PUE attack detection in CWSN using collaboration and learning behavior

Cognitive Wireless Sensor Network (CWSN) is a new paradigm which integrates cognitive features in traditional Wireless Sensor Networks (WSNs) to mitigate important problems such as spectrum occupancy. Security in Cognitive Wireless Sensor Networks is an important problem because these kinds of networks manage critical applications and data. Moreover, the specific constraints of WSN make the problem even more critical. However, effective solutions have not been implemented yet. Among the specific attacks derived from new cognitive features, the one most studied is the Primary User Emulation (PUE) attack. This paper discusses a new approach, based on anomaly behavior detection and collaboration, to detect the PUE attack in CWSN scenarios. A nonparametric CUSUM algorithm, suitable for low resource networks like CWSN, has been used in this work. The algorithm has been tested using a cognitive simulator that brings important results in this area. For example, the result shows that the number of collaborative nodes is the most important parameter in order to improve the PUE attack detection rates. If the 20% of the nodes collaborates, the PUE detection reaches the 98% with less than 1% of false positives.

Automatic design of Ant Colony Optimization for permutation problems

In this study, we present a framework based on ant colony optimization (ACO) for tackling combinatorial problems. ACO algorithms have been applied to many diferent problems, focusing on algorithmic variants that obtain high-quality solutions. Usually, the implementations are re-done for various problem even if they maintain the same details of the ACO algorithm. However, our goal is to generate a sustainable framework for applications on permutation problems. We concentrate on understanding the behavior of pheromone trails and specific methods that can be combined. Eventually, we will propose an automatic offline configuration tool to build an efective algorithm. ---RESUMEN---En este trabajo vamos a presentar un framework basado en la familia de algoritmos ant colony optimization (ACO), los cuales están dise~nados para enfrentarse a problemas combinacionales. Los algoritmos ACO han sido aplicados a diversos problemas, centrándose los investigadores en diversas variantes que obtienen buenas soluciones. Normalmente, las implementaciones se tienen que rehacer, inclusos si se mantienen los mismos detalles para los algoritmos ACO. Sin embargo, nuestro objetivo es generar un framework sostenible para aplicaciones sobre problemas de permutaciones. Nos centraremos en comprender el comportamiento de la sendas de feromonas y ciertos métodos con los que pueden ser combinados. Finalmente, propondremos una herramienta para la configuraron automática offline para construir algoritmos eficientes.

Distributed Estimation of Distribution Algorithms for continuous optimization: how does the exchanged information influence their behavior?

One of the most promising areas in which probabilistic graphical models have shown an incipient activity is the field of heuristic optimization and, in particular, in Estimation of Distribution Algorithms. Due to their inherent parallelism, different research lines have been studied trying to improve Estimation of Distribution Algorithms from the point of view of execution time and/or accuracy. Among these proposals, we focus on the so-called distributed or island-based models. This approach defines several islands (algorithms instances) running independently and exchanging information with a given frequency. The information sent by the islands can be either a set of individuals or a probabilistic model. This paper presents a comparative study for a distributed univariate Estimation of Distribution Algorithm and a multivariate version, paying special attention to the comparison of two alternative methods for exchanging information, over a wide set of parameters and problems ? the standard benchmark developed for the IEEE Workshop on Evolutionary Algorithms and other Metaheuristics for Continuous Optimization Problems of the ISDA 2009 Conference. Several analyses from different points of view have been conducted to analyze both the influence of the parameters and the relationships between them including a characterization of the configurations according to their behavior on the proposed benchmark.

Analysis of the problems associated with dynamic interaction between train, track and structure at transition zones

El gran desarrollo experimentado por la alta velocidad en los principales países de la Unión Europea, en los últimos 30 años, hace que este campo haya sido y aún sea uno de los principales referentes en lo que a investigación se refiere. Por otra parte, la aparición del concepto super − alta velocidad hace que la investigación en el campo de la ingeniería ferroviaria siga adquiriendo importancia en los principales centros de investigación de los países en los que se desea implantar este modo de transporte, o en los que habiendo sido ya implantado, se pretenda mejorar. Las premisas de eficacia, eficiencia, seguridad y confort, que este medio de transporte tiene como razón de ser pueden verse comprometidas por diversos factores. Las zonas de transición, definidas en la ingeniería ferroviaria como aquellas secciones en las que se produce un cambio en las condiciones de soporte de la vía, pueden afectar al normal comportamiento para el que fue diseñada la infraestructura, comprometiendo seriamente los estándares de eficiencia en el tiempo de viaje, confort de los pasajeros y aumentando considerablemente los costes de mantenimiento de la vía, si no se toman las medidas oportunas. En esta tesis se realiza un estudio detallado de la zonas de transición, concretamente de aquellas en las que existe una cambio en la rigidez vertical de la vía debido a la presencia de un marco hidráulico. Para realizar dicho estudio se lleva a cabo un análisis numérico de interacción entre el vehículo y la estructura, con un modelo bidimensional de elemento finitos, calibrado experimentalmente, en estado de tensión plana. En este análisis se tiene en cuenta el efecto de las irregularidades de la vía y el comportamiento mecánico de la interfaz suelo-estructura, con el objetivo de reproducir de la forma más real posible el efecto de interacción entre el vehículo, la vía y la estructura. Otros efectos como la influencia de la velocidad del tren y los asientos diferenciales, debidos a deformaciones por consolidación de los terraplenes a ambos lados el marco hidráulico, son también analizados en este trabajo. En esta tesis, los cálculos de interacción se han llevado a cabo en dos fases diferentes. En la primera, se ha considerado una interacción sencilla debida al paso de un bogie de un tren Eurostar. Los cálculos derivados de esta fase se han denominado cálculos a corto plazo. En la segunda, se ha realizado un análisis considerando múltiples pasos de bogie del tren Eurostar, conformando un análisis de degradación en el que se tiene en cuenta, en cada ciclo, la deformación de la capa de balasto. Los cálculos derivados de esta fase, son denominados en el texto como cálculos a largo plazo. Los resultados analizados muestran que la utilización de los denominados elementos de contacto es fundamental cuando se desea estudiar la influencia de asientos diferenciales, especialmente en transiciones terraplén-estructura en las que la cuña de cimentación no llega hasta la base de cimentación de la estructura. Por otra parte, tener en cuenta los asientos del terraplén, es sumamente importante, cuando se desea realizar un análisis de degradación de la vía ya que su influencia en la interacción entre el vehículo y la vía es muy elevada, especialmente para valores altos de velocidad del tren. En cuanto a la influencia de las irregularidades de la vía, en los cálculos efectuados, se revela que su importancia es muy notable, siendo su influencia muy destacada cuanto mayor sea la velocidad del tren. En este punto cabe destacar la diferencia de resultados derivada de la consideración de perfiles de irregularidades de distinta naturaleza. Los resultados provenientes de considerar perfiles artificiales son en general muy elevados, siendo estos más apropiados para realizar estudios de otra índole, como por ejemplo de seguridad al descarrilamiento. Los resultados provenientes de perfiles reales, dados por diferentes Administradores ferroviarios, presentan resultados menos elevados y más propios del problema analizar. Su influencia en la interacción dinámica entre el vehículo y la vía es muy importante, especialmente para velocidades elevadas del tren. Además el fenómeno de degradación conocido como danza de traviesas, asociado a zonas de transición, es muy susceptible a la consideración de irregularidades de la vía, tal y como se desprende de los cálculos efectuados a largo plazo. The major development experienced by high speed in the main countries of the European Union, in the last 30 years, makes railway research one of the main references in the research field. It should also be mentioned that the emergence of the concept superhigh − speed makes research in the field of Railway Engineering continues to gain importance in major research centers in the countries in which this mode of transportation is already implemented or planned to be implemented. The characteristics that this transport has as rationale such as: effectiveness, efficiency, safety and comfort, may be compromised by several factors. The transition zones are defined in railway engineering as a region in which there is an abrupt change of track stiffness. This stiffness variation can affect the normal behavior for which the infrastructure has been designed, seriously compromising efficiency standards in the travel time, passenger comfort and significantly increasing the costs of track maintenance, if appropriate measures are not taken. In this thesis a detailed study of the transition zones has been performed, particularly of those in which there is a change in vertical stiffness of the track due to the presence of a reinforced concrete culvert. To perform such a study a numerical interaction analysis between the vehicle, the track and the structure has been developed. With this purpose a two-dimensional finite element model, experimentally calibrated, in a state of plane stress, has been used. The implemented numerical models have considered the effects of track irregularities and mechanical behavior of soil-structure interface, with the objective of reproducing as accurately as possible the dynamic interaction between the vehicle the track and the structure. Other effects such as the influence of train speed and differential settlement, due to secondary consolidation of the embankments on both sides of culvert, have also been analyzed. In this work, the interaction analysis has been carried out in two different phases. In the first part a simple interaction due to the passage of a bogie of a Eurostar train has been considered. Calculations derived from this phase have been named short-term analysis. In the second part, a multi-load assessment considering an Eurostar train bogie moving along the transition zone, has been performed. The objective here is to simulate a degradation process in which vertical deformation of the ballast layer was considered. Calculations derived from this phase have been named long-term analysis. The analyzed results show that the use of so-called contact elements is essential when one wants to analyze the influence of differential settlements, especially in embankment-structure transitions in which the wedge-shaped backfill does not reach the foundation base of the structure. Moreover, considering embankment settlement is extremely important when it is desired to perform an analysis of track degradation. In these cases the influence on the interaction behaviour between the vehicle and the track is very high, especially for higher values of speed train. Regarding the influence of the track irregularities, this study has proven that the track’s dynamic response is heavily influenced by the irregularity profile and that this influence is more important for higher train velocities. It should also be noted that the difference in results derived from consideration of irregularities profiles of different nature. The results coming from artificial profiles are generally very high, these might be more appropriate in order to study other effects, such as derailment safety. Results from real profiles, given by the monitoring works of different rail Managers, are softer and they fit better to the context of this thesis. The influence of irregularity profiles on the dynamic interaction between the train and the track is very important, especially for high-speeds of the train. Furthermore, the degradation phenomenon known as hanging sleepers, associated with transition zones, is very susceptible to the consideration of track irregularities, as it can be concluded from the long-term analysis.

Critical behavior of the dilute antiferromagnet in a magnetic field

We study the critical behavior of the diluted antiferromagnet in a field with the tethered Monte Carlo formalism. We compute the critical exponents (including the elusive hyperscaling violations exponent θ). Our results provide a comprehensive description of the phase transition and clarify the inconsistencies between previous experimental and theoretical work. To do so, our method addresses the usual problems of numerical work (large tunneling barriers and self-averaging violations).

Logic-Based Outer-Approximation Algorithm for Solving Discrete-Continuous Dynamic Optimization Problems

We present an extension of the logic outer-approximation algorithm for dealing with disjunctive discrete-continuous optimal control problems whose dynamic behavior is modeled in terms of differential-algebraic equations. Although the proposed algorithm can be applied to a wide variety of discrete-continuous optimal control problems, we are mainly interested in problems where disjunctions are also present. Disjunctions are included to take into account only certain parts of the underlying model which become relevant under some processing conditions. By doing so the numerical robustness of the optimization algorithm improves since those parts of the model that are not active are discarded leading to a reduced size problem and avoiding potential model singularities. We test the proposed algorithm using three examples of different complex dynamic behavior. In all the case studies the number of iterations and the computational effort required to obtain the optimal solutions is modest and the solutions are relatively easy to find.

Global behavior of the Douglas–Rachford method for a nonconvex feasibility problem

In recent times the Douglas–Rachford algorithm has been observed empirically to solve a variety of nonconvex feasibility problems including those of a combinatorial nature. For many of these problems current theory is not sufficient to explain this observed success and is mainly concerned with questions of local convergence. In this paper we analyze global behavior of the method for finding a point in the intersection of a half-space and a potentially non-convex set which is assumed to satisfy a well-quasi-ordering property or a property weaker than compactness. In particular, the special case in which the second set is finite is covered by our framework and provides a prototypical setting for combinatorial optimization problems.

Essays on coordination problems in economics

No estudo da economia, há diversas situações em que a propensão de um indivíduo a tomar determinada ação é crescente na quantidade de outras pessoas que este indivíduo acredita que tomarão a mesma ação. Esse tipo de complementaridade estratégica geralmente leva à existência de múltiplos equilíbrios. Além disso, o resultado atingido pelas decisões decentralizadas dos agentes pode ser ineficiente, deixando espaço para intervenções de política econômica. Esta tese estuda diferentes ambientes em que a coordenação entre indivíduos é importante. O primeiro capítulo analisa como a manipulação de informação e a divulgação de informação afetam a coordenação entre investidores e o bem-estar em um modelo de corridas bancárias. No modelo, há uma autoridade reguladora que não pode se comprometer a revelar a verdadeira situação do setor bancário. O regulador observa informações idiossincráticas dos bancos (através de um stress test, por exemplo) e escolhe se revela essa informação para o público ou se divulga somente um relatório agregado sobre a saúde do sistema financeiro como um todo. O relatório agregado pode ser distorcido a um custo – um custo mais elevado significa maior credibilidade do regulador. Os investidores estão cientes dos incentivos do regulador a esconder más notícias do mercado, mas a manipulação de informação pode, ainda assim, ser efetiva. Se a credibilidade do regulador não for muito baixa, a política de divulgação de informação é estado-contingente, e existe sempre um conjunto de estados em que há manipulação de informação em equilíbrio. Se a credibilidade for suficientemente baixa, porém, o regulador opta por transparência total dos resultados banco-específicos, caso em que somente os bancos mais sólidos sobrevivem. Uma política de opacidade levaria a uma crise bancária sistêmica, independentemente do estado. O nível de credibilidade que maximiza o bem-estar agregado do ponto de vista ex ante é interior. O segundo e o terceiro capítulos estudam problemas de coordenação dinâmicos. O segundo capítulo analisa o bem-estar em um ambiente em que agentes recebem oportunidades aleatórias para migrar entre duas redes. Os resultados mostram que sempre que a rede de pior qualidade (intrínseca) prevalece, isto é eficiente. Na verdade, um planejador central estaria ainda mais inclinado a escolher a rede de pior qualidade. Em equilíbrio, pode haver mudanças ineficientes que ampliem a rede de qualidade superior. Quando indivíduos escolhem entre dois padrões ou redes com níveis de qualidade diferentes, se todos os indivíduos fizessem escolhas simultâneas, a solução eficiente seria que todos adotassem a rede de melhor qualidade. No entanto, quando há fricções e os agentes tomam decisões escalonadas, a solução eficiente difere ix do senso comum. O terceiro capítulo analisa um problema de coordenação dinâmico com decisões escalonadas em que os agentes são heterogêneos ex ante. No modelo, existe um único equilíbrio, caracterizado por thresholds que determinam as escolhas para cada tipo de agente. Apesar da heterogeneidade nos payoffs, há bastante conformidade nas ações individuais em equilíbrio. Os thresholds de diferentes tipos de agentes coincidem parcialmente contanto que exista um conjunto de crenças arbitrário que justifique esta conformidade. No entanto, as estratégias de equilíbrio de diferentes tipos nunca coincidem totalmente. Além disso, a conformidade não é ineficiente. A solução eficiente apresentaria estratégias ainda mais similares para tipos distintos em comparação com o equilíbrio decentralizado.

Costs and problems of completing the interstate highway system; report to the Congress.

Mode of access: Internet.

Urban intersection improvements for pedestrian safety. Volume II. Identification of safety and operational problems at intersections. Final report.

Federal Highway Administration, Office of Research and Development, Washington, D.C.

Solving public passenger transportation problems: a need for policy reorientation. Final report. Volume II.

Transportation Department, Office of University Research, Washington, D.C.

Highway operation problems of senior drivers in Illinois. Final report.

Illinois State Department of Transportation, Springfield

Comparative evaluation of microscopic car-following behavior

Microscopic traffic-simulation tools are increasingly being applied to evaluate the impacts of a wide variety of intelligent transport, systems (ITS) applications and other dynamic problems that are difficult to solve using traditional analytical models. The accuracy of a traffic-simulation system depends highly on the quality of the traffic-flow model at its core, with the two main critical components being the car-following and lane-changing models. This paper presents findings from a comparative evaluation of car-following behavior in a number of traffic simulators [advanced interactive microscopic simulator for urban and nonurban networks (AIMSUN), parallel microscopic simulation (PARAMICS), and Verkehr in Statiten-simulation (VISSIM)]. The car-following algorithms used in these simulators have been developed from a variety of theoretical backgrounds and are reported to have been calibrated on a number of different data sets. Very few independent studies have attempted to evaluate the performance of the underlying algorithms based on the same data set. The results reported in this study are based on a car-following experiment that used instrumented vehicles to record the speed and relative distance between follower and leader vehicles on a one-lane road. The experiment was replicated in each tool and the simulated car-following behavior was compared to the field data using a number of error tests. The results showed lower error values for the Gipps-based models implemented in AIMSUN and similar error values for the psychophysical spacing models used in VISSIM and PARAMICS. A qualitative drift and goal-seeking behavior test, which essentially shows how the distance headway between leader and follower vehicles should oscillate around a stable distance, also confirmed the findings.

A genetically informed study of the association between harsh punishment and offspring behavioral problems

Conclusions about the effects of harsh parenting on children have been limited by research designs that cannot control for genetic or shared environmental confounds. The present study used a sample of children of twins and a hierarchical linear modeling statistical approach to analyze the consequences of varying levels of punishment while controlling for many confounding influences. The sample of 887 twin pairs and 2,554 children came from the Australian Twin Registry. Although corporal punishment per se did not have significant associations with negative childhood outcomes, harsher forms of physical punishment did appear to have specific and significant effects. The observed association between harsh physical punishment and negative outcomes in children survived a relatively rigorous test of its causal status, thereby increasing the authors' conviction that harsh physical punishment is a serious risk factor for children.

Household waste recycling behavior: a market segmentation model

The potential of social marketing has been recognized in the United Kingdom by the Department for Environment, Food and Rural Affairs (DEFRA) as a useful tool for behavioral change for environmental problems. The techniques of social marketing have been used successfully by health organizations to tackle current public health issues. This article describes a research project which explored the current barriers to recycling household waste and the development of a segmentation model which could be used at the local level by authorities charged with waste collection and disposal. The research makes a unique contribution to social marketing through the introduction of a competencies framework and market segmentation for recycling behaviors.