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Ko Joo Suk,Kwak Sunghyun,Lee Kyungsu,Lyu Siwan 한국수자원학회 2019 한국수자원학회논문집 Vol.52 No.2
자연하천 유로의 선형과 단면 형상은 유수 흐름 및 유사이송과의 상호작용에 의해 시·공간적으로 연속적 변화를 거치게 된다. 본 연구에서는 4대강 살리기 사업을 통해 대규모 하상 준설과 시설물 공사가 이루어진 낙동강을 대상으로 인위적 변화가 가해진 유로의 형태학적 특성이 시간이 경과함에 따라 자연적으로 변화해가는 양상을 살펴보고 정량적으로 분석하고자 하였다. 이를 위해 강정고령보∼달성보 구간에 대한 수심 및 하천측량을 실시하고 하도 단면의 기하학적 특성치와 유로 선형(곡률)을 지표로 4대강살리기 사업 완료 후 지형의 변화양상과 형태학적 특성을 파악하고자 하였다. 4대강살리기 사업 종료 후 유의미한 지형변화가 발생하기에는 충분한 시간이 경과하지 않았기에 지형변화의 정도와 양상에서 특별한 경향 성을 추출할 수는 없었다. 하지만 본 연구에서 제안된 방법론을 활용한 지형특성 및 변화의 양상과 규모에 대한 지속적인 평가가 필요할 것으로 판단되는 바이다. The linear and cross-sectional shapes of the natural river channel are subjected to continuous changes in time and space due to the interaction with the flow of water and sediment transport. This study aims to investigate the morphological characteristics and change patterns of river channel quantitatively for the middle reach of Nakdong River, which has undergone large scale riverbed dredging and construction work, as Four Major River Restoration Project. A series of bathymetry and near-river survey has been conducted to obtain the detailed terrain information for the study area. The properties related to the linear and cross-sectional characteristics of river channel have been calculated based on the filed survey data and analyzed with comparing the survey data obtained in 2012 for the project completion. Since there has not been enough time for meaningful terrain change to take place, it was not possible to extract special tendency in the degree and aspect of terrain change. However, it is necessary to make regular examinations to the patterns and degree of river channel change using the proposed methodology.
Solid-State Pseudomorphic Synthesis of Hollow Silica Nanospheres Using Cyclic Diammonium Molecules
김용석,송요한,Chang Hyun Ko,고경철,Kyungsu Na 대한화학회 2021 Bulletin of the Korean Chemical Society Vol.42 No.3
A generalizable synthesis strategy for hollow silica nanospheres (HSNs) was developed using solid-state transformation of colloidal silica nanospheres (CSNs) via post synthetic leaching by NaOH in the presence of cyclic-diammonium molecule (CDM) as the pseudomorphic transforming agent, which can be used for the synthesis of HSNs with various sizes and HSNs encapsulating Pt metal nanoparticles.
고주석,이경수,곽성현,류시완,Ko, Joo Suk,Lee, Kyungsu,Kwak, Sunghyun,Lyu, Siwan 한국수자원학회 2020 한국수자원학회논문집 Vol.53 No.12
A methodology has been proposed to understand the spatiotemporal changes of the river topography through the longitudinal change of the geometric characteristics of the cross-sections and the properties related thereto. Three-dimensional spatial information of the riverbed was obtained through the detailed bathymetry survey using an acoustic echo sounder for the reach from Gumi Weir to Chilgok Weir in the Nakdong river. Geometric informations for the reference sections were extracted using the acquired bathymetry survey data. By comparing the geometric properties for the reference sections, it was possible to catch the topographic characteristics and its changes over a reach of the channel. Through comparison with past survey data, it was also possible to quantitatively grasp the amount of change in cross-sectional area and volumetric change of riverbed. It is expected that a quantitative evaluation of river topography changes will be possible by applying the method proposed in this study.
A New Scheme to Predict Erasures for Reed-Solomon Decoder in T-DMB Receiver
Minh Viet Nguyen,Kyungsu Ko,Woonsik Lee,Hwang Soo Lee IEEE 2007 IEEE transactions on broadcasting Vol.53 No.2
<P>In this paper, we introduce a new scheme to improve the performance of the terrestrial - digital multimedia broadcasting (T-DMB) system, which exploits the burst error characteristics at the output of the convolutional decoder and the properties of the Reed-Solomon (RS) decoder to correct more errors by predicting erasures in each RS packet in advance as many as possible before decoding in the RS decoder. Simulation results show that the proposed scheme yields performance gain of around 1 dB at BER of 10<SUP>-R</SUP> which can result in the extended coverage area of the T-DMB system.</P>
A highly compact coating responsible for enhancing corrosion properties of Al-Mg-Si alloy
Kaseem, Mosab,Choi, Kyungsu,Ko, Young Gun Elsevier 2017 Materials letters Vol.196 No.-
<P><B>Abstract</B></P> <P>The formation of a highly compact coating responsible for improvement in corrosion properties of Al-Mg-Si alloy was investigated. In this study, a plasma electrolytic oxidation (PEO) was performed in a citrate-aluminate electrolyte with potassium hexafluorosilicate (K<SUB>2</SUB>SiF<SUB>6</SUB>), and the results were compared to the counterpart without K<SUB>2</SUB>SiF<SUB>6</SUB>. The addition of K<SUB>2</SUB>SiF<SUB>6</SUB> to the present electrolyte would give rise to the highly compact coating due to the insoluble compounds of SiO<SUB>2</SUB> and AlF<SUB>3</SUB> which were incorporated uniformly throughout the coating. This would lead effectively to superior corrosion-protection properties to the case without K<SUB>2</SUB>SiF<SUB>6</SUB>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A compact coating was successfully fabricated on Al-Mg-Si alloy via PEO process. </LI> <LI> A significant change in the morphology is obtained with addition of K<SUB>2</SUB>SiF<SUB>6</SUB>. </LI> <LI> Effect of K<SUB>2</SUB>SiF<SUB>6</SUB> on corrosion properties of Al-Mg-Si alloy via PEO is significant. </LI> </UL> </P>