Nonlocal regularization for loss of ellipticity in inelastic problems

A mixed three-field finite element formulation is proposed as a method for the alleviation of mesh dependency in finite-deformation inelastic problems subjected to bifurcation. The additional fields in the formulation are the internal variables that cause bifurcation and the corresponding conjugate thermodynamic forces. The formulation leads to expressions for the additional fields that are akin to nonlocal averages that extend to a domain defined by the interpolation functions selected for these fields. The size of the nonlocal domain controls the length scale of the problem. The performance of the formulation is demonstrated by several examples where it is shown that it is effective in alleviating mesh dependence. The formulation provides effective regularization, entirely by-passes the introduction of new and independent mechanical variables into the problem, discretizes naturally, computes averages with regular interpolation functions, and does not require changes to constitutive relationships

A variational constitutive model for soft biological tissues

In this paper, a fully variational constitutive model of soft biological tissues is formulated in the finite strain regime. The model includes Ogden-type hyperelasticity, finite viscosity, deviatoric and volumetric plasticity, rate and microinertia effects. Variational updates are obtained via time discretization and pre-minimization of a suitable objective function with respect to internal variables. Genetic algorithms are used for model parameter identification due to their suitability for non-convex, high dimensional optimization problems. The material behavior predicted by the model is compared to available tests on swine and human brain tissue. The ability of the model to predict a wide range of experimentally observed behavior, including hysteresis, cyclic softening, rate effects, and plastic deformation is demonstrated

Meet you at the crossroads: the simulation analysis of an airport for identifying potential problems

The aeronautical industry is still under expansion in spite of the problems it is facing due to the increase in oil prices, limited capacity, and novel regulations. For this reason, it is necessary to have tools that help during the process of an expansion project, or during planning phases of new aeronautical infrastructures. For the particular case of a new airport project there are many variables to consider in order to minimize the risk of high costs or even serious problems during the operation of a new airport. The article presents a methodology that combines two simulation approaches that complement each other applied to the problem of the development of a new airport in The Netherlands. The use of the methodology gives light to the future problems that might be faced by the managers of the airport. One model focuses in the operative of the airport from a high-level angle taking into account the configurations that might be in place once the airport is under operation. The second model put focus in other technical aspects of the operation for challenging the feasibility of the proposed configurations and for identifying other issues that cannot be perceived with the first model. With the use of the methodology different problems and performance indicators can be foreseen and act in consequence. The combination of both approaches is a powerful one in which the overlapping of solutions will save a lot of money to the airport operators and/or airport developers.Trabajo publicado en Actas del VI Congreso Internacional de la Red Iberoamericana de Investigación en Transporte Aéreo RIDITA 2017.Grupo de Transporte Aéreo - Grupo de Ingeniería Aplicada a la Industri

R450A and R513A as lower GWP mixtures for high ambient temperature countries: Experimental comparison with R134a

In recognition of the impact of the refrigeration sector on climate change, global commitments are achieved to replace hydrofluorocarbon substances with more planet-friendly alternatives. In this regard, countries with high ambient temperatures (HAT) face additional problems in identifying suitable alternatives due to the impact of such temperatures on energy performance in vapor compression systems. This paper presents an experimental analysis using R134a and two lower global warming potential (GWP) mixtures in a small capacity vapor compression refrigeration system for HAT environments. The range of evaporating and condensing conditions was selected to simulate a refrigeration system working at HAT conditions. The experimental operating results show that although R450A values are acceptable, R513A shows better adaptation to the refrigeration system in terms of pressure ratio, discharge temperature, and mass flow rate. Then, attending to experimental energetic results, R450A energy performance (quantified by COP) and cooling capacity are lower than R513A and R134a. TEWI analysis of a small refrigeration unit shows CO2 equivalent emission saving when using R450A in the different condensation conditions. However, taking into account the variation of cooling capacity, R513A system results in the lowest TEWI when normalizing per unit of delivered cooling capacity

EL PRINCIPIO DE CONSERVACIÓN DE LA EMPRESA EN LOS PROCESOS FALENCIALES DESDE LA PERSPECTIVA DEL ANÁLISIS ECONÓMICO DEL DERECHO

RESUMENEl objetivo del presente trabajo es aportar una visión novedosa y moderna en torno al principio de la conservación de la empresa que impregna a todo nuestro ordenamiento jurídico tal como se aprecia en los aspectos teleológicos y ontológicos de las leyes de concursos y quiebras y de sociedades comerciales.La principal característica de este trabajo es que la metodología de investigación bajo la cual se efectúa es la del análisis económico del derecho, conocido en el mundo anglosajón bajo la denominación de law and economics; constituyendo ésta una las escuelas que ha efectuado múltiples críticas a las instituciones tradicionales del derecho tanto de raigambre romano continental como del common law.La metodología de investigación abarca tanto el estudio de los objetivos y funciones de las disposiciones normativas, reflexionando sobre la teorética jurídica vigente, así como su estructuración de sus preceptos, cuerpos normativos e instituciones.La utilización de herramientas propias de la economía, más específicamente de la microeconomía, como la teoría de precios, la moderna teoría de la oferta, de la demanda y de los mercados de producto así como también de la denominada economía de la regulación, que tiene por objeto estudio el efecto económico que las disposiciones normativas tienen en el desarrollo, tanto en la fluctuación positiva o negativa de los mercados como en la corrección de imperfecciones y la redistribución de la riquezas, constituyendo los pilares sobre los que se basa el análisis económico del derecho.En cuanto al sistema de investigación, el análisis económico del derecho permite respecto al estudio del mencionado principio de conservación de la empresa comprender la racionalidad estratégica y la eficiencia de su aplicación en los procesos concursales, permitiendo a los diversos operarios del derecho - sean estos juristas, magistrados, síndicos concursales o estudiosos de la materia - tener una visión más amplia y profunda de su importancia en la vida económica.Para ello hemos de exponer de manera breve y concisa las diversas aseveraciones del análisis económico respecto al derecho concursal, sus consideraciones en cuanto a la ontología, motivación y objetivos que se persiguen tanto en los mentados procesos de reorganización y liquidación empresarial.Como aclaración previa debemos señalar que el análisis económico del derecho no pretende suplantar ni constituirse en el método predominante en las investigaciones jurídicas sino aportar una visión enriquecedora para la problemática.En un mundo dinámico como el de hoy, donde los cambios revolucionarios han dejado de producirse en los campos políticos e ideológicos pasando a desarrollarse en la esfera de las comunicaciones, de la tecnología y del comercio internacional, pretender mantener una visión estrictamente dentro del formalismo jurídico no sólo resulta perjudicial para la comprensión de los novedosos fenómenos que han de sucederse sino que, como oportunamente indicó el Dr. Ricardo Lorenzetti, “es penoso que el derecho pretenda la autosuficiencia ante un mundo tan complejo”, señalando así la necesaria interdisciplinariedad que ha de primar, no sólo en el ámbito jurídico sino en el estudio de los mencionados fenómenos.PALABRAS CLAVES: eficiencia, falencia, liquidación, reorganización, empresa.ABSTRACTThe aim of this study is to provide a new and modern view on the principle of the conservation of the company that permeates our entire legal system as seen in teleological and ontological aspects of the laws on bankruptcy and commercial companies.The main feature of this work is that the research methodology under which it takes place is that of economic analysis of law, known in the English speaking world under the name of law and economics; constituting this one the schools that has made many criticisms of the traditional institutions of Roman law roots of both continental and common law.The research methodology includes both the study of the objectives and functions of regulatory requirements, reflecting on the current legal theoretical and structuring of its precepts, regulatory bodies and institutions.Using proprietary tools of economics, specifically microeconomics, price theory and the modern theory of supply, demand and product markets as well as the so-called economics of regulation, which has designed to study the economic impact that regulatory requirements are in development, both positive and negative market fluctuation and correcting imperfections, and the redistribution of wealth, constituting the pillars on which economic analysis is based right.As the research system, the economic analysis of law allows regarding the study of the aforementioned principle of conservation of the company understand the strategic rationale and efficiency of their application in bankruptcy proceedings, allowing different operators to the right - be they lawyers magistrates, bankruptcy trustees and students of the subject - have a broader and deeper understanding of its importance in the economic life vision.To do this we set forth briefly and concisely the various assertions of economic analysis regarding bankruptcy law, their considerations of ontology, motivation and objectives pursued mented both reorganization and liquidation business.As a preliminary explanation we note that the economic analysis of law is not intended to supplant or act as the predominant method in legal research but to provide an enriching vision for the issue.In a dynamic world like today, where the revolutionary changes are no longer produced in the political and ideological fields going to develop in the field of communications, technology and international trade, pretending vision within a strictly legal formalism not only detrimental to the understanding of the new phenomena that are to succeed but, as promptly Dr. Ricardo Lorenzetti said, "it is unfortunate that the law seeks self-sufficiency to such a complex world," noting that it has the necessary interdisciplinary to prevail, not only in the legal field but in the study of the phenomena mentioned.KEY WORDS: efficiency, bankruptcy, liquidation, reorganization, company

Simulation-Based Virtual Cycle for Multi-Level Airport Analysis

The aeronautical industry is expanding after a period of economic turmoil. For this reason, a growing number of airports are facing capacity problems that can sometimes only be resolved by expanding infrastructure, with the inherent risks that such decisions create. In order to deal with uncertainty at different levels, it is necessary to have relevant tools during an expansion project or during the planning phases of new infrastructure. This article presents a methodology that combines simulation approaches with different description levels that complement each other when applied to the development of a new airport. The methodology is illustrated with an example that uses two models for an expansion project of an airport in The Netherlands. One model focuses on the operation of the airport from a high-level position, while the second focuses on other technical aspects of the operation that challenge the feasibility of the proposed configuration of the apron. The results show that by applying the methodology, analytical power is enhanced and the risk of making the wrong decisions is reduced. We identified the limitations that the future facility will have and the impact of the physical characteristics of the traffic that will operate in the airport. The methodology can be used for tackling different problems and studying particular performance indicators to help decision-makers take more informed decisions.Grupo de Transporte Aéreo - Grupo de Ingeniería Aplicada a la Industri

Simulation-Based Virtual Cycle for Multi-Level Airport Analysis

The aeronautical industry is expanding after a period of economic turmoil. For this reason, a growing number of airports are facing capacity problems that can sometimes only be resolved by expanding infrastructure, with the inherent risks that such decisions create. In order to deal with uncertainty at different levels, it is necessary to have relevant tools during an expansion project or during the planning phases of new infrastructure. This article presents a methodology that combines simulation approaches with different description levels that complement each other when applied to the development of a new airport. The methodology is illustrated with an example that uses two models for an expansion project of an airport in The Netherlands. One model focuses on the operation of the airport from a high-level position, while the second focuses on other technical aspects of the operation that challenge the feasibility of the proposed configuration of the apron. The results show that by applying the methodology, analytical power is enhanced and the risk of making the wrong decisions is reduced. We identified the limitations that the future facility will have and the impact of the physical characteristics of the traffic that will operate in the airport. The methodology can be used for tackling different problems and studying particular performance indicators to help decision-makers take more informed decisions.Grupo de Transporte Aéreo - Grupo de Ingeniería Aplicada a la Industri

Three-dimensional fracture and fragmentation of artificial kidney stones

The brittle fracture of a gypsum cylinder, which is used as an artificial kidney stone in lithotripsy research, is simulated by the use of the finite element method. The cylinder is submerged in water and is subjected to a pressure front parallel to one of its planar faces. The stresses induced by the pressure wave lead to fracture in the interior of the cylinder, with the formation of a spall plane located about 2/3 of the length from the face on which the pressure is applied. We show that the simulation reproduces the salient features of experimental observations

Lie-group interpolation and variational recovery for internal variables

We propose a variational procedure for the recovery of internal variables, in effect extending them from integration points to the entire domain. The objective is to perform the recovery with minimum error and at the same time guarantee that the internal variables remain in their admissible spaces. The minimization of the error is achieved by a three-field finite element formulation. The fields in the formulation are the deformation mapping, the target or mapped internal variables and a Lagrange multiplier that enforces the equality between the source and target internal variables. This formulation leads to an L2 projection that minimizes the distance between the source and target internal variables as measured in the L2 norm of the internal variable space. To ensure that the target internal variables remain in their original space, their interpolation is performed by recourse to Lie groups, which allows for direct polynomial interpolation of the corresponding Lie algebras by means of the logarithmic map. Once the Lie algebras are interpolated, the mapped variables are recovered by the exponential map, thus guaranteeing that they remain in the appropriate space

A networked learning framework for effective MOOC design: the ECO project approach

In the past two years a lot of attention has been given by the European Commission, as well as the European open, distance and digital education community, to the development of an alternative, more collaborative approach to MOOC design that has the potential to represent a solid qualitative alternative to the most commonly used models today. These models, which basically follow a trend originated at the top US universities that is broadly identified in the literature as xMOOCs, are proving to be inconsistent with the European standards for formal higher education due to their low-level of learner support and lack of an enriched pedagogical approach. Within the framework of the EU-funded project Elearning, Communication and Open-data: Massive Mobile, Ubiquitous and Open Learning (ECO) a research team from a pool of institutions with experience in MOOC design conceived a model that attempts to meet the above-referred challenge. In this paper we present a description of the model and its most innovative features, its theoretical foundations and context of development, as well as scenarios of implementation. Through our definition of MOOCs and assumptions, principles and characteristics of the pedagogical framework it should become clear why a networked learning framework for effective MOOC design will be able to meet the ambition of European higher education institutions to develop an alternative, more quality-oriented and effective approach to a massive open online form of education delivery.Part of the work carried out has been funded with support from the European Commission, under the ICT Policy Support Programme, as part of the Competitiveness and Innovation Framework Programme (CIP) in the ECO project under grant agreement n° 21127