Mechanical Characterization of the Threshold Strain in Sand Liquefaction

DOBRY et al, YOUD have shown the existence of a shearing threshold strain in the vicinity of 10-4 which guides the occurrence of liquefaction. With tests on glass beads and sand from the Algiers bay, using a proper measuring system, we were able to arrive at a better resolution of this threshold and to the determination of its mechanical signification

Effet de l’oxygène sur les radiations optiques émises lors de la pulvérisation de l’aluminium par un faisceau d’ions

La présence de l’oxygène au voisinage d’une surface métallique lors d’unbombardement ionique, provoque une décroissance du rendement totalde pulvérisation mais elle modifie considérablement les proportions desdiverses espèces éjectées de cette surface. Dans ce travail, nous noussommes intéressés à l’effet de l’oxygène sur la lumière émise lors de lapulvérisation d’une surface d’aluminium par des ions Kr+ d’énergiecinétique de 5 keV. Le spectre de luminescence relevé à une pression de10-7 Torr est comparé à celui mesuré lorsque la cible est soumise à uneatmosphère d’oxygène. L’examen des intensités des raies spectralesmontre que toutes les raies Al I manifestent une dépendance positiveavec la pression en oxygène alors que des raies Al II manifestent unedépendance négative. Nous avons aussi enregistré que des raies Al IIIrestent insensibles à la présence de ce gaz. Ces observations sontcomparées avec les spectres de luminescences de l’alumine bombardéedans les mêmes conditions expérimentales. Les résultats obtenus sontinterprétés dans le cadre du modèle de transfert d’électrons entre lasurface et la particule éjectée. La validité du modèle suggère qu'en présence de l'oxygène, une structure est formée et dont le schéma debandes d'énergie est intermédiaire entre celui de l'aluminium et celui del'alumine.Mots-clés : pulvérisation, émission optique, aluminium, alumine, modèlede transfert d’électrons; analyse de surface, spectroscopie optique

Metal corrosion inhibition by triazoles : A review

Metal corrosion and the prospects of inhibiting this process have received much interest from society and scientific research. The annual global cost of corrosion is $2.5 trillion, equivalent to roughly 3.4% of the world's gross domestic product. Implementing corrosion prevention best practices could result in global savings of 15-35% of that cost. Numerous studies were documented and dedicated on the triazole nucleus based compounds as fascinating corrosion inhibitors of various metals in hostile media. Their unique electronic structure possessing conjugated pi and unshared pairs of electrons on the nitrogen atoms facilitates their adsorption on metal surfaces. Thus, physical and chemical interactions between the active centers of triazoles and d-orbitals of metallic materials occur to form a film on the surface. The nature of inhibitor activity is disclosed through polarization studies (cathodic, anodic or mixed-type). The range of various substituents on the triazole ring offers a vast array of inhibitory effects. temperature and inhibitor concentration effects must also be regarded when evaluating the corrosion activation and adsorption parameters supported further by the quantum chemical parameters such as DFT and molecular dynamics simulations. In this review, we looked through several instances of the use of distinct substituted triazole nucleus based compounds as significant corrosion inhibitors for different metals in various aggressive media.Peer reviewe

Learning from Demonstration and Safe Cobotics Using Digital Twins

The use of collaborative robots, or cobots, is nowadays continually increasing, especially in the small- and medium-sized manufacturing sector. For each particular use case, the integration and deployment of a cobot into a collaborative workspace faces a certain number of challenges. Programming industrial robots, for example, can be a relatively complex and time-consuming task. In this paper we report an accurate method to robot programming by using an optimized “learning from demonstration” technique. The operator/programmer performs in real-time the corresponding task to be automatized, and by means of a tracker sensor the programmer’s motions are captured and transmitted to the robot; the robot registers the trajectories and is now able to reproduce the human movements with high accuracy. Another fundamental issue for cobot deployment is safety. In this paper, we also present a virtual/augmented reality (VR/AR) environment to facilitate the design and operation of cobots in order to maximize human safety. The virtual reality environment operates as an aide tool during the design phase. The human operator and the robot’s digital twin work side-by-side while executing a collaborative task in a virtual reality space. Their movements are controlled and registered, and after a given period of test time, the data is analyzed to suggest modifications to ensure a safe workspace (collision free) and to increase productivity. For the regular real-time cobot operation, an augmented reality environment was developed, again, with the purpose of assuring a safe human-robot collaboration. The augmented reality environment keeps tracking permanently the cobot and the human manipulations. This system produces audio and visual alarm signals in unsafe situations and is also able to take actions, such as slowing down or stopping the robot, to preserve the physical integrity of the human operator