A numerical investigation has been performed to study the effect of eccentricity on unsteady state, laminar aiding mixed convection in a horizontal concentric and eccentric cylindrical annulus. The outer cylinder was kept at a constant temperature
while the inner cylinder was heated with constant heat flux. The study involved numerical solution of transient momentum (Navier-Stokes) and energy equation using finite difference method (FDM), where the body fitted coordinate system (BFC) was
used to generate the grid mesh for computational plane. The governing equations were transformed to the vorticity-stream function formula as for momentum equations and to the temperature and stream function for energy equation.
A computer progra

         A theoretical calculations of the rate constant of electron transfer (ET) in a dye – semiconductor system with variety solvent are applied on system contains safranineT dye with TiO₂ in many solvents like water, 1-propanol, Formamide, Acetonitrile and Ethanol.

    A matlap program has been written to evaluate many parameters such that, the solvent reorganization energy, effective free energy, activation free energy, coupling matrix element and the rate constant of electron transfer.

    The results of the rate constant of electron transfer calculated theoretically are in a good agreement with experimental and theoretical value

This work presents an experimental study of heat transfer and flow of distilled water and metal oxide nanofluid Fe₃O₄-distilled water at concentrations of (φ = 0.3, 0.6, 0.9 %) by volume in a horizontal pipe with constant magnetic field. All the tests are carried out with Reynolds number range (2900-9820) and uniform heat flux (11262-19562 W/m²). The results show that, the nanofluid concentration and magnetic intensity increase, the Nusselt number increases. The maximum enhancement in Nusselt number with magnetic nanofluid is (5.4 %, 26.4 %, 42.7 %) for volume concentration (0.3, 0.6, 0.9 %) respectively. The enhancement is maximized with magnetic intensity (0.1, 0.2, 0.3 tesla) respectively to (43.9, 44

A description of the theoretical of the reorganization energies have been described  according to the outer-sphere Marcus model .It  is a given expression according this model unable to evaluate the reorganization energy for electron transfer at liquid /liquid interface. The spherical model approach have been used to  evaluate the radius of donor and acceptor liquid alternatively .Theoretical results of  the reorganization free energy for electron transfer at liquid/liquid interface system was  carried out . Matlap program is then used to calculate 𝐸0 for electron transfer reaction between water donor stated and many liquid acceptor state. This shows a good  agreement with the experiment. The results