Effect of process parameters on the concentration,current efficiency and energy consumption of electro-generated silver(II)

Electro-membrane generation of Ag(II) in nitric acid was experimentally explored in a three-electrode laboratory cell with respect to various operating parameters. DSA-O₂, titanium plate and saturated Ag/AgCl were employed as the anode, cathode and reference electrode, respectively. The considered process parameters included anolyte temperature and Ag(I) initial concentration, electrolysis time, current density and supporting electrolyte concentration. Parameter effect on the Ag(II) concentration, current density and energy consumption were determined by the Taguchi and ANOVA methods for test design and data analysis, respectively. The results revealed that current density, AgNO₃ concentration and temperature had noticeable effect on the generation of Ag(II). On the other hand, AgNO₃ concentration and current density showed the most dominant effect on the Ag(II) current efficiency: 48.5% and 30.3%, respectively. AgNO₃ concentration and current density were also found to have the highest effect on the energy consumption: 72.4% and 15.9%, respectively. Validity of the Taguchi method was also assessed by collecting the actual data.     

Optimization strategies in credit portfolio management

This paper focuses on the application of an original global optimization algorithm, based on the hybridization between a genetic algorithm and a semi-deterministic algorithm, for the resolution of various constrained optimization problems for realistic credit portfolios. Results are analyzed from a financial point of view in order to confirm their relevance.     

Oxidation of some organic thiols with tetramethylammonium fluorochromate(VI)

Tetramethylammonium fluorochromate oxidizes alcohols to the corresponding aldehydes and ketones without polymerization of double bonds, overoxidation, and other side reactions. This reagent is effective for oxidation of thiols to disulfides. Original Russian Text H. Imanieh, S. Ghamami, M.K. Mohammadi, A. Jangjoo, 2007, published in Zhurnal Obshchei Khimii, 2007, Vol. 77, No. 2, pp. 310–312.     

Volumetric properties of the (tetrahydrofuran + water) and (tetra-n-butyl ammonium bromide + water) systems: Experimental measurements and correlations

In this communication, we report experimental density data for the binary mixtures of (water + tetrahydrofuran) and (water + tetra-n-butyl ammonium bromide) at atmospheric pressure and various temperatures. The densities were measured using an Anton Paar™ digital vibrating-tube densimeter. For the (tetrahydrofuran + water) system, excess molar volumes have been calculated using the experimental densities and correlated using the Redlich–Kister equation. The Redlich–Kister equation parameters have been adjusted on experimental results. The partial molar volumes and partial excess molar volumes at infinite dilution have also been calculated for each component. A simple density equation was finally applied to correlate the measured density of the (tetra-n-butyl ammonium bromide + water) system.     

Potassium aluminum sulfate (alum): an efficient catalyst for the one-pot synthesis of trisubstituted imidazoles

Trisubstituted imidazoles were synthesized in high yields in the presence of potassium aluminum sulfate (alum) as a non-toxic, reusable, inexpensive, and easily available reagent at 70°C.     

Recent advances in asymmetric multicomponent reactions (AMCRs)

Asymmetric multicomponent reactions (AMCRs) include the reaction of three or more reactants simultaneously to produce chiral products that they have some advantages containing simple procedures, saving time and energy, and being environmentally friendly processes. AMCRs have seen much development and their potent synthetic approaches are discussed in this review.     

Effects of longitudinal grooves on the Couette–Poiseuille flow

The effects of longitudinal grooves on the flow resistance in a channel where the flow is driven by movement of one of the walls and modified by a streamwise pressure gradient have been studied. The reducedorder geometrymodel has been used to extract geometric features that are hydraulically relevant. Three distinct zones leading to the reduced resistance have been identified, depending on the flow pressure gradient and the groove wave number. Two of these zones correspond to grooves with long wavelengths and one to grooves with short wavelengths. Optimization has been used to determine shapes that provide the largest flow rate. In the case of the long-wavelength grooves, the optimal shapes depend on the constraints. These shapes are well approximated by a certain universal trapezoid for grooves that have the same height and depth. There exists an optimum depth which, combined with the corresponding shape, defines the optimal geometry in the case of the unequal-depth grooves; this shape is well approximated by a Gaussian function. No optimal shape exists for the short-wavelength grooves if the groove amplitude is sufficiently small; the shortest admissible wavelength dominates system performance under such conditions. The most effective groove wave number does exist for higher grooves, but the optimal shape cannot be determined due to numerical limitations.