• Korean Journal of Agricultural and Forest Meteorology
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• v.22 no.3
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• pp.107-116
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• 2020

In this data paper, we share the dataset obtained during 2019 from the test-bed to develop soil moisture estimation technology for upland fields, which was built in Seosan and Taean, South Korea on May 3. T his dataset includes various eco-hydro-meteorological variables such as soil moisture, evapotranspiration, precipitation, radiation, temperature, humidity, and vegetation indices from the test-bed nearby the Automated Agricultural Observing System (AAOS) in Seosan operated by the Korea Meteorological Administration. T here are three remarkable points of the dataset: (1) It can be utilized to develop and evaluate spatial scaling technology of soil moisture because the areal measurement with wide spatial representativeness using a COSMIC-ray neutron sensor as well as the point measurement using frequency/time domain reflectometry (FDR/TDR) sensors were conducted simultaneously, (2) it can be used to enhance understanding of how soil moisture and crop growth interact with each other because crop growth was also monitored using the Smart Surface Sensing System (4S), and (3) it is possible to evaluate the surface water balance by measuring evapotranspiration using an eddy covariance system.

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.5
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• pp.350-355
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• 2005

The probes of fiber optic OTDR (Optical Time Domain Reflectometry) sensor was developed to measure displacements of social infrastructures. This probe was simply constructed with two conventional optical fiber connectors, and a fiber bending part, which transforms displacement to optical loss. When the displacement was affected on the bending loss part, the reflected light intensity of one optical connector was changed. The displacement was determined from this reflected light intensity change of the connector. fiber optic OTDR displacement sensor was developed as the multiplexed type of one fiber line with 5 sensor probes. Multiplexing operation was tested by these 5 sensor probes.

• Journal of Korea Water Resources Association
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• v.31 no.2
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• pp.123-132
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• 1998

Monitoring solute transport has been known to be difficult especially for the unsaturated soil. The object of this study is to investigate the TDR application to monitoring solute concentration in the vadose zone. The TDR calibration test was conducted for soil samples with various water contents and concentrations. The voltage attenuation of electromagnetic wave of TDR was used to estimate the bulk electrical conductivity of a soil. The relationship between the bulk soil electrical conductivity and the solute concentration was assumed to be linear at a constant volumetric soil water content. In this study four proposed relationships were compared using data obtained from KCI solution at three different concentrations. Relationships given by Topp, Daltaon, Yanuka showed the linearity between the bulk soil electrical conductivity and the solute concentration, which were more pronounced than Zegelin's. The three relationships were found to be useful to measure the solute concentration in the vadose zone. In addition, TDR method was proven to be a viable technique in monitoring solute transport through unsaturated soils in transient flow condition.

• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.184-189
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• 2004

A soil moisture measuring method for a hillslope of Korean watershed was developed to configure spatial-temporal distribution of soil moisture. Intensive surveying of topography had been performed to make a refined digital elevation model(DEM) and the hydrological interpretation from flow distribution algorithm was incorporated through reverse surveying. Moreover, A long term measurement system was established to maximize representative features of spatial variation of soil moisture and operated from October 19 to 21, 2003. TDR(Time Domain Reflectometry) with a multiplex monitoring system has been operated for accurate measurements. Measurements were performed at the right side hillslope of Buprunsa located at the sulmachun watershed. The data of temporal and spatial soil moisture variation by rainfall event were collected and the variations of soil moisture were well captured.

• Journal of Korea Water Resources Association
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• v.38 no.5 s.154
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• pp.345-354
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• 2005

Time Domain Reflectometry (TDR) with multiplex system has been installed to configure the spatial and temporal characteristics of soil moisture at the Bumreunsa hillslope of Sulmachun Watershed. An intensive surveying was performed to build a refined digital elevation model (DEM) and flow determination algorithms with inverse surveying have been applied to establish an efficient soil moisture monitoring system. Soil moisture data were collected through intensive monitoring during 380 hrs in November of 2003. Soil moisture data shows corresponding variation characteristics of soil moisture on the upper, middle and lower parts of the hillslope which were classified from terrain analysis. Measured soil moisture data have been discussed on the context of physical process of hydrological modeling.

• Journal of the Korean Society of Hazard Mitigation
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• v.3 no.2 s.9
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• pp.119-125
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• 2003

Water flow in unsaturated soils is affected by two mathematical equations called soil water-characteristic curve and permeability-suction relationship. Soil water-characteristic curve is an equation showing volumetric water content-suction relationship. Many researchers have presented equations for the relationships. This paper illustrates the importance of correctly determining the two relationships when analyzing unsaturated water flows. Results from two methods, Gardner (1958) and Fredlund et al. (1994), are used for comparison purposes. Numerical simulations of water flow by finite element method are performed using the two methods. The results by the numerical simulations are compared with the field data which was obtained from time-domain reflectometry (TDR) probes in Delaware County, Ohio. This data was obtained by the Seasonal Instrumentation Program which is included as a part of the Strategic Highway Research Program (SHRP).

• 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 Institute of Electronics Engineers of Korea SD
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• v.42 no.4 s.334
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• pp.45-52
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• 2005

This paper presents the characterization of through hole vias on printed circuit board (PCB) through the time domain and frequency domain measurements. The time domain measurement was performed on a single via using the TDR, and the model parameters were extracted by the fitting simulation using HSPICE. The frequency domain measurement was also performed by using 2 port VNA, and the model parameters were extracted by fitting simulation with ADS. Using the ABCD matrices, the do-embedding equations were derived probing in the same plane in the VNA measurement. Based on the single via characterization, the differential via characterization was also performed by using TDR measurements. The time domain measurements were performed by using the odd mode and even mode sources in TDR module, and the Parameter values were extracted by fitting with HSPICE. Comparing measurements with simulations, the maximum calculated differences were $14\%$ for single vias and $17\%$ for differential vias.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.5
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• pp.499-507
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• 2004

We have studied tile detection techniques, which can determine the location and the weight of an intruder into infrastructure, by using fiber-optic ROTDR (Rayleigh optical time domain reflectometry) sensor and fiber-optic BOTDA (Brillouin Optical time domain analysis) sensor, which can use an optical fiber longer than that of ROTDR sensor Fiber-optic sensing plates of ROTDR sensor, which arc buried in sand, were prepared to respond the intruder effects. The signal of ROTDR was analyzed to confirm the detection performance. The constructed ROTDR could be used up to 10km at the pulse width of 30ns. The location error was less than 2 m and the weight could be detected as 4 grades, such as 20kgf, 40kgf, 60kgf and 80kgf. Also, fiber optic BOTDA sensor was developed to be able to detect intrusion effect through an optical fiber of tells of kilometers longer than ROTDR sensor. fiber-optic BOTDA sensor was constructed with 1 laser diode and 2 electro-optic modulators. The intrusion detection experiment was peformed by the strain inducing set-up installed on an optical table to simulate all intrusion effect. In the result of this experiment, the intrusion effort was well detected as the distance resolution of 3m through the fiber length of about 4.81km during 1.5 seconds.

• Korean Journal of Soil Science and Fertilizer
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• v.36 no.1
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• pp.1-7
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• 2003

Time domain reflectometry (TDR) is a newly developed method for measuring simultaneously solute concentrations and volumetric water content of soil. Bulk electrical conductivity ($EC_a$) of soil is obtained from TDR signal using several equations proposed, and electrical conductivity of soil solution ($EC_w$) can be calculated using the linear relationship $EC_a=EC_w\theta(a\theta+b)+EC_s$ between $EC_a$ and $EC_w$ at constant soil water content. The objectives of this study were to evaluate $EC_a$ proposed by several workers and to obtain the empirical constants (a, b, and $EC_s$) for $EC_w$ of the soils from A, Bl, and B2 horizon of an agricultural field (Coarse loamy, Fluvaquentic Eutrudepts). The $EC_a$ proposed by Yanuka et al. responded most sensitively to the KCl solute concentrations. The empirical constants of a, b, and $EC_s$ for $EC_w$ were -0.249, 1.358, and 0.054 for A horizon, -2.518, 2.708, and 0.097 for Bl horizon, and 2.490, -0.250, and 0.103 for B2 horizon, respectively. Therefore, the results of this study showed that Yanuka et al. equation was most useful one in determining $EC_a$, from TDR signal for agricultural soil with low salinity and that the empirical constants for the calculation of $EC_w$, from $EC_a$ can be obtained through a simple calibration experiment.