Reducing global warming potential (GWP) of refrigerants is needed to the decrease of ozone-depleting of refrigeration systems leakages. Refrigerant R1234yf is now used to substitute R134a inside mobile air conditioning systems. Thermodynamic properties of R1234yf are similar to R134a. Also, it has a very low GWP of 4, compared to 1430 for R134a, making it a proper choice for future automobile refrigerants. The purpose of this research is to represent the main operating and performance differences between R1234yf and R134a. Experimental analysis was carried out on the automotive air conditioning system (AACS) with 3 kW nominal capacity, to test and compare the performance of R134a with R1234yf. Experiments were accomplished for both refrigerants in almost the same working conditions and procedure with a range of ambient temperature varied from 26oC to 50oC. Parameters studied were ambient temperature, type of refrigerant in the system at compressor speed 1450 rpm, and internal thermal loads of passenger room. The performance characteristics of the system, including COP and cooling capacity, were studied by changing different parameters. The results show that COP of R134a is higher than R1234yf by 12.6%, while the refrigeration effect of R134a is higher than R1234yf by 25%. This shows that R1234yf is a suitable and good candidate for drop-in replacement of R134a in AACS.
Background: Recurrent aphthous ulceration (RAU) is an inflammatory condition of unknown etiology characterized by painful recurrent (single or multiple) ulcerations of the oral mucosa. It is one of the most common and poorly understood mucosal disorders. It occurs more frequently in times of stress. Local and systemic conditions, genetic, immunologic, microbial factors, and oxidative stress may play a role in the pathogenesis of RAU. The objective of this study was to evaluate the free radical metabolism and antioxidant activity of RAU patients treated by lavender or flax oil paint.
Materials and Methods: Sixty-six RAU patients were enroll
... Show MoreThe current paper highlights an important character represented by the American president John Tyler 1841 – 1845, who is considered the tenth American president. The importance of this paper lies in identifying his personality in terms of his upbringing and the political activities he practiced before assuming the presidency and his most significant internal achievements, which showed his decisions as a president. He was fully prepared to support national policies since they do not exceed the authorities of the states. With his achievements in the foreign policy, he was capable to draw and define the features of the American foreign relations that were in harmony with the general situation in the United States of America at that time.
... Show MoreImage compression is one of the data compression types applied to digital images in order to reduce their high cost for storage and/or transmission. Image compression algorithms may take the benefit of visual sensitivity and statistical properties of image data to deliver superior results in comparison with generic data compression schemes, which are used for other digital data. In the first approach, the input image is divided into blocks, each of which is 16 x 16, 32 x 32, or 64 x 64 pixels. The blocks are converted first into a string; then, encoded by using a lossless and dictionary-based algorithm known as arithmetic coding. The more occurrence of the pixels values is codded in few bits compare with pixel values of less occurre
... Show MoreThe study aimed to explaining the concepts of water footprint and virtual water and how these two concepts could use to achieve water savings at the local level to meet the water supply deficit in Iraq, which is expected to increase in the coming years and influence of that on food security in Iraq by using these concepts when drawing production, irrigated and import plans in Iraq. The study aimed to studying the water footprint and virtual water and their impact on the foreign trade for wheat and rice crops during the period 2000-2022 and estimating the most important indicators of virtual water and the water footprint of the study crops due to the importance of these criteria in det
In the rapidly evolving telecommunications industry, accurate valuation of tangible assets remains a critical challenge that requires adherence to universally recognized standards. This study addresses the pressing need for transparent and precise asset valuation methodologies that are pivotal for informed investment decisions and financial reporting. It aims to bridge the theoretical and practical divide in asset valuation by applying International Valuation Standards (IVS) 300 and 400 to Asiacell Communications PJSC, a leading entity in the sector. Focusing on five key tangible assets from 2018 to 2022 – lands, buildings, plant and equipment, means of transport and transfer, and furniture and office equipment – the study emplo
... Show MoreIt is more beneficial science and created and the highest honor is the Koran Sciences, God has honored research in this fun science, came this research that shed the light on the radical incision, and Naughty derivatives as contained in the Koran, and illustrate the diversity of Saghma morphological, and fork them from derivatives what it entailed connotations, as well as the evacuation of cryptic in some of these verses from the biological secrets take minds newly exposed Anitrjt science under the name of scientific miracles.
The research methodology is revenue verse which included the word, and revenue lexical meaning and its meaning in the context of the Qur'an, and reflect the views of the commentators of the verse, and then the r
Longer Kurdish poetry translator important tributary of the tributaries of the Iraqi culture contemporary , and a wealth of knowledge rich experiences of an important segment of the Iraqi people , nicked culturally with the languages and cultures of the neighboring nations have , however, much of this potery under depends on the effect of the Arab form and complex , but suffered marginalization and loss as a result of repression by the governments of the country by successive throughout history , and tried to search that offers a vision on the theme of the place and its implications in the Kurdish poetry translator, through the election of a collection of poems and chisels, vertical than that of quantum poetic enormous , but thenature of
... Show MoreThe research entitled "The political changes and economic developments in contemporary Turkish Backgrounds, manifestations and future possibilities" consists of the introduction, four sections and conclusions. The background details, its developments, and the transformation in the economic sector in Turkey were reviewed. The first section concentrated on the brief introduction about the political developments which happened since the independence of Turkey at 1923 with the highlight on the years after the receipt of the Freedom and Justice Party (Ak PARTi) the Turkish Government rule. The second section demonstrated the reality of Turkish economy before 2002, while the
... Show MoreThis study was conducted at the Poultry Research Station in Abu Ghraib, Department of Agricultural Research, Ministry of Agriculture, the experimental field during three months (Three terms for a period of four weeks), from 10 th of December 2019 to the 10 th of January 2020. The study aimed to determine the effect of using different proportions of chlorella algae in layer hen ration and its effect on the hen's productive performance and numbers of lactobacilli bacteria in the intestine. The experiment included 400 laying hens (ISA Brown) of 54 week old which were fed according to the standard requirements mentioned in the guide for this breed (ISA Brown layer management guide). The hens raised using a 3 stage cages system with five hens in
... Show Moreهدف البحث الى بيان طبيعة ارتباط والتأثير بين الضغوط التنافسية (المتغير المستقل) والتجديد الاستراتيجي (المتغير التابع) ، تم تطبيق البحث في فنادق الدرجة الممتازة في بغداد. وبلغت عدد افراد عينة البحث (99) مديراً يعملون في (6) فنادق من الدرجة (الممتازة) ببغداد، وهي (فندق الرشيد، فندق عشتار، فندق ميريديان، فندق المنصور، فندق بابل، وفندق بغداد) وتم اجراء التحليل الاحصائي باستخدام البرنامج الاحصائي AMOS وظهرت وجود تنافسي
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