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        검색결과 66

        65.
        2018.09 KCI 등재 SCOPUS 서비스 종료(열람 제한)
        The characterization of detectors installed in space- and ground-based instruments is important to evaluate the system performance. We report the development of a detector performance test system for astronomical applications using the Andor iKon M CCD camera. The performance test system consists of a light source, monochromator, integrating sphere, and power meters. We adopted the Czerny–Tuner monochromator with three ruled gratings and one mirror, which covers a spectral range of 200–9,000 nm with a spectral resolution of ~1 nm in the visible region. Various detector characteristics, such as the quantum efficiency, sensitivity, and noise, can be measured in wide wavelength ranges from the visible to mid-infrared regions. We evaluated the Korea Astronomy and Space Science Institute (KASI) detector performance test system by using the performance verification of the Andor iKon-M CCD camera. The test procedure includes measurements of the conversion gain (2.86 e−/ADU), full well capacity (130 K e−), nonlinearity, and pixel defects. We also estimated the read noise, dark current, and quantum efficiency as a function of the temperature. The lowest measured read noise is 12 e−. The dark current at 223 K was determined to be 7 e−/s/pix and its doubling temperature is 5.3°C ± 0.2°C at an activation energy of 0.6 eV. The maximum quantum efficiency at 223 K was estimated to be 93 % ± 2 %. We proved that the quantum efficiency is sensitive to the operating temperature. It varies up to 5 % in the visible region, while the variation increases to 30 % in the near-infrared region. Based on the comparison of our results with the test report by the vendor, we conclude that our performance test results are consistent with those from the vendor considering the test environment. We also confirmed that the KASI detector performance test system is reliable and our measurement method and analysis are accurate.
        66.
        2015.01 KCI 등재 서비스 종료(열람 제한)
        Environmental problems caused by the occurrence of carbon dioxide are recognized as a critical issue throughout the world. As a result, a measure for the use of cement and improvement of its quality must be sought out. In order to reduce the occurrence of carbon dioxide during the manufacturing process of cement, this study creates an alkali-activated slag cement that utilizes ground granulated blast furnace slag, an industrial by-product, and substitutes metakaolin as an alternative for silica fume to improve the process of manufacturing high-strength concrete and its quality. The study discerns the mechanical characteristics by measuring the flexibility and compressive strength through the mortar matrix and discerns the durability by conducting an acid resistance test and chloride ion penetration resistance test. Also, the study discerns the hydration products through an XRD test. Based on the results of such tests, it is anticipated that it may be used as a secondary product for concrete or buildings that require superior long-term strength and durability compared to regular Portland cement. However, as no clear results were found in this study regarding the substitution of metakaolin, it displayed mixed results in comparison to previous studies. Nevertheless, it is expected that metakaolin will become a more superior admixture if its issues are improved through continuous research studies.
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