• Korean Journal of Ecology and Environment
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• v.36 no.3 s.104
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• pp.242-256
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• 2003

This study aimed to determine the relationship between rainfall-discharge patterns and maior aquatic environmental factors in a river-type reservoir. Specifically, daily monitoring was conducted in Paltang Reservoir from January 1999 to December 2001. Observation of the daily changes of the environment factors showed that natural meteorological factors and hydrological factors causing the change of water discharge had a major effect on the aquatic environment. Rainfall was the main source of hydrological changes, with its frequency a possible direct variable governing the range of discharge changes. Rainfall was weak in November${\sim}$May and heavy in June${\sim}$October (heavist in summer). The range of water discharge was greatest during summer (July to September) and lowest during winter (January to February). A principal component analysis (PCA) showed that aquatic environmental factors could be classified into three different types in the pattern of annual variation. First, type I included water temperature, turbidity, water color and organic matter (COD), which increased with increasing water discharge. Second, type ll consisted of DO and pH, which decreased with increasing water discharge. Third, type III included conductivity, alkalinity and chloride ion, which showed middle values with increasing water discharge. Monthly variation of aquatic environments explained by the first two dimensions of the PCA suggests that aquatic environments of Paltang Reservoir may have annual cycle typical of river-type reservoirs depending on hydrological factor such as water discharge.

• Journal of the Korean Institute of Gas
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• v.27 no.2
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• pp.39-48
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• 2023

This study presents the experimental results to measure the adsorption amount of methane gas by coal according to the conditions of a coalbed methane (CBM) reservoir. Adsorbed gas to coal seam particles was measured under reservoir conditions (normal pressure ~ 1,200 psi pressure range, temperature range15 ~ 45℃) using coal samples obtained from random mines in Kalimantan Island, North Indonesia. The obtained amount of absolute adsorbed gas was applied to triangular with linear interpolation to calculate the maximum amount of adsorbed gas according to temperature and pressure change, at which no experiment was performed. As a result, it was revealed that the amount of adsorbed gas to coal particles increased as the pressure increased and temperature decreased, but the increase of the amount of adsorbed gas decreased at more than an appropriate depth(1,000 ft). In the cleat permeability and cleat porosity for each depth of the coal bed considering the effective stress, the cleat permeability was 28.86 ~ 46.81 md, and the cleat porosity was 0.83 ~ 0.98%. This means that the gas productivity varies significantly with the depth because the reduction of the permeability according to the depth in the coal seam is significant. Therefore, a coalbed depth should be considered essential when designing the spacing of production wells in a coalbed methane reservoir in further study.

• Korean Journal of Microbiology
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• v.40 no.3
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• pp.237-243
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• 2004

The aim of this study is to investigate the detection rate of putative periodontopathogens, Porphyromonas gingivalis, Tannerella forsythia, and Actiobacillus actinomycetemcomitans, related to cardiovascular diseases(CVD). Plaques were sampled from 15 subjects (4 sites of denture base and/or tooth) with sterilized explorers and were transported in IX PBS. The detection of periodontopathogens was performed by polymerase chain reaction with species-specific primers based on 16S rDNA. The PCR products were cloned into pGEM-T easy vector and its nucleotides were sequenced in order to confirm the specificity. Our data showed that the detection rate of P. gingivalis and T forsythia in denture base of edentulous patients was 25％ and 75％, respectively. And the detection rate of P. gingivalis and T.forsythia in denture base of patient having one more tooth was 91％. The results indicate that plaque of denture base may serve as reservoirs of oral bacteria related to CVD.

• Korean Journal of Remote Sensing
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• v.37 no.5_1
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• pp.1207-1214
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• 2021

In thisletter, we developed technology which can exclude effect of cloudsto perform remote waterbody detection based on Sentinel-2 optical satellite imagery to calculate the area of ungauged reservoirs and applied to the Hwanggang dam reservoir, a representative ungauged reservoir, to verify usability. The remote waterbody detection technology calculates the cloud blocking ratio by comparing the cloud boundary in the Sentinel-2 imagery and the reservoir boundary first. Next, itselects data whose cloud blocking ratio does not exceed a specific value and calculates NDWI (Normalized Difference Water Index) with selected imagery. In last, it calculatesthe area of the reservoir by counting the number of grids which have NDWI value considered as waterbody within the boundary of the target reservoir and correcting with cloud blocking ratio. To determine cloud blocking ratio threshold forselecting image, we performed the area calculation of Hwanggang dam reservoir from July 2018 to October 2021. As a result, when the cloud blocking ratio threshold wasset 10%, we confirmed that the result with large error due to clouds were filtered well and obtained 114 results that can show changes in Hwanggang dam reservoir area among 220 images.

• Journal of Environmental Impact Assessment
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• v.30 no.4
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• pp.187-202
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• 2021

This study examined the effectiveness of wind corridor construction by analyzing the thermal environment, cold air generation, ventilation, and geographical characteristics to improve urban thermal environment and establish the basis for specialized strategy in Changwon-si, Gyeongsangnam-do. Using spatial analysis and remote sensing techniques, surface temperature, land cover and land use, wind field, and slope were measured and through this, a wind corridor analysis model was constructed. As a result of the analysis as of 2020, Changwon-si generally has land cover characteristics that are advantageous for the generation of cold air, but the temperature in most urban areas is the highest, and the temperature in areas such as north Changwon area, Jinbukmyeon, Ung-dong, and Ungcheon-dong are relatively high. There was a typical trend of high average wind speed in mountain regions and low average wind speed in urban areas. Accordingly, the north Changwon area, the former Changwon downtown area, the Hogye-ri and Pyeongseong-ri areas, and the Changpo Bay area are derived as vulnerable areas to thermal environment, and various measures to reduce temperature and improve air quality that the inflow of cold air into the area considering the characteristics of each area and securing wind ventilation between the surrounding mountains, reservoirs, and park areas were proposed.

• The Journal of Engineering Geology
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• v.31 no.1
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• pp.1-17
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• 2021

It is important to evaluate the fracture network in a rock volume because fractures control the ground conditions and fluid flow characteristics. Therefore, various attempts have been made to quantify fracture networks to better understand ground and flow conditions. The use of fracture density alone (a quantitative parameter based on geometric analysis) does not fully explain the evolution of fracture networks, or quantify the spatial relationship (e.g. connectivity) of fractures in a rock mass. Therefore, the need for fracture network characterization based on topological analysis has recently emerged. In Korea however, the topological analysis of fracture networks within a rock mass has rarely been studied. As such, the definition of the topological analysis of fracture networks and the graph theory related to the topological analysis are briefly summarized in this study. We also introduce an application method for these analyses to fracture characterization. If the topological method is used for the analysis of fracture networks, it can also be adopted to analyze fluid flow characteristics of groundwater, characterize petroleum reservoirs, and analyze the evolution of a fracture network. In addition, topological analysis can be useful for site selection of major facilities such as nuclear waste disposal sites because it can be used to evaluate the stability of the potential sites.

• Korean Journal of Ichthyology
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• v.33 no.2
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• pp.74-83
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• 2021

Distribution status, habitat characteristics, and extinction threat evaluation of the endangered species, Brachymystax lenok tsinlingensis were investigated in 2015 and 2019. Historical distribution reports of B. l. tsinlingensis were divided into before 1990, 1997~2006, 2000~2011, and 2010~2019. Among the 150 sampling sites investigated during the study period, number of individuals of B. l. tsinlingensis were collected 542 individuals from 67 sites. The streams inhabited of B. l. tsinlingensis were Naerincheon (11 stations), Odaecheon (11 stations), Bukcheon (10 stations), Bangtaecheon (8 stations), Songjeongricheon (4 stations), Suipcheon (3 stations), Inbukcheon (3 stations), Hyeondongcheon (3 stations) etc. The main habitat of B. l. tsinlingensis was upstream of the river with a high altitude of more than 400 m, 4~20 m water flow width, 1~2 m water depth, and high ratio (70~80%) boulder bottoms. The main reasons for the decline in population size were assumed as river works, construction of reservoirs and bridges, discharge of contaminated water into the river, the inflow of summer vacationers, and weir. Compared to our results there exists evidence that states a 20.7% reduction in occupancy within 10 years, in a small appearance range (7,732 km²) and occupancy area (268 km²), number of disconnected locations (15 locations), and a decline in habitat quality. Therefore, B. l. tsinlingensis is now considered as Near Threatened (NT) based on the results (Near meets VU A2acd, B1b(i,ii,iii)+B2b(i,ii,iii)) of IUCN Red List categories and criteria.

• Journal of Korean Society of Disaster and Security
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• v.17 no.2
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• pp.1-11
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• 2024

Most reservoirs in South Korea are earthen dams, mainly because they are cost-effective and easy to construct. However, earthen dams are highly vulnerable to seepage and overtopping, making them prone to sudden failure during excessive flooding. Such sudden failures can lead to a rapid increase in flood discharge, causing significant damage to downstream rivers and inhabited areas. This study investigates the effect of riprap placement on the slopes of earthen dams in delaying dam failure. Delaying the failure time is crucial as it allows more time for evacuation, significantly reducing potential casualties, which is essential from a disaster response perspective. Hydraulic experiments were conducted in a straight channel, using two different sizes of riprap for protection. Unlike previous studies, these experiments were performed under unsteady flow conditions to reflect the impact of rising water levels inside the dam. The target dam for the study was a cofferdam installed in a diversion tunnel. Experimental results indicated that the presence of riprap protection effectively prevented slope failure under the tested conditions. Without riprap protection, increasing the size of the riprap delayed the failure time. This delay can reduce peak discharge, mitigating damage downstream of the dam. Furthermore, these findings can serve as critical reference material for establishing emergency action plans (EAP) for reservoir failure.

• Geophysics and Geophysical Exploration
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• v.18 no.3
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• pp.143-153
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• 2015

Polymer flooding for enhancing hydrocarbon production injects into a reservoir polymer solution that is viscous. It is very important to monitor the behavior pattern of the polymer solution in order to evaluate the effectiveness of polymer flooding. To monitor the distribution of polymer solution and thus fluid substitution within the reservoir, we first construct seismic and resistivity rock physics models (RPMs), which are functions of reservoir parameters such as rocks and type of fluid, fluid saturation. For the seismic and resistivity RPMs, responses of seismic and electromagnetic (EM) tomography are numerically simulated as polymer injection, using two dimensional (2D) staggered-grid finite difference elastic modeling and 2.5D finite element EM modeling algorithms, respectively. In constructing RPM for EM tomography, three different reservoir rocks are considered: clean-sand, dispersed shale-sand, and sand-shale lamination rocks. The polymer solution is assumed to have 2 wt% of polymer as normally generated, while water is freshwater or saltwater. Further, neutron logging is also considered to check its sensitivity to polymer flooding. The techniques discussed in the paper are important in monitoring not only hydrocarbon but also geothermal reservoirs.

• Korean Journal of Microbiology
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• v.39 no.3
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• pp.175-180
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• 2003

Microbial Fe(III) reduction is an important factor for biogeochemical cycle in anaerobic environments, especially sediment of freshwater such as lakes, ponds and rivers. In addition, the Fe(III) reduction serves as a model for potential mechanisms for the oxidation of organic compounds and the reduction of toxic heavy metals, such as chrome or uranium. Shewanella putrefaciens DK-1 was a gram-negative, facultative anaerobic Fe(III) reducer and used ferric ion as a terminal electron acceptor for the oxidation of organic compounds to $CO_{2}$ or other oxidized metabolites. The ability of reducing activity and utilization of various electron acceptors and donors for S. putrefaciens DK-1 were investigated. S. putrefaciens DK-1 was capable of using a wide variety of electron acceptor, including $NO_{3}^{-}$, Fe(III), AQDS, and Mn(IV). However, its ability to utilize electron donors was limited. Lactate and formate were used as electron donors but acetate and toluene were not used. Fe(III) reduction of S. putrefaciens DK-l was inhibited by the presence of either $NO_{3}^{-}$ or $NO_{2}^{-}$. Further S. putrefaciens DK-1 used humic acid as an electron acceptor and humic acid was re-oxidized by nitrate. Environmental samples showing the Fe(III)-reducing activity were used to investigate effects of the limiting factors such as carbon, nitrogen and phosphorus on the Fe(III) reducing bacteria. The highest Fe (III) reducing activity was measured, when lactate as a carbon source and S. putrefaciens DK-1 as an Fe(III) reducer added in untreated sediment samples of Cheon-ho and Dae-ho reservoirs.