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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

Magnetic resonance imaging (MRI), as well as some volume selected spectroscopy methods, use pulsed magnetic field gradients which induce multi-exponentially decaying eddy currents in all non-laminated conductive parts of the superconducting magnets. This paper presents the analysis of the z gradient field distorsion due to the induced eddy currents and the corresponding correction in a 4 T / 30 cm bore superferric self-shielded magnet.

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.

This paper presents an approach utilizing a machine model to achieve an equivalent hardware representation of machines as a computational prototyping tool. The purpose of our study is to find a way to perform hardware experiments of machine control without the actual machine. The proposed approach provides a way to test the control before the machine is fabricated, or in the eases where the controller needs to be experimentally tested before being implemented onto the actual machine. The equivalent hardware of a machine is built using a current controllable load, a controller, and a machine model in a hardware-in-the-loop (HIL) real time simulation environment. The equivalent hardware representation of the machine is achieved by controlling the currents of the controllable load to be the same as the currents of the actual machine under the same operating conditions. The machine model is used to provide the reference signal for the control. In this paper, the introduction of the proposed approach is presented focusing on three issues: the machine model, the procedure to enable the machine model to be compatible with the HIL real time simulation, and performance examination. Finally, the validity of the proposed approach is demonstrated with the voltage and current waveforms and the torque and speed profiles measured at the developed equivalent hardware of the machine. A 2-hp surface mounted permanent magnet (PM) synchronous motor is used as an example machine to present and verify our work. Index Terms--Equivalent hardware representation, hardware-in-the-loop real time simulation, machine model, PM machines.

The purpose of this paper is to use a new rational approach for the design of some magnetic couplings. Our method is based on the association of analytical models and an exact global optimization algorithm named IBBA and developed by the third author. The analytical model presented in this paper is more sophisticated than those previously dealt using IBBA. Therefore, some under and over estimating functions have been constructed for those particular problems of design in order to improve the convergence of IBBA. Some optimal results highlight the efficiency of this approach. Index Terms--Analytical model, Branch&Bound, exact global optimization, interval arithmetic, inverse problem, magnetic coupling.

This paper shows applied sensitivity analysis for easier design and practical application of a planar half-wavelength low-pass filter (LPF) using defected ground structure (DGS). Typically, it is difficult to deploy planar half-wavelength low-pass filters when high power durability is required because of the very narrow line-widths of high impedance transmission line. Here, we propose a new configuration for the high impedance microstrip line using DGS structure to allow broader line width and high power handling capability. The sensitivity of the scattering parameters was calculated using the self-adjoint sensitivity formula in order to determine the proposed filter's dimension. The paper also highlights the validity of the proposed LPF optimization with its measured performance. Index Terms--Defected ground structure (DGS), low-pass filter (LPF), self-adjoint method, sensitivity analysis.

The overlapping method is a very convenient method to connect nonconforming meshes. It has been already developed in 2-D and in 3-D with hexahedron meshes. In this paper, we propose an extension to 3-D tetrahedron meshes. This extension is not obvious because the elements do not overlap on hedrahedra anymore but on polyhedra. In this paper, we propose a method to overcome that issue. First, the overlapping method is presented and the implementation in a finite-element method calculation code as well. Then, the overlapping method is tested successfully on two examples. Index Terms--Electromagnetism, finite-element methods (FEMs), mesh generation, overlapping elements.

This paper discusses interface conditions used in a domain partitioning method and their approximation with a reduced number of degrees of freedom called hooks. In the electrostatic and magnetostatic cases, electric or magnetic hook-connectors are, respectively, used to describe interactions. Better numerical results are obtained in the full wave regime by using both electric and magnetic hooks. This paper proposes an efficient approximation of the interface conditions by using a coarser grid on this surface. We have shown that the interface tends to become transparent for the electromagnetic (EM) field, when the number of hooks is increased and consider this convergence property as the main result of the paper. The proposed domain partitioning (DP) method was successfully applied as a particular domain decomposition (DD) technique for the EM modeling with parallel algorithms of RF-IC components. Unlike DD which is an iterative approach, the new DP approach is a direct one. The sub-domain models being independently extracted, DP is more effective and suitable for parallelization. The open problem of hooks identification is reformulated as a discrete optimization problem. Index Terms--Domain decomposition (DD)/partitioning, electromagnetic (EM) analysis, electromagnetic (EM) circuit element, finite integration technique (FIT).

In this paper, the vector magnetic property is explained first. And this paper also presents the magnetic characteristic analysis of the electrical machines by using the vector magnetic hysteretic E&S model. Furthermore, the dynamic E&S model, which can analyze the eddy current effect due to the distorted magnetic flux waveform, is presented. From this method, we can express the various kinds of magnetic properties directly, for example, vector hysteresis loops (Bx-Hx, By-Hy) magnetic power loss and the behavior of H and B vectors by using this model. Index Terms--E&S model, finite-element method (FEM), hysteresis loop, loss analysis, magnetic characteristic analysis, magnetic power loss, material modeling, vector magnetic property.

Our previous paper proposed two frameworks for iterative linear solvers: the implicit and explicit error correction methods. In this paper, we discuss the convergence property of these methods. A formula we derive explains the reasonability of the auxiliary matrix that Kameari suggested for thin elements. Additionally, an enhanced auxiliary matrix is devised for thin elements, in which the material property changes discontinuously. Index Terms--Finite element (FE) analysis, iterative solver, preconditioning, thin elements.

The paper introduces the concept of the complex inductance as a parameter of a coil loaded by sinusoidal current and placed near an electrically well conductive body in which the magnetic field of the coil induces eddy currents. Studied will be only axi-symmetric cylindrical coils and the paper shows how easily their complex inductances can be determined by means of professional programs for electromagnetic field analysis. The suggested methodology is illustrated on computation of the inductance of a ring coil placed near a conductive slab. Investigated is also dependence of the complex inductance on frequency. Index Terms--Coil inductance, eddy currents, quasi-stationary electromagnetic field.

The use of reduced magnetic vector potential (RMVP) in the three-dimensional finite element analysis of eddy current nondestructive testing (ECT) has demonstrated great flexibility, accuracy, and efficiency in case of coil excitation. This paper investigates the application of the RMVP in another class of eddy-current testing applications where the test sample of finite size is immersed in a uniform excitation field. The paper also shows that RMVP cannot be used in eddy-current testing problems having infinite current foil and infinite conducting plates. Index Terms--Eddy current testing, finite element method (FEM), reduced magnetic vector potential (RMVP), uniform excitation field.

This paper proposes a new approach to magnetic recording based on shingled writing and two-dimensional readback and signal-processing. This approach continues the use of conventional granular media but proposes techniques such that a substantial fraction of one bit of information is stored on each grain. Theoretically, areal-densities of the order of 10 Terabits per square inch may be achievable. In this paper we examine the feasibility of this two-dimensional magnetic recording (TDMR) and identify the significant challenges that must be overcome to achieve this vision. Index Terms--Areal-density, capacity, granular media, magnetic recording, shingled writing, two-dimensional.

For bit patterned media (BPM) applications, while significant progress has recently been made in demonstrating high-resolution dot patterning using e-beam direct writing, and followed by the successful imprint process, many serious issues in fabrication still remain. This paper will only discuss the key challenges in the BPM lithography, including 1) the commercial availability of a high-resolution rotating stage e-beam system; 2) the approach and limitation of directed polymer self-assembly for resist pattern quality improvement and resolution enhancement; 3) the difficulties and limitations in the fabrication and replication of a 1 x template with a density beyond 1 Tbit per square inch (Tb/[in.sup.2]), while the defectivity, lifetime, and damage of the template are still questionable; 4) the tight requirements of size uniformity and placement accuracy; and 5) the needs of advanced metrology associated with the very small dot size and defect characterization. In this paper, we will address the above challenges and present some experimental data along with possible solutions for the challenges. Index Terms--Advanced lithography, bit patterned media, directed self-assembly, nanoimprint lithography.

This paper presents the results of an investigation of the effects of broken squirrel-cage bars. In the investigation, a comprehensive time-stepping coupled finite element approach was fully used to compute stator current waveforms, torque, magnetic flux density waveform, the rotor bar currents, and end-ring currents for three cases: no broken bars, one broken bar, and two adjacent broken bars. The iron core loss distributions in the stator are computed, and the harmonic component of air gap flux density is analyzed. This paper also gives the computed rotor parameters and the vector diagram of the rotor current in cages with and without broken bars. From these data, the faulty signatures are extracted. Experimental results derived from a two-pole 1.1 kW induction motor confirm the validity of the proposed method. Furthermore, this method, which could help to develop diagnostics of broken bars and performance evaluation of induction motor, has great potential in future applications. Index Terms--Broken rotor bars, faulty cage, finite element method (FEM), induction motors.

The familiar method for reducing the space harmonic content of the magnetomotive force (MMF) produced by a distributed polyphase ac winding is by chording, although by itself this can eliminate only one of the major low-order harmonics. Other techniques are available that can further reduce the harmonic content, although these all require a more complex winding arrangement. This paper presents a novel approach by which the winding harmonics can be even further reduced. In addition to altering the winding layout, the method employs an unconventional slotting pattern. The layout and the slot layout are both optimized to produce an MMF distribution that contains fewer harmonics than any conventional arrangement, while still preserving a high fundamental winding factor. The paper presents an example of the new technique in the design of a squirrel cage induction motor, and compares important features of the design with those of a standard machine. It summarizes the advantages and disadvantages of the novel approach. Index Terms--Electrical machinery design, MMF optimization, space harmonics, windings in ac machines.

This paper focuses on the modeling and prediction of core losses in nonoriented magnetic materials of electrical machines. The aim is to investigate the accuracy, efficiency, and stability of certain models, including the commonly used and the advanced ones, and to discuss their advantages and disadvantages when they are implemented in the finite-element method (FEM). It is shown in the paper that the traditional technique based on the loss separation theory can efficiently produce reasonable results in specific operation conditions but can, on the other hand, over- or underestimate the core losses in other circumstances. The advanced model based on solving the one-dimensional (l-D) Maxwell equations can give accurate results for the prediction of core losses in a lamination strip, but its accuracy, stability, and computational burden are put under scrutiny when it is applied to the prediction of core losses in an electrical machine. A third technique, referred to as the hybrid model, which captures the advantages of the traditional and advanced techniques and merges them into one, has been found to be the best compromise. The principal aim of the hybrid model is to avoid the numerical procedure of the 1-D Maxwell equations while maintaining relatively accurate predictions with a reasonable computational burden. A comparative investigation has been conducted for the three core-loss models that have been incorporated into the 2-D FEM analysis of a 37-kW induction motor on which experiments were carried out for comparisons. Index Terms--Core loss, dynamic hysteresis, eddy currents, excess loss, finite-element method (FEM), harmonics, rotating electrical machines, soft magnetic materials, time-stepping.

This paper describes theoretical and experimental work aimed at the development of a new class of high-speed projectiles with superior penetration performance. Our earlier publications were focused on the finite element analysis of projectile-target interaction over a wide range of impact speeds. The projectiles were made of tungsten or alumina, and the target plates were made of aluminum, steel, or tungsten. Subsequently, finite element modeling was performed for ceramic rods encased in metal shells and launched against reinforced concrete. This paper expands the range of ceramic and ceramic-based composite materials for use in high-speed projectiles. Materials were compared based on their mass density, Hugoniot elastic limit, fracture toughness, deformability, and ability to withstand intense aerodynamic heat during high-speed flight and penetration. Finite element analysis was performed for ceramic and tungsten projectiles impacting metal plates at speeds ranging from 0.5 to 6.0 km/s. Several transient phenomena such as ceramic projectile self-sharpening, multiple impacts, spall, and buckling were observed. The computation results were used for the design and manufacture of high-speed projectiles with superhard tips made of commercially available diamond composites. Experiments involved several projectile configurations. The penetration depth of reference steel projectiles into concrete decreased with increased impact speed, while the penetration depth of the projectiles with diamond tips increased. Clusters of ceramic and metal--ceramic projectiles and fragments can find use against larger and softer targets and in the generation of debris. Index Terms--Ceramic projectile, concrete, high-speed penetration, metal, target.

A 500 kJ compact pulsed power supply (PPS) system used for electromagnetic railgun (EMG) system has been developed to investigate the influence of electric parameters on muzzle velocity in the paper, from which the stability and reliability of the PPS system can be evaluated. The pulsed power supply system consists of ten modules, and each module is composed of a high energy density capacitor, a triggered vacuum switch, a pulse shaping inductor, a dump resistor and a crowbar. Influence of different parameters on the velocity was analyzed by ATP simulations in this paper. The parameters include capacitance, equivalent series resistance (ESR) of the capacitor, inductance, natural electric parameter and jitter time of the TVS. The ESR and natural electric parameters are critical influencing factors by comparing the simulation and experimental results. In the end, muzzle velocity deduced by the current, which is obtained from a new model of actual circuit, is about twenty percent lower than that in ideal condition. It is pointed out that the velocity error is mostly caused by ESR and natural electric parameter. Index Terms--Electromagnetic railgun (EMG), equivalent serial resistor (ESR), pulse forming network (PFN), pulsed power supply (PPS) system.

This paper describes a series of experiments to study the efficiency of an electrothermal (ET) launcher. The launcher serves as a preaccelerator for a plasma-driven hypervelocity railgun experiment at the Institute for Advanced Technology. The ET launcher is designed to accelerate small polycarbonate projectiles to about 1 km/s. The objective of this paper was to understand how pulse duration affects the efficiency with which the pressure of the ET discharge is coupled to the projectile. This paper consisted of multiple tests for which the total energy of the discharge was kept constant, but the pulselength was varied. The dependent variable in the tests was the muzzle velocity of the projectile. The experimental results are presented and compared with gas-dynamic considerations. Index Terms--Electrothermal (ET) launcher, gas dynamics, plasma-driven railgun.

This paper expands upon previous research into developing a numerical model of a capillary plasma source for application to electrothermal--chemical (ETC) guns. The capillary model is comprised of a kinetic model simulating polyethylene ablation coupled to a 1-D time-dependent hydrodynamic model to determine the capillary outflow parameters. As input, the simulation requires the capillary internal radius, length, and applied electrical current. Previous work found that best agreement with experimentally measured ablated mass could be achieved with the application of a backflux parameter, representing the percentage of the ablated material that was allowed to return to the polyethylene surface and form a film. Using the model, a parameter study is conducted to determine the effects that varying the peak electrical current, internal capillary radius, and backflux parameter has on the plasma temperature, peak outflow pressure, and total ablated mass. A sinusoidal electrical current is assumed in this paper, with the peak current and discharge time taken over a range typically encountered in ETC gun application. An analysis of the dependence of total ablated mass and peak capillary pressure on the deposited electrical energy yields insight into nonlinearities in the capillary energy equation. Index Terms--Capillary, electrothermal chemical (ETC), energy density, modeling.

High energy density capacitor is a key device in power supply source in Electromagnetic Gun (EMG) system. The increase of energy density of capacitor is beneficial from emerge of metallized technology in electrode and advancement in manufacturing. The paper studies a kind of high energy density capacitor made of polypropylene with metallized electrode. The self-healing ability is improved by optimization of the structural parameter of the metal electrode. First, aimed to be used in EMG, experiments such as lifetime test and voltage withstand test are carried out to study the performance of the capacitor. The metallized film capacitor has an energy density of 1.6 J/[cm.sup.3] under 10 kV. And the lifetime test finds its lifespan of 2000 shots. Then, the influences of different impregnating materials on the voltage drop are compared in the paper for manufacture improvement purpose. Last, voltage maintaining test are carried out to observe the voltage drop of the capacitor. The output precision of the launch system will be consequently influenced. In order to obtain a stable voltage, a constant current and micropower charge control technique is applied to realize fast and high accuracy charge of capacitor to avoid fluctuation of output energy. Using micropower charge control, the voltage deviation in maintaining stage is less than [+ or -][per thousand]. And the charge system has a repeat accuracy of 0.520[per thousand] with high reliability. Index Terms--Metallized technology, micropower charge control, voltage maintaining test.

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 [mm.sup.2] and typical muzzle velocities up to 1600 m/s as well as peak currents of about 600 kA. Index Terms--Discrete elastic supports, electromagnetic railgun, finite-element (FE) method, transient dynamics.

This paper reports on the progress made within the rapid fire railgun (RAFIRA) project recently launched at the ISL. The goal of this project is to investigate the multishot capacity of the armature technology developed at ISL. This technology is characterized by the use of multiple metal fiber brush armatures. The project bases on results mainly obtained with the railgun EMA3 at ISL (muzzle velocity [v.sub.o] [less than or equal to] 2 km/s, applied energy per shot [E.sub.prim] < 1 MJ, l = 3 m, regular cal. = 15 mm x 30 mm). These results are characterized-by good contact performance with respect to friction, rail erosion and contact transition in the range up to 2 km/s. The paper summarizes the main results in single shot mode and introduces preliminary experiments with respect to multishot applications. Subsequently technical aspects about loading and switching technologies for a multishot system are discussed and last but not least concrete design considerations for the medium caliber system RAFIRA are presented. Index Terms--Armatures, electric contact, railgun.

This paper reports on the rapid fire railgun (RAFIRA) project recently launched at French-German Research Institute of Saint-Louis (ISL) with the aim of investigating the multishot capacity of the armature technology used at the ISL. The latter is characterized by the use of multiple metal fiber brush armatures. The project started with the development of a new medium-caliber launcher (25 mm x 25 mm) named RAFIRA and a suitable loading system, as described in part I of the set of papers. This part II summarizes the major results obtained with RAFIRA in a single-shot mode and briefly explains the method of optimizing its performance. The experimental realization of the loading system described in part I is presented. First results regarding the performance of this loader are presented. Suitable conditions allowing multishot experiments were worked out. This paper concludes by presenting the first multishot experiments performed using the ISL armature technology. Already in the first tests, RAFIRA has accelerated projectiles up to more than 1000 m/s while achieving cadences around 30 Hz. The sliding contact performance of these experiments is briefly discussed. Index Terms--Armatures, electric contact, railgun.

The Universities of Texas, Minnesota, and New Orleans, and Texas Tech University are undertaking research supported by the Air Force Office of Scientific Research on critical issues for a launch to space from a railgun carried on an airborne platform. The University of Texas at Austin is studying techniques to achieve hypervelocity with a goal of 7 km/s: So far, 5.2 km/s has been achieved in a 7-m augmented railgun using a preinjected plasma armature. Texas Tech University is studying distributed power feed concepts that will improve the efficiency of launch for a long railgun: So far, 11 km/s has been achieved with a plasma arc in a five-stage system. The Universities of Minnesota and New Orleans are investigating the aerothermal behavior of a 10-kg projectile for flight from a high-altitude launch into orbit: So far, the results show that an acceptable amount (~15 mm) of nosetip ablation will occur. This paper provides an overview of progress in these areas; more details on specific topics are provided in companion papers. Index Terms--Aerothermal, high velocity, railgun, space.

This paper describes the design optimization and analysis of reluctance-synchronous linear motor with a solid or laminated moving part (secondary). The calculation of the motor performance is described using analytical formulation and numerical method. The main advantage of this system is the removal of permanent-magnet secondary and replacing it with a reluctance-type secondary. The first purpose of this paper is designing a reluctance-synchronous linear motor with the maximum-output thrust force and optimum power factor. In this model, a long primary (armature) and a short secondary are evaluated. Distributed winding is considered for design and analysis. Finally, air-gap winding configuration is evaluated. Index Terms--Design and analysis, electromagnetic launcher, finite-element method, reluctance-synchronous linear motor.

Compared with steam catapult system, electromagnetic launcher (EML) system is highly integrated, and it has high and well matching performance. It will be widely used aircraft carriers ejection, rocket launchers etc in future. Double-side tabular permanent magnet linear synchronous motor (PMLSM) for electromagnetic launcher can meet the requirements of big thrust and high efficiency etc. It can accelerate the launcher at the expected speed in short time. The thrust characteristic of the launcher is essential to the whole electromagnetic launcher system. Large thrust and small thrust ripple are both expected. This paper studies thrust characteristic of different pole are coefficients, compares the series and parallel magnetic circuit structures, and analyses the method of staggering a certain distance between poles on both sides. In order to achieve the goal of large thrust, the Launcher is often designed with high current density. As a result, it is of great loss and has quick temperature rise. This paper establishes numerical model of the two-dimensional (2D) primary transient temperature field. The temperature field of the short-term system is analyzed. The calculated and experimental results of the electromagnetic launchers can provide a basis for optimum design. Index Terms--EML, linear motor, temperature rise, thrust force.

The efficiency of a railgun can be defined as the exchanged transferred electrical energy to the kinetic energy of the armature. According to the good relation between the applied force to the armature and the inductance gradient (L'), the importance of this parameter calculation is obviously clear. There are several researchers who calculated L' using different numerical and analytical methods in these years. The analytical method to solve the simple problems is suitable, and numerical methods include sufficient coding time and programmer performance time. A method will be introduced in this paper to extract a formula or formulas of L' using structural railgun parameters which can cause the results similar to the results of the numerical methods. This method has not any time problem, and so, there is a good accuracy of data analysis. In this technique, which is called intelligent estimation method, according to the behavior of the railgun magnetism and its geometrical structure, an equation with unknown multiplications for L' formula is defined. Then, by applying the reported data in different studies for L', these equations can be found. Finally, the proposed method introduces a closed formula for a given structure of railgun. A rectangular configuration is investigated as a case study in this paper. Index Terms--Formula, inductance gradient, intelligent estimation method (IEM), interpolation function, railgun.

In an electromagnetic launcher (EML), the magnetic field creates a dynamic force that moves the armature forward. During launch, electrical current creates high body forces and temperature distribution in the rails and the armature. As a result, the rails and armature experience high amplitude stress and strain, which damage the rails and the armature and reduce their life span. The purpose of this paper is to investigate the effect of body force, as well as the temperature distribution on the displacement of the rails in an EML. In this paper, the physical and geometrical properties of the rails are constant in location. In our formulation of governing nonlinear differential equations, Maxwell, energy, and Navier equations are applied to the rails under dynamic loading. To solve the nonlinear governing differential equations, a finite difference base code is developed and utilized. It is shown that the maximum volumetric forces take place where the highest magnetic field gradient occurs. In addition, the maximum magnetic force is accumulated at the trailing edge of the armature and portions of the rail interior. The thermal stress distribution follows the same trend as the displacement due to the temperature behavior of the rails. Index Terms--Electrical heat source, electromagnetic launcher (EML), energy equation, force distribution, Maxwell equation, Navier equation, thermal stresses.

This paper presents a detailed description of design and simulation of a self-excited All-Air-Core and fabrication of a separate-excited All-Iron-Core compensated pulsed alternators (compulsator), also including the similarity and difference in configuration and principle of two prototypes. Presented are fabrication techniques, assembly processes and design methods developed specifically for pulsed power generators, including the carbon fiber rein-forced epoxy resin composite material usage of stator and rotor core in All-Air-Core compulsator, and the armature and field winding fabrication techniques and conglutination processes in All-Iron-Core compulsator. The armature winding is wound concentric winding by flat copper bars, the end-turn superposition problem solved by heating the flat copper bar to soften them for taking shape. Designs of a lightweight self-excited All-Air-Core rotating-field passive compulsator and a separate-excited All-Iron-Core compulsator for comparison have been completed. They all have rotating-field, two-phase, four-pole, and slotless armature winding and passive compensation. The heart of the self-excited All-Air-Core passive compulsator is carbon fiber rein-forced epoxy resin composite rotor which rotates at 10000 rpm or more, and that epoxy composite resin stator reduces the saturation of the compulsator, which consequently reduces transient inductance of armature winding and increasing the magnitude of pulsed current. The usage of composite material also reduces the mass of the All-Air-Core compulsator and increases the velocity of the rotor and inertial energy storage, therefore increasing the energy density and power density. Another feature of the All-Air-Core PCPA is the use of two armature windings on the stator, which allows optimization of each armature winding to its specific duty cycle. Control of self-excited process is presented as well as the synchronous control of solid-state switch in excitation circuit and discharge main circuit by the special controller. The paper presents the simulation of magnetic field at no-load and discharge instance respectively. The paper analyzes the impact of the thickness of compensation shield to the performance of compulsator. Finally, the experiment schematic of All-Air-Core compulsator system is presented. Index Terms--All-air-core, All-iron-core, compulsator, simulation, technics.