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Performance Evaluation of Massive MIMO with Beamforming and Non Orthogonal Multiple Access based on Practical Channel Measurements
No full textInternational audienceThis paper presents a comprehensive performance analysis of a massive multiple-input multiple-output (MIMO) system using non-orthogonal multiple access (NOMA) in both indoor and outdoor environments, based on practical channel measurements. The latter are performed using frequency-domain channel sounding experiments conducted at 3.5 GHz with 18 MHz bandwidth. Multiuser beamforming and NOMA clustering are used in the massive MIMO system. The system performance is evaluated in terms of sum-rate capacity for two precoding schemes: zero-forcing (ZF) and maximum ratio transmission (MRT). Two inter-beam power allocation (PA) schemes are investigated: equal PA and water filling. Fractional transmit PA (FTPA) is used to perform intra-cluster PA between paired users. The study allows the identification of practical scenarios that are propitious to NOMA with beamforming. Results show that NOMA is particularly interesting with MRT, compared to ZF, especially when combined with water filling. However, ZF generally outperforms MRT for all system configurations
Method and apparatus for user distribution to sub-bands in multiple access communications systems
No full textDemandeurs : Institut Mines Télécom, Université Libanaise, Université Saint-Esprit de KaslikDate de dépôt : 28/03/2018 N° de dépôt : EP2018030535
Risk of damage and desiccation cracking of construction materials based on raw earth
No full textInternational audienceNowadays, structures are mainly constructed using natural aggregates as sand and gravels. In the future, we would increasingly have to consider replacing them by more abundant and ecological natural materials such as raw earth. However, despite its many qualities (low gray energy, thermal and hygrometric isolation), this eco-material has some defects: cracking by desiccation. The later prevent its widespread diffusion. This study aims to understand the mechanisms of appearance and propagation of cracks in order to try to either prevent or repair it. To carry out this study, digital image correlation technique is used. It consists in performing free desiccation tests to follow the initiation and propagation of cracks, from the beginning of homogeneous strain until the appearance of discontinuity, in order to determine the strains tensor in the massif. In order to understand the origin of cracking, desiccation is studied for different boundary conditions and according to different intrinsic characteristics of the material
Analyse des performances d’une installation photovoltaïque équipée de réflecteurs plans
No full textInternational audienc
Evaluation of the plane of array irradiance for a photovoltaic installation equipped with flat reflectors in different geographical locations
No full textInternational audienceThis work describes a plane of array irradiance (GPOA) estimation study performed for a PV system equipped with flat reflectors. In fact, adding planar reflectors in front of the PV arrays will result in an increased GPOA reaching the panel's surface. This paper focuses on the GPOA study for a PV-Reflector system architecture in six different geographical locations. The study was conducted over a five years period of time and under various weather conditions. An analytical model was developed and experimentally validated for that purpose allowing the estimation and assessment of the GPOA for such system. Therefore, the study was performed according to an architectural optimization approach considering several geometrical variations in order to achieve the highest plane of array irradiance. The highest annual gain in GPOA added by the reflectors was obtained for Athens (35%) and regions with close latitudes showed quite similar results
Assessing agricultural risk in Lebanon combining retrospective and community-based approaches with temporal dimensions implementation
No full textInternational audienc
Investigation of essential oil chemical polymorphism of <em>salvia fruticosa</em> naturally growing in lebanon
No full textInternational audienceSalvia fruticosaa perennial aromatic plant, endemic to the Mediterranean region, is the most used medicinal plant in Lebanon. S. fruticosa essential oils (EOs) are widely acknowledged in the Lebanese traditional medicine to treat several ailments. Plant samples were harvested at various months of the year 2013, from 4 different Lebanese areas: Baabda, Ansariyeh, Harissa and Nahr Ibrahim. Fresh herb was either air dried or lyophilized. EOs were obtained using 2 extraction techniques: Solvent-Free Microwave Extraction (SFME) and conventional hydro distillation. The chemical variability of Lebanese S. fruticosa EO quantity and quality was assessed according to harvesting time and region, drying methods and EO extraction techniques. GC/MS showed that the major compounds in the oils were: eucalyptol (18.3-83.7 %), trans-anethole (0.00-61.7 %), beta-caryophyllene (0.00-38 %), and camphor (0.00-16.7 %). EO yields were affected by plant's growth stages, drying methods and EO extraction techniques. EO extraction methods and harvesting time and region had an impact on EO chemical composition whereas tested drying methods had no significant influence. Our study highlighted 4 different chemotypes for S. fruticosa EO: eucalyptol, camphor, alpha-thujoneand trans-anethole. For the first time in our study, trans-anethole was found as distinguishable chemotype
Stabilisation d'une équation des ondes avec un amortissement de type Kelvin-Voigt localisé sous conditions géométriques optimales
No full textInternational audienceThe purpose of this note is to investigate the stabilization of the wave equation with Kelvin–Voigt damping in a bounded domain. Damping is localized via a non-smooth coefficient in a suitable subdomain. We prove a polynomial stability result in any space dimension, provided that the damping region satisfies some geometric conditions. The main novelty of this note is that the geometric situations covered here are richer than that considered in [25], [22], [16] and include in particular an example where the damping region is not localized in a neighborhood of the whole or a part of the boundary.Nous nous intéressons à l'étude de la stabilisation d'une équation des ondes avec un amortissement de type Kelvin–Voigt dans un domaine borné. L'amortissement est localisé via un coefficient singulier dans une partie du domaine. Nous montrons un résultat de stabilisation polynomiale en toute dimension d'espace dès que la région d'amortissement satisfait certaines conditions géométriques. La principale nouveauté de cette note est que les situations géométriques couvertes ici sont plus riches que celles considérées dans [25], [22], [16] et incluent notamment un exemple où la région d'amortissement n'est pas localisée dans un voisinage de la totalité ou d'une partie de la frontière
