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Al 5052 합금의 저입열 Pulse MIG 최적 현장 용접조건 산정에 관한 실험적 연구
김재성,이영기,안주선,이보영,Kim, Jae-Seong,Lee, Young-Gi,An, Ju-Sun,Lee, Bo-Young 대한용접접합학회 2011 대한용접·접합학회지 Vol.29 No.1
The weight reduction of the transportations has become an important technical subject Al and Al alloys, especially Al 5052 alloys have been being applied as door materials for automobile. One of the most widely known car weight-reduction methods is to use light and corrosion-resistant aluminum alloys. However, because of high electrical and thermal conductivity and a low melting point, it is difficult to obtain good weld quality when working with the aluminum alloys. Also, Pulse MIG welding is the typical aluminum welding process, but it is difficult to apply to the thin plate, because of melt-through and humping-bead. In order to enhance weld quality, welding parameters should be considered in optimizing the welding process. In this experiment, Al 5052 sheets were used as specimens, and these materials were welded by adopting new Cold Metal Transfer (CMT) pulse process. The proper welding conditions such as welding current, welding speed, torch angle $50^{\circ}$ and gap 0~1mm are determined by tensile test and bead shape. Through this study, range of welding current are confirmed from 100A to 120A. And, the range of welding speed is confirmed from 1.2m/min to 1.5m/min.
대신호 시영역 모델을 이용한 광섬유 격자 외부 공진 레이저 다이오드의 해석
김재성,정영철,조호성,Kim, Jae-Seong,Chung, Youngchul,Cho, Ho Sung 한국광학회 2012 한국광학회지 Vol.23 No.5
본 논문에서는 RLD (Reflective Laser Diode)와 FBG (Fiber Bragg Grating)가 하이브리드 집적된 LD (이하 FG-LD)의 정적 및 동적 특성을 해석하기 위하여 대신호 시영역 모델링 방법을 구현하였다. FBG의 유효길이 2.1 mm를 포함한 외부 집적 공진기의 길이가 8 m인 경우에 0.44GHz의 동적 주파수 요동과 6.4 GHz 정도의 동적 주파수 요동 결과를 나타내었다. 또한 10 Gbps NRZ 신호의 아이가 크게 오픈된 상태를 잘 유지함을 확인하였다. FG-LD는 50 km 정도의 길이를 커버하는 10 Gbps 급 단일파장 레이저로서의 효용성이 있을 것으로 기대된다. A large-signal time-domain model is implemented to analyze an FG-LD (Fiber Grating Laser Diode) in which a reflective laser diode is hybrid-integrated with a fiber Bragg grating (FBG). When the length of the externally integrated resonator is 8 mm, in which the effective FBG length of 2.1 mm is included, a static frequency chirp of 0.44 GHz and a dynamic frequency chirp of 6.4 GHz are observed. In addition, it is also observed that the eye of the 10Gbps NRZ signal is well open. The FG-LD is expected to be a cost-effective solution for a 10Gbps-class single wavelength laser covering a span of 50 km range.
ERW강관에서 홈부식의 가속화에 미치는 유동의 영향에 관한 연구
김재성,김용,이보영,Kim, Jae-Seong,Kim, Yong,Lee, Bo-Young 대한용접접합학회 2008 대한용접·접합학회지 Vol.26 No.4
The grooving corrosion is caused mainly by the different microstructures between the matrix and weld which is formed during the rapid heating and cooling cycle in welding. By this localized corrosion reaction of pipes, it evolves economic problems such as the early damage of industrial facilities and pipe lines of apartment, and water pollution. So lots of researches were carried out already about grooving corrosion mechanism of ERW carbon steel pipe but there is seldom study for water hammer happened by fluid phenomenon and corrosion rate by flow velocity. In this study, the analysis based on hydrodynamic and fracture mechanics was carried out. ANSYS, FLUENT and STAR-CD were used for confirmation of flow phenomenon and stress on the pipe. As the results, fatigue failure is able to be happened by water hammer and grooving corrosion rate is increased cause by turbulent. Grooving corrosion is happened on the pipe, then friction loss of fluid is occurred from corroded part. Erosion can be happened enough in corroded region of microscopic size that wear "V" form. Also pipe is able to be damaged by water hammer effects because of corroded region is general acting as a notch effects. Corrosion depth was more than half of total thickness, it can be damaged from water hammer pressure.
소프트웨어 거래의 UCC 제2편의 적용에 관한 연구 - 미국의 판례를 중심으로 -
김재성,Kim, Jae-Seong 한국무역상무학회 2002 貿易商務硏究 Vol.18 No.-
Owing to a tremendous progress of information technology we have faced a great change of a society. This change has happened to almost all of a society. As a result intangible goods are also included as a major concern in international trade. We may say U.S. is one of the countries transaction of software is the most flourishing. I have tried to classified the cases of software transaction in U.S. into five groups. As a result I have known the UCC had been applied to the almost transaction of standard software. However UCC had not been applied to custom software and data processing. In these days UCITA which is very similar to a previous proposal UCC 2B has been presented. This is a contract law that would apply to computer software, multimedia products, and databases. It has been designed to create a uniform commercial contract law for those products. Now therefore we should make observation of a tendency about transaction of software in U.S. The reason is that we pay attention to the symbol and dormant power of U.S. in international trade.
피스테리아와 피스테리아 유사종의 전복 유생 섭식 특성과 생존을 연구
김재성,이창원,이희만,정해진,Kim, Jae-Seong,Lee, Chang-Won,Lee, Hee-Mahn,Jeong, Hae-Jin 한국해양학회 2009 바다 Vol.14 No.3
종속영양 와편의류인 Pfiesteria 종과 이와 유사한 형태의 Pfiesteria-like 종간의 생태적 지위차를 확인하기 위해, Pfiesteria piscicida, Cryptoperidininopsis brodyi, Stoeckeria algicida 3종에 전복유생(abalone larvae)을 투입하여 그들의 섭식 여부를 확인하고, 이들의 농도변화에 따른 전복 유생의 생존율 변화를 확인하였다. P. piscicida와 C. brodyi는 부화 1일차의 전복 유생을 직접 공격하여 치사 시킨 후 peduncle이라는 섭식기관을 이용하여 개체 전체를 섭식하는 것으로 밝혀졌다. 하지만 형태적으로 이들과 매우 유사하고 peduncle도 가진 S. algicida는 전복 유생을 직접 공격하거나 섭식하지 않았다. 전복 유생의 생존율은 P. piscicida와 C. brodyi의 초기 투입농도가 증가함에 따라 상대적으로 낮아졌다. 이러한 결과는 형태적으로 매우 유사한 종속영양성 와편모류일지라도 그들이 가지는 생태적지위는 매우 다르며, 보다 명확한 해양 생태계 먹이사슬을 이해하기 위해서는 종(species) 수준의 명확한 종 동정연구가 필요함을 제시해 준다. To investigate the difference in the ecological niches between Pfiesteria piscicida and Pfiesteria-like species (Cryptoperidininopsis brodyi and Stoeckeria algicida), we have observed the feeding behavior of three potential predators on abalone larvae and measured the survival rates of abalone larvae as a function of initial predator concentration. When the predators were mixed with abalone larvae, P. piscicida and C. brodyi became active and exhibited attacking behavior on abalone larvae within a few seconds. They could ingest whole soft body of abalone larvae using a peduncle. In contrast, feeding and attacking behavior were not observed from S. algicida. Survival rates in abalone larvae decreased with an increase of the initial concentration of P. piscicida and C. brodyi. These results indicate that Pfiesteria and Pfiesteria-like species displaying the very same shape and size have different ecological niche in the marine food webs, which implies that identification to species level is definitely important to understand and discriminate the ecological roles of them.