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저전압 PEO 양극산화 공정을 위한 Ti 전처리 조건의 최적화 연구
하동흔(Dongheun Ha),최진섭(Jinsub Choi) 한국표면공학회 2017 한국표면공학회지 Vol.50 No.6
Plasma electrolyte oxidation (PEO) is a kind of anodization, in which a very high voltage or current is applied to a metal substrate in various electrolytes, allowing distinctly thick thickness of the oxide film with outstanding film properties, such as a good corrosion resistance, mechanical strength, thermal stability, and excellent adhesion to a substrate. Herein, we tried to find the optimal pretreatment conditions among commercially available solutions in order to produce PEO anodizing at relatively low voltage. We characterized the surface morphologies of the sample by scanning electron microscope (SEM), atomic force microscopy (AFM), and investigated color parameters of the pretreated surface of Ti by spectrophotometer.
수소 연소 리니어 동력/발전 시스템의 부하에 따른 연소 특성
하동흔(Dongheun Ha),이준혁(Junhyuk Lee),정익재(Ikjea Chung),강현석(Hyunsuk Kang),이길용(Kilyong Lee),나평철(Pyungchul Na),이용균(Yonggyun Lee) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
Hydrogen fueled linear power/generation system is higher efficiency then the crank engine. This system will applied possible the undersized Co-generation and hybrid car etc. In this paper, we performed a com Hydrogen fueled linear power/generation system is higher efficiency then the crank engine. Combustion test by adjusting load of hydrogen combustion linear power/generation system, based on test results we identified the characteristics of the system. As the results, frequency has close interrelation with mover's weight, operating frequency approximates in ideal frequency, confirmed that efficiency rises in hydrogen combustion linear power/generation system.
하동흔(Dongheun Ha),김민철(Mincheol Kim),박종상(Jongsang Park),염정국(Jungkuk Yeum),하종률(Jongyul Ha),정성식(Sungsik Chung) 한국자동차공학회 2008 한국자동차공학회 지부 학술대회 논문집 Vol.2008 No.11
This study was carried out to investigate the availability of using CNG fuel in a commercial two-cylinder gasoline engine and to derive the optimum performance of the engine. The results of this study is used to determine the optimized injection quantity at the time of dual injection and to improve the engine efficiency through comparing and investigating the performance of a PFI(Port Fuel Injection) and a sub-chamber DI(Direct Injection) type engine in order to establish the base of using PFI and sub-chamber DI type together in a multi-cylinder engine. A gasoline engine was adapted for this study, and air excess ratio was controlled using Lambda sensor and handle accelerator, and spark timing and injection timing were controlled using the ECU that was made personally. Combustion characteristics in accordance with air excess ratio and injection timing were investigated by multi-point injection using CNG fuel. On the basis of PFI type, the standard of fuel injection duration is obtained and it is applied to DI type. According to the air excess ratio, in-cylinder pressure, rate of heat release, IME(Indicated Mean Effective pressure), mass fraction burned, COVimep(Coefficient Of Variation), and so on are derived. As a result, the engine operation in PFI type is the safest at stoichiometric ratio and the engine operation in sub-chamber DI type is the safest at lean mixture ratio. This result is applied to the next study in order to obtain the optimized injection quantity and to improve the efficiency.
분광측색계, 색차계의 색 수치 값을 이용한 타이타늄 산화막의 두께 정량화
이다영(Dayoung Lee),한아영(Ayoung Han),하동흔(Dongheun Ha),유현석(Hyeonseok Yoo),김훈식(Hunsik Kim),정나겸(Nagyeom Jung),장관섭(Kwanseop Jang),최진섭(Jinsub Choi) 한국표면공학회 2018 한국표면공학회지 Vol.51 No.3
The anodic TiO₂ layers which are prepared in various anodization conditions exhibit their specific color depending on the thickness of TiO₂. In this study, the relationship between the color of TiO₂ layer, which is grown by PEO (Plasma electrolytic oxidation), and the thickness of the TiO₂ layer is investigated. To evaluate the color change of the TiO₂ layer, the value of color (dE<SUP>*</SUP>ab) is measured and calculated by spectrophotometer and chromameter. As a result, it is found that dE<SUP>*</SUP>ab values and thickness of TiO₂ layers form a linear relationship with meaningful formular. This formula can be helpful to quantify the thickness of the TiO₂ layer by the numerical dE<SUP>*</SUP>ab values. In this process, the spectrophotometer shows more precise results than the chromameter dose. If fluoride ions (F-) are included in the electrolyte, it will affect the dE<SUP>*</SUP>ab values of the TiO₂. layer. This is against the propensity, which is analyzed by XRD (X-ray diffraction) and XPS (X-ray photoelectron spectroscopy). It is important that the formular suggested in this study provides other metals which can be also anodized with the possibility of quantifying the thickness of the TiO₂ layer by the dE<SUP>*</SUP>ab values.
RI 방식 CNG 엔진의 분사시기가 연소특성에 미치는 영향
박종상(Jongsang Park),진종무(Jongmoo Jin),하동흔(Dongheun Ha),염정국(Jungkuk Yeum),이중순(Joongsoon Lee),정성식(Sungsik Chung) 한국자동차공학회 2007 한국자동차공학회 지부 학술대회 논문집 Vol.- No.-
The prior study for RI(radical ignition) method was carried out in the experimental ways using a CVC(constant volume combustor) and applying the basic results from the CVC to a real engine. The rapid combustion and the expansion of the combustible lean limit of RI method were realized by the 0.45% sub-chamber volume of the overall combustion chamber in the CVC. But the gasoline fueled RI engine showed the severe problem of high cycle variation due to the difficulty of the residual gas scavenge in the sub-chamber from the former cycle. To solve this problem, CNG fuel was directly supplied into the sub-chamber instead of the port fuel injection. A DI Diesel Engine with the same specifications used in a previous study was modified to a RI-CNG Engine, and injection pressure was constantly kept at 6㎫ by a regulator. This study was performed to investigate the effects of injection timings on the combustion and performances of the RI-CNG Engine. The excess air ratio was varied from 1.0 to the lean limit at the condition of 50% throttle open rate and 1700rpm. The combustion characteristics of the RI-CNG engine such as in-cylinder pressure, indicated thermal efficiency, cycle-by-cycle variation, combustion duration and emissions were investigated.