Mejora de la efectividad de la clasificación en la plataforma WEKA en base al uso de métodos de remuestreo sobre la distribución de clases óptima

Los problemas de clasificación de bases de datos desbalanceadas constituyen un paradigma específico dentro del Machine Learning que ha sido ampliamente estudiado en los últimos años y que puede ser abordado desde distintos puntos de vista. Hay distintos tipos de aproximaciones a este problema: las más comúnmente encontradas en literatura son aquellas de tipo algorítmico, las de selección de atributos (features) y las de tratamiento de datos o remuestreo. La ventaja de las aproximaciones de tratamiento de datos es que son versátiles y pueden aplicarse a cualquier tipo de algoritmo y se basan en la aplicación de un remuestreo de las instancias disponibles para tratar de balancear la clase minoritaria, con una aproximación clásica de rebalanceo al 50%. Este trabajo plantea un doble objetivo: por un lado, extender análisis empíricos previos que muestran que la distribución óptima no tiene por qué ser la del 50% que plantearon las primeras hipótesis y que dependerá del tipo de problema o conjunto de datos a estudiar, del tipo de clasificador elegido, del tipo de algoritmo de remuestreo aplicado y de la métrica que se defina para la evaluación del clasificador, lo que se refiere típicamente como dependencia del contexto. Del análisis de resultados, se comprobará si alguna de las variables de contexto obtiene un mejor desempeño que otra sobre el universo de análisis considerado. Por otro lado, se pretende poner a disposición de la comunidad un módulo sobre la plataforma WEKA que permita, no sólo automatizar el procedimiento para replicar el estudio, sino poder aplicar esta implementación de manera general para encontrar una distribución óptima para un contexto determinado, es decir, para un problema de clasificación, un método de remuestreo, un algoritmo de clasificación y una métrica de evaluación concreta que pueda definir el usuario

Localización de usuarios con coordenadas polares.

Currently, the increase of location aware services and network management has driven the demand for user location estimation schemes, although it is not usually available to operators. Moreover, commercial networks have limited access to specific user related metrics. In general, solutions with Machine Learning (ML) have reached high precisions, but only in a trained scenario, and with difficulties in predicting unseen areas. The approach proposed here solves the above limitation by a reference coordinate conversion, to obtain relative polar positions which create scenario agnostic models, and whose performance is demonstrated using a dataset recollected from a commercial mobile network.Ministerio de Asuntos Económicos y Transformación Digital y la Unión Europea - NextGenerationEU, en el marco del Plan de Recuperación, Transformación y Resiliencia y el Mecanismo de Recuperación y Resiliencia bajo el proyecto MAORI. Además, también está parcialmente financiado por la Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech., a través de II Plan Propio de Investigación y Transferencia y por el proyecto “Desarrollo de casos de uso para el diseño, optimización y dimensionado de redes móviles – Líneas B1 y D1” (Ref. 8.06/5.59.5705-3 IDEA)

Influence of polyhedral oligomeric silsesquioxanes on thermal and mechanical properties of melt-mixed poly(methyl methacrylate)/polyhedral oligomeric silsesquioxanes composites

In this study, the influence of the functionalization of fully or incomplete condensed polyhedral oligomeric silsesquioxanes composites (POSS) nanoparticles on the properties of poly(methyl methacrylate) (PMMA)-based composites has been studied. POSS with different organic substituents (methacryl, methacrylateisooctyl and trisilanolphenyl) are taken into account and added to the PMMA matrix by direct melt blending at loadings between 0 and 5 wt%. Significant differences in compatibility were observed depending on the structure of nanoparticles. POSS aggregation occurred during blending producing micron-sized aggregates in the composites. The thermal decomposition temperature of the composites with good dispersion of POSS aggregates increased under oxidative conditions. There were no significant changes in other thermal and mechanical properties of the composites. The relationships among these effects and the morphological characteristics of the systems were analysed.Peer Reviewe

Structure-property evaluation of trisilanolphenyl POSS®/polysulfone composites as a guide to POSS melt blending

A series of polysulfone/phenyl trisilanol POSS nanocomposites were produced by melt blending by twin screw batch mixing. These materials were then injec- tion molded, and their thermal, mechanical, and morpho- logical properties were tested. The tensile properties of polysulfone were moderately compromised by the addition of phenyl TPOSS, because of the formation of large ( 1 l m) voided POSS aggregates. These domains however did cause the improvement of the impact resistance of the composites as described by the mechanism of crack pinning and bow- ing. Flexural properties remained essentially unchanged, which is attributed to the formation of an aggregate free- skin layer, which formed in the injection molded parts. Thermal behavior of the composites also remained largely unchanged due to the lack of POSS-polymer interactions on the molecular/chain segment scale. Initially, it was hypothesized that a high degree of POSS-polymer interac- tions would be present in these composited based on exami- nation of their chemical structures. This however, was not the case as phase separation was clearly present. This work highlights the need for a better understanding of the predic- tion of POSS-polymer interaction.Peer Reviewe

Properties of POSS blends with pCBT, PMMA, PC and POM thermoplastics

The influence of the functionalisation of fully or partially condensed POSS cages on the properties of engineering thermoplastic-based nanocomposites is studied. POSS with different organic substituents were selected in accordance with the structure and chemical composition of the host polymer and melt mixed with the corresponding matrix. In general, good dispersion at the nanoscale level was achieved upon the addition of some functionalised POSS, leading to a remarkable increase on the thermal decomposition temperature under nitrogen atmosphere. However, for the polymers having high decomposition temperatures, there were no significant changes on the thermal properties of the nanocomposites. On the other hand, the dispersion of the POSS, whatever its functionalisation was, led to the presence of micron-sized aggregates. The relationships among these effects and the morphological characteristics of the systems were analysed.Peer ReviewedPostprint (published version

Properties of POSS blends with pCBT, PMMA, PC and POM thermoplastics

The influence of the functionalisation of fully or partially condensed POSS cages on the properties of engineering thermoplastic-based nanocomposites is studied. POSS with different organic substituents were selected in accordance with the structure and chemical composition of the host polymer and melt mixed with the corresponding matrix. In general, good dispersion at the nanoscale level was achieved upon the addition of some functionalised POSS, leading to a remarkable increase on the thermal decomposition temperature under nitrogen atmosphere. However, for the polymers having high decomposition temperatures, there were no significant changes on the thermal properties of the nanocomposites. On the other hand, the dispersion of the POSS, whatever its functionalisation was, led to the presence of micron-sized aggregates. The relationships among these effects and the morphological characteristics of the systems were analysed.Peer Reviewe

The morphology and properties of melt-mixed polyoxymethylene/ monosilanolisobutyl-POSS composites

In this study, the morphology and thermo-mechanical behavior of composites formed by a polyoxymethylene (POM) matrix and monosilanolisobutyl polyhedral oligomeric silsesquioxane (msib-POSS) filler have been studied. The msib- POSS molecules were added to the POM by direct melt blending at loadings between 0 and 10 wt.%. Hydrogen bonding interactions were detected between POM and msib-POSS Si–OH groups, increasing their mutual compatibility and leading to nanometer-size dispersion of some msib-POSS molecules. These interactions do not prevent POSS aggregation during blending, but lead to micron-scale msib-POSS domains. The thermal decomposition temperature of the composites remained practically constant under inert and oxidative conditions. The low temperature thermal transition (g) and glass transition temperature (Tg) of POM were found to move to higher temperatures only when 2.5 wt.% of msib-POSS was added, indicating that POSS is physically linked to the POM chains, restricting their motion under those conditions. Low content (2.5 wt.%) of msib-POSS results in antiplastization, whereas higher levels of POSS lead to a decrease in the storage modulus of the polymer. The relationships among these effects and the morphological characteristics of the systems will be discussed hereinPeer ReviewedPostprint (published version

The morphology and properties of melt-mixed polyoxymethylene/ monosilanolisobutyl-POSS composites

In this study, the morphology and thermo-mechanical behavior of composites formed by a polyoxymethylene (POM) matrix and monosilanolisobutyl polyhedral oligomeric silsesquioxane (msib-POSS) filler have been studied. The msib- POSS molecules were added to the POM by direct melt blending at loadings between 0 and 10 wt.%. Hydrogen bonding interactions were detected between POM and msib-POSS Si–OH groups, increasing their mutual compatibility and leading to nanometer-size dispersion of some msib-POSS molecules. These interactions do not prevent POSS aggregation during blending, but lead to micron-scale msib-POSS domains. The thermal decomposition temperature of the composites remained practically constant under inert and oxidative conditions. The low temperature thermal transition (g) and glass transition temperature (Tg) of POM were found to move to higher temperatures only when 2.5 wt.% of msib-POSS was added, indicating that POSS is physically linked to the POM chains, restricting their motion under those conditions. Low content (2.5 wt.%) of msib-POSS results in antiplastization, whereas higher levels of POSS lead to a decrease in the storage modulus of the polymer. The relationships among these effects and the morphological characteristics of the systems will be discussed hereinPeer Reviewe