820 research outputs found

    Técnicas de optimización paralelas : esquema híbrido basado en hiperheurísticas y computación evolutiva

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    Optimisation is the process of selecting the best element fr om a set of available alternatives. Solutions are termed good or bad depending on its performance for a set of objectives. Several algorithms to deal with such kind of problems have been defined in the literature. Metaheuristics are one of the most prominent techniques. They are a class of modern heuristics whose main goal is to com bine heuristics in a problem independent way with the aim of improving their per formance. Meta- heuristics have reported high-quality solutions in severa l fields. One of the reasons of the good behaviour of metaheuristics is that they are defin ed in general terms. Therefore, metaheuristic algorithms can be adapted to fit th e needs of most real-life optimisation. However, such an adaptation is a hard task, and it requires a high computational and user effort. There are two main ways of reducing the effort associated to th e usage of meta- heuristics. First, the application of hyperheuristics and parameter setting strategies facilitates the process of tackling novel optimisation pro blems and instances. A hyperheuristic can be viewed as a heuristic that iterativel y chooses between a set of given low-level metaheuristics in order to solve an optim isation problem. By using hyperheuristics, metaheuristic practitioners do no t need to manually test a large number of metaheuristics and parameterisations for d iscovering the proper algorithms to use. Instead, they can define the set of configur ations which must be tested, and the model tries to automatically detect the be st-behaved ones, in order to grant more resources to them. Second, the usage of pa rallel environments might speedup the process of automatic testing, so high qual ity solutions might be achieved in less time. This research focuses on the design of novel hyperheuristic s and defines a set of models to allow their usage in parallel environments. Differ ent hyperheuristics for controlling mono-objective and multi-objective multi-po int optimisation strategies have been defined. Moreover, a set of novel multiobjectivisa tion techniques has been proposed. In addition, with the aim of facilitating the usage of multiobjectivi- sation, the performance of models that combine the usage of m ultiobjectivisation and hyperheuristics has been studied. The proper performance of the proposed techniques has been v alidated with a set of well-known benchmark optimisation problems. In addi tion, several practical and complex optimisation problems have been addressed. Som e of the analysed problems arise in the communication field. In addition, a pac king problem proposed in a competition has been faced up. The proposals for such pro blems have not been limited to use the problem-independent schemes. Inste ad, new metaheuristics, operators and local search strategies have been defined. Suc h schemes have been integrated with the designed parallel hyperheuristics wit h the aim of accelerating the achievement of high quality solutions, and with the aim of fa cilitating their usage. In several complex optimisation problems, the current best -known solutions have been found with the methods defined in this dissertation.Los problemas de optimización son aquellos en los que hay que elegir cuál es la solución más adecuada entre un conjunto de alternativas. Actualmente existe una gran cantidad de algoritmos que permiten abordar este tipo de problemas. Entre ellos, las metaheurísticas son una de las técnicas más usadas. El uso de metaheurísticas ha posibilitado la resolución de una gran cantidad de problemas en diferentes campos. Esto se debe a que las metaheurísticas son técnicas generales, con lo que disponen de una gran cantidad de elementos o parámetros que pueden ser adaptados a la hora de afrontar diferentes problemas de optimización. Sin embargo, la elección de dichos parámetros no es sencilla, por lo que generalmente se requiere un gran esfuerzo computacional, y un gran esfuerzo por parte del usuario de estas técnicas. Existen diversas técnicas que atenúan este inconveniente. Por un lado, existen varios mecanismos que permiten seleccionar los valores de dichos parámetros de forma automática. Las técnicas más simples utilizan valores fijos durante toda la ejecución, mientras que las técnicas más avanzadas, como las hiperheurísticas, adaptan los valores usados a las necesidades de cada fase de optimización. Además, estas técnicas permiten usar varias metaheurísticas de forma simultánea. Por otro lado, el uso de técnicas paralelas permite acelerar el proceso de testeo automático, reduciendo el tiempo necesario para obtener soluciones de alta calidad. El objetivo principal de esta tesis ha sido diseñar nuevas hiperheurísticas e integrarlas en el modelo paralelo basado en islas. Estas técnicas se han usado para controlar los parámetros de varias metaheurísticas evolutivas. Se han definido diversas hiperheurísticas que han permitido abordar tanto problemas mono-objetivo como problemas multi-objetivo. Además, se han definido un conjunto de multiobjetivizaciones, que a su vez se han beneficiado de las hiperheurísticas propuestas. Las técnicas diseñadas se han validado con algunos de los problemas de test más ampliamente utilizados. Además, se han abordado un conjunto de problemas de optimización prácticos. Concretamente, se han tratado tres problemas que surgen en el ámbito de las telecomunicaciones, y un problema de empaquetado. En dichos problemas, además de usar las hiperheurísticas y multiobjetivizaciones, se han definido nuevos algoritmos, operadores, y estrategias de búsqueda local. En varios de los problemas, el uso combinado de todas estas técnicas ha posibilitado obtener las mejores soluciones encontradas hasta el momento

    Modelling auto-acceleration in DGEBA/diamine systems

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    Curing of epoxy resins with aliphatic diamines at low temperatures deviates from the 4EQ mechanism (catalytic and non-catalytic dual path) at relatively low conversions, far from vitrification. Although the Horie mechanism relies on a third order reaction it is possible a more realistic approach to epoxy curing kinetics if a detailed analysis of auto-acceleration is made. A single parameter dependent only on the nature of the amine is proposed.Authors gratefully acknowledge to CAM (Pricit) and to project Epoxsil (MAT2000-0391-P4-02) for financial support

    On the comparison of initialisation strategies in differential evolution for large scale optimisation

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    Differential Evolution (DE) has shown to be a promising global opimisation solver for continuous problems, even for those with a large dimensionality. Different previous works have studied the effects that a population initialisation strategy has on the performance of DE when solving large scale continuous problems, and several contradictions have appeared with respect to the benefits that a particular initialisation scheme might provide. Some works have claimed that by applying a particular approach to a given problem, the performance of DE is going to be better than using others. In other cases however , researchers have stated that the overall performance of DE is not going to be affected by the use of a particular initialisation method. In this work, we study a wide range of well-known initialisation techniques for DE. Taking into account the best and worst results, statistically significant differences among considered initialisation strategies appeared. Thus, with the aim of increasing the probability of appearance of high-quality results and/or reducing the probability of appearance of low-quality ones, a suitable initialisation strategy, which depends on the large scale problem being solved, should be selected

    Variability of Physical and Chemical Properties of TLUD Stove Derived Biochars

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    Biochar is a carbon-rich organic material, obtained by the thermochemical conversion of biomass in an oxygen-limited environment, used as a soil amendment to stimulate soil fertility and improve soil quality. There is a clear need in developing countries for access to low cost, low technology options for biochar production, for example, top-lit updraft (TLUD) stoves, which are popular and spread worldwide. However, TLUD biochars are inevitably very variable in their properties for a variety of reasons. We present laboratory triplicate tests carried out on TLUD biochars obtained from waste pinewood and a Guadua bamboo. Analyzed properties include specific surface area (A-BET), porosity, skeletal density, hydrophobicity, proximal and elemental composition, cation exchange capacity (CEC), relative liming capacity and pH. SEM images of the bamboo and wood biochars are compared. The biochars were mixed with composted human excreta at 5% and 10% biochar content, and available water content (AWC) was analyzed. Operating temperatures in the TLUD were recorded, showing different behaviors among the feedstocks during the process. Differences in operating temperatures during charring of the bamboo samples seem to have led to differences in A-BET, hydrophobicity and CEC, following unprecedented trends. For the mixtures of the biochars with compost, at 5% biochar no significant differences were observed for AWC. However, in the 10% biochar mixtures, bamboo biochar showed an unexpectedly high AWC. Overall, variations of chemical and physical properties between bamboo biochars were greater, while pinewood biochars showed similar properties, consistent with more homogeneous charring temperaturesThis research was funded by Vice-rector of Research and Extension of the Instituto Tecnológico de Costa Rica (TEC), trough the project VIE 1460065 and by the national foundation FITTACORI (Fundación para el Fomento y Promoción de la Investigación y Transferencia de Tecnología Agropecuaria)S

    Detection of anomalous samples based on automatic thresholds.

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    The high demand for better services in cellular networks is the motivation behind the evolution of said network. Currently, the Open Radio Access Network (O-RAN) paradigm was proposed to provide more intelligent management of the user radio access, improving the quality of services, by applying Artificial Intelligence (IA); and Machine Learning (ML) algorithms. Despite their high potential, ML is highly dependent on the integrity of applied data, especially in the training stage. To avoid any data alteration, in this work an algorithm for anomaly detection in network metrics is proposed. This approach is based on a state machine to determine the network behaviour and Otsu thresholding. The algorithm performance is evaluated on data obtained from a 5G microcell.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

    Efecto del contenido de Zr en aleaciones de alta conductividad base Cu sobre las propiedades térmicas

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    Una de las aplicaciones de aleaciones base cobre son aquellas en las que se requiere buenas propiedades mecánicas en conjunto con una elevada conductividad térmica. Una de ellas es el caso de las toberas y cámaras de combustión de motores para vehículos espaciales, donde es necesario extraer el calor generado durante la combustión sin perder estructuralidad. Las aleaciones base cobre de alta conductividad y buena resistencia mecánica han sido diseñada agregando pequeños porcentajes de elementos aleantes tales como Cr, Zr, Ag y Nb, los cuales mejoran las propiedades mecánicas a través de un endurecimiento por precipitación con el consecuente detrimento de su conductividad térmica. En particular el grupo de aleaciones de CuAgZr, resultan una buena alternativa para este tipo de aplicaciones, principalmente por su gran conductividad térmica, sobre todo cuando se trata de procesos de fabricación convencionales (fundición y forja). A fin de estudiar el efecto del Zr en estas aleaciones, considerando que es este el elemento de mayor influencia tanto mecánica como térmicamente se realizaron mediciones de conductividad térmica indirecta variando el contenido de circonio 0,1% - 0,6% en peso fijando el porcentaje de plata alrededor del 3%. Los ensayos fueron realizados en el rango de temperaturas de 25°C – 700°C siendo este un rango de interés para la aplicación en cuestión, pudiéndose observar la consecuente disminución de la conductividad térmica conforme se incrementa el porcentaje de circonio en todo el rango de trabajo.Facultad de Ingenierí

    On the Need to Further Refine Stock Quality Specifications to Improve Reforestation under Climatic Extremes

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    [EN] The achievement of goals in forest landscape restoration strongly relies on successful plantation establishment, which is challenging in drylands, especially under climate change. Improvement of field performance through stock quality has been used for decades. Here, we use machine learning (ML) techniques to identify key stock traits involved in successful survival and to refine previous specifications that were developed under more conventional stock quality assessments carried out at the lifting-shipping phases in the nursery. Two differentiated stocklots in each species were used, both fitting in the regional quality standard. ML was used to infer a set of attributes for planted seedlings that were subsequently related to survival at the short-term (two years) and mid-term (ten years) in six different species planted in a harsh site with shallow soil that suffered the driest year on record during this study. Whilst stocklot quality, as measured in the lifting-shipping stage, had very poor importance to the survival response, individual plant traits presented a moderate to high diagnostic ability for seedling survival (area under the receiver operating characteristic (ROC) curve between 0.59 and 0.99). Early growth traits catch most of the importance in these models (approximate to 40%), followed by individual morphology traits (approximate to 28%) and site variation (approximate to 2%), with overall means varying across species. Aleppo pine and Phoenician juniper stocklots presented survival rates of 66-78% after ten years, and these rates were below 27% for the remaining species that suffered during the historical drought. In Aleppo pine, the plant attributes related to early field performance (growth in the first growing season) were more important in the drought-mediated mid-term performance than stock quality at the nursery stage. Within the technical framework of this study, our results allow for both testing and refining the regional quality standard specifications for harsh conditions such as those found in our study.This study is part of research projects: "Comprehensive quality control of the reforestation works in the public forest of Cortes de Pallas, Valencia" signed between UPV-ReForeST and the state-owned company TRAGSA, and "Monitoring and evaluation of the reforestation in the forest V-143 Muela de Cortes, in the municipality of Cortes de Pallas (Valencia), 10 years after its execution" (contract number CNMY18/0301/26), signed between UPV-ReForeST and Valencia Regional Government (CMAAUV, Generalitat Valenciana).Campo García, ADD.; Segura-Orenga, G.; Molina, AJ.; González-Sanchis, M.; Reyna, S.; Hermoso, J.; Ceacero, CJ. (2022). On the Need to Further Refine Stock Quality Specifications to Improve Reforestation under Climatic Extremes. Forests. 13(2):1-20. https://doi.org/10.3390/f1302016812013

    Integración de las herramientas "Github education" en el aula

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    El sistema de control distribuido de versiones Git se ha convertido en el estándar de facto para manejar proyectos software. Uno de los motivos de la creciente popularidad de Git es el éxito de GitHub, una plataforma Web de desarrollo colaborativo. GitHub ofrece toda la funcionalidad de Git e integra diversas he- rramientas de control de acceso, colaboración, gestión de tareas y control de pro- yectos, todo ello en la nube. Educadores tanto del mundo académico relacionado con la Informática como de fuera de ella utilizan GitHub en sus cursos. En este trabajo se presenta cómo se han utilizado las herramientas Git, GitHub y GitHub Classroom para gestionar la parte práctica de varias asignaturas de los estudios del grado en Ingeniería Informática. Esta contribución se centra en motivar esta experiencia, explicar su implementación y discutir los resultados obtenidos.The distributed version control system Git has become the de facto standard for managing software projects. One of the reasons for the growing popularity of Git is the success of GitHub, a collaborative development Web platform. GitHub offers all the functionality of Git and integrates various tools for access control, collabo- ration, task management and project control, all of them in the cloud. Educators from both the academic world related to IT and from outside, are using GitHub in their courses. This paper presents how the Git, GitHub and GitHub Classroom tools have been used to manage the laboratories of several subjects of the degree studies in Computer Engineering. This contribution focuses on motivating this experience, explaining its implementation and discussing the results obtained

    Afectación gastroduodenal como presentación inusual de la enfermedad de Crohn

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    It is relatively uncommon for Crohn’s disease to implicate the gastric and duodenal regions and occasionally it can cause pyloric stenosis, in which medical therapy may be ineffective and surgery might be required. We report two exceptional cases with prepyloric stenosis secondary to Crohn’s disease, aiming to emphasize the clinical suspicion and to describe the diagnostic imaging procedure and surgical treatments.Es relativamente infrecuente que la enfermedad de Crohs afecte al estomago y duodeno y ocasionalmente puede producir estenosis pilórica, en estas situaciones el tratamiento médico suele ser ineficaz y se requiere tratamiento quirúrgico. Se exponen dos casos clínicos excepcionales de estenosis prepilórica asociada a la enfermedad de Crohn, dirigidos a enfatizar en la sospecha clínica y describir el diagnóstico y el tratamiento quirúrgico
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