• Journal of Korean Society of Environmental Engineers
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• v.29 no.5
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• pp.564-570
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• 2007

This study investigated the treatment of liquid waste containing highly concentrated iron(III)-ethylenediaminetetraaceticacid (Fe(III)-EDTA) of 70,000 mg/L by an underwater electrical discharge process using low voltage and high current. When AC voltage is applied to the discharging electrode with the other electrode grounded, the temperature of the liquid waste around the discharging electrode rapidly increases, and at the same time, hydrogen and oxygen gases are formed at the electrode as a result of electrochemical reactions. Ultimately, gases formed by vaporization of water and electrochemical reactions cover the electrode. Since the liquid waste is electrically conductive, it elongates the ground electrode up to the border of the gas layer, where electrical discharge occurs. Without hydrogen peroxide, electrical discharge was able to remove about 50% of Fe(III)-EDTA. As the concentration of hydrogen peroxide added increased, the removal efficiency of Fe(III)-EDTA increased. When the molar ratio of hydrogen peroxide to the initial Fe(III)-EDTA was higher than 24.7, more than 80 g of Fe(III)-EDTA was removed with an energy of 1 kWh. A comparison between tungsten and steel electrodes showed that electrode material did not affect the Fe(III)-EDTA removal. In the present underwater electrical discharge process, the removal of Fe(III)-EDTA was completed within 30 min at molar ratios of hydrogen peroxide to the initial Fe(III)-EDTA higher than 24.7.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.3
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• pp.405-412
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• 2023

With the development of drone and ICT convergence technology, the use of underwater drones such as leisure underwater drones such as underwater exploration for fishing and industrial drones such as bridge piers is increasing. Existing motor controllers are suitable for aerial drones and these can increase the completeness of underwater drones and their reliability in motor control by developing BLDC motor controllers dedicated to underwater drones. By developing a battery management system (BMS) exclusively for underwater drones, battery stability was ensured by checking the state of charge, checking the state of discharge, adjusting cell balancing, and implementing high/voltage protection functions.

• Journal of the Korean Geotechnical Society
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• v.26 no.3
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• pp.25-34
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• 2010

In the present paper, a numerical study was carried out to simulate ground expansion induced by an application of pulse discharge technology. Based on laboratory pulse discharge tests, the characteristics of shockwave were investigated, and then the laboratory tests were numerical1y simulated using underwater explosion model implemented in a coupled acoustic-structural finite element analysis. In addition, for clayey soils, the expansion of ground was also studied using soil properties obtained from empirical correlations with SPT N values. It was found that the calculation results well agreed with the field test results.

• Korean Journal of Environmental Biology
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• v.40 no.4
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• pp.641-650
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• 2022

The purpose of this study was to compare the efficiency of air and oxygen injected into the underwater non-thermal dielectric barrier discharge plasma (DBD plasma) device used to remove five types of antibiotics (tetracycline, doxycycline, oxytetracycline, clindamycin, and erythromycin) artificially contained in the fish farm discharge water. The voltage given to generate DBD plasma was 27.8 kV, and the measurement intervals were 0, 0.5, 1, 2, 4, 8, 16 and 32 minutes. Tetracycline antibiotics significantly decreased in 4 minutes when air was injected and were reduced in 30 seconds when oxygen was injected. After the introduction of air and oxygen at 32 minutes, 78.1% and 95.8% of tetracycline were removed, 77.1% and 96.3% of doxycycline were removed, and 77.1% and 95.5% of oxytetracycline were removed, respectively. In air and oxygen, 59.6% and 83.0% of clindamycin and 53.3% and 74.3% of erythromycin were removed, respectively. The two antibiotics showed lower removal efficiency than tetracyclines. In conclusion, fish farm discharge water contains five different types of antibiotics that can be reduced using underwater DBD plasma, and oxygen gas injection outperformed air in terms of removal efficiency.

• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.2
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• pp.255-265
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• 2019

In the present study, the effect of opening patterns of a flow control valve on underwater discharge systems using a linear pump was investigated numerically. For that, a improved mathematical model was developed. The improvement is to separate a middle tank from a water cylinder because the cross-section area of the inlet of the middle tank is an important parameter. To validate the improved model, calculation results were compared with a previous study. The results showed that $2^{nd}$ order or more polynomial opening patterns had an advantage over ramp opening patterns. Higher an order of polynomial resulted in wider operating limits. An escape velocity and a maximum acceleration of underwater vehicle were affected by time derivative of the cross-section area of the flow control valve. Besides, as a velocity profile of the vehicle got closer to linearity, the escape velocity got faster and the maximum acceleration got smaller. And velocities of the vehicle and piston had similar variation trend.

• Journal of the Korea Institute of Military Science and Technology
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• v.24 no.2
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• pp.219-227
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• 2021

In the present study, the effect of command signals of the flow control valve on performance of underwater discharge systems using a linear pump was investigated numerically. For that, the improved mathematical model was developed. The improvement is to calculate the flow leakage between the water cylinder and the piston. Also the model of the hydraulic cylinder is simplified. To validate the improved model, calculation results were compared with experiment results. The results of the study is as follows: Double ramp command signals of the flow control valve had an advantage over single ramp signals. The parametric study on the effect of double ramp command signals on performance of the system was performed. In case of using double ramp signals, the maximum acceleration of the underwater vehicle was reduced by approximately 50 % compared with using single ramp signals.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.55 no.6
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• pp.910-916
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• 2022

The purpose of this study is to evaluate the effect of underwater non-thermal dielectric barrier discharge plasma (DBD plasma) on the sterilization of three types of pathogenic bacteria that cause diseases in freshwater fish and the reduction of a tetracycline antibiotics. This experiment was conducted in the DBD plasma generator, and the voltages used to generate plasma were 11.6 kV and 23.1 kV. The measurement intervals were 0, 1, 5, 10 and 15 min. As a result of DBD plasma treatment, Aeromonas hydrophila, Edwardsiella tarda and Pseudomonas fluorescens were removed 93-99% after 5 min at 23.1 kV, and the tetracycline antibiotics were reduced 70-95% after 15 min at 23.1 kV. In this study, as a result of treating the effluent with DBD plasma at a fish farm where the medicinal bath was conducted with oxytetracycline-HCl (OTC-HCl) products, OTC-HCl decreased by 62% after 10 min at 23.1 kV.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.6
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• pp.567-572
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• 2009

The underwater launch system using an ATP consists of five parts: compressor tank, proportional flow control servo valve, expulsion spool valve, air turbine pump, and discharge tube. The purpose of this study is to develop an underwater launch system using an ATP and to verify the validity of the system. The proportional flow control servo valve is modeled as a 2nd order transfer function. The projectile is ejected by pressurized water through the air turbine pump, which is controlled by expulsion valve. The mathematical model is derived to estimate the dynamic characteristics of the system, and the important design parameters are derived by using simulations. The computer simulation results show the dynamic characteristics and the possibility of control for underwater launch system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.518-523
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• 2009

Main source of URN(Underwater Radiated Noise) which is related to the ship's survivability is divided into two groups. Cavitation is main source of URN when the speed of ship is upper than CIS(Cavitation Inception Speed). But when the speed of ship is lower than CIS, main source of URN is structure-borne noise on the hull which is originated from propulsion system, pump system or transmitted vibration of pipe system. In this paper, to reduce the vibration of discharge pipe and valve system, back flow prevent globe valve and new rubber mount are applied to the ship. As the result of applying new valve and mount, the vibration is reduced drastically.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.6
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• pp.599-606
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• 2009

Main source of URN(underwater radiated noise) which is related to the ship's survivability is divided into two groups. Cavitation is the main source of URN when the speed of ship is upper than CIS(cavitation inception speed). But when the speed of ship is lower than CIS, the main source of URN is the structure-borne noise on the hull which is originated from propulsion system, pump system and trnasmitted vibration of the pipe system. In this paper, to reduce the vibration of discharge pipe and valve system, back flow prevent globe valve and new rubber mount are applied to the ship. As the result of applying new valve and mount, the vibration is reduced drastically.