Abelian Lie symmetry algebras of two-dimensional quasilinear evolution equations

We carry out the classification of abelian Lie symmetry algebras of two-dimensional second-order nondegenerate quasilinear evolution equations. It is shown that such an equation is linearizable if it admits an abelian Lie symmetry algebra that is of dimension greater than or equal to 5 or of dimension greater than or equal to 3 with rank-one.     

Symmetry analysis of the charged squashed Kaluza–Klein black hole metric

In this research article, a complete analysis of symmetries and conservation laws for the charged squashed Kaluza–Klein black hole space‐time in a Riemannian space is discussed. First, a comprehensive group analysis of the underlying space‐time metric using Lie point symmetries is presented, and then the n‐dimensional optimal system of this space‐time metric, for n = 1,…,4, are computed. It is shown that there is no any n‐dimensional optimal system of Lie symmetry subalgebra associated to the system of geodesic for n≥5. Then the point symmetries of the one‐parameter Lie groups of transformations that leave invariant the action integral corresponding to the Lagrangian that means Noether symmetries are found, and then the conservation laws associated to the system of geodesic equations are calculated via Noether's theorem. Copyright © 2015 John Wiley & Sons, Ltd.     

Comparison of the performance of different hybrid catalysts for direct synthesis of dimethyl ether from synthesis gas

Nine hybrid catalysts have been prepared, characterized and tested in a micro reactor for the direct synthesis of dimethyl ether. The physical mixtures of H-MFI-90 with ICI or KMT catalysts showed better performance.     

One‐Pot Synthesis of Sulfonamides and Sulfonyl Azides from Thiols using Chloramine‐T

A convenient synthesis of sulfonamides and sulfonyl azides from thiols is described. In situ preparation of sulfonyl chlorides from thiols was accomplished by oxidation with chloramine‐T (=N‐chlorotosylamide=N‐chloro‐4‐methylbenzenesulfonamide), tetrabutylammonium chloride (Bu₄NCl), and H₂O. The sulfonyl chlorides were then further allowed to react with excess amine or NaN₃ in the same pot.     

Improving the Morphological Parameters of Aluminum Foam for Maximum Sound Absorption Coefficient using Genetic Algorithm

Fabricating of metal foams with desired morphological parameters including pore size, porosity and pore opening is possible now using sintering technology. Thus, if it is possible to determine the morphology of metal foam to absorb sound at a given frequency, and then fabricate it through sintering, it is expected to have optimized metal foams for the best sound absorption. Theoretical sound absorption models such as Lu model describe the relationship between morphological parameters and the sound absorption coefficient. In this study, the Lu model was used to optimize the morphological parameters of Aluminum metal foam for the best sound absorption coefficient. For this purpose, the Lu model was numerically solved using written codes in MATLAB software. After validating the proposed codes with benchmark data, the genetic algorithm (GA) was applied to optimize the affecting morphological parameters on the sound absorption coefficient. The optimization was carried out for the thicknesses of 5 mm to 40 mm at the sound frequency range of 250 Hz–8000 Hz. The optimized parameters ranged from 50% to 95% for porosity, 0.1 mm to 4.5 mm for pore size, and 0.07 mm to 0.6 mm for pore opening size. The result of this study was applied to fabricate the desired Aluminum metal foams for the best sound absorption. The novel approach applied in this study, is expected to be successfully applied in for best sound absorption in desired frequencies.     

Application of Ag2X (X = SO3, Cr2O7, C2O4 and CO3) solid-phase reagents for indirect determination of cyanide in the industrial effluent using FIA-FAAS system

Four solid-phase reagents have been tested for indirect determination of cyanide using flow injection analysis-flame atomic absorption spectrometry (FIA-FAAS). The method is based on insertion of aqueous cyanide solutions into an on-line Ag₂X (where X are SO₃²⁻, Cr₂O₇²⁻, C₂O₄²⁻ and CO₃²⁻) packed column (25%, m/m suspended on silica gel beads) and re-distilled water or sodium hydroxide are used as the carrier stream. The eluent containing the analyte as silver cyanide complexes, produced from reaction between Ag₂X and cyanide, measured by flame atomic absorption spectrometry. The method is simple, fast and selective than other published FIA procedures. A relative standard deviation (R.S.D.) better than 1.12% was obtained in a repeatability study. The method was applied to the determination of cyanide in industrial electrolytic baths.     

Combination of steepest descent and BFGS methods for nonconvex nonsmooth optimization

In this paper, a method is developed for solving nonsmooth nonconvex minimization problems. This method extends the classical BFGS framework. First, we generalize the Wolfe conditions for locally Lipschitz functions and prove that this generalization is well defined. Then, a line search algorithm is presented to find a step length satisfying the generalized Wolfe conditions. Next, the Goldstein e-subgradient is approximated by an iterative method and a descent direction is computed using a positive definite matrix. This matrix is updated using the BFGS method. Finally, a minimization algorithm based on the BFGS method is described. The algorithm is implemented in MATLAB and numerical results using it are reported.     

An Effective Nonsmooth Optimization Algorithm for Locally Lipschitz Functions

To construct an effective minimization algorithm for locally Lipschitz functions, we show how to compute a descent direction satisfying Armijo’s condition. We present a finitely terminating algorithm to construct an approximating set for the Goldstein subdifferential leading to the desired descent direction. Using this direction, we propose a minimization algorithm for locally Lipschitz functions and prove its convergence. Finally, we implement our algorithm with matrix laboratory (MATLAB) codes and report our testing results. The comparative numerical results attest to the efficiency of the proposed algorithm.     

A comparative study of AgX (X = Cl(-), Br(-), I(-) and N(3)(-)) solid-phase reactors for flow-injection determination of cyanide in electroplating wastewater.

In this study, a rapid flow injection-flame atomic absorption spectrometry for cyanide detection was developed. Different AgX (where X is Cl(-), Br(-), I(-) and N(3)(-)) solid-phase reagents (SPR) were tested for indirect determination of cyanide. In a single-line FIA system, the cyanide was allowed to react with AgX SPR, which in turn changed Ag ions in AgX to silver cyanide complexes in a sodium hydroxide carrier stream. The eluent containing the analyte as silver cyanide complexes was measured by FAAS. The calibration curve was linear up to 30 mg l(-1) with a detection limit of 0.05 mg l(-1) for cyanides. The sampling rate and the relative standard deviation were <1.09% and >200 h(-1), respectively. The method was applied to the determination of cyanide in electroplating wastewater.     

Synthesis of multiresponsive β‐cyclodextrin nanocomposite through surface RAFT polymerization for controlled drug delivery

In this study, a unique magnetic, pH, and thermo‐responsive hydrogel nanocomposite was synthesized via surface reversible addition fragmentation chain transfer (RAFT) copolymerization of acrylic acid (AA) and N‐isopropyl acrylamide (NIPAM) in the presence of magnetic β‐cyclodextrin (β‐CD). The nanocomposite demonstrated a pH‐responsiveness behavior at pHs 3 and 9. Moreover, swelling behaviors of nanocomposite were measured in solutions with various temperatures. Furthermore, the nanocomposites exhibited high swelling capacity by applying an external magnetic field because of the presence of Fe₃O₄ nanoparticles in the polymer structure. Besides, the doxorubicin (DOX) loading and releasing behaviors of the hydrogel nanocomposites were studied because of the stimuli‐responsive properties of the synthesized carriers. The adsorption of DOX obeyed a pseudo‐second‐order model and fitted well to the Langmuir isotherm model with the maximum adsorption capacity uptake of 291 mg g^?1. In conclusion, the hydrogel nanocomposites were found to be as potential nanocarriers for use in controlled release applications.