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안효석,장동영 한국공작기계학회 2008 한국공작기계학회 춘계학술대회논문집 Vol.2008 No.-
In micro/nano-scale contacts in MEMS and NEMS, capillary and van der Waals forces generated around contacting micro-asperities significantly influence the performance of concerning device as they are related to adhesion and stiction of interacting surfaces, In this regard, it is of prime importance to accurately estimate the magnitude of surface forces so that an optimal solution for reducing friction and adhesion of micro/nano-surfaces may be obtained. We introduce an effective method to calculate these surface forces based on topography information obtained from an atomic force microscope
조경석 표면 거칠기 측정을 위한 기준평면의 적용기법 연구
안기원,이효성,서두천,신석효 慶尙大學校 1999 論文集 Vol.38 No.-
This paper presents a procedure for precision measurements of stone surface roughness by close-range digital photogrammetric technique. To obtain the stone surface roughness from the ideal surface, the best fitting reference planes were determined by least square methods. The RMSE of the normal distance between the points of the sample areas and the reference planes did exceed 0.1mm.
안효석,김두인 한국공작기계학회 2008 한국공작기계학회 춘계학술대회논문집 Vol.2008 No.-
The running-in behaviour of the metal carbon coating (WC/C) has been evaluated with regard to its applicability as wear-resistant coating to key components in engines. Confocal microscopy and scanning electron microscopy were used to observe worn surfaces and the wear scars on the steel balls. Elemental composition of the coating and worn surfaces were characterized using Auger electron spectroscopy. The friction behavior of WC/C coating was comparable to common carbon-based coatings. Thin tribofilm was formed on the worn surface of the steel ball due to material transfer and tribochemical reaction whereas there was no evidence of tribofilm generation on the coating surface. indicating the chemical innertness of WC/C coating.
Tuning fork형 micro-cantilever sensor
김충현,안효석 한국공작기계학회 2005 한국공작기계학회 춘계학술대회논문집 Vol.2005 No.-
An experimental investigation of the basic characteristics of a micro-cantilever sensor was performed by inspecting the amplitude and frequency characteristics using a commercial tuning fork. Application of acetone and ethanol with a volume of 1μl on the tine of a vibrating tuning fork cause immediate response in its amplitude and frequency. It has shown that the tuning fork has ability to recognize a chemical agent with high sensitivity.
Landsat TM과 SPOT XS데이터를 이용한 디지털 모자이킹
서두천,이효성,안기원,신석효 慶尙大學校 1998 論文集 Vol.37 No.-
In digital processing of remotely sensed image data, digital mosaicking is required for display and analysis of large regions covered by more than one image. In this paper, digital mosaic process for any given multisensor data set of Landsat Thematic Mapper(TM) and SPOT multispectral(XS) data has been described. A statistical normalization was implemented to reduce radiometric discontinuity �� 새 the multisensor and multidata reflectance. An automated digital matching technique was used to find the corresponding ground control points in the overlapped area and to generate more geometrically accurate mosaic image.
An Innovative Educational Program for Nano-IT Integrated Technology
Hyo-Sok Ahn,Eun-Kyung Kim 한국통신학회 2009 한국통신학회 학술대회논문집 Vol.2009 No.6
The NT(nanotechnology) - IT(information technology) integrated technology has become new growth engine for the nation’s economy and technological competitiveness. A recent survey on the man power in NT- IT integrated field in Korea revealed that the demand is far greater than the supply. This causes an enormous expense to construct the state of art Nano and IT facilities and working environments. With the urgent needs and global technology trends, Seoul Technopark has been founded to assist and develop NIT based top-notch businesses, to train highly talented professionals, and to lead a major role in NIT research and manufacturing. As one of the core projects for Seoul Technopark, NIT University (NITU) program has been developed to bring forth a new future and new competitiveness for the nation. The NITU program has founded to foster talented experts in the field of Nano and IT integrated technologies, especially in the microsystems packaging (MSP) technology. It is confident that this program will continue to provide highly focused and practical education, to contribute human resource cultivation in the field of MSP technology and Nano and IT manufacturing equipment, which emerges as next generation growth industries, and to strengthen a global industrial competitiveness.
Optimal Condition of Hydroxyapatite Powder Plasma Spray on Ti6Al4V Alloy for Implant Applications
Ahn, Hyo-Sok,Lee, Yong-Keun Materials Research Society of Korea 2012 한국재료학회지 Vol.22 No.4
Optimal conditions for HA plasma spray-coating on Ti6Al4V alloy were investigated in order to obtain enhanced bone-bonding ability with Ti6Al4V alloy. The properties of plasma spray coated film were analyzed by SEM, XRD, surface roughness measurement, and adhesion strength test because the film's transformed phase and crystallinity were known to be influential to bone-bonding ability withTi6Al4V alloy. The films were formed by a plasma spray coating technique with various combinations of plasma power, spray distance, and auxiliary He gas pressure. The film properties were analyzed in order to determine the optimal spray coating parameters with which we will able to achieve enhanced bone-bonding ability with Ti6Al4V alloy. The most influential coating parameter was found to be the plasma spray distance to the specimen from the spray gun nozzle. Additionally, it was observed that a relatively higher film crystallinity can be obtained with lower auxiliary gas pressure. Moderate adhesion strength can be achievable at minimal plasma power. That is, adhesion strength is minimally dependent on the plasma power. The combination of shorter spray distance, lower auxiliary gas pressure, and moderate spray power can be recommended as the optimal spray conditions. In this study, optimal plasma spray coated films were formed with spray distance of 70 mm, plasma current of 800 A, and auxiliary gas pressure of 60 psi.
원자력현미경의 위상차영상을 이용한 나노표면의 미소기계적 특성 평가
안효석(Hyo-Sok Ahn) 한국생산제조학회 2007 한국공작기계학회 춘계학술대회논문집 Vol.2007 No.-
Phase contrast imaging in atomic force microscopy showed a promise as an effective tool for better understanding of micromechanical properties of surfaces at nano scale. A qualitative estimation model for phase contrast images obtained with a tapping mode AFM was developed. This investigation demonstrated the high efficiency of combined analysis of topography and phase contrast images for characterizing nanosurfaces. Phase contrast images allowed estimation of relative stiffness (elastic modulus) of the sample surface. The phase contrast images revealed a significant inhomogeneity of the nano scale worn surfaces. Phase contrast images are also capable of revealing the formation of tribofilms.