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WC-Co계 분말사출성형에서 초임계$CO_2$에 의한 결합제 제거
김용호,임종성,이윤우,김소나,박종구 한국분말야금학회 2001 한국분말재료학회지 (KPMI) Vol.8 No.2
The conventional debinding process in metal injection molding is very long time-consuming and unfriendly environmental method. Especially, in such a case of injection molded parts from hard and fine metal powder, such as WC-Co, an extremely long period of time is necessary in the conventional slow binder removal process. On the other hand, supercritical debinding is thought to be the effective method which is appropriate to eliminate the aforementioned inconvenience in the prior art. The supercritical fluid has high diffusivity and density, it can penetrate quickly into the inside of the green metal bodies, and extract the binder. In this paper, super-critical debinding is compared with wicking debinding process. Wax-based binder system is used in this study. The binder removal rate in supercritical $CO_2$ have been measured at $65^{\circ}C$, 75$^{\circ}C$ in the pressure range from 20 MPa to 28 MPa. Pores and cracks in silver bodies after sintering were observed using SEM When the super-critical $CO_2$ debinding was carried out at 75$^{\circ}C$, almost all the wax (about 70 wt% of binder) was removed in 2 hours under 28 MPa and 2.5 hours under 25 MPa.
이산 웨이블렛 변환과 프렉탈 이론을 이용한 영상부호화 기법
김용호,정종근,편석범,이윤배 대한전자공학회 2002 電子工學會論文誌 IE (Industry electronics) Vol.39 No.4
When JPEG, a standard of stopped image compression, is high compressed, the image is severely blocked. Since JPEG performs compression after taking DCT(Discrete Cosine Transform). It has a defect that the quality of image becomes low with aliasing in the case of high compression. Though transformation cipher method can have high compression rate, flame nay happen to quality of image by transformation and reverse transformation. In this paper, we use wavelet transform and fractal theory in order to solve these problems. After we apply these two methods to stopped image, we can get some good results, improvement of speed and compression rate, and elimination of blocking appearance. Besides, we show quality of restoration image is better than established one. 현재 정지 영상 압축의 표준인 JPEG은 DCT(discrete cosine transform)를 취한 후에 압축과정을 수행하기 때문에 고 압축을 할 경우 블록화 현상이 심하게 일어나며, 고 압축시에 복원된 영상에 나타나는 왜곡(aliasing)등으로 영상의 품질이 낮아지는 단점이 있다. 또한 변환 부호화 방법은 높은 압축률을 가질 수 있으나 변환과 역 변환에 의한 화질에 열화가 발생할 수 있다. 본 논문에서는 이러한 문제점을 해결하고자 웨이블렛 변환과 프렉탈 이론을 정지 영상에 적용한 결과 낮은 비트율에서 기존의 방법보다 압축 후 복원시 속도의 향상, 압축율의 향상, 블록현상을 제거하였다. 그리고 복원화질이 기존의 방법보다 우수함을 보였다.
백합의 생태에 관한 연구 (Ⅱ) : 크기와 육중량의 변화
김용호 군산대학교 1977 群山水産專門大學 硏究報告 Vol.11 No.3
Following data were obtained as a result of examniing on the meat weight variation for length of head clam, which was collected in Sunyounri, Mimyen, Jeonlabugdo, from Sep. to Oct. in 1975. 1.The meat weight variation showed the highest 15.3% in 3.7Cm, while the 29.9% the lowest in 4.5Cm, the average was 20.0%. 2.The shell weight variety showed the highest 70.4% in 3.7Cm, while the 43.9% the lowest in 4.5Cm, the average was 55.4%. 3.The ratio of the meat weight of the large size clam was lower than the average value.