Les neurones sensoriels réagissent à des stimuli externes en émettant des séquences de potentiels d’action (“spikes”). Ces spikes transmettent collectivement de l’information sur le stimulus en formant des motifs spatio-temporels qui constituent le code neural. On observe expérimentalement que ces motifs se produisent de façon irrégulière, mais avec une structure qui peut être mise en évidence par l’utilisation de descriptions probabilistes et de méthodes statistiques. Cependant, la caractérisation statistique des données expérimentales présente plusieurs contraintes majeures: en dehors de celles qui sont inhérentes aux statistiques empiriques comme la taille de l’échantillonnage, ‘le’ modèle statistique sous-jacent est inconnu. Dans cette thèse, nous abordons le problème d’un point de vue complémentaire à l’approche expérimentale. Nous nous intéressons à des modèles neuro-mimétiques permettant d’étudier la statistique collective des potentiels d’action et la façon dont elle dépend de l’architecture et l’histoire du réseau ainsi que du stimulus. Nous considérons tout d’abord un modèle de type Intègre-et-Tire à conductance incluant synapses électriques et chimiques. Nous montrons que la statistique des potentiels d’action est caractérisée par une distribution non stationnaire et de mémoire infinie, compatible avec les probabilités conditionnelles (left interval-specification), qui est non-nulle et continue, donc une distribution de Gibbs. Nous présentons ensuite une méthode qui permet d’unifier les modèles dits d’entropie maximale spatio-temporelle (dont la mesure invariante est une distribution de Gibbs dans le sens de Bowen) et les modèles neuro-mimétiques, en fou / Sensory neurons respond to external stimulus using sequences of action potentials (“spikes”). They convey collectively to the brain information about the stimulus using spatio-temporal patterns of spikes (spike trains), that constitute a “neural code”. Since spikes patterns occur irregularly (yet highly structured) both within and over repeated trials, it is reasonable to characterize them using statistical methods and probabilistic descriptions. However, the statistical characterization of experimental data presents several major constraints: apart from those inherent to empirical statistics like finite size sampling, ‘the’ underlying statistical model is unknown. In this thesis we adopt a complementary approach to experiments. We consider neuromimetic models allowing the study of collective spike trains statistics and how it depends on network architecture and history, as well as on the stimulus. First, we consider a conductance-based Integrate-and-Fire model with chemical and electric synapses. We show that the spike train statistics is characterized by non-stationary, infinite memory, distribution consistent with conditional probabilities (Left interval specifications), which is continuous and non null, thus a Gibbs distribution. Then, we present a novel method that allows us to unify spatio-temporal Maximum Entropy models (whose invariant measure are Gibbs distributions in the Bowen sense) and neuro-mimetic models, providing a solid ground towards biophysical explanation of spatio-temporal correlations observed in experimental data. Finally, using these tools, we discuss the stimulus response of retinal ganglion cells, and the possible generalization of the co

The goal of my thesis is to analyze the current situation in the market of rail freight transport and to find the potential of the international railway transport of goods in the Czech Republic and Slovakia. It is focused on the comparison of these countries. Main topics of this thesis are i. a. the competitive environment in the Czech and Slovak railway, combined transport, system trains and the expected future progress.

The drive train components and the machine control system significantly influence the fuel consumption of mobile machinery. The demonstrator vehicle “Green Wheel Loader” developed within the joint research project “TEAM” combines the most promising drive concepts currently available for mobile machines with an innovative operating strategy. The developed drive and control system proved its functionality and performance under realistic operation conditions in a gravel pit. Reference test showed 10 – 15 % fuel savings of the prototype vehicle compared to a state-of-the-art series machine.

To deal with an increasing demand in transportation, trains are made longer and faster. Higher speeds imply higher impacts on bridges. Therefore, structures have to be designed to resist these new constraints. The Eurocode (2002) introduced additional checks for the design of high-speed railway bridges. Among them, the maximum vertical deck acceleration criterion often determines alone the design of the structure. Tests on shake table brought to the conclusion that vertical bridge deck acceleration should never exceed 3.5 m/s2 for ballasted tracks. This master thesis investigates the optimization of cross section parameters of single-track simply supported and double-span bridges based on the limit of the maximum vertical deck acceleration criterion. The first natural frequency is considered as a proof of the feasibility of the structure. The optimization is carried out through MATLAB for both types of bridges. The deck acceleration of simply supported bridges is analytically calculated using the Train Signature (ERRI D214 1999) in MATLAB. The dynamic calculations of double-span bridges are implemented through the finite element software ABAQUS. The implemented programs have been verified by comparison to values of simple cases found in the literature. Structures are tested under the influence of the ten HSLM-A trains of the Eurocode running at speeds between 150 km/h and 350 km/h. Optimization algorithms are presented and compared in this study but their applicability in such context is questioned. Indeed, as the problem contains several suitable minima, the algorithms, which end in one solution, are not adapted. To overtake this difficulty, a scanning of the interesting zone is advised. However, the latter is very time consuming, even more if the finite element analysis is used. Suggestions to decrease analysis time are presented in this report. Single span composite bridges with a span longer than 20 m appeared to be impossible to optimize within the objectives defined in this work (i.e. considering limits of deck acceleration and first natural frequency), which draws doubts about their suitability for high-speed railways. Nevertheless, simply supported bridges made of concrete seem more adapted for high-speed railways and their optimized parameters are presented in this work. Optimized parameters for double-span concrete bridges are also presented.

No description available.

Indiana University-Purdue University Indianapolis (IUPUI) / Today transportation is one of the rapidly evolving technologies in the world. With the stringent mandatory emission regulations and high fuel prices, researchers and manufacturers are ever increasingly pushed to the frontiers of research in pursuit of alternative propulsion systems. Electrically propelled vehicles are one of the most promising solutions among all the other alternatives, as far as; reliability, availability, feasibility and safety issues are concerned. However, the shortcomings of a fully electric vehicle in fulfilling all performance requirements make the electrification of the conventional engine powered vehicles in the form of a plug-in hybrid electric vehicle (PHEV) the most feasible propulsion systems. The optimal combination of the properly sized components such as internal combustion engine, electric motor, energy storage unit are crucial for the vehicle to meet the performance requirements, improve fuel efficiency, reduce emissions, and cost effectiveness. In this thesis an application of Particle Swarm Optimization (PSO) approach to optimally size the vehicle powertrain components (e.g. engine power, electric motor power, and battery energy capacity) while meeting all the critical performance requirements, such as acceleration, grade and maximum speed is studied. Compared to conventional optimization methods, PSO handles the nonlinear constrained optimization problems more efficiently and precisely. The PHEV powertrain configuration with the determined sizes of the components has been used in a new vehicle model in PSAT (Powertrain System Analysis Toolkit) platform. The simulation results show that with the optimized component sizes of the PHEV vehicle (via PSO), the performance and the fuel efficiency of the vehicle are significantly improved. The optimal solution of the component sizes found in this research increased the performance and the fuel efficiency of the vehicle. Furthermore, after reaching the desired values of the component sizes that meet all the performance requirements, the overall emission of hazardous pollutants from the PHEV powertrain is included in the optimization problem in order to obtain updated PHEV component sizes that would also meet additional design specifications and requirements.

Carbody tilting is today a mature and inexpensive technology allowing higher speeds in curves and thus reduced travel time. The technology is accepted by most train operators, but a limited set of issues still holding back the full potential of tilting trains. The present study identifies and report on these issues in the first of two parts in this thesis. The second part is dedicated to analysis of some of the identified issues. The first part contains Chapters 2 to 5 and the second Chapters 6 to 12 where also the conclusions of the present study are given. Chapters 2 and 3 are related to the tilting train and the interaction between track and vehicle. Cross-wind stability is identified as critical for high-speed tilting trains. Limitation of the permissible speed in curves at high speed may be needed, reducing the benefit of tilting trains at very high speed. Track shift forces can also be safety critical for tilting vehicles at high speed. An improved track standard must be considered for high speed curving. Chapters 4 and 5 cover motion sickness knowledge, which may be important for the competitiveness of tilting trains. However, reduced risk of motion sickness may be contradictory to comfort in a traditional sense, one aspect can not be considered without also considering the other. One pure motion is not the likely cause to the motion sickness experienced in motion trains. A combination of motions is much more provocative and much more likely the cause. It is also likely that head rotations contribute as these may be performed at much higher motion amplitudes than performed by the train. Chapter 6 deals with services suitable for tilting trains. An analysis shows relations between cant deficiency, top speed, tractive performance and running times for a tilting train. About 9% running time may be gained on the Swedish line Stockholm – Gothenburg (457 km) if cant deficiency, top speed and tractive performance are improved compared with existing tilting trains. One interesting conclusion is that a non-tilting very high-speed train (280 km/h) will have longer running times than a tilting train with today’s maximum speed and tractive power. This statement is independent of top speed and tractive power of the non-tilting vehicle. Chapters 7 to 9 describe motion sickness tests made on-track within the EU-funded research project Fast And Comfortable Trains (FACT). An analysis is made showing correlation between vertical acceleration and motion sickness. However, vertical acceleration could not be pointed out as the cause to motion sickness as the correlation between vertical acceleration and several other motions are strong. Chapter 10 reports on design of track geometry. Guidelines for design of track cant are given optimising the counteracting requirements on comfort in non-tilting trains and risk of motion sickness in tilting trains. The guidelines are finally compared with the applied track cant on the Swedish line Stockholm – Gothenburg. Also transition curves and vertical track geometry are shortly discussed. Chapters 11 and 12 discusses the analysis, draws conclusions on the findings and gives proposals of further research within the present area. / QC 20101119

Le transport par train routier est de plus en plus présent sur les autoroutes canadiennes. Cette option de camionnage permet de transporter une plus grande charge de marchandises à l’aide d’un seul tracteur. Des multinationales utilisent ce type de transport pour leurs opérations quotidiennes et la popularité de cette stratégie est en croissance. De plus, la législation concernant le train routier se simplifie depuis quelques années. La majorité des recherches actuelles portent sur la mécanique du train routier, mais peu d’études sur la rentabilité de ces opérations sont disponibles dans la littérature scientifique. Ce présent mémoire propose une étude économique du train routier. En partenariat avec une entreprise québécoise implantée depuis 20 ans, l’étude économique vise à comparer les opérations en train routier à celle du camionnage régulier avec des remorques de cinquante-trois pieds. L’entreprise souhaite identifier les différences de coûts entre les deux types d’opérations afin d’implanter une stratégie d’affaires à long terme et durable. À l’aide de données réelles et d’observations de flux de marchandises, l’étude économique est basée sur différents scénarios vécus par l’entreprise. De plus, la sensibilité des différents paramètres est étudiée afin de mieux comprendre le comportement des coûts de l’entreprise. Les résultats ont démontré que le train routier permet dans certains cas une économie à la fois monétaire et temporelle pour l’entreprise. En analysant les demandes de transports et en calculant les coûts associés au camionnage traditionnel ainsi qu’au train routier, l’entreprise peut réduire ses frais opérationnels en choisissant le type de transport le plus rentable selon sa situation. / Road train transport is now often on Canadian highways. This variation of trucking allows a larger load of goods to be hauled with just one tractor. Multinationals use this type of transportation for their daily operations and use of this operational strategy is growing. Road trains regulation is less restrictive than it was before. The majority of current research is on the mechanics of the road train but few studies are available on the profitability of these operations. This report proposes an economic study of the road train. In partnership with a Quebec company established for 20 years, the economic study compares road train operations with that of regular trucking. The company wants to define the cost differences between the two types of operations in order to implement a long-term and sustainable business strategy. Using real data and observation of the flow of goods, the economic study is based on different scenarios experienced by the company. In addition, the sensitivity of the various parameters is studied to better understand the cost behavior of the company. Results showed that road train can in some cases save both money and time for the company. By analyzing transportation demands and calculating the costs associated with traditional trucking as well as road train, the company can reduce operational costs by choosing the most cost effective type of transportation according to its demand.

L’évolution des techniques d’acquisition de l’activité neuronale permet désormais d'enregistrer simultanément jusqu’à plusieurs centaines de neurones dans le cortex ou dans la rétine. L’analyse de ces données nécessite des méthodes mathématiques et numériques pour décrire les corrélations spatiotemporelles de la population neuronale. Une méthode couramment employée est basée sur le principe d’entropie maximale. Dans ce cas, le produit N×R, où N est le nombre de neurones et R le temps maximal considéré dans les corrélations, est un paramètre crucial. Les méthodes de physique statistique usuelles sont limitées aux corrélations spatiales avec R = 1 (Ising) alors que les méthodes basées sur des matrices de transfert, permettant l’analyse des corrélations spatio-temporelles (R > 1), sont limitées à N×R≤20. Dans une première partie, nous proposons une version modifiée de la méthode de matrice de transfert, basée sur un algorithme de Monte-Carlo parallèle, qui nous permet d’aller jusqu’à N×R=100. Dans la deuxième partie, nous présentons la bibliothèque C++ Enas, dotée d’une interface graphique développée pour les neurobiologistes. Enas offre un environnement hautement interactif permettant aux utilisateurs de gérer les données, effectuer des analyses empiriques, interpoler des modèles statistiques et visualiser les résultats. Enfin, dans une troisième partie, nous testons notre méthode sur des données synthétiques et réelles (rétine, fournies par nos partenaires biologistes). Notre analyse non exhaustive montre l’avantage de considérer des corrélations spatio-temporelles pour l’analyse des données rétiniennes; mais elle montre aussi les limites des méthodes d’entropie maximale. / Recent experimental advances have made it possible to record up to several hundreds of neurons simultaneously in the cortex or in the retina. Analyzing such data requires mathematical and numerical methods to describe the spatio-temporal correlations in population activity. This can be done thanks to Maximum Entropy method. Here, a crucial parameter is the product N×R where N is the number of neurons and R the memory depth of correlations (how far in the past does the spike activity affects the current state). Standard statistical mechanics methods are limited to spatial correlation structure with R = 1 (e.g. Ising model) whereas methods based on transfer matrices, allowing the analysis of spatio-temporal correlations, are limited to NR ≤ 20. In the first part of the thesis we propose a modified version of the transfer matrix method, based on the parallel version of the Montecarlo algorithm, allowing us to go to NR=100. In a second part we present EnaS, a C++ library with a Graphical User Interface developed for neuroscientists. EnaS offers highly interactive tools that allow users to manage data, perform empirical statistics, modeling and visualizing results. Finally, in a third part, we test our method on synthetic and real data sets. Real data set correspond to retina data provided by our partners neuroscientists. Our non-extensive analysis shows the advantages of considering spatio-temporal correlations for the analysis of retina spike trains, but it also outlines the limits of Maximum Entropy methods.

Made available in DSpace on 2016-04-27T18:15:49Z (GMT). No. of bitstreams: 1 Jose Carlos Brito Silva.pdf: 10582738 bytes, checksum: cf5493c30207a7fbda5b7e5f62e4d477 (MD5) Previous issue date: 2009-10-01 / This research analyzes and seeks to understand the increase in informal activities in general and mobile commerce as a particular case and the conflict between the public and employees of these itinerant trade. This analysis is performed as a result of the dynamics inherent in the capitalist system that is based on socioeconomic contradictions, among them the need to generate a surplus of labor to thus have its disposal an army reserve. In that sense this analysis takes into account the urbanization process as RMSP suffered by one of the promotion of unemployment which had their causes in several variables. The phenomenon of the increase in practice of these activities, named in this study as "independent work", practiced by itinerant workers in trains and other public spaces of RMSP, has widened from the 80's resulting from economic crises that hit the country causing huge recession unemployment and an economy that can be described as the results of politics applied at that moment. This unemployment is particularly accentuated in the 90s resulting from the economic opening process undertaken by the Brazilian Government as a way of integrating the country in the process of globalization. The way this integration, was made, marked by unbridled economic openness, reflected in several aspects of the economy of the country: it has a new territoriality of plants provided by the development of technical-scientific-media informational affectry RMSP mainly because this the most industrialized in the country, it also involves a process of productive restructuring in which the industrial sector loses its economic space and it is substituted by tertiary activities; as a consequence implemented a new model of administrative organization and the production process adopted by enterprises, the model flexible also called post-fordist, requiring a new profile with more and better professional qualifications to perform the tasks, now with a greater degree of complexity and flexibility. These changes reflected directly in the levels of unemployment now reaching ever higher rates. Informal activities in general and labor have become mobile, thus a way to ensure survival for the huge number of unemployed, to consolidate is not as alternatives but rather as a temporary work, by effective work. Just as the growing number of than practitioners in itinerant trade grew the conflicts that came to rely even violently with police actions undertaken. The territory of the CPTM trains as public spaces and great appeal to the trade due to the large flow of passengers, has become one of those places where this picture was reflected socioeconomic and conflict is fierce. This territory, which offers easier to enable practitioners of this activity a condition of legalization of the organization and activities to provide decent conditions for a significant number of workers was the locus chosen in this research as part of the complex and contradictory dynamics of capitalist economy / Esta pesquisa analisa e procura compreender o aumento das atividades informais de maneira geral e do comércio ambulante como um caso específico e os conflitos entre o poder público e esses trabalhadores do comércio ambulante. Esta análise é realizada enquanto resultante de uma dinâmica inerente ao próprio sistema capitalista que se assenta em contradições socioeconômicas, dentre elas a necessidade de geração de um excedente de mão-de-obra para, dessa maneira, ter a sua disposição um exército de reserva. Nesse sentido essa análise leva em consideração o processo de urbanização sofrido pela RMSP como um dos pressupostos de promoção do desemprego que teve suas causas em várias variáveis. O fenômeno do aumento na prática dessas atividades, denominadas nessa pesquisa como trabalho autônomo , praticada pelos trabalhadores ambulantes nos trens e outros espaços públicos da RMSP, se acentuou a partir das décadas de 80 resultantes de crises econômicas que atingiram o Brasil provocando enorme recessão econômica e um desemprego que pode ser caracterizado como conjuntural. Esse desemprego acentua-se de sobremaneira na década de 90 resultante do processo de abertura econômica empreendido pelo Estado brasileiro como forma de integração do País ao processo de globalização. A forma como se deu essa integração, marcada por uma abertura econômica desenfreada, repercutiu em vários aspectos da economia do País: empreendeu-se uma nova territorialidade das plantas industriais proporcionado pelo desenvolvimento dos meios técnico-científico-informacionais atingindo principalmente a RMSP por ser esta a mais industrializada do País; a mesma também passa por um processo de reestruturação produtiva em que perde espaço o caráter industrial e ganham espaço as atividades terciárias; implanta-se um novo modelo de organização administrativa e do processo de produção adotado pelas empresas, o modelo flexível também denominado pós-fordista, que exigem um novo perfil de profissional com maior e melhor qualificação para executar as tarefas, agora com um maior grau de complexidade e flexibilidade. Essas transformações repercutiram diretamente nos níveis de desemprego que passaram a atingir índices cada vez maiores. As atividades informais em geral e o trabalho ambulante tornaram-se, dessa forma, numa forma de garantir a sobrevivência para esse enorme contingente de desempregados, passando a se consolidarem não como alternativas temporárias e sim como trabalho de fato. Da mesma forma que crescia o número de praticantes no comércio ambulante cresciam os conflitos que passaram a contar inclusive com ações policiais empreendidas violentamente. O território dos Trens da CPTM, enquanto espaços públicos e de grande apelo para o comércio devido ao grande fluxo de passageiros, passou a ser um desses lugares onde este quadro socioeconômico se refletiu e os conflitos se acirraram. Esse território que oferece condições mais fáceis de possibilitar aos praticantes dessa atividade uma condição de organização e legalização da atividade visando proporcionar condições dignas a um número significativo de trabalhadores foi o lócus escolhido nesta pesquisa como uma das partes da complexa e contraditória dinâmica da economia capitalista