On the Design of a Novel Joint Network-Channel Coding Scheme for the Multiple Access Relay Channel

This paper proposes a novel joint non-binary network-channel code for the Time-Division Decode-and-Forward Multiple Access Relay Channel (TD-DF-MARC), where the relay linearly combines -- over a non-binary finite field -- the coded sequences from the source nodes. A method based on an EXIT chart analysis is derived for selecting the best coefficients of the linear combination. Moreover, it is shown that for different setups of the system, different coefficients should be chosen in order to improve the performance. This conclusion contrasts with previous works where a random selection was considered. Monte Carlo simulations show that the proposed scheme outperforms, in terms of its gap to the outage probabilities, the previously published joint network-channel coding approaches. Besides, this gain is achieved by using very short-length codewords, which makes the scheme particularly attractive for low-latency applications.Comment: 28 pages, 9 figures; Submitted to IEEE Journal on Selected Areas in Communications - Special Issue on Theories and Methods for Advanced Wireless Relays, 201

Espacios sublimados. Sofía Casanova y la representación del espacio público y privado en el diario ABC durante la Primera Guerra Mundial

Las modificaciones en la representación de lo que pertenece o no a lo público y a lo privado, pueden provocar la capacitación política por parte de aquellos sujetos que históricamente han sido subordinados dentro de los espacios de poder. Durante la Primera Guerra Mundial, la periodista del diario ABC Sofía Casanova, encontró diferentes formas de aproximación a la cuestión de qué es público y, por lo tanto, qué es político. Esto fue debido, en gran medida, a su propia experiencia personal, a su pasado como mujer escritora, pero también a las circunstancias y condiciones que la guerra iniciada en el verano de 1914 predispuso ante ella. Este trabajo trata de mostrar los límites de la capacitación política, los cambios y las resistencias que Sofía Casanova moduló durante ese periodo

Revisiting Complex Moments For 2D Shape Representation and Image Normalization

When comparing 2D shapes, a key issue is their normalization. Translation and scale are easily taken care of by removing the mean and normalizing the energy. However, defining and computing the orientation of a 2D shape is not so simple. In fact, although for elongated shapes the principal axis can be used to define one of two possible orientations, there is no such tool for general shapes. As we show in the paper, previous approaches fail to compute the orientation of even noiseless observations of simple shapes. We address this problem. In the paper, we show how to uniquely define the orientation of an arbitrary 2D shape, in terms of what we call its Principal Moments. We show that a small subset of these moments suffice to represent the underlying 2D shape and propose a new method to efficiently compute the shape orientation: Principal Moment Analysis. Finally, we discuss how this method can further be applied to normalize grey-level images. Besides the theoretical proof of correctness, we describe experiments demonstrating robustness to noise and illustrating the method with real images.Comment: 69 pages, 20 figure

An analysis of the relationship between higher education and development by applying Sen's human capabilities approach : the case of three technological universities in Mexico

Reading for a PhD at York could not have been possible without the financial support of the National Council of Science and Technology of Mexico (Conacyt) and, more recently, of the Secretariat of Public Education (Sep). I thank both institutions for helping to meet my academic objectives. I would like to express my deepest gratitude to my supervisor, Professor Haleh Afshar who taught me how to deal with the complexity of the academic world by giving me constructive comments and criticisms that have improved the quality of this dissertation. No doubt, Haleh has been a key person to improve my “functionings” as a researcher. Many people contributed at different points during the writing of this thesis. I am particularly grateful with doctors Roberto Rodriguez, Pablo Latapí Sarré, Rollin Kent, Carlos Muñoz Izquierdo, Felipe Martinez Rizo, Hugo Casanova, Julio Boltvinik, Fernando Arias Galicia and professors A. H. Halsey, Hugh Lauder and Walter W. MacMahon who kindly replied my e-mails or gave me part of their time to listen to my concerns about education and development (my apologies if I missed somebody). In constructing the research techniques I received the advice of Dr. Lorenza Villa. When I had problems, especially with some economic techniques, Alfonso Mendoza and Maria Elena Garcia were always in the mood of helping. During the pilot study and the field work, I received invaluable support from Dr. Arturo Nava, Jorge Acoltzi, Rosario Tapia, Javier Herrera, Gildardo Villalobos of the General Coordination of the UTs. I would like also to thank the logistic support of my friends of the GMCE: Silvia Coria, Dulce, Felipe, Eva Ruelas, and, my “eternal supervisor” Salvador Ruiz de Chávez. To apply 717 questionnaires and conduct more than a hundred interviews would have been an impossible task without the logistic support and facilities provided by the UTs. I am very grateful with Ing. Roberto Reyes, Nicolás Serna, Pascual Torres, contadora Ornelas, Esthela Maldonado and Alejandra of the UT of Neza; Mtro. Javier Hernández, Carlos M. Beckwith, Miguel A. Cruz, Gisela Girón, Angélica, Lorena and Horte of Tula; and Lie. Héctor Tiscareño, Juan Manuel Montañez, Paco, Daniel, Ricardo, Axel, Don Rafa, Jorge Marabotto, Amparo, Aurora, Claudine Ruiz-Esparza, Maru Robledo and Mónica Reyes of the UT of Aguascalientes. To my close friends Max Niño, Juancho Barron and Arturo Flores for their enjoyable company during this “academic” experience. Thanks, too, to those employers who illustrated with their particular visions this work. During the data collection process, I was very fortunate in meeting many committed graduates from Neza, Tula and Aguascalientes. Many thanks to all, this work is dedicated to them. Special thanks must go to Professor Amartya Sen with whom I had the chance to discuss a piece of this work. His comments were extremely useful in the final stage of my studies. To Heloise Brown, Sarah Marshall and Sam Clark for their remarkable proof reading. I would like also to thank the administrative and academic staff of the Department of Politics at York, especially, to my backup supervisors; Dr. Neil Carter, in the kickoff of the PhD, and Dr. Rob Aitken during the second half. Very special thanks to my family and friends for their love and support. They have flashed my life with happiness. To Deborah Fabri for her unconditional support and for sharing with me the sunshine of England

Mergers & acquisitions : the case Grupo Media Capital and PT Portugal

Over the last 2 years, Altice Group has been one of the most active telecommunication companies, making acquisitions in different countries, not only in the telecommunication sector but also in the media sector. According to the multinational company, the expansion into the media industry, in the countries where they have already telecommunication operations, brings many and important synergies to their overall operation. After Altice have bought PT Portugal, some rumors came up about the possibility of Altice also entering in the media market in Portugal. Taking up these rumors I decided to study the potential acquisition of Grupo Media Capital by Grupo Altice, through PT Portugal. Along the thesis, I explain relevant M&A literature, make a review on both sectors (media and telecommunication) and companies, and at the end also calculate the standalone valuation of both companies and the synergies that may arise from this deal. After all these procedures, I conclude that this is the perfect moment for PT Portugal to make an offer to Group Prisa (Grupo Media Capital major shareholder). Grupo Prisa should be willing to disinvest in their Portuguese position and taking into account my calculations, Grupo Media Capital share price is undervalued. PT Portugal should make an offer of €4.84 per share, if considering a premium composed by 75% of the cost reduction synergy and 25% of the advertising revenue synergy.Durante os últimos dois anos, o Grupo Altice tem sido uma das empresas mais activas na área das Telecomunições, fazendo aquisições em diferentes países, não apenas no sector das telecomunições mas também no sector dos media. De acordo com a empresa multinacional, a expansão para o sector dos media, nos países onde a empresa já tem operações na área das telecomunicações, pode trazer sinergias importantes. Depois da Altice ter comprado a PT Portugal, surgiram rumores sobre a possibilidade da empresa entrar no sector dos media em Portugal. Com base nestes rumores, decidi estudar a potencial acquisição do Grupo Media Capital pelo Grupo Altice, através da PT Portugal. Durante a tese, explico os conceitos relacionados com M&A e faço uma revisão dos dois sectores e das duas empresas. No final, calculo o valor das duas empresas individualmente e das sinergias que possam ser geradas com este negócio. Depois de todas estas fases, concluo que este é o momento ideal para a PT Portugal fazer uma oferta ao Grupo Prisa (accionista maioritário do Grupo Media Capital). O Grupo Prisa poderá estar disposto a desinvestir da sua posição em Portugal e para além disso, segundo os meus cálculos, o preço das acções da Media Capital está subavaliado. A PT Portugal deverá fazer uma oferta de 4.84 € por acção, considerando um prémio que corresponde a 75% da sinergia de redução de custos e 25% da sinergia de receitas de publicidade

The skewness of science in 219 sub-fields and a number of aggregates

This paper studies evidence from Thomson Scientific about the citation process of 3.7 million articles published in the period 1998-2002 in 219 Web of Science categories, or sub-fields. Reference and citation distributions have very different characteristics across sub-fields. However, when analyzed with the Characteristic Scores and Scales technique, which is replication and scale invariant, the shape of these distributions over three broad categories of articles appears strikingly similar. Reference distributions are mildly skewed, but citation distributions with a five-year citation window are highly skewed: the mean is twenty points above the median, while 9-10% of all articles in the upper tail account for about 44% of all citations. The aggregation of sub-fields into disciplines and fields according to several aggregation schemes preserve this feature of citation distributions. It should be noted that when we look into subsets of articles within the lower and upper tails of citation distributions the universality partially breaks down. On the other hand, for 140 of the 219 sub-fields the existence of a power law cannot be rejected. However, contrary to what is generally believed, at the sub-field level the scaling parameter is above 3.5 most of the time, and power laws are relatively small: on average, they represent 2% of all articles and account for 13.5% of all citations. The results of the aggregation into disciplines and fields reveal that power law algebra is a subtle phenomenon.

A comparison of the scientific performance of the U. S. and the European Union at the turn of the XXI century.

In this paper, scientific performance is identified with the impact journal articles achieve through the citations they receive. The empirical exercise refers to 3.6 million articles published in 1998-2002 in 22 scientific fields, and the more than 47 million citations they receive in 1998-2007. The first finding is that a failure to exclude co-authorship among member countries within the EU (European Union) may lead to a serious upward bias in the assignment of articles to this geographical area. In the second place, standard indicators, such as normalized mean citation ratios, are silent about what takes place in different parts of the citation distribution. Consequently, this paper compares the publication shares of the U.S. and the EU at every percentile of the world citation distribution in each field. In 15 disciplines, as well as in all sciences as a whole, the EU share of total publications is greater than that of the U.S. one. But as soon as the citations received by these publications are taken into account the picture is completely reversed. The mean citation rate in the U.S. is greater than in the EU in every one of the 22 fields. In seven fields, the initial gap between the U.S. and the EU widens up as we advance towards the more cited articles, while in the remaining 15 fields –except for Agricultural Sciences– the U.S. always surpasses the EU when it counts, namely, at the upper tail of citation distributions. For all sciences as a whole, the U.S publication share becomes greater than that of the EU one for the top 50% of the most highly cited articles.

The skewness of science in 219 sub-fields and a number of aggregates

This paper studies evidence from Thomson Scientific about the citation process of 3.7 million articles published in the period 1998-2002 in 219 Web of Science categories, or sub-fields. Reference and citation distributions have very different characteristics across sub-fields. However, when analyzed with the Characteristic Scores and Scales technique, which is size and scale independent, the shape of these distributions appear extraordinarily similar. Reference distributions are mildly skewed, but citation distributions with a five-year citation window are highly skewed: the mean is twenty points above the median, while 9-10% of all articles in the upper tail account for about 44% of all citations. The aggregation of sub-fields into disciplines and fields according to several aggregation schemes preserve this feature of citation distributions. On the other hand, for 140 of the 219 sub-fields the existence of a power law cannot be rejected. However, contrary to what is generally believed, at the sub-field level the scaling parameter is above 3.5 most of the time, and power laws are relatively small: on average, they represent 2% of all articles and account for 13.5% of all citations. The results of the aggregation into disciplines and fields reveal that power law algebra is a subtle phenomenon.

Ecophysiological study of the intertidal zonation of the estuarine rhodophytes Bostrychia scorpioides (Hudson) Montagne ex Kützing and Catenella caespitosa (Withering) L. M. Irvine

La presente tesis doctoral tiene como objetivo estudiar la ecofisiología de las macroalgas estuáricas Bostrychia scorpioides (Hudson) Montagne ex Kützing (Rhodophyta, Ceramiales) y Catenella caespitosa (Withering) L. M. Irvine (Rhodophyta, Gigartinales) y analizar el papel que desempeñan diferentes variables ambientales en su distribución y crecimiento en el intermareal del estuario del río Palmones. Desde el punto de vista ecofisiológico, estas especies destacan por su adaptación a bajas irradiancias, debido al efecto atenuante del dosel de vegetación sobre el que crecen, y su alta tolerancia a la desecación, la cual determina sus límites superiores de distribución. Los objetivos específicos son: 1) Evaluar la capacidad de fotoaclimatación y los requerimientos energéticos para la fotosíntesis y el crecimiento; 2) Determinar la capacidad de incorporación y requerimientos internos de nutrientes de cada especie; 3) Analizar el efecto individual e interactivo de las variables de emersión sobre las respuestas fisiológicas (tolerancia y recuperación); 4) Identificar la variabilidad intra- e interespecífica en la ecofisiología de B. scorpioides y C. caespitosa en relación al gradiente de marea; 5) Estudiar la dinámica estacional de la biomasa, crecimiento, fotosíntesis y composición interna de las especies objeto de estudio, a través de muestreos mensuales en el estuario. Bostrychia scorpioides posee una mayor variabilidad fenotípica a escala espacial y estacional, una alta plasticidad fotofisiológica, la capacidad de reducir las tasas de renovación de N y P internos en alturas de marea donde el aporte de nutrientes es menor y mantener tasas de crecimiento positivas en periodos severos de emersión diaria. Estas respuestas permiten a esta especie afrontar condiciones ambientales más fluctuantes, explicando su clara dominancia en lugares expuestos a mayor irradiancia, su presencia en los niveles más altos del intermareal y la distribución homogénea de su biomasa entre los distintos niveles mareales. Catenella caespitosa muestra una gran capacidad fotofisiológica adaptada a bajas irradiancias, con bajos requerimientos lumínicos para su crecimiento y la minimización de las tasas de respiración. Esta respuesta fisiológica, junto a su baja capacidad para reducir la demanda interna de N en posiciones más altas del intermareal y su mayor sensibilidad a las variables de emersión, explican su dominancia en las zonas intermareales más bajas y en lugares sombríos. El aumento de densidad en el dosel de vegetación aminora el estrés físico, facilitando el crecimiento de C. caespitosa, dada su menor tolerancia a la emersión, y limitando el de B. scorpioides, debido a sus mayores requerimientos lumínicos para crecer. La biomasa de ambas especies presentó un claro patrón estacional, con un aumento de fotosíntesis, crecimiento y contenido interno de nutrientes de invierno a primavera. Los factores físicos influyen de forma directa en la distribución espacial de B. scorpioides and C. caespitosa en el intermareal del estuario del río Palmones, teniendo las interacciones bióticas un papel marginal. Las variables de emersión y la disponibilidad de nutrientes establecen los límites superiores de distribución de ambas especies, e impiden el crecimiento de C. caespitosa en la zona superior del intermareal, mientras que la luz es el principal factor que limita la distribución de B. scorpioides a la zona intermedia y superior de éste