전극의 기하학적 형상이 전기비저항 탐사에 미치는 영향: 수치 해석 연구

김태영,이승훈,류희환,정성훈 사단법인 한국터널지하공간학회 2023 한국터널지하공간학회논문집 Vol.25 No.2

Electrical resistivity survey have been widely conducted at diverse scales, from a few centimeters for laboratory tests to kilometers for field tests. It measures electrical resistance through relationship of electric potential difference and current between two electrodes penetrated on the surface of medium, and eventually quantifies electrical resistivity known as inherent properties of the medium. In field or full-scale test, it assumes the electrodes as equivalent half-sphere electrodes that have a same surface area with different electrodes for ease of calculation because the contact area between electrode and medium is small and sufficient distance between two electrodes. However, small-scale laboratory test is significantly affected by the electrode geometries (penetrated depth, height, radius of electrode and distance between electrodes), which change the equipotential surface and electric current flow. Indeed, the electrode geometries may eventually cause a difference of electrical resistivity value. This study reviews the theoretical electrical resistance derived with various electrode geometries (half-sphere, cylinder, cylindrical with half-spherical tip, cylindrical with conical tip) and verifies the developed numerical module by comparing results with the theoretical electrical resistance. The distributions of electrical resistance around electrodes and among electrodes are analyzed. In addition, it is discussed how the electrical characteristic of cylindrical electrode with conical tip widely used in field test has effect on the electric current flow.

Electrical Resistance Evaluation Reliability under High Grade Temperature for Na-AMTEC(Natrium Alkali-Metal Thermal-to-Electric Convertor)

Min-Soo SUH(서민수) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.4

In general, an electrical circuit, electrical resistance is a measure of the opposition to current flow. Resistance is a measured in ohms, symbolized by the Greek letter omega(Ω). In practical, specialized on Na-AMTEC(Natrium Alkali-Metal Thermal-to-Electric Convertor), the input energy is directly converted to electrical energy. In microscopic view, the energy transforming of one source to another useful forms classified as storage, transportation and conversion is simultaneous taken place in one small circuit. In macroscopic view, thermal energy directly converted into electrical energy, in other words it is energy transforming primarily solar-to-thermal and thermal-to-electric. In case of metallic substances, free electrons are moving randomly in the crystal structure of it. Due mainly to the electric field across the resistance, free electrons drift from lower potential point to higher potential when voltage is applied. Free electron continually collides with atoms of the substance during drifting motion, this phenomenon prevents the free motion of electrons. The resistance is known to be caused by the collision of free electron with atoms of the substance. Physicist George Simon Ohm suggest the law ohm that electric resistance is equal to voltage per ampere on pure metal. Hence, resistance is defined as the ratio of the applied voltage to the current through the substance. Most of metallic substance with rising temperatures the inter atomic vibrations increase and consequently offer more resistance to the movement of electrons causing the current. Thus, with increasing temperature the resistance of metallic substances increases. Refractory metals are a class of metals that are extraordinarily resistant to heat. The well-known Na-AMTEC is working between 800 K to 1300 K. Most of materials does not meet the criteria of aforementioned working condition in sense of thermo-condition except the five elements two of fifth period (niobium and molybdenum) and three of the sixth period (tantalum, tungsten and rhenium). They all share some properties, including a melting point above 2,200 K and high hardness at room temperature, except ductile transition character of niobium. Pure niobium has a Mohs hardness rating similar to that of pure titanium. Hence, the selection of candidate materials for Na-AMTEC as electrical electrode, current collector and lead is narrowed down to the minimum requirement of temperature resistance and electrical conductivity. In case of electrical resistance of Na-AMTEC is derived as following that the total resistance, R_T of Na-AMTEC is sum of the following resistances R_B (Resistance of Beta-Alumina Solid Electrolyte, BASE) + R_S (sheet resistance) + R_C (contact resistance) + R_L (lead resistance). Mostly, the sum of the rest of resistances is larger than the resistance of BASE. ● Correlation of Voltage, Ampere and Resistance: V ∝ I , V = RI , R= V/I ● Total electrical resistance of Na-AMTEC: R_T = R_B + R_S + R_C + R_L, R_B < R_S + R_C + R_L ● Correlation of resistances of Na-AMTEC: R_T ∝ 2 R_B Nonetheless, there is a reliability issue when measuring the electrical resistance which is intricate compared to the concept of electrical conductivity measurement on room temperature by virtue of the continuous temperature deviation during the Na-AMTEC cell test under elevated temperature. This study is to report the effort to develop the methodology of measurement reliability of the electrical resistance under high temperature state.

콘크리트의 탄산화가 전기저항에 미치는 영향

윤인석 한국구조물진단유지관리공학회 2014 한국구조물진단유지관리공학회 논문집 Vol.18 No.5

전기저항은 콘크리트의 내구성을 판단하기 위하여 빠르고 간단히 측정하여 활용될 수 있으나, 탄산화가 진행되면 콘크리트의 미세구조가 크게 변화하기 때문에 측정의 오차를 초래한다. 본 연구의 목적은 콘크리트의 탄산화가 전기저항에 미치는 영향을 분석하고 정량화 하는데 있다. 다양한 물시멘트비 조건에서 시험편을제조하여 330일동안 탄산화 촉진을 시키면서 전기저항의 변화율을 고찰하였다. 탄산화된 콘크리트에서 전기저항 측정치가 높은 것으로 나타났으며, 이러한 경향은 탄산화가 진행됨에 따라 더욱 뚜렷한 경향을 보였다. 전기저항과 탄산화깊이와의 상관관계를 도출하였으며, 기중상태 대비 탄산화된 콘크리트의 전기저항 비율은 일정한 탄산화깊이까지는 급격히 낮아지는 경향을 보였으나, 포화상태 대비 탄산화된 콘크리트의 전기비율은 탄산화 깊이와 선형관계를 보였다. 본 연구를 토대로 탄산화로 인하여 전기저항치의 측정오차를 보정할 수 있는데 실질적으로 활용될 수 있을 것으로 기대된다. Electrical resistivity of concrete can be measured in a more rapid and simple way for estimating durability of the concrete, however, carbonation causes a result of misleading for durability testing because carbonation leads to a significant reduction in thepermeability and porosity of concrete.The purpose of this study is to estimate and quantify the effect of carbonation of concrete on a surface electrical resistivity measurement. Samples of three mixes with difference w/c were prepared and exposed in a carbonation chamber for 330 days. Theresults show that carbonation leads high electrical resistivity. The increase is substantial and has been shown to proportional to the extent of the carbonation by some of extent. The relationship between electrical resistivity and carbonation depth is taken in thestudy. Resistivity ratio of carbonated concrete to air concrete decreased significantly from the specific carbonation depth, however,resistivity ratio of carbonated concrete to air concrete had a linear relation with carbonation depth.From the relationship between electrical resistivity and carbonation depth, it is expected that the result should be subsequently used as a calibration curve for estimating carbonated concrete to overcome the interruption effect of carbonation on regular measurements of the electrical resistivity.

Influence of curing condition and carbonation on electrical resistivity of concrete

윤인석,홍성원,강현구 사단법인 한국계산역학회 2015 Computers and Concrete, An International Journal Vol.15 No.6

The electrical resistivity of air-dried, saturated, and carbonated concretes with different mixture proportions was monitored to evaluate and quantify the influence of the age of the specimen, carbonation, and curing condition. After 28 days of curing, four prepared specimens were stored in a vacuum chamber with 5% CO2 for 330 days to make carbonated specimens. Four of the specimens were placed in water, and four specimens were cured in air until the end of the experiments. It was observed that the electrical resistivity of the carbonated specimens increased as carbonation progressed due to the decrease of porosity and the increase of hydrated products. Therefore, in order to estimate the durability of concrete, its carbonation depth was used as the measurement of electrical resistivity. Moreover, an increase of electrical resistivity for air-dried and saturated concretes was observed as a function of age of the specimen. From the relationship between chloride diffusivity provided by Yoon et al. (2007) and the measurements of electrical resistivity, it is expected that the results well be of significant use in calibrating chloride diffusivity based on regular measurements of electrical resistivity during concrete construction.

Investigation of Slope Subsurface Structure using the Drone-Grounded Electrical Source Airborne Transient Electromagnetic System (D-GREATEM)

( Yohei Morifuji ),( Kenji Kubota ),( Shiro Tanaka ),( Akira Jomori ),( Atsuyoshi Jomori ) 대한지질공학회 2019 대한지질공학회 학술발표회논문집 Vol.2019 No.2

Slope failures due to heavy rain and earthquakes have occurred frequently in Japan. To evaluate the risk of slope failures, it is necessary to survey the subsurface structure and identify areas having risk of collapses. However, much time and labor is associated with conducting surveys on slopes, and the range of the survey area is often limited. Therefore, in this study, the grounded electrical source airborne transient electromagnetic system using a drone (D-GREATEM) was applied to a slope to reveal the resistivity structure which is an index of the rock geological features and the groundwater level. To avoid fall accidents, the drone flied at several constant elevations. Although the distance between the platform and the ground should be constant for analysis, it is difficult to maintain a specific flight height from the ground on a slope. This problem was approached by correcting the flight height in the analysis. To evaluate the resistivity results, a ground electrical survey was also conducted. The resistivity structure obtained from the electromagnetic survey conducted using the drone showed three layers of resistivity: a higher resistivity zone at depths shallower than 30 m, a lower resistivity zone from 50-100 m, and a higher resistivity zone at greater depth. The shallowest higher resistivity zone indicates the detritus and talus deposit distributed near the surface. The ground electrical survey also showed a higher resistivity zone in the area. The electromagnetic survey conducted using the drone could easily obtain the resistivity structure in the slope.

Use of Two Dimensional Electrical Resistivity Tomography to Identify Soil Water Dynamics and the Effective Plant Root Zone

윤성원,장용선,한경화,조희래,하상건,박삼규,손연규 한국토양비료학회 2012 한국토양비료학회지 Vol.45 No.3

The identification of effective root zone would clarify dynamics of plant available water and soil water balance. Using the relationship between soil properties and electrical resistivity (ER) the purpose of this research is to identify soil zone affected by a plant root activity using electrical resistivity tomography (ERT)technique. Four plastic containers were prepared for two different soil textures (clay and sandy loam) and one container for each texture was selected for planting four corn seedlings (Zea mays L.) and the others were prepared for the blank. For ERT monitoring, we prepared 0.8 m plastic sticks with 17 electrodes installed with 5 cm space. The Ministing (AGI Inc., Texas) instrument for electrical resistivity measurement and semi-auto converter of electrode arrangement were set up for dipole-dipole array. During 2 months of the corns growing,ERT monitoring was made 3 to 4 days after the irrigation practice. Despite of the same amount water supplied into soils, two textures showed very different apparent resistivity values due to different clay content. The apparent electrical resistivity is consistently lower in clay loam comparing to sandy loam soil implying that plant root does not significantly alter the overall trend of resistivity. When plant root system, however, is active both soils with plants showed 2-7 times higher electrical resistivity and higher coefficient variation than soils without plant, implying the effect of root system on the resistivity, in which may caused by . This result suggests plant root activities regulating the soil water dynamics mainly control the variation of electrical resistivity over soil textural difference. Therefore the identification of water uptake zone would highly be correlated to plant root activities, thus ERT will be feasible approach to identify spatial characteristics of a plant root activity.

Use of Two Dimensional Electrical Resistivity Tomography to Identify Soil Water Dynamics and the Effective Plant Root Zone

Sung Won Yoon,Yong Seon Zhang,Kyung Hwa Han,Hee Rae Jo,Sang Keun Ha,Sam Kyeu Park,Yeon Kyu Sonn 한국토양비료학회 2012 한국토양비료학회지 Vol.45 No.3

The identification of effective root zone would clarify dynamics of plant available water and soil water balance. Using the relationship between soil properties and electrical resistivity (ER) the purpose of this research is to identify soil zone affected by a plant root activity using electrical resistivity tomography (ERT) technique. Four plastic containers were prepared for two different soil textures (clay and sandy loam) and one container for each texture was selected for planting four corn seedlings (Zea mays L.) and the others were prepared for the blank. For ERT monitoring, we prepared 0.8 m plastic sticks with 17 electrodes installed with 5 cm space. The Ministing (AGI Inc., Texas) instrument for electrical resistivity measurement and semi-auto converter of electrode arrangement were set up for dipole-dipole array. During 2 months of the corns growing, ERT monitoring was made 3 to 4 days after the irrigation practice. Despite of the same amount water supplied into soils, two textures showed very different apparent resistivity values due to different clay content. The apparent electrical resistivity is consistently lower in clay loam comparing to sandy loam soil implying that plant root does not significantly alter the overall trend of resistivity. When plant root system, however, is active both soils with plants showed 2-7 times higher electrical resistivity and higher coefficient variation than soils without plant, implying the effect of root system on the resistivity, in which may caused by . This result suggests plant root activities regulating the soil water dynamics mainly control the variation of electrical resistivity over soil textural difference. Therefore the identification of water uptake zone would highly be correlated to plant root activities, thus ERT will be feasible approach to identify spatial characteristics of a plant root activity.

Use of Two Dimensional Electrical Resistivity Tomography to Identify Soil Water Dynamics and the Effective Plant Root Zone

Yoon, Sung-Won,Zhang, Yong-Seon,Han, Kyung-Hwa,Jo, Hee-Rae,Ha, Sang-Keun,Park, Sam-Kyeu,Sonn, Yeon-Kyu Korean Society of Soil Science and Fertilizer 2012 한국토양비료학회지 Vol.45 No.3

The identification of effective root zone would clarify dynamics of plant available water and soil water balance. Using the relationship between soil properties and electrical resistivity (ER) the purpose of this research is to identify soil zone affected by a plant root activity using electrical resistivity tomography (ERT) technique. Four plastic containers were prepared for two different soil textures (clay and sandy loam) and one container for each texture was selected for planting four corn seedlings (Zea mays L.) and the others were prepared for the blank. For ERT monitoring, we prepared 0.8 m plastic sticks with 17 electrodes installed with 5 cm space. The Ministing (AGI Inc., Texas) instrument for electrical resistivity measurement and semi-auto converter of electrode arrangement were set up for dipole-dipole array. During 2 months of the corns growing, ERT monitoring was made 3 to 4 days after the irrigation practice. Despite of the same amount water supplied into soils, two textures showed very different apparent resistivity values due to different clay content. The apparent electrical resistivity is consistently lower in clay loam comparing to sandy loam soil implying that plant root does not significantly alter the overall trend of resistivity. When plant root system, however, is active both soils with plants showed 2-7 times higher electrical resistivity and higher coefficient variation than soils without plant, implying the effect of root system on the resistivity, in which may caused by. This result suggests plant root activities regulating the soil water dynamics mainly control the variation of electrical resistivity over soil textural difference. Therefore the identification of water uptake zone would highly be correlated to plant root activities, thus ERT will be feasible approach to identify spatial characteristics of a plant root activity.

탄성계수 및 간극비 평가를 위한 현장 관입형 탄성파 및 전기비저항 프로브

윤형구(Yoon Hyung-Koo),김동휘(Kim Dong-Hee),이우진(Lee Woojin),이종섭(Lee Jong-Sub) 대한토목학회 2010 대한토목학회논문집 C Vol.30 No.2

전단 강성은 지반 거동을 이해하기 위한 필수적인 요소로 인식되고 있으며, 특히 탄성계수 및 간극비는 구조물의 기본적인 설계 정수로서 그 중요성이 점차 증가하고 있다. 본 연구의 목적은 전단파와 압축파 같은 탄성파 및 전기비저항 측정이 가능한 현장 탄성파 및 전기비저항 측정 장비(FVRP)를 개발하고, 이를 이용하여 대상지반의 탄성계수 및 간극비를 산정하는 것이다. 압축파 및 전단파는 각각 피에조 디스크 엘리먼트와 벤더 엘리먼트를 이용하여 측정하였다. 그리고 전기비저항은 소형 전기비저항 측정 프로브를 제작하여FVRP 선단에 설치하여 측정하였다. 개발된 장비는 실내의 대형토조와 현장에 적용되었다. 대형 토조실험의 경우, 모래와 점토를 슬러리 상태에서 혼합하여 지반을 조성한 후 상재하중을 가하여 조성된 지반을 압밀 시킨 후 진행되었으며, 탄성파 및 전기비저항의 측정은 매 심도 1㎝ 간격으로 수행되었다. 현장 실험은 남해안 지역에서 수행되었으며, 탄성파 및 전기비저항 측정은 관입심도 6m부터 20m까지 10㎝ 간격으로 수행하였다. 토조 및 현장실험을 통해 측정된 탄성파와 전기비저항은 이론적인 관계식을 이용하여 탄성계수 및 간극비로 환산되었다. 탄성파와 전기비저항을 이용한 간극비는 부피를 이용하여 산정한 간극비와 유사한 값을 나타내었다. 본 연구에서 개발된 탄성파와 전기비저항을 동시에 측정할 수 있는 FVRP는 연약지반의 탄성계수 및 간극비 산정에 유용한 장비가 될 수 있음을 보여준다. The shear stiffness has become an important design parameter to understand the soil behavior. In particular, the elastic moduli and void ratio has been considered as important parameters for the design of the geotechnical structures. The objective of this paper is the development of the penetration type Field Velocity and Resistivity Probe (FVRP) which is able to assess the elastic moduli and void ratio based on the elastic wave velocities and electrical resistivity. The elastic waves including the compressional and shear wave are measured by piezo disk elements and bender elements. And the electrical resistivity is measured by the resistivity probe, which is manufactured and installed at the tip of the FVRP. The penetration tests are carried out in calibration chamber and field. In the laboratory calibration chamber test, after the sand-clay slurry mixtures are prepared and consolidated. The FVRP is progressively penetrated and the data are measured at each 1 ㎝. The field experiment is also carried out in the southern part of Korea Peninsular. Data gathering is performed in the depth of 6~20 m at each 10 ㎝. The elastic moduli and void ratio are estimated based on the analytical and empirical solutions by using the elastic wave velocities and electrical resistivity measured in the chamber and field. The void ratios based on the elastic wave velocities and the electrical resistivity are similar to the volume based void ratio. This study suggests that the FVRP, which evaluates the elastic wave velocities and the electrical resistivity, may be a useful instrument for assessing the elastic moduli and void ratio in soft soils.

Optoelectronic properties of Cu1−xPtxFeO2 (0 ≤ x ≤ 0.05) delafossite for p-type transparent conducting oxide

Chesta Ruttanapun,Wutthisak Prachamon,Aree Wichainchai 한국물리학회 2012 Current Applied Physics Vol.12 No.1

The samples of Cu1-xPtxFeO2 (0 ≤ x ≤ 0.05) delafossite have been synthesized by solid-state reaction method to investigate their optical and electrical properties. The properties of electrical resistivity and Seebeck coefficient were measured in the high temperature ranging from 300 to 960 K, and the Hall effect and the optical properties were measured at room temperature. The obtained results of Seebeck showed the samples are p-type conductor. The optical properties at room temperature exhibited the samples are transparent visible light material with optical direct gap 3.45 eV. The low electrical resistivity,hole mobility and carrier density at room temperature displayed value ranging from 0.29 to 0.08Ω cm, 1.8 to 8.6 cm2/V s and 1.56 × 1018 to 4.04 × 1019 cm-3, respectively. The temperature range for transparent visible light is below 820 K because the direct energy gap contains value above 3.1 eV. Consequently, the Cu1-xPtxFeO2 delafossite enhance performance for materials of p-type transparent conducting oxide (TCO) with low electrical resistivity. The samples of Cu1-xPtxFeO2 (0 ≤ x ≤ 0.05) delafossite have been synthesized by solid-state reaction method to investigate their optical and electrical properties. The properties of electrical resistivity and Seebeck coefficient were measured in the high temperature ranging from 300 to 960 K, and the Hall effect and the optical properties were measured at room temperature. The obtained results of Seebeck showed the samples are p-type conductor. The optical properties at room temperature exhibited the samples are transparent visible light material with optical direct gap 3.45 eV. The low electrical resistivity,hole mobility and carrier density at room temperature displayed value ranging from 0.29 to 0.08Ω cm, 1.8 to 8.6 cm2/V s and 1.56 × 1018 to 4.04 × 1019 cm-3, respectively. The temperature range for transparent visible light is below 820 K because the direct energy gap contains value above 3.1 eV. Consequently, the Cu1-xPtxFeO2 delafossite enhance performance for materials of p-type transparent conducting oxide (TCO) with low electrical resistivity.