Analyse numérique de la portance d’un massif de fondation renforcé par des colonnes ballastées confinées dans des nappes géosynthétiques.

La technique des colonnes ballastées est une méthode de renforcement efficace, couramment utilisée pour augmenter la capacité portante et réduire le tassement des sols mous. Pour les sols très mous, la résistance latérale sont très faibles, et n’offrent plus un confinement pour les colonnes ordinaires. La solution appropriée consiste à enrober les colonnes par des géosynthétiques. L’objectif de la présente thèse est d’apporter une contribution à la détermination des conditions de renforcements performants, à travers le concept de la longueur critique des colonnes. Cette technique permet d’assurer une amélioration optimale de la capacité portante ultime des fondations placées sur des sols mous renforcés par des groupes de colonnes flottantes ordinaires ou confinées dans de géogrilles. Deux cas de fondations ont été considérés : des semelles filantes portées par des groupes ayant un petit nombre de rangées de colonnes, et une fondation carrée reposant sur un grand nombre de colonnes. Une étude numérique a été effectuée à l’aide du code en différence fini FLAC3D sur plusieurs modèles de fondations. L’étude a porté d’abord sur des semelles filantes de largeur différentes supportées par des colonnes non confinées. Les courbes des résultats obtenus ont été analysées et interprétées, ainsi les valeurs optimales des capacités portantes ont été déterminées, à travers la longueur critique des colonnes. Deux nouvelles formules analytiques, simples et pratiques ont été développées et validés pour la détermination de la longueur critique et la prédiction de la capacité portante ultime d’une semelle filante. L'analyse de l'influence du confinement des colonnes par des géogrilles sur l'amélioration de la capacité portante a été réalisée sur le modèle de la fondation carrée. L'influence des rigidités de la géogrille, de la longueur des colonnes et du taux de confinement des colonnes a été aussi analysée pour chaque cas d'étude. Les courbes des résultats obtenus ont permet de montrer une influence significative du confinement sur l'amélioration de la capacité portante de la fondation. Ce résultat a été confirmé par des tests réalisés sur des modèles réduits de fondations supportées par des colonnes confinées par des géogrille

Insights into gastrointestinal virome : etiology and public exposure

Funding: The authors extend their appreciation to the Deanship of Scientific Research at King Saud University for funding this work through research group no. RG-1441-492.Recycled wastewater is widely used owing to the potential shortage of water resources for drinking purposes, recreational activities, and irrigation. However, gut microbiomes of both human beings and animals negatively affect this water quality. Wastewater contamination is continuously monitored, using fecal contamination indicators or microbial source tracking approaches, to oppose arising enteric infections. Viral gastroenteritis is considered a principal manifestation of waterborne pathogenic virome-mediated infections, which are mainly transmitted via the fecal-oral route. Furthermore, acquired enteric viromes are the common cause of infantile acute diarrhea. Moreover, public exposure to wastewater via wastewater discharge or treated wastewater reuse has led to a significant surge of public health concerns. In this review, we discussed the etiology of waterborne enteric viromes, notably gastrointestinal virus infections, and public exposure to municipal wastewater. Conclusively, the early human virome is affected mainly by birth mode, dietary behavior, and maternal health, and could provide a signature of disease incidence, however, more virome diversification is acquired in adulthood. A multi-phase treatment approach offered an effective means for the elimination of wastewater reuse mediated public risks. The insights highlighted in this paper offer essential information for defining probable etiologies and assessing risks related to exposure to discharged or reused wastewater.Publisher PDFPeer reviewe

NEW APPROACH TO A DS-CDMA-UWB SYSTEM USING A PSEUDO ORTHOGONAL CODE (POC)

Ultra-Wideband Direct Sequences Code Division Multiple Access (DS-DMA) plays an important role in the case of multi-terminal multi-application communications of UWB devices. In the case of UWB systems that exploit the injection of the pulse itself directly to the antenna hence the very wide bandwidth, generation of suitable DS-CDMA codes poses a real challenge. In this paper we will describe our novel UWB transmission  which uses pseudo-orthogonal time code (POC) as DS-CDMA sequences. The suggested codes are unipolar sequences with chips that may be dynamically modified to target a certain number of users or applications. Our approach bypasses the modulations schemes commonly used on UWB systems. Moreover, as perspectives to our work, it would be very interesting to realize our new approach based on an FPGA circuit

Optimization of the Ultimate Bearing Capacity of Reinforced Soft Soils through the Concept of the Critical Length of Stone Columns

The objective of this paper is to develop an analytical equation based on the concept of the critical-length of columns in order to optimize the ultimate bearing-capacity of soft soils, supporting a strip footing and reinforced by a group of floating stone columns. Optimization procedure was performed on three-dimensional numerical models simulated on the Flac3D computer code, for various soft-soils with different undrained-cohesions (Cu=15–35kPa), reinforced by columns of varying lengths (L) and area replacement ratio (As=10-40%), considering different footing widths B. Obtained results indicate that the optimal bearing-capacity ratio (Ultimate bearing-capacity of reinforced soil/unreinforced soil) is reached for the column critical-length ratio (Lc/B) and increase with increase of the later ratio, depending  on As and Cu. Analysis of results also showed that the optimal values of the bearing-capacity ratio in the reinforced soils remain bounded between the lower and higher values (1.28-2.32), respectively for minimal and maximal values of the critical-length ratio (1.1) and (4.4). Based on these results, a useful analytical equation is proposed by the authors, for the expression of the critical-length; thus ensuring an optimal pre-dimensioning of the stone columns. The proposed equation was compared with the data available in the literature and showed good agreement. Doi: 10.28991/cej-2021-03091737 Full Text: PD

CUCKOO SEARCH ALGORITHM TO SOLVE THE PROBLEM OF ECONOMIC EMISSION DISPATCH WITH THE INCORPORATION OF FACTS DEVICES UNDER THE VALVE-POINT LOADING EFFECT

The essential objective of optimal power flow is to find a stable operating point which minimizes the cost of the production generators and its losses, and keeps the power system acceptable in terms of limits on the active and reactive powers of the generators. In this paper, we propose the nature-inspired Cuckoo search algorithm (CSA) to solve economic/emission dispatch problems with the incorporation of FACTS devices under the valve-point loading effect (VPE). The proposed method is applied on different test systems cases to minimize the fuel cost and total emissions and to see the influence of the integration of FACTS devices. The obtained results confirm the efficiency and the robustness of the Cuckoo search algorithm compared to other optimization techniques published recently in the literature. In addition, the simulation results show the advantages of the proposed algorithm for optimizing the production fuel cost, total emissions and total losses in all transmission lines

A COMPARATIVE STUDY OF OPTIMIZATION METHODS FOR EDDY-CURRENT CHARACTERIZATION OF AERONAUTICAL METAL SHEETS

This paper presents eddy current non-destructive characterization of three aeronautical metal sheets by deterministic and stochastic inversion methods. This procedure consists of  associating the finite element method with three optimization algorithms (Simplex method and genetic and particle swarm algorithms) simultaneously determine electric conductivity, magnetic permeability and thickness of Al, Ti and 304L stainless steel metal sheets largely used in aeronautical industry. Indeed, the application of these methods has shown the performance of each inversion algorithms. As a result, while doing a qualitative and quantitative comparison, it was found that the Simplex method is more advantageous in comparison with genetic and particle swarm algorithms, since it is faster and more stable