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        검색결과 216

        150.
        2004.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This study examined the knowledge and practices of scientific inquiry displayed by three student teachers and two beginning teachers at secondary levels. Observations using the instrument of OTOP designed by the research team of OCEPT (Oregon Collaborative for Excellent in the Preparation of Teachers) generalized similar teaching strategies of scientific inquiry between student and beginning teachers, such as using group work for students' first hand experience, using concrete materials for experimentation or visual tools for demonstration, using questions for factual knowledge mainly without opportunities to understand how scientific knowledge is constructed. Those scientific inquiry activities were very confirmative ones to follow the steps without opportunities of understanding nature of science or nature of scientific inquiry. However, all participants in this study hold knowledge of scientific inquiry envisioned by the National Science Education Standards [NSES] (NRC, 1996), where students identify their hypothesis, use critical and logical thinking, and consider alternative explanations through argumentation as well as experimentation. An inconsistent relationship between participating teachers knowledge and practices about scientific inquiry resulted from their lack of pedagogy skills of implementing it in the classroom. Providing opportunities for these teachers to reflect on their beliefs and practices about scientific inquiry was recommended for the future study. Furthermore, increasing college faculty interest in new teaching approaches for upgrading the content knowledge of student teachers and beginning teachers was recommended as a solution, since those teachers showed evidence of influence by college faculties at universities in their pedagogy skills.
        4,900원
        152.
        2003.03 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Recent observations have shown that coronal magnetic fields in the northern (southern) hemisphere tend to have negative (positive) magnetic helicity. There has been controversy as to whether this hemispheric pattern is of surface or sub-surface origin. A number of studies have focused on clarifying the effect of the surface differential rotation on the change of magnetic helicity in the corona. Meanwhile, recent observational studies reported the existence of transient shear flows in active regions that can feed magnetic helicity to the corona at a much higher rate than the differential rotation does. Here we propose that such transient shear flows may be driven by the torque produced by either the axial or radial expansion of the coronal segment of a twisted flux tube that is rooted deeply below the surface. We have derived a simple relation between the coronal expansion parameter and the amount of helicity transferred via shear flows. To demonstrate our proposition, we have inspected Yohkoh soft X-ray images of NOAA 8668 in which strong shear flows were observed. As a result, we found that the expansion of magnetic fields really took place in the corona while transient shear flows were observed in the photosphere, and the amount of magnetic helicity change due to the transient shear flows is quantitatively consistent with the observed expansion of coronal magnetic fields. The transient shear flows hence may be understood as an observable manifestation of the pumping of magnetic helicity out of the interior portions of the field lines driven by the expansion of coronal parts as was originally proposed by Parker (1974).
        4,000원
        153.
        2003.01 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In Namyang Bay of western Korea, macrotidal-flat deposits are divisible into three late Quaternary units: Unit M1 of upper marine mud, Unit T1 of middle siderite-bearing terrestrial clay, and Unit M2 of lower marine mud. Unit M1 represents typical Holocene intertidal mudflat deposits, showing a coarsening-upward textural trend. It probably resulted from the continual retrogradation of tidal flat during the mid-to-late Holocene sea-level rise. Reddish brown-color Unit T1 consists of homogeneous clay with abundant freshwater siderite grains and plant remains. Unit T1 is clearly separated from the overlying Unit M1 by a sharp lithologic boundary. Radiocarbon age, siderite grains and lithologic features indicate that Unit T1 is originated from freshwater bog or swamp deposition infilling the localized topographic lows during the early Holocene age. Overlain unconformably by early Holocene swamp clay, Unit M2 is orange to yellow in color and mottled, suggesting significant degree of weathering during the sea-level lowstand. Such subaerial oxidation is confirmed in the vertical profiles of geotechnical properties, clay mineral assemblages and magnetic susceptibility. Unit M2 appears to be correlated with the upper part of the late Pleistocene tidal deposits developed along the western Korean coast. The sedimentary succession of the Namyang-Bay tidal-flat deposit provides stratigraphic information for the Holocene-late Pleistocene unconformity and also permits an assessment of the preservation potential of the late Pleistocene marginal marine deposit along the western coast of Korea.
        4,800원