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)

The 6MV photon beam production by the Elekta Line accelerateur of Tripoli of medical center (TMC) was modeled using Beamnrc and Dosexyzne Monte Carlo codes. The Beamnrc code was used to model the accelerator head and generate phase files. The phase space files were then used as input to the Dosexyzne code to simulate octogenarian deth dose and beam profiles. simulation were first stared using nominal provided by the vendor, a field size of 10x10cm2 and Source to surface distance (SSD) of 100 cm. simulation were compared with experimental data and energy tuning procedures were applied to validate the model. Energy tuning procedures indicated that the nominal energy of 6 MV and a FWHM of the Gaussian distribution of the source of 0.35 cm were the optimal energy and FWHM for the model. The depth of maximum dose at 6 MV was found to be 1.5 cm. The percentage relative differences between calculated and experimental Pdd(s) ranged from 0.5% to 3% for field size of 10cm2 and reached a value of 8% at depths greater than 20cm, The model was later used to calculate PDD(s) and beam profile and output factors for different field size ranging from 3x3cm2 to 25x25cm2. Calculated output factors were in good agreement with experimental values (the percentage relative differences ranged from 1% to 4%). (Author) arabic 42 English 152
Karima Elmasri, Tawfik Giaddui(12-2012)

Cardiovascular disease (CVD) is a major cause of mortality and the main cause of morbidity worldwide. CVD may lead to heart attacks and strokes and most of these are caused by atherosclerosis; this is a medical condition in which the arteries become narrowed and hardened due to an excessive build-up of plaque on the inner artery wall. Arterial calcification and, in particular, abdominal aortic calcification (AAC) is a manifestation of atherosclerosis and a prognostic indicator of CVD. In this paper, a two-stage automatic method to detect and quantify the severity of AAC is described; it is based on the analysis of lateral vertebral fracture assessment (VFA) images. These images were obtained on a dual energy x-ray absorptiometry (DXA) scanner used in single energy mode. First, an active appearance model was used to segment the lumbar vertebrae L1-L4 and the aorta on VFA images; the segmentation of the aorta was based on its position with respect to the vertebrae. In the second stage, feature vectors representing calcified regions in the aorta were extracted to quantify the severity of AAC. The presence and severity of AAC was also determined using an established visual scoring system (AC24). The abdominal aorta was divided into four parts immediately anterior to each vertebra, and the severity of calcification in the anterior and posterior walls was graded separately for each part on a 0-3 scale. The results were summed to give a composite severity score ranging from 0 to 24. This severity score was classified as follows: mild AAC (score 0-4), moderate AAC (score 5-12) and severe AAC (score 12-24). Two classification algorithms (k-nearest neighbour and support vector machine) were trained and tested to assign the automatically extracted feature vectors into the three classes. There was good agreement between the automatic and visual AC24 methods and the accuracy of the automated technique relative to visual classification indicated that it is capable of identifying and quantifying AAC over a range of severity. arabic 30 English 163
Karima Mohamed Ali Elmasri, William Evans, Yulia Hicks(1-2016)