Selective reagents for solvent extraction of metals—III. Picolinic acids

Alkyl-substituted pyridine-2-carboxylic acids have been found to be efficient reagents for the extraction of Cu²⁺, Fe³⁺, Co²⁺ and Ni²⁺ from aqueous sulfate solutions at pH 1.7. The effects of the position and the nature of the substituent are discussed.     

Thermochemical decomposition of cobalt doped ammonium paratungstate precursor

The calcination is one of the important steps in the preparation of nanostructured WC and WC–Co powders from chemically co-precipitated W–Co precursors. In the present paper, the processing of the precursor prepared by co-precipitation from cobalt(II) hydroxide and ammonium paratungstate is reported. The precursor was calcined at different temperatures under various atmospheres. The resulting powders were investigated using scanning electron microscopy, X-ray diffraction, thermogravimetric analysis (TGA), differential TGA, BET, and mass spectrographic analysis techniques. The results showed that the precursor decomposes differently by calcination under different atmospheres, i.e. nitrogen, air, and helium–5% oxygen. Different decomposition behaviour was observed when the calcination was carried out at medium temperature in flowing and non-flowing air. Nanostructured powders with particle size of around 90 nm can be obtained after calcination. The precursor decomposes into CoWO₄ and WO₃ oxides at 520 °C in air after a weight loss of 10.3%.     

Multivariate padé approximation for solving partial differential equations (PDE)

In this paper, numerical solution of partial differential equations (PDEs) is considered by multivariate padé approximations. We applied these method to two examples. First, PDE has been converted to power series by two‐dimensional differential transformation, Then the numerical solution of equation was put into multivariate padé series form. Thus, we obtained numerical solution of PDE. Copyright © 2010 John Wiley & Sons, Ltd.     

Conjugate gradient predictor corrector method for solving large scale problems

In this paper, we give a new method for solving large scale problems. The basic idea of this method depends on implementing the conjugate gradient as a corrector into a continuation method. We use the Euler method as a predictor. Adaptive steplength control is used during the tracing of the solution curve. We present some of our experimental examples to demonstrate the efficiency of the method.

     

Synthesis of 4,5-diaryl-1,2,3-benzenetricarboxylates by reaction of 4-hydroxycyclopent-2-en-1-one-2-carboxylates with dimethyl acetylenedicarboxylate

4,5-Diaryl-1,2,3-benzenetricarboxylates were prepared by cycloaddition of 4-hydroxycyclo-2-penten-1-one-2-carboxylates with dimethyl acetylenedicarboxylate.     

Nonlinear eigenvalue problems with symmetry

In this paper we use the conjugate gradient predictor corrector method (CGPCM) in the context of continuation methods. By exploiting symmetry in certain nonlinear eigenvalue problems, we can decompose the centered difference discretization matrices into small ones and reduce computational cost. We use the cyclic group of order two to divide the system into two smaller systems. We reduce the cost and the computational time by combining CGPCM with the idea of the exploiting symmetries. Theoretical and numerical results are presented. Conclusions are given.     

Effects of heat and mass transfer peristaltic flow of?Williamson fluid in a vertical annulus

In the present investigation, we have studied the effects of mixed convection heat and mass transfer on peristaltic flow of Williamson fluid model in a vertical annulus. The governing equations of Williamson fluid model are simplified using the assumptions of long wavelength and low Reynold’s number. An approximated analytical and numerical solutions are found for the velocity field using (i) Perturbation method (ii) Shooting method. The comparisons of analytical and numerical solutions have been presented. The expressions for pressure rise, velocity against various physical parameter are discussed through graphs.