Abstract: Objectives: To investigate the effect of temperature elevation on the bonding strength of resin cement to the zirconia ceramic using fractional CO2 laser. Background: Fractional CO2 laser is an effective surface treatment of zirconia ceramic, as it increases the bonding strength of zirconia to resin cement. Methods: Thirty sintered zirconia discs (10 mm diameter, 2 mm thickness) were prepared and divided to three groups (N=10) and five diffident pulse durations were used in each group (0.1, 0.5, 1, 5 and 10 ms). Group A was treated with 10 W power setting, group B with 20 W and group C with 30 W. During laser irradiation, temperature elevation measurement was recorded for each specimen. Luting cement was bonded to the treated zirconia surfaces and cured for 30 seconds. Shear bond strength was evaluated by a testing machine (universal) with bond failure mode determination. Results: The lowest temperature elevation measurement of the irradiated specimen which gave maximum shear bond strength was about 1.6±0.3 Ċ higher than ambient room temperature (27±0.2 ºC). Apparent micromechanical irregularities were seen in the treated samples and cracks formation with increased pulse duration and power setting were also observed. Conclusions: The temperature elevation is a vital factor in the surface roughness of zirconia ceramic with fractional CO2 laser irradiation and the lowest temperature elevation at best shear bond strength of zirconia ceramic to the resin cement is satisfied with the shorter pulse duration of 0.1 millisecond.
بعد مرور عام واكثر على ظهور فيروس كورونا والعالم يواجه تسونامي تلك الجائحة التي تكاد تعصف بالوجود البشري برمته لذا اخذت البشرية على عاتقها مواصلة الجهود والابحاث للوصول الى علاج طبي يتم من خلاله مواجهة هذا الفيروس او التقليل من آثاره التي تهدد الحياة البشرية بالموت المباشر دون الاصابة، مما نتج عن تلك الجهود مجموعة من اللقاحات التي تبنتها الشركات العالمية المسؤولة الا ان الضرورة القصوى التي نتجت عنها تلك الل
... Show Moreيتناول البحث الحماية المدنية للمستهلك في المرحلة السابقة على التعاقد الالكتروني
This Kind of study has a special importance. Great numbers of Arab Muslims share a lot of their work, their Trans lations & new additions to scientific heritage. They facilitate the indirect way for Europeans to got Greek scientific knowledge. Ibn Sina classified & collected in his book (Law) Galen`s medical publications & he clarified, arranged & make them easy to understand.
يدرس هذا البحث مشكلة اعتماد الجمهور العراقي على الصحف، باعتبارها إحدى وسائل الإعلام التقليدية، في تكوين معلوماته ومعرفته العامة. وهي دراسة وصفية اعتمدت المنهج الوصفي المسحي الذي يصور الظروف أو الاتجاهات الحالية للظاهرة قيد الدراسة ويحاول تفسيرها. استخدم الباحث الاستبانة في المقام الأول كأداة بحث، حيث تم تصميمها وتوزيعها على عينة مكونة من 150 باحثا قصديا من قراء وقراء الصحف. وينتهي الباحث بالنتائج التالية: إ
... Show MoreIslam paid great attention to the youth, and took care of them because they
are the strength and movement, which is the preferrence stage in human life,
and they are the ones who
Each language in the world has its special methods in using articles that connected with nouns. There are languages do not have articles and others their articles from one class, that is to say it do not have masculine and feminine such as our Arabic language. Also in some languages the nouns come after article.
The main aim in our research is to analyze the usage of these articles and its presence or not in the structure of sentence for the learners of Spanish language as a foreign language.
The usage of these articles in Spanish language forms one of the problems that face students in the grammar of Spanish language, at the same time it stands as a problem in translation becau
... Show MoreEfforts of evaluating manuscripts have developed into sciences that take interest into the development of authorship movement. Expanding the rules and fundamentals of this scientific process along with the growing use of modern methods and techniques contributed further to its development.
Such a disciplinedemands comprehensive knowledge in various fields to reach the most valid results that help reveal significant aspects of the cultural heritage since such a process is an ethical responsibility .Therefore, the editor has to be patient and honest in correcting mistakes, choosing the most acceptable narration and pinpointing the additions and differences as well as other requirements of serious editing.
The study was divided into a
La stylistique, héritière de la rhétorique, est ‘la science du style’. La stylistique
qui a commencé, dès son apparition, par être divisée en stylistique de l’expression et
stylistique génétique s’est vu connaître d’autres classements en stylistique idéaliste,
structuraliste, fonctionnaliste ; générativiste….etc.
Cette évolution continuelle reflète la richesse de cette discipline. La diversité des
courants et écoles dans ce domaine se traduit sur le champ par une variété de méthodes
d’analyse stylistique.
L’enjeu principal dans la plupart de ces méthodes d’analyse est la manière selon la
quelle la relation entre langue et parole, langu
... Show MoreTelevision white spaces (TVWSs) refer to the unused part of the spectrum under the very high frequency (VHF) and ultra-high frequency (UHF) bands. TVWS are frequencies under licenced primary users (PUs) that are not being used and are available for secondary users (SUs). There are several ways of implementing TVWS in communications, one of which is the use of TVWS database (TVWSDB). The primary purpose of TVWSDB is to protect PUs from interference with SUs. There are several geolocation databases available for this purpose. However, it is unclear if those databases have the prediction feature that gives TVWSDB the capability of decreasing the number of inquiries from SUs. With this in mind, the authors present a reinforcement learning-ba
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