Ajuste entre estrategias de diversificación y estructuras multidivisionales: efecto sobre el resultado

El objetivo del presente trabajo es analizar la coherencia entre la estrategia de diversificación y la estructura multidivisional y su efecto sobre los resultados empresariales para el conjunto de los grandes grupos empresariales españoles diversificados. Para ello, y con el fin también de profundizar en los conceptos multidimensionales de estrategias de diversificación y estructuras multidivisionales, se utiliza el enfoque de la coherencia como desviación a un perfil “ideal”. Los resultados muestran que existen tres categorías estratégicas (diversificación relacionada, diversificación no relacionada y diversificación basada en el conocimiento, cada una de las cuales posee unas características estructurales “ideales” distintas. No obstante, sólo en el caso de la diversificación basada en el conocimiento se ha podido comprobar que la falta de coher encia entre la estrategia y la estructura tiene consecuencias negativas en la rentabilidad

Analysis, design and experimental evaluation of connectivity management in heterogeneous wireless environments

Mención Internacional en el título de doctorThe future of network communications is mobile as many more users demand for ubiquitous connectivity. Wireless has become the primary access technology or even the only one, leading to an explosion in traffic demand. This challenges network providers to manage and configure new requirements without incrementing costs in the same amount. In addition to the growth in the use of mobile devices, there is a need to operate simultaneously different access technologies. As well, the great diversity of applications and the capabilities of mobile terminals makes possible for us to live in a hyper-connected world and offers new scenarios. This heterogeneity poses great challenges that need to be addressed to offer better performance and seamless experience to the final user. We need to orchestrate solutions to increase flexibility and empower interoperability. Connectivity management is handled from different angles. In the network stack, mobility is more easily handled by IP mobility protocols, since IP is the common layer between the different access technologies and the application diversity. From the end-user perspective, the connection manager is in charge of handling connectivity issues in mobile devices, but it is an unstandardized entity so its performance is heavily implementation-dependent. In this thesis we explore connectivity management from different angles. We study mobility protocols as they are part of our proposed solutions. In most of the cases we include an experimental evaluation of performance with 3G and IEEE 802.11 as the main technologies. We consider heterogeneous scenarios, with several access technologies where mobile devices have also several network interfaces. We evaluate how connectivity is handled as well as its influence in a handover. Based on the analysis of real traces from a cellular network, we confirm the suitability of more efficient mobility management. Moreover, we propose and evaluate three different solutions for providing mobility support in three different heterogeneous scenarios. We perform an experimental evaluation of a vehicular route optimization for network mobility, reporting on the challenges and lessons learned in such a complicated networking environment. We propose an architecture for supporting mobility and enhance handover in a passive optical network deployment. In addition, we design and deploy a mechanism for mobility management based on software-defined networking.Programa Oficial de Doctorado en Ingeniería TelemáticaPresidente: Arturo Azcorra Saloña.- Secretario: Ramón Agüero Calvo.- Vocal: Daniel Nunes Coruj

Optimizacion de rutas para redes móviles en redes ad-hoc vehiculares

Hoy en día, el acceso a Internet y las comunicaciones se producen en escenarios muy diversos y con una gran variedad de dispositivos. Sobre todo, existe una tendencia creciente a la demanda de movilidad, es decir, a poder realizar la comunicación no sólo en cualquier sitio, sino también en movimiento. Pero, ¿cómo cambiaría nuestra vida si los dispositivos de comunicaciones fueran nuestros propios vehículos? Aunque pueda parecer ciencia-ficción, en los últimos años se han producido grandes avances en la investigación en el campo de las redes vehiculares, existiendo incluso propuestas de estandarización del protocolo de acceso al medio en entornos vehiculares (DSRC/802.11p). Por otro lado, el protocolo de soporte básico de movilidad de redes, NEMO BS, propone una extensión del protocolo de movilidad IP para gestionar el movimiento de redes completas, en lugar del movimiento de un terminal. NEMO BS hace posible que los nodos de la red móvil mantengan sus comunicaciones con el resto del mundo a través de las mismas direcciones IP(v6) que tienen en su red hogar. Sin embargo, presenta una desventaja ya que el enrutamiento del tráfico entre la red móvil y cualquier otro nodo pasa por la red hogar, independientemente de que exista o no una ruta más eficiente. A este respecto, NEMO BS no contempla ninguna optimización de rutas. La utilización del protocolo de movilidad de redes encaja en el entorno de las redes vehiculares, ya que se espera que en un vehículo existan numerosos dispositivos con necesidad de conectividad, desplazándose simultáneamente. De esta forma, dado que en algún momento las redes vehiculares serán una realidad, no es descabellado proponer una optimización de rutas para el protocolo de movilidad de redes (NEMO) en una red vehicular (contemplada como una red inalámbrica ad-hoc). Además, por las características propias de este tipo de redes, se hace necesario que los mecanismos de enrutado, gestión y configuración de los dispositivos de la red, se realicen de la forma más eficiente posible, ya que se trata de un entorno que puede cambiar rápidamente. En este proyecto se propone una optimización de rutas para NEMO en redes vehiculares. La idea principal es que dos vehículos presentes en la misma red puedan comunicarse entre sí directamente, a través de unos pocos saltos intermedios, en lugar de acceder a Internet para llegar a sus respectivas redes hogar, con el retardo que esto puede suponer. Para ello, se ha desarrollado, a partir de la optimización de rutas propuesta en VARON, una implementación en lenguaje C, que después ha sido puesta en práctica en un router comercial. Este router, que juega el papel de router móvil, es el elemento principal en este proyecto ya que se encarga de realizar todas las operaciones, tanto para la gestión de la movilidad de la red como para la creación de la ruta en la red vehicular. ---------------------------------------------------------------------------------------------------------------------------------------Nowadays, Internet access and communications occur in very different scenarios and with a wide variety of devices. Above all, there is a raising trend/fashion to demanding mobility, that is to say, to be able to communicate everywhere while in movement. How would our lives change if the communication device were our own vehicle? Although it could seem to be science fiction, there have been huge advances in research in the field of vehicular communications, arising standardization proposals for a medium access control layer in vehicular networks (DSRC/802.11p). On the other hand, there is a network mobility basic support protocol, NEMO BS, which propose an extension to the IP mobility protocol in order to manage the movement of a whole network, instead of the movement of a single terminal. This protocol has great advantages and keeps mobile network connected to the rest of the world through the same IP(v6) address while moving. However, it has a drawback because every datagram exchange with any other node, has to travel in a tunnel to the home network, no matter what, independently of the existence of more eficient routes or at less cost. Related to this, NEMO BS does not consider any route optimization mechanism. Right now, since is very likely that vehicular networks will become a reality not too far to come, it makes sense to propose a NEMO route optimization mechanism for ad-hoc vehicular networks. Moreover, due to the inherent characteristics of this kind of network, it is necessary to make routing mechanisms, manage and configuration as eficient as possible, because it is a frequently changing environment. This master thesis analyzes a vehicular ad-hoc route optimization for NEMO. The main idea is to make two vehicles in the same network able to communicate directly with each other, by a few intermediate hops, instead of using the Internet to reach their home networks, with the subsequent delay that it could mean. A prototype has been developed, based on the procedure defined in VARON, that has been later deployed in a commercial router. This router acts as a mobile router, being the main device in this project as it manages the mobility of the network as well as the route optimization, without leaving aside the tasks a proper router does.Ingeniería de Telecomunicació

Continuous symmetrized Sobolev inner products of order N (II)

Given a symmetrized Sobolev inner product of order N, the corresponding sequence of monic orthogonal polynomials {Qn} satisfies Q2n(x)=Pn(x2), Q2n+1(x)=xRn(x2) for certain sequences of monic polynomials {Pn} and {Rn}. In this paper we consider the particular case when all the measures that define the symmetrized Sobolev inner product are equal, absolutely continuous and semiclassical. Under such restrictions, we give explicit algebraic relations between the sequences {Pn} and {Rn}, as well as higher-order recurrence relations that they satisfy.The work of the authors has been partially supported by Dirección General de Investigación (Ministerio de Ciencia y Tecnología) of Spain under grants BFM 2003-06335-C03-02 (M.I.B., F.M., J.S.R.) and BFM2001-3878-C02-01 (J.S.R.), INTAS Research Network NeCCA INTAS 03-51-6637 (F.M.), and the Junta de Andalucía research group FQM-0207 (J.S.R)

Metodología de evaluación de accesibilidad Web para personas con limitaciones visuales

Una vez formulado el problema de la falta de condiciones para que las personas con limitaciones visuales accedan a la información Web y presentar una descripción del estado del arte de las organizaciones y pautas para el diseño de sitios Web accesibles se define el objetivo general de desarrollar una metodología de evaluación para el acceso a la información de las personas con limitaciones visuales. Se inicia con un estudio preliminar que reflexiona la hipótesis: ¿Gran parte de la información que hay en Internet no es accesible porque falta sensibilidad y conocimiento en los diseñadores Web, así como falta legislación que exija el diseño de páginas Web accesibles en Colombia¿. Se muestran los resultados de una encuesta de opinión con 10 preguntas que apuntan a medir la falta de sensibilidad(x), la falta de conocimiento de técnicas (y) y de una legislación (z) que exija el diseño de páginas Web Accesibles para 70 profesionales diseñadores Web en distintas ciudades de Colombia. Buscando obtener la mayor dependencia causal o mayor convergencia (mínima desviación estándar) de la hipótesis más dependiente de las demás, con objeto de conocer las causas primarias que podrían impactarse para mejorar las condiciones de una Internet muda para un nutrido grupo de personas y sorda porque no escucha las recomendaciones de expertos para volver la Web accesible a todos. Seguido se desarrolla un análisis de las 14 pautas de accesibilidad de la Guía de accesibilidad al contenido en la Web WCAG para clasificarlas y determinar el valor porcentual de cada punto de verificación y con ello proceder a desarrollar la evaluación de las páginas Web utilizando los resultados de los servidores HERA y EXAMINATOR. Luego se sientan las bases de una planeación metodológica para proyectarse hacia la completa metodología de evaluación propuesta

Experimental analysis of connectivity management in mobile operating systems

We are immerse in a world that becomes more and more mobile every day, with ubiquitous connectivity and increasing demand for mobile services. Current mobile terminals support several access technologies, enabling users to gain connectivity in a plethora of scenarios and favoring their mobility. However, the management of network connectivity using multiple interfaces is still starting to be deployed. The lack of smart connectivity management in multi interface devices forces applications to be explicitly aware of the variations in the connectivity state (changes in active interface, simultaneous access from several interfaces, etc.). In this paper, we analyze the present state of the connection management and handover capabilities in the three major mobile operating systems (OSes): Android, iOS and Windows. To this aim, we conduct a thorough experimental study on the connectivity management of each operating system, including several versions of the OS on different mobile terminals, analyzing the differences and similarities between them. Moreover, in order to assess how mobility is handled and how this can affect the final user, we perform an exhaustive experimental analysis on application behavior in intra- and inter-technology handover. Based on this experience, we identify open issues in the smartphone connectivity management policies and implementations, highlighting easy to deploy yet unimplemented improvements, as well as potential integration of mobility protocols.This work has been partially supported by the European Community through the CROWD project, FP7-ICT-318115.Publicad

Transfusion-associated adverse events incidence and severity after the implementation of an active hemovigilance program with 24 h follow-up. A prospective cohort study

Background: Hemovigilance (HV) is usually based on voluntary reports (passive HV). Our aim is to ascertain credible incidence, severity, and mortality of transfusion-associated adverse events (TAAEs) using an active HV program. Study Design and Methods: Prospective cohort study to estimate transfusion risk after 46,488 transfusions in 5830 patients, using an active HV program with follow-up within the first 24 h after transfusion. We compared these results to those with the previously established passive HV program during the same 30 months of the study. We explored factors associated with the occurrence of TAAEs using generalized estimating equations models. Results: With the active HV program TAAEs incidence was 57.3 (95% CI, 50.5–64.2) and mortality 1.1 (95% CI, 0.13–2.01) per 10,000 transfusions. Incidence with the new surveillance model was 14.0 times higher than with the passive. Most events occurred when transfusions had already finished (60.2%); especially pulmonary events (80.4%). Three out of five deaths and 50.3% of severe TAAEs were pulmonary. In the multivariate analysis surgical patients had half TAAEs risk when compared to medical patients (OR, 0.53; 95% CI, 0.34–0.78) and women had nearly twice the risk of a pulmonary event compared to men (OR, 1.84; 95% CI, 1.03–3.32). Patient's age, blood component type, or blood component shelf-life were unrelated to TAAEs risk. Discussion: Active hemovigilance programs provide additional data which may lead to better recognition and understanding of TAAEs and their frequency and severit

rQUIC: Integrating FEC with QUIC for robust wireless communications

QUIC, fostered by Google and under standardization in the IETF, integrates some of HTTP/s, TLS, and TCP functionalities over UDP. One of its main goals is to facilitate transport protocol design, with fast evolution and innovation. However, congestion control in QUIC is still severely jeopardized by packet losses, despite implemented loss recovery mechanisms, whose behavior strongly depends on the Round Trip Time. In this paper, we design and implement rQUIC, a framework that enables FEC within QUIC protocol to improve its performance over wireless networks. The main idea behind rQUIC is to reduce QUIC's loss recovery time by making it robust to erasures over wireless networks, as compared to traditional transport protocol loss detection and recovery mechanisms. We evaluate the performance of our solution by means of extensive simulations over different type of wireless networks and for different applications. For LTE and Wifi networks, our results illustrate significant gains of up to 60% and 25% savings in the completion time for bulk transfer and web browsing, respectively.Özgü Alay was partially supported the Norwegian Research Council project No. 250679 (MEMBRANE). Ramón Agüero was partially supported by the Spanish Government (MINECO, MCIU, AEI, FEDER) by means of the projects ADVICE: Dynamic provisioning of connectivity in high density 5G wireless scenarios (TEC2015-71329-C2-1-R) and FIERCE: Future Internet Enabled Resilient Cities (RTI2018-093475-A-100)

GABA Receptor Agonists Protect From Excitotoxic Damage Induced by AMPA in Oligodendrocytes

Oligodendrocytes are the myelin forming cells of the central nervous system, and their vulnerability to excitotoxicity induced by glutamate contributes to the pathogenesis of neurological disorders including brain ischemia and neurodegenerative diseases, such as multiple sclerosis. In addition to glutamate receptors, oligodendrocytes express GABA receptors (GABAR) that are involved in their survival and differentiation. The interactions between glutamate and GABAergic systems are well documented in neurons, under both physiological and pathological conditions, but this potential crosstalk in oligodendrocytes has not been studied in depth. Here, we evaluated the protective effect of GABAR agonists, baclofen (GABAB) and muscimol (GABAA), against AMPA-induced excitotoxicity in cultured rat oligodendrocytes. First, we observed that both baclofen and muscimol reduced cell death and caspase-3 activation after AMPA insult, proving their oligoprotective potential. Interestingly, analysis of the cell-surface expression of calcium-impermeable GluR2 subunits in oligodendrocytes revealed that GABAergic agonists significantly reverted GluR2 internalization induced by AMPA. We determined that baclofen and muscimol also impaired AMPA-induced intracellular calcium increase and subsequent mitochondrial membrane potential alteration, ROS generation, and calpain activation. However, AMPA-triggered activation of Src, Akt, JNK and CREB was not affected by baclofen or muscimol. Overall, our results suggest that GABAR activation initiates alternative molecular mechanisms that attenuate AMPA-mediated apoptotic excitotoxicity in oligodendrocytes by interfering with expression of GluR subunits in membranes and with calcium-dependent intracellular signaling pathways. Together, these findings provide evidence of GABAR agonists as potential oligodendroglial protectants in central nervous system disorders