Depuis les années 70-80, avec les travaux de Tinto (1975) notamment, la recherche en éducation révèle l’importance des processus interactionnels dans l’explication des parcours étudiants, démontrant l’influence significative de l’intégration sociale sur la persévérance à l’université. Les effets sur la réussite académique des étudiants sont à l’inverse peu explorés. De plus, la conceptualisation de ce facteur explicatif ne fait pas consensus, donnant à voir différentes dimensions de l’intégration sociale. A partir d’une collecte de données réalisée auprès de 1365 étudiants inscrits en 1ère, 2ème et 3ème année de Licences généralistes, cette recherche propose ainsi, dans un premier temps, une mesure affinée de l’intégration sociale étudiante rendant compte de son caractère multidimensionnel. Puis, dans un deuxième temps, les sources et conditions de cette intégration sont interrogées à travers l’influence de facteurs contextuels, institutionnels et individuels, parmi lesquels sont considérées les compétences transversales qui illustrent, entre autres, les aptitudes sociales des étudiants. Les analyses montrent ainsi que des besoins différents en matière de sociabilité étudiante s’expriment notamment en fonction de l’âge, du genre et des raisons d’étudier, alors que le contexte de formation détermine en premier lieu les opportunités offertes aux étudiants pour s’intégrer socialement. Il apparaît en outre que certaines compétences relatives à la gestion des émotions et à la collaboration constituent des ressources favorisant l’intégration sociale. Nos résultats permettent ainsi de dégager quatre profils distincts de la sociabilité étudiante en Licence. En dernier lieu, la place occupée par l’intégration sociale et les compétences transversales étudiantes au sein des parcours étudiants et des déterminants de leur réussite académique est questionnée. Les analyses révèlent à ce titre que l’intégration sociale étudiante présente des effets bruts et positifs sur la probabilité de réussir les examens et sur les notes obtenues par les étudiants, au travers des interactions studieuses et du sentiment d’intégration. En tenant compte des déterminants classiques de la réussite étudiante, l’influence « toutes choses égales par ailleurs » de ce facteur apparaît en revanche faible sur la réussite académique, bien que le sentiment d’intégration diminue les risques d’abandon chez les étudiants. A l’inverse, les compétences transversales renvoyant au goût de l’effort et à la confiance en soi se révèlent être de puissants prédicteurs de la réussite et des performances des étudiants. Si l’intégration sociale étudiante ne semble pas être un facteur clé et médiateur de la réussite académique, elle s’ajoute néanmoins, sous certaines formes, aux facteurs caractérisant les profils de réussite à l’université. En outre, elle influe de manière indirecte sur les performances des étudiants au travers de leur investissement académique. / Since 1970’s and 1980’s, educational research reveals the importance of interactional process in the explanation of student careers, especially with Tinto’s work (1975), by demonstrating the significant influence of social integration on student persistence in university. However, the effects on students’ academic success are rarely explored. Moreover, there is no consensus on the conceptualization of this explanatory factor since it shows different dimensions of social integration. From data collected from 1365 students enrolled in 1st, 2nd and 3rd grade of common “Licence”, this research proposes firstly to improve measurement of student social integration as a multidimensional concept. Then the sources and conditions of social integration are examined through the influence of contextual, institutional and individual factors. In this context, the transversal skills are considered as an illustration of student social abilities, among others. Statistical analyses show that students have different needs for social integration, depending on their age, gender and reasons for study. First, the academic context defines the opportunities offered to students for social integration. Moreover, it appears that some skills related to emotional management and collaboration turn into resources that promote social integration. Results lead to identify four different profiles of student social integration in “Licence” course. Lastly, questions arise about the role of social integration and transversal skills in student careers and factors of student achievement. Our results reveal that student social integration has a raw and positive effect on the probability of success and performances, through academic interactions and feeling of integrating. When the classical factors of student achievement are taking into account, the influence of social integration appears to be weak or lost. Only the feeling of integrating reduces the risk of student drop-outs. On the other hand, the transversal skills including the taste for work and the self-confidence prove to be powerful predictors of students' success and performances. While student social integration doesn’t seem to be a key factor with mediating effects on academic achievement, it appears to be another feature of student success profiles. Moreover, student social integration produces indirect effect on performances through academic commitment.

Conventional railway track is the structure consisting of the ballast or slab track, upon which sleepers, fasteners and two rails are laid, allowing the passage of trains equipped with a certain gauge. Due that trains cannot pass from a line with one track gauge to an-other (only possible where the difference between the two gauges is small), track gauge is a dominant parameter determining interoperability, used as a descriptor of a route or net-work. Where trains encounter a different gauge, a break-of-gauge occurs, which entails delays, costs, and inconveniences. However, special situations such as the Spanish rail network can occur, where new in-teroperability and connection facilities have resulted in the construction of certain lines with dual gauge track. A dual gauge track configuration consists of three rails, where the two adjacent outer rails provide each of the gauges (1435 mm / 1668 mm), while the single outer rail is common to trains of both gauges. This new track structure is an important modification of the classical rail track with two rails and one gauge. In addition, long stretches of dual gauge tracks have not been implement-ed yet, so it is necessary to develop new methodologies and studies to understand its be-haviour. Specifically, with the use of continuous welded rails, variations in rail temperature produce compression stresses that, under certain circumstances, can led to dangerous lateral track displacements and train derailment. With that motivation, this PhD Thesis is focused on an appropriate theoretical framework for conducting a study that evaluates the potential risk of buckling in dual gauge tracks. To accomplish this task, different methods and techniques in order to improve the knowledge of this phenomenon and track design. This approach will allow us to establish track condi-tions and maintenance works that ensures the stability of the dual gauge track under ther-mal and train loads. In addition, a risk based methodology allows us to revise and redefine conventional track design methods in order to increase track stability under thermal loads. / La superestructura de vía clásica está compuesta por una serie de capas portantes en las que se sitúan las traviesas o losas de hormigón y sobre las cuales se disponen 2 carriles que permiten la circulación de los vehículos, en base a su utilización con un único ancho de vía. Debido a que los vehículos ferroviarios no pueden circular desde una línea con un ancho de vía a otra con un ancho diferente (solo es posible si la diferencia de ancho es muy reducida) el ancho de vía se establece generalmente como un único valor común para toda una determinada red, pues de lo contrario se crean una serie de "fronteras" entre las líneas con diferente ancho de vía, lo que provoca importantes problemas en la explota-ción y gestión de la red. No obstante, existen situaciones especiales como la que se produce en España, donde las circunstancias y las nuevas necesidades de conexión e interoperabilidad han dado como resultado la construcción de tramos ferroviarios de doble ancho o ancho mixto. La carac-terística fundamental de este tipo de vías es la dotación de un tercer carril, de tal forma que se parte de una vía de ancho ibérico (1.668 mm) sobre la que se dispone en su interior un tercer carril para conseguir el ancho estándar (1.435 mm). Así pues, esta nueva configuración de vía supone una importante modificación respecto a la vía clásica de un ancho y 2 carriles. Además, el uso del tercer carril en tramos largos es totalmente novedosa, lo que obliga al estudio y análisis del comportamiento de esta nueva superestructura de vía. En especial, la vía debe resistir los esfuerzos longitudinales, pues el uso de la barra larga soldada genera esfuerzos térmicos en los carriles que pueden oca-sionar, bajo unas ciertas condiciones de vía, la desestabilización y, como resultado, impor-tantes deformaciones laterales con efectos muy perjudiciales. Por ello, la presente tesis tiene por objeto el estudio teórico del riesgo de pandeo en vías de doble ancho mediante el uso de diferentes métodos y técnicas que permitan una mejor comprensión de este fenómeno y el diseño seguro de este tipo de vías. El análisis permiti-rá establecer las condiciones que aseguran el correcto funcionamiento de la superestruc-tura de vía antes las diferentes solicitaciones que debe soportar. Además, el planteamiento de una metodología de evaluación del riesgo de pandeo en vías de doble ancho permitirá la revisión y reformulación de criterios de diseño, aplicables a vías existentes o de nueva construcción, según las oscilaciones térmicas a las que esté sometida. / La superestructura de via tradicional està composta per una sèrie de capes portants en què se situen les travesses o lloses de formigó i sobre les que es disposen 2 carrils que permeten la circulació dels vehicles, segon l'ús d'un únic ample de via. Pel fet que els vehicles ferroviaris no poden circular des d'una línia amb un ample de via a una altra amb un ample diferent de la primera (només és possible si la diferència d'amples és molt reduïda), l'ample de via s'estableix generalment com un únic valor comú per a tota una determinada xarxa, ja que en cas contrari es generen una sèrie de "fronteres" entre línies amb diferent ample de via, el que produeix importants problemes tant en l'explotació com en la gestió de la xarxa. No obstant això, existeixen situacions especials com la que es produeix a Espanya, on les circumstàncies i les noves necessitats de connexió i interoperabilitat han donat com a resultat la construcció de trams ferroviaris de doble ample o ample mixt. La característica fonamental d'aquest tipus de via d'ample mixt és la col·locació d'un tercer carril, de tal forma que partint d'una via d'ample ibèric (1.668 mm) es disposa a l'interior un tercer carril que permet aconseguir l'ample estàndard (1.435 mm). Així, aquesta nova configuració de via suposa una important modificació respecte de la via clàssica d'un sol ample i 2 carrils. A més a més, l'ús del tercer carril en trams llargs és totalment nova, el que obliga a estudiar i analitzar el comportament d'aquesta nova estructura. En especial, la via ha de resistir els esforços longitudinals, degut a que l'ús del carril continu soldat genera càrregues d'origen tèrmic en els carrils que poden ocasionar, baix unes certes condicions de via, la desestabilització i, com a resultat, importants deformacions laterals amb efectes molt perjudicials. Per açò, la present Tesi té com a objectiu l'estudi teòric del risc de pandeig en vies d'ample mixt (amb 3 carrils) a través de l'ús de diferents mètodes i tècniques tal que permeten un major coneixement d'aquest fenomen i el disseny segur d'aquest tipus de via. L'anàlisi permetrà establir les condiciones que asseguren el correcte funcionament de la superestructura de via enfront de les diferents càrregues que deu suportar. A més, el plantejament d'una metodologia d'avaluació del risc de pandeig en vies d'ample mixt permetrà la revisió i reformulació dels criteris de disseny, aplicables a vies existents o de nova construcció, d'acord amb les oscil·lacions tèrmiques a les quals estarà sotmesa. / Villalba Sanchis, I. (2017). STUDY, ANALYSIS AND DETERMINATION OF BUCKLING LOAD IN DUAL GAUGE TRACKS THROUGH ANALYTICAL AND NUMERICAL METHODS [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/93343 / TESIS

The aim of diploma thesis are modifications in mechanical design of the coherence controlled holographic microscope which will lead to reduction of some deficiencies. In this thesis there is a brief description of the history interference microscopy and differences between each types of interference microscopes. In this work there are stated some design deficiencies of actual condition of the microscope and also several solutions are suggested and shortly described. Then the best solution is chosen which is adjusted to a final form. It is described in detail and then realized. There is a summary included in the conclusion whether the new solution is suitable and if it fulfills the required condition.

The scope of the Master's thesis is the design, evaluation and the comparison of two variations of the solution for steel load-bearing structure which is a part of a gokart areal with adjacent refreshments. The construction is composed of three structurally dependent objects. For the first construction object, there were solved the variants with a truss and a frame structure. The construction has an irregular plan. The object plan dimensions are 75 x 45 m. The built up area covers 2450 m2. The construction reaches the height of 13,2 m. The thesis contains the design of dimensions, structural analysis and the evaluation of structural members. The calculation of internal forces was made by SCIA Engineer 16.1.62 software. Attached to the thesis is the drawing documentation.

Hydraulic main stages for off highway machines have usually electromagnetic driven pilot valves. You rarely find stepper motor driven pilot systems that are directly positioning the main spool in the sectional control valve. The presented concept shows the development of an actuator in a unique setup to fulfill the requirements of most off- highway applications. Precise positioning, strength, speed and fail safe requirements were the main goals of the concept. The concept has a two phase BLDC transversal flux motor with a single gear stage transmission. The software and control unit are specially designed for this electric motor setup. On a test bench some results of the first samples reveal the technical potential of this concept. The development of the actuator was done in-house of Thomas Magnete GmbH (mechanical, electronical, and software development).

That certain iron and nickel alloys exhibit an anomalously low thermal expansion of a wide temperature range has been observed since late 1800s, and this effect is known as the Invar effect. Since then, many theories have been proposed to explain the phenomenon. While it is generally agreed that the effect is related to magnetism, a full explanation of the effect has yet to be found. One recent theory connected the effect to spin-flips in the iron atoms' magnetic moment and that the probability for a spin-flip to occur depends on the atom's local chemical environment. The aim of this thesis is to perform a theoreticalinvestigation into the magneticenergy landscapes for atomic magnetic moments in different local chemical environments in disordered Fe64Ni36 alloys, and the change in pressure upon populating different parts of the magnetic energy landscape. Constrained calculations are performed to obtain the energy landscapes for both iron and nickel atoms in ferromagnetic Fe64Ni64. The calculated nickel atoms all show one global minimum between 0.64 to 0.72μB. The calculated iron atoms all exhibit two local minima: one where the magnetic moment's direction is the same as the ferromagnetic background's direction and has a size between 2 to 3μB, one where the magnetic moment is flipped and has a reversed direction in regards to the ferromagnetic background with a size between -2.5 to -1.9μB. A weak trend is seen for the energy difference between the two local minima: for iron-atoms with iron-rich local environments the energy difference is smaller than for iron-atoms with nickel-rich local environments. The energy landscapes for a moment rotated with respect to the background show that it is energetically favored to rotate the moment from the spin-up local minimum to the spin-flipped local minimum, rather than shrink in size and then increase in size in the opposite direction. This indicates that the negative local minimum might not be a local minimum, but further calculations are needed to determine if the spin-flipped state is a local minimum or just a saddle point in the complete size-and angle magnetic energy landscape. It is observed that the pressure varies little for different magnetic moment sizes for a nickel atom, but shows a larger variation for different magnetic moment sizes for an iron atom. The pressure difference between the magnetic local minima is about 6-9 kbar, and from thermodynamical simulations a small, nonlinear, decline in pressure with increased temperature is observed.

This investigation deals with the suspension of a lightweight medium-class vehicle for four passengers with a curb weight of 1000 kg. The suspension layout consists of a transversal leaf spring and is supported by an active air spring which is included in the damper. The lower control arms are replaced by the leaf spring ends. Active ride height control is introduced to compensate for different vehicle load states. Active steering is applied using electric linear actuators with steer-by wire design. Besides intense use of light material the inquiry should investigate whether elimination of suspension parts or a lighter component is concordant with the stability demands of the vehicle. The investigation is based on simulations obtained with MSC Software ADAMS/Car and Matlab. The suspension is modeled in Adams/Car and has to proof it's compliance in normal driving conditions and under extreme forces. Evaluation criteria are suspension kinematics and compliance such as camber, caster and toe change during wheel travel in different load states. Also the leaf spring deflection, anti-dive and anti-squat measures and brake force distribution are investigated. Based on a simplified version of the leaf spring suspension design a full vehicle model is created. The comparison between the suspension models evaluates the same basic suspension parameters to ensure the compliance. Additionally roll rate and understeer gradient are investigated. It can be shown that the vehicle equipped with transversal leaf spring instead of lower control arms fulfils the set kinematics and compliance requirements. Road holding performance is assured for normal driving conditions on public roads.

[pt] A disseminação de programas computacionais que implementam o Método dos Elementos Finitos (MEF) influenciou a forma como os projetos estruturais são executados. Em projetos de pontes, onde os métodos simplificados de cálculo foram por muitos anos as principais formas de análise, o MEF se tornou uma ferramenta importante no processo. Atualmente os métodos simplificados complementam a utilização do MEF de diversas formas, desde o pré-dimensionamento dos elementos estruturais e fornecendo uma estimativa dos esforços cortantes e momentos fletores a serem encontrados, reduzindo a possibilidade de erros durante o projeto. Nos Estados Unidos a AASHTO LRFD (2012) apresenta um método simplificado de distribuição transversal de solicitações em suas especificações normativas que exige apenas o cálculo de um fator de distribuição. O objetivo deste trabalho é avaliar se este método pode ser usado como uma alternativa racional para o dimensionamento de pontes no Brasil. Para isso, foi necessário entender a diferença entre as normas brasileiras e americanas, sugerir um modelo de cálculo baseado na norma americana e que atenda às recomendações normativas brasileiras e validar este modelo com análises por elementos finitos e outros métodos simplificados. Os modelos de elementos finitos utilizados foram validados por meio da comparação dos resultados de suas análises com os resultados de testes de cargas em pontes realizados por outros autores. O modelo de cálculo proposto obteve para todas as situações analisadas resultados seguros, se mostrando capaz de determinar a distribuição transversal das solicitações e o deslocamento máximo das longarinas de pontes de vão único com vigas de concreto. Em pontes com vigas metálicas o método também obteve resultados seguros nas análises das solicitações, porém assim como os outros métodos simplificados, não é capaz de determinar de maneira confiável os deslocamentos máximos sofridos. Conclui-se, portanto, que a metodologia proposta pode ser utilizada no dimensionamento de pontes de um único vão no Brasil, desde que considerados os limites de aplicabilidade especificados. / [en] The dissemination of softwares that implement the Finite Element Method (FEM) influences the way the structural projects are made. For bridge projects, where the simplified methods have been for many years the main type of analysis, the FEM has become an important tool in the process. Currently the simplified methods complement the use of FEM in different ways, in the pre-dimensioning of the structural elements and providing an estimate of the shear and bending moments, reducing the possibility of errors during the design process. In the United States, AASHTO LRFD (2012) provides a simplified method for transverse wheel load distribution into their regulatory specifications that requires only the calculation of a load distribution factor. The objective of this work is to evaluate if this method can be used as a rational alternative for the design of bridges in Brazil. For this purpose, it was necessary to understand the difference between Brazilian and American standards, suggest a calculation model based on the American standard that meets Brazilian regulation and validate this model with FEM analysis and other simplified methods. The finite element models were validated by the comparison of the results of its analysis with the results of actual load tests on bridges performed by other authors. Safe results are obtained for all analyzed cases when using the proposed calculation model, therefore it was able to determine the transverse wheel load distribution and the maximum displacement of the stringers of bridges with only one span and concrete beams. In bridges with steel beams, the method also obtained safe results in the analysis of transverse wheel load distribution, but just as the others simplified methods, it is not able to determine the maximum displacements with high reliability. It follows, therefore, that the proposed methodology can be used in the design of bridges with one span in Brazil, if the applicability limits are specified.

Vector field topology has a long tradition as a visualization tool. The separatrices segment the domain visually into canonical regions in which all streamlines behave qualitatively the same. But application scientists often need more than just a nice image for their data analysis, and, to best of our knowledge, so far no workflow has been proposed to extract the critical points, the associated separatrices, and then provide the induced segmentation on the data level. We present a workflow that computes the segmentation of the domain of a 2D vector field based on its separatrices. We show how it can be used for the extraction of quantitative information about each segment in two applications: groundwater flow and heat exchange.

No description available.