• Korean Journal of Agricultural Science
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• v.46 no.3
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• pp.507-517
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• 2019

To follow up on a 2017 survey of tomato virus diseases, samples with virus-like symptoms were collected from the same areas (Buyeo-gun, Chungchungnam-Do and Daejeon, Korea) in 2018. While in 2017 mixed infections of Tomato mosaic virus with either Tomato yellow leaf curl virus (TYLCV) or Tomato chlorosis virus were detected, only TYLCV was detected in symptomatic samples in 2018. TYLCV amplicons of c.777 bp representing the coat protein (CP) coding region were cloned from the TYLCV positive samples, and the sequence data showed a 97.17% to 98.84% nucleotide and 98.45% to 99.22% amino acid identity with the 2017 Buyeo-gun isolate (MG787542), which had the highest amino acid (aa) sequence identity of up to 99.2% with four 2018 Buyeo-gun sequences (MK521830, MK521833, MK521834, and MK521835). The lowest aa sequence identity of 98.45% was found in a 2018 Daejeon isolate (MK521836); the distance between Buyeo-gun and Daejeon is about 45 km. Phylogenetic analysis indicated that the currently reported CP sequences are most closely related to Korean sequences from Masan (HM130912), Goseong (JN680149), Busan (GQ141873), Boseong (GU325634), and the 2017 isolate TYLCV-N (MG787543) in the 'Japan' cluster of TYLCV isolates and distinct from the 'China' cluster isolates from Nonsan (GU325632), Jeonju (HM130913) and Jeju (GU325633, HM130914). Our survey data from 2017 and 2018 suggest that TYLCV has become established in Korea and may be spread by whitefly vectors from weed reservoirs within the farm environment.

• Journal of Korean Society on Water Environment
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• v.35 no.4
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• pp.316-331
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• 2019

Carbon dioxide($CO_2$) emission from rivers to the atmosphere is a key component in the global carbon cycle. Most of the rivers are supersaturated with $CO_2$. At a global scale, the amount of $CO_2$ emission from rivers is reported to be five-fold greater than that from lakes and reservoirs, but relevant data are rare in Korea. The objectives of this study is to estimate the $CO_2$ net atmospheric flux(NAF) from the upstream of Gangjeong-Goryeong Weir(GGW), Dalseong Weir(DSW), Hapcheon-Changnyeong Weir(HCW), and Changnyeong-Haman Weir(CHW) located in Nakdong River South Korea) using field and laboratory experiments and to apply data mining techniques to develop parsimonious prediction models that can be used to estimate $CO_2$ NAF with physical and water quality variables that can be collected easily. As a result, the study sites were all heterotrophic systems that often released $CO_2$ to the atmosphere, except when the algal photosynthesis was active.The median $CO_2$ NAF was minimum $391.5mg-CO_2/m^2$ day at GGW and maximum $1472.7mg-CO_2/m^2$ day at DSW. The $CO_2$ NAF showed a negative correlation with pH and Chl-a since the overgrowth of the algae consumed $CO_2$ in the water and increased the pH. As the parsimonious multiple regression model and random forest model developed, this study showed an excellent performance with the $Adj.R^2$ value higher than 0.77 in all weirs. Thus, these methods can be used to estimate $CO_2$ NAF in the river even if there is no $pCO_2$ measurement data.

• Korean Journal of Clinical Laboratory Science
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• v.51 no.3
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• pp.344-350
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• 2019

We investigated the distribution of chigger mites in Seogwipo, Jeju Island to conduct surveillance for the presence of Orientia tsutsugamushi. Using a total of 20 samplers, chigger mite larvas were sampled weekly from September to November in Rice field, Field, Waterway, and Glass field (4 locations), and we found up to 51 larvas of 3 different species of chigger mites. 64 field mice were captured when sampling for chigger mite-infested rodents in rice fields, waterways, fields, reservoirs and hills (5 locations) for 9 months from March, 2018 to November, using 100 Sherman traps with placing 20 traps in each location, and in each location the trap index was 0.08. Only back-striped field mice (Apodemus agrarius) were captured one at a time. They were most frequently captured in April with 15 mice, and then 436 chigger mites were collected from the total of 64 captured wild rodent, showing a chigger index of 6.8. The chigger index was the highest in November at 46.0, followed by 6.8 in July and 4.6 in June. PCR was performed to investigate if there were any O. tsutsugamushi hosts among the 487 chigger mites sampled from the captured rodents and this turned out to be negative.

• Journal of Korean Society of Forest Science
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• v.108 no.3
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• pp.329-340
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• 2019

Water pollution in erosion control dams is a major issue for forest watershed management, but the effects of erosion control dams on water quality remain poorly understood. In this study, water quality data from streams and dam reservoirs were collected over the Nakdong river basin. Monitored data were further analyzed to examine the relationship between watershed characteristics and water quality. Of the total 43 erosion control dams, less than 10% had lower water quality that was not suitable for agricultural use. TOC and oxygen demand, SS and turbidity, SS and Chl-a, and Chl-a and turbidity showed high correlations (p < 0.01) both in stream water and in detained water. BOD and SS, BOD and Chl-a, BOD and turbidity, and TOC and Chl-a showed high correlations only in stream water. Overall, the results demonstrated that for most erosion control dams the water quality was relatively good. In addition, the quality of downstream water is somewhat affected by the water detained by erosion control dams, in limited ways.

• Korean Journal of Ecology and Environment
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• v.54 no.2
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• pp.96-101
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• 2021

In this study, we wanted to obtain the information of the ecological impact of alien species on native fish communities. The Ichthyofauna and fish community in Joongchosan Reservoir and Bukchosan Reservoir in Gunsan-si Korea were investigated over the period from March to October 2020. During the survey period, a total of 1,895 individuals representing eight species, five families, and four orders were caught in the Joongchosan Reservoir. In the Bukchosan Reservoir, a total of 171 individuals were caught, representing seven species, five families, and three orders. The dominant species and subdominant species of Joongchosan Reservoir were Pseudorasvora parva (661 individuals, RA: 34.7%), and Rhodeus ocellatus (660 individuals, RA: 34.7%). Conversely, Micropterus salmoides (77 individuals, RA: 45.0%), and Carassius auratus (60 individuals, RA: 35.1%), were the two most common species in the Bukchosan Reservoir. The community indices showed a dominance of 0.697, diversity of 1.483, evenness of 0.713, and species richness of 0.928 in the Joongchosan Reservoir. In comparison, the community indices in the Bukchosan Reservoir showed a dominance of 0.801, diversity of 1.304, evenness of 0.670, and species richness of 1.167. This study confirms that the number of native fishes and the associated community diversity have decreased due to the influence of Micropterus salmoides. This highlights the need for removal of alien species from reservoirs, while simultaneously preventing future introductions.

• Journal of the Korean Institute of Gas
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• v.25 no.1
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• pp.20-29
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• 2021

During multi-stage fracturing in a low permeable shale formation, stress interference occurs between the stages which is called the "stress shadow effect(SSE)". The effect may alter the fracture propagation direction and induce ununiform geometry. In this study, the stress shadow effect on the hydraulic fracture geometry and the well productivity were investigated by the commercial full-3D fracture model, GOHFER. In a homogeneous reservoir model, a multi-stage fracturing process was performed with or without the SSE. In addition, the fracturing was performed on two shale reservoirs with different geomechanical properties(Young's modulus and Poisson's ratio) to analyze the stress shadow effect. In the simulation results, the stress change caused by the fracture created in the previous stage switched the maximum/minimum horizontal stress and the lower productivity L-direction fracture was more dominating over the T-direction fracture. Since the Marcellus shale is more brittle than more dominating over the T-direction fracture. Since the Marcellus shale is more brittle than the relatively ductile Eagle Ford shale, the fracture width in the former was developed thicker, resulting in the larger fracture volume. And the Marcellus shale's Young's modulus is low, the stress effect is less significant than the Eagle Ford shale in the stage 2. The stress shadow effect strongly depends on not only the spacing between fractures but also the geomechanical properties. Therefore, the stress shadow effect needs to be taken into account for more accurate analysis of the fracture geometry and for more reliable prediction of the well productivity.

• Journal of the Korean earth science society
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• v.42 no.6
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• pp.646-661
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• 2021

The Zagros fold-thrust belt formed from the collision of the Arabian and Eurasian plates during Cenozoic periods and extends for 2,000 km, from Turkey to the Hormuz Strait, in the northeast-southwest direction. Anticline traps in the front of the Zagros thrust fold hold approximately 8% of the world's petroleum reserves. Middle Cretaceous to Early Miocene petroleum systems of the belt have the largest original oil in place (OOIP). The oil is expelled from Kazhdumi and Pabdeh source rocks, and accumulated in the Asmari and Bangestan (including Sarvak and Ilam formations) reservoir rocks covered by the evaporitic Gachsaran and the marly Gurpi formations. The hydrocarbons trapped in the Asmari and Sarvak reservoirs are mainly charged (more than 90%) by the Kazhdumi Formation whereas the rest are charged by the Pabdeh Formation. In the Dezful Embayment, all the large high-relief anticlines have been drilled into, except in the Asmari, Sarvak and Khami formations, where a few anticlines of smaller size and deeper strata remain unexplored. Therefore, the exploration potential of these regions strengthens our understanding of the Zagros fold-thrust belt's petroleum system.

• Korean Journal of Ichthyology
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• v.34 no.1
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• pp.34-43
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• 2022

A distribution survey was conducted from March to August 2021 to evaluate the distribution status, habitat characteristics, and threat of extinction of the Korean cold-water fish Ladislabia taczanowskii Dybowski (Cypriniformes, Cyprinidae). Historical distribution reports were divided into 1997~2005, 2006~2012, 2013~2019, and distribution surveyed 169 sampling sites, and 1,040 individuals were collected from 72 sites. Areas where the habitat was confirmed were Namhan River (27 stations), Han River (17 stations), Bukhan River (16 stations), Samcheok Osipcheon (4 stations), Yeongokcheon (3 stations), Gangneung Namdaecheon (2 stations), Jeoncheon (1 station), Chucheon (2 stations). The main habitat of L. taczanowskii was upstream of the river with a high altitude of more than 300 m, 2~30 m water flow width, 0.3~1.5 m water depth, and high ratio (50~90%) 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 36.1% reduction in occupancy within 10 years, in a small appearance range (7,820 km²) and occupancy area (288 km²), number of disconnected locations (19 locations), and a decline in habitat quality. Therefore, L. taczanowskii is now considered as Vulnerable (VU) based on the results (VU A2ac, Near meets B1b (i, ii, iii)+B2b (i, ii, iii)) of IUCN Red List categories and criteria. Lastly, the conservation plan of Ladislabia taczanowskii was discussed.

• Journal of Korean Society of Disaster and Security
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• v.16 no.1
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• pp.13-22
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• 2023

The importance of preemptive flood preparation is growing as the importance of preparing for climate change increases due to record heavy rains in the Seoul metropolitan area in August 2022. Although it is responding to flood control through reservoirs and sediment sites, the government is preparing excellent spill reduction measures through a preliminary consultation system for Low Impact Development (LID). In this study, the depth of flooding was simulated when LID technologies were applied to the Sillim 2-drain region in Dorimcheon Stream basin, an urban stream, using XP-SWMM, a two-dimensional model. In addition, the analysis and applicability of the effect of reducing rainfall runoff for the largest rainfall in a day were reviewed, and it was judged to be effective as a method of reducing flooding in urban areas. Although there is a limitation in which the reduction effect is overestimated, it is thought that the LID technologies can be a significant countermeasure as a countermeasure for small-scale flooded areas where some flooding occurs after structural flooding measures are established.

• 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.