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Oxygen-Controlled Seed Layer in DC Sputter-Deposited ZnO:Al Substrate for Si Thin-Film Solar Cells
Seung-Yoon Lee,Taehyun Hwang,Woojin Lee,Sangheon Lee,Hongsik Choi,Seh-Won Ahn,Heon-Min Lee,Byungwoo Park IEEE 2015 IEEE journal of photovoltaics Vol.5 No.2
<P>Oxygen-controlled seed layer in Al-doped ZnO (ZnO:Al) thin films deposited by the industrially compatible dynamic dc magnetron sputter results in both enhanced electron mobilities and appropriate etched morphologies for the Si thin-film solar cells. At the relatively low deposition temperature of 300 °C, optimized ZnO:Al film grown on the seed layer has the carrier mobility of 45 cm<SUP>2</SUP>/V·s and proper postetching morphology with around 1-2-μm crater size. Reduced angular distribution of the (002) grains analyzed by the diffraction rocking curve is shown as the key structural feature for the improved carrier mobility. Finally, the performance of the microcrystalline Si solar cell on the developed ZnO:Al substrate shows high-efficiency potential of the tandem solar cell adapting this transparent conductive oxide substrate.</P>
Nanostructural analysis of ZnO:Al thin films for carrier-transport mechanisms
Seung-Yoon Lee,Woojin Lee,남창우,Jongmin Kim,Sujin Byun,Taehyun Hwang,Byung-Kee Lee,Young Il Jang,Sungeun Lee,Heon Min Lee,박병우 한국물리학회 2013 Current Applied Physics Vol.13 No.4
The carrier mobility of sputter-deposited Al-doped ZnO transparent-conducting (ZnO:Al) thin films was controlled between 22 and 48 cm2/Vs by varying the ZnO:Al seed layer. The statistical distribution of the [001] grain misorientation was characterized from the X-ray diffraction rocking curve in the range from 0.043 (2.5) to 0.179 rad (10.2). The grain-boundary energy barriers (Eb) from Seto’s model [1] clearly exhibit linear dependence on the grain-boundary misorientation angle (u) according to the equation Eb ¼ 78 4 þ 173 32 u meV.
증 례 : 위에서 발견된 함몰증식성 폴립 1예 보고 및 문헌고찰
이연호 ( Yeon Ho Lee ),주문경 ( Moon Kyung Joo ),이범재 ( Beom Jae Lee ),이지애 ( Ji Ae Lee ),김태현 ( Taehyun Kim ),윤진구 ( Jin Gu Yoon ),이정민 ( Jung Min Lee ),박종재 ( Jong Jae Park ) 대한소화기학회 2016 대한소화기학회지 Vol.67 No.2
An inverted hyperplastic polyp (IHP) found in stomach is rare and characterized by downward growth of hyperplastic mucosal component into the submucosa. Because of such characteristic, IHP can be misdiagnosed as subepithelial tumor or malignant tumor. In fact, adenocarcinoma was reported to have coexisted with gastric IHP in several previous reports. Because only 18 cases on gastric IHP have been reported in English and Korean literature until now, pathogenesis and clinical features of gastric IHP and correlation with adenocarcinoma have not been clearly established. Herein, we report a case of gastric IHP which was initially misdiagnosed as gastrointestinal stromal tumor and resected using endoscopic submucosal dissection. Literature review of previously published case reports on gastric IHP is also presented.
Taehyun Lee(이태현),Grimm Noh(노그림),Dongyoub Shin(신동엽) 한국전략경영학회 2019 전략경영연구 Vol.22 No.1
본 논문은 제휴가 기업이 직접적으로 진입하는 시장의 규모에 미치는 패러독스적 효과를 분석하였다. 제휴는 기업이 직접적으로 진입하는 시장의 규모를 성장시킬 수도 있지만, 한편으로는 직접 진입을 대체하는 효과도 있을 수 있다. 본 논문은 다자적 제휴그룹과 양자적 제휴의 차이를 구분함으로써 제휴의 종류에 따라 제휴가 기업의 직접 진입 시장의 규모에 미치는 영향이 달라질 수 있음을 보여주고자 하였다. 미국 항공사 데이터를 분석한 결과, 다자적 제휴그룹에 가입하는 것은 직접 진입 시장규모의 성장을 억제하는 효과가 있는 것으로 나타났고, 양자적 제휴 네트워크 상에서 구조적 공백에 위치하는 것은 직접 진입 시장규모를 확대시키는 효과가 있는 것으로 나타났다. 또한 환경의 위협은 구조적 공백의 효과를 조절하는 것으로 나타났다. This paper examines the paradoxical effects of alliances on the size of the market that a firm directly covers in-house. We argue that alliances may serve as a basis for the growth of directly-covered market or as a substitute for it due to two different functions of alliances as enablers and constraints for market expansion. Focusing on the distinction between multilateral alliance groups and bilateral alliances, we argue that the size of a firm’s directly-covered market is affected differently by the two types of alliances. Through empirical analysis of U.S. airline industry, we found that a focal firm’s membership to a multilateral alliance group negatively affects the size of its directly-covered market, whereas the structural holes of a focal firm’s position in its bilateral alliances have a positive effect. Furthermore, environmental threat turned out to weaken the positive effect of structural holes on the size of directly- covered market.
Lee, Sangheon,Flanagan, Joseph C.,Lee, Byungho,Hwang, Taehyun,Kim, Jaewook,Gil, Bumjin,Shim, Moonsub,Park, Byungwoo American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.37
<P>One-dimensionally elongated nanoparticles with type-II staggered band offset are of potential use as light-harvesting materials for photovoltaics, but only a limited attention has been given to elucidate the factors governing the cell performance obtainable from such materials. Herein, we describe a combined strategy to enhance charge collection from CdSe/CdSexTe1-x type-II heterojunction nanorods (HNRs) utilized as light harvesters for sensitized solar cells. By integrating morphology- and composition-tuned type-II HNRs into solar cells, factors that yield interfaces favorable both for the electron injection into TiO2 and hole transfer to electrolyte are examined. Furthermore, it is shown that a more efficient photovoltaic system results from cosensitization with CdS quantum dots (QDs) predeposited on a TiO2 scaffold, which improves charge collection from HNRs. Electrochemical impedance spectroscopy (EIS) analysis suggests that such a synergistically enhanced system benefits from the decreased recombination within HNRs and facilitated charge transport through the cosensitized TiO2 electrode, even with the activation of a recombination path presumably related to the photogenerated holes in CdS QDs.</P>
Lee, Jihye,Lee, Daeho,Park, Yuri,Lee, Sangwon,Ha, Taehyun Elsevier 2019 Transportation research. Part C, Emerging technolo Vol.107 No.-
<P><B>Abstract</B></P> <P>Autonomous vehicles are expected to be commercialized within a few years, and researchers have investigated various factors that influence their adoption. However, only a few studies have considered comparative and psychological perspectives that can affect user-vehicle relationships. Focusing on this limitation, this study investigates influential factors on the use of autonomous vehicles in terms of a technology acceptance model (which considers perceived ease of use, perceived usefulness, and intention to use) and factors for autonomous vehicle use (e.g., perceived risk, relative advantage, self-efficacy, and psychological ownership (i.e., feeling of ownership)). Our results show that self-efficacy positively affects the perceived ease of use and intention to use, while the relative advantage affects perceived usefulness. Psychological ownership affects the intention to use but not the perceived usefulness. This implies that encouraging a consumer to form a psychological bond (i.e., psychological ownership) with an autonomous vehicle may be an effective strategy for promoting the use of autonomous vehicles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> This study examines influential factors for intention to use autonomous vehicles. </LI> <LI> System and psychology level factors are identified by literature reviews. </LI> <LI> Perceived risk affects intention to use without any effects of antecedents. </LI> <LI> Self-efficacy is presented to affect perceived ease of use and intention to use. </LI> <LI> Psychological ownership significantly affects intention to use. </LI> </UL> </P>
Lee, Youngjun,Yoo, Euiyeon,Lee, Taehyun,Moon, Un-Chul The Korean Institute of Electrical Engineers 2018 Journal of Electrical Engineering & Technology Vol.13 No.1
This paper proposes supplementary control of conventional coordinated control of a power plant which directly affects network frequency. The supplementary control with dynamic matrix control is applied for 1000 MW power plant with ultra-supercritical (USC) once-through boiler. The supplementary control signal is added to the boiler feedforward signal in the existing coordinated control logic. Therefore, it is a very practical structure that can maintain the existing multi-loop control system. This supplementary controller uses the step response model for the power plant system, and on-line optimization is performed at every sampling step. The simulation results demonstrate the effectiveness of the proposed supplementary control in a wide operating range of a practical 1000 MW USC power plant simulator. These results can contribute the stable operation of power system frequency.
Nickel-based bilayer thin-film anodes for low-temperature solid oxide fuel cells
Lee, Yeageun,Park, Joonho,Yu, Wonjong,Tanveer, Waqas Hassan,Lee, Yoon Ho,Cho, Gu Young,Park, Taehyun,Zheng, Chunhua,Lee, Wonyoung,Cha, Suk Won Elsevier 2018 ENERGY Vol.161 No.-
<P><B>Abstract</B></P> <P>In this study, we investigate the possibility of using Ni-based anodes as alternatives to the Pt-based anodes for thin-film solid oxide fuel cells (SOFCs) operating at low temperatures. Anodes, electrolytes, and cathodes are sequentially sputtered onto a nanoporous substrate. The pure Ni anodes with modified nanostructures exhibit comparable performance as that of the optimized Pt anodes. Furthermore, a Ni/Ni-YSZ bilayer anode fabricated via a co-sputtering method exhibits approximately 37% higher peak power density than does the optimized Pt anode at 500 °C, demonstrating that noble metal anodes can be replaced by Ni-based anodes in low-temperature SOFCs by optimizing the anode nanostructure.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ni anodes with different nanostructures are fabricated for low-temperature SOFCs. </LI> <LI> The Ni anodes are inferior to an optimized Pt anode in terms of catalytic activity. </LI> <LI> A Ni/Ni-YSZ bilayer anode is introduced as an alternative to the Pt anode. </LI> <LI> The bilayer anode successfully substitutes the Pt anode with 37% higher performance. </LI> <LI> The full cell fabrication process is time-efficient and easy to scale-up. </LI> </UL> </P>
Lee, Sangwon,Ha, Taehyun,Lee, Daeho,Kim, Jang Hyun Elsevier 2018 Information processing & management Vol.54 No.6
<P><B>Abstract</B></P> <P>Majority opinions are often observed in the process of social interaction in online communities, but few studies have addressed this issue with empirical data. To identify an appropriate theoretical lens for explaining majority opinions in online environments, this study investigates the skewness statistic, which indicates how many “Likes” are skewed to major comments on a Facebook post; 3489 posts are gathered from the New York Times Facebook page for 100 days. Results show that time is not an influential factor for skewness increase, but the number of comments has a logarithmic relation to skewness increase. Regression models and Chow tests show that this relationship differs depending on topic contents, but majority opinions are significant in overall. These results suggest that the bandwagon effect due to social affordance can be a suitable mechanism for explaining majority opinion formation in an online environment and that majority opinions in online communities can be misperceived due to overestimation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> This study investigates how major opinions are constructed in online environments. </LI> <LI> Skewness statistic is adopted to describe distributional property of the Likes of comments on a Facebook post. </LI> <LI> The skewness statistic is logarithmically changed by the number of comments on a post. </LI> <LI> The results show that bandwagon effect is more suitable mechanism to explain the major opinion construction in online environments. </LI> <LI> This study discusses how the bandwagon effect can be afforded from the social affordance perspective. </LI> </UL> </P>