Localization of Spatially Distributed Near-Field Sources with Unknown Angular Spread Shape

International audienceIn this paper, we propose to localize and characterize coherently distributed (CD) sources in near-field. Indeed, it appears that in some applications, the more the sources are close to the array of sensors, the more they can seem scattered. It thus appears of the biggest importance to take into account the angular distribution of the sources in the joint direction of arrival (DOA) and range estimation methods. The methods of the literature which consider the problem of distributed sources do not handle with the case of near field sources and require that the shape of the dispersion is known. The main contribution of the proposed method is to estimate the shape of the angular distribution using an additional shape parameter to address the case of unknown distributions. We propose to jointly estimate the DOA, the range, the spread angle and the shape of the spread distribution. Accurate estimation is then achieved even when the shape of the angular spread distribution is unknown or imperfectly known. Moreover, the proposed estimator improves angular resolution of the sources

RIS-assisted Cell-Free MIMO with Dynamic Arrivals and Departures of Users: A Novel Network Stability Approach

Reconfigurable Intelligent Surfaces (RIS) have recently emerged as a hot research topic, being widely advocated as a candidate technology for next generation wireless communications. These surfaces passively alter the behavior of propagation environments enhancing the performance of wireless communication systems. In this paper, we study the use of RIS in cell-free multiple-input multiple-output (MIMO) setting where distributed service antennas, called Access Points (APs), simultaneously serve the users in the network. While most existing works focus on the physical layer improvements RIS carry, less attention has been paid to the impact of dynamic arrivals and departures of the users. In such a case, ensuring the stability of the network is the main goal. For that, we propose an optimization framework of the phase shifts, for which we derived a low-complexity solution. We then provide a theoretical analysis of the network stability and show that our framework stabilizes the network whenever it is possible. We also prove that a low complexity solution of our framework stabilizes a guaranteed fraction (higher than 78.5%) of the stability region. We provide also numerical results that corroborate the theoretical claims

Localisation des sources distribuées en champ proche

National audienceLa plupart des algorithmes du traitement d'antennes ont été développés avec l'hypothèse de sources ponctuelles situées en champ lointain. Certaines applications physiques n'obéissent pas à cet hypothèse, ainsi l'extension angulaire en champ proche doit être prise en compte dans le modèle. Dans ce papier, on propose un modèle généralisé pour la caractérisation des sources ayant une extension angulaire dans un champ proche. Nous proposons ensuite un algorithme d'estimation conjointe de la direction d'arrivée nominale, de la dispersion angulaire autour de cette direction et de la distance séparant la source de l'antenne. La méthode est basée sur une généralisation de l'estimateur MUSIC sur le principe de la minimisation d'un produit scalaire entre un vecteur fonction du vecteur directeur et le vecteur propre bruit de la matrice de corrélation. Nous comparons notre méthode avec un estimateur MUSIC conventionnel (source ponctuelle en champ proche). Les résultats montrent que le nouvel estimateur est plus performant en réduisant l'erreur quadratique moyenne des estimés pour les sources distribuées en champ proche. L'estimateur proposé est comparé avec la borne de Cramer-Rao (BCR)

La lumière naturelle dans l’abbaye de Belmond et dans les églises médiévales de l’époque franque au Liban

La question de l’éclairement naturel dans les églises et édifices médiévaux est un vaste sujet qui touche plusieurs domaines (Reveyron 1999 : 165). Le sujet de la lumière comporte deux aspects assez différents mais complémentaires. La lumière est un facteur naturel qui est nécessaire à la vie ; elle permet le développement de l’Homme et de toutes les créatures et les espèces. Généralement, le soleil ordonne, en Asie et en Europe, les constructions religieuses (Thibaud 2000 : 248). De même, la lumière dans les lieux de culte est un élément indispensable aux fidèles pour la pratique du culte. Par ailleurs, l’apport de la religion dans la vie des fidèles est souvent considéré comme une lumière divine et une manne dans la vie quotidienne et les difficultés de la vie terrestre

Validation of the Arabic version of the Cohen perceived stress scale (PSS-10) among pregnant and postpartum women

<p>Abstract</p> <p>Background</p> <p>This study was conducted to evaluate the validity of the Arabic translation of the Cohen Perceived Stress Scale (PSS-10) in pregnant and postpartum women.</p> <p>Methods</p> <p>A sample of 268 women participated. These included 113 women in their third trimester of pregnancy, 97 in the postpartum period and 58 healthy female university students. GHQ-12 and EPDS were also administered to the participants. Internal consistency reliability, assessed using Cronbach's α, was 0.74.</p> <p>Results</p> <p>PSS-10 significantly correlated with both EPDS and GHQ12 (ρ = 0.58 and ρ = 0.48 respectively), and significantly increased with higher scores on stressful life events. PSS-10 scores were higher among university students who also recorded higher stressful life events scores.</p> <p>Conclusion</p> <p>The Arabic translated version of the PSS-10 showed reasonably adequate psychometric properties.</p

Federated Learning Games for Reconfigurable Intelligent Surfaces via Causal Representations

In this paper, we investigate the problem of robust Reconfigurable Intelligent Surface (RIS) phase-shifts configuration over heterogeneous communication environments. The problem is formulated as a distributed learning problem over different environments in a Federated Learning (FL) setting. Equivalently, this corresponds to a game played between multiple RISs, as learning agents, in heterogeneous environments. Using Invariant Risk Minimization (IRM) and its FL equivalent, dubbed FL Games, we solve the RIS configuration problem by learning invariant causal representations across multiple environments and then predicting the phases. The solution corresponds to playing according to Best Response Dynamics (BRD) which yields the Nash Equilibrium of the FL game. The representation learner and the phase predictor are modeled by two neural networks, and their performance is validated via simulations against other benchmarks from the literature. Our results show that causality-based learning yields a predictor that is 15% more accurate in unseen Out-of-Distribution (OoD) environments.Comment: 6 pages, 4 figure

Initial Access Optimization for RIS-assisted Millimeter Wave Wireless Networks

Reconfigurable Intelligent Surfaces (RIS) are considered a key enabler to achieve the vision of Smart Radio Environments, where the propagation environment can be programmed and controlled to enhance the efficiency of wireless systems. These surfaces correspond to planar sheets comprising a large number of small and low-cost reflecting elements whose parameters are adaptively selected with a programmable controller. Hence, by optimizing these coefficients, the information signals can be directed in a customized fashion. On the other hand, the initial access procedure used in 5G is beam sweeping, where the base station sequentially changes the active beam direction in order to scan all users in the cell. This conventional protocol results in an initial access latency. The aim of this paper is to minimize this delay by optimizing the activated beams in each timeslot, while leveraging the presence of the RIS in the network. The problem is formulated as a hard optimization problem. We propose an efficient solution based on jointly alternating optimization and Semi Definite Relaxation (SDR) techniques. Numerical results are provided to assess the superiority of our scheme as compared to conventional beam sweeping

Entre Cosmopolitisme Beyrouthin et Logiques Missionnaires, L'inauguration de la Loge Maçonnique la Chaine D'union en 1870

La première loge maçonnique de Beyrouth, la loge Palestine2, inscrite sur le matricule de la Grande Loge d'Écosse sous le numéro 415, a été fondée et consacrée en 1861 , au lendemain de la guerre civile qui a touché le Mont Liban et Damas. Elle a travaillé dans la régularité depuis sa fondation jusqu 'à sa mise en sommeil en 1868 ; elle a été réveillée vingt ans plus tard, en 1888, mais sera fermée en 18953. Est-il surprenant que Beyrouth ait ouvert la première loge maçonnique dans la région, cette ville cosmopolite accueillant depuis longtemps des minorités originaires de I 'Empire ottoman, de la Méditerranée et d' ailleurs ? Les Beyrouthins avaient été confrontés aux idées nouvelles, surtout celles prônées par les divers courants de pensées réformateurs, et cela dans une ambiance passionnée et enthousiaste d'échanges littéraires et scientifiques qui visaient au progrès des populations. Robert Morris, franc-maçon américain effectuant un voyage au Proche-Orient, a visité la loge Palestine en 1868. II y a rencontré des frères venus de Gaza au sud et de Bagdad à l'est, d'autres encore de Sidon, de Saint-Jean d'Acre, de Naplouse, de Damas, d'Alep, de Homs et d'ailleurs, et avoua être « convaincu que l'ouverture d'une ère nouvelle de progrès maçonnique sur la côte syrienne n'est pas loin

Cognitive Reserve Factors in a Developing Country: Education and Occupational Attainment Lower the Risk of Dementia in a Sample of Lebanese Older Adults.

Background: Dementia secondary to neurodegenerative diseases is prevalent among older adults and leads to social, psychological and economic burden on patients, caregivers and the community as a whole. Cognitive reserve factors such as education, and mental stimulation among others were hypothesized to contribute to the resilience against age-related cognitive impairment. Educational attainment, occupation complexity, physical activity, and leisure activity are explored in the context of protecting the older adults' cognitive function. We investigated the cognitive reserve effect on dementia, cognitive decline and impairment, and global cognitive function. Methods: This study is a secondary analysis of data from a cross-sectional, community-based cohort study that aimed at investigating factors associated with dementia and their prevalence. The sample was of 508 community based older adults in Lebanon, aged 65 years and above in addition to 502 informants designated by these older adults. Older adults and informants answered structured questionnaires administered by interviewers, as well as a physical assessment and a neurological examination. Older adults were diagnosed for dementia. Global cognitive function, depression, and cognitive decline were assessed. Results: Older adults with dementia had lower levels of education, and attained lower occupational complexity. Factors such as high education, complex occupation attainment, and leisure activity, significantly predicted better global cognitive function. An older adult who attained high education levels or high complexity level occupation was 7.1 or 4.6 times more likely to have better global cognitive function than another who attained lower education or complexity level occupation respectively. Conclusion: These results suggest that cognitive reserve factors ought to be taken into consideration clinically during the course of dementia diagnosis and when initiating community-based preventive strategies.The study was funded by the Fogarty International Center, American National Institutes of Health and National Institute on Aging, grant no. 1R21AG039333-01, under the program Brain Disorders in the Developing World: Research across the Lifespan (BRAIN). The content is exclusively the responsibility of the authors and is not representative of the funding agencies' views. The funding agency had no roles in the study design; in the collection, analysis, and interpretation of the data; in the writing of the report; or in the decision to submit the article for publication

Localisation de sources aéroacoustiques et imagerie à haute résolution

Localization of Coherently Distributed (CD) source presents a challenge in the array signal processing. Our work motivates the localization of aero-acoustic source based on its spatial extension. This challenge is practically ignored in the literature of acoustic imaging field where many applications consist in mapping noisy source to reduce its contribution. The thesis presents the three following contributions. First, we propose a Joint Angle, Distance, Spread and Shape Estimator called JADSSE. The estimation of the so-called spread shape distribution parameter proposed by JADSSE avoids the modeling error due to the required a priori knowledge on the source shape when using classical estimators. Second, we expand the Decoupled DSPE to the near field. This method decouples the Direction of Arrival (DoA) and the range estimation from the spread estimation. Meanwhile, this method prevents the spread estimation for unknown shape distribution. Therefore, we propose the DADSSE to successively estimate the DOA, the range and then the spread and the shape distribution of the source. Third, we generalize the CD model and the JADSSE to consider the bi-dimensional spread of the source. Next, we propose two source power estimation approaches accounting the spatial spread of the source. The proposed methods are tested using a set of experimental data of the Renault wind tunnel application. Results show the presence of new aero-acoustic sources especially the overlapped ones with weak powers. We provide a tool to better map and characterize the aero-acoustic source by estimating the position, spread, power and shape.La localisation de source Distribuée Cohérente (DC) présente un défi du traitement d'antenne. Les contributions de cette thèse s’articulent principalement autour de trois aspects. Premièrement, un estimateur conjoint de l'angle, la distance, la dispersion et la forme de la source appelée JADSSE est proposé pour le cas champ proche. L’estimation d’un paramètre de forme de distribution de la dispersion permet d’éviter des erreurs de modèles sur l’a priori de la forme de la distribution. Deuxièmement, on généralise l'estimateur Decoupled DSPE en champ proche. Cette approche permet de découpler l'estimation de la Direction D’Arrivée (DDA) et de la distance de l'estimation de la dispersion. Afin de permettre l’estimation de la dispersion sans connaître a priori les formes de distribution, on propose le DADSSE qui consiste à estimer successivement la DDA, la distance et ensuite la dispersion et la forme de la distribution de la source. Troisièmement, on généralise le modèle DC avec une dispersion spatiale bidimensionnelle de la source ainsi que l’estimateur JADSSE. Deux approches sont proposées pour l’estimation de la puissance prenant en compte le modèle d’étalement des sources. Les méthodes proposées sont testées sur les données expérimentales de la soufflerie de Renault. Les résultats mettent en évidence des sources aéro-acoustiques proches et de faibles puissances. L’ensemble de ces travaux permet de fournir un outil pour une meilleure cartographie et caractérisation des sources aéro-acoustiques grâce à l’estimation de la position, l'étalement, la puissance et la forme