• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6A
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• pp.389-398
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• 2012

In this study, structural strain responses of the jacket-type Uldolmok tidal current power plant structure under severe tidal environments were measured and analyzed using long-term measurement system during construction and also operation. It was observed that there were significant changes in strain responses at the steps of jacket lifting, block loading, pile ejection and insertion. Strains due to dead loads and tidal loads were analyzed before and after removal of a jacket leg, and it was also found that the strains due to dead load were much significantly changed after jacket leg removal. From the measurement data during operation, it was found that strain responses were fluctuated with M2 and M4 tidal periods and also relatively short period of about 10 min due to the peculiar tidal characteristics in the Uldolmok strait. Finally, the neural network-based non-parametric estimation models were investigated to build up the signal-based structural damage monitoring system.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.2
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• pp.200-207
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• 2017

The purpose in having a control surface on ships is to control the motion of the ship. The control surface may be composed entirely of a single movable surface or of a combination of fixed and movable portions. A control surface has one sole function to perform in meeting its purpose, and that is to develop a control force in consequence of its orientation and movement relative to the water. The forces and moments generated as a result of this rotation and angle of attack then determine the manoeuvring characteristics of the ship. In this paper, two-dimensional flow characteristics of a flapped rudder and a water-blowing control rudder were accomplished respectively by PIV method in a circulating water channel. Model test has been carried out with different angles of attack of main foil (NACA 0012) and flap's deflection angles to predict the performance of the flapped rudder and the water-blowing control rudder. The 2-frame particle tracking method has been used to obtain the velocity distribution in the flow field. $Re{\fallingdotseq}3.0{\times}10^4$ has been used during the whole experiments and measured results have been compared with each other.

• Aerospace Engineering and Technology
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• v.11 no.1
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• pp.27-41
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• 2012

In this paper, there is analyzed the disturbances to impact on COMS attitude and the attitude error using the received telemetries in KARI ground station during normal mode of COMS. COMS was launched successfully at Kourou, French Guiana on the 26th of June, 2010. Up to now after IOT(in-orbit test), COMS is performing well the main mission to measure meteorology and ocean during about half and one year. The disturbances to impact on COMS attitude are mostly by the Sun, by the motion of payload mirror and by the spike happened during operation of earth sensor mirror and wheel. The analysis result on the other cases happened rarely during the nominal operation, is summarized.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.15 no.1
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• pp.87-94
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• 2016

Although studies and investments on electro-magnetic fields in terrestrial areas are being conducted, they are not applied to a ship. Especially ship is consist of Top Side, Bridge, and Engine Room. Top Side is mounted Antenna and radar. Bridge is mounted navigation and navigation equipment that have a safe voyage. Finally, Engine Room is mounted switchboard and this is used to ship propulsion system. Therefore the purpose of this paper is for suggesting optimized standard to apply to marine environment through analyzing electromagnetic wave environment in ship. For this, we were measured EMF in Hanbada ship in Korea Maritime and Ocean University and we compared and analyzed to measured values in Korea standards and international standards. Consequently, Engine Room of ship for the identified that there are limits to apply. The proposed results of this research will be expected to utilize for establishing standard a plan for EMF in ship.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.6
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• pp.472-482
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• 2019

This paper describes the stabilization of underwater TAS winch system Deploy/Recover operation performance. TAS winch installed on the stern of submarine performs to deploy/recover sensor, towing cable and rope tail which is deployed from the stern and separated from submarine itself. Also TAS winch provides transmission path of power to the sensor and data transmitting/receiving path which data are acquired from underwater environment like sound, depth and temperature. At the step of TAS winch evaluation test, sporadic standstill and rotating speed oscillation phenomenon were occurred. Winch motor provides the available torque to deploy/recover TAS and root cause analysis to the winch motor was done to find exact reason to sporadic malfunction. When winch motor was disassembled, eccentricity of rotor, slip-ring and the other composition part for winch motor were found. These might cause magnetic field distortion. To make TAS winch system more stable and block magnetic field distortion, this paper suggests methods to enhance fixing status installed in winch motor. For reliable data acquisition for TAS winch operation, the deploy/recover function of the improved type of TAS winch was verified in LBTS making similar condition with sea status. At the end of stage, improved type of TAS winch was tested on some functions not only deploy/recover function, but sustainability of TAS operation on specific velocity, steering angle of submarine in the sea trial. Improved type of TAS winch was verified in accordance with design requirement. Also, validity of suggested methods were verified by the sea trial.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.6
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• pp.180-188
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• 2020

To replace Japanese coal ash used in the domestic cement production and to recycle large quantities of domestic pond ash, it is essential to develop the technologies for quality control of cement by using the domestic pond ash. Thus, in this study, the feasibility of using the pond ash as a raw material for cement was investigated through chemical composition and microstructure analysis. As a result, most of the domestic pond ash contained slightly more Fe2O3, chloride, and unburned carbon contents than Japanese coal ash. In particular, the contents of chloride were considerably low in the pond ash that was transferred to fresh water or collected from surface of landfill area. However, since circulating fluidized bed boiler coal ash had relatively high SO3 contents causing durability problems of cement, it was not suitable for use as a raw material for cement. Thus, to replace Japanese coal ash with the domestic pond ash, it is necessary to introduce the adjustment of mixture proportion of cement raw materials and the process of removing chloride in the pond ash.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.2
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• pp.85-94
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• 2001

The vertical distribution and activity patterns of fishes during the evening and morning transitions were investigated acoustically and by pelagic trawling on October 2-10, 1997 in the Korean Eastern Sea. The acoustic data were collected from four stations with a scientific echo sounder operating at a frequency of 38 kHz, and the echogram was used to analyze the diel vertical migration of fish. Biological sampling was accomplished by pelagic trawling to identify fish species recorded on the echograms, and the species and length compositions were investigated. Vertical profiles of water temperature, salinity at the trawl station were taken with a CTD system and were related to the diel movement and the depth distribution of fish. During the day, one group of fish mainly distributed above the depth layer of 50 m, the other group was at deeper water, approximately 250 m, but began to migrate toward the surface before sunset with a time difference. During the night, they were dispersed between the surface and the depth of 125 m. Just prior to sunrise, the scattering layer was divided with 2 groups and began to migrate downwards, respectively. Several trials of pelagic trawling for scattering layers suggest that the most dominant scatterer in the survey area of this study was Japanese flying squid, Todarodes pacificus..

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.6
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• pp.481-495
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• 2020

After the resonator on the basis of the wave-filter theory was designed to control the waves with a specific frequency range surging into the harbor, the several case with the use of resonator have been reported in some part of sea, including the port of Long Beach, USA, and yacht harbor at Rome, Italy in order to control the long-period wave motion from the vessels. Recently, the utility and applicability of the resonator has been sufficiently verified in respect of the control of tsunami approximated as the solitary wave and/or the super long-period waves. However, the case with the application of tsunami in the real sea have not been reported yet. In this research, the respective case with the use of existing resonator at the port of Mukho and Imwon located in the eastern coast of South Korea were studied by using the numerical analysis through the COMCOT model adapting the reduction rate of 1983 Central East Sea tsunami and 1993 Hokkaido Southwest off tsunami. Consequently, the effectiveness of resonator against tsunami in the real sea was confirmed through the reduction rate of maximum 40~50% at the port of Mukho, and maximum 21% at the port of Imwom, respectively. In addition, it was concluded that it is necessary to study about the various case with application of different shape, arrangement, and size of resonator in order to design the optimal resonator considering the site condition.

• Journal of the Korean Society for Marine Environment & Energy
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• v.10 no.3
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• pp.127-137
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• 2007

To confirm whether or not the Electrochemical Disinfection System (EDS) meet with the D-2 regulation established by IMO (International Maritime Organization), the biological treatment efficacy of the EDS was assessed using three groups of natural marine plankton (bacteria, $10-50\;{\mu}m$ and $>50\;{\mu}m$ sized organisms). Influent water was passed through the EDS under the flow velocity ($23.8\;m^3/hr$) and test design was consisted of control (no treatment) and experimental (10 ppm and 30 ppm) condition for total residual chlorine (TRC). And the biological condition of the influent water followed the standards established by the guidelines for the approval of ballast water management systems. The disinfection efficacy of the $10-50\;{\mu}m$ sized organisms (phytoplankton) was assessed by three kinds of measurements using photomicroscope, epifluorescence microscope and fluorometer (fumer Designs 10-AU). After being passed through the EDS, all motile phytoplankton lost their motility under photomicroscope, the colour of chlorophyll fluorescence fumed from red into green under epifluorescence, and the high chlorophyll fluorescence (Expt. 1: 6.95, Expt. 2: 7.11) detected by fluorometer decreased into value not detected. These results indicated phytoplankton community was totally killed after electrochemical disinfection treatment. Survivorship of the larger organisms than $50\;{\mu}m$ was determined based on the appendage's movement under a stereomicroscope. Natural assemblage collected from ambient seawater was killed shortly after being passed through the EDS, whereas some Artemia remained alive. However, no live Artemia was found after 24 hour further exposure to each TRC concentration (10 and 30 ppm) under darkness. After electrochemical treatment, the target bacteria such as aerobes, coliform and Escherichia coli were completely killed on the basis of CFU (colony forming unit) on Petrifilm plate ($3\;M^{TM}$) after 48 hr incubation. Moreover, no regrowth was found in the three groups of plankton during five days under additional exposure to the treated water. These results indicated that the disinfection efficiency of the EDS on the three groups of plankton satisfy D-2 regulation.

• The Journal of the Acoustical Society of Korea
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• v.38 no.6
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• pp.661-669
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• 2019

High frequency active sonar is appropriate for detecting small targets such as a diver in coast environment. In case of using high frequency active sonar in shallow coastal environment, a false alarm rate is high due to clutters caused by marine biological noise, ship noise, wake, etc. In this paper, we propose an algorithm for target detection which is robust against clutter in active sonar system in shallow coastal environment. The proposed algorithm increases the rate of reduction clutter using calculation of statistical characteristics of signal and a clustering method. The algorithm is evaluated and analysed with sea trial data, as a result, that shows the rate of reducing rate of clutter of 96 % and over.