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        검색결과 143

        82.
        2006.04 구독 인증기관·개인회원 무료
        고주파유도가열 연소합성법으로 60MPa의 기계적 압력과 고주파유도가열 장치의 총용량 (15KW)의 90%의 출력을 가해 75초의 짧은 시간에 97%이상의 상대밀도를 갖는 복합체를 제조하였으며, 제조된 시편의 미세조직 사진으로부터 선형분석법으로 측정한 의 평균 결정립크기는 각각 250nm 과 60nm 이었다. 또한 제조된 시편을 연마하여 비커스 경도계를 이용하여 기계적 특성평가를 한 결과 경도 와 파괴인성은 각각 와 이었다.
        83.
        2005.08 KCI 등재 구독 인증기관 무료, 개인회원 유료
        ZnO nanostructures with various shapes were synthesized under ambient pressure condition by a wet chemical reaction method. Nanorods of ZnO with hexagonal cross-section and their aggregates with radiate shape were synthesized. Precursor concentration affected considerably the shape evolution of ZnO nanorods. Low precursor concentration was proved to be more preferable to the growth of ZnO nanorods, which is attributed to the intrinsic characteristics of chemical reaction in the synthesis of ZnO from zinc compounds.
        4,000원
        86.
        2005.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        데크플레이트와 콘크리트가 합성되어 있는 합성 바닥판 구조물은 데크플레이트의 골 방향과 골 직각방향에 대하여 강성이 다르므로 직교이방성판 거동을 보이고 있으며 테크플레이트와 콘크리트의 합성 거동으로 인하여 적층 바닥판 구조물로 평가할 수 있다. 이러한 합성데크 바닥판 구조물의 진동에 대한 정확한 사용성 평가를 위해서는 합성데크 바닥판 구조물의 정밀 진동해석을 수행하여야 한다. 이를 위해서는 합성데크 바닥판 구조물의 강성에 대한 직교이방성 그리고 데크플레이트와 콘크리트의 합성에 대한 정확한 거동 평가가 수반되어야 한다. 본 논문에서는 합성데크 바닥판 구조물의 골 직각 방향에 대한 강성을 계산하기 위하여 각각의 토핑 콘크리트 두께와 데크플레이트 두께를 적용하였다. 또한 골 방향에 대한 강성을 계산하기 위하여 콘크리트와 데크플레이트의 단면 강성을 구하여 등가두께를 적용하였다. 그리고 콘크리트와 데크플레이트의 합성거동을 표현하기 위하여 적층판에 대한 등가 강성식을 적용, 합성데크 바닥판 구조물의 강성을 나타내었다. 본 논문에서 제안한 합성데크 바닥판 구조물의 실용적인 모형화방법을 적용할 경우에 합성데크 바닥판 구조물의 강성에 대한 직교이방성과 콘크리트와 데크플레이트의 합성 거동을 잘 표현할 수 있었다
        4,000원
        87.
        2004.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Multi-walled carbon nanotubes (CNTs) were prepared by microwave plasma chemical vapor deposition (MPCVD) using various combination of binary catalysts and methane precursor. The maximum yield (10.3 %) of CNTs was obtained using a methane-hydrogen-nitrogen mixture with volume ratio of 1:1:2 at 1000 W of microwave power. As the microwave power increased up to 1000 W, the deposition yield of CNTs raised from 4.1 % to 10. 3 %. However, the prepared CNTs at 800 W showed the more crystalline structure than those prepared at 1000 W. The prepared CNTs over different binary catalysts had various structural conformations such as aligned cylinder, bamboo, and nanofibers. The Id/Ig value of CNTs overFe-Fe/Al2O3, Co-Co/Al2O3, and Co-Cu/Al2O3 were in the range of 0.89~0.93. Among the various binary catalysts used, Fe-Co./Al2O3 showed the highest yield.
        4,200원
        88.
        2004.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Fe(C) nanocapsules were prepared by the chemical vapor condensation(CVC) process using the pyrolysis of iron Their characterizations were studied by means of X-ray diffraction, X-ray photoelectron spectrometer and transmission electron microscopy. The long-chained Fe(C) nanocapsules hav-ing the mean size of under 70 nm could be obtained below in different gas flow rates. The particle size of the powders was increased with increasing decomposition temperature, but it was decreased with increasing CO gas flow rate. The Fe powders produced at consisted of three layers of phases, but it had two phase core-shell structure which consited of phase of core and graphite of shell at
        4,000원
        89.
        2004.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Although the structure of carbon nanotubes is important factor characterizing its properties, it is very difficult to control the structure of carbon nanotubes (MWNTs) and to predict the range of their diameter, which is the primary factor of MWNTs' physical properties. We tried to control the diameter of MWNTsby governing the feed injection temperature of floating catalyst method. The structure of MWNTs was influenced by the phase change of ferrocene fed as the catalyst,. The carbon nanotubes were very narrow at injection temperatures close to the sublimation pt. of ferrocene, in which most MWNTs had diameters in the range of 20~30 nm. At injection temperatures between the boiling pt. and melting pt. of ferrocene, the diameters became larger and had broad distribution. However, at injection temperatures higher than the boiling pt., the diameters became narrow again and had very uniform distribution.
        4,200원
        94.
        2003.08 구독 인증기관 무료, 개인회원 유료
        Recently, there has been a tendency to use composite deck plates in high-rise building and apartment construction due to its cost efficiency and less installation time. The purpose of current study is to clarify structural performance of deck plate and further safety through carefully designed experimental program. In order to clarify bending capacity and joint continuity, specimens were divided for positive and negative moment and testing parameters are thickness of deck plate, slab thickness, and various reinforcements The results of experimental test are following; (1) When the thickness of deck plate is 1.0mm, the strength increased by 1.3~10.1%, and 2.0~3.5% comparing the case of 0.8mm deck plate thickness. The thickness of deck plate did not play significant role in terms of strength of the slab in both positive and negative moment tests. (2) The yield strength of slab in positive moment test, having 200mm slab thickness and D13 reinforcement steel, was increased by 28.4~34.8% comparing 160mm slab thickness and D10 reinforcement steel case. And 22.4~25.1% of yield strength was increased after install bottom reinforcement steel. (3) In negative moment test results showed that the increase of yield strength when the bottom reinforcement installed was 2.0~2.3% in 200mm slab thickness and 2.0~3.0% in 160mm slab thickness. In positive moment test, the increase of yield strength was 22.8~26.7% in 200mm slab thickness due to bottom reinforcement, and 11.4~20.5% in 160mm slab thickness. The reason being bottom reinforcement in negative moment contributes less amount of yield strength compare to positive moment location is that the bottom reinforcement resists compression force where the deck plate has enough strength already.
        4,000원
        97.
        2003.02 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Porous TiNi bodies were produced by Self-propagating High-temperature Synthesis (SHS) method from a powder mixture of Ti and Ni. Porosity, pore size and structure, mechanical property, and transformation temperature of TiNi product were investigated. The average porosity and pore size of produced porous TiNi body are 63% and , respectively. XRD analysis showed that the major phase of produced TiNi body is B2 phase. Its average fracture strength and elastic modulus measured under dry condition were MPa and GPa, respectively. It could be strained up to 7.3 %. The transformation temperatures determined by DSC showed the temperature of and temperature of .
        4,000원
        99.
        2002.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Oligomer type anionic surfactants(RmM-Na or RmD-Na were synthesized from C8~C16 long chain alkylvinylether and maleic anhydride (or maleic diethylether). And also their fluorescent anionic surfactants (RmF- Na) were obtained from alkali neutralization which opens the lactone ring of the condensing materials produced by maleic anhydride alkylvinylether copolymer and 3-aminophenol. The measurement results for the surface active properties of water soluble oligomer type anionic surfactants with fluorescent structure (RmF-Na) exhibited a remarkable surface tension lowing property, foam breaking property, and a ernulsing power.
        4,200원
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