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Experimental study on kinetic energy conversion of horizontal axis tidal stream turbine
Seo, Jeonghwa,Lee, Seung-Jae,Choi, Woo-Sik,Park, Sung Taek,Rhee, Shin Hyung Elsevier 2016 RENEWABLE ENERGY Vol.97 No.-
<P><B>Abstract</B></P> <P>The present study aims to understand the energy conversion mechanism of a 100 kW horizontal axis tidal stream turbine by analyzing thrust, torque, and wake flow measurements. The scale ratio of the turbine model was 1/20 and model tests for power and wake measurements were conducted in a towing tank facility. Wake fields were measured by a towed underwater stereoscopic particle image velocimetry (SPIV) system. The chord-length based Reynolds number at 40% of the radius of the turbine ranged from 53,000 to 63,000 in the test conditions. The turbine model showed the highest power coefficient at a tip speed ratio (TSR) of 3.5, and the magnitude of power coefficient was 0.278. Three TSR conditions were selected for SPIV measurement after power measurement tests, representing heavy loading, highest efficiency, and light loading, respectively. In the wake field measurement results, conversion of kinetic energy of the turbine wake was investigated, decomposing it into effectively extracted work, loss due to the drag on the turbine system, kinetic energy of the time-mean axial flow, local flow structures, turbulence, and secondary flow loss. In high TSR conditions with a small angle of attack onto the turbine blade, the secondary flow loss was minimized.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Wake and force measurements of a HATST model were conducted in the towing tank. </LI> <LI> The measurements were characterized by a small blockage ratio and high Reynolds number. </LI> <LI> Energy conversion mechanism of a HATST was analyzed with measured data. </LI> <LI> Turbulence generation consumes only a small portion of the inflow kinetic energy. </LI> </UL> </P>
혈관내피세포 탈착에 미치는 melatonin의 병리학적 영향
Jeonghwa Seo(서정화),Sunghyen Kim(김성현),Sunyoung Ahn(안선영),Eunsil Jeong(정은실),Jingu Cho(조진구),Heonyong Park(박헌용) 한국생명과학회 2010 생명과학회지 Vol.20 No.6
항산화 기능과 면역 억제 기능을 갖는 것으로 알려진 melatonin이 혈관 내피층에서는 어떤 기능을 갖는지 알기 위한 일련의 실험을 수행하였다. 본 연구의 실험 결과, 혈관기능과 관련된 혈관내피세포의 성장, 사멸, 이동에 melatonin은 특이적인 효과를 나타내지 않았고, 백혈구의 혈관내피세포 부착과 백혈구 동종간의 응집에도 melatonin의 역할이 관찰되지 않았다. 이와는 대조적으로 melatonin은 PP2A를 통해 eNOS의 활성을 억제하여 산화질소의 양을 감소시키고, 이로 인해 혈관내피세포의 탈착이 유발되는 효과가 있음을 확인할 수 있었다. 종합해보면, 혈액 내 고농도의 melatonin은 PP2A 및 eNOS의 활성을 변화시켜 혈관내피세포의 탈착을 상승시킴으로써 혈관내에서 발생할 수 있는 혈전 형성에 의한 병리적 현상을 유발할 수 있다. In this study, we carried out a series of experiments to know whether melatonin, an anti-oxidative and immunosuppressive agent, played an important role in endothelial cells. It was revealed that melatonin had little or no effect on endothelial proliferation, cell death or migration. Additionally, melatonin had no effect on adhesion of THP-1 leukocytes to bovine aortic endothelial cells (BAECs) and THP-1 homotypic cell aggregation. In contrast, it was shown that melatonin diminished the basal level of nitric oxide by PP2A-mediated dephosphorylation of endothelial nitric oxide synthase (eNOS), leading to enhanced detachment of BAEC from the extracellular matrix. Collectively, melatonin in high doses decreases the NO production via regulations of PP2A and eNOS activities, inducing detachment of endothelial cells, a possible initial step for thrombosis.
Seo, Jeonghwa,Choi, Hak-Kyu,Jeong, Uh-Cheul,Lee, Dong Kun,Rhee, Shin Hyung,Jung, Chul-Min,Yoo, Jaehoon The Society of Naval Architects of Korea 2016 International Journal of Naval Architecture and Oc Vol.8 No.5
The resistance and seakeeping performance of a high-speed monohull vessel were investigated through a series of model tests in a towing tank. The hull had a slender wave-piercing bow, round bilge, and small deadrise angle on stern. Tests on the bare hull in calm water were first conducted and tests on spray rails followed. The spray rails were designed to control the flow direction and induce a hydrodynamic lift force on the hull bottom to reduce trim angle and increase rise of the hull. The maximum trim of the bare hull was $4.65^{\circ}$ at the designed speed, but the spray rails at optimum location reduced trim by $0.97^{\circ}$. The ship motion in head seas was examined after the calm water tests. Attaching the rails on the optimum location effectively reduced the pitch and heave motion responses. The vertical acceleration at the fore perpendicular reduced by 11.3%. The effective power in full scale was extrapolated from the model test results and it was revealed that the spray rails did not have any negative effects on the resistance performance of the hull, while they effectively stabilized the vessel in calm water and waves.
EFFECTS OF RESIDENTIAL MOBILITY ON TRUST IN THE DIGITAL CONSUMPTION CONTEXTS
Jeonghwa Seo,Sujeong Hong,Hakkyun Kim,Sangdo Oh 글로벌지식마케팅경영학회 2023 Global Marketing Conference Vol.2023 No.07
This research investigated how residential mobility affects consumers' trust in digital consumption environments (e.g., online shopping). Due to today's digitalization, consumers' trust in digital environments is treated as important. However, work has yet to be explored that the trust of digital environments can differ depending on residential mobility. This article highlights key findings from the relationship between residential mobility and trust in digital environments. Trust in digital environments may vary depending on residential mobility. As a result of the data analysis, the lower the residential mobility, the lower the trust in digital environments, while the higher the residential mobility, the higher the trust in digital environments.
서정화(Jeonghwa Seo),김정민(Jeongmin Kim),안선영(Sunyoung Ahn),조진구(Jingu Cho),김종민(Jongmin Kim),박헌용(Heonyong Park) 한국생명과학회 2009 생명과학회지 Vol.19 No.7
고대부터 식품으로 많이 이용되어 왔던 마늘의 성분중의 하나인 alliin의 혈관 생리활성을 조사하기 위해 다양한 실험을 수행하였다. Alliin은 혈관내피세포의 증식과 이동을 증진시키는 기능이 있으며, 이는 alliin이 혈관형성을 촉진하고 혈관의 상처 치유에 도움을 줄 수 있음을 의미한다. 또한 alliin은 염증반응을 일으키는 과정에 나타나는 THP-1 세포의 혈관내 피세포 부착을 억제하며, 혈전을 형성하는 THP-1 동종세포간 응집을 억제하는 기능도 갖고 있음이 확인되었다. 이와 같은 alliin의 세포 기능은 혈관의 주요 질환인 동맥경화의 발생 및 뇌졸증이나 심근경색의 원인이 되는 혈전의 형성 등을 억제할 수 있음을 의미한다. 한편 혈관의 주요 조절자 중의 하나인 산화질소의 생산에는 alliin이 관여하지 않음을 확인하였다. 종합해 보면, alliin은 혈관세포의 여러 가지 생리기능을 조절하는 혈관생리기능 개선제로 활용할 가능성이 있는 물질이다. Little is known about the cardiovascular roles of alliin, a functional component in garlic that has been used as food material. Thus, we examined a broad range of cardiovascular activities of alliin in this study. From our in vitro experiments, alliin was determined to act as a stimulant to induce endothelial cell proliferation and endothelial cell migration. Since endothelial cell proliferation and migration are highly associated with angiogenesis and wound healing, alliin is suggested as a regulator to control angiogenesis and wound healing. In addition, alliin was elucidated to prevent lipopolysaccharide (LPS)-induced adhesion of THP-1 leukocytes to endothelial cells and LPS-induced homotypic THP-1 cell aggregation. These inhibitory effects indicate that alliin is likely to act as an anti-atherosclerotic and anti-thrombotic factor, because leukocytic adhesion to endothelial cells and homotypic leukocyte aggregation are highly associated with atherosclerosis and thrombosis, respectively. Our additional findings show that alliin has no effect on the production of nitric oxide (NO), an important vasoregulator. In conclusion, alliin is suggested as a regulator for controlling various cardiovascular functions.
서정화 ( Jeonghwa Seo ) 중앙대학교 국가정책연구소 2018 국가정책연구 Vol.32 No.4
본 연구는 우리나라 성장동력사업에서 큰 변화가 나타난 노무현 정부와 이명박 정부를 대상으로 성장동력사업의 제도변화 원인과 양상을 설명해보고자 하였다. 이러한 목적을 달성하기 위해서, 본 연구는 신제도주의 관점에서 제도적 맥락, 이념, 행위자를 독립변수로 상정하여 성장동력사업의 제도변화 특성을 분석하였다. 분석 결과 수단 변화는 경로의존성에 영향을 받는 것으로 나타났으며 조직 및 구조는 이념과 행위자에 의해 조직 및 구조가 변화하는 것으로 나타났다. 이러한 분석 결과를 통해서 성장동력사업의 제도변화는 제도적 맥락, 이념, 행위자 간 상호작용을 통해 변화가 일어나고 있음을 확인할 수 있었다. This research aims to examine the causes and features of institutional change in the projects for the growth engine, focused on the former two Korean governments, namely the Roh Moo-Hyun government and the Lee Myung-Bak government, which showed significant changes in the projects. To achieve the aim, from new institutionalism perspective this study analyzes the characteristics of the institutional change in the projects of the two previous governments, using institutional context, idea, and actor as independent variables. The results show that the change of policy instrument was occurred by path dependency, while organization and organizational structure were changed not by path dependency, but by idea and actor. From the results, it can be said that the institutional changes in the projects for the growth engine in the Roh Moo-Hyun government and the Lee Myung-Bak government were occurred by the interplay among institutional context, idea, and actor.