Patrones generales de rendimiento en natación

Antecedentes: Diferentes variables afectan a la obtención del rendimiento en categoría absoluta. Existiendo gran controversia sobre el efecto de la especialización temprana en la obtención de rendimiento en posteriores categorías. Objetivos: El objetivo del presente estudio es analizar el efecto de la especialización temprana en natación. Además, observar la progresión de los nadadores españoles y estadounidenses que han participado en la final en Campeonatos del mundo en categoría junior, comprobando si logran obtener rendimiento en finales de Juegos Olímpicos y Campeonatos del Mundo absoluto entre los años 2006 y 2021, de todos los estilos y distancias. Método: La base de datos final está formada por 268 nadadores. Análisis descriptivos tales como conteo, tablas de contingencia se realizaron para saber el número total de nadadores en función del género y la categoría, también para conocer el número de nadadores en cada estilo en función de la competición y el país perteneciente, y por último para el tiempo medio de cada prueba. Resultados: Los resultados mostraron un mayor número de nadadores finalistas de EE. UU. en todos los estilos de las competiciones, y con un mayor número de participantes en estilo libre. De los nadadores junior 77 (28.41%) únicamente 7 (2.58%) nadadores llegaron a las finales de Campeonatos del Mundo junior, Campeonatos del Mundo absoluto y Juegos Olímpicos. Conclusiones: En conclusión, ser finalista de los Campeonatos del Mundo junior no influye en el éxito en las finales de Campeonatos del Mundo absoluto y Juegos Olímpicos para nadadores españoles y estadounidenses

Compacted bentonite hydro-mechanical modelling when interaggregate porosity tends to zero

A formulation is proposed for reproducing the hydro-mechanical behaviour of compacted bentonites as interaggregate porosity becomes negligible. In that case, the model assumes the bentonite deformability to be controlled only by the microstructural modelling level in a double porosity approach. Hence, the bulk stiffness of the system is defined by the relationship between the microstructural void ratio and the thermodynamic swelling pressure, requiring no additional parameters to simulate the overall behaviour. An experimental study has been conducted to check the conceptual consistency of the formulation, with favourable results. The quantitative potential of the model has also been satisfactorily verified by numerical simulation of the tests carried out in this study. A displacement-based finite-element model developed for double porosity systems has been modified to run the simulations. The proposed formulation has been implemented using a simple strategy that can be easily replicated for similar numerical models. Both the simulation capabilities and the computational cost efficiency of the proposed formulation confirm its practical interest.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. This publication is part of Grant PID2020-118291RB-I00 funded by MCIN/AEI/https://doi.org/10.13039/501100011033.Peer ReviewedPostprint (published version

Enhanced electrokinetic remediation of polluted soils by anolyte pH conditioning

n the treatment of a polluted soil, the pH has a strong impact on the development of different physicochemical processes as precipitation/dissolution, adsorption/desorption or ionic exchange. In addition, the pH determines the chemical speciation of the compounds present in the system and, consequently, it conditions the transport processes by which those compounds will move. This question has aroused great interest in the development of pH control technologies coupled to soil remediation processes. In electrokinetic remediation processes, pH has usually been controlled by catholyte pH conditioning with acid solutions, applied to cases of heavy metals pollution. However, this method is not effective with pollutants that can be dissociated in anionic species. In this context, this paper presents a study of the electrokinetic remediation of soils polluted with 2,4-Dichlorophenoxyacetic acid, a common polar pesticide, enhanced with an anolyte pH conditioning strategy. A numerical study is proposed to evaluate the effectiveness of the strategy. Several numerical tests have been carried out for NaOH solutions with different concentrations as pH conditioning fluid. The results show that the anolyte pH conditioning strategy makes it possible to control the pH of the soil and, consequently, the chemical speciation of pollutant species. Thus, it is possible to achieve an important flux of pesticide into the anolyte compartment (electro-migration of anionic species and diffusive transport of acid species). This way, it possible to maximise the pesticide accumulation in this compartment, allowing a much more effective removal of pollutants from the soil than without the anolyte pH conditioning strategy

A new double-porosity macroscopic model of bentonite free swelling

A macroscopic model based on a double-porosity approach is proposed to simulate the swelling caused by the subdivision of particles and aggregates that occurs when bentonites are hydrated under a high water content and low confinement. In the model, it is assumed that although the water that occupies this new porous structure can be considered mobile (associated with the macrostructure), its contribution to variations in the energy of the system is similar to that caused by the immobile water that occupies the microstructure. Assuming isothermal conditions, a functional relationship between the increase in the void ratio and the decrease in internal energy was defined from the Clausius-Duhem equation. From this functional relationship, a macroscopic constitutive model was derived to determine the macrostructural swelling as a function of the decrease in the microstructural effective stress. The model was applied to simulate both tests with a large void ratio (up to 50) and processes with a notable variation in salinity (from deionized water to 1 M solution), and satisfactory results were obtained in all cases. This study proposes a simple strategy to incorporate the model into the equations generally used to solve hydro-chemical-mechanical boundary problems at the engineering scale and is thus of direct practical interest.This study was funded by the Junta de Comunidades de Castilla-La Mancha and the European Regional Development Fund (European Union) through project SBPLY/19/180501/000222.Peer ReviewedPostprint (published version

Differentiated intra- and inter-aggregate water content models of MX-80 bentonite

The current research proposes a method for obtaining the intra-aggregate (microstructural) and inter-aggregate (macrostructural) water content of MX-80 bentonite using data from water retention curves. Data associated with high suction were used to define the microstructural water content model. By extrapolating this model to low suction, microstructural and macrostructural water contents were separated to obtain a macrostructural water content model. Micro- and macrostructural water content models have been used to simulate an isotropic swelling test, thus illustrating the advisability of using a double and differentiated macro/micro description of the water content to characterise the hydro-mechanical behaviour of MX-80 bentonite

Geotechnical behaviour of low-permeability soils in surfactant-enhanced electrokinetic remediation

Electrokinetic processes provide the basis of a range of very interesting techniques for the remediation of polluted soils. These techniques consist of the application of a current field in the soil that develops different transport mechanisms capable of mobilizing several types of pollutants. However, the use of these techniques could generate nondesirable effects related to the geomechanical behavior of the soil, reducing the effectiveness of the processes. In the case of the remediation of polluted soils with plasticity index higher than 35, an excessive shrinkage can be observed in remediation test. For this reason, the continued evaporation that takes place in the sample top can lead to the development of cracks, distorting the electrokinetic transport regime, and consequently, the development of the operation. On the other hand, when analyzing silty soils, in the surroundings of injection surfactant wells, high seepages can be generated that give rise to the development of piping processes. In this article methods are described to allow a reduction, or to even eliminate, both problems.Los procesos electrocinéticos proporcionan la base de una serie de técnicas muy interesantes para la remediación de suelos contaminados. Estas técnicas consisten en la aplicación de un campo actual en el suelo que desarrolla diferentes mecanismos de transporte capaces de movilizar varios tipos de contaminantes. Sin embargo, el uso de estas técnicas podría generar efectos no deseables relacionados con el comportamiento geomecánico del suelo, reduciendo la efectividad de los procesos. En el caso de la remediación de suelos contaminados con índice de plasticidad superior a 35, se puede observar una contracción excesiva en la prueba de remediación. Por este motivo, la evaporación continuada que se produce en la parte superior de la muestra puede provocar el desarrollo de fisuras, distorsionando el régimen de transporte electrocinético y, en consecuencia, el desarrollo de la operación. Por otra parte, al analizar suelos limosos, en el entorno de los pozos de inyección de surfactante, se pueden generar altas filtraciones que dan lugar al desarrollo de procesos de tubería. En este artículo se describen métodos para permitir una reducción, o incluso eliminar, ambos problemas

Precomputation of Critical State Soil Plastic Models

In this paper, a simple precomputing procedure is proposed to improve the numerical performance of the technological application of critical state soil models. In these models, if associated plasticity is assumed, the normalization of the stress space allows both the yield surface and the plastic components of the elastoplastic matrix to be defined as a function of a single variable. This approach facilitates their parameterization and precomputation, preventing the repetition of calculations when the boundary value problems appear at the yield surface with the calculation of plastic strain. To illustrate the scope of the procedure, its application on a modified Cam Clay model is analysed, which shows that the method allows a significant reduction of about 50% (as compared with the conventional explicit integration algorithm) in the computational time without reducing the precision. Although it is intended for critical state models in soils, the approach can be applied to other materials and types of constitutive models provided that parameterization is possible. It is therefore a methodology of practical interest, especially when a large volume of calculations is required, for example when studying large-scale engineering systems, performing sensitivity analysis, or solving optimization problems

A User-Friendly Tool to Characterize the Moisture Transfer in Porous Building Materials: FLoW1D

This paper presents a user-friendly tool—FLoW1D (One-Dimensional Water Flow)—for the estimation of parameters that characterize the unsaturated moisture transfer in porous building materials. FLoW1D has been developed in Visual Basic for Applications and implemented as a function of the well-known Microsoft Excel© spreadsheet application. The aim of our work is to provide a simple and useful tool to improve the analysis and interpretation of conventional tests for the characterization of the hygric behavior of porous building materials. FLoW1D embraces the conceptual model described in EN 15026 for moisture transfer in building elements, and its implementation has been verified and validated correctly. In order to show the scope of the code, an example of an application has been presented. The hygric characterization of the limestone that is mostly employed in the Cathedral of Santa Maria and San Julian in Cuenca (Spain) was conducted based on an analysis of the conventional water absorption by capillarity tests (EN 15801)