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Saka, Muhammet,Yuzugullu, Bulem The Korean Academy of Prosthodonitics 2013 The Journal of Advanced Prosthodontics Vol.5 No.4
PURPOSE. To evaluate the effects of surface treatments on shear bond strength (SBS) between microwave and conventionally sintered zirconia core/veneers. MATERIALS AND METHODS. 96 disc shaped Noritake Alliance zirconia specimens were fabricated using YenaDent CAM unit and were divided in 2 groups with respect to microwave or conventional methods (n=48/group). Surface roughness (Ra) evaluation was made with a profilometer on randomly selected microwave (n=10) and conventionally sintered (n=10) cores. Specimens were then assessed into 4 subgroups according to surface treatments applied (n=12/group). Groups for microwave (M) and conventionally (C) sintered core specimens were as follows; $M_C$,$C_C$: untreated (control group), $M_1,C_1:Al_2O_3$ sandblasting, $M_2,C_2$:liner, $M_3,C_3:Al_2O_3$ sandblasting followed by liner. Veneer ceramic was fired on zirconia cores and specimens were thermocycled (6000 cycles between $5^{\circ}-55^{\circ}C$). All specimens were subjected to SBS test using a universal testing machine at 0.5 mm/min, failure were evaluated under an optical microscope. Data were statistically analyzed using Shapiro Wilk, Levene, Post-hoc Tukey HSD and Student's t tests, Two-Way-Variance- Analysis and One-Way-Variance-Analysis (${\alpha}$=.05). RESULTS. Conventionally sintered specimens ($1.06{\pm}0.32{\mu}m$) showed rougher surfaces compared to microwave sintered ones ($0.76{\pm}0.32{\mu}m$)(P=.046), however, no correlation was found between SBS and surface roughness (r=-0.109, P=.658). The statistical comparison of the shear bond strengths of $C_3$ and $C_1$ group (P=.015); $C_C$ and $M_C$ group (P=.004) and $C_3$ and $M_3$ group presented statistically higher (P=.005) values. While adhesive failure was not seen in any of the groups, cohesive and combined patterns were seen in all groups. CONCLUSION. Based on the results of this in-vitro study, $Al_2O_{3-}$ sandblasting followed by liner application on conventionally sintered zirconia cores may be preferred to enhance bond strength.
Sensitive NDE of Small Fatigue Cracks
Saka, Masumi 한국비파괴검사학회 2001 한국비파괴검사학회지 Vol.21 No.1
Some techniques developed recently for sizing small fatigue cracks are described. One is an ultrasonic technique which deals with a small closed crack, where both the stress closing the crack and the crack size are determined by analyzing inverse problem, Here, difficulties encountered in NDE of closed cracks by usual ultrasonic techniques are summarized in advance. Secondly, the closely coupled probes potential drop (CCPPD) technique, which is based on d-c potential drop measurement, is explained for sizing small cracks. The CCPPD technique is not affected by crack closure. Finally, a discussion is given on NDE of materials degradation in conjunction with sensitive NDE of small cracks.
EFFECTIVE WAY OF MEASURING K₁ BY MEANS OF ACPD TECHNIQUE
Saka, M.,Abe, H.,Lee, J. H. ENGINEERING TRIBOLOGY RESEARCH INSTITUTE KYUNGPOOK 1998 INTERNATIONAL SYMPOSIUM ON HIGH PERFORMANCE OF TRI Vol.1998 No.-
In order to develop an effective way of meaduring the ModeⅠstress intensity factor, K₁, by means of the alternating current potential drop(ACPD) technique, the change in potential drop due to load for both ferromagnetic and paramagnetic materials contaning a two-dimensional surface crack was investigated. The effects of the magnetic field, the demagnetization and the crack length on the change in potential drop were examined. The amount of the change in potential drop was shown to increase largely by increasing the amount of the magentic flux in the measuring system. Also in the case of the measuring system with a large amount of the magnetic flux in the air, the relationship between the change in potential drop and that in K₁was indicated to be linear without any treatment and it was shown that the demagnetization had almost no effect on the change in potential drop. The change in potential drop was independent of the crack length. The effective way of determining K₁by means of the ACPD technique is to use a measuring system with a large amount of the magnetic flux in the air.
An Outlook of Research and Development for the Future Air Traffic Management in Japan
Sakae NAGAOKA 한국항공우주학회 2008 한국항공우주학회 학술발표회 논문집 Vol.- No.-
Air traffic management (ATM) is defined in an ICAD document as the dynamic, integrated management of air traffic and airspace - safely, economically and efficiently - through the provision of facilities and seamless services in collaboration with all parties. The concept presents the ICAD vision of an integrated, harmonized and globally interoperable ATM system. The planning horizon is up to and beyond 2025. Europe and the United States have developed their own visions/programs for the future ATM systems, i.e., SESAR (Single European Sky A TM Research) and NetGen (Next Generation Air Transportation System), respectively. These programs are based on the concept shown in the ICAD document. In Japan, the Electronic Navigation Research Institute (ENRJ), which is a core research organization of ATM systems, has recently developed its long term research and development (R & D) roadmap. It was developed taking into account those visions and conditions surrounding Japan. Reviewing the visions of ICAD, SESAR and NextGen, ENRI assumed that a key component of the future ATM will be the 4-dimentional trajectory based operation. This paper describes the shift from the current air traffic control (ATC) to the future ATM. Then, the operational concept of the future ATM and R&D towards future ATM systems are explained. Finally ENRI's long term vision and its R&D roadmap are briefly described.
RECENT DEVELOPMENT OF TECHNIQUES FOR SENSITIVE NONDESTRUCTIVE EVALUATION OF CRACKS
Saka, M. ENGINEERING TRIBOLOGY RESEARCH INSTITUTE KYUNGPOOK 1999 INTERNATIONAL SYMPOSIUM ON HIGH PERFORMANCE OF TRI Vol.1999 No.-
Recently developed techniques for sensitive nondestructive evaluation (NDE) of cracks are reviewed. Ultrasonic testing, d-c potential drop technique and microwave imaging for sensitive NDE of an isolated crack and also multiple cracks are explained.