• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.11
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• pp.1410-1413
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• 2016

Array beamforming for anti-jamming means that jamming signals are superposed destructively, while superposing information signals constructively at a receiver. However, according to channel state variation, the anti-jamming performance of the beamforming can be degraded because of large beamwidth of the sidelobe and lower selectivity of the mainlobe. To mitigate this problem, we introduce a beamformed decoy signal which uses frequency band distinguished from the information signal to make the jammer concentrate its jamming power to a wrong target under limited feedback. In this paper, we show that the performance of the proposed scheme can approach that of optimal one with perfect feedback.

• Journal of Fisheries and Marine Sciences Education
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• v.27 no.5
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• pp.1508-1521
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• 2015

Vibrio harveyi is a pathogenic marine bacterium causing systemic symptoms resulting in mass mortalities in fishes and shrimps in aquaculture. Outer membrane proteins(OMPs) are related to the pathogenicity and thus good targets for diagnosis and vaccination for Gram negative bacteria. Recently vaccination strategies using the OMPs have been suggested to control vibriosis in several fish species. In this study, we have isolated V. harveyi from diseased marine fishes from different regions of Korea and investigated genetic variations of four OMP genes including OmpK, OmpU, OmpV and OmpW. Consequently, OmpK and U genes could be divided into 3 subgroups of type I, II, III and type A, B, C, respectively, without any correlation with geographical regions and species while OmpV and W were highly homologous. OmpW gene of V. harveyi FP4138 was fully sequenced and predicted the deduced amino acid sequence to form ${\beta}-barrel$ with hydrophobic channel. Indeed, the immunogenicity of recombinant OmpW produced in Escherichia coli was assessed by vaccinating flounder. As a result, the high antibody response with antibody titer of $4.2{\pm}0.7$ and protection with relative percent survival of 60% against artificial infection of V. harveyi were demonstrated. This result indicates that OmpW is a virulence related factor and it can be a vaccine candidate to prevent a high mortality caused by V. harveyi infection in olive flounder, Paralichthys olivaceus.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.6
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• pp.1229-1236
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• 2015

In this study, flow characteristics and bed changes during a short term flood event were analyzed using the two-dimensional CCHE2D model for a meandering sand-bed river, the Naesung Stream. Flow and bed change simulation was carried along the three sub-reaches with sinuosity of 1.2, 1.6 and 2.2 for the 6-day flood event occurring in June 2011. The simulation results indicated that velocity variation due to flow concentration was larger along the sub-reach with the sinuosity less than 1.5 and bed erosion at the outside of the bend was increased by time. In the sub-reach with the sinuosity less than 1.5, the maximum flood discharge produced the maximum flow velocity over 1.6 m/s to 2 m/s locally.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.7
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• pp.692-697
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• 2004

OFDM system is very useful for the multi-path channel and highly bandwidth-efficient system. However, OFDM signal shows the high PAPR so that nonlinear distortion can happen in the HPA(high power amplifier). This paper studies BER performance variation according to IBO(input back off) values when the predistorter is used fur the compensation for the HPA nonlinearity. In case of the SSPA(solid state power amplifier) of nonlinearity parameter p=0.5 and IBO=0㏈, the system with predistorter is poorer than the one without predistorter. But this situation is inverted, if IBO is increased from 0㏈ to 3㏈. So, we can find that there is a threshold value of IBO for the predistorter to effectively compensate for the nonlinear SSPA when the sub-carrier number and p value are changed.

• Journal of the Korean Society of Visualization
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• v.5 no.1
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• pp.9-11
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• 2007

We introduce an in vivo imaging flow cytometer, which provides fluorescence images simultaneously with quantitative information on the cell population of interest in a live animal. As fluorescent cells pass through the slit of light focused across a blood vessel, the excited fluorescence is confocally detected. This cell signal triggers a strobe beam and a high sensitivity CCD camera that captures a snap-shot image of the cell as it moves down-stream from the slit. We demonstrate that the majority of signal peaks detected in the in vivo flow cytometer arise from individual cells. The instrument's capability to image circulating T cells and measure their speed in the blood vessel in real time in vivo is demonstrated. The cell signal irradiance variation, clustering percentage, and potential applications in biology and medicine are discussed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.7
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• pp.560-570
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• 2017

Recently, well-known SAR imaging algorithms have been developed to form the focused SAR images for stationary targets. In general, the conventional methods exploit the range variation only defined by the motion of radar platform and SAR geometry. However, for SAR imaging of ground moving targets, the motion of the targets induces an additional range shift, yielding the blurred SAR images. To overcome the problem, in this paper we propose an effective motion compensation algorithm operated under a multi-channel SAR, named along-track interferometry(ATI) and phase unwrapping to directly estimate the motion parameters of the targets. In simulations, 50 Monte-Carlo simulation results show the effectiveness of the algorithm in the presence of noise.

• Transactions on Electrical and Electronic Materials
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• v.15 no.6
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• pp.328-332
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• 2014

Thin film transistors (TFTs) with an amorphous silicon zinc tin oxide (a-2SZTO) channel layer have been fabricated using an RF magnetron sputtering system. The effect of the change of excitation electron on the variation of the total interfacial trap states of a-2SZTO systems was investigated depending on sputtering power, since the interfacial state could be changed by changing sputtering power. It is well known that Si can effectively reduce the generation of the oxygen vacancies. However, The a-2SZTO systems of ZTO doped with 2 wt% Si could be degraded because the Si peripheral electron belonging to a p-orbital affects the amorphous zinc tin oxide (a-ZTO) TFTs of the s-orbital overlap structure. We fabricated amorphous 2 wt% Si-doped ZnSnO (a-2SZTO) TFTs using an RF magnetron sputtering system. The a-2SZTO TFTs show an improvement of the electrical property with increasing power. The a-2SZTO TFTs fabricated at a power of 30 W showed many of the total interfacial trap states. The a-2SZTO TFTs at a power of 30 W showed poor electrical property. However, at 50 W power, the total interfacial trap states showed improvement. In addition, the improved total interfacial states affected the thermal stress of a-2SZTO TFTs. Therefore, a-2SZTO TFTs fabricated at 50 W power showed a relatively small shift of threshold voltage. Similarly, the activation energy of a-2SZTO TFTs fabricated at 50 W power exhibits a relatively large falling rate (0.0475 eV/V) with a relatively high activation energy, which means that the a-2SZTO TFTs fabricated at 50 W power has a relatively lower trap density than other power cases. As a result, the electrical characteristics of a-2SZTO TFTs fabricated at a sputtering power of 50 W are enhanced. The TFTs fabricated by rf sputter should be carefully optimized to provide better stability for a-2SZTO in terms of the sputtering power, which is closely related to the interfacial trap states.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.8
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• pp.1505-1512
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• 2009

This paper propose a new frame level rate control algorithm for improving video quality and decreasing quality variation of an entire video sequence in a very low bit rate environment. In the proposed scheme, the allocated bits to a GOP are distributed to each frame properly according to the frame characteristics as well as the buffer status and the channel bandwidth. The H.264 standard uses various coding modes and optimization methods to improve the compression performance, which makes it difficult to control the generated traffic accurately. In this paper, proper prediction models for low bit rate environments are lust proposed, and a target distortion is determined using the models. According to the target distortion, the bit budget is allocated to each frame. It is shown by experimental results that the new algorithm can generate the PSNR performance better than that of the existing rate control algorithm.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.4 no.3
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• pp.146-155
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• 1992

It has been conventional to treat the land boundary as a fixed one in numerical modeling of tidal flows, particularly in the finite element scheme. However conventional models using the fixed land boundary result in unrealistic tidal flows in inter-tidal zones which exist over wide coastal area in Korea. In this study, a 2-dimensional hydrodynamic model, using finite element method for moving boundary problems was developed. The performance of the model was tested in a rectangular channel with an open boundary at one end and a moving boundary at the other end. The model was applied to calculate the tidal currents in Maro Hae, located in the southwestern part of Korea where wide tidal flats develop. The behavior of tidal currents in the Udolmok and near the tidal flats in the study area was satisfactory when compared with the observed data. Variation of tidal currents due to the construction of Kochunam sea-dyke which barrages large area of tidal flat was presented. The results of this study confirm the efficiency of moving boundary treatment in coastal numerical models.

• Proceedings of KOSOMES biannual meeting
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• 2009.06a
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• pp.89-94
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• 2009

This study aims to examine the the characteristics if the sea water circulation in related to the change of the water exchange rate according to the the development phases of Busan Port. To clarify the characteristics, the water exchange caused by construction if new-port and river discharge conditions was examined by the numerical experiments using the Lagrangian particle tracking model based on 2-D shallow water equation. This study deals with the charge of flow field and water exchange after redevelopment using numerical simulation technique, based on the field observation and 4 rivers discharge flow. As a result if numerical simulation, Variation if current velocity in Busan North Port is almost nothing before and after construction. Water exchange of channel in area of redevelopment is a little. Futhermore, the tidal exchange had a tendency to be small both before and after redevelopment by 60%.