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Natural convection in a porous medium saturated with supercritical carbon dioxide (CO 2) which is bounded by square cavity is studied numerically by solving the governing Darcy equation using finite-differences method. The side walls of cavity were assumed to be isotherm with fixed temperature difference of 0.0152 K, while the upper and lower sides are assumed to be thermally insulated, the aspect ratio is chosen to be one, with cavity height of 0.01 m, the Darcy number adopted is 5 10  , usually these values lead to very small modified Rayleigh number. Despite all of this, the state of supercritical takes the fluid (CO 2) to a huge changes in its properties (

The magnetic electron objective lens is of a great importance which limit the resolving power of the electron microscope. The present work investigates the objective focal properties of a single polepiece magnetic electron lens of truncated cone polepiece shape of the selected geometrical dimensions for practical applications. The lens has been fabricated consist of cast shield made of mild steel combined with exciting isolated cooper coil of 500 turns. The theoretical and experimental results presented the magnetic flux density distribution and the objective focal properties of the lens, in mode of operation when the direction of incident electrons beam facing the lens back plate of the lens. Moreover, the theoretical and experimental results are in a good agreements.