• Journal of Navigation and Port Research
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• v.41 no.5
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• pp.345-352
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• 2017

Recently, a new port reserves deep water depth for safe navigation and mooring, following the trend of larger ship building. Larger port facilities include long and huge breakwaters, and mainly adopt vertical type considering low construction cost. A vertical breakwater creates stem waves combining inclined incident waves and reflected waves, and this causes maneuvering difficulty to the passing vessels, and erosion of shoreline with additional damages to berthing facilities. Thus, in this study, the researchers have investigated the response of stem waves at the vertical breakwater near the entrance channel and applied numerical models, which are commonly used for the analysis of wave response at the harbor design. The basic equation composing models here adopted both the linear parabolic approximation adding the nonlinear dispersion relationship and nonlinear parabolic approximation adding a linear dispersion relationship. To analyze the applicability of both models, the research compared the numerical results with the existing hydraulic model results. The gap of serial breakwaters and aligned angles caused more complicated stem wave generation and secondary stem wave was found through the breakwater gap. Those analyzed results should be applied to ship handling simulation studies at the approaching channels, along with the mooring test.

• Journal of Navigation and Port Research
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• v.29 no.7
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• pp.627-634
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• 2005

Gunsan-Janghang Harbor is located at the mouth of Gum River, on the central west coast of Korea The harbor and coastal boundaries are protected from the effects of the open ocean by natural coastal islands and shoals due to depositions from the river, and two breakwaters. The navigation channel commences at the gap formed by the outer breakwater and extends through a bay via a long channel formed by an isolated jetty. For better understanding and analysis of wave transformation process where a wide coastline changes appear due to on-going reclamation works, we applied the spectral wave model including wind effect to the related site, together with the energy balance models. This paper summarizes comparisons of coastal responses predicted by several numerical wave predictions obtained at the coastal waters near Gunsan-Janghang Harbor. Field and numerical model investigations were initially conducted for the original navigation channel management project. We hope to contribute from this study that coastal engineers are able to use safety the numerical models in the area of port and navigational channel design.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.594-599
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• 2009

Recent developments such as concern over global warming, depletion of fossil fuels and increase in energy demands by the increasing world population has eventually lead to mass production of electricity using renewable sources. Apart from wind and solar, ocean holds tremendous amount of untapped energy in forms such as geothermal vents, tides and waves. The current study looks at generating power using waves and the focus is on the primary energy conversion (first stage conversion) of incoming waves for different models. Observation of flow characteristics and the velocity in the augmentation channel as well as the front guide nozzle are presented in the paper. A numerical wave tank was used to simulate the waves and after obtaining the desired wave properties; the augmentation channel plus the front guide nozzle and rear chamber were integrated to the numerical wave tank. The waves in the numerical wave tank were generated by a piston type wave maker which was located at the wave tank inlet. The inlet which was modeled as a plate wall moved sinusoidally with the general function, x=asin$\omega$t The augmentation channel consisted of a front nozzle, rear nozzle and an internal fluid region representing the turbine housing. The analysis was performed using the commercial CFD code ANSYS-CFX.

• ETRI Journal
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• v.29 no.3
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• pp.363-370
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• 2007

In this paper, we propose a flexible turbo decoding algorithm for a high order modulation scheme that uses a standard half-rate turbo decoder designed for binary quadrature phase-shift keying (B/QPSK) modulation. A transformation applied to the incoming I-channel and Q-channel symbols allows the use of an off-the-shelf B/QPSK turbo decoder without any modifications. Iterative codes such as turbo codes process the received symbols recursively to improve performance. As the number of iterations increases, the execution time and power consumption also increase. The proposed algorithm reduces the latency and power consumption by combination of the radix-4, dual-path processing, parallel decoding, and early-stop algorithms. We implement the proposed scheme on a field-programmable gate array and compare its decoding speed with that of a conventional decoder. The results show that the proposed flexible decoding algorithm is 6.4 times faster than the conventional scheme.

• Journal of the Korean Society of Marine Environment & Safety
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• v.12 no.3 s.26
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• pp.211-218
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• 2006

Recently, many ships such as fishing boats, cargo ships, high speed ferry boats are visiting Mokpo harbor. In particular, many marine accidents have been occurred at this area due to the narrow channel, a thick fog, the existing of the shallow waters etc. However there is no suitable ships' routeing system which takes account of today's traffic situations in this area. This study aims at the settling of hazardous factors to mitigate the danger to vessels in Mokpo harbor and to secure the safety of maritime environment.

• Journal of Navigation and Port Research
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• v.32 no.5
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• pp.327-332
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• 2008

This paper analyzed the visual range and arrangement of light buoy on navigation officers as the primary material to establish the standard of optimal arrangement of light buoy on the channel of the domestic trade-port. About $30{\sim}150$ questionnaires by port were distributed according to the scale of trade-ports and then Effective total 356 copies were used in analysis. The distance, $2{\sim}4$mile, occupied the highest percentage 55.0% as the visual range with naked eyes at the daytime in bright weather. At the arrangement way of light buoy the both sides buoy method showed high in the preference 62.1% among the respondents. The preferred interval between sequence buoys was averagely 1.09mile. Also, the preferred number of light buoy was two in the preference 40.6% among them to cognize without binoculars.

• Journal of Navigation and Port Research
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• v.38 no.6
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• pp.689-694
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• 2014

The Korean government has introduced and enforced maritime traffic safety assessment to secure traffic safety since 2010. The maritime traffic safety assessment is needed by law to design a new port or modify an existing one. According to Korea Maritime Safety Act, in the assessment the propriety of marine traffic system consists of the safety of channel transit and berthing/unberthing maneuver, safety of mooring, and safety of marine traffic flow. The safety of channel transit and berthing/unberthing maneuver can be evaluated only by ship-handling simulation. The ship-handling simulation is carried out by sea pilots working with the port concerned. The vessel's proximity measure is an important factor to evaluate traffic safety. The proximity measure is composed of vessel's closest distance to channel boundary and probability of grounding/collision. What is more, the probability of grounding becomes important. According to central limit theorem, a sample has a normal distribution on condition that its size is more than 30. However, more than 30 simulation runs bring about the increase of assessment period and difficulty of employing sea pilots. Therefore this paper is to find out minimum sample size for evaluating vessel's proximity. First sample sets of size of 3, 5, 7, 9 etc. are selected randomly on the basis of normal distribution. And then KS test for goodness of fit and t-test for confidence interval are applied to each sample set. Finally this paper decides the minimum sample size. As a result this paper suggests the minimum sample size of 5, that is, the simulation of more than five times.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.65-66
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• 2005

This paper presents an adaptive satellite communication systems to adapt channel environment. High performance coding and modulation techniques are applied to poor channel condition, otherwise, bandwidth efficient coding and modulation techniques are applied to good channel condition to obtain high transmission rate.

• Journal of Navigation and Port Research
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• v.29 no.8 s.104
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• pp.693-699
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• 2005

To design ship channels is one of important factors for planning and developing a port. Bends in channels should be avoided if possible, but the channel should be widened, if channel bend is unavoidable, considering the swept path of a ship for safe passage. In this study, Variable Bumper Area(VBA) model is applied to determine the channel widths in bends. The result of this study shows that the width of the bend may be designed as nearly same size of that in straight channel in case that the angle of deflection is less than 30 degrees, and that of the bend with 60 degrees deflection should be widened based on the length of the largest ship using the channel and the angle of deflection.

• 한국지구물리탐사학회:학술대회논문집
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• 2005.05a
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• pp.293-298
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• 2005

In this study, we have developed the high resolution multichannel seismic data acquisition system and shallow marine seismic source. It is easy to operate and handle our source system which utilizes piezoelectric transducer of high electrical power. We have manufactured two 4-channel streamers for multi-channel marine seismic survey. In the recording part, we used 24bits and 8 channel high speed A/D board. Therefore, we could achieve the improvement of data quality and the efficiency of data acquisition. We compared the developed system with the conventional system to demonstrate its field applicability.