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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.
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>
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.
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.
Lee, Byungho,Lee, Sangheon,Cho, Duckhyung,Kim, Jinhyun,Hwang, Taehyun,Kim, Kyung Hwan,Hong, Seunghun,Moon, Taeho,Park, Byungwoo American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.45
<P>Organic-inorganic hybrid perovskite solar cells have emerged as promising candidates for next-generation solar cells. To attain high photovoltaic efficiency, reducing the defects in perovskites is crucial along with a uniform coating of the films. Also, evaluating the quality of synthesized perovskites via facile and adequate methods is important as well. Herein, CH3NH3PbI3 perovskites were synthesized by applying second solvent dripping to nonstoichiometric precursors containing excess CH3NH3I. The resulting perovskite films exhibited a larger average grain size with a better crystallinity compared to that from stoichiometric precursors. As a result, the performance of planar perovskite solar cells was significantly improved, achieving an efficiency of 14.3%. Furthermore, perovskite films were effectively analyzed using a conductive AFM and noise spectroscopy, which have been uncommon in the field of perovskite solar cells. Comparing the topography and photocurrent maps, the variation of photocurrents in nanoscale was systematically investigated, and a linear relationship between the grain size and photocurrent was revealed. Also, noise analyses with a conductive probe enabled examination of the defect density of perovskites at specific grain interiors by excluding the grain-boundary effect, and reduced defects were clearly observed for the perovskites using CH3NH3I-rich precursors.</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>
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>
A nanoporous substrate-based low temperature solid oxide fuel cell using a thin film Ni anode
Lee, Sanghoon,Cho, Gu Young,Park, Taehyun,Lee, Yoon Ho,Yu, Wonjong,Lee, Yeageun,Chang, Ikwhang,Cha, Suk Won Elsevier 2018 THIN SOLID FILMS - Vol.666 No.-
<P><B>Abstract</B></P> <P>A thin film solid oxide fuel cell (TF-SOFC) with a Ni anode on a nanoporous anodic aluminum oxide substrate was demonstrated. In our experiments, Ni was used as an anode material, while a very small amount of Pt was used as a cathode material, which reduced the thickness of the thin film cathode to 65 nm. In addition, a plasma-enhanced atomic layer deposition method was used to prepare a yttria-stabilized zirconia electrolyte. The open circuit voltage and the peak power density of the as-fabricated fuel cells, both of which were measured at 500 °C, were 1.04 V and 150 mW/cm<SUP>2</SUP>, respectively.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Thin film solid oxide fuel cell(TF-SOFC) with Ni/YSZ/Pt was demonstrated. </LI> <LI> The peak power density of 150 mW/cm<SUP>2</SUP> was measured at 500 °C. </LI> <LI> Ni is significantly comparable to Pt for hydrogen oxidation reaction. </LI> </UL> </P>