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- 저자 : 권영환(Younghwan Kwon) (검색결과 6 건)
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분자화약 구조를 포함하는 옥시란계 에너지화 단량체의 설계 및 합성
심엽신,권영환,김진석,Shen, Yechen,Kwon, Younghwan,Kim, Jin Seuk 한국군사과학기술학회 2015 한국군사과학기술학회지 Vol.18 No.2
Energetic monomers with new design concept were synthesized for energetic prepolymers. Novel energetic monomers consisted of ring-opening polymerizable oxirane and a molecular explosive moiety instead of small explosophores as energetic functional groups. According to the design concept, glycidyl dinitroazetidine (GDNAZ) and glycidyl nitroazetidinol(GNAZO) energetic monomers were synthesized, respectively, and characterized by NMR, EA and GC MS. Heat of formation and detonation performance were calculated by theoretical method to evaluate energy performance of these novel energetic monomers. The result revealed that GDANZ and GNAZO possessed high potential as new energetic monomers for synthesizing energetic prepolymers and binders in PBXs.
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나노유체 적용에 따른 판형 열교환기의 대류열전달 및 압력강하 특성에 관한 연구
조용현(Yonghyeon Cho),권영환(Younghwan Kwon),이성국(Chengguo Li),이재근(Jaekeun Lee),김두현(Doohyun Kim) 대한설비공학회 2010 대한설비공학회 학술발표대회논문집 Vol.2010 No.6
The purpose of this study is to investigate heat transfer characteristics and pressure drop in applying Al₂O₃ nanofluids to plate heat exchanger. Experiments were performed under Reynolds number from 100 to 500 and respective volumetric flow rate. The working temperature of heat exchanger was in the range of 20℃ to 40℃. The measured thermophysical properties, such as thermal conductivity and kinematic viscosity, were applied to calculating convective heat transfer coefficient of plate heat exchanger according to Al₂O₃ nanofluids made by two-step method. As the Reynolds number increases, the overall heat transfer coefficient under 6 vol% of Al₂O₃ went up to almost 30% respectively. But it was observed that for a given volumetric flow rate the performance is not increased. Also pumping power enhancement due to viscosity.
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폴리비닐알코올로 코팅된 마이크로스트립 결함 접지 구조 기반 마이크로파 센서를 이용한 습도 센서
여준호 ( Junho Yeo ),권영환 ( Younghwan Kwon ) 한국항행학회 2020 韓國航行學會論文誌 Vol.24 No.6
본 논문에서는 폴리비닐알코올로 코팅된 마이크로스트립 결함 접지 구조 기반 마이크로파 센서를 이용한 습도 센서의 개발에 대하여 연구하였다. 인터디지털 커패시터 모양의 결함 접지 구조를 마이크로스트립 선로의 접지면에 추가하여 피시험물의 유전율 변화에 민감한 고감도 마이크로파 센서를 설계하였다. 습도에 따라 유전율이 변하는 고분자 물질인 폴리비닐알코올을 제안된 센서의 결함 접지 구조에 얇은 두께로 코팅하였고, 습도에 따른 마이크로파 센서의 전달계수의 공진 주파수와 크기의 변화를 측정하였다. 온습도 챔버를 사용하여 25도에서 상대습도를 40%에서 80%까지 10% 간격으로 증가시켰을 때 전달계수의 공진 주파수는 1.475 GHz에서 1.449 GHz로 감소하였고, 크기는 -32.90 dB에서 -25.67 dB로 증가하였다. In this paper, we have studied a development of a humidity sensor using a microwave sensor based on a microstrip defected ground structure coated with polyvinyl alcohol. A high-sensitivity microwave sensor, which is sensitive to the changes in the permittivity of the material under test, is designed by adding an interdigital capacitor-shaped defected ground structure to the ground plane of a microstrip line. Polyvinyl alcohol, a polymer material whose permittivity varies depending on humidity, is coated with a thin thickness on the defected ground structure of the proposed microwave sensor, and the changes in the resonance frequency and magnitude of the transmission coefficient for the microwave sensor according to humidity are measured. When relative humidity increases from 40% to 80% in 10% increments at a temperature of 25 degrees using a temperature/humidity chamber, the resonant frequency of the transmission coefficient decreases from 1.475 GHz to 1.449 GHz, and the magnitude is increased from -32.90 dB to -25.67 dB.
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Synthesis and Thermal Characteristics of Nano-Aluminum/Fluorinated Polyurethane Binders
Qianqian Lan,Jin Seuk Kim(김진석),Younghwan Kwon(권영환) 한국추진공학회 2016 한국추진공학회지 Vol.21 No.1
현재 적용되고 있는 에너지화 가소제는 –NO₂, -ONO₂ 및 –N₃와 같은 에너지화 활성 그룹을 포함하고 있어서 충격, 쇼크, 열 등 외부환경에 상당히 민감하여 복합화약의 둔감 안정성을 취약하게 한다. 본 연구에서는 민감한 에너지화 활성 그룹이 아니라 근본적으로는 비활성 그룹으로 복합화약의 민감도에는 영향을 미치지 않지만, 복합화약의 반응 시에 테르밋반응에 의해 추가적인 에너지를 발생할 수 있는 불소계 반응성 가소제를 적용한 폴리우레탄 결합제를 클릭반응으로 합성하고 나노 알루미늄과의 테르밋반응에 대한 열적 특성을 고찰하였다. Energetic plasticizers containing explosophore groups such as –NO₂, -ONO₂, and –N₃ group are susceptible to impact, shock, heat, etc, finally deteriorating the insensitivity of PBXs. In this study, in an attempt to investigate the feasibility of replacing sensitive explosophore groups to fundamentally inactive but potentially (latent) energetic fluorine group which was known to have an exothermic thermite reaction with aluminum, nano-aluminum/fluorinated polyurethane binders were prepared by simultaneous polyurethane and catalyst-free azide-alkyne click reaction in the presence of nano-aluminum. Thermal characteristics of nano-aluminum/fluorinated polyurethane binders were monitored by using DSC with high pressure crucible pan.
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배진원(Bae, Jinwon),김륜희(Kim, Ryoonhee),권영환(Kwon, Younghwan),이미홍(Lee, Mihong) 한국지역개발학회 2019 韓國地域開發學會誌 Vol.31 No.3
There are increasing concerns of population decrease in South Korea because it brings loss of jobs, economic activity and quality of life as consequences. As one of the ways to sustain regions from population shrinkage, inter-regional linkage strategies have been proposed by sharing public facilities and services with neighboring cities. In this respect, this study aims to propose a linkage region that can support the region from population decline through interregional linkage. The analysis consists of three parts. First, we examine the centrality of facilities in all industrial sectors over the nation using the national point of interest (POI) provided from National Geographic Information Instiute (NGII) as of 2017. POI data is aggregated into the municipal unit to draw the most effective policy implications. Second, we perform divide-and-conquer analysis in order to subdivide multiple connected regions on the basis of the OD type of transportation data. Third, clusters of high and low values of centrality index in each region are calculated using Local Geary s cluster analysis method. The results show that the centrality of central cities in local regions ranges from 0.3 to 0.5, but when it is calculated it per population, some of the declining regions are highly centrally located. Service sector is more concentrated to metropolitan areas while leasure and culture related sectors are disseminated to shrinking or underdeveloped regions. Also, we derive 38 connected regions that seem to be most appropriate to sustain regional prosperity by providing necessary public and private services for people s living.
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