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치과임플란트용 Ti-25Ta-xHf 합금의 플라즈마 전해 산화
김정재,최한철,Kim, Jeong-Jae,Choe, Han-Cheol 한국표면공학회 2018 한국표면공학회지 Vol.51 No.6
Plasma electrolytic oxidation of Ti-25Ta-xHf alloy in electrolyte containing Ca and P for dental implants was investigated using various experimental techniques. Ti-25Ta-xHf (x=0 and 15 wt.%) alloys were manufactured in an arc-melting vacuum furnace. Micropores were formed in PEO films on Ti-25Ta-xHf alloys in 0.15 M calcium acetate monohydrate + 0.02 M calcium glycerophosphate at 240 V, 270 V and 300 V for 3 min, respectively. The microstructure of Ti-25Ta-xHf alloys changed from (${\alpha}^{\prime}+{\alpha}^{{\prime}{\prime}}$) phase to (${\alpha}^{{\prime}{\prime}}+{\beta}$) phase by addition of Hf. As the applied potential increased, the number of pore and the area ratio of occupied by micro-pore decreased, whereas the pore size increased. The anatase phase increase as the applied potential increased. Also, the crystallite size of anatase-$TiO_2$ can be controlled by applied voltage.
플로랄 형상의 구리관 고온흡수기의 열전달 성능 특성에 관한 실험적 연구
김정재(Jeong Jae Kim),배경진(Kyung Jin Bae),김인관(In Gwan Kim),김용찬(Yong Chan Kim),권오경(Oh Kyung Kwon) 대한설비공학회 2020 대한설비공학회 학술발표대회논문집 Vol.2020 No.6
The objective of this study is to investigate the heat transfer performance characteristics of a high temperature absorber with regard to the solution concentration. An experimental apparatus consists of a generator, a condenser, an evaporator, and the high-temperature absorber. The high temperature absorber is a falling film type with a small pressure drop, and floral copper tubes are employed. The experimental data was measured for about 30 minutes at steady state. The solution concentration was selected within the range of ±2 wt% based on 61 wt%, which has less crystallization risk and a stable heat transfer performance. When the solution concentration increase from 61 to 63 wt%, the heat transfer rate of the high temperature absorber increased by 22% and overall heat transfer coefficient decreased by 10%.
시장효율성과 회계수치의 가치관련성 - 거래소기업과 코스닥기업의 비교
김정재(Kim Jeong Jae) 한국산업경영학회 2006 經營硏究 Vol.21 No.4
본 논문은 회계수치의 가치관련성 분석을 통하여 회계수치가 기업가치에 반영되는 속도의 관점에서 시장효율성을 검증한다. 가치관련성 연구에서는 회계수치가 동일시점의 기업가치와 관련이 있으면 정보유용성이 있는 것으로 평가한다. 그러나 시장효율성이 완전하지 않다면 정보내용이 즉각 주가에 반영되지 못하여 가치관련성 연구결과의 해석에 심각한 영향을 미치게 된다. 본 연구는 거래소기업과 코스닥기업을 대상으로 당해년모형부터 3년시차모형까지 회계수치의 가치관련성을 살펴봄으로서 반영속도차이를 분석한다.<BR> 본 논문의 분석결과에 따르면 먼저 장부가액의 지연반응은 모든 표본기업에서 당해년모형부터 3년시차모형까지 꾸준히 나타나고 있다. 그러나 회계이익의 경우 거래소기업에서의 지연반응은 1년시차모형 이후에는 나타나지 않고 있다. 코스닥 일반기업에서는 3년시차모형에서 유의하게 나타나 지연반응이 강하게 나타났다. 코스닥 벤처기업에서는 거래소기업과 같이 1년시차모형이후에는 나타나지 않고 있다. 본 논문의 분석결과가 시사하는 바는 회계이익의 경우 거래소기업과 코스닥 벤처기업은 유사한 정보반영 속도를 보이고 있으나, 코스닥 일반기업에서는 회계이익의 가치관련성이 상대적인 지연반응을 보이고 있다. 따라서 기업가치 평가모형의 개발 및 해석에서 업력 및 소속 시장에 따른 기업의 특성 및 이에 따른 시차별 정보반영의 정도를 고려할 필요가 있음을 시사한다. 한편 본 연구의 당해년모형에서 코스닥기업의 가치관련성 분석결과는 선행연구와 차이를 보이고 있는데 이는 표본기업의 등록기간에 따른 차이로 판단된다. Some extant studies have suggested that stock market may not be completely efficient in its processing of public information including financial statements information. However, most value relevance studies appear to be interpreted based on the implicit assumption that the stock market is efficient in the semi-strong form. In reality, however, the value relevance of accounting variables hinges on the efficiency of capital market including information process speed because, in its conventional form of value relevance analysis, the market value as the dependent variable may not be the intrinsic value of the firm at that time. If that is the case, the results of value relevance studies should be cautiously interpreted because the significant association between accounting variables and the contemporaneous market value may not be a valid measure to determine the usefulness of accounting information.<BR> The objective of this study is to investigate whether the market efficiency affects the degree of timely market reaction in the KSE and KOSDAQ firms. To test the degree of market reaction speed, time lag models up to 3 year lag are used. In empirical analysis, the level and return models are used and the market value, dependent variable, is adjusted to control total market return and overall market movement.<BR> The results of this study indicate that all sample firms take up to 3 years in processing the implications of the book value. However, the earnings have shown different reaction patterns depending on where the firm is registered. In the KSE firms, earnings have relatively small delayed reaction showing little delayed reaction after one year lag model. In the KOSDAQ general firms, earnings have significant value relevance in the 3 year delayed model, indicating severe delayed market reaction. In the KOSDAQ venture firms, earnings have relatively small delayed reaction showing little delayed reaction after one year lag model. The results of the study imply that, in building, executing and interpreting the equity valuation model, lagged market reaction as well as company history and market affiliation should be considered.
김정재(Jeong-Jae Kim),김원기(Won-Gi Kim) 한국콘텐츠학회 2014 한국콘텐츠학회논문지 Vol.14 No.4
본 연구의 목적은 저탄성계수 Ti-30Ta 합금에 Zr 원소를 첨가하여 표면 특성 및 부식 거동을 조사하였다. 저탄성계수 Ti-30Ta-xZr(x : 3, 7, 15 wt %)합금은 아크 멜팅기로 제조하였고, 아르곤 분위기에서 1000 ℃ 24시간 동안 열처리하였다. 합금의 미세구조는 FE-SEM 그리고 XRD를 이용하여 조사하였다. 전기화학적 특성은 시편 작업전극, 고밀도 탄소 보조전극 그리고 포화칼로멜 기준전극의 통상적인 3상을 이용하여 수행하였다. Ti-30Ta-xZr 합금의 분극 거동 결과, 균질화 처리된 Ti-30Ta-15Zr 합금의 부동태 전류밀도가 다른 합금에 비해 낮았다. In this study, surface characteristics and corrosion behaviors have been investigated in addition to Zr elements on the low elastic modulus Ti-30Ta alloy. Low elastic modulus Ti-30Ta-xZr(x : 3, 7 and 15 wt %) alloys were prepared by arc melting and then heat treated at 1000 ℃ for 24 hrs in an argon atmosphere. Microstructures of the alloys were examined by field emission scanning electron microscope(FE-SEM) and X-ray diffractometer(XRD). Electrochemical experiments were performed using a conventional three-electrode configuration with a sample working electrode, a high density carbon counter electrode and a saturated calomel reference electrode. According to the result of polarization behavior in the Ti-30Ta-xZr alloys, the current density of homogenized Ti-30Ta-15Zr in the passive region was lower than the other alloys.