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        검색결과 22

        4.
        2010.02 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In this work, effect of various process-control agents (PCAs) on the mechanical alloying of amorphous alloy of has been investigated. The dependence of the particle shape, size and crystallization behavior of the amorphous alloy powders on the type of PCAs and their concentrations was investigated by using X-ray diffraction, field-emission scanning electron microscopy and differential scanning calorimetry. It was found that the additive of toluene could affect positively the amorphization and thermally induced crystallization processes, as well as the size refinement, morphology and particle-size distribution of as-milled powders in comparison with alloy obtained without PCA.
        4,000원
        5.
        2009.10 KCI 등재 구독 인증기관 무료, 개인회원 유료
        TiCuNiAl quaternary amorphous alloy was prepared by high-energy ball milling process. A complete amorphization was confirmed for the composition of TiCuNiAl after milling for 30hrs. Differential scanning calorimetry showed a large super-cooled liquid region (T = T T, T and T: glass transition and crystallization onset temperatures, respectively) of 80 K. Prepared amorphous powders of TiCuNiAl were consolidated by spark-plasma sintering. Densification behavior and microstructure changes were investigated. Samples sintered at higher temperature of 713 K had a nearly full density. With increasing the sintering temperature, the compressive strength increased to fracture strength of 756 MPa in the case of sintering at 733 K, which showed a 'transparticle' fracture. The samples sintered at above 693 K showed the elongation maximum above 2%.
        4,000원
        12.
        2003.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Resistance sintering under ultra-high pressure if developed to fabricate W-Cu composite containing 5 to 80v/o copper. The consolidation was carried out under pressure of 6 to 8 GPa and input power of 18 to 23 kW for 50 seconds. The densification effect and microstructure of these W-Cu composites are investigated. The effect of W particle size on ,sintering density was also studied. The micro hardness was measured to evaluate the sintering effect.
        4,000원
        15.
        1991.06 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Infrared emission maps are constructed at 12.5, 25, 60, and 100 μ m for dark globules B5, B34, B133, B134, B361, L134 and L1523 by using Infrared Astronomical Satellite data base. These clouds are selected on the basis of their appearance in Palomar print as dark obscuring objects with angular sizes in the range of 3 to 30 arcminutes. The short wavelength(12.5 and 25 μ m ) maps show the embedded infrared sources. We found many such sources only in B5, B361 and B34 regions, Diffuse component at 12.5 and 25 μ m , possibly arising from the stochastically heated very small dust grains(a < 0.01 μ m ) by interstellar radiation field, is found in B361 and L1523 regions. Such emission is characterized by the limb brightening, and it is confirmed in L1523 and in B361. Infrared emissions at the long wavelengths(60 and 100 μ m ) are due to colder dusts with temperature less than 20 K. The distribution of color index determined by the ratio 60 to 100 μ m intensities shows monotonic decrease of dust temperature toward the center. The black body temperature determined from these ratios is found to lie between 16 and 23 K. Such temperature is possible for small(i.e., a ≲ 0.01 μ m ) graphite grains if the grains are mainly heated by interstellar radiation field. Thus IRAS 100 and 60 μ m emissions are arising mainly from small grains in the colud. The distribution of such dust grains implied from the emissivity distributions at 100 and 60 μ m resembles that of isothermal sphere. This contrasts to earlier findings of much steeper distribution of dusts contributing visible extinction. These dust grains are mainly larger ones(i.e., a ≃ 0.1 μ m ). Therefore we conclude that the average grain size increase, toward the cloud center.
        4,900원
        17.
        1974.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        쇠파리의 실내 대량사육을 위한 시험에서 산란전기간을 단축 시킴으로써 사충율을 저하시키며 누대사육에 의한 위소현상을 조사하기 위해 각 세대별 용중량의 차이를 조사 하였으며 쇠파리는 성충기 이외에는 자웅구별이 불가능하므로 용중량에 의한 성구별을 시도한 결과는 다음과 같다. 1) 유충 media로부터 용을 분리할 때 사용하는 물을 약 로 가온하여 용을 채취한 결과 산란전기간이 8일로 단축되었다. 2) 누대사육에 의한 세대별 위소현상 조사에서 명세대별 용중량차이에는 유의성이 없었으며 사육온도에 따라서 많은 차이를 보였다. 3) 용중량의 차이에 의한 성구별은 약 의 웅충구별이 가능하였다
        3,000원
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