• Polymer(Korea)
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• v.28 no.2
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• pp.185-193
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• 2004

Elastomeric nanocomposites were prepared by employing zinc dimethacrylate into an acrylonitrile-butadiene rubber, and their network structures, mechanical properties, and fracture morphologies were investigated according to the adding methods and contents of zinc dimethacrylate. The total crosslink density increased with increasing the zinc dimethacrylate level, due to increased ionic bonds. Both the tensile strength and tear strength increased with increasing zinc dimethacrylate loadings, and then decreased after reaching a maximum value. It was found that the tear strength and crack resistance were greatly affected by the mixing method of zinc dimethacrylate. The in-situ nanocomposites, where zinc dimethacrylate particles were formed by the reaction of zinc oxide and methacrylic acid, showed much improved tear strength and crack resistance compared to those of the nanocomposites based on the direct mixing of zinc dimetacrylate powders. This was because of the finer zinc dimethacrylate particles and improved dispersion of the in-situ nanocomposites.

• 한국해양학회지
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• v.23 no.4
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• pp.159-168
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• 1989

Nutrients and trace metals of copper and nickel were investigated in the inner part of Deukryang Bay (southern coast of Korea) during 1980-81. This region is characterized as permanently well-mixed coastal waters. Because of this hydrographic condition, nutrients and trace metals showed interesting features in their seasonal cycles. The concentrations of dissolved nutrients and dissolved trace metals were higher in fall and winter than in spring and summer, while the concentrations of suspended particulates and particulate trace metals were much higher in winter than the rest of the year. Seasonal changes of nutrients suggest that the addition of nutrients via freshwater runoff during the late summer enhanced phytoplankton growth and subsequently caused phytoplankton blooms in winter. Depletion of nitrate seems to terminate phytoplankton bloom in this region, and copper and nickel appeared to be controlled by the in situ primary production.

• Korean Journal of Remote Sensing
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• v.35 no.6_3
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• pp.1187-1195
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• 2019

We, for the first time, developed a Raman lidar system which can remotely detect surface CO₂ volume mixing ratio (VMR). The Raman lidar system consists of the Nd: YAG laser of wavelength 355 nm with 80 mJ, an optical receiver, and detectors. Indoor CO₂ cell measurements show that the accuracy of the Raman lidar system is calculated to be 99.89%. We carried out the field measurement using our Raman lidar at Pukyong National University over a seven-day period in October 2019. The results show good agreement between CO₂ VMRs measured by the Raman lidar (CO₂ Raman Lidar) and those measured by in situ instruments (CO₂ In situ) which located 300 m and 350 m away from the Raman lidar system. The correlation coefficient (R), mean absolute error (MAE), and root mean square error (RMSE) between CO₂ In situ and CO₂ Raman Lidar are 0.67, 2.78 ppm, and 3.26 ppm, respectively.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.6B
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• pp.695-701
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• 2006

A toluene-degrading bacterial strain was isolated from a mixed culture that was maintained using toluene as a sole carbon and energy source. The isolated bacterium was classified as Pseudomonas sp. TBD4 based on the close relationship to bacteria belonging to this genus. A bottle study to determine biodegradation rates of individual aromatic compounds showed that the biodegradation was faster in the order of toluene, benzene, styrene, and p-xylene. However, when various mixtures were subjected to TDB4, styrene was degraded at the highest rate, indicating that both toluene and p-xylene could stimulate the degradation of other substrates whereas styrene played as an inhibitor. In addition, the mixed culture and TDB4 were inoculated to the bioactive foam reactor (BFR), and the reactor performance and the corresponding change of microbial community were monitored using the fluorescent in situ hybridization (FISH) method. When an inlet concentration of the VOC mixture increased to greater than 250 ppm, the overall removal efficiency dropped significantly. The FISH measurement demonstrated that the ratio of TDB4 to the total bacteria also decreased to less than 20% along with the decline in removal efficiency in the BFR. As a result, the periodic addition of the pre-grown TDB4 might have been beneficial to achieve a stable performance in the BFR operated over an extended period.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.23 no.4
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• pp.267-279
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• 1990

The temporal and spatial distribution of the coastal cold waters which was formed due to winter colling in the South Sea of Korea was analyzed by IR images from satellite and in situ data from shipboard observations. The coastal waters are known to be consisted of the Yellow Sea Coastal Waters(YSCW) and the South Korean Coastal Waters(SKCW). The former is driven around the Chuja-do and drifted into the Cheju Strait by residual currents, while the latter expands toward offsea by southward wind forcing. The expansion patterns of the SKCW were observed as sinking expansion or drifting expansion such that both were strongly dependent on the surface heat flux conditions. Under the condition of positive heat flux(warmer sea surface) or when the sea surface heat is lost to the atmosphere, the surface water started sinking and eventually expanded toward the open sea causing the cooling of the water column. For the negative heat flux the surface water was just drifted horizontally and expanded seaward and in this case only the surface layer of water was cooled.

• Microbiology and Biotechnology Letters
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• v.20 no.4
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• pp.451-458
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• 1992

Pervaporation which is capable of removing ethanol selectively was adopted to reduce the ethanol inhibition and in situ recovery of ethanol in ethanol fermentation, The composite membrane made of silicone and polysulfone was used to separate the ethanol selectively. The ethanol selectivity of the membrane was about 4 and the total flux was 300 g/m2 h at 301:: and 10 mmHg for 25 g/l of feed concentration. Saccharomyces cerevisiae entrapped within Ca-alginate gels was employed for ethanol fermentations in a fluidized-bed bioreactor. The pervaporation membrane unit and fluidized-bed bioreactor were combined into one system. The proposed model equations for the combined system showed good accordances with the experimental results. It was found from the simulation results that the ethanol concentration in the broth for the combined system was lower than that for the continuous fermentation system without a membrane unit. Ethanol productivity can be thus increased by employing the combined system.

• Journal of the Korean Geotechnical Society
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• v.32 no.9
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• pp.29-36
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• 2016

Backfill materials of rail abutment were commonly composed with cement treated aggregate, general aggregate and soil. The friction angle of cement treated aggregate increased up to $40^{\circ}$ or more due to strength enhancement. However, $30^{\circ}{\sim}35^{\circ}$ of friction angle was typically applied for in-situ condition. This phenomenon could cause over-designing, therefore, it is essential to determine reasonable material properties of cemented treated aggregate. In this study, a series of CBR tests and circular model tests have been conducted for cement treated aggregate, while changing cement mixing ratio. Based on test results, characteristics of settlement and strength have been analyzed quantitatively. The settlement of cement treated aggregate decreased with the number of cyclic loading and aging period. In addition, The strength increment ratio in CBR test increased up to 13~16 times at 28 days aging.

• KSBB Journal
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• v.28 no.2
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• pp.80-85
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• 2013

The bacterial community structure in a biological reactor fed influent from a wastewater treatment system was investigated by denaturing gradient gel electrophoresis (DGGE) and in situ hybridization. Sludges were collected from three biological reactors (aerobic, oxic, and anoxic tanks) at the M wastewater treatment facility (WTF). The influent of the MWTF consisted of mixed tannery wastewater (40~65%) and seafood wastewater (35~60%). The treatment processes resulted in a removal efficiency for BOD (biochemical oxygen demand) and COD (chemical oxygen demand) of 83.6~98.2% and 72.8~84.6%, respectively for tannery wastewater than for seafood wastewater resulted in greater survival of biomass in the biological reactors and a higher removal of BOD, COD, and T-N of about 8~18%. In contrast, addition of greater amounts of seafood wastewater decreased the amount of biomass in the bioreactors due to the increasing concentration of chromium from that wastewater and it also. The dominant bacterial species during the high seafood wastewater input period were Burkholderia cepacia (JX901049) and an uncultured bacterium (JF247555), while Pseudomonas geniculata (HQ256559) was dominant during the high tannery wastewater input period. Flavobacteriumsp. BF.107 (FM173271) and Hyphomicrobium zavarzinii (Y14306) were dominant under anoxic conditions.

• Journal of Soil and Groundwater Environment
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• v.14 no.2
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• pp.17-25
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• 2009

The applicability of soil washing/flushing to treat a contaminated soil with cadmium (Cd) and copper (Cu) using a mixture of organic/inorganic extractant was evaluated in laboratory-scale batch and column tests. Citric acid was the effective extractant to remove Cd and Cu from the soil among various organic acids except EDTA. Carbonic acid was chosen as inorganic extractant which was not only low toxicity to environment, but also increasing soil permeability. Moreover, the optimum ratio of organic and inorganic extractant to remove Cd and Cu was 10 : 1, and this ratio of organic and inorganic extractant achieved removal efficiencies of Cd (46%) and Cu (39%), respectively. The increasing flow rate of extractant could explain the phenomena of soil packing when carbonic acid was used with organic extractant (i.e. EDTA and citric acid). Therefore, a mixture of organic extractant with inorganic extractant, especially carbonic acid, could resolve a problem of soil packing when this extractant was applied to a field application to remove Cd and Cu using in-situ soil flushing process.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.15 no.1
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• pp.41-50
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• 2010

We have developed an in-situ benthic chamber (BelcI) for use in coastal studies that can be deployed from a small boat. It is expected that BelcI will be useful in studying the benthic boundary layer because of its flexibility. BelcI is divided into three main areas: 1) frame and body chamber, 2) water sampler, and 3) stirring devices, electric controller, and data acquisition technology. To maximize in-situ use, the frame is constructed from two layers that consist of square cells. All electronic parts (motor controller, pA meter, data acquisition, etc.) are low-power consumers so that the external power supply can be safely removed from the system. The hydrodynamics of BelcI, measured by PIV (particle image velocimetry), show a typical "radial-flow impeller" pattern. Mixing time of water in the chamber is about 30 s, and shear velocity ($u^*$) near the bottom layer was calculated at $0.32\;cm\;s^{-1}$. Measurements of diffusivity boundary layer thickness showed a range of $180-230\;{\mu}m$. Sediment oxygen consumption rate, measured in-situ，was $84\;mmol\;O_2\;m^{-2}\;d_{-1}$, more than two times higher than on-board incubation results. Benthic fluxes assessed from in-situ incubation were estimated as follows: nitrate + nitrite = $0.18\;{\pm}\;0.07\;mmol\;m^{-2}\;d^{-1}$ ammonium $23\;{\pm}\;1\;mmol\;m^{-2}\;d^{-1}$ phosphate = $0.09\;{\pm}\;0.02\;mmol\;m^{-2}\;d^{-1}$ and silicate = $23\;{\pm}\;1\;mmol\;m^{-2}\;d^{-1}$.