• Journal of Ocean Engineering and Technology
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• v.19 no.6 s.67
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• pp.22-28
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• 2005

We investigated the characteristics of the overflow/wave overtopping, induced by the storm surge and high waves in Masan bay and Busan Coast during Typhoon 'Maemi', which landed at the southeast coast of the Korean peninsula on September, of 2003, causing a severe inundation disaster. Characteristics of the water level, increase by the overflow / wave overtopping, were discussed in two patterns. One is the increase of water level in the region, located inside of a bay, like Masan fishing port, and the waves are relatively small. The other is in the open sea, in which the waves act directly, as on the seawall in Suyong bay. In the former region, the water level increase was affected by the storm surge, as well as the long period oscillation and waves. In Masan fishing port, about $80\%$ of the water level increase on the quay wall was caused by the storm surge. In the latter one, it was greatly affected by the wave run-up. In Suyong bay, about $90\%$ of the water level increase on the seawall was caused by the wave run-up.

• Journal of Navigation and Port Research
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• v.28 no.1
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• pp.37-41
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• 2004

In this paper, a reflector type frequency doubler for local oscillator at 24GHz is designed and fabricated with ne71300-N MESFET. Optimum source and load impedances are decided through a multiharmonic load pull simulation technique. A conversion gain can be improved using the reflector and fundamental and third harmonics are well suppressed with open stub of $\lambda$/4 length Measured results show output power at 0dBm of input power is -3.776dBm, conversion gain 0.736dB, harmonic suppression 41.064dBc, respectively.

• Journal of Navigation and Port Research
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• v.34 no.10
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• pp.793-797
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• 2010

The depleting fishes resource and water pollution in coast has a decisive effect on the fish farm and fisheries. For solving these problems the fish farms are moving to the offshore. The fish farms in offshore have to design the strong mechanism as compared with cost's fish farm, and operate by the remote feeding system and monitoring system for safety and management.. This paper describes a remote feeding system for fish farms in offshore. The amount of feed is depending on temperature and fish weight. The fish farm temperature is changed extremely in offshore than on land side. This paper described that the feed amount is calculated automatically according to temperature and fish weight, and the remote feed system. The performance of remote feed system is tested with model.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2018.11a
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• pp.210-211
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• 2018

In general, the dam break problem is demonstrated to simulate open-channel disturbance due to large violent waves. These days, the large violent waves at shore and coastline can be seen frequently such like tsunami. The conventional computational fluid dynamics program based on Grid system, can be used to simulate this problem with large deformation of free surface in the restricted condition due to its limitation. The particle method based on fully Lagrangian approach is able to simulate large deformation of free surface by tracking each particles. In this study, the simulation of disturbance of mobile-bed due to large violent waves was investigated by using particle method.

• Journal of Korea Port Economic Association
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• v.21 no.1
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• pp.45-58
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• 2005

The purpose of this study is to consider the problem on pursuit of logistics strategy by our international shipping company in international shipping business under the said circumstance due to the open international shipping market and to suggest the logistics strategy for the consideration of the logistics competition under new international shipping circumstances. The results of empirical analysis are mentioned as follows; First, it shall be considered to maintain the size of company bigger than a certain capability so that it may obtain the superior competition of logistics. Second, as there are the plus correlations between the competition of logistics and the logistic support, it is necessary to pursuit the upgrade service with using EDI system and making up the complex shipping and integrated logistics system in general. Third, with the rationalization of finance policy and the profitable management of shipping company the ratio of net worth can be raised and it can be achieved to make the sound financial structure as reducing the excessive debt ratio. Fourth, it can be effort continuously to perform the investment for the infrastructure of logistics support & the institutional supplement so that it may achieve to increase the efficiency of logistic support at pier and to reduce the cost of logistic support.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.77-82
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• 2006

Automatic vessel collision-avoidance systems have been studied in the fields of artificial intelligence and navigation for decades. And to facilitate automatic collision-avoidance decision-making in two-vessel-encounter situation, several expert and fuzzy expert systems have been developed. However, none of them can negotiate with each other as seafarers usually do when they intend to make a more economic overall plan of collision avoidance in the COLREGS-COST-HIGH situations where collision avoidance following the International Regulations for Preventing Collisions at Sea(COLREGS) costs too much. Automatic Identification System(AIS) makes data communication between two vessels possible, and negotiation methods can be used to optimize vessel collision avoidance. In this paper, a negotiation framework is put forward to enable vessels to negotiate to optimize collision avoidance in the COLREGS-COST-HIGH situations at open sea. A vessel vector space is defined and therewith a cost model is put forward to evaluate the cost of collision-avoidance actions. Negotiations between a give-way vessel and a stand-on vessel and between two give-way vessels are considered respectively to reach overall low cost agreements. With the framework proposed in this paper, two vessels involved in a COLREGS-COST-HIGH situation can negotiate with each other to get a more economic overall plan of collision avoidance than that suggested by the traditional collision-avoidance expert systems.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2009.10a
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• pp.38-39
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• 2009

Visual simulation technology is one of important constituents experienced directly by simulator users. Simulator users have a needs for more fast, realistic and intuitive visualization. Though hardwares such as computing power and visual equipment have been grown, the limits have been indicated in graphic rendering engine generally used in marine simulator up to now. This paper has focused on the review of applicability about graphic rendering engines for visual simulation. We had derived system requirements in visualization of tug-barge simulation, had surveyed graphic rendering engines as commercial and open source, and analyzed strengths and weakness of them.

• Journal of Korean Port Research
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• v.12 no.2
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• pp.349-362
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• 1998

Seascape means the scenery which is composed around the sea., Seascape has it's own characteristics compared with landscape and has many important roles in our urban life. Nowadays seascape is being destructed by the development in waterfront area and ocean space. Especially the various kind of buildings which are built in coastal area give great visual impact on seascape. But we have rare research on seascape and no guideline for seascape planning. Before any action against destroying seascape the assessment of seascape has to be preceded. The purpose of this study is to evaluate the representative seascapes which are selected from over 300 slides of various seascapes according to the types of seascapes. We used S.D (Semantic Differential) method with 35 adjective pairs in seven scale to evaluate each seascape. The results can be summarized as follows. 1) Seascapes can be classified as natural type and urban type. The natural type can be divided into beach type and rock-island type. 2) Natural type of seascape is more prefered than urban type. 3)Beach type is the most prefered among seascape types. 4) Natural elements of seascape such as sky, water, sand, trees, forest, mountain, open space, waterfront line, are evaluated as 'good' to see but artificial elements, such as buildings, persons, roads, structures, are evaluated 'bad' to see. 5)As a result of factor analysis five factors(axes) are found out. They are 'wildness', 'vividness', 'preference', 'interest', and 'openness'. These factors can be used for evaluting any seascape.

• Journal of Korean Port Research
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• v.14 no.4
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• pp.451-461
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• 2000

The design and maintenance of navigation channel and water facilities of an harbor which is located at the mouth of river or at the estuary area are difficult due to the complexity of estuarial water and sediment circulation. Effects of deepening navigable waterways, of changing coastline configurations, or of discharging dredged material to the open sea are necessary to be investigated and predicted in terms of water quality and possible physical changes to the coastal environment. A borad analysis of the transport mechanism in the estuary area was made in terms of sediment property, falling velocity, concentration and flow characteristics. In order to simulate the transport processes, a two-dimensional finite element model is developed, which includes erosion, transport and deposition mechanism of suspended sediments. Galerkin’s weighted residual method is used to solve the transient convection-diffusion equation. The fluid domain is subdivided into a series of triangular elements in which a quadratic approximation is made for suspended sediment concentration. Model could deal with a continuous aggregation by stipulating the settling velocity of the flocs in each element. The model provides suspended sediment concentration, bed shear stress, erosion versus deposition rate and bed profile at the given time step.

• ETRI Journal
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• v.41 no.2
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• pp.197-206
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• 2019

Software-defined networking (SDN) is a modern approach for current computer and data networks. The increase in the number of business websites has resulted in an exponential growth in web traffic. To cope with the increased demands, multiple web servers with a front-end load balancer are widely used by organizations and businesses as a viable solution to improve the performance. In this paper, we propose a load-balancing mechanism for SDN. Our approach allocates web requests to each server according to its response time and the traffic volume of the corresponding switch port. The centralized SDN controller periodically collects this information to maintain an up-to-date view of the load distribution among the servers, and incoming user requests are redirected to the most appropriate server. The simulation results confirm the superiority of our approach compared to several other techniques. Compared to LBBSRT, round robin, and random selection methods, our mechanism improves the average response time by 19.58%, 33.94%, and 57.41%, respectively. Furthermore, the average improvement of throughput in comparison with these algorithms is 16.52%, 29.72%, and 58.27%, respectively.