An RVE-based multiscale theory of solids with micro-scale inertia and body force effects

A multiscale theory of solids based on the concept of representative volume element (RVE) and accounting for micro-scale inertia and body forces is proposed. A simple extension of the classical Hill–Mandel Principle together with suitable kinematical constraints on the micro-scale displacements provide the variational framework within which the theory is devised. In this context, the micro-scale equilibrium equation and the homogenisation relations among the relevant macro- and micro-scale quantities are rigorously derived by means of straightforward variational arguments. In particular, it is shown that only the fluctuations of micro-scale inertia and body forces about their RVE volume averages may affect the micro-scale equilibrium problem and the resulting homogenised stress. The volume average themselves are mechanically relevant only to the macro-scale

Adaptación del sistema de control académico en el Departamento de Postgrado del Centro de Estudios del Mar y Acuicultura de la Universidad de San Carlos de Guatemala

Proporcionar a los estudiantes una herramienta en la cual puedan realizar una asignación de forma segura e inmediata por medio de una interfaz web, así controlar el proceso de ingreso de zonas, exámenes y notas finales de cada curso por parte de los catedráticos de forma electrónica y customizar una herramienta amigable e intuitiva para que todos los estudiantes, docentes y personal administrativo puedan utilizarla de manera simple

Damage-driven strain localisation in networks of fibres: A computational homogenisation approach

In many applications, such as textiles, fibreglass, paper and several kinds of biological fibrous tissues, the main load-bearing constituents at the micro-scale are arranged as a fibre network. In these materials, rupture is usually driven by micro-mechanical failure mechanisms, and strain localisation due to progressive damage evolution in the fibres is the main cause of macro-scale instability. We propose a strain-driven computational homogenisation formulationbased on Representative Volume Element (RVE), within a framework in which micro-scale fibre damage can lead to macro-scale localisation phenomena. The mechanical stiffness considered here for the fibrous structure system is due to: i) an intra-fibre mechanism in which each fibre is axially stretched, and as a result, it can suffer damage; ii) an inter-fibre mechanism in which the stiffness results from the variation of the relative angle between pairs of fibres. The homogenised tangent tensor, which comes from the contribution of these two mechanisms, is required to detect the so-called bifurcation point at the macro-scale, through the spectral analysis of the acoustic tensor. This analysis can precisely determine the instant at which the macro-scale problem becomes ill-posed. At such a point, the spectral analysis provides information about the macro-scale failure pattern (unit normal and crack-opening vectors). Special attention is devoted to present the theoretical fundamentals rigorously in the light of variational formulations for multi-scale models. Also, the impact of a recent derived more general boundary condition for fibre networks is assessed in the context of materials undergoing softening. Numerical examples showing the suitability of the present methodology are also shown and discussed

Rhamnogalacturonase lyase gene downregulation in strawberry and its potential on mechanical fruit properties

Strawberry softening is one of the main factors that reduces fruit quality and leads to economically important losses. Textural changes during fruit ripening are mainly due to the dissolution of middle lamellae, a reduction in cell-to-cell adhesion and the weakening of parenchyma cell walls as a result of the action of cell wall modifying enzymes. Functional studies of genes encoding pectinase enzymes (polygalacturonase, pectate lyase and -galactosidase) support a key role of pectin disassembly in strawberry softening. Evidence that RG-I may play an important role in strawberry texture has been obtained from the transient silencing of a RG-lyase gene. Pectins are major components of fruit cell walls and highly dynamic polysaccharides, but due to their heterogeneity the precise relation between the structures and functions is incomplete. In this work, stable transgenic strawberry lines with a rhamnogalacturonate lyase gene (FaRGLyase1) down-regulated have been analyzed. Several transgenic lines showing more than 95% silencing of FaRGLyase1 displayed fruit firmness values higher than control. Cell walls from these lines were extracted and analyzed by ELISA and Epitope Detection Chromatography (EDC). This last technique is based on the detection of specific cell wall oligosaccharide epitopes and provides information on sub-populations of pectins containing homogalacturonan and RG-I domains, but also reveals potential links with other cell wall polysaccharides such as xyloglucan. The results obtained indicate that the silencing of FaRGLyase1 reduces degradation of RG-I backbones, but also homogalacturonan, in cell walls, especially in pectin fractions covalently bound to the cell wall. These changes contribute to the increased firmness of transgenic fruits.This research was supported by FEDER EU Funds and the Ministerio de Economía y Competitividad of Spain (grant reference AGL2014-55784-C2), a Marie Curie IEF within the 7th European Community Framework Programme (reference: PIEF-2013-625270) for SP and a FPI fellowship (BES-2015-073616) to support PR-V. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Dissolution kinetics of cellulose in ionic solvents by polarized light microscopy

Aiming to increase the scarce information available on the kinetics of cellulose dissolution, we have applied an image-assisted technique based on the luminance evolution as cellulose dissolves to study this process under different experimental conditions. This protocol was validated via direct determination of the cellulose dissolved. In all cases datapoints were linearly fitted assuming a pseudo-zero order reaction which facilitates the comparison between datasets. To study the solvent effect we have used three ionic liquids with large basicity and found significantly different rates of dissolution, from faster to slower: [C2 C1 Im][OAc]>[C1 C1 Im][DMP]>[C2 C1 Im][DEP]. Solvatochromic parameters and viscosity of the solvent media were determined and the latter was identified as a key factor slowing the process as it reduces ionic mobility. The weight of viscosity was estimated by removing the viscosity effect with a tuned solvent media doped with DMSO. Activation energy was 70% lower at constant viscosity. On the substrate side, particle size is the main factor affecting the dissolution rate. All samples were milled to homogenise the starting material and minimise the distortions caused by the size distribution. After, dissolution of three cellulose substrates under the same experimental conditions was analysed. Dissolution of natural fibers took twice as long as dissolving pulp which dissolves slower than lyocell fibers. This trend correlates with the roughness of the samples obtained by optical perfilometry which is consistent with the dissolution mechanism proposed in the literature.Xunta de Galicia | Ref. ED481A 2021/341Xunta de Galicia | Ref. ED481D-2022-022Agencia Estatal de Investigación | Ref. RYC2021- 033826-IUniversidade de Vigo/CISU

La variabilidad de las anomalías baroclínicas en diferentes escalas de tiempo y su papel para la persistencia de la corriente en chorro

Ponencia presentada en: XXXII Jornadas Científicas de la AME y el XIII Encuentro Hispano Luso de Meteorología celebrado en Alcobendas (Madrid), del 28 al 30 de mayo de 2012

Mecanismos de sincronización en programación funcional concurrente

Muchas aplicaciones y o algoritmos se expresan de manera más sencilla utilizando lenguajes con estructuras o primitivas de concurrencia. En este tipo de problemas es necesaria la presencia y manipulación de variables o estructuras de estados las cuales se utilizan como mecanismos de sincronización y comunicación entre los procesos Los semáforos son herramientas utilizadas para solucionar problemas de secciones críticas e implementar protocolos de sincronización en programación concurrente Los lenguajes funcionales son her ramientas propicias para expresar paralelismo Concurrent Haskell es una extensión concurrente del lenguaje funcional puro y lazy Haskell. En este trabajo se presentan varias implementaciones de semáforos en Concurrent Haskell y se propone una generalización de las técnicas y mecanismos de sincronización y comunicación de procesos utilizando funciones de alto orden como así también la posibilidad de expresar nuevas estructuras de manipulación de concurrencia como tipo de datos abstractos Un punto importante es estudiar la posibilidad de utilizar lógicas aptas para la concurrencia en la verificación de programas funcionales concurrentes De esta manera se muestra que la programación funcional presenta una alternativa para el desarrollo de aplicaciones concurrentes .Eje: Conferencia latinoamericana de programación funcionalRed de Universidades con Carreras en Informática (RedUNCI

Mecanismos de sincronización en programación funcional concurrente

Muchas aplicaciones y o algoritmos se expresan de manera más sencilla utilizando lenguajes con estructuras o primitivas de concurrencia. En este tipo de problemas es necesaria la presencia y manipulación de variables o estructuras de estados las cuales se utilizan como mecanismos de sincronización y comunicación entre los procesos Los semáforos son herramientas utilizadas para solucionar problemas de secciones críticas e implementar protocolos de sincronización en programación concurrente Los lenguajes funcionales son her ramientas propicias para expresar paralelismo Concurrent Haskell es una extensión concurrente del lenguaje funcional puro y lazy Haskell. En este trabajo se presentan varias implementaciones de semáforos en Concurrent Haskell y se propone una generalización de las técnicas y mecanismos de sincronización y comunicación de procesos utilizando funciones de alto orden como así también la posibilidad de expresar nuevas estructuras de manipulación de concurrencia como tipo de datos abstractos Un punto importante es estudiar la posibilidad de utilizar lógicas aptas para la concurrencia en la verificación de programas funcionales concurrentes De esta manera se muestra que la programación funcional presenta una alternativa para el desarrollo de aplicaciones concurrentes .Eje: Conferencia latinoamericana de programación funcionalRed de Universidades con Carreras en Informática (RedUNCI

Automated test data generation using a scatter search approach

The techniques for the automatic generation of test cases try to efficiently find a small set of cases that allow a given adequacy criterion to be fulfilled, thus contributing to a reduction in the cost of software testing. In this paper we present and analyze two versions of an approach based on the Scatter Search metaheuristic technique for the automatic generation of software test cases using a branch coverage adequacy criterion. The first test case generator, called TCSS, uses a diversity property to extend the search of test cases to all branches of the program under test in order to generate test cases that cover these. The second, called TCSS-LS, is an extension of the previous test case generator which combines the diversity property with a local search method that allows the intensification of the search for test cases that cover the difficult branches. We present the results obtained by our generators and carry out a detailed comparison with many other generators, showing a good performance of our approac

Boltzmann kinetic equation for a strongly confined gas of hard spheres

A Boltzmann-like kinetic equation for a quasi-two-dimensional gas of hard spheres is derived. The system is confined between two parallel hard plates separated a distance between one and two particle diameters. An entropy Lyapunov function for the equation is identified. In addition to the usual Boltzmann expression, it contains a contribution associated to the confinement of the particles. The steady properties of the system agree with equilibrium statistical mechanics results. Equations describing the energy transfer between the degrees of freedom parallel and perpendicular to the confining plates are obtained for some simple initial configurations. The theoretical predictions are compared with molecular dynamics simulation data and a good agreement is foun