White dwarf evolutionary sequences for low-metallicity progenitors: The impact of third dredge-up

We present new white dwarf evolutionary sequences for low-metallicity progenitors. White dwarf sequences have been derived from full evolutionary calculations that take into account the entire history of progenitor stars, including the thermally-pulsing and the post-asymptotic giant branch phases. We show that for progenitor metallicities in the range 0.00003--0.001, and in the absence of carbon enrichment due to the occurrence of a third dredge-up episode, the resulting H envelope of the low-mass white dwarfs is thick enough to make stable H burning the most important energy source even at low luminosities. This has a significant impact on white dwarf cooling times. This result is independent of the adopted mass-loss rate during the thermally-pulsing and post-AGB phases, and the planetary nebulae stage. We conclude that in the absence of third dredge-up episodes, a significant part of the evolution of low-mass white dwarfs resulting from low-metallicity progenitors is dominated by stable H burning. Our study opens the possibility of using the observed white dwarf luminosity function of low-metallicity globular clusters to constrain the efficiency of third dredge up episodes during the thermally-pulsing AGB phase of low-metallicity progenitors.Comment: To be published in Astronomy and Astrophysics. 12 pages, 11 figure

Constraining the neutrino magnetic dipole moment from white dwarf pulsations

Pulsating white dwarf stars can be used as astrophysical laboratories to constrain the properties of weakly interacting particles. Comparing the cooling rates of these stars with the expected values from theoretical models allows us to search for additional sources of cooling due to the emission of axions, neutralinos, or neutrinos with magnetic dipole moment. In this work, we derive an upper bound to the neutrino magnetic dipole moment using an estimate of the rate of period change of the pulsating DB white dwarf star PG 1351+489. By comparing the theoretical rate of change of period expected for this star with the rate of change of period with time of PG 1351+489, we assess the possible existence of additional cooling by neutrinos with magnetic dipole moment. Our models suggest the existence of some additional cooling in this pulsating DB white dwarf, consistent with a non-zero magnetic dipole moment. Our upper limit for the neutrino magnetic dipole moment is somewhat less restrictive than, but still compatible with, other limits inferred from the white dwarf luminosity function or from the color-magnitude diagram of the Globular cluster M5. Further improvements of the measurement of the rate of period change of the dominant pulsation mode of PG 1351+489 will be necessary to confirm our bound.Comment: 18 pages, 10 figures, 3 tables. Accepted for publication in Journal of Cosmology and Astroparticle Physic

Knowledge dynamics in a khepera robots’ application

The theory change area have defined several operators trying to model the dynamic of knowledge. The goal of this work is to introduce a preprocessor of perceptions that could be part of an agent. The purpose of the preprocessor is to select an adequate change operator to store the perceptions that the agent perceives from the environment where their activities are performed. An agent receives perceptions, and classifies them according to how they were obtained by him/her. Once are the perceptions classified, the preprocessor selects one of the change operators to store the new information in the belief base. Then the preprocessor of perceptions sends the selected method and the perceptions to a change machine in the agent. When the change machine receives the mentioned inputs, it interacts with the belief base of the agent to store the new information.VIII Workshop de Agentes y Sistemas InteligentesRed de Universidades con Carreras en Informática (RedUNCI

An comparative analysis of different models of belief revision using information from multiple sources

In this work we analyze the problem of knowledge representation in a collaborative multi-agent system where agents can obtain new information from others through communication. Namely, we analyze several approaches of belief revision in multi-agent systems. We will describe different research lines in this topic and we will focus on Belief Revision using Information from Multiple Sources. For this, we are going to accomplish a comparative analysis of different models of belief revision that use information from multiple sources.Workshop de Agentes y Sistemas Inteligentes (WASI)Red de Universidades con Carreras en Informática (RedUNCI

A Junction and Drop-Shaft Boundary Conditions for Modeling Free Surface, Pressurized, and Mixed Free Surface-Pressurized Transient Flows

A junction and drop-shaft boundary conditions (BCs) for one-dimensional modeling of transient flows in single-phase conditions (pure liquid) are formulated, implemented and their accuracy are evaluated using two Computational Fluid Dynamics (CFD) models. The BCs are formulated for the case when mixed flows are simulated using two sets of govern- ing equations, the Saint Venant equations for the free surface regions and the compressible water hammer equations for the pressurized regions. The proposed BCs handle all possible flow regimes and their combinations. The flow in each pipe can range from free surface to pressurized flow and the water depth at the junction or drop-shaft can take on all possible levels. The BCs are applied to the following three cases: a three-way merging flow, a three- way dividing flow and a drop-shaft connected to a single-horizontal pipe subjected to a rapid variation of the water surface level in the drop-shaft. The flow regime for the first two cases range from free surface to pressurized flows, while for the third case, the flow regime is pure pressurized flow. For the third case, laboratory results as well as CFD results were used for evaluating its accuracy. The results suggest that the junction and drop-shaft boundary conditions can be used for modeling transient free surface, pressurized, and mixed flow conditions with good accuracy

Reformulación del modelo Linda para compartir conocimiento en sistemas multi-agente

The aim of this work is to analyze the knowledge interchange on multi-agent systems using shared knowledge areas. The project involves the analysis and reformulation of some aspects of the Linda model, adding new model level features. This work proposes the idea of distributed tuples spaces, offering the possibility of coexistence among different tuples spaces with distinct features, being stored in remote sites. This distributed model requires the definition of new operations whose domain and range are tuples spaces, and the formulation of access constraints for the agentsRed de Universidades con Carreras en Informática (RedUNCI

Bases de conocimiento en sistemas multi-agente

Esta línea de investigación tiene como objetivo analizar los distintos operadores de mezcla de múltiples fuentes de información desde diferentes teorías. El proyecto involucra el análisis de los operadores de mezcla de la teoría de Revisión de Creencias, Argumentación y desde las Lógicas proposicional y posibilística. En este trabajo, en primer lugar se describen algunos operadores de mezcla desde las teorías ya mencionadas. En base a estas alternativas se propondrá relacionar estos operadores entre sí, y se propondrá redefinir sus conceptos orientando los comportamientos de los mismos a los sistemas multi-agente.Eje: Agentes y Sistemas InteligentesRed de Universidades con Carreras en Informática (RedUNCI

Manipulación de conocimiento en sistemas multi-agentes por medio de espacios de tuplas

Esta línea de investigación tiene como objetivo analizar el intercambio de conocimiento en sistemas multi-agente utilizando áreas de conocimiento compartidas. El proyecto involucra la extensión del modelo Linda con el objetivo de lograr adaptarlo a un entorno distribuido en un sistemas multi-agente con agentes con conocimiento. En este trabajo, en primer lugar se describe el conjunto de operaciones sobre espacios de tuplas que hemos propuesto en [1]. En base a estas operaciones se propondrá una extensión y finalmente se describirá el trabajo a futuro a realizar en esta línea de investigación.Eje: Agentes y Sistemas InteligentesRed de Universidades con Carreras en Informática (RedUNCI

Bases de conocimiento en sistemas multi-agente

Esta línea de investigación tiene como objetivo analizar los distintos operadores de mezcla de múltiples fuentes de información desde diferentes teorías. El proyecto involucra el análisis de los operadores de mezcla de la teoría de Revisión de Creencias, Argumentación y desde las Lógicas proposicional y posibilística. En este trabajo, en primer lugar se describen algunos operadores de mezcla desde las teorías ya mencionadas. En base a estas alternativas se propondrá relacionar estos operadores entre sí, y se propondrá redefinir sus conceptos orientando los comportamientos de los mismos a los sistemas multi-agente.Eje: Agentes y Sistemas InteligentesRed de Universidades con Carreras en Informática (RedUNCI