Battery Recharging Time Models for Reconfigurable Intelligent Surface-Assisted Wireless Power Transfer Systems

In this paper, we develop an analytical framework for the statistical analysis of the battery recharging time (BRT) in reconfigurable intelligent surfaces (RISs) aided wireless power transfer (WPT) systems. Specifically, we derive novel closed-form expressions for the probability density function (PDF), cumulative distribution function, and moments of the BRT of the radio frequency energy harvesting wireless nodes. Moreover, closed-form expressions of the the PDF of the BRT is obtained for two special cases: i) when the RIS is equipped with one reflecting element (RE), ii) when the RIS consists of a large number of REs. Capitalizing on the derived expressions, we offer a comprehensive treatment for the statistical characterization of the BRT and study the impact of the system and battery parameters on its performance. Our results reveal that the proposed statistical models are analytically tractable, accurate, and efficient in assessing the sustainability of RIS-assisted WPT networks and in providing key design insights for large-scale future wireless applications. For example, we demonstrate that a 4-fold reduction in the mean time of the BRT can be achieved by doubling the number of RIS elements. Monte Carlo simulation results corroborate the accuracy of the proposed theoretical framework

Prédiction et gestion de l’énergie dans un réseau de capteurs sans fil récolteurs d’énergie vibratoire pour les applications industrielles de l’internet des objets

La question de l’autonomie énergétique des capteurs sans fil (WS pour Wireless Sensor), indispensables pour l’automatisation de nombreux procédés industriels, est aujourd’hui une limite fondamentale dans l’atteinte des objectifs de l’industrie 4.0. Pour surmonter cette limite, la piste de solution la plus prometteuse est celle de la récolte de l’énergie ambiante (EH pour Energy Harvesting). L’EH consiste à identifier une source d’énergie primaire (soleil, vibrations, ondes radiofréquences, chaleur, etc.), disponible dans l’environnement immédiat du capteur et de la transformer en énergie électrique pour son alimentation. Cette thèse est une contribution dans ce domaine de recherche en pleine expansion, pour des applications dans l’environnement industriel. Les vibrations qui abondent dans la plupart des procédés industriels sont considérées comme source d’alimentation des WS capables de remplacer les capteurs filés actuellement utilisés. Prenant en considération le caractère aléatoire de la quantité d’énergie récoltable, deux contributions majeures sont proposées dans cette thèse à savoir la conception d’un Prédicteur de l’Énergie Récoltable des vibrations (PERV) et la mise en place d’une solution permettant de gérer efficacement l’énergie récoltée à travers un Protocole Hiérarchique à Équilibrage d’Énergie (PHEE). La conception du PERV est basée sur des données de vibrations enregistrées à 12 emplacements différents, et ce pendant un mois, sur le processus de concassage des minerais par un broyeur semiautogène. La périodicité observée dans les signaux est exploitée pour minimiser la quantité de données devant être stockées pour l’estimation de la puissance à un instant donné. Les performances du PERV sont ensuite comparées à un prédicteur de l’état de l’art le EWMA (Exponentially Weighted Moving-Average qui utilise l’historique des données d’énergie pour estimer les quantités d’énergie récoltable dans le futur) et il est obtenu que l’erreur quadratique moyenne pour les 12 points de mesure subie des améliorations allant de 10 % à 90.5 % comparé au prédicteur EWMA. Le PERV permet ainsi d’augmenter la précision dans la prédiction tout en réduisant la quantité des données devant être stockées. Sous la base de l’énergie prédite, le PHEE est conçu avec pour objectif d’optimiser à la fois la Qualité de Service individuelle de chacun des noeuds, mais aussi celle du réseau en entier. De façon plus spécifique, sous la base de l’énergie prédite, les noeuds capteurs contrôlant le procédé sont capables d'opérer de façon perpétuelle lorsque le coût énergétique par cycle de mesure est inférieur à 160

African Handbook of Climate Change Adaptation

This open access book discusses current thinking and presents the main issues and challenges associated with climate change in Africa. It introduces evidences from studies and projects which show how climate change adaptation is being - and may continue to be successfully implemented in African countries. Thanks to its scope and wide range of themes surrounding climate change, the ambition is that this book will be a lead publication on the topic, which may be regularly updated and hence capture further works. Climate change is a major global challenge. However, some geographical regions are more severly affected than others. One of these regions is the African continent. Due to a combination of unfavourable socio-economic and meteorological conditions, African countries are particularly vulnerable to climate change and its impacts. The recently released IPCC special report "Global Warming of 1.5º C" outlines the fact that keeping global warming by the level of 1.5º C is possible, but also suggested that an increase by 2º C could lead to crises with crops (agriculture fed by rain could drop by 50% in some African countries by 2020) and livestock production, could damage water supplies and pose an additonal threat to coastal areas. The 5th Assessment Report produced by IPCC predicts that wheat may disappear from Africa by 2080, and that maize— a staple—will fall significantly in southern Africa. Also, arid and semi-arid lands are likely to increase by up to 8%, with severe ramifications for livelihoods, poverty eradication and meeting the SDGs. Pursuing appropriate adaptation strategies is thus vital, in order to address the current and future challenges posed by a changing climate. It is against this background that the "African Handbook of Climate Change Adaptation" is being published. It contains papers prepared by scholars, representatives from social movements, practitioners and members of governmental agencies, undertaking research and/or executing climate change projects in Africa, and working with communities across the African continent. Encompassing over 100 contribtions from across Africa, it is the most comprehensive publication on climate change adaptation in Africa ever produced

Performance analysis for wireless G (IEEE 802.11G) and wireless N (IEEE 802.11N) in outdoor environment

This paper described an analysis the different capabilities and limitation of both IEEE technologies that has been utilized for data transmission directed to mobile device. In this work, we have compared an IEEE 802.11/g/n outdoor environment to know what technology is better. The comparison consider on coverage area (mobility), throughput and measuring the interferences. The work presented here is to help the researchers to select the best technology depending of their deploying case, and investigate the best variant for outdoor. The tool used is Iperf software which is to measure the data transmission performance of IEEE 802.11n and IEEE 802.11g

Performance Analysis For Wireless G (IEEE 802.11 G) And Wireless N (IEEE 802.11 N) In Outdoor Environment

This paper described an analysis the different capabilities and limitation of both IEEE technologies that has been utilized for data transmission directed to mobile device. In this work, we have compared an IEEE 802.11/g/n outdoor environment to know what technology is better. the comparison consider on coverage area (mobility), through put and measuring the interferences. The work presented here is to help the researchers to select the best technology depending of their deploying case, and investigate the best variant for outdoor. The tool used is Iperf software which is to measure the data transmission performance of IEEE 802.11n and IEEE 802.11g