• Journal of Navigation and Port Research
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• v.29 no.6 s.102
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• pp.573-581
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• 2005

The outbound containers in a container terminal are classified into a few groups by their weights and stacked separately in a yard for easy and efficient handling. In order to maintain the balance of a ship during loading, containers of heavier weight groups should be fetched out of a yard and loaded onto the ship before those of lighter weight groups. However, the weight information used to determine the weight group is usually imprecise. Therefore stacks will actually be filled with mixture of different weight groups and rehandlings are unavoidable during loading operation. This paper presents a method for estimating the number of rehandlings caused by imprecise information and a scheme for generating a simple but efficient slot assignment rule. Experiments have shown that a rule generated by the proposed method can reduce the number of rehandlings by about $20\%$ compared to the traditional slot assignment method which stacks only the containers of the same weight group in a single stack.

• Journal of Navigation and Port Research
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• v.36 no.10
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• pp.825-832
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• 2012

GPS signal delay that caused by dry gases and water vapor in troposphere is a main error source of GPS point positioning and it must be eliminated for precise point positioning. In this paper, we implemented to generate tropospheric delay grid map over the Korean Peninsula based on post-processing method by using the GPS permanent station network in order to determine the availability of tropospheric delay generation algorithm. GIPSY 5.0 was used for GPS data process and nationwide AWS observation network was used to calculate the amount of dry delay and wet delay separately. As the result of grid map's accuracy analysis, the RMSE between grid map data and GPS site data was 0.7mm in ZHD, 7.6mm in ZWD and 8.5mm in ZTD. After grid map accuracy analysis, we applied the calculated tropospheric delay grid map to single frequency relative positioning algorithm and analyzed the positioning accuracy enhancement. As the result, positioning accuracy was improved up to 36% in case of relative positioning of Suwon(SUWN) and Mokpo(MKPO), that the baseline distance is about 297km.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.29 no.1
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• pp.359-367
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• 2005

In order to increase the productivity of container terminals, automation is being considered seriously in nowadays. A yard is usually automated by running autumated RMGs (rail mounted gantries) which may require somewhat a different stacking strategy to archive a better performance. In this paper, we present a simulation model for RMGs and summarize experimental results with two different stacking strategies applied to a horizontal block which has two non-crossable RMGs. The concentrating strategy, which stacks containers belong to a single ship together and dedicateds each RMG to either ship services or external truck services, showed a good performance in ship unloading. In the contrast, the distributing strategy, which partitions a block into two regions and binds each RMG to one of the regions to improve the productivity of ship services by running each RMG alternately, is suggested for blocks of exporting.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.29 no.1
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• pp.391-398
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• 2005

The outbound containers in a container terminal are classified into a few groups by their weights and stocked separately in a yard for easy and efficient handling. In order to maintain the balance of a ship during loading, containers of heavier weight groups should be fetched out of a yard and loaded onto the ship before those of lighter weight groups. However, the weight information used to determine the weight group is usually imprecise. Therefore stacks will actually be filled with mixture of different weight groups and rehandlings are unavoidable during loading operation. This paper presents a method for estimating the number of rehandlings caused by imprecise information and a scheme for generating a simple but efficient slot assignment rule. Experiments have shown that a rule generated by the proposed method can reduce the number of rehandlings by about 20%compared to the traditional slot assignment method which stacks only the containers of the same weight group in a single stack.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2013.10a
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• pp.69-70
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• 2013

IPCC (International Panel on Climate Change) reported that the arctic sea-ice extent has been decreased by 2.7% per decades since satellite observations in 1978. The decreased sea-ice extent has gained an international attention due to its economical benefits from the NSR (Northen Sea Route). The NRS - not a clearly defined single route, but a number of alternative routes across the top of Russiahas a 37 % reduction in sailing distance, comparing to the SSR (Southen Sea Route) passing thourgh the Suez Canal. Sailing days are consequently reduced from 30 days to 20 days. Also, it is estimated that the Northen Sea has 20 to 25% of world's oil resources and occupies 40% of the world's fishery production. As Republic of Korea was admitted as an observer to the Arctic Council on May 15, 2013, there has been increasing needs to explore new route in the Northen Sea. In this situation, Korea Institute of Ocean Science & Technology (KIOST) is preparing a plan for the development of Arctic-circle Ocean Environmental Information System to support the ice navigation and resource exploration in the Arctic. We will introduce a conceptual design of a satellite-based ice navigation supporting system for the northern sea route.

• Journal of Navigation and Port Research
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• v.39 no.1
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• pp.69-75
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• 2015

The concrete purpose of this study is to suggest actually a debt ratio to optimize the capital structure providing a kind of approach to estimate the proper debt ratio with an analytical model and empirical data in Korean shipping industry. The mathematical and analytical model is started from the first equation about ROE, return of net operating income on equity, with an independent variable, debt ratio. It is constructed with several parameters, ROS(return of operating income on sales), TAT(total assets turnover), and NFCL(net finance cost to liabilities). There could not be a certain relationship between debt ratio and ROS or TAT, while some correlation or causality between debt ratio and NFCL. In other words, most of firms with high debt ratio is likely to burden higher finance cost than others with low one. In this case, there is a linearity relationship between debt ratio and NFCL, so then the second equation considering this relation could be included within the analytical approach of this paper. To be short, if the criteria of adequate debt ratio has to be defined as some level of debt ratio to optimize ROE, the ROE could be illustrated as a quadratic equation to debt ratio from two equations. Next, this research estimated those parameters' numbers through the single regression method with data over 12 years of Korean shipping industry, and identified empirically the fact that optimal debt ratio would be approximately 400%. To conclude, if that industry's sales and operating incomes are stable, the debt ratio could be accepted until twice of 200% had forced in order to guarantee its financial safety in past time.

• Journal of Navigation and Port Research
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• v.30 no.8 s.114
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• pp.711-719
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• 2006

A series of geotechnical centrifuge model tests and numerical modelling have been performed to study engineering characteristics of the composite ground reinforced by both the Sand Compaction Piles(SCPs) and the deformation-reducing sheet piles. The research has covered several key issues such as the load-settlement relation, the stress concentration ratio and the final water content of the ground Totally three centrifuge tests have been conducted by changing configuration of the sheet piles, i.e., a test without the sheet pile, a test with the sheet pile at a single side and a test with the sheet piles at the both sides. In the model tests, a vertical load was applied in-flight on the ground surface. On the other hand, class-C type numerical modelling has been performed by using the SAGE-CRISP to compare the centrifuge test results using an elasto-plastic model for SCPs and the Modified Cam Clay model for the soft clay. It has been found that the sheet piles can restraint failure of foundation, thereby increasing yield stress of the ground. The stress concentration ratio was in the range of $2{\sim}4$. In addition, numerical analysis results showed reductions both in the ground heave($20{\sim}30%$) and in the horizontal movement($28{\sim}43%$), demonstrating the deformation-reducing effect of the sheet piles.

• Journal of the Korean Society of Marine Environment & Safety
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• v.14 no.2
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• pp.163-168
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• 2008

Ship detection from satellite remote sensing is a crucial application for global monitoring for the purpose of protecting the marine environment and ensuring marine security. It permits to monitor sea traffic including fisheries, and to associate ships with oil discharge. An automatic ship detection approach for RADARSAT Fine Synthetic Aperture Radar (SAR) image is described and assessed using in situ ship validation information collected during field experiments conducted on August 6, 2004. Ship detection algorithms developed here consist of five stages: calibration, land masking, prescreening, point positioning, and discrimination. The fine image was acquired of Ulsan Port, located in southeast Korea, and during the acquisition, wind speeds between 0 m/s and 0.4 m/s were reported. The detection approach is applied to anchoring ships in the anchorage area of the port and its results are compared with validation data based on Vessel Traffic Service (VTS) radar. Our analysis for anchoring ships, above 68 m in length (LOA), indicates a 100% ship detection rate for the RADARSAT single beam mode. It is shown that the ship detection performance of SAR for smaller ships like barge could be higher than the land-based radar. The proposed method is also applied to estimate the ship's dimensions of length and breadth from SAR radar cross section(RCS), but those values were comparatively higher than the actual sizes because of layover and shadow effects of SAR.

• Journal of IKEEE
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• v.9 no.1 s.16
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• pp.19-30
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• 2005

Packet classification is defined as the action to match the packet with a set of predefined rules. One of classification is to use Ternary Content Addressable Memory hardware search engine that has faster than other algorithmic methods. However, TCAM has some limitations. One of them is that TCAM can not perform range matching efficiently. A range has to be expanded into prefixes to fit the boundary. In general, the number of expansion could be up to 2w-2, where w is the width of the field. For example, if two range fields with 16 bits are used, there could be up to $30\;{\times}\;30\;=\;900$ expansions for a single rule. In this paper, we describe the novel algorithm for converting range matching rules into TCAM entry efficiently. The number of maximum entry is 2w-4 when using the algorithm. Furthermore, it has also benefit about the negation range. In the result of experimentation, the new scheme practically reduces 14 percent in case that searched fields are source port and destination port number.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2015.10a
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• pp.87-90
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• 2015

Equipments that can transmit maritime distress signals in accordance to Global Maritime Distress Safety System are the followings: A1 water(Very High Frequency, SART), A2 water(MF/HF Radio Equipment), A3 water(INMARSAT), A4 water(Emergency Position Indicating Radio Beacon). Institutions with the capacity to receive distress signals are Korea Coast Guard affiliated radio stations, patrol ships, Rescue Coordination centers, Vessel Traffic centers, Complex problems regarding repetitive distress alarms, inaccurate statistics, multiple control towers are existent. Consequently, effective measurement to resolve dispersed operating maritime distress signal system are in time of need. Moreover, current KCG Headquarter is considering to integrate five distress radio stations dispersed across nation into a single international safety communication center. The integration of radio stations are efficient in terms of information coordination between nations, however, it cannot support efficient response to real-time maritime incident. Therefore, in this study, a new system that can rapidly response to real-time maritime incident will be proposed.