• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.5
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• pp.196-201
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• 2014

We investigated defects and surface polarity in AlN and GaN by using wet chemical etching. Therefore, the effectiveness and reliability of estimating the single crystals by defect selective etching in NaOH/KOH eutectic alloy have been successfully demonstrated. High-quality AlN and GaN single crystals were etched in molten NaOH/KOH eutectic alloy. The etching characteristics and surface morphologies were carried out by scanning electron microscope (SEM) and atomic force microscope (AFM). The etch rates of AlN and GaN surface were calculated by etching depth as a function of etching time. As a result, two-types of etch pits with different sizes were revealed on AlN and GaN surface, respectively. Etching produced hexagonal pits on the metal-face (Al, Ga) (0001) plane, while hexagonal hillocks formed on the N-face. On etching rate calibration, it was found that N-face had approximately 109 and 15 times higher etch rate than the metal-face of AlN and GaN, respectively. The size of etch pits increased with an increase of the etching time and they tend to merge together with a neighbouring etch pits. Also, the chemical mechanism of each etching process was discussed. It was found that hydroxide ion ($OH^-$) and the dangling bond of nitrogen play an important role in the selective etching of the metal-face and N-face.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.3
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• pp.99-105
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• 2014

$LiCoO_2$ thin film have received attention as cathodes of thin-film microbatteries. In this study, $LiCoO_2$ thin films were synthesized on Au substrates by sol-gel spin coating method and electrochemical properties were investigated under annealing temperature and time. The phycochemical properties of $LiCoO_2$ thin film were investigated by X-ray diffraction, scaning electron microscopy and atomic force microscopy. The electrochemical properties were characterized using galvanostatic charging/discharging cycling tests. From X-ray diffraction, as-grown films annealed at $550^{\circ}C$ and $750^{\circ}C$ are presumed to be spinel structure and a single phase of the layered-rock-salt, respectively. The RMS roughness and grain size of the films which annealed at $750^{\circ}C$ has similar values for annealing time 10 and 30 min, while for annealing time 120 min surface roughness, grain size increase and pore appearance were observed. The first discharge capacity of $LiCoO_2$ thin films annealed at $750^{\circ}C$ for 10, 30 and 120 min is about 54.5, 56.8 and $51.87{\mu}Ah/cm^2{\mu}m$, respectively. Corresponding capacity retention at 50th cycle is 97.25, 76.69, 77.19%.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.2
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• pp.89-93
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• 2017

GaN single crystals were grown by controlling of various processing parameters such as growing temperature, V/III ratio and growing rate. We optimized thickness of bulk GaN single crystal by analyzing defect of surface and inside of the GaN single crystal for application to high brightness and power device. 2-inch bulk GaN single crystals were grown by HVPE (hydride vapor phase epitaxy) on sapphire and their thickness was 0.3~7.0 mm. Crystal structure of the grown bulk GaN was analyzed by XRD (X-ray diffraction). The surface characteristics of the grown bulk GaN were observed by OM (optical microscope) and SEM (scanning electron microscopy) with measuring EPD (etch pits density) of the GaN crystals.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.2
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• pp.94-98
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• 2017

In the past few years, Sn-3.0Ag-0.5Cu (weight%) solder composition has been a representative material to electronic industries as a replacement of Pb-base solder alloy. Therefore, extensive studies on process and/or reliability related with the composition have been reported. However, recent rapid rise in Ag price has demanded solder compositions of low Ag content. In this study, Sn-3.0Ag-0.5Cu solder bar sample was fabricated by melting of Sn, Ag and Cu metal powders. Crystal structure and element concentration were analyzed by XRD, optical microscope, FE-SEM and EDS. The Sn-3.0Ag-0.5Cu solder sample was composed of ${\beta}$-Sn, ${\varepsilon}-Ag_3Sn$ and ${\eta}-Cu_6Sn_5$ phases.

• Korean journal of communication and information
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• v.62
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• pp.179-199
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• 2013

This study is aimed to draw the meaning and possibility of political participation of the SNS users through a phenomenological analysis of participation and awareness of authentication shot for vote of the users. Especially, the reason for focusing on 'SNS vote authentication shot' is because the creative imagination of the users and the meaning and possibility of collective intelligence are drew while citizens are participating in political activities for themselves. Theory resources are based on technical imagination of Vil$\acute{e}$m Flusser that is concerned with users and political practice in the New Media Era, creative imaginer and discussions of collective intelligence of Pierre L$\acute{e}$vy. Based on these theoretical discussions, it is aimed to select the SNS users experienced in authentication shot for the by-election for mayor of Seoul in 26. Oct. 2011 and to use phenomenological analysis model on materials collected after in-depth interview. The researchers take contextual circumstance into consideration for experiences of study participants sticking to SNS users' opinions and intersubjectivity and approach prejudice of their experiences to untouched structure of phenomenon and meaning. It is because a phenomenological study exploring "the own meaning of 'die Sachen'" is 'strict study' and method focusing on the political participation of SNS users itself.

• Korean journal of communication and information
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• v.62
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• pp.264-285
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• 2013

The goal of the study is to analyze some structural issues of e-sport industry which has rapidly developed since 2000. Most of the previous studies regarding e-sport dealt with e-sport in terms of industrial prospect and economic values. In this study, we attempted to focus on employees of the field using in-depth interview method. Research findings show that there were several reasons for younger workers to early enter into the industry such as individualized labor market of post-modern era, growth of IT industry, and diversion of related occupational categories. The development of e-sport industry was possible with the youth' passion for the industry. However, their labor so called "professional" is vulnerable without systematic structure for them. This indicates that industrial prospect of e-sport industry and business models are not healthy. In addition, some implications of the findings were discussed.

• Journal of the Korean Association of Geographic Information Studies
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• v.3 no.2
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• pp.1-10
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• 2000

The purpose of this study is to develope a parcel-based automatic simulation system of land price through the integration of urban mathematical model and GIS. The appraisal process of public land price by the local government is simple but is a great time-consuming task. Moreover, it doesn't provide any statistical analysis and spatial presentation tools. So, it is difficult for planners or administrative officials to analyze the variation of land price with spatial idea. From these, a system is developed combining two sub-systems, they are ANN(Artificial Neural Network) for the calculation of land price and GIS for visual presentation. Using Matlab application, ANN model was designed having 3-layer structure and was trained with the sample data taken from Chinju city. With the trained network, the impact of 'road', 'parks', 'height control district' and 'beauty district' on land price in 9 regions(dong) are simulated. The results of the simulation were visualized with ArcView GIS. The automatic simulation system operated through the DDE(Dynamic Data Exchange) conversation between two applications. ArcView was set as client and Matlab as server. Scripting in ArcView and customizing a window of ArcView, this system can execute the whole process of simulation by just clicking a button with mouse. As a conclusion, this system was proved to be an effective and easily controllable planning support system for the land price simulation.

• Journal of the Korean Association of Geographic Information Studies
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• v.14 no.3
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• pp.203-222
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• 2011

The characteristics of flood damages have been increasingly strengthened and take the form of unpredictable and unusual weather phenomena caused by climate change and climate anomalies. To prevent inundation damage caused by breach of hydraulic structure such as dam or levee, and trouble of drainage of inner basin, the prediction necessity of flood inundation area, flood risk analysis, and drawing flood risk maps have been on the rise, and the national flood risk maps have been produced. In this study, the quantitative flood vulnerability analysis was performed, which represents population living within flood-affected areas, types of economic activities, facilities affected by flood, in order to extend flood risk mapping from simple hazard concept into risk based idea. By applying it to Nakdong River basin, the flood vulnerability indices were estimated to draw flood risk maps subdivided into administrative districts. The result of this study can be applied to establish the disaster prevention measures and priority decision of disaster prevention project.

• Journal of the Korean Association of Geographic Information Studies
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• v.17 no.3
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• pp.82-92
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• 2014

The ratio of using soil as the main material in construction is quite numerous, and it covers many parts in forms and bases of the structure. Thus, the earthwork forms many structures for social infrastructure, and the stability of these structures is most crucial when completed than under construction. This study executed a field experiment to evaluate the accuracy and utility of the slope, which is an important part in earthwork, when terrestrial LiDAR is obtained, and the results are as follow. First, as the result of the observation using Total Station and terrestrial LiDAR, the horizontal error RMSE was ${\pm}2.2cm$, and the vertical error RMSE was ${\pm}3.0cm$. As the result of the comparison between the errors and permissible range of public surveying regulation, it sufficiently secure the accuracy. Also, the extraction of the check section, which covers the most important part among the stability checks could be scientifically and rationally processed, and these extraction results are expected to be provided as important basic materials for the earthwork slop stability evaluation.

• Journal of the Korean Association of Geographic Information Studies
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• v.17 no.3
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• pp.104-115
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• 2014

A levee is defined as an man-made structure protecting the areas from temporary flooding. This paper suggests a methodology for establishing the levee GIS database using the airborne topographic LiDAR(Light Detection and Ranging) data taken in the Nakdong river basins and the WAMIS(WAter Management Information System) information. First, the National Levee Database(NLD) established by the USACE(United States Army Corps Engineers) and the levee information tables established by the WAMIS are compared and analyzed. For extracting the levee information from the LiDAR data, the DSM(Digital Surface Model) is generated from the LiDAR point clouds by using the interpolation method. Then, the slope map is generated by calculating the maximum rates of elevation difference between each pixel of the DSM and its neighboring pixels. The slope classification method is employed to extract the levee component polygons such as the levee crown polygons and the levee slope polygons from the slope map. Then, the levee information database is established by integrating the attributes extracted from the identified levee crown and slope polygons with the information provided by the WAMIS. Finally, this paper discusses the advantages and limitations of the levee GIS database established by only using the LiDAR data and suggests a future work for improving the quality of the database.