• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.203-206
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• 2008

There are lots of the narrow pass on alluvial channel of Korea. Most of research about this narrow pass of channel were focused on incremental effect of water level at backwater segment. In the meantime this research showed that it is important to valuate the river-bed variation at backward and forward around narrow pass. The sediment deposit at not only the backward of narrow pass but also the forward affected incremental effect of water level. The sediment deposit at the forward of narrow pass headed by sediment that passed through the narrow passed or scoured right around it.

• Journal of Korea Water Resources Association
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• v.42 no.2
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• pp.141-148
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• 2009

Each river in each country has peculiar channel characteristics at every section. Korea consists of mountains at the rate of 70%. Due to this, the sections that display unique channel form are scattered. One of the typical features is the narrow pass of channel section that presents in the process of the generation of alluvial channel and deformation channel. Around as this narrow pass of channel, it often comes to be regular flood disaster section. Regardless of this situation, investigations and plans that reflect channel characteristics at the narrow pass of channel have been wholly wanting until now. In accordance with this, we have investigated and analysed hydraulic significance and channel form of the narrow pass of channel in Seonsan in this study. The study has found real minute classification of sediment phenomenon at river bed of low flow channel on investigation section which is sand-bed river, but it was vaguely difficult to conclude that classification of sediment arises from explicit natural force. We were able to assume that the phenomenon comes from gentle bed slope, supply of river bed materials which is nearly uniformity. However, classification of sediment would come from collecting an aggregate rather than natural force. And we found that compound cross section conversion has been developing dramatically with channel form of movable bed section referring to movement which was active before at drainage district of the narrow pass of channel. With this, we could find the phenomenon that river width of low flow channel diminished largely. This kind of situation implies that it may cause compound section weighting, flood dimension decreasing, revetment at low flow channel or the local scour at bottom of levee when extraordinary flood occurs.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.4
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• pp.525-532
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• 2022

The port of Mokpo operates the largest number of coastal passenger ships and routes in Korea. These coastal passenger ships pass through narrow channels in the south-west coast of Korea owing to the geographical effect. It is difficult to find a research for the safety of the marine traffic environment in the narrow channel used by coastal passenger ship. Therefore, in this study, the navigation safety of the target coastal passenger ship was analyzed in the narrow channel near the port of Mokpo using the Korea design standard for port and harbour facilities. As a result of the analysis, the width of the narrow channel between Maek-island and Dali-island is narrower than 1.5 times of the target ship's length over all, the degree of curvature of the narrow channel exceeds the standard value of 30°, and several fishing gears exist near the narrow channel. Finally, the following were suggested to improve the safety of navigation on the narrow channel: keeping one-way traffic during the day-time, and navigating through the designated fairway during night·visibility restriction·low tide.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.9
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• pp.2218-2230
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• 2012

In this paper, we propose an efficient channel delay estimation method for orthogonal frequency-division multiplexing (OFDM) systems, especially over doubly-selective fading channels which are selective in both the symbol time domain and subcarrier frequency domain. For the doubly-selective fading channels in single frequency network (SFN), long and strong echoes exist and thus the conventional discrete Fourier Transform (DFT) based channel delay estimation system often fails to produce the exact channel delay profile. Based on the analysis of the discrete-time frequency response of the channel impulse response (CIR) coefficients in the DFT-based channel delay estimation system, we develop a method to effectively extract the true CIR from the aliased signals by employing a simple narrow-band low-pass filter (NB-LPF). The performance of the proposed system is verified using the COST207 TU6 SFN channel model.

• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.265-266
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• 2015

A multiple output dc-dc resonant converter topology for an independent voltage control technique is proposed, using a narrow frequency selection band-pass filters. The multi-output converter is supplied by a single source inverter with the superposed sinusoidal signals reserved for each output. A series-series parallel resonant topology is utilized to implement the narrow frequency selection channels for minimum interference. Finally the experimental setup for four output dc-dc converter is verified with the narrow channel frequencies of 26 kHz, 32 kHz, 38 kHz and 46 kHz.

• Journal of Korean Society of Water and Wastewater
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• v.26 no.4
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• pp.503-512
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• 2012

In Yongwon channel, its natural flow of seawater is blocked by the construction of Busan New Port including the container berth. The channel was transformed into a narrow and long one, where it is possible that ships are only allowed to pass through the north-side channel of Gyeonmado located at the point of river mouth to Songjeongcheon. In addition, Yongwon channel is approximately 100 m wide on average and 3,600 m long, and has the highest slenderness ratio (length/width = 36). So it is considered that the changes in the terrain characteristics of Yongwon channel is likely to alter the circulation of sea water, thereby changing its water quality. In this study, the bottom sediment were collected from the 48 points of the Yongwon channel and the long-term leaching characteristics were analyzed. Thus, changes in sediment and water quality were analyzed through the sediment release test to investigate the degree of contamination. The sediment release from the inside region was higher than the outer region, which is due to the pollutant that comes form the downtown area. The results of this study can be used to predict the water quality in the future and prepare the economically optimized countermeasures to improve the water quality of Yongwon channel, Busan New Port.

• Journal of Korean Society of Water and Wastewater
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• v.27 no.2
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• pp.185-196
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• 2013

In Yongwon channel, its natural flow of seawater is blocked by the construction of Busan Newport including the container berth. The channel was transformed into a narrow and long one, where it is possible that ships are only allowed to pass through the north-side channel of Gyeonmado located at the point of river mouth to Songjeongcheon. In addition, Yongwon channel is approximately 100 m wide on average and 3,600 m long, which has the highest slenderness ratio (length/width=36). So it is considered that the changes in the terrain characteristics of Yongwon channel is likely to alter the circulation of sea water, thereby changing its water quality. In this study, the seasonal change and the spatial variation of the water quality in Yongwon channel was analyzed for the effect of land pollution using the measurement data. The mass balance calculation method is used to analyze the water pollution resulting from sediment pollutants. This result shows that the improvement of the water quality in Yongwon channel can be obtained from the sewer pipe modification and the environmental dredging.

• Journal of Advanced Navigation Technology
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• v.11 no.1
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• pp.9-16
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• 2007

In this paper, the Bit Error Ratio (BER) performances of the D8PSK modulation schemes for VDL Mode-2 are analyzed according to the matched and unmatched cases of the channel filters. The carrier frequency and phase offset effects are analyzed with unmatched case. Generally in digital transmission techniques, the Root Raised Cosine filters which are used as channel filters are applied to both sides at transmitter and receiver in order to achieve no ISI, but in VDL Mode-2, the Raised Cosine Filter is used only in transmission section and the receiver section uses general low pass filter, therefore we could not achieve ISI reduction effects but can have better spectrum quality. From the simulation results, the error probability is increased slightly (1~2dB) with use of un-matched channel filter, we got the conclusions that carrier phase offset do not effect to bit error ratio, but the frequency offset effect is so serious. Finally, narrow band D8PSK modulation signals are generated by the use of Digital Up-Converter and then its features are compared with analog modulator.

• Nuclear Engineering and Technology
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• v.52 no.12
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• pp.2771-2788
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• 2020

Experiments are conducted to study bubble flow behavior during the instability of subcooled boiling under uniform and non-uniform transverse heating. The non-uniform heat distribution introduces nonuniform bubble generation and condensation rates on the heated surface, which is different from the uniform heating. These bubble generation and condensation characteristics introduce a non-uniform local pressure distribution in the transverse direction, which creates an extra non-uniform pressure on the flowing bubbles. Therefore, different bubble flow behavior can be observed between uniform and non-uniform heating conditions. In the uniform heating, bubble velocity fluctuations are low, and the bubbles travel straight along the axial direction. In the non-uniform heating, more fluctuation in the bubble velocity occurs at low mass flow rate and high subcooled inlet temperatures, and reverse flow is observed. Additionally, the bubbles show a zigzag trajectory when they pass through the channel, which indicates the existence of cross flow in the transverse direction.

• Journal of electromagnetic engineering and science
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• v.4 no.1
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• pp.23-29
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• 2004

In this paper we analyze convergence constraints and time constant of IT-LMS algorithm and derive a method of making it's time constant independent of signal power by using input variance estimation. The method for estimating the input variance is to use a single-pole low-pass filter(LPF) with common smoothing parameter value, θ. The estimator is with narrow bandwidth for large θ but with wide bandwidth for small θ. This small θ gives long term average estimation(low frequency) of the fluctuating input variance well as short term variations (high frequency) of the input power. In our simulations of multipath communication channel equalization environments, the method with large θ has shown not as much improved convergence speed as the speed of the original IT-LMS algorithm. The proposed method with small θ=0.01 reach its minimum MSE in 100 samples whereas the IT-LMS converges in 200 samples. This shows the proposed, tap-power normalized IT-LMS algorithm can be applied more effectively to digital wireless communication systems.