Turbulent liquid film evaporation in a partially heated wall along a vertical tube

In this numerical study, the evaporative heat and mass transfer of a turbulent falling liquid film in a finite vertical tube are investigated. The liquid film flows in the tube's inner wall, whose outer wall is partially subject to thermal flux. Here, different configurations corresponding to thermal flux imposed on different external surface wall percentages are examined. External face zones where the heat flux is not applied are maintained insulated. The nonlinear set of parabolic mass, momentum, energy, and mass fraction conservation equations combined with boundary and interfacial conditions are treated numerically using implicit finite difference procedure. For falling liquid film analysis, an adapted Van Driest turbulence model is used. For the present work, it is supposed that gas flows in a laminar regime. We examine in this paper the impact of the percentage of heated surface area on flows as well as on heat and mass transfer. Obtained results for a partially heated wall are compared with those produced for an entirely heated wall.     

Chemical Synthesis of Organo-siloxene 2D Materials from Calcium Di-Silicide: Characterization,Dielectric and Electrochemical Studies

Silicon - Silicon is one of the most used materials in semiconductors and electronic devices. Its miniaturization in two-dimensional (2D) scale is now a great challenge to improve and/or extend its...     

Numerical modeling of conjugate heat transfer through concrete hollow bricks

The purpose of this study is to determine the thermal conductance of concrete hollow bricks, which is necessary for the evaluation of the energy efficiency of a building. The three varieties of hollow concrete bricks that are often used to build walls in Morocco are the subject of this study. A computational model created using the finite volume method is used to evaluate the conjugate heat transfer through concrete hollow bricks. According to the results, the use of hollow brick type A_h3 reduces the heat flux by approximately 86% compared with type A_h1. It is undeniable that hollow bricks type A_h3 with a thermal conductivity of 1 W/m K can improve the thermal characteristics of building walls.     

Polyol Mediated Solvothermal Synthesis and Characterization of CuIn<Subscript>(1−x)</Subscript>Ga<Subscript>x</Subscript>S<Subscript>2</Subscript> Nanocrystals

Gallium-substituted copper indium sulfide (CuIn_(1?x)Ga_xS₂) nanoparticles have been synthesized by a convenient solvothermal method without usage of surfactants or toxic reductants such as hydrazine. Thiourea, sodium hydroxide, CuCl₂·2H₂O, InCl₃ and GaCl₃ were used as starting materials and ethylene glycol as solvent and reducing agent. The reactions were performed at 200 °C for 16 h. Effect of sodium hydroxide on the reaction products is analyzed. The powders are mainly characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy, BET surface area measurements and UV–Vis absorption spectroscopy. The results show that the gallium is successfully incorporated into the chalcopyrite crystal structure. The homogeneous powders obtained are constituted of nanoparticles with sizes in the range 20–30 nm and exhibit a specific surface area close to 65 m²/g. Further, the possible mechanism for the formation of CuIn_(1?x)Ga_xS₂ nanocrystals is explained. The optical band gap energies of the nanoparticles were in the range 1.48–1.75 eV.     

Design of circular patch antenna with a high gain by using a novel artificial planar dual‐layer metamaterial superstrate

This study presents a new dual‐layer metasurface structure proposed to enhance the performance of a circular patch antenna. A novel unit cell planar metasurface is characterized by nearly equal enhanced effective permeability and permittivity ε_r ? μ_r > 1 at the resonant frequency. In addition, a 5*5 array of these unit cells are used as a superstrate over a circular patch antenna which is fed by 50 Ω microstrip line and operating at 2.45 GHz for improving the antenna performance. The patch antenna gain is increased by creating an in‐phase electric field area on the top surface of the metasurface. The obtained results showed that the maximum gain of the antenna increased from 2.31 dBi to 7.5 dBi. A 30% increase in the bandwidth is also remarked. The proposed antenna with metasurface occupies an overall volume of 1.01λ_g ×1.01λ_g ×0.025λ_g . The simulation analysis and measured results were performed using the microwave studio, high frequency structure simulator software, and vector network analyzer. The proposed antenna prototype has been fabricated. The measured results indicate that the antenna has a good impedance matching in the desired operating band (2.37‐2.49 GHz) with the resonant frequency of 2.44 GHz which make the proposed antenna appropriate for microwave applications.     

ECG signal filtering based on CEEMDAN with hybrid interval thresholding and higher order statistics to select relevant modes

Multimedia Tools and Applications - In this paper, we propose a novel ECG signal enhancement method based on Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (CEEMDAN) and Higher...     

Corrosion inhibition activity of carbon steel in 1.0 M hydrochloric acid medium using Hammada scoparia extract: gravimetric and electrochemical study

The interest for the environment is becoming more demanding with regard to the use of toxic and non-biodegradable substances and their impacts on different environments. Therefore, the need to develop ‘green inhibitor’ to preserve the nature from pollution is urgent. In this context, an investigation of medicinal plant (Hammada scoparia; HSP) as a corrosion inhibitor on C-steel in 1.0 M HCl solution has been implemented. To accomplish this work, several methods were used as weight loss, electrochemical measurements and surface analysis. Polarization curves show that HSP extract acts as mixed inhibitor type with cathodic predominance. The efficiency of C-steel protection increases with increasing the HSP extract concentration but decreases with the temperature in the range of 303–333 K. The effect of the temperature on the inhibition efficiency, as well determination of the different kinetic and activation parameters, make it possible to deduce a physisorption mechanism of HSP extract on the surface of C-steel. The theoretical fitting of different isotherms was also investigated. It was found the results obeyed the Langmuir isotherm. Surface analysis using FT-IR, UV-visible, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD) allowed the clarification of the inhibition mechanism and the relative inhibition efficiency.     

Theory of anisotropic oxygen polarizability in the tetragonal phase of PbTiO3

The optical anisotropy of the tetragonal phase of PbTiO₃, is discussed according to the point-dipole approach. In this microscopic model, we have taking into account of the electronic polarization and the lattice deformation and it is shown that anisotropic electronic polarizabilities are the dominant source of the optical properties of PbTiO₃. This anisotropy is attributed to the O_z, oxygen ion and it is due to the Ti-Oz and Pb-O_z overlap in the tetragonal phase.

By analyzing the optical refractive index data of PbTiO₃ at 0.589 μm, we have determined the temperature dependence of the oxygen polarizabilities. Based on the dispersion data of the refractive index of PbTiO₃, the dispersion of the oxygen polarizabilities are similarly calculated at room temperature.