• Journal of The Korean Astronomical Society
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• v.47 no.1
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• pp.1-13
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• 2014

We analyze the dependence of disk morphology (arm class, Hubble type, bar type) of nearby spiral galaxies on the galaxy environment by using local background density (${\Sigma}_n$), projected distance ($r_p$), and tidal index (T I) as measures of the environment. There is a strong dependence of arm class and Hubble type on the galaxy environment, while the bar type exhibits a weak dependence with a high frequency of SB galaxies in high density regions. Grand design fractions and early-type fractions increase with increasing ${\Sigma}_n$, $1/r_p$, and T I, while fractions of flocculent spirals and late-type spirals decrease. Multiple-arm and intermediate-type spirals exhibit nearly constant fractions with weak trends similar to grand design and early-type spirals. While bar types show only a marginal dependence on ${\Sigma}_n$, they show a fairly clear dependence on $r_p$ with a high frequency of SB galaxies at small $r_p$. The arm class also exhibits a stronger correlation with $r_p$ than ${\Sigma}_n$ and T I, whereas the Hubble type exhibits similar correlations with ${\Sigma}_n$ and $r_p$. This suggests that the arm class is mostly affected by the nearest neighbor while the Hubble type is affected by the local densities contributed by neighboring galaxies as well as the nearest neighbor.

• Journal of the Korean Data and Information Science Society
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• v.18 no.1
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• pp.141-148
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• 2007

Recently, Korean national center for education statistics & information exhibits the results of forecast educational statistics from 2007 to 2021 year. The purpose of this paper is to suggest the errors and problems on the results of forecast educational statistics and the distribution of the number of students.

• Advances in nano research
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• v.2 no.2
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• pp.111-119
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• 2014

The chemical synthesis of anisotropic defective polyaniline/Ag composite (PANI/Ag) is explored using silver nitrate ($AgNO_3$) as the precursor material. This study provides a simple method for the formation of PANI/Ag nanocomposites at two different aniline concentrations $5{\mu}l$ (PANC5) and $10{\mu}l$ (PANC10). The composite PANC5 exhibits UV-Visible absorption peaks at 436 nm and 670 nm whereas, PANC10 exhibits absorption peaks at 446 nm and 697 nm. This shift is caused by the strong interaction between polyaniline and silver. The characterized FTIR peaks observed at around $3410cm^{-1}$ (PANC5) and $3420cm^{-1}$ (PANC10) was due to the N-H stretching vibrations. The appearance of a broad band instead of a sharp peak can be attributed due to the presence of a high concentration of N-H groups in the nanocomposite. The TEM images show that the sample contains defective spherical, truncated triangular and rod shaped particles. The results showed that the PANI/Ag nanocomposites are composed of nano-sized particles of 43-53 nm that contain Ag domains of 33-37 nm with polymer thickness 5.7-11.2 nm at two different aniline concentrations.

• Bulletin of the Korean Chemical Society
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• v.33 no.6
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• pp.1929-1933
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• 2012

Two cobalt(II) compounds $[Co(2,2{^\prime}-bipy)(H_2O)_2(SO_4)]_n$ (1) and $[Co_2(2,2^{\prime}-bipy)_2(btec)(H_2O)_6]{\cdot}2H_2O$ (2) (2,2'-bipy = 2,2'-bipyridine, $H_4btec$ = 1,2,4,5-benzenetetracarboxylic acid), have been simultaneously synthesized by a one-pot slow solvent evaporation reaction. Their structures were determined by single-crystal X-ray diffraction and further characterized by X-ray powder diffraction (XRPD), IR, elemental and thermogravimetric analysis (TGA). The structural analysis reveals that compound 1 exhibits an infinite 1D chain structure with the octahedral Co(II) centers bridging by the tetrahedral ${\mu}_2-SO{_4}^{2-}$ ligands, while compound 2 possesses a dinuclear $Co_2(2,2^{\prime}-bipy)_2(btec)(H_2O)_6$ unit and the two adjacent octahedral Co(II) ions are linked by the bismonodentately coordinated btec ligand. Additionally, compound 2 exhibits blue fluorescent emission in the solid state at room temperature.

• Journal of Sensor Science and Technology
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• v.29 no.6
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• pp.382-387
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• 2020

Hydrogen (H₂) is considered as a new clean energy resource for replacing petroleum because it produces only H₂O after the combustion process. However, owing to its explosive nature, it is extremely important to detect H₂ gas in the ambient atmosphere. This has triggered the development of H₂ gas sensors. 2-dimensional (2D) graphene has emerged as one of the most promising candidates for chemical sensors in various industries. In particular, graphene exhibits outstanding potential in chemoresistive gas sensors for the detection of diverse harmful gases and the control of indoor air quality. Graphene-based chemoresistive gas sensors have attracted tremendous attention owing to their promising properties such as room temperature operation, effective gas adsorption, and high flexibility and transparency. Pristine graphene exhibits good sensitivity to NO₂ gas at room temperature and relatively low sensitivity to H₂ gas. Thus, research to control the selectivity of graphene gas sensors and improve the sensitivity to H₂ gas has been performed. Noble metal decoration and metal oxide decoration on the surface of graphene are the most favored approaches for effectively controlling the selectivity of graphene gas sensors. Herein, we introduce several strategies that enhance the sensitivity of graphene gas sensors to H₂ gas.

• Journal of the Korean earth science society
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• v.37 no.6
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• pp.373-386
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• 2016

This study aims to investigate the kinds of content and science communication included in the exhibits and the exhibition panels in order to suggest a direction of desirable educational development in the nuclear power information halls in Korea. The four local nuclear power information halls in Korea and the nuclear power science center in Japan are selected as the subject. The results of this study show that the 'conceptual' exhibits are a dominant topic among the four topics of contents, and the concept (CON) and interest (INT) are found as the most dominating component of science communication. Meanwhile, the nature of science (NOS), awareness (AW), enjoyment (ENJ), and opinion (OP) components are little exhibited. The findings of this study indicate that the nuclear power information halls can be more professional to enhance scientific literacy, as the informal education institutions, providing information of nuclear energy and radiation on various perspectives for visitors to make decisions by themselves and to improve their scientific attitudes and understanding of science communication. In addition, the limited science communication can be fully reinforced by docents or commentators. Further research needs to investigate the development of a specialized program to produce professional docents or commentators.

• Applied Science and Convergence Technology
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• v.23 no.5
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• pp.261-264
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• 2014

$SrTiO_3$ (STO) single crystal irradiated with a 3-MeV proton beam exhibits blue and green mixed luminescence. However, the same proton beam when used to irradiate STO with a very thin layer of deposited Pt does not show any luminescence. This Pt layer prevents any damage which may otherwise be caused by arcing, which stems from the accumulated surface voltage of tens of kV due to the charge induced by secondary electrons on the surface of the insulator during the ion beam irradiation process. Hence, the luminescence of ion-irradiated STO originates from the modification of the STO surface layer caused by arcing rather than from any direct ion beam irradiation effect. STO treated with atmospheric-pressure plasma, a simple and cost-effective method, also exhibits the same type of blue and green mixed luminescence as STO treated with an ion beam, as the plasma also creates a layer of surface damage due to arcing.

• Journal of The Korean Association For Science Education
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• v.36 no.2
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• pp.191-202
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• 2016

In this study, a science museum teaching-learning model was developed with emphasis on play. In order to do this, the models of factor-centered museum education and process-centered museum education were reviewed and characteristics of science museum education were considered. The model developed in this study is called 'Play-Learning Model in Science Museum', and 'play' is defined as activities to achieve the mission in accordance with methods and rules set by individuals or small groups including scaffolding and play is divided into competition, simulation, and chance. 'Play-Learning Model in Science Museum' emphasizes learning using the articles on exhibition, scaffolding and interaction in small groups, and play. The model consists of four steps: 'Preparation', 'Exploring the exhibits', 'Experience', and 'Summary of learning content'. In the 'Preparation' step, the students form related knowledge and are ready to play. The 'Exploring the exhibits' step is the core step of this model, and entails the students solving problems in the mission by interacting with members of the small group. When they cannot find resolution, they get help. In the 'Experience' step, hands-on activities related to the prior step are included. In the 'Summary of learning content' step, the students summarize what they learned while playing. As science museum education is implemented in a variety of forms, continuous research about the science museum learning model and development of various programs are needed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.1
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• pp.1-9
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• 2014

In this paper, a reconfigurable polarization patch antenna that uses a Y-shaped feed is proposed. The proposed antenna consists of a square patch, a Y-shaped feeding structure, a PIN diode, and a bias circuit for diode operation. The structural symmetry/asymmetry of the feeding structure is determined by the on/off operation of the PIN diode that inserted into the side of one of the lines of the Y-shaped feeding structure. For the proposed reconfigurable antenna, the two microstrip lines of the feeding structure have the same length when the PIN diode operates in the on state, and the antenna exhibits linear polarization(LP). On the other hand, when the PIN diode operates in the off state, the length of one side line of the feeding structure is relatively shorter than that of the other line. Therefore, the antenna exhibits circular polarization(CP). From the measurement results, it is found that the proposed antenna exhibits good impedance matching and axial ratio. In addition, polarization switching can be easily achieved in the same operating band.

• Journal of The Korean Association For Science Education
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• v.25 no.3
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• pp.336-345
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• 2005

This study examined the efforts of both national and international science museums and centers to educate the public on recent developments in science, technology, social issues, and ethical issues by analyzing STS-related content exhibits. The results indicated that all science centers informed the public about recent science technology and relevant social and ethical issues by a variety of channels. However, science museums in Korea merely introduced new science and technology at the rudimentary level and used attractions to gather people's attention, which contributed in eliciting distorted thoughts on science and new technology. Science centers in Korea are in need of an upgrade. By analyzing science museums in foreign countries, a unique education on STS themes or scientific issues in Korea can be developed.