인공판막 재대치험예에서의 판막실패의 양상

박영배,김유호,서정돈,최윤식,이영우,오병희,도문홍,최동주,전은석 대한내과학회 1987 대한내과학회지 Vol.32 No.3

In order to observe the aspects of prosthetic cardiac valve failure, we analyzed 26 cases of Redo operation among 1081 cases of valve replacemant performed from Jan. 1961. to July 1986. The results are as follows; 1) Crude Redo operation rate was 2.4%. 2) The most common cause or prosthetic cardiac valve failure was the primary tissue failure (73%) 8r the PVE was the 2nd (15.4%). 3) Mean valve implantation time was 47.7 months. Implantation time in the child group was shorter than in adult by 6.8 months, In the primary tissue failure group (19 cases) implantation time in the child was 42.8 months 8z in adult, 66.8 months. (P$lt;0.05) In conclusion, the durability of tissue valves was significantly decreased in the child age group because of increased propensity for calcification, so the preference of tissue valves especially in this age group should be reconsidered.

미세현미조작된 생쥐배의 발생과 단일할구의 성감별 기술에 관한 연구 (1) 2. 미세조작에 의해 분리된 할구의 염색체 분석조건에 관한 연구

박수봉,최광수,전익수,정범식 경북대학교 유전공학연구소 1995 遺傳工學硏究所報 Vol.10 No.1

The study was carried out to investigate the optimum condition of C-handing for sexing mouse embryo by chromosome analysis of single blastomere. The sexing rate was 42.9% with the 114 blastocyst embryos which were used C-handing after being hypotonic-treated in 1% sodium citrate for 30 minutes. The separated blastomeres for 4-cell embryos were used For C-banding after being hypotonic-treated in 1% sodium citrate for 20-30, 10-15 and 1-2 min., and the sexing rate For different treatment times were 5.5%, 0% and 0%, respectively. The separated blastomeres from 4-cell embryos were used for C-banding after being hypotonic-created in 30% fetal calf serum for 20-30. 10-15 and 1-2 min., and the sexing rate for different treatment tunes were 18.5%. 0% and 0%, respectively.

WC-TiN 초고경도 복합재료 박막 합성 및 기계적 특성에 관한 연구

한전건,명현식,윤주선 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.4

Composite films have been one of approaches for new hard coating development and provided properties which are unachievable in uniform materials. Structurally, composite films tended to have dense and fine granular structure because column propagation was periodically interrupted by the nucleation of another phase. In this study, WC-TiN composite films were deposited on cemented carbide substrates by cathodic arc ion plating process. The chemical compositions and crystal structures were evaluated by energy dispersive spectroscopy(EDS) and X-ray diffractometry(XRD), respectively. Film thickness and fracture morphologies were investigated by using scanning electron microscopy(SEM). The mechanical properties such as film adhension and microhardness were evaluated by scratch test, microknoop hardness test and nano indentation hardness test. The microhardness of the WC-TiN composite film on cemented carbide was measured to be 4000(㎏/㎟) which is 1.5 times higher than that of the WC and TiN single layer. The critical load(Lc) of WC-Ti/WC-TiN multi-layer film was measured to be 48.5N in scratch test.

Arc-Magnetron 복합 코팅 공정에 의한 (TiAl)N 박막 합성에 관한 연구

한전건,윤주선,한준희 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.3

(TiAl)N films deposited by cathodic arc process employing two separate targets of Al and Ti have lots of macro-particles on the surface. The macro-particles were found out to be generated mainly from Al cathode of low melting temperature. In the previous study, TiN films deposited with external magnetic field showed remarkable reduction of surface droplet. For the (TiAl)N coatings, however, the efficiency of Al droplet removal was not so much as TiN films. A new coating concept combining magnetron sputtering and arc evaporation for improved coating properties was made in this study. (TiAl)N and Al-gradient (TiAl)N coatings were deposited by arc-magnetron hybrid process and content of Al in the films was changed by power density of Al magnetron sputtering source. This hybrid process allowed compositionally gradient (TiAl)N coatings to be deposited with low macro-particles and excellent adhesion. It is noted that Al-gradient (TiAl)N coating showed micro hardness of 3,000 ㎏/㎟ and good adhesion of HF2 grade. The present study introduces the hybrid process parameters involved. The formation behavior of (TiAl)N and Al-gradient (TiAl)N coatings were investigated by SEM, EDX AES and XRD.

레이저 용접을 위한 박판재의 정밀 전단 메카니즘 개발 : 유한요소법을 이용한 정밀 전단 공정해석 Analysis of Precise Shearing Process using FEM

조명래,표창률,전병희 한국산업안전학회 1999 한국안전학회지 Vol.14 No.4

Recently, Tailor Welded Blank (TWB) is widely used in automotive industry since the trans formation characteristic of its material can be changed. However, clearance between welding surfaces becomes the important factor which affect the quality of the laser weld, causing difficulties in preparing the sheet. The objective of this paper is to systematically evaluate the effects of previously presented fracture criterion and shearing condition on precise mechanical shearing simulation result. For this purpose, a parametric study was performed to investigate the effect of finite element size and fracture criterion on simulation result. Also, in order to predict the optimum shearing condition, effect of shearing conditions such as clearance and punch radius on the shear plane shape was evaluated.

미세현미조작된 생쥐배의 발생과 단일할구의 성감별 기술에 관한 연구 (1) 1. 미세조작된 배의 생존성과 분리된 단일할구의 체외 발생태에 관한 연구

박수봉,최광수,전익수 경북대학교 유전공학연구소 1995 遺傳工學硏究所報 Vol.10 No.1

This study investigated survival and development in vitro of micromanipulated embryos and biopsied blastomeres during early development of mouse embryos. The micromanipulated 4-cell and intact 4-cell embryos in Medium 2 developed to blastocyst stage by 83.3% and 90.4%, respectively. Blastomeres either biopsied or separated of 4-cell embryos in vitro developed to trophoblastic vesicle by 80.8% and 83.3%, respectively. After transfer to pseudopregnant recipient mice, the offspring races of biopsied embryos and intact embryos were 36% and 48.6%, respectively. The results suggest that the biopsy of single blastomeres from 4-cell mouse embryos have no detrimental effect on survival of embryos and blastomeres.

Bias Voltage 에 따른 WC 박막의 형성거동 및 밀착력 향상에 관한 연구

김상식,한전건,명현식 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.11

WC mono- and multilayer films were deposited on STD61 and cemented carbide substrates by Cathodic Arc Ion Plating process in various bias voltages of 0V to 200V. Chemical compositions and deposition rates were investigated using Energy Dispersive Spectroscopy(EDS) and Scanning Electron Microscopy(SEM). Microstructures of WC films were analysed by X-ray Diffractometer(XRD). The adhesion and microhardness were evaluated by Rockwell-C indentation test method, Scratch test and Microknoop hardness test. The films were formed in a mixture of α-W₂C(hexagonal structure) and β-WC(B1 NaCl structure) phase and the preferential orientation of β-WC have been changed from [311] to [220] with increasing bias voltage. The microhardness of the deposited WC films on cemented carbide were evaluated up to Hk3000 and WC multilayer films exhibited good adhesion in Rockwell-C indentation test and Scratch test.

Al 첨가에 의한 CV 흑연주철의 흑연조직 및 성질에 관한 연구

김수영,전대진,허보녕 대한금속재료학회(대한금속학회) 1984 대한금속·재료학회지 Vol.22 No.9

In this study, CV graphite cast iron was made from adding small amount of A1 after making an incomplete spheroidal graphite by adding small amount of Fesi-Mg alloy. As a result, it was found that CV ratio and graphite length were increased as increasing amount of Al addition and holding time, but graphite width was decreased, Also, it was found that brinell hardness value 170-190 HB and tensile strength value 38-40 ㎏/㎟ of the CV graphite cast iron were closer to those values of the spheroidal than those values of the flake graphite cast iron, but thermal diffusivity value 7.8×10^(-6)㎡/sec of the CV graphite cast iron was closer to that value of the flake than that value of the spheroidal graphite cast iron.

PETRI NET 를 이용한 평행 예측 - 교정 연산에 관한 연구

전흥우,차균현 고려대학교 공학기술연구소 1982 고려대학교 생산기술연구소 연구보고 Vol.17 No.1

Petri Net is a modeling device for representing and studying concurrent and parallel systems. In this paper, the papallol predictor-corrector algorithm using Petri net is discussed. And, an application of this model to the computation of the test equation and the state equation for the tunnel diode oscillator is presented. In this way, algorithms and systems can be analyzed concretely, and programed according to the transition firing sequence.

Arc-Magnetron 복합코팅 공정에 의해 합성된 초고경도 WC-(TiAl)N 복합화합물 코팅의 특성평가 연구

한전건,윤주선 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.4

Multi-phase composite coating which provides mechanical properties unachievable in uniform materials is a promising technique for new hard coating development. Structural1y, multi-phase composite films tend to be dense and fine granular structure because column propagation is periodically interrupted by the nucleation of another phase. Recently, we have synthesized WC-TiN multi-phase films by cathodic arc process. The microhardness of the WC-TiN films on cemented carbide were measured to be up to 4,000 ㎏/㎟ and these values were 1.5 times as hard as that of the WC and TiN single layer. Arc spot movement on WC cathode, however, is so slow that explosive particle emissions occur, resulting in lots of macro-particles and damages on the coating surface. In this study, super-hard WC-(TiAl)N coatings were deposited by arc-magnetron hybrid process and content of WC in the films were varied with power density of WC magnetron source. Hybrid process allowed compositionally gradient WC-(TiAl)N multi-phase coatings to be deposited with low macro-particles and good adhesion. It is noted that compositionally gradient WC-(TiAl)N coatings show super hardness of 5,000 ㎏/㎟. The present study introduces the hybrid process parameters involved and the formation behavior of WC gradient WC-(TiAl)N coatings were investigated by SEM, AES and XRD.