«La lámpara en la tierra»: un símbolo unificador de "CantoGeneral".

Sin resume

Systems with Massive Number of Antennas: Distributed Approaches

As 5G is entering maturity, the research interest has shifted towards 6G, and specially the new use cases that the future telecommunication infrastructure needs to support. These new use cases encompass much higher requirements, specifically: higher communication data-rates, larger number of users, higher accuracy in localization, possibility to wirelessly charge devices, among others.The radio access network (RAN) has already gone through an evolution on the path towards 5G. One of the main changes was a large increment of the number of antennas in the base-station. Some of them may even reach 100 elements, in what is commonly referred as Massive MIMO. New proposals for 6G RAN point in the direction of continuing this path of increasing the number of antennas, and locate them throughout a certain area of service. Different technologies have been proposed in this direction, such as: cell-free Massive MIMO, distributed MIMO, and large intelligent surface (LIS). In this thesis we focus on LIS, whose conducted theoretical studies promise the fulfillment of the aforementioned requirements.While the theoretical capabilities of LIS have been conveniently analyzed, little has been done in terms of implementing this type of systems. When the number of antennas grow to hundreds or thousands, there are numerous challenges that need to be solved for a successful implementation. The most critical challenges are the interconnection data-rate and the computational complexity.In the present thesis we introduce the implementation challenges, and show that centralized processing architectures are no longer adequate for this type of systems. We also present different distributed processing architectures and show the benefits of this type of schemes. This work aims at giving a system-design guideline that helps the system designer to make the right decisions when designing these type of systems. For that, we provide algorithms, performance analysis and comparisons, including first order evaluation of the interconnection data-rate, processing latency, memory and energy consumption. These numbers are based on models and available data in the literature. Exact values depend on the selected technology, and will be accurately determined after building and testing these type of systems.The thesis concentrates mostly on the topic of communication, with additional exploration of other areas, such as localization. In case of localization, we benefit from the high spatial resolution of a very-large array that provides very rich channel state information (CSI). A CSI-based fingerprinting via neural network technique is selected for this case with promising results. As the communication and localization services are based on the acquisition of CSI, we foresee a common system architecture capable of supporting both cases. Further work in this direction is recommended, with the possibility of including other applications such as sensing.The obtained results indicate that the implementation of these very-large array systems is feasible, but the challenges are numerous. The proposed solutions provide encouraging results that need to be verified with hardware implementations and real measurements

The internet: strategy and boundaries of the firm

Many advantages have been ascribed to the Internet. Although it lacks the necessary elements to be regarded as a strategic resource, the Internet seems to be a useful tool to provide support for business strategies.In this work we discuss how the Internet can be used to support the development of capabilities and define firm boundaries. Using a sample of Spanish firms, empirically analysed, we find positive relationships between the use of the Internet and product differentiation, as well as the introduction of organizational changes. In addition, we present evidence that the Internet reduces both internal coordination costs and transaction costs as a result of the positive relationships found between the use of the Internet, the degree of vertical integration and the establishment of technological agreements with suppliers and customers

Guadalupe Fernández Ariza: Alejo Carpentier. Ante el espejo del Barroco.

Sin resume

Seasonal dynamic factor analysis and bootstrap inference : application to electricity market forecasting

Year-ahead forecasting of electricity prices is an important issue in the current context of electricity markets. Nevertheless, only one-day-ahead forecasting is commonly tackled up in previous published works. Moreover, methodology developed for the short-term does not work properly for long-term forecasting. In this paper we provide a seasonal extension of the Non-Stationary Dynamic Factor Analysis, to deal with the interesting problem (both from the economic and engineering point of view) of long term forecasting of electricity prices. Seasonal Dynamic Factor Analysis (SeaDFA) allows to deal with dimensionality reduction in vectors of time series, in such a way that extracts common and specific components. Furthermore, common factors are able to capture not only regular dynamics (stationary or not) but also seasonal one, by means of common factors following a multiplicative seasonal VARIMA(p,d,q)×(P,D,Q)s model. Besides, a bootstrap procedure is proposed to be able to make inference on all the parameters involved in the model. A bootstrap scheme developed for forecasting includes uncertainty due to parameter estimation, allowing to enhance the coverage of forecast confidence intervals. Concerning the innovative and challenging application provided, bootstrap procedure developed allows to calculate not only point forecasts but also forecasting intervals for electricity prices

Optimization of connections for spatial modular structures

Congreso celebrado en la Escuela de Arquitectura de la Universidad de Sevilla desde el 24 hasta el 26 de junio de 2015.Every year Seville’s city Council orders the construction of a giant gateway for the celebration of the April Fair. These constructions, whose dimensions are approximately 50 meters length, 40 meters height and variable depth of 4 to 5 meters, are spatial modular structures composed of steel tubular elements connected by clamps and covered by wood boards. The consideration or not of the eccentricities introduced by the connection element as well as the determination of the stiffness to consider is one of the major problems when developing the analysis model. The construction company aims to achieve their optimization in order to reduce the final cost. This paper investigates about how different ways of modeling these connections affects the optimization of the final model. The extent to which the modification of the position of the eccentricities influences the optimization is also discussed, as this aspect is difficult to control on site

Does R&D offshoring lead to SME growth? Different governance modes and the mediating role of innovation

In this article, we address the role of R&D offshoring strategies in the sales growth of small - and medium-sized enterprises (SMEs). We propose that different governance modes of R&D offshoring - insourcing versus outsourcing - may lead to growth, but that they differ in their effects. In turn, we argue that innovation mediates the relation between international R&D sourcing strategies and sales growth. Based on a large database of SME manufacturing enterprises in Spain, we find that offshore outsourcing positively affects sales growth both directly and indirectly, while offshore insourcing only affects sales growth indirectly via innovation results. The analysis reveals different contributions of each governance mode to sales growth and the mediating role of innovation in the relation between R&D offshoring and firm growth

Power-aggregation of pseudometrics and the McShane-Whitney extension theorem for Lipschitz p-convace maps

[EN] Given a countable set of families {Dk:k¿N} of pseudometrics over the same set D, we study the power-aggregations of this class, that are defined as convex combinations of integral averages of powers of the elements of ¿kDk. We prove that a Lipschitz function f is dominated by such a power-aggregation if and only if a certain property of super-additivity involving the powers of the elements of ¿kDk is fulfilled by f. In particular, we show that a pseudo-metric is equivalent to a power-aggregation of other pseudometrics if this kind of domination holds. When the super-additivity property involves a p-power domination, we say that the elements of Dk are p-concave. As an application of our results, we prove under this requirement a new extension result of McShane-Whitney type for Lipschitz p-concave real valued maps.Both authors gratefully acknowledge the support of the Ministerio de Ciencia, Innovación y Universidades, Agencia Estatal de Investigaciones and FEDER under each grants MTM2015-64373-P (MINECO/FEDER, UE) and MTM2016-77054-C2-1-P.Rodríguez López, J.; Sánchez Pérez, EA. (2020). Power-aggregation of pseudometrics and the McShane-Whitney extension theorem for Lipschitz p-convace maps. Acta Applicandae Mathematicae. 170:611-629. https://doi.org/10.1007/s10440-020-00349-3S611629170Dahia, E., Achour, D., Rueda, P., Sánchez Pérez, E.A., Yahi, R.: Factorization of Lipschitz operators on Banach function spaces. Math. Inequal. Appl. 21(4), 1091–1104 (2018)Beliakov, G.: Optimization and aggregation functions. In: Lodwick, W.A., Kacprzyk, J. (eds.) Fuzzy Optimization: Recent Advances and Applications, pp. 77–108. Springer, Berlin (2010)Beliakov, G., Bustince Sola, H., Calvo Sánchez, T.: A Practical Guide to Averaging Functions, vol. 329. Springer, Heidelberg (2016)Botelho, G., Pellegrino, D., Rueda, P.: A unified Pietsch domination theorem. J. Math. Anal. Appl. 365(1), 269–276 (2010)Botelho, G., Pellegrino, D., Rueda, P.: On Pietsch measures for summing operators and dominated polynomials. Linear Multilinear Algebra 62(7), 860–874 (2014)Chávez-Domínguez, J.A.: Duality for Lipschitz p-summing operators. J. Funct. Anal. 261, 387–407 (2011)Chávez-Domínguez, J.A.: Lipschitz $p$-convex and $q$-concave maps (2014). arXiv:1406.6357Defant, A.: Variants of the Maurey-Rosenthal theorem for quasi Köthe function spaces. Positivity 5, 153–175 (2001)Defant, A., Floret, K.: Tensor Norms and Operator Ideals. Elsevier, Amsterdam (1992)Diestel, J., Jarchow, H., Tonge, A.: Absolutely Summing Operators. Cambridge University Press, Cambridge (1995)Dugundji, J.: Topology. Allyn and Bacon, Needham Heights (1966)Farmer, J., Johnson, W.: Lipschitz $p$-summing operators. Proc. Am. Math. Soc. 137(9), 2989–2995 (2009)Juutinen, P.: Absolutely minimizing Lipschitz extensions on a metric space. Ann. Acad. Sci. Fenn., Math. 27, 57–67 (2002)Marler, T.R., Arora, J.S.: The weighted sum method for multi-objective optimization: new insights. Struct. Multidiscip. Optim. 41(6), 853–862 (2010)Mustata, C.: Extensions of semi-Lipschitz functions on quasi-metric spaces. Rev. Anal. Numér. Théor. Approx. 30(1), 61–67 (2001)Mustata, C.: On the extremal semi-Lipschitz functions. Rev. Anal. Numér. Théor. Approx. 31(1), 103–108 (2002)Pellegrino, D., Santos, J.: Absolutely summing multilinear operators: a panorama. Quaest. Math. 34(4), 447–478 (2011)Romaguera, S., Sanchis, M.: Semi-Lipschitz functions and best approximation in quasi-metric spaces. J. Approx. Theory 103, 292–301 (2000)Willard, S.: General Topology. Addison-Wesley, Reading (1970)Yahi, R., Achour, D., Rueda, P.: Absolutely summing Lipschitz conjugates. Mediterr. J. Math. 13(4), 1949–1961 (2016

Actividad física extraescolar y su relación con el rendimiento académico en alumnos de Educación Primaria

Hoy en día, la actividad físico-deportiva es uno de los fenómenos que mayor interés despierta en nuestra sociedad. Cada vez más son los niños que usan parte de su tiempo libre en practicar deporte, lo que conlleva un aumento de la demanda de actividades físicas extraescolares. El rendimiento académico y la actividad física siempre han estado en relación. Por ello, con este estudio se pretende conseguir dos objetivos principales. El primero, describir características sociales, personales y físico-deportivas en una población de alumnos de Educación Primaria de Granada. El segundo, analizar la relación entre el rendimiento escolar de los estudiantes en función de la actividad deportiva extraescolar realizada. Para esta investigación, se contó con la colaboración de 257 alumnos de entre 10-12 años. El instrumento utilizado para la recogida de datos ha sido un cuestionario de elaboración propia con preguntas relacionadas con la actividad física, rendimiento académico… Finalmente, para el análisis de datos, se utilizó el programa estadístico software SPSS 20.0. Los resultados obtenidos muestran que se produce una mejora del rendimiento académico si se combina con la realización moderada de actividad física. Por el contrario, se producen efectos negativos cuando la práctica deportiva es excesiva.Nowadays, Physical activity is one of the most interesting phenomenon in our society. Increasingly are children who use part of their free time in sports and this causes an increase in demand of extracurricular physical activities. Academic achievement and physical activity have always been related. For this reason, this study seeks to achieve two objectives. First, to describe social, personal and physical sporting characteristics in a population of Primary students of Granada. Second, to analyze the relationship between students’ academic performance based on extracurricular sports activities performed. In order to do this research, we had the collaboration of 257 students aged 10 to 12 years. It has used a handmade questionnaire with questions on physical activity and school performance. Finally it has used a statistical program called SPSS 20.0 in order to analyze data. The results showed that improved academic performance occurs with moderate sport. However, negative effects occurs with excessive physical activity.Universidad de Granada. Facultad de Ciencias de la Educación. Grado en Educación Primari

Reinforcement and Curriculum Learning for Off-Road Navigation of an UGV with a 3D LiDAR

This paper presents the use of deep Reinforcement Learning (RL) for autonomous navigation of an Unmanned Ground Vehicle (UGV) with an onboard three-dimensional (3D) Light Detection and Ranging (LiDAR) sensor in off-road environments. For training, both the robotic simulator Gazebo and the Curriculum Learning paradigm are applied. Furthermore, an Actor–Critic Neural Network (NN) scheme is chosen with a suitable state and a custom reward function. To employ the 3D LiDAR data as part of the input state of the NNs, a virtual two-dimensional (2D) traversability scanner is developed. The resulting Actor NN has been successfully tested in both real and simulated experiments and favorably compared with a previous reactive navigation approach on the same UGV.Partial funding for open access charge: Universidad de Málag