Modelar a dinâmica de neurônios é relevante em estudos de neurociências. Neste trabalho, propõe-se um modelo computacional de neurônio baseado no comportamento dos canais iônicos presentes na sua membrana. O modelo combina elementos microscópicos, como o comportamento dos canais individuais, com elementos macroscópicos, como a tensão ao longo de um trecho de membrana. Simulações foram realizadas com o objetivo de reproduzir dados biológicos e resultados obtidos de modelos teóricos clássicos da área. Foi possível reproduzir com boa concordância o potencial de ação, o fenômeno da adaptação, a curva da corrente de entrada versus a frequência de disparos e o potencial excitatório pós-sináptico. / Modelling the dynamics of neurons is relevant in studies on neurosciences. In this work, a computational model of neuron based on the behavior of the ionic channels found in its membrane is proposed. The model comprises microscopic elements, as the behavior of the individual channels, and macroscopic elements, as the tension along a membrane patch. Simulations were performed with the aim of reproducing biological data and results derived from classical theoretical models of the field. It was possible to reproduce with good agreement the action potential, the phenomenon of adaptation, the curve of the input current versus the spike frequency, and the excitatory postsynaptic potential.

The objective of the research presented in this thesis has been to develop a physics-based dislocation density-based numerical framework to simulate microstructure evolution in severe plastic deformation (SPD) manufacturing processes for different materials. Different mechanisms of microstructure evolution in SPD manufacturing processes were investigated and summarized for different materials under dynamic or high strain rates over a wide temperature range. Thorough literature reviews were performed to clarify discrepancies of the mechanism responsible for the formation of nanocrystalline structure in the machined surface layer under both low-temperature and high-temperature conditions. Under this framework, metallo-thermo-mechanically (MTM) coupled finite element (FE) models were developed to predict the microstructure evolution during different SPD manufacturing processes. Different material flow stress responses were modeled subject to responsible plastic deformation mechanisms. These MTM coupled FE models successfully captured the microstructure evolution process for various materials subjected to multiple mechanisms. Cellular automaton models were developed for SPD manufacturing processes under intermediate to high strain rates for the first time to simulate the microstructure evolution subjected to discontinuous dynamic recrystallization and thermally driven grain growth. The cellular automaton simulations revealed that the recrystallization process usually cannot be completed by the end of the plastic deformation under intermediate to high strain rates. The completion of the recrystallization process during the cooling stage after the plastic deformation process was modeled for the first time for SPD manufacturing processes at elevated temperatures.

<p>The aim of this master's thesis is to implement and evaluate a method for estimating the indicated engine torque. The method is developed by IAV GmbH, Fraunhofer-Institut and Audi AG. The determination of the indicated torque is based on high resolution engine speed measurements. The engine speed is measured with a hall sensor, which receives the signal from the transmitterwheel mounted on the crankshaft. A transmitterwheel compensation is done to compensate for the partition defects that arises in the production and thus enable a more precise calculation of the angular velocity. The crankshaft angle, angular velocity and angular acceleration are estimated and the helpvariable effective torque is calculated using these signals as input. Through a relationship between effective torque and the indicated pressure the indicated pressure is extracted from a map. The indicated torque is then calculated from the pressure. </p><p>The method is validated with data from an engine test bed. Because of the low obtainable sample rate at the test bed, 4MHz, quantisation errors arises at engine speeds over 1000 rpm. Therefore the model is validated for low engine speeds and the result is promising.</p>

La formation de la structure de grains dans les métaux pendant la solidification est déterminante pour les propriétés mécaniques et électroniques des pièces coulées. En plus de la texture donnée au matériau, la germination et la croissance des grains sont liées en particulier avec la formation des phases thermodynamiques et les inhomogénéités en composition d'éléments d'alliage. La structure de grains est rarement modélisée à l'échelle macroscopique, d'autant plus que l'approximation 2D est très souvent injustifiée. Dans ces travaux, la germination et la croissance de chaque grain individuel sont suivies avec un modèle macroscopique 3D CAFE. La microstructure interne des grains n'est pas explicitement résolue. Pour valider les approximations faites sur cette microstructure, une comparaison directe avec un modèle microscopique "champ de phase" a été réalisée. Celle-ci a permis de valider les hypothèses de construction du modèle CAFE, de mettre en avant le lien entre données calculées par les modèles microscopiques et paramètres d'entrée des modèles à plus grande échelle, et les domaines de validité de chaque modèle. Dans un deuxième temps, un couplage avec la ségrégation chimique et les bases de données thermodynamiques a été mise en place et appliquée sur un alliage binaire étain-plomb. Une expérience de macroségrégation par convection naturelle a été simulée. L'accord entre les courbes de température expérimentales et simulées atteint une précision de l'ordre de 1K, et la recalescence est correctement prédite. Les cartes de compositions sont comparables qualitativement, ainsi que la structure de grains. Les avantages du suivi de la structure ont été mis en évidence par rapport à une simulation par éléments finis classique. De plus, il a été montré que le calcul 3D était ici indispensable. Enfin, une implémentation parallèle optimisée du code a permis d'appliquer le modèle CAFE à un lingot de silicium polycristallin industriel de dimensions 0,192 x 0,192 x 2,08m, avec une taille de cellules de 250µm. Au total, 4,9 milliards de cellules sont représentées sur le domaine, et la germination et la croissance de 1,6 million de grains sont suivies.

The aim of this master's thesis is to implement and evaluate a method for estimating the indicated engine torque. The method is developed by IAV GmbH, Fraunhofer-Institut and Audi AG. The determination of the indicated torque is based on high resolution engine speed measurements. The engine speed is measured with a hall sensor, which receives the signal from the transmitterwheel mounted on the crankshaft. A transmitterwheel compensation is done to compensate for the partition defects that arises in the production and thus enable a more precise calculation of the angular velocity. The crankshaft angle, angular velocity and angular acceleration are estimated and the helpvariable effective torque is calculated using these signals as input. Through a relationship between effective torque and the indicated pressure the indicated pressure is extracted from a map. The indicated torque is then calculated from the pressure. The method is validated with data from an engine test bed. Because of the low obtainable sample rate at the test bed, 4MHz, quantisation errors arises at engine speeds over 1000 rpm. Therefore the model is validated for low engine speeds and the result is promising.

The syntactic complexity of a regular language is the cardinality of its syntactic semigroup. The syntactic complexity of a subclass of the class of regular languages is the maximal syntactic complexity of languages in that class, taken as a function of the state complexity n of these languages. We study the syntactic complexity of suffix-, bifix-, and factor-free regular languages, star-free languages including three subclasses, and R- and J-trivial regular languages. We found upper bounds on the syntactic complexities of these classes of languages. For R- and J-trivial regular languages, the upper bounds are n! and ⌊e(n-1)!⌋, respectively, and they are tight for n >= 1. Let C^n_k be the binomial coefficient ``n choose k''. For monotonic languages, the tight upper bound is C^{2n-1}_n. We also found tight upper bounds for partially monotonic and nearly monotonic languages. For the other classes of languages, we found tight upper bounds for languages with small state complexities, and we exhibited languages with maximal known syntactic complexities. We conjecture these lower bounds to be tight upper bounds for these languages. We also observed that, for some subclasses C of regular languages, the upper bound on state complexity of the reversal operation on languages in C can be met by languages in C with maximal syntactic complexity. For R- and J-trivial regular languages, we also determined tight upper bounds on the state complexity of the reversal operation.

The heart is a muscular organ which acts as a biomechanical pump. Electrical impulses are generated in specialized cells and flow through the heart myocardium by the ion changes on the cell membrane which is the beginning of both the electrical and the mechanical activity. Both the electrical and the mechanical states of the organ will directly affect the pumping activity. The main motivation of this thesis is to better understand physiological and pathological properties of the heart muscle via studying the electro-mechanics of the heart. This model could be used to gain better solutions of the ill-posed inverse problem of ECG and Body Surface Potential Maps (BSPM) or to estimate the electrical propagation and mechanical response on patient specific heart geometry models which can be obtained by using MRI technique. Cellular automaton technique will be used to simulate the physiological function of the left ventricle to estimate the cardiac functions. To model the heart tissue firstly the anatomical knowledge of the heart will be used such as properties of the myocardium, fiber orientations, etc. to simulate the three dimensional electrical propagation. Then the mechanical activity consisting of contraction and relaxation will be simulated according to the material properties of the heart. Using this simulation, the effects of the cardiac arrhythmias such as reentry will be generated. In this study, electrical and mechanical properties of the heart tissue are modeled for normal heart beat and heart beat in case of ischemic heart tissue. Contraction of the tissue via electrical activation has also been considered in terms of time synchronization. &ldquo / Cellular automaton&rdquo / method is used for modeling the electromechanical interactions in the heart tissue. A simplified left ventricle model is used to observe the electrical and the mechanical behavior. Using this method, both the normal heart beat&rsquo / s electrical activation and the arrhythmia excitation could be taken on, without using complex differential equations. To consider the anisotropy of the heart tissue, fiber orientations have also been added to the model. In this thesis work, electro-mechanic models at cellular, macroscopic and heart left ventricle level are presented. The electro-mechanical adaptation is performed by cellular electrophysiology and cellular force development due to intercellular excitation propagation. Varying densities of transmembrane proteins, changes on concentration of calcium, metabolic and hormonal effects are neglected. Also in simplified ventricular model the fluid mechanics and mechanoelectrical feed-back is not taken into-account.

The syntactic complexity of a regular language is the cardinality of its syntactic semigroup. The syntactic complexity of a subclass of the class of regular languages is the maximal syntactic complexity of languages in that class, taken as a function of the state complexity n of these languages. We study the syntactic complexity of suffix-, bifix-, and factor-free regular languages, star-free languages including three subclasses, and R- and J-trivial regular languages. We found upper bounds on the syntactic complexities of these classes of languages. For R- and J-trivial regular languages, the upper bounds are n! and ⌊e(n-1)!⌋, respectively, and they are tight for n >= 1. Let C^n_k be the binomial coefficient ``n choose k''. For monotonic languages, the tight upper bound is C^{2n-1}_n. We also found tight upper bounds for partially monotonic and nearly monotonic languages. For the other classes of languages, we found tight upper bounds for languages with small state complexities, and we exhibited languages with maximal known syntactic complexities. We conjecture these lower bounds to be tight upper bounds for these languages. We also observed that, for some subclasses C of regular languages, the upper bound on state complexity of the reversal operation on languages in C can be met by languages in C with maximal syntactic complexity. For R- and J-trivial regular languages, we also determined tight upper bounds on the state complexity of the reversal operation.

During braking, both the disc and pads in disc brakes are worn. Since disc brakes are not sealed,some of the wear particles generated can become airborne. Several studies have found anassociation between adverse health effects and the concentration of particles in the atmosphere,so it is of interest to improve our knowledge of the airborne wear particles generated by discbrakes. This thesis deals with experimental and computational methods focusing on airborne wearparticles from disc brakes. The eight appended papers discuss the possibility to both measure andnumerically determine the concentration and size distribution of airborne wear particles thatoriginate from the pad-to-disc contact. The objective is to increase the scientific knowledge ofairborne wear particles generated from disc brakes. Papers A, B and C describe tests of disc brake materials conducted in a modified pin-on-discmachine. The results show that the test set-up can be used to measure and rank disc brakematerials with respect to the concentration of airborne particles generated. Ultrafine (nanosized),fine and coarse airborne wear particles that contain metals such as iron, copper and tin werefound. Papers D and E describe a novel disc brake assembly test stand and tests of disc brake materialsconducted in it. The results show that the test set-up can be used to measure the concentrationand size distribution of airborne wear particles generated from disc brake materials. The resultsalso indicate an ability to rank different pad/disc combinations with respect to the concentrationof airborne wear particles. Furthermore, the results suggest that this test stand can be used tostudy rust layer removal from the disc and that airborne particles are generated even at low brakepressures, such as used to remove dirt from the disc. Paper F compares measurements made in passenger car field tests with measurements made in adisc brake assembly test stand and in a pin-on-disc machine. A promising correlation between thethree different test methods is found. Paper G presents and discusses a simulation methodology that numerically determines theconcentration and size distribution of airborne wear particles generated from the pad-to-disccontact in disc brakes by using general-purpose finite element software. Paper H discusses a cellular automaton model that describes the microscopic contact situationbetween the pad and disc in disc brakes. This model is used to numerically determine the amountof wear that leaves the contact. The results correlate qualitatively with experimental observationsfound in the literature. / QC 20110317

Caenorhabditis elegans is a natural predator of the mushroom pathogen Pseudomonas fluorescens NZI7. The bacterial mechanisms for reducing predation by the nematode through the secretion of secondary metabolites have been described, but not yet fully explored. The behaviour of nematodes is influenced by the different factors produced by the pseudomonads. In this thesis we develop a range of assays to link the behaviour of C. elegans to these factors to identify their role in bacteria-nematode interactions. We show that these factors play two distinct roles: they may either repel nematodes, or harm them. This permits the classification of mutants of P. fl. NZI7 lacking these factors as either attractive, edible or both. Many studies of C. elegans behaviour have demonstrated that the nematode can distinguish between different food sources. Our results show two distinct types of response: chemotaxis drives the response to attractive or repellent stimuli, and nematodes also show a choice behaviour that is independent of chemotaxis. This choice behaviour is determined by bacterial edibility and requires nematodes to come into contact with the bacteria. This contact is the foundation of the bacterial dispersal by nematodes. By making use of the luminescence property of the available bacterial mutants, we demonstrate an intimate link between the behaviour of C. elegans and the success with which bacteria are disseminated: if nematodes are induced to regularly leave a bacterial colony, whether through their genotype or the low edibility of the food, then they will spread bacteria effectively. Throughout this thesis, we use computational simulations based on a hybrid cellular automaton model to represent the nematode-bacteria interactions. These simulations recreate the observed behaviour of the system, thus they help to confirm our hypotheses and establish the fundamental aspects of the interactions between the two species.