Bounds on the sum-rate capacity of the Gaussian MIMO X channel

We consider the MIMO X channel (XC), a system consisting of two transmit-receive pairs, where each transmitter communicates with both the receivers. Both the transmitters and receivers are equipped with multiple antennas. First, we derive an upper bound on the sum-rate capacity of the MIMO XC under individual power constraint at each transmitter. The sum-rate capacity of the two-user multiple access channel (MAC) that results when receiver cooperation is assumed forms an upper bound on the sum-rate capacity of the MIMO XC. We tighten this bound by considering noise correlation between the receivers and deriving the worst noise covariance matrix. It is shown that the worst noise covariance matrix is a saddle-point of a zero-sum, two-player convex-concave game, which is solved through a primal-dual interior point method that solves the maximization and the minimization parts of the problem simultaneously. Next, we propose an achievable scheme which employs dirty paper coding at the transmitters and successive decoding at the receivers. We show that the derived upper bound is close to the achievable region of the proposed scheme at low to medium SNRs.

Fair Scheduling in Cellular Systems in the Presence of Noncooperative Mobiles

We consider the problem of ``fair'' scheduling the resources to one of the many mobile stations by a centrally controlled base station (BS). The BS is the only entity taking decisions in this framework based on truthful information from the mobiles on their radio channel. We study the well-known family of parametric alpha-fair scheduling problems from a game-theoretic perspective in which some of the mobiles may be noncooperative. We first show that if the BS is unaware of the noncooperative behavior from the mobiles, the noncooperative mobiles become successful in snatching the resources from the other cooperative mobiles, resulting in unfair allocations. If the BS is aware of the noncooperative mobiles, a new game arises with BS as an additional player. It can then do better by neglecting the signals from the noncooperative mobiles. The BS, however, becomes successful in eliciting the truthful signals from the mobiles only when it uses additional information (signal statistics). This new policy along with the truthful signals from mobiles forms a Nash equilibrium (NE) that we call a Truth Revealing Equilibrium. Finally, we propose new iterative algorithms to implement fair scheduling policies that robustify the otherwise nonrobust (in presence of noncooperation) alpha-fair scheduling algorithms.

The Structure of the Holo-Acyl Carrier Protein of Leishmania major Displays a Remarkably Different Phosphopantetheinyl Transferase Binding Interface

The genome of Leishmania major encodes a type II fatty acid biosynthesis pathway for which no structural or biochemical information exists. Here, for the first time, we have characterized the central player of the pathway, the acyl carrier protein (LmACP), using nuclear magnetic resonance (NMR). Structurally, the LmACP molecule is similar to other type II ACPs, comprising a four-helix bundle, enclosing a hydrophobic core. Dissimilarities in sequence, however, exist in helix II (recognition helix) of the protein. The enzymatic conversion of apo-LmACP into the holo form using type I (Escherichia coli AcpS) and type II (Sfp type) phosphopantetheinyl transferases (PPTs) is relatively slow. Mutagenesis studies underscore the importance of the residues present at the protein protein interaction interface of LmACP in modulating the activity of PPTs. Interestingly, the cognate PPT for this ACP, the L. major 4'-phosphopantetheinyl transferase (LmPPT), does not show any enzymatic activity toward it, though it readily converts other type I and type II ACPs into their holo forms. NMR chemical shift perturbation studies suggest a moderately tight complex between LmACP and its cognate PPT, suggesting inhibition. We surmise that the unique surface of LmACP might have evolved to complement its cognate enzyme (LmPPT), possibly for the purpose of regulation.

Necessary and sufficient conditions for optimality in constrained general sum stochastic games

In this paper we first derive a necessary and sufficient condition for a stationary strategy to be the Nash equilibrium of discounted constrained stochastic game under certain assumptions. In this process we also develop a nonlinear (non-convex) optimization problem for a discounted constrained stochastic game. We use the linear best response functions of every player and complementary slackness theorem for linear programs to derive both the optimization problem and the equivalent condition. We then extend this result to average reward constrained stochastic games. Finally, we present a heuristic algorithm motivated by our necessary and sufficient conditions for a discounted cost constrained stochastic game. We numerically observe the convergence of this algorithm to Nash equilibrium. (C) 2015 Elsevier B.V. All rights reserved.

A Model of Evolutionay Drift

Drift appears to be crucial to study the stability properties of Nash equilibria in a component specifying different out-of-equilibrium behaviour. We propose a new microeconomic model of drift to be added to the learning process by which agents find their way to equilibrium. A key feature of the model is the sensitivity of the noisy agent to the proportion of agents in his player population playing the same strategy as his current one. We show that, 1. Perturbed Payoff-Positive and PayoffMonotone selection dynamics are capable of stabilizing pure non strict Nash equilibria in either singleton or nonsingleton component of equilibria; 2. The model is relevant to understand the role of drift in the behaviour observed in the laboratory for the Ultimatum Game and for predicting outcomes that can be experimentally tested. Hence, the selection dynamics model perturbed with the proposed drift may be seen as well as a new learning tool to understand observed behaviour.

Automatismos y racionalidad en la toma de decisiones para sustituir a un deportista en momentos decisivos

[ES] Cada vez más el deporte-espectáculo se está abriendo paso como objeto de estudio en los centros de investigación avanzada, como consecuencia de la necesidad de gestionar los altos presupuestos de las entidades deportivas.

Particularidades de China para el desarrollo empresarial: reflexión a partir de casos de estudio

[ES] China ha irrumpido como actor principal del escenario global al haber protagonizado, durante las tres últimas décadas, un proceso de transformación económica y social de gran magnitud. Ahora bien, vender productos –sobre todo, del sector de alimentación– de origen occidental en China es, con diferencia, el reto más complicado al que deben enfrentarse las compañías de deciden entrar a operar en este mercado.

Asymmetric flow networks

This paper provides a new model of network formation that bridges the gap between the two benchmark models by Bala and Goyal, the one-way flow model, and the two-way flow model, and includes both as particular extreme cases. As in both benchmark models, in what we call an "asymmetric flow" network a link can be initiated unilaterally by any player with any other, and the flow through a link towards the player who supports it is perfect. Unlike those models, in the opposite direction there is friction or decay. When this decay is complete there is no flow and this corresponds to the one-way flow model. The limit case when the decay in the opposite direction (and asymmetry) disappears, corresponds to the two-way flow model. We characterize stable and strictly stable architectures for the whole range of parameters of this "intermediate" and more general model. We also prove the convergence of Bala and Goyal's dynamic model in this context.

Games with perceptions

We assume that 2 x 2 matrix games are publicly known and that players perceive a dichotomous characteristic on their opponents which defines two types for each player. In turn, each type has beliefs concerning her opponent's types, and payoffs are assumed to be type-independent. We analyze whether the mere possibility of different types playing different strategies generates discriminatory equilibria. Given a specific information structure we find that in equilibrium a player discriminates between her types if and only if her opponent does so. We also find that for dominant solvable 2x2 games no discriminatory equilibrium exists, while under different conditions of concordance between players' beliefs discrimination appears for coordination and for competitive games. A complete characterization of the set of Bayesian equilibria is provided.

Os atores-chave no processo decisório no âmbito das comissões permanentes

Descreve os atores-chave no processo decisório no âmbito das comissões permanentes da Câmara dos Deputados, a partir de uma análise de como influenciam na tomada de decisões naqueles órgãos. Essa análise parte de três variáveis: poder de agenda, poder de veto (veto player) e capacidade de influenciar na decisão final do colegiado. Para tanto, o método utilizado foi de levantar as atribuições regimentais de cada um dos atores definidos em comparação com os poderes dos demais parlamentares. Concluiu-se que a concentração de poderes em determinados atores pode influenciar na tomada de decisões

Learning in Network Games

We report the findings of an experiment designed to study how people learn and make decisions in network games. Network games offer new opportunities to identify learning rules, since on networks (compared to e.g. random matching) more rules differ in terms of their information requirements. Our experimental design enables us to observe both which actions participants choose and which information they consult before making their choices. We use this information to estimate learning types using maximum likelihood methods. There is substantial heterogeneity in learning types. However, the vast majority of our participants' decisions are best characterized by reinforcement learning or (myopic) best-response learning. The distribution of learning types seems fairly stable across contexts. Neither network topology nor the position of a player in the network seem to substantially affect the estimated distribution of learning types.

Deportividad y violencia en el fútbol base: un programa de evaluación y de prevención de partidos de riesgo

Este trabajo ha recibido el “Primer Premio Delegación del Gobierno en Aragón a las buenas prácticas contra la delincuencia juvenil” (Convocatoria 2007).

Automatización de los recorridos del robot en un sistema de exploración basado en comportamientos

Automatización de los recorridos del robot en un sistema de exploración basado en comportamientos. Se muestran los resultados obtenidos en las simulaciones con Player/Stage de un sistema de exploración basado en comportamientos, donde la localización se realiza mediante los estadísticos de INCA.

Cine Digital y sus Contenedores. Herramientas de Software libre basadas en las Especificaciones DCI

El Cine Digital es aquel que utiliza la tecnología digital para grabar, distribuir y proyectar películas. En los años 90, el cine comenzó un proceso de transición, del soporte fílmico a la tecnología digital. Pero el salto definitivo se dio con las grandes superproducciones de principios del 2000. Con este cambio de era y debido a la rápida difusión del digital y la proliferación de formatos se creo el DCI (Digital Cinema Initiative), para cambiar el modo en que las personas consumen cine. Trabajando junto con los miembros del comité SMPTE (Organización americana encargada de crear los estándares de la industria audiovisual formada por ingenieros, técnicos y fabricantes) publicó un sistema de especificaciones que han adoptado las mayores productoras estadounidenses. Mediante este acuerdo, aseguraban la calidad técnica de las producciones, la compatibilidad entre sistemas y como no, su hegemonía particular. Entre las especificaciones técnicas que suscribieron que son la base actual del DCI figuran la resolución de fotograma, el espacio de color, la compresión de imagen, la encriptación y el método de empaquetado de archivos. Y hoy en día son un estándar en la masterización, distribución y en la proyección final en las salas de cine. Una de las grandes esperanzas que hay puestas en la tecnología digital es la democratización en el mundo del cine y la supuesta abolición de las barreras económicas a la hora de realizar películas, dado lo barato que puede resultar la grabación digital y la posibilidad de pasar el material a video y editarlo en un ordenador domestico. Independientemente de los sistemas de edición que se utilicen, el formato de archivo o incluso el códec usado, los servidores de cine digital solo aceptan un tipo de archivo llamado DCP (Digital Cinema Package). Hay que aclarar que el DCP es abierto, documentado y que esta basado en los estándares SMPTE. Por lo tanto, existen en el mercado actual herramientas de software libre que permiten crear un DCP válido según las normas del DCI y compatible con los actuales servidores de cine digital. El propósito de este proyecto principalmente es documentar desde un punto de vista técnico la creación de un archivo DCP y analizar las diferentes herramientas existentes en el mercado para poder realizarlo: tanto las de uso comercial, como las de software libre. Como base se partirá de las aplicaciones creadas por la empresa alemana Fraunhofer (EasyDCP Creator, Player) - es el software utilizado en el estudio REC - y de otras herramientas más rudimentarias y escritas en C++ como (asdcplib) de Cinecert.

Automatización de los recorridos del robot en un sistema de exploración basado en comportamientos

Automatización de los recorridos del robot en un sistema de exploración basado en comportamientos. Se muestran los resultados obtenidos en las simulaciones con Player/Stage de un sistema de exploración basado en comportamientos, donde la localización se realiza mediante los estadísticos de INCA.