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우치에서 레진 침투법 및 불소 적용의 탈회 저항성 비교
이두영,김익환,송제선,김성오,손흥규,이제호,Lee, Doo-Young,Kim, Ik-Hwan,Song, Je Seon,Kim, Seong-Oh,Son, Heung Kyu,Lee, Jaeho 대한소아치과학회 2018 大韓小兒齒科學會誌 Vol.45 No.2
본 실험의 목적은 초기 우식 부위에 레진 침투법과 불소 적용 후 탈회 저항성을 비교하기 위함이다. 인공 우식을 유발한 시편을 대조군, 1.23% 산성불화인산염(Acidulated phosphate fluoride(APF))군, 레진 침투군으로 분류하고 각 재료를 적용 후 재탈회시켰다. 이후 공초점 레이저 현미경(Confocal Laser Scanning Microscope(CLSM))을 이용하여 탈회 깊이를 측정하였고 주사전자현미경(SEM)을 이용하여 법랑질 표면 거칠기를 관찰하였다. CLSM을 이용하여 탈회 깊이를 측정하였을 때 대조군, 1.23% 산성불화인산염군, $Icon^{(R)}$ caries infiltrant군 순으로 감소하였다. 탈회 깊이는 1.23% 산성불화인산염군, $Icon^{(R)}$ caries infiltrant군이 대조군에 비해서는 유의성 있는 차이를 보이지만 두 군 간의 차이가 없었다(p < 0.05). 표면거칠기는 대조군에서 매우 거칠고 표면이 불규칙한 양상을 보였고 1.23% 산성불화인산염군, $Icon^{(R)}$ caries infiltrant 군으로 갈수록 표면 거칠기와 불규칙성은 감소하였다. The aim of this study is to compare the differences of the demineralization resistance of resin infiltration and 1.23% acidulated phosphate fluoride in bovine teeth with artificial caries. We applied 1.23% Acidulated phosphate fluoride (APF) gel and $Icon^{(R)}$ caries infiltrant on the artificial bovine enamel carious lesion and then demineralized all samples. The depth of demineralization was measured by using Confocal Laser Scanning Microscope (CLSM) and observed the roughness and irregularity of the enamel was observed by Scanning Electron Microscope (SEM). In this experiment with demineralization resistance on smooth artificial carious lesion, less depth of demineralization, roughness, and irregularity of enamel was observed in APF gel and $Icon^{(R)}$ group than in the control group. There was no significant difference between the depth of demineralization of 1.23% APF gel and $Icon^{(R)}$ caries infiltrant group. However, resin infiltration is beneficial as less roughness and irregularity was observed on the enamel surface than when 1.23% APF gel is applied.
1000MW급 초초임계압 화력발전소 주기기에 관한 진동기반 통합 감시시스템 개발
김연환(Yeon-Whan Kim),배용채(Yong_Chae Bae),윤병동(Byeng-D. Youn),김동환(Dong-Hwan Kim),이두영(Doo-Young Lee),손석만(Seok-Man Sohn) 한국소음진동공학회 2015 한국소음진동공학회 학술대회논문집 Vol.2015 No.4
KEPRI will apply the diagnostic monitoring system developed with domestic technology for the integrated monitoring of Korea Type 1000MW-class ultra-supercritical power plant made from high-efficiency power generation technology. The diagnostic monitoring system has been developed through the advanced malfunction diagnosis algorithm processing the data treated as a statistical data-driven method, based on the rotor vibration signals of the rotating equipments such as turbine-generator, boiler feed water pumps, large fans in the power plant. The diagnostic algorithm uses Fisher discriminant analysis machine learning technique. In order to determine the anomaly state-level for the equipments, the diagnostic system uses the specially designed parameters as Anomaly Probability and Anomaly Index. In addition, the 3D visualization technique of structural vibration signals is applied for the large boiler which is one of main equipments.
구재량(Koo, Jae Raeyang),배용채(Bae, Young Chae),이두영(Lee, Doo Young),김희수(Kim, Hee Soo),손석만(Son, Suk Man),김동환(Kim, Dong Hwan) 한국소음진동공학회 2015 한국소음진동공학회 학술대회논문집 Vol.2015 No.4
The damages of overhead electrical transmission lines by the icing and the snow accretion lines may be significant enough in some cases to cause broken strands in conductors and to result in complete failure of phase conductors and to destroy even the supporting structures. Galloping, sleet jump and unbalance snow accretion are typical physical phenomenons that are closely related with ice and snow build-up on transmission lines. It is fundamentally impossible to prevent the phenomenons completely in advance because ice and snow build-up is much weather-dependent. Therefore, various devices and techniques have been proposed and used for preventing or at least minimizing its effects. In this paper, typical damages caused by ice and snow build-up are introduced and the advanced techniques to protect equipment are described.
급냉응고 Al-Li-X (Zr, Cu, Mg) 합금에서 첨가 합금원소가 미세조직 및 기계적 성질에 미치는 영향
김영환,이두영,이성학,김낙준 대한금속재료학회(대한금속학회) 1991 대한금속·재료학회지 Vol.29 No.1
A study was made of the effects of alloying elements on the structure and mechanical properties of high Li($gt;3wt%) containing RSP Al-Li-X(X=Zr, Cu, Mg) alloys. Particular emphasis was placed on the role of Mg and Cu, which are the major alloying elements in ingot metallurgy (IM) Al-Li alloys. RSP Al-Li-X alloys with several alloy compositions were subjected to various thermal treatments without any pre-aging cold working such as stretching. It has been found that, in the case of plain Al-Li-Zr alloy, the deformation behavior and the resultant mechanical properties are mainly controlled by the presence of uniformly distributed composite Al₃Li/Al₃Zr precipitates. Composite precipitates are also the major strengthening precipitates which control the deformation behavior of the alloys containing Cu and Mg. Addition of Cu and Mg to Al-Li-Zr alloys, when subjected to thermal treatment without any mechanical working, do not promote the precipitation of other strengthening phases such as T₁ and S' as expected ; however, they have a very important effect on increasing the ultimate tensile strength of Al-Li-Zr alloys due to their solid solution strengthening effects. Comparison of the present results with those of IM Al-Li alloys indicates that optimum mechanical properties can be achieved in high Li and Zr containing Al-Li alloys by simple thermal treatment without stretching, and this is due to the presence of uniformly distributed composite precipitates.
주조 A356.0 Al-SiC 복합재료의 기계적 성질과 파괴과정에 대한 공정 Si 입자의 영향
김영환,이두영,이성학,김낙준 대한금속재료학회(대한금속학회) 1991 대한금속·재료학회지 Vol.29 No.2
In this study an attempt has been made to improve mechanical properties of a cast aluminum matrix composite. Detailed microstructural analyses of a cast A356.0 Al-SiC composite indicated that SiC particulates and eutectic Si particles were segregated to the intercellular regions. The presence of these eutectic Si particles resulted in cleavage fracture along the intercellular regions, which deteriorated mechanical properties of the cast composite. In-situ SEM fracture observations clearly showed that eutectic Si particles were cracked first before the matrix-SiC decohesion or the SiC breakage occurred. In order to modify the distribution of eutectic Si particles the cast composite was re-cast with adding small amount of Sr. Tensile properties of the re-cast composite with 0.03wt.% Sr were significantly improved. The improvement of mechanical properties is attributed to a more homogeneous distribution of SiC and eutectic Si particles due to the addition of Sr and recasting.
SiC 휘스커 보강 Al 복합재료의 미세조직과 기계적 특성에 관한 연구
김영환,이두영,이성학,김낙준 대한금속재료학회(대한금속학회) 1990 대한금속·재료학회지 Vol.28 No.7
This study aims at establishing the correlation of microstructure and mechanical properties of 2124-T6 Al composites reinforced with 7, 15, 20 v/o SiC whiskers. Tensile tests along with Charpy impact tests were conducted over the test temperature range from -196℃ to 100℃. Notched round tensile tests and subsequent metallographic observations as well as in-situ SEM observation of crack opening processes were performed for the purpose of identifying the micro-mechanical processes involved in void initiation. The experimental results indicated that the impact energy was found to increase monotonically with decreasing the amount of SiC whiskers and with inceasing the test temperature. Microvoids were observed to nucleate at the interface between the aluminum matrix and SiC whikskers, confirming that the formation of voids at the interfaces is the main metallurgical factor which contributes to the reduction of fracture toughness. In addition, the Mn-containing intermetallic particles strongly affect the fracture processes in these composites.