Integrating multiple sources to answer questions in Algebraic Topology

We present in this paper an evolution of a tool from a user interface for a concrete Computer Algebra system for Algebraic Topology (the Kenzo system), to a front-end allowing the interoperability among different sources for computation and deduction. The architecture allows the system not only to interface several systems, but also to make them cooperate in shared calculations.Comment: To appear in The 9th International Conference on Mathematical Knowledge Management: MKM 201

España 92: arquitectura y ciudad. 25 años después. José Ramón Alonso Pereira (Comp.)

Book reviewReseña de libr

SWIPT techniques for multiuser MIMO broadcast systems

In this paper, we present an approach to solve the nonconvex optimization problem that arises when designing the transmit covariance matrices in multiuser multiple-input multiple-output (MIMO) broadcast networks implementing simultaneous wireless information and power transfer (SWIPT). The MIMO SWIPT design is formulated as a nonconvex optimization problem in which system sum rate is optimized considering per-user harvesting constraints. Two different approaches are proposed. The first approach is based on a classical gradient-based method for constrained optimization. The second approach is based on difference of convex (DC) programming. The idea behind this approach is to obtain a convex function that approximates the nonconvex objective and, then, solve a series of convex subproblems that, eventually, will provide a (locally) optimum solution of the general nonconvex problem. The solution obtained from the proposed approach is compared to the classical block-diagonalization (BD) strategy, typically used to solve the nonconvex multiuser MIMO network by forcing no inter-user interference. Simulation results show that the proposed approach improves both the system sum rate and the power harvested by users simultaneously. In terms of computational time, the proposed DC programming outperforms the classical gradient methods.Peer ReviewedPostprint (author's final draft

Joint optimization of power and data transfer in multiuser MIMO systems

We present an approach to solve the nonconvex optimization problem that arises when designing the transmit covariance matrices in multiuser multiple-input multiple-output (MIMO) broadcast networks implementing simultaneous wireless information and power transfer (SWIPT). The MIMO SWIPT problem is formulated as a general multiobjective optimization problem, in which data rates and harvested powers are optimized simultaneously. Two different approaches are applied to reformulate the (nonconvex) multiobjective problem. In the first approach, the transmitter can control the specific amount of power to be harvested by power transfer whereas in the second approach the transmitter can only control the proportion of power to be harvested among the different harvesting users. We solve the resulting formulations using the majorization-minimization (MM) approach. The solution obtained from the MM approach is compared to the classical block-diagonalization (BD) strategy, typically used to solve the nonconvex multiuser MIMO network by forcing no interference among users. Simulation results show that the proposed approach improves over the BD approach both the system sum rate and the power harvested by users. Additionally, the computational times needed for convergence of the proposed methods are much lower than the ones required for classical gradient-based approaches.Peer ReviewedPostprint (author's final draft

Stochastic resource allocation with a backhaul constraint for the uplink

We propose a novel stochastic radio resource alloca- tion strategy for the uplink that achieves long-term fairness in terms of similar bitrates considering backhaul and air-interface capacity limitations. We focus on a single cell scenario based on WCDMA technology. We propose to use a maximin criteria to introduce fairness among the different users’ throughputs. An stochastic approximation is implemented to obtain an online algorithm where the Lagrange multipliers are estimated at each scheduling period. Our results show that the proposed scheme achieves higher fairness among the users and, in some cases, a higher sum-rate compared with the well-known proportional fair scheduler.Postprint (author's final draft

User grouping and resource allocation in multiuser MIMO systems under SWIPT

This paper considers a broadcast multiple-input multiple-output (MIMO) network with multiple users and simultaneous wireless information and power transfer (SWIPT). In this scenario, it is assumed that some users are able to harvest power from radio frequency (RF) signals to recharge batteries through wireless power transfer from the transmitter, while others are served simultaneously with data transmission. The criterion driving the optimization and design of the system is based on the weighted sum rate for the users being served with data. At the same time, constraints stating minimum per-user harvested powers are included in the optimization problem. This paper derives the structure of the optimal transmit covariance matrices in the case where both types of users are present simultaneously in the network, particularizing the results to the cases where either only harvesting nodes or only information users are to be served. The trade-off between the achieved weighted sum rate and the powers harvested by the user terminals is analyzed and evaluated using the rate-power (R-P) region. Finally, we propose a two-stage user grouping mechanism that decides which users should be scheduled to receive information and which users should be configured to harvest energy from the RF signals in each particular scheduling period, this being one of the main contributions of this paper.Peer ReviewedPostprint (published version

Itinerario didáctico por la sierra de Albarracín

El espacio geográfico es un ente activo que se construye a partir de las interacciones entre los elementos naturales y antrópicos que lo constituyen. En la comarca de Albarracín, los elementos de su estructura territorial originan un modelo muy interesante. El objetivo básico de este trabajo es mostrar e interpretar las claves territoriales esenciales de ese modelo con una finalidad didáctica, porque pensamos que se trata de un ámbito muy adecuado para la realización de un itinerario didáctico con estudiantes de Geografía, que recorra los diferentes ambientes paisajísticos comarcales. Los componentes y procesos territoriales se identifican con claridad y otro tanto cabe decir de sus interrelaciones. En clave fenomenológica, nos atrevemos a decir que en ese espacio es posible una mirada integral del mismo, abarcadora, a un tiempo, de las apariencias y esencias ligadas a la variedad y fuerte identidad de su patrimonio territorial, sobre el que ha tenido una enorme influencia el particular modelo histórico de gobernanza que se ha desarrollado. Partimos de una reflexión previa sobre el interés y efectividad didáctica de los trabajos de campo en el marco de la metodología ECTS. A continuación, planificamos la salida propiamente dicha, con los objetivos de que los estudiantes sean capaces de: aplicar, mediante observación directa, los conceptos geográficos asimilados en el aula; utilizar de forma práctica las habilidades y destrezas adquiridas mediante el empleo de medios de observación indirecta; analizar las características y magnitudes de los componentes naturales y antrópicos de ese sistema territorial; identificar e interpretar el impacto de los procesos territoriales; comprender las relaciones causales y/o de implicación entre los componentes, teniendo en cuenta las interrelaciones entre ellos y los paisajes resultantes; determinar qué componentes tienen mayor valor explicativo para entender el modelo territorial; interpretar la variedad de paisajes naturales y humanos presentes; y, finalmente, evaluar cualitativamente el capital territorial disponible y su distribución y potencial para el desarrollo socioeconómico. Por último, aportamos algunas consideraciones sobre las características naturales y socioeconómicas y la identidad histórico-cultural del territorio comarcal.The geographic space is an active entity that is constructed through interactions between natural and human elements that constitute it. In the region of Albarracin, the territorial structure elements originate a very interesting model. The basic objective of this paper is to show and interpret the territorial key of this model with a didactic purpose, because we think that it is a very suitable environment for the settlement of a didactic project with students of geography that tours the different local landscape environments. Territorial components and processes are clearly identified and the same goes for their interrelationships. In phenomenological key, we can say that an integral view thereof is possible in this space, containing at a time appearances and essences linked to the variety and strong identity of its territorial heritage on which the particular historical model of governance that has been developed has had an enormous influence. We start from a prior discussion of the educational effectiveness and interest of the field work within the framework of the ECTS methodology. Then, we plan the field trip itself, so that the students are able: to apply, by direct observation, the assimilated geographic concepts in the classroom; to use the skills and the abilities acquired through the use of indirect means of observation; to analyze the characteristics and magnitudes of natural and anthropogenic components of the territorial system; to identify and interpret the impact of territorial processes to understand the causal and/or implication relations between the components taking into account the interrelationships between them and the resultant landscape; to determine which components are a more explicatory value for understanding the territorial model; to interpret the actual variety of natural and human landscapes; and, finally, they evaluate qualitatively the territorial capital available and their distribution and potential for the socioeconomic development. Finally, we provide some observations about the natural and socioeconomics, cultural and historical haracteristics of the territory

Itinerario didáctico por la sierra de Albarracín

El espacio geográfico es un ente activo que se construye a partir de las interacciones entre los elementos naturales y antrópicos que lo constituyen. En la comarca de Albarracín, los elementos de su estructura territorial originan un modelo muy interesante. El objetivo básico de este trabajo es mostrar e interpretar las claves territoriales esenciales de ese modelo con una finalidad didáctica, porque pensamos que se trata de un ámbito muy adecuado para la realización de un itinerario didáctico con estudiantes de Geografía, que recorra los diferentes ambientes paisajísticos comarcales. Los componentes y procesos territoriales se identifican con claridad y otro tanto cabe decir de sus interrelaciones. En clave fenomenológica, nos atrevemos a decir que en ese espacio es posible una mirada integral del mismo, abarcadora, a un tiempo, de las apariencias y esencias ligadas a la variedad y fuerte identidad de su patrimonio territorial, sobre el que ha tenido una enorme influencia el particular modelo histórico de gobernanza que se ha desarrollado. Partimos de una reflexión previa sobre el interés y efectividad didáctica de los trabajos de campo en el marco de la metodología ECTS. A continuación, planificamos la salida propiamente dicha, con los objetivos de que los estudiantes sean capaces de: aplicar, mediante observación directa, los conceptos geográficos asimilados en el aula; utilizar de forma práctica las habilidades y destrezas adquiridas mediante el empleo de medios de observación indirecta; analizar las características y magnitudes de los componentes naturales y antrópicos de ese sistema territorial; identificar e interpretar el impacto de los procesos territoriales; comprender las relaciones causales y/o de implicación entre los componentes, teniendo en cuenta las interrelaciones entre ellos y los paisajes resultantes; determinar qué componentes tienen mayor valor explicativo para entender el modelo territorial; interpretar la variedad de paisajes naturales y humanos presentes; y, finalmente, evaluar cualitativamente el capital territorial disponible y su distribución y potencial para el desarrollo socioeconómico. Por último, aportamos algunas consideraciones sobre las características naturales y socioeconómicas y la identidad histórico-cultural del territorio comarcal.The geographic space is an active entity that is constructed through interactions between natural and human elements that constitute it. In the region of Albarracin, the territorial structure elements originate a very interesting model. The basic objective of this paper is to show and interpret the territorial key of this model with a didactic purpose, because we think that it is a very suitable environment for the settlement of a didactic project with students of geography that tours the different local landscape environments. Territorial components and processes are clearly identified and the same goes for their interrelationships. In phenomenological key, we can say that an integral view thereof is possible in this space, containing at a time appearances and essences linked to the variety and strong identity of its territorial heritage on which the particular historical model of governance that has been developed has had an enormous influence. We start from a prior discussion of the educational effectiveness and interest of the field work within the framework of the ECTS methodology. Then, we plan the field trip itself, so that the students are able: to apply, by direct observation, the assimilated geographic concepts in the classroom; to use the skills and the abilities acquired through the use of indirect means of observation; to analyze the characteristics and magnitudes of natural and anthropogenic components of the territorial system; to identify and interpret the impact of territorial processes to understand the causal and/or implication relations between the components taking into account the interrelationships between them and the resultant landscape; to determine which components are a more explicatory value for understanding the territorial model; to interpret the actual variety of natural and human landscapes; and, finally, they evaluate qualitatively the territorial capital available and their distribution and potential for the socioeconomic development. Finally, we provide some observations about the natural and socioeconomics, cultural and historical haracteristics of the territory

Desarrollo local y patrimonio cultural. El parque cultural de Albarracín

The cultural patrimony derives from the collective behavoir of a people in a place and a time and forms a part consubstantially of the territorial dimension. It constitutes an example of endogenous resource to which an high potential place of development is awarded in the local scale, in a double dimension, economic, as agent and mercantile by means of its tourist utilization, and social, aselement of identity. In Aragon, the Law 12/1997 of Cultural Parks contributes a own normative frame for the management-protection of the cultural patrimony from the generic purpose of the global sustainable arrangement of rural areas with patrimonial and landscape-environmental values which singularity constitutes an estructurante element of the territory. There proposes a model of economic and social alternative development productivist and related to the emergency of a postmodern approach of flexible multifunctionality. The development of the law has given place to the delimiting of five parks, among them that of Albarracín.El patrimonio cultural deriva del comportamiento colectivo de un pueblo en un lugar y un tiempo y forma parte consustancial de la dimensión territorial. Constituye un ejemplo de recurso endógeno al que se adjudica un alto potencial de desarrollo en la escala local, en una doble dimensión, económica, como agente y bien mercantil mediante su aprovechamiento turístico, y social, como elemento de identidad. En Aragón, la Ley 12/1997 de Parques Culturales aporta un marco normativo propio para la gestión-protección del patrimonio cultural desde el fin genérico de la ordenación global sostenible de ámbitos rurales con valores patrimoniales y paisajístico-ambientales cuya singularidad constituye un elemento estructurante del territorio. Propone un modelo de desarrollo económico y social alternativo al productivista y relacionado con la emergencia de un enfoque postmoderno de multifuncionalidad flexible. El desarrollo de la ley ha dado lugar a la delimitación de cinco parques, entre ellos el de Albarracín