• Title/Summary/Keyword: small-loop electromagnetic

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Spatial analysis of small-loop electromagnetic survey data in a seawater intrusion region (해수침투 지역에서 소형루프 전자탐사 자료의 공간 분석)

  • Song, Sung-Ho
    • Geophysics and Geophysical Exploration
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    • v.9 no.1
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    • pp.114-120
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    • 2006
  • The main purpose of this study is to apply spatial analysis using semivariograms to small-loop electromagnetic survey data to assess the extent of seawater intrusion in an experimental watershed. To indicate the extent of seawater intrusion over the study area, vertical electrical soundings at 33 points and electrical conductivity logging in two wells were conducted. From the correlation between resistivities obtained by inversion and the depth of the aquifer at the two wells, the region of seawater intrusion was identified and demonstrated by electrical conductivity logging results obtained over two years. To measure the variation of apparent conductivity with depth, an electromagnetic survey in six frequency bands was adopted. Apparent conductivity mapping with spatial analysis using semivariograms is an effective technique for identifying the region of seawater intrusion at shallow depth.

Design of a Triple-Mode Bandpass Filter Using a Closed Loop Resonator

  • Myung, Jae-Yoon;Yun, Sang-Won
    • Journal of electromagnetic engineering and science
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    • v.17 no.2
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    • pp.86-90
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    • 2017
  • In this study, a novel third-order bandpass filter, which is based on a rectangular closed loop resonator, is presented. By adding a series resonator to the conventional loop resonator, the resonator's even resonant mode is split into two modes, while the odd resonant mode is not affected. Therefore, by varying the values of the series resonator elements, the resonant frequencies of two even modes can be determined independent of the odd-mode resonant frequency. In the proposed triple-mode filter design, instead of using a lumped series resonator, a T-shaped transmission line is coupled to the resonator via a small gap. To verify the design method, a filter is designed at 2.4 GHz with a bandwidth of 100 MHz. The improved performances of the proposed triple-mode filter are compared with those of the conventional dual mode filter.

Analysis of Soil Properties in a Rice Field Using Small Loop EM Method (소형루프 전자탐사에 의한 논 토양분석)

  • Yong Hwan-Ho;Song Sung-Ho;Kim Jin-Ho;Cho In-Ky
    • Geophysics and Geophysical Exploration
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    • v.6 no.4
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    • pp.207-214
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    • 2003
  • To analyze soil properties with depth in rice field, we compared resistivity distributions obtained from soil analysis with one dimensional inversion of small loop electromagnetic (EM) data. Although it didn't show consistency exactly between the two resistivity distributions, low resistivity zones in soil analysis, appeared to agree with low resistivity zones in EM result. Therefore, small loop EM method can be applied to obtain rapidly the soil properties such as salt accumulation in a rice field. If research on soil property and EM responses of unsaturated zone would be conducted consistently, small loop EM method can be used effectively to detect salt accumulated zone in agricultural area.

Loop Probe Design and Measurement of Electromagnetic Wave Signal for Contactless Cryptographic Analysis (비접촉 암호 분석용 루프 프로브 설계 및 전자파 신호 측정)

  • Choi, Jong-Kyun;Kim, Che-Young;Park, Jea-Hoon;Moon, Snag-Jae
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.18 no.10
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    • pp.1117-1125
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    • 2007
  • In this paper, a study has been performed on the design of small loop probe and analysis of induced electromagnetic wave signal from a smartcard for contactless cryptographic analysis. Probes for cryptographic analysis are different from conventional EM probes, because the purpose of proposed probe is to obtain the information for secret key analysis of cryptographic system. The waveform of induced voltage on probe must be very close to radiated waveform from IC chip on smartcard because electromagnetic attack makes an attempt to analyze the radiated waveform from smartcard. In order to obtain secret key information, we need to study about cryptographic analysis using electromagnetic waves, an approximate model of source, characteristic of probe for cryptographic analysis, measurement of electromagnetic waves and calibration of probes. We measured power consumption signal on a smartcard chip and electromagnetic wave signal using proposed probe and compared with two signals of EMA point of view. We verified experimently the suitability of the proposed small loop probe for contactless cryptographic analysis by applying ARIA algorithm.

Development of the Water-leakage Detection Method Through the Geophysical Test on the Artificial Ground (모의지반 실험을 통한 누수영역 탐지기술 개발)

  • Kwon, Hyoung-Seok;Mitsuhata, Yuji;Uchida, Toshihiro
    • Journal of Korean Society of societal Security
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    • v.2 no.3
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    • pp.39-46
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    • 2009
  • A small loop-loop multi-frequency electromagnetic(EM) induction method is a useful technique to map a resistivity distribution efficiently and non-destructively. However, for quantitative interpretation and depth sounding, the quality of measured data is crucial. In this paper, we propose a bias correction of measured data by using background noise measurements to obtain reliable data, and propose an evaluation technique of apparent that can provide a resistivity image easily. We have performed small loop-loop EM measurements to detect water saturation in a man-made test site. The application of our proposed techniques to the measured data was successful.

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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.

A Study on SAR Attenuation by Using Loop-type Ground for Mobile Handsets (루프 형태의 접지판을 이용한 휴대폰의 SAR 감쇄에 관한 연구)

  • Lee Won-Kew;Son Ji-Myoung;Han Jun-Hee;Yang Woon-Geun
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.17 no.9 s.112
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    • pp.821-828
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    • 2006
  • In this paper, we investigated SAR(Specific Absorption Rate) value variation by the position and size of the loop-type ground located in a test mobile handset. We carried out simulations on SAR value with loop-type grounds in rear case of a mobile handset, and obtained results showed that different positions and sizes of loop-type grounds had different SAR values. Among investigated positions and sizes of loop-type grounds, the small size case-C showed the best performance; i.e., it showed a decrease efficiency of 8.70 %. And in this case, it showed the highest induced electric-field distribution in the loop-type ground. In the simulation, the folding angle was set to $160^{\circ}$.

Applicability of the Small-Loop EM Method in the Sallow Marine Environment (천해 환경에서 소형루프 전자탐사의 적용성)

  • Song, Sung-Ho;Kim, Rae-Young;Kang, Hye-Jin;Cho, In-Ky
    • Geophysics and Geophysical Exploration
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    • v.14 no.2
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    • pp.152-157
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    • 2011
  • The small-loop electromagnetic (EM) method is one of the rapid and non-destructive geophysical methods and has been used widely for many geophysical investigations, particularly for shallow engineering and environmental surveys. Especially in the shallow marine environment, the small-loop EM technique is very effective because of rapid and convenient data acquisition, large signal and low noise level. However, the method has been rarely applied in the very conductive marine environment since it's penetration or investigation depth might be considered too low. In this study, we demonstrated that the small-loop EM method can be effectively applied in the extremely conductive marine environment through the analysis of 1D small-loop EM data. Furthermore, we confirmed that the resistivity distribution under the sea bottom can be quantitatively predicted from the 1D inversion results of synthetic and field data.

A Microstrip Antenna with a Small Loop (미소 루프 마이크로스트립 안테나)

  • Ko, Young-Hyuk;Park, Soo-Bong;Ryu, Hyun
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.8 no.4
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    • pp.354-362
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    • 1997
  • In this paper, a microstrip antenna with a small loop consisting of the left and right parallel plate to load a capacitor is proposed. It is obtained the improved high gain and bandwidth than the antenna consisting of the right parallel plate to load a capacitor on QMSA (Quarter-Wavelength Mi- crostrip Antenna). Also, the designed and manufactured antenna can receive both vertically and horizontally polarised waves to operating frequency of 1.5 GHz; therefore this is available as a small antenna for wireless telephones and will be quite useful for indoor communication.

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Case History for Safe Diagnosis of Embankment Dike using Composite Analysis of Various Geophysical surveys (물리탐사 결과 복합해석을 통한 방조제 제체 정밀안전진단 사례)

  • Song, Sung-Ho;Seong, Baek-Uk;Kim, Young-Gyu;Kang, Mi-Kyung;Lee, Gyu-Sang;Kim, Yang-Bin
    • 한국지구물리탐사학회:학술대회논문집
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    • 2007.06a
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    • pp.107-112
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    • 2007
  • To establish the reinforce region and technique through the embankment dike after identifying the region of seawater inflow, we carried out small-loop electromagnetic (EM) survey, electrical resistivity survey and refraction seismic method. We also analyzed the distribution of electrical conductivity in reservoir with depth every two month and monitored water level variations with tidal variation in four observation wells located at seaside and reservoir side in order to analyze the relationship with survey results. From both the cross-correlation between tidal and water level variation at four wells and the distribution of electrical conductivity in reservoir with depth, the major portion of seawater inflow are identified through the embankment dike. From electromagnetic and electrical resistivity survey results, it was found that the seawater inflow were happened through several small regions at seaside and became wider near reservoir side. The 2-D inversion sections of refraction seismic method showed that the pebble-bearing sand layer is spread over the whole region with two to four width. From the this study, small-loop EM, electrical resistivity and refraction seismic surveys accompany with the distribution of electrical conductivity in reservoir with depth and the monitoring results for water level variations are revealed to be effective to identify seawater inflow pathway through embankment dike and to establish the reinforce region and technique through the embankment dike.

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