• Journal of Korea Water Resources Association
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• v.32 no.3
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• pp.311-319
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• 1999

Membrane separation process is considered as an alternative of conventional water purification system using coagulationㆍsedimentation＋sand filtration. In this study, it was examined that the application possibility of Hollowfiber Microfiltration membrane for water purification process. A $20m^3/day$ scale pilot plant was used for studying the possibility of long-term operation and the stability of water quality under the optimum conditions, 0.03m/h permeate flux, filtration for 10 minutes, pause for 2 minutes(including air-scrubbing for 30 seconds), obtained by lab-scale experiment. As a result, it was proved stability of pilot plant over one year and filtrate quality(Turbidity. SS etc). Therefore, it was proved that membrane separation process using Hollowfiber Microfiltration membrane can be applied for water purification system

• Journal of Preventive Medicine and Public Health
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• v.53 no.2
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• pp.106-116
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• 2020

Objectives: This study aimed to develop a valid social contact survey instrument and to verify its feasibility for use among Korean adults. Methods: The Delphi technique was used to develop an instrument to assess social contacts, which was then applied in a cross-sectional pilot study. A panel of 15 medical professionals reviewed the feasibility and validity of each item. The minimum content validity ratio was 0.49. Thirty participants used the developed measure to record contacts during a 24-hour period. Results: After a systematic review, the survey instrument (parts I and II) was developed. Part I assessed social contact patterns over a 24-hour period, and part II assessed perceptions of contacts in daily life and preventive behaviors (hand hygiene and coughing etiquette). High validity and feasibility were found. In the pilot study, the 30 participants had a combined total of 198 contacts (mean, 6.6 daily contacts per person). The participants' age (p=0.012), occupation (p<0.001), household size (p<0.001), education (p<0.001), personal income (p=0.003), and household income (p<0.001) were significantly associated with the number of contacts. Contacts at home, of long duration, and of daily frequency were relatively likely to be physical. Assortative mixing was observed between individuals in their 20s and 50s. Contact type differed by location, duration, and frequency (p<0.001). Conclusions: The developed social contact survey instrument demonstrated high validity and feasibility, suggesting that it is viable for implementation.

• Korean Journal of Food Science and Technology
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• v.33 no.6
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• pp.808-811
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• 2001

Performance of pilot plant scale extraction and concentration of purple-fleshed sweet potato anthocyanin pigment was tested and the characteristics of pigment extracts and concentrates were investigated. Fifty kilograms of purple-fleshed sweet potato was extracted with 500 L of 1% citric acid in 20% ethanol. As a whole, extraction pattern of the large scale extraction was similar to that of the laboratory scale extraction. The extracted pigment solution was filtered twice with a bag filter and a winding type microfilter and the filtrate was concentrated by a large scale vacuum evaporator at $40^{\circ}C$ and 600 mmHg vac. The mean values of total optical density (TOD) of the extract and the concentrate were 6.53 and 120.45, respectively. Browning index (BI) and Degradation index (DI) of extract were 5.86 and 1.55 and those of concentrate were 5.89 and 1.56, respectively, which indicated that the pigments were not changed or degraded through the extraction and concentration process.

• Journal of Korean Society of Water and Wastewater
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• v.31 no.3
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• pp.229-236
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• 2017

In this study, a direct contact membrane module was manufactured to be used in a pilot scale membrane distillation process to treat $3m^3/day$ of the digestate produced from anaerobic digestion of livestock manure. In order to investigate the performance of the membrane module, permeate flux was measured with and without spacer inside the module under various condition of temperature difference and cross flow velocity (CFV) through the membrane surfaces. Flux recovery rate after chemical cleaning was also investigated by applying three different cleaning methods. Additionally, thermal energy consumption was theoretically simulated based on actual pilot plant operation conditions. As results, we observed flux of the module with spacer was almost similar to the theoretically predicted value because the installation of spacer reduced the channeling effect inside the module. Under the same operating condition, the permeate flux also increased with increasing temperature difference and CFV. As a result of chemical in-line cleaning using NaOCl and citric acid for the fouled membranes, the recovery rate was 83.7% compared to the initial flux when NaOCl was used alone, and 87% recovery rate was observed when only citric acid was used. However, in the case of using only citric acid, the permeate flux was decreased at a rapid rate. It seemed that a cleaning by NaOCl was more effective to recover the flux of membrane contaminated by the organic matter as compared to a cleaning by citric acid. The total heat energy consumption increased with increasing CFV and temperature difference across the membrane. Thus, further studies should be intensively conducted to obtain a high permeate flux while keeping the energy consumption to a minimum for a practical application of membrane distillation process to treat wastewater.

• Journal of Advanced Navigation Technology
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• v.25 no.1
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• pp.52-59
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• 2021

According to the International Air Transport Association (IATA), 61% of the accidents occurred during the approach and landing phase of the flight, with 16% of the accidents caused by unstable access of the commercial aircraft. It was identified that the pilot's unstable approach and poor manipulation of correction led to accidents by continuing the excessive approach without go-around manuever. The causes of unstable access may vary, including airport approach procedures, pilot error, misplanning, workload, ATC (Air Traffic Contol) congestion, etc. In this study, we use the flight data analysis system to select domestic case airports and aircraft type where unstable approach events occur repeatedly. Through flight data analysis, including main events, airport approach procedures, pilot operations, as well as various environmental factors such as weather and geographical conditions at the airport. It aims to identify and eliminate the tendency of unstable approach events and the causes and risks of them to derive implications for mitigating unstable approach events and for developing navigation safety measures.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.1
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• pp.79-86
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• 2008

In Korea, most of the drinking water treatment relied upon the availability of the surface water, of which the raw water quality varied significantly by season and location. Therefore, the comparison of two operation modes (Pressurized type and Submerged type membrane system) must be estimated before the long-term establishment of two systems. In this study, two pilot-scale microfiltration systems with the capacity of $50m^3/day$ were installed and operated in two different modes, and the applicability of the system was determined based on the results such as the TMP (Trans-Membrane Pressure) and flux. For quantitatively comparing the two systems, a new concept, DRF (Differential Resistance Fraction) was introduced. The accumulated sum of the permeate after each cycle of chemical cleaning was also used as a tool for the system comparison.

• Journal of the Korean GEO-environmental Society
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• v.10 no.3
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• pp.21-28
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• 2009

As the natural aggregates such as sand and clay are getting exhausted, the quantity of utilizing geosynthetics is being increased in the solid waste landfill. Especially, the waste landfills have been constructed at the gorge in the mountainous area and reclaimed land from the sea in the Korean Peninsula. Those areas are not favorable for construction of waste landfill in geotechnical engineering aspect. In this study, the frictional characteristics of geosynthetics that used in the waste landfill were estimated. Then, the studies of the behavior of geosynthetics and stability of LDCRS (Leachate Detection, Collection, and Removal System) of side slope were conducted in the waste landfill by means of the pilot test, and numerical analysis. Geocomposite which is combined type or separated type is influenced on the strain itself, and also implicated in the stress and strain of geomembrane at the lower layer. The strain on the combined type of geocomposite is about 50% smaller than that of the separated type at the side slope. The lateral displacement and settlement of top at the slope with the separated type are three times greater than that of the combined type. In the numerical analysis, discontinuous plans in between ground and geosynthetic, geosynthetic and geosynthetic, goesynthetic and waste have been modeled with the interface element. The results gave a good agreement with the field large-scale model test. The relative displacements of geosynthetics were also investigated and hence the interface modeling of liner system is appropriate for analysis of geosynthetics liner system in the waste landfill.

• Korean Chemical Engineering Research
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• v.44 no.6
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• pp.650-658
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• 2006

The recycling of TDA from solid waste of TDI plant(TDI-R) by near-critical hydrolysis reaction had been studied by means of a statistical design of experiment. The main and interaction effects of process variables had been defined from the experiments in a batch reactor and the correlation equation with process variables for TDA yield had been obtained from the experiments in a continuous pilot plant. It was confirmed that the effects of reaction temperature, catalyst type and concentration, and the weight ratio of water to TDI-R(WR) on TDA yield were significant. TDA yield decreased with increases in reaction temperature and catalyst concentration, and increased with an increase in WR. As a catalyst, NaOH was more effective than $Na_2CO_3$ for TDA yield. The interaction effects between catalyst concentration and temperature, WR and temperature, catalyst type and reaction time on TDA yield had been defined as significant. Although the effect of catalyst concentration on TDA yield at $300^{\circ}C$ as subcritical water was insignificant, the TDA yield decreased with increasing catalyst concentration at $400^{\circ}C$ as supercritical water. On the other hand, the yield increased with an increase in WR at $300^{\circ}C$ but showed negligible effect with WR at $400^{\circ}C$. The optimization of process variables for TDA yield has been explored with a pilot plant for scale-up. The catalyst concentration and WR were selected as process variables with respect to economic feasibility and efficiency. The effects of process variables on TDA yield had been explored by means of central composite design. The TDA yield increased with an increase in catalyst concentration. It showed maximum value at below 2.5 of WR and then decreased with an increase in WR. However, the ratio at which the TDA yield showed a maximum value increased with increasing catalyst concentration. The correlation equation of a quadratic model with catalyst concentration and WR had been obtained by the regression analysis of experimental results in a pilot plant.

• Journal of the Korean Professional Engineers Association
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• v.30 no.4
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• pp.99-116
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• 1997

In order to obtain safe drinking water, free from surface contamination, a study to determine the potential for developing a bank-filtrate system in the Iryong and Yongsan, Nakdong River Basin, Korea was conducted. The main type of aquifer In the study area is alluvial, consisting mostly of sand and gravel. The hydraulic conductivity(k) of the Iryong and Yongsan test areas were 8.63${\times}$10$^-2$cm/s and 9.90${\times}$10$^-2$cm/s, respectively, indicating that these areas are satisfactory for bank filtrate production. Pilot plants(IRPL and YSPL) were set up In Iryong and Yongsan to monitor the change in the quality of bank-filtered water and to determine the effect pumping had on the surrounding hydrogeologic system. The pilot plants operated continuously for about two months and the data obtained were used to validate the groundwater flow model. Computer simulations were conducted to predict the effects of producing bank filtrate using MODFLOW. MODPATH was also linked with the flow model to analyze particle tracking. According to the results of the model simulations and the hydrogeologlc study, long-term pumping, the minimization of drawdown and the availability of uncontaminated sell and groundwater conditions for the catchment area were all Important factors for successful bank-titrate system development.

• Child Health Nursing Research
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• v.26 no.4
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• pp.393-401
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• 2020

Purpose: This pilot study aimed to describe children's social contact patterns and to analyze factors related to their social contacts. Methods: The participants were 30 children aged ≥13 months to <7 years, whose teachers at childcare centers and parents at home were asked to maintain diaries of their social contacts prospectively for 24 hours. Data were collected from November 30, 2018, to January 7, 2019. Results: The 30 participating children were in contact with 363 persons in a 24-hours period (mean, 12.1±9.1). The number of contacts showed significant relationships with day of the week (p<.001), number of family members/cohabitants (p=.015), area of residence (p=.003), and type of housing (p=.002). A multiple regression model showed significantly higher numbers of contacts on weekdays (B=10.64, p=.010). Physical versus non-physical types of contact showed significant differences in terms of duration, location, and frequency (p<.001). The duration of contacts showed significant relationships with their location and frequency (p<.001), while the frequency of contacts was significantly related to their location (p<.001). Conclusion: This is the first survey describing the characteristics of Korean preschool children's social contacts. Further large-scale social contact studies of children should be conducted.