• Journal of Environmental Impact Assessment
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• v.21 no.5
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• pp.649-664
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• 2012

The grid cell analysis is used to select good sites as habitats at the region. The northern area of Yeongjong Island, Incheon has been disturbing by habitat loss due to human activities such as residential development, deforestation. In order to determine significant places as bird habitats and to select conservation areas at this island, the study area was divided into 70 grid cells($500{\times}500m$ each grid) and then each grid was ranked by spatial analysis using the species diversity index. Fieldwork was carried out in Spring and Autumn of 2010. To examine grid cells which were ranked high in both seasons in common, we used the average ranking value, combined data from two seasons. This area consists of mainly agricultural areas and forests(more than 68%) among eight habitat types: the agricultural land, forest, coast, lake, meadow, stream, city and other things. A total of 110 species was recorded: 4,183 birds of 102 species in Spring and 3,326 birds of 58 species in Autumn. In other words, the number of individuals and species was higher in Spring than in Autumn. Species diversity index presented the highest value at M8 grid cell in Spring(3.380) and at A4 gird cell in Autumn(2.736). In 18 of 22 grid cells where the average ranking value was higher than 3, the forest was distributed and in 4 grid cells, the coast and wetland were widely distributed, in which theses were located apart from human-associated disturbances such as construction works for a leisure complex. Our results present a new estimate method not only to minimize loss of bird habitats but also to conserve important habitats when the large-scale development takes place at particular region.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.6
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• pp.634-643
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• 2020

Because of the continuous increase in the demand for and importance of marine space, marine exploration and survey activities are being actively conducted in Korea actively. Because the marine survey vessels used for these activities have special operational patterns depending on the purpose and probe vessels, research on maritime traffic risk is required. In this study, an attempt was made to determine the correlation of each factor with the effect of marine exploration and survey vessel operation on maritime traffic. The status of ocean exploration and survey vessels in operation in Korea was identified, as well as the special operational conditions of some of the ocean physical probes. Generally, the number of exploration and survey vessels involved per hour, total vessel length(including exploration equipment), operation, interval distance of exploration as per plan, and marine traffic conditions(traffic volume and speed) can be classified as operating factors. To compare the results of the environmental stress, a maritime traffic flow simulation based on the "ES" Model was performed with each of the identified operating factors as independent variables. The results of the analysis confirmed that the environmental stress significantly changed in the order of traffic volume, ship length and speed. In addition, it was confirmed that the environmental stress is reduced when the operation course is set at an angle with the nearby maritime traffic flow. Accordingly, it can help reduce the operator's burden if the survey vessel operator understands nearby maritime traffic conditions and reflects them in the operation method when setting the operation plan.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.6
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• pp.511-524
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• 2016

Since a room-and-pillar underground structure is characterized by its grid-type array of room and pillar, its economical efficiency can be governed by excavation sequence. In this study, the construction period by the drill-and-blast method as a excavation method for a room-and-pillar underground structure was examined. In addition, the parallel excavation sequence was considered as the main sequence of a room-and-pillar underground structure. Sequences of mucking and support installation were derived to estimate the total excavation cycle by taking the case of a road tunnel into consideration. From the excavation cycle of room-and-pillar underground structure, the relationship between available maximum and minimum numbers of jumbo drill machines depending on the number of faces in operation was suggested.

• Journal of Astronomy and Space Sciences
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• v.26 no.4
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• pp.555-566
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• 2009

Precipitable water vapor (PWV) derived from a numerical weather prediction (NWP) model were compared to observations derived from ground-based Global Positioning System (GPS) receivers. The model data compared were from the Weather Research and Forecasting (WRF) model short-range forecasts on nested grids. The numerical experimets were performed by selecting the cloud microphysics schemes and for the comparisons, the Changma period of 2008 was selected. The observational data were derived from GPS measurements at 9-sites in South Korea over a 1-month period, in the middle of June-July 2008. In general, the WRF model demonstrated considerable skill in reproducing the temporal and spatial evolution of the PWV as depicted by the GPS estimations. The correlation between forecasts and GPS estimates of PWV depreciated slowly with increasing forecast times. Comparing simulations with a resolution of 18 km and 6 km showed no obvious PWV dependence on resolution. Besides, GPS and the model PWV data were found to be in quite good agreement with data derived from radiosondes. These results indicated that the GPS-derived PWV data, with high temporal and spatial resolution, are very useful for meteorological applications.

• Journal of Korea Water Resources Association
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• v.51 no.8
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• pp.629-642
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• 2018

Future variability of the spatial patterns of rainfall events is the point of water-related risks and impacts of climate change. Recent related researches are mostly conducted based on the outcomes from General Circulation Models (GCMs), especially Coupled Model Intercomparison Project, phase 5 (CMIP5) GCMs which are the most advanced version of climate modeling system. GCM data have been widely used for various studies as the data utility keep getting improved. Meanwhile the model performances especially for raw GCM outputs are rarely evaluated prior to the applications although the process would essential for reasonable use of model forecasts. This study attempt to quantitatively evaluate the skills of 29 CMIP5 GCMs in reproducing spatial climatologies of precipitation in East Asia. We used 3 different gridded observational data as the references available over the study area and calculated correlation and errors of spatial patterns simulated by GCMs. As a result, the study presented diversity of the GCM evaluation in the performance, rank, or accuracy by different configurations, such as target area, evaluation method, and observation data. Yet, we found that Hadley-centre affiliated models comparatively performs better for the meso-scale area in East Asia and MPI_ESM_MR and CMCC family showed better performance specifically for the korean peninsula. We expect that the results and thoughts of this study would be considered in screening suitable GCMs for specific area, and finally contribute to extensive utilization of the results from climate change related researches.

• Journal of the Korean Chemical Society
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• v.39 no.5
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• pp.421-426
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• 1995

The hydrogels of hydrophilic three-dimensional methacrylate polymer networks were prepared from 2-hydroxyethyl methacrylate (HEMA) and ethylene glycol dimethacrylate (EDGMA) in aqueous solution. The interaction of water with the hydrophilic methacrylate polymers in the hydrogels was studied by pulse NMR spectroscopy. The spin-lattice relaxation times (T1) of low water content hydrogels showed the different double environments, resulting in two spin-lattice relaxation times (T1a and T1b). The values of T1a and T1b were 16.4${\times}$10-3 sec and 58.2${\times}$10-3 sec for a p(HEMA)-(10% H2O) system, and 13.2${\times}$10-3 sec and 23.1${\times}$10-3 sec for a crosslinked EGDMA-p(HEMA)-(10% H2O) system, respectively. The spin-spin relaxation times (T2) of the hydrogels were also measured as a function of water content in the p(HEMA)-(H2O)n and crosslinked EGDMA-p(HEMA)-(H2O)n system. The values of T2 were approximately 10 times less than those of T1 in agreement with the principles of spin relaxations.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.6
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• pp.237-241
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• 2014

We investigated the optimal etching conditions and properties of the surface change due to molten KOH/NaOH chemical wet etching using an AlN wafer which has been put to practical use in the present study. Results were observed using a scanning electron microscope after 5 minutes etching at $350^{\circ}C$, was found to have a surface form of the respective other Al-face, the N-face. In particular, etch-pit in the form of a hexagon, which is observed in the Al-face appeared, It was calculated at $2{\times}10^6/cm^2{\sim}10^{10}/cm^2$ dislocation density. In the case of N-face, lattice defects in the form of the hexagonal pyramids is formed. It was discovered that in order to observe the orientation of the wafer, which corresponds to the C-axis direction of the resulting hexagonal AlN which was analyzed using XRD (0002) and is a state of being oriented in the (0004) plane. The Radius of curvature of AlN wafer was 1.6~17 m measured by DC-XRD rocking curve position.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.5
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• pp.213-217
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• 2013

The GaN layer was typical III-V nitride semiconductor and was grown on the sapphire substrate which cheap and convenient. However, sapphire substrate is non-conductivity, low thermal conductivity and has large lattice mismatch with the GaN layer. In this paper, the poly GaN epilayer was grown by HVPE on the metallic compound graphite substrate with good heat dissipation, high thermal and electrical conductivity. We tried to observe the growth mechanism of the GaN epilayer grown on the amorphous metallic compound graphite substrate. The HCl and $NH_3$ gas were flowed to grow the GaN epilayer. The temperature of source zone and growth zone in the HVPE system was set at $850^{\circ}C$ and $1090^{\circ}C$, respectively. The GaN epilayer grown on the metallic compound graphite substrate was observed by SEM, EDS, XRD measurement.

• Journal of the Korean Association of Geographic Information Studies
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• v.17 no.4
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• pp.40-51
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• 2014

This study aims to investigate urban inundation considering building footprints based on dual-drainage scheme. For this purpose, LiDAR data is cultivated to generate two original data set in terms of DEM with $1{\times}1$ meter and building layer of the study drainage area in Seoul and then the building layer is overlapped as vector polygon with the mesh data with the same size as DEM. Then, terrain data for modeling were re-sampled to reduce resolution as $10{\times}10$ meters. As results, the simulated depth without considering building footprints has a tendency to underestimate the inundation depth compared to observed data analized by CCTV imagery. Otherwise, the simulation result considering building footprints revealed definitely higher fitness. The difference of inundation depth came from the variation of inundation volume which was relevant to inundation extent. If the building footprints are enlarged, the possible inundation depth is increased, which results in being inundation depth higher because hydrological conditions such as rainfall depth are conservational. Otherwise, according to comparison of inundation extents, there were no significant difference but the case of considering building footprint was revealed slightly higher fitness. Thus, it is concluded that the considering building footprint for inundation analysis of urban watershed should be required to improve simulation accuracy synthetically.

• Journal of the Korean Magnetics Society
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• v.14 no.1
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• pp.33-37
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• 2004

Cu$_{0.1}$Fe$_{0.9}$Cr$_2$S$_4$ has been studied with Mossbauer spectroscopy, x-ray diffraction, vibrating sample magnetometer (VSM), and magnetoresistance (MR) measurement. The crystal structure was determined to be a cubic spinel with lattice parameter a$_{0}$=9.9880 $\AA$. The MR measurements show a semiconductor behavior below 110 K and metal behaved above 100 K. The temperature dependence of magnetization of Cu$_{0.1}$Fe$_{0.9}$Cr$_2$S$_4$ was reported. In addition to a large irreversibility between the zero-field-cooling (ZFC) and the field-cooling (FC) magnetization at applied field H=100 Oe, a cusp-like anomaly was observed in both the FC and ZFC curves. It shifted toward the lower temperature region with increasing magnetic field, and then showed convex type maximum at 110 K, under the applied field of 5 kOe. The Mossbauer spectra were measured from 15 K to room temperature. The asymmetric line broadening was observed for the sample Cu$_{0.1}$Fe$_{0.9}$Cr$_2$S$_4$, and it was considered to be dynamic Jahn-Teller relaxation. The charge state of Fe ions was ferrous in character. The unusual reduction of magnetic hyperfine field below 110 K was interpreted in terms of cancellation effect between the mutually opposite orbital current field (H$_{L}$) and Fermi contact field (H$_{C}$).