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

REVIEW: SYNTHETIC NITROGEN COMPOUNDS AS EFFICIENT CORROSION INHIBITORS FOR METALLIC MATERIALS IN AGGRESSIF MEDIUM

Pluridisciplinary research by chemists, physics, biologists and mathematics is a primordial task to find and discover new molecules which are beneficial for humanity in many areas such as the inhibition of corrosion of materials in drastic medium. The nitrogen heterocyclic coumpounds based on pyrazole, bipyrazole, bispyrazole, imidazole and triazole, constitute a large bank of compounds with chemical, and industrial interest. In this context, we decided to present a review about the preparation of a series of heterocyclic compounds from literature and our group works (20 years experiences in this area). Then we focused on their anti corrosion activities in drastic medium

Optical Emission Spectroscopy Study Of RF Sputtered A-C/WOX Interface

Amorphous carbons on tungsten oxide (a-C/WOX) bi-layers were deposited on silicon substrates by rf sputtering. The WOX layers were obtained from a pure tungsten target, in a gas mixture of argon and oxygen, whereas those of a-C were obtained from a graphite target, in pure argon plasma. The reactivity of the a-C/WOX interface and the ion bombardment effects have been studied by Optical Emission Spectroscopy (OES) technique. The OES spectra show that the a-C/WOX interface is reactive in accordance with previous results obtained by X-ray reflectometry. The inter-diffusion depth is estimated to be greater than 56 nm. Emission lines of W are still observed even after an ion bombardment time of about 45 minutes. This result confirms the presence of the Knock-on effect.Amorphous carbons on tungsten oxide (a-C/WOX) bi-layers were deposited on silicon substrates by rf sputtering. The WOX layers were obtained from a pure tungsten target, in a gas mixture of argon and oxygen, whereas those of a-C were obtained from a graphite target, in pure argon plasma. The reactivity of the a-C/WOX interface and the ion bombardment effects have been studied by Optical Emission Spectroscopy (OES) technique. The OES spectra show that the a-C/WOX interface is reactive in accordance with previous results obtained by X-ray reflectometry. The inter-diffusion depth is estimated to be greater than 56 nm. Emission lines of W are still observed even after an ion bombardment time of about 45 minutes. This result confirms the presence of the Knock-on effect

Catecholase catalytic properties of copper (II) complexes prepared in-situ with heterocyclic ligands: Experimental and DFT study

  The objective of our work is the preparation of the new catalysts for catecholase, whose principle is based on the catechol oxidation reaction which presents a major challenge in both biology and medicine.First, we synthesized nine pyrazole and triazole ligands, then we evaluated the catalytic properties of certain of those ligands in situ complexes to catalyze the oxidation reaction of catechol to o-quinone. The aim of this study is to find the right models to reproduce the catalytic activity of the enzyme (catecholase), so we used complexes formed in situ by pyrazole and triazole derivatives with copper (II) salts. The reason behind the interest of these complexes is their resemblance to biological systems, capability of activating the catalyst for many chemical reactions. Among these complexes, some of them showed good catalytic activity for this reaction. We have demonstrated that the nature of ligand, the concentration of ligand, the nature of the solvent and the nature of the copper (II) salt, influences the efficiency of the catecholase activity.Pyrocatechol is benzene-1,2-diol (nomenclature IUPAC), also known as catechol with formula C6H6O2 crude used in many organic syntheses. Some catecholamines have important physiological functions. The Government of Canada has determined that catechol is "toxic" as defined by the Canadian Environmental Protection Act, 1999. So, to reduce the toxic effect of catechol we try to oxidize o-quinone which is less dangerous than catechol.The DFT study has big interest in many researches to know the reactivity of the ligands by calculating different quantum descriptors as: EHOMO, ELUMO, The gap energy, Ionisation potential, The electron affinity and The hardness. 

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

Two tripodal pyrazolic ligands: application against corrosion of mild steel in HCl 1M

Two tripodal pyrazolic ligands: N,N-bis((3,5-diméthyl-1H-pyrazol-1-yl)methy)-2,4-difluoroaniline (2Fpyr 1) and N,N-bis((1H-pyrazol-1-yl)methyl)-2,4-difluoroaniline (2Fpyr 2) were synthetized in good yiels. Then we applied them against corrosion of mild steel in HCl 1M solution. Weight loss measurement give us the inhibition efficiencies values reached 80.2 % for 2Fpyr1 and 77.3 % for 2Fpyr 2 at the concentration 10-3, then by changing the temperature from 313K to 343 K, which give us the activation and adsorption parameters, and we reveal from it that the ligands 2Fpyr 1 were adsorbed according to Langmuir Isotherm, but 2Fpyr 2 were was adsorbed according to El-Awady adsorption Isotherm, we obtain these results using certain isotherms as Langmuir, Freundlich, Temkin, Frumkin, Florry-Huggins, Adejo-Ekwenchi and El-Awady. We conclude from polarization curves that all the ligands are mixed type inhibitors (anodic and cathodic type inhibitors), and from the impedance diagrams in the Nyquist presentation which are in the form of one half loop because that the corrosion is controlled by charge transfer process. We used GAUSSIAN 09W program to do theoretical investigations by considering the Density Functional Theory (DFT) method to calculate quantum parameters as EHOMO, ELUMO, ∆EHOMO-ELUMO and μ dipolar moment that allows us to confirm experimental results obtained from gravimetric and electrochemical studies

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