No campo da medicina diagnóstica através de imagens, o baixo custo e a característica não-invasiva da ultrassonografia modo-B favoreceram as pesquisas que analisam a relação entre a espessura íntima-média (EIM) da artéria carótida e o desenvolvimento de doenças cardiovasculares. Outra técnica de ultrassonografia, baseada no efeito Doppler, também tem sido extensivamente empregada em ambientes clínicos para a medição da velocidade e do fluxo de sangue das artérias periféricas, oferecendo uma abordagem distinta para estudar as doenças cardiovasculares. Neste trabalho, métodos computacionais foram implementados e analisados para extrair informações quantitativas de artérias a partir de imagens 2D. Os ensaios com imagens em modo-B contemplaram a combinação de técnicas de filtragem e algoritmos de contornos ativos para a detecção das interfaces das paredes arteriais e medições da EIM e do diâmetro da luz (DL). Um modelo matemático e 7 imagens reais da artéria carótida comum foram utilizados neste estudo que, dentre as diversas combinações de filtros e algoritmos, apresentou resultados quantitativos similares no cálculo do DL. Para a EIM, porém, a reduzida dimensão da camada íntima-média proporcionou variações indesejadas dos cálculos. Para medir a velocidade do sangue utilizando o modo Doppler, um método semiautomático foi incorporado a um aplicativo computacional para a detecção da envoltória do espectro do gráfico de velocidades. Uma análise comparativa entre sistemas de ultrassonografia comerciais operados por especialistas e este aplicativo incluiu a velocidade de pico sistólico e a integral de velocidade e tempo (VTI) das artérias carótida comum e braquial e de exames ecocardiográficos. A análise de Bland-Altman e o coeficiente de correlação validaram esta metodologia que, complementada pela interface gráfica amigável do aplicativo, pode auxiliar os clínicos em seus estudos de larga escala, baseados nas imagens Doppler ultrassonográficas, com as seguintes vantagens: redução do tempo operacional e de resultados subjetivos e aumento do grau de reprodutibilidade dos resultados. / In the field of image-based diagnostic medicine, low cost and noninvasive B-mode ultrasound technique have supported the researches which investigates the relation between the carotid intima-media thickness (IMT) and the development of cardiovascular diseases. Other ultrasound technique, that offers a different approach to study these diseases, is based on Doppler effect and has also been extensively used in clinical sites to measure blood velocity and flow in peripheral arteries. In this work, computational methods were implemented and analyzed to extract quantitative data from 2D images of arteries. Tests with B-mode images covered the combination of filtering techniques and active contour algorithms, in order to detect the arterial wall interfaces and to measure IMT and lumen diameter (LD). One mathematical model and seven real images of the common carotid artery were used in this study which, among several filters and algorithms combinations, showed similar quantitative results for DL measurements. However, for IMT, the small thickness of intima-media layer led to undesirable variation results. To measure blood velocity by using Doppler mode, a semi-automatic methodology was implemented in a computational tool to detect the spectrum envelope of the velocity graphic. A comparative analysis between commercial ultrasound systems operated by specialists and this tool included systolic peak velocities and velocity-time integral (VTI) of the common carotid and brachial arteries and of echocardiographic exams. Bland-Altmans analysis and the correlation coefficient validated this methodology which, besides the user friendly graphical interface of the tool, may help the clinicians for their large-scale studies based on Doppler ultrasound images, with the following advantages: to save operational time, to lower subjective results, and to support measurement reproducibility.

HTLV-I is the first discovered human retrovirus and a causative agent of both adult T-cell leukemia (ATL) and HTLV-I-associated myelopathy (or tropical spastic paraparesis) (HAM/TSP). Previous models have been successful in providing insight into the progression of HTLV-I infection. The relative simplicity of HTLV as well as its similarities to HIV and other diseases allow HTLV-I research to have diverse applications. The development of HAM/TSP is precipitated by a CTL immune response. Previous models for CTL response to HTLV-I infection have had relatively simple behaviours. A novel sigmoidal CTL response function results in complex behaviours previously unobserved. We establish the existence of bistability between solutions corresponding to carrier and endemic states. In addition, both super- and sub-critical Hopf bifurcations as well as the resulting stable and unstable periodic solutions are observed. Analytical and numerical results are discussed, as well as the biological consequences of the aforementioned behaviours. / Applied Mathematics

In this thesis, the focus has been on micro-mechanical mechanisms in polymer-based materials and structures. The first part of the thesis treats length-scale effects on polymer materials. Experiments have showed that the smaller the specimen, the stronger is the material. The length-scale effect was examined experimentally in two different polymers materials, polystyrene and epoxy. First micro-indentations to various depths were made on polystyrene. The experiments showed that length-scale effects in inelastic deformations exist in polystyrene. It was also possible to show a connection between the experimental findings and the molecular length. The second experimental study was performed on glass-sphere filled epoxy, where the damage development for tensile loading was investigated. It could be showed that the debond stresses increased with decreasing sphere diameter. The debonding grew along the interface and eventually these cracks kinked out into the matrix. It was found that the length to diameter ratio of the matrix cracks increased with increasing diameter. The experimental findings may be explained by a length-scale effect in the yield process which depends on the strain gradients. The second part of the thesis treats mechano-sorptive creep in paper, i.e. the acceleration of creep by moisture content changes. Paper can be seen as a polymer based composite that consists of a network of wood fibres, which in its turn are natural polymer composites. A simplified network model for mechano-sorptive creep has been developed. It is assumed that the anisotropic hygroexpansion of the fibres leads to large stresses at the fibre-fibre bonds when the moisture content changes. The resulting stress state will accelerate creep if the fibre material obeys a constitutive law that is non-linear in stress. Fibre kinks are included in order to capture experimental observations of larger mechano-sorptive creep effects in compression than in tension. Furthermore, moisture dependent material parameters and anisotropy are taken into account. Theoretical predictions based on the developed model are compared to experimental results for anisotropic paper both under tensile and compressive loading at varying moisture content. The important features in the experiments are captured by the model. Different kinds of drying conditions have also been examined. / QC 20100910

Šiame darbe nagrinėjama geležinkelio vagonų, reikalingų tam tikros apimties krovinių vežimams, poreikio problema. Ypatingas dėmesys atkreipiamas į vagonų parko rezervo sudarymą. Pagal pateiktas matematines formules, įvertinus visas vagonų eksploatavimo sąnaudas, nustatomas reikalingų vagonų skaičius. Taip pat yra aprašomas „MS Excel“ programa sudarytas matematinis modelis operatyviniam bei planiniam vagonų poreikiui apskaičiuoti. Šiuo modeliu apskaičiuota reikšmė yra optimali ir yra 1,4 % mažesnė, negu vagono poreikio reikšmė, apskaičiuota remiantis praėjusių metų statistiniais rezultatais. Siekiant visapusiškai išnagrinėti problemą, papildomai buvo tiriamas prekinių vagonų parko amžius, atlikta vagonų prastovų laiko analizė, nustatyti prekinių vagonų poreikio ekonominiai aspektai. / This paper considers the need of the rail cars for the determined volume of the freight traffic. The special attention is drawn to the composition of the railway wagon reserve park. The mathematical equations evaluating the operational elements of the wagons are determined. An experimental mathematical model which describes the operational need of wagons is calculated using supportive software Excel; the model estimates that the optimized need for wagons are by 1.4 % lower then the need has been calculated by last year statistical data. Furthermore the work also observes the performance and the age of the freight Wagon Park. The analysis performed to analyze the wagons idle time and other economic issues concerning the matter of the freight wagons are observed.

No description available.

Sedimentary basins form when water-borne sediments in shallow seas are deposited over periods of millions of years. Sediments compact under their own weight, causing the expulsion of pore water. If this expulsion is sufficiently slow, overpressuring can result, a phenomenon which is of concern in oil drilling operations. The competition between pore water expulsion and burial is complicated by a variety of factors, which include diagenesis (clay dewatering), and different modes (elastic or viscous) of rheological deformation via compaction and pressure solution, which may also include hysteresis in the constitutive behaviours. This thesis is concerned with models which can describe the evolution of porosity and pore pressure in sedimentary basins. We begin by analysing the simplest case of poroelastic compaction which in a 1-D case results in a nonlinear diffusion equation, controlled principally by a dimensionless parameter lambda, which is the ratio of the hydraulic conductivity to the sedimentation rate. We provide analytic and numerical results for both large and small lambda in Chapter 3 and Chapter 4. We then put a more realistic rheological relation with hysteresis into the model and investigate its effects during loading and unloading in Chapter 5. A discontinuous porosity profile may occur if the unloaded system is reloaded. We pursue the model further by considering diagenesis as a dehydration model in Chapter 6, then we extend it to a more realistic dissolution-precipitation reaction-transport model in Chapter 7 by including most of the known physics and chemistry derived from experimental studies. We eventually derive a viscous compaction model for pressure solution in sedimentary basins in Chapter 8, and show how the model suggests radically different behaviours in the distinct limits of slow and fast compaction. When lambda << 1, compaction is limited to a basal boundary layer. When lambda >> 1, compaction occurs throughout the basin, and the basic equilibrium solution near the surface is a near parabolic profile of porosity. But it is only valid to a finite depth where the permeability has decreased sufficiently, and a transition occurs, marking a switch from a normally pressured environment to one with high pore pressures.

Die Temperaturverhältnisse beim Ziehen und Wärmebehandeln von Draht werden mit mathematisch-analytischen Methoden auf der Grundlage der FOURIERschen Wärmeleitungsgleichung eingehend untersucht. Insbesondere wird unter den spezifischen Wärmeübergangsbedingungen zwischen Draht und Ziehdüse sowie zwischen Draht und Ziehtrommel deren thermische Wechselwirkung analysiert. Ein Näherungsverfahren zur Berechnung der Drahttemperaturen in Zugfolgen unter Berücksichtigung des Ziehdüseneinflusses wird angegeben und mit einem Beispiel zum Nassziehen stark verzinkten Stahldrahts illustriert. Aus geschwindigkeitsabhängig gemessenen Änderungen des Drahtdurchmessers werden unter thermoelastischer Ziehringdurchmesserkorrektur Schmierfilmdicken bestimmt. Diffusionsgleichungen werden analysiert und ein Zusammenhang zur Reaktionskinetik wird hergestellt. Ein neues reaktionskinetisches Werkstoffmodell, das insbesondere auch im Falle stärker anisothermer Verhältnisse, also bei Kurzzeitwärmebehandlung anwendbar ist, wird vorgestellt.

Made available in DSpace on 2014-06-11T19:26:56Z (GMT). No. of bitstreams: 0 Previous issue date: 2005-02-23Bitstream added on 2014-06-13T20:55:45Z : No. of bitstreams: 1 silva_alo_me_sjrp.pdf: 1157182 bytes, checksum: 08ed86b39eb7aa9014461e7988e01266 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Neste trabalho apresentamos conceitos teþoricos fundamentais como os Príncipios da Boa Continuação de Gestalt e da Conectividade de Kanizsa, os quais estão intimamente relacionados `a percepção visual humana estudada por psicólogos. Tais conceitos são muito importantes no contexto do processamento de imagens, principalmente no que se refere ao processo de Retoque Digital de Imagens, influenciando e auxiliando pesquisadores a criar modelos matemáticos que imitem o sistema visual humano, com a intenção de deixar o processo mais real possþývel. Apresentamos também, diversos modelos matemþaticos propostos para solucionar o problema de retoque digital, bem como técnicas para implementação computacional de tais modelos. / In this work we present fundamental theoretical concepts like the Gestalt s Good Continuation Principle and the Kanizsa s Connectivity Principle, which are closely related to human visual perception studied by psychologists. Such concepts are very important in the context of the image processing, mainly in those related to the inpainting process. These concepts are influencing and helping researchers to create mathematical models that imitate the human visual system, with the purpose to make the process as real as possible. We also present, various mathematical models developed to solve the inpainting problem and techniques for the computational implementation of theses models.

In this thesis the cubic spline guidance law and its variants are derived. A detailed analysis is carried out to find the initial conditions for successful interception. The results are applied to three dimensional guidance design and for solving waypoint following problems. The basic cubic spline guidance law is derived for intercepting a stationary target at a desired impact angle in a surface-to-surface engagement scenario. The guidance law is obtained using an inverse method, from a cubic spline curve based trajectory. For overcoming the drawbacks of the basic cubic spline guidance law, it is modified by introducing an additional parameter. This modification has an interesting feature that the guidance command can be obtained using a single cubic spline polynomial even for impact angles greater than π/2, while resulting in substantial improvement in the guidance performance in terms of lateral acceleration demand and length of the trajectory. For imparting robustness to the cubic spline guidance law, in the presence of uncertainties and acceleration saturation, an explicit guidance expression is also derived. A comprehensive capturability study of the proposed guidance law is carried out. The capturability for the cubic spline guidance law is defined in terms of the set of all feasible initial conditions for successful interception. This set is analytically derived and its dependence on various factors, such as initial engagement geometry and interceptor capability, are also established. The basic cubic spline guidance and its variants are also derived for a three dimen- sional scenario. The novelty of the present work lies in the particular representation of the three dimensional cubic spline curve and the adoption of the analytical results available for two dimensional cubic spline guidance law. This enables selection of the boundary condition at launch for given terminal boundary condition and also in avoiding the singularities associated with the inverse method based guidance laws. For establishing the feasibility of the guidance laws in the real world, the rigid body dynamics of the interceptor is presented as a 6 degrees-of-freedom model. Further, using a simplified model, elementary autopilots are also designed. The successful interception of the target in the presence of the rigid body dynamics proves practical applicability of the cubic spline based guidance laws. Finally, the theory developed in the first part of the thesis is applied to solve the waypoint following problem. A smooth path is designed for transition of vehicle velocity from incoming to outgoing direction. The approach developed is similar to Dubins’ path, as it comprises line–cubic spline–line segments. The important feature of this method is that the cubic spline segments are fitted such that the path curvature is bounded by a pre-specified constrained value and the acceleration demand for following the smooth path obtained by this method, gradually increases to the maximum value and then decreases. This property is advantageous from a practical point of view. All the results obtained are verified with the help of numerical simulations which are included in the thesis. The proposed cubic spline guidance law is conceptually simple, does not use linearised kinematic equations, is independent of time-to-go es- timates, and is also computationally inexpensive.

Made available in DSpace on 2016-08-31T13:24:10Z (GMT). No. of bitstreams: 1 JeovanizelioFG_DISSERT.pdf: 2944061 bytes, checksum: b719d6cdb79773d0a7ede20c0370bab2 (MD5) Previous issue date: 2009-08-28 / The knowledge of the characteristics and dimensions of wetted bulb is substantially important in the measured of the drip irrigation. Due to the complexity of the physical phenomena involved in the infiltration and redistribution process of water in the soil, develop a mathematical model that simulates the flow of water in the soil is not a very simple task. The objective of this work was developed a mathematical model semi-analytic for predicting dimensions of wetted bulb that it depends on parameters of easy obtaining in the field, just as, the superficial diameter of the wetted bulb. The model allows the simulation of the format and dimensions of the wetted bulb for three different forms: when the diameter of the bulb is given in two depths of easy obtaining in the field, that is, in the surface of the soil and in the depth of 10 cm; starting from the superficial diameter and standards existent for the maximum depth in agreement with the texture of the soil; starting from the surfaces of answers. The mathematical model was obtained by numeric simulation of the equations that govern the flow of water in the soil, originating like this, semi-analytic solution for the formation of the wetted bulb. The model was validate, starting from field data of a soil with medium texture after compared with the simulate data. The accomplished comparisons demonstrate that the proposed model predicting the dimensions of the wetted bulb satisfactorily and it can be used as auxiliary tool in the measurement of the drip irrigation. / O conhecimento das características do bulbo molhado é substancialmente importante para o dimensionamento da irrigação por gotejamento. Devido à complexidade dos fenômenos físicos envolvidos no processo de infiltração e redistribuição de água no solo, desenvolver um modelo matemático que simule o fluxo de água no solo é uma tarefa não muito simples. O objetivo desse trabalho é desenvolver um modelo matemático semi-analítico para estimar as dimensões do bulbo molhado que depende de parâmetros de fácil obtenção no campo, tal como o diâmetro superficial do bulbo molhado. O modelo permite a simulação do formato e as dimensões do bulbo molhado por três formas diferentes: quando é dado o diâmetro do bulbo em duas profundidades de fácil obtenção no campo, isto é, na superfície do solo e na profundidade de 10 cm; a partir do diâmetro superficial e padrões existentes para a profundidade máxima de acordo com a textura do solo; a partir das superfícies de respostas. O modelo matemático foi obtido por simulação numérica das equações que governam o fluxo de água no solo, originando assim, solução semi-analítica para a formação do bulbo molhado. O modelo foi validado, a partir de dados de campo de um solo com textura média e, em seguida comparados com os dados simulados. As comparações realizadas demonstram que o modelo proposto estima satisfatoriamente as dimensões do bulbo molhado e pode ser utilizado como ferramenta auxiliar no dimensionamento da irrigação por gotejamento.