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Search Results: 1 - 10 of 191241 matches for " G; Ochoa "
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Diversity under variability and extreme variability of environments
Juan G. Diaz Ochoa
Physics , 2008,
Abstract: We conducted an investigation of the effect that extreme variability of the individual's environment has in the individual's adaptability and, in general, in the co-evolution of a population. First we assume that the individuals are a kind of perceptrons with a given memory size that adapt to their environment; second we consider co-evolution not only of the individual actions but also of the memory size, depending on the individual's fitness; and third we assume strong variability of the environment. We show that changes in the intensity of the environmental fluctuations introduce a phase transition in the frequency of cooperators and the diversity of the population. We also find out that extreme variability of the environment induces changes in the critical exponents and that this variability can promote more diversity in the population.
Evolutionary dynamics and diversity in populations
Juan G. Diaz Ochoa
Physics , 2007,
Abstract: The dynamics of populations is rich, taking into account that both, the individual's actions and the population's fitness are coupled. The way in which an individual chooses a strategy depends off course on the interaction with other individuals and the relation between selection and mutation within the population. The present model considers individuals with {\it memory}. This memory is represented by a device where information of past actions is stored as bits in a 1D Ising chain. The selection of a new individual action depends on the individual's memory. If the selection of a strategy does not improve the individual's fitness, a new individual with different memory size replaces it. Both, actions and memory are observables that characterize the population. They can change in time, and both depend on the fitness of the population. This model allows the implementation of {\it learning} parameters as well as an {\it external information source}, acting as an {\it external field} which drives individuals to select one preferred action. In particular we show that the {\it diversity} of the population, measured as a {\it Shannon's diversity index} (equivalent to a neg-entropy), is not only related to the {\it energy consumption and size} of the system, but is also related to the way in which the individuals are influenced by the {\it external field}.
Memory distribution in complex fitness landscapes
Juan G. Diaz Ochoa
Physics , 2007, DOI: 10.1016/j.physa.2007.07.048
Abstract: In a co-evolutionary context, the survive probability of individual elements of a system depends on their relation with their neighbors. The natural selection process depends on the whole population, which is determined by local events between individuals. Particular characteristics assigned to each individual, as larger memory, usually improve the individual fitness, but an agent possess also endogenous characteristics that induce to re-evaluate her fitness landscape and choose the best-suited kind of interaction, inducing a non absolute value of the outcomes of the interaction. In this work, a novel model with agents combining memory and rational choice is introduced, where individual choices in a complex fitness landscape induce changes in the distribution of the number of agents as a function of the time. In particular, the tail of this distribution is fat compared with distributions for agents interacting only with memory.
General Relativity at an interface
Juan G. Diaz Ochoa
Physics , 2006,
Abstract: In this work a simple toy model for a free interface between bulk phases in space and time is presented, derived from the balance equations for extensive thermodynamic variables of Meinhold-Heerlein. In this case the free interface represents geodesics in the space-time, allowing the derivation of the Einstein's equations for gravitational fields. The effect of the balance equation is examined and a simple expression for cold dark matter is derived. The thermodynamically meaning of this model is also discussed.
Simple Human Gesture Detection and Recognition Using a Feature Vector and a Real-Time Histogram Based Algorithm  [PDF]
Iván Gómez-Conde, David Olivieri, Xosé Antón Vila, Stella Orozco-Ochoa
Journal of Signal and Information Processing (JSIP) , 2011, DOI: 10.4236/jsip.2011.24040
Abstract: Gesture and action recognition for video surveillance is an active field of computer vision. Nowadays, there are several techniques that attempt to address this problem by 3D mapping with a high computational cost. This paper describes software algorithms that can detect the persons in the scene and analyze different actions and gestures in real time. The motivation of this paper is to create a system for thetele-assistance of elderly, which could be used as early warning monitor for anomalous events like falls or excessively long periods of inactivity. We use a method for foreg-round-background segmentation and create a feature vectorfor discriminating and tracking several people in the scene. Finally, a simple real-time histogram based algorithm is described for discriminating gestures and body positions through a K-Means clustering.
Conservación de las últimas fronteras forestales de la guayana venezolana: Propuesta de lineamientos para la cuenca del río caura
Bevilacqua,Mariapía; Ochoa G,José;
Interciencia , 2001,
Abstract: venezuela includes an important proportion of the world′s threatened ecosystems and an extensive surface of natural areas in primary conditions. many of these areas correspond to forest ecosystems considered as the last frontier forests of the tropical region. social and environmental conflicts occur in these areas, as result of their value for natural resources use, their potential for extractive activities and the proposal of large scale environmental projects. the caura watershed, in the venezuelan guayana region, is one of the most important frontier forests in the world, due to its extension (45336km2), high level of biodiversity, and the presence of a significant proportion of the venezuelan indigenous population. the highest proportion of its territory is included in geographic units corresponding to the areas under special administrative regime (abrae). among them, the caura forest reserve (with wood production objectives) and the natural monument sierra of maigualida (with restrictive protection objectives) embrace the largest surface. these units show a high level of overlapping, in addition to opposite objectives. furthermore, management plans and other conservation tools are lacking in the abrae from the caura region and many of their boundaries correspond to traditional indigenous territories. land use is mainly associate with shifting cultivation, extensive cattle raising, small forestry plantations, the development of towns, and the presence of indigenous communities. in addition, several large scale projects have been proposed for this area. among the opportunities for the conservation of the region are: its territory extension, the pristine condition of its ecosystems, the availability of basic information, the social acceptance and the presence of institutional webs. any strategy focused to the long-term conservation of this region must be conducted taking into account: 1) the protection and management of natural resources; 2) the inventories and e
Divulgación de Información sobre Empleados y Medio Ambiente en Espa a y Alemania: Una Nota de Investigación.
Nagore Aranguren Gómez,Elena Ochoa Laburu
Revista de Contabilidad : Spanish Accounting Review , 2008,
Abstract: El objetivo de este estudio es el de analizar y comparar las prácticas de divulgación de información sobre empleados y medio ambiente entre las empresas espa olas que cotizan en el Ibex35 y las empresas alemanas que cotizan en el Dax30. Para este fin se construye un índice de divulgación mediante un análisis de contenido de los informes anuales y de otras publicaciones anuales utilizadas por la empresa para dar a conocer su comportamiento socialmente responsable. El estudio concluye que existe coincidencia en el grado y contenido de la información sobre empleados divulgada por las empresas de los dos países, mientras que en la categoría de medio ambiente las empresas alemanas presentan un mayor índice de divulgación.The aim of this study is to analyse and compare environmental and employee disclosure by Spanish Ibex35 and German Dax30 companies. For this purpose we construct a disclosure index through the content analysis of disclosures in annual reports and other corporate social responsibility reports. This research concludes with the existence of a noticeable coincidence on employee disclosure in both countries, unlike environmental disclosure, where German companies show a higher disclosure index.KEY WORDS: Enviado/Submitted: 5/11/2008Aceptado/Accepted: 27/11/2008Vol. 11 - No 2 - Pag. 123-142
General multistate models for agents with internal bias
Juan G. Diaz Ochoa,Elena Ramirez Barrios
Physics , 2007,
Abstract: We present a model of interpersonal comparisons appearing as a generalization of a multi-state model for elements with internal bias. Within this model agents suffering under dissatisfaction compare them with their neighbors. The internal bias are the pre-formed preferences, and the states are represented by the visual contacts that an agent makes to the baskets of her/his neighbors. The topology of the comparisons is a random network. We compare the behavior between altruistic and non-altruistic agents and we find out that altruistic behavior alters the robustness of the network.
Denaturation transition of stretched DNA
Andreas Hanke,Martha G. Ochoa,Ralf Metzler
Quantitative Biology , 2007, DOI: 10.1103/PhysRevLett.100.018106
Abstract: We generalize the Poland-Scheraga model to consider DNA denaturation in the presence of an external stretching force. We demonstrate the existence of a force-induced DNA denaturation transition and obtain the temperature-force phase diagram. The transition is determined by the loop exponent $c$ for which we find the new value $c=4\nu-1/2$ such that the transition is second order with $c=1.85<2$ in $d=3$. We show that a finite stretching force $F$ destabilizes DNA, corresponding to a lower melting temperature $T(F)$, in agreement with single-molecule DNA stretching experiments.
Fairness State with Plastic Preferences
Elena Ramirez Barrios,Juan G. Diaz Ochoa
Quantitative Finance , 2006,
Abstract: The definition of preferences assigned to individuals is a concept that concerns many disciplines, from economics, with the search of an acceptable outcome for an ensemble of individuals, to decision making an analysis of vote systems. We are concerned in the phenomena of good selection and economic fairness. In Arrow's theorem this situation is expressed as the impossibility of aggregate preferences among individuals falling down into some unfairness state. This situation was also analyzed in a previous model in a network of individuals with a random allocation. Both analysis are based on static preferences. In a real society the individuals are confronted to information exchange which can modify the way that they think. Also, the preference formation of each individual is influenced by this exchange. This consideration reveals why the actual theory is not able to make an accurate analysis of the influence of the individual, or cluster of individuals, in the fairness state. The aim of this investigation is to consider the coupling of two systems, one for the formation of preferences and a second where an allocation of goods is done in an evolutionary environment.
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