O sistema de suspensão de um veículo desempenha papel fundamental na isolação das vibrações provenientes da pista e de outras fontes de excitações e tem como alguns de seus objetivos: melhoria do conforto dos passageiros, manutenção da integridade das cargas e das vias (asfalto), aumento da segurança, proporcionando melhores condições de aderência pneu-piso, etc. A predição do desempenho de um sistema de suspensão veicular antes da construção de um protótipo físico, permite o dimensionamento prévio dos componentes que o integram com maior precisão, otimizando-se, desta forma, o custo final do produto bem como custos e prazos decorrentes de modificações para solucionar problemas que seriam detectados somente na experimentação do protótipo físico. Este trabalho apresenta um comparativo entre os resultados analíticos obtidos utilizando-se as funções transferências de um modelo simplificado (ou clássico) linear de uma suspensão automotiva de 1/4 de veículo (quarter-car); dos obtidos através da utilização de um protótipo virtual do mesmo modelo simplificado (ou clássico) de 1/4 de veículo e, por fim, dos obtidos utilizando-se um protótipo virtual de um sistema de suspensão do tipo MacPherson, sendo que os protótipos virtuais podem trabalhar com não-linearidades. São obtidas as respostas dinâmicas no domínio da frequência (0 a 30 Hz) e também no domínio do tempo, neste último caso utilizando-se como entrada um pulso no pneu, que simula a passagem do veículo sobre um obstáculo a 18 Km/h. Os resultados são comparados objetivamente e conclui-se sobre as limitações de utilização do modelo simplificado (ou clássico) de 1/4 de veículo. / The performance of the suspension system of a vehicle is fundamental to isolate the vibrations from road and from other sources and has the following objetives: improve the comfort of passengers (ride), protect the cargo and the road (asphalt), improve vehicle handling, etc. The prediction of the performance of a vehicle´s suspension system prior to the real prototype construction, allows the previous optimization of the design of the suspension´s components, obtaining a low cost product, in a shorter timming, with lower development costs, by solving problems that would be evident only during the tests with the real prototype. This study presents a comparison between analitycal results obtained by the use of transfers functions of a plain or classical linear model of a automotive suspension system named quarter-car; the results obtained from a virtual prototype of the same plain or classical model and, finally, the results obtained from a virtual prototype of a Macpherson suspension system, considering that the virtuals prototypes are be able to work with non-linearities. The dynamic response are obtained in the frequency domain (0 a 30 Hz) and in the time domain too, in this last case, with a pulse input in the tire, that simulates the car passing over a bump with a speed of 18 Km/h. Through the comparison of the results is possible to conclude about the limitations of the classical model.

abstract: This dissertation examines travelers’ innovation adoption and repurchase behaviors in the sharing economy. The central question is to what extent the tourism industry embraces service innovations in the sharing economy. Predicated upon behavioral reasoning theory, this research makes a contribution to the tourism study and diffusion of innovation literature, by exploring the influence of travelers’ reasonings in the innovation decision process. The dissertation follows a two-study format. The analysis contextualizes reasons for and against adoption, by incorporating appropriate constructs relevant to service innovations in social dining services (Study 1) and ride-sharing services (Study 2). An exploratory mixed methods approach is taken in both studies. The survey data and the semi-structured interviews are used to identify the context-specific reasons for and against adoption. And, a series of statistical analyses are employed to examine how reasonings influence intentions to adopt social dining services (Study 1) and intentions to repurchase ride-sharing services for the next trip (Study 2). The main results suggest that both reasons for and reasons against adoption have countervailing influences in the psychological processing, supporting the validity of the research models. The findings also reveal that different psychological paths in travelers’ adoption and repurchase intentions. In Study 1, the trustworthiness of service providers attenuates the reasons against adoption and enhances the likelihood of adopting social dining services in the pre-adoption stage. In Study 2, attitude strength functions as an additional construct, which mediates travelers’ attitudes and ultimately intentions to repurchase ride-sharing services for the next trip in the post-adoption stage. By developing and testing a framework comprising a set of consumers’ beliefs, reasonings for adoption and resistance, attitudes towards adoption, and behavioral responses to the sharing economy, the insights gleaned from this research allow practical recommendations to be made for service providers, platform providers, and policy makers in the tourism industry. / Dissertation/Thesis / Doctoral Dissertation Community Resources and Development 2019

This research investigates whether Transportation Network Companies (TNCs), such as Uber and Lyft, live up to their stated vision of reducing congestion by complementing transit and reducing car ownership in major cities. The objective of this research study is to answer the question: are TNCs are correlated to traffic congestion in the city of San Francisco? If found to be so, do they increase or decrease traffic congestion for the case of San Francisco? If and how TNC pickups and drop-offs impact traffic congestion within San Francisco? And finally, how does the magnitude of this measured command of TNCs on congestion compare to that caused by pre-existing conventional drivers of traffic and congestion change? Apart from answering these questions, it is also sought to establish a framework to be able to include TNCs, a seemingly fledgling mode of transportation but one that is demonstrably shaping and modifying extant transportation and mode choice trends, as part of the travel demand models estimated by any geographic jurisdiction. Traffic congestion has worsened noticeably in San Francisco and other major cities over the past few years. Part of this change could reasonably be explained by strong economic growth or other standard factors such as road and transit network changes. The sharp increase in travel times and congestion also corresponds to the emergence of TNCs, raising the question of whether the two trends may be related. Existing research has produced conflicting results and been hampered by a lack of data. Using data scraped from the Application Programming Interfaces (APIs) of two TNCs, combined with observed travel time data, this research finds that contrary to their vision, TNCs are the biggest contributor to growing traffic congestion in San Francisco. Between 2010 and 2016, weekday vehicle hours of delay increased by 62%, compared to 22% in a counterfactual 2016 scenario without TNCs. The findings provide insight into expected changes in major cities as TNCs continue to grow, informing decisions about how to integrate TNCs into the existing transportation system. This research also decomposes the contributors to increased congestion in San Francisco between 2010 and 2016, considering contributions from five incremental effects: road and transit network changes, population growth, employment growth, TNC volumes, and the effect of TNC pick-ups and Drop-offs. It is so done through a series of controlled travel demand model runs, supplemented with observed TNC data. The results show that road and transit network changes over this period have only a small effect on congestion, population and employment growth are important contributors, and that TNCs are the biggest contributor to growing congestion over this period, contributing about half of the increase in vehicle hours of delay, and adding to worsening travel time reliability. This research contradicts several studies that suggest TNCs may reduce congestion and adds evidence in support of a recent empirical analysis showing that their net effect is to increase congestion. This research gives transportation planners a better understanding of the causes of growing congestion, allowing them to more effectively craft strategies to mitigate or adapt to it.

La frontière tectonique entre les plaques indienne et birmane est principalement décrochante avec une faible composante de raccourcissement. La plaque subduite, le bassin du Bengale, est parcourue par des hétérogénéités crustales majeures acquises lors de son processus de formation et de migration vers le Nord (rides de point chaud, failles transformantes...). La plaque supérieure, la microplaque birmane, délimitée à l'Est par la faille décrochante dextre de Sagaing, est dans la zone d'influence du flux crustal Est-Tibétain. <br />Le long d'une large coupe Terre-Mer depuis le bassin du Bengale jusqu'au Nord de la Birmanie, je me suis intéressé à la géométrie structurale et à la cinématique de la subduction hyper-oblique Indo-Birmane en insistant sur les effets d'éléments perturbateurs (flux et hétérogénéités crustaux). Par une approche pluridisciplinaire combinant des observations géologiques structurales de terrain, des données géophysiques marines et des mesures géodésiques, je présente un modèle d'évolution néogène de la subduction oblique en réponse à ces perturbations. Une étude de la sismicité et quelques mesures paléomagnétiques ont complété ce travail.<br /><br />La ride de 90°E, formée au sein de la croûte océanique du Bengale vers 100Ma, est entrée en collision avec la marge Birmane au Miocène supérieur. Elle a probablement bloqué la subduction dans sa partie méridionale de telle sorte que seule une déformation décrochante dextre le long de son flanc Est est exprimé structuralement. Au Nord de la ride, le prisme externe Indo-Birman est libre de se développer rapidement vers l'Ouest depuis 2Ma à la faveur d'une forte épaisseur de sédiments déposés sur la plaque plongeante (delta du Ganges-Brahmapoutre).<br />Ce prisme Indo-Birman, construit en convergence hyper-oblique, a enregistré un partitionnement de la déformation : les zones internes sont cisaillées sur une direction Nord-Sud et les zones externes sont raccourcies sur une direction Est-Ouest. <br />La faille de Sagaing est défléchie de plus de 100km vers l'Ouest dans sa partie Nord. Je propose un modèle dans lequel le flux crustal résultant de l'effondrement du Tibet, est responsable de cette inflexion. Ce modèle questionne le rôle de ce flux dans la construction du prisme partitionné. Appuyé sur l'ensemble des données géodésiques disponibles autour de la syntaxe Est Himalayenne, il établit un lien entre les déformations finis néogènes de la région.<br /><br />Les données de sismique réflexion ont apporté des contraintes fortes sur la partie marine de la section. Ainsi, la présence de la ride de 90°E et la nature océanique de la croûte du Bengale ont pu être fixées. En revanche, le flux crustal Est-Tibétain reste mal compris. Les données géodésiques permettent d'en approcher la cinématique mais il est nécessaire, pour en connaître la nature, d'y combiner des données géologiques de terrain, qui sont les seuls à permettre l'observation direct de la déformation crustale profonde aujourd'hui exhumée. Ces observations géologiques peuvent aussi apporter des éléments de réponses sur la stabilité du flux au cours du temps. Un travail de modélisation doit encore être mené pour confronter ces idées nouvelles aux propriétés physiques de la lithosphère continentale en cours de déformation.

<p>The demands for ride comfort quality in today's long haulage trucks are constantly growing. A part of the ride comfort problems are represented by internal vibrations caused by rotating mechanical parts. This thesis work focus on the vibrations generated from radial runout on the wheels. These long haulage trucks travel long distances on smooth highways, with a constant speed of 90 km/h resulting in a 7 Hz oscillation. This frequency creates vibrations in the cab, which can be found annoying. To help out with the vibration diagnosis when a truck enters a mechanical workshop, this work studies methods for radial runout detection using the wheel speed sensors.</p><p>The main idea is to represent the varying radius signal with a sinusoid, where the calculations are based on Fourier series. The estimated radial runout value is then the amplitude of the sinusoid. In addition to the detection part, the work also present results regarding how the relative phase difference between two wheels with radial runout effects the lateral motion of the cab.</p><p>This thesis work was performed at Scania CV AB in Södertälje, Sweden and all measurements have been full scale experiments on real trucks.</p>

Carbody tilting is today a mature and inexpensive technology that allows higher train speeds in horizontal curves, thus shortening travel time. This doctoral thesis considers several subjects important for improving the competitiveness of tilting trains compared to non-tilting ones. A technology review is provided as an introduction to tilting trains and the thesis then focuses on enhancing the benefits and strategies for less motion sickness. A tilting train may run about 15% faster in curves than a non-tilting one but the corresponding simulated running time benefit on two Swedish lines is about 10%. The main reason for the difference is that speeds are set on other grounds than cant deficiency at straight track, stations, bridges, etc. The possibility to further enhance tilting trains’ running speed is studied under identified speed limitations due to vehicle-track interaction such as crosswind requirements at high speed curving. About 9% running time may be gained on the Stockholm–Gothenburg (457 km) mainline in Sweden if cant deficiency, top speed, and tractive performance are improved compared with existing tilting trains. Non-tilting high-speed trains are not an option on this line due to the large number of 1,000 m curves. Tilting trains run a greater risk of causing motion sickness than non-tilting trains. Roll velocity and vertical acceleration are the two motion components that show the largest increase, but the amplitudes are lower than those used in laboratory tests that caused motion sickness. Scientists have tried to find models that can describe motion sickness based on one or more motion quantities. The vertical acceleration model shows the highest correlation to motion sickness on trains with active tilt. However, vertical acceleration has a strong correlation to several other motions, which precludes vertical acceleration being pointed out as the principal cause of motion sickness in tilting trains. Further enhanced speeds tend to increase carbody motions even more, which may result in a higher risk of motion sickness. However, means to counteract the increased risk of motion sickness are identified in the present work that can be combined for best effect. Improved tilt control can prevent unnecessary fluctuations in motion sickness related quantities perceived by the passengers. The improved tilt control can also manage the new proposed tilt algorithms for less risk of motion sickness, which constitute one of the main achievements in the present study. Local speed restrictions are another means of avoiding increased peak levels of motion sickness when increasing the overall speed. The improved tilt control and the proposed tilt algorithms have proven to be effective in on-track tests involving more than 100 test subjects. The new tilt algorithms gave carbody motions closer to non-tilting trains. Rather unexpectedly, however, the test case with the largest decrease in tilt gave a greater risk of motion sickness than the two test cases with less reduction in tilt. It is likely that even better results can be achieved by further optimization of the tilt algorithms; the non-linear relation between motions and motion sickness is of particular interest for further study. / QC 20110429

Traditional public transport systems are most often insufficient to provide a good transport service to everyone. Especially, it is not always possible for elderly and disabled persons to use the regular system consisting of timetabled services operating along fixed routes. Normally there is some specific service, often called paratransit, offered to these groups of customers. Such transport services provide better service to these customers, but to a higher cost. This thesis considers planning and evaluation of public transport services that are based on the concept of a dial-a-ride service. This kind of service is suitable for elderly and disabled and often operated as a door-to-door service, where customers are served on demand and rides are coordinated via a call-center. The thesis is divided into two parts. In the first part, a modeling system for simulation of dial-a-ride services is presented. It can be used as a tool to study how different ways of operating a dial-a-ride service, affect the performance and efficiency of the service. This system is used to evaluate how algorithmic changes, based on ruin-and-recreate methods, can improve the replanning of already inserted requests, and thereby improve the scheduling. The modeling system is also used to examine the effects of using zone-based distance estimates instead of true, address-based, distances when computing the schedules. The results show that only small differences are found.The second part of the thesis concerns an extension to dial-a-ride services. By combining a dial-a-ride service with a fixed route service, an integrated dial-a-ride service is created, where some part of each journey may be carried out by the fixed route service. An exact mathematical formulation of this problem is presented and it is shown that the formulation is strengthened by valid inequalities, variable substitution and subtour elimination constraints. Simulations of an integrated service are also performed to analyze and evaluate how the attractiveness and operating costs of the service depend on how the demand responsive service is operated.

The aim of this work is to evaluate ride quality of a typical passenger car. This requires both identifying the excitation resources, which result to undesired noise inside the vehicle, and studying human reaction t applied vibration. Driveline linear torsional vibration will be modelled by a 14-degress of freedom system while engine cylinder pressure torques are considered as an input force for the structure. The results show good agreement with the corresponding reference output responses which proves the accuracy of the numerical approach fourth order Runge-kutta. An eighteen-degree of freedom model is then used to investigate coupled motion of driveline and the tire/suspension assembly in order to attain vehicle body longitudinal acceleration subject to engine excitations. Road surface irregularities is simulated as a stationary random process and further vertical acceleration of the vehicle body will be obtained by considering the well-known quarter-car model including suspension/tire mechanisms and road input force. Finally, ISO diagrams are utilized to compare RMS vertical and lateral accelerations of the car body with the fatigue-decreased proficiency boundaries and to determine harmful frequency regions. According to the results, passive suspension system is not functional enough since its behaviour depends on frequency content of the input and it provides good isolation only when the car is subjected to a high frequency excitation. Although longitudinal RMS acceleration of the vehicle body due to engine force is not too significant, driveline torsional vibration itself has to be studied in order to avoid any dangerous damages for each component by recognizing resonance frequencies of the system. The report will come to an end by explaining different issues which are not investigated in this thesis and may be considered as future works.

The demands for ride comfort quality in today's long haulage trucks are constantly growing. A part of the ride comfort problems are represented by internal vibrations caused by rotating mechanical parts. This thesis work focus on the vibrations generated from radial runout on the wheels. These long haulage trucks travel long distances on smooth highways, with a constant speed of 90 km/h resulting in a 7 Hz oscillation. This frequency creates vibrations in the cab, which can be found annoying. To help out with the vibration diagnosis when a truck enters a mechanical workshop, this work studies methods for radial runout detection using the wheel speed sensors. The main idea is to represent the varying radius signal with a sinusoid, where the calculations are based on Fourier series. The estimated radial runout value is then the amplitude of the sinusoid. In addition to the detection part, the work also present results regarding how the relative phase difference between two wheels with radial runout effects the lateral motion of the cab. This thesis work was performed at Scania CV AB in Södertälje, Sweden and all measurements have been full scale experiments on real trucks.

Great portion of today's industry are <em>Adjustable Speed Drives</em> (<em>ASD's</em>) operated in order to fulfill certain processes. When these processes are critical ones or sensitive to voltage disturbances, that might take place due to inserting high load in an area near to the Point of Common Coupling (<em>PCC</em>) of the process or due to a short term outage, few tens of thousands up to millions of dollars will be lost once such interruptions (voltage sags) take place as a result of the process failure. On the other hand, a distorted voltage waveform at the PCC for some sensitive process might malfunction as a result of the high harmonic content of the voltage waveform. Utilities are required to deliver as pure as possible sinusoidal voltage waveform according to certain limits; thus, they might apply fines against the consumers who are responsible for producing high amounts of current harmonics that affect the voltage wave shape at the <em>PCC</em> in order to force them to improve the consumer's load profile by adding filters at <em>PCC</em> for instance. Utilities are charging the consumers who are drawing power at poor power factor as well. <br /><br /> This thesis presents an <em>ASD</em> retrofitted with a dual-functional piece of hardware connected in series to its <em>DC-link</em> that is capable of handling the previously two mentioned problems. In other words, hardware that is capable of providing <em>voltage sag ride-through</em> during the voltage sag conditions on one side, on the other side, during the normal operating conditions, it is capable to mitigate the harmonic contents of the drawn current by the ASD's rectifier and to improve the power factor. <br /><br /> Survey on voltage sag ride-through for ASD's approaches are presented in the literature has been made. Approaches are classified as the topology utilized; first, topologies that utilizes energy storage elements that store energy to compensate the DC-link voltage with during the voltage sags, second, topologies retrofitting the DC-link itself with additional hardware to compensate the DC-link voltage. The first group is capable to provide voltage compensating during the full outages while the second can't. The presented voltage sag ride-through work of this thesis belongs to the second group. <br /><br /> Boost converter has been used as the hardware to compensate the DC-link voltage because of its simplicity and cheap price. An adaptive linear network (ADALINE) is investigated as the detection system to detect the envelope of the input voltage waveform. Once the envelope of the voltage goes below a certain level, the boost converter is activated to compensate the difference between voltage set point and the actual DC-link voltage. Simulation results supporting the proposed configuration are presented. <br /><br /> A third-harmonic current injection approach is utilized in this work in order to achieve <em>total harmonic distortion</em> (<em>THD</em>) mitigation from 32% to 5. 125% (theoretically). Two third-harmonic current injection networks have been investigated; one utilizes a real resistor, the other utilizes a resistor emulator to reduce the energy dissipated. The proposed controller for the resistor emulator does not require a proportional-integral (PI) controller. <br /><br /> As a result of the common devices between the voltage sag ride-through circuitry and the harmonic mitigation one, they can be integrated together in one circuitry connected in series with the DC-link of the ASD. And hence, the dual functionality of the hardware will be achieved. Simulation results supporting the theoretical results have been presented.