• Journal of Korean Society of Environmental Engineers
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• v.35 no.9
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• pp.624-629
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• 2013

The relation between performance maintenance conditions and those cost efficiency was studied to choose an optimum operating condition in the seawater desalination pretreatment system. A hollow fiber microfiltration module, which was developed with domestic technology, was tested with the various operating conditions such as chemically enhanced backwash cycles and design dosages of a cleaning chemical. Transmembrane pressure was measured to investigate membrane fouling status and cleaning degree. In addition, economic analysis was performed to compare water production costs by the operation condition. As a result, The operation mode III, chemically enhanced backwash at once a day with 100 mg/L of sodium hypochlorite (NaOCl) was selected. The concurrent evaluation between membrane filtration performance and its economic analysis will be suitable to choose an efficient optimum condition.

• Korean Journal of Ecology and Environment
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• v.33 no.2 s.90
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• pp.145-151
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• 2000

A porous silicate material named as CellCaSi was tested for the removal of microalgae in the water sample from a eutrophic pond. The effects of the CellCaSi on water qualities were investigated on the basis of both the particle size (under 1, 2,and 4 mm) and the added amount (0, 1, 5, and 10 g/l) of the CellCaSi. The removal efficiency of chlorophyll-a was highest at 79% by the addition of 10 g/l of the CellCaSi (under 1 mm) at day 3 after treatment. That is, the removal efficiency of chlorophyll-a by the CellCaSi increased with smaller particle size and more added amount. The dominant species, Chlorella ellipsoidea, was not changed by the addition of the CellCaSi, but the species number and standing crop of the algae diminished. Total nitrogen concentration was not changed much by the addition of the CellCaSi, whereas total phosphorus concentration was reduced. pH and turbidity were not changed by the addition of the CellCaSi, whereas conductivity showed a high correlation with the amount of added CellCaSi ($Y\;=\;29.2 {\cdot}X+306$, $r^2\;=0.984$). Therefore, it seems to be necessary to limit the amount of the CellCaSi under 6.6 g/1 in consideration of a registered maximum conductivity of $500\;{\mu}mhos/cm$ for raw and potable waters.

• Journal of the Korean GEO-environmental Society
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• v.9 no.3
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• pp.35-43
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• 2008

This study was carried out to estimate the performance of modified sequencing batch reactor (SBR) process by the application of SBR process for small advanced wastewater treatment plant. Organic, nitrogen and phosphorus were able to remove in the unit reactor by SBR process and it would be able to select the suitable operation method. The plant was operated to achieve high performance with influent control, optimum anoxic/oxic condition using intermediate aeration method, and solid (sludge) /liquid (effluent) separation by modified decanter. The optimum operating mode was 3Cycles a day and intermediate input and aeration. Under these conditions, the treatment efficiencies were good with 60% of designed flow rate and low influent quality. When the influent concentrations of BOD and CODMn were 120.4 mg/L and 95.7 mg/L, respectively. The effluent concentrations of BOD and CODMn were 6.8 mg/L and 11.0 mg/L, respectively. The average removal efficiencies of BOD and CODMn were 94.4% and 88.5%, respectively. The removal efficiencies of T-N and T-P were 69.6% and 73.6%, respectively when the average T-N and T-P concentrations were 32.2mg/L and 4.65mg/L, respectively. The T-N and T-P removal efficiencies were slightly decreased to 58.8% and 68.5%, respectively in the winter season but its were also stable efficiencies. BOD, T-N and T-P were removed by 90%. 67% and 46% respectively in the first anoxic/oxic condition, in addition to T-P was removed by 70% in the second anoxic/oxic condition. From the results, modified sequencing batch reactor (SBR) process is suitable for small advanced wastewater treatment.

• Journal of Korea Water Resources Association
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• v.35 no.2
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• pp.221-229
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• 2002

For the efficient design of baffled Powdered activated carbon(PAC) contractor, which has been widely used in water treatment plant(WTP) against the algae-related odor problems, a CFD(computational fluid dynamics) program was applied. In order to verify the performance of FLOW-3D program, the previously reported results of tracer tests from a pilot-scale PAC contractor(working volume of 288 liters) were compared to those from FLOW 3D. The results of FLOW-3D simulation were very similar to those from tracer tests conducted with the Pilot-scale PAC contactor. On the other hand, the hydrodynamic characteristics of baffled contractor in the P-WTP were simulated by using FLOW-3D. Simulation results on the distribution of PAC particles showed that there are some stagnant parts in the back side of baffles in which PAC Particles are not present. These stagnant parts might decrease the adsorption capacity of PAC particles. When the baffles were changed to maze-type intra-basin baffling, PAC particles were evenly distributed and the amount of stagnant parts reduced. In conclusion, it is anticipated that FLOW-3D simulation could be a viab1e tool for analyzing the hydrodynamic characteristics of structures used in drinking water treatment plant.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.1
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• pp.1-6
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• 2012

Down Stream K River has high COD (4-10 mg/L) and high $NH_3$-N concentration (3.5 mg/L during winter period). Although $NH_3$-N itself is not reported harmful at this level, it must be removed to meet drinking water standard (0.5 mg/L). We constructed a pilot plant modifying the processes of conventional drinking water facilities. Prechlorination and powdered activated carbon (PAC) dechlorination was adopted prior to a flocculation tank to remove ammonia and prevent disinfection byproducts (DBPs) formation. Also, GAC processes was included after sand filter to remove residual DOC. This pilot having a capacity of 36 ton/day was operated for one year. The GAC processes were successful to remove ammonia and many organic pollutants (DOC, MBAS, UV-254 nm absorbance, etc). Influent DOC concentrations were very high as 3~6 mg/L throughout the plant operation. It was impossible to achieve 1.0 mg/L effluent DOC, indicating that bed depth (2 m) should be increased to achieve more strict DOC quality standards. When $Cl_2$ dose was well controlled ($Cl_2/NH_3$-N ratio 10~11 on a weight basis), $NH_3$-N removal was 98% and THMs was very low possibly due to low free residual chlorine and PAC dechlorination.

• Journal of Nutrition and Health
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• v.52 no.4
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• pp.383-398
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• 2019

Purpose: This study investigated an association between dietary quality and use of convenience foods at convenience stores among high school students. Methods: A total of 474 high school students (225 boys and 249 girls) residing in Incheon participated in this questionnaire survey in June 2018. The subjects were divided into three groups according to the frequency of consumption of convenience foods at convenience stores; less than once a week, 1 ~ 2 times a week, and more than 3 times a week. Dietary quality was assessed using a nutrient quotient for adolescents (NA-Q). Logistic regression was used to investigate an association between dietary quality and use of convenience foods at convenience stores among high school students. Results: For boys and girls, higher monthly allowance was significantly associated with the higher frequency of consumption of convenience foods at convenience stores, whereas school grade, mother's occupational status, family size, extracurricular study, and eating speed were not significantly associated with the frequency of consumption of convenience foods. Higher intake frequency of cookies or sweet and greasy bread, processed beverage, Ramyon, night-time snack, and street food was significantly associated with the higher frequency of consumption of convenience foods for boys or girls. Boys and girls, who had a higher frequency of consumption of convenience foods at convenience stores had significantly greater odds for being in the low grade of dietary quality, especially in the moderation factor. Conclusion: The students who used convenience stores more often appeared to have more monthly allowance and to consume undesirable foods more often. Higher frequency of using convenience foods at convenience stores among high school students was associated with lower dietary quality. These study results can support efforts to provide nutrition education programs and guidelines to students who frequently use convenience foods at convenience stores.

• Korean Journal of Ecology and Environment
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• v.53 no.4
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• pp.365-373
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• 2020

Biomonitoring Survey and Assessment Manual for lake ecosystem suggest zooplankton collection methods to compare relatively the number of species, population density, and community indices, taking into account the convenience of the field sampling according to the sites' water depth. In this study, the oblique towing and 20 m vertical towing methods presented in the manual were respectively compared with the whole water column-vertical towing and we analyzed the differences and characteristics of zooplankton community information gathered by each collection method. For community indices, there was no difference in the comparison of oblique/vertical towing methods in the shallow lake, but in the deep lake, the diversity and richness indices increased when vertically towing through whole water column rather than when limiting the towing depth to 20 m. In addition, the total zooplankton density collected by the oblique/20 m vertical towing methods was about three times higher than the whole water column-vertical towing method, which means that the density of zooplankton community can be overestimated depending on the collection methods. It appears to be results of differences in the zooplankton density by water layer arising from their vertical distribution and in filtered raw water quantity according to the towing depth/distance. Hence, for zooplankton community information to be used as a functional quantitative indicator representing the entire lake, it would be more appropriate to apply the whole water column-vertical towing method with considering the distribution of zooplankton density by depth and contribution rate of each water layer when converting total zooplankton density.

• Journal of Korea Technology Innovation Society
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• v.19 no.3
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• pp.465-482
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• 2016

Previous researches have introduced various ways to analyze the impact of standardization on innovation while the works are not only small in number but based on interview or case study. This paper addresses the impact of standardization activities within South Korean industries on technological innovation applying an empirical analysis of standardization activities and technological innovation. Drawing on Korean Industrial Standards Classification from panel data of 2003 to 2012, we employed corresponding data of each industrial classification: Number of standards, Accumulated number of standards, Number of patents applied in Korea, Sales, Operational profit, Intangible asset, and R&D invest. In the first model, we run panel data models employing the number of patents applied in Korea as an independent variable, and the number of standards, accumulated number of standards, sales, and operational profit as dependent variables to observe industrial impacts upon the relationship between standards and patents, along with time lagged consideration. The result shows that number of standards are revealed to have a negative influence on patent applications in the year of research, and no significant effect appears for the next two years while positive effect shows up on the third year. Meanwhie, accumulated number of standards turned out to have positive effects on patent applications in Korea. This implies it takes time for innovation subjects to embrace newly established standards while having a significant amount of positive effect on technological innovation in the long term. In the second model, we use canonical correlation analysis to find industrial-wide characteristics. The result of this model is equivalent to the result of panel data analysis except in a few industries, where some industry specific characteristics appear. The implications of our results present that Korean policy makers have to take account of industrial effects on standardization to promote technological innovation.

• Korean Security Journal
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• no.14
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• pp.413-429
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• 2007

The Guard over the royal household in the "Goryeo" era was the same as if was over the President or Ruler of a nation today. In those days, a king represented a nation and any threat to the safety of a king could bring the destruction of a nation and the dispersion of the people. by reviewing the change of the 2-Gun 6-Wi system of the era, it can be, summed up as follow, Ther will be suggestions. The Guard might focus on a king's personal safety in the wake of the system of the Silla and Taebong dynasties until the establishment of the Goryeo Dynasty's unique political system. "Goryeo" rebuilt the royal palace in Gyeonyeong-gun to take the shape of unified country after its accomplishment of unification of the late three countries, Then it was afraid of the rebellion and uprising of local powerful clans, The country put them under control and organized the local army with them in the era of Kings, Seongjong, through the kings, Seongjong and Gwangjong. The army system of "Goryeo" consisted of 2-Gun and 6-Wi, and 2-Gun placed above the 6-Wi played the role of the Royal guards, and among the organizations a certain army under the specific name of "Gyeonyong-gun" guarded the kings in the nearest position. An aristocratic culture enjoyed its golden age in the period of stability of the aristocracy of "Goryeo", but afterward in the confusion of the aristocratic disruption and incompatible confrontation the country lost its control, and faced military rebellions by treating civil officials well and ill-treating military officials The safety of kings become unstable with the grasping political power by the military officials, and "Dobang" was established in the era of Choi's family to grasp political power. In the era of Choi Woo, he gathered his men and organized his familys army with them and managed the personnel administration with the civil officials of "Jeongbang and Seobang under his command. Such a fact shows the similarity to today's task of guarding. Considering the facts that "Sambyeolcho, the military ground of the military-men-rule, was at the center of the struggling against Mongolia and that even after the fall of the military regime, they rebelled and fought against Mongolia to the end, we came to know that the nationalism in the era of the military era was great. In the transition of external situations from "Myeong" to "Won"(Chinese dynasties), the conflict between the old "Won"-friendly power and the new "Myeong"-friendly power caused the weakness of the power to guard the royal household, and "Goryeo" at last gave way to the newly rising "Joseon" led by Lee, Seong Gye who won the people's confidence.

• Korean Journal of Ecology and Environment
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• v.41 no.spc
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• pp.35-41
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• 2008

Nutrient Enrichment Bioassays (NEBs) were conducted in the laboratory during June $22{\sim}28$, 2006 in order to determine primary limiting factor on the phytoplankton growth. For the NEBs, the water was sampled using a 10L polyethylene-lined container and dispensed into 2.5L container in the laboratory. The algal growths response in the control (C) and three treatments of phosphorus (P), 2-fold phosphorus (2P), and nitrate nitrogen $(NO_3-N)$ were monitored during 7 days. In the cubitainers which were spiked as P (T1) and 2P (T2) Chl-${\alpha}$ concentrations were decreased during the test period and the final concentrations was low than initial values. However, Chl-${\alpha}$ in the cubitainers which were spiked as $NO_3$(T3) and $P+NO_3$(T4) showed significant increases compared to the initial values, indicating that in the short-term experiments, nitrogen seemed to be a primary limiting nutrient during the periods of NEBs experiment. Long-term ambient nutrient data of TP and TN, and TN:TP mass ratios, however, showed a potential phosphorus limitation on phytoplankton growth and previous other researchers showed a variations of limiting nutrients by nitrogen or phosphorus depending on the seasons sampled and locations. In this study nitrogen as primary limiting nutrient in the NEBs seem to be an seasonal effect rather than the consistent nitrogen limitation.