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Stretchable Electroluminescent Display Enabled by Graphene-Based Hybrid Electrode
Shin, Heechang,Sharma, Bhupendra K.,Lee, Seung Won,Lee, Jae-Bok,Choi, Minwoo,Hu, Luhing,Park, Cheolmin,Choi, Jin Hwan,Kim, Tae Woong,Ahn, Jong-Hyun American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.15
<P>Stretchable alternating-current electroluminescent (ACEL) devices are required due to their potential in wearable, biomedical, e-skin, robotic, lighting, and display applications; however, one of the main hurdles is to achieve uniform electroluminescence with an optimal combination of transparency, conductivity, and stretchability in electrodes. We therefore propose a fabrication scheme involving strategically combining two-dimensional graphene layers with a silver nanowire (Ag NW)-embedded PEDOT:PSS film. The developed hybrid electrode overcomes the limitations of commonly known metallic NWs and ionic conductor-based electrodes for ACEL applications. Furthermore, the potential of the hybrid electrode is realized in demonstrating large-area stretchable ACEL devices composed of an 8 × 8 passive array. The prototype ACEL passive array demonstrates efficient and uniform electroluminescence under high levels of mechanical deformation such as bending, rolling, twisting, and stretching.</P> [FIG OMISSION]</BR>
공유피드백 유로를 갖는 초음속 유체진동기의 진동특성에 관한 연구
이승헌(SeungHeon Lee),박상훈(SangHoon Park),고희창(HeeChang Ko),서송현(SongHyun Seo),이열(Yeol Lee) 한국항공우주학회 2020 韓國航空宇宙學會誌 Vol.48 No.3
내부에 공유피드백 유로를 갖는 공유형 초음속 유체진동기에서 나타나는 유동특성에 관한 연구가 수행되었다. 비정상 전산유체역학적 해석이 수행되었고 수치해석 결과는 동일한 운용조건에서 수행된 실험결과와 비교 검증되었다. 수치해석 결과, 공유피드백 유로가 해당 유체진동기의 진동 메커니즘에 큰 영향을 주어 진동기 출구 각 제트유동의 동조화에 큰 역할을 하고 있음이 확인되었다. 공유형 유체진동기는 동일 형상의 단일형 유체진동기와 비교하여 진동수가 증가하나 압력손실 또한 커짐이 확인되었다. A study of flow characteristics of supersonic fluidic oscillators with shared feedback channel inside was carried out. Unsteady CFD analysis were performed and the numerical results were validated by comparison with the experimental ones observed for the same operation conditions. It was found that the mass flow between individual oscillators through the shared feedback channel directly influenced on the oscillating flow mechanism inside the oscillator, and finally on the synchronization of the jet oscillations. It was also observed that the oscillator with shared feedback channel provided higher pressure loss as well as higher oscillation frequency as compared to the single oscillator of the same geometric shape.
보일러 송풍기 내부 형상 변화에 따른 유동 특성에 관한 연구
이영태(YoungTae LEE),장성호(SungHo JANG),이주용(JooYong LEE),권오붕(OhBoong KWON),임희창(HeeChang LIM) 한국연소학회 2011 KOSCOSYMPOSIUM논문집 Vol.- No.42
This study has been conducted to enhance the performance of a centrifugal blower inside condensing gas boiler. In order to increase the outlet flow rate, the flow characteristics inside the blower were investigated and the case shape of the blower was modified and tested numerically and experimentally. In this study, it has been mainly focused on the flow characteristics inside the air blower and at the exit. The results are all compared with the experiment.
가솔린 연료 개질 기술을 이용한 SI 엔진 열효율 향상
이승우(Seung Woo Lee),백홍길(Hong-kil Baek),오희창(Heechang Oh),이종혁(Jonghyeok Lee),정진영(Jinyoung Jung),김준석(Joonsuk Kim),송순호(Soonho Song),전광민(Kwang Min Chun) 한국자동차공학회 2018 한국자동차공학회 부문종합 학술대회 Vol.2018 No.6
A well-known effective way to improve SI engine thermal efficiency is to use hydrogen mixed with gasoline. Hydrogen, even in small amounts, it makes flame speed faster, knock mitigation and improves combustion stability. These benefits enable higher compression ratios, higher EGR rates and improved SI engine thermal efficiency. Fuel reforming is one way to get hydrogen from the internal combustion engine, using hydrocarbon fuel, exhaust gas steam and heat, hydrogen reformation is achieved using species already available in the exhaust gas. However, for steam reforming to be valuable, the catalyst temperature should be above its light off temperature under engine operating condition. This study investigates how the combustion characteristics are affected by the addition of reformed hydrogen in the presence of EGR on a 4 cylinder turbo gasoline direct injection (TGDI) engine. It is in the current research that the combustion speed is increased when hydrogen from on-board fuel reforming system is supplied into combustion chamber by means of EGR gas. It is also found that total engine fuel consumption is improved with EGR limit expansion and knock mitigation. And it is confirmed that catalyst degradation should be prevented under real engine operating condition for serial production.
Bivariate Data Analysis for the Lifetime and the Number of Indicative Events of a System
Lee, Sukhoon,Park, Heechang,Park, Raehyun The Korean Reliability Society 2000 International Journal of Reliability and Applicati Vol.1 No.1
This research considers a system which has an ultimate terminal event such as death, critical failure, bankruptcy together with a certain indicative events (temporary malfunction, special treatment, kind of defaults) that frequently occurs before the terminal event comes to the system. Some investigation of a model for the corresponding bivariate data of the system have been done with an explanation of the situation in terms of two continuous variables instead of continuous-discrete variables and some other properties. Also an analysis has been carried out to evaluate the effect of intermediate observation of occurrence of indicative event so that the result can be used for a possible suggestion of an intermediate observing schedule.
Jeon, Heechang,Yoon, Eul Sik,You, Hi-Jin,Kim, Hyon-Surk,Lee, Byung-Il,Park, Seung Ha Korean Society of Plastic and Reconstructive Surge 2014 Archives of Plastic Surgery Vol.41 No.6
Background Perineal reconstruction following pelvic exenteration is a challenging area in plastic surgery. Its advantages include preventing complications by obliterating the pelvic dead space and minimizing the scar by using the previous abdominal incision and a vertical rectus abdominis musculocutaneous (VRAM) flap. However, only a few studies have compared the complications and the outcomes following pelvic exenteration between cases with and without a VRAM flap. In this study, we aimed to compare the complications and the outcomes following pelvic exenteration with or without VRAM flap coverage. Methods We retrospectively reviewed the cases of nine patients for whom transpelvic VRAM flaps were created following pelvic exenteration due to pelvic malignancy. The complications and outcomes in these patients were compared with those of another nine patients who did not undergo such reconstruction. Results Flap reconstruction was successful in eight cases, with minor complications such as wound infection and dehiscence. In all cases in the reconstructed group (n=9), structural integrity was maintained and major complications including bowel obstruction and infection were prevented by obliterating the pelvic dead space. In contrast, in the control group (n=9), peritonitis and bowel obstruction occurred in 1 case (11%). Conclusions Despite the possibility of flap failure and minor complications, a VRAM flap can result in adequate perineal reconstruction to prevent major complications of pelvic exenteration.
성층희박연소 운전조건에서 분사시기에 따른 분무유도식 직접분사 가솔린엔진의 분무 및 화염특성
오희창(Heechang Oh),이민석(Minsuk Lee),박정서(Jungseo Park),배충식(Choongsik Bae) 대한기계학회 2013 大韓機械學會論文集B Vol.37 No.3
분무유도식 DISI엔진의 성층연소운전조건에서 분무 및 화염특성에 대한 실험적 연구가 수행되었다. 연소가시화를 통하여 성층연소 DISI의 연소는 희박 예혼합 연소와 확산연소의 성격을 모두 가지고 있는 것으로 확인되었다. 분사시기에 따른 혼합기 형성특성이 연소의 특성을 결정하는 중요한 인자임을 관찰하였다. 분무와 혼합기 가시화를 통해 낮은 분위기압에서의 over-mixing , 높은 분위기압에서의 under-mixing이 발생하는 것을 확인하였으며 이러한 혼합기 형성과정의 결과에 따라 화염특성, 연소효율 등의 연소특성이 결정되는 것을 살펴볼 수 있었다. 또한, NOx, IMEP도 분사시기에 따른 경향성을 보였으며, 분사시기에 따른 연소상의 변화에 의한 영향임을 확인하였다. An experimental study was carried out to investigate the effects of the injection timing on the spray and combustion characteristics in a spray-guided direct-injection spark-ignition (DISI) engine under lean stratified operation. An in-cylinder pressure analysis, exhaust emissions measurement, and visualization of the spray and combustion were employed in this study. The combustion in a stratified DISI engine was found to have both lean premixed and diffusion controlled flame combustion characteristics. The injection timing condition corresponding to the stratified mixture characteristics was verified to be a dominant factor for these flame characteristics. For the early injection timing, a non-luminous blue flame and low combustion efficiency were observed as a result of the lean homogeneous mixture formation. On the other hand, a luminous sooting flame was shown at the late injection timing because of an under-mixed mixture formation. In addition, the smoke emission and incomplete combustion products were increased at the late injection timing as a result of the increased locally rich area. On the other hand, the NOx emissions decreased and IMEP increased as the injection timing retarded. The combustion phasing produced by the injection timing was verified as the reason for this observation.