Formulation, implementation and validation of a scalar damage model for brittle materials applied to three- dimensional solid elements

La mecánica del daño continuo describe el deterioro progresivo de las propiedades mecánicas de los materiales a partir de un modelo fenomenológico. En este trabajo se presenta la formulación, implementación y validación de un modelo de daño escalar aplicado a elementos sólidos tridimensionales. Se trata de un modelo de gran versatilidad definido a partir de una superficie de falla y una variable de daño escalar. Su campo de aplicación es la modelación numérica de materiales elásticos isótropos con degradación de la rigidez cuya tensión límite a tracción es igual a la de compresión. El modelo queda definido a partir de cuatro propiedades del material determinables en un ensayo Tensión-Desplazamiento. El modelo es implementado en el software ABAQUS por medio de una subrutina UMAT. Para la resolución de las ecuaciones de equilibrio no lineal se propone un algoritmo de tipo implícito (Método de Backward Euler). La validación a esfuerzos de tracción muestra una adecuada correlación entre los resultados numéricos y los experimentales, con una dispersión de la energía disipada del 6%. Finalmente, se presenta un ejemplo de aplicación. Los resultados alcanzados demuestran que se trata de una herramienta sencilla y, a la vez, poderosa para el análisis numérico de materiales frágiles.Continuum Damage Mechanics describes the progressive degradation of the material properties based on a phenomenological model. This work presents the formulation, implementation and validation of a scalar damage model applied to three-dimensional solid elements. It is a highly versatile model defined from a fault surface and a scalar damage variable. Isotropic elastic materials with softening behavior and a single threshold surface can be simulated by this model. Four parameters are necessary to define the model and they derive from the classical stress-strain test. The model is implemented through a user-defined UMAT subroutine in software ABAQUS. The non-linear equilibrium equations are solved by an implicit algorithm based on the Backward Euler Method. The tensile stress validation shows an adequate correlation between the numerical and experimental results, with a 6% dispersion of dissipated energy. Finally, an illustrative example is presented. The results show that it is a simple but powerful tool for the numerical analysis of brittle materials.Fil: González del Solar, Gerardo Andrés. Universidad Tecnológica Nacional. Facultad Regional Mendoza. Centro Regional de Desarrollos Tecnológicos para la Construcción, Sismología e Ingeniería Sísmica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Martín, P.. Universidad Tecnológica Nacional. Facultad Regional Mendoza. Centro Regional de Desarrollos Tecnológicos para la Construcción, Sismología e Ingeniería Sísmica; ArgentinaFil: Maldonado, N.. Universidad Tecnológica Nacional. Facultad Regional Mendoza. Centro Regional de Desarrollos Tecnológicos para la Construcción, Sismología e Ingeniería Sísmica; Argentin

Metodología para seleccionar oportunidades de mejora continua en promociones de viviendas

Continuous improvement should always be present in business, have they or not management systems on hand according to the UNE EN ISO 9001:2008 Standard. However, its application in the construction sector is especially hard due to the particular characteristics of this business (1). This paper focuses on how to apply four of the seven basic statistical continuous improvement tools (Data collection sheet, Stratification, Histogram and Pareto Diagram) in order to select improvement opportunities within the planification phase of a continuous improvement project whose aims is the reduction of the construction failures in housing blocks which would be detected during the pre-delivery phase. The conclusion is that the three works in which it would be convenient to act in order to reduce significantly the construction failures during the pre-delivery phase are: Wood Carpentry, Ceramic Tile and Electricity.La mejora continua debería estar presente siempre en las empresas, dispongan o no de sistemas de gestión conforme a la Norma UNE EN ISO 9001:2008. Sin embargo, su aplicación en el sector de la construcción es especialmente difícil debido a las características particulares del mismo (1). Este articulo describe cómo aplicar cuatro de las siete herramientas estadísticas básicas de la mejora continua (Hoja de recogida de datos, Estratificación, Histograma y Diagrama de Pareto) para seleccionar oportunidades de mejora, dentro de la fase de planificación de un proyecto de mejora continua que tenga como objetivo reducir los defectos de construcción en edificios de viviendas detectados en la fase de pre-entrega. Concluyendo que los tres oficios en los que convendría actuar para reducir de manera significativa los fallos de construcción en la fase de pre-entrega son: Carpintería de Madera, Revestimientos Cerámicos e Instalación de Electricidad

Relationship between the degree of market orientation and the business geographical scope: the case of the spanish company at the end of the 20th century: Relação entre o grau de orientação do mercado e o âmbito geográfico da empresa: o caso da empresa española no final do século XX

Este estudo tenta analisar a relação entre o grau de orientação de mercado das empresas espanholas no final do século XX e o seu âmbito geográfico, que se compreende na sua tripla faceta: local, nacional e internacional. Em suma, a orientação de mercado é a filosofia empresarial que orienta as suas ações para a satisfação do cliente, procurando rentabilidade a longo prazo e tendo em conta a concorrência. A literatura existente mostra uma clara ligação entre o nível de orientação de mercado e o desempenho empresarial, daí a sua importância

Evolution of central pattern generators for the control of a five-link bipedal walking mechanism

Central pattern generators (CPGs), with a basis is neurophysiological studies, are a type of neural network for the generation of rhythmic motion. While CPGs are being increasingly used in robot control, most applications are hand-tuned for a specific task and it is acknowledged in the field that generic methods and design principles for creating individual networks for a given task are lacking. This study presents an approach where the connectivity and oscillatory parameters of a CPG network are determined by an evolutionary algorithm with fitness evaluations in a realistic simulation with accurate physics. We apply this technique to a five-link planar walking mechanism to demonstrate its feasibility and performance. In addition, to see whether results from simulation can be acceptably transferred to real robot hardware, the best evolved CPG network is also tested on a real mechanism. Our results also confirm that the biologically inspired CPG model is well suited for legged locomotion, since a diverse manifestation of networks have been observed to succeed in fitness simulations during evolution.Comment: 11 pages, 9 figures; substantial revision of content, organization, and quantitative result

Sociobiological Control of Plasmid copy number

Background:
All known mechanisms and genes responsible for the regulation of plasmid replication lie with the plasmid rather than the chromosome. It is possible therefore that there can be copy-up mutants. Copy-up mutants will have within host selective advantage. This would eventually result into instability of bacteria-plasmid association. In spite of this possibility low copy number plasmids appear to exist stably in host populations. We examined this paradox using a computer simulation model.

Model:
Our multilevel selection model assumes a wild type with tightly regulated replication to ensure low copy number. A mutant with slightly relaxed replication regulation can act as a “cheater” or “selfish” plasmid and can enjoy a greater within-host-fitness. However the host of a cheater plasmid has to pay a greater cost. As a result, in host level competition, host cell with low copy number plasmid has a greater fitness. Furthermore, another mutant that has lost the genes required for conjugation was introduced in the model. The non-conjugal mutant was assumed to undergo conjugal transfer in the presence of another conjugal plasmid in the host cell.

Results:
The simulatons showed that if the cost of carrying a plasmid was low, the copy-up mutant could drive the wild type to extinction or very low frequencies. Consequently, another mutant with a higher copy number could invade the first invader. This process could result into an increasing copy number. However above a certain copy number within-host selection was overcompensated by host level selection leading to a rock-paper-scissor (RPS) like situation. The RPS situation allowed the coexistence of high and low copy number plasmids. The non-conjugal “hypercheaters” could further arrest the copy numbers to a substantially lower level.

Conclusions:
These sociobiological interactions might explain the stability of copy numbers better than molecular mechanisms of replication regulation alone

Measurements of Higgs boson production and couplings in diboson final states with the ATLAS detector at the LHC

Measurements are presented of production properties and couplings of the recently discovered Higgs boson using the decays into boson pairs, H →γ γ, H → Z Z∗ →4l and H →W W∗ →lνlν. The results are based on the complete pp collision data sample recorded by the ATLAS experiment at the CERN Large Hadron Collider at centre-of-mass energies of √s = 7 TeV and √s = 8 TeV, corresponding to an integrated luminosity of about 25 fb−1. Evidence for Higgs boson production through vector-boson fusion is reported. Results of combined fits probing Higgs boson couplings to fermions and bosons, as well as anomalous contributions to loop-induced production and decay modes, are presented. All measurements are consistent with expectations for the Standard Model Higgs boson

Standalone vertex finding in the ATLAS muon spectrometer

A dedicated reconstruction algorithm to find decay vertices in the ATLAS muon spectrometer is presented. The algorithm searches the region just upstream of or inside the muon spectrometer volume for multi-particle vertices that originate from the decay of particles with long decay paths. The performance of the algorithm is evaluated using both a sample of simulated Higgs boson events, in which the Higgs boson decays to long-lived neutral particles that in turn decay to bbar b final states, and pp collision data at √s = 7 TeV collected with the ATLAS detector at the LHC during 2011

Measurement of the top quark-pair production cross section with ATLAS in pp collisions at \sqrt{s}=7\TeV

A measurement of the production cross-section for top quark pairs(\ttbar) in $pp$ collisions at \sqrt{s}=7 \TeV is presented using data recorded with the ATLAS detector at the Large Hadron Collider. Events are selected in two different topologies: single lepton (electron $e$ or muon $\mu$) with large missing transverse energy and at least four jets, and dilepton ($ee$, $\mu\mu$ or $e\mu$) with large missing transverse energy and at least two jets. In a data sample of 2.9 pb-1, 37 candidate events are observed in the single-lepton topology and 9 events in the dilepton topology. The corresponding expected backgrounds from non-\ttbar Standard Model processes are estimated using data-driven methods and determined to be $12.2 \pm 3.9$ events and $2.5 \pm 0.6$ events, respectively. The kinematic properties of the selected events are consistent with SM \ttbar production. The inclusive top quark pair production cross-section is measured to be \sigmattbar=145 \pm 31 ^{+42}_{-27} pb where the first uncertainty is statistical and the second systematic. The measurement agrees with perturbative QCD calculations.Comment: 30 pages plus author list (50 pages total), 9 figures, 11 tables, CERN-PH number and final journal adde

Measurement of the top quark pair cross section with ATLAS in pp collisions at √s=7 TeV using final states with an electron or a muon and a hadronically decaying τ lepton

A measurement of the cross section of top quark pair production in proton-proton collisions recorded with the ATLAS detector at the Large Hadron Collider at a centre-of-mass energy of 7 TeV is reported. The data sample used corresponds to an integrated luminosity of 2.05 fb -1. Events with an isolated electron or muon and a τ lepton decaying hadronically are used. In addition, a large missing transverse momentum and two or more energetic jets are required. At least one of the jets must be identified as originating from a b quark. The measured cross section, σtt-=186±13(stat.)±20(syst.)±7(lumi.) pb, is in good agreement with the Standard Model prediction

Expected Performance of the ATLAS Experiment - Detector, Trigger and Physics

A detailed study is presented of the expected performance of the ATLAS detector. The reconstruction of tracks, leptons, photons, missing energy and jets is investigated, together with the performance of b-tagging and the trigger. The physics potential for a variety of interesting physics processes, within the Standard Model and beyond, is examined. The study comprises a series of notes based on simulations of the detector and physics processes, with particular emphasis given to the data expected from the first years of operation of the LHC at CERN