• Journal of the Korean institute of surface engineering
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• v.35 no.5
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• pp.305-311
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• 2002

Optical measurements have been used to study the biaxial tensile strain in heteroeptaxial ZnTe epilayers on the (100) GaAs substrate by hot wall epitaxy (HWE) with Zn reservoir. It is effect on the low-temperature photoluminescence spectrum of the material. Optimum growth condition has been determined by a four-crystal rocking curve (FCRC) and a low temperature photoluminescence measurement (PL). It was found that Zn partial pressure from Zn reservoir has a strong influence on the quality of grown films. Under the determined optimum growth condition, ZnTe epitaxial films with thickness of 0.72~24.8$\mu\textrm{m}$ were grown for studying the effect of the thickness on crystalline quality. The PL and FCRC results indicated that the quality of ZnTe films becomes higher rapidly with increase of thickness up to 6$\mu\textrm{m}$. The best value of the FWHM of the four crystal rocking curve, 66 arcsec, was obtained on the film with 12$\mu\textrm{m}$ in thickness. The PL spectrum shows the splitted strong free exciton emissions and very weak deep band emissions. These results show the high quality of films.

• Journal of Environmental Science International
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• v.29 no.7
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• pp.691-702
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• 2020

Carbon biomass of plankton community, Total Organic Carbon (TOC) and Chlorophyll a (chl.a) concentration were examined in the SeoNakdong river from January to December in 2014, to assess composition of phyto- and zoo-plankton variation, to certify the correlation between chl.a and TOC and to determine the level of contribution of plankton carbon content to TOC in the reservoir-river ecosystem. The correlation level between TOC and chl.a was low in the year 2014 but exceptionally was highly correlated only during the period with cyanobacterial bloom. The high level of contribution of plankton carbon content to TOC was attributed to cyanobacterial carbon biomass from May to November and to Cladocera carbon biomass from March to May, November and December despite of its low abundance. These results suggest that there were inter-relationships between phytoplankton, zooplankton and TOC and also subtle consistency of their properties through the year. These patterns should be discussed in relation to the physiochemical and biological characteristics of the environment, as well as to allochthonous organic matters from non-point pollution sources.

• Journal of the Korean Institute of Landscape Architecture
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• v.31 no.2
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• pp.102-112
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• 2003

This study was carried out to research and develop a shallow green rooftop system which would require low maintenance and therefore could be used for existing rooftops. To achieve these goals, the conceptual model was induced by past studies and the experimental systems were deduced from the conceptual model. On the growth of Sedum sarmentosum grown in these rooftop systems, the effects of artificial substrate type, soil depth, and drainage type were investigated from 3 April to 11 October 2002. Artificial substrates were an alone type and a blending type. The alone type was an artificial substrate formulated by blending crushed porous glass with bark(v/v, 6:4). The blending type was formulated by blending the alone type with loam(v/v, 1:1). Soil depths were 5cm, loom, and 15cm. Drainage types were a reservoir-drainage type and a drainage type. The reservoir-drainage type could keep water and drain excessive water at the same time. The drainage type could drain excessive water but could not keep water. Covering area, total fresh and dry weight, visual quality, and water content per 1g dry matter were measured. All the variables were analyzed by correlation analysis and factor analysis. The results of the study are summarized as follows. The growth increment was higher in the blending type than in the alone type, the highest in loom soil depth and higher in the reservoir-drainage type than in the drainage type. The growth quality was higher in the blending type than in the alone type, the highest in l0cm soil depth, and higher in the drainage type than in the reservoir-drainage type. In consideration of the permissible load on the existing rooftops and the effects of the treatments on the growth increment and quality, the system should adopt the blending type in artificial substrate types, 5~10cm in soil depths, and the drainage type in drainage types. This system will be well-suited to the growth of Sedum sarmentosum, and when the artificial substrate was in field capacity, the weight will be 75~115kg/$m^2$.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.31 no.6_1
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• pp.439-446
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• 2013

This paper is about assessment of soil loss in irrigation reservoir based on GIS. Natural disaster caused by soil loss whose natural incidence has been rapidly reduced due to successful tree planting campaign shows high potential risk, since the latest localized heavy rain resulted from extreme weather event and artificial land development acts as direct factors for land disaster. To prevent it, various techniques and technologies have been used to predict effect of soil loss. However, reliability of techniques and technologies to predict its effect precisely is relatively low so far because the natural disaster by soil loss is taken place by complicated interaction between possible factors and direct factors. Geospatial approach is essential to examine these interactions. In this regard, this study will provide detailed plan to improve prediction reliability for soil loss of irrigation reservoir, using GIS that has Hydrologic -Topographical parameter and digital map as its input parameters.

• Parasites, Hosts and Diseases
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• v.28 no.4
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• pp.221-234
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• 1990

The present study was performed to know the epidemiological statug of echinostomiasis in the Chungju Reservoir and upper streams of Namhan River, together with an experimental study on the life history o( Echinostoma hortense. The stool specimens of 169 inhabitants and 473 junior high school students from 5 different villages revealed 3(0.5%) echinostomatid egg Positive cases. E. hortense adult worms were recovered from one patient after a treatment and purgation. For the other two patients, it was presumed that one had 2. hortense and another E. cinetorchis infection, based on the morphology of eggs. Five kinds of freshwater snails(168 Radix auricularia coreane, 534 Physa arutp, 144 Hippeutis cnntori, 56 Cipcngopaludina chinensis malleata and 125 Semiiulcospira nediila glebus) examined for the cercariae of echinostomes showed negative results. Ten kinds of freshwater fishes examined for E. herten-'emetacercariae revealed positive rates as Misgurnus anguillicaudatus 40.5%, Odentobutis obscura interrupta 20.3%, Moroco onycephalus 3.9%, and Coreoperca hawamebari 2.0%. In the experimental study, the metacercariae of E. horlense were infected to rats, eggs were collected from adult worms and cultivated, and miracidia were obtained. The miracidia were artificially infected to freshwater snails (R. auricularia), and cercarial shedding was studied. It was revealed that, when the snails were kept at a low temperature ($24^{\circ}C$), only 523 cercariae (on average) were produced during 24 hrs, while they were at a high temperature ($30^{\circ}C$), as many as 9, 990 cercariae (on average) were shed during the same time. The experimental infection of E. hortense cercariae to freshwater fishes was successful in 0. obscura interrupta 52.0%, M. anguillicaudatus 30.3%, C. kawamebari 27.0%, Cobitis lutheri 15.0%, M. cxycephazus 7.3%, Pseudogobio esocinus 4.3%, Squalidus cereanus 2.0%, Zccco platypus 1.3%, and Pungtungia herzi 1.3%. However, infection was not successful to snails, C. chinensis. It has been proved that the Chungju Reservoir and upper streams of Namhan riyrr are endemic areas of echinostomiasis, especially of E. horfense, and snails such as R. auritulerie coreana and fishes such as O. obscura interrupts, M. gnguillicgudgtus, and others are taking the role of 6rst and second intermediate hosts, respectively.

• Journal of the Korea Organic Resources Recycling Association
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• v.21 no.3
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• pp.93-98
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• 2013

Main causes of algal bloom was studied in Paldang reservoir. Statistical approach was tried using meteorological and water quality data. Algae alert system showed that more than ten days were counted in a year, once it happened in Paldang reservoir. Alert dates increased in recent 5 years. Correlation coefficients between chlorophyll-a and other indexes did not showed strong relations resulting in coefficients less than 0.4. Among them, sunshine duration, BOD, and flow rate were appeared relatively main causes of algal blooming. Sunshine duration and BOD showed positive relation while flow rate did negative one, which is resonable for photosynthetic microorganisms. Water temperature and total phosphorus, which were presumed probable main causes before study, resulted in low correlation coefficients. Correlation coefficients between discharge flow and rainfall, water temperature showed positive relation due to seasonal effect.

• Journal of Environmental Science International
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• v.23 no.7
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• pp.1321-1332
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• 2014

The key objective of this study was to evaluate trophic state and empirical water quality models along with analysis of fish trophic guilds in relation to water chemistry (N, P). Trophic state index (TSI), based on total phosphorus (TP) and chlorophyll-a (CHL), ranged between oligotrophic and hypereutrophic state, by the criteria of Nurnberg(1996), and was lower than the trophic state of total nitrogen (TN). Trophic relations of Secchi depth (SD), TN, TP, and CHL were compared using an empirical models of premonsoon (Pr), monsoon (Mo), and postmonsoon (Po). The model analysis indicated that the variation in water transparency of Secchi depth (SD) was largely accounted (p < 0.001, range of $R^2$ : 0.76-0.80) by TP during the seasons of Mo and Po and that the variation of CHL was accounted (p < 0.001, $R^2=0.70$) up to 70% by TP during the Po season. The eutrophication tendency, based on the $TSI_{TP}$ vs. $TSI_{N:P}$ were predictable ($R^2$ ranged 0.85-0.90, p < 0.001), slope and y intercept indicated low seasonal variability. In the mean time, $TSI_{N:P}$ vs. $TSI_{CHL}$ had a monsoon seasonality in relation to values of $TSI_{N:P}$ during the monsoon season due to a dilution of reservoir waters by strong monsoon rainfall. Trophic compositions of reservoir fish reflected ambient contents of TN, TP, and CHL in the reservoir waters. Thus, the proportions of omnivore fish increased with greater trophic conditions of TP, TN and CHL and the proportions of insectivore fish decreased with greater trophic conditions.

• Journal of Environmental Impact Assessment
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• v.15 no.2
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• pp.121-127
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• 2006

The conventional water quality measurements by point sampling provide only site specific temporal water quality information but not the synoptic geographic coverage of water quality distribution. To circumvent these limitations in temporal and spatial measurements, the use of remote sensing is increasingly involved in the water quality monitoring research. In other to assess a trophic state of Yongdam reservoir using satellite imagery data, I obtained Landsat ETM data and water quality data on 16th September and 18th October 2001. The approach involved acquisition of water quality samples from boats at 33 sites on 16th September and 30 sites on 18th October 2001, simultaneous with Landsat-7 satellite overpass. The correlation coefficients between the DN values of the imagery and the concentrations of chlorophyll-a were analyzed. The visible bands(band 1,2,3) and near infrared band(band 4) data of September image showed the correlation coefficient values higher than 0.9. The October image showed the correlation coefficient values about 0.7 due to the atmospheric effect and low variation of chlorophyll-a concentration. Regression models between the chrophyll-a concentration and DN values of the Landsat imagery data have been developed for each image. The regression model was determined based on the spectral characteristics of chlorophyll, so the green band(band 2) and near infrared band(band 4) were selected to generate a trophic state map. The coefficient of determination(R2) of the regression model for 16th September was 0.95 and that of the regression model for 18th October was 0.55. According to the trophic state map made based on Aizaki's TSI and chlorophyll-a concentration, the trophic state of Yongdam reservoir was mostly eutrophic state during this study.

• Journal of Korean Society on Water Environment
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• v.21 no.2
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• pp.125-131
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• 2005

Natural organic matter(NOM) is defined as the complex matrix of organic material and abundant in natural waters. It affects the performance of unit operations for water purification. Several kinds of analytical indicators such as DOC, specific ultraviolet absorbance(SUVA), apparent molecular weight (AMW), fractionation and high performance size exclusive chromatography(HPSEC) have been used to understand characteristics and variations of NOM. This study aims to evaluate the characteristics of NOM in the Geum River system comprising with stream flows and reservoirs. It was identified that SUVA denoting the portion of humic substance in water ranged within 1.60~3.36. Using resin adsorbents, dissolved organic carbon(DOC) was fractionated into three classes: hydrophobic bases(HOB), hydrophobic acids(HOA) and hydrophilic substances(HI). HI dominates in all samples, collectively accounting for more than 62% of the DOC. HOA was the second dominated fraction and it varied considerably but accounted for about 30% of the DOC. The distribution of high molecular weight(HMW) measured by HPSEC being used to determine the molecular weight distribution of aquatic humic substances was 40.1% and 38.7% in reservoir and stream flow, respectively. The distribution of low molecular weight(LMW) in stream flow was 13.2% higher than that in reservoir. And apparent molecular weight less than 1KDa, which include the molecular weight of hydrophilic organic matter, occupied with 69.2% and 68.2% in stream flow and reservoir, respectively. While the molecular weight of 1 to 100 KDa including humic substances ranged with 18.6% and 21.6% in stream flow and reservoir, respectively. Seasonal variation of refractory dissolved organic carbon was similar to that of SUVA.

• 한국지구물리탐사학회:학술대회논문집
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• 2008.10a
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• pp.47-50
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• 2008

Streamer resistivity surveys in shallow marine environments were carried out to analyze sediment characteristics at the bottom of reservoir. Because the resistivity values of reservoir water are very low and those of sediment are relatively high, apparent resistivity values increase with depth. And it is necessary to eliminate the apparent resistivity data decreased highly when the number of separation increases. According to the repeated data processing, we proposed the resistivity ratio of upper-to-lower layer is $0.6{\sim}0.8$ because the RMS error of inversion leads to the minimum in these range. As a result of the inversion for two- and three-layer model, the inversion including water depth is proved to be more effective than conventional method.