• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.5B
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• pp.517-529
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• 2011

In this paper, the parameters of the RTT (Radio Transmission Techniques) for SANET (Ship Ad-hoc NETwork), which is considered for the next generation maritime communication systems, are set up. A channel model has been analyzed based on the practical measured maritime wireless channel in VHF (Very-High Frequency) for SANET system. Also, by considering the frame structure including preamble, guard time and pilots for both single and multi-carrier systems, the BER (Bit Error Rate) performances are evaluated and analyzed in the aspects of channel compensation and channel coding techniques. Based on the simulation results, optimal modulation & coding schemes are suggested for SANET. That is, in single-carrier system by using differential modulation schemes, channel compensation is not necessary. However, channel coding is helpful to achieve additional gain. On the other hand, when 16-QAM modulation is employed in multi-carrier system, the implementation of both channel compensation and channel coding techniques show huge performance gain for various of K values, which are related to different maritime environments, and the rolling effects of wave.

• Journal of Advanced Navigation Technology
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• v.11 no.1
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• pp.1-8
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• 2007

Loran-C of ground transmitting station base that can prevent confusion of country navigation system and give BACK-UP function about electric wave navigation comparing utilization incapability state about GPS(Global Positioning System) infra that user is spreading rapidly over our society whole such as sea/aviation safety, vehicles navigation, minuteness agriculture, minuteness measurement in this treatise practical use of Loran-C navigation propose. Executed ASF(Additional Secondary Phase Factor) production and an application experiment Loran-C by location error improvement way to enhance practical use value. By the result Loran-C in conclusion that can improve location error 100~400m remarkably by 10~65m reach. Also, production extent is latitude when go composition medium and bends cotton at ASF revision table utilization of land area, this smell is judged to be suitable hardness 10 minutes. And notable location error improvement and numeric of GPS BACK-UP function are judged to be possible at a ASF revision table application to Korea Peninsula whole area hereafter.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.7
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• pp.844-853
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• 2014

Since the active sonar for a naval vessel is usually installed in a bulbous bow, GRP(Glass reinforced plastic) material with low density and high strength is used for the material of the sonar dome window in order to prohibit impact by slamming wave or foreign material in the sea. The structural safety of the sonar dome is varied according to the interior and exterior distributed pressure on the sonar dome. Therefore, the variation of the structural safety according to the pressure variation of the sonar dome window caused by the drain valve state is studied by CAE.

• The Korean Journal of Petroleum Geology
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• v.12 no.1
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• pp.14-19
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• 2006

The electromagnetic (light) waves have a limitation to penetrate media, ie, water and sea-bottom layers, due to high energy attenuation, but acoustic (sound) waves play as the good messenger to gather the underwater target information. Therefore, the acoustic methods are applied to almost all of ocean equipments and technology in terms of in-water and sub-bottom surveys. Generally the sound character is controlled by its frequency. In case that the sound source is low frequency, the penetration is high and the resolution is low. On the other hand, its character is reversed at the high frequency. The common character at the both of light and sound is the energy damping according to the travel distance increase.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.15 no.3
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• pp.176-185
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• 2003

In order to ensure that submarine pipelines are stable and functional during their project lives, attention must be paid to possibility of their local scouring. When a pipeline is placed on an erodible bed, scour will develop and cause the spanning of the pipeline. U they were destroyed partially or fully, it might cause enormous restoration expenses and contamination of sea water. This paper aims at examining the characteristics of the scour End the prediction of the local scour depths around the submarine pipelines. The pipelines on the model beach with the uniform slope are placed, and the local scour depths around the pipelines are obtained according to the various wave steepnesses. Using the experimental results, some parameters needed for analyses are calculated. Finally, empirical equations of the scour depth around the pipelines are suggested through the correlation analyses between the rotative scour depth. the KC number and Modified Ursell number.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.16 no.2
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• pp.75-82
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• 2004

The changes of sea bottom configuration, which may cause the coastal disasters, have been considered as social problems. It is obvious that the beach deformation is attributable to the sediment transport associated with erosion and acceration. The prediction method and countermeasures for them, however, are not on the level of satisfaction, which indicates that efforts should be made on developing them. In this study, it is found at the groin constructed in Sangju beach on e purpose of beach protection did the aversive function. The reason for this was judged that they accelerated the speed of erosion by increasing the velocity wave-induced current rather than brought storage effect of sediment. Authors found that the storage sediment estimation model by Sonu and Beek(1971) is a useful model at the Sangju beach with the use of topographical survey data from July, 1987 to March, 2003.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.23 no.1
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• pp.11-17
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• 1987

This paper describes an availability of the teltmeter device made as a trial to measure the under-water noise, and the results of the test. This telemeter device adopts FM-FM system, and its main carrier wave is 146.2MHz. The trans-mission power is about 1w, and the available distance of transmission is 2.5KM. The timer built in the telemeter device controls transmission time and pause time automatically by the R-C time-constant. The former is 30-32 seconds and the latter is 10-12 seconds. The underwater noise in the set net fishing ground and at the breeding tank was measured, and recorded simultaneously on land and at sea with the telemeter device. When the input voltages of the transmitter is 100-300mV, the value of telemetering ambient noise and bio-acoustic underwater noise well agreed with that of the direct measurement. And the teleme-tered underwater noise decreases in proportion the distance between the transmitter and receiver.

• Journal of the Korean Society of Marine Environment & Safety
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• v.14 no.4
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• pp.303-307
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• 2008

The tug boat is restricted in her maneuvering ability due to the towed barge, and tug-barge has been strongly affected by the external forces, i.e. the wind, wave, currents, and so on. Therefore, it is difficult to get the safety of tug-barge operation. It is necessary for the captain of tug boat, VTS and operation department to develope the system which can keep observing the course, speed and position of the towed barge in actual sea and prevent the marine accidents in advance. In this study, we proposed the basic method to develope the safety towing system for barge using portable GPS which was easily movable and relatively inexpensive. Then we conducted the test on the real barge. As a result, we could obtain diverse navigation data to make a safety towing work. It was noted that these data could be used for carious purposes.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.10 no.4
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• pp.237-241
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• 1977

Optical properties were studied in the Northwest Pacific near Kamchatka Peninsula based on ten oceanographic stations from September 20 to 24, 1976. Submarine light intensity was measured by usins a submarine illuminometer (RIGO, Type: 2501-A) ; equipped with a red filter (RIGO, Type: V-R-60, wave length: 600-620 nm). Light intensity in the upper 40 m depth layer was measured at 1 m depth intervals. The absorption coefficient for red color in the area ranged from 0. 178 to 0.376 (mean 0.278) : the Secchidisc depth in the area ranged from 9 to 12 meters (mean 10.6 meters). The relationship between absorption coefficient (m) and transparency depth (D) was m=5.347/D. The rates of light penetration for red color at three different depths are computed with reference to the surface light intensity. The mean rates of light penetration were $16.36\%\;(6.45\~23.5\%),\;3.65\%\;(1.38\~7.31\%)\;and\;0.276\%(0.048\~0.647\%) $ at the depths of s m, 10 m, and 20 m, respectively.

• Journal of the Korean association of regional geographers
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• v.19 no.2
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• pp.223-233
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• 2013

Yeonpyeong Island, an island of Ong-jin County, is a very important and meaningful area in terms of its geo-politics and natural environment. But in spite of well preserved natural environment, because of limited access and security risk, there were little researches. In this sense this study would be meaningful for inquiring into the regional geomorphology of Yeon-pyeong Island. The major findings of this study are as follows. 1) 12 sites among 20 sites was evaluated 1st grade, and this means that geomorphic value of Yeon-pyeong Island is very excellent. 2) Coastal landforms of Yeon-pyeong Island are classified three major types which are rocky coast which consist of wave-cut platform and sea cliffs, sand or shingle beaches and coastal plain in the embayment area, and tidal flat areas and small uninhabited islands. 3) Cross sectional shape of Yeon-pyeong Island is asymmetric, since coastal erosion of island concentrate on the northern and western shore. 4) Quality and value of tidal flats will be deteriorate unless the dyke construction is stopped.