• Fire Science and Engineering
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• v.20 no.2 s.62
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• pp.44-53
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• 2006

We have conducted a numerical simulation under two-dimensional unsteady conditions in order to analyze the effect according to the injection angle and velocity of the $CO_2$ agent nozzle which is one of the elements for the fixed type $CO_2$ fire extinguishing system installed in a ship on the characteristics of flow and $CO_2$ concentration distribution. The flow fields and concentration fields were measured and analyzed. We can found that the difference of flow patterns according to the conditions of $CO_2$ agent injection nozzle, and in all the conditions of $CO_2$ agent injection nozzle, the iso-concentration line was expanded from the region at which vortex was generated to the surroundings. We can expected that the intensity of the wall jet on the bottom floor was generated differently and the iso-concentration lines were expanded or shrunk according to the angle of $CO_2$ agent injection nozzle. In case of increasing $CO_2$ agent injection velocity maintaining the flow quantity of the $CO_2$ agent injection equally, the iso-concentration line of $CO_2$ agent on bottom floor can be formed more higher than in case of decreasing $CO_2$ agent injection velocity.

• Journal of Navigation and Port Research
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• v.47 no.4
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• pp.256-270
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• 2023

In this study, a sliding mode (SM) controller for dynamic positioning (DP) was specifically designed for a turret connection operation of a ship or an offshore structure in which an arbitrary point on the structure could be controlled as the motion center instead of the center of mass. The SM controller allows control of the arbitrary point and provides capability to manage uncertainties in the dynamics of ships and offshore structures, external forces caused by unknown changing marine environments, and transient performance of DP systems. The Jacobian matrix included in kinematic equations of the controlled object was modified to design the SM controller to control based on an arbitrary point of ships or offshore structures. To ensure robustness of the controller, the Lyapunov stability theory was applied in the design of the SM controller. In general, for robustness in DP control, gain scheduling based on a proportional-derivative (PD) control algorithm is employed. However, finding appropriate gains for gain scheduling complicates the application of DP systems. Therefore, in this study, the SM control algorithm was considered to mitigate the complexity of the DP controller for ships and offshore structures. To validate the proposed SM control algorithm, time-domain simulations were conducted and utilized to evaluate the performance of the control algorithm. The effectiveness of the proposed SM controller was assessed by comparing simulation results with results of a conventional PD control algorithm applied in DP control.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.7
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• pp.613-621
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• 2016

This research connected network equipment, including CCTV, PAGA, IP-PBX, and Legacy, in order to enable the operation and configuration of internal IP-based network equipment in maritime plants and vessels, both in the field and from remote places, and to allow for the support of remotely controlling such equipment. It also realized an operating program for the integrated network equipment management system to enable the monitoring and control of equipment status, operation condition, and notifications from distant places. By applying the operating program to satellite stations and vessels sailing on the sea, a performance test was conducted to evaluate data loss and transmission/reception delay in the communication section between the land and vessels. As a result, this research verified the normal operation of CCTV control and of real-time monitoring and control of the network equipment, including PAGA, IP-PBX, and Legacy under the FBB and MVSAT environments. It was observed that the transmission of CCTV video images with a large volume of data as well as the transmission and reception of voice data were found to be slightly delayed, indicating the need to develop technology to compress and convert data for real-time transmission and reception.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.7
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• pp.910-914
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• 2023

With the technological innovation owing to the 4th industrial revolution, the maritime transportation is rapidly being developed with autonomous ships and systems. Particularly, autonomous ships will partially replace the manned ships and navigation among them remotely upon the degree of autonomy suggested by IMO. Accordingly, the remote operator and related research have increased as well. However, the data on the minimum required manpower for remote operators are lacking such as considering engage required situations and their co-occurrence probability. Therefore, this study proposes a simulation model that calculates the number of remote engage required situations by defining restricted water area and remote engage required situation as close-quarter situations based on accumulated trajectory data of actual ships. The findings are expected to be used as background materials to establish the appropriate manpower distribution of remote operators in remote operation centers.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.3
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• pp.175-185
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• 2000

This paper described on a basic study to organize fishing vessel control system in order to control efficiently fishing vessel in Korean offshore. It was digitalized ARPA image on the fishing processing of a fleet of purse seiner in conducting fishing operation at Cheju offshore in Korea as a digital camera and then simulated by used VTMS. Futhermore, it was investigated on the application of FVTMS which can control efficiently fishing vessels in fishing ground. The results obtained were as follows ; (1) It was taken 16 minutes and 35 minutes to casting and hauling net in fishing processing respectively. The length of rope pulled by scout boat was 200m, tactical diameter in casting net was 340.8m, turning speed was 6kts as well. (2) The processing of casting and hauling net was moved to SW, NE as results of simulation when the current direction and speed set into NE, 2kts and SW, 2kts respectively. Such as these results suggest that can predict to control the fishing vessel previously with information of fishing ground, fishery and ship's maneuvering, etc. (3) The control range of VTMS radar used in simulation was about 16 miles. Although converting from a radar of the control vessel to another one, it was continuously acquired for the vector and the target data. The optimum control position could be determined by measuring and analyzing to distance and direction between the control vessel and the fleet of fishing vessel. (4) The FVTMS(fishing vessel traffic management services) model was suggested that fishing vessels received fishing conditions and safety navigation information can operate safely and efficiently.

• Journal of the Korean Society for Marine Environment & Energy
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• v.11 no.1
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• pp.42-45
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• 2008

It has been reported that FRP (fiber reinforced plastic) can be recycled by separating into layers instead of crushing into powder. F-fiber obtained from roving layer separated from FRP, has bigger tensile strength than the bundle of glass fibers of which FRP was made (more than 90%). SEM image of F-fiber shows the presence of some resin. Under the proposition of usage of F-fiber in the concrete material, tensile strength is examined after soaking in a basic solution (NaOH+KOH). The reaction mechanism of strength loss may be considered as an attack of hydroxide ion ($OH^-$) on a chemical bond of Si-O-Si of glass fiber. The simulation graph of the strength loss data implies certain reaction mechanism. While in the early stage kinetically controlled reaction results in a fast drop of tensile strength, after 30 days dispersion rate of hydroxide ion plays a major role in strength loss. This result is similar to the one for the AR glass. An extrapolation of the graph would make an assumption about the lift time of F-fiber possible.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.7
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• pp.744-753
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• 2015

This paper presents the results of research on developing marine unified communications to provide VoIP service based on marine satellites. With the recent popularity of smart-phones and other mobile devices, the demand for Internet-based wired and wireless unified technology has been growing in marine environments, and increasing interest is being directed to VoIP products and service models with high price competitiveness and the ability to deliver a variety of services. In this regard, this research designed three instruments, developed their unit modules, and verified their performances. These three instruments included the following: (1) a marine VoIP module equipped with an analogue gateway that can be linked to the existing devices used in vessels, which is more than 80% smaller than that of a land system; (2) a text/voice/video engine for marine satellite communications that runs on technology that minimizes communication data usage, which is a core technology for a marine VoIP service; and (3) a unified communication service that can support multilateral cloud-based message conversations, telephone number-based call functions, and voice/video calling between a private space in a ship and shore.

• Journal of Navigation and Port Research
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• v.36 no.3
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• pp.205-213
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• 2012

This study focused on the supply-demand and training system of the crew for domestic coastal shipping. First of all, it forecasted the prospect and effect in the future of the crew supply-demand through the analysis to the current situation of crew employment and the internal and external environment changes. Next, it suggested the specific role and alternatives of government, industry and educational institutions after the comparison and examination of the sailor policies among Korea and major shipping countries. In regard to the demand of crew manpower in coastal shipping, it figured out the bottoms and the current circumstances of sailors, and it could anticipate the future demand by the gradational approach. According to the findings, firstly the result of this simulation by the changes of the ship numbers demonstrated that the demand over the next 10 years will be 7,890~8,025 in the case of the growth 0.4%, and 7,894~8,063 in 0.5%. Secondly, assuming the growth 0.1~1%, the result illustrated that the demand will come to 7,879~8,258. This means the fact that the additional manpower has to be input to 20~430 annually from now on. To conclude, this study showed the more rational numbers about the supply-demand than the past researches and displayed the systematic approach to supply and train the crew in domestic coastal shipping.