Growth temperature impact on MOVPE-grown BInGaAs/GaAs QWs designed for optoelectronic applications

Journal of Materials Science: Materials in Electronics - In this work, quaternary BInGaAs single quantum wells have been grown on GaAs substrate by metal–organic vapor-phase epitaxy. The...     

Preparation,characterization and evaluation of the catalytic power of an hybrid compound [H3PMo12O40-chitosan] for the azoic-colored solutions

Inorganic–organic hybrid structures have become novel alternatives for many applications as they combine the advantages of both systems. In this current study, a hybrid compound [H₃PMo₁₂O₄₀-chitosan] was prepared using a wet impregnation method with different proportions (0-100 wt. %, considering the polymer as the main component). The chemical structure and the morphology of the synthesized compounds were studied using FT-IR and SEM. Their catalytic powers were evaluated for Naphtol Blue Black and Eriochrome Blue Black B. Experimental data revealed that the decolorization phenomenon depends on the structure of the dye it-self, the pH value, the initial dye concentration, the time contact, the oxidant dose and the temperature. Kinetic data, well described using the first order model, allowed us to establish the thermodynamic parameters. The calculated low values of Ea (7.48 and 8.14 KJ. mol-1) proved the efficiency of the prepared catalyst. Eriochrome Blue Black B could be decomposed more rapidly than Naphtol Blue Black. As example, after a period of 30 min of reaction, the target removals were, respectively, 70% and 15% for mono and bi-azoic dyes. The reuse of the catalyst is carried out and it was found to be recyclable more than three consecutives cycles.     

Fleece Production,Scouring Yield,and Down Hair Yield of Tunisian Dromedary

The results show that the greasy fleece weight varied from 0.3 kg to 2.42 kg with an average of 0.75 kg. The fleece weight decreases according to the animal age. In fact, the factor “age” has a significant effect on the dromedary fleece weight. Average scoured yield was 96% with V% of 1.6%. This indicated that matter loss, after scouring dromedary fibres, was lower than wool and cashmere. Scoured yield did not vary between samples of varied dromedary body areas in any age. The down hair yield for the fleece of the Tunisian dromedary varies between 34% and 61% with a mean of 45%. This raises interest when compared to the cashmere yield. There is a clearly decreased dromedary down hair yield according the factor “age”. The analysis of the variance shows that the dromedary down hair yield was affected by the factors “age” and body area of the animal.

Following this work it will be possible to predict the amount of down yield in the fleece of Tunisian dromedary knowing age. Consequently, it will be possible to estimate the total amount of textile material camel from dromedary located in Tunisia.     

Iron(III) and Cobalt(III) Complexes with Oxalate and Phenanthroline: Synthesis,Crystal Structure,Spectroscopy Properties and Magnetic Properties

We report herein the synthesis and physicochemical characterization of two mixed-ligand complexes of the following stoichiometric formulae: [Fe(phen)₂(ox)](NO₃)?2H₂O (1) and [Co(phen)₂(ox)](NO₃)?4H₂O (2) (as phen: 1,10-orthophenanthroline; ox: oxalate dianion). Both compounds have been prepared by slow evaporation at room temperature and characterized by single-crystal X-ray diffraction. They have been characterized by IR and UV–Vis spectra and thermoanalysis (TG and DTA) The structures of these compounds are highly symmetric. Indeed, the two compounds are isomorphous and crystallize in the orthorhombic space group Ibca. In each material, the M^III ion has a slightly distorted square bipyramidal environment, coordinated by one oxalate ion and two 1,10-orthophenanthroline ligands. Structural cohesion is established essentially by π–π interactions between the rings of phen groups and intermolecular O–H…O hydrogen bonds connecting the ionic entities and uncoordinated water molecules. Magnetic susceptibility measurements of (1) in the range 5–300 K exhibit paramagnetic behavior at high temperature. However, at low temperature, the magnetic data show the occurrence of weak antiferromagnetic intermolecular interactions between the local spins.     

Formation of machine groups and part families in cellular manufacturing systems using a correlation analysis approach

The important step in the design of a cellular manufacturing (CM) system is to identify the part families and machine groups and consequently to form manufacturing cells. The scope of this article is to formulate a multivariate approach based on a correlation analysis for solving cell formation problem. The proposed approach is carried out in three phases. In the first phase, the correlation matrix is used as similarity coefficient matrix. In the second phase, principal component analysis (PCA) is applied to find the eigenvalues and eigenvectors on the correlation similarity matrix. A scatter plot analysis as a cluster analysis is applied to make simultaneously machine groups and part families while maximizing correlation between elements. In the third stage, an algorithm is improved to assign exceptional machines and exceptional parts using respectively angle measure and Euclidian distance. The proposed approach is also applied to the general group technology (GT) problem in which exceptional machines and part are considered. Furthermore, the proposed approach has the flexibility to consider the number of cells as a dependent or independent variable. Two numerical examples for the design of cell structures are provided in order to illustrate the three phases of proposed approach. The results of a comparative study based on multiple performance criteria show that the present approach is very effective, efficient and practical.     

Numerical investigation of heat and mass transfer during the desorption process of an Mg2Ni–H2 reactor

In this paper, a numerical study of coupled heat and mass transfer during the desorption process of metal–hydrogen reactor (Mg₂Ni–H₂), is presented. Analytical expressions describing, the reaction kinetic and the equilibrium pressure of the Mg₂Ni-H₂ system have been determined and integrated into a theoretical model that describes the dynamic behavior of the reactor. This model, which takes into account radiative heat transfer, is solved by the control volume finite element method (CVFEM). The numerical simulation is used to present the time–space evolutions of the temperature and the hydride density within the reactor and to evaluate the effect of radiative heat transfer and the governing operating parameters (outlet pressure, temperature of heating fluid, heat exchange coefficient) on the dynamic behavior of the reactor. In addition, a new geometric configuration of the reactor is proposed and simulated.     

Numerical study of a water distillation system using solar energy

This paper tackles an optimization approach in order to boost the fresh water production of a new design of a solar still which is located at Sfax engineering national school in Tunisia. This optimization approach is based upon the above mentioned design’s improvement by coupling the conventional solar still into at a condenser, solar air and water collector and humidifier. This new concept of a distiller solar still using humidification- dehumidification processes (HD) is exploited for the desalination purpose. As a result of this work, the humidification- dehumidification processes have an essential effect in improving the solar still performance. Performance has been predicted theoretically in terms of water and inner glass cover temperatures, the inlet temperature of air and water of the new concept of distiller on water condensation rate and fresh water production. A general model based on heat and mass transfers in each component of the unit has been developed in steady dynamic regime. The developed model is used, simulating the HD system, to investigate the influence of the meteorological and operating parameters on the system productivity. The obtained set of ordinary differential equations has been converted to a set of algebraic system of equations by the functional approximation method of orthogonal collocation. The developed model is used to simulate the HD system in order to investigate the steady state behavior of each component of the unit and the entire system exposed to a variation of the entrance parameters and meteorological conditions. The obtained results were compared with those of other studies and the comparison gives a good validity of the present results.

     

Fatty acids, 4‐desmethylsterols,and triterpene alcohols from Tunisian lentisc (Pistacia lentiscus) fruits

A comparative study was performed to determine the fatty acid, 4‐desmethylsterol and triterpenic alcohols compositions of three different Tunisian populations of Pistacia lentiscus fruit Rimel (RM), Korbous (KO), and Tebaba (TB). Fruits are rich in lipids, which varied from 39.37% (KO) to 42.48% (TB) on a dry weight basis. Qualitatively, fatty acid, sterol, mono‐ and dimethylsterol composition is identical for all populations. Oleic acid was the major fatty acid for all samples, accounting from 40.49% in TB population to 50.72% in RM population followed by the palmitic and linoleic acids. Other fatty acids are present at lower levels. Total sterol amount varied from 109.72 mg/100 g of oil (KO) to 434.26 mg/100 g of oil (RM) with an average of 248.74 mg/100 g of oil. The major 4‐desmethylsterol component in all studied Tunisian populations of P. lentiscus oil was ß‐sitosterol followed by campesterol in TB and KO, and by stigmasterol in RM. The amount of total triterpenic alcohols varied from 42.39 mg/100 g of oil in RM population to 70.41 mg/100 g oil in TB population. The quantitative difference in the fatty acids and 4‐desmethylsterols of the different populations studied could be due to the effect of geographic region and soil type.     

A non‐linear viscoelastic model for describing the fatigue behaviour of braided artificial ligaments

The objective of this paper is the determination of the dynamic fatigue behaviour of braided ligaments made of polypropylene by using a rheological model and an experimental fatigue tester. A non‐linear viscoelastic model has been proposed to describe the time‐dependent deformation behaviour of braided anterior cruciate ligament prosthesis. The elastic modulus and viscous modulus are calculated for different fatigue tests. The developed fatigue tester allows to combine simultaneous cyclic solicitations of bending and traction. These combined cyclic solicitations generate new mechanical properties of the prosthesis such as increasing of the dissipative factor, the material damping and the residual deformation with the number of fatigue cycles.