• Journal of the Korean Society of Marine Environment & Safety
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• v.14 no.1
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• pp.89-93
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• 2008

Stiffened panels are basic strength members which have been used widely in a vessel or an offshore. They have been used often a deck, a side and a bottom structure of ship and have a number of one sided stiffener in either one or both directions called grillage. Their buckling and plastic collapse become damaged reason of the hull girder so it needs to investigate accurately buckling and ultimate strength of stiffened panels. In the present paper, using the ANSYS, a commercial finite element analysis code, we conducted the evaluation regarding buckling and post-buckling behaviour of stiffened panels, and analyzed stiffener's web height change, considering the effect of lateral pressure load against compression ultimate strength.

• Journal of the Korean Society of Marine Environment & Safety
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• v.14 no.1
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• pp.15-20
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• 2008

Contaminated sediments are the actual cause for deterioration of coastal-ecosystem. So the developed countries have been in the process of making an effort to develop new techniques for monitoring and solving this problem since 1960. In this research, suction type pump dredging system of pilot size for collecting the filth from the seabed has been designed and manufactured that can prevent or minimize the secondary pollution by filth diffusion. For the practical use, the application possibility of the developed system has been checked through a system performance test. And, the evaluation of system performance according to the underwater body type has been carried out for system optimization by using CFD. The performance tests for checking the efficiency of sediment collecting system are done under two conditions i.e. when the system is non-operational and when the system is self-propelled. The results of this research showed the possibility of the development of dredging system to remove just the upper parts of filth from seabed.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.1
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• pp.145-151
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• 2017

In this paper, we propose the design and implementation of the system that is predicting the failure of ballast water treatment system by analysing its sensor datum and is reserving the most effective service center for sellecting the repair location on the way to the destination port. These data are collected in real time during draining or filling up the sea water from/to the ship, and it is essential to preliminarily repair the equipment showing unstable characteristics by analyzing the normal and abnormal data characteristics. We proposed a software platform for predicting and repairing faults by selecting the most efficient repair center based on this e-Navigation while the vessel is navigating to the next destination port. This system, as announced by the IMO Convention for the Prevention of Marine Pollution in 2017, provides a stable economic impact from stable cargo operation and stable out/in from/to port and marine ecosystem.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.1
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• pp.28-36
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• 2018

The experimental results of the model tests for the twin propeller cavitation noise are presented. The model test was carried out by means of procedure of noise measurement followed by the signal processing and full-scale extrapolation. In order to convert the measured sound pressure level into the sound source level, transfer function measurements for three conditions were performed according to the combination of locations and number of virtual sources. White noise and LFM signal were used as a source signals to examine the influence of the input signal. For the twin propellers, 5 transfer functions were defined and the results were discussed. Cavitation noise measurement tests were performed similarly to the transfer function measurement test. Noise source localization analysis was performed to confirm the test effectiveness. It was confirmed that the source level of the twin propeller can be estimated reliably by using transfer function corrections. Finally, the model test results were converted into full-scale by applying the ITTC '87 model-ship scaling raw, and the validity of the model test was confirmed by comparison with the full-scale measurement result.

• Journal of Power System Engineering
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• v.19 no.3
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• pp.16-21
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• 2015

Nitrous oxide($N_2O$) concentration in the atmosphere has been constantly increased by the human activities with industrial growth after the industrial revolution. One of factors to increase $N_2O$ concentration in the atmosphere is the $N_2O$ emission caused by the combustion of marine fuel. Especially, a sulfur component included in marine fuel oils is known as increasing the $N_2O$ formation in diesel combustion. Form this point of view, $N_2O$ emission from a ship is not negligible. On the other hand, Exhaust gas recirculation(EGR) that have thermal, chemical and dilution effect is effective method for reducing the NOx emission. In this study, an author investigated $N_2O$ reduction by using EGR on a direct injection diesel engine. The test engine was a 4-stroke diesel engine with maximum output of 12 kW at 2600rpm, and operating condition of the engine was a fixed load of 75%. The experimental oil was a blend-fuel that were adjusted with sulfur ratio of 3.5%, and EGR ratio of 0%, 10%, 20% and 30%. In conclusion, diesel fuel that contained 3.5% sulfur component increased $SO_2$ emission in exhaust gas, and increment of EGR ratio reduced NO emission. Moreover, $N_2O$ emission was decreased as over 50% at EGR ratio of 10% and reduced 100% at EGR ratio of 30% compared with $N_2O$ emission of 0% EGR ratio.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.49 no.3
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• pp.270-281
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• 2013

Hydro-acoustic surveys with scientific echo sounder were carried out to estimate the total density and distribution of the juvenile cod in Jinhae bay, Korea. The surveys were conducted 4 times from May to June using 2 frequency method (38kHz and 120kHz) and beam trawl were used to investigate the species composition. Also the catch amounts of juvenile cod were compared with the cod density estimated by the hydro-acoustic method. It was confirmed that the juvenile cod was stayed in Jinhae bay in early June and There was the relationship between catch of juvenile cod and the estimated density by hydro-acoustic survey. The number of juvenile cod was consequently about 365,000 fish (CV 12.9%) in May and 113,000 fish (CV 9.2%) in May based on the hydro-acoustic data.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.9
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• pp.940-946
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• 2015

In this paper, we study a method that amplifies the output gain of a high voltage pulse using 300 kHz or higher frequency. We conducted a study on a method for amplifying the output gain using the resonance between the capacitance components of the load and the parasitic components of the circuit, instead of the conservative method for amplifying the pulse-amplitude by raising the voltage of the power stage. In particular, the method simplifies the circuit configuration throughout the appliance of flyback-type topology instead of the bridge-type. There are advantages that prevent damage from overload and the heat in the output circuit through the hard switching by amplifying the gain of the output voltage applying to the load as given by the capacitance component of the output electrode to the output pulse waveform. This study proposed a method to enhance the spatial and electrical efficiency of the contact-type heating device through the dielectric heating method applied to the field of medical and industrial heating.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.9
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• pp.935-939
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• 2015

This paper describes sensorless speed control of brushless DC motors by using direct torque control. Direct torque control offers fast torque response, robust specification of parameter changes, and lower hardware and processing costs compared to vector-controlled drives. In this paper, the current error compensation method is applied to the sensorless speed control of a brushless DC motor. Through this control technique, the controlled stator voltage is applied to the brushless DC motor such that the error between the stator currents in the mathematical model and the actual motor can be forced to decay to zero as time proceeds, and therefore, the motor speed approaches the setting value. This paper discusses the composition of the controller, which can carry out robust speed control without any proportional-integral (PI) controllers. The simulation results show that the control system has good dynamic speed and load responses at wide ranges of speed.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.9
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• pp.973-980
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• 2015

With their wide geographical distribution, unconventional resources are continuously compared against conventional resources, but their development is expanding because TRRs (Technical Recoverable Resources) are similar to conventional resources. In particular, there is active development of unconventional gas resources such as shale gas, tight gas, CBM (coalbed methane) and gas hydrate. However, it is difficult to calculate the material properties of unconventional resources, especially the gas content, with current geophysical logging technology. Additionally, some overseas companies have monopolies on related equipment and materials. Therefore, this study developed a reservoir PCS (Pressure Core Sampler). It can collect core samples without gaseous loss by maintaining high pressure from the moment the core is sampled and record pressure and temperature in real time. Successful performance testing was also carried out for official verification of the manufactured PCS. The reservoir PCS will contribute to the acquisition of geophysical well logging data as well as accurate and reliable cores.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.3
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• pp.325-332
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• 2014

In installing ballast water treatment system, the cost of the system is high and many technical aspects are to be considered and also it takes significant time to retro-fitting on the existing ships. In addition, in the current circumstance which the Ballast Water Management Convention has not been entered into force, the 28th IMO Assembly adopted a resolution to mediate the implementation schedule of the treatment systems. In the mean time, California State and New York State have declared more stringent discharge requirements of ballast water and are planning to implement them earlier than the schedule of the Convention. In these circumstances, the implication in the difference between ballast water treatment system manufacturers and ship owners need to be considered. In this study, through the review on the considerations when installing the system onboard, stringent requirements of United States of America, and determent or mediated implementation schedules of Convention and California and New York States, the author would like to suggest the strategy of concerned parties for anticipated entrry into force of the Convention and implementation of the stringent requirements of United States of America.