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.
Footnotes are considered as an important phenomenon in the lectures of grammar. Al-Khudari's footnote is one of the most distinguished one other than its counterparts due to the prestigious and scientific status of its author
The goal of this paper is to design a robust controller for controlling a pendulum
system. The control of nonlinear systems is a common problem that is facing the researchers in control systems design. The Sliding Mode Controller (SMC) is the best solution for controlling a nonlinear system. The classical SMC consists from two phases. The first phase is the reaching phase and the second is the sliding phase. The SMC suffers from the chattering phenomenon which is considered as a severe problem and undesirable property. It is a zigzag motion along the switching surface. In this paper, the chattering is reduced by using a saturation function instead of sign function. In spite of SMC is a good method for controlling a nonlinear system b
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العقيدة الدينية وأثرها على منهج التفكير السياسي للولايات المتحدة الامريكية
استخدام سلاسل ماركوف في التعرف على تعقبات الحامض النووي DNA
The research aims to:
- Show the effect of corporate governance on the quality performance of certified public accountants through establish the concept and principles of corporate governance and the concepts, importance, standards of quality auditing.
- Forming a proposed framework for quality performance of certified public accountants under the corporate governance, which show the concepts objectives, principles, standards, and constraints of the proposed framework.
The research in one aspect of it based on the study of theoretical background which re which relate to the subject beside the global experiments and opinions of the specialists
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يعد موضوع الثورات العربية من الموضوعات التي تحظى بأهمية كبيرة على المستويين الاقليمي والدولي، لذا فقد طورت مؤسسات الابحاث الدولية ومراكز صنع القرار السياسي والاستراتيجي الاطر والمفاهيم الجديدة في مجال السياسة الدولية، نظرا للتطورات التي شهدتها المنطقة العربية والتي استدعت التطرق الى مجموعة من المفاهيم النظرية ذات العلاقة الوثيقة بما هو حاصل في المنطقة العربية من تغييرات مما تطلب الامر البحث والتدقيق ومن
... Show MoreThe kinds of financial and administrational corruption have an important
dimensions and affects on human rights because of all events which happened in the world
made tackles concerning with this phenomena.
This article has been researched about an impacts of it to the nature of structural
social system especially its scopes items in institutionally and politically and economically
and culturally to be an obvious in all fields.
This phenomena should be studied carefully in order to put all remedies required
for set up with measures and procedures such as following :
1-the dependency on respecting all laws in the country.
2-the work with principles of accountability transparency in pro-active cooperation level.<
إنَّ من أجلِّ العلومِ علوم العربيَّة , إذْ هيَ المَرقاة إلى فهمِ كتابِ الله , وقد بذلَ سلفُنا الصالح في هذا المجال جهودًا مضنية , وقفوا من خلالِها على أسرارِ الكثيرِ من لطائفِ هذه اللغةِ الشريفة, وتركوا لنا تراثًا ضخمًا أودعوه دقائقَ فكرهِم وعميقَ نظرهِم وهو عنوان لحضارة ِهذه الأمة وأمجادها .
أمَّا ابنُ خروف فهو من أشهر نحاة الأندلس في القرن السادس والسابع الهجريين , ومن أشهرِ شُرَّاح كتاب سيبويه ,
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