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        검색결과 7

        1.
        2017.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Debris disks are important observational clues to understanding on-going planetary system formation. They are usually identi ed by signi cant mid-infrared excess on top of the photospheric emission of a central star on the basis of prediction from J-, H-, and Ks-band uxes and the stellar model spectra. For bright stars, 2MASS near-infrared uxes suffer large uncertainties due to the near-infrared camera satu- ration. Therefore we have performed follow-up observations with the IRSF 1.4 m near-infrared telescope located in South Africa to obtain accurate J-, H-, and Ks-band uxes of the central stars. Among 754 main-sequence stars which are detected in the AKARI 18 m band, we have performed photometry for 325 stars with IRSF. As a result, we have successfully improved the ux accuracy of the central stars from 9.2 % to 0.5 % on average. Using this dataset, we have detected 18 m excess emission from 57 stars in our samples with a 3 level. We nd that some of them have high ratios of the excess to the photospheric emission even around very old stars, which cannot be explained by the current planet-formation theories.
        3,000원
        2.
        2012.09 KCI 등재 구독 인증기관·개인회원 무료
        Using the AKARI mid-infrared all-sky survey catalogue, we are searching for debris disks which are important objects as an observational clue to on-going planetary system formation. Debris disk candidates are selected through a significant excess of the measured flux over the predicted flux for the stellar photospheric emission at 18 μm . The fluxes were originally estimated based on the near-infrared spectral energy distributions (SEDs) of central stars constructed from the 2MASS J-, H-, and Ks-band fluxes. However, we found that in many cases the 2MASS photometry has large errors due to saturation in the central part of a star image. Therefore we performed follow-up observations with the IRSF 1.4m near-infrared telescope in South Africa to obtain accurate fluxes in the J-, H-, and Ks-bands. As a result, we have succeeded in improving the SEDs of the central stars. This improvement of the SEDs allows us to make more reliable selection of the candidates.
        3.
        2006.04 구독 인증기관·개인회원 무료
        SUS316L stainless steel, commercial pure Titanium and Ti-6Al-4V alloy powders applied by Mechanical Milling (MM) process are sintered by Hot Roll Sintering (HRS) process. Microstructure and mechanical properties of those HRS materials is investigated. The microstructures of materials produced by HRS process consist of fine grains and work-hardened structure, that is, the hybrid microstructure. Tensile test of the HRS material demonstrated the good mechanical properties. These results show that the HRS process is very effective to the improvement of mechanical properties in the SUS316L stainless steel, commercial pure Titanium and Ti-6Al-4V alloy.
        4.
        2006.04 구독 인증기관·개인회원 무료
        In this study, nano grain W is fabricated by Severe Plastic Deformation-Powder Metallurgy (SPD-PM) process. W powder and W-Re powder mixtures are processed by SPD-PM process, a Mechanical Milling (MM) process. As results, a nano grain structure, whose grain size is approximately 20nm, is obtained in W powder after MM for 360ks. A nano grain W compact, whose grain size 630nm, has excellent deformability above 1273K. A nano grain W-10Re compact is composed of equiaxed grain, a grain growth is restrained and has low dislocation density after the large deformation; therefore it is considered that W-Re compact shows superplasticity.
        5.
        2006.04 구독 인증기관·개인회원 무료
        The relationship between the powder particle size change and a mechanical property of the Metal Injection Molding (MIM) product was examined in detail. The XRD results indicate that the diffraction peaks of BCC appeared in compacts of powder particle size of 4 to as well as the bulk SUS630. However, the diffraction peaks from both BCC and FCC were observed in the compact with powder size less than . TEM observation revealed that the powder with those BCC/FCC two phase structure have a finely dispersed precipitates. Because the Si is ferrite stabilizing element, decrease of Si composition in the matrix phase by the precipitation resulted in formation of the retained austenite. Therefore, controlling the elements such as Si as well as oxygen decrease is very important to obtain a normal microstructure in ultra-fine powder (<3μm) injection molding.
        7.
        2013.11 서비스 종료(열람 제한)
        In the sustainable society, the recycling of resources should achieve the preservation of regional and global environment and should be coordinated with regional agricultural and industrial activities. Especially for waste biomass resources, it will be supplied or discharged by multiple industries as agriculture, forestry, fisheries, manufacturing, commerce and living, and will be demanded by multiple purposes as foods, supplements, feeds, fertilizers, industrial materials and fuels. Therefore, waste biomass flows connecting these supplies to demands will be extremely complex. In order to judge the effectiveness of introducing technologies for recycling, a comprehensive framework, which can estimate impacts of technologies on regional material cycles and regional and global environment, is need. For this purpose, we are developing a physical input-output table (PIOT) for describes complex material flows of waste biomass, water and their constituents (e.g. carbon, nitrogen and phosphorus) in a region by integration of quantity data. This PIOT sets not only industries but also activities on recycling, waste disposal and wastewater handling in detail as sectors. Import and export between regions, and emissions to environment are also set in the table. Applying content rates of carbon, nitrogen and phosphorus to mass flows of each item, elemental flows of those are accounted for estimating emission to water (as organic pollutant and nutrients) and atmosphere (as greenhouse gas) from the whole system. The energy consumed by activity in each sector is also accounted for estimating greenhouse gas emission. Another originality of this PIOT is that physical data obtained from relevant statistics will be directly integrated to values in the table. As a case study, we are surveying the waste biomass flow at the Kochi prefecture, Japan. Administrative information on industrial waste was acquired from the Kochi Prefecture and the Kochi City with their cooperation. For municipal waste, annual survey on municipal solid waste business by the ministry of the environment was used. For by-product, generation amount, sort, composition and usage of biomass waste were surveyed by hearing, sampling and questionnaire at recyclers of biomass waste. Amounts of generation, recycling and disposal of each biomass waste item, disposal method and municipality were built up from these reports and survey. Using above information, flows of each lot (the annual generation an item of waste from a source) of biomass waste from generation via treatment to disposal or reuse were compiled in the database and set into the PIOT. The current biomass PIOT for Kochi Prefecture is shown in Figure. This table shows weight of materials as wet basis. The 1.43 × 108 tons/year of total demand and the 1.34 × 108 tons/year of total supply were accounted at this time. The difference between demand and supply would mainly be resulted from unrecorded flows in our database, especially on supply of water from the waterworks and the natural water, and the biomass production. We will survey constituents of carbon and nutrients in materials and expand our PIOT to depict the substance flows of elements, in order to estimate quality and quantities of emissions.