Natural convection in a trapezoidal enclosure with partial heating from below and symmetrical cooling from the sides has been investigated numerically. The heating is simulated by a centrally located heat source on the bottom wall, and four different values of the dimensionless heat source length, 1/5, 2/5, 3/5, 4/5 are considered. The laminar flow field is analyzed numerically by solving the steady, two-dimensional incompressible Navier-Stokes and energy equations. The Cartesian velocity components and pressure on a collocated (non-staggered) grid are used as dependent variables in the momentum equations discretized by finite volume method; body fitted coordinates are used to represent the trapezoidal enclosure, and grid generation technique based on elliptic partial differential equations is employed. SIMPLE algorithm is used to adjust the velocity field to satisfy the conservation of mass. The range of Rayleigh number is (103≤ Ra ≤105) and Prandtl number is 0.7. The results show that the average Nusselt number increases with the increases of the source length.
In this study, pure SnO2 Nanoparticles doped with Cu were synthesized by a chemical precipitation method. Using SnCl2.2H2O, CuCl2.2H2O as raw materials, the materials were annealed at 550°C for 3 hours in order to improve crystallization. The XRD results showed that the samples crystallized in the tetragonal rutile type SnO2 stage. As the average SnO2 crystal size is pure 9nm and varies with the change of Cu doping (0.5%, 1%, 1.5%, 2%, 2.5%, 3%),( 8.35, 8.36, 8.67, 9 ,7, 8.86)nm respectively an increase in crystal size to 2.5% decreases at this rate and that the crystal of SnO2 does not change with the introduction of Cu, and S
... Show More
(22)
(7)
The caliphs of Tukalti Able III (Tiglath-pileser) sustained their extension and enclosure strategy whom they were highly talented with outstanding potentialities. They performed their political plan of extinguishingthe ambitions of the upper class and the internal uprisings. The Assyrian Kingdom, in the eighth century BC reached to the highest degree of expansion that no other ancient Iraqi kingdom had reached It dominated the whole near eastbut it did not have absolute command due to the subsequent uprisings that out bursted in the regions attached to the kingdom near the borders.
Number theorists believe that primes play a central role in Number theory and that solving problems related to primes could lead to the resolution of many other unsolved conjectures, including the prime k-tuples conjecture. This paper aims to demonstrate the existence of this conjecture for admissible k-tuples in a positive proportion. The authors achieved this by refining the methods of “Goldston, Pintz and Yildirim” and “James Maynard” for studying bounded gaps between primes and prime k-tuples. These refinements enabled to overcome the previous limitations and restrictions and to show that for a positive proportion of admissible k-tuples, there is the existence of the prime k-tuples conjecture holding for each “k”. The sig
... Show More
تعرضت المواقع الاثریة في الع ا رق الى النبش والتخریب،وقد أدى ذلك الى أستخ ا رج أعداداً كبیرة من النصوص المسماریة وتهریبها الى خارج الع ا رق. ومن ضمنها نصوص مدینة أ ري- ساكرك، فقد درست مجموعة من هذه النصوص والبالغ عددها ( ١١٥٩ ) نصاً التي نش رت في في هذا البحث قمنا بد ا رسة ( ٤) نصوص مصادرة لصالح المتحف .(Nisaba مجلد ( 15 الع ا رقي ذات مضامین أقتصادیة تتعلق بالحیوانات،ارخت بین السنة الثانیة والاربعین من حكم الملك شولكي وحت
... Show MoreThe wear behavior of alumina particulate reinforced A332 aluminium alloy composites produced by a stir casting process technique were investigated. A pin-on-disc type apparatus was employed for determining the sliding wear rate in composite samples at different grain size (1 µm, 12µm, 50 nm) and different weight percentage (0.05-0.1-0.5-1) wt% of alumina respectively. Mechanical properties characterization which strongly depends on microstructure properties of reinforcement revealed that the presence of ( nano , micro) alumina particulates lead to simultaneous increase in hardness, ultimate tensile stress (UTS), wear resistances. The results revealed that UTS, Hardness, Wear resistances increases with the increase in the percentage of
... Show MoreLet M is a Г-ring. In this paper the concept of orthogonal symmetric higher bi-derivations on semiprime Г-ring is presented and studied and the relations of two symmetric higher bi-derivations on Г-ring are introduced.
(1)
تكمن مشكلة البحث في أن كليات التربية عامةً وكلية التربية /ابن الهيثم خاصة ما زالت تسير وفق أنماط إدارية تقليدية وأن هناك شكوى تلهج بها الألسن في المجتمع المحيط بأن المخرجات التعليمية لا توازي تطلعات المجتمع وتوجهاته المستقبلية، كذلك الأهمية لتطبيق معايير ضمان جودة تحقق المستوى المطلوب لهذه الكلية أسوة بالمعايير العالمية، إذ هدف البحث في معرفة واقع معايير ضمان الجودة في الكلية والانتقال إلى رؤية مستقبلية ل
... Show Moreهدفت الدراسة التعرف على الضغوط النفسية والخوف من المستقبل لدى أمهات أطفال طيف التوحد، بلغت عينة الدراسة )60( ام لديهن طفل توحدي، تم استخدام المنهج الوصفي التحليلي وبعد تطبيق مقياسي الدراسة ومعالجة البيانات احصائيا توصلت الدراسة ان األمهات لديهن درجة عالية من الضغوط النفسية ودرجة عالية من الخوف حول مستقبل اطفالهن، وفي ضوء نتائج الدراسة خرجت الباحثة ببعض التوصيات والمقترحات.
Offline handwritten signature is a type of behavioral biometric-based on an image. Its problem is the accuracy of the verification because once an individual signs, he/she seldom signs the same signature. This is referred to as intra-user variability. This research aims to improve the recognition accuracy of the offline signature. The proposed method is presented by using both signature length normalization and histogram orientation gradient (HOG) for the reason of accuracy improving. In terms of verification, a deep-learning technique using a convolution neural network (CNN) is exploited for building the reference model for a future prediction. Experiments are conducted by utilizing 4,000 genuine as well as 2,000 skilled forged signatu
... Show More
(2)
(1)