• Proceedings of the KIEE Conference
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• 2003.07d
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• pp.2262-2264
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• 2003

본 논문에서는 도선의 결함 유무와 결함 위치를 측정하는 방법으로 널리 사용되고 있는 시간 영역 반사파 처리 기법(Time Domain Reflectometry : TDR)의 성능 향상을 위하여 가우시안 형태를 가지는 입력 신호와 상호 상관 관계 함수를 이용한 신호 처리 방법을 제안한다. 일반적으로 TDR은 입력 신호와 반사 신호의 시간 지연을 측정해서 결함 위치를 측정하게 되므로, TDR 방법으로 결함 위치를 측정하는데 있어 시간축 분해능의 정도에 따라 측정 방법의 성능이 크게 좌우된다. 따라서, 본 논문에서는 제한된 시간축 분해능에서 결함 위치 측정의 정확도를 향상시키기 위해 가우시안 형태를 갖는 입력 신호 및 반사 신호와의 상호 상관관계 함수를 사용한다. 한편, 실제 도선에 적용하여 기존의 TDR 방법과 측정 성능을 비교 분석함으로써 본 논문에서 제안하는 방법의 우수성을 검증한다.

• Magazine of the Korean Society of Agricultural Engineers
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• v.41 no.1
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• pp.86-96
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• 1999

Laboratory experiment was performed for the TDR to measure the soil moisture, and the results, were compared with the design water content and the one measured by oven-try method. Sand and kaolinite were used . Varaiables for the experiment were water content (10-50%), void ration (0.7 -1.3), mixture rate of kaolinite (10-30%), and measurement methods (TDR and oven-dry). In all cases , TDR method showed very accurage and reliable results , and average error and error range were far lews than the oven-dry method which is widely used. Considerable error was noticed when water contnet was 50% where saturation was achieved for both methods. Therefore, TDR was thought to be applicable to the field moisture measurement if it is unsaturated. For field scale application of TDR, more research and verification of the accuracy with diverse soil conditions including physical ,chemical and mineral properties are recommended.

• Proceedings of the Korea Water Resources Association Conference
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• 1997.05a
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• pp.475-479
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• 1997

다공질매체에서의 포화-비포화 흐름 거동을 파악하기 위하여는 시간에 따른 함수량의 변화과정을 정확하고 빠르게 측정하여야 한다. 본 연구는 실험실에서 함수량을 측정하는 방법의 하나로서 TDR(Time Domain Reflectometer)을 사용하는 실험 방법에 관한 연구이다. TDR 이란 전기신호의 전도특성 이용하여 토양내 설치된 탐침(probe)의 전기신호 반향시간을 측정하는 기기로서 이 반향시간과 토양의 유전율상수(dielectric constant)의 관계를 이용하여 함수량을 추정할 수 있다. 본 연구에서는 TDR의 원리설명과 이를 이용한 함수량측정방법을 제시하고 있다.

• Economic and Environmental Geology
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• v.29 no.6
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• pp.699-712
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• 1996

Field scale experiments using an automated 144-channel TDR system were conducted which monitored the movement of solute through unsaturated loamy soils. The experiments were carried out on two different field plots of 0.54 ha to study the vertical movement of solute plume created by applying a square pulse of $CaCl_2$ as a tracer. The residence concentration was monitored at 24 locations on a transect and 5 depths per location by horizontally-positioning 50 cm long triple wire TDR probes to study the heterogeneity of solute travel times and the governing transport concept at field scale. This paper describes details of experimental methodology and calibration aspects of the TDR system. Three different calibration methods for estimation of solute concentration from TDR-measured bulk soil electrical conductivity were used for each field site. Data analysis of mean breakthrough curves (BTCs) and parameters estimated using the convection-dispersion model (CDE) and the convective-lognormal transfer function model (CLT) reveals that the automated TDR system is a viable technique to study the field scale solute transport providing a normal distribution of resident concentration in a high resolution of time series, and that calibration method does not significantly affect both the shape of BTC and the parameters related to the peak travel time. Among the calibration methods, the simple linear model (SLM), a modified version of Rhoades' model, appears to be promising in the calibration of horizontally-positioned TDR probes at field condition.

• Water for future
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• v.29 no.4
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• pp.119-129
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• 1996

The daily soil water contents were obtained from the time domain reflectometry (TDR) method and energy balance-water budget approach with eddy correlation at the two small semiarid watersheds of Lucky Hills and Kendall during the summer rainy period. There was a comparison of daily soil water content measured and estimated from these two different approaches. The comparison is valuable to evaluate the accuracy of current soil water content measuring system using TDR and energy balance-water budget approach using eddy correlation method at small watersheed scale. The degree of similarity between the regressions of these two methods of measuring soil water content was explained by determining the correlations between these methods. Simple linear regression analyses showed that soil water content measured from TDR method was responsible for 58% and 63% of the variations estimated from energy balance-water budget approach with eddy correlation at Lucky Hills and Kendall, respectively. The scatter plots and the regression analyses revealed that two different approaches for soil water content measurement at small watershed scale have no significant difference.

• Journal of Korea Water Resources Association
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• v.30 no.6
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• pp.587-595
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• 1997

Experimental study on unsaturated flow in the soil is important to understand the characteristics of the water flow. Measurement of unsteady-state water movement using the traditional equipment (e.g. tensiometer) has a problem that requires relatively a long response time. In this study a quick measurement method of soil water flow using TDR is introduced. TDR consists of an electronic function generator which generates a squared wave, and an oscilloscope which catches the reflected wave. The wave is reflected where both the impedance of the transmission line and the propagation velocity are changed. The water content can be obtained from the travel time measured by means of TDR because the dielectric constant is affected by the change of soil water content. From the result of TDR calibration. TDR measurement error for the oven dried soil was found to be less than 3.5%. This supports that TDR is a viable technique to measure the unsteady-state water movement.

• Journal of the Korean Geotechnical Society
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• v.33 no.11
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• pp.5-19
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• 2017

This study has been conducted to improve the conventional compaction management method by measuring the water content and dry unit weight of soil using the Time Domain Reflectometry (TDR) method. In order to verify the measured value of the developed flat TDR system, laboratory tests were conducted on six soils. Also, based on laboratory experiments, field tests were conducted to evaluate the applicability of the developed flat TDR system. Also, a comparison experiment was conducted with the Purdue TDR system. In addition, FE analysis was done to confirm the influence range of the Flat probe. As a result, it was confirmed that the influence range was about 10 cm. As a result of laboratory experiment, the water content ratio showed an error of about 0.4% on the average, and in the case of dry unit weight, it showed an error of about 1.6%. For the field test, the water content ratio and unit weight showed an error of 0.8% and 2.5%, respectively. Through the experimental results, it was confirmed that the measured value of the Flat TDR system is more accurate than that of the conventional TDR system.

• Journal of the Korean Geosynthetics Society
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• v.13 no.3
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• pp.1-10
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• 2014

Several types of methods such as resistivity survey, ground penetration radar, etc are used for detection of levee leakage and according to the river design guidelines detection of levee leakage is performed by measuring the hydraulic conductivity of levee soil. But, the former can not verify the leakage point and degree of saturation, the latter is an after treatment method. Movable sensor, which is a high-tech TDR system developed since 2000, can obtain directly the dielectric constant profile covering the whole depth of levee. In this study, laboratory and field model experiments were carried out using movable TDR sensor in order to evaluate the applicability as detection system of levee leakage, As the result, movable TDR system has proven to be 3 times more sensitive to water contents than dry unit weight, and the results conclude that the dielectric constant, water contents and density of the ground proved to have a correlation among them, and the dielectric constant is expected to be a basic data on detection of levee leakage.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.3
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• pp.310-315
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• 2013

This paper presents a two-port time-domain reflectometry(TDR) measurement technique for extracting the complex propagation constant of a cross-linked polyethylene(XLPE) cable. For the extraction, a short pulse transmitted through the cable is measured in the time domain and analyzed in the frequency domain. The propagation constant of a 22.9 kV XLPE cable with a conductor area of 325 $mm^2$ is extracted up to a frequency of approximately 2.14 GHz. The $S_{21}$ measured using a network analyzer and the two-port TDR technique are compared for verification. As a result compared with previous TDR method, the upper possible frequency limit for extracting the propagation constant increases and the measurement error decreases.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1477-1480
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• 2015

본 논문은 TDR(Time Domain Reflectometry)을 이용하여, 비유전율내에서 PD(Partial Discharge) 발생 시 부분방전 위치를 추적할 수 있는 한분야의 방법으로 비율전율간의 이동속도를 적용하여 PD위치를 쉽게 겁근할 수 있는 방법이다. 기존에는 절연유와 SF6 가스의 연결부에서 부분방전 발생 시 30cm/ns의 이동속도를 이용하여 위치를 추적함으로써 약 31% 오차가 발생하였다. 절연유내에서의 이동속도를 20cm/ns의 상수를 적용하여 현장에 적용결과 PD위치의 오차를 저감할 수 있었으며, PD발생 부분을 절연유와 SF6 가스구역으로 구분을 할 수가 있었으며, 이를 통하여 점검예산을 확보할 수 있는 계기가 되었다. 비유전율 상수를 이용한 이동속도를 산출하여 PD위치를 추적하는 방법을 활용하면, 기존의 PD발생위치 추적을 보다 용이하게 접근할 수 있는 방법이라 생각한다.