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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.
71

Enklare redovisning : Granskning av Statens Offentliga Utredning 2008:67 / Simplified Accounting : Review of the Swedish Government Official Report 2008:66

Lexell, Anna, Lindstedt, Kristina, Valkonen-Evertsson, Marina January 2009 (has links)
<p>Regeringen gav år 2007 en grupp i uppdrag att leda förenklingen gällande enklare redovisning som en del av det stora förenklingsarbetet i Sverige. Förenklingsarbetet går ut på att sänka de administrativa lagreglerade kostnaderna för svenska företag med 25 procent till 2010. Under 2008 presenterades en av åtgärderna inom förenklingsarbetet; ”Delbetänkandet om Enklare redovisning – SOU 2008:67”.</p><p>Några av de föreslagna förändringarna innebära att normgivande organ och i synnerhet Bokföringsnämnden ges mer ansvar genom utökad normgivning. I och med att förslaget presenterar flera ändringar som kan påverka företag, intressenter och revisorer, var det intressant att undersöka remissinstansernas svar och kommentarer till utredningen. Samtidigt var det intressant och se hur revisorer ser på utredningen, då de ofta har en annan insynsvinkel. Syftet lyder därför som följer:</p><p><p><em>Syftet med denna uppsats är att undersöka hur revisionsbolag och remissinstanser till SOU:n uppfattar förslaget om Enklare redovisning (SOU 2008:67).</em></p><p>Undersökningen är gjord utifrån en så kallad fenomenografisk metod, vilket innebär att det endast är remissinstansernas och revisorernas uppfattningar som har undersökts – inte hur det faktiskt är. En stor del av arbetetstiden har distribuerats till att läsa, tolka och förstå utredningen samtidigt som mycket av innehållet har fått kompletterats och undersökts i annan litteratur. Intervjuerna har gjorts via personliga möten samt internetbaserade dialoger i form av e-post.</p><p>Resultatet visar att alla välkomnar förenklingsarbetet och anser att det är viktigt, då svenska företag ska ha en jämförlig konkurrensmöjlighet gentemot europeiska företag. Vissa av aspekterna, såsom borttagandet av det vanliga årsbokslutet, har bemötts positivt av remissinstanserna, men inte från revisorerna. Slutsatsen av detta är att från ett bredare intressentperspektiv, spelar inte det vanliga årsbokslutet en avgörande roll. Borttagandet av förvaltningsberättelsen för mindre företag anses som onödigt då den mesta informationen ändå kommer att bibehållas i noterna. Då de flesta mindre företag har mer eller mindre standardiserade förvaltningsberättelser, innebär det ändå ingen förenkling, utan kanske till och med en försvåring.</p></p> / <p>During 2007, the Swedish government issued a group to be in charge of the simplification regarding simpler accounting as a part of the large simplification in Sweden. The goal is to lower the administrative costs that are regulated by law with 25 per cent until 2010. During 2008, one of the Swedish Government Official Reports regarding the simplification was presented named; ”Delbetänkandet om Enklare redovisning – SOU 2008:67”.</p><p>Some of the suggested changes would result in that normative organs, and especially the Swedish Accounting Standard Board, should be given more responsibility through standardsetting. Since the proposal presents several changes that could affect companies, interested parties and auditors, the authors found it interesting to investigate the answers and comments from consultation bodies of the proposal. At the same time, it was interesting to investigate how the auditors perceive the proposal, since they often has another point of view. The purpose is therefore:</p><p><p><em>The purpose with this thesis is to investigate how auditing firms and consultation bodies to the Swedish Government Official Report perceive the proposal regarding simplified accounting. (SOU 2008:67)</em></p><p>The investigation is done from a phenomenographical method, which means that it is only the consultation bodies and the auditors’ perception that is investigated – not how the reality actually is. A large part of the working hours has been distributed to read, interpret and understand the investigation. At the same time, a lot of the content had to be complemented and investigated in literature. The interviews have been done through face-to-face dialogues and via e-mail dialogues.</p><p>The result shows that everyone welcomes the simplification and believes it is important, since Swedish companies should have an even chance towards the rest of Europe when it comes to competition. Some of the aspects, such as the removal of the “ordinary” annual accounts, have been treated positively from the consultation bodies, but not from the auditors. The conclusion from this is that from the interested parties’ point of view, the ordinary annual accounts are not considered to be of great importance. The removal of the management report for smaller companies is perceived as unnecessary, since most of the content will be kept and placed in the notes. Since most of the smaller companies have more or less standardized management reports, will the change not result in a simplification,</p><p>but perhaps instead make it even more difficult.</p></p>
72

Assessment of tools for environmentally preferable procurement with a life cycle perspective : the case of acquisition in Swedish defence

Hochschorner, Elisabeth January 2004 (has links)
<p>Procurement in public and non-public organisations has the potential to influence product development towards more environmentally preferable products. In 2003, public procurement in Sweden was 28% of GDP. Different types of approaches can contribute some knowledge and thereby facilitate the choice of environmentally preferable products. The thesis focuses on procurement in Swedish Defence. According to a decision by the Swedish government in 1998, the Swedish Armed Forces (SAF) and Defence Materiel Administration (FMV) are required to take environmental consideration in all phases of the acquisition process. The importance of a life cycle perspective is stressed in several SAF and FMV environmental documents. The starting point of this thesis was that environmental consideration should be taken in the Swedish acquisition of defence materiel, considering the whole life cycle of products. The aim was to produce suggestions for how this can be done.</p><p>In order to make this suggestion some Ecodesign tools were reviewed and evaluated and two methods for simplified Life Cycle Assessment (LCA) were compared. Suggestions of tools and methodology recommendations for environmentally preferable procurement in the Swedish defence are presented. For this purpose qualitative and/or simplified LCAs were suggested. The suggestions have been evaluated through interviews with actors in the process. When a simplified LCA is needed, the MECO assessment is recommended. Methodology recommendations for use of the MECO method in the Swedish Defence are presented. LCA is an appropriate tool for taking environmental consideration into the acquisition process, since it focuses on a product and includes its life cycle. If the environmental work lacks a life cycle perspective, there is a risk that the most significant aspects will not be considered. Four areas for use of LCA in the acquisition process were identified: Learning about environmental aspects of the product; fulfilling requirements from customers; setting environmental requirements; and choosing between alternatives.</p><p>The actors interviewed were interested in using LCA methods, but there is a need for an initiative by one or several actors if the method is to be used regularly in the process. It is important that the results are communicated within the organisations involved in the procurement process. Environmental consideration should preferably be taken early in the acquisition process and environmental questions should be integrated into other activities of the organisations involved in the procurement process. Such work would be facilitated if there were greater cooperation between the procuring and environmental units, in this case at FMV, SAF and the Swedish Ministry of Defence.</p> / QC 20100616
73

Vertical-flow constructed wetlands for the treatment of wastewater and stormwater from combined sewer systems

Arias Lopez, José Luis 30 September 2013 (has links) (PDF)
French vertical-flow constructed wetlands (VFCW) directly treating raw wastewater are known to perform well on for SS, COD and nitrification. They are also known to robustly cope with hydraulic overloads during rainfall events. Although numerous systems have been installed in areas equipped with a combined sewer, the limits of stormwater acceptance remain ill-defined and need to be improved. Looking at the various VFCW designs and usages reported in the literature, it is difficult to draw any consensus on their hydraulic limits. Consequently, designing VFCW to accept hydraulic overloads is a complex task, as local context strongly impacts inlet flows produced during rainfall events. Dynamic models appear a requisite for filter design in such cases. Numerical CW models have essentially focused on horizontal flow, with few attempting to study VFCW dynamics which are more commonly tackled via mechanistic models. Although mechanistic models are powerful tools for describing processes within the VFCW, they are generally too complicated to be readily used by designers. The choice between detailed description and easy handling will depend on the modelling aims. If the aim is a global design tool, simplified models offer a good alternative. However, the simplified models geared to studying VFCW dynamics are extremely reduced. They are easy-handling for design and well-adapted to specific purposes (combined sewer overflow -CSO- treatment) but not necessarily to VFCW treating combined sewer wastewater, where long-term infiltration rates vary significantly. Consequently, this PhD thesis work focused on developing a simplified hydraulic model of VFCW to guide designers through the process of adapting VFCW systems to treat domestic wastewater in both dry and rain events. The simplified model makes it possible to link (i) hydraulics, by simulation of ponding time variations, (ii) biological performances, by establishing "dysfunction alerts" based on treatment performance assessment and variations in online N forms effluent from the young VFCW. These "dysfunction alerts" plot the maximal hydraulic load that a filter can accept without compromising its biological activity. The simplified model was used to model long-term hydraulics in the VFCW (i) to analyze the impact of local context and filter design on hydraulic overload acceptance (using "dysfunction alerts" and bypass discharges) and (ii) to propose VFCW designs for accepting hydraulic overload in different contexts. The modelling demonstrates that VFCW can limit days with bypass discharges to less than 20 times per year without jeopardizing filter performances. Moreover, the most problematic scenario on stormwater treatment remains a watershed with high imperviousness coefficient and low slope under a Bretagne-type climate, demonstrating that the filter is more sensitive to periodicity and duration than to intensity of rainfall events.
74

Neutron transport in hexagonal reactor cores modeled by trigonal-geometry diffusion and simplified P3 nodal methods

Duerigen, Susan 01 October 2013 (has links) (PDF)
The superior advantage of a nodal method for reactor cores with hexagonal fuel assemblies discretized as cells consisting of equilateral triangles is its mesh refinement capability. In this thesis, a diffusion and a simplified P3 (or SP3) neutron transport nodal method are developed based on trigonal geometry. Both models are implemented in the reactor dynamics code DYN3D. As yet, no other well-established nodal core analysis code comprises an SP3 transport theory model based on trigonal meshes. The development of two methods based on different neutron transport approximations but using identical underlying spatial trigonal discretization allows a profound comparative analysis of both methods with regard to their mathematical derivations, nodal expansion approaches, solution procedures, and their physical performance. The developed nodal approaches can be regarded as a hybrid NEM/AFEN form. They are based on the transverse-integration procedure, which renders them computationally efficient, and they use a combination of polynomial and exponential functions to represent the neutron flux moments of the SP3 and diffusion equations, which guarantees high accuracy. The SP3 equations are derived in within-group form thus being of diffusion type. On this basis, the conventional diffusion solver structure can be retained also for the solution of the SP3 transport problem. The verification analysis provides proof of the methodological reliability of both trigonal DYN3D models. By means of diverse hexagonal academic benchmark and realistic detailed-geometry full-transport-theory problems, the superiority of the SP3 transport over the diffusion model is demonstrated in cases with pronounced anisotropy effects, which is, e.g., highly relevant to the modeling of fuel assemblies comprising absorber material.
75

Pagreitintas procesas: reglamentavimo ir taikymo problemos / Accelerated process: problems of legal regulation and its application

Roščinienė, Kristina 28 January 2008 (has links)
Darbe analizuojamos Lietuvos Respublikos baudžiamojo proceso kodekso (LR BPK), XXXI skyriaus, antrame skirsnyje, įtvirtinto pagreitinto proceso instituto problemos. Pirmiausia remiantis Lietuvos ir užsienio moksline literatūra yra supažindinama su sąvokomis: baudžiamasis procesas ir forma. Plačiau analizuojama supaprastinto proceso samprata, jo formos, pagreitinto proceso sąvoka ir samprata. Aptariami pagreitintą procesą įtakoję Vokietijos ir Prancūzijos pagreitinto proceso modeliai bei iki 2003-05-01 Lietuvoje galiojęs sumarinis procesas. Jis lyginamas su pagreitintu procesu, kaip labiausiai nulėmęs pagreitinto proceso taikymo praktiką. Didžiausias dėmesys, žvelgiant per hipotezės „pagreitinto proceso taikymo problemų kilimą praktikoje įtakoja ne tik įstatyminis reguliavimas, bet ir praktikos vienodinimo teisės aktai, taip pat žmonių psichologija ir organizacijų vadyba“ prizmę, skiriamas pagreitinto proceso procedūrai nagrinėti. Analizuojamos ikiteisminio tyrimo ir teisminio nagrinėjimo apylinkės teisme stadijos. Darbe aptariamos teorinės ir praktinės problemos aštriausiais klausimais: normų kolizijos, baudžiamojo proceso principų ir įtariamojo procesinių garantijų užtikrinimo, galimybės nepateikti teismui jokios ikiteisminio tyrimo medžiagos, aiškių nusikaltimo padarymo aplinkybių suvokimo, pagreitinto proceso taikymo sunkiems nusikaltimams, tyrimo termino klausimais. Gvildenamos kitos – vadybinės ir psichologinės problemos, tiesiogiai įtakojančios praktines problemas. / The final Master's paper work analyses problematic aspects of the institute of the accelerated process legitimated in the XXXI chapter of the Lithuania code of criminal procedure. First of all, referring to the Lithuanian and foreign scientific literature the following concepts are introduced: the criminal process and its form. The concept and forms of the simplified process as well as the concept of the accelerated process are analyzed more precisely. The models of the accelerated process in Germany and France and the summary process valid in Lithuania till May 01, 2003 and their influence to the development of the accelerated process are discussed. The summary process is compared to the accelerated process as the most determining feature to the practice of accelerated process. The most attention is paid to the analysis of the procedure of the accelerated process looking in the light of hypothesis “the change of problems of the practical appliance of accelerated process are influenced not only by legal regulation but also by practical regulation as well as human psychology and organizational management”. Stages of pre-trial investigation and trial in the district court are being analyzed. The following sensitive problems are discussed in this paper work: collision of legal norms, the assurance of the principals of criminal process and process guarantees of the suspect, possibility not to present any pre-trial investigation material to the judge, clear perception of... [to full text]
76

Caractérisation expérimentale et numérique du chargement généré par une explosion sur un bâtiment / Experimental and numerical characterization of the load generated by an explosion on a building

Blanc, Ludovic 09 December 2016 (has links)
Les travaux présentés dans ce mémoire s'inscrivent dans le cadre de deux projets, l'un européen, BASIS (Blast Actions on Structure In Steel), et l'autre français BATIRSÛR (Bâtiment en acier en zone PPRT de surpression), qui visent à mieux appréhender la vulnérabilité des bâtiments à ossature métallique face à un aléa de surpression. En particulier, ce travail a consisté à étudier les interactions entre une onde de souffle et une structure afin de caractériser le chargement global induit par une explosion. À partir de la génération d’ondes de souffle par détonation ou déflagration d'une charge gazeuse de propane oxygène, des campagnes expérimentales à petite échelle ont été conduites. Elles ont permis de mettre en défaut pour les faibles niveaux de surpressions étudiés (< 200 mbar) certaines approches simplifiées existantes. Des alternatives ont alors été proposées. Les coefficients de réflexion, caractérisant le chargement, ont été mesurés. De nouvelles valeurs sont proposées, notamment pour caractériser la diffraction d'une onde issue d'une déflagration. Les données du chargement résultant d’une déflagration et d’une détonation ont été comparées dans des configurations identiques. La propagation en champ libre de l’onde de souffle issue d’une déflagration a été reproduite au moyen du modèle du piston sphérique. Pour une de détonation, un modèle prédictif de ballon d'air comprimé, reposant sur la donnée de la masse volumique et l’énergie interne spécifique de l’explosif, a été développé et validé en champ lointain par comparaison avec les essais expérimentaux. Son utilisation a permis de mettre en évidence les atouts et les limites des simulations numériques pour reproduire le chargement. / The work presented in this thesis fall within two project, one European, BASIS (Blast Actions on Structure In Steel), and the other French BATIRSÛR (steel building in PPRTs area overpressure), which both aimed at better understanding the vulnerability of metal framed buildings against an overpressure hazard. In particular, our objective was to study the interaction between a shock wave and a structure in order to characterize the overall loading induced by an explosion. From the generation of blast wave by deflagration or detonation of an oxygen propane mixture, small-scale experimental campaigns were conducted. These experimental campaigns highlighted for low levels of overpressure (<200 mbar) some limitations in the existing simplified approaches. Alternatives have then been given. Reflection coefficients, characterizing the loading, were measured. New values were obtained, especially to characterize the diffraction. Data resulting from deflagration and detonation we recompared under identical configurations. The free field propagation of the blast wave generated by a deflagration was reproduced by using the model of the spherical piston. For a detonation, a predictive model of compressed balloon based on the data of the density and the specific internal energy has been developed and validated in far-field range using comparison with experimental tests. Its use has helped highlight the assets and limits of numerical simulation in order to reproduce the loading induced by a detonation.
77

Comparação de modelos hidrodinâmicos simplificados de propagação de vazão em rios e canais

Pontes, Paulo Rógenes Monteiro January 2011 (has links)
Esse trabalho identificou, testou e aprimorou modelos de propagação de vazão simplificados a fim de verificar as vantagens e desvantagens dos modelos. As soluções apresentadas por esses modelos foram testadas com um modelo hidrodinâmico completo, considerado nesse trabalho como resultados ideias. Os modelos hidrodinâmicos simplificados testados foram: Um modelo não linear de Onda Cinemática, o modelo Muskingum-Cunge linear, duas versões do modelo Muskingum-Cunge não linar, o modelo Muskingum-Cunge modificado por Todini e o modelo IPHS1. O modelo hidrodinâmico completo utilizado nesse trabalho foi o modelo HEC-RAS. Desenvolveu-se ainda uma metodologia para representar o efeito da planície de inundação. Essa metodologia foi implementada nos modelos hidrodinâmicos simplificados. Para avaliar o comportamento dos diferentes modelos de propagação disponíveis foram criados testes numéricos em que foram aplicados os diferentes modelos, com variação de características dos hidrogramas sintético de entrada, das características do leito do rio e da planície de inundação, e dos critérios de discretização temporal e espacial. A avaliação dos resultados foi feita através dos erros de conservação de volume, de vazão de pico e de tempo de ocorrência da vazão de pico. Além disso, também foram considerados, em alguns testes, os critérios de aplicabilidade de Ponce para onda cinemática e difusão além da formulação do Δx ideal proposto por Fread. Os resultados mostram que o modelo Muskingum-Cunge Todini, modificado para representar o efeito da planície de inundação, é muito promissor. Esse modelo apresentou resultados que se aproximaram muito dos resultados obtidos pelo HEC-RAS, enquanto os outros modelos hidrodinâmicos simplificados apresentaram resultados piores. Com relação aos critérios de aplicabilidade, recomenda-se o uso de um Δx três vezes menor do que o valor sugerido por Fread. Além disso, pode-se concluir que os modelos simplificados podem ser utilizados fora dos limites de aplicabilidade sugeridos por Ponce. / This work has identified, tested and improved simplified flood routing models to verify the advantages and disadvantages presented. The solutions provided by these models were tested by using a full hydrodynamic model considered in this work as an ideal result. The simplified hydrodynamic models used were: A variable parameter kinematics wave model, the Muskingum-Cunge flood routing model, the variable parameter Muskingum-Cunge flood routing model (three and four points scheme) the Muskingum-Cunge modified by Todini (MCT) and the model IPHS1. The full hydrodynamic model used was HEC-RAS. It was also proposed a procedure to represent the effect of the floodplain rivers. To evaluate the behavior of different flood routing models numerical tests were created and were applied to then. The characteristics of synthetic inflow hydrographs, the characteristics of riverbed and floodplain, and the criteria for temporal and spatial discretization were perturbed. The evaluation of the results was made through the errors of conservation of volume, peak flow and time of occurrence of peak flow. Moreover, it was also considered, in some tests, applicability criteria recommended by some authors for different models, such as models of kinematic flood wave and diffusive flood wave. The results show that the Muskingum Cunge Todini, modified to represent the effect of the floodplain flow is very promising. Finally, it is also shown that this model closely approaches the full Saint Venant equation solution (HEC-RAS). The others models were worse than HEC-RAS and MCT. About applicability criteria, it recommends the use of the Δx three times smaller than the value suggested by Fread. Moreover, the simplified hydrodynamic models can be used outside limits of applicability suggested by Ponce about kinematic and diffusive wave.
78

Assemblages collés : modélisation, simulation et caractérisation expérimentale / Adhesively Bonded Joints : Modeling, Simulation and Experimental Characterization

Lélias, Guillaume 08 July 2016 (has links)
Dans le cadre d'un projet de recherche interne nommé JoSAT (Joint Stress Analysis Tool), Sogeti High Tech a développé depuis 2008 un outil de simulation simplifié d'analyse de joints collés. Cet outil permet d'obtenir à la fois la répartition des efforts internes dans chacun des substrats mais également la répartition des contraintes adhésives le long du recouvrement, tout en ayant l'avantage d'être beaucoup moins chronophage que la méthode des Éléments-Finis (EF). En 2011, cet outil a été étendu de sorte à supporter différents comportements adhésifs non-linéaires sous la forme de relations contrainte-déformation spécifiée par l'utilisateur. Cependant, le champs d'application de cette nouvelle théorie fut démontré comme limitée aux jonctions en simple recouvrement, et dans le cas de faible non-linéarité uniquement. Dans ce contexte, l'objectif de la thèse est double. Premièrement, étendre et valider l'outil d'analyse simplifiée aux cas de comportement non-linéaire adhésif mais également des substrats. Deuxièmement, proposer et développer de nouvelles méthodes visant à caractériser le comportement non-linéaire d'un film adhésif. / In the frame of an internal research program called JoSAT (Joint Stress Analysis Tool), SogetiHigh Tech has suggested developing since 2008 a simplified tool for the stress analysis ofadhesively bonded joints. This tool allows for the distribution of both the internal forces anddisplacements in the adherends as well as the adhesive stresses along the overlap to beestimated from specified loads and boundary conditions, and has the advantage of beingextremely time saving compared to conventional Finite Element (FE) analyses.In 2011, this tool was extended to support adhesive material nonlinearities in the form ofspecified adhesive stress-strain evolution laws. However the theory developed wasdemonstrated as valid for the Single-Lap Joint (SLJ) configuration only, and limited to smalllevels of adhesive material nonlinearities. In this context, the objective of the thesis is double. First, extend and validate the simplified tool for the analysis of adhesively bonded joints in the case of nonlinear adhesive as well asadherends stress-strain constitutive behaviors. Then, suggest and develop experimentalprotocols for the characterization of the cohesive properties of thin adhesive layers so that thesimplified tool can be sustained with relevant experimental data in terms of adhesive stressstainconstitutive relationships.
79

Modélisation simplifiée des processus de laminage / Simplified modeling of rolling process

Le Dang, Huy 10 December 2013 (has links)
L'objectif initial de la thèse était de proposer une nouvelle modélisation simplifiée du laminage permettant un calcul rapide, si possible en temps réel, afin que le modèle soit éventuellement intégré à un outil de pilotage des machines de production. Ce modèle ne doit pas négliger les déformations élastiques afin de pouvoir être éventuellement appliqué à l'étude de phénomènes associés à la variation de largeur de la bande ou à des phénomènes de planéité. Il doit par ailleurs être assez ouvert pour que l'on puisse y intégrer éventuellement une description de la microstructure du matériau polycristallin et prendre en compte la déformation des cylindres de laminage. Pour atteindre cet objectif, nous avons proposé de tenter de construire un modèle simplifié semi-analytique du laminage. Dans ce type de modèle, le gradient de la transformation globale peut alors être décomposé multiplicativement en un produit d'une première transformation locale « plastique » , qui transforme le voisinage local initial de dans la configuration relâchée, par une seconde transformation locale « élastique » qui transforme la configuration relâchée dans la configuration actuelle . Cette décomposition est à la base de l'analyse thermodynamique de l'évolution mécanique lorsque le matériau subit de grandes transformations élastoplastiques, laquelle analyse fournit les concepts d'efforts intérieurs et de variables d'état nécessaires à l'écriture de ce comportement. Nous avons montré deux approches permettant le calcul analytique de ces champs lorsque l'histoire de est connue au voisinage d'une particule .Nous avons ensuite proposé l'étude d'une classe particulière d'évolutions élastoplastiques que nous avons appelées « simples radiales » et nous avons montré que les évolutions obéissaient à un principe de minimum énergétique. Nous avons enfin conjecturé que ce principe pouvait être étendu en régime permanant pour permettre de construire une modélisation simplifiée des processus de laminage / The initial aim of the thesis was to propose a new simplified model for rolling allowing a rapid calculation, if possible, in real time, so that the model would eventually integrate into a management tool production machines. This model should not neglect the elastic deformations in order to be applied to the study of phenomena associated with the change in bandwidth or flatness phenomena. It must also be open enough that we can integrate the description of microstructure of polycrystalline material and possibly take into account the deformation of rolling rolls. To achieve this goal, we proposed to build a simplified semi-analytical model of rolling. In this type of model, the gradient of global transformation can be multiplicatively decomposed of the first local transformation "plastic" which transforms the initial local neighborhood of in the relaxed configuration, and the second local transformation "elastic" which transforms the relaxed configuration in the current configuration. This decomposition is the basis of thermodynamic analysis of the mechanical evolution when the material undergoes large elastoplastic transformations, which provides the concepts of internal forces and necessary variable state to write this behavior. We showed two approaches to the analytical calculation of the mechanical fields when the history of was known in the neighborhood of particle .We then proposed to study a particular class of elastoplastic evolution that we called "simple radial" and we showed that the evolutions followed the principle of minimum energy. Finally, we conjectured that this principle can be extended in steady state, which allowed to build a simplified model of the rolling process
80

Aspectos relacionados com o impacto semi-frontal em ônibus rodoviário

Goedel, Fábio January 2013 (has links)
O comportamento estrutural de veículos de transporte coletivo, quando submetido a eventos de impacto, é de grande relevância na engenharia automobilística, pois principalmente o ônibus, vem se tornando um dos meios de transporte de elevada importância, sendo que seu uso vem aumentando a cada ano. No entanto, as estruturas de ônibus que circulam nas estradas brasileiras não são capazes de resistir, sem causar danos aos passageiros, a eventos de impacto em acidentes, o que pode ser verificado em pesquisas divulgadas pela Agência Nacional de Transportes Terrestres (ANTT) em 2007, que mostra a evolução de acidentes e vítimas envolvendo ônibus, que cada ano aumentam consideravelmente. Neste contexto, pretende-se desenvolver um absorvedor de impacto que aumente a capacidade de absorção da energia de impacto e evite a invasão da região de sobrevivência dos passageiros, e desta forma diminuindo o número de vítimas em acidentes. Serão abordados neste trabalho eventos de impacto semi-frontal, justificado pela gravidade dos acidentes desse tipo nas estradas, sendo este o tipo de acidente que deixa um maior número de vítimas, pois geralmente parte da estrutura lateral do ônibus é removida, expondo os passageiros no período de impacto. Esse efeito é conhecido como “Efeito Abridor de Latas”. O modelo numérico deste trabalho será formado por elementos unifilares, sendo a estrutura do ônibus formada por vigas flexíveis e/ ou rígidas, unidas através de juntas não lineares rotacionais e translacionais. A rigidez de cada junta não linear é obtida a partir de métodos analíticos que descrevem o comportamento do tubo de parede fina quando submetido a impacto. / The structural behavior of transportation vehicles when subjected to events of impact is of great relevance in automotive engineering, mainly because the bus has become a highly important alternative means of transportation, and its use is increasing every year. However, the structures of the buses circulating on Brazilian roads are not able to withstand strong impact, without causing passengers’ injury in events where accidents occur, which can be shown in surveys released by the National Transport Agency (ANTT) in 2007, presenting that the great incidence of accidents with victims involving buses is increasing considerably every year. In this context, the development of an impact absorber that had the capability to increase the impact energy absorption and prevent the invasion of part of bus on the region where passengers are located (reducing the number of fatalities in accidents) are the objectives of this work. In this work, a semi-frontal impact will be presented and studied due to the severity of such accident, as the side of the bus structure is removed, exposing the passengers during the impact. This is the effect known as “Can opener effect”. The numerical model of this study will consist of a single-wire element, with a bus structure formed by flexible and/or rigid beams joined by nonlinear rotational and translational joints. The rigidity of each nonlinear joint is obtained by analytical methods describing the behavior of a thin-walled tube subjected to an impact force.

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