The design, construction and investigation of experimental study of two compound parabolic concentrators (CPCs) with tubular absorber have been presented. The performance of CPCs have been evaluated by using outdoor experimental measurements including the instantaneous thermal efficiency. The two CPCs are tested instantly by holding them on a common structure. Many tests are conducted in the present work by truncating one of them in three different levels. For each truncation the acceptance half angle (θc) was changed. Geometrically, the acceptance half angle for standard CPC is (26o). For the truncation levels for the other CPC 1, 2 and 3 the acceptance half angle were 20o, 26o and 59o, consequently. A significant difference between the instantaneous thermal efficiency of 3.86× CPC (θc=20o) and 2.32× CPC (θc=26o), and between that for 3.61× CPC (θc=26o) and 2.32× CPC (θc=26o). It's noticed that the difference between the instantaneous thermal efficiency of 2.32× CPC (θc=59o) and 2.32× CPC (θc=26o) is small compared with the difference of the first and second cases, the instantaneous thermal efficiency of 2.32× CPC (26o) was higher than those for other three CPCs. The experimental results show that the maximum thermal efficiency of the full 2.32×CPC (26o) is 0.708, the maximum thermal efficiency of the 3.93×CPC (15o), when it's truncated to 3.84× CPC (20o), 3.61× CPC (26o) and 2.32× CPC (59o) are 0.51, 0.52 and 0.66, respectively. As the concentration ratio decreases from (3.93× to 1×), the thermal efficiency, energy losses and optical efficiency increase from (0.47 to 63), (1.58 to 7.2 K.m2/W) and (0.494 to 0.797), respectively.
Praisebe to God, Lord of the worlds, and blessings and peace be upon the most honorable messengers, our Prophet Muhammad, may God bless him and granthim peace. And after
Thank for Allah lord of worlds and peace be upon his messenger last one of them Muhammad
and his followers.
The honored thing which the searcher can present to serve the holly quran and all its sciences
in their searching and composing .
The straight is the order of Allah is great goal and elite target in this life and every Muslim
should follow and aim to get it and from the mercy of Allah to us he ordered us to follow it
and he showed to us how to and to obey him and showed the way to it as was mentioned in
the Quarn ( this is my straight way so you follow it and do not follow other ways ) and the importance of straight he ordered the prophet peace be upon him to catch the right and
straight and warned us f
لقد حمَّلت مفردة الإرهاب بكمٍ هائلٍ من المفاهيم والدلالات المُتباينة والمُتناقضة . لذا حاول البحث التأكيد على أهمية وضع تعريفٍ مُحدد لظاهرة الارهاب،ومن ثم توضيح ماهي الاسباب الحقيقية وراء تنامي الارهاب في العراق بعد 2003 ،وما هي المتغيرات الاجتماعية والسياسية التي اسهمت في تصاعد وتيرة العمليات الارهابية في العراق،لاسيما وإن المجتمع العراقي مجتمع متعدد الشرائح الاجتماعية،وبشكلٍ قد يُمَّ
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in his Diwan, and standing on them, and determines This study dealt with the lexical and semantic fields in the sentimental poems in Walid Hussein's Diwan (I do not desire to whisper the question) that the classification
يعد العقد من اهم مصادر الالتزام كونه الوسيلة الفاعلة التي يمكن من خلالها المتعاقد التحقق من مصالحه واهدافه مادامت لا تتعارض مع النظام العام ، ومتى مانشأ صحيحاً وفقاً للاركان والشروط التي يتطلبها القانون اصبح ملزماً لكلا طرفيه ، بحيث يخضعان بموجبه لقوة العقد ، وقد لا ينعقد وفقاً للسياق السابق بسبب عدم استكماله لشروط صحته فينعدم اثره بين المتعاقدين او الغير ، وتلك هي فكرة البحث .
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CdS films were prepared by thermal evaporation technique at thickness 1 µm on glass substrates and these films were doped with indium (3%) by thermal diffusion method. The electrical properties of these have been investigated in the range of diffusion temperature (473-623 K)> Activation energy is increased with diffusion temperature unless at 623 K activation energy had been decreased. Hall effect results have shown that all the films n-type except at 573 and 623 K and with increase diffusion temperature both of concentration and mobility carriers were increased.
Abstract: In this research we study the of added NaCl with concentration (0.2, 0.02)M on the spectral of cationically charged dye (cresyl violet) and anionically charged surfactant (sodium dodecyl sulphate) with different concentration, the result show two peaks appearance the first attributed to micelle and the other formation of dye surfactant complex, in addition to the increase in the quantum efficiency of emission spectrum and shifted toward long wavelength (λmax=692.5nm-626nm).
Is the subject of Facebook of more topics that aroused interest and that it provides the features and services that allows users to direct communication and interaction and dialogue with others, and deals with the subject of research the use of Facebook and its effects left by the social relations, as the field study was conducted on a sample of 130 students from students Baghdad University of males and females in the Faculty of Political Science and Agriculture, Science and Education, Girls, and limited the sample to Facebook users exclusively to test the study hypotheses and relationships connectivity, and the results revealed the presence of a significant impact of Facebook in th
... Show MoreThis research aimed to evaluate the level of readiness to teach science in the light of the information, media, and technology skills among undergraduate students at the Faculty of Edu-cation, King Khalid University. To achieve this goal, a descriptive and analytical approach was used. A list of readiness to teach science was prepared in the light of Information, media, and technology skills, and in the light of this list, a cognitive test, observation sheet, and attitude scale were prepared to assess readiness to teach science in its three aspects, cognitive, behavioral, and emotional. The sample of the research consisted of (42) students enrolled in field training courses at the sixth, seventh and eighth levels. Research tools were app
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