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This paper introduces a possible mechanism to explain the changes in neurons following extremely low frequency magnetic fields (ELF-MFs). The model in this paper contains two parts: the physical part and the bio-trigger part. The first part is an electric current equation, which is a generalization of the Nernst–Plank equation with the exposure of ELF-MF, and the second bio-part is a phenomenological model, which is a simple two-state channel with two steady state open (O) state and closed state (C). The two parts are complementary. The first part is utilized to explain changes about synaptic plasticity following ELF-MF exposure at embryonic and postnatal age. The second part is used to simulate the process of three different types of neurons reported by previous papers. According to the results, the present model is feasible for the simulation process. The concept of ion mobility or permeability is emphasized in this paper in part I, and channel state transition probabilities are paid much attention to in part II. In this paper, the ion mobility or permeability is supposed to have close relationships with ion channel transition probabilities, which connects the two parts of the model together. [ABSTRACT FROM PUBLISHER]

This paper presents a novel approach for incorporating noncuboidal and rotated cuboidal sources of magnetic field in 3-D Fourier modeling. Based on the periodicity present in the geometry, a Fourier integral is applied in two directions. By changing the integration boundaries in the $y$ -direction to a linear function of the $x$ -direction, nonideally shaped magnetic field sources (i.e., coils and permanent magnets) are incorporated. From the electromagnetic example geometries analyzed in this paper, the magnetic field as derived with 3-D Fourier is over 99% accurate compared to 3-D finite-element models. [ABSTRACT FROM AUTHOR]

This paper presents a simple dynamic vector-play model to calculate the iron loss and describe the vector hysteresis behavior of a non-oriented (NO) electrical steel sheet (ESS) under 50 Hz rotating magnetic fields. Based on the iron loss separation theory, the proposed model is separated to the static hysteresis component and eddy current component. The static hysteresis component is constructed by vector play model, which is identified by using 1 Hz minor B – H loops. And two coefficients \omega x and \omega y are introduced to consider the anisotropic property of NO ESS and the excess loss of eddy-current component under 50 Hz magnetic field. The validity of the proposed dynamic vector hysteresis model is verified by comparing it with the experimental results under various 50 Hz magnetic field conditions. [ABSTRACT FROM AUTHOR]

This paper develops a novel magnetomotive forces (mmfs) distribution model along the transverse direction for the 3-D analysis of linear induction motor, and it investigates the influence of a laterally asymmetric cap-secondary on the thrust, vertical force, lateral force, and efficiency in a prototype single-sided linear induction motor for linear metro. First, the mmf distribution model and its working conditions are defined, and the model is transferred into a mathematical model. Second, the air-gap flux and secondary eddy current in a prototype linear motor with a cap-secondary are obtained by a 3-D space harmonic analytical method. Third, the thrust, vertical force, lateral force, and efficiency of the test motor are analyzed with various lateral deflection, and the power factor in secondary is also presented. Finally, these results are experimentally verified by measurements on the test rig of the linear motor, and the comprehensive effect on the operating performance can be accurately calculated by the mmf model. [ABSTRACT FROM PUBLISHER]

In this paper, we present a micromagnetic modeling study on the switching property of segmented grains assisted by circularly polarized magnetic field at microwave frequencies and the actual recording process. This paper provides insightful understanding of the switching dependence on the Gilbert damping constant and the optimization for suppressing the impact of possible damping constant distribution. The recording processes with ac field generated by a spin torque oscillator on the media consisting of segmented grains are also investigated. In this microwave assisted magnetic recording (MAMR) process, the segmentation of the grains with exchange breaking layers enables the best utilization of the ac field. The MAMR simulations show significant signal-to-noise ratio (SNR) gain over today's perpendicular recording for medium for media with grain pitches <8~nm. Grain-pitch limited SNR performance can be achieved for medium grain pitches as small as 5 nm while achieving sufficient thermal stability simultaneously. At 4.5 nm grain pitch, MAMR shows significantly higher SNR than that predicted by corresponding HAMR simulations. It is concluded that MAMR should enable areal density capability of 4 Tb/in^2 and beyond and its SNR performance is superior to HAMR at all densities. [ABSTRACT FROM PUBLISHER]

This paper presents an analytical method for evaluating the magnetic flux density produced by spherical permanent magnet arrays used in spherical actuators. To investigate the performances of magnetic arrays, analytical models are used due to their lower computational time compared to 3-D finite element analysis. This paper presents an analytical model for the calculation of the magnetic field produced by a spherical permanent magnet array using magnetic charge modeling. To obtain the total magnetic field solution, first the magnetic field produced by a single spherical tile is considered. By means of superposition, the magnetic field produced by the array is obtained. Two magnet array topologies are modeled and the analytical results are validated using finite element analysis. [ABSTRACT FROM AUTHOR]

In this paper, a semi-analytical model is derived to calculate the magnetic flux density around a magnetic shield with finite dimensions. The proposed modeling is based on Fourier modeling, which is extended with mode-matching. The described model has less than 0.2(%) error with respect to finite element modeling for the given configuration. Furthermore, the paper shows that assuming a magnetic shield with infinite dimensions introduces a significant error with respect to a magnetic shield with finite dimensions. [ABSTRACT FROM AUTHOR]

This paper proposes an equivalent magnetic hysteresis (B–H) curve for magnetic multiscale problems of complex materials composed of electrical conductors separated by insulating material. The conventional method, which assigns equivalent material constants to each material, cannot properly express the local eddy current loss and the extra magnetic field derived from the local eddy current. To solve this problem, we derive the magnetic hysteresis curve from the volume-averaged magnetic flux density and the surface magnetic field in the micro-model, and apply this curve to the macro-model. The mesh number of the novel macro-model is reduced to around one-tenth that of the micro-model. Magnetic hysteresis is treated by a free energy magnetic hysteresis model, and the macro-model ignores electrical conductivity. The magnetic hysteresis curve and the numerically calculated losses are consistent in the micro- and macro-models. The proposed method well expresses the local eddy current phenomena. [ABSTRACT FROM AUTHOR]

This paper deals with the modeling of vector fields that exhibit hysteresis. A general class of models of vector magnetizations with hysteresis that form a natural extension of the Classical Scalar Preisach Model is defined. Although the modeling was done for the 2-d case, the same theory can be extended to the 3-d case as well. After reviewing some general properties of conservative fields, the specific case of unit magnitude vector fields is discussed. The paper focuses on discussing the properties of a general vector hysteresis operator (hysteron). The mathematical approach followed here can be applied not only to the magnetic hysteresis, but also to any hysteresis process. Some examples of vector hysterons, deduced from the general definition, are presented and their properties analyzed. [ABSTRACT FROM PUBLISHER]

This paper presents an improved integration-type E&S modeling for applications under high magnetic flux density conditions. In the conventional integration-type dynamic E&S modeling, we assumed linear increment of higher harmonic components including in the magnetic field strength waveforms versus the magnetic flux density. However, the higher harmonic components decrease after getting a peak value in the rotational magnetization process around the saturation region (1.5–1.8 T). The integration-type dynamic E&S modeling was improved with the measured database, and the verification with a simple problem for high magnetic flux conditions was demonstrated in this paper. [ABSTRACT FROM PUBLISHER]

This paper deals with the mathematical definition of a general vector hysteresis operator in 3-D, as an extension of previous papers where the theory has been limited to the 2-D case. Although the paper is mainly focused on magnetic hysteresis, the definitions and the results reported can be applied to any general physical phenomenon that exhibits hysteresis. We show here the main general properties of the general hysteresis operator in 3-D. [ABSTRACT FROM AUTHOR]

In this paper, the finite-element method (FEM) is used to calculate the spinning torque of the permanent-magnet (PM) spherical motor. Three-dimensional (3-D) FE model of the PM spherical motor is established. Spinning torque distribution on the spherical surface and its variation curve on the equator are obtained respectively. In order to avoid the complicated torque calculation process under 3-D magnetic field and thus reduce the computational burden, the torque calculation method based on the 2-D conversion model is proposed. This method equivalently simplifies the magnetic field of the spherical PMs and the shape of cylindrical stator windings to be simulation parameters of the 2-D conversion model. With these parameters, 2-D conversion model of the PM spherical motor is established. Spinning torque variation curves obtained by the 3-D model and the 2-D conversion model respectively are compared and the results agree extremely well. By comparing the maximum static torque (MST) obtained under different configuration parameters of the PM spherical motor, it is found that the errors are within the allowable range. Therefore, the reliability of the proposed torque calculation method in the paper is verified. Finally, based on the 2-D conversion model, variation curves of the MST with the length of the air gap, the ampere turns, the length of stator windings and the outer radius of stator windings are obtained, and they are validated by those based on the 3-D model. These results can provide the basis for the optimization of the PM spherical motor. [ABSTRACT FROM PUBLISHER]

This paper compares two different identification methods of a static rate-independent energy-based hysteresis model with regard to the dynamic hysteresis loop shape prediction when coupled to the parametric magnetodynamic lamination model. The values of hysteresis model parameters are determined solely based on the quasi-static major loop. A semiphysical approach identifying the reversible and irreversible field components independently and a purely mathematical scheme using a differential evolution optimization algorithm determining all parameters simultaneously are compared. Both variants of parameter identification are analyzed in terms of hysteresis loop shape prediction for quasi-static as well as dynamic loops. [ABSTRACT FROM AUTHOR]

Recent advances have been made into modeling the soft-magnetic materials using the surface charge model. Until now, the model has only been used to model the field outside the soft-magnetic material. To include the saturation in the future, the magnetic field inside the material should be known. In this paper, the model is used to calculate the field inside the material when three different shapes of boundaries are considered. Comparing the results with Finite Element Method shows that the differences in the air region are <1 mT and those in the soft-magnetic region are <4 mT. Larger discrepancies can, however, occur near the corner of the material. [ABSTRACT FROM AUTHOR]

In this paper, a methodology to calculate the shielding effectiveness of enclosures with slots at low frequency in the near magnetic field is presented. This modeling technique is based on the magnetic moments and the transmission line approach and makes specific assumptions. It is applied to a slot of small size relative to the dimensions of the enclosure. The slot is electrically short. This technique is validated in the case of a real enclosure with numerical simulations and experimental data. This method is dedicated to the case of mechatronics boxes using in electric and hybrid vehicles, it allows obtaining the results with sufficient accuracy precision for dimensioning a magnetic shielding in a short time. [ABSTRACT FROM PUBLISHER]

The magnetic tunnel junction (MTJ) effect has been widely applied in information technology and has brought about many revolutionary products in the past decade. In the meantime, many research studies on linear magnetoresistive sensors based on MTJ have been published to improve their performance metrics, such as linear field range, sensitivity, hysteresis, and noise. Though the frequency response of high-speed magnetic reading has been researched, the performance and application of linear magnetoresistive sensors with bridge configuration for high-frequency sensing remain underexplored. In this paper, we proposed an equivalent impedance network model of packaged linear magnetoresistive sensors based on MTJ with Wheatstone bridge configuration, and derived the corresponding frequency-dependent performance model, considering the influences of the parasitic capacitances and the amplitude of the applied magnetic field. Our work shows that the frequency characteristics of linear magnetoresistive sensors are closely associated with their $RC$ time constants, which depends on their resistances and parasitic capacitances. The useful bandwidth of an MTJ linear sensor is also related to the amplitude of the applied magnetic field. The bandwidth changes negligibly with the varying magnetic field in the range of less than 30% of the saturation field, but increases rapidly when it exceeds 30% of the saturation field. [ABSTRACT FROM AUTHOR]

This paper investigates the interaction of an initially uniform magnetic field with an electrically conducting slab that moves perpendicularly to the magnetic field with arbitrary time-dependent velocity. It is demonstrated that the problem of determining the time-dependent Lorentz force and the time-dependent Joule heat in the slab is mathematically equivalent to solving a 1-D heat diffusion problem with time-dependent boundary conditions and to submitting the solution to a nonstandard postprocessing procedure. For the particular case of an impulsively driven slab we exploit the mathematical analogy between magnetic diffusion and heat diffusion by translating a textbook solution of the corresponding heat-transfer problem into exact and previously unknown relations for Lorentz force and Joule heat. Moreover, we use a 1-D finite-difference code to investigate more general time dependencies of the velocity including smooth accelerations and random velocity changes. Our numerical determination of reaction times ( \(\boldsymbol {T_{98}}\) ) of the Lorentz force in the case of smooth accelerations provides a useful design tool for the development of Lorentz force flowmeters with short reaction times. [ABSTRACT FROM AUTHOR]

In this paper, we present a 3-D numerical model of an integral formulation for the efficient computation of 3-D magnetic fields in hysteretic media with (time) periodic sources. The hysteretic medium is described by an isotropic vector generalization of the classical scalar Jiles–Atherton model. The nonlinear algebraic system is solved using Picard–Banach iterations in the frequency domain. The full matrices arising after the discretization of the main (linear) operators are suitably compressed and distributed among the nodes of a parallel computer system. The numerical model is applied for the nondestructive micromagnetic characterization (of mechanical properties) in metallic materials. In particular, the problem of estimating incremental permeability is analyzed. [ABSTRACT FROM AUTHOR]

This paper presents comparative studies of magnetic characteristics and dynamic performances for two mutually coupled dual-channel switched reluctance machines (DCSRMs) with the same properties and different winding connections. A 2D/3D finite element method (FEM) is used to analyze the magnetic field distributions and calculate the static inductance and torque characteristics of these two DCSRMs. The different static magnetic characteristics, details of mathematical models and dynamic performances prediction at transient and steady states for these two DCSRMs under single- and dual-channel operation modes are presented and compared. Finally, an experimental setup for two high speed 12/8-pole DCSRMs with different winding connections is built. The experimental results of these two DCSRMs such as phase current, average torque, copper loss, iron loss and efficiency under different operation modes are presented and compared to verify the analytical and simulation results. [ABSTRACT FROM PUBLISHER]

Recent advancements in micro/nano-domain technologies have led to a renewed interest in ultra-high resolution magnetic navigation platforms. A magnetic navigation platform (MNP) has been developed at the MagLev Microrobotics Lab of the University of Waterloo, Waterloo, ON, Canada. This platform consists of two separate basic components: a magnetic drive unit and a microrobot. The magnetic drive unit produces and regulates the magnetic field for noncontact propelling of the microrobot in an enclosed environment. The MNP is equipped with an eddy-current damper to enhance its inherent damping factor in the microrobot's horizontal motions. This paper deals with the modeling and analysis of an eddy-current damper that is formed by a conductive plate placed below the levitated microrobot to overcome inherent dynamical vibrations and improve motion precision. The modeling of eddy-current distribution in the conductive plate is investigated by solving the diffusion equation for vector magnetic potential. An analytical expression for the horizontal damping force is presented and experimentally validated. It is demonstrated that eddy-current damping is a key technique to increase the damping coefficient in a noncontact way and improve levitation performance. This damping can be widely used in applications of magnetic actuation systems in micromanipulation and microfabrication. [ABSTRACT FROM PUBLISHER]

Heat-assisted magnetic recording (HAMR) is likely the successor of perpendicular magnetic recording (PMR) technology. The quality of HAMR writing is dominated not by the magnetic field gradient (as in PMR), but by the high thermal gradient generated by the laser heating spot. Knowledge of temperature dependence of magnetic parameters: anisotropy field Hk(T), saturation moment Ms(T) and anisotropy field distribution (\sigma Hk) in the proximity of Curie temperature (Tc) is crucial for media development. Here we describe a new system to probe the magnetic properties close to Tc, as well as a semianalytical model to explain the results. The model takes into account the thermal fluctuations; input into the model are experimentally measured data for Ms(T), Hk(T), mean field demagnetization factor, \sigma Hk and grain size distribution. In the paper we present two types of data: 1) thermal erasure in the absence of a magnetic field; and 2) thermomagnetic writing, allowing the estimate of the switching field distribution at high temperatures. [ABSTRACT FROM AUTHOR]

In this paper, a new iterative algorithm for the analysis of properties of magnetic shielding systems is proposed. Since such shielding systems for low frequency applications are composed of thin-walled shells with magnetic materials of high permeability, the thin shell approximation is adopted and a numerical integral formulation of the ensuing magnetostatic problem is obtained in the form of a convolution equation. This algebraic system is eventually solved iteratively by exploiting the convolution properties of the discrete Fourier transform. The convergence properties of the procedure are analyzed and tested on two case studies where isotropic and anisotropic magnetic shields are used. [ABSTRACT FROM AUTHOR]

The effects of the element-edge shape on the stepped impedance properties are investigated in this paper. Stepped giant magnetoimpedance elements with three types of edge shape were fabricated, and their impedance profiles were examined. The stepped impedance property of all elements was obtained, and it was confirmed by domain observation that impedance jumps occurred at the transition points of the domain structure between the single and multiple domains. The strength of the magnetic field in which the impedance jump occurs depends on the edge shape. The impedance jump that occurs under the smallest field strength for elements with edge shape broadens gradually toward the end of the element, whereas that under the strongest field strength for elements with edge shape becomes sharp. The difference in the properties of the stepped impedance due to the different edge shapes is explained by the change in the shape anisotropy effect based on a simplified domain-structure model. [ABSTRACT FROM AUTHOR]

This paper proposes a new quantum cellular automaton (quantum CA) for simulating macroscopic electromagnetic fields. The final target is to simulate the macroscopic electromagnetic fields on a quantum computer. In the proposal approach, Maxwell's historical model, which was explained the nature of electromagnetic fields in 1861, has been modified for a quantum CA model to simulate the electromagnetic fields. Then, a state transition rule for CA is determined by a strategy based on the quantum mechanics and the quantum computation theories. One of originalities of the proposed approach is that a system using quantum gates is superstructed to simulate magneto-static fields from currents. First, a modified Maxwell model for applying to quantum CA was shown. Second, by using the quantum computation theory, a quantum gate system to simulate the magnetic fields from currents was described. Finally, the proposed approach was applied to an example of magnetostatic field simulation. [ABSTRACT FROM PUBLISHER]

Low-frequency magnetic shielding is usually made with finite-size metallic plates. The discontinuity on the shield is unavoidable, and degrades the performance of shielding. In this paper an equivalent circuit method was proposed to model the joint of conductive plates, and to evaluate the magnetic fields around the joint. The circuit equation using total cell current was presented. The modeling method was validated experimentally. Shielding performance of a shield against various joint parameters was also investigated. It is found that reasonable shielding performance can be achieved if the joint is provided with an adequate mating surface area and multiple fixing points. [ABSTRACT FROM AUTHOR]

The analytical surface charge model is used to calculate the magnetic field of magnets in 3D in an unbounded domain. The method combines high accuracy with a short calculation time. However, in the classical method the relative permeability of the magnet is assumed to be equal to air. This introduces an error in the resulting magnetic field strength. In this paper the permeability of the magnet is taken into account in the form of a redistribution of magnetic surface charge. As such, an exact solution for the magnetic field at low relative permeability is obtained. The interaction force between two magnets is calculated using the newly obtained expressions for the magnetic field and compared with FEM and measurements. [ABSTRACT FROM AUTHOR]

The paper proposes a fast and accurate modeling technique for calculating the electromagnetic fields around a planar surface crack with arbitrary depth profile in a ferromagnetic metal, induced by a high-frequency ac current-carrying wire of arbitrary shape. The proposed technique first reduces the governing 3-D problem into two new equivalent 2-D electrostatic Dirichlet problems. Then, the method-of-moments is used to solve the new resultant problems. The main feature of the proposed technique is its remarkable high computation speed as compared to the conventional methods. The efficiency of the proposed technique is demonstrated by comparing the experimental and theoretical results. [ABSTRACT FROM AUTHOR]

Direct-drive electromagnetic actuators with multiple degrees of freedom emerge to replace cascaded actuators to improve performance and reliability. An example is the rotary-linear actuator as widely described in literature and used in robotic applications. Checkerboard permanent magnet (PM) arrays are exploited to create a suitable magnetic field distribution. In this paper, a novel PM-array is presented which can be used in combination with classical windings for rotation and translation to realize a cost-efficient actuator. A 2D model is presented and validated to approximate the rotational and translational performance of the actuator. [ABSTRACT FROM PUBLISHER]

This paper describes the magnetic field analysis of a ring core taking account of hysteretic properties of magnetic materials by the play model. The numerical results are compared with the measured results to demonstrate the effectiveness of the play model and some features of the play model due to its rate-independent properties are discussed. Furthermore, the novel time-periodic explicit error correction method suitable for the magnetic field analysis taking account of the hysteretic property by the play model is proposed for the improvement of the convergence to the steady state in the time-periodic transient analysis. [ABSTRACT FROM PUBLISHER]

Magneto-rheological elastomers (MREs) are a class of smart materials which can adjust their modulus or stiffness by an applied magnetic field. Thus, MREs can be used as controllable stiffness elements in various engineering systems. In order to use them for engineering applications, characterizations of MRE behaviors under magnetic fields and developments of dynamic models (such as a phenomenological model) that can capture the behaviors must be studied well. This paper focuses on modeling of MRE samples under shear deformation, which is a common mode of operation of MRE materials in structural engineering. It proposes a dynamic model that combines the Ramberg-Osgood model and the Maxwell model. The model is validated using experimental characterization test data. The results show that the proposed dynamic model can be effectively used for predicting the dynamic behavior of MREs under shear deformation. [ABSTRACT FROM AUTHOR]

A three-dimensional analytical modeling of the magnetic field of the stator-ironless axial flux permanent magnet (AFPM) machine under open-circuit condition is presented in this paper. It involves the analytical solution of the governing field equations in the region between back-irons in the cylindrical coordinate, in which the magnets are assumed to be axially magnetized and have constant relative recoil permeability. The proposed modeling method is applied to a specific AFPM machine, and the analytical results are in good agreement with those of three-dimensional finite element analysis (FEA). [ABSTRACT FROM AUTHOR]

In this work we present a physical-related model of vector hysteresis for magnetic simulation of nanometric structures. The mathematical formulation, based on a generalization of the Preisach and Stoner-Wohlfarth models, is very simple and elegant. The numerical implementation is very easy and the computation time required for the simulations is extremely fast. However the accuracy is not comparable with the codes based on the micromagnetic theory, but it is sufficient for the use as preprocessing of more accurate and more complex methods, in order to speed up the convergence. In this paper the model identification is performed for a nanoscale spin valve using the data generated by a 3D micromagnetic code. [ABSTRACT FROM AUTHOR]

In this paper, a novel rectangular waveguide-based technique to accurately characterize linear and resonant microwave materials is presented. The proposed method resolves major challenges associated with phase ambiguities and guess parameters that have appeared in waveguide techniques reported thus far and establishes new, accurate formulations for simultaneous calculations of complex permittivity and permeability of microwave materials and systems under tests. It is shown that the proposed method works very accurately by presenting results obtained for linear materials of reasonable thickness and resonant non-reciprocal microwave systems. In doing so, the permittivity fluctuation is observed by such first research due to the ferromagnetic resonance of ferrites; here it is attributed to an induced voltage from the uniform flow of angular momentum in excited ferrites and this phenomenon is deemed as a distinct source of voltage from excited ferrite at room temperature for technologies. [ABSTRACT FROM AUTHOR]

In electromagnetic machines, ferromagnetic material is one of the key components that affect the magnetic field and thus the output performance significantly. The objective of this paper is to study the influence of ferromagnetic material on magnetic field distribution of tubular electromagnetic linear machines. Generic magnetic field models are obtained for linear machines with various structure designs based on magnetic vector potential and Bessel functions. The magnetic field model is validated with numerical results from finite element calculations. The comparison between them shows that the flux model fits closely with the numerical computation. The obtained analytical model can be employed to study the flux density distribution of machine designs with single-sided, double-sided, and non back irons. It shows that the use of back iron, especially for the internal side, helps to greatly enhance the radial component of magnetic field. This component contributes to the axial force generation of tubular linear machines. The study could be useful for the design optimization of permanent-magnet linear machines. [ABSTRACT FROM PUBLISHER]

In this paper, a proposal for a field weakening method for a permanent-magnet synchronous motor is evaluated. The method consists in inserting giant magnetostrictive elements between permanent magnets. The magnetic permeability of these magnetostrictive parts is modified when the speed increases. The field leakages around the permanent magnets are consequently increased, thus reducing the electromotive forces in the armature windings. An original modeling approach, based on the concept of equivalent stress, is proposed in order to evaluate this field weakening solution. [ABSTRACT FROM PUBLISHER]

Implantable system is widely used for functional electrical stimulation to repair the damaged nerve function. We propose a multichannel wireless implantable system using micro-coil array to implement parallel signal transmission based on inductive coupling, which meets the increasing requirement of some implantable system for high data rate and high power efficiency. However, the magnetic coupling among carrier from different channels will affect the operation of each link. In this paper, this interference is analyzed and design equations are derived, which are used to design coils, arrange their position and apply carrier for each channel to maximize the data signal level received at the implant side. A prototype of multichannel system has been built and experimental results show that data can be transmitted parallelly and high data rate can be achieved. This theoretical calculation verifies the feasibility of using the micro-coil array to achieve multichannel transcutaneous transmission for neural electrical stimulation. [ABSTRACT FROM PUBLISHER]

The paper proposes an improved analytical model, valid for a wide frequency range, of interlaminar short-circuits on the edges of the sheets of high power transformers working at 50–60 Hz. This model is able to determine the current flowing in the microscopic interlaminar contacts formed by burrs, in order to estimate the maximum power dissipated in such hot spots. With this theoretical approach, it is also possible to get an interpretation of impedance measurements on a test coil wound around the core, in order to define a new index able to characterize the part of the shearing burrs in the manufacturing factor of large transformer cores. This new index will help the transformer manufacturers to improve their processes. [ABSTRACT FROM PUBLISHER]

This paper presents a new methodology called Flex-CM for Flexible Compact Modeling to generate and reuse compact models, in order to build a full model of a complex electronic system at an early stage of the design flow. The system is split into independent parts. Each part is numerically modeled using a discrete approach then reduced to save memory and time at the simulation stage. The resulting pluggable and reduced model is called a micro-model. Then, a fast-to-simulate macro-model of a full system can be obtained by assembling the micro-models. The Flex-CM model is presented as a trade-off between reluctance networks and numerical models to perform a magnetic analysis at an early stage of the system design. The Flex-CM models are found to have number of advantages over both methods, resulting however on larger models than reluctance networks. [ABSTRACT FROM PUBLISHER]

To calculate the iron loss in an electric machine accurately, the anomalous eddy current loss generated by domain wall motion should be considered. A simple numeric modeling of anomalous eddy current loss by modifying the conductivity of steel plates is sometimes used. However, investigation on this method in detail has not been carried out. In this paper, this method is investigated in two iron-loss models neglecting and including the skin effect and then applied to the loss calculation of various kinds of nonoriented and oriented silicon steel plates. Then, the dependence of the modified conductivity on the amplitude and frequency of the induction magnetic field for each material is obtained and the appropriate iron-loss model and method for modifying the conductivity are proposed for the nonoriented and oriented silicon steel plates. The calculated iron losses using the appropriate iron-loss model with modified conductivity are compared with the measured data. It is clarified that for nonoriented materials, the iron-loss model including the skin effect with constant modified conductivity shows good agreement. And for oriented materials, the model neglecting the skin effect with the modified conductivity depending on frequency is better. [ABSTRACT FROM PUBLISHER]

This paper presents a method for calculating eddy current loss based on reluctance network analysis (RNA) considering the magnetic reaction field caused by the eddy current. First, an electric network model for calculating eddy current is indicated. Next, RNA model considering the magnetic reaction field by using magnetic inductance is presented. The validity of the proposed model is proved by comparing with the finite-element analysis and experiment. [ABSTRACT FROM AUTHOR]

Radial basis function (RBF) collocation method is a kind of pure meshless numerical method and has been applied to solve static and transient electromagnetic problems. Especially, it shows a great advantage in the computation of moving conductor eddy current magnetic problems. To simulate the conductor movement, the field equations are decoupled with superposition principle and solved by time-domain iteration under moving coordinate systems. One problem is that the coefficient matrix of RBF governing equations, which needs to be computed in each iteration step, is full. As the number of RBF nodes increases, the computational capacity will grow rapidly. The domain decomposition method (DDM), which divides the solving domain into several subdomains, could be conveniently combined with RBF collocation method. This paper first applies DDM combined RBF collocation method to compute transient eddy current magnetic field problems with moving conductors. With this novel method, the iteration only proceeds in the subdomains containing conductors. And the magnetic field in the subdomains without conductors needs to be computed just once before the iteration. The dimension of the coefficient matrix computed in the iteration is only determined by the number of nodes in the corresponding subdomains and on the interfaces. An engineering problem is computed to show that the DDM combined RBF collocation method is much more efficient than the normal one. [ABSTRACT FROM AUTHOR]

In order to reduce the thrust ripple of linear servo system, a double-sided air core permanent magnet linear servo motor with trapezoidal shape permanent magnets (TDAPMLSM) is proposed in this paper. An analytical model of the motor for predicting the magnetic field in the air-gap at no-load is introduced. This model is derived based on the equivalent magnetization intensity method, and its accuracy is validated by using the results obtained from the finite-element method. The key dimensions that affect the air-gap magnetic field are analyzed based on the analytical model, and the design is optimized by using genetic algorithm. A thrust ripple reduction of 70.6% is achieved by optimization. The proposed analytical model may be used for a quick and reliable design and design optimization of the TDAPMLSM. [ABSTRACT FROM AUTHOR]

Pulsed eddy current (PEC) inspection is widely used in nondestructive evaluation of the integrity of conductive structures employed in such engineering fields as aerospace, energy, nuclear, and transportation. In contrast to conventional eddy current (EC) inspection, in PEC magnetic field signals in lieu of impedance signals are obtained during the course of inspection. It is noted that liftoff intersection (LOI) can be found also in PEC with variant liftoffs, whose analytical expressions are beneficial to forward and inverse problems of PEC. In this paper, the generalized closed-form expression of LOI occurring in magnetic field signals, which are acquired from the solid-state magnetic field sensors placed in arbitrary locations within the excitation coil, is formulated based on extended truncated region eigenfunction expansion (ETREE) modeling of PEC. Following this, regarding a coated thick plate, an inverse model based on the analytical expressions of LOI is established in a bid to inversely retrieve the thickness of the nonconductive coating and the conductivity of the base material simultaneously. The inverse model is verified by experiments. It has been found that the estimated values of the two unknown parameters have good agreement with the true values, which indicates that the inverse model is valid and applicable to evaluation of coated materials. [ABSTRACT FROM AUTHOR]

This paper presents a comparative analysis of the characteristics of high-speed permanent magnet synchronous machines (PMSMs) with diametrically magnetized rotors under different construction conditions of the rotor magnetic circuit. An analytical method is adopted to predict the magnetic field distribution and to calculate the electrical parameters by using the transfer relations based on a two-dimensional model in a polar coordinate system. In addition, three types of PMSMs with diametrically magnetized permanent magnets are proposed in this work. The electrical parameters are estimated and the magnetic field distribution is analyzed for those models, and these results are compared with those obtained using the finite element method; the two sets of results are found to be in good agreement. On the basis of the analysis results, a real model manufactured and the validity of our results is demonstrated by performing suitable experiments. [ABSTRACT FROM AUTHOR]

In this paper, the effect of a symmetric distribution of dipolar fields acting along the applied field on the magnetization curve of a superparamagnetic nano-granuler system is examined. The calculations show that the magnetization curves are depressed when the spread of dipolar fields is increased. This reduction in magnetization is attributed to the nonlinear response of magnetization which weighs negative dipolar fields more strongly than the positive dipolar fields. Thus, the reduction in magnetization is not indicative of a predominant negative interaction field, since positive and negative fields are equally probable. Also, for the system examined, the nonlinear response of magnetization is responsible for the predicted negative average ordering temperature in the temperature variation of the initial susceptibility. Thus, in random systems, the interpretation of a negative ordering temperature as antiferromagnetic order, or the positive ordering temperature as a ferromagnetic order should be cautiously stated. [ABSTRACT FROM AUTHOR]

This paper considers analytical and numerical techniques to model the magnetic field distribution in a tubular actuator with skewed permanent magnets (PMs). A fast 3-D analytical model based on Fourier analysis is developed for calculation of the various field components resulting from the skewed PMs for various skewing topologies. This techniques provides means for validating the assumptions of 2.5-D multilayer methods. Furthermore, a 2.5-D analytical multilayer model is derived for calculation of the cogging force due to the slot openings including skewed PMs. The analytical methods are validated by means of 3-D finite element analysis. [ABSTRACT FROM PUBLISHER]

This paper presents a general analytical model for predicting the magnetic field of slotless permanent-magnet machines. The model takes into account the effect of eddy currents in conductive regions and notably in conductive permanent magnets without neglecting their remanent field. The modeling of this effect is important for the design of very high speed slotless permanent-magnet machines, as the power losses are linked with the frequency of the field. The model takes into account any number of layers. It implies that, for one, the fields can easily be calculated in a design including a permanent magnet and a conductive retaining sleeve. The model is applicable both to internal rotor and external rotor permanent-magnet machines. The effect of the relative permeability and of the conductivity of the permanent magnet or of the yoke on the magnetic fields is also taken into account. Any magnetization can be taken into account, in particular a Halbach type permanent magnet, or a radially magnetized permanent magnet can be considered. [ABSTRACT FROM AUTHOR]

This paper presents a generalized Chua-type vector hysteresis model, and a precise magnetic field analysis method is developed by combining the proposed model with the finite element method. The proposed model takes account of all the significant harmonic components of the measured H-waveforms. The validity of the proposed model is investigated through an application to a three-phase transformer model and comparison to experimental measurement. [ABSTRACT FROM PUBLISHER]

This paper presents a generalized Chua-type vector hysteresis model to describe both the static and dynamic vector magnetic properties of electrical steel sheets. The proposed model takes into account all significant harmonic components of the measured H-waveforms, thus it provides precise prediction of H-waveforms even under highly saturated magnetic flux densities under alternating, rotating, and distorted magnetic fields conditions. The validity of the proposed vector hysteresis model was investigated by comparison to experimental results under various magnetic field conditions for both the non-oriented and grain-oriented silicon steel sheets. [ABSTRACT FROM PUBLISHER]

In this paper, the actual synthesis of the thermal field is proposed and solved as an inverse problem, considering a fully coupled magnetic-thermal analysis as for the direct problem. Reference is made to an air-cored inductor for magnetic fluid hyperthermia (MFH). [ABSTRACT FROM PUBLISHER]