Instituto Superior Técnico

About: Instituto Superior Técnico is a based out in . It is known for research contribution in the topics: Catalysis & Finite element method. The organization has 10085 authors who have published 30226 publications receiving 667524 citations. The organization is also known as: IST & Instituto Superior Tecnico.

A hierarchical model for concurrent material and topology optimisation of three-dimensional structures

Abstract: This paper presents an extension of the hierarchical model for topology optimisation to three-dimensional structures. The problem addressed covers the simultaneous characterisation of the optimal topology of the structure and the optimal design of the cellular material used in its construction. In this study, hierarchical suggests that the optimisation model works at two interconnected levels, the global and local levels identified, respectively, with the structure and its material. The class of cellular materials, defining the material microstructure, is restricted to single scale cellular materials, with the cell geometry locally optimised for the given objective function and constraints. The model uses the asymptotic homogenisation model to obtain the equivalent material properties for the specific local microstructures designed using a SIMP based approach. The necessary optimality conditions for the hierarchical optimal design problem are discussed and approximated numerically by a proper finite element discretisation of the global and local analysis and design problems. Examples to explore and demonstrate the model developed are presented.

Empathy in Virtual Agents and Robots: A Survey

Abstract: This article surveys the area of computational empathy, analysing different ways by which artificial agents can simulate and trigger empathy in their interactions with humans. Empathic agents can be seen as agents that have the capacity to place themselves into the position of a user’s or another agent’s emotional situation and respond appropriately. We also survey artificial agents that, by their design and behaviour, can lead users to respond emotionally as if they were experiencing the agent’s situation. In the course of this survey, we present the research conducted to date on empathic agents in light of the principles and mechanisms of empathy found in humans. We end by discussing some of the main challenges that this exciting area will be facing in the future.

The PREDICTS database: a global database of how local terrestrial biodiversity responds to human impacts

Abstract: Biodiversity continues to decline in the face of increasing anthropogenic pressures such as habitat destruction, exploitation, pollution and introduction of alien species Existing global databases of species’ threat status or population time series are dominated by charismatic species The collation of datasets with broad taxonomic and biogeographic extents, and that support computation of a range of biodiversity indicators, is necessary to enable better understanding of historical declines and to project – and avert – future declines We describe and assess a new database of more than 16 million samples from 78 countries representing over 28,000 species, collated from existing spatial comparisons of local-scale biodiversity exposed to different intensities and types of anthropogenic pressures, from terrestrial sites around the world The database contains measurements taken in 208 (of 814) ecoregions, 13 (of 14) biomes, 25 (of 35) biodiversity hotspots and 16 (of 17) megadiverse countries The database contains more than 1% of the total number of all species described, and more than 1% of the described species within many taxonomic groups – including flowering plants, gymnosperms, birds, mammals, reptiles, amphibians, beetles, lepidopterans and hymenopterans The dataset, which is still being added to, is therefore already considerably larger and more representative than those used by previous quantitative models of biodiversity trends and responses The database is being assembled as part of the PREDICTS project (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems – wwwpredictsorguk) We make site-level summary data available alongside this article The full database will be publicly available in 2015

Self-consistent kinetic model of low-pressure - flowing discharges: I. Volume processes

Abstract: This work is the first of two companion papers devoted to the kinetic modelling of low-pressure DC flowing discharges in - mixtures. While the present paper is mainly concerned with bulk discharge processes, the second one investigates surface processes involving dissociated N and H atoms, which are essential to understand the discharge properties. The global model combining bulk and surface processes as described in these two papers is self-contained in the sense that the sole input parameters it requires are those that can externally be chosen in experiments, namely: total gas pressure, radius and length of the discharge tube, discharge current, gas flow rate and initial gas temperature and composition (e.g., the relative hydrogen concentration X in the binary mixture at the discharge inlet). For a given set of input parameters, this model enables one to calculate the following bulk plasma properties as a function of the axial coordinate z: concentration of , , NH, , molecules and N, H atoms in the ground electronic state; population in the electronically excited states , (an effective high Rydberg state) and ; concentration of the ions , , , , , and ; vibrational level populations of and molecules; electron density , mean kinetic energy , characteristic energy and drift velocity ; discharge sustaining electric field E; average gas temperature across the tube T and wall temperature . The calculations are compared with data from different experiments in pure and discharges (measurements of electric field as a function of current and pressure) and in - discharges (measurements of relative changes in the electric field and the , concentrations as a function of the percentage). From the comparison to experiment, rate coefficients for associative ionization upon collisions between two excited molecules and deactivation of and by H atoms have been estimated from the model.