Liste des documents
Kinetics study and neural network modeling of degradation of Naphtol Blue Black by electro-Fenton process: effects of anions, metal ions, and organic compound
In the present work, the degradation of azo dye Naphtol Blue Black (NBB) in aqueous solution by electro-Fenton process was investigated. The results indicated that the degradation of NBB by electro-Fenton process followed the second-order reaction kinetics. The experimental results were also modeled by artificial neural network (ANN) with mean squared error of 10-5. This model was developed in Matlab using a feed forward back propagation network; multilayered perceptron. The input variables to the feed-forward neural network were as follows: initial Fe3+ concentration, initial pH, concentration of Na2SO4, temperature, applied current, and initial dye concentration. The degradation efficiency and rate constant were chosen as the experimental responses or output variables. The findings indicated that ANN provided reasonable predictive performance (R2 > 0.99). Effects of additives such as anions, metal ions, and organic compound on the efficiency and on the rate constant of NBB degradation were also studied under optimum conditions. Voir les détails
Mots clés : degradation, Electro-Fenton, Naphtol Blue Black, Artificial neural network
Removal of AY99 from an aqueous solution using an emulsifiedliquid membrane. Application of Plackett-Burman Design
Water contaminated with dyes presents serious environmental problems. An important quantity of dyes is released asindustrial waste in nature. As part of the recovery and the regeneration of these complexes, the extraction of a cationic dye AcidYellow 99 has been the subject of this work. To removal dyes from industrial wastewater, the technique of extraction byemulsion liquid membrane could provide an industrial success. The membrane used in this study consisted of SPAN80 asemulsifier and aliquat 336 as extractant. The stability of the emulsified liquid membrane has a very important role in theextraction. A study of the effects of different components of the membrane is necessary. The process parameters were studiedusing a statistical method of experimental Plackett-Burman design, This method allows us to study the effects of different factorssimultaneously and determines which factors are most important parameters. The modeling was done by a mathematical modelrepresenting the extraction yield according to various factors. The most significant factors on the elimination of the acid yellow99by the emulsion liquid membrane were then studied. Voir les détails
Mots clés : emulsified liquid membrane, modeling, recovery, acid yellow, design of experiment (DOE).
First principles calculations of structural, electronic and opticalproperties of Zn1-xBexSeyTe1-y quaternary alloys
The structural, electronic and optical properties of Zn1-xBexSeyTe1-y quaternary alloys are investigatedusing the full potential-linearized augmented plane wave (FP-LAPW) method within density functionaltheory (DFT). We used both the Wu–Cohen and the Engel–Vosko generalized gradient approximationsof the exchange-correlation energy that are based on the optimization of the total energy and the corre-sponding potential, respectively. Some basic physical properties, such as lattice constant, bulk modulus,electronic band structures, and optical properties (dielectric constant and refractive index) are calculated,nonlinear dependence on the compositions x and y are found. In addition, the energy band gap of zinc-blende Zn1-xBexSeyTe1-y quaternary alloys lattice matched to GaAs substrate is investigated. To ourknowledge this is the first quantitative theoretical investigation on Zn1-xBexSeyTe1-y quaternary alloysand still awaits experimental confirmations Voir les détails
Mots clés : alloys, Ab initio calculations, Electronic structure, optical properties
Extended Kalman Filter and Markov Chain Monte Carlo Method for Uncertainty Estimation. Application to X-Ray Fluorescence Machine Calibration and Metal Testing
This paper is concerned with a method for uncertainty evaluation of steel samplecontent using X-Ray Fluorescence method. The considered method of analysis is acomparative technique based on the X-Ray Fluorescence; the calibration step assumes theadequate chemical composition of metallic analyzed sample.It is proposed in this work a new combined approach using the Kalman Filter and MarkovChain Monte Carlo (MCMC) for uncertainty estimation of steel content analysis. The Kalmanfilter algorithm is extended to the model identification of the chemical analysis process usingthe main factors affecting the analysis results; in this case the estimated states are reducedto the model parameters. The MCMC is a stochastic method that computes the statisticalproperties of the considered states such as the probability distribution function (PDF)according to the initial state and the target distribution using Monte Carlo simulationalgorithm. Conventional approach is based on the linear correlation, the uncertainty budgetis established for steel Mn(wt%), Cr(wt%), Ni(wt%) and Mo(wt%) content respectively. Acomparative study between the conventional procedure and the proposed method is given.This kind of approaches is applied for constructing an accurate computing procedure ofuncertainty measurement. Voir les détails
Mots clés : Kalman filter, Markov Chain Monte Carlo, X-Ray fluorescence calibration and testing, steel content measurement, uncertainty measurement
Effects of sol concentration on structural, morphological and optical waveguiding properties of sol-gel ZnO nanostructured thin films
Nanostructured ZnO thin films with different precursor concentrations (0.5-0.8 M) have been deposited on glass substrates by sol-gel dip coating technique. X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), UV-visible spectrophotometer, and m-lines spectroscopy have been employed to investigate the effect of solution concentration on structural, morphological, optical and waveguiding properties of ZnO thin films. XRD spectra have shown that all the films are polycristalline and exhibit the wartzite hexagonal structire. SEM micrographs and AFM images have revealed that morphology and surface routhness of the thin films deprnd on sol concentration. The UV-visible transmittanceresults show a high transparency in the visible range and a shift of the maximum transmittance to the higher wavelength with increasing sol concentration. Waveguiding properties such as refractive index, number of propagating modes and attenuation coefficient measered at 632.8 nm wavelength by m-lines spectroscopy indicate that our ZnO slab waveguides are single mode and demonstrate optical losses estimated around 1.5 decibel per cm (dB/cm) for the thin film prepared with a sol concentration of 0.7 M. Voir les détails
Mots clés : ZnO, sol-gel, thin film
Ultra-wideband DRA Integrated with Narrow-band Slot Antenna
A new ultra-wideband (UWB) antenna integrated with a narrow-band (NB) antenna has been designed and fabricated. The UWB antenna consists of a U-shaped dielectric resonator fed by a microstrip line. In addition, the proposed structure integrates an NB slot with the same polarization. The electromagnetic analysis is carried out by using two commercial software tools. To validate the proposed concept, experimental measurements have also been performed. The measured results show that the dielectric resonator antenna (DRA) provides a wide bandwidth from 2.94 to 11.34 GHz (covering the UWB spectrum, 3.1–10.6 GHz) while the slot antenna provides a 2:1 voltage standing wave ratio bandwidth for 5.71–6.13 GHz. Moreover, the proposed design allows an efficient integration with very good isolation between the two ports (transmission coefficient S21 <−20 dB in the whole operating frequency band). Voir les détails
Mots clés : ultra-wideband (UWB) antenna, Integrated antenna, DRA
Modeling of InGaN / GaAs Photovoltaic Tandem with GaAs/AlAs Bragg Mirror Rear Surface Reflector
In this work, a parametric study of a dual junction tandem based on In0.53Ga0.47N on GaAs has been carried. In order to obtain reflection of unabsorbed photons from the bottom of the device, Bragg reflectors (BR) composed of GaAs/AlAs, with appropriate thicknesses, was placed in the rear surface of the GaAs sub-cell. With this intention, the current-voltage curves are calculated for different front recombination velocities and the influence of the bottom cell thickness on efficiency has been studied. The results of simulation show that the structure’s efficiency can attain 29% under 1-sun AM1.5 illumination, for a front recombination velocity value of 1e3cm/s and 10μm bottom cell thickness. This efficiency will decrease with increasing the operating temperature. Voir les détails
Mots clés : Bragg Reflector, Carrier Lifetimes, Recombination Velocity, Efficiency, Temperature
First-principles prediction of the structural, elastic, thermodynamic, electronic and optical properties of Li4Sr3Ge2N6 quaternary nitride
Structural parameters, elastic constants, thermodynamic properties, electronic structure and optical properties of the monoclinic Li4Sr3Ge2N6 quaternary nitride are investigated theoretically for the first time using the pseudopotential plane-wave based first-principles calculations. The calculated structural parameters are in excellent agreement with the experimental data. This serves as a proof of reliability of the used theoretical method and gives confidence in the predicted results on aforementioned properties of Li4Sr3Ge2N6. The predicted elastic constants Cij reveal that Li4Sr3Ge2N6 is mechanically stable but anisotropic. The elastic anisotropy is further illustrated by the direction-dependent of the linear compressibility and Young’s modulus. Macroscopic elastic parameters, including the bulk and shear moduli, the Young’s modulus, the Poisson ratio, the velocities of elastic waves and the Debye temperature are numerically estimated. The pressure and temperature dependence of the unit cell volume, isothermal bulk modulus, volume expansion coefficient, specific heat and Debye temperature are investigated through the quasiharmonic Debye model. The band structure and the density of states of Li4Sr3Ge2N6 are analyzed, which reveals the semiconducting character of Li4Sr3Ge2N6. The complex dielectric function, refractive index, extinction coefficient, absorption coefficient, reflectivity and electron energy-loss function are calculation for incident radiation polarized along the crystallographic directions and for energy up to 40 eV. Voir les détails
Mots clés : Quaternary nitride, First-Principles calculations, Elastic constants, Electronic structure, optical properties, Thermal Properties
Structural, elastic, electronic, chemical bonding and optical properties of Cu-based oxides ACuO (A = Li, Na, K and Rb): An ab initio study
Ab initio total energy calculations were performed to study in details the structural, elastic, electronic, chemical bonding and optical properties of Cu-based ternary oxides ACuO (A = Li, Na, K and Rb). Optimized atomic coordinates and lattice constants agree well with the existing experimental and theoretical data. Numerical estimations of the six independent elastic constants Cij and their related properties for monocrystalline ACuO were obtained. A set of elastic moduli for polycrystalline ACuO, namely bulk modulus B, shear modulus G, Young’s modulus E, Poisson’s ratio r, Lamé coefficients k and Debye temperature hD were evaluated. Band structure, total and site-projected l-decomposed densities of states, charge-carrier effective masses, charge transfers and charge density distribution maps were obtained; analyzed and compared with the available theoretical data. Complex dielectric function, refractive index, extinction coefficient, reflectivity and loss function spectra were calculated with an incident radiation polarized parallel to both [100] and [001] crystalline directions. Voir les détails
Mots clés : Cu-based oxides Ab initio calculations Elastic constants Electronic properties Chemical bonding
Three Nematogen Azobenzene-Based Stationary Phases for Capillary GC: Synthesis and Comparative Study
In this paper, three laterally substituted liquid crystals termed LCC1, LCC3 and LCC4 were synthesized. Characterization of these substances was carried out by 1H NMR and 13C NMR; they possess similar core and differ in their lateral substituents. Their thermal stability was conducted by thermogravimetric analysis and showed decomposition beginning at 212, 233 and 264 °C related to LCC1, LCC3 and LCC4, respectively. Thermal properties were determined by differential scanning calorimetry, thermomicroscopy and inverse gas chromatography. The three novel compounds exhibited a nematic mesophase at a defined range of temperatures, which varied from 81 to 55 °C. Lengthening of the lateral substituent seemed to affect the nematic range by decreasing it. Fused-silica capillary columns (30 m × 0.32 mm) were employed for the analytical study. Numerous mixtures of components of various properties were injected. Particular attention was given to the selectivity towards the close-boiling isomers. These investigations indicated that lateral attached groups had considerable effect on the thermal and chromatographic properties of the liquid crystal compounds. These interesting results may guide in improving the development of new type of liquid crystals with desired properties for a widespread application. Voir les détails
Mots clés : Capillary gas chromatography, Liquid crystals, Thermal Properties, Analytical properties