Apresenta-se uma formulação de adaptação de malha para problemas com grandes deformações. A formulação Arbitrária Lagrangeana-Euleraina (ALE) permite manter a qualidade dos elementos finitos durante o processo de cálculo através de rearranjo ou movimento de malha independente do movimento material. Nas formulações Lagrangeanas a malha fica “colada” ao corpo durante toda a análise, logo quando este sofre grandes deformações diferenciais o mesmo se reproduz numa malha distorcida. A formulação ALE desacoplada consta de dois passos: O passo Lagrangeano onde são aplicados os incrementos de carga, a malha permanece “colada” à matéria durante a análise. E cada certo “tempo” o passo Euleriano onde “descola-se” a malha da matéria e efetua-se o movimento de malha que se ajusta melhor ao corpo deformado. São apresentados assim métodos de realocação da malha e transferência ou atualização das variáveis necessárias para, depois do passo Euleriano, continuar a análise com a nova malha sem grandes distorções dos elementos. Os problemas de grandes deformações e deslocamentos são acompanhados de não linearidades físicas e geométricas, assim, são abordados os métodos para o tratamento destas não linearidades. Trabalha-se com o elemento hexaédrico tri-linear com integração reduzida e controle dos modos espúrios que tem demostrado um bom comportamento frente a grandes não linearidades geométricas assim como para as não linearidades físicas. A formulação ALE tem ganhando seu espaço na mecânica dos sólidos, em problemas de conformação mecânica e impacto, devido às grandes deformações e na última década está abrindo-se passo na área da geomecânica tratando problemas recalque e penetração de fundações em solos. / This work presents remeshing techniques for finite element simulation and investigates their performance for large deformation problems. Lagrangian formulation generally results in excessive mesh distortion owing to its attachment to the material. Meanwhile, the Lagrangian- Eulerian (ALE) formulation alouds to keep the finite element quality through the arbitrarily rearrangement or movement of the mesh, to optimize the element’s shape. The decoupled Arbitrary Lagrangian-Eulerian approach consists in a sequence of Lagrangian and Eulerian steps. The mesh is “coupled” to the material during the Lagrangian steps. From step to step, mesh is decoupled from the system material (Eulerian step), the nodes corresponding to free boundaries are relocated using an analytical approach, remeshing is performed and finally the state variables are remapped. Rearrangements methods for the element’s node are presented, as well as the variables remapping algorithms at the new quadrature points, in order to continue with the finite element analysis without altering the element topology of the original mesh. Special attention is given to methods dealing with geometric and physical nonlinearities. A trilinear hexahedral element is used with reduced integration and hourglass control. This combination has shown well behavior in front of large geometric and physical nonlinearities. ALE formulation field has considerably grown in geotechnical research, especially in impact and mechanical extrusion problems. Over the last decade, geomechanic is dealing with settlement problems and foundation penetration in soils.

Apresenta-se uma formulação de adaptação de malha para problemas com grandes deformações. A formulação Arbitrária Lagrangeana-Euleraina (ALE) permite manter a qualidade dos elementos finitos durante o processo de cálculo através de rearranjo ou movimento de malha independente do movimento material. Nas formulações Lagrangeanas a malha fica “colada” ao corpo durante toda a análise, logo quando este sofre grandes deformações diferenciais o mesmo se reproduz numa malha distorcida. A formulação ALE desacoplada consta de dois passos: O passo Lagrangeano onde são aplicados os incrementos de carga, a malha permanece “colada” à matéria durante a análise. E cada certo “tempo” o passo Euleriano onde “descola-se” a malha da matéria e efetua-se o movimento de malha que se ajusta melhor ao corpo deformado. São apresentados assim métodos de realocação da malha e transferência ou atualização das variáveis necessárias para, depois do passo Euleriano, continuar a análise com a nova malha sem grandes distorções dos elementos. Os problemas de grandes deformações e deslocamentos são acompanhados de não linearidades físicas e geométricas, assim, são abordados os métodos para o tratamento destas não linearidades. Trabalha-se com o elemento hexaédrico tri-linear com integração reduzida e controle dos modos espúrios que tem demostrado um bom comportamento frente a grandes não linearidades geométricas assim como para as não linearidades físicas. A formulação ALE tem ganhando seu espaço na mecânica dos sólidos, em problemas de conformação mecânica e impacto, devido às grandes deformações e na última década está abrindo-se passo na área da geomecânica tratando problemas recalque e penetração de fundações em solos. / This work presents remeshing techniques for finite element simulation and investigates their performance for large deformation problems. Lagrangian formulation generally results in excessive mesh distortion owing to its attachment to the material. Meanwhile, the Lagrangian- Eulerian (ALE) formulation alouds to keep the finite element quality through the arbitrarily rearrangement or movement of the mesh, to optimize the element’s shape. The decoupled Arbitrary Lagrangian-Eulerian approach consists in a sequence of Lagrangian and Eulerian steps. The mesh is “coupled” to the material during the Lagrangian steps. From step to step, mesh is decoupled from the system material (Eulerian step), the nodes corresponding to free boundaries are relocated using an analytical approach, remeshing is performed and finally the state variables are remapped. Rearrangements methods for the element’s node are presented, as well as the variables remapping algorithms at the new quadrature points, in order to continue with the finite element analysis without altering the element topology of the original mesh. Special attention is given to methods dealing with geometric and physical nonlinearities. A trilinear hexahedral element is used with reduced integration and hourglass control. This combination has shown well behavior in front of large geometric and physical nonlinearities. ALE formulation field has considerably grown in geotechnical research, especially in impact and mechanical extrusion problems. Over the last decade, geomechanic is dealing with settlement problems and foundation penetration in soils.

Semantic segmentation is one of classic computer vision problems and strong tool for machine processing and understanding of the scene. In this thesis we use semantic segmentation in mountainous environment. The main motivation of this work is to use semantic segmentation for automatic location of geographic position, where the picture was taken. In this thesis we evaluated actual methods of semantic segmentation and we chose three of them  that are appropriate for adapting to mountainous environment. We split the dataset with mountainous environment into validation, train and test sets to use for training of chosen semantic segmentation methods. We trained models from chosen methods on mountainous data. We let segments from the best trained models get evaluated in electronic survey by respondents and we evaluated these segments in process of camera orientation estimation. We showed that chosen methods of semantic segmentation are possible to use in mountainous environment. Our models are trained on 11, 5 or 4 mountainous classes and the best of them achieve on 4 class mean IU 57.4%. Models are usable in practise. We show it by their deployment as a part of camera orientation estimation process.

The presented diploma thesis is focused on the preparation and the monitoring of the biological stability of beer enriched with probiotics. Probiotic bacterial strains of Lactobacillus acidophilus, Bifidobacterium breve and Bifidobacterium bifidum were used in this study. The theoretical part is divided into two sections. In the first section, probiotics are generally characterized, and their role within a gut microbiota is described. Next, the microbiology of particular probiotic microorganisms including the genera of Lactobacillus and Bifidobacterium is described. Then, some factors influencing the viability and the growth of probiotics are stated. In this section, biological effects of probiotics on the human organism and their potential clinical applications are described. The second section of the theoretical part deals with the technology of brewing, the chemical composition of beer and particular beer styles. In the experimental part, the methods of probiotic bacterial cell concentration and viability determination were optimized. Several techniques for determination of these parameters were selected, particularly the cultivation method, flow cytometry and the spectrophotometric measurement of turbidity. Then, the growth curves of the probiotic strains were measured in MRS medium. Probiotic bacteria were cultivated in model beer samples, i.e. in MRS media with several different concentrations of ethanol. It is possible to say that ethanol did not have significant effect on probiotics growth. Next, experimental cultivations of individual probiotic bacteria and their mixtures in nine real beer samples were conducted. No increase of viable cells concentrations was detected in the samples. On the contrary, a decrease of the concentrations was observed, mainly in the samples with individual bacterial strains. However, certain values of viable cells concentrations were determined at the end of the cultivations in all cases. A pale, top-fermented beer was brewed and supplemented with probiotics, and the concentrations of viable probiotic cells were monitored during 37 days of fermentation. A decrease of concentrations by two orders of magnitude of CFU/ml was observed in almost all samples. Yet, viable cells of probiotic bacteria were detected in all samples of beer at the end of the fermentation. Maximal concentration of viable probiotic cells in the brewed beer was determined with the cultivation method at (3,80 ± 0,14)10^5 CFU/ml. Chosen samples were analyzed with HPLC-RI method that quantified the common beer concentrations of ethanol in all chosen samples, lactic acid was not detected. Sensory analysis was conducted as well. Based on the results of the experimental part and the bibliography, an optimal technology of the preparation of beer enriched with probiotics is discussed in this study.

No description available.

Finite element(FE) method has been used to model cutting process since 1970s. However, it requires special techniques to cope with the difficulties in simulating extremely large strain when compare to static or small deformation problems. With the advancement of FE techniques, researchers can now have a deeper insight of the mechanism of material flow and chip formation of metal cutting process. Even the stagnation effect of the workpiece material in front of the cutting edge radius can be captured by using FE techniques such as Remeshing and Arbitrary Lagrangian Eulerian(ALE) formulation. However most of this models are limited to plane strain assumption which means they are 2-dimensional. Although 3D models are existing in the literatures, most of them employ Remeshing technique which is very computationally intensive and has many critics regarding its accuracy due to its frequent remeshing and mapping process. The rest of the 3D models employ Lagrangian formulation. The 3D models by Lagrangian formulation have the same limitations and drawbacks as in 2D models, as it requires failure criteria and in most of the cases predefined partition surfaces are also required. ALE technique on the other hand resolves all the drawbacks of the other formulations, it not only inherits the advantages of the other techniques but also has its own unique advantages such as it can simulate a longer time span up to couple seconds more economically by fixing the number of elements used. Although it's commonly accepted that ALE formulation is superior to other formulations of techniques in modeling metal cutting process, its usage is only limited to 2D models. Limited 3D ALE metal cutting models is available in the literature. Thus the main objective of this research is to explore the possibility of building a 3D metal cutting model with ALE formulation. The reliability and limitations will also be studied. Furthermore, Couple Eulerian-Lagrangian(CEL) formulation is a recent developed formulation that has a lot of potential in modeling metal cutting process in 3D. It will be compared with ALE models to study its potential and limitations in modeling metal cutting process. A new frictional model will also be proposed, which suggests that the frictional phenomenon in metal cutting is a consolidated effect of both friction between material interface and shear yield of the workpiece material. This idea provide a brand new perspective of viewing the friction phenomenon of metal cutting compared to those existed models. / Thesis / Master of Science (MSc)

Airbags are a passive safety technology, required to function with zero failure rate. Advances in Computer Aided Engineering have allowed vehicle manufacturers to predict material and system behavior in the event of a crash. The sudden and rapid nature of a vehicle frontal crash, together with strict requirements put on safety make this a sensitive task. This thesis focuses on the front passenger airbag deployment and the instrument panel’s response. Various airbag modelling techniques are studied and presented in this document. This work is part of a larger-scale attempt to model a generic-sled that is physically representative of a real vehicle. Various component tests are to be performed in the sled environment, as opposed to a real vehicle, to save costs. Various modules are added to the sled once their behavior is verified by testing and in simulations. Software are advanced enough to identify location and magnitude of stress concentrations that develop during crash. LS-DYNA is used for explicit finite element simulations of the instrument panel (IP) in question with different airbag models. Verification has been achieved by design of experiment (DOE); with tests conducted to capture both the movements of the airbag housing and IP movements in response. These movements are broken down in various phases, facilitating implementation in the sled environment. Simplifications are made both to the computer models as well as the physical testing environment. The effects of these simplifications are quantified and discussed. Theoretical background is provided where fit while assumptions are justified wherever made. DYNAmore recommendations regarding costeffective calculations as well as result verification are followed. The obtained results show that the FE models replicate the real event with acceptable precision. The findings in this work can, by minor tweaks, be implemented on other IP models in the Volvo Cars range, leading to cost-saving solutions. This thesis provides the necessary information for sled implementations as well as future improvement suggestions. / Krockkudde är en s.k. passiv säkerhetsteknik som krävs att fungera felfritt. Framsteg inom Computer Aided Engineering har tillåtit biltillverkare att förutsäga material och systembeteende i samband med krock. Den plötsliga karaktären av krock, tillsammans med höga säkerhetskrav, gör detta till en känslig uppgift. Denna avhandling fokuserar på passagerarsidans krockkudde och instrumentbrädans (IP) respons under uppblåsning. Olika metoder för modellering av krockkuddar har studerats och presenteras i detta dokument. Arbetet är en del av en större skala försök att modellera en generisk-släde som är fysiskt representativ av en riktig bil; där olika komponent-tester skall utföras för att minska kostnader. När olika modulers beteende verifieras läggs de till släden. Denna verifiering sker genom finita element (FE) simuleringar så väl som fysiska tester. FE mjukvara är idag tillräckligt avancerad för att identifiera samt visualisera spänningskoncentrationer som uppstår i en konstruktion vid krock. LS-DYNA används i detta arbete för explicita FE simuleringar av en Volvo XC90 IP, lastad med olika krockkudde-modeller. Modell verifiering har uppnåtts genom försöksplanering (DOE); med tester utförda för att fånga rörelser av IP så väl som krockkudde-behållaren. Dessa rörelser är sedan uppdelade i olika faser för enklare genomförande i släde miljön. Förenklingar och antaganden görs både till FE modeller och fysiska testmiljön. Effekter av dessa har kvantifierats och relevant teoretisk bakgrund har inkluderats. Dokumentet innehåller även diskussion kring val av mätutrustning samt förbättringsförslag för fortsatt arbete. DYNAmore rekommendationer gällande kostnadseffektiva beräkningar och verifiering av simulerings-resultat har följts. Under arbetet visade sig att FE modellerna kan återskapa händelsen med hög noggrannhet; dessa trotts svårigheter i modellering av plast material. Möjligtvis kan man, genom mindre modifieringar, relatera slutsatserna i detta arbete till olika IP modeller i företagets produktkatalog vilket förmodligen leder till ytterligare kostnadsbesparingar. Denna avhandling ger den information som behövs för genomföranden i den generiska miljön.

Le delta du fleuve Sénégal est le théâtre de crues importantes, le plus souvent catastrophiques et la dernière en date a nécessité l'ouverture d'une brèche dans la Langue de Barbarie qui est une fine bande de sable séparant le delta du fleuve de la mer. Depuis, cette brèche ne cesse de s'agrandir sous l'action conjuguée des eaux du fleuve et de la mer. Modéliser ce phénomène d'élargissement nécessite de connaître à tout moment les caractéristiques de l'écoulement des eaux dans le delta, y compris en période de crue. Nous avons opté pour la réalisation de deux algorithmes de simulation. C'est ce travail que je présente ici. D'une part, nous considérons l'équation de Navier-Stokes tridimensionnelle et nous faisons l'hypothèse d'une faible épaisseur d'eau, ce qui est acceptable comparé aux dimensions du delta. Cette hypothèse nous permet de faire, en chaque point, une intégration selon la verticale pour obtenir une équation de Saint-Venant bidimensionnelle simplifiée dans un plan xoy sans les hypothèses approximatives (fond plat ou conditions aux limites trop généreuses dans l'un ou l'autre, qui ne reproduisent pas fidèlement le phénomène étudié). Cette équation ne nous permet d'obtenir les champs de vitesses et de pressions que dans un plan horizontal. Pour prendre en compte les apports extérieurs responsables d'une crue, nous introduisons une équation 1D de conservation de la masse d'eau. Le couplage entre l'équation de Saint-Venant 2D et l'équation de conservation 1D conduit à une modélisation (2D1/2 et non 3D) du phénomène étudié. D'autre part, la phase d'élargissement de la brèche résulte de la problématique fluide-structure, une intéraction entre un écoulement et une structure fortement déformable. Il s'agit d'un problème multi-physique reposant sur plusieurs équations d'état (Darcy, poroélastique ...) et impliquant divers couplages. Sous l'hypothèse que les déformations de la structure dues à l'hydrodynamique restent à l'échelle microscopique, nous obtenons des résultats analytiques et numériques de l'évolution de l'interface à long terme.

Dans cette thèse on a développé des algorithmes semi-implicites procédures partagées et monolithiques pour l'interaction entre un fluide gouverné par le modèle de Navier Stokes et une structure. Dans le premier chapitre, on présente un algorithme semi-implicite procédures partagées pour l'interaction entre un fluide et une structure gouvernée soit par les équations d'élasticité linéaire ou soit par le modèle de Saint-Venant Kirchhoff non linéaire. Dans le second chapitre, on propose un algorithme semi-implicite procédures partagées pour l'interaction entre un fluide et une structure de modèle linéaire et on montre un résultat de stabilité inconditionnelle en temps de l'algorithme. Un problème d'optimisation est résolu dans les deux algorithmes précédents, afin de satisfaire les conditions de continuité des vitesses et d'égalité des contraintes à l'interface. Durant les itérations de BFGS pour résoudre le problème d'optimisation, le maillage fluide reste fixe et la matrice fluide n'est factorisée qu'une seule fois, ce qui réduit l'effort de calcul. Dans le troisième chapitre, un algorithme semi-implicite monolithique pour l'interaction entre un fluide et une structure de modèle linéaire est proposé. L'algorithme utilise un maillage global pour le domaine fluide structure. La condition de continuité des vitesses à l'interface est automatiquement satisfaite et celle de l'égalité des contraintes n'apparaît pas explicitement dans la formulation faible. A chaque pas de temps on résout un système monolithique d'inconnues vitesse et pression définies sur le domaine global. Le temps CPU est réduit quand l'approche monolithique est utilisée à la place des procédures partagées.

La predicción precisa de los efectos producidos por el acoplamiento fluido estructura para cuerpos parcial o totalmente sumergidos, incluyendo superficies libres, es un problema de gran relevancia en la ingeniería naval así como en muchos otros campos del diseño de estructuras sometidas a la acción de fluidos.Las dificultades que se encuentran en la resolución de los problemas de interacción fluido estructura se deben principalmente a las siguientes causas:1. La dificultad de resolver numéricamente las ecuaciones de la dinámica de un fluido incompresible que, en general, si descartamos el caso más simple del modelo del flujo potencial, tienen un importante carácter no lineal. 2. Los obstáculos que se presentan al resolver la ecuación de la superficie libre, que constriñen el movimiento de las partículas a una superficie fluida de posición a priori desconocida.3. Las dificultades asociadas a la resolución del problema del movimiento de un cuerpo sumergido debido a las fuerzas de interacción, minimizando la deformación de los elementos de la malla y reduciendo, de esta manera, la necesidad del remallado.En la presente tesis se presenta un método estabilizado basado en el método de los elementos finitos que pretende solventar cada uno de los problemas anteriores. La metodología se basa en la modificación de las ecuaciones diferenciales de la dinámica de fluidos que gobiernan el flujo viscoso incompresible y el movimiento de la superficie libre, mediante la aplicación del método de cálculo finitesimal (FIC) propuesto en este trabajo.En el presente caso las ecuaciones modificadas son resueltas usando un esquema de pasos fraccionados semi-implícito y el método de los elementos finitos (FEM). El movimiento del cuerpo sumergido en el fluido debido a las fuerzas de interacción se calcula resolviendo un problema estructural dinámico, para el cual las fuerzas del fluido son las condiciones iniciales. Se incluye, además, un algoritmo para el movimiento de la malla debido a la deformación del dominio de cálculo. Este método minimiza la distorsión de la malla debida al movimiento del sólido rígido y al cambio de posición de la superficie libre. Este algoritmo se basa en la solución iterativa por el método de elementos finitos de un problema lineal, donde la malla de cálculo se considera un sólido elástico sometido a la deformación prescrita por el cambio en el dominio de cálculo. Las características de elasticidad del sólido, y en concreto su rigidez, se aplican de manera que los elementos que más se deforman tienen una rigidez mayor. Por último se presentan varios ejemplos de interés industrial, aplicación de la metodología propuesta en diferentes campos de la ingeniería naval.