• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.5
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• pp.549-556
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• 1995

Experiments were carried out to examine the combined effects of hypoxia and hydrogen sulfide on survival, feeding activity and metabolic rata or Blue crab, Portunus trituberculatus. Survival rate of the crab was significantly affected by $\leq2.14mg/l$ dissolved oxygen, and feeding activity was also reduced below 1.41mg/l dissolved oxygen. Metabolic rate of the crab exosed to hypoxia $(\leq3.35mg/l)$ was significantly reduced than that exposed to normoxia. The combined effects of hypoxia $(\leq1.86mg/l)$ and hydrogen sulfide $(12.35 {\mu}g/l)$ on the survival rate were highly toxic than each single effect. Feeding activity was also decreased by the combinedexposure to $\leq1.86mg/l$ dissolved oxygen and $(12.35 {\mu}g/l)$ hydrogen sulfide compared with single effect.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.18 no.1_2
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• pp.21-25
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• 2012

This study was conducted to investigate the effects of filling and packaging temperatures on the quality changes of retorted Samgyetang during storage. The samples were manufactured after filling the broth maintained either at $50^{\circ}C$ (T1) or $85^{\circ}C$ (T2) into pouch and followed by sterilizing them at $120^{\circ}C$ for 65 min under the F value of approximately 8.0. The samples were stored at $25^{\circ}C$ up until 6 months and various physic-chemical parameters including pH, oxygen ratio in the headspace of package, residual dissolved oxygen concentration in the broth, acid value, volatile basic nitrogen value (VBN), apparent viscosity, spreadability of porridge, and sensory attributes were analyzed periodically at month 0, 1, 3, and 6, respectively. During storage time, the dissolved oxygen concentration and acid values of T2 samples tended to increase slower than T1 (p<0.05). Between T1, and T2 samples, significant differences were observed for pH and dissolved oxygen concentration over the storage period while acid values and VBN values were significantly different from 3 months (p>0.05). Contrarily, no apparent differences were observed between two samples in the apparent viscosity, spreadability of porridge, and sensory attributes over the storage period (p>0.05).

• Journal of Aquaculture
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• v.13 no.1
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• pp.87-99
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• 2000

Field survey on the variational characteristics of water quality and chlorophyll a concentraion were carried out at the 25 stations for four seasons in Kogum-sudo(Straits) southern coast of Korean Peninsula from Feburuary to October in 1993. We made an analysis on biological factor as chlorophyll a concentraion as well as physicio-chemical factors such as water temperature salinity sigma-t transparency dissolved oxygen(DO) chemical oxygen demand(COD) nutrients (ammonia, nitrite, nitrate, phosphate, and silicate) N/P ratio and suspended solid(SS). The waters in the Kogum-sudo were not stratified due to the tidal mixing. And the high productivity in photic layer were supported by high nutrients concentration from bottom waters. The high concen-trations of suspended solid in straits had a bad influence upon marine biology of nature and cultivations. In Kogum-sudo had a sufficient nutrients for primary productivity during a year. Especially phosphate and inorganic nitrogen were high the other side silicate was very low. The source of nutrients supply depend on rather mineralization of organic matters and input of seawater from outside than input of freshwaters from lands. Phytoplankton biomass as measured by chlorphyll a concentratiion was very high all the year round and it was controlled by the combination o f several environmental factors especially of phosphate in summer and dissolved nitrogen in other seasons.

• Journal of Aquaculture
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• v.8 no.4
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• pp.251-260
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• 1995

Experimental transportations of the olive flounder (Paralichthys olivaceus) seedlings (body weight $2.1\pm0.39g$) with polyethylene vinyl bag were Performed to study the change of dissolved oxygen (DO) during transportation, survival rate and feeding activity of seedlings after transportation. The distance and time required for the transportations were 272 km and 11 hours, respectively. DO was rapidly decreased within 3 hours (P<0.05) during the transportation of seedlings of 40 fish in 10l of sea water at $15.6\~17.8^{\circ}C$ of initial water temperature with 5 ml/l of initial DO. The decreasing tendency of DO (Y) according to elapsed time (X) was expressed an equation of $Y\;=\;2.7444X^{-0.4780}$ (r=0.8071). Feeding activity of the seedlings after transportation supplemented with oxygen and icepack besides above transport conditions was significantly higher than that of fish supplemented with icepack only (P<0.05). It was desirable to starve the seedlings for 36 hours before transportation. Survival rate of seedlings was greatly reduced, when the dissolved oxygen concentration was lowered below the range of $0.7\~0.94ml/l$ just after transportation.

• Journal of Korea Water Resources Association
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• v.56 no.11
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• pp.801-813
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• 2023

Recently, as studies about Artificial Neural Network (ANN) are actively progressing, studies for predicting water quality of rivers using ANN are being conducted. However, it is difficult to analyze the operation process inside ANN, because ANN is form of Black-box. Although eXplainable Artificial Intelligence (XAI) is used to analyze the computational process of ANN, research using XAI technology in the field of water resources is insufficient. This study analyzed Multi Layer Perceptron (MLP) to predict Water Temperature (WT), Dissolved Oxygen (DO), hydrogen ion concentration (pH) and Chlorophyll-a (Chl-a) at the Dasan water quality observatory in the Nakdong river using Layer-wise Relevance Propagation (LRP) among XAI technologies. The MLP that learned water quality was analyzed using LRP to select the optimal input data to predict water quality, and the prediction results of the MLP learned using the optimal input data were analyzed. As a result of selecting the optimal input data using LRP, the prediction accuracy of MLP, which learned the input data except daily precipitation in the surrounding area, was the highest. Looking at the analysis of MLP's DO prediction results, it was analyzed that the pH and DO a had large influence at the highest point, and the effect of WT was large at the lowest point.

• Journal of the Korean earth science society
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• v.22 no.3
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• pp.195-207
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• 2001

The variations of D.O and pH due to the inflow of seawater by sluice gates operation were observed in the Lake Shihwa, Korea. The distributions of D.O and pH were investigated at 11 stations during Feburary 1997 to July 1998. The concentration of D.O before gate operation was 10 mg/l or more all over the watershed, yet 5 mg/l or less in the water layers of 11 m or below from March to June 1997. Anoxic layer appeared in June 1997 and expanded during rainy season. The anoxic layer in the lake depleted the oxygen in seawater as seawater was inflowed. It may be interpreted that the phenomenon comes from the contact of seawater to lower fresh water. The contact of seawater in pH 7.8 to 8.2 to lower water less than pH 7.4 enhanced to oxidize. After January 1998, D.O of the lake increased over 10 mg/l and the stratification was weakened. As a result, it may be concluded that the best way to improve the water qualities is to increase the amount of seawater inflow and outflow so as not to be generated pycnocline in summer.

• Microbiology and Biotechnology Letters
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• v.20 no.3
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• pp.348-354
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• 1992

In order to improve the productivity of invertase by recombinant Saccharomyces cerevisiae containing SUC2 gene, the effect of amino acids and dissolved oxygen concentration on the gene expression was investigated. Optimal concentrations of leucine and histidine for cell growth and cloned gene expression were 0.03 gig and 0.04 gig, respectively, expressed as the ratio of amino acid/glucose. The lack or excess of leucine and histidine has inhibitory effect on cell growth and invertase expression. In batch culture, the less aeration was, the higher invertase activity was. In continuous culture at a dilution rate of 0.09 h 1 with controlled dissolved oxygen tension, invertase activity increased dramatically at DOT levels below 5% air saturation, and a maximum activity of 215.54 KUlg cell was obtained under unaerated condition.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.388-388
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• 2022

하수처리 공정 중 생물반응조에서는 미생물의 산화 반응을 통해 하수 내 각종 유기물들을 처리하고 있다. 블로워는 호기조를 유리산소상태로 만들어 미생물들의 유기물 제어, 질산화가 원활하게 이루어질 수 있도록 지원하는 역할을 담당하고 있다. 그러나 실제 하수처리장에서는 유기물을 원활하게 처리하기 위하여 과도하게 블로워를 가동하고 있어 경제적인 측면에서 문제를 겪고 있다. 블로워를 통해 수중에 산소를 부족하게 공급할 경우 활성슬러지의 침전성이 저해되어 방류수 수질이 저해되는 반면, 용존산소가 과도하게 공급되어도 유기물질의 처리 효율은 증대되지 않으며 잉여용존산소는 대기 중으로 방류된다. 이러한 이유로 국내 하수처리장에서는 강화된 방류수 수질 기준을 만족하기 하고자 유입수질에 관계없이 과도하게 송풍기를 운영하고 있다. 이러한 하수처리장의 운영 및 경제적인 문제점을 해결하고자, 본 연구에서는 하수처리장으로 유입되는 원수의 수질을 처리하는 데 실제로 미생물이 필요한 산소요구량 및 공기공급량을 산정하는 프로그램을 개발하였다. 이를 통해 실제 하수처리장에서 필요한 산소요구량, 공기공급량을 산출하여 효율적인 하수처리장 운영이 가능하다. 실제 하수처리장에서의 프로그램을 통한 송풍량 절감 효율을 분석하고자 한 달간의 A 하수처리장 수질 데이터를 기반으로 하수처리에 필요한 산소요구량 및 공기공급량을 산정하였다. 실험 결과 프로그램 적용시 약 평균적으로 10%의 송풍량을 절감이 가능하며, 연구 결과를 바탕으로 효율적이고 경제적인 송풍기 운영조건의 기준을 제시하고자 한다.

• Korean Journal of Ecology and Environment
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• v.34 no.2 s.94
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• pp.126-132
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• 2001

Urbanization and population increase result in the construction of STPs (Sewage Treatment Plants). Discharge from STPs greatly influences on the water quality in the stream which receives discharges. The decision of STP location should be considered with the discharge capacity of STP and self-purification of river in the water quality perspectively. In this study, a change of dissolved oxygen (DO) in a river being affected by STP discharge was simulated by the STELLA model. Minimum DO was 4.98 ppm in 42.6 km downstream of STP. Approximately, it takes 8days to recover the DO by the self-purification and this location is 340 km down-stream from the STP. If the model run for the consideration of the self-purification without phytoplankton algorithms, minimum DO was 4.92 ppm. It took 0.25 day longer to be the minimum DO than that with the phytoplankton functions. Without the phytoplankton algorithm, it took 11days to recover the DO. This proves the importance of phytoplankton in the self-purification processes. Additionally, the effect of adjacent STP discharge should be considered in the construction of new STP.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.9
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• pp.847-854
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• 2013

The objective of this study is to experimentally investigate the mixed flow and oxygen transfer characteristics of a horizontally injected aeration process using an annular nozzle ejector. The flow rate ratio, pressure ratio and ejector efficiency are calculated using the measured flow rate and pressure with the experimental parameters of the ejector pitch and primary flow rate. The visualization images of mixed flow issuing from the ejector are analyzed qualitatively, and the volumetric oxygen transfer coefficients are calculated using the measured dissolved oxygen concentration. The mixed flow behaves like a buoyancy jet or horizontal jet owing to the momentum of primary flow and air bubble size. The buoyancy force of the air bubble and the penetration of mixed flow are found to be important parameters for the oxygen transfer rate owing to the contact area and time of two phases.