Studies on the sorption of praseodymium (III), holmium (III) and cobalt (II) from nitrate medium using TVEX-PHOR resin

The use of TVEX-PHOR resin for the sorption of praseodymium (III), holmium (III) and cobalt (II) from nitrate medium was carried out using batch and column techniques. Various parameters affecting the uptake of these metal ions such as v/m ratio, pH and the metal ion concentration were separately studied. Effect of temperature on the equilibrium distribution values has been studied to evaluate the changes in standard thermodynamic quantities. Experimental results of the investigated metal ions were found to fit to Freundlich isotherm model over the entire studied concentration range. Selectivity sequence of the resin for these metals is Ho>Pr>Co. The recovery of the investigated metals from the loaded resin is preformed with 0.1M sulphuric acid.     

Evaluation of refined theories for multilayered shells via Axiomatic/Asymptotic method

This paper is devoted to refined shell theories for the analysis of isotropic and laminated shells. Refined theories are built by assuming higher expansion order for the displacement field in the shell thickness directions. The implementation of these theories is made according to the Carrera unified formulation (CUF) which makes it possible to obtain shell governing equations in terms of fundamental nuclei whose form is independent of the chosen theory shell. Equivalent single layer and layer wise schemes are used. The axiomatic/ asymptotic technique is employed to evaluate the effectiveness of each displacement variable in the adopted displacement expansion. The error introduced by each term deactivation is evaluated with respect to a reference solution and according to a given error criterion; if the error computed does not exceed an a priori defined threshold the term is considered as not relevant and discarded. In this way it is possible to construct reduced models for each stress/displacement component. Attention has been restricted to closed form Navier type solutions and simply supported orthotropic shells are considered in the numerical investigation. Analysis of the displacement variables relevance is performed considering the influence of the kind of material and of the geometry, specifically isotropic and laminated materials and thick and thin shells. “Best”′ reduced models are proposed and related distributions are discussed.     

Effect of olive ripeness on chemical properties and phenolic composition of chétoui virgin olive oil

BACKGROUND: The aim of the present work was to investigate the influence of fruit ripening on oil quality in an attempt to establish an optimum harvesting time for Chétoui olives, the second main olive variety cultivated in Tunisia. RESULTS: Our results showed that many analytical parameters, i.e., peroxide value, UV absorbance at 232 and 270 nm, chlorophyll pigments, carotenoids and oleic acid contents decreased during ripening, whilst oil content and linolenic acid increased. Free acidity remained practically stable with a very slight rise at the highest maturity index. The trend of oxidative stability, total phenols and o‐diphenols, showed an increase at the early stages followed by a reduction at more advanced stages of maturity. The major phenolic compounds, such as hydroxytyrosol, ligstroside aglycon, elenolic acid, acetoxy‐pinoresinol and oleuropein aglycon, seemed to have the same behaviour. In the case of tyrosol, a strong decrease was observed directly related with the ripening progress. CONLUSION: On the basis of the evolution of the analytical parameters studied, the best stage of Chétoui olive fruits for oil processing seems to be at ripeness index higher than 2.0 and lower than 3.0. Copyright © 2009 Society of Chemical Industry     

Performance analyses of Cu–Cl hydrogen production integrated solar parabolic trough collector system under Algerian climate

The potential of hydrogen production by thermochemical cycle in Algeria using solar radiation as heat sources is estimated under the climate conditions of the country. The study analyzes an integrated copper–chlorine (Cu–Cl) thermochemical cycle with solar parabolic trough system for hydrogen production. In order to determine the most promising solar sites available for deploying the integrated system, the direct normal solar irradiance (DNI) for horizontal tracking system oriented in North-South has been estimated and compared for different locations. Heat gain from parabolic trough collector model is evaluated under Algerian conditions. To describe the different steps of the Cu–Cl cycle for hydrogen production, we perform a thermodynamic analysis accounting for relevant chemical reactions and including the determination of the energy necessary to the cycle. A parametric study is conducted to investigate the effect of heat gain from the parabolic trough collector (PTC) on the hydrogen production rate. Furthermore, the rate production of hydrogen by the Cu–Cl cycle is analyzed and compared for performance improvement of the system for different climatic regions in Algeria. Simulation results reveal great opportunities of hydrogen production using Cu–Cl cycle combined with solar PTC in the south of Algeria with annual hydrogen production exceeds 84 Tons H₂/year (around 0,30 kg/m²/day).     

Spark plasma sintering versus hot pressing – densification,bending strength,microstructure, and tribological properties of Ti5Al2.5Fe alloys

Ti5Al2.5Fe alloys were fabricated by the spark plasma sintering (SPS) and hot pressing (HP) pressure-assisted sintering techniques from pre-alloyed powders with a particle size of about 200?μm. The powders were sintered at 850 °C for two different holding times (5 and 8 min) and heating rates (50 and 150°C?min^?1) at 25?MPa. The maximum relative densities were 99.70 and 98.78% for SPS and HP samples, respectively. All the alloys prepared by the SPS process had significantly higher bending strengths (1825–2074?MPa) than the alloys prepared by the HP process (648–1330?MPa). A decrease in the heating rate from 150 to 50°C min^?1 enhanced the wear resistance of the Ti5Al2.5Fe alloys prepared by both the SPS and HP processes.     

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...