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.
This narrative review focused on research investigating the impact of loneliness on the prevalence of dementia and its relationship with other risk factors. A comprehensive and rigorous search was conducted using a variety of scientific databases with specific keywords to identify all prior studies that examined the correlation between dementia and loneliness. The inquiry was confined to articles published in English from January 2017 to March 2024. The narrative review identified a consensus regarding the role of loneliness in enhancing the risk of all‐cause dementia, with a particular emphasis on the subjective perception of loneliness. This phenomenon may be caused by the sensations of exclusion, discrimination, and alienation that are
... Show More
The current research aims to validate the Effect of technical innovation on human resources management ambidexterity through job embeddedness. The current research was done in Al-Etihad Food Industries Co. Ltd. And within the industrial environment, the research was designed according to the descriptive research. And to achieve the main goal of the research above, the researcher used the questionnaire as a key instrument to collect data through the views of a sample of managers, and employees at the senior, middle and executive management level. The research sample reached (107) individuals, the data were analysed using the statistical packages (SPSS v. 26) and ( SMART PLS v 3. 3. 8) the group of statistical
... Show More
Abstract Introduction: Aphthous stomatitis is a recurring oral ulceration condition that affects a significant proportion of the population. While several factors have been proposed to contribute to its occurrence, the link between caffeine consumption, anxiety levels, and the development of aphthous stomatitis remains unknown. This survey-based study aimed to understand the association between coffee, anxiety, and the development of aphthous stomatitis in this specific demographic, which can provide useful insights for medical management as well as preventive strategies. Material and methods: A structured online questionnaire was distributed via various social media platforms targeting a sample of the Armenian population. The quest
... Show More
(5)
(1)
Water one of the most important sources Which is no doubt essential for life surviving, water is vital in many sectors of life e.g. ( agriculture, industrial, power and so many things can’t be restricted on the mentioned items, water has become major problem facing the world today. Competition over water resources between nations has made it as a vital commodity and a justification for waging wars against its neighbor’s countries, there are currently 263 rivers that either cross or demarcate international political boundaries. Geographically, Europe has the largest number of international basins (69), followed by Africa (59), Asia (57), North America (40), and South America (38).The absolute numbers of international basins, as well as t
... Show MoreAn Expression for the transition charge density is investigated
where the deformation in nuclear collective modes is taken into
consideration besides the shell model transition density. The
inelastic longitudinal C2 and C4 form factors are calculated using
this transition charge density for the Ne Mg 20 24 , , Si 28 and S 32
nuclei. In this work, the core polarization transition density is
evaluated by adopting the shape of Tassie model togther with the
derived form of the ground state two-body charge density
distributions (2BCDD's). It is noticed that the core polarization
effects which represent the collective modes are essential in
obtaining a remarkable agreement between the calculated inelastic
longi
This research sought to detect the level of organizational culture prevailing in the Integrity Commission as well as the level of the organizational citizenship behavior of staff of the Commission and the impact of organizational culture in these behaviors. To achieve the objectives of the research and test the validity of hypotheses have been used questionnaire derived from measurements ready modern researchers foreigners have been adapted to suit the Iraqi environment, have been distributed (189) questionnaire on the number of employees from the Integrity Commission, which represented the research sample where the research community has a number is (1365) employees in the Baghdad was the use of a number of statistical met
... Show More
(1)