Highly reflective Al-based alloy ohmic contact to p-type GaN

Sanghan Lee,Jun Ho Son,Gwan Ho Jung,Kisoo Kim,Jong-Lam Lee 대한전자공학회 2008 ICEIC:International Conference on Electronics, Inf Vol.1 No.1

We report a metallization scheme of high-reflectance, low-resistance ohmic contact on p-type GaN. The high reflectance of 84 % at the 460 ㎚ wavelength and the specific contact resistivity as low as 8.59 × 10??㎠ were obtained from MgAl-alloy(50 A )/ Ag(3000 A) / Ru(500 A) after annealing at 450 ℃ in air. The formation of Ag-Ga solid solution due to the outdiffusion of Ga after annealing leads to ohmic behavior of the contact. Employing highly reflective MgAl as an contact layer and Ru as an overlayer that suppress the agglomeration and the oxidation of Ag resulted in the high reflectance of the contact.

A Genetic Algorithm and Discrete-Event Simulation Approach to the Dynamic Scheduling

윤상한(Sanghan Yoon),이종환(Jonghwan Lee),정관영(Gwan-Young Jung),이현수(Hyunsoo Lee),위도영(Doyeong Wie),정지용(Jiyong Jeong),서영복(Yeongbok Seo) 한국산업경영시스템학회 2013 한국산업경영시스템학회지 Vol.36 No.4

This study develops a dynamic scheduling model for parallel machine scheduling problem based on genetic algorithm (GA). GA combined with discrete event simulation to minimize the makespan and verifies the effectiveness of the developed model. This research consists of two stages. In the first stage, work sequence will be generated using GA, and the second stage developed work schedule applied to a real work area to verify that it could be executed in real work environment and remove the overlapping work, which causes bottleneck and long lead time. If not, go back to the first stage and develop another schedule until satisfied. Small size problem was experimented and suggested a reasonable schedule within limited resources. As a result of this research, work efficiency is increased, cycle time is decreased, and due date is satisfied within existed resources.

A Study on the Effect of Aligning with Management Strategy and Strategic Performance Management on Firm's Performance in Medium and Small Firm

Jonghwan Lee,Sanghan Yoon,Jung-ho Lee,Sang-Jung Kim,Min-Suk Byon,Moon-Soo Kwon,Se-in Jang 한국산업경영시스템학회 2014 한국산업경영시스템학회 학술대회 Vol.2014 No.춘계

본 연구는 대구경북의 중소기업을 대상으로 전략유형과 성과관리시스템이 경영성과에 미치는 영향에 대한 연구를 통해 중소기업에 적합한 전략유형을 알아보고 그에 맞는 성과관리시스템의 설계를 통해 기업의 경영성과를 개선하고자 하였다. 연구결과 전략유형 중에서 기술혁신형과 생산중점형은 경영성과에 유의적인 영향을 미치는 것으로 나타났으며, 성과관리시스템은 재무적성과와 비재무적성과에 부분적으로 영향을 미치는 것으로 나타났다. 또한 전략유형과 성과관리시스템의 상호작용은 기술혁신형 기업의 경영성과에 유의적인 영향을 미치는 것으로 나타났다. 이러한 결과는 중소기업들이 전략유형에 맞는 성과관리시스템의 구축을 통해 경영성과를 향상 시킬 수 있음을 지지하고, 이를 통해 기업들은 자원의 제약과 무한 경쟁을 이겨내고 지속적인 성장을 할 수 있을 것으로 보인다. The purpose of this study is to whether management strategy types are archived improving the organizational performance and strategic performance management system are makes a significant influence on the organizational performance. Another objective is to identify whether the interaction between management strategy types and strategic performance management system makes a significant influence on the organizational performance. The results of this study indicate that diversity performance measures(strategy types) are effect partially presented on the firm's performances. And, firms which have the higher using diversity performance measures(strategy types) are achieve the higher firm's performances than lower using firm's(strategy types). And, the interaction of Management strategy types and diversity performance measures are effect partially presented on the firm's performances.

The Role of Chloramination Methodologies on the Yield of N-nitrosodimethylamine from Ranitidine

( Mingizem Gashaw ),( Kangwoo Cho ),( Subramaniyan Ramasundaram ),( Sanghan Jung ),( Seok Won Hong ) 한국물환경학회(구 한국수질보전학회) 2016 한국물환경학회·대한상하수도학회 공동 춘계학술발표회 Vol.2016 No.-

전력 사용량 데이터 분석 사례 연구 (공장)

임호정(Hojung Lim),강정훈(Jeonghoon Kang),김상한(Sanghan Kim),정혜동(Hyedong Jung) 대한전자공학회 2016 대한전자공학회 학술대회 Vol.2016 No.11

지방농정 거버넌스 구축 요인들 간의 우선순위에 관한 연구

문유석(Moon, Yuseok),이시원(Lee, See-won),정준금(Jung, Joon Keum),최상한(Choi, Sanghan) 한국지방정부학회 2013 지방정부연구 Vol.17 No.4

그동안 우리나라 농정은 전문가들의 참여가 어느 정도 있긴 하였지만 정부주도의 틀을 벗어나지 못하였다. 그러나 근래 들어 우리 농정을 둘러싼 대내외적 환경변화에 효율적으로 대응하기 위해서는 다양한 이해관계자들의 실질적 참여가 보장되는 거버넌스 체제로의 전환이 필요하다는 주장이 제기되어 왔다. 특히 기초자치단체 수준에서의 농정 거버넌스의 필요성이 강조되고 있다. 시ㆍ군 등 기초자치단체는 농정이 이루어지는 최일선으로서 자체농정을 실현할 수 있는 최소단위의 정부이기 때문이다. 공동체 의식을 바탕으로 농정 관련 이해관계자들 간의 네트워크를 통한 상호협력체제의 구축을 통해 지역실정에 맞는 정책의 결정과 집행이 가능하도록 해야 한다는 주장이 설득력을 얻고 있는 것이다. 이러한 맥락하에서 본 연구는 우리나라 기초자치단체 수준의 수평적 거버넌스 구축을 위한 요인들을 알아보고 이들 간의 우선순위를 분석하여 보았다. 선행연구의 검토와 농어업회의소 사무국장들과의 면담결과를 바탕으로 지방농정 거버넌스 구축을 위한 요인들을 추출하여, 그 요인들을 상위요인과 세부요인으로 나눈 후 지방농정 전문가들을 대상으로 설문조사를 실시하여 계층화분석(AHP)을 실시하였다. 총 28명의 전문가 조사에서 파악된 지방농정 거버넌스 구축을 위한 우선순위 분석 결과, 5개의 상위 요인 중에서는 농민(단체포함)의 농정 거버넌스에 대한 역량 및 태도개선의 중요도가 가장 높고, 그 다음으로 지방정부(단체장 및 공무원)의 농정 거버넌스에 대한 역량 및 태도 개선, 이해관계자들간의 상호신뢰 구축, 농정 거버넌스 기구의 정비ㆍ보완, 지방농정 거버넌스에 대한 환경 지지 확보 순으로 나타났다. 본 연구에서는 이러한 분석결과를 바탕으로 기초자치단체에서의 수평적 거버넌스 구축을 위한 몇 가지 전략적 방안들을 제시하였다. Governance can be seen as an alternative way of doing public affairs through cooperative work among relevant stake-holders. Like in many other fields, experts in the field of agricultural administration have suggested that governance needs to replace government to secure effectiveness of agricultural administration. Being the frontier of agricultural administration with the presence of strong sense of community, local governments are believed to be the right places where governance can be effectively operated among relevant stake-holders including local governments, farmers, local assemblies, agencies of central governments, and others. When local agricultural governance is properly operated, both responsiveness and democracy in agricultural administration can be substantially improved. Governance also can play a role of educational incubator for direct democracy, which will help farmers explore their own future for themselves through enlightenment and training. Because of these features, many advanced countries have replaced traditional agricultural administration into agricultural governance. But, in Korea, local governance is still at the beginning stage so that collective wisdom to build governance is needed. Under these contexts, this study attempts to find out essential factors of local agricultural governance and evaluate their significance by using the method of Analytic Hierarchy Process(AHP). 28 experts evaluated that, among the five factors, improvement of farmers' capacity and attitude toward local agricultural governance(LAA) is the most important one followed by improvement of local governments' capacity and attitude toward LAA. Among the twenty-five sub-factors, the experts evaluated that farmers' sense of participation is the most important one followed by mayor's recognition on the need for LAA, mayor's strong support for LAA, cultivation of leadership of farmers' associations, improvement of representation of farmers' associations, and so on. Based on these results, this study suggests some feasible policy alternatives to build LAA.

Efficient Light Absorption by GaN Truncated Nanocones for High Performance Water Splitting Applications

Kim, Yeong Jae,Lee, Gil Ju,Kim, Seungkyu,Min, Jung-Wook,Jeong, Sang Yun,Yoo, Young Jin,Lee, Sanghan,Song, Young Min American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.34

<P>Despite the importance of gallium nitride (GaN) nanostructures for photocatalytic activity, relatively little attention has been paid to their geometrical optimization on the basis of wave optics. In this study, we present GaN truncated nanocones to provide a strategy for improving solar water splitting efficiencies, compared to the efficiency provided by the conventional geometries (i.e., flat surface, cylindrical, and cone shapes). Computational results with a finite difference time domain (FDTD) method and a rigorous coupled-wave analysis (RCWA) reveal important aspects of truncated nanocones, which effectively concentrate light in the center of the nanostructures. The introduction of nanostructures is highly recommended to address the strong light reflection of photocatalytic materials and carrier lifetime issues. To fabricate the truncated nanocones at low cost and with large-area, a dry etching method was employed with thermally dewetted metal nanoparticles, which enables controllability of desired features on a wafer scale. Experimental results exhibit that the photocurrent density of truncated nanocones is improved about three times higher compared to that of planar GaN.</P> [FIG OMISSION]</BR>

Structural, electro-magnetic, and optical properties of Ba(Fe,Ni)₂As₂ single-crystal thin film

Yoon, Sejun,Seo, Yu-Seong,Lee, Seokbae,Weiss, Jeremy D,Jiang, Jianyi,Oh, MyeongJun,Lee, Jongmin,Seo, Sehun,Jo, Youn Jung,Hellstrom, Eric E,Hwang, Jungseek,Lee, Sanghan IOP 2017 Superconductor science & technology Vol.30 No.3

<P>We investigated the superconducting transition temperature (<I>T</I> <SUB>c</SUB>), critical current density (<I>J</I> <SUB>c</SUB>) and optical properties of optimally doped Ba(Fe<SUB>0.95</SUB>Ni<SUB>0.05</SUB>)<SUB>2</SUB>As<SUB>2</SUB> (Ni-Ba122) single-crystalline epitaxial thin films grown by pulsed laser deposition for the first time. The <I>T</I> <SUB>c</SUB> at zero resistivity was about 20.5 K and the <I>J</I> <SUB>c</SUB> at self-field and 4.2 K was 2.8 MA cm<SUP>−2</SUP> calculated by the Bean model. The superconducting properties such as <I>T</I> <SUB>c</SUB> and <I>J</I> <SUB>c</SUB> of thin films are comparable to those of bulk single-crystal samples. The superfluid plasma frequency (<I>λ</I> <SUB>p,S</SUB>) of Ni-Ba122 thin film is ∼7033 cm<SUP>−1</SUP> obtained by optical spectroscopic technique. Based on this plasma frequency, we obtained the London penetration depth (<I>λ</I> <SUB>L</SUB>), ∼226 nm at 8 K, which is comparable to those of optimally Co- and K-doped BaFe<SUB>2</SUB>As<SUB>2</SUB> single crystals.</P>

High critical current density over 1 MA cm⁻² at 13 T in BaZrO₃ incorporated Ba(Fe,Co)₂As₂ thin film

Lee, Jongmin,Jiang, Jianyi,Kametani, Fumitake,Oh, Myeong Jun,Weiss, Jeremy D,Collantes, Yesusa,Seo, Sehun,Yoon, Sejun,Tarantini, Chiara,Jo, Youn Jung,Hellstrom, Eric E,Lee, Sanghan IOP 2017 Superconductor science & technology Vol.30 No.8

<P>Achieving high critical current density (<I>J</I> <SUB>c</SUB>) under a high magnetic field in Fe based superconductors is indispensable for practical applications. Here we report that high critical current density over 1 MA cm<SUP>−2</SUP> in high field (13 T) can be achieved in BaZrO<SUB>3</SUB> (BZO) incorporated Ba(Fe,Co)<SUB>2</SUB>As<SUB>2</SUB> (Co-Ba122) thin film grown on CaF<SUB>2</SUB> substrate using pulsed laser deposition. The magnetization <I>J</I> <SUB>c</SUB> of Co-Ba122 thin film incorporated with 2 mol.% BZO reaches 1.3 MA cm<SUP>−2</SUP> (<I>H</I>ǁ<I>c</I>, 13 T and 4.2 K), 14 times higher than that of pure Co-Ba122 thin film. Transmission electron microscopy observation revealed that BZO forms nanorods of ∼4 nm in average diameter with mean separation of 10–11 nm which corresponds to a matching field of about 17–20 T. Incorporating BZO in Co-Ba122 thin films led to a strong vortex pinning effect and a significant enhancement of <I>J</I> <SUB>c</SUB> because a high density of BZO nanorods could form in the superconducting matrix without significant degradation of <I>T</I> <SUB>c</SUB>, and the diameter of BZO nanorods is approximately twice the coherence length of Co-Ba122 (<I>ξ</I> <SUB>ab</SUB>(0) ∼ 2.5 nm) which is the optimal size as pinning centers.</P>

Vortex pinning in artificially layered Ba(Fe,Co)₂As₂ film

Oh, M.J.,Lee, Jongmin,Seo, Sehun,Yoon, Sejun,Seo, M.S.,Park, S.Y.,Kim, Ho-Sup,Ha, Dong-Woo,Lee, Sanghan,Jo, Youn Jung Elsevier 2018 Cryogenics Vol.92 No.-

<P><B>Abstract</B></P> <P>Static high critical current densities (<I>J</I> <SUB>c</SUB>) > 1 MA/cm<SUP>2</SUP> with magnetic field parallel or perpendicular to <I>c</I>-axis were realized in Co-doped/undoped multilayerd BaFe<SUB>2</SUB>As<SUB>2</SUB> films. We made a current bridge by FIB to allow precise measurements, and confirmed that the boundary quality using FIB was considerably better than the quality achieved using a laser. The presence of a high in-plane <I>J</I> <SUB>c</SUB> suggested the existence of <I>c</I>-axis correlated vortex pinning centers. To clarify the relationship between the <I>J</I> <SUB>c</SUB> performance and superstructures, we investigated the magnetic flux pinning mechanism using scaling theory of the volume pinning force <I>F</I> <SUB>p</SUB>(<I>H</I>). The <I>J</I> <SUB>c</SUB>(<I>H</I>) curves, <I>F</I> <SUB>p</SUB>/<I>F</I> <SUB>p,max</SUB> vs. h = <I>H</I>/<I>H</I> <SUB>irr</SUB> curves, and parameters <I>p</I> and <I>q</I> depended on the characteristics of the flux pinning mechanism. It was found that the dominant pinning mechanism of Co-doped/undoped multilayerd BaFe<SUB>2</SUB>As<SUB>2</SUB> films was Δl-pinning and the inserted undoped BaFe<SUB>2</SUB>As<SUB>2</SUB> layers remained non-superconducting. The dominant pin geometry varied when the magnetic field direction changed. It was concluded that the artificially layered BaFe<SUB>2</SUB>As<SUB>2</SUB> film is a 3-D superconductor due to its long correlation length compared to the thickness of the non-superconducting layer.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Co-doped BaFe<SUB>2</SUB>As<SUB>2</SUB> and pure BaFe<SUB>2</SUB>As<SUB>2</SUB> layers are deposited periodically. </LI> <LI> The Δl-pinning dominance shows that the pure Ba122 layer is the non-superconductor. </LI> <LI> The dominant geometry of pin is changed as a direction of magnetic field. </LI> <LI> The 3-D superconductor originated by its long correlation length is found. </LI> </UL> </P>