a été réalisée afin d'identifier les problèmes techniques qui empêchent l'utilisation efficace des centrales hydroélectriques dans les pays en développement. Le système est modélisé numériquement en tenant compte de toutes les variables et paramètres impliqués dans le fonctionnement optimal. L'approche la plus appropriée est choisie afin de maximiser l'utilisation efficace de l'eau et de minimiser les pertes économiques, où différents scénarios sont simulés afin de valider les solutions adoptées. / This research work aims to optimize the operational procedure of cascade hydro plants in order to be efficiently used for power generation and irrigation. The challenge was to find the most realistic model based on the stochastic feature of water resources, on the power demand and on the irrigation profile. All these aspects are affected on the short and on the long run by a wide range of different conditions (hydrological, meteorological and hydraulic). During this project a bibliographic study was done in order to identify the technical issues that prevent the efficient use of hydro plants in developing countries. The system is numerically modelled taking into consideration all the variables and parameters involved in the optimal operation. The most appropriate approach is chosen in order to maximize the efficient use of water and to minimize economical losses, where different scenarios are simulated in order to validate the adopted suggestions.
349

Spåren i bäcken : En undersökning om kvarnlämningar i Forshälla socken, Inlands Fräkne härad Bohuslän / Traces in the stream : An investigation on watermill remains in Forshälla parish, Inlands Fräkne härad Bohuslän

Mattsson, Eva January 2023 (has links)
Syftet med denna uppsats är att undersöka vad som skiljer de lämningar åt från kvarnverksamhet som inte finns i  Fornsök från de som är registrerade som kulturlämning. Historiskt kartmaterial har studerats för att försöka få en uppfattning om det är så att de inte platsar i ramen för en forn- kulturlämning, dvs tillkommen efter år 1850 och om det är därför de inte finns i registret. Alla lämningarna  från kvarnar i Forshälla socken går att återfinna på kartor före år 1850. Uppsatsen önskar också öka uppmärksamheten på denna typ av lämningar i skog och mark så att de erhåller ett starkare skydd när skogen ska avverkas. En analys har gjorts gällande var och en av lämningarna och miljön runt dessa och om de riskerar att skadas vid en avverkning av skogen. / The purpose of this essay is to investigate what distinguishes the remains from mill activities that are not found in Fornsök from those that are registered as cultural remains. Historical map material has been studied to try to get an idea of whether it is the case that they do not fit within the framework of an ancient cultural relic, i.e., added after the year 1850 and if that is why they are not in the register. All the remains from water mills in Forshälla parish can be found on maps before the year 1850. The essay also wishes to increase attention to this type of remains in forest and land so they can receive stronger protection when the forest is cut down. An analysis has been made of each of the remains and the environment around them and whether they are at risk of damage when the forest is harvested.
350

Dynamic Warning Signals and Time Lag Analysis for Seepage Prediction in Hydropower Dams : A Case Study of a Swedish Hydropower Plant

Olsson, Lovisa, Hellström, Julia January 2023 (has links)
Hydropower is an important energy source since it is fossil-free, renewable, and controllable. Characteristics that become especially important as the reliance on intermittent energy sources increases. However, the dams for the hydropower plants are also associated with large risks as a dam failure could have fatal consequences. Dams are therefore monitored by several sensors, to follow and evaluate any changes in the dam. One of the most important dam surveillance measurements is seepage since it can examine internal erosion. Seepage is affected by several different parameters such as reservoir water level, temperature, and precipitation. Studies also indicate the existence of a time lag between the reservoir water level and the seepage flow, meaning that when there is a change in the reservoir level there is a delay before these changes are reflected in the seepage behaviour. Recent years have seen increased use of AI in dam monitoring, enabling more dynamic warning systems.  This master’s thesis aims to develop a model for dynamic warning signals by predicting seepage using reservoir water level, temperature, and precipitation. Furthermore, a snowmelt variable was introduced to account for the impact of increased water flows during the spring season. The occurrence of a time lag and its possible influence on the model’s performance is also examined. To predict the seepage, three models with different complexity are used – linear regression, support vector regression, and long short-term memory. To investigate the time lag, the linear regression and support vector regression models incorporate a static time lag by shifting the reservoir water level data up to 14 days. The time lag was further investigated using the long short-term memory model as well.  The results show that reservoir water level, temperature, and the snowmelt variable are the combination of input parameters that generate the best results for all three models. Although a one-day time lag between reservoir water level and seepage slightly improved the predictions, the exact duration and nature of the time lag remain unclear. The more complex models (support vector regression and long short-term memory) generated better predictions than the linear regression but performed similarly when evaluated based on the dynamic warning signals. Therefore, linear regression is deemed a suitable model for dynamic warning signals by seepage prediction.

Page generated in 0.0326 seconds