Estrategias hacia la sostenibilidad en el Mercosur

Se analiza brevemente el proceso de avance de la economía ecológica en el marco de la conformación de sociedades regionales en América Latina. La creación de la Sociedad Brasileña de Economía Ecológica, la Asociación Argentino Uruguaya de Economía Ecológica y la Red Iberoamericana de Economía Ecológica. Asimismo, se presenta información sobre las Segundas Jornadas de Economía Ecológica, desarrolladas durante el año 2004 y el enfoque de algunos de los documentos expuestos en la reunión. Finalmente, se realiza un análisis a nivel regional de la situación de la biodiversidad en el plano del Mercosur, las amenazas y las políticas alternativas necesarias para un ordenamiento territorial bajo un paraguas de desarrollo sostenible con base local

The Use of Rank Histograms and MVL Diagrams to Characterize Ensemble Evolution in Weather Forecasting

13 páginas, 9 figuras.-- El pdf del artículo es la versión pre-print.Rank Histograms are suitable tools to assess the quality of ensembles within an ensemble prediction system or framework. By counting the rank of a given variable in the ensemble, we are basically making a sample analysis, which does not allow us to distinguish if the origin of its variability is external noise or comes from chaotic sources. The recently introduced Mean to Variance Logarithmic (MVL) Diagram accounts for the spatial variability, being very sensitive to the spatial localization produced by infinitesimal perturbations of spatiotemporal chaotic systems. By using as a benchmark a simple model subject to noise, we show the distinct information given by Rank Histograms and MVL Diagrams. Hence, the main effects of the external noise can be visualized in a graphic. From the MVL diagram we clearly observe a reduction of the amplitude growth rate and of the spatial localization (chaos suppression), while from the Rank Histogram we observe changes in the reliability of the ensemble. We conclude that in a complex framework including spatiotemporal chaos and noise, both provide a more complete forecasting picture.We acknowledge financial support from MEC, Spain, through Grant No. CGL2007- 64387/CLI, and also thank the AECID, Spain, for support through projects A/013666/07 and A/018685/08. JAR thanks the MEC, Spain, for the award of a Juan de la Cierva fellowship. HSW thanks to the European Commission for the award of a Marie Curie Chair during part of the development of this work.Peer reviewe

Estrategias hacia la sostenibilidad en el Mercosur

Se analiza brevemente el proceso de avance de la economía ecológica en el marco de la conformación de sociedades regionales en América Latina. La creación de la Sociedad Brasileña de Economía Ecológica, la Asociación Argentino Uruguaya de Economía Ecológica y la Red Iberoamericana de Economía Ecológica. Asimismo, se presenta información sobre las Segundas Jornadas de Economía Ecológica, desarrolladas durante el año 2004 y el enfoque de algunos de los documentos expuestos en la reunión. Finalmente, se realiza un análisis a nivel regional de la situación de la biodiversidad en el plano del Mercosur, las amenazas y las políticas alternativas necesarias para un ordenamiento territorial bajo un paraguas de desarrollo sostenible con base local.

Universal temporal features of rankings in competitive sports and games

Many complex phenomena, from the selection of traits in biological systems to hierarchy formation in social and economic entities, show signs of competition and heterogeneous performance in the temporal evolution of their components, which may eventually lead to stratified structures such as the wealth distribution worldwide. However, it is still unclear whether the road to hierarchical complexity is determined by the particularities of each phenomena, or if there are universal mechanisms of stratification common to many systems. Human sports and games, with their (varied but simplified) rules of competition and measures of performance, serve as an ideal test bed to look for universal features of hierarchy formation. With this goal in mind, we analyse here the behaviour of players and team rankings over time for several sports and games. Even though, for a given time, the distribution of performance ranks varies across activities, we find statistical regularities in the dynamics of ranks. Specifically the rank diversity, a measure of the number of elements occupying a given rank over a length of time, has the same functional form in sports and games as in languages, another system where competition is determined by the use or disuse of grammatical structures. Our results support the notion that hierarchical phenomena may be driven by the same underlying mechanisms of rank formation, regardless of the nature of their components. Moreover, such regularities can in principle be used to predict lifetimes of rank occupancy, thus increasing our ability to forecast stratification in the presence of competition

Development of a novel synthesis method of a rigid-body four-bar linkage into a compliant mechanism

The four-bar linkage mechanism is widely used in various machinery applications. This study presents a synthesis method to transform a rigid-body four-bar mechanism into a compliant mechanism using four leaf-type hinges based on linear theory and Castigliano's Theorem. The objective is to determine the dimensions and configuration of a flexible four-bar mechanism that replicates the behavior of the initial rigid-body mechanism. The meeting point between the two mechanisms is the flexure hinge of the compliant mechanism, which is determined using the Pseudo-Rigid-Body model (PRBM). To validate the proposed method, a program based on non-linear theory is employed. The results confirm that the dimensional differences between the two are minimal, ranging from 0% to 0.13%. This study demonstrates the feasibility of synthesizing a Rigid-Body Four-Bar Mechanism into a compliant mechanism using the PRBM, as long as the deformations are within the linear domain

WMR Kinematic Control Using Underactuated Mechanisms for Goal Direction and Evasion

This work presents the mechanical design and the kinematic navigation control system for a tricycle-wheeled robot (one drive-steer and two lateral fixed passive) with two underactuated mechanisms: a global compass and local evasive compass. The proposed goal-reference mechanism is inspired by the ancient Chinese south-seeking chariot (c. 200–265 CE) used as a navigation compass. The passive lateral wheels transmit an absolute angle from its differential speeds to automatically steer the front wheel. An obstacle-evasive compass mechanism is commutated for steering control when detecting nearby obstacles. The absolute and local compass mechanisms commutate each other to control to the robot’s steering wheel to reach a goal while avoiding collisions. A kinematic control law is described in terms of the robot’s geometric constraints and is combined with a set of first-order partial derivatives that allows interaction between the global and local steering mechanisms. Animated simulations and numerical computations about the robot’s mechanisms and trajectories in multi-obstacle scenarios validate the proposed kinematic control system and its feasibility