• Journal of the Korean earth science society
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• v.32 no.6
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• pp.654-664
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• 2011

A field campaign of magnetotelluric (MT) and audio-frequency MT (AMT) survey was done at 36 measurement points as a complementary for the previous 44 MT measurements completed during the period of 2005-2006. The purpose of additional MT survey is to investigate the possible fracture system in Seokmo Island, which is conceived to be crucial in accumulation and migration of geothermal hot spring in this area. We have done 2D and 3D inversions of overall MT and AMT data distributed on a grid to interpret subsurface of extended area. The inversion results reveal that at least two major faults are imaged in the inversion results, one of which is in NNE-SWW with steep dip, and another is in E-W direction.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.1
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• pp.205-212
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• 2010

This paper describes a core generator (FCore_Gen) which generates Verilog-HDL models of 640 different FFT/IFFT cores with selected parameter value for OFDM-based communication systems. The generated FFT/IFFT cores are based on in-place single memory architecture and use a hybrid structure of radix-4 and radix-2 DIF algorithm to accommodate various FFT lengths. To achieve both memory reduction and the improved SQNR, a conditional scaling technique is adopted, which conditionally scales the intermediate results of each computational stage. The cores synthesized with a $0.35-{\mu}m$ CMOS standard cell library can operate with 75-MHz@3.3-V, and a 8,192-point FFT can be computed m $762.7-{\mu}s$, thus the cores satisfy the specifications of wireless LAN, DMB, and DVB systems.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.4
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• pp.693-699
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• 2006

Digital airborne image must be precisely orthorectified to become geographical information. For orthorectification of airborne images, GPS/INS (Global Positioning System/Inertial Navigation System) and LIDAR (LIght Detection And Ranging) elevation data were employed. In this study, 635 frame airborne images were produced and LIDAR data were converted to raster image for applying to image orthorectification. To derive images with constant brightness, flat field correction was applied to images. The airborne images were geometrically corrected by calculating internal orientation and external orientation using GPS/INS data and then orthorectified using LIDAR digital elevation model image. The precision of orthorectified images was validated by collecting 50 ground control points from arbitrary five images and LIDAR intensity image. As validation result, RMSE (Root Mean Square Error) was 0.387 as almost same as only two times of pixel spatial resolution. It is possible that this automatic orthorectification method of airborne image with higher precision is applied to airborne image industry.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.179-179
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• 2011

근래 농촌지역에서의 하천 및 저수지의 수질오염에 관하여 관심이 고조됨에 따라 비오염원에 대한 파악과 대책을 세우기 위해 관련분야에서 많은 연구가 진행 되고 있다. 비점오염원은 주로 강우나 유출에 의해 배출되기 때문에 배출 장소와 경로가 불분명하고 다양하다. 비점오염의 관리를 위한 유역모델로 SWAT (Soil and Water Assessment Tool) 모델을 이용한 연구가 광범위하게 사용되고 있다. 그러나 SWAT 모델은 유역모델로써 농촌지역에 논, 밭에서의 비점오염원 기작을 표현하기에는 공간적 범위의 한계가 있다. 이에 본 연구에서는 예당저수지 유역(465.12 km2)을 대상으로 유역규모의 SWAT 모델과 유역-필드규모에 적용 가능한 SWAT-APEX (Agricultural Policy/Environmental eXtender) 모델의 수질(T-N, T-P) 모의결과를 비교하여 SWAT-APEX 모델의 적용성을 평가하고자 하였다. 모형의 적용을 위한 입력자료로 기상자료와 지형자료를 구축하였으며 기상자료로 예당저수지유역 3개의 강우관측소 자료를 수집하여 구축하였으며, 지형자료로 격자크기 30m의 DEM (Digital Elevation Model)과 농촌진흥청에서 제공하는 1:25,000 정밀토양도와 토지이용도는 환경부로부터 1:25,000 중분류 토지이용도를 이용하였다. 또한 환경부에서 제공하는 월단위 하천수질 자료(기간)를 구축하여 모형의 검증을 실시하였다. 분석과정으로 SWAT 모델에서의 유역차원 수문, 수질 모의를 한 후, APEX 모델을 이용하여 소유역별 논, 밭에 대한 필드단위에 오염물질 모의 후 각각 소유역 출구에서 APEX 모델에 결과를 반영한 SWAT-APEX 모의를 거쳐 최종 유역출구에서의 유출량과 수질항목을 분석하였다. 모의 결과 유출량에 대해 Nash와 Sutcliffe (1970)가 제안한 모델효율성계수 (Model Efficient, ME)는 0.67, 결정계수는 0.69 그리고 수질항목의 결정계수는 각각 0.77, 0.75으로 분석되었다. 또한, SWAT-APEX 모의 결과 수질항목의 결정계수는 각각 0.80, 0.72이었다. 따라서, 본 연구에서 농촌지역의 비점오염원 모의는 필드모의를 반영한 SWAT-APEX 모델 결과가 SWAT 모델만 적용한 결과보다 정확한 비점오염 모의가 이루어졌다고 판단 할 수 있다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.3
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• pp.1294-1298
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• 2014

Comparative analysis study of the flow characteristics and the experiment was done to try to present the orientation of the solenoid structure to be produced in the future. The comparative analysis of the analysis and experimental values was performed using the experiments and ANSYS CFD. 3D modeling of the structure are designed by the CATIA V5R18, meshing process of the flow section was used by ICEM CFD program. Flow rate was indicated by using the experimental values appear in $0-10{\ell}/min$, the result of the flow analysis, was $0.18{\ell}/min$ Max. It was possible to suggest a solenoid structure more efficient through comparative analysis of experimental values and flow analysis.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.9
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• pp.1108-1119
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• 2016

This paper presents the spectral analysis and radiation pattern of low-frequency electromagnetic(EM) leakage signals according to the fundamental operations of smartphones. The EM leakage signals generated by the activation of four I/O sensor modules such as a touch-screen, a camera, a microphone and a speaker are captured by the commercial near-field magnetic probe with 1cm spatial resolution. The analysis results show that the leakage of the EM wave occurs strongly around the activated I/O sensor modules, AP(Application Processor) and memory modules. Also, the distinguishable frequency characteristic is shown in each spectrum of EM leakage signals.

• Geophysics and Geophysical Exploration
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• v.22 no.3
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• pp.160-167
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• 2019

Resistivity inversion result may be distorted if the seepage line fluctuation within central core with the change of reservoir water level as well as the conductivity of the reservoir water is not taken into consideration because the reservoir dike is composed of three-dimensional (3D) resistivity structure. Consequently, to accurately analyze the resistivity changes inside the reservoir dike according to the change of reservoir water level, 3D electrical resistivity modeling for the 2D survey line considering topography and physical properties of dam components was carried out. In addition, 2D inversion was performed with the simulated 2D resistivity data for a given 3D model in order to compare it with the inversion result of real field data. For 283 reservoirs in Korea, 2D inversion results for the simulated 2D data and field 2D resistivity data were compared. Finally, the reservoirs with an inversion ratio of 50% or less were selected as reservoirs that require further precise investigation.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.479-479
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• 2021

최근 기상이변으로 인한 자연재해 발생이 증가하고 있고, 그에 따라 도시의 재난 대응력 강화가 국내에서는 물론 국제적으로도 중요한 이슈가 되고 있다. 특히 쇠퇴지역은 재난재해 발생 시 인적·물적 피해가 일반 지역 보다 상대적으로 크며, 복구에도 많은 시간과 예산이 소요되므로 대응책 마련을 위한 도시재생지역의 정밀한 재난재해의 위험성 분석 기술이 필요하다. 이에 본 연구에서는 도시재생사업 대상지(311개)에 대한 재난재해 유형별 위험성 및 회복성을 종합적으로 분석하는 종합진단 기법을 개발하고, 이를 적용한 프로토타입 시스템을 개발하였다. 재난재해의 범위는 「재난 및 안전관리 기본법」을 준용하여 이에 도시재생사업 시행에 영향을 받아 재난재해 발생에 따른 위험정도가 변화할 가능성이 높은 자연재해 (폭우, 폭염, 폭설, 강풍, 지진)5종과 사회재난 (화재, 붕괴, 폭발) 3종 총 8종으로 정의하였다. 종합진단 기법은 기후변화에 관한 정부간 협의체(IPCC) 위험도 평가 방법을 준용하여 위험요소 (위해성·취약성·노출성)와 대비·대응요소 (회복성)로 구분하고, 전문가 자문회의를 거쳐 재난재해에 특히 취약한 쇠퇴지역의 특성을 반영할 수 있는 종합진단지수 산정식을 개발하였다. 또한 쇠퇴지역 재난재해 종합진단 시스템은 도시재생 업무를 수행하는 사용자가 신속히 정보를 분석하고 활용에 용이하도록 Web-GIS 기반으로 설계하였으며, 종합진단 기법에 의해 산정된 분석결과를 100m × 100m 격자 단위의 등급으로 가시화한다. 분석 결과는 지속적인 연구 개발을 통해 최적의 도시재생사업 의사결정 지원 서비스를 위한 기초 분석 자료로 연계하여 활용되며, 분석 DB는 클라우드 서비스 기반의 도시재생 데이터 플랫폼을 통해 공유된다.

• Journal of Aerospace System Engineering
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• v.17 no.2
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• pp.26-37
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• 2023

Urban air mobility (UAM) is being developed as part of the next-generation aircraft, which could be a viable solution to entrenched problems of urban traffic congestion and environmental pollution. A new airport platform called vertiport as a space where UAM can take off and land vertically is also being introduced. Noise regulations for UAM will be strict due to its operation in a highly populated urban area. Ground effects caused by vertiport can directly affect aerodynamic forces and noise characteristics of UAM. In this study, ground effects of vertiport on aerodynamic loads, vorticity field, and far-field noise were analyzed using Lattice-Boltzmann Method (LBM) simulation and Ffowcs Williams and Hawkings (FW-H) acoustic analogy with a permeable surface method.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.2D
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• pp.191-198
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• 2010

The displacement of slope is a key factor in predicting the risk of a landslide. Therefore, the slope displacement should be continuously observed with high accuracy. Recently, high-tech equipment such as optical fiber sensor, GPS, total station and measuring instrument have been used. However, such equipment is poorly used in fields due to economics, environment, convenience and management. Because of this, development of substantial observational techniques for varied slope observation and field applications is needed. This study analyzed the possibility of terrestrial LiDAR for slope monitoring and suggested it as information-obtaining technique for slope investigation and management. For that, this study evaluated the monitoring accuracy of terrestrial LiDAR and performed GRID analysis to read the displacement area with the naked eye. In addition, it suggested a methodology for slope monitoring.