• Journal of Korean Society of Coastal and Ocean Engineers
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• v.9 no.2
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• pp.57-62
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• 1997

Based on the facts that significant parts of the harbor response spectrum usually reside in the vicinity of the Helmholtz mode in the eastern part of Korea. economically feasible redemption measures of seiches for malfunctioned harbors already in service is proposed by extending the wisdom of perforated breakwaters and adjusting the width of entrance channel as a control tool. It turns out that as the entrance channel is getting narrower, the harbor system is getting slender due to the increase of added hydrodynamic length so that harbor response can be effectively diminished and separated from the incident wave spectrum where considerable amount of wave energy is located at the lower frequency range.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.9
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• pp.739-743
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• 2013

In this paper, a two-dimensional (2-D) channel code for magnetic patterned media is proposed. Patterned media records an information bit on a magnetized dot. Since the space between adjacent tracks is narrow in order to increase the storage density, inter-track interference (ITI) and inter-symbol interference (ISI) can be problems. The amplitude of a bit signal can be corrupted by the 2-D ISI. The signal of the bit surrounded by the same value can be especially destructive, i.e. when its value is the same as the values of the eight surrounding bits. The proposed modulation coding scheme improves the decoding performance of patterned media by preventing this worst case and provides a better code rate than conventional channel codes.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.421-424
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• 2004

As the deep sub-micron devices are recently integrated high package density, novel process method for sub $0.1{\mu}m$ devices is required to get the superior thin gate oxide characteristics and reliability. However, few have reported on the electrical quality and reliability on the thin gate oxide. In this paper I will recommand a novel shallow trench isolation structure for thin gate oxide $30{\AA}$ of deep sub-micron devices. Different from using normal LOCOS technology, novel shallow trench isolation have a unique 'inverse narrow channel effects' when the channel width of the devices is scaled down shallow trench isolation has less encroachment into the active device area. Based on the research, I could confirm the successful fabrication of shallow trench isolation(STI) structure by the SEM, in addition to thermally stable silicide process was achiever. I also obtained the decrease threshold voltage value of the channel edge and the contact resistance of $13.2[\Omega/cont.]$ at $0.3{\times}0.3{\mu}m^2$. The reliability was measured from dielectric breakdown time, shallow trench isolation structure had tile stable value of $25[%]{\sim}90[%]$ more than 55[sec].

• Nuclear Engineering and Technology
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• v.53 no.9
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• pp.2847-2858
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• 2021

When a nuclear reactor with rectangular fuel assemblies runs for a long time, impurities and debris may be taken into coolant channels, which may cause flow blockage, and the blocked fuel assemblies might be destroyed. Therefore, the purpose of this study is to perform a thermal-hydraulic analysis of a rectangular fuel assembly by STAR-CCM+, under the condition of one subchannel with 80% blockage ratio. A rectangular fuel assembly of the International Atomic Energy Agency (IAEA) 10 MW material test reactor (MTR) is chosen. In view of the gasket material taken into the coolant channel is close to the single side of the coolant channel, in the flow blockage accident of the Oak Ridge Research Reactor (ORRR), a new blockage category called single side blockage is attempted. The blockage positions include inlet, middle and outlet, and the blockage is set as a cuboid. It is found by simulations that the blockage redistributes the mass flow rate, and large vortices appear locally. The peak temperature of the cladding is maximum, when the blockage is located at the single side of the coolant channel inlet, and no boiling occurs in all blockage cases. Moreover, as the height of the blockage increases, the damage caused by the blockage increases slightly.

• The Journal of the Acoustical Society of Korea
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• v.27 no.8
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• pp.418-426
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• 2008

In this paper, we propose an algorithm for the frequency channel segmentation using peaks and valleys in spectrogram. The frequency channel segments means that local groups of channels in frequency domain that could be arisen from the same sound source. The proposed algorithm is based on the smoothed spectrum of the input sound. Peaks and valleys in the smoothed spectrum are used to determine centers and boundaries of segments, respectively. To evaluate a suitableness of the proposed segmentation algorithm before that the grouping stage is applied, we compare the synthesized results using ideal mask with that of proposed algorithm. Simulations are performed with mixed speech signals with narrow band noises, wide band noises and other speech signals.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.21 no.4
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• pp.125-133
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• 2016

We investigated the distribution of organic matter and trace metals in surface sediment from Tonyeong coast. To determine the status of trace metal pollution, we also conducted an ecological risk assessment. Relatively high concentration of TN (total nitrogen), TOC (total organic carbon), and AVS (acid volatile sulfide) was found in surface sediment located in the narrow channel (site 35-38). Spatial distribution of Cd, Cr, Ni, Co, Hg, and Zn in surface sediment was similar and high Cu concentrations were found in narrow channel. The assessment of heavy metal pollution was derived using the Enrichment factors (EF). The enrichment factor indicated that Cd was no enrichment (EF<1), Pb, Cr, Ni, Co, Zn, and Hg were minor enrichment (1

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.21 no.4
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• pp.301-307
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• 2009

The Korean peninsula has a number of coastal sites where the rhythmic rising and lowering of water surface due to tides results in strong tidal current. The kinetic energy of these currents can be efficiently exploited by use of tidal current turbines. This paper investigates the characteristics of helical turbine based on in-field test. The experimental frame was constructed at the Uldolmok narrow channel between Jindo and Haenam and installed the helical turbine of diameter 2.2 m and height 2.5 m. 3-blade turbine had the maximum efficiencies of about 30% in the current velocity range between 1.5 and 2.3 m/s and 6-blade turbine han the maximum efficiencies of about 25%. The efficiency was constant with the current velocity. TSRs of 3-blade and 6 blade turbines were observed as 2.4 and 1.9 respectively.

• Journal of the Korean Electrochemical Society
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• v.10 no.4
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• pp.245-251
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• 2007

The performance of fuel cell is enhanced with increasing reaction surface. Narrow flow channels in flow plate cause increased pumping power. Therefore it is very important to consider the pressure drops in the flow channel of fuel cell. Previous research for pressure drop for micro channel of fuel cell was focused on effects of various configuration of flow channel without electrochemical reaction. It is very important to know pressure loss of micro flow channel with electrochemical reaction because fluid density in micro channel is changed due to chemical reaction. In this paper, it is investigated that the pressure drops in micro channel of various geometries at anode and cathode with electrochemical reaction and compared them to friction coefficient (fRe), velocity, pressure losses for corresponding non reacting flow channel. The results show that friction factors for cold flow channel could be used for parallel and bended flow channel for flow channel design of fuel cell. In the other hand, pressure drop for serpentine flow channel is the lowest among flow channels due to bypass flow across gas diffusion layer under reacting flow condition although its pressure drop is highest for cold flow condition.

• The Journal of the Acoustical Society of Korea
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• v.23 no.1
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• pp.17-23
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• 2004

The mobile radio channel can be simulated as a complex-valued random process with narrow-band spectrum. This paper describes a real-time implementation of that process using a INS320C6414 digital signal processor and XC2VP30 Virtex FPGA. The simulator presented here is not only a comprehensive model of the flat fading but also frequency selective fading mobile channel conditions. To replicate the statistical characteristics of the multipath fading environment with the minimum computational burden, multi-rate techniques are employed to resolve practical problems such as variable sampling rate. The simulator produces accurate and consistent results due to digital implementation. It is very flexible and simple to program for various field conditions in mobile communications with a graphical user interface.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.5
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• pp.567-573
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• 2008

Water quality in the longitudinal and cross section was measured and analyzed at Dal stream. The change of water quality was compared with the change of discharge at the important points. When discharge was increased by rainfall, the concentration of BOD was decreased and the concentrations of TN and TP were increased. The correlation coefficient of BOD, TN, TP showed large with the water velocity and depth in the Case 2 that discharge was increased. Rainfall had much influenced in water quality because of moving the nonpoint source to the channel. Water velocity was analyzed by numerical model(Surface water Modeling System). Velocity was comparatively fast in the upstream that had a steep slope and narrow channel. The characteristics of pollution transfer was simulated in 2-dimensional channel, the pollution diffused rapidly to the center of flow in the main channel. Flow had much influenced in diffusion of pollution.