Diffusion

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Self-Adaptive Multilevel Methods for Fluid Flow Problems

Journal Title, Volume, Page: 
Ph.D. Thesis Clarkson Univ., Potsdam, NY
Year of Publication: 
1994
Authors: 
Anwar Saleh
Current Affiliation: 
Department of Mathematics, Faculty of Science, An-Najah National University, Nablus, Palestine
Preferred Abstract (Original): 

A computational study of self-adaptive multilevel methods for complex fluid flow problems is made to test the efficiency of these methods. The model problem is time-dependent, nonlinear, convective dominated, and diffusion-limited. Numerical solutions exist, although not multilevel or adaptive ones. A comparison of two adaptive multilevel methods, the multilevel adaptive technique (MLAT) and the fast adaptive composite grid method (FAC), is given to show the possible advantages of the FAC method over the MLAT method by applying them to solve a Poisson equation with an analytical solution. The model problem consists of the quasi-compressible system of the anelastic equations with an initial condition representing a negatively buoyant blob of cold air, which descends to the ground and spreads laterally forming a cold front. A multilevel solution is first obtained on a staggered grid using finite differencing both in time and space. Then the two self-adaptive multilevel methods (MLAT ant FAC) are applied. Numerical results are discussed and compared to numerical solution obtained by Fulton (18) using a Fourier-Chebyshev spectral method with a semi-implicit Runge-Kutta scheme for time integration. Numerical results, as expected, show the FAC is more accurate (at interface) than the MLAT when applied to a Poisson equation. When the self-adaptive versions of the FAC and the MLAT are applied to the complex anelastic equations, computational results show little difference between the two methods and a saving of up to 70 percent in execution time (compared to uniform grid methods of the same accuracy), and when compared to a Fourier-Chebyshev spectral model of the same problem, they are faster for modest accuracy, while the spectral method is faster for higher accuracy.

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The Study of Kinetics and Thermodynamics of Selected Pharmaceuticals and Personel Care Products on Agriculture Soil

Journal Title, Volume, Page: 
European Journal of Chemistry, 3 (4), 468-474
Year of Publication: 
2012
Authors: 
shehdeh jodeh
Chemistry Department, An‐ Najah National University, Nablus, 11347, Palestine
Current Affiliation: 
Department of Chemistry, An- Najah N. University, PO Box 7, Nablus, West Bank, Palestine
Preferred Abstract (Original): 

Pollution of the aquatic environment by human and veterinary waste pharmaceuticals is an increasing area of concern but little is known about their ecotoxicological effects on wildlife. In this study, three pharmaceuticals were selected (ibuprofen, amoxicillin and caffeine) as examples that are released in the environment. All of them are marketed in the Palestinian market (Pharmacies), private clinics and hospitals. The adsorption of the selected pharmaceuticals was examined by batch sorption experiments onto agriculture soil. Pharmaceuticals adsorption kinetics followed the pseudo-second-order adsorption model. Adsorption isotherms were best fitted by the Freundlich isotherm model. The “n” parameters were higher than 1 and the Kf values for all of them were less than 1. High removal rates of amoxicillin and ibuprofen were achieved in acidic media (pH = 1-4) and reached more than 88% Except for the caffeine increased at higher pH and reached more than 92%. The thermodynamics parameters showed that the adsorption process on soil was spontaneous and exothermic.

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