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        검색결과 41

        1.
        2022.10 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Hydrogen infrastructure, for instance, such as hydrogen stations, supply chain network, is important in society of hydrogen economy. Special alloy are frequently used to prevent the hydrogen embrittlement in hydrogen vehicles, semiconductor factories and so on. Because special alloy including Monel material has high strength and high hardness, it is known as the hard-to-cut or roll material. This paper aims to investigate the characteristics and safety on bearing and shaft, which consist of key parts of rolling unit, through structural analysis. As the results, it showed that the bearing was weaker than shaft. Further the bearing was safe up to 20.4 ton, which was about 2 times of maximum of roller reaction force in case of considering as static load. However, the bearing was safe up to 10.2 ton in case of considering as repeated load.
        4,000원
        2.
        2019.07 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        The College Scholastic Ability Test (CSAT) has focused on relative ranks among students since it started from 1993. In December 2014 The Ministry of Education (MOE) announced that it would adopt an absolute grading system (AGS) for English scores in the CSAT, starting from November 2017, and discard the relative grading. The MOE hoped that the AGS of CSAT English would eventually serve to normalize English education by having teachers place more emphasis on improving students’ communication skills rather than on solving CSAT questions. This paper describes the rationale behind the implementation of AGS for CSAT English by the MOE and how the criteria and grades of AGS have been developed and set. Then current problems arising from the AGS for CSAT English are discussed by touching on its theoretical, practical and political issues based on relevant literatures, public hearings and news media reports, and informal interviews with contemporary teachers of English.
        6,000원
        3.
        2019.04 KCI 등재 구독 인증기관 무료, 개인회원 유료
        SUS hexagonal bar have been widely used to manufacture the hexagonal bolt/nut, adapter and fittings. Raw SUS circular bar is used to make SUS hexagonal bar using drawing system. The purpose of this study is to investigate the characteristics, for instance, such as stress, strain and reduction ratio of area for bar. As the results, it was confirmed that the maximum stresses were occurred at edge of hexagonal bar, thus it could be worked as residual stress of hexagonal bar. The phenomenon of spring back was almost no found in all parts of hexagonal bar. Furthermore it showed that the reduction ratios of area were about mean 26% when SUS circular bar was changed to SUS hexagonal bar in this study.
        4,000원
        4.
        2018.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In order to remove rust and impurities from surface of raw SUS circular bar, peeling machine is used to make lustrous and clean surface of SUS circular bar. Drawing process system is used to manufacture SUS hexagonal bar. SUS hexagonal bar have been widely used to make hexagonal bolt/nut, adapter and fittings and so on. The purpose of this study is to investigate the stabilities for guide bar of clamp in drawing process system. As the results, the guide bar showed structural stability in cases of below load of 50 Ton and over hook radius of 3.0mm. Further as the thickness of guide bar hooking with jaw was increased, minimum safety factor was decreased.
        4,000원
        5.
        2018.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        SUS hexagonal bar has been widely used to make many kinds of hexagonal bolt/nuts and fittings. Peeling machine is used to make lustrous and clean surface of SUS circular bar in order to remove rust and impurities from surface of raw SUS circular bar. Similarly, roll unit system is used to make SUS hexagonal bar from SUS circular bar with lustrous and clean surface. Roll unit system is mainly divided into two parts ; one is roll unit and the other is mold frame. The purpose of this study was to evaluate the structural stability of mold frame supporting roll unit with numerical analysis. As the numerical analysis result, higher structural stability was gradually shown in order of models 4, 2, 3 and 1. It was considered that the structural stability of this study was influenced by the decrease of mold frame size, especially height decrease.
        4,000원
        6.
        2017.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        SUS hexagonal bar, which is manufactured by drawing process of SUS circular bar, have been widely used to make various adapters and fittings. The purpose of this study is to investigate the characteristics and stability of variable roll unit including stand module. Stand module is essential part of variable roll unit. Structural analysis was performed to predict the stability of stand module using 3 loads (50, 75, 100 Ton), thus it may be of help to the manufacture of stand module. As the results, internal ring of bearing showed maximum equivalent stress, and moreover bearing, shaft and roller had to be preferentially considered in order to maintain its stability. In cases of 50 and 75 Ton, there were no problems for stabilities, respectively, on the other hand, problem for stability may occur in case of 100 Ton.
        4,000원
        7.
        2014.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This paper aims to analyze the scores assigned to compositions of Korean as a foreign language (KFL) in terms of the many-facet Rasch measurement (MFRM) model. The MFRM computer program Facets has recently been updated and this research uses it in order to investigate the scoring reliability of KFL writing test. For the research data the Korean compositions written by 270 KFL learners were collected and rated by eleven Korean raters. At first a brief theoretical basis for the Facets is introduced based on the MFRM model. Then focusing on the raters’ characteristics such as rating consistency and fitness in terms of the rating scheme of content/organization and language, the collected scores of KFL compositions are analyzed and the analysis results are interpreted. As a result, a few cases of unreliable scoring of Korean raters are identified, but it appears that the ratings of Korean raters for a standardized KFL writing test are generally reliable. Finally it is suggested that the Facets program of MFRM offer many potential advantages for validating the scoring reliability of Korean writing assessment.
        5,700원
        8.
        2011.12 구독 인증기관 무료, 개인회원 유료
        We investigated short-term variations of phytoplankton community structure according to marine environmental condition with data set of phytoplankton composition, nutrients, physical parameters and precipitation. The 13 sampling stations were located in the southeast coastal waters of Korea, the survey monthly carried out from March to November. The study area can be divided into two zone according to the characteristics of marine environment. Zone I is the occupied with Thalassiosira decipiens, Skeletonema costatum, Eucampia zodiacus, Cheatoceros spp. and Asterionellopsis glacialis due to continuous freshwater input and high concentration of nutrients. Zone II was dominated by Pseudo-nitzschia spp. probably due to rainfall and self eutrophication of aquaculture farm.
        4,000원
        9.
        2007.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Physicochemical and sensory properties of sponge cakes using 2 kinds of domestic wheat flour(white flour, whole wheat flour) and imported cake flour were investigated. In the proximate analysis, white flour had higher contents of water and protein compared with those of imported flour. Whole wheat flour had the highest contents of protein, lipid and ash. Regarding the batter, imported flour sample showed lower specific gravity and higher viscosity than those of domestic flour sample, implying that there was more air incorporation and higher batter stability. As a result, imported flour batter produced larger cake compared to that of domestic flour batter. But indexes of symmetry and uniformity showed no significant difference among the samples. In textural analysis using rheometer, cakes with imported flour were softer compared with that with domestic flour. In gumminess and brittleness, cakes with domestic white flour showed the highest value while that with the imported flour showed the lowest value. For the color measurements of cake crumb, no significant difference in DE was found among the samples. Regarding the cross-sections of the cake observed using SEM, imported flour produced cake with smaller and more even air cells compared to that with the domestic flour cake. In sensory evaluation, cakes with the domestic white flour showed the highest moistness value. But there was no significant difference in springiness, firmness, adhesiveness and ease of swallow among the samples. In conclusion, cakes with domestic white flour and whole wheat flour were as good as that with imported cake flour for the sponge cake preparation.
        4,000원
        10.
        2007.10 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Physicochemical and sensory characteristics of the green tea dasik varying the added value of oligosaccharide were investigated and the products were surveyed by elementary school students regarding the acceptability. Protein and ash contents were significantly higher and fat contents were significanlty lower in the samples with oligosaccharides compared to those in commercial ones(p<0.05). Commercial samples had significantly higher values in all of the textural characteristics using textural analyzer compared to those of the developed dasik sample groups. In analytical sensory evaluation, varying the amount of oligosaccharide, commercial samples had significantly higher values of sweetness, hardness, and cohesiveness and lower values of savory aroma and falvor compared to those of developed dasik(p<0.05). Savory aroma and flavor were highly negatively correlated with textural hardness, springiness, chewiness, gumminess, and cohesiveness(p<0.01), while sensory sweetness and hardness were significantly positively correlated with textural springiness(p<0.05), chewiness, gumminess, and cohesiveness(p<0.01). When surveying elementary school students regarding the acceptability of green tea dasik and commercial samples, green tea dasik 2 was the most preferred with significance in color. Regarding aroma, green tea dasik 1 received the highest acceptability (p<0.05). In the flavor, both dasik 1 and 2 received higher score than those of the commercial dasik. In overall acceptability, both green tea dasik 1 and 2 were preferred to the commercially sold ones with significance(p<0.05).
        4,000원
        11.
        2006.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        가막만 소호 인근해역의 용존산소 농도에 따른 등물 플랑크톤 군집 동태를 연구하기 위해 2005년 8월 22일 부터 9월 15일까지 연구를 실시하였다. 본 연구결과 저층의 용존산소 농도가 3mgL-1 이하일 때는 동물플랑크톤 출현 개체수는 현저히 낮게 나타나거나 전혀 나타나지 않았다. 수층별 분포와 출현 개체수에 대한 저층의 저산소화 영향을 연구한 결과, 용존산소 농도는 저층으로 갈수록 낮게 나타났으며, 연구해역의 동물플랑크톤 출현 개체수는 대부
        4,000원
        12.
        2006.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        연안해역의 수질특성 및 일차생산 증가 메커니즘을 이해하는 데에 기초 자료로 활용하기 위하여, 많은 양의 담수 유입 후 규조류가 대량 번식한 상태와 담수가 유입되지 않고 적조가 발생하지 않은 상태의 해수의 수질특성을 조사차였으며 그 결과를 요약하면 아래와 같다. 1) 호우로 많은 양의 담수가 유입된 해역에서 규조류인 Skeletonema costatum와 Thalassiosira spp.가 각각 1,200~5,000cells/mL, 750~1,200cells/mL의 농도로 관찰되었다. 2) 규조류가 대량으로 증식하지 않은 곳보다 규조류가 대량으로 증식한 곳에서 수온, PH, 용존산소농도가 높게 조사되어, 두 곳 사이의 거리가 20m 정도에 불과함에도 불구하고 두 곳의 수질특성 차이는 뚜렷하게 나타났다. 3) 규조류가 대량으로 증식하지 않은 곳보다 규조류가 대량으로 증식한 곳에서 질소 인, 규소의 농도가 낮게 조사되어, 호우로 질소, 인, 규소보다는 규조류가 증식하기 위해 필요한 미량원소가 육지로부터 풍부하게 유입된 것으로 보인다. DIN/DIP, DIN/SiO2-Si 비는 모두 규조류가 대량 증식한 정점과 그렇지 않은 정점간의 뚜렷한 차이는 없었다.
        4,000원
        13.
        2004.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Even though performance-based language tests are often multivariate by design, previous validation studies have analyzed the dependability of ratings of such tests within univariate analytic frameworks. In an attempt to address this limitation, the present study investigated the dependability of judgements made based on ratings of a German speaking test using a multivariate generalizabilitiy theory (MGT) analysis. Data obtained from 88 students were analyzed in G- and D-studies of a two-facet crossed design. A D-study with two raters and two tasks supported the high dependability of the ratings and the placement decisions made at the pre-determined cut scores. An optimization analysis of the measurement procedure suggested that the desired level of dependability of ratings has already been achieved by the use of two raters and two tasks. The MGT analysis also generated other useful information about the convergent/ discriminant validity of the five subscales. Specifically, the universe score variance-covariance matrix obtained from the D-study showed that the underlying subscales were interrelated but distinct. Furthermore, the analysis of effective weights of the scales revealed that the Grammar subscale played the dominant role in the composite universe score variance.
        5,100원
        15.
        2001.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        4,000원
        16.
        2000.06 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        5,100원
        18.
        2000.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        We have presented detected molecules, atoms, radicals, ions, and dimers in the atmospheres of planets and comets from Earth-based and spaceborne observatories during the last 3 decades. We have reviewed spectroscopic studies on the auroral emissions and air glows of the giant planets, and briefly summarized spectroscopic observations of dimers in the atmospheres of the giant planets and Titan. In particular, we highlighted the recent detections of new molecular emissions and absorptions in the spectra of the giant planets, Titan, and recent bright comets from spaceborne or ground-based observatories. We also reviewed current models and theories of the origin and evolution of the solar system, and implications of isotopic ratios in these atmospheres.
        4,000원
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