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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

Roman and Islamic water-lifting wheels

Schiøler, Thorkild. January 1973 (has links)
Thesis--Copenhagen. / Summary in Danish. Includes bibliographical references and index.
42

Estudo de caso : aplicação de otimização topológica no desenvolvimento de um protótipo de cubo de roda

Perini, Gustavo 26 November 2013 (has links)
A Otimização Topológica (OT) tem se mostrado uma ferramenta eficiente na busca de produtos de baixo custo, alta qualidade e alto desempenho. Esta dissertação trata da aplicação da OT, por meio do software Altair Optistruct, no desenvolvimento do projeto de um Cubo de Roda. O objetivo da aplicação da OT foi auxiliar na busca por um componente mecânico otimizado atendendo os requisitos da aplicação. Utilizou-se de ensaios experimentais para validação das análises estruturais, realizadas por meio do Método de Elementos Finitos, onde as diferenças encontradas entre os valores medidos e calculados foram considerados satisfatórios. Para tanto, foi fundamental os cuidados na realização da discretização do sistema, a escolha dos pontos de instrumentação baseado nas direções principais e baixo gradiente de tensões. Também foi realizado o ensaio de aprovação do desenvolvimento de um protótipo de Cubo de Roda, utilizando-se da norma SAE n095 como critério de homologação, onde o componente otimizado foi aprovado. / Submitted by Marcelo Teixeira (mvteixeira@ucs.br) on 2014-07-10T13:30:09Z No. of bitstreams: 1 Dissertacao Gustavo Perini.pdf: 27046982 bytes, checksum: 0dfa07feee25bbc0c0434b8c0c09e4d0 (MD5) / Made available in DSpace on 2014-07-10T13:30:09Z (GMT). No. of bitstreams: 1 Dissertacao Gustavo Perini.pdf: 27046982 bytes, checksum: 0dfa07feee25bbc0c0434b8c0c09e4d0 (MD5) / This dissertation presents an application of Topology Optimization (TO) on Wheel Hub project development, through the software Altair Optistruct. The objective of the application of TO was to minimize the Wheel Hub mass meeting the application requirements. This work employs experimental validation of structural analysis, where the differences between the measured and calculated values were considered satisfactory, therefore, the way performing the discretization of the system and the choice of instrumentation points based on the principal stresses directions and low gradient were essential. The optimized Wheel Hub was also submitted to the fatigue test (SAE 11095) as a criterion for approval of the prototype, where the optimized component was considered approved.
43

Projeto de experimentos em rodas ferroviárias fundidas em aço, com o uso da técnica de Taguchi /

Ribeiro, Carlos Barbosa. January 2008 (has links)
Resumo: Aplicou-se experimentos em rodas ferroviárias tipo D-38 (38 polegadas de diâmetro), fundidas em aço, obtidas pelo processo de pressão controlada. Estudou-se a influência de 15 fatores (variáveis de entrada), com o objetivo de minimizar ou eliminar a descontinuidade interna denominada "microrechupe", a qual apresentou-se como variável de saída constante em todas as rodas experimentadas, na região do aro das rodas (região de contato com os trilhos da ferrovia). As descontinuidades internas foram detectadas por ensaio ultrassônico, através do método indireto de avaliação, com o auxílio do diagrama AVG, e uso de transdutor normal. Em função da quantidade e tamanhos diferenciados das descontinuidades internas detectadas em todas as rodas experimentadas, foi criado um método específico para mensurá-las, estabelecendo desta forma, respostas diferenciadas que possibilitaram a análise da influência dos fatores (variáveis de entrada). Para estudo e análise da influência das variáveis de entrada e suas respectivas interações, foi utilizado o método de Taguchi, com um Arranjo Ortogonal L-16. Os fatores (variáveis de entrada) operaram em dois níveis com uma razão sinal / ruído para a função "maior é melhor", sendo utilizada a análise de variância ANOVA para testar a significância dos efeitos. Os resultados demonstraram que as variáveis "posição relativa da roda na corrida de vazamento" e "tempo de cura dos massalotes radiais" tiveram maior significância para a redução da descontinuidade microrechupe (output). / Abstract: It was applied experiments in railroad wheels, casting in steel, D-38 type (38- inches- diameter), produced by controlled pressure process. It was studied influence of the 15 factors (entrance variables) with objective to minimize or to eliminate a internal discontinuity, called microshrinkage, which was presented as constant output in all tried wheels, inside the rim wheels (region of contact with railroad tracks). The internal discontinuities had been detected by ultrasonic test, through the indirect method of evaluation, with aiding of AVG diagram, with the use of normal transducer. In function of the amount and different sizes of the internal discontinuities detected in all the tried wheels, a new method was created to measure them, establishing different answers, in such a way that make possible the factors influence analysis. For study and analysis of the factors and its interactions, the Taguchi approach was used, with L-16 Ortogonal Array. The process factors had operated in two levels with a signal-to-noise ratio called "bigger is better" function and it was used variance analysis by ANOVA to determine the main significance of the effects. The results had demonstrated that, the factors "relative position of the wheel in the production line" and "cure time of radial risers" had greater significance for the reduction of the discontinuity microshrinkage (output) / Orientador: Messias Borges Silva / Coorientador: Antonio Fernando Branco Costa / Banca: Jorge Muniz Júnior / Banca: José RobertoAlves de Mattos / Mestre
44

Estudo de caso : aplicação de otimização topológica no desenvolvimento de um protótipo de cubo de roda

Perini, Gustavo 26 November 2013 (has links)
A Otimização Topológica (OT) tem se mostrado uma ferramenta eficiente na busca de produtos de baixo custo, alta qualidade e alto desempenho. Esta dissertação trata da aplicação da OT, por meio do software Altair Optistruct, no desenvolvimento do projeto de um Cubo de Roda. O objetivo da aplicação da OT foi auxiliar na busca por um componente mecânico otimizado atendendo os requisitos da aplicação. Utilizou-se de ensaios experimentais para validação das análises estruturais, realizadas por meio do Método de Elementos Finitos, onde as diferenças encontradas entre os valores medidos e calculados foram considerados satisfatórios. Para tanto, foi fundamental os cuidados na realização da discretização do sistema, a escolha dos pontos de instrumentação baseado nas direções principais e baixo gradiente de tensões. Também foi realizado o ensaio de aprovação do desenvolvimento de um protótipo de Cubo de Roda, utilizando-se da norma SAE n095 como critério de homologação, onde o componente otimizado foi aprovado. / This dissertation presents an application of Topology Optimization (TO) on Wheel Hub project development, through the software Altair Optistruct. The objective of the application of TO was to minimize the Wheel Hub mass meeting the application requirements. This work employs experimental validation of structural analysis, where the differences between the measured and calculated values were considered satisfactory, therefore, the way performing the discretization of the system and the choice of instrumentation points based on the principal stresses directions and low gradient were essential. The optimized Wheel Hub was also submitted to the fatigue test (SAE 11095) as a criterion for approval of the prototype, where the optimized component was considered approved.
45

Estudo de durabilidade de rolamentos de roda baseado em rotas brasileiras / Durability study of wheel bearings, based on Brazilian route data

Fescina, Edson Lelis 16 August 2018 (has links)
Orientador: Auteliano Antunes dos Santos Júnior / Dissertação (mestrado profissional) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-16T19:44:45Z (GMT). No. of bitstreams: 1 Fescina_EdsonLelis_M.pdf: 8360535 bytes, checksum: cd1344b578904ea0f2c401cc6869f15f (MD5) Previous issue date: 2010 / Resumo: O presente trabalho tem por objetivo definir um modelo de carregamento para o calculo de vida em rolamentos de rodas, baseado nas condições reais de esforços característicos das vias no Brasil. Uma analise comparativa entre os modelos de rota atualmente disponíveis na literatura e na pratica foi elaborada e seu efeito sobre a vida do rolamento analisado. O histórico de carregamentos, nas condições reais de percurso, foi levantado para a rota nacional. Os dados foram medidos com extensômetros fixados no rolamento e na suspensão, bem como um acelerômetro fixado na altura do centro de gravidade do veiculo, circulando numa rota utilizada em teste de durabilidade de veículos no Brasil. Os carregamentos foram analisados e comparados com os modelos de carregamentos levantados anteriormente. Apos as analises, adotou-se o modelo de carga mais adequado as condições reais das vias brasileiras para o calculo de vida do rolamento de rodas / Abstract: The present work has the objective of defining a load model to estimate the life of wheel bearing, suitable to the conditions of roads in Brazil. A comparative analysis of models of the routes currently available in the literature and practice was conducted and the effect of their loads on the bearing life was analised. A composition of loads extracted from the actual conditions of route was proposed to define the national route. To get the actual loads the data were measured by strain gages fixed in the wheel bearing and the strut body, and also by an accelerometer sensor fixed in the gravity center of the vehicle, circulating in a route used for vehicle durability test in Brazil. The loads were analyzed and compared with the loads previously proposed. After that, a more appropriate load model was adopted to calculate the durability of the bearing for the real conditions of the Brazilian roads / Mestrado / Dinâmica / Mestre em Engenharia Automobilistica
46

Mechanisms influencing railway wheel squeal excitation in large radius curves

Fourie, Daniël Johannes 31 July 2012 (has links)
M.Ing. / Sound pressure levels exceeding acceptable limits are being generated by trains travelling on the 1000 m radius curved railway line past the town of Elands Bay. Unacceptable sound levels are attributed mainly to top of rail wheel squeal. Top of rail wheel squeal belongs to the family of selfinduced vibrations and originates from frictional instability in curves between the wheel and the rail under predominantly saturated lateral creep conditions. In small radius curves, saturated lateral creep conditions occur due to the steering of railway wheelsets with large angles of attack. Given the large curve radius and the utilisation of self-steering bogies on the Sishen-Saldanha Iron Ore railway line, curve squeal is a highly unexpected result for the 1000 m radius curved railway line. This is because curving of bogies in large radius curves are achieved without high wheelset angles of attack leading to saturated creep conditions. An experimental and analytical investigation was carried out to identify the mechanisms influencing the generation of wheel squeal in large radius curves. Simultaneous measurement of sound pressure and lateral wheel-rail forces were made during regular train service in one of the two 1000 m radius curves at Elands Bay to characterise the bogie curving behaviour for tonal noise due to wheel squeal occurring in the large radius curve. The lateral force curving signature not only reveals the levels of lateral wheel-rail forces required for bogie curving, but also whether the bogie is curving by means of the creep forces generated at the wheel-rail interface only or if contact is necessitated between the wheel flange and rail gauge corner to help steer the bogie around the curve. The test set-up consisted of two free field microphones radially aligned at equivalent distances towards the in – and outside of the curve in line with a set a strain gauge bridges configured and calibrated to measure the lateral and vertical forces on the inner and outer rail of the curve. This test set-up allowed the squealing wheel to be identified from the magnitude difference of the sound pressures recorded by the inner and outer microphones in combination with comparing the point of frequency shift of the squeal event due to the Doppler Effect with the force signals of the radially aligned strain gauge bridges. From the experimental phase of the investigation, it was found that wheel squeal occurring in the 1000 m radius curve at Elands Bay is characteristic of empty wagons and is strongly related to the squealing wheel’s flange/flange throat being in contact with the gauge corner of the rail. Here high levels of spin creepage associated with high contact angles in the gauge corner lead to high levels of associated lateral creepage necessary for squeal generation. This is in contrast to lateral creepage due to high wheelset angles of attack being the key kinematic parameter influencing squeal generation in small radius curves. Furthermore, the amplitude of wheel squeal originating from the passing of empty wagons was found to be inversely proportional to the level of flange rubbing on the squealing wheel i.e. increased flange contact on the squealing wheel brings about a positive effect on squeal control. Contrary to the empty wagons which are characterised by tonal curve squeal, loaded 4 wagons requiring contact between the wheel flange and rail gauge corner in the 1000 m curve was characterised by broadband flanging noise. It was concluded from measurements that flange contact occurring under high lateral forces for steady state curving of loaded wagons provides the complete damping necessary for squeal control. The curve squeal noise that originated from the passing of empty wagons in the Elands Bay curve could further be classified according to the frequency at which the squeal event manifested itself in the curve, i.e. low frequency audible (0 – 10 kHz), high frequency audible (10 – 20 kHz) and ultrasonic squeal (> 20 kHz). The vast majority of low frequency audible squeal events recorded in the 1000 m Elands Bay curve occurred at approximately 4 kHz and originated from the low rail/trailing inner wheel interface, whilst the vast majority of high frequency audible squeal events occurred in the frequency range between 15 and 20 kHz and originated from both the high rail/leading outer wheel and low rail/trailing inner wheel interfaces.
47

Linking Wheels for use in quantum information processing

Carthy, Laura January 2010 (has links)
Heterometallic Cr7Ni-containing wheels have been identified as potential qubits for use in quantum information processing. The work described in this thesis details attempts to form a variety of multi-qubit systems for the purposes of better understanding the interactions occurring between the wheels and also forming potential 2-qubit quantum gates using redox/photo-active links. Mono-substituted wheels of type [Pr2NH2][Cr7MF8(O2CCMe3)15(L)], where L is acarboxylate with a pendant coordinating group, have been synthesised for use as bulky ligands in coordination chemistry with metal complexes. Various carboxylates have been substituted into the wheels and the products reacted with first row transition metal complexes in order to extend the series of linked-wheel systems. Many of these novel complexes have been characterised by X-ray crystallography, and in certain cases EPR studies have been undertaken to probe the strength of interactions occurring via different bridging units. The first well-established substituted wheel, [Pr2NH2][Cr7NiF8(O2CCMe3)15(O2CPy)] (Py= pyridine), has also been used in reactions with second and third row transition metal centres to show its ability to act as a ligand under more harsh conditions. In addition, the disubstituted product [Pr2NH2][Cr7NiF8(O2CCMe3)14(O2CPy)2] has been reacted with a copper complex in order to form a polymeric structure. Purple wheels of type [Cr7NiF3(O2CCMe3)15(EtGu)(H2O)] have been linked through a variety of extended organic molecules containing a minimum of two pendent pyridyl groups. Use of a ligand containing four pyridyl groups, 2,2´:4,4´´:4´,4´´´-quaterpyridyl(qpy) produced a three-wheel-containing system, creating an interesting modification of the wheel backbone not seen before. A series of transition metal complexes, containing qpy and its extended derivative bbpe, has been synthesised in order to form linked-wheel systems. While none of these systems has to date yielded a crystal structure, a significant amount of evidence has been collected to confirm successful formation of the desired products. UV-vis spectroscopic and electrochemical measurements show that these compounds are photo and/or redox-active,and preliminary luminescence studies indicate that the presence of the wheels quenches the emission from metal-to-ligand charge-transfer excited states. A series of mixed-wheel systems has been synthesised by reacting four different monosubstituted green wheels with four purple wheels (Cr7M, where M = Ni, Co, Mn or Zn). A total of fourteen novel systems has been formed, with two of the attempted reactions failing to occur. EPR studies on Cr7Ni-Cr7Ni linked systems show that the strongest interaction occurs when using isonicotinate as a link, with 4-pyridazinecarboxylate giving the weakest coupling. Studies have also been undertaken on Cr7Ni-Cr7Mn and Cr7Ni-Cr7Zn systems, with the former showing interactions and the latter showing none. Initial work to link wheels together indirectly via their templates was ultimately unsuccessful, but a variety of potential linker molecules were synthesised and are described.
48

Vliv rotace kol na aerodynamické charakteristiky vozu / Influence of rotating wheels on vehicle aerodynamic characteristics

Oslizlo, Aleš January 2010 (has links)
The diploma thesis is focused on computational examination of influence of boundary condition settings in CFD software on the final aerodynamic characteristics of a vehicle. The flow analysis is carried out around a vehicle with and without the rotation of the wheels and along with the stationary and moving road. Furthermore, there is demonstrated the method of the CFD model composition and there is described the influence of rotating wheels on vehicle aerodynamic characteristics.
49

<b>Corn Response to Nitrogen Fertilizer Application Timings and After-Market Planter Equipment in a Rye Cover Crop System</b>

Riley J Seavers (18430155), Daniel Quinn (18430316) 25 April 2024 (has links)
<p dir="ltr">Previous research has documented rye (Secale cereale L.) cover crop (RCC) benefits on weed suppression, erosion control, and water quality. However, RCC adoption is often low prior to corn (Zea mays L.) due to observed yield losses caused by a RCC. Therefore, further research is required to understand and develop corn agronomic, planting equipment, and N fertilizer timing recommendations following a RCC to minimize crop stress and yield losses. The objective of this research was to evaluate corn performance and yield in response to different N fertilizer application timings and after-market closing wheel types following a RCC using multiple field-scale environments. Treatments within the N timing study included three N fertilizer timings (2x2 starter + V5 sidedress, 2x2 + V10, and 2x2 + V5 + V10) and two RCC treatments (RCC and no RCC). Treatments within the closing wheel study included three closing wheel types: Standard Rubber (SR), Cruiser Extreme (CE), and Cupped Razor (MCR), and two RCC treatments (RCC and no RCC. Both studies were conducted at field-scale using commercial equipment at four locations in Indiana in 2022 and 2023. In the N timing study a significant (P<0.1) RCC x N timing interaction was observed in 5 of 6 site-years, indicating optimum N fertilizer timing differs with the presence of a RCC. Without the inclusion of a RCC, the use of a 5x5 + V10 or 5x5 + V5 + V10 N application decreased yield in 4 of 6 and 0 of 6 site-years, respectively when compared to a 5x5 + V5 N application. Whereas, with a RCC the use of a 5x5 + V10 or 5x5 + V5 + V10 N decreased yield in 6 of 6 and 2 of 6 site-years, respectively when compared to a 5x5 + V5 N application. In the closing wheel study, aftermarket closing wheels showed no difference in daily emergence timing and/or final plant stand in no-till conditions without a RCC. However, in RCC treatments, the CE improved total percent corn emergence [7 – 12 days after planting (DAP)] by 6 and 15% at 2 of 3 site-years. Whereas, the MCR improved percent corn emergence (7-12 DAP) by 8% in 1 of 3 site-years. Furthermore, corn grain yield was increased by 5-8 bu ac-1 at 2 of 3 site-years with CE when following a RCC and by 7 bu ac-1 at 1 of 3 site-years with MCR when following a RCC. Overall, results suggest farmers can combine the use of after-market closing wheels designed for high residue/RCC systems and optimum N fertilizer application timing (5x5 + V5 sidedress) to improve corn emergence, reduce N stress, and improve yield following a RCC.</p>
50

An Autonomous Underwater Vehicle for Validating Internal Actuator Control Strategies

Schultz, Christopher R. 13 July 2006 (has links)
There are benefits to the use of internal actuators for rotational maneuvers of small-scale underwater vehicles. Internal actuators are protected from the outside environment by the external pressure hull and will not disturb the surrounding environment during inspection tasks. Additionally, internal actuators do not rely on the relative fluid motion to exert control moments, therefore they are useful at low speed and in hover. This paper describes the design, fabrication and testing of one such autonomously controlled, internally actuated underwater vehicle. The Internally Actuated, Modular Bodied, Untethered Submersible (IAMBUS) can be used to validate non-linear control strategies using internal actuators. Vehicle attitude control is provided by three orthogonally mounted reaction wheels. The housing is a spherical glass pressure vessel, which contains all of the components, such as actuators, ballast system, power supply, on-board computer and inertial sensor. Since the housing is spherically symmetric, the hydrodynamics of IAMBUS are uncoupled (e.g. a roll maneuver does not impact pitch or yaw). This hull shape enables IAMBUS to be used as a spacecraft attitude dynamics and control simulator with full rotational freedom. / Master of Science

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