Asymptotically Exact Approximations for the Symmetric Difference of Generalized Marcum-Q Functions

(c) 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works. DOI: 10.1109/TVT.2014.2337263In this paper, we derive two simple and asymptotically exact approximations for the function defined as ΔQm(a, b) =Δ Qm(a, b) - Qm(b, a). The generalized Marcum Q-function Qm(a, b) appears in many scenarios in communications in this particular form and is referred to as the symmetric difference of generalized Marcum Q-functions or the difference of generalized Marcum Q-functions with reversed arguments. We show that the symmetric difference of Marcum Q-functions can be expressed in terms of a single Gaussian Q-function for large and even moderate values of the arguments a and b. A second approximation for ΔQm(a, b) is also given in terms of the exponential function. We illustrate the applicability of these new approximations in different scenarios: 1) statistical characterization of Hoyt fading; 2) performance analysis of communication systems; 3) level crossing statistics of a sampled Rayleigh envelope; and 4) asymptotic approximation of the Rice Ie-function.Universidad de Málaga. Campus de Excelencia Internacional. Andalucía Tech

An evolutionary behavioral model for decision making

For autonomous agents the problem of deciding what to do next becomes increasingly complex when acting in unpredictable and dynamic environments pursuing multiple and possibly conflicting goals. One of the most relevant behavior-based model that tries to deal with this problem is the one proposed by Maes, the Bbehavior Network model. This model proposes a set of behaviors as purposive perception-action units which are linked in a nonhierarchical network, and whose behavior selection process is orchestrated by spreading activation dynamics. In spite of being an adaptive model (in the sense of self-regulating its own behavior selection process), and despite the fact that several extensions have been proposed in order to improve the original model adaptability, there is not a robust model yet that can self-modify adaptively both the topological structure and the functional purpose\ud of the network as a result of the interaction between the agent and its environment. Thus, this work proffers an innovative hybrid model driven by gene expression programming, which makes two main contributions: (1) given an initial set of meaningless and unconnected units, the evolutionary mechanism is able to build well-defined and robust behavior networks which are adapted and specialized to concrete internal agent's needs and goals; and (2)\ud the same evolutionary mechanism is able to assemble quite\ud complex structures such as deliberative plans (which operate in the long-term) and problem-solving strategies

Composite Fading Models based on Inverse Gamma Shadowing: Theory and Validation

We introduce a general approach to characterize composite fading models based on inverse gamma (IG) shadowing. We first determine to what extent the IG distribution is an adequate choice for modeling shadow fading, by means of a comprehensive test with field measurements and other distributions conventionally used for this purpose. Then, we prove that the probability density function and cumulative distribution function of any IG-based composite fading model are directly expressed in terms of a Laplace-domain statistic of the underlying fast fading model and, in some relevant cases, as a mixture of wellknown state-of-the-art distributions. Also, exact and asymptotic expressions for the outage probability are provided, which are valid for any choice of baseline fading distribution. Finally, we exemplify our approach by presenting several application examples for IG-based composite fading models, for which their statistical characterization is directly obtained in a simple form.Comment: This work has been submitted to the IEEE for publication. Copyright may be transferred without notice, after which this version may no longer be accessibl

El contexto de la democracia y la participación en el sistema capitalista

La siguiente reflexión analiza las estructuras y los elementos del Estado moderno, sus primeras manifestaciones, pasando por su evolución y los fundamentos teóricos que se le fueron sumando en el contexto de la democracia capitalista y sus diversas formas de expresión en las distintas sociedades. Ubicadas en el marco formal del Estado moderno encontramos al mercado político en el que aparecen tanto la teoría de la representatividad como los partidos políticos; organizaciones indispensables para efectuarla y sin los cuales sería difícil comprender la política en sus modalidades de interlocución, negociación y demandas sociales. En este sentido también se mencionan cuestiones referentes a la administración tecnocrática del Estado y la precisión de los marcos teóricos de algunos de sus principales representantes, así como las referentes a la construcción de la ingeniería social de la democracia

Holographic Relaxation of Finite Size Isolated Quantum Systems

We study holographically the out of equilibrium dynamics of a finite size closed quantum system in 2+1 dimensions, modelled by the collapse of a shell of a massless scalar field in AdS4. In global coordinates there exists a variety of evolutions towards final black hole formation which we relate with different patterns of relaxation in the dual field theory. For large scalar initial data rapid thermalization is achieved as a priori expected. Interesting phenomena appear for small enough amplitudes. Such shells do not generate a black hole by direct collapse, but quite generically an apparent horizon emerges after enough bounces off the AdS boundary. We relate this bulk evolution with relaxation processes at strong coupling which delay in reaching an ergodic stage. Besides the dynamics of bulk fields, we monitor the entanglement entropy, finding that it oscillates quasi-periodically before final equilibration. The radial position of the traveling shell is brought into correspondence with the evolution of the entanglement pattern in the dual field theory. The entanglement entropy is not only able to portrait the streaming of entangled excitations, but it is also a useful probe of interaction effects.Comment: 37 pages, 27 figure

Heat asymmetries in nanoscale conductors: The role of decoherence and inelasticity

We investigate the heat flow between different terminals in an interacting coherent conductor when inelastic scattering is present. We illustrate our theory with a two-terminal quantum dot setup. Two types of heat asymmetries are investigated: electric asymmetry $\Delta_E$, which describes deviations of the heat current in a given contact when voltages are exchanged, and contact asymmetry $\Delta_C$, which quantifies the difference between the power measured in two distinct electrodes. In the linear regime, both asymmetries agree and are proportional to the Seebeck coefficient, the latter following at low temperature a Mott-type formula with a dot transmission renormalized by inelasticity. Interestingly, in the nonlinear regime of transport we find $\Delta_E\neq\Delta_C$ and this asymmetry departure depends on the applied bias configuration. Our results may be important for the recent experiments by Lee et al. [Nature (London) 498, 209 (2013)], where these asymmetries were measured.Comment: 9 pages, 5 figures. Minor changes; published versio

A Multifunctional Comparison of Conventional versus Alternative Olive Systems in Spain by Using AHP

Sustainability of agriculture is strongly related to the multifunctional role implicitly or explicitly recognized to it in the framework of the European Union CAP. This multifunctional role entails a multicriteria approach when assessing the performance and value for society of farming systems. Multicriteria assessment of agricultural systems is characterized by the existence of many criteria often conflicting among then, many stakeholders and decision-makers with competing interests, and lack of information. Analytic Hierarchy Process (AHP) is a multicriteria methodology that allows dealing with these problems, in a relatively easy, flexible and economical manner, and therefore it is a potentially useful tool in this field, although its application with this purpose has not been found in the literature. Therefore, this paper aims (1) to present AHP as a useful methodology to effectively assess and compare the multifunctional performances of agricultural systems, and (2) to apply AHP in the comparison, on the basis of experts' knowledge, of multiple functions -economic, technical, sociocultural and environmental- of conventional, organic and integrated olive producing systems in a region of Spain, and test the hypothetical superiority of the alternative systems with respect to the conventional one in the medium/long term and the average conditions of the region. Results confirm this global superiority thus providing a scientific base to endorse institutional and social support regarding the promotion and implementation of these alternative farming techniques. However, environmental issues are the more conflictive among experts and require a more in depth research in the future to clarify many of them.organic farming, integrated farming, olive-growing systems, AHP, multicriteria analysis., Crop Production/Industries, Q50, Q57, Q51, Q56, C6,