On-the-fly adaptivity for nonlinear twoscale simulations using artificial neural networks and reduced order modeling

A multi-fidelity surrogate model for highly nonlinear multiscale problems is proposed. It is based on the introduction of two different surrogate models and an adaptive on-the-fly switching. The two concurrent surrogates are built incrementally starting from a moderate set of evaluations of the full order model. Therefore, a reduced order model (ROM) is generated. Using a hybrid ROM-preconditioned FE solver, additional effective stress-strain data is simulated while the number of samples is kept to a moderate level by using a dedicated and physics-guided sampling technique. Machine learning (ML) is subsequently used to build the second surrogate by means of artificial neural networks (ANN). Different ANN architectures are explored and the features used as inputs of the ANN are fine tuned in order to improve the overall quality of the ML model. Additional ANN surrogates for the stress errors are generated. Therefore, conservative design guidelines for error surrogates are presented by adapting the loss functions of the ANN training in pure regression or pure classification settings. The error surrogates can be used as quality indicators in order to adaptively select the appropriate -- i.e. efficient yet accurate -- surrogate. Two strategies for the on-the-fly switching are investigated and a practicable and robust algorithm is proposed that eliminates relevant technical difficulties attributed to model switching. The provided algorithms and ANN design guidelines can easily be adopted for different problem settings and, thereby, they enable generalization of the used machine learning techniques for a wide range of applications. The resulting hybrid surrogate is employed in challenging multilevel FE simulations for a three-phase composite with pseudo-plastic micro-constituents. Numerical examples highlight the performance of the proposed approach

Principal Typings in a Restricted Intersection Type System for Beta Normal Forms with De Bruijn Indices

The lambda-calculus with de Bruijn indices assembles each alpha-class of lambda-terms in a unique term, using indices instead of variable names. Intersection types provide finitary type polymorphism and can characterise normalisable lambda-terms through the property that a term is normalisable if and only if it is typeable. To be closer to computations and to simplify the formalisation of the atomic operations involved in beta-contractions, several calculi of explicit substitution were developed mostly with de Bruijn indices. Versions of explicit substitutions calculi without types and with simple type systems are well investigated in contrast to versions with more elaborate type systems such as intersection types. In previous work, we introduced a de Bruijn version of the lambda-calculus with an intersection type system and proved that it preserves subject reduction, a basic property of type systems. In this paper a version with de Bruijn indices of an intersection type system originally introduced to characterise principal typings for beta-normal forms is presented. We present the characterisation in this new system and the corresponding versions for the type inference and the reconstruction of normal forms from principal typings algorithms. We briefly discuss the failure of the subject reduction property and some possible solutions for it

Preferencia de hábitat de la Ballena Jorobada (Meganoptera novaeangliae) en la costa de Esmeraldas, Ecuador

Habitat is a space that contains the physical and biological characteristics that allows to the survival and reproduction of a species. Each species has habitat preferences according to complex interaction between its biological requirements and environmental conditions, as well as their behaviors. These variables are difficult to determine for some species, but it is more complicated for migratory marine mammals, like the humpback whales (Megaptera novaeangliae).El hábitat es el espacio que contiene las características físicas y biológicas que permite la supervivencia y reproducción de una especie. Cada especie tiene preferencias de hábitat según la compleja interacción entre sus requerimientos biológicos y condiciones ambientales, así como sus comportamientos. Estas variables son difíciles de determinar para algunas especies, pero es más complicado para mamíferos marinos migratorios, como las ballenas jorobadas (Megaptera novaeangliae)

Francisco Cortés Gabaudán y Julián Víctor Méndez Dosuna (eds.). Dic Mibi, Musa, Virum. Homenaje al profesor Antonio López Eire. Salamanca, Ediciones Universidad de Salamanca, 2010, 725 pp.

Fil: Fernández Nuin, Mauricio. Universidad Nacional de Cuy

Acerca del poema A la fabricación del vidrio (XIII Heitsh) atribuido a Mesomedes

Los poetas de la Época Imperial grecolatina recurrían a las fuentes de inspiración más diversas y peculiares. Mesomedes de Creta (s. II) reaviva el género inspirándose en temas que, para la época, constituirían sin duda algo al menos cercano a lo maravilloso. Más allá de su altura lírica, el fragmento de lo que se cree fue su poema A la fabricación del vidrio aporta un poderoso rasgo de novedad al género. El trabajo presenta la primera traducción española y un breve comentario de este poema, en búsqueda de una apropiada interpretación del texto.The Greek poets of the Roman period resorted to the most diverse sources of inspiration. Mesomedes of Crete (2nd Century) revives the lyric genre inspired by themes that would surely been considered as something at least close to the marvellous. Aside from the lyrical fineness, the fragment of his poem On glass making represents a powerful and new feature in the genre. This paper presents the first Spanish translation, and a brief commentary of this poem, seeking a proper interpretation of the text.Fil: Fernández Nuin, Mauricio. Universidad Nacional de Cuy

Desafios da globalização econômica

This article aims to analyze the main elements of the current process of economic globalization as trade liberalization and the flow of foreign direct investment and capital mobility. The consequences of these elements demand a series of criticisms and proposals on how local governments must address globalization and what should be the role of international institutions as an instrument that contributes to integration, particularly of the least developed nations, in the world economy. The purpose of this study is to empirically determine the positive and negative effects of economic globalization on national societies, in order to create better public policies that allow an alternative to global governance and a rapid adaptation to global integration.Este artículo pretende analizar los elementos principales del proceso actual de globalización económica como lo son la liberalización del comercio y el flujo de inversión extranjera directa y la movilidad de capital. Las consecuencias de estos elementos exigen una serie de críticas y propuestas relacionadas con la forma en la que los gobiernos locales deben enfrentar la globalización y cuál debería ser el papel de las instituciones internacionales como instrumentos que contribuyan a la integración a la economía mundial, sobre todo en el caso de los países menos desarrollados. El propósito de este estudio es determinar empíricamente los efectos positivos y negativos de la globalización económica en las sociedades nacionales, para poder generar mejores políticas públicas que permitan una alternativa a la gobernabilidad global y una rápida adaptación a la integración global.Este artigo pretende analisar os elementos principais do processo atual da globalização econômica como são a liberalização do comércio e o fluxo de inversão estrangeira direta e o movimento do capital. As consequências de estes elementos, exigem uma série de críticas e propostas relacionadas com a forma na qual os governos locais devem enfrentar a globalização e qual deveria ser o papel das instituições internacionais como instrumentos que proporcione na integração à economia mundial sobre tudo no caso dos países menos desenvolvidos. O propósito deste estudo é determinar empiricamente os efeitos positivos e negativos da globalização econômica nas sociedades nacionais para poder gerar políticas públicas melhores que permitam uma alternativa à governabilidade global e uma rápida adaptação à integração global

Nominal C-Unification

Nominal unification is an extension of first-order unification that takes into account the \alpha-equivalence relation generated by binding operators, following the nominal approach. We propose a sound and complete procedure for nominal unification with commutative operators, or nominal C-unification for short, which has been formalised in Coq. The procedure transforms nominal C-unification problems into simpler (finite families) of fixpoint problems, whose solutions can be generated by algebraic techniques on combinatorics of permutations.Comment: Pre-proceedings paper presented at the 27th International Symposium on Logic-Based Program Synthesis and Transformation (LOPSTR 2017), Namur, Belgium, 10-12 October 2017 (arXiv:1708.07854

Bryophyte and lichen biomass and nitrogen fixation in a high elevation cloud forest in Cerro de La Muerte, Costa Rica

Cloud forests have been found to lose more nitrogen in stream discharge than they gain from atmospheric deposition. They also support a large diversity and biomass of tree epiphytes, predominately composed of cryptogams. Since cryptogam epiphytes harbor nitrogen fixing cyanobacteria, they may help make up for the nitrogen loss from ecosystems. We assessed cryptogam biomass on the ground, boles and branches in Quercus costaricensis dominated stands near the tree line in the Cordillera de Talamanca, Costa Rica. Nitrogen fixation was assayed using 15N2 uptake. Total cryptogam biomass was 2 977 kg ha−1, with 67% being found on the lower branches. Bryophytes and chlorolichens made up 53% and 44%, respec- tively, of the biomass. Half of the bryophyte mass was composed of the liverwort Plagiochila heterophylla, and 66% of the chlorolichen of Lobariella pallida. There were no significant differences in nitrogen fixation rates between the cryptogam species, with a mean rate of 5.04 µg N g−1 day−1 during the predominantly wet condition in the forest. The overall nitrogen input from fixation was 6.1 kg N ha−1 year−1, of which 78% came from bryophytes, 18% from chlorolichens, and 4% from cyanolichens. Only 2.0% of the fixation occurred in cryptogams on the ground, whereas 67%, 24%, and 7% occurred on the lower branches, boles, and upper branches, respectively. These results show that tree epiphytes constitute a significant source of nitrogen for these forests, due to the trees’ large surface area, and can make up for the nitrogen lost from these ecosystemsUCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de BiologíaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Biodiversidad y Ecología Tropical (CIBET

Criterios de evaluación de los procesos de enseñanza y aprendizaje de un programa de ajedrez digital

El presente artículo sintetiza un proyecto de tesis realizado en la Provincia de San Luis, en la República Argentina sobre los procesos de enseñanza y aprendizaje del Ajedrez a distancia, a través de la utilización de las nuevas tecnologías. La pertinencia de esta investigación se fundamenta en que en la actualidad hay una carencia de estudios sistemáticos, en general, sobre el uso de TIC con fines educativos en la enseñanza del ajedrez en el nivel primario. El objetivo de este artículo es proporcionar una serie de criterios que consideramos importantes al momento de evaluar el proceso de enseñanza y aprendizaje del ajedrez de manera online: la evaluación del entorno virtual de aprendizaje y su implementación, la valoración sobre los materiales didácticos y la evaluación de la acción tutoria