• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.4
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• pp.69-76
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• 2015

This paper presents the results of an investigation into the frequency-dependent electrical parameters for different types of soil as a function of moisture content. The frequency dependence of soil electrical parameters is very important in the design of grounding systems. In fact, the performance of grounding systems is greatly dependent upon various factors such as soil type, particle size, water content, temperature, frequency, and the like. The resistivity and relative permittivity for four different soils were measured and analyzed in the frequency range of 1kHz - 1MHz. Soil resistivity declined as moisture content and frequency increased. In particular, the frequency dependence of soil resistivity was significant as the moisture content was low. In contrast, the relative permittivity of soil dramatically declined at the frequency of 10kHz or below as the moisture content increased, showing the opposite pattern in terms of variation patterns, compared to resistivity.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.6
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• pp.68-74
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• 2014

The electrical parameters of soils are highly dependent on the various factors such as types of soil, chemical compositions, moisture content, temperature, frequency, and so on. The analysis of soil parameters is of fundamental importance in design of grounding systems. In this paper, we present the experimental results of frequency-dependent impedance, resistivity, permittivity of soils as functions of types of soil and moisture content. The impedance and resistivity of soils are decreased as the moisture content and the frequency increase. In particular, the variation of the soil resistivity with the frequency is pronounced in the conditions of high resistivity and low moisture content. On the contrary, the permittivity of soils are sharply decreased with increasing the frequency below 10kHz and the frequency-dependent permittivity of soils are highly changed in the conditions of high moisture and low resistivity.

• Journal of The Korean Society of Agricultural Engineers
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• v.50 no.5
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• pp.63-72
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• 2008

This study was conducted to define a characteristics of Electrical Resistivity of weathered soil against volumetric water content and frequency. It is essential to analyze and understand a characteristics of the Electrical Resistivity for evaluation of soil as subsurface contaminant detection. Before the test, an effect of pore water and ion were checked using four liquids(distilled water, tap water, potassium chloride 1.8mM, and 3.7mM). As a result, the correlation between the volumetric water content and the Electrical Resistivity was estimated. The Electrical Resistivity decreases with increasing frequency and water content. Also, Electrical Resistivity could be described by an exponential function of volumetric water content with the constants.

• Smart Structures and Systems
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• v.8 no.3
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• pp.321-341
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• 2011

Acoustic emission (AE) monitoring was conducted for mortar specimens under three types of static loading patterns (cubic-splitting, direct-shear and pull-out). Each of the applied loading patterns was expected to produce a particular fracture process. Subsequently, the AEs generated by various fracture or damage processes carried specific information on temporal micro-crack behaviors of concrete for post analysis, which was represented in the form of detected AE signal characteristics. Among various available characteristics of acquired AE signals, frequency content was of great interest. In this study, cement-based piezoelectric sensor (as AE transducer) and home-programmed DEcLIN monitoring system were utilized for AE monitoring on mortar. The cement-based piezoelectric sensor demonstrated enhanced sensitivity and broad frequency domain response range after being embedded into mortar specimens. This broad band characteristic of cement-based piezoelectric sensor in frequency domain response benefited the analysis of frequency content of AE. Various evaluation methods were introduced and employed to clarify the variation characteristics of AE frequency content in each test. It was found that the variation behaviors of AE frequency content exhibited a close relationship with the applied loading processes during the tests.

• Journal of Biosystems Engineering
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• v.17 no.1
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• pp.79-90
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• 1992

Viscoelastic characteristics of agricultural products may be determined through three basic tests ; stress relaxation, creep, and dynamic test. Considering the changeability of living materials, dynamic test in which information is derived in a relatively short time appears to be highly desirable, in which either cyclic stress or cyclic strain is imposed and the remaining quantity (strain or stress) is measured. The periodically varying stress will also result in periodically varying strain which in a viscoelastic material should theoretically be out of phase with the stress, because part of the energy subjected to sample is stored in the material as potential energy and part is dissipated as heat. This behavior results in a complex frequency-dependent compliance denoted by J($i{\omega}$). The complex compliance and therefore the storage compliance, the loss compliance, the phase angle, and percent energy loss for the sample should be obtainable with a given static viscoelastic property of the material under static load. The complex compliance of the rough rice kernel were computed from the Burger's model describing creep behavior of the material which were obtained in the previous study. Also, the effects of cyclic load and moisture content of grain on the dynamic viscoelastic behavior of the samples were analyized. The results obtained from this study were summarized as follows ; 1. The storage compliance of the rough rice kernel slightly decreased with the frequency applied but at above the frequency of 0.1 Hz it was nearly constant with the frequency, and the loss compliance of the sample very rapidly decreased with increase in the frequency on those frequency ranges. 2. It was shown that the storage compliance and the loss compliance of the sample increased with increase in grain moisture content. Effect of grain moisture content on the storage compliance of the sample was highly significant than effect of the frequency applied, but effect of the frequency on the loss compliance of the sample was more significant than effect of grain moisture content. 3. In low moisture content, the percent energy loss of Japonica-type rough rice was much higher than that of Indica-type rough rice, but, in high moisture content, vice versa.

• Journal of Biosystems Engineering
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• v.16 no.3
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• pp.263-271
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• 1991

When grains is subjected to oscillating load, the dynamic viscoelastic behavior of the material will be describe the complex modulus of the material. The complex modulus and therefore the storage modulus, the loss modulus, and the phase angle for the sample should be obtainable with a given static viscoelastic property of the material under static load. The complex relaxation moduli of the rough rice kernel were computed from the Burger's model describing creep behavior of the material which were obtained in the previous study. Also, the effects of cyclic load and moisture content of grain on the dynamic viscoelastic behavior of the samples were analized. The storage modulus of the rough rice kernel slightly increased with the frequency applied but at above the frequency of 0.1 Hz it was nearly constant with the frequency, and the loss modulus of the sample very rapidly decreased with increase in the frequency on those frequency ranges. It was shown that the storage modulus and the loss modulus of the sample increased with decrease in grain moisture content. Effect of grain moisture content on the storage modulus of the sample was highly significant than effect of the frequency applied, but effect of the frequency on the loss modulus of the sample was more significant than effect of grain moisture content.

• Earthquakes and Structures
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• v.1 no.2
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• pp.147-162
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• 2010

The ground acceleration measured at a point on the earth's surface is composed of several waves that have different phase velocities, arrival times, amplitudes, and frequency contents. For instance, body waves contain primary and secondary waves that have high frequency content and reach the site first. Surface waves are composed of Rayleigh and Love waves that have lower phase velocity, lower frequency content and reach the site next. Some of these waves could be of more damage to the structure depending on their frequency content and associated amplitude. This paper models critical earthquake loads for single-degree-of-freedom (SDOF) inelastic structures considering evolution of the seismic waves in time and frequency. The ground acceleration is represented as combination of seismic waves with different characteristics. Each seismic wave represents the energy of the ground motion in certain frequency band and time interval. The amplitudes and phase angles of these waves are optimized to produce the highest damage in the structure subject to explicit constraints on the energy and the peak ground acceleration and implicit constraints on the frequency content and the arrival time of the seismic waves. The material nonlinearity is modeled using bilinear inelastic law. The study explores also the influence of the properties of the seismic waves on the energy demand and damage state of the structure. Numerical illustrations on modeling critical earthquake excitations for one-storey inelastic frame structures are provided.

• Journal of Biosystems Engineering
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• v.24 no.2
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• pp.123-134
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• 1999

The electrical properties such as dielectric constant, dielectric loss factor and AC conductivity of grain were presented to measure the moisture content of grain using RF impedance. At frequency ranging from 1 to 10MHz and room temperature, $20^{\circ}C$, vector network analyzer(HP4195) and coaxial type sample holder were used to analyze the electrical properties of paddy(11∼24%w.b.), brown rice(11∼18%w.b.), barley(11∼21%w.b.) and wheat(11∼23%w.b.) depending on the moisture content, frequency and bulk density. The dielectric constant and AC conductivity of grain samples increased with moisture content and bulk density. The dielectric constants decreased with frequency and could be expressed as function of the moisture density(decimal moisture $content{\times}bulk$ density).

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.59-60
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• 2021

The unit-water content has a major problem in concrete structures which leads to micro cracks on the concrete during drying time. Thus, the compressive strength and durability of the concrete structures are significantly reduced. Several techniques have been developed to measure the unit-water content in concrete structures such as heating drying, unit volume mass, and capacitance measurements. However, these techniques have problems in during measurement such as longer time, expensive and difficult in analysis of data. Frequency Domain Reflectivity (FDR) is one of the sensors which used to measure the water content. This method has several advantages including easy to measure, inexpensive, and capable of measuring moisture in real time. In this study, an attempt has been made to evaluate the unit-water content in concrete using the FDR sensor and interpret the data with deep learning method.

• Agricultural and Biosystems Engineering
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• v.1 no.1
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• pp.30-37
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• 2000

Wet porous media representing agronomic soil that contains variable water content with variable electrolyte concentration was measured to study the shape of the curves of the electric double layer capacitance versus frequency (from 10 KHz to 10 MHz. This was done in an attempt to find the lowest practical operating frequency for developing low cost dielectric constant soil moisture probes. Cellulose sponge was used as the porous media. A high frequency electronic bridge circuit was developed for measuring the equivalent network parallel resistance and capacitance of porous media. It appears that the effects of the electric double layer component of the total parallel network capacitance essentially disappear at operating frequencies greater than approximately 25 MHz at low electrolyte concentrations but are still important at 50 MHz at higher concentrations. At these frequencies, the double layer capacitance masks the diffusion region capacitance where true water content capacitance values reside. The general shape of the curve of volumetric water content versus porous media dielectric constant is presented, with an empirical equation representing data for this type of curve. It was concluded that the lowest frequency where dielectric constant values which represent true water content information will most likely be found is between 30 and 50 MHz at low electrolyte concentrations but may be above 50 MHz when the total electrolyte concentration is near the upper level required for most mesophyte plant nutrition.