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- Aplicação de problemas de controlo a uma estenose idealizadaPublication . Guerra, Telma; Tiago, JorgeNeste trabalho apresentamos, de forma sucinta, simulações numé-ricas de fluidos, de problemas do tipo Assimilação de Dados numa aborda-gem variacional. Apresentamos resultados aplicados à Hemodinâmica consi-derando uma geometria tridimensional na forma de uma estenose idealizadae recuperamos o perfil da velocidade do sangue nesta geometria.
- Combining Models in Discrete Discriminant AnalysisPublication . Marques, Anabela; Ferreira, Ana Sousa; Cardoso, Margarida
- Cross-diffusion-driven instability for reaction-diffusion systems: analysis and simulationsPublication . Madzvamuse, Anotida; Ndakwo, Hussaini; Barreira, RaquelBy introducing linear cross-diffusion for a two-component reaction-diffusion system withactivator-depletedreaction kinetics (Gierer and Meinhardt,Kybernetik 12:30–39,1972;PrigogineandLefever,JChemPhys48:1695–1700,1968;Schnakenberg, J Theor Biol 81:389–400,1979), we derivecross-diffusion-driveninstability conditions and show that they are a generalisation of the classical diffusion-driveninstabilityconditionsintheabsenceofcross-diffusion.Ourmostrevealingresultis that, in contrast to the classical reaction-diffusion systems without cross-diffusion,it is no longer necessary to enforce that one of the species diffuse much faster than theother.Furthermore,it is no longer necessary to have an activator–inhibitor mecha-nism as premises for pattern formation, activator–activator,inhibitor–inhibitorreac-tion kinetics as well asshort-range inhibitionandlong-range activationall have thepotential of giving rise to cross-diffusion-driven instability. To support our theoreti-cal findings, we compute cross-diffusion induced parameter spaces and demonstratesimilarities and differences to those obtained using standard reaction-diffusion theory.Finite element numerical simulations on planary square domains are presented to back-up theoretical predictions. For the numerical simulations presented, we choose parameter values from and outside the classical Turing diffusively-driven instability space;outside, these are chosen to belong to cross-diffusively-driven instability parameterspaces. Our numerical experiments validate our theoretical predictions that parameterspaces induced by cross-diffusion in both theuandvcomponents of the reaction-diffusion system are substantially larger and different from those without cross-diffusion. Furthermore, the parameter spaces without cross-diffusion are sub-spacesof the cross-diffusion induced parameter spaces. Our results allow experimentalists tohave a wider range of parameter spaces from which to select reaction kinetic parametervalues that will give rise to spatial patterning in the presence of cross-diffusion.
- Exhibiting cross-diffusion-induced patterns for reaction-diffusionsystems on evolving domains and surfacesPublication . Madzvamuse, Anotida; Barreira, RaquelThe aim of this manuscript is to present for the first time the application of the finite element method for solvingreaction-diffusion systems with cross-diffusion on continuously evolving domains and surfaces. Furthermore wepresent pattern formation generated by the reaction-diffusion system with cross-diffusion on evolving domains andsurfaces. A two-component reaction-diffusion system with linear cross-diffusion in bothuandvis presented. Thefinite element method is based on the approximation of the domain or surface by a triangulated domain or surfaceconsisting of a union of triangles. For surfaces, the vertices of the triangulation lie on the continuous surface. Afinite element space of functions is then defined by taking the continuous functions which are linear affine on eachsimplex of the triangulated domain or surface. To demonstrate the role of cross-diffusion to the theory of patternformation, we compute patterns with model kinetic parameter values that belong only to the cross-diffusionparameter space; these do not belong to the standard parameter space for classical reaction-diffusion systems.Numerical results exhibited show the robustness, flexibility, versatility, and generality of our methodology; themethodology can deal with complicated evolution laws of the domain and surface, and these include uniformisotropic and anisotropic growth profiles as well as those profiles driven by chemical concentrations residing inthe domain or on the surface
- Existence of optimal boundary control for the Navier-Stokes equations with mixed boundary conditionsPublication . Guerra, Telma; Sequeira, Adélia; Tiago, JorgeVariational approaches have been used successfully as a strategy to takeadvantage from real data measurements. In several applications, this approach allowsto increase the accuracy of numerical simulations. In the particular case of fluid dy-namics, it leads to optimal control problems with non-standard cost functionals which,when subject to the Navier-Stokes equations, require a non-standard theoretical frameto ensure the existence of solution. In this work, we prove the existence of solution fora class of such type of optimal control problems. Before doing that, we ensure the ex-istence and uniqueness of solution for the 3D stationary Navier-Stokes equations, withmixed-boundary conditions, a particular type of boundary conditions very common inapplications to biomedical problems
- Improving Blood Flow Simulations Using Known DataPublication . Guerra, Telma; Tiago, JorgeNumerical simulations applied to blood flow together with the imaging processing advances are a powerful tool in the prevention and treatment of some diseases. The inclusion of real data in the numerical blood flow simulations allowsthe achievementofmore realistic and accurate results. In the literature, these techniques areknown asData Assimilation (DA)techniques.In this work we solve a variational DA problem to numerically reconstruct the blood flow circulation inside a real artery,deformed by a saccular aneurysm obtained from medical images and then importedto COMSOL Multiphysics®.We propose a weighted cost function that accurately recovers both the velocity and the wall shear stress profiles. The robustness of such cost function is tested with respect to different velocity inlet profiles
- Investigação em educação em engenharia: um campo emergentePublication . Williams, Bill; Hattum-Janssen, Natascha van; Oliveira, José ManuelNum mundo cada vez mais globalizado e em que o rápido desenvolvimento científico e tecnológico ocupa um papel central no desenvolvimento das sociedades, torna-se cada vez mais relevante discutir o perfil desejável dos profissionais de engenharia capazes de dar resposta a estes desafios, e consequentemente, discutir as processos de formação desses futuros engenheiros. No contexto internacional, estas necessidades têm vindo a fazer emergir a Investigação em Ensino de Engenharia (IEE) como um campo de investigação autónomo. Norteando-se pelos critérios de identidade para um campo de investigação de Fensham (2004), usado também por Borrego (2007), como princípios orientadores de análise, este artigo pretende discutir a identidade do campo de IEE, caraterizar o seu estado atual no contexto internacional e no contexto Português e posicioná-lo relativamente às Ciências de Educação. Os autores visam igualmente identificar os desafios emergentes no crescimento e amadurecimento deste campo de investigação específico, de forma a que possa granjear reconhecimento quer nas Ciências da Educação, quer nas Engenharias, no contexto Português.
- ITs in engineering education: joining efforts between SPEE and IGIPPublication . Williams, Bill; Neto, Pedro; Cardoso, Alberto; Carvalho, Carlos Vaz de; Magalhães, Fernão de; Rasteiro, M. Graça; Restivo, Maria Teresa; Zutin, Danilo G.The International Society for Engineering Education (IGIP) and The Portuguese Society for Engineering Education (SPEE), the first being the oldest European Society for Engineering Education in Europe and the second the very young Society for Engineering Education in Portugal, have been intensifying the collaboration between the two societies as well as the exchange and dissemination of information about their relevant activities, whilst promoting understanding and cooperation between their respective members. One possible way is to create joint working groups, open to the members of both societies, on common topics of interest. In fact, both societies already kicked off this activity. The first initiative happened during the 1st World Engineering Education Flash Week (WEE), Lisbon, 2011. The SPEE-IGIP Flash Moment was a one day event integrated in the main Conference, which was dedicated to “Information & Communication Technologies in Engineering Education”. ITs allow the development of different teaching strategies which contribute to enhance the learning outcomes of students. ITs are also particularly suited to develop Life Long Learning tools, in a broad range of Engineering subjects, either open to the general market or oriented to a very specific public. Examples of teaching strategies involving ITs have been addressed during the Flash Moment SPEE-IGIP which took place during WEE, and some are described in detail in the present work.
- Keeping them involved: encouraging and monitoring student activityPublication . Williams, Bill; Neto, Pedro; Carvalho, IsabelIn the teaching of engineering, lecture classes are often essentially expository with students in a passive role, not preparing learners for autonomous work and this may contribute to high failure and attrition rates. One way to combat this is through the application of Active Learning (AL) methodologies. In this paper results are presented from the application of an AL Methodology in the classroom and outside it for a last year subject of a BEng degree. A Learner Activity Monitoring Matrix has been used to monitoring in-class learner activity. Also described is the implementation of AL outside class using an online learner management system (LMS) which permits voting by students on the quality of solutions proposed by their peers to resolve engineering problems posed by the lecturer. Empirical data regarding the online participation in the process of each learner is provided. A pre-post survey to reveal student perceptions regarding these methodologies is also presented.