• Title/Summary/Keyword: electromagnetic survey

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Case histories of geotechnical survey for civil construction in rural sites (농촌지역 토목공사를 위한 지반조사 사례)

  • Kwon, Hyoung-Seok;Oh, Se-Young;Kim, Ki-Seog
    • 한국지구물리탐사학회:학술대회논문집
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    • 2000.09a
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    • pp.87-111
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    • 2000
  • In this study, we describe the principle and result of geophysical techniques which are widely used in geotechnical survey. Also we discuss two case histories. One is discrimination of limestone cavity areas by resistivity, seismic tomography, televiewer, well logging, and the other is discrimination of coal by resistivity, electromagnetic method, resistivity tomography.

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Mechanical and Electrical Properties of Hydrate-bearing Sediments (하이드레이트 함유 퇴적물의 역학적 성질 및 지구물리 특성)

  • Lee, J.Y.;Francisca, F.;Santamarina, J.C.;Ruppel, C.
    • 한국신재생에너지학회:학술대회논문집
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    • 2007.11a
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    • pp.594-596
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    • 2007
  • Using an oedometer cell instrumented to measure the evolution of electromagnetic properties, small strain stiffness, and temperature, we conducted consolidation tests on four types of sediments. The tested specimens include sediments with different gas hydrate saturation at four stages of loading. The test results show that the electromagnetic and mechanical properties of hydrate-bearing marine sediments are governed by the vertical effective stress, stress history, porosity, hydrate saturation, fabric, ionic concentration of the pore fluid, and temperature. The results also show that permittivity and electrical conductivity data can be combined to estimate hydrate volume fraction in laboratory sediments, methodology that might eventually be extended for estimation of hydrate concentrations in field settings.

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A Survey of Essential Considerations in the Desist of Downlink Beamforming of Smart Antenna System (순방향 빔형성 스마트 안테나 시스템 설계의 필수 고려 사항에 대한 연구)

  • 이원철;최승원
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.15 no.6
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    • pp.627-633
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    • 2004
  • Downlink beamforming is very important in recent mobile communications which requires wireless internet, VOD(Video-On-Demand), multimedia services. This paper addresses and analyzes the essential considerations fur downlink beamforming of smart antenna system to provide wanted characteristics. Major considerations in this paper are HPA power allocation for downlink beamforming, received power at mobile terminal, concept and performance of auxiliary pilot channel, importance and moth of array calibration, and throughput comparison of downlink and uplink. All above mentioned items are investigated in this paper.

Application of geophysical methods to determine the extent of the Dongrae Fault in the Oedong-eup area, Gyeongju City (경주시 외동읍 구어리 일대 동래단층 연장성 확인을 위한 물리탐사 적용)

  • Hwang, Hak-Soo;Hamm, Se-Yeong;Lee, Cheol-Woo;Lee, Chung-Mo;Kim, Sung Wook
    • The Journal of Engineering Geology
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    • v.27 no.3
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    • pp.207-215
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    • 2017
  • The northern extension of the Dongrae Fault is inferred to transect the Ulsan Fault in the Gueo-ri area, Oedong-eup, ~15 km SE of Gyeongju City, Gyeongbuk province, S Korea. We conducted geological and geophysical (magnetic, electrical resistivity, and frequency domain electromagnetic) surveys to identify the extent and orientation of the Dongrae Fault in this region. Through joint interpretation of the geological and geophysical data sets, we confirm the presence of the Dongrae Fault and determine its strike ($N14^{\circ}E$). The Dongrae Fault is thought to cross the Ulsan Fault near Ipsil Bridge in the Gwangeo-ri area. Geophysical surveying revealed a fault damage zone that widens to the south, with a typical width of >200 m. Geological field surveys did not delineate the geometry of the Dongrae Fault because alluvial deposits overlie the fault in this area.

Layered-earth Resistivity Inversion of Small-loop Electromagnetic Survey Data using Particle Swarm Optimization (입자 군집 최적화법을 이용한 소형루프 전자탐사 자료의 층서구조 전기비저항 역해석)

  • Jang, Hangilro
    • Geophysics and Geophysical Exploration
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    • v.22 no.4
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    • pp.186-194
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    • 2019
  • Deterministic optimization, commonly used to find the geophysical inverse solutions, have its limitation that it cannot find the proper solution since it might converge into the local minimum. One of the solutions to this problem is to use global optimization based on a stochastic approach, among which a large number of particle swarm optimization (PSO) applications have been introduced. In this paper, I developed a geophysical inversion algorithm applying PSO method for the layered-earth resistivity inversion of the small-loop electromagnetic (EM) survey data and carried out numerical inversion experiments on synthetic datasets. From the results, it is confirmed that the PSO inversion algorithm could increase the inversion success rate even when attempting the inversion of small-loop EM survey data from which it might be difficult to find a best solution by applying the Gauss-Newton inversion algorithm.

Agricultural Geophysics in South Korea: Case Histories and Future Advancements (우리나라 농업 물리탐사: 적용 사례와 향후 과제)

  • Song, Sung-Ho;Cho, In-Ky
    • Geophysics and Geophysical Exploration
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    • v.21 no.4
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    • pp.244-254
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    • 2018
  • The first geophysical technique applied to the agricultural sector in Korea was electrical resistivity sounding and conducted in purpose of groundwater exploitation in the 1970s. According to the diversity of agricultural activities since the 1990s, various geophysical methods including electrical resistivity, electromagnetic induction, and self-potential method were applied to several agricultural fields such as soil characterization with saline concentration in vast reclaimed area, delineation of seawater intrusion regions in costal aquifer, safety inspection of embankment dikes with leakage problem, detection of ground subsidence from overpumping and tracing of groundwater aquifer contamination by leachate from livestock mortality burial or waste burial site. This paper introduces representative geophysical techniques that have been utilized in various agricultural fields and suggests several ways to develop the geophysical methods required for the precision agriculture field in the near future based on the past achievements.

Comparison of Flood Discharge and Velocity Measurements in a Mountain Stream Using Electromagnetic Wave and Surface Image (전자파와 수표면 영상을 이용한 산지하천 홍수유량 및 유속 계측 비교 연구)

  • Yang, Sung-Kee;Kim, Dong-Su;Yu, Kwon-Kyu;Kang, Meyong-Su;Jung, Woo-Yul;Lee, Jun-Ho;Kim, Yong-Seok;You, Ho-Jun
    • Journal of Environmental Science International
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    • v.21 no.6
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    • pp.739-747
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    • 2012
  • Due to the difficulties for measuring flood discharge in the dangerous field conditions, conventional instruments with relatively low accuracy such as float still have been widely utilized for the field survey. It is also limited to use simple stage-discharge relationship for assessment of the flood discharge, since the stage-discharge relationship during the flood becomes complicated loop shape. In recent years, various non-intrusive velocity measurement techniques such as electromagnetic wave or surface images have been developed, which is quite adequate for the flood discharge measurements. However, these new non-intrusive techniques have little tested in the flood condition, though they promised efficiency and accuracy. Throughout the field observations, we evaluated the validity of these techniques by comparing discharge and velocity measurements acquired concurrently during the flood in a mountain stream. As a result, the flood discharge measurements between electromagnetic wave and surface image processing techniques showed high positive relationship, but velocities did not matched very well particularly for the high current speed more 3 m/s. Therefore, it should be noted here that special cares are required when the velocity measurements by those two different techniques are used, for instance, for the validation of the numerical models. In addition, authors assured that, for the more accurate flood discharge measurements, velocity observation as well as stage height is strongly necessary owing that the unsteady flow occurs during the flood.

Three-dimensional Finite Difference Modeling of Time-domain Electromagnetic Method Using Staggered Grid (엇갈린 격자를 이용한 3차원 유한차분 시간영역 전자탐사 모델링)

  • Jang, Hangilro;Nam, Myung Jin;Cho, Sung Oh;Kim, Hee Joon
    • Geophysics and Geophysical Exploration
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    • v.20 no.3
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    • pp.121-128
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    • 2017
  • Interpretation of time-domain electromagnetic (TEM) data has been made mostly based on one-dimensional (1-D) inversion scheme in Korea. A proper interpretation of TEM data should employ 3-D TEM forward and inverse modeling algorithms. This study developed a 3-D TEM modeling algorithm using a finite difference time-domain (FDTD) method with staggered grid. In numerically solving Maxwell equations, fictitious displacement current is included based on an explicit FDTD method using a central difference approximation scheme. The developed modeling algorithm simulated a small-coil source configuration to be verified against analytic solutions for homogeneous half-space models. Further, TEM responses for a 3-D anomaly are modeled and analyzed. We expect that it will contribute greatly to the precise interpretation of TEM data.

The Effects of Productization, Organizational, Overseas Market Adaptation Competences on Export Performance: Focus on Korean Electromagnetic Wave Shielding Firms (기업의 제품화 역량, 조직역량, 해외시장 적응역량이 수출성과에 미치는 영향: 전자파 차폐 기업을 중심으로)

  • Park, Won-Cheol;Oh, Ka-Young
    • Asia-Pacific Journal of Business
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    • v.11 no.3
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    • pp.307-344
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    • 2020
  • Purpose - The purpose of this study is to examine effects of productization and organizational competences on export performance of electromagnetic shielding companies and to analyze moderating effects of overseas market adaptation competences. For this, hypotheses were established by reviewing previous studies and an empirical analysis was conducted for testing. Design/methodology/approach - For this study, a survey was conducted for workers at electromagnetic shielding companies and 250 valid responses out of 300 questionnaires were aquired. A frequency analysis of related variables was conducted. Through an exploratory factor analysis, validity and reliability tests of measuring tools were conducted and a descriptive statistics was analyzed for collected data result and hypotheses testing. Findings - A correlation analysis was conducted to examine relationships among variables. Construct, convergent and discriminant validities were analyzed after a confirmatory factor analysis and a multi-group confirmatory factor analysis. Finally, with a verified model, the hypotheses and the moderating effects were tested. The results are as follows: First, the productization competence has a positive effect on export performance; Second, the organizational competence has a positive effect on export performance. Especially, the organizational competence has more effect on export performance than the productization competence. Although a development of new technology and product is important in terms of performance, along with these competences, a way of acquiring new skills and knowledge, and internalization and adaptation in organizations have more effect on export performance. Third, overseas market adaptation competence moderates effects of organizational and productization competences. Research implications or Originality - It is necessary to seek out opportunities for workers to participate in actively, such as conferences and seminars, to strengthen organizational competence. It is strongly believed that a constant development of high quality product will contribute to export performance. Lastly, in a policy level, supports on SMEs by governments are to be strengthened by providing with finance and human resource.

Electric and Electromagnetic Surveys of the Hongseong Fault Zone (홍성 단층대에서의 전기, 전자 탐사 연구)

  • Kwon, Byung-Doo;Lee, Heui-Soon;Park, Gye-Soon;Oh, Seok-Hoon;Lee, Choon-Ki
    • Journal of the Korean earth science society
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    • v.24 no.4
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    • pp.361-368
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    • 2003
  • We have investigated the electric resistivity structure of the fault zone located in the Hongseong area where a big earthquake with M 5.0 occurred in 1978. Usually, Electric and Electromagnetic methods are broadly operated in the field of engineering works since these methods are effective to understand the distribution of geological weak zones - fault or fracture zones. We have conducted the dipole-dipole array resistivity method and MT(magnetotelluric) method and interpreted the resistivity distribution of the fault zone with the aid of various inversion methods. An MT survey was performed at 18 points along a 2.9 km survey line perpendicular to the fault line and a magnetic dipole source was used to enhance the S/N ratio in the high frequency. A Electric dipole-dipole array resistivity survey with the dipole length of 50 meters was carried out perpendicular to the fault. In view of two survey results, the fault marks the boundary between two opposite resistivity structures, especially the low resistivity zone is exhibited deeply through the prospective fault line. The result that the low resistivity zone is located at the center of the fault zone corresponds with the fact that the fault zone of the Hongseong area is active. We expect these results to provide basic information about the physical properties of fault zones in Korea.