Analysis of water hammer in pipelines by partial fraction expansion of transfer function in frequency domain

이준신,김봉기,Wook-Ryun Lee,오기용 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.10

Understanding water hammer is very important to the prevention of excessive pressure build-up in pipelines. Many researchers have studied this phenomenon, drawing effective solutions through the time- and frequency-domain approaches. For the purposes of enhancing the advantages of the frequency-domain approach and, thereby, rendering investigations of the dynamic characteristics of pipelines more effective, we propose partial fraction expansion of the transfer function between the unsteady flow source and a given section. We simulate the proposed approach using a vibration element inserted into a simple pipeline, deducing much useful physical information pertaining to pipeline design. We conclude that locating the resonance of the vibration element between the first and second resonances of the pipeline can mitigate the excessive pressure build-up attendant on the occurrence of water hammer. Our method of partial fraction expansion is expected to be useful and effective in analyses of unsteady flows in pipelines.

Effect of Defect Densities and Band Offsets on Carrier Transport Mechanisms in Mixed phase Silicon/Crystalline Silicon Heterojunction

이준신,Vinh Ai Dao,김경해,김영국,Duy Nguyen Van,Zhenghai Jin 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.2

Thin-film silicon/crystaline silicon heterojunction-type solar cels, combining the low-cost, low- temperature and light-weight of thin-film silicon with the high efficiency and high stability of crystaline silicon (c-Si), are studied widely due to the increased need for terrestrial and satelite applications. A major aspect when dealing with thin-film silicon/crystaline silicon heterojunction solar cels is quality of the silicon film-crystaline silicon hetero-interface. In this study, the carrier transport mechanisms in mixed phase (amorphous and microcrystaline) thin-film silicon/p type crystaline silicon heterojunction for various thin-film thicknesses and SiH4/H2 ratios are investi- gated. The electrical properties are strongly affected by the defect state distribution and the band offset at the hetero-interface. Two carrier transport mechanisms are recognized. The recombination process involving the interface states on the thin-film silicon side dominates at low forward bias (V < 0.4 V), whereas multi-step tunneling capture emission (MTCE) dominates at the high forward bias (0.4 < V < 0.8 V).

주거지 인근 발전소의 환경소음 저감 적용사례

이준신 한국소음진동공학회 1998 한국소음진동공학회 세미나 Vol.1998 No.12-2

Electrical Properties of Organic Light-Emitting Diodes Fabricated on HfOX-Treated Indium-Tin-Oxide Surfaces by Using an Impedance Spectroscopy Analysis

이준신,조재현,박형준,김현민,손혁주,김재홍,허종규,손선영,박근희,남은경,정동근 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.6

In organic light-emiting diodes (OLEDs), both the electrons and the holes ned to be injected efficiently to obtain the best device performance. This means that a smal injection barier height at the indium-tin oxide (ITO)/organic interface is required. The insertion of an insulating layer betwen the ITO and the organic layers leads to a significant improvement in the charge injection and the electroluminescence output. In this study, the surface of the ITO anode in OLEDs was treated with an HfOX deposition proces by using an atomic-layer chemical- vapor deposition system (ALCVD). The OLEDs fabricated on the HfOX-treated ITO anode showed a lower impedance and a higher conductance and capacitance. The changes in the capacitance, the conductance and the impedance were atributed to the enhanced carier tunneling and to a change in the work function of ITO. In this work, we used an impedance spectroscopy analysis to determine the effect of the HfOX treatment on the surface of ITO and to model the equivalent circuit for OLEDs. Impedance spectroscopy is one of the most powerful tools used to study equivalent circuit models for and the charge carier dynamics and the dielectric properties of organic devices. Devices with an ITO/organic material/Al structure could be modeled as resistances and capacitances aranged in paralel or in series. The number of elements depend on the composition of the structure, esentialy the number of layers and the contacts.

태양광산업 글로벌 리더 양성 고급인력양성센터

이준신 한국태양광발전학회 2015 한국태양광발전학회지 Vol.1 No.2

뷰티샵 종사자의 직무스트레스가 직무만족에 미치는 영향

이준신 한국뷰티경영학회 2014 한국뷰티경영학회 학술지 Vol.2014 No.11

Brief Review of Silicon Solar Cells

이준신,Yi, Jun-Sin The Korean Vacuum Society 2007 Applied Science and Convergence Technology Vol.16 No.3

태양광발전이란 태양에너지를 직접 전기 에너지로 변환시키는 것이다. 지난 5년 동안 태양광발전은 세계적으로 높은 성장률을 보여 왔다. 특히 2006년에는 30%, 이상의 성장을 가져왔으며 앞으로 20년 동안 평균 생산 성장률은 매년 27%-34%가 될 것으로 예상하고 있다. 현재까지는 태양광발전을 이용해 생산된 전력의 가격은 기존 전력발전의 가격보다 높지만 태양광 기술의 발전과 효율의 향상으로 점점 그 가격이 떨어지고 있다. 뿐만 아니라 태양전지용의 실리콘 기판의 대량생산은 점점 더 태양전지의 가격 저하를 가져오고 있다. 태양전지의 변화효율의 한계는 30%이다. 현재에는 결정질 실리콘 태양전지가 주를 이루고 있지만 미래에는 박막 실리콘 태양전지가 주도를 이룰 것이다. 2030년에는 박막 태양전지가 90%이상을 이루고 결정질 태양전지는 10% 이하로 떨어질 것을 예상하고 있다. 성균관대학교에서는 결정질 실리콘 태양전지의 저가화와 고효율화를 주 연구로 수행하고 있다. 현재 성균관대학교에서는 스크린 프린트를 이용해서 16% 이상의 다결정 실리콘 태양전지와 17% 이상의 단결정 실리콘 태양전지를 성공적으로 제작하였다. 제 1세대에서 다음 세대의 태양전지 발전의 과정은 새로운 접근법으로 확대되지만 여전히 실리콘이 지금까지 주된 재료로 쓰이고 있다. 2010년까지 이러한 기술들에 대한 격차는 여전히 있지만 태양광발전을 통한 전력생산의 가격은 60 cent/watt 정도로 예상하고 있다. 태양광발전은 청정에너지로서 재생불가능 하고 고갈되어가고 환경오염을 일으키는 다른 에너지와 비교하여 점점 대체에너지로서의 자리를 확립해 가고 있다. Photovoltaic (PV) technology permits the transformation of solar light directly into electricity. For the last five years, the photovoltaic sector has experienced one of the highest growth rates worldwide (over 30% in 2006) and for the next 20 years, the average production growth rate is estimated to be between 27% and 34% annually. Currently the cost of electricity produced using photovoltaic technology is above that for traditional energy sources, but this is expected to fall with technological progress and more efficient production processes. A large scale production of solar grade silicon material of high purity could supply the world demand at a reasonably lower cost. A shift from crystalline silicon to thin film is expected in the future. The technical limit for the conversion efficiency is about 30%. It is assumed that in 2030 thin films will have a major market share (90%) and the share of crystalline cells will have decreased to 10%. Our research at Sungkyunkwan University of South Korea is confined to crystalline silicon solar cell technology. We aim to develop a technology for low cost production of high efficiency silicon solar cell. We have successfully fabricated silicon solar cells of efficiency more than 16% starting with multicrystalline wafers and that of efficiency more than 17% on single crystalline wafers with screen printing metallization. The process of transformation from the first generation to second generation solar cell should be geared up with the entry of new approaches but still silicon seems to remain as the major material for solar cells for many years to come. Local barriers to the implementation of this technology may also keep continuing up to year 2010 and by that time the cost of the solar cell generated power is expected to be 60 cent per watt. Photovoltaic source could establish itself as a clean and sustainable energy alternate to the ever depleting and polluting non-renewable energy resource.

[세계의 기계기술] 열음향 냉동기 기술

이준신 대한기계학회 2005 기계저널 Vol.45 No.2

Flip Chip PKG 신뢰성 향상을 위한 Flux Immunity 개선 MUF 구현 방안 연구

이준신,이현숙,김민석,김성수,문기일 한국마이크로전자및패키징학회 2022 마이크로전자 및 패키징학회지 Vol.29 No.2

As the difficulty of flip chip products increase, interest in stable PKG material technology from the viewpoint of reliability is increasing. Currently, the representative of poor reliability that are mainly occurring in flip chip PKG are Sn bridge and Cu dendrite. Two type defects are caused by void generated by the flux residue around the bump. In order to essentially minimize the risk of this type of reliability failure, the linkage between the composition of Molded Underfill (MUF) and flux, which is related material, was reviewed. In this study, the correlation between base resin and filler, which is the main component of MUF, and flux, was defined, and the material composition design was carried out by refer to lesson learn. With the current material composition, it was confirmed that moisture absorption reliability 85%/ 85%/24hrs pass result and void did not occur during destructive analysis, and developed MUF has shown flux immunity improving result in flip Chip PKG. We think this study can be used in yield enhancement of flip chip process and give insights to study in compatibility between MUF and flux. Flip Chip 제품 난이도 증가에 따라 신뢰성 관점에서 안정적인 Package (이하 PKG) 소재 기술에 대한 관심이점차 높아지는 추세이다. 현재 flip chip PKG의 주요 신뢰성 불량은 Sn bridge와 Cu 확산 이다. 위 2가지 형태 모두 본질적으로는 bump 주변 잔류한 flux residue에 의하여 발생한 미세 공극이 유발하는 불량이다. 이러한 형태의 신뢰성 불량발생 문제점을 최소화하기 위해 Molded Under-Fill (이하 MUF) 소재의 핵심 조성과 flux 간 상관 관계를 검토하였다. 금번 연구를 통하여 MUF 소재의 main 구성 요소인 base resin, filler와 flux에 대한 상관 관계를 정의 하였으며, 이러한lesson learn을 토대로 flux immunity가 개선된 MUF 소재 조성을 설계할 수 있었다. 현재 해당 소재 조성으로 흡습 신뢰성 85%/85%/24hrs 확보와 파괴 분석으로 bump 주변 미세 공극의 미 발생을 확인 하였다. 본 연구 결과는 양산 단계에서의 flip chip 공정 수율 향상과 MUF와 flux 간 상용성 연구에 대한 이해를 돕는데 기여할 것으로 예상된다.

Display 기술 Roadmap과 신기술 동향

이준신,Lee, Jun-Sin 한국정보디스플레이학회 2000 한국정보디스플레이학회지 Vol.1 No.1