• The Mathematical Education
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• v.53 no.3
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• pp.313-327
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• 2014

'Tangent' is one of the most important concepts in the middle and high school mathematics, especially in dealing with calculus. The concept of tangent in the current textbook consists of the ways which make use of discriminant or differentiation. These ways, however, do not present dynamic view points, that is, the concept of variation. In this paper, after applying 'Roberval's way of finding tangent using vectors in terms of kinematics to parabola, ellipse, circle, hyperbola, cycloid, hypocycloid and epicycloid, we will identify that this is the tangent of those curves. This trial is the educational link of mathematics and physics, and it will also suggest the appropriate example of applying vector. We will also help students to understand the tangent by connecting this method to the existing ones.

• Journal of Korean Home Economics Education Association
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• v.10 no.1
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• pp.153-169
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• 1998

The purposes or this study were to develop the scientific experimental model, experimental guidelines for teachers, experiment planning & report form for students, and evaluation scales for the Home Economics Textiles class in high school. First, through review of literature concerned, scientific experimental model was defined, and the usefulness of this model on the teaching situation testified on other subjects such as Physics and Bilolgy, was reviewed. Secondly, scientific experimental model, experimental guidelines for teachers, experiment planning & report form for students, and evaluation scale were developer on the bases on APU evaluation model, experimental guidelines for teachers, experiment planning & report form for students, evaluation scale applicable to the teaching situation ere established by analysing the significant differences scientifically.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.74-75
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• 2008

This work has suggested corrugation beam as a new structure for mechanical resonators. Micro beam resonators based on 3C-SiC films which have two side corrugations along the length of beams were simulated by finite-element modeling and compared to a flat rectangular beam with the same dimension. With the dimension of $36\times12\times0.5{\mu}m^3$, the flat cantilever has resonant frequency of 746 kHz. Meanwhile, this frequency reaches 1.252 MHz with the corrugated cantilever which has the same dimension with flat type but corrugation width of $6{\mu}m$ and depth of $0.4{\mu}m$. It is expected that mechanical resonators with corrugations will be very helpful for the research of sensing devices with high-resolution, high-performance oscillators and filters in wireless communications as well as measurement in basic physics.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.1
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• pp.79.2-79.2
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• 2012

This study is aim to understand the distribution and the property of LISM (local interstellar medium) using the high resolution spectra of the 26 early type stars in the five open clusters ( IC 4665, Stephenson 1, Collinder 359, Roslund 5 and Collinder 70). These spectra have been observed by BOES in Bohyunsan observatory from 2009 November to 2011 Feburary, of which resolution is 45,000. We used IRAF for the data reduction (Bias subtraction, Flat-field division, and wavelength calibration) and DECH for the deriving the equivalent widths of 4 interstellar lines - Ca II K (3934${\AA}$), Na I D (5890, 5896${\AA}$) and K I (7698${\AA}$) and the column densities of those elements in LISM toward the clusters. The results of this study provide clues for better understanding of the LISM toward these clusters.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.46.1-46.1
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• 2017

Late-type galaxies falling into a cluster would evolve being influenced by the interactions with both the cluster and the nearby cluster member galaxies. Most numerical studies, however, tend to focus on the effects of the former with little work done on those of the later. We thus perform numerical study on the evolution of a late-type galaxy falling radially toward the cluster center interacting with neighbouring early-type galaxies, using N-body, hydrodynamical simulations. Based on the information about the typical galaxy encounters obtained by using the galaxy catalog of Coma cluster, we run the simulations for the cases where a Milky Way Galaxy-like late-type galaxy, flying either edge-on or face-on, experiences six consecutive collisions with twice more massive early-type galaxies having hot gas in their halos. Our simulations show that the evolution of the late-type galaxy can be significantly affected by the high-speed multiple collisions with the early-type galaxies, such as on the cold gas content and the star formation activity, particularly through the hydrodynamic interactions between the cold disk and the hot gas halos. By comparing our simulation results with those of others, we claim that the role of the galaxy-galaxy interactions on the evolution of late-type galaxies in clusters could be comparable with that of the galaxy-cluster interactions, depending on the dynamical history.

• Progress in Superconductivity and Cryogenics
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• v.12 no.2
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• pp.9-12
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• 2010

A lamination system using reflow soldering was developed to enhance the mechanical properties of high temperature superconductor (HTS) tape. The laminated coated conductor tape was fabricated using the continuous lamination process. The mean, maximum, and minimum tensile loads in a T-peel test of the laminated coated conductor were 9.9 N, 12.5 N, and 7.6 N, respectively. The critical current ($I_c$) distributions of the non-laminated and laminated coated conductor were compared using anon-contact Hall probe method. The transport $I_c$ nearly matched the non-contact $I_c$; however, some degraded Ic regions were found on the length of 800 cm of laminated coated conductor. We confirmed that the cause of the partially degraded $I_c$ was due to an increase in line tension by (1) solidification induced by a change of composition that usually occurs in molten brass (Cu, Zn) in solder, or (2) non-homogeneity of the thickness of the coated conductor or metal tapes. We suggest that reflow soldering is a promising method for reinforced HTS tape if the controlling solder thickness and lamination guide are modified.

• Journal of The Korean Association For Science Education
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• v.20 no.1
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• pp.77-87
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• 2000

The purpose of the study is to understand the change process of middle school students' physics conceptions by the presented types of conflict situations. 274 middle school students were selected from one school in Pusan, however 257 students were participated in all the procedure of the study. After we classified students' physics conceptions into scientific and unscientific conceptions, presented three types of conflict situations. In this study three different cognitive conflict strategies were adopted; the first one is logical arguments(LCS: logical conflict situation), the second is actual demonstration(DCS: demonstrational conflict situation), and the third is two strategies together(DLCS). In this study, first, we investigated the change process of students' physics conceptions by three types of conflict situations. Second, we compared the effect of three conflict situations presentation, which includes positive effect by conceptual change from misconception to scientific conception and negative effect by conceptual change from scientific conception to misconception. Third, we studied characteristics of conceptual change by characteristics of conflict situations. In result, DLCS group and DCS group were more positive effect than LCS group in mechanics, DLCS group and LCS group were more positive effect than DCS group in electricity. It seems that mechanics are closely related to physical experiences, while electricity are more abstract.

• Journal of Science Education
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• v.43 no.2
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• pp.195-206
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• 2019

The study aims to find a way to guarantee high school students choose science subjects by exploring its necessity as a prerequisite for admission to university science and engineering major courses. For this purpose, a survey was administered to 516 science & engineering college students to investigate their cognition and completion of the prerequisite science subjects related to their major, department adjustment, and influence on their major of study. Among nine major clusters, Physics was identified as a science domain with a high relevance to majors in five major clusters, and Chemistry in three. The students who completed both science I and II subjects related to their majors responded most positively to the usefulness of prerequisite subjects to their studies. Suggestions include conditions for the opening of science II subjects, strengthening the connection between science subjects and IT, promotion of linkage between the prerequisite subject and major studies to assert students' choice of science subjects in high school.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1163-1164
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• 2006

TZM alloy having elongated coarse-grain structure was developed by three-step internal nitriding treatment at 1423 to 1873 K in $N_2$ and subsequent recrystallization treatment at 2173 K in vacuum. Some specimens were subjected to re-nitriding treatment at 1873 K for 16 h. After the recrystallization treatment, aspect ratio (L/W) of grains for rolling direction was about 50 at the maximum. Yield stress obtained at 1773 K after re-nitriding treatment was about 6 times as large as that of recrystallized specimen. Re-nitriding was very effective in the improvement in strength of TZM alloy having elongated coarse-grain structure.

• Proceedings of the KSRS Conference
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• v.1
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• pp.316-319
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• 2006

Monthly-mean aerosol parameters derived from the 1998-2004 SeaWiFS observations over East Asian waters are analyzed. SeaWiFS GAC Level 1 data covering the Northeast Asian area are collected and processed by the standard atmospheric correction algorithm released by the SeaWiFS Project to produce daily aerosol optical thickness (AOT) and ${{\AA}}ngstr{\ddot{o}}m$ exponent imageries. Monthly mean AOT and ${{\AA}}ngstr{\ddot{o}}m$ exponent values are extracted from the daily composite images for six study areas chosen from the surrounding waters of Japan. A slight increasing trend of ${{\AA}}ngstr{\ddot{o}}m$ exponent is found and interpreted as about 4-5% increase in submicron fraction of aerosol optical thickness at 550nm. Two cloud screening methods, including the standard cloud masking method of SeaWiFS and the one based on the local variance method, are applied to the SeaWiFS data processing, in an attempt to inspect the influence to the observed statistical uptrend which probably induced by different cloud mask algorithms. The variability comes from the different cloud masking algorithms are discussed.