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김재혁,정진형,임성빈,홍기석,Kim, Jae-Hyuk,Chung, Chin-Hyung,Lim, Sung-Bin,Hong, Ki-Seok 대한치주과학회 2008 Journal of Periodontal & Implant Science Vol.38 No.3
Purpose: The purpose of this research is to study about initial adhesion, proliferation and activation of osteoblast to titanium surface treated with machined, hydroxyapatite coating, resorbable blast material blasting and anodizing method. Material and Methods: After treating the titanium surface of each block with machined, impurities were removed and sterilized. The number of cells attached from cultured osteoblast of respective experimental groups were measured at 1, 4, 7, and 14day and alkaline phosphatase, calcium, and inorganic phosphate concentration of cultured solution was measured. Result: Anodizing group showed the highest rate of cell attachment and proliferation activity. RBM treated group showed the highest increasing on their alkaline phosphatase activity, on the calcium apposition, on inorganic phosphate apposition of 1 and 4 days in cultured osteoblast to compare with other groups. Conclusion: On the basis of these findings, we conclude that surface modification of titanium was profoundly effected on the attachment, proliferation and activation of osteoblast in initial stage osseointegration.
Curet과 Ultrasonic Scaler를 이용한 치주치료후 SEM과 EPMA를 이용한 잔존치근면에 대한 연구
김재혁,김종여,임성빈,정진형,Kim, Jae-Hyuk,Kim, Chong-Yeo,Lim, Sung-Bin,Chung, Chin-Hyung 대한치주과학회 1999 Journal of Periodontal & Implant Science Vol.29 No.2
One of the fundamental causes of periodontal disease is accumulation of bacterial plaque and calculus and most effective method of removing these plaque and calculus are scaling and root planning using hand curet and ultrasonic scaler. Many studies concerning residual degenerated mineral content after periodontal therapies have been carried out, but some problems about these studies were also known. This research studies mineral concents and distribution of residual root surfaces after perfoming hand curet and ultrasonic scaler on root surfaces of single rooted teeth which were extracted for periodontal reasons. EPMA were used to avoid errors from chemical quantative analysis and in addition SEM observation was also performed. The results were as follows. 1. No differences were found between curet group andultrasonic scaler group in Ca, P, Mg and Na level. 2. Concentration level was decreased in the sequence of Ca, P, Mg and Na. 3. Ca and P level were decreased as going to apical portion at curet group and ultrasonic scaler group. 4. More cementum was removed at cervical portion compared to other portion at curet group and ultrasonic scaler group. 5. Ca, P, Mg level was higher in dentin compared to cememtum. There was no difference in mineral level for Ca, P, Mg and Na between root surfaces treated with hand curet and ultrasonic scaler.
김재혁,김시연,최정식,여동훈,신효순,남산,Kim, Jae Hyuk,Kim, Shi Yeon,Choi, Jeoung Sik,Yeo, Dong-Hun,Shin, Hyo-Soon,Nahm, Sahn 한국분말야금학회 2019 한국분말재료학회지 (KPMI) Vol.26 No.5
Piezoelectric ceramic specimens with the $Pb(Mg_{1/3}Nb_{2/3})_{0.65}Ti_{0.35}O_3$ (PMN-PT) composition are prepared by the solid state reaction method known as the "columbite precursor" method. Moreover, the effects of the $Li_2O-Bi_2O_3$ additive on the microstructure, crystal structure, and piezoelectric properties of sintered PMN-PT ceramic samples are investigated. The addition of $Li_2O-Bi_2O_3$ lowers the sintering temperature from $1,200^{\circ}C$ to $950^{\circ}C$. Moreover, with the addition of >5 wt.% additive, the crystal structure changes from tetragonal to rhombohedral. Notably, the sample with 3 wt.% additive exhibits excellent piezoelectric properties ($d_{33}=596pC/N$ and Kp = 57%) and a sintered density of $7.92g/cm^3$ after sintering at $950^{\circ}C$. In addition, the sample exhibits a curie temperature of $138.6^{\circ}C$ at 1 kHz. Finally, the compatibility of the sample with a Cu electrode is examined, because the energy-dispersive X-ray spectroscopy data indicate the absence of interdiffusion between Cu and the ceramic material.
김재혁(Kim Jae hyuk) 영상영어교육학회 2002 영상영어교육 (STEM journal) Vol.3 No.1
Recently learner-centered teaching has been in vogue especially in the area of elementary English education. This may be the reason that the 7th National English Curriculum directs considerable attention to learner-centered teaching, and each of the national English textbooks in elementary schools has a variety of learning activities and tasks aimed at two levels: intensive for fast learners and supplementary for slower learners. Thus there seems to be a strong consensus of opinion among ELT researchers and teachers that we should teach English in a learner-centered way, taking the wants and needs of the leaners into account. It must be pointed out, however, that very little attention has been paid to how we educate teachers so that they can teach English in a learner-centered way. Considering this, the aim of this paper is to suggest a model of, and some theoretical basis for learner-centered elementary English teacher education. To this end, the problems our current elementary English teacher education often faces were looked at in terms of learner-centered education. This paper also investigated the TESOL programs offered in the major universities in the USA.
김재혁(Kim Jae hyuk) 한국초등영어교육학회 2017 초등영어교육 Vol.23 No.2
This study aims to investigate the learning styles that elementary school students prefer to use in learning English. In particular, this study intends to examine a) what learning styles elementary school students prefer to use in learning English, b) how their learning styles differ from one another in terms of grade and sex, c) how the two independent variables, grade and sex, interact in their preferences of learning styles, and d) how the students are grouped and what characteristics each group has in terms of learning style preferences. To this end, a learning style questionnaire was designed and administered to 406 elementary students at G city. Data analysis revealed that the students preferred to use perceptual, independent, cooperative learning styles rather than kinesthetic, competitive, independent or mixed styles. It was also found that the students’ learning styles changed as they moved into higher grades and that those who showed positive responses to competitive and dependent styles increased. The difference between the male and female students in cooperative, competitive, and independent styles was significant (p< .05), but no significant difference was found between the two groups in perceptual, kinesthetic and independent learning styles (p> .05). And the students were divided into the three groups: active, ordinary and passive users of learning styles. Pedagogical implications of those findings are provided.