Abstract: In this study, a three dimensional computer code based on the so called SIMPLE algorithm (which stands for Semi-Implicit Method for Pressure-Linked Equations) developed by McGill University-Montréal-Canada is used for the numerical solution of a laminar fluid flow and heat transfer of impinging four jets in the presence of crossflow with constant temperature boundary condition on the impingement surface. The governing equations solved by the computer code are the continuity equation, three components of the momentum equation and the energy equation. The finite volume method is adopted for the discretisation of the governing equation. In the computer program, the finite difference equations are solved via the primitive pressure-velocity approach where the hybrid difference scheme, which is a combination of the central and upwind differences, is used to represent the convective and diffusive fluxes over the control volume surfaces. The results obtained show that in general, for multiple jets, the induced and imposed crossflow have significant effects on both the flow and temperature fields near the impingement surface. A strong crossflow deflects the jet and prevents it from impinging on the surface resulting in lower heat transfer rates and hence lower temperatures difference.The results also show that reducing the jet separation distances causes an increase of the temperature of the flow, and hence better cooling of impingement surface.
إبتسام عمارة (2008)

Abstract: Modern PET/CT clinics consist of a scanner room housing PET/CT unit and a control area, two or more waiting rooms where patients rest prior to scanning, and a hot lab where doses are prepared. The 511 keV photons from the PET positron emitting isotopes are the source term for the waiting rooms and the hot lab, while both the 511 keV photons and the polyenergtic spectrum of x-rays from the CT unit must be considered in the scanning roomThis study is intended to estimate dose distribution resulting from using a FDG procedure (555 MBq). The dose distribution is evaluated in injection room, waiting room, and scanning room using two methods. The first method is the analytical method whids is based on AAPM report № 108, while in the second method the dose distribution was simulated using the Monte Carlo code EGSXYZnrc .In the Monte Carlo method some parameters such as the optimal number of histories and the cut off energy of the electron are found to have a significant effect on the results. These parameters are tested and those values with less statistical error are adapted for the calculations.A good agreement between the two methods has been achieved. The dose distribution in the uptake room , waitting room and the scanning room appears to be below the annually dose limit and does not exceed 1% at the adjacent areas.
مريومة البهلول القرقني (2009)

The huge volume of Naturally Occurring Radioactive Materials (NORM) wastes produced annually by the oil and gas industry in Libya deserves the attention of the national environmental protection authority, radioactive waste management and regulatory bodies. An investigation was carried out to find out the concentration of (NORMs) in evaporation ponds sludge in south eastern oilfield (A/100) of Libya. Twenty soil samples were collected from five evaporation ponds sludge. Activity concentrations of 226Ra, 232Th and 40K in soil generated during oil production operations were determined using a gamma spectroscopy system based on High Purity Germanium (HPGe) detector. Concentrations ranged from 83 to 1000 Bq kg–1 for 226Ra, 59 to 315 Bq kg–1 for 232Th and 109 to 304 Bq kg–1 for 40K. To evaluate the radiological effects, radium equivalent activity and external hazard are calculated. The magnitude of these results demonstrates the need of screening oil residues for their radionuclide content in order to decide about possibility of minimize the environmental impact of NORM and their final disposal. Disposal of NORM waste has to be in accordance with national regulations, environmental policy and international agreements and conventions. The researchers recommend limits for clearance and disposal, based on best international practice. arabic 18 English 82
Usama Elghawi (1-2021)