• Journal of the Korean GEO-environmental Society
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• v.13 no.1
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• pp.45-51
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• 2012

This article aims to find method to mix a harmless hardening agent and soil generated during construction to make paving materials. The main purpose of this research is to get rid of the harmfulness(Chromium (VI), etc.) of cement which has been generally and frequently used as a hardening agent and strengthen it so that it can be used for the general foundation solidification and stabilization of civil engineering/construction structures such as dredging soil treatment, marine structure foundation treatment, surface soil stabilization, and river bank erosion prevention. NSS(Natural Stabilizer Soil) used for this study takes as its chief ingredient the mixture of lime and staple fibers extracted from natural fibers. It increases the shearing strength of soil that it improves the support and durability of the foundation and prevents flooding and frost as well. The pH measured to know its eco-friendliness was 6.67~7.15, and according to the migration testing, only Pb and CN were lower than the standards, so it can be said that NSS has almost no harmful components in it. According to the result of uniaxial strength testing, when the mixture ratio of weathered soil to NSS was 6%, about 1,850kpa strength was expressed. And according to the result of CBR. testing to figure out its appropriateness as a paving material, the CBR of the foundation was 4%~6%. But when the mixture ratio of NSS is over 6%, the water immersion CBR. is over 100%; thus, it is expected that it will show great utility as a paving material.

• The Korean Journal of Ecology
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• v.22 no.3
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• pp.131-137
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• 1999

This study was carried out to investigate the activity of nitrogen fixation and accumulation of heavy metal and inorganic matter in Vicia amoena community at lower region in Kumho riverside, including Youngchon, Chimsangyo, Paldalgyo, Talseochon and Kumhogyo. The contents of inorganic matter and heavy metal of Kumho riverside soil increased in the down stream in each organ of the plant growing in the riverside. Generally, V. amoena community showed rapid growth of shoot and high value of Top/Root ratio. V. amoena community showed higher water content of shoot at late growth stage and higher chlorophyll content. The root nodule of V. amoena community appeared in April and increased by 0.30, 0.27, 0.24, 0.06 and 0.14 g/plant, and nitrogen fixation activity of nodule attained 20.1, 16.8, 15.4, 8.5 and 5.3 μmol·C₂H₄·g fw nodule/sup -1/·h/sup -1/ for non-contaminated area Youngchon, Chimsangyo, Paldalgyo, Talseochon and Kumhogyo, respectively, in June:. Nodule formation and nitrogen fixation activity were reduced in the down stream by the soil contamination and heavy metal accumulation and showed minimum values. at Talseochon and Paldalgyo. V. amoena showed growth adaptation against heavy metal toxicity by restricting heavy metal such as Pb, Cu, Zn, Fe from transport, and by accumulating high Ca ion in shoot, nitrogen and phosphorus in root at late growth stage than those at early one, respectively, but total heavy metal per plant showed higher values in shoot than those in root by high T/R ratio of plant growth.

• Korean Journal of Ecology and Environment
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• v.38 no.4 s.114
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• pp.445-453
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• 2005

Relative importance between bottom-up and top-down controls on phytoplankton dynamics was investigated in the Juam Reservoir, Chonnam based on the results from statistical analyses including regression and artificial neural network (ANN) modeling. Effects of nutrients on size-structured phytoplankton dynamics were explored by simple linear regression analysis and relative importance between bottom-up and top-down controls was estimated based on results from the artificial neural network analyses. Although there is a limitation in determining direct grazing effects since chlorophyll a : pheopigments ratios, indirect index for grazing activity rather than grazing rates or herbivores biomass were used, the results from regression analysis showed that nutrients especially orthophosphates were positively correlated with the phytoplankton biomass and chlorophyll a : pheopigments ratios were also positively correlated with the phytoplankton biomass at lower coefficient of determination ($r^2$) compared to orthophosphates. The simulation results from ANN suggested that the bottom-up mechanisms including water temperature and availability of nutrients, especially orthophosphates were more important than top-down mechanisms such as grazing in the phytoplankton dynamics.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.1
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• pp.45-57
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• 2019

The resident characteristics of land-based pollutants were analyzed to manage the pollution sources affecting Suyeong Bay. These characteristics were analyzed using a hydrodynamic model and particle tracking model. Pollutants were represented by particles, and the amount of particles and pollutants was represented proportional. The resident characteristics were analyzed by comparing the amount of pollutant load, resident pollutants, and the ratio of resident pollutants remaining in the bay relative to the incoming load for each the of pollution sources. The order of the pollution sources was as follows, according to the amount of resident pollutants at Suyeong Bay. the Suyeong WasteWater Treatment Plant(WWTP), Nambu WWTP, Suyeong river and so on. The amount of resident pollutants was smaller for small load farther away from the interior of bay. Nambu WWTP had the greatest load among the pollution sources, but it showed the smallest ratio of pollutants remaining in the bay relative to incoming load among the pollution points. The result indicates that pollutants affect sea areas differently according to the characteristics each area and the topographic characteristics of pollution sources.

• Journal of Korea Water Resources Association
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• v.42 no.10
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• pp.845-855
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• 2009

In this study, changing characteristics of bed materials downstream of Daecheong Dam by flushing flow was investigated. Flushing flow affected the downstream environment in such a way that the mean diameter of bed material was increased and the standard deviation was decreased. The vertical sorting of bed materials composed of mixed sediment in the sediment box was observed. The surface layer was composed of gravels, and uniform sand material was buried below it. Relative fractions (Di/D50) of the bed material trapped in the box was nearly 1.0 for the bed material coarser than D$_{50}$ at Hyundo gauging station, and was between two values on the bed surface before and after the flushing flow at Bugang gauging station. Ratio of driving force to resisting force for each fraction ($\tau_i^*$) with the faction size maintained constant for the bed material coarser than D$_{50}$ at Hyundo station. At Bugang station, however, it was rapidly decreased. It means that pavement of the surface layer of bed material at Bugang station was developed, with the sediment particles moving downstream uniformly by flushing flow.

• Korean Journal of Ichthyology
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• v.17 no.3
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• pp.195-204
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• 2005

The population ecology of Rhinogobius brunneus was investigated on, tributaries of the Bukhan River from May 2003 to June 2005. The habitat was mostly a rapids area with pebbles and cobles in the lower part of the stream. The cohabitation fishes were Zacco platypus, Zacco temmincki, Microphysogobio yaluensis and Iksookimia koreensis. The males and females become sexually mature after one year. Spawning season was from May to June with water temperatures in the range $22{\sim}25^{\circ}C$. The prosperous period was from late May to early June. The average number of eggs in the ovary was $989{\pm}511$ (range, 151~2,209). The year-round sex ratio of female to male was 1 : 0.90. The total length in this population indicated that the below-40 mm group is one year old, 40~52 mm group is two years old, 52~65 mm group is three years old, and the longer-than-65 mm group is over four years old. There were no differences in total length distribution between the males and females. Nests were built up at a water depth of $13.7{\pm}5.8$ (5~31) cm and a current velocity of $9.6{\pm}4.8$ (10~19) cm/sec. Brood size (egg number) of the parental male was $1,974{\pm}1810$ (egg number = $95.022_{TL}-3507$, $r^2=0.3591$, N = 33). Newly hatched larvae that drifted downstream to the lake returned to the stream during late June to August; the smallest size in this population was 20 mm in total length.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.8
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• pp.5636-5645
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• 2015

Physical characteristics of aggregates affect the workability and strength of mortar and concrete, which include their fineness ratio, particle size distribution and water absorption. The workability of construction materials decreases if the incorporated fine aggregates show improper size distribution of their particles. This study shows the particle size effect on the rheological behavior of mortar and provides basic information for evaluating its workability. A mini-slump flow test was adopted to evaluate the workability of mortar. In addition, its plastic viscosity and yield stress were measured using a rheometer for building materials. The sand samples were prepared by sieving river sand and sorting out with their particle sizes. As a result, it was observed that the fines less than 0.7 mm increases the yield stress and plastic viscosity of the mortar samples. If the fines are less than 0.34 mm, the water absorption of the fines dominates change on the workability.

• Journal of Korea Water Resources Association
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• v.38 no.11
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• pp.917-925
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• 2005

LSIV (Large Scale Image Velcocimetry) Is one of the image-based velocity measurement techniques. Since it measures surface velocities, it gives simple and inexpensive way to measure velocity, compared to other methods. Because of these advantages, there have been many studies to apply LSIV to the river discharge measurement in the field. Measuring the discharge by using LSIV requires a method which converts a surface velocity to a mean velocity In the present study, experiments and analysis of vortical velocity profile of open-channel flow in various conditions were performed to develop methods which estimate a mean velocity from a surface velocity. The result of this experiment reveals that velocity-dip phenomena occur at free-surface layer in open channel flow and Froude number affects more than bed roughness does. Two methods for estimating the mean velocity were proposed. One is to correct the wake law's profiles by using the difference of surface velocity from the mean velocity, and the other is to use the ratio of mean and surface velocities. The result of applying these methods in an experiment shows that they are quite accurate having an error of approximately $6\%$ only.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.3345-3350
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• 2014

We investigated to assess the relationships between the major nutrients and phytoplankton dynamics during the spring season in 2010 and 2011 at 23 stations in Jinhae Bay, Korea. The bay is divided into four different zones based on pollutant sources and geographical characteristics. Nutrient limitation (>80%) was significant in Zone II, which is located in central bay and is influenced by the water well mixed from outer bay. The limited nutrient was followed in Zone III and IV that was occupying between 17% and 83%. However, the low levels are being kept below 35% in Zone I, which is characterized by the semi-enclosed eutrophic area of Masan and Haegam bays. Based on the PCA (principle component analysis) analysis, the nitrogen (N) sources in 2010 were particularly dominant and it may be due to the water mixing and wastewater formed from bottom layers and sewage. In 2011, major nutrients including nitrogen, silicon and phosphorus were dominant in the bay and are supplied by the river discharge after rainfalls with low salinity conditions. In particular, the N nutrients being supplied in 2010 are correlated with pennate diatoms Pseudo-nitzchia spp. and is not related to the phytoplankton population densities in 2011. The present study suggests that N sources play an important role in the proliferation of diatom, and the rapid nutrient uptakes by them are potential nutrient limitation factors in the bay.

• Korean Journal of Environment and Ecology
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• v.35 no.3
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• pp.277-284
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• 2021

This study surveyed the ecological characteristics of Squalidus gracilis majimae at Nakdong River tributary Sinan Stream from January to December 2020. The species inhabited the riverbed that was mostly covered with gravel and sand. The water depth was 27-158 cm, and the average was rather deep at 54 cm. The stream velocity was slow at 0.41±0.19 (0.24-0.86) m/sec. The gender ratio of females to males was 1:0.73. According to the total length-frequency distribution, the age indicated that the group with less than 50 mm in total length was one year old, the group with 70-69 mm was two years old, and the group over 70 mm was three years old. The total length of sexually mature fishes was 50 mm for females and 60 mm for males. The spawning season was from June to July, and the water temperature was 20.9-23.4℃ during the period. The prosperous spawning season was July. The average number of eggs in the ovaries was 1,009 (595-1,630) per matured female, and the matured eggs were yellowish and spherical with a mean diameter of 0.78±0.08 (0.57-0.83) mm. The live foods were S. gracilis majimae Protozoa, attached algae, zooplankton, and aquatic insects. The feeding habits of S. gracilis majimae are omnivorous, but more than 80% of the stomach content was aquatic insects, Chironomidae spp. The larger the size of this species, the greater the amount and frequency of eating aquatic insects, which are animal feeds. The population that ate aquatic insects did not eat vegetable food.