• Atmosphere
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• v.31 no.4
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• pp.377-394
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• 2021

The recent largest forest fire in the Yeongdong region, Goseung/Okgae fires of 2019 occurred during YangGang wind event. The wind can be locally gusty and extremely dry, particularly in the complex terrain of Yeongdong. These winds can cause and/or rapidly spread wildfires, the threat of which is serious during the dry spring season. This study examines the spatial variability of the surface wind and its coupling with the upper atmospheric wind using the data during the IOP of the Gangwon Yeongdong Wind Experiments (G-WEX) conducted in 2020 and the data during YangGang wind event on 4~5 April 2019. In the case of IOPs, strong wind at the surface with a constant wind direction appears in the mountain area, and weak wind with large variability in wind direction appears from foothill to the coast in the vicinity of Gangneung region. However, in the 2019 event, strong wind at the surface with a constant wind direction appears in the entire region from the mountain to the coast, even with the stronger wind in the coast than in some part of the mountain area. The characteristics of the upper atmospheric wind related with the spatial distribution of surface wind show that during IOPs of G-WEX, a strong downdraft exists near the mountaintop in the level of about 1 to 4 km. However, in the 2019 event a strong downdraft is reinforced, when its location moves toward the coast and descends close to the ground. These downdrafts are generated by the breaking of mountain waves.

• Atmosphere
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• v.33 no.3
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• pp.307-317
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• 2023

This study investigates the physical mechanisms that contributed to the 2022 European record-breaking heatwave throughout May-August (MJJA). The European climate has experienced surface warming and drying in the recent decade (1979~2022) which influences the development of the 2022 European heatwave. Since its spatial pattern resembles the 2003 European heatwave which is a well-known case developed by the strong coupling of near-surface conditions to land surface processes, the 2022 heatwave is compared with the 2003 case. Understanding heatwave development is carried out by the European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis version 5 (ERA5) and daily maximum surface temperature released by NCEP (National Centers for Environmental Prediction) CPC (Climate Prediction Center). The results suggest that the persistent high pressure along with clear sky tends to increase the downward shortwave radiation which leads to enhanced sensible heat flux with the land surface dryness. Terrestrial Coupling Index (TCI), a process-based multivariate metric, is employed to quantitatively measure segmented feedback processes, separately for the land, atmosphere, and two-legged couplings, which appears to the development of the 2022 heatwave, can be viewed as an expression of the recent trends, amplified by internal land-atmosphere interactions.

• Korean Journal of Materials Research
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• v.10 no.3
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• pp.212-217
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• 2000

Dielectric thin films for TFT(thin film transistor)s, such as silicon nitride$(Si_3N_4)$ and silicon oxide$(SiO_2)$, are usually deposited at $200~300^{\circ}C$. In this study, authors have tried to form dielectric films not by deposition but by oxidation with ECR(Electron Cyclotron Resonance) oxygen plasma, to improve the interface properties was not intensionally heated during oxidation. THe oxidation was performed consecutively without breaking vacuum after the deposition of a-Si: H films on the substrate to prevent the introduction of impurities. In this study, especially pulse mode of microwave power has been firstly tried during FCR oxygen plasma formation. Compared with the case of the continuous wave mode, the oxidation with the pulsed ECR results in higher quality silicon oxide$SiO_X$ films in terms of stoichiometry of bonding, dielectric constants and surface roughness. Especially the surface roughness of the pulsed ECR oxide films dramatically decreased to one-third of that of the continuous wave mode cases.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.92-92
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• 2014

Recently, many state-of-art spectroscopy techniques are used to unravel the mysteries of condensed matters. And numerous heterostructures have provided a new avenue to search for new emergent phenomena. Especially, near the interface, various forms of symmetry-breaking can appear, which induces many novel phenomena. Although these intriguing phenomena can be emerged at the interface, by using conventional measurement techniques, the experimental investigations have been limited due to the buried nature of interface. One of the ways to overcome this limitation is in situ investigation of the layer-by-layer evolution of the electronic structure with increasing of the thickness. Namely, with very thin layer, we can measure the electronic structure strongly affected by the interface effect, but with thick layer, the bulk property becomes strong. Angle-resolved photoemission spectroscopy (ARPES) is powerful tool to directly obtain electronic structure, and it is very surface sensitive. Thus, the layer-by-layer evolution of the electronic structure in oxide heterostructure can be investigated by using in situ ARPES. LaNiO3 (LNO) heterostructures have recently attracted much attention due to theoretical predictions for many intriguing quantum phenomena. The theories suggest that, by tuning external parameters such as misfit strain and dimensionality in LNO heterostructure, the latent orders, which is absent in bulk, including charge disproportionation, spin-density-wave order and Mott insulator, could be emerged in LNO heterostructure. Here, we performed in situ ARPES studies on LNO films with varying the misfit strain and thickness. (1) By using LaAlO3 (-1.3%), NdGaO3 (+0.3%), and SrTiO3 (+1.7%) substrates, we could obtain LNO films under compressive strain, nearly strain-free, and tensile strain, respectively. As strain state changes from compressive to tensile, the Ni eg bands are rearranged and cross the Fermi level, which induces a change of Fermi surface (FS) topology. Additionally, two different FS superstructures are observed depending on strain states, which are attributed to signatures of latent charge and spin orderings in LNO films. (2) We also deposited LNO ultrathin films under tensile strain with thickness between 1 and 10 unit-cells. We found that the Fermi surface nesting effect becomes strong in two-dimensions and significantly enhances spin-density-wave order. The further details are discussed more in presentation. This work was collaborated with Hyang Keun Yoo, Seung Ill Hyun, Eli Rotenberg, Ji Hoon Shim, Young Jun Chang and Hyeong-Do Kim.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.3
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• pp.180-198
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• 2019

In recent years, countries like Europe and Japan have been involved in many researches on the Low-Crested Structure (LCS) which is the method to protect beach erosion and it is regarded as an alternative to the submerged breakwaters, and compiled its results and released the design manual. In the past, studies on LCS have focused on two-dimensional wave transmission and calculating required weight of armor units, and these were mainly examined and discussed based on experiments. In this study, three-dimensional numerical analysis is performed on permeable LCS. The open-source CFD code olaFlow based on the Navier-Stokes momentum equations is applied to the numerical analysis, which is a strongly nonlinear analysis method that enables breaking and turbulence analysis. As a result, the distribution characteristics of the LCS such as water level, water flow, and turbulent kinetic energy were examined and discussed, then they were carefully compared and examined in the case of submerged breakwaters. The study results indicate that there is a difference between the flow patterns of longshore current near the shoreline, the spatial distribution of longshore and on-offshore directions of mean turbulent kinetic energy in case of submerged breakwaters and LCS. It is predicted that the difference in these results leads to the difference in sand movement.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.3
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• pp.162-168
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• 2017

Shallow-water bathymetry survey has been conducted using high definition color images obtained at the altitude of 100 m above sea level using a drone. Shallow-water bathymetry data are one of the most important input data for the research of beach erosion problems. Especially, accurate bathymetry data within closure depth are critically important, because most of the interesting phenomena occur in the surf zone. However, it is extremely difficult to obtain accurate bathymetry data due to wave-induced currents and breaking waves in this region. Therefore, optical remote sensing technique using a small drone is considered to be attractive alternative. This paper presents the potential utilization of image processing algorithms using multi-variable linear regression applied to red, green, blue and grey band images for estimating shallow water depth using a drone with HD camera. Optical remote sensing analysis conducted at Wolpo beach showed promising results. Estimated water depths within 5 m showed correlation coefficient of 0.99 and maximum error of 0.2 m compared with water depth surveyed through manual as well as ship-board echo-sounder measurements.

• Proceedings of the KSEG Conference
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• 2005.04a
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• pp.101-106
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• 2005

The three-dimensional Tomography developed by Kim and Bae(2004) was applied to 64,024 P and 64,618 S wave arrival times observed at 238 seismic stations for 4050 local earthquakes in the depth range from 0 to 300 km in and around Hokkaido, Japan. High and low velocity zones for Vp/Vs were clearly imaged in and around Hokkaido. The upper seismic planes of the double seismic zone (DSZ) were found in the subducted Pacific Plate beneath Hokkaido at depth of 40- 80 km, which produced high seismicity around Hokkaido. The findings of high Vp/Vs anomalies beneath the Moho discontinuity supports an evidence of a surface triple-collision hypothesis prepared by Moriya(1994) that the Kuril Arc(Okhotsk Plate or North American Plate) is colliding against the NE Japanese Arc(Amurian Plate or Eurasian Plate), along and beneath the Hidaka Mountain Range, and at the same time the Pacific Plate is subducting into these two plates, making an equilibrium of tectonic forces along the Hikada Mountain Range (HMR) corner and the central tectonic axis(142 ~ 143E) in Hokkaido. The low Vp and Vs were also found in east and west along the central tectonic axis in which the focal mechanism represents the extensional forces. These phenomena are also consistent with low Bouguer gravity anomalies in this region. It is understood why most of great earthquakes occurred outside Hokkaido where the balance of tectonic forces are breaking from the triple junction of three tectonic forces in Hokkaido.

• The Journal of the Korea Contents Association
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• v.12 no.7
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• pp.86-93
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• 2012

The foundation of the development in modern typography is based on the era of International Typographical Style and Modern Typography that valued morphological functionality and rationality to achieve an accurate conveyance of meaning. However, with the advance of postmodernism, the view that the aesthetic and conceptual aspect must be included in its interpretation rather than its rational functionality was prominent. Indeed, the works of Dan Friedman and April Greiman, two graphic designers that are known to be the most representative of the post-modernistic era, displayed that graphic design works can also serve as a method for a more free artistic expression, unlike works of Modern Typography. This move towards aesthetic graphics was first started by Wolfgang Weingart. His various attempts at expanding the concept of typography had a significant impact on the development of New Wave and his experimentalist attitude brought about a ground-breaking change to the functional design and formative expression of modern typography. However, this thesis will consider the theoretical background of the typographical designs displayed in Wiengart's works and the experimental methods thereof, and will not attempt to evaluate Weingart's pioneering role and achievements. Furthermore, this thesis will shed new light on the argument that the Weingart's works are not based on the authorship view of post-modernistic typography and are rather utilized to expand the concept of typography based on a syntactical approach.

• Journal of Navigation and Port Research
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• v.46 no.6
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• pp.483-490
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• 2022

Floating LiDAR is a system that provides a new paradigm for wind condition observation, which is essential when creating an offshore wind farm. As it can save time and money, minimize environmental impact, and even reduce backlash from local communities, it is emerging as the industry standard. However, the design and verification of a stable platform is very important, as disturbance factors caused by fluctuations of the buoy affect the reliability of observation data. In Korea, due to the nation's late entry into the technology, a number of foreign equipment manufacturers are dominating the domestic market. The west coast of Korea is a shallow sea environment with a very large tidal difference, so strong currents repeatedly appear depending on the region, and waves of strong energy that differ by season are formed. This paper conducted a study examining buoys suitable for LiDAR operation in the waters of Korea, which have such complex environmental characteristics. In this paper, we will introduce examples of optimized design and verification of ship-type buoys, which were applied first, and derive important concepts that will serve as the basis for the development of various platforms in the future.