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벤조산 폴리카프로락톤 폴리올을 함유한 2성분계 폴리우레탄 도료의 합성과 도막물성에 관한 연구
홍의석,김성계,Hong, Ui-Seok,Kim, Seong-Gye 한국섬유공학회 1997 한국섬유공학회지 Vol.34 No.11
Two-component polyurethane coatings were prepared by blending benzoic acid poIycaprolactone modified polyester polyol (BZAOs), synthesized with components of adipic acid/1,4-butanediol/polycaprolactone/bensoic acid, and polyisocyanate (TDI- adduct). Kinematic viscosity of BZAO was gradully decreased with increasing benzoic acid content in BZAO. The kinematic viscosity of modified polyesters are decreased as the benzoic acid content increases. After the film was coated with the prepared polyurethane coatings, the various physical properties were measured. They showed drying time of 4~6 hour and pot-life time of 15~27 hour, so they were proved to be coatings with long pot-life time. They showed good physical properties such as flexibility, impact resistance, cross hatch adhesion, and rust resistance. These advantages are the results of introducing polycaprolactone polyol.ram and conventional Avraml plot. At PPG contents greater than 10%, the overall crystallization rate decreased because of the uncrystallizable PPG unit. The induction time for crystallization increased, and the ratio of primary crystallization to overall crystallization increased at the same degree of undercooling. On the other hand, crystal growth rate increased with PPG content. The presence of PPG unit in the block copolymer has two opposing effects on crystallization. First, as the amount of PPG unit increases it interferes with nucleation. As a result the induction time for crystallization increases and the crystallization rate decreases. Secondly, it increases the mobility of the block copolymers because of the ether linkage and allows faster diffion of the copolymer chain to the crystal surface. Consequently the crystal growth rate after nucleation increases. Between the two effects the first one seems to be dominating and the overall crystallization rate decreases with increasing PPG content in block copolymers. Furthermore there are some different crystallization behaviors between the block copolymers and PCL homo polymer. Nucleation of block copolymers of PPG content up to 10% occurs faster than in the case of homo PCL because small amounts of PPG unit may act as heterogeneous nuclei. Also the chain mobility increased with the introduction of PPG unit, therefore the overall crystallization rate was faster than homo PCL. But if the PPG content exceeds 10% the overall crystallization rate of the block copolymers becomes slower than homo PCL.
홍의석,오일덕,Hong, Ui-Seok,Oh, Ell-Duck 대한전자공학회 1989 전자공학회논문지 Vol. No.
유한 스트립 장애물에 대한 신호 세기의 변화를 Fresnel의 회절 이론을 근거로 유도하였다. 장애물의 여러가지 파라메터 변화에 따른 신호의 세기를 이론적으로 계산하였으며 결과를 실험치와 비교하였다. 실험 데이타를 얻기 위해서 3mm 두께의 아크릴 판을 이용하였고 그 표면에 Elecoat라는 특수 페인트를 칠하여 표면에서 생기는 반사파와 투과파를 제거하였다. 송수신 안테나는 10소자는 Yagi 안테나를 사용하였으며 주파수는 820MHz를 선택하였다. 끝으로 유한 스트립 장애물의 조합으로서 tree model을 만들어서 이러한 tree로 인한 신호 감쇠를 이론 및 실험적으로 구했다. 수치해석으로 계산된 결과는 실험 데이타와 잘 일치함을 볼 수 있었다. Using Fresnel diffraction theory a formula is drived for signal intensity variation caused by finite strip obstacles. Signal intensity according to parameter variation of the obstacle is theoretically calculated by a computer and compared with experimental results. For the experiment, an acryl board 3 mm thick was used on which a special material was painted to prevent some reflections and transmissions of the incident wave. 10-element Yagi antennas were used for transmitting and receiving antenna and the frequency was 820 MHz. Finally a tree model was made as a combination of many different finite strip obstacles. Signal attenuation calculated from numerical analysis agree reasonably with experimental data.
홍의석,정명희,Hong, Ui-Seok,Jeong, Myeong-Hui 한국정보처리학회 2000 정보처리논문지 Vol.7 No.4
Design metrics that quantify the design phase play an important role in reducing system development cost because the problems in early phases of software development seriously affected the quality of the late products. Real-time systems such as telecommunication systems are so large that design quantification is more important in real-time system design. Although many metrics have been proposed, few of them are correctly validated. This paper revises the SDL metrics set proposed in earlier study [9] and perform an analytical validation o the metrics set. Axiomatic approach and dimensional analysis are used for metrics validation and the old metrics are revised ot satisfy the validation criteria.
홍의석(Ui Seok Hong),정소라(So La Jung),장호(Ho Jang),김성진(Seong Jin Kim) 한국트라이볼로지학회 2007 한국트라이볼로지학회 학술대회 Vol.2007 No.11
Tribological properties of phenolic resins in the friction materials for C-SiC brake systems were investigated. Boron-phosphorus modified resin, silicon modified resin, and straight resin were used as binders of friction materials. A simple formulation containing aramid pulp, potassium titanate, zircon silicate, and phenolic resin was used to investigate the effect of the resins at elevated temperatures up to 400℃. Friction stability and wear rate of the three friction materials were compared as a function of temperature and the activation energy for the wear rate of the three phenolic resins were obtained from Arrhenius type plot. It was found that the composite materials clearly exhibit different wear mechanisms below and above the critical temperatures. The friction materials with B-P modified resin showed good wear resistance and friction stability compared with the others.