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李榮雨 忠州大學校 1998 한국교통대학교 논문집 Vol.33 No.2
The thermal and mechanical properties of DGEBA/DDM epoxy resin systems with and without siloxane modifier have been studied as a function of cure conditions and the reactant monomer ratio. The control resin system used in this study was prepared from a diglycidyl ether of bisphenol-A(DGEBA) type epoxy resin and an aromatic amine curing agent, diamino diphenyl methane(DDM). To prepare modified resin systems, a siloxane modifier, DSiOD prepolymer was first obatined by prereacting the epoxy terminated siloxane oligomer to the excess amount DDM in the molten state, and then mixed with DGEBA resin monomers and cured in an air oven according to the prefixed cure conditions. The glass transition temperature, Tg, and theflexural modulus of pure resin system were strongly influenced by cure conditions. They both increased noticeably with the increase of cure temperature and cure time. The optimum cure condition for the specified DGEBA/DDM resin system of 1 : 1 reactant monomer ratio was 3hr curing at 150℃. While the Tg of the resin system was sacrificed noticeably in the siloxane modified resin system, the thermal stability studied by measuring the initial degradation temperature was increased. The flexural and the impact strengths of the modified resin system were higher than those of pure resin system while the flexural modulus was slightly lower in the modified system.
이영우,임희창 한국화재소방학회 2018 한국화재소방학회논문지 Vol.32 No.4
This paper presents a numerical analysis of flow inside a water nozzle for fire fighting and observes the effect of thevariation in primary components on internal flow. In order to observe the performance of water nozzles, they have beensystematically designed and modelled, applying boundary conditions obtained from field experiments (inlet pressure at pump: 4 bar, and pressure outlet : atmospheric pressure). In addition, the governing equations were calculated to obtain velocity,pressure inside the nozzle. Two main parameters (the presence and length of sub-pipes) were considered with the aim toobserve the detail internal flow characteristics. It is found that the base model is not significant on flow characteristics, buta negative effect (i. e. the reverse flow) at the entrance region of sub-pipe. On the other hand, the reverse flow wasvanished when making the length of sub-pipe double. 본 논문은 화재의 발생 및 전파를 억제하기 위해 방수총의 내부 유체유동특성을 파악하는 것을 목적으로 한다. 본 연구를 위해 개발 중인 워터노즐을 모델링하였고, 필드실험에서 얻은 경계조건(펌프의 가압력 : 4 bar, 방수총 출구압력 : 대기압)을 적용하였으며, 유동에 대한 운동량 지배방정식을 이용하여 방수총 내부 유동에 대한 속도 및 압력분포를 얻었다. 서브파이프의 유무와 길이를 기준으로 방수총 출구의 노즐에서의 성능 특성에 영향을 미치는 2가지 주요 인자로 고려하였다. 해석 결과 기존 모델의 경우에는 서브파이프의 길이가 변하더라도 방수총의 출구영역에서 성능특성에 그다지 영향을 미치지 않았다. 이에 반해서, 서브파이프를 단관형으로 교체한 경우에는 서브파이프의입구에서 역류가 발생하였고, 이를 제거하기 위해 서브파이프의 길이를 2배로 변화시켜 역류를 제거할 수 있었다.