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The accuracy of finite element approximation on tetrahedral elements is studied using the previously derived maximum eigenvalue condition. This condition is linked with the minimum singular value of the element 'edge shape matrix' that characterizes the flatness of an element. A geometric interpretation of these results is discussed. From the theoretical viewpoint, a better insight into the mechanism of approximation errors is gained. From the practical perspective, a precise characterization of shape of tetrahedral elements becomes possible. Index terms - finite elements, tetrahedral mesh, error estimate, approximation, interpolation, shape, singular value

3-D optimization method using the combined experimental design method and direct search method is developed to apply to the optimal design of a permanent magnet type of retarder. It is shown that the braking torque is increased by using the optimization method. The CPU time can be considerably reduced by utilizing the initial values obtained by the experimental design method. Index terms - Optimization, finite element method, direct search method, retarder, eddy current

Resistive switching memory with good performance can be possibly used in next-generation nonvolatile memory and flexible electronics. In the previous studies, some of the flexible resistive switching layers were organic materials. In this paper, an inorganic Al/Al2O3/ZrO2/Al flexible resistive switching memory fabricated at room temperature is proposed for the first time. The resistive switching can be reproduced for over 100 times with stable resistive switching characteristics. In addition, a possible resistive switching filamentary model of the flexible device is demonstrated in this paper. The flexibility and nonvolatility of the flexible device are also demonstrated. Based on the experimental results, the proposed Al/Al2O3/ZrO2/Al flexible device is possibly used in next-generation flexible electronics. [ABSTRACT FROM PUBLISHER]

Previous research on the utilization of an optical pickup head (OPH) as the source for exposing inorganic photo resists uses only one wavelength. However, these single-wavelength OPHs are not appropriate for exposing organic resists. Because the optical power required for exposing the organic resists is too small to produce large enough focusing error signal (FES). To add another wavelength for the focusing servo is essential to eliminate this problem. This paper presents a design of an OPH with blue and red lasers for submicron-scale and nano-scale lithography. The blue laser is used for exposing the resists, while the red laser is used for the focusing servo. The numerical aperture (NA) of the objective lens is 0.6. And the linear range of the focusing error signal (FES) is about 3.0 \mum. In addition, this paper also discusses the variation of linear range due to fabrication error. Three types of different optical structures in the return path are compared. The simulation results show that the adoption of a plano-convex lens and a slanted beam-splitter (BS) plate is the best choice. This combination owns the best immunity to the variation of the linear range due to the fabrication errors. [ABSTRACT FROM AUTHOR]

Slim pump for cooling devices play an important role for cooling the electronics apparatus. This paper develops an axial-flux internal rotor type motor for the low-profile vortex pump. The integrated motor-pump structure is composed of an internal permanent magnet (PM) disc rotor and double-sided external coreless stators with windings piled up on the printed circuit board (PCB). The impeller is disposed on the periphery of the magnet and a fluid dynamic bearing (FDB) is set in the centre of the magnet to rotate relative to the centre shaft. A prototype of the axial-flux motor pump and drive circuit has been made and tested. Both simulated and experimental results show that the proposed motor would be an acceptable solution for the slim notebook (NB) applications. [ABSTRACT FROM AUTHOR]

In this paper, numerical calculations concerning the dynamic behavior of a railgun are presented. At the first stage, the structural problem can be decoupled from electromagnetic phenomena as well as from the local projectile behavior. The magnetic pressure repelling the rails from each other and expanding with the speed of the projectile serves as a boundary condition for purely mechanical calculations. The particularity of the investigation is represented by the type of railgun housing. For some years, the ISL has been using laboratory housings of an open design allowing, for instance, to take flash radiographs during launch. The repelling forces are mainly taken by discrete supports in the form of steel bolts. These bolts are connected to bars made of glassfiber-reinforced plastics, while the rails are mounted on these bars. A 2-D finite-element model of a complex housing was developed in this paper. Bars, including rails, are described by plane-stress elements, while bolts, playing the role of discrete elastic supports, are presented by truss elements. The model is implemented using the ANSYS code. Deformation properties of the rail section and elastic supports are examined by considering a static solution, assuming constant loading. Differences between 2-D and conventional beam models being of importance for this kind of problem are briefly discussed. Transient analysis was performed for a set of constant loading velocities (600-1600 m/s) and for the experimentally derived transient-loading profile. The latter was obtained in the railgun experiments performed using the ISL-railgun EMA3 with a caliber of 15 x 30 mm² and typical muzzle velocities up to 1600 m/s as well as peak currents of about 600 kA. [ABSTRACT FROM AUTHOR]

This paper presents an analytical method for the design of permanent-magnet (PM) traction-drive motors with emphasis on calculation of the magnet's volume and size. The method uses a set of formulas to properly size the magnets without the high effort of finite-element analysis (FEA). The formulas not only give optimized magnet sizes, but also provide quick solutions for the preliminary designs. The method can be used in the initial design stage to set up the base for FEA and optimization, as well as throughout the entire design and optimization process to validate a PM motor design. Numerical methods and experiments confirm the accuracy of the proposed method. [ABSTRACT FROM AUTHOR]

This paper demonstrates new systematic approaches to equivalent circuit model extraction for defected ground structure (DGS) directly from full-wave frequency domain simulation. The DGS circuits being modeled may be either lossy or lossless. Adaptive frequency sampling (AFS) is used to minimize the computational effort of electromagnetic (EM) simulation while critically assisting in determining the cutoff frequency and attenuation pole location of the DGS circuits. A simple circuit model for lossy DGS circuits without any optimization of lumped element component values is presented. Furthermore, lossless circuit model relative complex along with a determined starting point of optimization of lumped element values is also presented in detail. The overall results are an efficient and accurate means to produce the complete equivalent models of DGS circuit for the design of various RF and microwave circuits such as oscillators that may require the high accurate nonlinear design procedures. [ABSTRACT FROM AUTHOR]

For a high-speed electrical alternator, the rotor outer banding and stator inner liner are typically made of high strength graphite epoxy composites due to their high strength and stiffness. Machine structural integrity at high rotating speeds degrades significantly as the composite resins lose their strength at high temperatures. The magnitude of the frictional windage losses generated in the air gaps and the splits of the windage losses between the rotor and stator become crucial to the machine design since these windage losses greatly influence the rotor outer and stator inner surface temperatures. Splits of windage losses generated by an enclosed high-speed composite rotor in low air pressure environments were investigated by The University of Texas at Austin Center for Electromechanics and described in a companion paper. The windage splits are dictated by the air temperature gradients at the rotor outer and stator inner surfaces. Unique heating, cooling, and component material properties of a typical high-speed alternator during repetitive-discharge events make its transient air-gap windage splits very much different from those of the test setup. This paper describes transient windage splits in integrated rotor and stator thermal analyses of a high-speed alternator designed for multiple discharges. The transient windage splits in the air-gap air flow were obtained through multiple iterations on windage losses, air-gap air temperatures, and rotor and stator surface temperatures. [ABSTRACT FROM AUTHOR]

This paper introduces a frequency-controlled low-voltage, high-current inverter power supply suitable for use in spot welders. The design of the proposed power supply was based on the fact that the voltage drop caused by leakage inductance in the transformer is proportional to the excitation frequency. In this power supply, the inverter frequency can be varied to easily control load current. This paper compares the reflux current effect when the transformer is operated in inverter control with operation using an AC sine wave. [ABSTRACT FROM AUTHOR]

This paper deals with a numerical model of the switched reluctance generator (SRG) for use on a general-purpose circuit simulation program "SPICE." In the model, the electric circuit and magnetic circuit are coupled by proper controlled sources. Using the numerical model, we can readily calculate the dynamic behavior of the SRG. The method presented here is useful for circuit analysis and design optimization of the SRG. [ABSTRACT FROM AUTHOR]

This paper deals with temperature performance of induction heating roll with or without heat pipes. The focus of this paper is to improve nonuniformity of the outer surface temperature of the roll by inserting heat pipes with very high thermal conductivity. In our work, the coupled magneto-thermal finite-element analysis considering skin effect is employed for evaluating the surface temperature. The predicted results are verified with experimental data. [ABSTRACT FROM AUTHOR]

In this paper, we first propose a simple but general analytical channel model for bit-patterned media (8PM) systems. It facilitates the generation of accurate readback signals with a large amount of media noise, as well as the analytical design of equalizer and channel partial response (PR) target. We further propose an analytical approach to jointly design the two-dimensional (2-D) equalizer with one-dimensional (1-D) channel PR target for BPM systems with media noise, according to the minimum mean square error (MMSE) criterion with monic constraint. Simulation results show that the proposed 2-D equalizer with 1-D target based approach achieves significant performance gain over the system designed without considering media noise. [ABSTRACT FROM AUTHOR]

In this paper, a giant magnetoimpedance (GMI) element with stepped impedance property was reported for rectangular amorphous soft magnetic thin film with an in-plane uniaxial easy axis in a controlled direction. This stepped change of impedance occurs simultaneously with a change in a magnetic domain, and its physical basis was explained as the intersection of the level of magnetic energy in each case of these domain structures. The variation of stepped impedance as a function of external magnetic field typically has a hysteretic property. The hysteretic property is explained based on an existence of threshold energy barrier which is needed overcoming to change the magnetic domain. In this paper, we will show experimentally both an existence of three stable magnetic domains around zero external magnetic field by using the stepped GMI element, and a possibility to detect these states by impedance measurement. We also propose an application of this phenomenon for a magnetic sensor which has a memory function. [ABSTRACT FROM AUTHOR]

A novel two-objective optimization design model for pulsed power supply (PPS) is proposed in this paper. The objectives are the muzzle velocity and the stored-to-kinetic energy efficiency. The design variables include the operating voltage and the trigger delay times between segments. The acceleration of the armature is constrained to lower than 106 m/s². The optimization results for the muzzle velocity and the efficiency separately show the following: 1) The acceleration constraint has great influence on the performance; 2) wide current pulse yields high velocity but low efficiency; and 3) the operating voltage has to be increased to accelerate a heavier projectile to a certain velocity or at a certain efficiency. Pareto solution fronts for various projectile masses are found using the nondominated sorting genetic algorithm (NSGA-II) under the integration environment of iSIGHT software. Numerical results show that the NSGA-II can provide a set of feasible Pareto solutions for the two-objective optimization design model of PPS, among which the "best" one is to be extracted according to the designer's requirements. [ABSTRACT FROM AUTHOR]

This paper presents the use of coupled inductors to allow interleaved switching of the upper and lower switches of three-phase inverters. The approach increases the number of output voltage levels and reduces the magnitude of the output line currents at switching frequency. Two possible inductor topologies are investigated. Individual toriodal inductors for each phase are shown to provide more switching possibilities, at the cost of size and required DC fluxes. Three-phase three-limb inductors require more careful operation of the power electronics, but with significantly smaller core requirements. Simulated and measured inductor performance is presented, along with comments on the design of future inductors for similar applications. [ABSTRACT FROM AUTHOR]

In high-density perpendicular magnetic recording channels, nonlinear transition shift (NLTS) is one of the distortions that can degrade the system performance. Write precompensation is a standard method used to combat the negative effect of NLTS. In this paper, we propose a modified pattern-dependent noise predictive (PDNP) detection algorithm for use on channels with electronics noise, transition jitter noise, and NLTS. We show that this detector can offer significant improvement in bit-error-rate (BER) compared to conventional Viterbi and PDNP detectors. Moreover, the system performance can be further improved by combining the new detector with a simple write precompensation scheme. [ABSTRACT FROM AUTHOR]

This paper presents a dynamic model to simulate high-power single-phase "written pole" motors. The basis of the model is the generalized theory of electrical machines. From this theory, the required equations governing the dynamic behavior of these motors are obtained. Then, the equations are solved in a special reference frame that is valid for the unique properties of single-phase written pole motors. Comparison of simulation results of the model with experimental data shows very good agreement. [ABSTRACT FROM AUTHOR]

Baseline wander (BLW) is one of major sources of bit errors in perpendicular recording. In this paper, we present a method to compensate for BLW by per-survivor processing (PSP), i.e., along each surviving path in the Viterbi algorithm (VA). We apply the PSP method in VA in timing recovery loop and SOVA for iterative decoding. Simulation results show that the cycle slip rate and bit error rate are lowered and approach ideal case where there is no BLW. [ABSTRACT FROM AUTHOR]

In this paper, we propose a simple method to concatenate a structured low-density parity-check (LDPC) code and a high rate constrained code such that three goals are achieved simultaneously: 1) soft information is available to the LDPC decoder; 2) the structure of the LDPC code is retained after concatenation to facilitate hardware implementation; and 3) the system has the ability to correct long erasure bursts. We consider both a runlength-limited code and a dc-free runlength-timited code. For the RLL case, we use a technique we call parity insertion. For the dc-free case, we apply polarity flipping to a subset of the LDPC code parity bits. [ABSTRACT FROM AUTHOR]

High-performance microspeakers with broad-band frequency are essential for multimedia function in cellular phones. With the increased size of multimedia liquid crystal display window, space for microspeakers is relatively reduced to maintain the same phone size. This paper introduces elliptical microspeakers that have an advantage in mounting space over circular types. For sound pressure level analysis of the microspeakers, electromagnetic, mechanical, acoustic, and their coupling effects are considered for the analysis. Results show that the elliptical speakers have the equivalent performance as circular speakers with similar surface area. [ABSTRACT FROM AUTHOR]

Switch mode power supplies are the predominant form through which power conversion is currently implemented in electronic equipment. Within such power supplies, ferrite cored magnetic components are commonly placed under dc bias conditions which, due to magnetomechanical effects, can result in higher than expected core losses. This paper presents measurements that show the impact of magnetomechanical effects on the losses of a MnZn ferrite core material under low ac excitation and high dc bias conditions. The measurements are made using an accurate measurement circuit, and the results show the impact on losses of magnetomechanical resonance. In addition distorted, figure-eight shaped B-H loops are measured, which are also believed to manifest from magnetomechanical interactions. These B-H loops show that, on a transient basis, magnetomechanical interactions may take place in a manner that is not only lossless, but returns energy back to the excitation supply. [ABSTRACT FROM AUTHOR]

Under a Navy SBIR, Diversified Technologies, Inc. (DTI) will design and demonstrate scalable solid state switches in support of future U.S. Navy needs related to power supplies and inverters. One switch approach being developed consists of a massive series-parallel array of high-voltage insulated gate bipolar transistors that are switched synchronously in order to achieve high peak currents. DTI is evolving its technology in high-voltage switching to include very high peak currents. As an objective of the SBIR effort, DTI will utilize these high-power switches to build a power converter. From a practical viewpoint, high-voltage switches that can operate reliably at large currents have potential applications in missile launchers, high-power actuators, and radar power supplies. The massive series-parallel switch array approach has the potential to provide a compact, reliable, and effective switching solution to converting sufficient electrical energy to kinetic energy that could meet a variety of Navy applications. In this paper, DTI reviews current switch requirements and recent SBIR progress toward the goal of demonstrating massive series-parallel high-voltage switching that meets the Navy SBIR requirements. [ABSTRACT FROM AUTHOR]

The unique properties of the plasma utilized in ETC guns, such as the low viscosity, high momentum and high temperature, can lead to a more uniform ignition over the entire cartridge volume, even in large-caliber guns. Since 2002, the united research group leaded by Beijing Institute of Special Electromechanical Technology (BISET) has completed a lot of experiments with a novel surface discharge plasma igniter, which generates plasma from a cylindrical surface and distributes it through radial port. The results of these experiments have shown this igniter can present perfect ignition. This paper presents an overview of this ETC program including the igniter, pulsed power supply, 120 mm ETC launchers, and some experimental results. The further experimental studies are being continued. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the feasibility of using a magnetic force microscopy scheme for recording and retrieving magnetic marks for ultrahigh-density, ultralow power applications. We will address the main design considerations while designing such a system. Then, using the impulse-response and inverse-convolution technique, we deduce a novel tip trajectory for the optimum recording process. We will also apply extensive optimization for a Cox, CryPt1-x-y perpendicular media structure to maximize the signal-to-noise ratio (SNR). An areal density of up to 0.3 Tb/in² is shown to be achievable with thermally stable magnetic marks and a SNR of 20-25 dB in the existence of additional electronic noise. [ABSTRACT FROM AUTHOR]

The University of Texas at Austin Center for Electromechanics (UT-CEM) has designed and conducted a series of composite rotor spin tests to measure the windage losses and temperature distributions of a test setup at high rotor speeds and low air pressures. The intent of the windage tests is to validate the windage loss predictions and investigate how the air-gap windage is distributed between the rotor and stator. The findings of the spin tests will then be used to perform windage-related thermal design and analysis of a high-speed electrical machine. The radial air-gap flows under the test conditions, a low rotor cavity air pressure of 1 torr and high rotor surface velocities of 333 and 614 m/s, were in a laminar flow regime. Transient rotor and stator finite-element thermal analyses, using the measured windage losses and predicted laminar-flow windage splits, have been carried out to analyze the rotor and stator temperature distributions. This paper shows the detailed thermal analysis and compares the predictions with the measurements. The predicted and measured transient rotor and stator temperatures are in good agreement. [ABSTRACT FROM AUTHOR]

The proper design of a disk drive's channel front-end is important to ensure data integrity and to achieve future high data rates. The front-end contains various interconnects which link the read/write (R/W) electronics with the recording heads and the channel module. This paper discusses the design aspects, which are to guarantee that the read path and the write path pass-on the signals and maintain the proper signal wave shape for high data recording. Impedance matching, line losses, signal-to-noise ratio, and crosstalk all are important aspects of a front-end system, and are therefore reviewed. The R/W electronics are to provide low-noise signal amplification and write head excitation. Various requirements which need to be satisfied to achieve this are discussed such as "cold" termination resistance, symmetrical write drivers, etc. [ABSTRACT FROM AUTHOR]

Microfluxgate sensors have been developed to measure very low magnetic fields, of about some nanotesla. This paper describes a recent integrated solution coupled with the basic microfluxgate component. The objective is to decrease the noise level of the sensor down to a few nanotesla per square root of hertz. The technological solution consists of adding coils or single layers, thanks to which the required ac transverse magnetic field can be applied. A large enhancement of the sensor sensitivity is put in evidence on output signal figures with and without stabilization signal. The specifications of the sensor connected with its electronics are also presented. [ABSTRACT FROM AUTHOR]

This paper describes the use of a dc constant current power supply to power a multilayer launching system. The power supply showed good constant current performance and satisfactorily gave constant acceleration to the launch package. The working principles of a multilayer launching system are given briefly and the means for using lower current to provide the same electromagnetic thrust are analyzed. The dc constant current power supply was used to experiment with a range of pure resistances as the load. We have also demonstrated the concept of increasing electromagnetic thrust for a given current by using multilayer rails. [ABSTRACT FROM AUTHOR]

Recently, the demand for micro hard disk drive that provides high-capacity removable storage for handheld electronic devices is increasing very rapidly. The major concern in the design of seek servo controller in micro disk drives is to reduce power consumption. The input power delivered to the seek servo system is consumed by the transistors of power amplifier and motor coil resistance. In this paper, we present a new seek servo controller for minimizing the power consumption. We use a Fourier decomposition and constrained nonlinear programming to determine the optimum seek profile that minimizes the power consumption. Finally, we present some experimental results using a commercially available micro disk drive. [ABSTRACT FROM AUTHOR]

Hybrid conductive-permeable electromagnetic shields are a key passive approach in the mitigation of undesired alternating magnetic fields. An efficient design presented in this paper is a combination of variable permeable belts and a thin conductive nonmagnetic pipe. The shield is capable of satisfying severe performance criteria, in terms of shielding factor, weight, and cost, while providing adaptive timing for an individual inducing source inside the shield. The potential for the shield is discussed using an extended qualitative and quantitative analysis of the experimental results obtained at a magnetic test facility and shown to be promising. [ABSTRACT FROM AUTHOR]

In this paper, the amplitude asymmetry effects on playback waveforms in a perpendicular recording system are characterized in the time domain utilizing three different recording patterns. New recording patterns are developed to reduce the baseline shift induced by measurements through ac-coupled electronics. Advanced single-pole type heads with giant magnetoresistive playback sensors and double-layer perpendicular media are utilized. The experimental results indicate that the new recording patterns show advantages in better characterization of the playback amplitude asymmetry. The system performance of the bit-error rate (BER) is evaluated utilizing an advanced PRML channel for perpendicular recording. The experimental results indicate that BER correlates well with the playback signal asymmetry of the new recording pattern. [ABSTRACT FROM AUTHOR]

Magnetic particle imaging (MPI) was first presented in 2005. It is based on the nonlinear response of ferromagnetic material and the fact that the magnetization saturates at sufficiently high magnetic fields. In contrast to magnetic resonance imaging (MRI), MPI directly detects the concentration and distribution of superparamagnetic iron-oxide nanoparticles without any background of any tissue. To overcome this issue, a traveling wave MPI (TWMPI) device was combined with a low field MRI scanner to demonstrate the feasibility of a hybrid scanner, which contains both imaging modalities in a single device. The hardware of both separate approaches should be improved and optimized to reach higher fields and a higher resolution, especially for the MRI measurement. Therefore, the dynamic linear gradient array from the TWMPI scanner was modified in a way to produce also a homogenous magnetic field, which can be used for MRI. [ABSTRACT FROM AUTHOR]

This paper deals with the calculation of the force and the stiffness between two ring permanent magnets whose polarization is axial. Such a configuration corresponds to a passive magnetic bearing. All the calculations are determined by using the Coulombian model. The paper also discusses the optimal ring dimensions that provide a large force or stiffness between the rings. Such properties are commonly sought in passive magnetic bearings. We propose a three-dimensional method for optimizing these parameters. An important result is established in this paper: the exact relative position of the rings for which the force is the strongest depends on the air gap dimension. As the expressions in this paper give this exact relative position, manufacturers can easily optimize their passive magnetic bearings. This result is new because the curvature effect is taken into account. Such semianalytical expressions are more precise than the numerical evaluation of the magnetic forces obtained with the finite-element method. In addition, semianalytical expressions have a low computational cost whereas the finite-element method is computation-intensive. Such calculations make it easy to optimize quadripolar lenses and other devices utilizing permanent magnets. Index Terms--Analytical calculation, magnetic bearing, magnetic forces, ring permanent magnet.

This paper presents an analytic model of a read head with shields of finite length and width, suitable for replay at 1 Tb/[in.sup.2]. The model determines the shield potential by iterative solution of the equations governing the Fourier coefficients, given an initial guess. The model is used to demonstrate the effect of varying the length and width of the shields. The paper gives results for the shield potential, equipotentials, vertical head field, and spectral response function. A head with shields that are the same length as the semi-shield--shield gap offers an almost constant magnitude response over a broad range of along-track frequencies, and the use of sufficiently wide side shields is advantageous. Index Terms--Digital recording, frequency response, magnetic recording/reading heads, perpendicular recording, 3-D response.

This paper outlines a technique for predicting the residual field in magnetizable media after the source is removed. Ship builders are considering the use of dc cables, and many land-based power systems have dc links as a power feed. What will the neighboring steel's remanent field be if the cables are excited with a large current, e.g., under short circuit conditions? This paper presents a procedure for replacing the steel with a continuum of nonlinear permanent magnets. The technique consists of discretizing the magnetizable medium into subregions, as defined by a contour plot of [absolute value of [??]]. Each subregion is assigned a magnetization curve according to the characteristic B in that region. The source field is used to assign local magnetization within these regions. The technique is novel, but the real contribution is a technique that can be implemented by any user of a commercial code, and not isolated to developers. Index Terms--Computation, hysteresis, magnetization, remanence.

This paper deals with analysis and experiment of an axial flux permanent magnet (AFPM) brushless direct current (BLDC) motor with minimized cogging torque. Recently, many optimal designs for the AFPM motor have been done by finite-element (FE) analysis, but such analysis generally is time-consuming. In this study, the equation of magnetic flux lines existing between PMs and cores is assumed mathematically and the minimum cogging torque is calculated theoretically and geometrically without FE analysis. The form of equation is assumed to be a second-order polynomial in this paper. The skew angle that makes the cogging torque minimized is calculated theoretically, and the value of minimum cogging torque is confirmed by FE analyses and experiments. In the theoretical analysis, the maximum cogging torque of a proposed AFPM motor has the smallest value approximately at a skew angle of 4[degrees] and that value is about the same as those of FE analyses and experiments. Compared with the nonskewed motor, the cogging torque of the skewed motor can be decreased to over 90%, which has a value of 5 % of the rated torque. Two types of stator cores, with the skew angle of 0[degrees] (nonskewed) and 4[degrees] (skewed optimally), are analyzed, manufactured, and tested experimentally in this paper. Index Terms--Axial flux motors, cogging torque, permanent magnet (PM) motors, synchronous motors.

The permanent magnet (PM) flux-switching linear motor, which is developed from the PM flux-switching rotary machine, possesses similar advantages such as high power density and simple structure. Furthermore, the PM flux-switching linear motor has a potential for mass production at low cost, since the expensive coils and magnets are both set on the short mover. However, the detent force which is induced by both slot-effect and end-effect deteriorates the motor performance. Some methods to reduce detent force which are effective in PM linear synchronous motors do not work in PM flux-switching linear motors, due to their special structure. This paper describes a new method to reduce the detent force by fixing assistant teeth on the mover ends. Finite element analysis shows some interesting results which will be detailed in this paper. Index Terms--Detent force, finite element method (FEM), flux-switching, linear motor, permanent magnet machine.

This paper shows a study on the demagnetization performance analysis of permanent magnet according to three kinds of rotor types of an interior permanent magnet synchronous motor (IPMSM). It is very important to consider demagnetization performance as well as motor performance such as rated torque, output current, and efficiency when designing IPMSM. Three kinds of rotor types according to permanent magnet arrangement; single layer type, v shape type, and double layer type are generally used for IPMSM. In the paper, the magnetic equivalent circuits according to each rotor type are proposed in order for initial design of thickness of permanent magnets considering demagnetization by lumped constant related to magnetic circuit. The volume of permanent magnets per pole and back EMF of each rotor type is assumed to equal for the comparison of demagnetization of IPMSMs with same performance each other. Next, distribution of demagnetization in the permanent magnet is analyzed by using finite element method (FEM) for the verification of the results by magnetic equivalent circuit. Index Terms--Demagnetization of permanent magnet, finite element method, interior permanent magnet synchronous motor, magnetic equivalent circuit.

This paper proposes a novel MRAM using perpendicular magnetic tunnel junction device for high capacity. Conventional MRAM has weak points to realize high capacity in the design structure of the cell, one of which is that using simple current injection system can generate only weak switching field. As a solution, we propose a novel MRAM that has two additional poles in this paper. Proposed novel MRAM has a strong switching field owing to two poles added on both sides of the free layer, just like perpendicular magnetic recording heads. In this paper, analysis of the switching field and useful designs for high Gb/Chip are presented. This research was done using three dimensional FEM with injected current density of 8 x [10.sup.7] A/[cm.sup.2]-6 x [10.sup.8] A/[cm.sup.2]. Index Terms--Magnetoresistive random access memory (MRAM), perpendicular magnetic tunnel junction (pMTJ), perpendicular MRAM, pole type perpendicular MRAM (PTP MRAM).

In this paper, we propose a method of position error signal (PES) generation for read-only-memory (ROM) type scanning probe microscopy (SPM)-based data storage (SDS) systems. Conventionally, PES is generated by using servo bursts similar to those of hard disk drives. Recently, it was reported that stripe patterned media enables the generation of PES without using servo bursts as hard disk drives. In this paper, we report the fabrication of patterned media and its experimental results. Servo patterns are nanoimprinted on polymer medium film. We succeed in reading data and the servo patterns with a 1 x 3 cantilever. We also demonstrate track follow control with the PES of the ROM type SDS through simulations. Index Terms--Position error signal, scanning probe microscopy, SPM-based data storage.

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. Index Terms--Maximum static torque (MST), PM spherical motor, spinning torque, torque calculation, 2-D conversion model.

Recently, high-speed axial flux generator (HSAFG) has come to attention because of its some advantages such as high power density and efficiency. This paper presents a modeling and designing procedure of HSAFG with some details. The back iron of the permanent magnet is the main design subject investigated in this paper. Optimized thickness of the back-iron used in the rotor of two ends is determined for a HSAFG by carefully considerations of the terminal voltage, output power, and efficiency. These all vary by thickness of back-iron variation significantly. It is illustrated that a very small thickness of the rotor yoke reduces the terminal voltage and efficiency and a very large value of it increases the rotor inertia, mechanical problems and cost of the machine with no significant improvement of the machine performance characteristics. It is concluded that back-iron thickness of the rotor plays a singular and important role in the HSAFG and requires more carefully attention when designing the machine. Index Terms--Axial flux machine, coreless stator, high speed generator, rotor yoke thickness.

In this paper, we present simulation results and analysis of 3-D magnetic flux leakage (MFL) signals due to the occurrence of a surface-breaking defect in a ferromagnetic specimen. The simulations and analysis are based on a magnetic dipole-based analytical model, presented in a previous paper. We exploit the tractability of the model and its amenability to simulation to analyze properties of the model as well as of the MFL fields it predicts, such as scale-invariance, effect of lift-off and defect shape, the utility of the tangential MFL component, and the sensitivity of MFL fields to parameters. The simulations and analysis show that the tangential MFL component is indeed a potentially critical part of MFL testing. It is also shown that the MFL field of a defect varies drastically with lift-off. We also exploit the model to develop a lift-off compensation technique which enables the prediction of the size of the defect for a range of lift-off values. Index Terms--Flaw sizing, lift-off, magnetic flux leakage, nondestructive evaluation, tangential component.

We are concerned with the simulation of low-frequency transient magnetic fields and currents in conductors as modeled by the vector diffusion equation. In particular, the key topic of this paper is the diffusion of fields and currents into a conductor due to a rapidly varying magnetic field in the surrounding air. As an example, an explosive magnetic flux compression generator may be designed to produce an exponentially increasing magnetic field in the in the air gap between armature and stator. As a second example, in a standard railgun the motion of the armature causes a rapidly increasing magnetic field in the air ahead of the armature, inducing currents in the rails ahead of the armature. It has been observed that for these types of transient magnetics problems finite-element simulations can produce nonphysical 'reverse currents' in conductors, currents that are flowing in the wrong direction. In this paper the root cause of these nonphysical reverse currents is explained, and several mitigation strategies are discussed. Index Terms--Current distribution, eddy currents, finite-element analysis, transient analysis.

This paper presents three-dimensional expressions for the optimization of permanent-magnet couplings. First, we give a fully analytical expression of the azimuthal field created by one arc-shaped permanent magnet radially polarized which takes into account its magnetic pole volume density. Such an expression has a very low computational cost and is exact for all points in space. Then, we propose two semianalytical expressions of the azimuthal force and the torque exerted between two arc-shaped permanent magnets. These expressions are valid for thick or thin arc-shaped permanent magnets. Furthermore, this approach allows us to realize easily parametric studies and optimizations. The analytical approach taken in this paper, based on the Coulombian model, is a good alternative compared to the finite element method generally used to study such configurations. Index Terms--Analytical, azimuthal force, couplings, permanent magnet, radial magnetization, torque.

This paper presents a comparison between three architectures of line-start PM motors for oil-pump application. This paper is focused on the performances in synchronous operation as well as the self-starting operations. Effects of electrical parameters on the starting and steady performance characteristics are demonstrated to find a satisfying design to meet required performances, it seems that the interior permanent magnet motor yields an impressive starting performance. Index Terms--Cogging torque, interior PM motor, line-start motor, permanent magnet motors, solid rotor.

This paper deals with a method for dynamic characteristic analysis considering core losses in transverse flux linear machines (TFLMs) with solid cores. This paper focuses on how to calculate the core losses of solid cores and how to apply the core losses to the dynamic simulation. The magnetic field characteristics, which are used for the core loss calculation and dynamic simulation, are calculated by using a 3-D equivalent magnetic circuit network analysis method. The accuracy of the proposed core loss calculation and dynamic simulation methods are examined by comparing the input currents of the dynamic simulation model with the measured input current of two TFLM prototypes. Index Terms--Core losses, dynamic characteristic analysis, solid core, transverse flux machine (TFM).

This paper presents an axial-flux permanent magnet (AFPM) machine with an internal coreless stator and twin external permanent magnet (PM) rotors, based on the finite-element method (FEM) by robust design, call Taguchi method to the optimum design for minimum the torque ripple and maximum the ratio between torque ripple and average torque. The optimization is realized by analyses and simulations with finite-element analysis (FEA). The design optimization process is described and the results are presented in this paper. Index Terms--Axial flux permanent magnet (AFPM), finite-element analysis (FEA), Taguchi method, torque ripple.