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동일 저부하에서 흡기압에 따른 프로판-디젤 혼소연소 특성에 관한 연구
이효원(Hyowon Lee),최승목(Seungmok Choi),이정우(Jeongwoo Lee),신승협(Seunghyup Shin),이승현(Seunghyun Lee),민경덕(Kyungdong Min) 한국자동차공학회 2011 한국자동차공학회 부문종합 학술대회 Vol.2011 No.5
대체연료 중에서 가스연료는 저탄소 청정연료이며 기존 엔진에 특별한 변경 없이 적용 가능하다. 또한 높은 옥탄가를 가지고 있어 열효율이 높은 압축착화 엔진에 사용할 수 있어 혼소연소(Dual-fuel combustion)에 사용된다. 혼소연소는 기체연료를 공기와 섞어서 흡입시킨 후 소량의 디젤연료를 착화유로 사용하여 압축착화 시키는 방법을 말한다. 이러한 착화방식에 따라 복잡한 연소특징을 보이는데 부분예혼합 확산화염과 난류화염전파가 동시에 일어난다. 기존의 연구들은 가스연료에 추가에 따른 당량비 변화나 동일 부하에서 혼소연료의 비율에 초점을 맞춰왔다. 하지만 각 비율에 따라 다른 점화지연 때문에 연소가 지각되어 효율이 나빠지거나 조건에 따라 질소산화물(NOx)의 증감에 이견이 있으며 가스연료를 증가시켜가는 실험 방식에 의해 저부하에 낮은 당량비 영역에서 일산화탄소(CO)와 탄화수소(THC)가 디젤에 비해 다량 발생한다. 본 연구에서는 부분예혼합 확산화염과 난류화염전파가 동시에 일어나는 점에 초점을 맞춰 당량비가 높은 영역에서 혼소연소의 연소효율이 증가하여 일산화탄소(CO)가 낮아짐을 확인하였고 다른 배기 성분 및 연소 특성에 대한 분석을 하였다.
A computational study of DME-methanol fractions with controlling several factors on HCCI combustion
Hyowon Lee,임옥택 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.4
Two-stage fuel and single stage fuel have different effects on ignition delay and other combustion characteristics. If we mix two fuels with variable fractions, combustion characteristics will be represented with dependence on the fraction. We first investigated the change of combustion characteristics and combustion ranges by dimethyl ether (DME)/methanol fraction, IVC temperature and IVC pressure. By increasing methanol fraction, Heat release rate (HRR) showed higher rate than the case containing less methanol after 1250 K. However, it didn't mean that Accumulated heat release (AHR) was also higher than the cases which contained less methanol. AHR of D90/M10 was the first case which surpassed AHR of D100 at about 1808K, and D80/M20 surpassed D100 at about 2318K. The result was caused by change of reaction mechanism and the change was remarkably shown in the Thermal ignition preparation (TIP) range and the Thermal ignition (TI) range. Above all, strengthened H 2 O 2 Loop reactions affected heat production to increase in TIP range, and also one of the loop reactions, CH 2 O + OH = HCO + H 2 O, quickly produced formyl radical with increase of net reaction rate by methanol. Those results naturally led to higher reaction rates of HCO-CO-CO 2 oxidation with higher heat production. As a result, D50/M50 case showed the highest maximum Pressure rise rate (PRR). Furthermore, dispersion rate of PRR was increased by increasing methanol fraction in the range which was from back end of TIP to forepart of TI range. Finally, we focused the reaction paths of two fuels and the production and consumption rate of main radicals on the basis of combustion ranges such as LTO, Negative temperature coefficient (NTC), Thermal ignition preparation (TIP) and Thermal ignition (TI) to understand the results of this study.
Lee, Eun Ji,Park, Eun Young,Mun, HyoWon,Chang, EunSun,Ko, Je Yeong,Kim, Do Yeon,Park, Jong Hoon The Federation of American Societies for Experimen 2015 The FASEB Journal Vol.29 No.8
<P>Autosomal polycystic kidney disease (ADPKD) is a highly prevalent genetic renal disorder in which epithelial-lining fluid-filled cysts appear in kidneys. It is accompanied by hyperactivation of cell proliferation, interstitial inflammation, and fibrosis around the cyst lining cells, finally reaching end-stage renal disease. Previously, we found high expression of ligands stimulating the receptor for advanced glycation end products (RAGE) in ADPKD mice. Furthermore, gene silencing of RAGE was revealed to cause reduction of cystogenesis <I>via</I> down-regulation of cell proliferation <I>in vitro</I>, and intravenous administration of anti-RAGE adenovirus <I>in vivo</I> also displayed alleviation of the disease. Here, we attempted to identify the role of soluble RAGE (sRAGE) in inhibiting the progression of ADPKD using 2 different ADPKD mouse models. sRAGE is an endogenously expressed form of RAGE that has no membrane-anchoring domain, thereby giving it the ability to neutralize the ligands that stimulate RAGE signals. Both overexpression of sRAGE and sRAGE treatment blocked RAGE-mediated cell proliferation <I>in vitro</I>. In addition, sRAGE-injected ADPKD mice showed reduced cysts accompanied by enhanced renal function, inhibition of cell proliferation, inflammation, and fibrosis. These positive therapeutic effects of sRAGE displayed little liver toxicity, suggesting it as a new potential therapeutic target of ADPKD with low side effects.—Lee, E. J., Park, E. Y., Mun, H., Chang, E., Ko, J. Y., Kim, D. Y., Park, J. H. Soluble receptor for advanced glycation end products inhibits disease progression in autosomal dominant polycystic kidney disease by down-regulating cell proliferation.</P>
Hyowon Bae,Jung Yeol Lee,Hae June Lee 한국진공학회(ASCT) 2017 Applied Science and Convergence Technology Vol.26 No.4
The discharge characteristics of the radio frequency (RF) surface dielectric barrier discharge have been simulated for the investigation of the ratio of the ion transit time to the RF period. From one-dimensional particle-incell (PIC) simulation for a planar dielectric barrier discharge (DBD), it was observed that the high-frequency driving voltage confines the ions in the plasma because of a shorter RF period than the ion transit time. For two-dimensional surface dielectric barrier discharges, a fluid simulation is performed to investigate the characteristics of RF discharges from 1MHz to 40 MHz. The ratio of the peak density to the average density decreases with the increasing frequency, and the spatiotemporal discharge patterns change abruptly with the change in the ratio of ion transit time to the RF period.
Hyowon Lee,Jungil Hong 한국식품영양과학회 2021 한국식품영양과학회 학술대회발표집 Vol.2021 No.10
Riboflavin (Rb) has widely been used as a cosmetic agent for skin conditioning. Rb is photolyzed under light into lumichrome (LC) and lumiflavin (LF), all of which have a light-sensitive isoalloxazine structure. In this study, photosensitizing properties of Rb and its photo-degradation products were investigated. Their induction of cytotoxicity and inflammatory events in keratinocyte (HaCaT) and fibroblast (HDF) under light were also evaluated. Rb showed the strongest photosensitizing activity. LC promoted lipid oxidation potently under fluorescent light (FL, 4,000 lx, 2h); Rb also induced lipid peroxidation significantly. Rb, however, inhibited the Fenton reaction-induced lipid oxidation under light; the inhibitory effects of LC and LF was not observed. Rb induced the most potent photo-toxicity in both HaCaT and HDF. In the HaCaT treated with Rb, the levels of pro-inflammatory cytokines, IL-1β, IL-6, and IL-8 were elevated under light (2,000 lx, 1h). The results indicate that Rb and its photo-degradation products could cause photo-damages in the skin through promoting lipid peroxidation and inducing inflammatory and cytotoxic processes, which should be carefully considered.