Three-Dimensional Subsurface Resistivity Profile using Electrical Resistance Tomography for Designing Grounding Grid

Anil Kumar Khambampati(캄밤파티 아닐 쿠마),Kyung Youn Kim(김경연) 대한전자공학회 2016 전자공학회논문지 Vol.53 No.4

대지의 접지 시스템 설치는 안전성과 전기 기기의 올바른 작동을 위해 필수적이며, 대지 파라미터, 특히 토양의 저항률은 대지 접지 시스템 설계에서 결정되어야 한다. 토양의 저항률을 측정하기 위한 가장 흔한 방법은 Wenner의 4전극 방법이 있으며, 이 방법은 1차원의 저항률을 얻기 위하여 가변 전극 간격을 갖는 큰 측정 세트가 요구되어 번거롭고, 시간소모가 많으며 비용이 많이 든다. 전기 저항 단층촬영법은 저비용이며 빠른 측정이 가능하다는 장점 때문에 토양의 저항률 분포를 추정하기 위해 적용될 수 있다. 전기 저항 단층은 관심지역에 놓인 전극에서 얻은 측정데이터를 사용하여 토양 저항률 분포를 특성화한다. 이때 전기 단층 촬영법의 역문제는 비선형성이 강하여 저항률 분포를 추정하기 위하여 Tikhonov 조정 방법을 갖는 반복적 Gauss-Newton 방법을 사용한다. 다양한 시뮬레이션을 수행하여 3차원 토양의 저항률 분포를 추정하는데 전기 저항 단층 촬영법은 유용한 성능을 제공하고 있음을 확인하였다. Installation of earth grounding system is essential to ensure personnel safety and correct operation of electrical equipment. Earth parameters, especially, soil resistivity has to be determined in designing an efficient earth grounding system. The most common applied technique to measure soil resistance is Wenner four-point method. Implementation of this method is expensive, time consuming and cumbersome as large set of measurements with variable electrode spacing are required to obtain a one dimensional resistivity plot. It is advantageous to have a method which is of low cost and provides fast measurements. In this perspective, electrical resistance tomography (ERT) is applied to estimate subsurface resistivity profile. Electrical resistance tomograms characterize the soil resistivity distribution based on the measurements from electrodes placed in the region of interest. The nonlinear ill-posed inverse problem is solved using iterated Gauss-Newton method with Tikhonov regularization. Through extensive numerical simulations, it is found that ERT offers promising performance in estimating the three-dimensional soil resistivity distribution.

Study of Temperature Effect on Conductivity Distribution in Monolayer Graphene Using Electrical Resistance Tomography

Anil Kumar Khambampati,Felipe Alberto Solano Sanchez,Sunam Kumar Sharma,Kyung Youn Kim 대한전자공학회 2022 대한전자공학회 학술대회 Vol.2022 No.6

Unscented Kalman filter approach to tracking a moving interfacial boundary in sedimentation processes using three-dimensional electrical impedance tomography.

Khambampati, Anil Kumar,Rashid, Ahmar,Ijaz, Umer Zeeshan,Kim, Sin,Soleimani, Manuchehr,Kim, Kyung Youn The Royal Society 2009 Philosophical transactions. Series A, Mathematical Vol.367 No.1900

<P>The monitoring of solid-fluid suspensions under the influence of gravity is widely used in industrial processes. By considering sedimentation layers with different electrical properties, non-invasive methods such as electrical impedance tomography (EIT) can be used to estimate the settling curves and velocities. In recent EIT studies, the problem of estimating the locations of phase interfaces and phase conductivities has been treated as a nonlinear state estimation problem and the extended Kalman filter (EKF) has been successfully applied. However, the EKF is based on a Gaussian assumption and requires a linearized measurement model. The linearization (or derivation of the Jacobian) is possible when there are no discontinuities in the system. Furthermore, having a complex phase interface representation makes derivation of the Jacobian a tedious task. Therefore, in this paper, we explore the unscented Kalman filter (UKF) as an alternative approach for estimating phase interfaces and conductivities in sedimentation processes. The UKF uses a nonlinear measurement model and is therefore more accurate. In order to justify the proposed approach, extensive numerical experiments have been performed and a comparative analysis with the EKF is provided.</P>

Phase boundary estimation in electrical impedance tomography using the Hooke and Jeeves pattern search method

Khambampati, Anil Kumar,Ijaz, Umer Zeeshan,Lee, Jeong Seong,Kim, Sin,Kim, Kyung Youn IOP Pub 2010 Measurement Science and Technology Vol.21 No.3

<P>In industrial processes, monitoring of heterogeneous phases is crucial to the safety and operation of the engineering structures. Particularly, the visualization of voids and air bubbles is advantageous. As a result many studies have appeared in the literature that offer varying degrees of functionality. Electrical impedance tomography (EIT) has already been proved to be a hallmark for process monitoring and offers not only the visualization of the resistivity profile for a given flow mixture but is also used for detection of phase boundaries. Iterative image reconstruction algorithms, such as the modified Newton–Raphson (mNR) method, are commonly used as inverse solvers. However, their utility is problematic in a sense that they require the initial solution in close proximity of the ground truth. Furthermore, they also rely on the gradient information of the objective function to be minimized. Therefore, in this paper, we address all these issues by employing a direct search algorithm, namely the Hooke and Jeeves pattern search method, to estimate the phase boundaries that directly minimizes the cost function and does not require the gradient information. It is assumed that the resistivity profile is known a <I>priori</I> and therefore the unknown information will be the size and location of the object. The boundary coefficients are parameterized using truncated Fourier series and are estimated using the relationship between the measured voltages and injected currents. Through extensive simulation and experimental result and by comparison with mNR, we show that the Hooke and Jeeves pattern search method offers a promising prospect for process monitoring.</P>

An interactive multiple model method to identify the in-vessel phenomenon of a nuclear plant during a severe accident from the outer wall temperature of the reactor vessel

Khambampati, Anil Kumar,Kim, Kyung Youn,Hur, Seop,Kim, Sung Joong,Kim, Jung Taek Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.2

Nuclear power plants contain several monitoring systems that can identify the in-vessel phenomena of a severe accident (SA). Though a lot of analysis and research is carried out on SA, right from the development of the nuclear industry, not all the possible circumstances are taken into consideration. Therefore, to improve the efficacy of the safety of nuclear power plants, additional analytical studies are needed that can directly monitor severe accident phenomena. This paper presents an interacting multiple model (IMM) based fault detection and diagnosis (FDD) approach for the identification of in-vessel phenomena to provide the accident propagation information using reactor vessel (RV) out-wall temperature distribution during severe accidents in a nuclear power plant. The estimation of wall temperature is treated as a state estimation problem where the time-varying wall temperature is estimated using IMM employing three multiple models for temperature evolution. From the estimated RV out-wall temperature and rate of temperature, the in-vessel phenomena are identified such as core meltdown, corium relocation, reactor vessel damage, reflooding, etc. We tested the proposed method with five different types of SA scenarios and the results show that the proposed method has estimated the outer wall temperature with good accuracy.

Three-dimensional phase boundary estimation in sedimentation process using electrical impedance tomography with the aid of unscented Kalman filter

Anil Kumar Khambampati,Ahmar Rashid,Jeong Seong Lee,Sin Kim,Kyung Youn Kim 대한전자공학회 2008 ITC-CSCC :International Technical Conference on Ci Vol.2008 No.7

This work is related to interfacial phase bounadry estimation in sedimentation monitoring using electrical impedance tomography. The fluid is assumed to settle into three different phases separated by sharp interfacial boundary. The time evolution of the phase interface gives important information about the sedimentation process which can be used to control and optimize the sedimentation process. Phase interface location and their corresponding conductivities estimation is treated as a stochastic nonlinear state estimation problem with the nonstationary interfacial phase boundary (state) being estimated online with the aid of unscented Kalman filter. Numerical experiments are performed to evaluate the performance of the proposed approach and is compared with conventional extended Kalman filter.

An analytical boundary element integral approach to track the boundary of a moving cavity using electrical impedance tomography

Khambampati, Anil Kumar,Lee, Bo An,Kim, Kyung Youn,Kim, Sin IOP Pub 2012 Measurement Science and Technology Vol.23 No.3

<P>This paper is about locating the boundary of a moving cavity within a homogeneous background from the voltage measurements recorded on the outer boundary. An inverse boundary problem of a moving cavity is formulated by considering a two-phase vapor–liquid flow in a pipe. The conductivity of the flow components (vapor and liquid) is assumed to be constant and known a priori while the location and shape of the inclusion (vapor) are the unknowns to be estimated. The forward problem is solved using the boundary element method (BEM) with the integral equations solved analytically. A special situation is considered such that the cavity changes its location and shape during the time taken to acquire a full set of independent measurement data. The boundary of a cavity is assumed to be elliptic and is parameterized with Fourier series. The inverse problem is treated as a state estimation problem with the Fourier coefficients that represent the center and radii of the cavity as the unknowns to be estimated. An extended Kalman filter (EKF) is used as an inverse algorithm to estimate the time varying Fourier coefficients. Numerical experiments are shown to evaluate the performance of the proposed method. Through the results, it can be noticed that the proposed BEM with EKF method is successful in estimating the boundary of a moving cavity.</P>

Boundary element method to estimate the time-varying interfacial boundary in horizontal immiscible liquids flow using electrical resistance tomography

Khambampati, Anil Kumar,Kim, Kyung Youn,Lee, Yeon-Gun,Kim, Sin Elsevier 2016 Applied mathematical modelling Vol.40 No.2

<P><B>Abstract</B></P> <P>Flow of immiscible liquids through horizontal pipe is observed in many industrial process applications. The flow is mainly characterized by its flow regime, relative phase velocities, liquid fraction and water holdup. Electrical resistance tomography (ERT) that provides a cross-sectional image of flow distribution is helpful in monitoring the process. In this paper, the moving interfacial boundary between the immiscible liquids of stratified flow is estimated based on the measured voltages on the pipe surface. Determining the time-varying shape and location of the interfacial boundary has a practical significance. It gives us the cross-sectional liquid fraction which is a key parameter to analyze the hydrodynamic properties of flow. The interfacial boundary shape and location is parameterized with discrete front points and the forward solution is formulated using analytical boundary element method (BEM). The analytic formulation of BEM is simple with less number of unknowns therefore it is computationally efficient. Moreover, BEM discretizes the boundaries alone and is therefore appropriate choice for interfacial boundary estimation. To estimate the time-varying boundary, conventional methods that assume no change in flow distribution within the measurement time of full frame of voltage data are inadequate. Dynamic imaging methods that use one or few sets of data can improve the temporal resolution and hence they are more accurate and practical in realistic situations. Inverse problem is treated as a state estimation problem where the front points are considered as state variables and are estimated using extended Kalman filter. Numerical simulations and phantom experiments are performed to validate the performance of the proposed method.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A numerical solution based on BEM is formulated for moving interfacial boundary. </LI> <LI> Boundary between immiscible liquids is parameterized using discrete front points. </LI> <LI> Analytic BEM is formulated for ERT boundary estimation problem. </LI> <LI> The moving front points that determine the boundary shape are estimated using EKF. </LI> <LI> Number of front points and contrast ratio of liquids affects estimation performance. </LI> </UL> </P>

COMPENSATION OF SERVO TRACK WRITING ERROR IN HIGH TRACK DENSITY DISK DRIVES

Anil Kumar Khambampati,Umer Zeeshan Ijaz,Kyung Youn Kim,Chang Ik Kang 대한전자공학회 2006 ITC-CSCC :International Technical Conference on Ci Vol.2006 No.3

Estimating aquifer location using deep neural network with electrical impedance tomography

Sunam Kumar Sharma,Anil Kumar Khambampati,Kyung Youn Kim 한국전기전자학회 2020 전기전자학회논문지 Vol.24 No.4

Groundwater is essential source of the freshwater. Groundwater is stored in the body of the rocks or sediments, called aquifer. Finding an aquifer is a very important part of the geophysical survey. The best method to find the aquifer is to make a borehole. Single borehole is not a suitable method if the aquifer is not located in the borehole drilled area. To overcome this problem, a cross borehole method is used. Using a cross borehole method, we can estimate aquifer location more precisely. Electrical impedance tomography is use to estimate the aquifer location inside the subsurface using the cross borehole method. Electrodes are placed inside each boreholes and area between these boreholes are analysed. An aquifer is a non-uniform structure with complex shape which can represented by the truncated Fourier series. Deep neural network is evaluated as an inverse problem solver for estimating the aquifer boundary coefficients.