Noticias en español
Seminars appear in decreasing order in relation to date. To find an activity of your interest just go down on the list. Normally seminars are given in English. If not, they will be marked as Spanish Only.
Image Reconstruction in Dynamic PET Imaging & Regularisation Methods for Joint Image Reconstruction.
Abstract: Dynamic positron emission tomography (PET) imaging captures temporal information of biological processes in living tissue. This technique can be used, for example, for diagnosis and treatment monitoring of cancers and brain diseases by studying the activity distribution of radioactively-labelled pharmaceuticals injected into the patient’s body. Reconstructing time-varying images from a set of physical measurements (photon counts) is challenging due to the low signal-to-noise ratio and low spatial resolution of standard PET scanners....
Variations of the infimal convolution and application to the minimal time function.
Abstract: We establish in the Banach setting a relationship between the variations of the infimal convolution of a fairly general function and a proper continuous convex function. Namely, we compare the Clarke subdifferential of all these functions at points where the infimal convolution is attained, or strongly attained. This work extends and adapts many of the existing results in the literature. We apply this work to investigate the differentiability of a minimal time function. We also discuss necessary optimality conditions for a location...
Extracción jerárquica no-supervisada de características mediante Autoencoders.
Abstract: La creciente aplicación de redes profundas para la realización de tareas mediante aprendizaje automático, ha creado la necesidad de buscar metodologías para lidiar con el conocido problema de la desaparición del gradiente (Vanishing gradient problem) en el entrenamiento de redes neuronales con más de una capa oculta. Una de estas metodologías utiliza un modelo de aprendizaje no supervisado llamado Autoencoder, capaz de realizar un acercamiento “seguro” de los parámetros de la red a su valor óptimo. En esta charla se...
Investigaciones de enseñanza de las matemáticas de pregrado
Resumen: La investigación de la enseñanza de las matemáticas en los institutos comunitarios revela un patrón de interacción que se puede describir como presentación interactiva (“interactive lecture”). En este patrón, el profesor presenta los temas, los ejemplos, y los problemas. El papel del estudiante consiste en hacer preguntas que aclaren el contenido. Los estudiantes rara vez discuten ideas entre sí y las preguntas que se proponen tienden a enfatizar procesos que requieren pocos recursos cognitivos. El uso de este patrón se justifica en...
Limiting laws for some integrated processes
Resumen: The study of limiting laws, or penalizations, of a given process may be seen (in some sense) as a way to condition a probability law by an a.s. infinite random variable. The systematic study of such problems started in 2006 with a series of papers by Roynette, Vallois and Yor who looked at Brownian motion perturbed by several examples of functionals. These works were then generalized to many families of processes: random walks, Lévy processes, linear diffusions… We shall present here some examples of penalization of a non-Markov...
“Sufficient optimality conditions hold for almost all nonlinear semidefinite programs”
Abstract: We derive a new genericity result for nonlinear semidefinite programming (NLSDP). Namely, almost all linear perturbations of a given NLSDP are shown to be nondegenerate. Here, nondegeneracy for NLSDP refers to the transversality constraint qualification, strict complementarity and second-order sufficient condition. A reduced NLSDP is locally considered by transforming equivalently thesemidefinite constraint to a smaller dimension via Schur complement. While deriving optimality conditions for the reduced NLSDP, the...
Phase Transitions on the Long Range Ising Models in presence of an random external field
Resumen: We study the ferromagnetic one-dimensiosnal Random Field Ising Model with (RFIM) in presence of an external random field. The interaction between two spins decays as $d^{\alpha-2}$ where $d$ is the distance between two sites and $\alpha \in [0,1/2)$ is a parameter of the model. We consider an external random field on $\mathbb{Z}$ with independent but not identically distributed random variables. Specifically for each $i \in \mathbb{Z}$, the distribution of $h_i$ is $P[h_i=\pm \theta(1+|i|)^{-\nu/2}]$. This work, whose main goal is...
Robust shape optimisation with small uncertainties
Abstract: In this talk we propose two approaches for dealing with small uncertainties in geometry and topology optimisation of structures. Uncertainties occur in the loadings, the material properties, the geometry or the imposed vibration frequency. A first approach, in a worst-case scenario, amounts to linearise the considered cost function with respect to the uncertain parameters, then to consider the supremum function of the obtained linear approximation, whichcan be rewritten as a more `classical’ function of the design,...
Asymptotic properties of an optimization-based matching estimator for average treatment effects
Abstract: This paper investigates the asymptotic properties of a novel matching estimator for the average treatment effects of binary programs. In order to impute the missing potential outcome for each unit, this approach employs both a number of neighbors and a weighting scheme that are endogenously determined by solving a nested pair of optimization problems associated with an individual covariate balancing criterion. Under mild conditions, our main contributions are: (i) the asymptotic normality and a consistent estimator...
Desarrollo Profesional Docente e Investigación: Los modelos de Ciclo de Resolución de Problemas y de Preparación de Líderes en Matemática.
Resumen: En los últimos años ha habido una creciente demanda por oportunidades de desarrollo profesional para profesores en ejercicio. Los líderes educacionales y los administradores están buscando modelos de desarrollo profesional que puedan realizarse a gran escala, a nivel del sistema y que den lugar a mejoras en la enseñanza y a un aumento en los aprendizajes de todos los estudiantes. Están pidiendo a la comunidad de investigación en educación respuestas a preguntas como: ¿Cuáles son los programas de desarrollo profesional efectivos y de...
