Conductivity Of Medium Research Articles

Improved methane production from anaerobic organic wastewater treatment by nitrogen-doped carbon

The nitrogen-doped carbons (NC) were prepared by a simple pyrolysis method using polyaniline as the precursor. The effect of carbonization temperature on the properties of the synthesized NC was investigated. The optimal temperature was determined as 600 °C according to the properties of the obtained materials and the performance on improving the methane production by the anaerobic sludge. When the optimal NC was used as the conductive medium in the anaerobic sludge, the methane yield and production rate were increased by 35% and 10%, respectively. The effect of the NC loading on the activity of the microorganisms was also investigated. It was found that the degradation of the organics in the bacteria was enhanced by adding NC. Moreover, the bacterial and archaeal communities were significantly affected by the added NC material, and Methanosaeta with the direct interspecific electron transfer (DIET) ability have been enriched in anaerobic sludge. This indicated that the NC materials with surface defects can improve the organics degradation and the microbial extracellular electrons transfer, thereby promoting the methane production during the anaerobic wastewater treatment.

Performance evaluation of combined radio frequency heating and conductive medium injection for heavy oil recovery

At present, radio frequency heating is regarded as a novel approach for crude oil extraction from heavy oil reservoir. But in the absence of any external assistance, it is difficult to further improve its heating performance, especially for the reservoirs with poor thermal conductivity and low electrical conductivity. Therefore, to solve the problem, this paper proposes a hybrid technique that combines the radio frequency heating and injection of conductive medium into hydraulic fractures. A mathematical model is firstly established to describe the radio frequency heating process, and then the model is verified by the temperature data obtained from laboratory experiment. Finally, the effects of the conductive medium properties, fracture position and width on reservoir temperature distribution are analyzed. Simulation results indicate that the specific heat, thermal conductivity and density of conductive medium have no obvious effect on reservoir temperature distribution, but the electrical conductivity within the range of 10–30 S/m can apparently cause temperature variation. Additionally, the influence of fracture position on temperature distribution is tremendous, but the fracture width fails to impact the temperature distribution due to small width ranges. This investigation provides a better solution for radio frequency heating to obtain greater heat extraction performance.

Electric field assisted motion of a mercury droplet

Field-assisted self-assembly, motion, and manipulation of droplets have gained much attention in the past decades. We exhibit an electric field manipulation of the motion of a liquid metal (mercury) droplet submerged in a conductive liquid medium (a solution of sulfuric acid). A mercury droplet moves toward the cathode and its path selection is always given by the steepest descent of the local electric field potential. Utilizing this unique behavior, we present several examples of droplet motions, including maze solving, electro-levitation, and motion on a diverted path between parallel electrodes by controlling the conductivity of the medium. We also present an experimental demonstration of Fermat's principle in a non-optical system, namely a mercury droplet moving along a refracted path between electrodes in a domain having two different conductivities.

Effect of Different Carbon Materials on the Conductivity of Epoxy Resin Conductive Coatings

In this work, the conductive coating was prepared by electrostatic spraying with graphene and Multi-walled carbon nanotube (MWCNTs) as conductive medium and epoxy resin powder as film-forming material, in order to solve the pro·blem of high content and uneven dispersity of conductive particles in conductive coatings prepared by brushing method. The resistance of the coating was measured by four probe method, the dispersity of conductive particles in the coating was analyzed by scanning electron microscope (SEM), and the conductive mechanism of the coating was analyzed by percolation theory model. The results show that the conductive particles can be dispersed evenly in the whole coating by electrostatic force. Meanwhile, the electrostatic force can also stretch the conductive particles in the coating along the direction of the thickness of that. The flake graphene is vertically arranged in the coating, and the curled MWCNTs forms the conductive network of "island-bridge" structure. The conductive particles laped each other to form a conductive path, which greatly reduced the content of conductive particles. The seepage threshold of graphene conductive coating was only 1.5 wt.%, which lower than that of the MWCNTs conductive coating, which is 3 wt.%. The resistance of epoxy coating containing with 0.5 wt.% graphene is 3397 Ω·m, and that of epoxy coating containing with 0.5 wt.% MWCNTs is 1049 Ω·m.

A Comparison of Different Divergence-free Solutions for 3D Anisotropic CSEM Modeling Using Staggered Finite Difference Method

This paper presents a staggered finite difference (FD) method for numerical modeling of 3D controlled-source electromagnetic (CSEM) data in an anisotropic conductive medium. The traditional Krylov subspace methods may not be convergence for EM modeling in strong electrical anisotropy due to the variation of the conductivity in the sea-bottom sediments over a range of frequencies (0.1-10 HZ). The algorithm is based on a modified version of the curl-curl equations with scaled grad-div operator (CCGD) in frequency domain. In this approach, we integrate the divergence correction term in the original system with its importance controlled by scaling factors (the same values as model resistivities are used in this paper) and avoid the application of the iterative divergence correction. The corresponding responses calculated by the CCGD and the traditional CC-DC approach for the VTI ocean canonical reservoir model are nearly identical. Then based on the case, we examine the numerical performance of the CCGD approach, and compare it with the CC-DC in terms of computing time and iteration number. The results indicate that the proposed CCGD approach is efficient and stable over different frequencies.

Numerical simulation of the relationship between resistivity and microscopic pore structure of sandstone

The microscopic pore structure of the sandstone rock layer determines the water richness and permeability of the rock layer. Mastering the relationship between the resistivity of the sandstone rock layer and the microscopic pore structure is an important way to evaluate the water richness of the water-bearing rock layer from qualitative analysis to quantitative calculation. Using the finite element method to study the basic single and double modal structures in the sandstone layer of constant current field, the matrix resistivity, pore throat water resistivity, pore shape and difference in single sand model, pore throat model and capillary model are studied. The relationship between the direction of the current and the resistivity of the rock layer. The results show that the resistivity of the sandstone rock layer changes with the change of the matrix resistivity and has a linear relationship. When the contrast ratio between the sand and the matrix resistivity is between 10−1 and 10, the resistivity of the rock layer changes linearly with the resistivity of the sand; when the contrast ratio is greater than 10, the influence of the resistivity of the matrix is smaller. And when the contrast is greater than 103, the resistivity of the rock layer tends to be constant; when the contrast is less than 10−2, the smaller the resistivity of the sand grains, the smaller the effect on the resistivity of the rock layer, and when the contrast is less than 10−3, the resistivity of the rock layer tends to constant. Since the water in the sandstone rock layer is the main conductive medium, when the water resistivity is fixed, the smaller the water saturation or the smaller the porosity, the smaller the pores through which water can flow and the greater the resistivity of the sandstone formation. When the microstructures of the horizontal and vertical rock layers are different, different transmitting and receiving electrode layouts have a greater impact on the resistivity of the rock layer, and the different microstructures lead to electrical anisotropy of the rock layer. The research results of this paper lay the foundation for the analysis of the relationship between the more complex sandstone rock model resistivity and micro-pore structure, and the quantitative calculation of the water richness of the sandstone rock layer.

Magnetic convection in a nonuniformly rotating electrically conductive medium in an external spiral magnetic field

The research is devoted to the stability of convective flow in a nonuniformly rotating layer of an electrically conducting fluid in a spiral magnetic field. The stationary and oscillatory modes of magnetic convection are considered depending on the profile of the angular rotation velocity (Rossby number Ro) and on the profile of the external azimuthal magnetic field (magnetic Rossby number Rb). The non-linear dynamic system of Lorentz type equations is obtained by using the Galerkin method. Numerical analysis of these equations has shown the presence of chaotic behavior of convective flows. The criteria of the occurrence of chaotic movements are found. It depends on the parameters of convection: dimensionless numbers of Rayleigh Ra, Chandrasekhar Q, Taylor Ta, and external azimuthal magnetic field with the Rossby magnetic number Rb for Rayleigh (Ro = −1) and Kepler profiles of the angular rotation velocity of the medium.

Conceptual design, manufacturing and investigation of dipole plasma ‎antenna with the capability of frequency variation in the VHF band

In this article, we simulate and manufacture a dipole plasma antenna whose frequency is variable in the VHF band. The conductive medium of antenna is the plasma created by the DC discharge in a glass tube. To excite the antenna, we use a cylindrical aluminum coupler installed at the middle of the antenna. By varying values of gas pressure, input impedance of circuit and the voltage deference between two ends of the plasma medium, one can change the working area of antenna at a few hundred gigahertz frequency interval. Simulation and numerical calculations are carried out for an antenna with 78cm length and 2cm radius at 0.8 bar pressure exerted under 15KV voltage difference. At constant pressure, by using some parallel resistors in the antenna circuit, the impedance of discharge circuit is changed and consequently the plasma density is varied. For plasma frequencies and , using semi-experimental formulae, analysis shows resonances at frequencies 250MHz and 311MHz, respectively, which are in good agreement with the experimental results which take place at frequencies 217MHz and 272MHz. Additionally, simulation is accomplished for a metal antenna with corresponding geometry whose working frequency detected at 184MHz.

High-efficiency, fifth-harmonic generation of a joule-level neodymium laser in a large-aperture ammonium dihydrogen phosphate crystal.

High-energy deep ultraviolet (UV) sources are required for high-density plasma diagnostics. The fifth-harmonic generation of large-aperture neodymium lasers in ammonium dihydrogen phosphate (ADP) can significantly increase UV energies due to the availability of large ADP crystals. Noncritical phase matching in ADP for (ω + 4ω) was achieved by cooling a 65 × 65-mm crystal in a two-chamber cryostat to 200 K. The crystal chamber used helium as the thermally conductive medium between the crystal and the crystal chamber, which was surrounded by a high-vacuum chamber with a liquid nitrogen reservoir. A temperature variation of 0.2 K across the crystal aperture was obtained. The total conversion efficiency from the fundamental to the fifth harmonic at 211 nm was 26%.

Activation of Nanocomposite Liposomal Capsules in a Conductive Water Medium by Ultra-Short Electric Exposure

In a system that simulates aquatic biological media, the possibility of activating nanocomposite liposomal capsules (NLCs) containing spherical electrically conductive nanoparticles on the outer and inner surfaces of the liposomal membrane, using an external ultrashort electric action, has been shown. The decapsulation effect was registrated by fluorimetry methods. The key role of conducting nanoparticles in increasing the sensitivity of NLCs to external ultrashort electrical impact is shown. A theoretical model of nonthermal interaction of NLCs with ultrashort electric pulses is constructed, within the frame of which an expression is obtained for the critical value of the electric field strength, which determines the threshold for the appearance of the decapsulation effect in a conducting medium. The described mechanism of decapsulation explains the selective nature of ultrashort pulsed electrical impact on the NLCs.

Surface Layer Formation at Dynamic Combined Exposure by Two-Component Electrode

This article is devoted to the study of workpieces surface layer state, resulting from dynamic exposure of a two-component electrode with imposition of electric field. The objects considered in the work are details with complex profile. Such parts are used in aviation, rocket and space technology and in oil and gas industry. They include impellers and flow part of turbopump bodies, augers, blade wheels, which have areas of variable curvature with limited tool access to treatment area. The authors show that mixture in combined process of two-component processing media from current-carrying granules and conductive liquid medium supplied at high speed to the treatment area, provides the required quality of surface layer due to the combined dynamic exposures on the material being treated. The parameters combination of electric field and kinetic energy of conductive granules allows you to control the magnitude and depth of material hardened layer in treatment area. Experimental studies have shown the increase in resource and durability of critical assemblies for aerospace equipment and oil and gas apparatus.

On one version of the Godunov method for calculating elastoplastic deformations of a medium

Godunov's hybrid method suitable for numerical calculation of elastoplastic deformation of a solid body within the framework of the classical Prandtl-Reis model with the non-barotropic state equation is described. Mises’ fluidity condition is used as a criterion for the transition from elastic to plastic state. A characteristic analysis of the model equations was carried out and their hyperbolicity was shown. It is noted that, if one takes the Maxwell-Cattaneo law instead of the Fourier law, then the Godunov hybrid method can be applied to calculate the deformation of a thermally conductive elastoplastic medium, since in this case the medium model is of a hyperbolic type. The algorithm for solving the systems in which there are equations that do not lead to divergence form is described in detail; Godunov's original method serves to integrate systems of equations represented in divergence form. When calculating stream variables on the faces of adjacent cells, a linearized Riemannian solver is used, the algorithm of which includes the right eigenvectors of the model equations. In the proposed approach, the equations written in divergence form look like finite-volume formulas, and others that do not lead to divergence form look like finite-difference relations. To illustrate the capabilities of the Godunov hybrid method, several one- and two-dimensional problems were solved, in particular, the problem of hitting an aluminum sample against a rigid barrier. It is shown that, depending on the rate of interaction, either single-wave or two-wave reflections described in the literature can be implemented with an elastic precursor.

Uniform null controllability for parabolic equations with discontinuous diffusion coefficients

In this article, we study the null-controllability of a heat equation in a domain composed of two media of different constant conductivities. In particular, we are interested in the behavior of the system when the conductivity of the medium on which the control does not act goes to infinity, corresponding at the limit to a perfectly conductive medium. In that case, and under suitable geometric conditions, we obtain a uniform null-controllability result. Our strategy is based on the analysis of the controllability of the corresponding wave operators and the transmutation technique, which explains the geometric conditions.

Galvanic Impulse Wireless Communication for Biomedical Implants

Wireless intra-body communication is a promising approach for providing efficient and secure connectivity for medical implants. The low power consumption of the electronics and the conductivity of the biological tissues facilitate the system implementation, which makes the technique more power-efficient than the traditional radio frequency wireless systems. The galvanic intra-body communication uses the electrical current for signal transmission in the conductive medium of the biological tissues. In this paper, we propose an ultra-low-power communication approach by implementing a galvanic impulse method for communication between an implant and an on-body device. The communication system is designed, manufactured with off-the-shelf electronic components, and measured in the phantom and in-vivo animal experiment. The implant power consumption is 45 μW for the data rate of 64 kbps with a bit error percentage below 0.5% for the implant depth of 14 cm. The design supports long-lasting battery-powered implant sensory and communication system.

A Modular Magnetic Induction Tomography System for Low-Conductivity Medium Imaging

Due to the noncontact, nonradiative, and low-cost features, magnetic induction tomography (MIT) is highly applicable in conductive medium imaging. To meet the demands of low-conductivity medium imaging in industrial and biomedical applications, a portable, flexible, and extensible MIT system with high-phase detection precision is proposed. The proposed system is designed with different modules. Therefore, it is flexible to extend and meet different applications. The sensor modules can be used as both the excitation and the detection. The detected signal is directly demodulated at the sensor end, which avoids the external interference that may be introduced into the transmission of the detected signal. A phase demodulation part is designed which can achieve 0.0068° phase detection precision. Furthermore, the designed system does not need to rely on other instruments to realize the signal generation and demodulation, which makes the MIT system independent and portable in the practical application. The sensing coils have high consistency, and the signal-to-noise ratio (SNR) of the demodulated signal is over 60 dB. To illustrate the performance of the system, the capability of reconstructing low-conductivity saline solutions is studied. The images of conductivity distribution are obtained using the Tikhonov regularization method. The minimum detectable volume of saline solution is 10 mL, with a spatial resolution of 16.6%. The minimum detectable conductivity is 0.1 S/m, and the maximum detectable depth is 40 mm. The reconstructed results indicate the feasibility of low-conductivity medium imaging in the industrial and biomedical applications by the proposed MIT system.

Quantification of Displacement for Tactile Sensation in a Contact-type Low Intensity Focused Ultrasound Haptic Device

Tactile threshold of low-intensity focused ultrasound (LIFU) haptic devices has been defined as the minimum pressure required for tactile sensation. However, in contact-type LIFU haptic devices using an elastomer as a conductive medium, the tactile threshold is affected by the mechanical properties of the elastomer. Therefore, the tactile threshold needs to be redefined as a parameter that does not change with the mechanical properties of the elastomer. In this study, we used the LIFU haptic device to investigate the displacement of the elastomer surface at the tactile threshold while controlling the pulse duration, pulse repetition frequency, and pressure. We analyzed the displacement magnitude and rate to determine their relationship to the pressure. The displacement magnitude is the spatiotemporal peak of the displacement, and the displacement rate is the initial slope of the displacement at the starting point of LIFU pulse. The tactile threshold measured by the applied pressure showed the U-shaped graph, and the minimum pressure of 475 kPa at 2 ms and 407 kPa at 300 Hz was measured. The tactile threshold measured by the displacement show that the tactile sensation can be evoked at the small displacement magnitude (<3 μm) when the high displacement rate is present (>1.56 mm/s). Furthermore, the large displacement magnitude is required to induce the tactile sensation when the displacement rate is low. This result shows that the tactile threshold of a contact-type LIFU haptic device is affected by both the displacement magnitude and rate of the conductive medium. Our findings can be used as a guideline for developing a contact-type LIFU haptic device regardless of the elastomer used.

The Phenomenon of Electroohmic Transformation

Peculiarities of electric current distribution in an anisotropic electrically conductive medium are considered and dependences of its longitudinal and transverse components on geometrical factors are established. In the case of a rectangular plate of length a, height b, and width c, the selected crystallographic axes are located in the plane of the side face (a × b), and one of these axes is oriented at an angle α to the edge α. Application to the upper and lower end faces of the plate of some potential difference leads to the appearance of longitudinal and transverse components of the flowing electric current. This leads to the possibility of transforming the electric current magnitude. The methods of optimizing the transformation coefficient magnitude which is determined by both the magnitude of the anisotropy of the electrical conductivity of the plate material and the coefficient of its shape k = a/b. The design variants of anisotropic electrically conductive transformers are proposed. The use of this transformation effect makes it possible to expand the practical use of electroohmic phenomena. This principle of transformation will expand the areas of its use in metrology and measurement technology.

Efficient two-dimensional atom localization in a five-level conductive chiral atomic medium via birefringence beam absorption spectrum

We have theoretically investigated two-dimensional atom localization using the absorption spectra of birefringence beams of light in a single wavelength domain. The atom localization is controlled and modified through tunneling effect in a conductive chiral atomic medium with absorption spectra of birefringent beams. The significant localization peaks are investigated in the left and right circularly polarized beam. Single and double localized peaks are observed in different quadrants with minimum uncertainty and significant probability. The localized probability is modified by controlling birefringence and tunneling conditions. These results may be useful for the capability of optical microscopy and atom imaging.

The impact of diagenesis precipitation on fracture permeability in naturally fractured carbonate reservoirs

Naturally fractured carbonate reservoirs are often described as very heterogeneous systems due to the carbonate depositional environment and to the subsequent diagenesis processes such as mineral precipitation in fractures. Fluid flow behaviour in fractures is highly influenced by the fracture aperture size and its morphology. Mineral precipitation can alter the fracture effectiveness to the fluid flow and cause a partial or entire blockage of fractures. Therefore, accurate characterisation of the fracture morphology can help to enhance the prediction of the fluid flow behaviour in naturally fractured carbonate reservoirs. Mineral precipitation on fracture walls can reduce the fracture aperture significantly. As a result, the fracture permeability affected notably, which reduces the flow potential through fractures as well as changes the flow pattern. The objective of this work is to predict the flow behaviour in fractures under various levels of mineral precipitation to mimic reality. We have approached this objective by using outcrop-based models supported by a set of rock and fluid properties of a nearby fractured formation. Then, the model tested for the gas flow using the derivative plot technique of the synthetic well testing data. The simulation results have shown that mineral cementation can cause a partial blockage in fractures, hence a reduction in their flow capacity, as fractures become a less conductive medium. Nevertheless, the matrix medium can enhance the fluid flow in fractures by providing a bypass path to the fluid to overcome the sealed fractures. In this work, a formula has concluded to estimate the reduction in fracture permeability based on the fraction of the precipitated cement. In the studied formation, the core description has shown that 34% of fractures were blocked, which can lead to a reduction in the permeability by 29–64% and by 37–83% with and without matrix contribution, respectively. Thus, including the fracture morphology in the simulation model enables us to predict the performance of fractured carbonate reservoirs accurately.

The Proximity Effect in Twin Line with Round Conductors Placed in Conductive Medium

Power lines are often placed in ground or sea water, which are weakly conductive media. In the paper, a new analytical formula, taking into account the proximity effect in a twin line placed in a weakly conductive medium, is derived, and the effect of the conductive medium is considered. In the first step, one of the wires is replaced by a current filament, and the solution is sought for magnetic vector potential around the filament. In the next step, an analytical formula for eddy currents induced in a long straight conductor of circular cross-section placed near to the current filament in the extensive conductive medium is found by using the method of separation of variables. The correctness of the formula is checked by comparison with the results obtained via other methods like finite and boundary element methods. Then, the effect of various parameters on the eddy current distribution is tested. Next, the proximity effect in a twin symmetrical line is considered, and the effect of the conductivity of the surrounding medium is investigated. The results indicate that the conductive medium weakens the proximity effect, but in typical cases (ground and sea water), the effect is very small.