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Optical and Near-IR Photometry of the NGC 4874 Globular Cluster System with the Hubble Space Telescope

  • Cho, Hyejeon;Blakeslee, John P.;Peng, Eric W.;Lee, Young-Wook
    • The Bulletin of The Korean Astronomical Society
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    • v.38 no.2
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    • pp.37.1-37.1
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    • 2013
  • We present our study of analyzing the photometric properties of the globular cluster (GC) system which resides in the extended halo of the central bright Coma cluster galaxy NGC 4874. The core of the Coma cluster of galaxies (Abell 1656) was observed with both the HST Advanced Camera for Surveys (ACS) in the F475W (g475) and F814W (I814) and Wide Field Camera 3 IR Channel (WFC3/IR) in the F160W (H160) filters. The data analysis procedure and GC candidate selection criteria are briefly described. We investigate the interesting "tilt" features in color-magnitude diagrams for this GC system and their link to the nonlinear color-metallicity relation for GCs. The NGC 4874's GC system exhibits a bimodal distribution in the optical g475-I814 color and much more than half the GCs fall in the red side at g475-I814 ~ 1.1. This bimodality is weakened in the optical-IR I814-H160 color; the quantitative analysis on the features of both color distributions using the Gaussian Mixture Modeling code proves the bimodalities are different. Both colors, thus, cannot linearly reflect the bimodality of an underlying metallicity, supporting the suggestion that observed bimodalities in extragalactic GC colors are the metallicity-to-color projection effect.

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A Study on the Monitoring of Laser Welding for S45C Steel Sheets Using Nd:YAG Laser with Continuous Waves (연속파형 Nd:YAG레이저를 이용한 S45C 강판의 레이저 용접 모니터링에 관한 연구)

  • Kim, Do-Hyoung;Shin, Ho-Jun;Yoo, Young-Tae
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.21 no.5
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    • pp.814-823
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    • 2012
  • Fluctuation of light intensity from the keyhole becomes more significant in full penetration welding than partial penetration welding, since the plasma produced in the keyhole can escape from the rear side of the keyhole. The plasma optical radiation emitted during Nd:YAG laser welding of S45C steel samples has been detected with a Photodiode and analyzed under different process conditions. As the results, the BOP was performed for welding, behavior of plasma, spatter or plume was monitored to determine the reference signal. Then, random combination was made for comparison with the reference signal, which aimed at verifying reliability of the welding monitoring system that this study intended to develop.

The Development and Application of Strategies using Children's Science Verses in Elementary Science Teaching (초등학교 과학수업에서 과학동시를 활용하는 전략의 개발과 적용)

  • Jeong, Shin-Ae;Kwon, Nan-Joo
    • Journal of The Korean Association For Science Education
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    • v.28 no.8
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    • pp.814-822
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    • 2008
  • This study plans to develop strategies using children's verse in science education and investigate the effects of instruction using children's verses on the attitude toward science. The study tried to determine strategies using children's science verse in order to find out their value. For the purpose of this, two classes of the 6th grade were selected in an elementary school for tests. The results from this research showed that strategies using children's verse in science education were developed and applied in teaching/learning purposes as well as in the area of literature. A strategy for remembering was applied widely. A strategy for understanding scientific principles and for quest methods, writing children's science verses directly helped in scientific conceptual formation. Instruction using children's science verses had a positive effect on the attitudes toward science. Students maintained positive attitudes throughout instruction that used children's science verses. In conclusion, instruction using children's science verses can be applied to science education, and the attitudes toward science and learning achievements can be improved.

Determination of Design Parameters of Stockbridge Damper (스톡브리지 댐퍼 설계 파라미터 선정)

  • Kim, Chan-Jung
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.26 no.7
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    • pp.814-819
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    • 2016
  • The Stockbridge damper is used to control the aeolian vibration of a overhead transmission line due to the natural wind under a low velocity, between 1 m/s to 7 m/s. The damper model can be simply derived with several design parameters and the location of eigenvalues of design parameters are important to determine the efficiency of energy dissipation by excitation itself with two counterweights. First, the importance of resonance frequencies of Stockbridge damper was reviewed through the analysis of frequency response function of damper system. Then, the best selection of design parameters was investigated with the introduction of objected function that minimize the distance between the calculated eigenvalues and target frequency points. The best choice of design parameters was reviewed using the simulated results from the objective function and the effectiveness of selected design case was discussed at the point view of practical implementation.

A study on Dutch populace's costumes in the 16th century- Focusing on men's costumes depicted in Pieter Bruegel the Elder's paintings - (16세기 네덜란드 서민복식에 대한 연구- 피터 브뤼겔의 회화 작품에 묘사된 남성복식을 중심으로 -)

  • Hyun Jin, Cho
    • The Research Journal of the Costume Culture
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    • v.30 no.6
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    • pp.814-827
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    • 2022
  • This study examines the social and artistic aspects of the Netherlands in the 16th century, focusing on the paintings of Pieter Bruegel the Elder (1525-1569), a repre- sentative Dutch painter at that time. Also analyzed were the types and characteristics of each item of the male populace's and nobles' costumes at that point in the Renaissance. The results are as follows: most of the populace's chemises do not have frills on the neckline and sleeves; the doublet has a loose body and sleeves overall; and the sleeves and armholes are fixed with sewing rather than being detachable, making the epaulet invisible. The neckline of the doublet usually does not have a collar, but it sometimes has a hood. In the case of trousers, most males are shown wearing waist-high stockings, and a piece of cord is visible. It seems that the populace's coats were mainly Spanish-style capes. The 16th-century Dutch populace's costumes are imitative-reflecting a desire to emulate the codpieces and hairstyles of the aristocrats-while providing individuality through hats and belts. In terms of practicality, it appears that a knife and pouch were used in various living environments. This trend can be seen as a reflection of populace's perception of the costume at the time.

Electrochemical Ionic Mass Transfer Correlation in Fluid-Saturated Porous Layer

  • Cho, Eun Su
    • Korean Chemical Engineering Research
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    • v.53 no.6
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    • pp.814-817
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    • 2015
  • A new ionic mass transfer correlation is derived for the fluid-saturated, horizontal porous layer. Darcy-Forchheimer model is used to explain characteristics of fluid motion. Based on the microscales of turbulence a backbone mass transfer relation is derived as a function of the Darcy-Rayleigh number, $Ra_D$ and the porous medium Schmidt number, $Sc_p$. For the Darcy's limit of $Sc_p{\gg}Ra_D$, the Sherwood number, Sh is a function of $Ra_D$ only. However, for the region of high $Ra_D$, Sh can be related with $Ra_DSc_p$. Based on the present backbone equation and the electrochemical mass transfer experiments which are electro plating or electroless plating, the new ionic mass transfer correlation is suggested in the porous media.