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Currently, nanostructures such as nanobeams, nanomembranes and nanoplates have been a hot area of research triggering. The contribution of this research article deals with both the effect of the free and dynamic vibration of a nanobeam as well as the use of the FGM material by integrating the piezoelectric effect. In fact, incorporating the initial stress for a nanoscale beam has not been considered yet. This paper displays an analysis of dynamic and free vibration of power-law functionally graded piezoelectric materials (FGPM) subjected to thermal-electro-mechanical loads with initial stress. The model was resolved based on nonlocal Timoshenko beams theory. The dimensionless fundamental frequency gradually improved with the new configuration of the FGPM nanobeam by 5% compared to the FGM nanobeam. The accuracy of this model is highlighted via numerical examples for different boundary conditions. To solve the governing equations, the polynomial differential quadrature method (PDQM) was elaborated and resolved numerically using MATLAB. For various configurations of the FGPM nanobeams, the effect of scaling parameters, volume fraction and slenderness ratios were discussed. In addition, for different edge conditions, variations of the first four frequencies with volume fraction indices and for different scaling parameters were set forward. This study corroborated that the power exponent, nonlocal parameter, slenderness ratio and thermo-electro-mechanical loads have significant effects on the dimensionless frequencies of various FGPM nanobeams. The present work provides an enlightening as guideline for the draft of a nanoscale beams based thermo-electro-mechanical actuators. [ABSTRACT FROM AUTHOR]

The Mingo'o locality belongs to the Nyong Complex, located on the northern edge of the Congo Craton. In order to estimate the depth parameter of iron mineralization, outcrop studies, and ground magnetic geophysical surveys have been conducted. The petrographic analysis of outcrops reveals that Mingo'o's banded iron formations comprise quartz-hematite BIFs (QHB) and quartz-magnetite BIFs (QMB). Also, the rocks are magnetic, with well-expressed millimetric dark bands of magnetite and hematite alternating with light bands of quartz. Magnetite and hematite crystals ranged in size from 0.1 to 3 mm, while quartz crystals were between 0.1 and 2 mm. The use of a ground magnetic survey reveals the presence of BIFs highlighted by total magnetic intensity, reduction to the equator, and total gradient, with values of 524.9-8,866.7 nT, -1,464.9 to -41.8 nT, and 36.781-86.470 nT/m, respectively. The 3D modeling shows that magnetic susceptibility values ranging between 0.6 and 3 SI are associated with BIFs. This model shows that the iron mineralization body extends 800 m N-S and 1,000 m E-W, with depth > 500 m, which is also confirmed by the Euler deconvolution method. The correlation of all these results shows a high BIF occurence in the elevated zone (> 400 m). This is a similar hypothesis to some of the previous surveys executed on the northern edge of the Congo Craton. [ABSTRACT FROM AUTHOR]

Cracks are described as sharp and diffusive surfaces in failure mechanical models. In this paper, a finite element model is developed by using a diffusive description of crack discontinuities. The main objective of this study is to prove the accuracy of the phase-field model in which the alternate minimization iteration and the spectral decomposition formulation are considered. We conduct a set of benchmark numerical tests on notched specimens using the phase-field model, which allows the prediction of the quasi-brittle failure. The fracture surface is approximated by a diffusive field, which interpolates between undamaged and fully damaged states. A mechanical loading was applied on quenched C90 steel and different obtained crack patterns are discussed. Microstructural analyses are performed to prove the accuracy of the proposed numerical approach. Through the determination of microstructural properties of untreated and quenched C90 steel, it is concluded that the presence of the micro-cracks may have a great influence on the crack path evolution. [ABSTRACT FROM AUTHOR]

Titanium-vanadium oxo-alkoxy (VTOA) nanoparticles with vanadium addition (V:Ti) between 0 and 20 mol% were prepared via sol-gel method in a chemical reactor with ultra-rapid micromixing. A control of the nucleation and growth process in the reactor permitted synthesis of size-selective V-TiO2 nanoparticles, which were used for the nanocoatings deposition on glass beads. The activity of the prepared photocatalysts (after calcination at 450 °C) was studied by the degradation of methylene blue in aqueous solutions under UVA illumination. A steady decrease of the reaction rate was observed with an increase of the vanadium content. This effect was explained by the residual presence of non-crystallized oxide, which elimination requires further studies. [ABSTRACT FROM AUTHOR]

In a previous work in our team (Oualha et al., Chem Eng Trans, vol 73, 67-72 (2019)) it was shown that at large Reynold numbers (Re > 8000) a vapor phase appears by cavitation in T-mixer reactors used for chemical precipitation of nanoparticles. This phenomenon can affect dramatically the properties of the obtained nanoparticles. In the work of Oualha et al (2019), the apparent size (more precisely the hydrodynamic diameters) of vapor bubbles due to the cavitation, was in situ monitored in the reactor by using SLS (Static Light Scattering) and DLS (Dynamic Light Scattering) methods. A modeling was also given using Fluent software: calculated size population of bubble was provided. Unfortunately this population could not be directly compared to experimental data since the relationship between apparent and real size was unknown. In the present work, new DLS measurements using particles of calibrated sizes are presented to help us to interpret and comment our previous results on bubbles size distribution. They were obtained using a new apparatus designed and realized for the purpose of defining a method of true diameters measurement. [ABSTRACT FROM AUTHOR]

Vanadium oxo-alkoxy nanoparticles were prepared via sol-gel method, manually and in a chemical reactor with ultra-rapid micromixing. The materials were characterized by DLS, ATG-ATD, XRD and SEM methods. The influence of micromixing conditions on the particle size and growth kinetics was evaluated. Complementary, the preparation of mixed-oxide nanoparticles in presence of vanadium and titanium precursors was performed, showing a strong interaction between the two systems, promising for the fabrication of size- and compositional selective Ti-V oxide nanoparticles for photocatalysis. [ABSTRACT FROM AUTHOR]

A comparative evaluation of the antibacterial effect of silver in the form of nanoparticles and Ag+ ions was performed. Silver nanoparticulate coatings of stable and reproducible morphology were prepared on monolayer size-selected titanium-oxo-alkoxy nanoparticles deposited on glass substrates. The coatings exhibit a strong antibacterial activity towards Escherichia coli K12 AB 1157 and suppress biofilms formation. This activity is mainly related to the Ag+ ions release into aqueous solutions in dark. The deposited silver mass ~1 μg.cm -2 is smaller compared to that of Ag+ ions and nanoparticles generally reported for inhibiting Escherichia coli. The synergetic effect of the deposited nanoparticles and Ag+ ions can be suggested. [ABSTRACT FROM AUTHOR]

The aquifer basin of Figuig is located at the eastern extremity of High Atlas of Morocco. It is a multi-layer aquifer system. The Triassic formation is characterized by clay and the Jurassic formation by the carbonate, while the Quaternary formation is formed by alluvial silts and sands. The present work focuses on the study of salinity and contamination of groundwater by discharges of wastewater into septic tanks in this region. The methodology used was to map the spatial and temporal variation of salinity and to define the spatial extent of the contamination. The results obtained for (1) salinity, (2) bacteriology (faecal and total coliforms), and (3) nitrates and (4) a simulation of contaminant transport using the MODPATH code indicate that the southern zone has high salinity and the south and southeast areas are contaminated by wastewater discharges. For this purpose, the quality of groundwater in the oasis of Figuig deteriorated over time. This work is expected to assist local authorities in developing plans and in reducing the pollution to acceptable levels. [ABSTRACT FROM AUTHOR]

V-TiO2 photocatalyst with 0 ≤ V ≤ 20 mol% was prepared via the sol–gel method based on mixed oxide titanium–vanadium nanoparticles with size and composition control. The mixed oxide vanadium–titanium oxo-alkoxy nanonoparticles were generated in a chemical micromixing reactor, coated on glass beads via liquid colloid deposition method and underwent to an appropriate thermal treatment forming crystallized nanocoatings. X-ray diffraction, Raman, thermogravimetric and differential thermal analyses confirmed anatase crystalline structure at vanadium content ≤ 10 mol%, with the cell parameters identical to those of pure TiO2. At a higher vanadium content of ~20 mol%, the material segregation began and orthorhombic phase of V2O5 appeared. The crystallization onset temperature of V-TiO2 smoothly changed with an increase in vanadium content. The best photocatalytic performance towards methylene blue decomposition in aqueous solutions under UVA and visible light illuminations was observed in V-TiO2 nanocoatings with, respectively, 2 mol% and 10 mol% vanadium. [ABSTRACT FROM AUTHOR]