• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.328-331
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• 2005

Cheonggyecheon, covered and Paved with concretes for about more than 50 years, is a losing stream crossing over the downtown of Seoul, Korea. Due to several environmental and economic Problems about the Cheonggyecheon area, the Cheonggyecheon restoration construction has started in 2003. In restoration of Cheonggyecheon, hydraulic barriers are to be installed so as to reduce stream depletion rates for maintaining the stream flow with supplying a certain amount of water. This study evaluates the groundwater-stream interaction by analyzing stream depletion rates of Cheonggyecheon. Results show that significant stream depletion occurs at the up-midstream where the Seoul subway lines are concentrated. Simulation results demonstrate that both horizontal and vertical hydraulic barriers impeding groundwater flow into subway lines are more efficient than a horizontal barrier only for stream depletion rate reduction.

• The Korean Journal of Ecology
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• v.25 no.4
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• pp.247-252
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• 2002

Vegetation and riverine structures were compared among urban and several semi-natural rivers by applying direct gradient analysis and ordination method. Urban rivers showed different species composition from the semi-natural ones. Species composition of semi-natural rivers depended on the geographical positions, such as the upstream, midstream, and downstream and on micro-topographies, such as the waterside, flooding bed, and embankment. Semi-natural rivers showed gentle change in micro-topography, whereas urban one did not so. Our restoration plan to improve the ecological quality of the degraded urban river by imitating semi-natural river was prepared based on those data.

• The Korean Journal of Mycology
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• v.46 no.4
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• pp.447-457
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• 2018

In this paper, the screening of potent acetylcholinesterase (AChE) inhibitor - producing yeasts from wild yeasts and the condition for the production of anti-dementia AChE inhibitors are described. Among one hundred and seven non-pathogenic wild yeast strains from the waters and soils of three main rivers in Daejeon metropolitan city and midstream of Yeongsangang river in Sangju, sporogenous Saccharomyces cerevisiae WJSL0113 and asporogenous Wickerhamomyces anomalus JSF0128 were selected as useful strains for the production of potent AChE inhibitors. The AChE inhibitors of S. cerevisiae WJSL0113 and W. anomalus JSF0128 had a maximum yield when they were incubated in yeast extract-peptone-dextrose media (pH 6.0 in S. cerevisiae WJSL0113 and pH 5.0 in W. anomalus JSF0128) for 18 hr at $30^{\circ}C$, respectively.

• Korean Journal of Ecology and Environment
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• v.33 no.1 s.89
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• pp.51-60
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• 2000

In order to understand the trend and assessment of water pollution, seasonal water quality was determined in the main river and the tributaries from midstream to downstream of the Kum River from March 1998 to June 1999. Among environmental factors, the variation of nitrogen, phosphorus and chlorophyll-a was distinctive on an aspect of increase and decrease relatively to others, and particularly the impact of inorganic N ${\cdot}$ P inflowing into the main river was observed to be more significant at the Kapchon, Mihochon and Soksongchon among the tributaries. Water quality was highly related to hydrologic factor, and it was more deteriorated when water discharge maintains for a long time below normal flow or relatively at low condition of minimum and drought flow. These phenomena were remarkablee from December to March of the next year. $NH_4$ and SRP were decreased dramatically flowing toward the lower part of the river and chl-a was increased exponentially. While, the variations of $NO_3$ and $BOD_5$ were regular from midstream to downstream and there was no significant difference between the stations. Limiting nutrient for Phytoplankton growth seemed to be P than N because the ratio of TN/TP or DIN/SRP was relatively high as 42 or 544 in the main river, respectively. The main river and tributaries were ranked to be third grade, based on the assessment of BOD as an indirect indicator of organics, but particularly Kapchon was ranked to be over fifth grade. In addition, the inflow of high N ${\cdot}$ P nutrients from tributaries including Kapchon and Mihochon seemed to be major factor of the development of water pollution of the Kum River. On the other hand, persistent bloom of phytoplankton in lower part of the river was observed. As a conclusion, management of water quality for main source of pollution is urgent.

• The Korean Journal of Mycology
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• v.47 no.1
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• pp.51-61
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• 2019

The goal of this study was to elucidate wild yeast diversity of Geumgang midstream near Sejong metropolitan autonomous city, Korea. Thirty-seven strains of 32 species of wild yeasts were isolated from 43 water and soil samples under the Bulti bridge of Sejong city, Korea. Seven yeasts of each Candida spp. and Cryptococcus spp. were the predominant species isolated from samples near the Bulti bridge. Holtermanniella takashimae SW048 (NNIBRFG9314), Cystofilobasidium infirmominiatum SW013 (NNIBRFG9310), Mrakia cryoconite SW015 (NNIBRFG9316), Pichia sporocuriosa SW085 (NNIBRFG9326) and Cryptococcus aspenensis SW008 (NNIBRFG9309) represented novel yeast strains found in Korea for the first time. All of these previously unrecorded yeasts, except for Mrakia cryoconite SW015 had ascospores and grew well in yeast extract-peptone-dextrose (YPD), yeast extract-malt extract (YM) and potato-extrose (PD) media. Pichia sporocuriosa SW085 grew well in vitamin-free medium and Holtermanniella takashimae SW048, which was a halotolerant wild yeast, grew well YPD medium containing 5 % NaCl. Twenty-six strains representing eight species of wild yeast were isolated from 22 water and soil samples under the Haetmuri bridge of Sejong city, Korea. Candida pseudolambica (12 strains) and Aureobasidium pullulans (11 strains) were the predominant isolates from samples near the Haetmuri bridge. Occultifur kilbournensis HB060 (NNIBRFG9317), Sampaiozyma vanillica HB014 (NNIBRFG9332), Xenoramularia neerlandica HB039 (NNIBRFG9335), Candida norvegica HB315 (NNIBRFG9306), C. melibiosica HB316 (NNIBRFG9305), C. quercuum GB014 (NNIBRFG9307), and C. succiphila GB015 (NNIBRFG9308) represented novel yeast strains recorded in Korea for the first time. O. kilbournensis HB060 and X. neerlandica HB039 did not form ascospores or pseudo-mycelia. All of these previously unrecorded yeasts, except S. vanillica HB014 and X. neerlandica HB039, grew well in vitaminfree medium, and C. norvegica HB315 and C. succiphila GB015, which were halotolerant wild yeasts, which grew well in YPD medium containing 5 % NaCl.

• Korean Journal of Environmental Agriculture
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• v.23 no.1
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• pp.41-46
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• 2004

The influence of pollutant loads on the water quality in Jeongeupcheon of Dongjin river was evaluated from Jan. 2002 to Dec. 2003 for two years. The range of pH in water was $6.87{\sim}7.53$. The EC level in upstream ranged from 83 to $95\;{\mu}s/cm$ with the highest value in autumn. The BOD level in upstream rang ed from 0.61 to 1.27 mg/L, which would be I grade according to water quality criteria by Ministry of Environment, but that in downstream was III grade. The average T-N level in midstream ranged from 6.10 to 10.84 mg/L which was the highest values throughout the stretch of the river. The average T-P levels ranged from. 0.41 to 0.98 mg/L Jeongeupcheon was suitable for the agricultural usage based upon one year analysis of river water quality. The effluent loads of BOD was high in midstream (J4) with 553 kg/day. The major sources of T-N loads were livestock, population, land use, and industry in order. The effluent loads of T-N was high in J4 by population and industry while that of T-N was high in J5 and J6 by livestock and land use. The delivered loads of T-N was high in downstream The delivered loads of T-P was low as compared with those of BOD and T-N. The delivery ratio of T-N ranged from 6 to 38%.

• Journal of the Economic Geographical Society of Korea
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• v.17 no.4
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• pp.817-831
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• 2014

In this paper insights from studies on the middle income trap and value chains analyses are combined to investigate one particular industry in one particular region: the sugarcane industry in Northeastern Thailand. Focusing on this region enables an in-depth focus on geographical differentiation of the middle income trap. The empirical outcomes demonstrate that policymakers involved with sugar should look at the particular challenges in Northeastern Thailand: 1. The role of brokers which is unaddressed in the current regulatory environment; 2. A lack of information of the regulatory environment among growers; 3. Distrust between growers and millers; 4. Alack of implementation of R&D efforts; 5 .A lack of support from associations; 6. The labor shortage problem, and 7. No incentives for growers, brokers and millers to improve quality and embark on upgrading. Since agricultural value chains in Southeast Asia often start in relatively poor rural areas it is imperative that policymakers balance the interests of upstream, midstream and downstream actors. Unfortunately, this is rather difficult as midstream actors (millers) and wholesalers are powerful and therefore, are in the best position to defend their interests. Our insights could function as comparative material for similar studies within other Southeast Asian upstream value chains.

• The Korean Journal of Mycology
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• v.46 no.2
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• pp.98-104
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• 2018

The goal of this study was to elucidate wild yeast diversity of the midstream region of the Geumgang river, Gongju, Chungnam province, Korea. Fifty strains of 24 species of wild yeasts were isolated from 45 water and soil samples among which Cryptococcus spp. (11 strains), Cryptococcus magnus (7 strains), Rhodotorula spp. (9 strains), and Hanseniaspora spp. (6 strains) were dominant. Four species, Candida chauliodes WJSF 0201, Candida oleophila WJSF 0202, Candida catenulata WJSF 0203, and Candida jaroonii WJSF 0204, represented newly recorded yeasts in Korea. All of these unrecorded yeasts were oval in shape, formed ascospores and pseudomycelium, and grew in vitamin-free medium. Candida oleophila WJSF 0202 was thermophilic which can grow at $37^{\circ}C$.

• Journal of The Korean Society of Agricultural Engineers
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• v.61 no.4
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• pp.11-22
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• 2019

The objective of this study was to improve the cross-sectional area and height estimation method using stream width. Stream water levels should be calculated together to simulate inundation of agricultural land. However, cross-sectional survey data of small rural rivers are insufficient. The previous study has developed regression equations between the width and the cross-sectional area and between the width and the height of stream cross-section, but can not be applied to a wide range of stream widths. In this study, cross-sectional survey data of 6 streams (Doowol, Chungmi, Jiseok, Gam, Wonpyeong, and Bokha stream) were collected and divided into upstream, midstream and downstream considering the locations of cross-sections. The regression equations were estimated using the complete data. $R^2$ between the stream width and cross-sectional area was 0.96, and $R^2$ between width and height was 0.81. The regression equations were also estimated using divided data for upstream, midstream and downstream considering the locations of cross-sections. The range of $R^2$ between the stream width and cross-sectional area was 0.86 - 0.91, and the range of $R^2$ between width and height was 0.79 ? 0.92. As a result of estimating the cross-sections of 6 rivers using the regression equations, the regression equations considering the locations of cross-sections showed better performance both in the cross-sectional area and height estimation than the regression equations estimated using the complete data. Hydrologic Engineering Center - River Analysis System (HEC-RAS) was used to simulate the flood stage analysis of the estimated and the measured cross-sections for 50-year, 100-year, and 200-year frequency floods. As a result of flood stage analysis, the regression equations considering the locations of cross-sections also showed better performance than the regression equations estimated using the complete data. Future research would be needed to consider the factors affecting the cross-sectional shape such as river slope and average flow velocity. This study can be useful for inundation simulation of agricultural land adjacent to an unmeasured stream.

• Journal of Wetlands Research
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• v.23 no.1
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• pp.27-34
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• 2021

In this study, the main influencing factors of the occurrence of cyanobacteria at each of the eight Multifunctional weirs were derived using a random forest, and a categorical prediction model based on a Algal bloom warning system was developed. As a result of examining the importance of variables in the random forest, it was found that the upstream points were directly affected by weir operation during the occurrence of cyanobacteria. This means that cyanobacteria can be managed through efficient security management. DO and E.C were indicated as major influencers in midstream. The midstream section is a section where large-scale industrial complexes such as Gumi and Gimcheon are concentrated as well as the emissions of basic environmental facilities have a great influence. During the period of heatwave and drought, E.C increases along with the discharge of environmental facilities discharged from the basin, which promotes the outbreak of cyanobacteria. Those monitoring sites located in the middle and lower streams are areas that are most affected by heat waves and droughts, and therefore require preemptive management in preparation for the outbreak of cyanobacteria caused by drought in summer. Through this study, the characteristics of cyanobacteria at each point were analyzed. It can provide basic data for policy decision-making for customized cyanobacteria management.