Numerical Integration and Dynamic Discretization in Heuristic Search Planning over Hybrid Domains

In this paper we look into the problem of planning over hybrid domains, where change can be both discrete and instantaneous, or continuous over time. In addition, it is required that each state on the trajectory induced by the execution of plans complies with a given set of global constraints. We approach the computation of plans for such domains as the problem of searching over a deterministic state model. In this model, some of the successor states are obtained by solving numerically the so-called initial value problem over a set of ordinary differential equations (ODE) given by the current plan prefix. These equations hold over time intervals whose duration is determined dynamically, according to whether zero crossing events take place for a set of invariant conditions. The resulting planner, FS+, incorporates these features together with effective heuristic guidance. FS+ does not impose any of the syntactic restrictions on process effects often found on the existing literature on Hybrid Planning. A key concept of our approach is that a clear separation is struck between planning and simulation time steps. The former is the time allowed to observe the evolution of a given dynamical system before committing to a future course of action, whilst the later is part of the model of the environment. FS+ is shown to be a robust planner over a diverse set of hybrid domains, taken from the existing literature on hybrid planning and systems.Comment: 17 page

BIRTH SEASONALITY IN THE BAKA PYGMIES

International audienc

Kilo-instruction processors: overcoming the memory wall

Historically, advances in integrated circuit technology have driven improvements in processor microarchitecture and led to todays microprocessors with sophisticated pipelines operating at very high clock frequencies. However, performance improvements achievable by high-frequency microprocessors have become seriously limited by main-memory access latencies because main-memory speeds have improved at a much slower pace than microprocessor speeds. Its crucial to deal with this performance disparity, commonly known as the memory wall, to enable future high-frequency microprocessors to achieve their performance potential. To overcome the memory wall, we propose kilo-instruction processors-superscalar processors that can maintain a thousand or more simultaneous in-flight instructions. Doing so means designing key hardware structures so that the processor can satisfy the high resource requirements without significantly decreasing processor efficiency or increasing energy consumption.Peer ReviewedPostprint (published version

Dependence of samarium-soil interaction on samarium concentration: Implications for environmental risk assessment

The sorption and desorption behaviour of samarium (Sm), an emerging contaminant, was examined in soil samples at varying Sm concentrations. The obtained sorption and desorption parameters revealed that soil possessed a high Sm retention capacity (sorption was higher than 99% and desorption lower than 2%) at low Sm concentrations, whereas at high Sm concentrations, the sorption-desorption behaviour varied among the soil samples tested. The fractionation of the Sm sorbed in soils, obtained by sequential extractions, allowed to suggest the soil properties (pH and organic matter solubility) and phases (organic matter, carbonates and clay minerals) governing the Sm-soil interaction. The sorption models constructed in the present work along with the sorption behaviour of Sm explained in terms of soil main characteristics will allow properly assessing the Sm-soil interaction depending on the contamination scenario under study. Moreover, the sorption and desorption K-d values of radiosamarium in soils were strongly correlated with those of stable Sm at low concentrations (r = 0.98); indicating that the mobility of Sm radioisotopes and, thus, the risk of radioactive Sm contamination can be predicted using data from low concentrations of stable Sm. (C) 2017 Elsevier Ltd. All rights reserved

Extending classical planning with state constraints: Heuristics and search for optimal planning

We present a principled way of extending a classical AI planning formalism with systems of state constraints, which relate - sometimes determine - the values of variables in each state traversed by the plan. This extension occupies an attractive middle ground between expressivity and complexity. It enables modelling a new range of problems, as well as formulating more efficient models of classical planning problems. An example of the former is planning-based control of networked physical systems - power networks, for example - in which a local, discrete control action can have global effects on continuous quantities, such as altering flows across the entire network. At the same time, our extension remains decidable as long as the satisfiability of sets of state constraints is decidable, including in the presence of numeric state variables, and we demonstrate that effective techniques for cost-optimal planning known in the classical setting - in particular, relaxation-based admissible heuristics - can be adapted to the extended formalism. In this paper, we apply our approach to constraints in the form of linear or non-linear equations over numeric state variables, but the approach is independent of the type of state constraints, as long as there exists a procedure that decides their consistency. The planner and the constraint solver interact through a well-defined, narrow interface, in which the solver requires no specialisation to the planning contextThis work was supported by ARC project DP140104219, “Robust AI Planning for Hybrid Systems”, and in part by ARO grant W911NF1210471 and ONR grant N000141210430

‘Selling your own’. Nature, tourism and rice in Isla Mayor (Seville)

La historia y desarrollo del turismo de base local en Isla Mayor podríamos decir que es la historia de una “joven promesa”, tanto por el tiempo como por el potencial que encierra. El papel de la naturaleza en la construcción del producto turístico, así como el protagonismo de “lo local”, son las claves para entender el proceso que supone el turismo en este municipio. Partimos del presupuesto que entiende los procesos de apropiación por parte de la sociedad local, como uno de los factores condicionantes para el desarrollo del turismo de base local. El caso etnográfico que compone la experiencia turística desarrollada en Isla Mayor (Sevilla) expone la relación naturaleza-sociedad como eje central tanto de la posible oferta turística, como de los procesos de construcción social de la realidad local. La falta de vinculación o la ruptura que parece existir en ese binomio (naturaleza-sociedad) nos ayuda a analizar y centrar nuestro objetivo en dimensionar el papel que juega la apropiación (local) dentro del desarrollo del Turismo de Base Local.The history and development of local-based tourism in Isla Mayor we could say it is the story of a "young promise" as much as for the short time it accrues as for its potential. The role of nature in the construction of the tourist product as well as the role of "the local" are the keys to understand the process involving tourism in this municipality. We start from an assumption that understands the processes of appropriation by the local society as one of the determining factors for the development of local-based tourism. The ethnographic case that makes up the tourist experience developed in Isla Mayor (Seville), describes the nature-society relationship as the core of the tourist offer as much as the processes of social construction of local reality. The lack of connection or even rupture that seems to exist in this binomial (nature-society), leads us to analyse and focus our objective on dimensioning the role of appropriation in the development of this local-based tourism.- Grupo de investigación Antropología y Filosofía (SEJ-126). Universidad de Granada. - Área de Antropología Social. Universidad de Jaén. - Laborarorio de Antropología Social y Cultural (HUM-472). Universidad de Almería. - Departamento de Filosofía II. Universidad de Granada

Condition monitoring strategy based on spectral energy estimation and linear discriminant analysis applied to electric machines

Condition-based maintenance plays an important role to ensure the working condition and to increase the availability of the machinery. The feature calculation and feature extraction are critical signal processing that allow to obtain a high-performance characterization of the available physical magnitudes related to specific working conditions of machines. Aiming to overcome this issue, this research proposes a novel condition monitoring strategy based on the spectral energy estimation and Linear Discriminant Analysis for diagnose and identify different operating conditions in an induction motor-based electromechanical system. The proposed method involves the acquisition of vibration signals from which the frequency spectrum is computed through the Fast Fourier Transform. Subsequently, such frequency spectrum is segmented to estimate a feature matrix in terms of its spectral energy. Finally, the feature matrix is subjected to a transformation into a 2-dimentional base by means of the Linear Discriminant Analysis and the final diagnosis outcome is performed by a NN-based classifier. The proposed strategy is validated under a complete experimentally dataset acquired from a laboratory electromechanical system.Peer ReviewedPostprint (published version

Visual faunistic exploration of geomorphological human-impacted deep-sea areas of the north-western Mediterranean Sea

This study reports the composition and distribution of demersal megafauna from various north-western Mediterranean submarine areas such as canyons, seamounts and landslides between 60-800 m depth, based on remotely operated vehicle (ROV) observations. From a total of 30 h of video, 4534 faunistic observations were made and analysed in relationship to environmental factors (i.e. topography, substrate type and depth). In addition, anthropogenic impact was quantified by grouping observations in four categories: fishing nets, longlines, trawl marks and other litter. The different targeted environments showed similarities in faunal composition according to substrate, depth and topography. Our results also indicated the presence of anthropogenic impact in all the sampled areas in which litter and trawl marks were the most observed artefacts