Developing models of the cardiovascular system that simulates the dynamic behavior of a virtual patient’s condition is fundamental in the medical domain for predictive outcome and hypothesis generation. These models are usually described through Ordinary Differential Equation (ODE). To obtain a patient-specific representative model, it is crucial to have an accurate and rapid estimate of the hemodynamic model parameters. Moreover, when adequate model parameters are found, the resulting time series of state variables can be clinically used for predicting the response to treatments and for non-invasive monitoring. In the Thesis, we address the parameter estimation or inverse modeling, by solving an optimization problem, which aims at minimizing the error between the model output and the target data. In our case, the target data are a set of user-defined state variables, descriptive of a hospitalized specific patient and obtained from time-averaged state variables. The Thesis proposes a comparison of both state-of-the-art and novel methods for the estimation of the underlying model parameters of a cardiovascular simulator Aplysia. All the proposed algorithms are selected and implemented considering the constraints deriving from the interaction with Aplysia. In particular, given the inaccessibility of the ODE, we selected gradient-free methods, which do not need to estimate numerically the derivatives. Furthermore, we aim at having a small number of iterations and objective function calls, since these importantly impact the speed of the estimation procedure, and thus the applicability of the knowledge gained through the parameters at the bedside. Moreover, the Thesis addresses the most common problems encountered in the inverse modeling, among which are the non-convexity of the objective function and the identifiability problem. To assist in resolving the latter issue an identifiability analysis is proposed, after which the unidentifiable parameters are excluded. The selected methods are validated using heart failure data, representative of different pathologies commonly encountered in Intensive Care Unit (ICU) patients. The results show that the gradient-free global algorithms Enhanced Scatter Search and Particle Swarm estimate the parameters accurately at the price of a high number of function evaluations and CPU time. As such, they are not suitable for bedside applications. Besides, the local algorithms are not suitable to find an accurate solution given their dependency on the initial guess. To solve this problem, we propose two methods: the hybrid, and the prior-knowledge algorithms. These methods, by including prior domain knowledge, can find a good solution, escaping the basin of attraction of local minima and producing clinically significant parameters in a few minutes. / Utveckling av modeller av det kardiovaskulära systemet som simulerar det dynamiska beteendet hos en virtuell patients är grundläggande inom det medicinska området för att kunna förutsäga resultat och generera hypoteser. Dessa modeller beskrivs vanligtvis genom Ordinary Differential Equation (ODE). För att erhålla en patientspecifik representativ modell är det viktigt att ha en exakt och snabb uppskattning av de hemodynamiska modellparametrarna. När adekvata modellparametrar har hittats kan de resulterande tidsserierna av tillståndsvariabler dessutom användas kliniskt för att förutsäga svaret på behandlingar och för icke-invasiv övervakning. I avhandlingen behandlar vi parameteruppskattning eller invers modellering genom att lösa ett optimeringsproblem som syftar till att minimera följande felet mellan modellens utdata och måldata. I vårt fall är måldata en uppsättning användardefinierade tillståndsvariabler som beskriver en specifik patient som är inlagd på sjukhus och som erhålls från tidsgenomsnittliga tillståndsvariabler. I avhandlingen föreslås en jämförelse av befintlinga och nya metoder. för uppskattning av de underliggande modellparametrarna i en kardiovaskulär simulator, Aplysia. Alla föreslagna algoritmer är valts och implementerade med hänsyn tagna till de begränsningar som finnis i simulatorn Aplysia. Med tanke på att ODE är otillgänglig har vi valt gradientfria metoder som inte behöver uppskatta derivatorna numeriskt. Dessutom strävar vi efter att ha få interationer och funktionsanrop eftersom dessa påverkar hastigheten på estimeringen och därmed den kliniska användbartheten vid patientbehandling. Avhandlingen behandlas dessutom de vanligaste problemen vid inversmodellering som icke-konvexitet och identifierbarhetsproblem. För att lösa det sistnämnda problemet föreslås en identifierbarhetsanalys varefter de icke-identifierbara parametrarna utesluts. De valda metoderna valideras med hjälp av data om hjärtsvikt som är representativa för olika patologier som ofta förekommer hos Intensive Care Unit (ICU)-patienter. Resultaten visar att de gradientfria globala algoritmerna Enhanced Scatter Search och Particle Swarm uppskattar parametrarna korrekt till priset av ett stort antal funktionsutvärderingar och processortid. De är därför inte lämpliga för tillämpningar vid sängkanten. Dessutom är de lokala algoritmerna inte lämpliga för att hitta en exakt lösning eftersom de är beroende av den ursprungliga gissningen. För att lösa detta problem föreslår vi två metoder: hybridalgoritmer och algoritmer med förhandsinformation. Genom att inkludera tidigare domänkunskap kan dessa metoder hitta en bra lösning som undviker de lokala minimernas attraktionsområde och producerar kliniskt betydelsefulla parametrar på några minuter.

This thesis considers the practical problem of constrained and unconstrained local optimization. This subject has been well studied when the objective function f is assumed to smooth. However, nonsmooth problems occur naturally and frequently in practice. Here f is assumed to be nonsmooth or discontinuous without forcing smoothness assumptions near, or at, a potential solution. Various methods have been presented by others to solve nonsmooth optimization problems, however only partial convergence results are possible for these methods. In this thesis, an optimization method which use a series of local and localized global optimization phases is proposed. The local phase searches for a local minimum and gives the methods numerical performance on parts of f which are smooth. The localized global phase exhaustively searches for points of descent in a neighborhood of cluster points. It is the localized global phase which provides strong theoretical convergence results on nonsmooth problems. Algorithms are presented for solving bound constrained, unconstrained and constrained nonlinear nonsmooth optimization problems. These algorithms use direct search methods in the local phase as they can be applied directly to nonsmooth problems because gradients are not explicitly required. The localized global optimization phase uses a new partitioning random search algorithm to direct random sampling into promising subsets of ℝⁿ. The partition is formed using classification and regression trees (CART) from statistical pattern recognition. The CART partition defines desirable subsets where f is relatively low, based on previous sampling, from which further samples are drawn directly. For each algorithm, convergence to an essential local minimizer of f is demonstrated under mild conditions. That is, a point x* for which the set of all feasible points with lower f values has Lebesgue measure zero for all sufficiently small neighborhoods of x*. Stopping rules are derived for each algorithm giving practical convergence to estimates of essential local minimizers. Numerical results are presented on a range of nonsmooth test problems for 2 to 10 dimensions showing the methods are effective in practice.

La compression élastique (CE) est un traitement médical qui est prescrit en cas d'insuffisance veineuse. Récemment, la CE rencontre aussi un certain succès auprès des sportifs pour la récupération. Cependant, malgré l'utilisation de plus en plus massive de la CE, son action biomécanique sur le membre inférieur n'est pas encore bien caractérisée. Pour contribuer à cette caractérisation, un modèle biomécanique 3D des tissus mous de la jambe sous CE a été développé et appliqué à un panel de sujets. Chaque modèle est personnalisé : la géométrie est reconstruite à partir des images tomographiques 3D de la jambe de chaque sujet et les conditions aux limites reproduisent fidèlement la pression localement appliquée par la CE sur la peau. De plus, les propriétés hyper-élastiques des tissus mous sont identifiées pour chaque sujet par recalage du modèle. Une méthode de recalage originale a été spécifiquement développée et mise en œuvre pour cette application : elle consiste à utiliser les images tomographiques 3D de la jambe déformée comme données expérimentales pour le recalage. Finalement, le modèle donne accès au champ de pression transmis par la CE aux tissus mous internes. Les principales conclusions sont que le champ de pression à l'intérieur de la jambe n'est pas transmis uniformément et qu'il y a de fortes variabilités inter-sujets. En outre, le modèle permet d'obtenir des indications sur le confort et l'efficacité de la CE. Il a ainsi été possible de montrer que l'intensité des pressions maximales subies par les tissus mous de la jambe est inversement proportionnelle à l'épaisseur du tissu adipeux. Les principales perspectives du travail concernent la validation clinique de ces conclusions sur un nombre significatif de sujets, puis leur exploitation en vue d'améliorer les traitements.

<p>This essay revolves around <em>Micrographia </em>written by the English 17th century experimental philosopher Robert Hooke and the way it mediated microscopic experience. The focus of this study is on one hand the strategies Hooke used to communicate experience and on the other the responses by some of Hooke’s contemporary readers. By comparing <em>Micrographia </em>to Henry Power’s <em>Experimental Philosophy</em>, we see that <em>Micrographia </em>uses images where the author is invisible and textual narrations with an explicit authorial voice to mediate experimental experience to his contemporaries. Samuel Pepys uses the mediated experiences to learn how to see through the microscope and to become more like the author in <em>Micrographia</em>, Margaret Cavendish does not trust the representational techniques of Hooke and the playwright Thomas Shadwell satirizes the gentleman virtuoso that constitutes the narrative voice in <em>Micrographia</em>. By the study of these three readers, I build on Peter Dears definition of a scientific text as having an inherent reference to an experimental situation. By seeing <em>Micrographia </em>as defined through the interactions between the author and the readers, we see that this reference, and therefore a text’s scientific status, is defined by a relation between author and reader based on trust. The reader has to trust both the author and the representational techniques used in the text. The appropriation of <em>Micrographia </em>by readers who do not possess this trust, results in the redefinition of <em>Micrographia </em>into other kinds of texts that fill different purposes defined by the readers. <em></em></p>

This essay revolves around Micrographia written by the English 17th century experimental philosopher Robert Hooke and the way it mediated microscopic experience. The focus of this study is on one hand the strategies Hooke used to communicate experience and on the other the responses by some of Hooke’s contemporary readers. By comparing Micrographia to Henry Power’s Experimental Philosophy, we see that Micrographia uses images where the author is invisible and textual narrations with an explicit authorial voice to mediate experimental experience to his contemporaries. Samuel Pepys uses the mediated experiences to learn how to see through the microscope and to become more like the author in Micrographia, Margaret Cavendish does not trust the representational techniques of Hooke and the playwright Thomas Shadwell satirizes the gentleman virtuoso that constitutes the narrative voice in Micrographia. By the study of these three readers, I build on Peter Dears definition of a scientific text as having an inherent reference to an experimental situation. By seeing Micrographia as defined through the interactions between the author and the readers, we see that this reference, and therefore a text’s scientific status, is defined by a relation between author and reader based on trust. The reader has to trust both the author and the representational techniques used in the text. The appropriation of Micrographia by readers who do not possess this trust, results in the redefinition of Micrographia into other kinds of texts that fill different purposes defined by the readers.

No description available.

This work aims at enhancing the understanding and to provideimproved models of the dynamic behavior of rubber vibrationisolators which are widely used in mechanical systems.Initially, a time domainmodel relating compressions tocomponent forces accounting for preload effects, frequency anddynamic amplitude dependence is presented. The problem ofsimultaneously modelling the elastic, viscoelastic and frictionforces are removed by additively splitting them, where theelastic force response is modelled either by a fully linear ora nonlinear shape factor based approach, displaying resultsthat agree with those of a neo-Hookean hyperelastic isolatorunder a long term precompression. The viscoelastic force ismodelled by a fractional derivative element, while the frictionforce governs from a generalized friction element displaying asmoothed Coulomb force. This is a versatile one-dimensionalcomponent model effectively using a small number of parameterswhile exhibiting a good resemblance to measured isolatorcharacteristics. Additionally, the nonlinear excitationeffects on dynamic stiffness and damping of a filled rubberisolator are investigated through measurements. It is shownthat the well-known Payne effect - where stiffness is high forsmall excitation amplitudes and low for large amplitudes whiledamping displays a maximum at intermediate amplitudes -evaluated at a certain frequency, is to a large extentinfluenced by the existence of additional frequency componentsin the signal. Finally, a frequency, temperature and preloaddependent dynamic stiffness model is presented covering theranges from 20 to 20 000 Hz, -50 to +50 °C at 0 to 20 %precompression. A nearly incompressible, thermo-rheologicallysimple material model is adopted displaying viscoelasticitythrough a time - strain separable relaxation tensor with asingle Mittag-Leffler function embodying its time dependence.This fractional derivative based function successfully fitsmaterial properties throughout the whole audible frequencyrange. An extended neo-Hookean strain energy function, beingdirectly proportional to the temperature and density, isapplied for the finite deformation response with componentproperties solved by a nonlinear finite element procedure. Thepresented work is thus believed to enlighten workingconditions’impact on the dynamic properties of rubbervibration isolators, while additionally taking some of thesemost important features into account in the presentedmodels.

<p>This work aims at enhancing the understanding and to provideimproved models of the dynamic behavior of rubber vibrationisolators which are widely used in mechanical systems.Initially, a time domainmodel relating compressions tocomponent forces accounting for preload effects, frequency anddynamic amplitude dependence is presented. The problem ofsimultaneously modelling the elastic, viscoelastic and frictionforces are removed by additively splitting them, where theelastic force response is modelled either by a fully linear ora nonlinear shape factor based approach, displaying resultsthat agree with those of a neo-Hookean hyperelastic isolatorunder a long term precompression. The viscoelastic force ismodelled by a fractional derivative element, while the frictionforce governs from a generalized friction element displaying asmoothed Coulomb force. This is a versatile one-dimensionalcomponent model effectively using a small number of parameterswhile exhibiting a good resemblance to measured isolatorcharacteristics. Additionally, the nonlinear excitationeffects on dynamic stiffness and damping of a filled rubberisolator are investigated through measurements. It is shownthat the well-known Payne effect - where stiffness is high forsmall excitation amplitudes and low for large amplitudes whiledamping displays a maximum at intermediate amplitudes -evaluated at a certain frequency, is to a large extentinfluenced by the existence of additional frequency componentsin the signal. Finally, a frequency, temperature and preloaddependent dynamic stiffness model is presented covering theranges from 20 to 20 000 Hz, -50 to +50 °C at 0 to 20 %precompression. A nearly incompressible, thermo-rheologicallysimple material model is adopted displaying viscoelasticitythrough a time - strain separable relaxation tensor with asingle Mittag-Leffler function embodying its time dependence.This fractional derivative based function successfully fitsmaterial properties throughout the whole audible frequencyrange. An extended neo-Hookean strain energy function, beingdirectly proportional to the temperature and density, isapplied for the finite deformation response with componentproperties solved by a nonlinear finite element procedure. Thepresented work is thus believed to enlighten workingconditions’impact on the dynamic properties of rubbervibration isolators, while additionally taking some of thesemost important features into account in the presentedmodels.</p>

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2018-09-12T10:47:41Z No. of bitstreams: 2 Dissertação - Airton Modesto da Cunha - 2018.pdf: 36005906 bytes, checksum: 5f095bd3c548d6f6e958d83f126908ef (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-09-12T10:50:15Z (GMT) No. of bitstreams: 2 Dissertação - Airton Modesto da Cunha - 2018.pdf: 36005906 bytes, checksum: 5f095bd3c548d6f6e958d83f126908ef (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-09-12T10:50:15Z (GMT). No. of bitstreams: 2 Dissertação - Airton Modesto da Cunha - 2018.pdf: 36005906 bytes, checksum: 5f095bd3c548d6f6e958d83f126908ef (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-08-09 / The present dissertation is the result of the educational, “Teaching model of electrical resistors to describe fractures in physical systems”, product worked in a class of the third year of high school of the State School Prof. Marcolino de Barros of the municipality of Patos de Minas-MG. In which, we present a simple pedagogical model with the purpose of studying the complex process of ruptures in physical systems. For this, we developed an experimental model together with its theoretical counterpart where we consider a system of electric resistors network subject to a potential difference and analyze the current that passes through the system as a function of the random removal of their resistive components. We use a circuit board, voltage source stabilized at a pre-established potential difference, and a resistor network with a few ohms units each. After the proposed experiments are executed, we obtained appropriate experimental data and from these graphs are generated with which the dependence of the current through the circuit with the interruption of the joints is shown. Taking into account that this system behaves as an ohmic system, the model is used to study several relevant physical concepts. As is the case of an elastic solid subject to Hooke’s law- like deformations, this is then a very broad model. / A presente dissertação é resultado de nosso produto educacional, “Modelo pedagógico de resistores elétricos para descrever fraturas em sistemas físicos”, trabalhado em uma turma do terceiro ano do ensino médio da Escola Estadual Prof. Marcolino de Barros do município de Patos de Minas-MG. No qual, apresentamos um modelo pedagógico simples com a finalidade de estudar o complexo processo de rupturas em sistemas físicos. Para tanto, desenvolvemos um modelo experimental munido de sua contraparte teórica onde consideramos um sistema de resistores elétricos sujeito a uma diferença de potencial e analisamos a corrente que passa através do sistema em função da remoção aleatória doscomponentes resistivos. Usamos uma placa de circuitos, fonte de tensão estabilizada em uma diferença de potencial pré -estabelecida e uma malha de resistores com algumas unidades de ohms cada. Realizadas as experiências propostas obtivemos apropriados dados experimentais e a partir destes foram gerados gráficos com os quais são mostrados a dependência da corrente através do circuito com a interrupção das junções. Levando em consideração que este sistema se comporta como um sistema ôhmico, o modelo é usado para estudar vários conceitos físicos relevantes. Como é o caso de um solido elástico sujeito a deformações do tipo lei de Hooke, sendo este então um modelo de caráter bem amplo.

In vielen industriellen Anwendungen sind Dichtungen im Einsatz. Vergleicht man den Preis mit dem eines Gesamtsystems, in denen Dichtungen verwendet werden, so sind Dichtungen verhältnismäßig günstig. Jedoch führt ein Versagen von Dichtungen meist zu schwerwiegenden Konsequenzen. Dichtungen sind komplexe Subsysteme und ihre Auslegung erfordert umfangreiche Kenntnisse im Bereich Materialmodellierung, Belastung und Versagenskriterien. Die heutige Simulationstechnologie ermöglicht einen parametrischen Workflow für die Berechnung des Verhaltens von Dichtungen mit den auftretenden Effekten wie nichtlinearem Materialverhalten, wechselnden Kontaktbedingungen und Flüssigkeitsunterwanderung bei Druck. Als ein führendes Simulationswerkzeug für diese physikalische Fragestellung wird ANSYS Mechanical für die Auslegung herangezogen. Desweiteren kann das Verständnis für das Produkt erhöht werden, was zu einer Verbesserung der Funktionalität und der Zuverlässigkeit führt. Versuchsdaten können als Spannungs-Dehnungskurven in ANSYS importiert werden, welche das Materialverhalten des hyperelastischen Werkstoffs mit traditionellen Materialmodellen wie Mooney Rivlin, Ogden and Yeoh oder einer neueren Formulierung, der Antwortfunktionsmethode, widerspiegeln. Robuste Kontakttechnologien beschleunigen die Simulation und Entwicklungszeit-Berechnungszeiten und gewährleisten ein genaues Verhalten des Simulationsmodells. Insbesondere bei Dichtungen ist die druckbeaufschlagte Fläche in 2D und 3D Anwendungen von Bedeutung. ANSYS berechnet diese automatisch in Abhängigkeit des aktuellen Kontaktzustandes. Diese benutzerfreundliche Unterstützung führt zu einer höheren Genauigkeit des Simulationsergebnisses, da ein manuelles Schätzen der Druckflächen entfällt. Mit einem parametrischen und durchgängigen Ansatz innerhalb von ANSYS Workbench, beginnend bei der CAD-Geometrie, über die Vernetzung, Material- und Randbedingungsdefinition und Lösung. können eine Reihe von Varianten in kurzer Zeit berechnet werden. Neben einem besseren Verständnis für das Produkt hilft dies dem Ingenieur Änderungen vorzunehmen, was zu exakten und aussagekräftigen Ergebnissen führt. Desweiteren kann der Einfluss von Unsicherheiten berücksichtigt werden, sodass der Berechnungsingenieur fernab von idealen Bedingungen robuste und zuverlässige Dichtungen entwickeln kann.