• Title/Summary/Keyword: Polar Region

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Mesozooplankton Community Structure in the Yellow Sea in Summer (여름철 황해의 중형동물플랑크톤 군집 구조)

  • Kim, Garam;Kang, Hyung–Ku
    • Ocean and Polar Research
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    • v.43 no.4
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    • pp.269-277
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    • 2021
  • We investigated mesozooplankton community in the Yellow Sea in summer immediately after the typhoon passed. Total mesozooplankton density ranged from 1,323 to 6,397 ind. m-3 and the biomass ranged from 3 to 28 mg C m-3 by stations. The dominant species of the research area were Paracalanus parvus s.l., Oithona atlantica, Acartia omorii, Oikopleuridae, Sagittoidae juvenile and Calanus sinicus in that order. Mesozooplankton community was divided into two groups by cluster analysis : the stations located in coastal and open seas as one group, and the stations located in the middle into another group. The number of species, density and richness of mesozooplankton were significantly lower in the middle region. Mesozooplankton density and biomass were not significantly correlated with chl-a concentrations, unlike previous studies in spring and autumn. This community characteristic in summer may be due to the passing of the typhoon, or other environmental influences.

Productivity Analysis for Multi-Wells Depressurization of Gas Hydrate Bearing Sediments in Ulleung Basin, East Sea of Korea (동해 울릉분지 가스하이드레이트 퇴적층 내 다중정 감압에 따른 생산성 분석)

  • Moon, Seo-Yoon;Shin, Hyo-Jin;Lim, Jong-Se
    • Ocean and Polar Research
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    • v.43 no.4
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    • pp.295-306
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    • 2021
  • A field scale productivity analysis is required for the development of gas hydrate in marine sedimentary layers to verify the field applicability of production techniques and to improve productivity. In this study, the productivity resulting from the application of depressurization using multi-wells for the development of gas hydrate in the Ulleung Basin, East Sea of Korea, was determined. A numerical analysis model reflecting the conditions of candidate sites for the Ulleung Basin was constructed, and the productivity and dissociation behavior were comparatively analyzed. The pressure propagation and gas hydrate dissociation region by the multi-wells were wider and the productivity was higher than that of a single well. Different depressurization effects according to the spacing of multi-wells affected productivity. The results provide basic data for productivity analysis when establishing a field test production plan for the Ulleung Basin.

Development of a Low-power Walk-way for Anti-Icing (결빙 방지를 위한 저전력 갑판이동로 개발)

  • Bae, Sang-Eun;Cho, Su-gil;Lee, Woon-Seek
    • Journal of the Korean Society of Industry Convergence
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    • v.22 no.3
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    • pp.353-364
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    • 2019
  • The walk-way means a passage installed on the deck of a ship so that a person can safely move under any circumstances. So, the walk-way has to maintain a temperature of $5^{\circ}C$ or more for anti/de-icing even at an ambient temperature of $-62^{\circ}C$, a temperature in polar region. At present, the walk-way with heating cable is used, but the anti/de-icing effect is insufficient due to low heat transfer efficiency. Also, it has a construction problem due to heavy weight. In this study, an walk-way with a CNT surface heating element is proposed for the high anti/de-icing effect and the heating value per unit volume. The international standard survey, conceptual design, and simulation for the structural safety and the heat transfer are performed for the development of the proposed walk-way. To enhance the performance, the case studies based on the simulation analysis are conducted. Finally, the final prototype, applying the optimum material and thickness (3.2t of SS400) based on the case study results, is fabricated and experimented.

Land Cover Classification Map of Northeast Asia Using GOCI Data

  • Son, Sanghun;Kim, Jinsoo
    • Korean Journal of Remote Sensing
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    • v.35 no.1
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    • pp.83-92
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    • 2019
  • Land cover (LC) is an important factor in socioeconomic and environmental studies. According to various studies, a number of LC maps, including global land cover (GLC) datasets, are made using polar orbit satellite data. Due to the insufficiencies of reference datasets in Northeast Asia, several LC maps display discrepancies in that region. In this paper, we performed a feasibility assessment of LC mapping using Geostationary Ocean Color Imager (GOCI) data over Northeast Asia. To produce the LC map, the GOCI normalized difference vegetation index (NDVI) was used as an input dataset and a level-2 LC map of South Korea was used as a reference dataset to evaluate the LC map. In this paper, 7 LC types(urban, croplands, forest, grasslands, wetlands, barren, and water) were defined to reflect Northeast Asian LC. The LC map was produced via principal component analysis (PCA) with K-means clustering, and a sensitivity analysis was performed. The overall accuracy was calculated to be 77.94%. Furthermore, to assess the accuracy of the LC map not only in South Korea but also in Northeast Asia, 6 GLC datasets (IGBP, UMD, GLC2000, GlobCover2009, MCD12Q1, GlobeLand30) were used as comparison datasets. The accuracy scores for the 6 GLC datasets were calculated to be 59.41%, 56.82%, 60.97%, 51.71%, 70.24%, and 72.80%, respectively. Therefore, the first attempt to produce the LC map using geostationary satellite data is considered to be acceptable.

Discrepancies between Mitochondrial DNA and AFLP Genetic Variation among Lineages of Sea Slaters Ligia in the East Asian Region

  • Kang, Seunghyun;Jung, Jongwoo
    • Animal Systematics, Evolution and Diversity
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    • v.36 no.4
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    • pp.347-353
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    • 2020
  • Although sea slaters Ligia have a significant role in rocky shore habitats, their taxonomic entities have not been clearly understood. In this study, we investigated whether genetic variation inferred from a nuclear genetic marker, namely amplified fragment length polymorphism (AFLP), would conform to that of a mitochondrial DNA marker. Using both the mitochondrial DNA marker and the AFLP marker amplified by the six selective primer sets, we analyzed 95 Ligia individuals from eight locations from East Asia. The direct sequencing of mitochondrial 16S rRNA gene revealed three distinct genetic lineages, with 9.8-11.7 Kimura 2-parameter genetic distance. However, the results of AFLP genotyping analysis with 691 loci did not support those of mitochondrial DNA, and revealed an unexpectedly high proportion of shared polymorphisms among lineages. The inconsistency between the two different genetic markers may be explained by difference in DNA evolutionary history, for example inheritance patterns, effective population size, and mutation rate. The other factor is a possible genomic island of speciation, in that most of the genomic parts are shared among lineages, and only a few genomic regions have diverged.

Isolation and characterization of four unrecorded wild yeasts from the soils of Republic of Korea in winter

  • Yuna Park;Soohyun Maeng;Sathiyaraj Srinivasan
    • Journal of Species Research
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    • v.12 no.3
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    • pp.197-202
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    • 2023
  • The purpose of this study was to isolate and identify wild yeasts from the soil collected in Gwangju and Pocheon City, Gyeonggi Province, Republic of Korea. Among 10 strains, six strains were already reported, but four strains were unrecorded in Republic of Korea. To identify wild yeast strains, pairwise sequence comparisons of the D1/D2 region of the 26S rRNA gene sequence were performed using Basic Local Alignment Search Tool (BLAST). The cell morphologies were observed by phase contrast microscope and assimilation tests were carried out using API 20C AUX kit. The 10 strains were assigned to the phyla Basidiomycota (8 strains) and Ascomycota (2strains). The unrecorded four yeast strains, NH33, NH19, NH20, and YP416, belong to the phylum Basidiomycota and the genera Buckleyzyma, Leucosporidium, Holtermanniales, and Mrakia, respectively. All strains had oval-shaped and polar budding cells. In this research, the morphological and biochemical properties of four unreported yeast species were characterized intensively, which were not officially reported in Korea.

Modeling Grain Rotational Disruption by Radiative Torques and Extinction of Active Galactic Nuclei

  • Giang, Nguyen Chau;Hoang, Thiem
    • The Bulletin of The Korean Astronomical Society
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    • v.46 no.2
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    • pp.66.1-66.1
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    • 2021
  • Extinction curves observed toward individual Active Galactic Nuclei (AGN) usually show a steep rise toward Far-Ultraviolet (FUV) wavelengths and can be described by the Small Magellanic Cloud (SMC)-like dust model. This feature suggests the dominance of small dust grains of size a < 0.1 ㎛ in the local environment of AGN, but the origin of such small grains is unclear. In this paper, we aim to explain this observed feature by applying the RAdiative Torque Disruption (RATD) to model the extinction of AGN radiation from FUV to Mid-Infrared (MIR) wavelengths. We find that in the intense radiation field of AGN, large composite grains of size a > 0.1 ㎛ are significantly disrupted to smaller sizes by RATD up to dRATD > 100 pc in the polar direction and dRATD ~ 10 pc in the torus region. Consequently, optical-MIR extinction decreases, whereas FUV-near-Ultraviolet extinction increases, producing a steep far-UV rise extinction curve. The resulting total-to selective visual extinction ratio thus significantly drops to RV < 3.1 with decreasing distances to AGN center due to the enhancement of small grains. The dependence of RV with the efficiency of RATD will help us to study the dust properties in the AGN environment via photometric observations. In addition, we suggest that the combination of the strength between RATD and other dust destruction mechanisms that are responsible for destroying very small grains of a <0.05 ㎛ is the key for explaining the dichotomy observed "SMC" and "gray" extinction curve toward many AGN.

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Prediction of Global Industrial Water Demand using Machine Learning

  • Panda, Manas Ranjan;Kim, Yeonjoo
    • Proceedings of the Korea Water Resources Association Conference
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    • 2022.05a
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    • pp.156-156
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    • 2022
  • Explicitly spatially distributed and reliable data on industrial water demand is very much important for both policy makers and researchers in order to carry a region-specific analysis of water resources management. However, such type of data remains scarce particularly in underdeveloped and developing countries. Current research is limited in using different spatially available socio-economic, climate data and geographical data from different sources in accordance to predict industrial water demand at finer resolution. This study proposes a random forest regression (RFR) model to predict the industrial water demand at 0.50× 0.50 spatial resolution by combining various features extracted from multiple data sources. The dataset used here include National Polar-orbiting Partnership (NPP)/Visible Infrared Imaging Radiometer Suite (VIIRS) night-time light (NTL), Global Power Plant database, AQUASTAT country-wise industrial water use data, Elevation data, Gross Domestic Product (GDP), Road density, Crop land, Population, Precipitation, Temperature, and Aridity. Compared with traditional regression algorithms, RF shows the advantages of high prediction accuracy, not requiring assumptions of a prior probability distribution, and the capacity to analyses variable importance. The final RF model was fitted using the parameter settings of ntree = 300 and mtry = 2. As a result, determinate coefficients value of 0.547 is achieved. The variable importance of the independent variables e.g. night light data, elevation data, GDP and population data used in the training purpose of RF model plays the major role in predicting the industrial water demand.

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Evaluation of Active Layer Depth using Dynamic Cone Penetrometer (동적 콘 관입기를 이용한 활동층 심도평가)

  • Hong, Won-Taek;Kang, Seonghun;Park, Keunbo;Lee, Jong-Sub
    • Journal of the Korean GEO-environmental Society
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    • v.17 no.1
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    • pp.49-54
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    • 2016
  • An active layer distributed on surface of an extreme cold region causes a frost heave by repeating the freezing and thawing according to the seasonal temperature change. Since the height of frost heave is greatly affected by the thickness of active layer, an accurate evaluation of the thickness of active layer is necessary for the safe design and construction of the infrastructure in the extreme cold region. In this study, dynamic cone penetrometer, which is miniaturized in-situ penetration device, is applied for the evaluation of active layer depth distribution. As the application tests, two dynamic cone penetration tests were conducted on the study sites located in Solomon and Alaska. In addition, ground temperature variations were obtained. As the results of the application tests, the depth of interface between the active layer and the permafrost was evaluated from the difference in dynamic cone penetration indexes of the active layer and the permafrost, and a layer was detected around the interface considered as an ice lens layer. Also, the interface depths between the above zero and the below zero temperature determined from the ground temperature variations correspond with the interface depths evaluated from the dynamic cone penetration tests. This study demonstrates that the dynamic cone penetrometer may be a useful tool for the evaluation of the active layer in the extreme cold region.

Distribution of Bacterial Decomposers in Lake Khuvsgul, Mongolia (몽골 훕스굴 호수 수층에서 유기물질 분해세균의 분포)

  • Jung, You-Jung;Jung, Da-Woon;Kim, Ju-Young;Zo, Young-Gun;Yim, Joung-Han;Lee, Hong-Kum;Ahn, Tae-Seok
    • Korean Journal of Microbiology
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    • v.45 no.2
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    • pp.119-125
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    • 2009
  • To understand the ecological function of heterotrophic bacterial community in water column of large freshwater lakes in the permafrost zone, we investigated the structure and function of bacterial community in Lake Khuvsgul, Mongolia. Species composition of overall bacterial community was analyzed by denaturing gradient gel electrophoresis (DGGE) of 16S rRNA gene fragments, and bacteria that can be cultured at 10oC were isolated and characterized. Based on the depth profile of environmental parameters, thermocline and chemocline were recognized at the 5~10 m zone of the water column. The stratified DGGE profile indicated that the discontinuity of water properties might influence the structure of bacterial community: band profiles in the 0~5 m zone were diverse with large change by depth, but the profile was relatively stable at the $\geq$10 m zone, with predominance of the band identified as Acidovorax facilis. Bacterial cultures were screened for protease, cellulase, amylase and lipase activity, and 23 isolates were selected for high activity of the hydrolytic enzymes. The isolates were identified based on their 16S rRNA gene sequences. In the surface water (zero meter depth), Acidovorax defluvii and Sphingobacterium faecium with high cellulase activity were present. Flavobacterium succinicans, Mycoplana bullata and A. facilis were stably predominant isolates at 2 m, 5 m, and $\geq$10 m depths, respectively. F. succinicans isolates showed high protease activity while M. bullata isolates showed moderate levels of protease and celluase activity. A. facilis isolates showed either cellulase or lipase activity, exclusively to each other. According to the profile of growth rates of the isolates in the temperature range of $0\sim42^{\circ}C$, the surface-zone (0~5 m) isolates were facultative psychrophiles while isolates from $\geq$10 m depth were typical mesophiles. This stratification is believed to be due to stratified availability of organic materials to the bacterial decomposers. In the water column below the chemoline, the environment is extremely oligotrophic so that the trait of rapid growth in low temperature might not be demanded by deep-lake decomposers. The stratified distribution of community composition and decomposer activity in Lake Khuvsgul implies that ecological functions of bacterial community in lakes of cold region are sharply divided by water column stratification.