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Article
HIGH ALTITUDE PLATFORM STATIONS IN DESIGN WIRELESS COMMUNICATION SYSTEM FOREAR COVER THE SPECIFIC A

Author: Yousif Mohsin Hasan
Journal: Al-Qadisiyah Journal for Engineering Sciences مجلة القادسية للعلوم الهندسية ISSN: 19984456 Year: 2017 Volume: 10 Issue: 4 Pages: 600-611
Publisher: Al-Qadisiyah University جامعة القادسية

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Abstract

This paper explains how to design a wireless communication system via high altitude platform stations HAPS to cover the specific area (Using Diwaniyah city area as a model). High altitude platform station HAPS is unmanned airplane provides the wireless communication service to the wider area. It is designed to work at high altitude between (17-22 Km) and coverage area 400 Km. This study illustrated for calculating the co-channel interference between HAPS ground station with a terrestrial station and satellite station. Free space losses for a HAPS ground station has been applied to meet the geographic of Diwaniyah city. In addition, explaining the relationship between elevation angles with the radius of the coverage area. Interference mitigation techniques have been given, such as improving the antenna radiation pattern, then it proposed the elevation angle for the HAPS's ground stations to reduce an interference between HAPS network with Fixed Service (FS) and fixed satellite service (FSS). Finally, this study explains the relationship between elevation angles with the radius of the coverage area. For more reliability, the Scenario for covers the city of Diwaniya. Two ground stations have been proposed to connect with high-altitude platform station.


Article
Improvement Of Free Convection From Three horizontal Finned Cylinders Fixed Between Two Walls
تحسين انتقال الحرارة الحر من ثلاث اسطوانات أفقية مزعنفة مثبتة بين جدارين

Authors: Hassan K. Abdullah حسن كريم عبد الله --- Haneen H. Rahman Haneen H. Rahman
Journal: Wasit Journal of Engineering Sciences مجلة واسط للعلوم الهندسية ISSN: 23056932 Year: 2018 Volume: 6 Issue: 2 Pages: 99-114
Publisher: Wassit University جامعة واسط

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Abstract

Improvement of free convection heat transfer from three finned cylinders arranged at a triangle shape fixed between two walls has been investigated in this study. Three mild steel finned cylinders fixed between two walls from Pyrex glass have been used as a test rig. It has been changed the spacing between the cylinders (X/D=1,2,3 & S/D=2,4,6) and the head orientation of a triangle to the top under constant heat flux values (38, 254, 660, 1268) W/m2 and compare with case of three finned cylinders arranged in vertical array in line fixed between two wall. The experiments are carried for Rayleigh number (Ra) from (15x103 to 14 x104 ) and Prandtl number from (0.706-0.714 ). The results indicated an increase in Nu with increasing Ra for all cylinders. Furthermore,hx and Nu increased proportionally with the increasing of cylinder spacings for all heat fluxes. Also the experimental results show the case of triangle arrangement is improvement the heat transfer more than case of vertical arrangement. Heat transfer dimensionless correlating equation is also proposed. Nomeclature: Ax: surface area(m2), T∞: surrounding temperature(k), D: the outer diameter of fin (m), Kf: the thermal conductivity for air at film temperature(W/m.k), hx: Local convection heat transfer(W/m2.k), g: Gravitational acceleration(m/s2), I: Electric current (Amp), Nu: Nusselt number, Pr: Prandtl number

تحسين انتقال الحرارة الحر من ثلاثة اسطوانات مزعنفة مرتبة أفقيا على شكل مثلث ومثبتة بين جدارين، قد تم دراسته عملياً. ثلاثة اسطوانات مزعنفة متكونة من الفولاذ الطري ] القطر الخارجي (12 ملم)، القطر الداخلي (10ملم) ، قطر الزعنفة الخارجي (30ملم) [ مثبتة بين جدارين من مادة البايركس استخدمت كجهاز اختبار. تم تغيير المسافات بين الاسطوانات ثلاث مرات (X/D=1,2,3 & S/D=2,4,6)، أتجاه رأس المثلث للأعلى .تم في الدراسة اختبار أربعة مستويات من الفيض الحراري (38 ، 254 ، 660 ، 1268 ) وات/ م2 وكذلك تم المقارنة مع حالة ثلاثة اسطوانات مزعنفة مرتبة على شكل عمودي ومثبتة بين جدارين. أجريت الدراسة ضمن مدى عدد رايلي 15x103) -14 x104 ) وعدد برانتل (0.706- 0.714). أظهرت النتائج زيادة عدد نسلت مع زيادة عدد رايلي لجميع الاسطوانات وكذلك زيادة معامل انتقال الحرارة وعدد نسلت مع زيادة المسافات بين الاسطوانات لجميع مستويات الفيض الحراري. كذلك أظهرت النتائج ان حالة ترتيب الاسطوانات على شكل مثلث تحسن انتقال الحرارة بمقدار (1.34) أكثر من ترتيب الاسطوانات بشكل عمودي.

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