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The subgrade under a rail track, also known as the formation layer, performs a vital role in rail track stability. Its primary function is to withstand load imposed from rolling stock distributed through the track structure. Since common practice is to build rail track on the natural surface of the land, there is a considerable inherent variation. Problem soils such as expansive clays are common in Australia, which can suffer significant decreases in strength and stiffness when the soil moisture state is altered. A weak formation layer may experience plastic deformation and possibly shear failure leading to sever track geometry problems. Although there are many existing methods to remediate the causes of a loss in track geometry, most are expensive and also require track closure. / Thesis (MEng(CivilEngineering))--University of South Australia, 2006.

Thesis (Ph. D.)--Missouri University of Science and Technology, 2008. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed June 1, 2009) Includes bibliographical references (p. 117-124).

Orientadores: Julio Cesar Hadler Neto, Peter Christian Hackspacher / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-11T05:57:37Z (GMT). No. of bitstreams: 1 Palissari_Rosane_D.pdf: 15939989 bytes, checksum: f455fc1254ec2dd67bb39d1df46cce88 (MD5) Previous issue date: 2007 / Resumo: O Método dos Traços de Fissão (MTF)é uma das técnicas mais poderosas usadas para descrever as histórias térmicas de rochas presentes na camada da superfície terrestre,sob condições de baixa temperatura.Se a rocha hospedeira teve a temperatura elevada em um dado período,os traços de fissão que se formaram desde então,são encurtados irreversivelmente ou apagados (os traços sofrem annealing ),como conseqüência de um processo de difusão termicamente ativada. Os minerais mais comumente utilizados no MTF são a apatita e o zircão,sendo este último o objetivo deste trabalho.O zircão é sensível ao annealing térmico sob temperaturas mais altas que a temperatura de fechamento da apatita,que é aproximadamente 120 o C . As características do annealing dos traços de fissão em zircão têm sido obtidas utilizando-se dados de experimentos de laboratório,que são executados em tempos menores que 1 ano,e comumente em tempos ainda menores.Estes dados são usados para calibrar modelos de annealing empíricos,que descrevem a dependência do encurtamento dos traços com o tempo e a temperatura.No entanto,um problema de ordem prática é a incerteza introduzida na extrapolação para tempos geológicos (10 6 ¿ 10 8 anos),através dos modelos calibrados pelos dados de laboratório (<1 ano). Um dos objetivos deste estudo é fornecer condições de contorno adicionais para a faixa de tempo-temperatura da zona de annealing do zircão,através de dados de zircões de poços, cujas amostras foram expostas a temperaturas estáveis por ~1 milhão de anos.Desta forma, o problema da extrapolação é abordado explicitamente ajustando-se os modelos a dados geológicos. Vários modelos de annealing foram propostos na literatura de traços de fissão.A formulação básica destes modelos baseia-se na equação de Arrhenius e foi apresentada por Laslett et al.(1987).Existem outros modelos de annealing que são baseados no mesmo princípio:Crowley et al.(1991);Laslett e Galbraith (1996);Rahn et al.(2004)e Yamada et al. (2007).Estes modelos têm sido usados preferencialmente,uma vez que inúmeros fenômenos, desde a formação dos traços até o ataque químico,não são bem entendidos ainda.orém,dois outros modelos calibrados no presente trabalho (Carlson,1990;Guedes et al.,2005a), procuram estabelecer uma correlação direta entre seus parâmetros e os fenômenos envolvidos.Os ajustes dos vários modelos foram comparados entre si,levando-se em conta considerações estatísticas. Além das calibrações efetuadas ajustando-se os modelos a dados geológicos, foram abordadas comparações de previsões dos modelos (relacionadas com as fronteiras da Zona de Annealing Parcial)com outros dados geológicos baseados em densidades de traços de fissão / Abstract: Fission-track (FT)analysis has developed into one of the most useful technique used to constrain the low-temperature thermal history of rocks in the upper part of the Earth's crust.If a host rock is subjected to elevated temperatures,fission tracks that have formed up to that point in time are shortened irreversibly or annealed,as a consequence of a thermally activated diffusion process. The most commonly analysed minerals are apatite and zircon and the latter is the focus of this work,since this mineral is sensitive to thermal annealing at higher temperatures,while the close temperature for apatite is around 120 o C. Short-term annealing characteristics of FT in zircon are generally based on laboratory experiments which are performed on timescales of less than 1 year,and typically much less. These data have been used to calibrate annealing empirical models,that describe the temperature and time dependence of fission track shortening.However,a practical problem is the uncertainty introduced through the extrapolation of laboratory calibrated models (<1 year)to geological timescales (10 6 ¿ 10 8 years). One of the purpose of this study is to give further constraints on the temperature range of the zircon annealing zone over a geological time scale using zircons data from boreholes,which samples have been exposed to a stable temperature for ~1 Ma.In this way,the extrapolation problem is explicity adressed by fit the zircon annealing models with geological timescale data. Several empirical models formulations have been proposed to perform these calibrations and have been compared in this work.The basic formulation is an Arrhenius-type model and is given by Laslett et al.(1987).There are other annealing models which are based on the same general formulation:Crowley et al.(1991);Laslett and Galbraith (1996);Rahn et al.(2004)and Yamada et al.(2007).These models equations have been preferred due to the great number of fenomena from track formation to chemical etching that are not well understood.However,two other calibrated models in this work (Carlson,1990;Guedes et al.,2005a)try to stablish a direct correlation between their parameters and the related fenomena.Several model fits are compared by themselves,considering statistical data. Besides calibrating annealing models with geological timescale data,model predictions (related with Parcial Annealing Zone boundaries)were compared with another geological data / Doutorado / Geofísica Nuclear / Doutor em Ciências

The South African railway company makes use of a train wheel detection system to monitor the trains present on a particular track, noting their lengths, positions and speeds. Interference due to distorted traction currents cause havoc with this system rendering the information gathered unreliable. To combat this interference two paths are available to reduce the detection systems susceptibility. These paths include the addition of shielding between the railway track and the wheel detectors, which form the functional entities of the train wheel detection system, and the installation of a cable running parallel to the railway track with connections to it some distance before and after the position of the wheel detector. To verify these paths, high frequency experiments were performed in the lab as well as FEM simulations. To perform the high frequency experiments a source capable of producing the high frequency current needed was designed and constructed, along with a well shielded measurement system to enable the mapping of the flux density within the region occupied by and surrounding the wheel detector. The results of both the experimental measurements and simulations yielded that the interfering magnetic field could indeed be reduced through the use of the two available paths, when they are both applied separately and in combination. To obtain the greater reduction in the interfering field within the area occupied by and surrounding the wheel detector the paths should be used in combination. Therefore through the use of a shield that is constructed from a magnetic material and the installation of a parallel cable the train wheel detection system can be made more robust. / Prof. W.A Cronjé Prof. I.W. Hofsajer

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: The vibrations and noise “pollution” that rail vehicles produce have become of particular concern in recent years. More pressure is being placed on operators of trains and trams (especially those operating in urban environments) to reduce their impact on neighbouring infrastructure. This project investigated the infrastructure available for vibration and noise mitigation and generated material models for some of the materials used in these types of rail infrastructure. The most common type of rail infrastructure used in South Africa is ballasted sleepers. Rail pads are sometimes used to reduce the transmitted vibration of these sleepers; this study focused on the materials used in the manufacture of these pads. Since most of these materials can be described as resilient/viscoelastic, the study of literature regarding these materials is essential within the scope of this project. Models found in literature were adapted by the addition of a non-linear stiffness element to account for the material behaviour at higher preloads. Three commercially available materials were tested and optimisation algorithms applied to determine their material coefficients (damping and stiffness), focusing on the preload and frequency dependency of these coefficients. / AFRIKAANSE OPSOMMING: Die vibrasie en geraas “besoedeling” wat spoor voertuie genereer het in die in die afgelope paar jare van kritieke belang geword. Meer druk word op operateurs van treine en trems geplaas (veral die operateurs met operasies in stedelike gebiede) om hulle impak op aangrensende infrastruktuur te verminder. Hierdie projek is dus daarop gemik om te bepaal watter infrastuktuur beskikbaar is vir die vermindering van vibrasie en geraas asook die ontwikkeling van materiaal modellle vir sommige van die materiale wat gebruik word in hierdie tipes van spoor infrastruktuur. Die mees algemene spoor infrastruktuur wat gebruik word in Suid-Afrika is dwarslêers met ballas. Spoor blokke word soms gebruik om die oordrag van vibrasies te verminder vir hierdie dwarslêers en daarom het hierdie studie fokus geplaas op die materiale wat gebruik word in die vervaardiging van hierdie blokke. Aangesien die meeste van hierdie materiale beskryf kan word as veerkragtig/visco, is 'n literatuurstudie oor hierdie materiale noodsaaklik binne die bestek van hierdie projek. Modelle wat gevind is in die literatuur is aangepas deur 'n nie-lineêre styfheids element by te voeg wat voorsiening maak vir die materiale se gedrag by hoër voorspannings. Drie algemene kommersieël beskikbare materiale is getoets en optimeringsprossesse is toegepas om hulle materiaal koëffisiënte (demping en styfheid) te bepaal met die klem geplaas op die voorspanning en frekwensie afhanklikheid van hierdie koëffisiënte.

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Ph.D. (Physics) / Please refer to full text to view abstract

Este trabalho apresenta o impacto de medidas de gestão como a implantação das faixas exclusivas no tráfego da cidade de São Paulo que, associada à reestruturação semafórica, tem melhorado a mobilidade urbana em São Paulo. Para tanto, traça-se o cenário da mobilidade urbana e, em seguida, analisa-se o quanto a implantação de mais de 400 km de faixas exclusivas nos últimos dois anos impacta no aumento da velocidade média dos ônibus e na redução do crescimento da lentidão do tráfego. A experiência de outras grandes cidades indica que a adesão a novas ferramentas de gestão é alternativa viável para a promoção de avanços qualitativos no transporte coletivo urbano e no transporte em geral, bem como na integração entre modais de transporte motorizado e não motorizado, no deslocamento de pessoas e cargas com mais eficiência e segurança. Por fim, apontam-se outras possibilidades tecnológicas que poderão ampliar os resultados positivos obtidos na mobilidade paulistana. / This work presents the impact of management measures such as the establishment of exclusive tracks in the city of São Paulo traffic that is associated with the semaphore restructuring, has improved urban mobility in São Paulo. To do so, construct the scenario of urban mobility and then analyzed how much the deployment of more than 400 km of exclusive tracks for the past two years impacts on increasing the average speed of buses and reduced growth of traffic slowdowns. The experience of other major cities indicates that membership of the new management tools is a viable alternative to the promotion of qualitative advances in urban mass transit and transportation in general, as well as in the integration between motorized transport modal and non-motorized, the displacement of people and cargo with more efficiency and safety. Finally, point out other technological possibilities that can magnify the positive results obtained in mobility in Sao Paulo.