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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

The Optimization of Offshore Wind Turbine Towers Using Passive Tuned Mass Dampers

Yilmaz, Onur Can 29 August 2014 (has links)
Increasing energy demand and carbon emissions have driven the development of alternative energy solutions. One promising technology is wind energy. Wind energy technology developments has advanced substantially since the 1980s. Offshore wind turbines have become a major research focus, due to the promising offshore wind resource. However, challenges in offshore wind energy have arisen due to the additional wave loading and strong wind loads. Structural control systems have been implemented and researched in order to decrease dynamic response of these systems. The previous studies were successful at decreasing fatigue loads in the tower and support structure of offshore wind turbines. Giving these results, it is still unknown if the reduced loading enabled by structural control systems can allow for reduced material costs in the major structural components. This research examines on an offshore wind turbine's tower-monopile structure by adding several configurations of passive tuned mass dampers, while simultaneously reducing the thickness of the structure in order to reduce costs. A range of candidate tower-monopile systems are created, and simulated in FAST-SC with and without passive tuned mass dampers. Fatigue and ultimate loads are calculated and analyzed. A variety of design criteria are considered including fatigue and ultimate loads, as well as local and global buckling. The results demonstrate that the tower-monopile thickness may be reduced up to 6.2% and still satisfy all design criteria.
42

Návrh zvýšení traťové rychlosti v úseku mezi žst. Hanušovice a žst. Bludov / Study of Speed Increasing of Hanušovice - Bludov Track Section

Lehnert, Jan January 2015 (has links)
In this thesis I propose increasing of the speed on the railway line No. 292 on the section žst.Bludov - žst. Hanušovice. It includes is complete design of horizontal and vertical ratios, eventually relocation of the track. Railway substructure is solved in selected sections. The thesis solves also editing of platforms and crossing structures.
43

Decentralized structural damage detection and model updating with mobile and wireless sensors

Zhu, Dapeng 07 January 2016 (has links)
Recent years have seen increasing research interest in structural health monitoring (SHM). Among the many advances in SHM research, “smart” wireless sensors capable of embedded computing and wireless communication have been highly attractive. Wireless communication in SHM systems was originally proposed to significantly reduce the monetary and time cost for installing lengthy cables in an SHM system. Besides wireless sensing, the next revolution in sensor networks has been predicted to be mobile sensor networks that implant mobility into traditional wireless sensor networks. This research explores decentralized structural model updating and damage detection using mobile and wireless sensors. In the first stage of this research, mobile sensing nodes (MSNs) are developed for SHM purposes. The MSNs can maneuver upon structures built with ferromagnetic/steel materials, conduct measurement, and communicate with pears or remote servers wirelessly. The performance of the MSNs is validated through laboratory and field experiments. To further investigate the mobile sensing strategy, a decentralized structural damage detection procedure is proposed herein for the MSNs using transmissibility functions. Laboratory experiments are conducted on a steel portal frame where various structure damage scenarios are emulated. Besides experiments with MSNs, this study also investigates the nature of transmissibility functions for damage detection in an analytical manner based on a general multi-DOF spring-mass-damper system. Finally, this research also explores substructure model updating through minimization of modal dynamic residuals, which can best benefit from dense mobile or wireless sensor data concentrated in one area. Craig-Bampton transform is adopted to condense the structural model, and minimization of the modal dynamic residuals is determined as the optimization objective. An iterative linearization procedure is adopted for efficiently solving the optimization problem. The presented substructure updating method is validated through a few numerical examples. For comparison, a conventional approach minimizing modal property differences is also applied, and shows worse updating accuracy than the proposed approach. The performance of the proposed substructure model updating approach is further investigated on the effects of substructure location and size.
44

Controlled Damage Rocking Systems for Accelerated Bridge Construction

White, Samuel Lewis January 2014 (has links)
Bridge substructures are generally constructed using cast-in-place concrete and designed to undergo inelastic deformation in earthquake events. Although this construction approach has proven to be economical and provides adequate seismic performance through the formation of ductile plastic hinges, there are downsides relating to construction speed and quality, and post-earthquake repairability. This thesis explores two categories of Accelerated Bridge Construction (ABC) connection types, which use precast concrete instead of cast-in-place concrete to offer advantages including increased construction speed and quality. High Damage (HD) ABC connection types emulate the seismic behaviour of cast-in-place construction through the formation of ductile plastic hinges. Controlled Damage (CD) ABC connection types use unbonded post-tensioned precast connections to offer additional advantages including reduced residual drifts, limited and controlled damage and simple repair options. Novel buckling-restrained, fused mild steel energy dissipators suitable for use in CD connections are also developed and tested. These designs utilise 'dry' fabrication to simplify the fabrication process and minimise cost. Half-scale experimental testing is carried out to demonstrate both the assembly processes and behaviour under reversed cyclic uniaxial and biaxial loading representing an earthquake event. Following benchmark testing, repair strategies are applied to the CD connection types and the columns are tested again, representing a subsequent earthquake event. Good results are obtained from all cases with relatively straightforward construction and repair processes. With further developments and testing, the connection types proposed can provide competitive alternatives to conventional bridge pier design with regard to seismic performance and life cycle costs, with the additional benefits associated with precast construction.
45

On the hydro-mechanical behavior of ancient railway flatforms in term of reinforcement by soil-mixing

Duong, Trong Vinh, Duong, Trong Vinh 25 November 2013 (has links) (PDF)
The present work deals with the behavior of ancient railway sub-structure in France. A statistical study was firstly undertaken on problems occurred in the whole ancient French railway network. The analysis evidenced the particular importance of sub-grade quality for the performance of the sub-structure and the track geometry. Afterwards, an ancient railway line in the West of France was investigated. The analysis showed that the degradation speed of this line was correlated with different parameters such as the nature of sub-grades and the thickness of different layers. An increase trend of degradation speed with the increase in interlayer thickness was identified. The interlayer has a positive impact since it reduces the train-induced stress applied to the sub-grade. The hydro-mechanical behavior of interlayer soil under different conditions (water content, fines content, stress, number of cycles) was investigated. A set of triaxial tests and infiltration tests were performed for this purpose. By analyzing the shear strength properties, the permanent axial strain and the resilient modulus of interlayer soil, we found that the water content and the fines content must be considered together. Adding more fines into the interlayer presents a positive impact under unsaturated conditions thanks to the suction effect, but a negative impact under saturated conditions. The infiltration column tests with drying/wetting cycles showed that the hydraulic conductivity of interlayer soil is governed by fines fraction but did not change significantly with fines content. In order to study the mechanism of interlayer creation and mud pumping, a physical model of 550 mm inner diameter was developed. Soil samples representing the ancient French railway substructure with a ballast layer overlying an artificial silt layer (mixture of crushed sand and kaolin were tested. The effects of monotonic and cyclic loadings, water content and dry unit mass of sub-soil were investigated. It was found that the pore water pressure developed in the sub-soil and the sub-soil stiffness are the key factors for the migration of fine particles or the creation of interlayer/mud pumping. Water is the necessary condition, but it is the soil compressibility that governs the phenomenon to occur
46

Políticas públicas urbanas da infraestrutura dos serviços telemáticos: conceito, estrutura e legislação / Urban public policies of the infrastructure of the telematics services: concept, structures and legislation

Daou, Gabriel Claude Joseph 13 November 2006 (has links)
Esta pesquisa tem por objetivo obter um panorama das políticas públicas urbanas em telemática ao longo da sua recente história visando sua melhor compreensão. Isto se deve principalmente à necessidade de compreender como tais políticas evoluíram ao longo do tempo e como estas vêm influenciando a sociedade como um todo e principalmente o conjunto de lugares, tais como residência, trabalho, locais de lazer e o próprio tecido urbano que esta mesma sociedade ocupa e convive. Para esse entendimento será necessário compreender a história das comunicações em sua evolução em direção às telecomunicações, à telemática e às novas tecnologias da Informação (TIC\'s) para em seguida conhecer os serviços telemáticos que são oferecidos ao usuário final. Mas, além do conhecimento da sua história e também conhecer quais são estes serviços temos que conhecer, devido à importância, à complexidade e à velocidade em que estes serviços evoluem, as políticas públicas, no nível das esferas federal e municipal, a fim de, pesquisando a evolução temporal das políticas públicas urbanas de telemática, no nosso caso dentro do município de São Paulo, perceber toda a complexidade de sua influência, já citada anteriormente, sobre a sociedade e sobre a própria cidade. / This research is intended to obtain a general view of the urban public policies in telematic along their recent history and for a better comprehension of them. That is, mainly, due to the necessity of recognizing how such policies have developed through the time and how they have been influencing the society as a whole and, mostly, the set of places, such as residence, work, leisure areas and the urban net itself, which this same society inhabits and lives with. For this, recognition will be necessary to understand the history of communication in its evolution towards the telecommunications, telematic and the new technologies of information (TIC`s) to know, afterwards, the telematic services which are offered to the final user. But besides the knowledge of its history, and also know which these services are, we have gotten to learn, due to the importance, to the complexity and to the velocity in which these services develop, the public policies at the federal and municipal level in order to, researching the time evolution of the urban public policies of telematic, in our case, inside of the municipal area of São Paulo, to perceive in all the complexity of their influence, already mentioned formerly, over the society and over the city itself.
47

A hidrovia Tietê-Paraná e a intermodalidade no Estado de São Paulo

Felipe Júnior, Nelson Fernandes [UNESP] 03 November 2008 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:28:25Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-11-03Bitstream added on 2014-06-13T18:57:33Z : No. of bitstreams: 1 felipejunior_nf_me_prud.pdf: 1667952 bytes, checksum: 4e69adf6cb5421b52dff3902f3f771fd (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A mundialização do capital se caracteriza pela existência de espaços relativos, que são decorrentes da própria lógica do sistema capitalista. Partindo dessa premissa, é notório que o crescimento da produção da natureza, das paisagens materiais e dos meios de produção conduz ao aumento progressivo da divisão do trabalho e das contradições sociais, diante de uma dialética intrínseca aos diferentes espaços geográficos. A acumulação de capitais no início do século XXI se baseia em processos de re-ordenamentos, como os de caráter técnicocientífico- informacional e público-privado, resultando num desenvolvimento desigual entre os diferentes territórios, sendo que as ações, articulações e investimentos do capital privado são fatores que possibilitam a existência desses antagonismos. A Hidrovia Tietê-Paraná e os portos interiores de Pederneiras-SP, Anhembi-SP e Santa Maria da Serra-SP representam a utilização da intermodalidade visando a otimização do transporte de mercadorias, a integração de diferentes territórios e a intensificação das interações espaciais e econômicas. / The mundialization of capital is characterized by the existence of relative spaces resulted from the logic of the capitalistic system. Thus, it’s notorious that the growth of nature production, material landscapes and productive forces lead to a progressive increase of the work division and social antagonisms, in front of a dialectic common to different geographic spaces. The capital accumulation in the beginning of the 21st century is based on the reorganization of technical, scientific, informative and public private proceedings, resulting in an unequal development among the different territories. The actions, articulations and investments on private capital are factors that enable the existence of these contradictions. The Tietê-Paraná Waterway and the inside ports of Pederneiras-SP, Anhembi-SP e Santa Maria da Serra-SP represents the use of the intermodality aiming the improvement on merchandises transportation, the integration of different territories and intensification of spatial and economical interactions.
48

Análise de populações estelares e subestruturas em aglomerados de galáxias

Soares, Natthan Ruschel 25 August 2015 (has links)
Conselho Nacional de Desenvolvimento Científico e Tecnológico / In this work, we investigated differences between stellar populations of galaxies that are part of a cluster with and without substructures. We used optical spectra obtained from Sloan Digital Sky Servey III DR10 for the galaxies of a sample of 1052 clusters selected from Wen et al. (2012) and Tempel et al. (2012) catalogues. For the Wen et al. (2012) catalog, we excluded interlopers by applying the method Shifting gapper to the coordinates and redshifts of all extended sources inside 5 Mpc of radial distance to the center of each system. In order to detect substructure and to estimate the velocity dispersion of individual structures, we used the LocKE algorithm. The individual systems inside clusters with substructure have been classified between primary and secondary, according to their mass dominance. We used the stellar populations synthesis program starlight from Cid Fernandes et al. (2005) to characterize the stellar populations of the galaxies in each structure, and we compared the average results obtained for different types of structure. Substructures have been found in 44% of our sample. The average masses of individual structures, estimated by virial analysis, is 4.5×1014M⊙. The mean stellar age and the mean metallicity obtained for the galaxies is 8.7 ± 2.0×109 years and Z=0.023 ± 0.009, respectively. The mean stellar age distribution for the clusters without substructure, and the primary and secondary structures, show some significant differences. Investigating the stellar populations according to the galaxy luminosity, we found that, in any type of structure, the mean stellar age grows with luminosity, while the fraction of galaxies with mean stellar age less than 6×109 years, decreases. For clusters without substructures, primary and secondary with less mass than 1014.5M⊙, the mean stellar age and luminosity do not show significant differences; however, in massive structures, the mean stellar age increases in the order secondary-primary-without substructure, while the fraction of galaxies with mean stellar age less than 6×109 years decreases. This result suggests that, although the main parameter that affects the stellar age of a galaxy is its mass, the environment also play a significant role, particularly in massive systems. / Neste trabalho, investigamos diferenças entre populações estelares de galáxias que fazem parte de aglomerados com e sem subestruturas. Para isso, utilizamos espectros óticos obtidos pelo Sloan Digital Sky Survey III DR10 para as galáxias de uma amostra de 1052 aglomerados oriundos dos catálogosWen et al. (2012) e Tempel et al. (2012). Para os aglomerados do catálogoWen et al. (2012), realizamos a exclusão de galáxias intrusas aplicando o método shifting gapper às coordenadas e redshifts de todas as fontes extensas a 5 Mpc de distância radial ao centro de cada sistema. Para detectar subestruturas e estimar a dispersão de velocidades das estruturas individuais, utilizamos o algoritmo LocKE. Os sistemas individuais de aglomerados com subestruturas foram separados entre estrutura primária e secundária, de acordo com sua dominância em massa. Utilizamos o programa de síntese de populações estelares Starlight de Cid Fernandes et al. (2005) para caracterizar as populações estelares das galáxias de cada estrutura, e comparamos os resultados médios obtidos entre os diferentes tipos de estrutura. Foram detectadas subestruturas em 44% de nossa amostra. O valor médio das massas das estruturas individuais, estimadas via análise virial, é de 4.5×1014M⊙. A idade estelar média e a metalicidade média obtidas para as galáxias da amostra são de 8.7 ± 2.0×109 anos e Z=0.023 ± 0.009 respectivamente. As distribuições de idade estelar média entre aglomerados desprovidos de subestrutura, e as estruturas primária e secundária, apresentam diferenças pouco significativas. Investigando as populações estelares em função da luminosidade das galáxias, encontramos que, em qualquer tipo de estrutura, a idade estelar média cresce com a luminosidade, enquanto que a fração de objetos com idade estelar média menor do que 6×109 anos diminui. Para aglomerados sem subestrutura, primários e secundários e com massa inferior a 1014.5 M⊙, a idade estelar média e a luminosidade não apresentam diferenças significativas; porém, em estruturas mais massivas, a idade estelar média aumenta no sentido secundária-primária-sem subestrutura, enquanto que a fração de galáxias com idade estelar média menor do que 6×109 anos diminui. Esse resultado sugere que, embora o principal parâmetro que afeta a idade estelar de uma galáxia seja sua massa, o ambiente também desempenha um papel significativo, em particular em sistemas mais massivos.
49

Políticas públicas urbanas da infraestrutura dos serviços telemáticos: conceito, estrutura e legislação / Urban public policies of the infrastructure of the telematics services: concept, structures and legislation

Gabriel Claude Joseph Daou 13 November 2006 (has links)
Esta pesquisa tem por objetivo obter um panorama das políticas públicas urbanas em telemática ao longo da sua recente história visando sua melhor compreensão. Isto se deve principalmente à necessidade de compreender como tais políticas evoluíram ao longo do tempo e como estas vêm influenciando a sociedade como um todo e principalmente o conjunto de lugares, tais como residência, trabalho, locais de lazer e o próprio tecido urbano que esta mesma sociedade ocupa e convive. Para esse entendimento será necessário compreender a história das comunicações em sua evolução em direção às telecomunicações, à telemática e às novas tecnologias da Informação (TIC\'s) para em seguida conhecer os serviços telemáticos que são oferecidos ao usuário final. Mas, além do conhecimento da sua história e também conhecer quais são estes serviços temos que conhecer, devido à importância, à complexidade e à velocidade em que estes serviços evoluem, as políticas públicas, no nível das esferas federal e municipal, a fim de, pesquisando a evolução temporal das políticas públicas urbanas de telemática, no nosso caso dentro do município de São Paulo, perceber toda a complexidade de sua influência, já citada anteriormente, sobre a sociedade e sobre a própria cidade. / This research is intended to obtain a general view of the urban public policies in telematic along their recent history and for a better comprehension of them. That is, mainly, due to the necessity of recognizing how such policies have developed through the time and how they have been influencing the society as a whole and, mostly, the set of places, such as residence, work, leisure areas and the urban net itself, which this same society inhabits and lives with. For this, recognition will be necessary to understand the history of communication in its evolution towards the telecommunications, telematic and the new technologies of information (TIC`s) to know, afterwards, the telematic services which are offered to the final user. But besides the knowledge of its history, and also know which these services are, we have gotten to learn, due to the importance, to the complexity and to the velocity in which these services develop, the public policies at the federal and municipal level in order to, researching the time evolution of the urban public policies of telematic, in our case, inside of the municipal area of São Paulo, to perceive in all the complexity of their influence, already mentioned formerly, over the society and over the city itself.
50

Návrh rekonstrukce železniční stanice Horní Cerekev / Design of reconstruction of the Horní Cerekev railway station

Syrový, Aleš January 2019 (has links)
The subject of the diploma thesis is to design a redevelopment of railway station Horni Cerekev, in order to meet current traffic and legislation on access of persons with reduced mobility. Two platforms with the platform edge height of 550 mm above the top of the rail have been designed. The amount of five running tracks through the station remains unchanged. Furthermore, the railway superstructure, railway substructure and conceptual design of space in front of the station.

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