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나노유체를 이용한 평판형 태양열 집열기의 효율에 관한 연구
이승현(Seung-Hyun Lee),이승윤(Seoung Youn Lee),장석필(Seok Pil Jang) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11
In this paper, an analytical study is conducted to assess the efficiency of a flat-plate solar collector using the nanofluids. We obtain a simplified analytical solution for the flat-plate solar collector by assuming the wavelength-independent extinction coefficient and spectral intensity, and then a dimensionless temperature distribution in the flat-plate solar collector is obtained using the extinction coefficient of single wall carbon nanohorn (SWCNH) nanofluids. Finally, we show the effect of volume fraction, heat loss magnitude and collector depth on the dimensionless temperature distributions and evaluate the efficiency of the nanofluid-based flat-plate solar collector according to the particle concentrations.
나노유체 : 화학적 환원법의 혼합방법이 주석 나노유체의 입자 크기에 미치는 영향
장석필 ( Seok Pil Jang ),이승윤 ( Seoung Youn Lee ),이승현 ( Seung Hyun Lee ),김상훈 ( Sang Hoon Kim ) 한국액체미립화학회 2012 한국액체미립화학회 학술강연회 논문집 Vol.2012 No.-
being changing as alternative materials instead of tin-lead solder ball as following development of ecofriendly industry. However, one of the adverse effect of this change is tin-alloys have higher melting temperature (232oC) compared with tin-lead (~183oC). For this reason, electronic assembly has disadvantages such as warpage, electrical energy consumption, thermal stress and thermal cracking. Therefore studies of lowering meting temperature of tin are intensively investigating as a fundamental study of reducing tin-alloys melting temperature. In previous researches, the melting temperature of nanoparticle is non-linearly decreased with decreasing particle size which is the most dominant effect to determine the melting temperature1). Therefore decreasing the size of particle is core parameter to reduce the melting temperature of tin nanoparticle. Furthermore, to use these lead-free tin nano solder ball practically in industrial part, cost problem should be accompany with the investigation of lead-free solder ball. So, not only decreasing of the particle size but also improving of the production efficiency has to be considered. In this paper, tin nanoparticles are synthesized by chemical reduction method in ethylene glycol using stirrer and ultra-sonic wave bath respectively. Tin (II) acetate, Sodium borohidride and Polyvinylpyrrolidone (PVP) are used as precursors, reducting agents and surfactants respectively. Transmission electron microscopy (TEM) and particle size analyzer (PSA) are used to characterize particle size, shape and distribution of Sn particle and surfactant. Fig. 1, 2 show the well-made Sn nanoparticle manufactured with stirring method and ultra-sonic energy respectively. The stirring method and ultra-sonic energy method both well manufactured 45 ± 5 nm and 10 ± 5 nm average diameters sized tin nanoparticle respectively. The using of ultra-sonic energy is able to make much smaller sized tin nanoparticle than the using of stirrer and it has alternative advantages. As follows, Benefits of using ultrasonic energy are large quantity production due to shorten manufacturing time that only 5 minute and better dispersion stability. While the stirring method need at least two or more hours for one case of experiment. Fig.3 shows the manufacturing time effect on the particle size with ultra-sonic energy. Except for the time problem, the main prohibited problem to manufacture large quantity of Sn nanoparticle is dispersing of surfactant. It was identified that the suspension stability of surfactant effect on particle size and dispersing of surfactant is not easy in bulky amount of base fluid2). By so using of ultrasonic energy comparatively solved these problems not only prohibit aggregation of surfactant during reacting but also easily control large quantity of experimental specimens. Fig.4 shows the 0.01 vol. % of the optimum volume fraction of Tin (II) acetate respect on decreasing of the particle size. Additionally, the using of ultrasonic energy is helpful to reduce 80% of the integrating watt which is 25kWh and 125kWh for using of ultrasonic energy and using of stirrer respectively for each experiment.
Web Services 상호 운용성을 위한 테스트 프레임워크 구축 및 시뮬레이션
임산송,이원석,이강찬,전종흥,이승윤,정회경,Im San-Song,Lee Won-Suk,Lee Kang-Chan,Jeon Jong-Hong,Lee Seung-Youn,Jung Hoe-Kyung 한국정보통신학회 2004 한국정보통신학회논문지 Vol.8 No.7
최근 많은 기업들이 플랫폼 또는 프로그래밍 언어에 의존적이지 않고 상호간의 원활한 정보 교환을 지원하는 HTTP와 같은 인터넷 표준 프로토콜과 XML 표준 기술 기반의 새로운 분산 컴퓨팅 환경인 웹서비스를 도입하고 있지만, 각각의 업체에서 제공하는 플랫폼들이 지원하는 표준들의 버전 불일치 문제로 인해 상호 운용성에 어려움을 겪고 있다. 이러한 상호 운용성 문제를 해결하기 위해 WS-I 에서는 기본 프로파일 및 사용 시나리오를 제공하는 둥 일련의 표준화 작업을 진행하고 있지만, 아직 국내에서는 관련 연구가 미흡한 상태이다. 이에 본 논문에서는 주위에서 쉽게 접할 수 있는 도서 정보 검색 서비스를 서로 다른 플랫폼을 기반으로 웹서비스를 개발하여 상호 운용성 테스트 프레임워크를 구축하고 WS-I 기본 프로파일을 적용하여 상호 운용성을 시뮬레이션 및 검증하였다. Recently many corporations are introducing web services which supports mutual smooth information exchange without depending on platform or programming language and new distributed computing environment based on U standard technology and internet standard protocol such as HTTP. However they are suffering difficulty in interoperability because of the problem of version inconsistency of standards supported by platforms that each vender offers. To solve these interoperability problem, although WS-I is progressing a consecutive standardization work by method of that offer Basic Profile and Usage Scenario, it is in the state that the domestic research connected with this is not sufficient yet. Accordingly, this treatise constructed interoperability Test framework by developing web services on the basis of different platform from books information retrieval services that can easily be come with and simulated and verified the interoperability by applying WS-I Basic Profile.