A Contribution to Secure the Routing Protocol "Greedy Perimeter Stateless Routing" Using a Symmetric Signature-Based AES and MD5 Hash

This work presents a contribution to secure the routing protocol GPSR (Greedy Perimeter Stateless Routing) for vehicular ad hoc networks, we examine the possible attacks against GPSR and security solutions proposed by different research teams working on ad hoc network security. Then, we propose a solution to secure GPSR packet by adding a digital signature based on symmetric cryptography generated using the AES algorithm and the MD5 hash function more suited to a mobile environment

Caracterización experimental y modelado numérico de una instalación para la generación de ACS con bomba de calor

[SPA] En esta tesis, la eficiencia energética de una bomba de calor trans-crítica de CO2 acoplada a un tanque de almacenamiento de agua caliente para la producción de agua caliente sanitaria se caracteriza y analiza bajo la norma europea EN16147. Se desarrollado una instalación experimental para realizar los ensayos mencionados en la norma y determinar el rendimiento termodinámico de la bomba de calor y el rendimiento energético del sistema de generación de agua caliente sanitaria. Las condiciones de los ensayos de este estudio se realizaron según las condiciones de la norma europea EN16147. Al principio, se estudiaron dos configuraciones de la bomba de calor, con y sin intercambiador de calor interno bajo las mismas condiciones de funcionamiento para mostrar el impacto del intercambiador de calor interno en el rendimiento termodinámico de la bomba de calor de CO2. Los resultados mostraron que la introducción de un intercambiador de calor interno da un mejor rendimiento termodinámico. El COP global de los ciclos con y sin intercambiador de calor interno tenía el valor de 3.28 y 3.14 respectivamente, lo que significa que el COP global del sistema se mejora de aproximadamente 4.42% al agregar el intercambiador de calor interno. Luego, se realizaron tres pruebas principales bajo las condiciones del estándar: el paso de calentamiento, el paso de enfriamiento y el paso del perfil de carga. El proceso de calentamiento del tanque de almacenamiento se llevó a cabo bajo varias condiciones de caudal de gas cooler y varias temperaturas de entrada del evaporador con el objetivo de determinar y caracterizar la evolución temporal del COP de la bomba de calor y analizar el rendimiento termo-hidráulico de la estratificación dentro del tanque de almacenamiento bajo estas condiciones de operación. Los resultados mostraron que el caudal del gas cooler tiene un impacto importante en la estratificación térmica dentro del tanque de almacenamiento. Los caudales más bajos del gas cooler dan una mejor estratificación y un mejor COP. El proceso de extracción y el proceso de enfriamiento también se realizan y analizan bajo las condiciones de perfil de extracción 3XL. Los resultados del proceso de extracción según el perfil 3XL, muestran que la bomba de calor se pone en marcha tras la cuarta extracción y el proceso de calentamiento de este ensayo tarda 6 horas hasta que el tanque de almacenamiento se calienta de nuevo a 60 ºC, y se obtiene un COP global de 2,89. La caracterización del proceso de enfriamiento del tanque de almacenamiento se realizó bajo tres caudales de extracción. Los resultados muestran que, a medida que aumenta el caudal de extracción, el tiempo de enfriamiento disminuye. Además, se desarrolló y discretizó un nuevo modelo numérico de un tanque de almacenamiento estratificado utilizando el método de diferencia finita para su uso en simulación numérica utilizando el software TRNSYS. La comparación de los resultados numéricos con los resultados obtenidos de la configuración experimental mostró una buena concordancia.[ENG] In this thesis, the energetic efficiency of a trans-critical CO2 heat pump coupled to a hot water storage tank for domestic hot water production is characterized and analyzed under the European standard EN16147. An experimental facility is set up in order to realize the tests mentioned in the standard and determine the thermodynamic performance of the heat pump and the energetic performance of the domestic hot water generation system. The tests conditions of this study were performed according the European standard EN16147 conditions. In the beginning, two configurations of the heat pump, with and without internal heat exchanger were studied under the same operating conditions to show the impact of the internal heat exchanger on the thermodynamic performance of the CO2 heat pump. The results showed that the introduction of an internal heat exchanger give better thermodynamic performance. The global COP of the cycles with and without internal heat exchanger had the value of 3.28 and 3.14 respectively, which means that the global COP of the system is enhanced of about 4.42% by adding the internal heat exchanger. Then, three main tests were realized under the standard´s conditions: the heating step, the cooling step, and the load profile step. The heating process of the storage tank was effectuated under various gas cooler flowrate conditions and various evaporator inlet temperature with objective to determine and characterize the time evolution of the COP of the heat pump and analyze the thermo-hydraulic performance of the stratification within the storage tank under these operating conditions. results showed that the gas cooler flowrate plays important role on the thermal stratification inside the storage tank. Lower gas cooler flowrates give better stratification, and better COP. The extraction process and the cooling process also are performed and analyzed under the 3XL extraction profile conditions. The results of the extraction process according to the 3XL profile, show that the heat pump starts up after the fourth extraction and the heating process of this step take time of 6 hours until the storage tank heated up again to 60 ºC, and globa COP of 2.89 is obtained. The characterization of the cooling process of the storage tank was performed under three extraction flowrates. Results show that, as the extraction flowrate increases, the cooling time decreases. In addition, a new numerical model of a stratified storage tank was developed and discretized using the finite difference method for the use in numerical simulation using TRNSYS software. The comparison of the numerical results with the results obtained from the experimental set up showed a good agreement.Escuela Internacional de Doctorado de la Universidad Politécnica de CartagenaUniversidad Politécnica de CartagenaPrograma de doctorado en Energías Renovables y Eficiencia Energétic

On The Feasibility Of Centrally-Coordinated Peer-To-Peer Live Streaming

In this paper we present an exploration of central coordination as a way of managing P2P live streaming overlays. The main point is to show the elements needed to construct a system with that approach. A key element in the feasibility of this approach is a near real-time optimization engine for peer selection. Peer organization in a way that enables high bandwidth utilization plus optimized peer selection based on multiple utility factors make it possible to achieve large source bandwidth savings and provide high quality of user experience. The benefits of our approach are also seen most when NAT constraints come into play

A Risk-Averse Framework for Non-Stationary Stochastic Multi-Armed Bandits

In a typical stochastic multi-armed bandit problem, the objective is often to maximize the expected sum of rewards over some time horizon $T$. While the choice of a strategy that accomplishes that is optimal with no additional information, it is no longer the case when provided additional environment-specific knowledge. In particular, in areas of high volatility like healthcare or finance, a naive reward maximization approach often does not accurately capture the complexity of the learning problem and results in unreliable solutions. To tackle problems of this nature, we propose a framework of adaptive risk-aware strategies that operate in non-stationary environments. Our framework incorporates various risk measures prevalent in the literature to map multiple families of multi-armed bandit algorithms into a risk-sensitive setting. In addition, we equip the resulting algorithms with the Restarted Bayesian Online Change-Point Detection (R-BOCPD) algorithm and impose a (tunable) forced exploration strategy to detect local (per-arm) switches. We provide finite-time theoretical guarantees and an asymptotic regret bound of order $\tilde O(\sqrt{K_T T})$ up to time horizon $T$ with $K_T$ the total number of change-points. In practice, our framework compares favorably to the state-of-the-art in both synthetic and real-world environments and manages to perform efficiently with respect to both risk-sensitivity and non-stationarity

Introduction to Traffic-Sign Classification with Parallel CNNs Using Semantic Adversarial Examples

This work presents a new CNN based architecture for the classification of Traffic Signs. It is based on the fact that current solutions for Traffic Signs Recognition lose their effectiveness when the input data have been subject to special transformations, which are part of the Semantic Adversarial Examples. These transformations do not modify the main features of the image but change dramatically the pixel space of the image. The proposed architecture uses CNNs mounted in parallel, each one processes a version of the input image, each version having undergone a particular transformation. The other parts of the network combine features extracted by CNNs while preserving spatial information, allowing the network to prioritize the most important features.This article will present the state of the art in the field of TSR and will detail the components of the network. A future article will present the details of the implementation and the results obtained and will establish a benchmark of the different possible configurations by comparing them with the other techniques used in the TSR

Cas rare de sangsue laryngée chez un homme de 70 ans

La dyspnée laryngée représente une urgence extrême en otorhinolaryngologies. Elle répond à des étiologies multiples et reste souvent graves. La dyspnée laryngée causée par une sangsue est exceptionnellement décrite dans la littérature surtout chez l’adulte. Nous rapportons une observation particulière d’infestation de l’arbre respiratoire par une sangsue ayant entraîné une dyspnée laryngée