Electrical Field Lines Research Articles

Electrical current-assisted reactive crucible melting technique: Case study of the Fe-Sn system

Modern materials science relies heavily on the advancement of combinatorial high-throughput experimental and computational methods to discover new advanced materials. Among these methods, the reactive crucible melting (RCM) technique stands out as particularly promising. However, a significant challenge in RCM combinatorial analysis is the occurrence of "missing" phases. In this study, we successfully addressed this limitation through the application of electrical current stressing. Furthermore, we investigate the influence of electric current stressing on diffusion rates and the phase formation processes within the reactive crucible. We employed Comsol Multiphysics modeling to analyze the experimental results in the framework of electromigration theory, focusing on the distribution of electrical field lines, temperature gradients, and current density values. Additionally, through the integration of finite element calculations with analysis of Electron Backscatter Diffraction (EBSD) and Magneto-Optical Kerr Effect (MOKE) data, we estimated the gradient of internal stresses along the boundaries of the crucible's reaction volume induced by the diffusion of electrically-induced vacancies and adatoms. Due to modest values of the current density in our experiment and the disparity between the rates of crucible body dissolution and vacancy diffusion, no compressive or tensile stresses were observed. Nonetheless, we propose that the developed electrical current-assisted reactive crucible melting technique holds promise for synthesizing metastable phases existing under high positive or negative pressures.

Conductivity in partially saturated porous media described by porosity, electrolyte saturation and saturation‐dependent tortuosity and constriction factor

ABSTRACTModelling the relationships among bulk conductivity, electrolyte conductivity, porosity and fractional electrolyte‐saturation continues to be based on empirical relationships such as Archie's law or the Bruggeman correlation. Several authors have attempted to connect such empirical models to first principles. This article presents a complete first principles‐based description of conductivity in partially saturated porous media. A geometrical factor is introduced which, together with porosity and saturation, describes the conductivity of partially saturated porous media. This geometrical factor is separated into two intrinsic geometrical descriptors of the electrolyte distribution accounting for tortuosity and constriction. This tortuosity and constriction factor are obtained from integration over the electrical field lines traversing the electrolyte. Bulk and saturation‐dependent conductance descriptions are illustrated using three‐dimensional pore space models and simulated fluid distributions. Describing conductance through porosity, saturation and a geometrical factor, decomposed into separate terms accounting for tortuosity and constrictivity, permits more insightful understanding of conductance in partially saturated porous media. Use and efficacy of this full conductance description is illustrated throughout this article.

Investigation of Electrical Properties of TiO2 Nanocomposite Based Polymer

Past research has reported the challenges regarding on degradation and aging due to high localization of electric field at triple point areas of polymeric insulator. The different materials and designs of polymeric insulator have initiated the partial discharge and arching activities which eventually lead to the insulation failures. The compounding of nanomaterials in the polymer shows a promising result to overcome this problem by redistributing the uniformity of electrical field lines on the insulator. In the present work, ethylene-propylene-diene rubber (EPDM) and titanium dioxide (TiO2) is introduced as nano composites that been embedded into insulator’s housing made of 1) silicone rubber (SiR) and 2) Ethylene Propylene Diene Monomer (EPDM) Rubber. Titanium dioxide (TiO2) is a semiconductor material that can be formed in different sizes either micron or nano-sized filler and has high relative permittivity that be able to reduce the high electrical stresses on high voltage equipment. Meanwhile EPDM shows good mechanical profile, excellent resistance properties and low cost. Therefore, it brings to the new opportunity to fabricate the nanocomposite based on both materials which exhibits an improved electrical properties and good distribution of electric field on polymeric outdoor insulators. In depth investigation was carried out to analyze the effect of different nano-filler loading in the compound and behavior of nanocomposites at different polymer base. An 11kV polymeric insulator is modelled to be simulated by using COMSOL Multiphysics software under dry-clean surface conditions to investigate the electric field distribution at terminal ends and along the insulator creepage path. The Electrostatics interface from the AC/DC Module is used in the evaluation of electric field distribution of insulator model correspondingly with the variations in filler percentage in the host matrix.

Simulation and Visualization of the electrical Activity of the Heart with focal ventricular tachycardia in a 3D Model

Abstract Patients with focal ventricular tachycardia are at risk of hemodynamic failure and if no treatment is provided the mortality rate can exceed 30%. Therefore, medical professionals must be adequately trained in the management of these conditions. To achieve the best treatment, the origin of the abnormality should be known, as well as the course of the disease. This study provides an opportunity to visualize various focal ventricular tachycardias using the Offenburg heart rhythm model. Modeling and simulation of focal ventricular tachycardias in the Offenburg heart rhythm model was performed using CST (Computer Simulation Technology) software from Dessault Systèms. A bundle of nerve tissue in different regions in the left and right ventricle was defined as the focus in the already existing heart rhythm model. This ultimately served as the origin of the focal excitation sites. For the simulations, the heart rhythm model was divided into a mesh consisting of 5354516 tetrahedra, which is required to calculate the electric field lines. The simulations in the Offenburg heart rhythm model were able to successfully represent the progression of focal ventricular tachycardia in the heart using measured electrical field lines. The simulation results were realized as an animated sequence of images running in real time at a frame rate of 20 frames per second. By changing the frame rate, these simulations can additionally be produced at different speeds. The Offenburg heart rhythm model allows visualization of focal ventricular arrhythmias using computer simulations. By selecting the frame rate, the speed of the simulation results can be adjusted accordingly to visualize the electric field lines of focal ventricular tachycardias in more detail. The static and dynamic simulation results could be used in the future for teaching and research, including the training of medical professionals.

Fabrication of Carbon Nanotube Gas Sensor Using Stepwise Dielectrophoretic Deposition Onto Interdigitated Pyrolyzed Carbon Electrodes

Abstract Carbon nanotubes (CNTs) have been implemented in the creation of many micro- and nanodevices due to their physical properties such as large volume-to-surface area as well as their high thermal and electrical conductivity. The paper describes a novel dielectrophoretic stepwise deposition of CNTs (that alternates deposition of CNTs and drying steps) between the interdigitated fingers of carbon electrodes. Multiphysics simulation illustrates the physics of CNT alignment along the electrical field lines that forms a basis for dielectrophoretic deposition of CNTs. This fabrication methodology resulted in creation of proof-of-concept nitrogen gas sensor.

Study on Controllable Thickness and Flatness of Wafer-Scale Nickel Shim in Precision Electroforming Process: Simulation and Validation

Abstract A new approach to precision electroforming of a wafer scale nickel shim using a rotating cathode with an auxiliary cathode mask is developed to improve thickness uniformity and flatness. The effects of critical process parameters, including cathode rotating speed, cathode mask size, and current density, on the thickness uniformity and flatness of electroformed nickel shim are systematically studied based on experiments and simulations. The results show that the thickness uniformity of the deposits is highly dependent on the current density distribution, where a cathode mask can effectively tune electrical field lines and induce a more uniform current density distribution. The simulations and experimental results consistently agree that a minimum thickness nonuniformity of 8% and below 1% on the wafer with a diameter of 80 mm and 40 mm, respectively, can be achieved using a mask with a 70 mm opening size. However, for flatness, the cathode rotating speed influences the surface warpage due to the intrinsic stress. It is also found that the gradient current density can significantly reduce the intrinsic stress with better flatness. The best flatness is controlled below 47 µm and 32 µm on the wafer with diameters of 80 mm and 40 mm, respectively, under the synergistic effect of optimal cathode rotating speed (30 rpm) and gradient current density.

Electrical Signatures of Diffusion-Limited Mixing: Insights from a Milli-fluidic Tracer Experiment

We investigate how diffusion-limited mixing of a layered solute concentration distribution within a porous medium impacts bulk electrical conductivity. To do so, we perform a milli-fluidic tracer test by injecting a fluorescent and electrically conductive tracer in a quasi two-dimensional (2D) water-saturated porous medium. High resolution optical- and geoelectrical monitoring of the tracer is achieved by using a fluorimetry technique and equipping the flow cell with a resistivity meter, respectively. We find that optical and geoelectrical outputs can be related by a temporal re-scaling that accounts for the different diffusion rates of the optical and electrical tracers. Mixing-driven perturbations of the electrical equipotential field lines cause apparent electrical conductivity time-series, measured perpendicularly to the layering, to peak at times that are in agreement with the diffusion transport time-scale associated with the layer width. Numerical simulations highlight high sensitivity of such electrical data to the layers’ degree of mixing and their distance to the injection electrodes. Furthermore, the electrical data correlate well with time-series of two commonly used solute mixing descriptors: the concentration variance and the scalar dissipation rate.

A Creative “Spark” for High-Entropy Alloys

In this issue of Matter, Feng et al. make a breakthrough understanding of an aerosol system for manufacturing unprecedented alloys with excellent catalytic properties. This work will inspire improved 3D nanoprinting techniques for creating new matter forms for broad applications, including additive manufacturing, catalysts, and metallurgy.

Inverse Radon Method Based on Electrical Field Lines for Dual-Modality Electrical Tomography

Usually, the sensitivity matrix-based algorithms are used for image reconstruction in electrical tomography. These algorithms assume that the inverse problem is like that in the well-established medical CT and find successful applications. In the medical CT, rather than using the matrix-based algorithms, the inverse Radon transform and its derivatives dominate. However, these inverse transforms have not been introduced to electrical tomography due to a lack of the link between the parallel projections and electrical distributions. This article presents a map from electrical field lines to parallel lines in the inverse Radon transform and a novel image reconstruction algorithm by using the transform for dual-modality electrical tomography. The transform is realized through mapping the coordinates in electric field to the assumed parallel projections. The points of intersections between electrical field lines from different exciting electrodes are mapped to those of parallel lines from the related projections in a typical inverse Radon transform. Unlike the medical CT, different excitation schemes are related to distinct equivalent projections, and iterative scanning is used to apply all available projected data. Simulated and experimental data are implemented to validate the feasibility and effectiveness of the proposed algorithm, and performance comparisons are made with three algorithms, such as Calderon’s method, iterative method based on electrical field lines, and typical Landweber method. The proposed method yields good quality images in the least time and dynamic flames are monitored. Dual-modality images of material distributions are obtained to capture the ignition and blowout of the flame evolution in a Bunsen burner.

A finite element method for the determination of the relative response of ionization chambers in MR-linacs: simulation and experimental validation up to 1.5 T

In magnetic resonance (MR) guided radiotherapy, the magnetic field-dependent change in the dose response of ionization chambers is typically included by means of a correction factor . This factor can be determined experimentally or calculated by means of Monte Carlo (MC) simulations. To date, a small number of experimental values for at magnetic flux densities above 1.2 T have been available to benchmark these simulations. Furthermore, MC simulations of the dose response of ionization chambers in magnetic fields (where such simulations are based on manufacturer blueprints) have been shown to converge with results that deviate considerably from experimental values for orientations where the magnetic field is perpendicular to the axis of the ionization chamber and the influence of the magnetic field is largest.In this work, was simulated for a PTW 30013 Farmer ionization chamber using an approach based on finite element simulations. First, the electrical field inside the ionization chamber was simulated using finite element methods. The collecting volume of the ionization was not defined in terms of the physical dimensions of the detector but in terms of the simulated electrical field lines inside the chamber. Then, an MC simulation of the dose response of a Farmer type chamber (PTW 30013) was performed using EGSnrc with a dedicated package to consider the effect of the magnetic field. In the second part, was determined experimentally for two different PTW 30013 ionization chambers for a range of magnetic flux densities between B = 0 and 1.5 T, covering the range of commercially available MR-linacs.In the perpendicular orientation, the maximum difference between the simulated values for and the experimental values for was 0.31(30)% and the minimum difference was 0.02(24)%. For the PTW 30013 ionization chambers, the experimental values for were 0.9679(1) and 0.9681(1) for a magnetic flux density of 1.5 T. The value resulting from the simulation was 0.967(3).The comparison of the correction factors simulated using this new approach with the experimental values determined in this study shows excellent agreement for all magnetic flux densities up to 1.5 T. Integrating the explicit simulation of the collection volume inside the ionization chambers into the MC simulation model significantly improves simulations of the chamber response in magnetic fields. The results presented suggest that intra-type variations for may be neglectable for ionization chambers of the PTW 30013 type.

A comparison of methods for in situ discrimination of imaged phase boundaries using electrical capacitance tomography

The detection of hard boundaries using tomographic techniques is challenging due to the measurement resolution inherent in the hardware and smoothing effects created during image reconstruction. This paper is concerned with the development of data processing approaches which enable the use of electrical capacitance tomography (ECT) in real-time applications to visualise interfaces in liquid/liquid and solid/liquid systems based upon phase permittivity differences in media with a high di-electric continuum. The methodologies developed were applied to a series of phantoms to investigate their validity as a tool for imaging phase boundaries in two and three phase systems.In an ECT based tomogram, the interface between phases is exhibited as a transition region; by applying a threshold technique based upon known areas of each respective phase within the system, the transient region can be resolved into a sharp interface. The image error of a tomogram, defined as the deviation of all pixels from their theoretical value, has been calculated using a pixel-by-pixel approach; however this requires exact a priori knowledge and is unsuitable for in-line application; the areal method used in this paper requires global phase distribution information thereby allowing for real-time application. A range of threshold values were applied to tomograms of phantoms of varying geometry and the corresponding image error for each threshold value calculated using both the areal and pixel-by-pixel approaches given above. The threshold value yielding lowest image error from this range is further used in the binary images giving improved tomograms with approximately 40% increase in image accuracy when compared with a default threshold value. Close to the sensor wall, the image becomes distorted due to reconstruction errors arising from decreased density in the electrical field lines, resulting in a circular phantom appearing elongated by approximately 10% when positioned near the wall.

MINIATURE PARALLEL ECT: A PRELIMINARY STUDY USING COMSOL

The usage of Electrical Capacitance Tomography (ECT) is not limited to the imaging of mixtures in process equipment, it also can be used to measure the concentration profiles of component, and in certain case ECT is being used to investigate the boundaries and phase sizes within vessels and pipelines. There are quite a number of type of ECT sensors such as circular structure, square structure, concentric -annulus and parallel structure which are used for particular applications. In this paper, a study was carried out in order to investigate the behavior of electric field on the miniature parallel ECT. Simulations using COMSOL Multiphysics are being done to study the effect of increasing the size of the test object and the effect of increasing the permittivity of the test object. The results show that (1) the electric field lines relatively follow the phantom shape corresponding to the increasing of the size of the phantom and (2) the electrical field lines seems to bend more around the when the permittivity increases. Presented simulations establish first step of investigation, however already proved its usefulness for ECT performance model validation.

Boosting the total ionizing dose tolerance of digital switches by using OCTO SOI MOSFET

This paper performs an experimental comparative study of the total ionizing dose effects due to the x-ray radiation between the silicon-on-insulator (SOI) metal-oxide semiconductor field-effect transistors (MOSFETs) manufactured with octagonal gate geometry and the standard counterpart. Our main focus is on integrated transceivers for wireless communications and smart-power dc/dc converters for mobile electronics, where the transistor is used as the key switching element. It is shown that this innovative layout can reduce the total ionizing dose (TID) effects due to the special characteristics of the OCTO SOI MOSFET bird’s beak regions, where longitudinal electrical field lines in these regions are not parallel to the drain and source regions. Consequently, the parasitic MOSFETs associated with these regions are practically deactivated.

MEMS reconfigurable millimeter-wave surface for V-band rectangular-waveguide switch

This paper presents for the first time a novel concept of a microelectromechanical systems (MEMS) waveguide switch based on a reconfigurable surface, whose working principle is to block the wave propagation by short-circuiting the electrical field lines of the TE10 mode of a WR-12 rectangular waveguide. The reconfigurable surface is only 30 µm thick and consists of up to 1260 micromachined cantilevers and 660 contact points in the waveguide cross-section, which are moved simultaneously by integrated MEMS comb-drive actuators. Measurements of fabricated prototypes show that the devices are blocking wave propagation in the OFF-state with over 30 dB isolation for all designs, and allow for transmission of less than 0.65 dB insertion loss for the best design in the ON-state for 60–70 GHz. Furthermore, the paper investigates the integration of such microchips into WR-12 waveguides, which is facilitated by tailor-made waveguide flanges and compliant, conductive-polymer interposer sheets. It is demonstrated by reference measurements where the measured insertion loss of the switches is mainly attributed to the chip-to-waveguide assembly. For the first prototypes of this novel MEMS microwave device concept, the comb-drive actuators did not function properly due to poor fabrication yield. Therefore, for measuring the OFF-state, the devices were fixated mechanically.

Formation of an out-of-electrode plasma in a high-voltage gas discharge

The formation of an out-of-electrode plasma in a high-voltage gas discharge is studied. The occurrence and self-maintenance of a gas discharge and its associated plasma fluxes on the straight portions of electrical field lines are predicted theoretically and confirmed experimentally. It is shown that the focusing of the gas discharge and plasma fluxes is provided by increasing the length of the field line straight portions toward the symmetry axis of a hole in the anode. It is found that, when the discharge power (more specifically, an accelerating voltage applied to the electrodes of the gas-discharge tube) rises, the straight portions of the field lines elongate and concentrate near the symmetry axis of the hole in the anode. Recommendations are given on using the out-of-electrode plasma in surface micro- and nanostructuring.

Gustav Mie's longitudinal electrical field lines and superluminal signals and longitudinal waves

In his textbook, Gustav Mie states, that the radiation field consists solely of transverse electrical field lines, which are closed. The longitudinal field lines goes without interruption from the positive to the negative charges; they cannot be expelled. This raises the question about the speed of propagation along them. For this, a mathematical description of Mie's field lines is developed the Helmholtz-transverse and longitudinal components of \vec{E} are non-local auxiliary quantities and thus not suitable for that. On the other hand, Mie also states, that the propagation of electromagnetic fields is governed by Maxwell's equations and Poynting's theorem. Here, however, there is a single wave equation for all vector components of the electrical field. In this contribution, a minimum modification of Maxwell's equations is proposed, which yields both, an instantaneous Coulomb field and longitudinal electrical radiation.

Gustav Mie's longitudinal electrical field lines and superluminal signals and longitudinal waves

In his textbook, Gustav Mie states, that the radiation field consists solely of transverse electrical field lines, which are closed. The longitudinal field lines goes without interruption from the ...

Parameter Analysis of Millimeter-Wave Waveguide Switch Based on a MEMS-Reconfigurable Surface

This paper presents a novel concept of a millimeter-wave waveguide switch based on a microelectromechanical (MEMS)-reconfigurable surface with insertion loss and isolation very similar to high performance but bulky rotary waveguide switches, despite its thickness of only 30 μm. A set of up to 1470 micromachined cantilevers arranged in vertical columns are actuated laterally by on-chip integrated MEMS comb-drive actuators, to switch between the transmissive state and the blocking state. In the blocking state, the surface is reconfigured so that the wave propagation is blocked by the cantilever columns short-circuiting the electrical field lines of the TE 10 mode. A design study has been carried out identifying the performance impact of different design parameters. The RF measurements (60-70 GHz) of fabricated, fully functional prototype chips show that the devices have an isolation between 30 and 40 dB in the off state and an insertion loss between 0.4 and 1.1 dB in the on state, of which the waveguide-assembly setup alone contributes 0.3 dB. A device-level yield analysis was carried out, both by simulations and by creating artificial defects in the fabricated devices, revealing that a cantilever yield of 95% is sufficient for close-to-best performance. The actuation voltage of the active-opening/active-closing actuators is 40-44 V, depending on design, with high reproducibility of better than (σ = 0.0605 V). Lifetime measurements of the all-metal, monocrystalline-silicon core devices were carried out for 14 h, after which 4.3 million cycles were achieved without any indication of degradation. Furthermore, a MEMS-switchable waveguide iris based on the reconfigurable surface is presented.

Engineering of oriented myocardium on three-dimensional micropatterned collagen-chitosan hydrogel.

Surface topography and electrical field stimulation are important guidance cues that aid the organization and contractility of cardiomyocytes in vivo. We report here on the use of these biomimetic cues in vitro to engineer an implantable contractile cardiac tissue. Photocrosslinkable collagen-chitosan hydrogels with microgrooves of 10 µm, 20 µm and 100 µm in width were fabricated using polydimethylsiloxane (PDMS) molds. The hydrogels were seeded with cardiomyocytes, placed into a bioreactor array with the microgrooves aligned with the electrical field lines, and stimulated with biphasic square pulses at 1 Hz and 2.5 V/cm. At Day 6, cardiomyocytes were aligned in the direction of the microgrooves. When cultivated without electrical stimulation, the excitation threshold of engineered cardiac tissues using micropatterned hydrogels was significantly lower than using smooth hydrogels, thus showing the importance of cell alignment to cardiac function. The success rate of achieving beating constructs was higher with the application of electrical stimulation. In addition, formation of dense contractile cardiac organoids was observed in groups with both biomimetic cues. The cultivation of cardiomyocytes on hydrogels with 10 µm grooves yielded 100% beating tissues with or without electrical stimulation, thus suggesting a smaller groove width is necessary for cells to communicate and form proper gap junctions. However, electrical field stimulation further increased cell density and enhanced tissue morphology which may be essential for the integration of the tissue construct to the native heart tissue upon implantation. The biodegradability of the hydrogel substrate allows for the rapid translation of the engineered, oriented cardiac tissue to clinical applications.

Particle Collecting in a 13.56-MHz Radio-Frequency Methane Discharge

Radio-frequency methane plasmas are widely used for deposition of amorphous hydrogenated coatings a-C:H in PECVD reactors. According to our experimental conditions, particles are also generated in the plasma. The study of the chemical nature of these particles requires a sufficient quantity to be collected at the end of the experiment. We show that a modification of the electrical field lines above the grounded electrode improves particle collecting.