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)

There are three main aims that make this study particularly important and interesting to radiometric studies. Firstly, it will provides information on the concentration composition of natural and the associated man-made radioactivity of imported dental porcelain materials to be used by most dental laboratories in Great Jamahiriya. Since these materials do not pass radiation inspection tests before their entry or use and there is a large variety of supply source of these dental materials to be used for all dental works on Libyan patients, anomalies can be identified easily. Secondly, the analysis of selective elemental abundance (U, Th, and K ) and dose rate calculations may be used to calculate effective dose rates to dental laboratory technicians and also to the patient who will be using these specific materials. This research project will provide the first results of such measurements and the corresponding average annual effective dose rates equivalent to the patients using these materials and also to the dental technician and doctors work in the various dental laboratories that make use of these materials in their daily work. A total number of 30 dental powder samples were collected from a number of dental laboratories around Tripoli area will be analyzed. In this research project, the results from this preliminary survey regarding Th, U and K elemental concentrations in a wide variety of dental materials by means of high-resolution X-ray spectrometry will be presented. Further results from these investigations concerning activity concentrations and the associated dose rates, effective dose and the committed dose due to the use of these materials are going to be calculated and compared with other published data elsewhereandrecommendationoftheirusewillbederivedaccordingly. arabic 10 English 74
Karima Mohamed Ali Elmasri, Nouri A. Droughi(9-2010)

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)