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30 wt% β-Tricalcium Phosphate/Al<sub>2</sub>O<sub>3</sub> 복합재료의 제조 및 특성
정희철,하정수,Jeong, Heecheol,Ha, Jung-Soo 한국재료학회 2018 한국재료학회지 Vol.28 No.3
${\beta}-Tricalcium$ phosphate (TCP) was added to $Al_2O_3$ to make a biomaterial with good mechanical properties. Using a TCP powder synthesized by a polymer complexation method, $Al_2O_3$ composites containing 30 wt% TCP were fabricated and characterized for densification, phase, microstructure, strength, and fracture toughness. With optimizing the powder preparation conditions, a high densification of 97 % was obtained by sintering at $1350^{\circ}C$ for 2 h. No reaction between the two components occurred and there was no transition to ${\alpha}-TCP$. TCP grains with a size of $2-4{\mu}m$ were well surrounded by $Al_2O_3$ grains with a size of $1{\mu}m$ or less. Strength 61(Brazilian) or 187(3-p MOR) MPa, and fracture toughness 1.7 (notched beam) or 2.5 (indentation) $MPa{\cdot}m^{1/2}$ were obtained, which are large improvements over the strength of $TCP/Al_2O_3$ composites and toughness of TCP and hydroxyapatite in previous studies.
손의 마디지문과 손의 형상을 이용한 하이브리드 개인식별 알고리즘에 관한 연구
정희철,신창호,이현열,최환수 明知大學校 産業技術硏究所 2000 産業技術硏究所論文集 Vol.19 No.-
This paper proposes an hybrid person identification algorithm utilizing finger crease pattern and finger thickness profiles which is assumed to improve the performance of the person identification algorithm utilizing only finger crease pattern. We tracked boundaries of the fingers and computed the thickness of the boundaries, thereafter performed the verifications of a person by matching one dimensional profiles of finger crease and finger thickness profiles together. This algorithm shows the possibility of an hybrid biometrics identification system. Lastly, the comparative evaluation on our system and the other algorithm is presented.
손을 이용한 생체인식 알고리즘 용도의 경계추적 알고리즘 개발
이현열,정희철,신창호,최환수 明知大學校 産業技術硏究所 2000 産業技術硏究所論文集 Vol.19 No.-
Biometrics has been getting more interests in the recent decade as a method of personal identification system. It identifies a person by recognizing the unique physiological or behavioral characteristics of a person. As a new biometric system, finger crease pattern identification system is under development. For the algorithm, the extraction of exact finger area is essential. In this paper, a new boundary tracking algorithm for extracting finger area, which can be utilized by a finger crease pattern recognition algorithm, is proposed. Due to noise and irregular illumination, conventional algorithms for boundary tracking such as skeleton-based tracking methods were not suitable for typical image of hand, So I proposed a finger boundary tracking algorithm utilizing a boundary-point-detection mask. We have observed that the proposed method provides stable and optimized boundary tracking.
Key-Pad Dynamics를 이용한 생체인식 시스템 성능향상에 관한 연구
신창호,이헌열,정희철,최환수 明知大學校 産業技術硏究所 2000 産業技術硏究所論文集 Vol.19 No.-
This paper describes a study on a person identification system which can improve currently available biometric systems. In the procedure of PIN(Personal Identification Number) input, holding time, interkey time between key presses are measured, and normalized. Person identification is performed by matching of Euclidean distances of these punching dynamics. The experimental results show the possibility of improvement of the overall system performance when keypad dynamics feature is applied to the biometric systems which take PIN input using keypads.