Nonconducting Medium Research Articles

Electrocoalescence of unequal-sized aqueous droplet pair in non-conductive medium

Electrocoalescence of unequal-sized aqueous droplet pair in non-conductive medium

DEVELOPMENT OF IMAGE RECONSTRUCTION FOR DETECTING STATIC OIL-GAS REGIMES USING INVASIVE ELECTRICAL CAPACITANCE TOMOGRAPHY IN STEEL PIPE APPLICATION – AN INITIAL STUDY An Initial Study

Electrical Capacitance Tomography (ECT) is a well-known technique for identifying two-phase regimes when a non-conducting medium is the main medium inside a pipe. However, the common non-invasive techniques of ECT are not suitable for monitoring non-conducting systems that use steel pipes. This is because the placement of the common ECT sensor is outside of the pipe and thus cannot penetrate the conducting pipe. Therefore, this paper presents the development of image reconstruction techniques for invasive Electrical Capacitance Tomography (ECT) in steel pipe applications. The study uses eight electrodes for invasive ECT that are independently designed for easy replacement. The shield guard of each electrode is individually designed, unlike the common sensor of ECT. Moreover, it produces a sensitivity map in the forward problem by modeling the geometry to mimic the real hardware of invasive ECT in Comsol Multiphysics livelink with MATLAB. The data from real hardware is exported offline and a linear back projection algorithm is used as the inverse problem. The phantom of gas-oil with different sizes, positions, and multiple phantoms from the range of 20mm, 25 mm and 33mm are tested. The tomograms of the region of interest can be obtained as a result. The paper concludes that the developed image reconstruction techniques for invasive ECT in steel pipe applications can provide acceptable and reliable results. This study can be useful for researchers and practitioners in the field of ECT and steel pipe applications.

Propagation of electromagnetic pulses with nonzero area in dissipative media

The propagation of ultrashort electromagnetic pulses with a nonzero electric area in dielectric and conducting media is studied in the frame of a unidirectional propagation model. General solutions for the electric pulse area are obtained for different types of media with a linear response to the external field. It is shown that the evolution of the electric area of the pulse is dramatically different for conducting and non-conducting media. In the case of dielectrics, where the current induced by an external field arises from the polarization of bound electrons, the electric pulse area is an invariant of pulse propagation in spite of the dissipation process. For media with free charge carriers (plasma or semiconductors), the electric pulse area decreases with time due to Joule heating of the media by the static component of the field.

DEVELOPMENT OF A DEVICE FOR POSITIONING AND SIZING OF SMALL-SIZED METALLIC INCLUSIONS IN NON-CONDUCTIVE MATERIALS

The technology and equipment for eddy current detection of small-sized metal inclusions in products made of non-conductive materials has been developed. The developed technology and equipment can be used to detect small-sized metal inclusions ranging in size from 0.2 to 2.0 mm at a depth of up to 50 mm in non-conductive media, in particular polymer composite materials, to assess the quality of products and the stability of their manufacturing technology. Mathematical modeling of the process of detection and identification of small-sized metal inclusions using a multicoil eddy current transducer is carried out, which makes it possible to determine the control modes and characteristics of the device without carrying out expensive experimental work. The simulation results allow developing methods for processing signals from eddy current transducers, taking into account the characteristics of the material of the test object and small-sized metal inclusions. Experimental studies of the developed technology and equipment have been carried out, confirming the results of theoretical studies and the capabilities of the developed technology and equipment, with validation by alternative methods and means of control.

DETERMINATION OF THE SPECIFIC RESISTANCE OF COATINGS FROM HIGH-ENTROPY ALLOYS

In order to use the four-probe method to determine the resistivity of a coating of high-entropy alloys, the correction functions were calculated when determining the resistivity based on measuring the potential difference between the probes placed on a hexagonal stainless steel sample coated with a conductive coating. The presence of boundaries with a non-conductive medium (air) and the presence of a conductive substrate with a conductive coating were taken into account. The method of mirror images was used for the calculation. Correction functions for a hexagonal sample with a thin coating are obtained.

Analytical Method of Probe Footprint Based on Equivalent Model of Pulsed Eddy Current Field

In the pulsed eddy current testing for the local wall-thinning corrosion of ferromagnetic components, it is significative to accurately calculate the effective coverage area of the probe for analyzing the spatial resolution of corrosion detection. Based on the analytical expressions of the pulsed eddy current field of ferromagnetic plate, an equivalent model is established to analyze the probe footprint, by taking the eddy current ring in the conductor as the excitation source, and by replacing the conductor region with non-conductive and magnetic conductive medium. First, the boundary value problem of the equivalent model is solved analytically, and the contribution function of the eddy current loop is proposed to calculate the voltage signal in the detection coil induced by a single eddy current loop in the conductor. Then, the voltage induced by the eddy current field in the equivalent model is derived by integrating the contribution function in the whole conductor region, and the equivalent model is verified by comparing with the existing analytical results. Finally, combined with the thickness detection results of a steel plate with rectangular groove defects, the analysis method for the footprint of the probe is proposed using the contribution function. Considering not only the distribution of eddy current field induced by the excitation coil but also the influence of the shape and position of the detection coil, the analytical method for the probe footprint proposed in this article can provide more detailed and accurate guidance for the probe design in the eddy current testing.

О ВЫДЕЛЕНИИ СИГНАЛА ВЫСОКОЧАСТОТНОГО ЭМ-ПОЛЯ ЛИТОСФЕРНОГО ПРОИСХОЖДЕНИЯ: ТЕОРЕТИЧЕСКИЙ АСПЕКТ

The complexity of isolating the electromagnetic field of lithospheric origin, recorded on the day surface, is the influence on the registered signals of various electromagnetic field sources of both artificial and natural origin. The paper provides an overview of such electromagnetic field sources in the kilohertz range. A mathematical model describing the shape of pulses (in the time domain) that have passed through a conducting medium is presented. Based on the above mathematical model, it is concluded that the shape of the pulse can be used to judge whether the pulse has passed through a conductive rock or through air (non-conductive medium). The simulation results obtained allow us to determine the criteria for creating a prototype of a generalized pulse shape, which can be used in algorithms for the extraction of signals of lithospheric origin from the observed electromagnetic field for their further study.

Plane one-dimensional MHD flows: Symmetries and conservation laws

The paper considers the plane one-dimensional flows for magnetohydrodynamics in the mass Lagrangian coordinates. The inviscid, thermally non-conducting medium is modeled by a polytropic gas. The equations are examined for symmetries and conservation laws. For the case of finite electric conductivity we establish Lie group classification, i.e. we describe all cases of the conductivity σ(ρ,p) for which there are symmetry extensions. The conservation laws are derived by direct computation. For the case of infinite electrical conductivity the equations can be brought into a variational form in the Lagrangian coordinates. Lie group classification is performed for the entropy function as an arbitrary element. Using the variational structure, we employ the Noether theorem for obtaining conservation laws. The conservation laws are also given in the physical variables.

A phaseless inverse problem for electrodynamic equations in the dispersible medium

ABSTRACT For electrodynamic equations related to non-conducting dispersible medium we consider the inverse problem of recovering two variable coefficients from a given phaseless information of solutions to the equations. One of these coefficients is the permittivity while the second one characterizes the time dispersion of the medium. We suppose that unknown coefficients differ from given constants inside of a compact domain Ω. A plane electromagnetic wave going in the direction ν from infinity fall down on this domain and modulus of the electric strength is measured on a part of the boundary of Ω for all . The inverse problem consists in determining unknown functions from this information. We reduce the inverse problem to two problems: (1) the inverse kinematic problem for recovering the refractive index and (2) the integral geometry problem for recovering the second coefficient related to the dispersion. An uniqueness theorem for the first problem is stated on the base of known results. The second problem differs from have studied by the more general weight function and it is still open. Then we demonstrate that under some natural assumption the weight function uniformly close to 1. Replacing the weight function by 1, we obtain the integral geometry problem for which the uniqueness theorem and stability estimate are established and some numerical algorithms are proposed.

Three Numerical Eigensolvers for 3-D Cavity Resonators Filled With Anisotropic and Nonconductive Media

This paper mainly investigates the classic resonant cavity problem with anisotropic and nonconductive media, which is a linear vector Maxwell's eigenvalue problem. The finite element method based on edge element of the lowest-order and standard linear element is used to solve this type of 3-D closed cavity problem. In order to eliminate spurious zero modes in the numerical simulation, the divergence-free condition supported by Gauss' law is enforced in a weak sense. After the finite element discretization, the generalized eigenvalue problem with a linear constraint condition needs to be solved. Penalty method, augmented method and projection method are applied to solve this difficult problem in numerical linear algebra. The advantages and disadvantages of these three computational methods are also given in this paper. Furthermore, we prove that the augmented method is free of spurious modes as long as the anisotropic material is not magnetic lossy. The projection method based on singular value decomposition technique can be used to solve the resonant cavity problem. Moreover, the projection method {cannot} introduce any spurious modes. At last, several numerical experiments are carried out to verify our theoretical results.

ON THE SIMILARITY OF PLANE PULSED MAGNETIC FIELDS CONTINUED FROM DIFFERENT COORDINATE AXES

Purpose. The purpose of this work is formulation of similarity conditions for plane magnetic fields at a sharp skin-effect continued in non-conducting and non-magnetic medium from different axes bounding plane surfaces of conductors. Methodology. Classic formulation of Cauchy problem for magnetic vector potential Laplace equations, mathematic physics methods and basics similarity theory are used. Two problems are considered: the problem of initial field continuation from one axis and the problem of similar field continuation form other axis on which magnetic flux density or electrical field strength in unknown. Results. Necessary and sufficient similarity conditions of plane pulsed or high-frequency magnetic fields continued from different axes of rectangular coordinates are formulated. For the given odd and even magnetic flux density distributions on axis of initial field corresponding the distributions on axis and solution of continued similar field problem are obtained. Originality. It is proved that for similarity of examined fields the proportion of corresponding vector field projections represented by dimensionless numbers in similar points of axes is necessary and sufficient.

Numerical study of coalescence and non-coalescence of two conducting drops in a non-conducting medium under electric field

A numerical study, employing boundary element method (BEM), on the interaction of two perfectly conducting drops in a perfectly dielectric medium (PCPD), under electric field, is presented here. A scaling analysis is carried out to show that electric stress is balanced by the hydrodynamic stress while the capillary stress becomes subdominant as the drops approach each other under electric field. Parameters such as initial separation distance and electrocapillary number are numerically studied using BEM to see their effects on deformation of drops, characterized by their cone angle β at contact, in pre-contact phase. In the post-contact phase, the drops are bridged using Bird et al. (2009)’s analytical model, which is solved numerically. Thereafter BEM is employed to realize coalescence and non-coalescence as exhibited by the bridged drops, depending on critical cone angle. It is also shown numerically, that electrostatics play no part for PCPD system once the charges at the tips of the drop poles are neutralized on bridging thus validating Bird et al. (2009)’s assumption.

Electrorheological properties of polyimide nanoparticles suspensions

Suspensions of polyimide particles were obtained, in which 2,5-diaminobenzenesulfonic acid was used as a diamine component. Their electrorheological properties in a nonconducting medium were studied depending on the parameters of deformation and the intensity of the external electric field. It is established that the electro-rheological suspensions obtained based on particles of polyimide PI-I–PI-IV have a powerful electro-rheological response, ten times higher than the electro-rheological effect of suspensions based on traditional micro-sized particles of the dispersed phase.

Modelling, Calibration and Fabrication of Electrical Capacitance Tomography Sensor for Bone Imaging

Electrical capacitance tomography is a technique to measure internal permittivity distribution based on external capacitance measurements which in turn generate a cross-sectional image representing the permittivity distribution thereby the material distribution. It possesses the advantages of non-radioactive, non-intrusive, non-invasive, high imaging speed and low cost over the conventional medical imaging techniques. Inter-electrode measurements are done by placing electrodes around the non-conductive dielectric medium cylinder inside which, the medium to be imaged is placed. This paper emphasizes on modelling and fabricating an electrical capacitance tomography sensor using ANSYS APDL for bone for which the sensor is calibrated using air and water. ECT sensor is modelled and fabricated by mounting 12 identical rectangular copper electrodes were placed symmetrically outside the Poly-vinyl chloride (PVC) cylindrical tube. The output from sensors can be converted to digital voltage values used for image reconstruction in MATLAB.

Graphene Oxide and Its Inorganic Composites: Fabrication and Electrorheological Response.

Composite particles associated with graphene oxide (GO) and inorganic materials provide the synergistic properties of an appropriate electrical conductivity of GO with the good dielectric characteristics of inorganic materials, making them attractive candidates for electrorheological (ER) materials. This review paper focuses on the fabrication mechanisms of GO/inorganic composites and their ER response when suspended in a non-conducting medium, including steady shear flow curves, dynamic yield stress, On-Off tests, and dynamic oscillation analysis. Furthermore, the morphologies of these composites, dielectric properties, and sedimentation of the ER fluids are covered.

Plane Wave Solutions to the Equations of Electrodynamics in an Anisotropic Medium

Under examination is the system of equations of electrodynamics for a nonconducting nonmagnetic medium with the simplest anisotropy of permittivity. We assume that permittivity is characterized by the diagonal matrix ϵ = diag(e1, e1, e2), with the functions e1 and e2 equal to positive constants beyond a bounded convex domain Ω ⊂ ℝ3. Two modes of traveling plane waves exist in a homogeneous anisotropic medium. The structure is studied of the solutions related to the traveling plane waves incident from infinity on an inhomogeneity located in Ω.

A Numerical Method of Determining Permittivity from the Modulus of the Electric Intensity Vector of an Electromagnetic Field

The system of equations of electrodynamics is considered for a nonmagnetic nonconducting medium. For this system, the problem is under study of determining the permittivity e from the given modulus of the electric intensity vector of the electromagnetic field that is the result of the interference of the two fields generated by some point sources of an extraneous current. It is assumed that permittivity is different from a given positive constant e0 only inside a compact domain Ω0 ⊂ ℝ3, whereas the modulus of the electric field intensity vector is given for all frequencies starting from a fixed frequency ω0 on the boundary S of some domain Ω that includes Ω0. It is shown that this information allows us to reduce the original problem to the well-known inverse kinematic problem of determining the refraction index inside Ω by the travel time of the electromagnetic wave between the points of the boundary of this domain. The algorithm for numerical solution of the inverse problem is constructed, and the test calculations on the simulated data are presented.

ГИПОТЕТИЧЕСКАЯ ВИХРЕДВИЖУЩАЯ СИЛА ИЛИ О РЕАЛИЗАЦИИ ТУРБУЛЕНТНОГО ВИХРЕВОГО ДИНАМО В ТРОПИЧЕСКОЙ АТМОСФЕРЕ

The review (Levina et al., 2000) contains a detailed discussion of a series of studies of 1983–1999 related to the creation (1983) and the further development of the mathematical model of a turbulent vortex dynamo. The model was obtained by the methods of the mean-field theory (Krauze and Redler, 1984) and for the first time contained a largescale instability in an electrically non-conducting medium (hydrodynamic alpha effect) generated by the special properties of small-scale helical turbulence of the velocity field. By analogy with the model of the alpha effect in magnetohydrodynamics, such instability is described by a generating term obtained by averaging the equations for the turbulent velocity field and representing a force of some kind in the physical sense. However, unlike the magnetohydrodynamics, where the mean electromotive force acts as the generating term, the interpretation of the result obtained in the model of the hydrodynamic alpha effect caused serious difficulties for a long time. Indeed, the emergence of the mean electromotive force can be explained by the interaction of the magnetic field and the velocity field. In the case of a non-conducting medium, the obtained hypothetical force, for definiteness, let us call it, for example, a “vortex-motive” force, should be created by the velocity field alone. In nature, such force is unknown, but on the basis of new knowledge about atmospheric convection in the tropics, we have been able to interpret the vortex-motive force as a parameterization (Levina, 2018) of the interaction of several effects - rotating deep moist convection (Hendricks et al., 2004), accompanied by intense volumetric heat release, and vertical shear horizontal wind. The proposed parameterization allows us to explain the implementation of turbulent vortex dynamo in the tropical atmosphere. This work was supported by the Russian Foundation for Basic Research (RFBR) under Grant 16-05-00551a

On determination of the permittivity through the module of the vector of the electric strength of the high-frequency electromagnetic field

For nonmagnetic and nonconductive medium the system of electrodynamic equations that corresponds to periodic in time oscillations is considered. An inverse problem of determining permittivity in this system by the given module of the electric strength is studied. It is supposed that the electric fields is a result of the interference of two fields created by point sources. The permittivity e(x) is assumed to be differ from a given positive constant e0 inside of a compact domain W0 Ì R3 only. An information on module of the electric strength is given on the boundary of the domain W contained W0 inside itself and for all frequencies beginning with some fixed frequency w0. The asymptotic behavior of solution of a direct problem related to the electrodynamic equations is studied and the original inverse problem is reduced to the well known inverse kinematic problem. This reduction open a way for constructive solution of the inverse phaseless problem.

Determination of Permittivity from the Modulus of the Electric Strength of a High-Frequency Electromagnetic Field

For an unmagnetized nonconducting medium, a system of electrodynamic equations corresponding to time-periodic oscillations is considered. For this system, we study the problem of determining the permittivity $$\varepsilon $$ from a given electric field magnitude in the electromagnetic field resulting from the interference of two fields produced by external point current sources. It is assumed that the permittivity differs from a given positive constant $${{\varepsilon }_{0}}$$ only inside a compact domain $${{\Omega }_{0}} \subset {{\mathbb{R}}^{3}}$$ and the electric field magnitude is given for all frequencies, starting at a fixed one $${{\omega }_{0}}$$ , on the boundary $$S$$ of a domain $$\Omega $$ surrounding $${{\Omega }_{0}}$$ . By analyzing an asymptotic expansion of the solution to a direct problem at high frequencies, it is shown that, with the use of given information, the original problem is reduced to the well-known inverse kinematic problem of determining the refraction coefficient inside $$\Omega $$ from the travel times of an electromagnetic wave propagating between boundary points of this domain. This reduction opens up the possibility of obtaining a constructive solution of the original problem.