A logic-based approach to deal with implicational systems and direct bases

El tratamiento de la información y el conocimiento es uno de los muchos campos en los que confluyen los métodos matemáticos y computacionales. Una de las áreas donde encontramos de forma clara esta concurrencia es en el Análisis de Conceptos Formales, donde los métodos de almacenamiento, descubrimiento, análisis y manipulación del conocimiento descansan sobre las sólidas bases del Álgebra y de la Lógica. En el Análisis de Conceptos Formales la información se representa en tablas binarias en las que se relacionan objetos con sus atributos. Dichas tablas, denominadas contextos formales, son el repositorio de datos del que se extrae el conocimiento mediante la utilización de técnicas algebraicas. Este conocimiento se puede representar de diversas formas, entre ellas se encuentran los conjuntos de implicaciones. Una de las principales ventajas de usar sistemas de implicaciones para representar el conocimiento es que admiten un tratamiento sintáctico por medio de la lógica, segundo pilar matemático en el que se sustenta la tesis. La mejor alternativa de cara al razonamiento automático viene de mano de la Lógica de Simplificación. El conjunto de axiomas y reglas de inferencias de esta lógica lleva directamente a un conjunto de equivalencias que permiten eliminar redundancias en los sistemas de implicaciones. La extracción de sistemas de implicaciones, y su posterior tratamiento y manipulación, constituyen un tema de actualidad en la comunidad del Análisis de Conceptos Formales. Los conjuntos de implicaciones extraídos pueden contener gran cantidad de información redundante, por lo que el estudio de propiedades que permitan caracterizar conjuntos equivalentes de implicaciones con menor redundancia o sin ella, se erige como uno de los retos más importantes. Sin embargo, como sucede en otras áreas, en algunas ocasiones puede ser interesante almacenar cierta clase de información redundante en función del uso posterior que se le pretenda dar. Sobresale pues, entre los temas de interés del área, el problema de la búsqueda de representaciones canónicas de sistemas de implicaciones que, satisfaciendo ciertas propiedades, permitan compilar todo el conocimiento extraído del contexto formal. Estas representaciones canónicas para los sistemas de implicaciones suelen recibir el nombre de `bases'. En esta tesis ponemos nuestra atención en un grupo de bases conocidas como `bases directas', que son aquellas que permiten calcular el cierre de cualquier conjunto en un único recorrido del sistema de implicaciones. Los objetivos generales de la tesis son dos: - El estudio de las bases directas en Análisis de Conceptos Formales clásico con la finalidad de obtener algoritmos eficientes para calcular dichas bases. Para ello analizamos las definiciones que aparecen en la bibliografía (base directa-optimal y D-base) y proponemos una alternativa (base dicótoma directa), así como métodos para su cálculo. - Establecer las bases para la extensión de estos resultados al Análisis de Conceptos Triádicos, en particular, introducir una lógica que permita el razonamiento automático sobre implicaciones en esta extensión. Se presentan dos lógicas: CAIL y CAISL. La primera permite caracterizar la semántica de las implicaciones y la segunda el razonamiento automático

A geometrical model for the Monte Carlo simulation of the TrueBeam linac

Monte Carlo (MC) simulation of linacs depends on the accurate geometrical description of the head. The geometry of the Varian TrueBeam (TB) linac is not available to researchers. Instead, the company distributes phase-space files (PSFs) of the flattening-filter-free (FFF) beams tallied upstream the jaws. Yet, MC simulations based on third party tallied PSFs are subject to limitations. We present an experimentally-based geometry developed for the simulation of the FFF beams of the TB linac. The upper part of the TB linac was modeled modifying the Clinac 2100 geometry. The most important modification is the replacement of the standard flattening filters by ad hoc thin filters which were modeled by comparing dose measurements and simulations. The experimental dose profiles for the 6MV and 10MV FFF beams were obtained from the Varian Golden Data Set and from in-house measurements for radiation fields ranging from 3X3 to 40X40 cm2. Indicators of agreement between the experimental data and the simulation results obtained with the proposed geometrical model were the dose differences, the root-mean-square error and the gamma index. The same comparisons were done for dose profiles obtained from MC simulations using the second generation of PSFs distributed by Varian for the TB linac. Results of comparisons show a good agreement of the dose for the ansatz geometry similar to that obtained for the simulations with the TB PSFs for all fields considered, except for the 40X40 cm2 field where the ansatz geometry was able to reproduce the measured dose more accurately. Our approach makes possible to: (i) adapt the initial beam parameters to match measured dose profiles; (ii) reduce the statistical uncertainty to arbitrarily low values; and (iii) assess systematic uncertainties by employing different MC codes

Removing redundancy for attribute implications in data with grades

Reasoning with if-then rules –in particular, with those taking from of implications between conjunctions of attributes– is crucial in many disciplines ranging from theoretical computer science to applications. One of the most important problems regarding the rules is to remove redundancies in order to obtain equivalent implicational sets with lower size.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Open innovation : organizational challenges of a new paradigm of innovation management

The goal of this paper is to analyze the main problems that emerge from the open innovation model. Adopting as analytical framework an organizational perspective we divide the main challenges that arise from the management of open innovation in two main categories: coordination problems as a result of open the innovation system to ideas and knowledge that may lie outside the boundaries of the firm and, incentive problems related with the creation and value capture of ideas an knowledge by the innovator. We describe and analyze several problems related with coordination and incentives.peer-reviewe

Enhancing Coexistence in the Unlicensed Band with Massive MIMO

We consider cellular base stations (BSs) equipped with a large number of antennas and operating in the unlicensed band. We denote such system as massive MIMO unlicensed (mMIMO-U). We design the key procedures required to guarantee coexistence between a cellular BS and nearby Wi-Fi devices. These include: neighboring Wi-Fi channel covariance estimation, allocation of spatial degrees of freedom for interference suppression, and enhanced channel sensing and data transmission phases. We evaluate the performance of the so-designed mMIMO-U, showing that it allows simultaneous cellular and Wi-Fi transmissions by keeping their mutual interference below the regulatory threshold. The same is not true for conventional listen-before-talk (LBT) operations. As a result, mMIMO-U boosts the aggregate cellular-plus-Wi-Fi data rate in the unlicensed band with respect to conventional LBT, exhibiting increasing gains as the number of BS antennas grows.Comment: To appear in Proc. IEEE ICC 201

Indoor Massive MIMO Deployments for Uniformly High Wireless Capacity

Providing consistently high wireless capacity is becoming increasingly important to support the applications required by future digital enterprises. In this paper, we propose Eigen-direction-aware ZF (EDA-ZF) with partial coordination among base stations (BSs) and distributed interference suppression as a practical approach to achieve this objective. We compare our solution with Zero Forcing (ZF), entailing neither BS coordination or inter-cell interference mitigation, and Network MIMO (NeMIMO), where full BS coordination enables centralized inter-cell interference management. We also evaluate the performance of said schemes for three sub-6 GHz deployments with varying BS densities -- sparse, intermediate, and dense -- all with fixed total number of antennas and radiated power. Extensive simulations show that: (i) indoor massive MIMO implementing the proposed EDA-ZF provides uniformly good rates for all users; (ii) indoor network densification is detrimental unless full coordination is implemented; (iii) deploying NeMIMO pays off under strong outdoor interference, especially for cell-edge users