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.
يسلط هذا البحث الضوء على ظاهرة لغوية، والتي يطلق عليها تسمية "التضاد". يبين هذا البحث مفهوم هذه الظاهرة، خصائصها، أنواعها، وأسبابها، في اللغتين الساميتين: السريانية والعبرية. حيث تم اعتماد المنهج المقارن في دراسة هذه الظاهرة اللغوية وتبيان وجوه التشابه واالختالف في ماهية هذا النوع من المفردات، أي األضداد، في اللغتين: السريانية والعبرية. ويشير البحث إلى نوعين من التضاد وهما: التضاد الذي يكون بين مفردتين مستقل
... Show MoreThis research discussed the freedom of Iraqi women in the thought of Dr. Nazeeha Al-Dulaimi.
This paper shed light on castles in Iraq through Othman reign to know their sorts , and studying planning concentrating on the nature of architecture , this is a serious trying to study and important side of military architecture in Iraq with its reasons of building them which had related with political, military , social ,and economical circumstances of country .
The argumentation find its origins in some conceptions laid by Aristote. A speaker always intends to influence his hearers to change their beliefs. Therefore, this study deals with texts of the political speech of the French presidents Nicolas Sarkozy and François Hollande in the treatment of argumentative strategies.
Each of the languages possesses a set of phenomena that researchers in its sciences should stop at to explain the secrets of this language, including the phenomenon of idiomatic expression. Perhaps this phenomenon may constitute an obstacle to non-native speakers of the language or even the native speakers themselves. The Arabic language is full of these expressions, Which needs us to dedicate its own studies to it so that we can collect it in a dictionary that includes and collects it with explanation and interpretation of its semantics
The current research seeks to shed light on the role that social media can play, through the optimal use of it by students, in achieving academic excellence. The most prominent aims that constitute it are:Identifying the social sites most used by students; learning how students interact with the published study material on communication sites and benefit from them to achieve their academic excellence; and knowing the connection between using social media and achieving academic excellence, and the role that these sites play in achieving academic excellence.That incorrect use by students leads to adverse results, and thus affects their academic level. Failure of parents to monitor their student’ use of social media leads
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The research aims to improve the performance of the Directorate of Maysan water by reconciling the objectives of the employees of the directorate with the objectives of the Directorate itself, as well as to identify the strengths and weaknesses in the performance of the Directorate (Leadership - Individuals - Knowledge - Operations - Financial) and presented to experts and arbitrators of specialized, and the researchers have relied on the case study methodology as a descriptive approach is comprehensive analysis, and draws on more than one approach, method and scientific design, has been interviewed a number of experts in the Directorate Maysan's water Identify the weaknesses and strengths of the Directorate, the research has reached a numb
... Show Moreتمت دراسة سرعة الاخلاف في النوع Branchiura sowerbyi وعلاقتها بدرجات الحرارة حيث لوحظ ان قابلية هذه الديدان على اخلاف الحلقات الجسمية التي تحوي على الخيوط الغلصمية تكون اسرع من قابليتها على اخلاف الحلقات الجسمية الاخرى وبنسبة موت اقل خاصة في درجة حرارة ( 20 ± 3 ) م°.
Numerous integral and local electron density’s topological parameters of significant metal-metal and metal-ligand bonding interactions in a trinuclear tetrahydrido cluster [(Cp* Ir) (Cp Ru)2 (μ3-H) (μ-H)3]1 (Cp = η5 -C5Me5), (Cp* = η5 -C5Me4Et) were calculated and interpreted by using the quantum theory of atoms in molecules (QTAIM). The properties of bond critical points such as the delocalization indices δ (A, B), the electron density ρ(r), the local kinetic energy density G(r), the Laplacian of the electron density ∇2ρ(r), the local energy density
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