• Journal of Advanced Navigation Technology
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• v.10 no.3
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• pp.262-267
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• 2006

For growing need for the multimedia application in the vehicles, the MOST protocol has been focused on. The MOST protocol supports three kinds of communication modes; short control message, asynchronous packets, and reserved synchronous stream data. Because of a variety of transportation, the MOST is suitable for various applications in vehicle environment. In this paper, we implemented embedded system which is MOST-enabled AMS platform and tested the network communication operation through the control port and the synchronous channel of the source port. We implemented the prototype platforms which communicate each other on the MOST's POF network. Moreover we implemented the DivX decoder attached AMS platform and verified the operation by transferring the video stream and the control messages through the MOST network.

• Journal of Navigation and Port Research
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• v.31 no.10
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• pp.833-837
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• 2007

In this study, we have fabricated a gain flattened erbium-doped optical fiber amplifier. Gain flattening filters were realized by the strain-induced long period fiber gratings, which are made of periodically arrayed metal wires. Using the filter of $550{\mu}m$ period, spontaneous emission amplified at C-band wavelength by a 980nm pumping laser was flattened within 1dB of gain ripple. The performance of the simultaneous multi channel amplification was measured using a fabry-perot laser diode. Amplification ratio was above 20dB. This amplifier can be applied to the long distance transmission system based on a wavelength division multiplexing for boosting an attenuated signal.

• Journal of the Korean Society of Marine Environment & Safety
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• v.12 no.2 s.25
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• pp.139-144
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• 2006

Recently, ships' average navigation speed become faster than before because of the increasing of high-speeds vessel including container ships and passenger-ferries. So, it is considered that the speed limit in the navigation channel in Korea isn't proper for vessel management in these days. Also, there is rare paper studies about the speed limit quantitatively and numerically, especially the speed limit is discussing continuously, as abrogation of Incheon Port's speed limit and alleviation of Gwang-yang Port's speed limit according to the requests by the navigating mariners. Consequently this paper deals with the effectiveness of speed limits using the Environmental Stress Model, after replay of the navigation traffic flow in the straight waterway using marine traffic flow simulation technique.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2013.10a
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• pp.149-150
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• 2013

Recently, various types of perforated breakwaters are being constructed for protecting offshore storm waves. In general, perforated breakwaters have wave chambers with perforated walls at seaside. Purposes of the wave chambers are to reduce wave reflections and maximum wave forces acting on the breakwater. Impact wave forces due to wave breaking can attack to the perforated wall directly, so the effects have to be considered in the design of the perforated wall carefully. Using resonance channels for wave energy dissipation, a new concept perforated breakwater is proposed, which is free from impact loads. Numerical simulation was made for wave reflection characteristics of the breakwater with respect to major design parameters. Numerical analysis was carried out using the Galerkin's FE model based on the linear potential theory considering energy dissipation on the perforated plate. Variations of wave reflection was investigated according to perforated ratios of perforated plate.

• Journal of Navigation and Port Research
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• v.36 no.3
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• pp.169-173
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• 2012

In this paper, we propose an equalizer to minimize the inter-symbol interference when PSSK(Phase Silence Shift Keying) technique is applied to the low power underwater acoustic communication. PSSK is a QPSK(Quadrature Phase Shift Keying) modulation combined with PPM(Pulse Position Modulation), and it was proposed for low power communication. However, it has poor performance due to delay spread of underwater channel. In this paper, we propose a decision feedback equalizer to minimize the error in PSSK receiver. The sea trial was performed to evaluate the performance of the proposed method. In the result, the BER of PSSK was $4.36{\times}10^{-2}$ before the equalizer was applied, but the BER of PSSK was $3.95{\times}10^{-4}$ after the proposed equalizer was applied.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2006.06b
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• pp.235-239
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• 2006

The keel attached on bottom of hull part prevents yacht from flowing sideway by sailing posture. So this study has compared with characteristics of resistance depending on the shape af the lower part of fin keel in the same surface af water submersion, we have attached three different types of models of lower part of fin keels to the model ships using circulating water channel and analyzed resistance characteristics per shape to arrive at the optimum shape of reduction of resistance.

• Journal of Navigation and Port Research
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• v.35 no.10
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• pp.811-816
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• 2011

In this paper, we analysis to consider the performance of PSPM (Phase Shift Pulse-position Modulation), the one of the low power communication technique, in near-field underwater sound channel by sea trial. PSPM is a QPSK(Quadrature Phase Shift Keying) modulation combined with PPM(Pulse Position Modulation) for low power communication in WBAN(Wireless Body Area Network). It is known that the bandwidth efficiency of PSPM is lower than conventional PSK but the power efficiency increases. In this paper, we will analyze the BER performance of PSPM using data acquired from the sea trials. The BER of QPSK was $6.04{\times}10^{-2}$, PSPM was $3.5{\times}10^{-1}$. Also, PSNR of QPSK was 9.37 dB and in case of PSPM was 9.11 dB.

• Journal of Advanced Navigation Technology
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• v.21 no.5
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• pp.485-490
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• 2017

In this paper, we propose a technique for high speed removal of sea-fog using a graphic processor. This technique uses a host processor(CPU) and several graphics processors(GPU) capable of parallel processing to remove sea-fog from the input image. In the process of removing sea-fog, the dark channel extraction, the maximum brightness channel extraction, and the calculation of the transmission are performed by the host processor, and the process of refining the transmission by applying the bidirectional filter is performed in parallel through the graphic processor. To verify the proposed parallel processing method, three NVIDIA GTX 1070 GPUs were used to construct the verification environment. As a result, it takes about 140ms when implemented with one graphics processor, and 26ms when implemented using OpenMP and multiple GPGPUs. The proposed a parallel processing algorithm based on the graphics processor unit can be used for safe navigation, port control and monitoring system.

• Journal of Korea Water Resources Association
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• v.39 no.2 s.163
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• pp.179-186
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• 2006

We analyzed the harmonic and non-harmonic constant of Geum River estuary to know tidal change of the before and after construction at Geum River estuary dike. As a result of analysis, the harmonic and non-harmonic constant after estuary dike building increased. Also, depth change analyzed at each section by using each year chart data. As a result, scour was occurred in the channel between south and north side guide bank. And accretion was occurred at channel from Kunsan outer port to estuary dike. Tidal change was judged as the effect of construction and dredge, watergate closing at Geum River estuary dike. And water depth change is a cause by effection of Geum River estuary dike construction and, south-north side guide bank, Kunjang country industrial complex furtherance business, seamangeum 4th sea bankment construction.

• Design & Manufacturing
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• v.17 no.4
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• pp.63-71
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• 2023

In order to increase the extrusion production speed of aluminum, extrusion die cooling technology using liquid nitrogen has recently attracted a lot of attention. Increasing the extrusion speed increases the temperature of the bearing area of extrusion dies and the extrusion profile, which may cause defects on the surface of extruded profile. Extrusion die cooling technology is to directly inject liquid nitrogen through a cooling channel formed between the die and the backer inside the die-set. The liquid nitrogen removes heat from the die-set, and gaseous nitrogen at the exit of the channel, covers the extrusion profile of an inert atmosphere reducing the oxidation and the profile temperature. The aim of this study is to evaluate the cooling capacity by applying die cooling to extrusion of Al-Mn-based aluminum alloy flat tubes, and to investigate the effects of die cooling on the change in extrusion characteristics of flat tubes. Cooling capacity was confirmed by observing the temperature change of the extrusion profile depending on whether or not die cooling is applied. To observe changes in material characteristics due to die cooling, surface observation is conducted and microstructure and precipitate analysis are performed by FE-SEM on the surface and longitudinal cross section of the extruded flat tubes.