• Korean Journal of Fisheries and Aquatic Sciences
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• v.43 no.1
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• pp.54-62
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• 2010

With the aim of developing and indoor overwintering technique for Pearl oyster, Pinctada fucata martensii, the metabolic rates of young oysters (52.4-83.0 mm in shell length) were measured for 2 weeks at water temperatures of 8, 10, 12, and $14^{\circ}C$. The filtration rate (FR) ranged 0 to $4.84\;L\;h^{-1}gDW^{-1}$ (mean, $0.02{\pm}0.06 $ to $3.12{\pm}1.45$), with significant changes observed over thme except for the case of a water temperature of $14^{\circ}C$. Respiration rate (R) ranged from 0 to $2.370\;mgO2\;h^{-1}gDW^{-1}$ (mean, 0 to $1.77{\pm}0.37$), with significant respiratory disorders observed at temperatures below $12^{\circ}C$; in contrast, the rate increased on the $14^th$ day of the experiment in the case of a temperature of 14$^{\circ}C$. No significant difference was observed among the different water temperatures in terms of excretion rate (E) or absorption efficiency (Abs.eff), except for a significant decrease in aerobic metabolism in the case of water temperature of $8^{\circ}C$. The estimated scope for growth (SFG) ranged from -9.1 to $126.9\;J\;h^{-1}gDW^{-1}$ (mean. $-4.1{\pm}2.6$ to $82.85{\pm}42.6$). A significant energy Joss was found at $8^{\circ}C$, with negative SFG observed throughout the experiment and a gradual energy decrease observed over time at water temperatures of $10^{\circ}C$ and 120C. However. SFG remained positive throughout the experiment in the case of $14^{\circ}C$. The estimated minimum energy requirement, assessed from energy expenditure, is $8.00-34.24\;J\;h^{-1}gDW^{-1}$ (mean, $17.67{\pm}6.17$). In conclusion, the lowest temperature suitable for indoor overwintering is above $14^{\circ}C$.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.7
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• pp.1285-1294
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• 2000

In this study, we investigated the possibility of the elimination of suspended solid and the factors affecting effluent water quality, and the amount of treated water, using the SS removal equipment adapted capillary-syphon phenomenon. Treated water quantity decreased as the accumulation time and the increase of head of capillary syphon, whereas the effluent water quality was improved. At coagulant dosage 0, 0.45, $1.82mg/{\ell}$ (as $Al^{+3}$) and limiting flux $107{\ell}/m/day$. turbidity of treated water was 2, 1, 0.5 NTU in each case. During operating period 15~17 days, the amount of washing water was just used 0.5~0.7% of the amount of treating water. So it is expected that coagulation & sedimentation and rapid filtration process can be replaced with the SS removal equipment adapted capillary-syphon phenomenon in water purification process.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.1
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• pp.45-53
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• 2008

In this paper, the property of influent water and variations of removal efficiencies in each unit processes were studied based on the experiment data from the advanced water treatment plant in a city of Korea. The microbial species in the biological activated carbon(BAC) after backwashing of activated carbon filtration tank(ACFT) were also identified. The property and the removal efficiencies were evaluated by considering 8-9 items. The variations of 4 items were investigated from the influent and effluent of ACFT. SEM recording were conducted on BAC samples before and after backwashing. And the existence of attached microorganisms were identified through HPC(Heterotrophic Plate Counter) investigation. For the property of influent water, the concentrations of most items were maintained in the constant ranges, some items had seasonal properties. For the removal efficiencies, there were some items showing similar monthly-pattern and increasing with time, other items decreasing at the ozone contactor. Through these investigations, it was possible to distinguish the target items, which were removed by the advanced processes. The existence of microorganisms in ACFT could be predicted based on the variation curve of NH$_3$-N, and this fact were proved by SEM and HPC.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.5
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• pp.671-675
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• 2012

This study was conducted to establish the BMPs (Best Management Practices) for preventing pollutant loadings from paddy rice field applied livestock liquid manure from 2008 through 2011. Cultivated paddy rice fields (Gyeonggi province, Korea) were treated with SCB (Slurry composting and bio-filtration process) liquid fertilizer. The BMPs for paddy rice field developed in this study includes: 1) the controlling a drainage water gate in paddy rice field from right after SCB liquid fertilizer application to 3 weeks after rice transplanting; 2) livestock liquid fertilizer application to paddy rice soils in 20 days before rice transplanting to encourage the utilization of liquid fertilizer; 3) preservation of surface water depth to 5 cm in a paddy field right after SCB liquid fertilizer applied to minimize a water pollution and enhance the utilization of liquid fertilizer; and 4) blocking a water gate at least for 2 days to inactivate E. coli survival. The findings of this study will provide useful and practical guideline to applicators of agricultural soil in deciding appropriate handling and time frames for preventing pollution of water quality for sustainable agriculture.

• The Journal of Engineering Research
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• v.6 no.1
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• pp.97-109
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• 2004

The synthesis and crystal structure of amorphous calcium carbonate obtained from gas-liquid reaction of CaO-$C_2 H_5 OH$-$CO_2$ system according to change of added amount of calcium oxide by blowing $CO_2$ gas and reaction time using ethanol and ethylene glycol were investigated by electric conductivity, X-ray diffraction, and scanning electron microscope. The powdery or gelatinous phases were prepared by passing $CO_2$ gas at a flow rate of 1$\ell$/min into the suspensions containing 10~40g of CaO in mixing solutions 900ml of $C_2 H_5 OH$- and 100ml of ethylene glycol. By rapid filtration and drying the both phases at $60^{\circ}C$ under reduced pressure, the phases converted to the spherical vaterite and amorphous phase. The stable phase of amorphous calcium carbonate(ACC) was formed in the region pH 7-9 but the formation regions of amorphous phase were remarkably affected by pH in the mother liquor. It seems that a part of ACC changed into chain calcite as an intermediate products. The initial reactants prior to the formation of precipitated calcium carbonate is ACC. And ACC is unstable in the aqueous solution and crystallizes finally to calcite by the through-solution reaction. Especially ACC was produced or gelatinous phase which precipitated from the reaction of CaO-$C_2 H_5 OH$-$CO_2$ system.

• Membrane Journal
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• v.25 no.1
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• pp.75-83
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• 2015

In this study, chlorophylls were been extracted from common local plants, deposited on polypropylene (PP) substrate using various approaches, and the oxygen generation effect of the chlorophylls were investigated. The loading of chlorophylls on the substrates was achieved by dipping and spraying methods, where the spraying coating showed overall better results regarding oxygen generation from the combustion experiments in the closed vessel or in the isolated vacuum oven cell than those of dip coating. In addition, a composite substrate was prepared by nylon6/6 nanofiber on the PP substrate, and it exhibited an increase in the activation of chlorophylls. In the case of samples containing titanium dioxide ($TiO_2$), the reaching time of oxygen concentration from 16% to 21% and the combustion test using a candle for a sample with 50% chlorophylls showed similar results to those of a sample without $TiO_2$. As such, combining a spray coating and $TiO_2$ incorporation into gas separation membrane systems are expected to be useful to understand the fundamentals of material properties for their applications as oxygen generation membranes and air filtration systems.

• The Korean Journal of Ecology
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• v.24 no.1
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• pp.35-43
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• 2001

Accumulation, elimination and subcellular distribution of heavy metals in Littorina brevicula exposed to cadmium and zinc separately and concurrently were investigated. When the winkles had been exposed to 400 ㎍/L CdCl₂ and 3000 ㎍/l ZnSO₄ separately for 90 days, each of the metal body burden in the whole sofl parts increased in proportion to time of exposure until 70 days. But it didn't increase after 70 days. But when the winkles had been exposed to cadmium and zinc simultaneously, cadmium body burden decreased but zinc body burden increased as compared to the winkles exposed to each of the metal. We also found that cadmium accumulated in the winkles was not depurated for 42 days, but zinc accumulated in them was depurated. Especially, zinc was depurated faster when they had been exposed to mixture of cadmium and zinc. After the winkles had been exposed to cadmium and zinc separately for 70 days, about 60% cadmium of the total body burden was associated with the soluble fraction, while about 75% zinc of the total body burden was associated with insoluble fraction. And these trends of metal partitioning did not alter when the winkles had been exposed to metal mixture. After the soluble fraction applied to gel-filtration chromatography column, the distribution patterns of cadmium and zinc associated with proteins or ligands were different each other. Most of cadmium (＞90%) in the soluble fraction was bound to MBP-1 (Metal-binding protein-1), about 6.5 kDa), while zinc was distributed evenly to HMW (High molecular weight fraction, >60 kDa), MBP-1, MBP-2 (about 5 kDa), LMW (Low molecular weight fraction, <1 kDa).

• Journal of Environmental Science International
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• v.16 no.4
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• pp.449-458
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• 2007

Research results for the pressure drop variance depending on operation conditions such as change of inlet concentration, pulse interval, and face velocity, etc., in a pulse air jet-type bag filter show that while at $3kg/cm^2$ whose pulse pressure is low, it is good to make an pulse interval longer in order to form the first layer, it may not be applicable to industry because of a rapid increase in pressure. In addition, the change of inlet concentration contributes more to the increase of pressure drop than the pulse interval does. In order to reduce operation costs by minimizing filter drag of a filter bag at pulse pressure $5kg/cm^2$, the dust concentration should be minimized, and when the inlet dust loading is a lower concentration, the pulse interval in the operation should be less than 70 sec, but when inlet dust loading is a higher concentration, the pulse interval should be below 30 sec. In particular, in the case that inlet dust loading is a higher concentration, a high-pressure distribution is observed regardless of pulse pressure. This is because dust is accumulated continuously in the filter bag and makes it thicker as filtration time increases, and thus the pulse interval should be set to below 30 sec. If the equipment is operated at 1m/min of face velocity, while pressure drop is low, the bag filter becomes larger and thus, its economics are very low due to a large initial investment. Therefore, a face velocity of around 1.5 m/min is considered to be the optimal operation condition. At 1.5 m/min considered to be the most economical face velocity, if the pulse interval increases, since the amount of variation in filter drag is large, depending on the amount of inlet dust loading, the operation may be possible at a lower concentration when the pulse interval is 70 sec. However, for a higher concentration, either face velocity or pulse interval should be reduced.

• Korean Journal of Food Science and Technology
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• v.31 no.4
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• pp.1017-1023
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• 1999

Several extraction conditions of mussel were investigated for preparation of the extract as a natural shellfish seasoning. The conditions studied were extraction temperature and time, addition of sodium phosphates and citrate and hydrolysis with commercial proteolytic enzymes. The extracts were prepared by deshelling, grinding and aqueous extraction followed by centrifugation and filtration. Extraction at $90^{\circ}C$ for 40min showed the highest solids yield with less fishy and high umami taste. Among the several phosphates and citrate added, $Na_{3}PO_{4}$ and $Na_{4}P_{2}O_{7}$ at 1% level were most effective in terms of the yield and umami taste. The pH effects showed that pH 10 resulted the highest solids yield of 28% with less fishy taste. Even though the effect of enzymatic hydrolysis was not greatly different among the commercial enzymes tested, Protamex and Protease II were somewhat better than other enzymes in taste. When the mussel were extracted by the combined conditions, hydrolysis with Protamex followed by extraction at $90^{\circ}C$ for 40min with addition of $Na_{3}PO_{4}$ at pH 10, the solid yields increased up to 30% which was about 58% improvement and high intensity of umami taste and less fishy flavor.

• Korean Journal of Environmental Biology
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• v.31 no.3
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• pp.204-212
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• 2013

This study analyzed the occurrence of tunic softness, survival rate, metabolic rate and histopathologic changes arising from the effect of hypoxic environment in order to find the causes of occurrences of tunic softness, which manifests as the key phenomenon of mass mortality of Halocynthia roretzi. Regarding the survival of H. roretzi with reduction in dissolved oxygen, all the entities died on the 4th day of exposure to the dissolved oxygen concentration of $2mg\;L^{-1}$ while 50% mortality was observed on the 5th day of exposure to the dissolved oxygen concentration of $3mg\;L^{-1}$. Therefore the 5 days-$LC_{50}$ was found to be $3.55mg\;L^{-1}$ (1.86~$4.96mg\;L^{-1}$). However, occurrence of tunic softness was not observed during the period of exposure to low oxygen concentration. The oxygen consumption rate significantly decreases at the dissolved oxygen concentration of less than $5mg\;L^{-1}$ in comparison to the control group. Therefore, it is presumed that H. roretzi controls the respiration rate for prescribed period of time when exposed to hypoxic environment. Regarding the histopathologic changes in the gill, digestive gland and cyst of H. roretzi due to hypoxic environment, necrosis of epithelial layer, in filtration of blood cells, and condensation of nucleus that compose each of the organs were observed. Regarding morphological changes, the decrease in volume with shrinking of the tunic, discoloration of the internal organs and necrosis of gill and hepatopancreas were observed.