Alcohol-Soluble Small Host and Hole-Transporting Material for Solution Processed PhOLEDs

Lee, Sungkoo,Seo, Min Hye American Scientific Publishers 2017 Journal of Nanoscience and Nanotechnology Vol.17 No.10

<P>A new alcohol-soluble hole transporting material and host material were synthesized and their device performances were investigated. The synthesized host material exhibits energy gap (3.37 eV) and HOMO level (5.95 eV) and hole transporting material shows energy gap (3.05 eV) and HOMO level (5.5 eV). These materials showed good solubility in alcohol. The solution-processed PhOLEDs employing Bis(2,4-difluorophenylpyridinato)-tetrakis(1-pyrazolyl) borate iridium(III) as the blue dopant exhibits up to 11.7 cd/A as a maximum current efficiency. This performance was improved compared to that of the device made using a thermal evaporator.</P>

Polymeric white organic light-emitting diodes with two emission layers.

Lee, Sungkoo,Im, Yirang,Lee, Kyeong K,Lim, Eunhee American Scientific Publishers 2012 Journal of Nanoscience and Nanotechnology Vol.12 No.4

<P>A white light-emitting diode was fabricated by preparing multilayer emitting films with an inserted buffer layer. The device structures are ITO/PEDOT:PSS/Emissive layer/LiF/Al. The emissive layer comprises a yellow-emitting layer of Poly[9,9-dioctylfluorenyl-2,7-diyl]-co-1,4-benzo-(2,1,3)-thiadiazole (F8BT), a blue-emitting layer of Poly[9,9-di-(2'-ethylhexyl)fluorenyl-2,7-diyl] (BEHF) and PEDOT:PSS as a buffer layer between the emission layers. The solution processed multi-layer polymer light-emitting diodes (PLED) were prepared by introduction of a water-soluble buffer layer between organic solvent soluble layers. We present white organic light-emitting diodes (WOLEDs) that has bilayer emission zones. This device exhibits a brightness of 280 cd/m2 and emission efficiency of 1.18 cd/A at 12.6 V. The device with a doped PEDOT:PSS layer and a thicker blue-emission layer exhibits CIE color coordinates of (0.30, 0.34), which is close to the white coordinates of (0.33, 0.33) used by the standard CIE color coordinates.</P>

Synthesis and characterization of regioregular alkyl-substituted poly(3,4-ethylenedioxythiophenes).

Lee, Sungkoo,Lee, Kyeong K,Lim, Eunhee,Son, Ha-Young American Scientific Publishers 2012 Journal of Nanoscience and Nanotechnology Vol.12 No.5

<P>In order to increase the solubility of PEDOT, we introduced an alkyl chain into polymer backbone. Depending on the position of the alkyl bond, the steric hindrance between the alkyl chains can also leads to regioregularity in the polymer. The regioregular polymers can easily occur self-assembly, both in solution and in the solid state, resulting in highly ordered two- and three-dimensional polymer architectures. A series of soluble regioregular alkyl-substituted PEDOTs were synthesized using the Grignard Metathesis (GRIM) for the purpose of study on regiorandom and regioregular PEDOT. The ethylene proton adjacent to the oxygen atom of regioregular methoxydodecyl-PEDOT appears at 3.51 ppm, whereas the corresponding peak of regiorandom methoxydodecyl-PEDOT appears at 3.42 ppm.</P>

TORSIONAL FILTRATION IMPROVEMENT WITH CENTRIFUGAL PENDULUM DMF IN REAR WHEEL DRIVE SYSTEM

Sungkoo Lee,Suresh Kumar Jayachandran,Yongho Jang,Dongsoo Lee 한국자동차공학회 2019 International journal of automotive technology Vol.20 No.5

All countries regulate CO2 emissions, triggering similar evolution on powertrain at a similar pace all over the planet. Engine irregularities are more severe due to downsizing and uptorquing. Torsional filtration targets are also challenging powertrain performance. This drives powertrain market and more efficient torque transfer system. Conventional filtration solutions such as clutch/dampers and DMF have their own limitations. For the past few years the addtion of centrifugal pendulum absorber meets the required filtration target. The vehicle architecture and type of damper accompanying pendulum absorber contribute to the dynamic stability and performance. In this study, we have shown the behaviors of DMF pendulum in rear wheel driveline with six speed manual transmission. Normally the performance of a pendulum in high engine speed range is not so efficient compare to lower speed range. This study mainly focuses on variations on design parameters of pendulum, which enables better filtration in high speed range.

Scratch resistance and oxygen barrier properties of acrylate-based hybrid coatings on polycarbonate substrate

Sungkoo Lee,오경근,Sunyoung Park,김준석,김현준 한국화학공학회 2009 Korean Journal of Chemical Engineering Vol.26 No.6

Organic/inorganic hybrid coating materials were synthesized using acrylate end-capped polyester, 1,6- hexanediolacrylate, tetraethoxysilane (TEOS), and 3-trimethoxysilylpropylmethacrylate (TMSPM). The hybrid materials were cast onto a polycarbonate (PC) substrate and cured by UV irradiation to give a hybrid film with covalent linkage between the inorganic and the organic networks. The coating layer was characterized by FT-IR and 29Si-NMR, and pencil hardness and oxygen permeation rate of coated films were investigated. The pencil hardness of all samples examined in this study was higher than 1H, whereas that of uncoated PC substrate was 6B. The hardness enhancement after coating may due to incorporation of organic acrylate resin. The oxygen permeability coefficient of the film coated with hybrid material on 3-aminopropyltriethoxysilane (APTEOS) pretreated polycarbonate substrate was 1.67×10−3 GPU, the lowest value in this work, whereas that of uncoated PC substrate was 8.07×10−3 GPU. The lower oxygen permeation rates of these films are attributed to the good adhesion between organic/inorganic hybrid coating layer and PC substrate and a dense structure induced by an increase of network density.

< 기술논문 >클러치 동적 토크 계측에 관한 연구

이성구(Sungkoo Lee),김동영(Dongyoung Kim),허만대(Mandae Hur) 한국자동차공학회 2012 한국 자동차공학회논문집 Vol.20 No.5

원화 실질실효환율과 기초경제변수

이성구 ( Sungkoo Lee ) 명지대학교 금융지식연구소 2016 금융지식연구 Vol.14 No.2

본 논문에서는 1990년부터 최근까지의 분기별 자료를 이용하여 우리나라의 주요 교역국을 대상으로 원화의 종합적인 가치변동을 측정할 목적으로 활용되는 원화 실질실효환율이 어떤추이를 가지고 변동해 왔는지 알아보았다. 원화 실질실효환율이 그동안 균형수준을 유지해왔는지 평가할 목적으로 원화의 실질가치에 장기적으로 영향을 미치는 기초경제변수를 선정하였으며, 공적분 검정에 기초한 장기 균형관계 모형을 이용하여 교역조건, 개방도, 정부지출, 이자율 차이 등의 변수와 실질실효환율의 관계로부터 원화의 장기 균형환율을 추정하였다. 이 값을 실제 원화 실질실효환율의 추이와 비교하고, 또 이로부터 실제 환율이 장기 균형환율로부터 얼마나 차이를 보이는지 환율의 괴리율을 측정함으로써 현재 환율의 적정성 여부를 평가할 수 있는 기준을 제시하였다. This paper estimates Korea’s long-run equilibrium exchange rate using a set of macroeconomic fundamentals for the period 1990Q1 to 2016Q1. The cointegrating estimation results provide evidence in favor of the presence of long-run equilibrium relationship between the real effective exchange rate of Korean won and its economic fundamentals - terms of trade, openness, government spending, and interest rate differentials. With respect to the direction and extent of exchange rate misalignment, the Korean Won was undervalued after the Asian crisis and the global financial crisis, reaching a maximum of less than 20%. The degree of misalignment has been lessened since then, and the real effective exchange rate of Korean Won does not deviate much from its long-run equilibrium levels in recent years.

거시경제환경의 변화가 환율전가도에 미치는 영향

이성구 ( Sungkoo Lee ) 명지대학교 금융지식연구소 2017 금융지식연구 Vol.15 No.2

본 논문에서는 1980년부터 2016년까지 우리나라의 분기별 자료를 이용하여 국내 물가수준에 대한 환율의 전가도를 추정함으로써 우리나라에서도 주요 선진국과 유사하게 환율전가도의 감소 추세가 존재하는지, 그리고 물가지수의 선택에 따라 환율전가도에 차이가 존재하는지 등의 여부를 확인하였다. 환율전가도가 시간과 경제환경의 변화에 따라 변할 수 있다는 점을 감안하여 상태-공간 모형의 일종인 시간변동계수 모형을 적용하여 가변 환율전가도를 추정하였는데, 회귀계수가 무작위 보행과정을 따르는 것으로 가정하고 칼만 필터를 적용하여 가변적인 환율전가도의 추이를 추정한 결과 환율전가도가 2000년대 이후 다소의 등락을 보이면서도 전반적으로 감소하는 추세를 확인할 수 있었다. 또한 거시경제여건의 변화에 초점을 맞추어 무역의존도, 환율 변동성, 인플레이션, 인플레이션 변동성, 생산 변동성 등의 주요 거시경제변수와 환율전가도의 관계를 분석한 결과 환율 변동성과 인플레이션은 환율전가도에 정(+)의 영향을 주는 것으로, 무역의존도, 인플레이션 변동성, 생산 변동성은 환율전가도에 각각 부(-)의 영향을 주는 것으로 확인되었다. The extent to which exchange rate changes affect price levels is referred to as exchange rate pass-through(ERPT) in the literature and lies at the heart of various policy debates and numerous empirical studies. Using the quarterly data from 1980-2016, I employed the time varying parameter(TVP) model to capture the time varying ERPT estimates for different Korean price indices such as consumer price index, producer price index, and import price index. This study also examined whether macroeconomic fundamentals, such as trade openness, inflation, the volatilities of exchange rates, inflation and industrial production affect the time varying ERPT. The results indicate that these macroeconomic fundamentals significantly affect the slow adjustments of the recent ERPT in Korea.

Design and manufacturing of automobile side mirror with wide field of view and progressive surface

Syed Azkar Ul Hasan,Gang Lee(이강),Sungkoo Lee(이성구),Hocheol Lee(이호철) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11

Is higher dose always the right answer in stereotactic body radiation therapy for small hepatocellular carcinoma?

Lee, Kyung Hwa,Yu, Jeong Il,Park, Hee Chul,Park, Su Yeon,Shin, Jung Suk,Shin, Eun Hyuk,Cho, Sungkoo,Jung, Sang Hoon,Han, Young Yih,Lim, Do Hoon The Korean Society for Radiation Oncology 2018 Radiation Oncology Journal Vol.36 No.2

Purpose: This study was conducted to compare clinical outcomes and treatment-related toxicities after stereotactic body radiation therapy (SBRT) with two different dose regimens for small hepatocellular carcinomas (HCC) ${\leq}3cm$ in size. Materials and Methods: We retrospectively reviewed 44 patients with liver-confined HCC treated between 2009 and 2014 with SBRT. Total doses of 45 Gy (n = 10) or 60 Gy (n = 34) in 3 fractions were prescribed to the 95% isodose line covering 95% of the planning target volume. Rates of local control (LC), intrahepatic failure-free survival (IHFFS), distant metastasis-free survival (DMFS), and overall survival (OS) were calculated using the Kaplan-Meier method. Results: Median follow-up was 29 months (range, 8 to 64 months). Rates at 1 and 3 years were 97.7% and 95.0% for LC, 97.7% and 80.7% for OS, 76% and 40.5% for IHFFS, and 87.3% and 79.5% for DMFS. Five patients (11.4%) experienced degradation of albumin-bilirubin grade, 2 (4.5%) degradation of Child-Pugh score, and 4 (9.1%) grade 3 or greater laboratory abnormalities within 3 months after SBRT. No significant difference was seen in any oncological outcomes or treatment-related toxicities between the two dose regimens. Conclusions: SBRT was highly effective for local control without severe toxicities in patients with HCC smaller than 3 cm. The regimen of a total dose of 45 Gy in 3 fractions was comparable to 60 Gy in efficacy and safety of SBRT for small HCC.