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Electrorheological Properties of Polyaniline Composite Microparticle Suspensions
이충혁,전정배,서경도,박종헌 한국공업화학회 2001 한국공업화학회 연구논문 초록집 Vol.2001 No.-
Electrotheoiogical fluid (ERF) behaves like a Bingham fluid under an applied electric Held, whereas it exhibits the characteristics of Newtonian fluid when the electric field is turned off. ER materials generally need high yield stress under electric field and low zero-field viscosity, wide operating temperature, rapid response and stable dispersion property. Polyaniline is an air-stable conducting polymer and easy to prepare by chemically oxidative polymerization. However, it has poor processibility, irregular shape and size. In order to solve these problems, we synthesized micron-sized polyaniline composite particles by coating porous polymer particles with polyaniline. In the presence of monodisperse porous polymer particles by two-staged swelling and polymerization method, aniline was polymerized and in situ deposited onto the surface of the porous substrate. Product polyaniline composite particles were suspended in silicone oil and rheological properties of these suspensions under electric fields were then investigated with regulating the properties of the composite particles, such as conductivity and composition ratio.
해석적 기법을 이용한 흡기포트 형상에 따른 유량계수와 스월유동 특성에 대한 상관성 분석
이충혁(Chung hyuk Lee),이준호(Joon ho Lee),김득상(Duk-Sang Kim),조용석(Yong-Seok Cho) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.5_1
Configurations of intake port in small direct injection diesel engines play a key role on improving engine performance by maximizing volumetric efficiency or optimizing in-cylinder swirl motion. In-cylinder flow characteristics are considered to make significant effects on fuel air mixing, combustion and emissions. Furthermore, volumetric efficiency and in-cylinder swirl motion are deeply related to geometries of cylinder shape, piston head, intake valves and ports. In this paper, the study is concentrated on the effects of intake port angle and swirl angle on flow coefficients and swirl motion. Swirl strength and flow coefficient for the variable intake ports are examined by steady flow analysis through CFD. Correlations of the swirl strength and flow coefficient are also estimated when the intake port configurations are modified. Through the analysis, it is observed that the increased swirl angle and port angle lead to the increase in swirl. However, flow coefficients show critical points in which they become minimal with given swirl angle and curvature radius. The results reported here reveal information related to the intake port configuration, which is necessary to obtain the desired swirl characteristics and volumetric efficiency for improving engine performance.
CRFM Baffle 적용에 따른 Front End Airflow와 Aerodynamic Drag 변화에 대한 해석적 평가
이충혁(Chunghyuk Lee),김용년(Yongnyun Kim),하종백(Jongpaek Ha) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
Development and integration of the front end cooling system for an automotive vehicle requires a balancing work between several performance and styling objectives. Especially the cooling system needs to provide sufficient airflow for heat rejection with minimum impact on the aerodynamic drag for fuel economy and powertrain cooling performance. However unfortunately, increased front end airflow has a negative impact on the vehicle aerodynamic drag. Therefore, the vehicle needs to be designed for optimum cooling airflow such that cooling requirements are met without incurring penalty on the aerodynamic performance. For example, increment of front end opening and fan capacity increase the amount of airflow passing through the radiator while deteriorating aerodynamic drag. But CRFM baffle of Front end components is obviously one of key factors to improve powertrain cooling and aerodynamic performance at once. In this paper, influence of various CRFM baffle designs on front end airflow and aerodynamic drag is evaluated by CFD analysis.
이상훈,이충혁,강현,이원수 대한피부과학회 2022 대한피부과학회지 Vol.60 No.6
Background: Contact immunotherapy with diphenylcyclopropenone is one of the first-line treatments for extensive alopecia areata, despite its adverse effects (AEs). Objective: This study aimed to investigate whether a modified contact immunotherapy treatment protocol can safely promote hair regrowth in children. Methods: Children with alopecia areata who were treated with modified contact immunotherapy with diphenyl- cyclopropenone were retrospectively reviewed. All patients were sensitized with 0.1% diphenylcyclopropenone and began treatment at subsequent increasing concentrations. The efficacy, AEs, and demographic factors were evaluated. Results: A total of 32 patients, aged 9 to 17 years (mean age, 14.6 years), were included in the study. The mean disease duration was 26.8 months. Ten (31.3%) and 11 patients (34.4%) showed complete and partial responses, respectively. No AEs were observed after the sensitization. During treatment, 13 patients (40.6%) did not experience any AEs. Sixteen patients (50.0%) showed mild to moderate pruritus, and only three patients (9.4%) had severe pruritus. However, all AEs were well controlled. Conclusion: A modified diphenylcyclopropenone treatment protocol with subclinical sensitization could induce a favorable therapeutic response and fewer AEs in children. (Korean J Dermatol 2022;60(6):371∼377)
전정배,이충혁,서경도 한국공업화학회 2002 한국공업화학회 연구논문 초록집 Vol.2002 No.0
ER fluids have been the subject of intensive theoretical and experimental researches due to their great potential to technological applications. Among various polarizable particles, anhydrous ER materials have attracted wide interest with their superior ER properties and other physical properties, such as thermal, mechanical, chemical, and electrical properties. Recently the composite of organic polymers with inorganics has been reported as anhydrous ER material, showing good ER effect. In this study, we introduced a clay, montmorillonite, to organic polymer as intercalation structure to obtain a novel ER material. Polymer-clay nanocomposite particles were synthesized by in-situ suspension polymerization method. First, clay was dispersed into the monomer mixture, which contained the PPG-methacrylate monomer. The above caly-monomer mixture was then suspended in 2wt% PVA aqueous solution and polymerized at 60℃ for 12h. Characterization of the composite particles was carried out by FT-IR spectroscopy, X-ray diffraction, thermogravimetric analysis and scanning electron microscopy. ER characteristics of the particle suspensions in silicone oil were investigated under different electric fields by a rotational ARES rheometer.
Grille opening size 변화에 따른 soaking구간에서의 underhood 온도변화에 대한 해석적 연구
유연준(Yeunjun Yoo),이충혁(Chunghyuk Lee),하종백(Jongpaek Ha),이태원(Taewon Lee) 한국자동차공학회 2010 한국자동차공학회 부문종합 학술대회 Vol.2010 No.5
Heat source information on design parameters of components located in and underbody are required because these parameters affect final heat damage. Most of automotive makers have their own data of heat impact on the relationship between design parameters and heat source, which was mostly obtained by experimental and trial-and-error methods in the past. Thermal soak study and issues execute in an early stage of the development phase of a new vehicle. Thermal soak results from vehicle with high load after driving and shutting off engine. Underhood and underbody flow are stagnant pattern, and these are simulated by natural convection. At this time, the components close to exhaust system are affected by thermal fluid. For the complex geometry, a 3-D computational program is used to consider heat transfer, which results in steady and transient analysis. Based on these premises a numerical method is developed and validated for a simplified test case as well as for a full vehicle.
Nanoporous ZnO Nanoball for Efficient CdS/CdSe Co-Sensitized Quantum Dot Sensitized Solar Cells#
Sher Bahadur Rawal,성상도,이충혁,이완인 대한화학회 2015 Bulletin of the Korean Chemical Society Vol.36 No.3
Highly monodispersed, nanoporous ZnO nanoballs (NBs) with a diameter of 120 nm were synthesized by a wet chemical method and successfully applied to photoelectrode of CdS/CdSe co-sensitized quantum dot (QD) sensitized solar cells (QDSSCs). In fabricating the QDSSCs by the successive ionic layer adsorption and reaction (SILAR) method, the optimized CdS and CdSe depositions were obtained by nine and four SILAR cycles, respectively. The ZnO/CdS(9)/CdSe(4)/ZnS(1) cell exhibited a photovoltaic conversion efficiency (PCE) of 2.21%, which is significantly higher than the QDSSC adopting conventional ZnO nanorods (NRs) of 1.33%, indicating that the prepared nanoporous ZnO NB is a highly efficient structure for the deposition of CdS/CdSe quantum dots (QDs) as well as transport of charges.