• Journal of the Society of Naval Architects of Korea
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• v.40 no.6
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• pp.80-87
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• 2003

Tank structures in ships are in contact with various fluid. The vibration characteristics of those structures are strongly affected by the added mass due to containing fluid. It is important to predict vibration characteristics of tank structures, but it is difficult to do. That's because the interaction problem concerned with the free surface, the variation of water depth and stiffener is to be considered between the fluid and the structure. Many authors have studied vibration of rectangular tank structures containing water. Kito studied added mass effect of water in contact with thin elastic flat plates. Kim et al. studied flexural vibration of stiffened plates in contact with water. However, few researches on dynamic interaction tank walls with water are reported in the vibration of rectangular tanks recently. in the present report, the coupling effect of added mass of fluid and structural constraint between panels on each vibration mode changing breadth of elastic plate, and dynamic pressure distribution have investigated numerically and discussed.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.10
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• pp.916-921
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• 2016

It is possible for humans to breathe underwater using dissolved oxygen. However, unlike fish, humans need large amounts of oxygen to breathe underwater. Water generally contains small amounts of dissolved oxygen. To get enough dissolved oxygen from water, great volumes of it should be supplied into a separation device. If exhalation gases are used, the amounts of water supplied into the membrane can be decreased. However, the characteristics of exhalation gases after passage through the separation device need to be investigated. To reuse the exhalation gases, the concentration of carbon dioxide should be decreased. A compressor is needed to supply the exhalation gases because of the high pressure generated in the membrane inlet. However, compressors require a lot of power and are heavy, so it is not proper to get the portable separation device. A system without the compressor is needed. If the pressure of the position mixed from the exhalation is less than atmosphere, the compressor is not needed. In this thesis, characteristics of the gases which are mixed with exhalation gases and separated from water after passing the membrane are investigated. The compositions of carbon dioxide, oxygen, and nitrogen are measured with the gas chromatography. The effects of water and exhalation gas flow rates on characteristics of gases separated from water after the membrane are showed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.157-162
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• 2012

The basic study for combustion characteristics of micron-sized aluminum powder with water suspension was carried out. Under atmospheric pressure, the combustion characteristics of aluminum powder with water suspension was studied by adjust the equivalent ratio and the density of a mixture which effect on burning rate. Based on atmospheric pressure's result, the device for the combustion characteristics of aluminum powder with water suspension under high-pressure environment was developed. In the pressure range from 2 to 50 atm the effect of pressure to burning rate was same as the case of nano-aluminum with water suspension, but the pressure range from 50 to 70 atm the sharp increase in burning rate was observed. In the experiment of varying the equivalence ratio, the combustion did not proceed in the condition of excess oxidizer (eq = 1.5).

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.55 no.3
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• pp.273-283
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• 2019

The authors has predicted the maneuvering characteristics of a fishing vessel in deep water using Kijima's empirical formula in a previous study. Since the Kijima's empirical formula was developed by a regression analysis of merchant vessels which have dimensions ($C_b$, L/B, etc.) that are different from those of fishing vessels, it was possible to make a prediction approximately even with inaccurate estimation. In this study, the authors estimated the turning-motion characteristics of a model ship of fisheries training ship in shallow water based on the results of its previous study. The turning-motion characteristics of the model ship in shallow water was found out through quantitative analysis according to the water depth to ship draft ratio (H/d). In conclusion, the turning-motion characteristics of the model ship had significant changes immediately after an H/d 1.5, and this result will be helpful for sailing in shallow water.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1C
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• pp.53-63
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• 2010

Since the water retention curve is considered as a major parameter to evaluate the unsaturated ground or soils, overburden pressure and clay content on soils underneath ground surface have not been considered for estimating water retention characteristics. Therefore, a need exists that the effect of overburden pressure and clay content on water retention characteristics was assessed in typical weathered soils found in Korea. Soil-Water Characteristic Curve and the unsaturated hydraulic conductivity were estimated using water retention characteristics under the condition of different overburden pressure, clay content, and de-saturation path. Then, these effects are evaluated with the results of SWCC tests from the laboratory. In addition to that, the unsaturated moisture capacity and diffusivity of each case is discussed.

• KCID journal
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• v.18 no.2
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• pp.15-24
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• 2011

This study was carried out to analyze characteristics of water quality and correlation among water quality parameters in Idong reservoir used for agricultural water. The pH and concentrations of DO, SS, BOD, COD, TP, Chl-a in Idong reservoir almost met the water quality standards for agricultural water, but TN concentration exceeded the water quality standards for agricultural water. All of water quality items had no significant difference between horizontal points at 95% confidence level and the Idong reservoir was possible to be treated as the single water body. As NIP ratio of the Idong reservoir is 52, TP is a limiting nutrient salt. As TN exceeds the water quality standards, it is required to preserve TP below current state to prevent water bloom by eutrophication. Therefore, reduction of phosphorus from the watershed is necessary for controlling the eutrophication of Idong reservoir.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.5
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• pp.731-739
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• 2011

To investigate corrosivity characteristics of tap water in Korea, Langelier index (LI) of 30 multi-regional water treatment plants (WTPs) were evaluated. Weekly LI values of 30 WTPs were all negative, which means tap water in Korea might be very corrosive. Maximum LI decrease through water treatment processes was 0.95 under no additional corrosion control process. Based on the correlation results between LI and tap water qualities, pH and calcium concentration were confirmed as major parameters for LI control. Addition of calcium hydroxide with $CO_{2}$ or calcium hydroxide or sodium hydroxide can be chosen based on water quality. Continuous monitoring of LI and related parameters is recommended in water distribution system.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3418-3422
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• 2007

The neutron imaging technique was used to investigate the water discharge characteristics at PEMFC. Prior to investigation of water discharge characteristics, the linear attenuation coefficient for water at Neutron Radiography Facility (NRF) was calibrated. The feasibility test apparatus was consisted of pressurized air and water in order to simulate the actual operating PEMFC. The feasibility tests have been performed at 1-parallel serpentine type with 100 $cm^2$ active area and different air flow rate (1, 2, and 4 lpm). The total water volume variations at each condition were calculated from the neutron images. The water at channel is well discharged as soon as supplying the pressurized air into the PEMFC. However, because the water at MEA isn't removed the total water volume is constant after 150. Therefore more effective method is needed in order to discharge water at MEA, and the neutron imaging technique is helpful for it.

• Journal of Power System Engineering
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• v.19 no.2
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• pp.84-89
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• 2015

The occurrence of algae caused by eutrophication of fresh water is a pollution source to destroy the aquatic environment. When the high voltage electric field is applied in the water, When a high voltage is applied to the electric field in the water, the algae can be broken the balance of cell membranes, and is dead. In this paper, we develop a water quality improvement system for generating an electric field having a higher energy than the zeta potential when a high voltage is applied to 4,000V. To ensure the mobility of the water quality improvement system, we designed the PV generation system using the optimal size technique that is based on the model of power lack ratio. By evaluating the output characteristics of the water quality improvement system, power generation characteristics of the PV generation system, and battery charging characteristics, we can show that the proposed system can be applicable to the water quality improvement system inhibiting the growth rate of the algae in the fresh water.

• Journal of Korean Society of Water and Wastewater
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• v.23 no.5
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• pp.609-618
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• 2009

Repeated phenol spill in the Nakdong River has been a big issue in Korea since 1991. In this study, treatment of phenol in each water treatment process and total water treatment system is evaluated. Phenol was highly volatile, easily oxidized by ozone, and readily absorbed onto GAC. When there was phenol of 0.3mg/L in water, by ozonation of 1mg/L or by GAC adsorption with EBCT of 10minutes or longer, it could be treated to lower than 0.005mg/L, the national drinking water standard of phenol. Even when a sufficient contact time(70minutes) was allowed, only 35 to 40% of phenol could be removed by powdered activated carbon(PAC). Based on the test results, it can be concluded that 1.0mg/L or less concentration of phenol can be treated at the plants adopting the combination process of ozone and GAC down to the safe level. In this study, removal characteristics for phenol were evaluated with the existing pilot plant and demo plant in different advanced water treatment processes(AWTPs). In the future, studies on changes in oxidation and adsorption characteristics caused by competitive matters such as DOC and removal characteristics by other various AWTPs including ozone/filter adsorber need to be performed.