Experimental and numerical investigations have been performed to study the natural convection heat transfer from a vertical rectangular fin arrays at different orientation angles.An experimental setup was constructed and calibrated to test different fin configurations. It basically consists of base plate, an array of parallel longitudinal fins, heating unit and layers of thermal insulation. Fin length (L) and fin thickness (t) were kept fixed at 187 and 6.5 mm respectively, while fin spacing (S) was varied from 3 to 16 mm and fin height (H) was varied from 15 to 45 mm. The orientation angle (β) was changed from 0° to 60°, and temperature difference between fin and surrounding (∆T) from 30 to 95 o C.Base-to-ambient temperature difference was also varied through a calibrated wattmeter ranging from 10 to 180W. To understand the general flow patterns dominating flows from the heat sink, the three-dimensionless elliptic governing equations were solved using finite volume computational fluid dynamics (CFD) code. A comparative study between the experimental and numerical results was performed to verify the numerical code. It was found for the configuration tested that the heat transfer rate per unit base area increases with the increase in the fin spacing and reaches a maximum value then decreases with farther increase in the fin spacing. The maximum heat dissipation occurs at optimal spacing S opt =7 mm. Empirical correlations between Nussult number, Rayleigh number, fin spacing, fin height, orientation angle, temperature difference between the fin and surroundings were derived. Finally the present work general empirical formula is given in the form =. .. .. Where , 15 mm ≤ H ≤ 45 mm, 3mm ≤ S ≤ 16 mm, °0 ≤ β ≤°60, t = 6.5 mm, L = 187 mm.

In this paper, the discrete–time periodic static output feedback control design problem is considered. A

hybrid conjugate gradient methods are analyzed and studied to tackle an equivalent optimization problem of this

optimal control problem. Finally, the proposed algorithms are tested numerically through several test problems

from the benchmark collection.

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يحلل المقال المنظمات الدولية مثل (عصبة الأمم) التي أنشئت في عام 1919م و الأمم المتحدة في عام 1945م وكذلك المنظمات الإقليمية مثل منظمة الدول الأمريكية (1948)، جامعة الدول العربية (1949)، منظمة حلف شمال الأطلسي، الناتو (1949)، منظمة معاهدة وارسو (1955) منظمة التعاون الاقتصادي و التنمية OECD) (1961))، منظمة الوحدة الأفريقية OAU) (1963))، رابطة أمم جنوب شرق آسيا (1967) (ASEAN) و الاتحاد الأوروبي (1957) (EU) ويقيم دورها في تحقيق السلام والأمن، وكذلك توفير الرفاهية والاستقرار الاقتصادي في جميع أنحاء العالم. 

التحول من منظمة الوحدة الأفريقية إلى الاتحاد الأفريقي. هل يحدث ذلك فرقًا؟