• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.44-51
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• 2005

Water flow in rivers during flood season can be 10 to 100 fold higher than normal seasons (low precipitation) in Japan and predicting flood runoff is essential for operating reservoirs with discharging gates. Abundant experiences and knowledge are requisites for operators to be able to make efficient decisions at work. This research investigated a method to transfer technical knowledge by acquiring skills and knowledge from actual dam operators and by using the information to construct an educational training system. The purpose of the research was to enable the execution of a secure and rational reservoir operation during flood period. The educational training system for reservoir operation was developed with the focuses on acquiring knowledge on hydraulics and hydrology and learning about decision making related to the reservoir operation as well as the timing of control. The system is capable of conducting education that corresponds to individual levels in each location. Of the educational training methods, a lecture method that uses textbooks is effective for the understanding of basic knowledge and concepts while a training method that uses a simulation device is essential for the practice of advanced and specialized procedures in specific fields. Simulation devices are used in operational training for airplane flight and driving cars and trains. The educational system presented here was designed to provide further assistance to those who have acquired basic knowledge and concepts through textbooks and also to at low them to perform the satisfactory operation of dam equipment. Our research proposes a method which can realize a system to acquire technical skills-the skills which are the foundation of technical knowledge and operation.

• Journal of Korea Water Resources Association
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• v.33 no.2
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• pp.237-245
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• 2000

Sihwa seadike is originally designed to control the water level In lake Sihwa. However the sluice gate is being operated everyday to preserve the water quality of lake. Due to the frequent operation of gates the bottom of drainage canal which is composed of weathered rock and soft rock is being scoured. Recently the bottom in the front area of apron was protected by putting underwater concrete. This study is carried out to understand the hydraulic situation for protection, and to estimate the trend of scouring by comparing between energy dissipation and registance of bottom rock. Annandale(1995) introduced the erodibility index theory, and suggested a criteria to judge the erodibility of rock through the relation between the erodibility index and energy dissipation. Determenation of erodibility index of rock is based on the results of sample core analysis, and the energy dissipation of flow is calculated from the estimation of total head on the scale model. These two values are plotted on the criteria, and the erodibility of rock is determined.

• Journal of Wetlands Research
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• v.13 no.3
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• pp.481-488
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• 2011

Various development activities have lead to the destruction of the ecosystem such as natural wetlands. In order to protect these natural wetlands, the Ministry of Environment (MOE) in Korea enacted the Wetland Conservation Act in 1999 and designated protected areas for wetland conservation. The MOE adapted the use of Best Management Practices (BMP) such as retention ponds and constructed wetlands to treat the polluted water before entering the water system. One of these projects was a free-water surface flow (FWS) constructed wetland built as a secondary treatment unit for piggery wastewater effluent coming from a livestock wastewater treatment facility. Water quality monitoring for the constructed wetland was conducted during rainfall events. The results showed that the average removal efficiencies of TSS, BOD, TN, TP were 86, 60, 45, 70%, respectively. It was observed that the removal efficiency of particulate matter and phosphorus was high compared to nitrogen. Therefore, a longer hydraulic retention time was needed in order to improve the treatment efficiency of nitrogen. The results of this study can contribute to the wetland design, operation and maintenance of constructed wetlands.

• Korean Journal of Materials Research
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• v.24 no.6
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• pp.285-292
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• 2014

Commercial activated-carbon used as the electrode material of an electric double-layer capacitor (EDLC) was posttreated with various acids and alkalis to increase its capacitance. The carbon samples prepared were then heat-treated in order to control the amount of acidic functional groups formed by the acid treatments. Coin-type EDLC cells with two symmetric carbon electrodes were assembled using the prepared carbon materials and an organic electrolyte. The electrochemical performance of the EDLC was measured by galvanostatic charge-discharge, cyclic voltammetry, and electrochemical impedance spectroscopy. Among the various activated carbons, the carbon electrodes (CSsb800) prepared by the treatments of coconutshell-based carbon activated with NaOH and $H_3BO_5$, and then heat treated at $800^{\circ}C$ under a flow of nitrogen gas, showed relatively good electrochemical performance. Although the specific-surface-area of the carbon-electrode material ($1,096m^2/g$) was less than that of pristine activated-carbon ($1,122m^2/g$), the meso-pore volume increased after the combined chemical and heat treatments. The specific capacitance of the EDLC increased from 59.6 to 74.8 F/g (26%) after those post treatments. The equivalent series resistance of EDLC using CSsb800 as electrode was much lower than that of EDLC using pristine activated carbon. Therefore, CSsb800 exhibited superior electrochemical performance at high scan rates due to its low internal resistance.

• Journal of Korea Multimedia Society
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• v.2 no.3
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• pp.265-276
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• 1999

Video on Demand (VOD) system is definitely one of main applications in upcoming multimedia era. In this research, we have designed and implemented a host-based scalable VOD system (SVOD) which is composed of low cost PC servers and runs on Linux kernel that is currently spotlighted in enterprise and research domains. Our contribution is as follows: first, the previous Ext2 file system was modified to efficiently support continuous media like MPEG stream. Second, the storage server features a host-based scalable architecture. Third, a software MPEG decoder was implemented using Microsoft's DirectShow$\circledR$COM. Finally, flow control between client and server is provided to suppress overflow and underflow of client circular buffer and supports FF VCR operation. We have known that it is possible to develop a thread-based and scalable VOD system on low cost PC servers and free Linux kernel.

• The Korea Journal of Herbology
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• v.25 no.3
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• pp.65-71
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• 2010

Objectives：To develop and validate HPLC-PDA methods for simultaneous determination of seven constituents in Samchulkunbi-tang (SKT). Additionally, we investigated the cytotoxicity against BEAS-2B cell line and splenocytes of SKT. Methods：Reverse-phase chromatography using a Gemini $C_{18}$ column operating at $40^{\circ}C$, and photodiode array (PDA) detection at 230, 254 and 280 nm, were used for quantification of the three marker components of SKT. The mobile phase using a gradient flow consisted of two solvent systems. Solvent A was 1.0% (v/v) aqueous acetic acid and solvent B was acetonitrile with 1.0% (v/v) acetic acid. The cytotoxicity of SKT were measured by the CCK-8 assay method. Results：Calibration curves were acquired with $r^2$>0.9999, and the relative standard deviation (RSD) values (%) for intra- and inter-day precision were less than 6.0%. The recovery rate of each compound was in the range of 86.89-109.78%, with an RSD less than 4.0%. The contents of seven compounds in SKT were 1.39-6.84 mg/g. SKT had no cytotoxicity effect at 50-200 ${\mu}g$/mL concentrations. Conclusions：The established method will be helpful to improve quality control and in vitro efficacy study of SKT.

• Journal of Environmental Science International
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• v.20 no.7
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• pp.845-855
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• 2011

The aim of this paper is to correlate the release characteristics of marine and lake sediment with their vicinal oxic conditions. We performed lab-scale simulation experiments using field sediment and water in order to compare the release concentrations and the release rates one another. To provide a few different kinds of oxic environments we used natural air flow and some oxygen releasing compounds such as $CaO_2$ and $MgO_2$. In case of phosphates, in each oxic condition, removal of phosphorus via biological activity and that via salt precipitation with the metal ions lowered the release rates. The behavior of the nitrogen-origin salts seemed to greatly depend on the typical biological actions - growth of biomass, nitrification, and partial denitrification. Generally speaking, the control of releases of $NH_3$-N, $PO_4$-P, T-N and T-P was successful under the oxic conditions meanwhile COD, nitrates and nitrites were difficult to reduce the releases into the bulk water because of the considerable microbial oxidation. Based on typical diffusive mass transfer kinetics the changes of concentrations of the nutrients were computed for qualitative and quantitative comparisons.

• Preventive Nutrition and Food Science
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• v.16 no.2
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• pp.104-109
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• 2011

Recently, we have demonstrated that green tea extract (GTE) decreases the intestinal absorption of benzo[a]pyrene (BAP), which is an extremely lipophilic food contaminant. The present study was conducted to examine if an enteral infusion of GTE would influence the biliary secretion of BAP and lipids in rats. Female rats were fed an AIN-93G diet with or without (control) GTE at 5 g/kg diet for 4 week. Following the 4-week dietary treatment, rats with bile duct cannula were infused continuously for 8 hr at 3.0 mL/hr via a duodenal catheter with a lipid emulsion containing $4.0\;{\mu}mol$ BAP labeled with $^{14}C$ ($^{14}C$-BAP), $20.7\;{\mu}mol$ cholesterol, $452\;{\mu}mol$ triolein, and $3.1\;{\mu}mol$ ${\alpha}$-tocopherol, and $396.0\;{\mu}mol$ Na-taurocholate with or without 76.1 mg GTE powder in PBS buffer (pH, 6.4). Bile was collected hourly via bile cannula for an 8 hr period. Our results showed that bile flow did not differ between groups. However, the biliary secretion of $^{14}C$-BAP was significantly enhanced by GTE infusion, compared with those infused with the lipid emulsion alone. However, GTE did not affect the biliary outputs of cholesterol, fat, phospholipid and ${\alpha}$-tocopherol. These findings indicate that GTE has a profound stimulatory effect on the biliary excretion of BAP in rats, without affecting other biliary lipids. The mechanism(s) by which GTE enhances the biliary secretion of BAP remains to be investigated.

• Restorative Dentistry and Endodontics
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• v.13 no.1
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• pp.123-129
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• 1988

The purpose of this study was to evaluate the bond strength of glassionomer cement against cut dentin surface which was treated with various surface cleaning agents. 48 freshly extracted human 3rd molars were ground flat through the enamel into the dentin using 600 grit silicone carbide paper under a flow of water. The were divided into four groups by the following cleaning procedure on cut dentin surface; Group I : No surface treatment after grinding with 600 grit silicone carbide paper as control group Group II : Surface treatment with 50% citric acid for 30 seconds. Group III : Surface treatment with 37% phosphoric acid for 30 seconds. Group IV : Surface treatment with 10% poly acrylic acid for 30 seconds. The specimens in 4 groups were immersed in distilled water at $37^{\circ}C$ for 24 hours before testing after cleanising with water-spray and drying with air. Bond strength was measured with Instron Universal Testing Machine (Autograph S-100, Shimadzu, Kyoto, JAPAN). The results were as follows: 1. The bond strengths of group II, III & IV were not seemed to be shown more significant improvement than a group I. 2. The bond strengths in groups which were treated with 50% citric acid, 37% phosphoric acid and 10% polycrylic acid, were ranked 24.70kg/$cm^2$, 22.02kg/$cm^2$ and 31.13kg/$cm^2$, but its difference was not significant, statistically.

• Transactions on Electrical and Electronic Materials
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• v.12 no.2
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• pp.56-59
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• 2011

The characterization of the chemical mechanical polishing (CMP) process for undensified phophosilicate glass (PSG) film is reported using design of experiments (DOE). DOE has been used by experimenters to understand the relationship between the input variables and responses of interest in a simple and efficient way, and it typically is beneficial for determining the appropriatesize of experiments with multiple process variables and making statistical inferences for the responses of interest. The equipment controllable parameters used to operate the machine consist of the down force of the wafer carrier, pressure on the back side wafer, table and spindle speeds (SS), slurry flow (SF) rate, pad condition, etc. None of these are independent ofeach other and, thus, the interaction between the parameters also needs to be understoodfor improved process characterization in CMP. In this study, we selected the five controllable equipment parameters the most recommendedby process engineers, viz. the down force (DF), back pressure (BP), table speed (TS), SS, and SF, for the characterization of the CMP process with respect to the material removal rate and film uniformity in percentage terms. The polished material is undensified PSG which is widely used for the plananization of multi-layered metal interconnects. By statistical modeling and the analysis of the metrology data acquired from a series of $2^{5-1}$ fractional factorial designs with two center points, we showed that the DF, BP and TS have the greatest effect on both the removal rate and film uniformity, as expected. It is revealed that the film uniformity of the polished PSG film contains two and three-way interactions. Therefore, one can easily infer that process control based on a better understanding of the process is the key to success in current semiconductor manufacturing, in which the size of the wafer is approaching 300 mm and is scheduled to continuously increase up to 450 mm in or slightly after 2012.