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불소계 플라즈마에 노출된 YAG 세라믹스의 식각거동 및 XPS 분석
김경범,김대민,이정기,오윤석,김형태,김형순,이성민,Kim, Kyeong-Beom,Kim, Dae-Min,Lee, Jung-Ki,Oh, Yoon-Suk,Kim, Hyung-Tae,Kim, Hyung-Sun,Lee, Sung-Min 한국세라믹학회 2009 한국세라믹학회지 Vol.46 No.5
Chemical composition and status of chemical bonding of the YAG($Y_3Al_5O_{12}$) ceramics after the exposure to fluorine plasma have been investigated using X-ray photoelectron spectroscopy, with the analysis on its erosion behavior. On the surface, F showed the maximum content, decreasing with depth, meanwhile the cation composition remained almost constant, irrespective of the position. The peaks due to Y in the reaction layer consisted of two kinds, showing the Y-O and Y-F bonds. These surface modifications under fluorine plasma seem to promote the erosion of the YAG ceramics. Excess addition of $Al_2O_3$ or $Y_2O_3$ into stoichiometric YAG produced 2nd phases of $Al_2O_3$ and $YAlO_3$, respectively, resulting in the slight difference in the local erosion rates. But, the overall average erosion rate was not sensitive to such excess additions of $Al_2O_3$ or $Y_2O_3$.
MFFM System을 이용한 손가락 별 파지 폭들의 변화에 따른 악력 및 개인 선호도에 대한 연구
김대민(Dae Min Kim),공용구(Yong?Ku Kong) 대한인간공학회 2008 大韓人間工學會誌 Vol.27 No.3
Individual finger/total grip forces, and subjective preferences for various individual finger grip spans (i.e., four fingers had identical grip spans or different grip spans) were evaluated by using an "Adjustable Multi-Finger Force Measurement (MFFM) System". In this study, three grip spans were defined as follows: a 'favorite grip span' which is the span with the highest subjective preference; a 'maximum grip span' which is the span with the highest total grip force; a 'maximum finger grip span' which is a set of four grip spans that had maximum finger grip forces associated with the index, middle, ring, and little fingers, respectively. Ten males were recruited from university population for this study. In experiment I, each participant tested the maximum grip force with five grip spans (45 to 65㎜) to investigate grip forces and subjective preferences for three types of grip spans. Results showed that subjective preferences for grip spans were not coincidence with the performance of total grip forces. It was noted that the 'favorite grip span' represented the lowest total grip force, whereas the 'maximum finger grip span' showed the lowest subjective preferences. The individual finger forces and the average percentage contribution to the total finger force were also investigated in this study. The findings of this study might be valuable information for designing ergonomics hand-tools to reduce finger/hand stress as well as to improve tool users' preferences and performance.
시체 손 실험연구를 이용한 손 내부 건의 힘과 외부 악력과의 관련성 연구
김대민(Dae-Min Kim),공용구(Yong-Ku Kong),최경희(Kyeong-Hee Choi) 대한인간공학회 2020 大韓人間工學會誌 Vol.39 No.5
Objective: The purpose of this study was to investigate the relationship between internal tendon exertion and external total grip strength through the cadaver hands experiment. Background: Many previous studies have been conducted to accurately measure the strength of the internal muscles of the human body, but there have been many difficulties in research, including the supply and demand of cadaver hands and the establishment of systems for data collection. Method: The donated four fresh cadaver hands were used, and the Cadaver Finger Force Measurement (CFM) system was developed to control the strength of the hand muscles. Grip span (4 levels: 45, 50, 55, 60mm), total tendon force (3 levels: 70, 105, 140N), and tendon force ratio (1:1, 1:1.5, 1:2, 1:3) were selected as independent variables, and total grip strength and internal tendon force/external force ratio (I/E ratio) were selected as dependent variables. Results: Grip span 55 and 60mm had a total grip strength of 28.8N and 27.5N, respectively, showing a relatively larger (approximately 15%) than 24.7N and 24.3N of 45mm and 50mm, respectively. The total grip strength for tendon forces showed the lowest total grip strength (19.0N) at 70N and the largest total grip strength (33.7N) when increased to 140N tendon force. The I/E ratio according to grip span was low in 55mm and 60mm grip span, and the ratio was relatively high in 45mm and 50mm grip span. The I/E ratio based on total tendon was the lowest (3.9) at tendon force of 70N and the highest at tendon force of 4.5 at 140N. Conclusion: It was confirmed that the external force of the hand grows together as the internal force (tendon exertion) increases, and that the rate of increase also depends on the magnitude of the external force. Application: The findings of this study provide useful insights and information for understanding the relationship between the external force of the hand and the force of the internal muscles that exert various grip or force.
체압 분포를 고려한 자동차 시트용 플라스틱 서스펜션에 대한 기초적 연구
박대민(Park, Dae-Min),김기선(Kim Key-Sun),최두석(Choi, Doo-Seuk),김세환(Kim Sei-hwan),박원식(Park, Won-Sik),조재웅(Cho Jae-Ung) 한국산학기술학회 2011 한국산학기술학회논문지 Vol.12 No.11
본 연구는 자동차용 시트 Back frame 내부에 설치하여 탑승자의 등부분을 지지하며 편안한 승차감을 제공하 는 시트용 서스펜션 시스템에 대한 연구이다. 운전자의 등 전체를 고르게 지지하는 구조로 설계하고 시트 백 프레임과 플라스틱 서스펜션의 조립을 효과적으로 할 수 있는 구조로 개발 하고자 한다. 서스펜션 단품은 운전자의 체압 분포를 고려하여 설계하고 시뮬레이션 해석에 있어서는 실제 모델과 같은 크기를 가지고 하였다. 플라스틱 서스펜션의 해석결 과가 실제 측정값에 근접함을 확인하였으며 기존 Wire Type에 비해 양호한 체압분포를 얻을 수 있었다. This study investigates the plastic suspension assembly which is installed on inside of vehicle seat and support passenger's back to supply the comfortable ride performance. It aims to develop the structural design in order to support driver's back uniformly and assemble seat back frame with plastic suspension effectively. The part of suspension is designed by considering the body pressure distribution of driver and it has the same size as the practical model on simulation analysis. It is confirmed that the analysis result of plastic suspension approaches the practical measured values and the better body pressure distribution can be obtained as compared with the existing wire type.
EB-PVD법으로 코팅된 Y<sub>2</sub>O<sub>3</sub>의 내플라즈마 특성
김대민,윤소영,김경범,김희식,오윤석,이성민,Kim, Dae-Min,Yoon, So-Young,Kim, Kyeong-Beom,Kim, Hui-Sik,Oh, Yoon-Suk,Lee, Sung-Min 한국세라믹학회 2008 한국세라믹학회지 Vol.45 No.11
Plasma resistant nanocrystalline $Y_2O_3$ films were deposited on alumina substrates through the electron-beam PVD technique. Increasing substrate temperature to $600^{\circ}C$ resulted in the textured microstructures with significantly enhanced adhesion force of the coating to the substrate. During the exposure to fluorine plasma, erosion rate of the coated specimen was higher than that of a sintered yttria specimen, but significantly lower than that of a single crystalline alumina. Considering the adhesion and erosion behaviors observed in the coated specimen prepared at $600^{\circ}C$, the deposition technique appears effective in reducing contamination particles generated from the ceramic parts in the plasma environment.
불소계 플라즈마에 노출된 Al<sub>2</sub>O<sub>3</sub>의 미세구조 변화
김대민,이성민,김성원,김형태,오윤석,Kim, Dae-Min,Lee, Sung-Min,Kim, Seong-Won,Kim, Hyung-Tae,Oh, Yoon-Suk 한국세라믹학회 2008 한국세라믹학회지 Vol.45 No.7
Ceramics are widely used as plasma resistant materials in semiconductor industries. However, the plasma erosion resistance has not been properly evaluated in terms of microstructural changes during the exposure to plasma. In this study, microstructure developments of $Al_2O_3$ were investigated under the fluorine plasma conditions. In polycrystalline alumina, uniform erosion throughout the specimen as well as spatially distributed local erosion were observed. Local erosion was much more severe in lower purity alumina. In contrast to the polycrystalline alumina, only uniform erosion was observed in single crystalline sapphire. These specimens, however, had practically the same erosion depth, which results in the incorrectly similar plasma resistance. This implies that the plasma erosion resistance of ceramics should be evaluated in terms of the microstructural changes, as well as the conventionally accepted erosion depth.
PZT를 이용한 RC부재 내부의 단층촬영기술에 관한 연구
김화중 ( Kim Wha-jung ),김홍진 ( Kim Hong-jin ),김대민 ( Kim Dae-min ),조충재 ( Cho Choong-jae ) 한국구조물진단유지관리공학회 2007 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.11 No.1
The increasing usage of high strength concrete has issued the need of paying special attention on the maintainability and safety involved in RC member. Non-Destructive Testing (NDT) method is simple to use, effective and reliable for periodical investigation of RC structure. This paper presents the PZT-based tomography method to estimate the velocity distribution in RC members. The velocity estimation is performed using Impact-Echo method and its results are compared with traditional tomography method. Experiment and analysis results indicate that PZT-based tomography method estimates the strength distribution of RC members quite accurately.
PZT를 이용한 RC부재 내부의 단층촬영기술에 관한 연구
김화중(Kim Wha-Jung),김홍진(Kim Hong-Jin),김대민(Kim Dae-Min),조충재(Cho Choong-Jae) 한국구조물진단유지관리학회 2007 한국구조물진단학회 학술발표회논문집 Vol.11 No.1
The increasing usage of high strength concrete has issued the need of paying special attention on the maintainability and safety involved in RC member. Non-Destructive Testing(NDT) method is simple to use, effective and reliable for periodical investigation of RC structure. This paper presents the PZT-based tomography method to estimate the velocity distribution in RC members. The velocity estimation is performed using Impact-Echo method and its results are compared with traditional tomography method. Experiment and analysis results indicate that PZT-based tomography method estimates the strength distribution of RC members quite accurately.
파지 폭과 손 크기에 따른 각 손가락이 총 악력에 미치는 영향 분석
정명철,김대민,공용구,Jung, Myung-Chul,Kim, Dae-Min,Kong, Yong-Ku 대한인간공학회 2007 大韓人間工學會誌 Vol.26 No.3
In this study, six grip spans (45mm-65mm) were tested to evaluate the effects of handle grip span and user's hand size on maximum grip strength, individual finger force, and subjective ratings of comfort using a digital dynamometer with individual force sensors. Forty-six males were assigned into three hand size groups according to their hand lengths. Results showed that overall 55mm and 50mm grip spans were the most comfortable sizes and associated with the highest grip strength in the maximum grip force exertions, whereas 65mm grip span was rated as the least comfortable size as well as the lowest grip strength. In the interaction effect of grip span and hand size, small and middle hand sized participants rated the best preference and the least preference grip spans differently with large hand sized participants. With respect to the analysis of individual finger force, the middle finger force was the strongest and the highest contribution to the total finger force, followed by ring, index and little fingers. In addition, it was noted that each finger had a different optimal grip span for exerting maximum force resulting in a bowed contoured shaped handle for two-handle hand tools. Thus, the grip spans for two-handle hand tools might be designed according to the users' hand and finger anthropometrics to maximize performance and subjective perception of comfort.