New methodology for calculating damage variables evolution in Plastic Damage Model for RC structures

The behavior of reinforced concrete (RC) structures under severe demands, as strong ground motions, is highly complex; this is mainly due to joint operation of concrete and steel, with several coupled failure modes. Furthermore, given the increasing awareness and concern for the important seismic worldwide risk, new developments have arisen in earthquake engineering. Nonetheless, simplified numerical models are widely used (given their moderate computational cost), and many developments rely mainly on them. The authors have started a long-term research whose final objective is to provide, by using advanced numerical models, solid basis for these developments. Those models are based on continuum mechanics, and consider Plastic Damage Model to simulate concrete behavior. Within this context, this paper presents a new methodology to calculate damage variables evolution; the proposed approach is based in the Lubliner/Lee/Fenves formulation and provides closed-form expressions of the compressive and tensile damage variables in terms of the corresponding strains. This methodology does not require calibration with experimental results and incorporates a strategy to avoid mesh-sensitivity. A particular algorithm, suitable for implementation in Abaqus, is described. Mesh-insensitivity is validated in a simple tension example. Accuracy and reliability are verified by simulating a cyclic experiment on a plain concrete specimen. Two laboratory experiments consisting in pushing until failure two 2-D RC frames are simulated with the proposed approach to investigate its ability to reproduce actual monotonic behavior of RC structures; the obtained results are also compared with the aforementioned simplified models that are commonly employed in earthquake engineering.Postprint (published version

Paragénesis mineral del depósito tipo five element Purísima-Rumicruz, Jujuy

Fil: López, Luciano. Instituto de Recursos Minerales (INREMI). Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Etcheveste, Horacio. Instituto de Recursos Minerales (INREMI). Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; Argentin

A Multi-Agent System for the Solution of Fuzzy Incidents in Telecommunications

This article presents a multi-agent expert system (SMAF) , that allows the input of incidents which occur in different elements of the telecommunications area. SMAF interacts with experts and general users, and each agent with all the agents? community, recording the incidents and their solutions in a knowledge base, without the analysis of their causes. The incidents are expressed using keywords taken from natural language (originally Spanish) and their main concepts are recorded with their severities as the users express them. Then, there is a search of the best solution for each incident, being helped by a human operator using a distancenotions between them

Personal de enfermería de reciente ingreso

La adaptación es la acción y efecto de adaptar o adaptarse, un verbo que hace referencia a acomodar o ajustar algo a otra cosa. El concepto tiene diferentes aceptaciones según a lo que se aplica. Cuando hablamos de adaptación al trabajo, se enfoca en la adaptación que tiene el individuo en común en una organización que lo identifica como trabajador. Las organizaciones, en este caso instituciones de salud, se rigen por normas o códigos de conducta, las cuales rigen el comportamiento que deben seguir los trabajadores en cuanto a su actuar propiamente dicho y en cuanto a las relaciones interpersonales, tanto con el paciente como con sus pares profesionales. La contratación e incorporación de enfermeros en las instituciones tiene como función primordial en el marco de la organización hospitalaria ocupar puestos de trabajo provisionalmente vacantes. Para los profesionales contratados, recién obtenido su título académico, éste será su primer puesto de trabajo, debiendo, en consecuencia, ejercer las competencias y atribuciones que les son propias a su cualificación, así como integrarse en el marco de una organización hospitalaria sumamente compleja. En muchas ocasiones no se concreta la adaptabilidad al lugar de trabajo por parte del personal de reciente ingreso, y estos es debido a múltiples factores, lo que provoca que estos trabajadores migren de sector en sector. Este trabajo de investigación tiene como objetivo determinar cuáles son los factores que influyen en la adaptación o no del personal de nuevo ingreso a la práctica laboral de enfermería en el Hospital Dr. J. Humberto Notti, durante el primer semestre del año 2011.Fil: López, Horacio. Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Escuela de Enfermería..Fil: Rivera, Lourdes. Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Escuela de Enfermería..Fil: Salazar, Norma. Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Escuela de Enfermería.

Microstructural model for cyclic hardening in F-actin networks crosslinked by α-actinin

open2siThe rheology of F-actin networks has attracted a great attention during the last years. In order to gain a complete understanding of the rheological properties of these novel materials, it is necessary the study in a large deformations regime to alter their internal structure. In this sense, Schmoller et al. (2010) showed that the reconstituted networks of F-actin crosslinked with α-actinin unexpectedly harden when they are subjected to a cyclical shear. This observation contradicts the expected Mullins effect observed in most soft materials, such as rubber and living tissues, where a pronounced softening is observed when they are cyclically deformed. We think that the key to understand this stunning effect is the gelation process. To define it, the most relevant constituents are the chemical crosslinks - α-actinin -, the physical crosslinks - introduced by the entanglement of the semiflexible network - and the interaction between them. As a consequence of this interaction, a pre-stressed network emerges and introduces a feedback effect, where the pre-stress also regulates the adhesion energy of the α-actinin, setting the structure in a metastable reference configuration. Therefore, the external loads and the evolvement of the trapped stress drive the microstructural changes during the cyclic loading protocol. In this work, we propose a micromechanical model into the framework of nonlinear continuum mechanics. The mechanics of the F-actin filaments is modelled using the wormlike chain model for semiflexible filaments and the gelation process is modelled as mesoscale dynamics for the α-actinin and physical crosslink. The model has been validated with reported experimental results.López-Menéndez, Horacio; Rodríguez, José FélixLópez Menéndez, Horacio; RODRIGUEZ MATAS, JOSE FELI

Numerical solution of the equations of motion of multi-story buildings with severe nonlinearities

Este artículo presenta un algoritmo para resolver las ecuaciones del movimiento de edificios de varias plantas que incorporan disipadores de energía friccionales como protección sismorresistente. El comportamiento de los disipadores se representa mediante modelos de Coulomb de rozamiento seco; estos introducen no linealidades severas en el comportamiento dinámico de la estructura cada vez que cambian las condiciones de contacto (bloqueo o deslizamiento) en los disipadores. Estas no linealidades complican la resolución de las ecuaciones del movimiento, ya que habitualmente este se describe mediante modelos planos de masas concentradas cuyos grados de libertad son los desplazamientos de las plantas y, al variar las condiciones de bloqueo o de deslizamiento, los grados de libertad deben ser modificados: para condiciones de bloqueo estos son solamente los desplazamientos de las plantas, mientras que para condiciones de deslizamiento han de considerarse, además, los desplazamientos de los disipadores. En artículos previos se ha verificado la exactitud del algoritmo comparándolo satisfactoriamente con resultados experimentales; asimismo, se ha constatado la eficacia computacional del algoritmo comparando ventajosamente los recursos requeridos (en términos de tiempo de cálculo o de asignación de memoria) con los de otros algoritmos. Los objetivos de este artículo son, por un lado, describir en detalle la resolución numérica de las ecuaciones del movimiento y, por otro, presentar ejemplos representativos que confirmen la capacidad del algoritmo para reproducir el comportamiento dinámico de edificios con disipadores y que ilustren de forma preliminar la utilidad de dichos dispositivos para reducir las oscilaciones de la estructura que proteger.This paper presents a new algorithm for solving the equations of motion of multi-storey buildings that incorporate frictional energy dissipators as seismic protection. The behavior of the dissipators is represented by Coulomb dry friction models; they introduce severe nonlinearities in the dynamic behavior of the structure every time that the contact conditions (stick or slip) change in the dissipators. These nonlinearities complicate the resolution of the equations of motion as it usually is described by lumped masses models whose degrees of freedom are the displacements of the floors and, as the stick or slip conditions change, the degrees of freedom must be modified: for blocking conditions they are only the displacements of the storeys while under sliding conditions the displacements of the dissipators have to be also considered. In previous articles the accuracy of the proposed algorithm has been verified by comparison with experimental results; as well, the computational efficiency of the algorithm has been confirmed by comparing the required resources (in terms of computation time and of memory allocation) with those of other algorithms. The objectives of this paper are to describe in detail the numerical solution of the equations of motion and present representative examples confirming the ability of the algorithm to reproduce the dynamic behavior of buildings with friction dissipators and reporting preliminarily about the usefulness of such devices to reduce the oscillations of the structure to be protected.Peer Reviewe

Geology of the Manantial Espejo epithermal district, Deseado Massif, Patagonia Argentina

The silver–gold epithermal mining district, Manantial Espejo, is located southwest of the Deseado Massif, Patagonia. The district is set into Jurassic volcaniclastic rocks of the Bahía Laura Group. A geological map of the district, at a scale of 1:50,000 drawn over a base map prepared from the fusion of satellite imagery and aerial photographs, is included. A suite of andesitic to rhyolitic eruptive units was identified, with prevailing high-grade rhyolitic ignimbrites. Travertine levels show the beginning of a hot-spring system in the region. Quartz veins, with typical crustiform–colloform banded structures, fill WNW, sub-vertical, normal faults, originating from extensional tectonics. The silicification of travertines, tuffs and breccia is the most common hydrothermal alteration.Facultad de Ciencias Naturales y Muse

El largo y tortuoso camino hacia la Patria Grande

The paper start from the estimation of the objectives that supported the great men of the Spanish-American war of Independence, among which were found, in addition to independence, freedom and equality, integration, that is, institutional unity of young republics. The last objective could not be accomplished and Spanish-America became fragmented in dispersed areas. In this present change of era, the idea of Patria Grande, contains those ideas taken up by patriots like Bolivar, San Martin, Artigas, and many others. Today those ideals were raised and are raised by leaders like Hugo Chavez, Evo Morales, Rafael Correa; and progress towards institutional unity -not exempt of danger and circumstantial regressions - results in creations like ALBA, Unasur and CELAC.Fil: López, Horacio. Centro Cultural de la Cooperación Floreal GoriniApresentação parte da valoração dos objectivos que sustentassem os grandes homens da guerra de independência hispanoamericana , entre os que se encontravam, além da independência, a liberdade e a igualdade, o da integração, ou seja a unidade institucional das jovens repúblicas que iam surgindo. Este último objectivo não pode ser alcançado e Hispanoamérica se foi fragmentando em espaços dispersos. Na presente mudança de época, dentro da ideia da Pátria Grande que se vem sustentando contêm-se aquelas ideias levadas em alto então por patriotas como como Bolívar, San Martín, Artigas, e tantos outros. Hoje em dia essas velhas bandeiras levantaram-nas e levantam líderes como Hugo Chávez, Evo Morales, Rafael Correa, e o avanço para a unidade institucional –não isenta de perigos e retrocessos circunstanciales- se traduz em criações como a ALBA, UNASUR y CELAC.La ponencia parte de la valoración de los objetivos que sustentaran los prohombres de la guerra de independencia hispanoamericana, entre los que se encontraban, además de la independencia, la libertad y la igualdad, el de la integración, o sea la unidad institucional de las jóvenes repúblicas que iban surgiendo. Este último objetivo no pudo concretarse e Hispanoamérica se fue fragmentando en espacios dispersos. En el presente cambio de época, dentro de la idea de la Patria Grande que se viene sustentando, se contienen aquellas ideas llevadas en alto entonces por patriotas como Bolívar, San Martín, Artigas, y tantos otros. Hoy en día esas viejas banderas las levantaron y levantan líderes como Hugo Chávez, Evo Morales, Rafael Correa, y el avance hacia la unidad institucional —no exenta de peligros y retrocesos circunstanciales— se traduce en creaciones como la ALBA, Unasur y CELAC

Dynamics of one- and two-dimensional fronts in a bistable equation with time-delayed global feedback : propagation failure and control mechanisms

We study the evolution of fronts in a bistable equation with time-delayed global feedback in the fast reaction and slow diffusion regime. This equation generalizes the Hodgkin-Grafstein and Allen-Cahn equations. We derive a nonlinear equation governing the motion of fronts, which includes a term with delay. In the one-dimensional case this equation is linear. We study the motion of one- and two-dimensional fronts, finding a much richer dynamics than for the previously studied cases (without time-delayed global feedback). We explain the mechanism by which localized fronts created by inhibitory global coupling loose stability in a Hopf bifurcation as the delay time increases. We show that for certain delay times, the prevailing phase is different from that corresponding to the system in the absence of global coupling. Numerical simulations of the partial differential equation are in agreement with the analytical predictions