Coil Dimensions Research Articles

Magnetometric Investigations of Biomagnetic Signals: Magnetocardiography

Introduction. Superconducting magnetometers based on SQUIDs (SQUID- Superconducting QUantum Interference Device) are currently used to register weak magnetic fields generated in various human organs and measured outside the body (in the environment). The creation of information technology, which is a set of methods and software tools combined into a technological chain that ensures registration, storage, pre-processing, analysis of measurement data and automatic diagnostic output, is an essential science-intensive component that determines the possibilities and success of the applied use of non-contact diagnostic systems of the human heart The purpose. Article presents new algorithms for spatial analysis of cardiomagnetic signal measurement results. The algorithms are based on the inverse problem solution, when the magnetic field source is matched to the spatial distribution of the magnetic signal and the parameters and spatial configuration of the source are determined. A model of the cardiomagnetic source was used in the form of a system of current density vectors, which are distributed in a plane that is parallel to the measurement plane and crosses the volume of the heart. Results. The inverse problem is solved using the apparatus of two-dimensional integral Fourier transformations. The data transformation algorithm allows to correctly take into account the design of the magnetic flux transformer (the dimensions of the pickup coils, their spatial location and the electrical connection scheme). Algorithm modifications have been developed for most of the known (implemented in existing magnetocardiographs) designs of magnetic flux transformers of the first and second order gradientometers. The operation of the algorithm is modeled on real data of magnetometric investigations of the human heart. Investigations have shown that the application of the proposed algorithms allows obtaining new information about the spatial configuration of the magnetic signal source in the human heart, which can be used in the future for the diagnosis of human heart diseases. Keywords: magnetocardiography, inverse problem of magnetostatics, Fourier transform, SQUID gradientometer.

On-demand ferrofluid droplet formation with non-linear magnetic permeability in the presence of high non-uniform magnetic fields

The magnetic actuation of ferrofluid droplets offers an inspiring tool in widespread engineering and biological applications. In this study, the dynamics of ferrofluid droplet generation with a Drop-on-Demand feature under a non-uniform magnetic field is investigated by multiscale numerical modeling. Langevin equation is assumed for ferrofluid magnetic susceptibility due to the strong applied magnetic field. Large and small computational domains are considered. In the larger domain, the magnetic field is obtained by solving Maxwell equations. In the smaller domain, a coupling of continuity, Navier Stokes, two-phase flow, and Maxwell equations are solved by utilizing the magnetic field achieved by the larger domain for the boundary condition. The Finite volume method and coupling of level-set and Volume of Fluid methods are used for solving equations. The droplet formation is simulated in a two-dimensional axisymmetric domain. The method of solving fluid and magnetic equations is validated using a benchmark. Then, ferrofluid droplet formation is investigated experimentally, and the numerical results showed good agreement with the experimental data. The effect of 12 dimensionless parameters, including the ratio of magnetic, gravitational, and surface tension forces, the ratio of the nozzle and magnetic coil dimensions, and ferrofluid to continuous-phase properties ratios are studied. The results showed that by increasing the magnetic Bond number, gravitational Bond number, Ohnesorge number, dimensionless saturation magnetization, initial magnetic susceptibility of ferrofluid, the generated droplet diameter reduces, whereas the formation frequency increases. The same results were observed when decreasing the ferrite core diameter to outer nozzle diameter, density, and viscosity ratios.

Analysis of coil element distribution and dimension for matrix gradient coils.

The goal of this work is to analyze the influence of the distributions and dimensions of the coil elements and to present a method for improving the performance of the matrix gradient coil. Three typical models (five structures in total) are presented, and a double-layer biplanar matrix gradient coil is used to install coil elements. Two metrics, namely, the role of coil elements and mutual inductance between coil elements, are proposed to assess the performance of coil systems. An optimization approach to design matrix gradient coils is introduced based on analyzing the distributions and dimensions of coil elements. The flexibility of the magnetic field generation of the designed coil structure is demonstrated by generating full third-order spherical harmonic fields and different oblique gradient fields. Matrix gradient coils with suitable distributions are capable of generating target magnetic fields. The role of coil elements quantitatively illustrates that the coil elements have different impacts on generating magnetic fields. Increasing the coil element dimension within a certain range can reduce the mutual inductance between coil elements and improve the performance of the coil system. The designed novel double-layer biplanar matrix gradient coil achieves an acceptable performance in generating different magnetic fields. The proposed metrics can provide theoretical support for designing matrix gradient coils and evaluating their performance. The role of coil elements contributes to analyzing the distributions of coil elements to decrease the number of coil elements and power amplifiers. The mutual inductance between coil elements can be a reference for designing the dimensions of coil elements.

Physics-based modeling and multi-objective parameter optimization of excitation coil for giant magnetostrictive actuator used on fuel injector

Serving as one of the core component, the excitation coil can exert remarkable influence on the output performance of giant magnetostrictive actuator (GMA) for electronic controlled fuel injector. In this paper, a multi-objective coil optimization scheme is proposed to balance the conflicting response speed and magnetic field intensity determined by the coil parameters. Firstly, a physics-based coil model is established for optimization, whose parameters can be directly calculated by the coil dimensions. Then, with the current response of the coil calculated, a multi-objective optimization framework is conducted attempting to get the selection guideline for the enameled wire diameter of the coil. The optimal choices exist when the outer diameter of the enameled wire falls in 0.9∼1.6 mm, and the inner/outer diameter ratio is relatively high. Finally, a series of experiments are conducted and the results indicate that the proposed model is able to accurately describe the current response throughout the operating frequencies, and the optimization scheme can provide a valuable roadmap to design coil for high performance GMA.

Fast Design Optimization Method Utilizing a Combination of Artificial Neural Networks and Genetic Algorithms for Dynamic Inductive Power Transfer Systems

Multiple parameters with large nonlinear characteristics must be considered simultaneously to design the coil dimensions of static inductive power transfer (SIPT) systems. The design of dynamic inductive power transfer (DIPT) systems is more challenging due to the large number of parameters needed to be considered. In the conventional artificial neural network (ANN)-based design approach, optimal coil dimensions are found using ANN that has learned the nonlinear characteristics between coil dimensions and magnetic characteristics using the finite element method (FEM). However, this approach requires a large amount of training data, and it is difficult to reach an optimum design if there are many design criteria. In order to overcome these challenges, this paper proposes a design optimization method using two approaches: improving the time efficiency of ANN training data collection by superposing the magnetic fields from the coils and improving the input value of ANN using a genetic algorithm. Design results predicted by the ANN are compared with FEM simulation, circuit simulations, and experimental results to verify the validity of the proposed algorithm. The FEM and circuit simulation results and the ANN prediction results match with errors of 10.2% or less for all design requirements. Experimental results are provided for a 3 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\;$</tex-math></inline-formula> kW DIPT system with four transmitter coils and an automated test rail. Comparison results between ANN predicted values and experimental values match with an error of less than 12.7%.

Numerical Analysis and Design of an EMF Birdcage Wearable Device for the Treatment of Alzheimer's Disease: A Feasibility Study.

In this study, we performed a numerical analysis of a novel EMF Birdcage wearable device for the treatment of Alzheimer’s disease (AD). We designed the new device to generate and radiate a frequency of 64 MHz and a specific absorption rate (SAR) of 0.6 W/kg to a simulated human brain tissue. We determined these parameters from our experimental studies on primary human brain cultures at the Indiana University School of Medicine (IUSM). We found that this frequency and SAR decreased the toxic Aβ levels in the cell cultures. The frequency of 64 MHZ has good skin depth penetration, which will easily pass through the various head layers, including hair, skin, fat, dura, the cerebrospinal (CSF), and grey matter, and reach deeply into the brain tissues. The SAR of 0.6 W/kg was achieved with lower power input and energy, decreasing the probability of thermal injury. Therefore, these parameters enhance the safety of these potential treatments. This Birdcage device emulates a small-scale MRI machine, producing the same 64 MHz frequency at much lower operating input power. In this work, we utilized a high-frequency simulation system (HFSS/EMPro) software to produce the birdcage structure for the required EMF parameters. The 64 MHz radiating frequency produced the scattering S11 parameter of −15 dbs. We obtained a SAR of 0.6 W/kg when an input power of 100 W was applied. The coil dimensions were found to be near 15 cm in height and 22 cm in diameter, which fits in wearable systems. We found that the distribution of the electric field and SAR radiate homogeneously over the simulated human head with good penetration into the brain, which proves to be an appropriate potential therapeutic strategy for Alzheimer’s disease.

A Comparative Study on Overall Efficiency of Two-Dimensional Wireless Power Transfer Systems Using Rotational and Directional Methods

Two-dimensional (2-D) wireless power transfer (WPT) systems can be controlled by either the directional method or the rotational method. The rotational method refers to the use of omnidirectional transmitter generating rotational flux regardless of the load positions, while the directional method refers to the use of omnidirectional transmitter generating magnetic flux directly toward the power-consuming load directions. This article compares the overall efficiency of the two methods for 2-D WPT systems. Theoretical analysis reveals that the directional WPT can be more efficient than the rotational WPT with either single or multiple loads when the magnetic field vector is controlled within the feasible zones; and the efficiency difference between the two methods are more significant when the dimensions of the receiver coils are smaller. Both simulation and experimental results are consistent in validating the two discoveries. They indicate that the averaged efficiency of the directional method is at least 5% higher than that of the rotational one.

Planar Pose Estimation System Design via Explicit Spatial Representation Model of Concurrent AC Magnetic Fields

This study proposes a new approach to pose estimation algorithm and system implementation based on concurrent AC magnetic fields from an array of magnetic coils. The typical dipole model used in the existing research has inappropriate prediction characteristics when the operating range of dynamic objects is widened, as in the cases of mobile robots or drones. An enlarged circular loop with a meter-sized coil dimension and its corresponding excitation electronics are developed to overcome this shortcoming. In designing a pose estimation algorithm, a compact mathematical model is derived through the suggested spatial representation and the partial derivatives with respect to states. As a result, an accurate and computationally efficient pose estimation framework has been achieved, which validates the feasibility of the developed spatial representation model with actual magnetic measurements. While the proposed method can provide a general formula for a 3D dynamic case, yet a reduced model is specifically presented for a typical indoor 2D application. The performance of the proposed algorithm is demonstrated through the ground experiment in an indoor building environment with 50m2 coverage. Compared with the ground truth, static error variation from the low-order polynomial case is computed to be sub-centimeter, which allows an onboard algorithm implementation. Finally, the experiment via dynamic trajectory tests demonstrated the relative position accuracy of 1.2 % and heading error of about 2 degrees within the operating range.

ArTGen: An Arduino-based trigger generator to remotely handle pulse timing in TMS units

Abstract Introduction: Transcranial magnetic stimulation (TMS) protocols are associated with specific combinations of stimulation parameters, including the location of the targeted site, E-field intensity and orientation, pulse shape and duration, variable/fixed inter-pulse interval (IPI), and coil shape and dimension. Among these parameters, IPI may significantly affect the direction of induced neuroplasticity and the possible interference of habituation and expectation effects with TMS-evoked potentials. The TMS units are not always flexible enough to generate customized pulse sequences, thus external devices/software are commonly used. To remotely handle the randomization of IPI, we designed an effective and cheap device (ArTGen – Arduino Uno-based Trigger Generator) for generating arbitrary sequences of square-wave digital pulses. Materials and methods: Using an external foot-switch pedal the TMS experimenter is able to handle the ArTGen’s firmware to remotely drive a customized sequence of pulses in the TMS unit. We designed the firmware to switch among four conditions (single pulse, sequence of jittered pulses, pause and stop) based on a single and double foot-switch taping. We used two BNC sockets to manage respectively the foot-switch signal and the randomized TTLs in output to ArTGen. We tested ArTGen on Magstim Rapid2 with AirFilm® figure-8 coil in tasks with the following characteristics: (i) %Maximal Stimulation Output at 50%; (ii) 100 pulses and (iii) central pulse frequencies set to either 0.1, 5, 10, 15, or 20 Hz. Results: Our results show that all the TTLs released by ArTGen were correctly detected by Magstim Rapid2, and highlight a short delay (computed as the difference between the Arduino trigger and the Magstim Rapid2 output) of about 5μsec across all pulse frequencies. Conclusion: ArTGen is a stand-alone, portable, and not cumbersome opensource device used to randomize TMS pulses or to trigger/synchronize different devices in a closed-loop TMS system with microseconds of accuracy. Keywords: TMS unit, Arduino board, Inter Pulse Interval randomization, Closed Loop TMS System Synchronization

Reconfigurable Coil Array for Near-Field Beamforming to Compensate for Misalignment in WPT Systems

This work develops a reconfigurable coil array that compensates for the misalignment between coils in magnetic resonance coupled wireless power transfer (WPT) systems. By tuning the magnitude of the currents induced in the coil array with the variable capacitors that load them, the effect of reconfiguring the size and/or shape of the coil can be achieved. Therefore, the near field can be steered in a certain direction to overcome the notorious misalignment problem in WPT systems. For experimental demonstration, a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\times 1$ </tex-math></inline-formula> array is designed and fabricated for a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$60\times 60$ </tex-math></inline-formula> mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> coil. For a vertical distance between Tx and Rx coils of 10 mm, which is 16.7% of the largest coil dimension, the transfer efficiency maintains more than 40% and up to 141.6% misalignment. This is more than an 81% increase over the conventional coil. For a vertical distance of 30 mm or 50%, the minimum transfer efficiency is 37.1% up to 100% misalignment, which is almost 5.5 times that of the conventional counterpart. The results suggest that the demonstrated technology successfully overcomes the notorious misalignment problem in both short-range and midrange WPT systems and even in asymmetric systems where the reconfigurable coil array technique is applied only on the Rx.

A Position Sensor With Novel Configuration of Linear Variable Differential Transformer

This paper presents a position sensor based on a novel configuration of linear variable differential transformer. Design and optimization of the position sensor using finite element method are presented. The measurements are also conducted to validate experimentally the sensor performance. The sensor has short air core coils and long magnetic armatures. The axis of the rectangular excitation coil and two antiserially connected rectangular pick up coils is perpendicular to the motion direction of the position sensor. The coils are located between two parallel silicon steel laminations serving as the armatures. The position sensor is optimized with compromise between minimization of nonlinearity error and maximum sensitivity. The main advantage of the proposed position sensor is the small ratio of coils dimensions to the working range. The position sensor is operated for excitation frequencies of 500 Hz, 1000 Hz, and 2000 Hz. The maximum nonlinearity error is less than 1.5% for the theoretical results and it is less than 2% for the measured results in ±90 mm position range.

DESIGN OF INDUCTION COIL FOR OXYGEN FREE COPPER PRODUCTION

This paper deals with the design of an induction coil (IC) intended to be used for an oxygen free copper production. This coil differs in design because it should be placed in a vacuum or in a chamber filled with noble gas, such as Argon. The designed coil must be suitable for melting the copper in this environment. The coil design means, using the simulation of the melting process to determine the best, coil geometry, type of crucible, the required current, frequency, the consumed power, and time required for this process. These results will be used to determine the parameters of the induction furnace AC power source suitable for feeding such a melting process efficiently. The Finite Element Analysis (FEA) intended to simulate the heating process to determine the best coil dimensions, and choosing the crucible. It is found that the best crucible used for the melting of copper is the carbon crucible.

Development of Superconducting Coils using (Ba, Na)Fe2As2 Round Wires with Large Critical Current

We report the fabrication of 10 m-class (Ba, Na)Fe2As2 long round wires and coils using these round wires. Round wires are fabricated by powder-in-tube (PIT) method and hot-isostatic-press (HIP) technique. To increase Ic keeping the diameter of the wire constant, the cross section area of the superconducting core is enlarged by changing the dimensions of metal sheaths. At 4.2 K under a high field of 100 kOe, Jc of a short segment of HIP wire reaches 42 kAcm-2, which is comparable to the highest Jc of IBS round wires of 44 kAcm-2. Furthermore, Ic of the HIP wire at 4.2 K under 10 kOe and 100 kOe reaches 95 A and 54 A, respectively, which is about twice the value of the previous report. We also fabricated a small demonstration superconducting coil using 12.5 m long PIT wires by HIP method. Ic of the whole coil is ∼60 A under the self-field, and magnetic field at the center of the coil reaches 2.6 kOe. The coil generated the magnetic field of 43 Oe/A, which is almost consistent with the calculated field from the coil dimensions.

Intrinsic Conformational Preferences of the Charged Amino Acids in Disordered Proteins

Conformational equilibria in the unfolded states of proteins have many important biological roles, from regulating how some proteins fold and maintain structural stability, to describing the macromolecular details of intrinsically disordered proteins (IDPs), a protein class that does not adopt physiologically stable structures and instead utilizes unfolded states to facilitate their functions. Recently, to better understand the structural properties of IDPs, we analyzed both the sequence dependence to the mean hydrodynamic size of IDPs in water, as well as the impact of heat on the coil dimensions, showing that the sequence dependence and thermodynamic energies associated with intrinsic biases for the polyproline II (PPII) backbone conformation could be obtained. This result is important because PPII is used biologically for protein–protein and protein–nucleic acid interactions and thus has a role in molecular recognition. Experiments that evaluate how the hydrodynamic size changes with compositional changes in the IDP revealed amino acid-specific preferences for PPII that were in excellent quantitative agreement with calorimetry-measured values from small unfolded peptides and also those inferred by a survey of the protein coil library. Here, a set of charge-substitution experiments were used to measure the intrinsic preferences of the charged amino acids (i.e., lysine, arginine, glutamic acid, and aspartic acid) for the PPII backbone conformation, the results of which provide insight into how long-range charge-charge interactions and short-range effects, such as hydration and sterics, can modulate the structural and dynamical properties of IDPs, an increasingly important protein class in cell function.

Stress-deformed state of the coil of the pyrolysis furnace at deviation of the shape of pipes

A distinctive feature of the pyrolysis furnaces of hydrocarbon raw materials from other types of furnaces operated at the facilities of oil and gas chemical enterprises is the strict operating conditions necessary for the implementation of this process. At the same time, the temperature of the radiant coil in operating conditions can reach 1050 ° C. In this regard, the probability of failure of coils of pyrolysis furnaces due to defects and damages during operation is extremely high. In addition, variations in coil shape and dimensions that occur during manufacturing or operation can negatively affect the overall stress-strain state of the coil during operational loads. In this work, the influence of permissible deviations in the shape and dimensions of pipes used in the welding of the coil on its stress-strain state in working conditions is investigated.

Design generator of magnetic power (Based on gap rotor-stator motor magnet)

The paper discusses magnetic power generators; if a conductor moves across the magnetic field, a voltage difference will occur at the ends of the conductors. The voltage rises as it approaches the area and vice versa, so electricity arises in cycles: positive - zero - negative - zero. In this study utilizing the rotation of a magnetic motor caused by the unbalance repulsive force between magnets. The design of the tool starts with designing a generator model that will be made. The design of generators is based on calculations obtained through the reference of generator design. The generator design uses magnets instead of anchor coils on the rotor (source of magnetic flux) and copper wire coils as anchor coils on the stator. This design considers rotor and stator parameters, including the distance between magnets, rotor diameter, rotor plate thickness, area of a magnetic area, number of stator coils, number of stator windings, and stator coil dimensions, and calculate generator output power. Tool testing is done to obtain data from tools that have been made. In testing the comparison of the results obtained from the study of the target to be achieved, if the results have not yet reached the target, then improvements are made to the results obtained as expected. Tests were carried out with no load and burden. The results showed that the rotor speed in the generator design could be achieved by determining the number of rotor poles, the generator voltage is influenced by the flux density produced by permanent magnets and the number of stator windings.

Structural and Energetic Characterization of the Denatured State from the Perspectives of Peptides, the Coil Library, and Intrinsically Disordered Proteins.

The α and polyproline II (PPII) basins are the two most populated regions of the Ramachandran map when constructed from the protein coil library, a widely used denatured state model built from the segments of irregular structure found in the Protein Data Bank. This indicates the α and PPII conformations are dominant components of the ensembles of denatured structures that exist in solution for biological proteins, an observation supported in part by structural studies of short, and thus unfolded, peptides. Although intrinsic conformational propensities have been determined experimentally for the common amino acids in short peptides, and estimated from surveys of the protein coil library, the ability of these intrinsic conformational propensities to quantitatively reproduce structural behavior in intrinsically disordered proteins (IDPs), an increasingly important class of proteins in cell function, has thus far proven elusive to establish. Recently, we demonstrated that the sequence dependence of the mean hydrodynamic size of IDPs in water and the impact of heat on the coil dimensions, provide access to both the sequence dependence and thermodynamic energies that are associated with biases for the α and PPII backbone conformations. Here, we compare results from peptide-based studies of intrinsic conformational propensities and surveys of the protein coil library to those of the sequence-based analysis of heat effects on IDP hydrodynamic size, showing that a common structural and thermodynamic description of the protein denatured state is obtained.

A new semi-analytical approach for self and mutual inductance calculation of hexagonal spiral coil used in wireless power transfer systems

Several methods have been proposed in the literature for the calculation of self and mutual inductance. These methods include the use of complex integral analysis, the necessity of having primary and secondary coils with the same dimensions and the limitations of the ratio of the coil dimension to the distance between the coils. To overcome these restrictions, a new semi-analytical estimation method has been proposed in this paper. Calculation the self and mutual inductance by using the same basic formula which is based on Biot Savart Law prevents the formation of complex integrals and helps create a simple solution method. In order to verify the results obtained with the analytical approach, two hexagonal coils with 10 and 20 cm outer side lengths were produced by using litz wire with a conductive cross section of 1.78 mm2. The results obtained with the new approach are compared with the finite element analysis, other work presented in the literature and experimental results in order to prove the accuracy of the proposed method.

An analysis of coil dimensions on induction heating machine against microstructure and hardness distribution as new candidate of projectile-resistant steel plates materials

The field of defense and security requires ballistic resistant materials for self-protection. Ballistic resistant materials must be able to withstand projectile spin rate and absorb impact energy. A combination of hardness on the surface and ductility on the other side is required to make the projectile resistance plate. Hardness is required to withstand the projectile rate, while ductility is required to reduce cracking, brittle fracture and absorption of impact energy. The objective of this study is to find the effect of the coil shape on microstructure and hardness distribution on the steel plate that is carried out by surface hardening using an induction machine. Medium carbon steel plate with the thickness 8 mm is austenitized using the induction heating machine with coil dimension and shape variations. Austenizing on the surface and rapid quenching in oil media are up to 900 °C. A micro-observation was conducted on quench plates and hardness distribution on their cross-section. The result of microstructure observation and micro Vickers hardness test of coil variation at a diameter 5 mm and with the number of turns of 2 and 3 is microstructures on all sides formed with martensite structure and equal hardness on the entire cross-section, so that no surface hardening formed. Micro-observations showed martensite structure on the surface side and the ferrite and perlite structures are still visible on the middle and lower sides using 8 mm diameter coils and 2 turns. The maximum hardness is 497 HVN on the upper side surface and 257 HVN on the lower side surface using an 8 mm diameter coil and 2 turns. An increased hardness on one of the plate surfaces while maintaining the ductile on the opposite side can be proposed as a candidate for a ballistic-resistant plate through further research

A New Magnetic Structure of Unipolar Rectangular Coils in WPT Systems to Minimize the Ferrite Volume While Maintaining Maximum Coupling

In the wireless power transfer system, the transmission efficiency and power transfer capability depend on the coupling coefficient ( k). Usually, the coupling of the air-core unipolar coil system is weak. For improving k, the ferrite core is used. In traditional ferrite arrangement, the ferrite core size is kept approximately equal to the coil dimensions, which increases the overall weight and volume of the system. This brief proposes a novel and simple ferrite arrangement of unipolar rectangular coils, which maintains the maximum achievable k and minimizes the volume of ferrite used. Pythagoras' theorem is used to calculate the position and length of the ferrite bars. Furthermore, various possible ferrite arrangements are studied and compared with the proposed ferrite arrangement (PFA). The proposed arrangement saves 81.24% volume of the ferrite used with a decrement of only 6.93% in k (at the 150-mm air gap) over the traditional arrangement. Finally, a prototype of the PFA is developed, and the results are verified.