Enseignement Cours – HJB, MFG et les autres Le cours a eu lieu du 9 novembre 2018 au 18 janvier 2019. Introduction Le cours de cette année a porté sur diverses questions relatives aux équations de ...type Hamilton-Jacobi-Bellman, aux systèmes provenant de la théorie des jeux à champ moyen (MFG en abrégé) et aux équations de type Hamilton-Jacobi stochastique. Les questions mathématiques introduites et étudiées dans le cours ont pour origine des modèles mathématiques en contrôle stochatique et en ...
Abstract An algorithm framework is proposed for minimizing nonsmooth functions. The framework is variable metric in that, in each iteration, a step is computed using a symmetric positive-definite ...matrix whose value is updated as in a quasi-Newton scheme. However, unlike previously proposed variable-metric algorithms for minimizing nonsmooth functions, the framework exploits self-correcting properties made possible through Broyden–Fletcher–Goldfarb–Shanno-type updating. In so doing, the framework does not overly restrict the manner in which the step computation matrices are updated, yet the scheme is controlled well enough that global convergence guarantees can be established. The results of numerical experiments for a few algorithms are presented to demonstrate the self-correcting behaviours that are guaranteed by the framework.
We introduce the concept of epidemic-fitted wavelets which comprise, in particular, as special cases the number I(t) of infectious individuals at time t in classical SIR models and their derivatives. ...We present a novel method for modelling epidemic dynamics by a model selection method using wavelet theory and, for its applications, machine learning-based curve fitting techniques. Our universal models are functions that are finite linear combinations of epidemic-fitted wavelets. We apply our method by modelling and forecasting, based on the Johns Hopkins University dataset, the spread of the current Covid-19 (SARS-CoV-2) epidemic in France, Germany, Italy and the Czech Republic, as well as in the US federal states New York and Florida.
We introduce the concept of epidemic-fitted wavelets which comprise, in particular, as special cases the number I(t) of infectious individuals at time t in classical SIR models and their derivatives. ...We present a novel method for modelling epidemic dynamics by a model selection method using wavelet theory and, for its applications, machine learning-based curve fitting techniques. Our universal models are functions that are finite linear combinations of epidemic-fitted wavelets. We apply our method by modelling and forecasting, based on the Johns Hopkins University dataset, the spread of the current Covid-19 (SARS-CoV-2) epidemic in France, Germany, Italy and the Czech Republic, as well as in the US federal states New York and Florida.
Motivated by the general question of existence of open A(1)-cylinders in higher dimensional projective varieties, we consider the case of Mori Fiber Spaces of relative dimension three, whose general ...closed fibers are isomorphic to the quintic del Pezzo threefold, the smooth Fano threefold of index two and degree five. We show that the total spaces of these Mori Fiber Spaces always contain a relative A(2)-cylinder, and we characterize those admitting relative A(3)-cylinders in terms of the existence of certain special lines in their generic fiber.
Dans le contexte général de l’étude de l’existence de A1-cylindresouverts dans les variétés projectives de dimension supérieure, nous considérons le cas des fibrations de Mori de dimension relative trois, dont les fibres générales sont isomorphes au volume quintique de del Pezzo, l’unique variété de Fano lisse de degré cinq et d’indice deux. Nous établissons que les espaces totaux de fibrations de Mori de ce type contiennent toujours unA2-cylindre relatif au-dessus de la base de la fibration. Nous donnons également une caractérisation reliant l’existence deA3-cylindres relatifs à l’existence de certaines droites spéciales dans la fibre générique de ces fibrations
Abstract We consider an abstract inclusion in a real Hilbert space, governed by an almost history-dependent operator and a time-dependent multimapping with prox-regular values. We establish the ...unique solvability of the inclusion under appropriate assumptions on the data. The proof is based on the arguments of monotonicity, fixed point, and prox-regularity. We then use our result in order to deduce some direct consequences, including an existence and uniqueness result for a class of sweeping processes associated with prox-regular sets. Finally, we provide an example in a finite dimensional case inspired by a rheological model in solid mechanics.
The objective of this study is to characterize the literacy and probabilistic thinking skills that trainee and currently active mathematics teachers use when faced with real-world problems, in which ...uncertainty plays a role. A qualitative methodology was used, applying a case study design and the content analysis method. As a technique to obtain information, an open-question instrument was prepared based on two problem situations, which the participants were asked to complete. The 55 participants were selected through intentional or disposition sampling, 26 of whom were actively teaching, and 29 of whom were trainee teachers. Among the main results, it is worth noting that all teachers that participated in the study, both active and trainees, have not developed probabilistic skills that allow them to consider problems from the intuitive, classical and frequency perspectives, essentially resorting to the classical meaning of probability. In addition, there is little evidence of the development of conceptual and argumentative skills that allow comparing empirical and theoretical results. In conclusion, it was observed that both active and trainee teachers have not developed literacy skills and probabilistic thinking which would allow a way of teaching probability that goes beyond the purely algorithmic, promoting learning environments for the probabilistic literacy of students during their school years.
El objetivo del presente artículo es caracterizar las habilidades de alfabetización y pensamiento probabilístico que las personas docentes de matemática, en formación inicial y en activo, utilizan cuando se enfrentan a problemas reales, donde interviene la incertidumbre. Para tal efecto, se siguió una metodología cualitativa, mediante un diseño de estudio de casos y el método de análisis de contenido. Como técnica para obtener información, se aplicó un instrumento de dos situaciones problemas en las cuales se solicitó respuesta a preguntas abiertas. Se realizó la selección de 55 participantes mediante un muestreo del tipo intencionado o por disposición, de los cuales 26 eran docentes en activo y 29 docentes en formación inicial. Entre los principales resultados se destacan que las personas docentes del estudio, tanto en formación inicial como en activo, no han desarrollado una competencia probabilística que transite por lo intuitivo, lo clásico y lo frecuencial, recurriendo esencialmente al significado clásico de probabilidad. Además, se evidencia un escaso desarrollo de ideas conceptuales y argumentativas que permitan comparar resultados empíricos y teóricos. En conclusión, se observa que las personas docentes seleccionadas, en formación inicial y en activo, no han desarrollado habilidades de alfabetización y pensamiento probabilístico, que posibiliten una enseñanza de la probabilidad que vaya más allá de lo algorítmico, promoviendo ambientes de aprendizaje para la alfabetización probabilística de los estudiantes en la etapa escolar.
O objetivo deste artigo é caracterizar as habilidades de alfabetização e pensamento probabilístico que os professores de matemática, na formação inicial e ativos, utilizam diante de problemas reais, onde a incerteza intervém. Para isso, seguiu-se uma metodologia qualitativa, por meio de desenho de estudo de caso e método de análise de conteúdo. Como técnica de obtenção de informações, foi aplicado um instrumento de duas situações problemáticas em que foram solicitadas respostas a perguntas abertas. A seleção de 55 participantes foi feita por meio de amostragem do tipo intencional ou por disposição, dos quais 26 eram professores ativos e 29 professores em formação inicial. Entre os principais resultados estão que os professores do estudo, tanto na formação inicial quanto ativos, não desenvolveram uma competência probabilística que passa pelo intuitivo, pelo clássico e pela frequência, recorrendo essencialmente ao significado clássico da probabilidade. Além disso, há pouco desenvolvimento de ideias conceituais e argumentativas que permitem comparar resultados empíricos e teóricos. Em conclusão, observa-se que os professores selecionados, na formação inicial e ativos, não desenvolveram habilidades de alfabetização e pensamento probabilístico que possibilitem um ensino de probabilidade que vá além do algorítmico, promovendo ambientes de aprendizagem para a alfabetização probabilística dos alunos na etapa escolar.
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