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Flots géométriques d'ordre quatre et pincement intégral de la courbure / Fourth-order geometric flows and integral pinching of the curvatureBour, Vincent 11 July 2012 (has links)
On étudie des flots géométriques d'ordre quatre sur des variétés riemanniennes compactes, qui apparaissent naturellement comme flots de gradient de fonctionnelles quadratiques en la courbure. Lorsque la constante de Yamabe reste minorée par une constante strictement positive le long du flot, on montre que la variété ne s'effondre pas, et qu'une suite de métriques dilatées au voisinage d'un temps singulier converge vers une variété complète qui modélise la singularité. En particulier, en dimension quatre, cette hypothèse est vérifiée pour une certaine classe de flots de gradients, du moment que l'énergie initiale est inférieure à une constante explicite. Les singularités de ces flots sont alors modélisées par des variétés complètes et non compactes, dont le tenseur de Bach et la courbure scalaire s'annulent. En combinant une formule de Weitzenböck avec l'inégalité de Sobolev induite par la positivité de la constante de Yamabe, on montre une série de résultats de rigidité pour des métriques dont la courbure est intégralement pincée. En particulier, on prouve un théorème de rigidité pour les variétés de dimension quatre à tenseur de Bach et à courbure scalaire nuls, qui implique que les singularités de notre classe de flots de gradient ne peuvent exister que si l'énergie initiale est supérieure à une certaine constante. Dans le cas contraire, ces flots existent pour tous temps positifs et convergent vers une métrique à courbure sectionnelle constante et positive. On retrouve ainsi un "théorème de la sphère" pour les variétés compactes de dimension quatre dont la courbure est intégralement pincée. En appliquant cette même méthode aux formes harmoniques d'une variété à courbure intégralement pincée, on démontre une version intégrale du théorème de Bochner-Weitzenböck. On en déduit l'annulation des nombres de Betti sous diverses conditions de pincement intégral, et on caractérise les cas d'égalité. / We study fourth-order geometric flows on compact Riemannian manifolds, which naturally appear as gradient flows of quadratic curvature functionals. When the Yamabe constant remains bounded from below by a positive constant along the flow, we show that the manifold doesn't collapse, and that a sequence of dilated metrics near a singular time converges to a singularity model. In particular, in dimension four, this assumption is satisfied by a class of gradient flows, provided that the initial energy is less than an explicit constant. The singularities of these flows are then modeled by complete non-compact manifolds, which are Bach-flat and scalar-flat. By combining a Weitzenböck formula with the Sobolev inequality induced by the positivity of the Yamabe constant, we prove several rigidity results for metrics with integral pinched curvature. In particular, we prove a rigidity result for Bach-flat and scalar-flat manifolds in dimension four, which implies that the singularities of our gradient flows can only exist when the initial energy is bigger than a given constant. When this is not the case, these flows exist for all time, and converge to a metric with constant positive curvature. It provides a proof of a "sphere theorem" for closed four-dimensional manifolds with integral pinched curvature. Applying the same method to harmonic forms on an integral pinched manifold, we prove an integral version of the Bochner-Weitzenböck theorem. As a corollary, we obtain the vanishing of Betti numbers under various integral pinching conditions, and we characterize the equality cases.
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Efeito da história experimental na sensibilidade às contingências em participantes flexíveis e inflexíveisZerbinatti, Ana Lídia Fonseca 07 April 2016 (has links)
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Previous issue date: 2016-04-07 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / This study aimed to investigate whether a previous history of learning by
instructional control, in both the previous story of the subject or immediately
following an experimental condition, could differentially affect the sensitivity to
contingencies. Replicating previous studies, the authors sought to address a possible
history of control by following rules, assessing the presence of flexibility or
inflexibility indicator’s in their repertoire. Therefore, we evaluated 212 undergraduate
students who responded to the Rigidity Scale of Rehfisch; 114 were implemented by
virtual media and 98 during individual meeting. Of the 23 participants assessed who
met inclusion’s criteria, 13 agreed to participate in the study, seven were recruited by
personal application and six through online assessment. Eight participants were males
and five females, aged 18-31; nine participants presented scores agreed as flexible
and 4 others as inflexible. The experimental condition is the execution of tasks on a
matching-to-sample schedule (MTS), arranged in two phases, through appropriate
software. In Phase 1, the participants were divided into the training of two different
instructional conditions: 1) instructions corresponding to the contingencies
programmed; and 2) discrepant instructions. Considering the participants of the
Group Flexible, 5 were exposed to instructional correspondence training and 4 the
discrepancy; two inflexible participants were assigned to each instructional training
conditions. Eleven of thirteen participants reach the learning criteria, required in
Phase 1, during 69 or less trials; the two participants who did not meet the criteria
were allocated in the Flexible Group (P167 and P184) and were submitted to the
discrepant training. In Phase 2 was scheduled during a single experimental condition,
similar to all participants, with the presentation of 80 trials, divided into 4 blocks of
20 each. The first and third blocks have been programmed accordingly to the
instructions; the second and fourth block presented contingencies that were
instructions’ discrepant. Six of the nine flexible participants presented a percentage of
responses equal to or greater than 70% accuracy, in the first block of discrepant trials,
during the Phase 2; two of the three participants presented lower percentage of correct
answers, had a history of learning by discrepant instructions. Participants of the
inflexible Group showed higher percentage of correct answers, when they had been
subjected to a discrepancy during in training. It was addressed how these results
either replicate or present differences from the literature in the area. / O presente estudo teve como objetivo investigar se uma história prévia de
aprendizagem por controle instrucional, anterior às condições experimentais, ou uma
história de exposição a regras correspondentes ou discrepantes poderiam afetar
diferencialmente a sensibilidade às contingências. Replicando estudos anteriores, os
autores buscaram endereçar uma possível história prévia de controle por seguimento
de regras, avaliando a presença de indicador de flexibilidade ou inflexibilidade no
repertório. Para tanto, foram avaliados 212 estudantes universitários que responderam
à Escala de Rigidez de Rehfisch; 114 foram implementados por mídia virtual e 98
presencialmente. Dos 23 participantes avaliados que atingiram critério de inclusão, 13
aceitaram participar do estudo, sendo (07) recrutados por aplicação presencial e seis
(06) na condição online. Oito participantes eram do sexo masculino e cinco do
feminino, com idade variando de 18 a 31 anos; nove obtiveram escores
convencionados como flexíveis e 4 como inflexíveis. A condição experimental
consistia na realização de tarefas programadas num procedimento de escolha de
acordo com o modelo (MTS), organizado em duas fases, através de software
apropriado. Na Fase 1, os participantes foram divididos em duas condições de
aprendizagem de seguimento de instruções: 1) instruções correspondentes às
contingências em operação; e, 2) instruções discrepantes das mesmas. Dos
participantes flexíveis, 5 foram expostos a treino de correspondência instrucional e 4
à discrepância; dois participantes inflexíveis foram designados para cada uma das
condições de treino instrucional. Onze dos treze participantes alcançam os critérios de
aprendizagem, exigidos na Fase 1, com 69 tentativas ou menos; os dois participantes
que não atingiram os critérios estavam alocados do Grupo Flexível (P167 e P184), na
condição de treino discrepante. Na Fase 2 foi programada uma única condição
experimental, similar para todos os participantes, com a apresentação de 80 tentativas,
divididas em 4 blocos de 20 tentativas cada. O primeiro e o terceiro foram
programados de forma correspondente às instruções; no segundo e no quarto bloco, as
contingências programadas eram discrepantes das instruções. Seis dos nove
participantes flexíveis, apresentaram uma porcentagem de respostas igual ou maior
que 70% de acertos, no primeiro bloco de tentativas discrepantes da Fase 2; dois dos
três deste grupo com menor porcentagem de acertos tinham uma história de
aprendizagem por instrução discrepante. Participantes do Grupo inflexível mostraram
maior porcentagem de acertos, quando haviam sido submetidos a um treino de
discrepância entre instrução e contingências. Discute-se como estes resultados
replicam ou divergem da literatura na área.
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HipersuperfÃcies com bordo livre e rigidez de superfÃcies mÃnimas / Hypersurfaces with free board and rigidity of minimal surfacesCÃcero Tiarlos Nogueira Cruz 27 February 2015 (has links)
CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / Nesta tese, provamos estimativas para o volume e Ãrea do bordo de hipersuperficies estÃveis ∑n-1 com invariante de Yamabe nÃo positivo satisfazendo à condiÃÃo de bordo
livre em uma variedade Riemanniana de dimensÃo n com limitaÃÃo na curvatura escalar e curvatura mÃdia do bordo. Supondo ainda que ∑ Ã localmente minimizante de volume em
uma variedade M com curvatura escalar limitada inferiormente por uma constante nÃo positiva, concluÃmos que localmente M divide-se ao longo ∑ como (-Є, Є)x ∑, para algum Є > 0. No caso em que ∑ localmente minimiza um funcional adequado inspirado pelo trabalho de Yau (2001), uma vizinhanÃa de ∑ em M à isomÃtrica a ((-Є, Є) x ∑, dt2 +e2tg), onde g à Ricci plana. Na segunda parte, estudamos outro fenÃmeno de rigidez pela curvatura escalar adaptando a tÃcnica desenvolvida por MÃximo e Nunes (2013) para mostrar um resultado local de rigidez para uma variedade Riemanniana tridimensional M3 cuja curvatura escalar à limitada inferiormente por um constante negativa. Provamos o seguinte resultado: Seja ∑2 ⊂ M3 uma superfÃcie mÃnima estritamente estÃvel que localmente maximiza a massa Hawking em M. EntÃo M perto de ∑ à um pedaÃo de um dos espaÃos de Kottler. / In this thesis, we prove estimates for the volume and boundary area of stable hypersurfaces ∑n-1 with nonpositive Yamabe invariant satisfying the free boundary condition in a Riemannian manifold Mn with bounds for the scalar curvature and the mean curvature of the boundary. Assuming further that ∑ is locally volume-minimizing in a manifold M with scalar curvature bounded below by a nonpositive constant, we conclude that locally M splits along ∑ as (-Є, Є)x ∑, for some Є > 0. In the case that ∑ locally minimizes a certain functional inspired by the work of Yau (2001), a neighborhood of ∑ in M is isometric to ((-Є, Є) x ∑, dt2 + e2tg), where g is Ricci at. In the second part, we study other scalar curvature rigidity phenomena adapting a technique developed by MÃximo e Nunes (2013) to show a local rigidity result for three-dimensional Riemannian manifold M3 whose scalar curvature is bounded from below by a negative constant. We prove the following result: Let ∑2 ⊂ M3 be a stable minimal surface which locally maximizes the Hawking mass on M. Then M near ∑ is a piece of one the Kottler space.
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Análise estrutural de pórticos planos de elementos pré-fabricados de concreto considerando a deformabilidade das ligações / Structural analysis of precast concrete portal frames considering the semi-rigid behavior of the connectionsAnamaria Malachini Miotto Soares 19 June 1998 (has links)
Os sistemas pré-fabricados vêm conquistando espaço em todo o Brasil. Dentre eles, os pórticos planos de elementos pré-fabricados de concreto com sistema estrutural para telhado de duas águas, comumente denominados de galpões, tem sido amplamente aplicados. Os galpões, como a matona das estruturas pré-moldadas de concreto, apresentam suas ligações, em maior ou menor grau, deformáveis. Portanto, este trabalho refere-se ao estudo da deformabilidade de uma de suas ligações: a ligação viga-pilar executada através de consolo e chumbador, e da sua influência na distribuição dos esforços solicitantes destas estruturas. Neste sentido, foram realizadas simulações numéricas, com o emprego do Método dos Elementos Finitos e ensaios físicos. Através do ensaio físico realizado no modelo da ligação viga-pilar foi possível determinar sua deformabilidade à flexão e observar seu modo de ruptura. As simulações numéricas foram realizadas tanto para obter teoricamente o valor da deformabilidade à flexão da ligação em análise, como para avaliar sua influência no comportamento estrutural dos galpões pré-moldados. Com base nos resultados obtidos, foram elaboradas algumas recomendações de projeto para os galpões pré-moldados. / The use of precast concrete structures has increased in Brazil. Among them, the precast concrete portal frames with sloping beams have been extensively used in storehouses and commercial and industrial buildings. This type of portal frame, as the most precast concrete structures, has semirigid connections. So, this work deals with the study of the semi-rigid behavior of one beam-column connection type frequently used in these structures. In this kind of connection the beam rests on a corbel which has two projecting bolts connecting it. The aim of this thesis is also to determine the influence of the flexibility connection on the structure behavior. Numerical modeling applying the Finite Element Method and experimental tests were done to analyse these aspects. The test results of a beam-column model allowed the construction of the moment-rotation diagram and the failure mode observation. The numerical modeling was done to get the value of the connection flexibility and to study its influence on the precast concrete portal frame behavior. Based on the results some design recommendations were established.
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Ligações viga-pilar de estruturas de concreto pré-moldado: análise com ênfase na deformabilidade ao momento fletor / Precast concrete beam-to-column connections: emphasis on the deformability analysisAnamaria Malachini Miotto 20 December 2002 (has links)
No presente trabalho foram estudadas duas ligações viga-pilar de estruturas de concreto pré-moldado com ênfase na deformabilidade ao momento fletor. A primeira é muito utilizada em galpões com sistema estrutural de pórticos para telhado com duas águas. A segunda é utilizada em estruturas de edifícios com múltiplos pavimentos. Foram realizados ensaios físicos em dois modelos de cada tipo de ligação. Com base nos resultados experimentais, foram propostos modelos analíticos, baseados no Método dos Componentes, e realizadas simulações numéricas, baseadas no Método dos Elementos Finitos, através dos quais determinou-se a curva momento-rotação das ligações em estudo. As curvas momento rotação teóricas, para as duas ligações estudadas, ficaram bastante próximas das experimentais. De acordo com os resultados, pode-se dizer que a primeira ligação teve um comportamento próximo ao de uma ligação perfeitamente rígida. Isso porque, para uma estrutura típica, ela transmitiu mais de 90% do momento equivalente ao de uma estrutura monolítica. A segunda ligação também garantiu uma boa transferência de momento fletor. Observou-se que, ao considerar a semi-rigidez dessa ligação na análise estrutural, há uma redução significativa no momento na base dos pilares mais solicitados, o que permite uma redução na armadura dos pilares e nas dimensões da fundação / The present research deals with the study of two types of precast beam-to-column connections with emphasis on the deformability analysis. The first one is extensively used in precast concrete portal frames with sloping beams. The second one is used in multi-storey framed structures. Experimental tests on two models of each type of beam-to-column connections were done. Based on the experimental results, analytical models, based on the Component Method, were proposed and numerical simulations, based on the Finite Element Method, were developed, which provide the moment-rotation curves of the studied connections. The theoretical moment-rotation curves, for both studied connections, are in good agreement with the experimental ones. According to the results, the first connection had almost the same behaviour of a rigid one. It transmitted about 90% of the bending moment of an equivalent monolithic structure. The second connection also transmitted a good portion of bending moment. It was observed that when its semi-rigidity is considered on the structural analysis there was a significant reduction on the column base bending moment and on the foundation dimensions
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Rigidez de política fiscal e default na dívida soberanaFernandes, Renato José Rodrigues 09 April 2013 (has links)
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Previous issue date: 2013-04-09 / This work aims to investigate the quantitative implications of a fiscal policy rigidity model developed by Gonçalves e Guimaraes (2012) and to answer if it is able to generate more defaults in equilibrium without using a strong ad hoc assumption about the costs in terms of product of a default on sovereign debt in order to be able to generate the desired results according to what is observed in economic data, i.e., that defaults tend to occur in bad times. The main hypothesis of this model is that the government cannot commit to a fiscal adjustment to repay the debt that is coming due because it chooses the tax rate in the previous period. Thus, when facing a low product in a given period, the sovereign cannot adjust its revenue to meet his obligations and has to decide either to increase the level of debt or to repudiate its debt and not repay. In the results, we have that the fiscal rigidity increases the occurrence of defaults in at least one order of magnitude in comparison to other quantitative models of sovereign debt and helps to explain the occurrence of defaults in periods of low product in the Economy. / Este trabalho tem como objetivo investigar as implicações quantitativas do modelo de rigidez de política fiscal desenvolvido por Gonçalves e Guimaraes (2012) e responder se ele é capaz de gerar mais defaults em equilíbrio sem se utilizar de uma forte hipótese ad hoc acerca dos custos em termos do produto de um calote na dívida soberana, a fim de conseguir gerar os resultados desejados de acordo com o que se observa nos dados econômicos, isto é, que os calotes tendem a ocorrer em tempos ruins. A principal hipótese deste modelo é que o Governo não pode se comprometer com um ajuste fiscal para repagar a dívida que está vencendo porque ele escolhe a alíquota de imposto no período anterior. Logo, ao se deparar com um produto baixo em determinado período, o soberano não pode ajustar a arrecadação a fim de fazer frente às suas obrigações e se vê diante da decisão de aumentar o nível do endividamento ou de repudiar sua dívida e não pagá-la. Nos resultados, tem-se que a rigidez fiscal aumenta a ocorrência de defaults em pelo menos uma ordem de magnitude comparado a outros modelos quantitativos de dívida soberana e ajuda a explicar a ocorrência de calotes em períodos de baixo produto na Economia.
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Définition d'une méthodologie d'allègement de structures sous contrainte de rigidité fonctionnelle, cas d'une machine-outil. / Definition of a methodology for lightening structures constrained by a functional rigidity, case of a machine toolDeneffle, Romain 20 June 2017 (has links)
En réponse à des contraintes écologiques et économiques de plus en plus forte dans l’industrie, la problématique de réduction et de maîtrise de la consommation énergétique est aujourd’hui prise en considération dans le domaine de la machine-outil. Cette thèse s’inscrit dans le cadre du projet Green HSM porté par l’entreprise PCI-SCEMM ayant pour but de réduire la consommation énergétique d’une machine-outil de 30%. L’étude s’est focalisée sur le thème spécifique de l’allègement de structure. L’objectif est de concevoir des structures de machines-outils avec des masses mobiles les plus faibles possibles tout en gardant une rigidité fonctionnelle.Deux méthodes d’allègement de structures sont proposées dans le cadre de cette thèse. La première présente une méthode d’optimisation de structure de machines-outils par analyse de contraintes. Cette méthode a permis un allègement de deux pièces principales de la structure de 6,5% et 9% pour une réduction globale de la consommation énergétique de 3%.Une autre méthode pour concevoir une structure de machines-outils plus légère utilisant l’optimisation topologique est proposée. La méthode s’appuie sur deux paramètres spécifiques : l’espace de conception et DISCRETE. Cette méthode est présentée dans l’optimisation d’un cas simple de poutre encastrée soumise à un effort de flexion et donne de bons résultats. L’utilisation de la méthode sur le chariot X d’une machine-outil met en évidence les limitations de l’optimisation topologique dans le cas d’étude de structures complexes et l’influence du choix de la solution initiale. / In response to the increase of environmental and economic constraints in industry, the issue of reducing and controlling energy consumption is highlighted in machine tool context. This thesis is part of the Green HSM project carried out by the PCI-SCEMM company with the aim of reducing the energy consumption of a machine tool by 30%. The study focused on the specific topic of lightweight design. The objective is to design machine tool structures with the smallest mass while maintaining functional rigidity.Two methods of lightening structures are proposed in the framework of this thesis. The first one presents a method for optimizing the structure of machine tools by stress analysis. This method allows reducing the mass of two main parts of the structure of 6.5% and 9% for an overall reduction in energy consumption of 3%. Another method for designing a lighter machine structure using topological optimization is proposed. The method is based on two specific parameters: the space design and DISCRETE. This method is presented in the optimization of a simple case of embedded beam subjected to a bending effort and gives good results. The use of the method on the X-axis carriage of a machine tool highlights the limitations of topological optimization in the case of complex structure studies and the influence of the initial solution choice.
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Sources and costs of labor market fluctuations and the role of stabilization policies / Fluctuations du marché du travail et politiques de stabilisation économiqueLepetit, Antoine 16 December 2015 (has links)
Cette thèse cherche à expliquer les origines des fluctuations sur le marché du travail, à évaluer le coût de ses fluctuations et à comprendre si la politique monétaire doit chercher à les stabiliser. Notamment elle aborde plusieurs questions. Premièrement, quelles forces sous-tendent les fluctuations du marché du travail ? Ces forces trouvent-elles leur origine sur le marché du travail ? Deuxièmement, le marché du travail a-t-il tendance à amplifier ou atténuer l'effet de ces « chocs » sur l'activité économique ? Finalement, quel est le coût de ces fluctuations et quel rôle doivent jouer les politiques de stabilisation économique, notamment la politique monétaire ? Le premier chapitre cherche à répondre à la première question. Il identifie séparément deux chocs trouvant leur origine sur le marché du travail, un choc d'offre de travail et un choc sur le pouvoir de négociation des salariés, et quantifie leurs contributions respectives aux fluctuations d'un certain nombre de variables macroéconomiques au sein d'un modèle Vector Auto Regressive (VAR). Les deux chocs sont identifiés à l'aide de restrictions de signe. Le résultat principal de cette analyse est que les deux chocs expliquent une part importante des fluctuations de la production et du chômage à court terme comme à long terme. Le deuxième chapitre s'intéresse à la littérature sur les rigidités de salaire. Il montre qu'une forme analytique simple pour le salaire réel peut être obtenue à partir d'un modèle de négociations salariales à offres alternées à la Hall et Milgrom (2008) lorsqu'une restriction paramétrique plausible est imposée. Le troisième chapitre cherche à comprendre comment la nature des fluctuations du chômage affecte la conduite optimale de la politique monétaire. Il montre qu'en présence de fluctuations du chômage asymétriques, l'arbitrage de politique monétaire entre la stabilisation de l'inflation et la stabilisation du chômage décrit par Taylor (1994) devient un arbitrage entre la stabilisation de l'inflation et le chômage moyen. Dans ce cadre, il est préférable pour une banque centrale de mettre un poids important sur la stabilisation de l'activité réelle. En adoptant cette politique plutôt qu'une politique de stabilité des prix, l'autorité monétaire peut générer des gains de bien-être conséquents. / The goal of this thesis is twofold: (1) uncover the sources of labor market fluctuations and evaluate their costs, (2) understand whether monetary policy should be concerned with stabilizing these fluctuations. More precisely, it addresses a certain number of intertwined questions. First, which disturbances underlie labor market fluctuations? Do they find their origin within or outside the labor market? Second, are there key characteristics of the labor market that tend to amplify or dampen the effects of these shocks on economic activity? Third, how costly are these fluctuations, and what does this imply for stabilization policies, especially monetary policy? The first chapter addresses the first question. It identifies and quantifies the importance for economic fluctuations of two labor market shocks, a labor supply shock and a wage bargaining shock, within a Vector Auto Regressive (VAR) mode!. The shocks are identified with sign restrictions. The main result that emerges from this analysis is that both shocks are important for output and unemployment fluctuations in the short run and in the long run. The second chapter is related to the literature that argues that wage rigidity is key to explaining the size of labor market fluctuations. It derives an analytical solution for the wage from an alternating-offer wage bargaining game à la Hall and Milgrom (2008) under a plausible parameter restriction. The third chapter addresses the third question. It tries to understand how the nature of unemployment fluctuations shapes the optimal design of monetary policy. It shows that, when unemployment fluctuations are asymmetric, the standard macroeconomic trade-off between inflation and unemployment stabilization becomes a trade-off between inflation stabilization and average unemployment. In this environment, it is optimal for the central bank to adopt a dual mandate, that is, a policy that features a strong response to employment alongside inflation. The welfare gains of adopting this policy rather than a policy of price stability are found to be substantial.
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Beteende hos laminerade glasbalkar med och utan sprickor / Behaviour of laminated glass beams with and without cracksBasim, Weaam, Abdul Khader, Nour, Rehsid, Vijan January 2020 (has links)
Det blir allt vanligare att använda laminerat glas som ett konstruktionsmaterial. Men glas är ett känsligt och genomskinligt material som kan ge en obehaglig känsla om det spricker. Särskilt om det handlar sig om en glaskonstruktion som ska hålla en stor del av en byggnad. En glaskonstruktion bör upplevas trygg att vistas i. Idag är det svårt att ersätta bärande konstruktionsdelar med glas i Sverige eftersom det inte finns några särskilda dimensioneringsregler för glas. I det här examensarbetet genomförs en undersökning om hur laminerat glas böjer sig när det utsätts för belastning och varierande temperaturer under en kort tid. Det studeras hur tjockleken på mellanskiktet påverkar spänningen samt skjuvstyvheten i glasen. För att få relevanta jämförelser studeras även beteendet hos en osprucken och en sprucken laminerad balk. Med hjälp av litteraturstudier och teoretiska beräkningar har beteendet hos laminerade glasbalkar med olika förutsättningar undersökts. Resultatet visar att belastningar som verkar på en laminerad balk under en kort tid leder till ett varierande beteende och deformationer beroende på temperatur, skjuvstyvhet och tjocklek hos laminatet. Det upptäcktes ett gränsvärde vid temperaturen 50 °C där en förändring sker i sambandet mellan laminatets tjocklek, temperatur och nedböjningen. Beteendet och deformationen hos en laminerad balk varierar också beroende på om balken är sprucken eller inte. / It is becoming increasingly common to use laminated glass as a construction material. But glass is a sensitive and translucent material that can give an unpleasant feeling if it cracks. Especially if it is a glass structure that will hold a large part of a building. A glass structure should be considered safe to stay in. Today, it is difficult to replace supporting structural parts with glass in Sweden due to the lack of design rules. In this thesis, a study is conducted on how laminated glass bends when exposed to mechanical loads and varying temperatures for a short time. It is studied how the thickness of the middle layer plays a role, how the tension and the shear stiffness vary in the glass. In order to obtain relevant comparisons, the behavior of an unbroken and a cracked laminated beam is also studied. With the help of literature studies and theoretical calculations, the behavior of laminated beams under different conditions was examined. The results show that loads that act on a laminated beam for a short time lead to varying behavior and deformations depending on temperature, shear stiffness and interlayer thickness. A limit value was detected at the temperature of 50 °C where a change in the relation between interlayer thickness, temperature and deformation occurs. The behavior and deformation of a laminated beam also varies whether the laminate is cracked or not cracked.
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Možnosti stroje Vernet Behringer při CNC programování / Vernet Behringer tools for CNC programmingMana, Marek January 2014 (has links)
The master’s thesis is focused on the possibilities of machining lines of the company Vernet – Behringer. The theoretical part is a brief inclusion of the control system ProNC2 between selected commercially available control systems and are compared ways of programming CNC machine tools. On the machine tool of company Vernet – Behringer are processed mainly thin-walled components, that is why is part of the work focuses on the issue of machining thin-walled parts, the distribution of deflection tools and machined parts. The next part of thesis deals with the design and processing of technical documentation for the machined model part. The practical part deals with the possibilities of the machine and method of programming the control system ProNC2. Programming and practical production on machine were proceeded in company SSI Schäfer s.r.o. The work is focused on practical verification of the production process using simulation and production itself. Finally, it was performed technical - economic evaluation of production.
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