Unified formalism for higher-order non-autonomous dynamical systems

This work is devoted to giving a geometric framework for describing higher-order non-autonomous mechanical systems. The starting point is to extend the Lagrangian-Hamiltonian unified formalism of Skinner and Rusk for these kinds of systems, generalizing previous developments for higher-order autonomous mechanical systems and first-order non-autonomous mechanical systems. Then, we use this unified formulation to derive the standard Lagrangian and Hamiltonian formalisms, including the Legendre-Ostrogradsky map and the Euler-Lagrange and the Hamilton equations, both for regular and singular systems. As applications of our model, two examples of regular and singular physical systems are studied.Comment: 43 pp. We have corrected and clarified the statement of Propositions 2 and 3. A remark is added after Proposition

ESTADO DE TABASCO: POBLACIÓN, ESTRUCTURA ECONÓMICA, PETRÓLEO Y OPCIONES DE RECONFIGURACIÓN TERRITORIAL

El trabajo que se presenta a continuación deriva del interés de iniciar una serie de estudios sobre las nuevas condiciones que enfrenta la economía mexicana, las cuales tiene potencial tanto para causar impactos favorables como otros más bien adversos. En esta oportunidad el caso de estudio es el Estado de Tabasco y sus municipios, en un intento de dimensionar el efecto de dos hechos específicos y de actualidad, cuyos resultados todavía están por determinarse. De manera específica se hace referencia a la Reforma Energética y a la caída de los precios del petróleo, donde el primero limitará en mucho la actividad de la paraestatal Petróleos Mexicanos (PEMEX), mientras el segundo será un elemento que afectará de manera sustancial a los productores. En este contexto, Tabasco amerita un análisis a fondo, debido a su elevada dependencia hacia la explotación e industria de hidrocarburos, buscando cuáles son los municipios con mayor vulnerabilidad económica por su extrema especialización hacia la industria petrolera. Se inicia planteando la realidad de un medio físico poco favorable para el poblamiento y el desarrollo económico, más allá de las actividades primarias y mineras. Luego se revisan las principales tendencias poblacionales, seguido del análisis de su estructura ocupacional, para terminar explicando a detalle la estructura sectorial que caracteriza al estado en general y a los municipios en particular. Con el apoyo de cartografía temática se muestran diversas regionalizaciones de los parámetros analizados, encontrando un crecimiento demográfico acelerado en la parte media del estado, coincidente con el mayor incremento económico, pero también relacionado con los casos municipales más dependientes del petróleo. Finalmente, se revisan algunas alternativas territoriales para proponer establecer en ellas nuevas actividades poco relacionadas con la explotación de hidrocarburos

Forecasting Recharging Demand to Integrate Electric Vehicle Fleets in Smart Grids

Electric vehicle fleets and smart grids are two growing technologies. These technologies provided new possibilities to reduce pollution and increase energy efficiency. In this sense, electric vehicles are used as mobile loads in the power grid. A distributed charging prioritization methodology is proposed in this paper. The solution is based on the concept of virtual power plants and the usage of evolutionary computation algorithms. Additionally, the comparison of several evolutionary algorithms, genetic algorithm, genetic algorithm with evolution control, particle swarm optimization, and hybrid solution are shown in order to evaluate the proposed architecture. The proposed solution is presented to prevent the overload of the power grid

Nonholonomic constraints in classical field theories

A multisymplectic setting for classical field theories subjected to non-holonomic constraints is presented. The infinite dimensional setting in the space of Cauchy data is also given.Comment: 14 pages; 1 figur

An improved method for the identification of galaxy systems: Measuring the gravitational redshift by Dark Matter Haloes

We introduce a new method for the identification of galaxy systems in redshift surveys based on the halo model. This method is a modified version of the K-means identification algorithm developed by Yang et al (2005). We have calibrated and tested our algorithms using mock catalogs generated using the Millennium simulations (Springel et al. 2005) and applied them to the NYU-DR7 galaxy catalog (based on the SDSS datasets). Using this local sample of groups and clusters of galaxies we have measured the effect of gravitational redshift produced by their host dark matter haloes. Our results shows radial velocity decrements consistent with general relativity predictions and previous measurements by Wojtak et al (2011) in clusters of galaxies.Comment: Accepted for Publication in MNRAS Letters, 2 figures. arXiv admin note: text overlap with arXiv:astro-ph/0405234, arXiv:astro-ph/0406593 by other author

Key Production Parameters to Obtain Transparent Nanocellular PMMA

Transparent nanocellular polymethylmethacrylate (PMMA) with relative density around 0.4 is produced for the first time by using the gas dissolution foaming technique. The processing conditions and the typical characteristics of the cellular structure needed to manufacture this novel material are discovered. It is proved that low saturation temperatures (−32 °C) combined with high saturation pressures (6, 10, 20 MPa) allow increasing the solubility of PMMA up to values not reached before. In particular, the highest CO2 uptake ever reported for PMMA, (i.e., 48 wt%) is found for a saturation pressure of 20 MPa and a saturation temperature of −32 °C. Due to these processing conditions, cell nucleation densities of 1016 nuclei cm−3 and cell sizes clearly below 50 nm are achieved. The nanocellular polymers obtained, with cell sizes ten times smaller than the wavelength of visible light and very homogeneous cellular structures, show a significant transparency

Las profesoras universitarias: el caso de una élite discriminada.

Sin resume

Los Estudios de Género en España (Un balance).

Sin resume

Maggie Lane. Hijas escritoras.

Sin resume