• 한국진공학회지
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• 제7권1호
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• pp.59-65
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• 1998

13.56MHz를 사용하는 r.f.PACVD(Plasma assisted chemical vapor deposition)방법 으로 다층 다이아몬드상 카본(DLC)필름을 Si wafer기판 위에 합성하였다. 다층 DLC필름은 2.5$\mu$m두께의 순수한 DLC필름과 0.2$\mu$m두께의 Si이 함유된 Si-DLC필름으로 구성되었으 며, ball on disk type의 tribometer를 이용하여 대기 중에서 다층 DLC필름의 마모거동을 고 찰하였다. 표면층으로 합성된 Si-DLC필름내의 Si함량이 증가함에 따라 다층 DLC필름과 AISI52100 steel ball 사이에 0.1 이하의 낮은 마찰계수를 유지하는 기간이 증가하였다. 44,000cycle과 158,400cycle의 마모실험 후 측정된 다층 DLC필름의 마모율은 각각 $2.5\times10^{-8}\sim1.8\times10^{-7}\textrm{mm}^3$/rev.과 $7.1\times10^{-9}\sim1.8\times10^{-8}\textrm{mm}^3$/rev.로 나타났다. 158,400cycle의 마모실험 후 측정된 마모율은 내마모 특성이 우수한 DLC필름보다도 2배 정도 우수한 것으로 나타났 다. 마모시험에 의해 형성된 debris의 조성을 분석한 결과, 이런 낮은 마찰계수와 우수한 내 마모 특성은 steel ball의 wear 표면을 덮고 있는 Si oxide debris층의 형성에 따른 결과로 판단되었다. 또한, 이러한 steel ball의 wear scar표면에 형성된 debris층을 제거하여도, 새로 운 Si oxide debris층이 wear scar표면에 다시 생성되어 낮은 마찰계수를 유지하고 있었다.

• 한국지반환경공학회 논문집
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• 제14권1호
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• pp.15-22
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• 2013

강원도 인제지역의 토석류 사방시설 유형에 따른 준설 및 퇴적특성을 알아보기 위하여 불투과형 및 투과형 사방댐을 각각 5개소를 선정하고 선정된 사방댐에 대한 퇴적특성 및 지하수위 분포에 대한 현장조사와 지역 내에 분포하는 51개 사방시설에 대한 유역면적, 저장능력, 준설량 등의 자료를 분석하였다. 현장조사 결과 불투과형 사방댐은 평상 시 대규모 토석류가 발생하지 않았음에도 불구하고 퇴적물이 쌓여있어 대규모 토석류 발생 시 사방댐 저장능력이 작아질 수 있음을 나타내었다. 불투과형 사방댐의 평상 시 수위는 퇴적토의 지표에 위치하여 배수가 원활하게 이루어지지 않을 수 있으나, 투과형 사방댐 수위는 버트리스 부분 하단에 존재하여 큰 강우에서도 사방댐으로 인하여 지반 포화를 발생하지 않을 것으로 나타났다. 또한, 사방시설의 저장능력과 유역면적, 준설량의 상관성 분석결과, 사방시설의 설치에 있어 유역면적에 따른 사방시설의 규모가 잘 반영되지 않았으며 큰 사방댐 시설을 건설하였으나 실제 퇴적량은 작게 나타나 향후 효율적인 사방시설의 계획 및 시공이 이루어져야 할 것으로 나타났다.

• 한국생산제조학회지
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• 제7권4호
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• pp.42-49
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• 1998

This wear debris can be harvested from the lubricants of operating machinery and its morphology is directly related to the damage to the interacting surface from which the particles originated. The morphological identification of wear debris can therefore provide very early detection of a fault and can also often facilitate a diagnosis. The purpose of this study is to attempt the developement of intelligent system for moving condition diagnosis of the machine driving system. The four shape parameter(50% volumetric diameter, aspect, roundness and reflectivity) of war debris are used as inputs to the neural network and learned the moving condition of five values(material3, applied load 1, sliding distance 1). It is shown that identification results depend on the ranges of these shape parameter learned. The three kinds of the wear debris had a different pattern characteristics and recognized the moving condition and materials very well by neural network.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.85-89
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• 1996

This paper was undertaken to analyze the morphology of wear debris for operating condition evaluatio of lubricated machine surfaces. The lubricating wear test was carried out under different experimental conditions using tile wear test device was made in our laboritory and wear testing spcimen of the pin on disk type was rubbed in paraffine series base oil, by varying specimen, applied load, sliding distance. The four shape parameters (50% volumetric diameter, aspect, roundness and reflectivity) to describe morphology of wear debris have been developed and are outlined in tile paper. A system using such techniques promises to obviate the need for subjective, human interpretation of particle morphology in machine condition monitoring

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1996년도 제24회 춘계학술대회
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• pp.60-67
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• 1996

This paper was undertaken to analyze the morphology of wear debris on operating condition of lubricated machine surfaces. The lubricating wear test was carried out under different experimental conditions using the wear test device was made in our laboritory and wear testing spcimen of the pin on disk type was rubbed in paraffine series base oil, by varying specimen, applied load, sliding distance. The four shape parameters (50% volumetric diameter, aspect, roundness and reflectivity) to describe morphology of wear debris have been developed and are outlined in the paper. A system using such techniques promises to obviate the need for subjective, human interpretation of particle morphology for machine condition monitoring.

• 한국정밀공학회지
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• 제14권5호
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• pp.143-149
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• 1997

This paper was undertaken to do image analysis of wear debris on operating condition of the lubricated moving surfaces. This lubricating wear test was performed under different experimental conditions using the wear test device was made in our laboratory and wear testing specimen of the pin on dist type was rubbed in paraffine series base oil, by materials, varying applied load, sliding distance. The four shape parameters (50% volumetric diameter, aspect, roundness and reflectivity) to describe wear debris have been developed and are outlined in the paper. A system using such techniques promises to obviate the need for subjective, human interpretation of particle morphology for machine condition monitoring, this to overcome many of the difficulties with current methods and facilitating wider use of wear particle analysis in machine condition monitouing.

• The Journal of Advanced Prosthodontics
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• 제7권2호
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• pp.151-159
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• 2015

PURPOSE. To describe and characterize the surface topography and cleanliness of CAD/CAM manufactured zirconia abutments after steaming and ultrasonic cleaning. MATERIALS AND METHODS. A total of 12 ceramic CAD/CAM implant abutments of various manufacturers were produced and randomly divided into two groups of six samples each (control and test group). Four two-piece hybrid abutments and two one-piece abutments made of zirconium-dioxide were assessed per each group. In the control group, cleaning by steam was performed. The test group underwent an ultrasonic cleaning procedure with acetone, ethyl alcohol and antibacterial solution. Groups were subjected to scanning electron microscope (SEM) analysis and Energy-dispersive X-ray spectroscopy (EDX) to verify and characterize contaminant chemical characterization non- quantitatively. RESULTS. All zirconia CAD/CAM abutments in the present study displayed production-induced wear particles, debris as well as organic and inorganic contaminants. The abutments of the test group showed reduction of surface contamination after undergoing an ultrasonic cleaning procedure. However, an absolute removal of pollutants could not be achieved. CONCLUSION. The presence of debris on the transmucosal surface of CAD/CAM zirconia abutments of various manufacturers was confirmed. Within the limits of the study design, the results suggest that a defined ultrasonic cleaning process can be advantageously employed to reduce such debris, thus, supposedly enhancing soft tissue healing. Although the adverse long-term influence of abutment contamination on the biological stability of peri-implant tissues has been evidenced, a standardized and validated polishing and cleaning protocol still has to be implemented.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1998년도 제14회 학술발표회 논문개요집
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• pp.44-44
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• 1998

It was observed that the friction coefficient decreased with increasing Si concentration in the l ilms. Furthermore, the friction behavior became more s때ble even when very small amount of S Si of less than 0.5 at. % was incorporatA:회 By analyzing the composition of the debris f formed, we could show that the low and stabilized friction coefficient is in마nately relatA:었 w with the formation of the Si rich oxide debris. These result supports the mechanism that the h hydrated silica debris is the reason for low friction coefficient in humid environment. Second e evidence of the role of Si rich oxide debris could be found in the triOO-chemical reactions d during initial stage of triho-test. When the Si concen$\sigma$ation was less than 5 at.%, initial t transient period of high friction coefficient was commonly observed. Mter the transient period, m the friction coefficient becomes lower with increasing contact cycles. The initial $\sigma$ansient p peri여 becomes shorter and the starting and maximum friction coefficients in $\sigma$ansient 야,riod d decreased with increasing Si concentration. Composition of the debris on the wear scar s surface was analyzed by Auger spe따'Oscopy at v뼈ous stages in the initial transient period. W We observed that when the friction coefficient increased in earlier stage of the $\sigma$'ansient p period, iron and oxygen was observed in the debris. However, decrease in the 당iction c coefficient in the later stage of the transient period was associated with the formation of s silicon rich oxide debris. This result also supports the friction mechanism of Si-DLC films t that the formation of Si rich oxide debris results in low friction coefficient in ambient a atmosphere. atmosphere.

• Nuclear Engineering and Technology
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• 제55권8호
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• pp.3017-3029
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• 2023

In the late in-vessel phase of a nuclear reactor severe accident, the internal heat transfer and crust evolution during the debris bed melting process have important effects on the thermal load distribution along the vessel wall, and further affect the reactor pressure vessel (RPV) failure mode and the state of melt during leakage. This study coupled the phase change model and large eddy simulation to investigate the variations of the temperature, melt liquid fraction, crust and heat flux distributions during the debris bed melting process in the hypothetical severe accident of HPR1000. The results indicated that the heat flow towards the vessel wall and upper surface were similar at the beginning stage of debris melting, but the upward heat flow increased significantly as the development of the molten pool. The maximum heat flux towards the vessel wall reached 0.4 MW/m². The thickness of lower crust decreased as the debris melting. It was much thicker at the bottom region with the azimuthal angle below 20° and decreased rapidly at the azimuthal angle around 20-50°. The maximum and minimum thicknesses were 2 and 90 mm, respectively. By contrast, the distribution of upper crust was uniform and reached stable state much earlier than the lower crust, with the thickness of about 10 mm. Moreover, the sensitivity analysis of initial condition indicated that as the decrease of time interval from reactor scram to debris bed dried-out, the maximum debris temperature and melt fraction became larger, the lower crust thickness became thinner, but the upper crust had no significant change. The sensitivity analysis of in-vessel retention (IVR) strategies indicated that the passive and active external reactor vessel cooling (ERVC) had little effect on the internal heat transfer and crust evolution. In the case not considering the internal reactor vessel cooling (IRVC), the upper crust was not obvious.

• 한국레이저가공학회:학술대회논문집
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• 한국레이저가공학회 2004년도 추계학술대회논문집
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• pp.73-77
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• 2004