International Journal of Applied Electromagnetics and Mechanics

Preface to the Proceedings of the tenth International Symposium on Applied Electromagnetics and Mechanics ISEM-Tokyo

Engineering use of jointed materials requires quantitative inspection of the joints, though it has not been established yet. Electromagnetic acoustic transducers (EMATs) can generate and detect ultrasonic waves in a conductive specimen by electromagnetic coupling without any contact with a specimen. This feature gives EMATs an advantage over conventional ultrasonic transducers: theoretical modeling and formulation based on elastodynamics and electromagnetics can be obtained. In this research, a process of joint inspection using EMATs was analyzed numerically. Numerical results of the wave propagation explain effects of the joint interface and of a joint failure on the propagation of ultrasonic waves and on the receiver signals, in terms of reflection and diffraction of the waves. Predicted receiver signals agree well with experimental results, which verifies our numerical approach. These results show a possibility of quantitative joint inspection using EMATs.

Several types of finite element methods have been developed and shown the validity and the effectiveness for eddy current testing (ECT) problem. However, it is difficult to analyze the finite element model including two or more objects whose positions relatively change, such as conductor plate and ECT probe. Furthermore, it takes a large amount of computer resources to compute an accurate finite element model for a natural crack, because of the complex shapes and the narrow gap. In this paper, a superposition method to avoid the finite element mesh regeneration for the relative position change is presented, and the method is applied to the ECT probe with a ferrite core. Furthermore, the finite element model for the natural crack is shown and the model is applied to the ECT problem with the fatigue crack.

This paper presents simulated amplitude and phase characteristics obtained during the inspection of printed circuit board by an eddy-current testing probe. The simulation is based on the ``two-components'' nature of the output signal. Amplitude and phase characteristics, obtained during the experimental inspection and simulation, are presented.

The paper presents a simplified mathematical model of a magnetoresistive transducer, which is used for eddy current non-destructive testing of conducting materials.

The eddy current testing is used for a testing of the steam generator tubes in pressurized water reactor nuclear power plants because of its high accuracy and high speed. It is important to judge shape of cracks from measured signals. We have developed a rotating type probe using an excitation coil that generates uniform eddy current distribution. Because the shape of excitation current source has no influence on detecting cracks, numerical analyses for this probe are handled simply by devising boundary condition. Aid of numerical analyses has enhanced the evaluation of complicated cracks.

The purpose of this paper is to present the results of observation of concrete damage using a newly developed eddy current sensor and a high performance multi-frequency system. Selected digital signal processing algorithms were applied in order to enhance the obtained signals. The experimental verification of the developed technique is done and the elected results are presented.

An automated algorithm is presented for the analysis and classification of eddy current bobbin probe data obtained from nuclear power plant steam generator tubes (SGT). This algorithm attempts to find a balance between the two seemingly conflicting requirements of SGT eddy current data analysis, namely, detecting and identifying as many of the actual defects as possible, whilst limiting the number of false alarms to a minimum. Initial results presented in this paper look very promising.

We have developed a GMR line sensor which can arrange many GMR elements in a line on a polyimide film. This GMR line sensor detects the magnetic field distribution in a plane by only a single scan. We use the multilayer GMR element. This element can detect a magnetic field impress from directions of an element length and an element width. And the GMR line sensor has omnidirectional magnetic sensitivity. We applied this sensor to a nondestructive magnetic leakage flux testing. The output of this sensor does not depend on the direction of leakage flux, therefore, this sensor can detect any direction of defect. Using the GMR line sensor, the shape of the defect will be identified by a single scan.

Detection of internal flaws in conducting materials with considerable thickness is difficult using eddy current tests. This paper presents an alternative method, which uses dc magnetic field excited by the current impressed across the conducting material. In this case the internal flaws give rise perturbations of current flow and consequently the magnetic field is also changed. Perturbations in the magnetic field can be detected by dc (direct current) sensors such as magnetoresistive or Fluxset sensors. In this work numerically performed experiments are presented to recover flaws at the interfaces of metal parts jointed at high temperature by high intensity pressure.

The paper presents new developments in the detection of inner and outer defects in welds by using magnetic methods. A new yoke based on permanent magnets was designed. Signals from different types of cracks, inner and outer, are measured. Difficulties arising in detection of outer defects, in thick welded parts are also discussed.

This work is concerned with an experimental study on online measurement of the states of ID saw blade cutting a 12-inch crystal ingot. An online monitoring system consisting of a 3-axis piezoelectric sensor, a three-band digital filter, a digital oscilloscope and computer was developed. Since the acoustical and chatter vibration signals during cutting ingot were complex, they are decomposed in three frequency regions to evaluate the blade extension circumstance, the sharpness of blade edge and the interference between blade and ingot. The proposed ID-Blade slicer monitoring system is validated for evaluation of the blade slicing 12-inch silicon ingots.

The present paper deals with the utilization of the electromagnetic-acoustic transducer (EMAT) for the non-destructive testing of conducting materials. The principle of the EMAT consists in the interaction of the electrodynamic structure of materials with an external electromagnetic (EM) field under influence of a bias magnetic field. It offers the possibility to generate an acoustic mode of the penetrating EM wave with the slow velocity and the attenuation of the acoustic wave or on the other hand to detect the EM wave due to its radiation from the surface of a conducting sample. The main advantage of the EMAT is the contactless generation and detection of the acoustic wave, or the acoustic mode of EM wave in a wide range of frequencies and temperatures. The special properties of EMAT's driving and detecting devices are presented in the paper.

A design criteria for brushless dc motors for high-speed sensorless operation is described. It is shown that motors can be designed such that the free-wheeling diodes in the power electronic drive have a low conduction angle, while exhibiting high efficiency. Thus, established sensorless commutation strategies based on the detection of the zero-crossing of the back-emf waveform can be employed.

Giant magneto-resistive (GMR) elements are applied to several industrial magnetic sensors. This paper deals with the directional sensitivity of GMR elements, and their industrial applications. The use of GMR element has several advantages for other sensors. In the area of data storage, GMR elements are generally used to detect the magnetic field impressed in the direction of the stripe width. However, the GMR element has high sensitivity in the direction of the length as well as the width, even if it is a stripe shape. In addition, we obtain an omnidirectional sensitivity of GMR elements. Using the GMR element, we developed a GMR line sensor. This sensor visualized a magnetic field by only a single scan.

Lead acid batteries loose their nominal capacity by time due to the normal aging and by sulfatation. More than 500 experiments proved that batteries regain more than 85% of their capacity being regenerated by the described electromagnetic procedure. Results on strongly sulfated lead acid batteries with a loss of capacity more than 90% show a success rate of more than 55%. Doing the regeneration with lead acid batteries which are still functional (loss of capacity less than 20%), showed that 95% of the nominal capacity could be achieved.

The density distribution of the magnetic field and the overheating distribution were simultaneously submitted to a coupled analysis by the Finite Element Method. A 2-D model was adopted for the magnetic field as well as for the thermal field.

We investigated the application of a magnetic ribbon to a highly sensitive magnetic sensor. The sensor employs the impedance change in a coupled magnetic ribbon when a radio frequency (rf) current is passed through it and an external magnetic field is applied. When the non-uniform external field was applied the coupled ribbon structure was conformed to have high sensitivity, which was about ten times higher than that in the uniform external field. This phenomenon was attributed to the magnetostatic coupling between coupled magnetic ribbons.

This paper has reported the development and performance of a flux-concentration type linear induction motor (FCLIM) utilizing the effect of flux-concentration by eddy currents. In the developed FCLIM, the slot-leakage flux is reduced and as a result more flux is concentrated into the air gap. The key element of the FCLIM is the conducting plate inserted between the exciting coils in each slot. Thrust characteristics of conventional tubular LIM and FCLIM are compared using the equivalent circuit parameters. Though some losses are occurred in the plate, the overall efficiency of FCLIM is better at higher output force.

This Paper describes the method for effective extraction of spectral features of signals under the noisy environment. Further examination showed that extraction of the features of signals under the noisy environment is possible using modification of spectral envelopes by rule. In this modification method, vanished valleys of spectral envelopes under the noisy environment are recovered. However, the incorrect valleys are sometimes added and the obtained envelopes have bad influences on performance of systems using these features. In this paper, smoothing functions are used for avoiding wrong spectral valleys by rule and the improvement of performance for extraction of spectral features is shown. Four kinds of smoothing functions are defined and evaluated. Experimental results of pattern recognition using proposed spectral parameters are presented.

In recent years, linear motors are gaining wide popularity in the field of office and factory automation. Therefore, small and high thrust linear motors are needed. This paper deals with a proposal of a new interior permanent magnet type linear pulse motor and it's characteristics. The thrust density of the interior permanent magnet linear pulse motor is larger compared to the other type linear pulse motors.

As a two-dimensional movement motor, the double-sided X-Y linear synchronous motor without armature core has been proposed as a precise positioning device. The linkage flux density and thrust are studied analytically by using three-dimensional numerical analysis. The results show that this motor has sufficiently large values on them and the satisfied thrust per mass in the air core type for the double-sided pole configuration. There is little ripple in the thrust in the motion to any position as there is no detent force.

Permanent magnet brushless ac machines are ideally suited for traction applications, since they are energy efficient and have a high specific torque and a high peak to continuous torque capability. Further, they can be field-weakened to facilitate constant power operation over an extended speed range without compromising the VA rating of the drive. However, they must be design optimised with due regard to their duty cycle, their thermal management, the volt-ampere constraint of the drive and any space envelope constraints. A design methodology which accommodates these aspects into the electromagnetic design synthesis process has been developed and employed to design a traction machine for a small urban vehicle.

It is explained why a polyphase (m > 3) induction motor supplied separately by single consecutive symmetrical components of voltage behaves as a multi-speed motor. As an example a 9-phase 4-speed motor is considered and results of computer simulations are presented. As regards the theory of polyphase machines it is shown that the so-called diagram of decomposition of polyphase induction motor into elementary machines (the graphical representation of a motor model in αβ 0 coordinates) is very convenient means for their analysis and modelling.

Reciprocating air-compressors inherently generate high vibrational forces, which are transmitted to supporting structures and may result in a high level of acoustic noise. In many applications, this cannot be tolerated, and, therefore, an effective means of controlling the transmitted vibration energy between a compressor and its surroundings must be employed. In this paper, an analysis of a typical reciprocating actuator is described, and an active method for suppressing the transmission of vibrations is proposed.

This paper deals with the efficiency characteristics of a moving-magnet-type linear oscillatory actuator (LOA) for compressor by using a novel measuring method. In this measurement, another linear motor is used as the load instead of compressor. The relationship between efficiency and the phase of the load current is investegated. Maximum efficiency of the LOA reaches to 87% at the output power of 61 W.

The authors have proposed new compensation methods for a solution of the end effect of the linear induction motor (LIM), which is to supply the eddy current with minimum power loss in front of LIM. As one of proposed methods, the magnet rotator type compensator is discussed in the paper. The effect is studied analytically on the LIM parameters used in subways in Japan. The thrust density distribution of the LIM with the compensator clearly shows the improvement in the front region. The thrust and the output kW per input kVA of the LIM at the slip of 0.1 increase by 58% and 45% respectively by using the compensator.

The VR type Resolver is an angle sensor for the motor of electric vehicles and hybrid electric vehicles. The static angle accuracy of the Resolver affects the dynamic error during rotation of the motor. Therefore, for the purpose of reducing the static error of the Resolver, the cause of error was investigated by means of experiment and FEM analysis, especially regarding the effect of leakage flux distribution around the coils. As a result, it became evident that the flux distribution in stator slots is not equal, thus uniform winding and balance between 2-phase output coils are needed.

Running characteristics of permanent magnet linear synchronous motor(PMLSM) which is usually used in the system requiring the high acceleration and the accurate position precision are investigated. Also, employment of partial excitation of primary current according to the mover position for the efficient motor drive, and its influence on the EMF and thrust force ripple are considered in detail. Furthermore, capability of PMLSM manifesting the speed-force feasibility under the running condition will be followed.

The paper presents a very useful method for computation of the sensitivities of electrical machines, taking into account the non-linearity of the ferromagnetic bodies. In the first step, the magnetic field in non-linear media and the performances of the given machine are calculated. The non-linear medium is replaced with a linear medium having a magnetic polarization that is iteratively corrected by the flux density. Each linear field problem is solved using the periodic Green function. In the second step, the difference of the magnetic field due to the small modification is computed directly. The polarization of the eliminated ferromagnetic domain is the field source. The{\bf B-I} relation is given by Frechet first derivative.

We present in this paper a displacement-frequency sensor including a non-linear resistor with a dynatron-type i(v) dependence, a variable coil and a d.c. voltage source. A general relation is given for the dependence of the period of the oscillations on the coil inductance and on the negative variable resistance of the non-linear resistor respectively. The functioning data of the sensor are presented, for linear and angular displacement respectively. Our sensors could find interesting applications in cardiology.

The performance of electric vehicles may be improved significantly by incorporating a flywheel peak power buffer into the power-train. An annular carbon fibre composite flywheel rim offers a high specific energy capability, although a high rotational speed is necessary for a high stored energy, whilst operation in a vacuum is conducive to a low aerodynamic loss, and necessitates the use of magnetic bearings. The electromagnetic design of such a flywheel system is described, and a dynamic analysis that predicts the free vibration modes and frequencies, is presented. Finally, the magnetic bearing control system is described, and it is shown that the vibration damping capability of the bearings is such that natural vibration frequencies within the flywheel operating speed range can be accommodated, and performance objectives commensurate with operation in a vehicle drive-train can be achieved.

A procedure for the determination of the distribution of magnetization in an object of interest using measured disturbances of external magnetic field is described in the paper. The object is divided into a finite number of brick-shaped elements and we prescribe uniform distribution of magnetization within each element. The contribution of each element to the total magnetic field may be calculated analytically in terms of unknown coefficients of magnetization distribution. These coefficients are determined from a set of measured magnetic field values by application of the least square deviations criterion. Such an approach enables a priori analysis of stability of computation. The application of the procedure is illustrated by an example.

A boundary-oriented method for 2D electromagnetic inverse scattering in TM polarization and time-harmonic dependence is presented for perfectly conducting objects [1,2]. Key points of the method include a kinematical description of the contours of the objects, the introduction of pseudo-currents to ensure stability and the use of a level set method for deforming the contours. Level set methods [3] allow to handle automatically the changes of topology and to regularize naturally the contours. In this way, several objects can be retrieved starting from one single initial guess. The frequency hopping technique turns out to play a very important role in the inversion process. This method gives highly accurate reconstructions within relatively short computational times.

The mobile usage of a magnetic resonance imaging device commonly known as MRI requires a handy kind of magnetic circuit device for production of the main magnetic field B_0 . This device is called a Mobile Universal Surface Explorer (MOUSE). The requirements of homogeneity and field strength for MRI applications as well as low weight make great demands on the geometrical shape of the magnetic circuit. By genetic optimization of several FEM models of the MOUSE a suitable solution shall be found which meets the demanded requirements. The paper presents a genetic optimizer for static computation of the MOUSE' field distribution and describes the implementation using object-oriented design patterns.

A neural network (NN) model of scalar hysteresis phenomena has been developed for modeling the behavior of magnetic materials. The function approximation ability of NNs has been applied. The virgin curve and a set of the first order reversal branches can be stored preliminary in a system of three NNs. Different properties of magnetic materials can be simulated by a knowledge-based algorithm. Value of differential susceptibility, dM/dH can be expressed in analytical form. Finally hysteresis characteristics predicted by the introduced model are compared with the results of the Preisach simulation technique.

The reduction of computational cost of evolutionary multiobjective Pareto-optimization algorithms is necessary when time-consuming objective functions evaluation is required. To this end neural network interpolation techniques are used for objective response surface building; evolutionary multiobjective Pareto-optimization is then performed on interpolated functions. Both analytical multiobjective test problems and numerical electromagnetic design problems are considered; the study of Pareto optimal front interpolation accuracy versus neural network training cost is performed.

This paper reports about the validity of the numerical model for presuming the internal current of the superconductor that is difficult to measure. The validity of the numerical method is confirmed by the simple analysis model. This model is constituted applying boundary element method and the difficulty of measuring the internal current is solved by the inverse problem from the exterior flux density distribution. Since the application of this model draws the solution of an irreversible magnetization phenomenon not clarified, the apparatus that uses the superconductor will develop.

This paper is concerned with a shape recovery of natural cracks in steam generator tubes of the PWR nuclear power plant. A three dimensional forward model is developed for analyzing accurate probe response evaluation in eddy current testing. Using the evolutionary programming, an efficient inverse scheme is proposed for recovering natural cracks. The proposed algorithm is tested for stress corrosion cracks of the steam generator tube samples.

The present paper presents an inversion scheme that reconstructs crack profile from eddy current signals. The scheme is based upon the genetic algorithm and reconstructs crack profile from the signals obtained by numerical simulations with use of an accelerated FEM-BEM coupling code. The cracks are assumed to have uniform electrical conductivity in order to model natural cracks that occur in steam generator tubes of pressurized nuclear power plants. On the basis of calculated eddy current signals in the previous generations, the inversion scheme is accelerated by eliminating individuals that are obviously different from the global optimum solution. Reconstruction results are shown in the paper, which reveal that the scheme is very promising.

This paper discusses reconstruction of magnetic charge distribution on a planar region for non-destructive evaluation. Reconstruction is performed by using the magnetic fields measured on a plane above the charge region as input data. The present method needs only one matrix inversion whose computational time is expected to be shorter than the method based on optimization processes. It is shown that the reconstruction is successful when the unknown vector is appropriately regularized in order that the corresponding singular vectors become smooth. The L-curve method works well for determination of the value of the regularization parameter.

The electric potential CT (computed tomography) method proposed by the present authors was applied to the identification of delamination defect in layered carbon fiber reinforced plastics (CFRP) composites, which have strong anisotropy in electric conductivity. The electric potential readings on the top surface of the layered composite materials was used for the identification. The anisotropy of the electric conductivity of each layer was taken into account in the boundary element calculations of electric potential distribution. Numerical simulations were made on the identification of elliptical delaminations on the interface of layers. It was found that the method was applicable for the estimation of the location and size of delamination even in the presence of considerable measurement noise.

Nondestructive characterization (NDC) of materials is a technology of increasing application by industrial users for process monitoring and control as well as in predictive maintenance procedures integrated in plant lifetime management systems. The main reason for this fact in materials processing is the need for a better process understanding and mastering in order to produce quality according to a zero-defect-principle and the objective to reduce non-conformities compared with a given quality specification. This means: Integration of NDC by use of intelligent sensors into monitoring and control systems to predict mechanic properties and to detect and document their discontinuities. For lifetime management of components in plants NDC is asked for to support lifetime prediction procedures, which have to be observed if lifetime extension is an objective to reduce costs.

The bending of through-cracked ferromagnetic plates in a static magnetic field is investigated to show the effect of induced magnetization. A simple experimental technique employing strain gages is used to determine the magnetic moment intensity factor. The theoretical results agree very well with the experimental data. The scattering of time harmonic flexural waves by a through crack in an infinite plate under a uniform magnetic field is also studied.

B-H curve reconstruction starting from magnetic flux leakage (MFL) signals measured outside the tested specimen is attempted. Non-linear constitutive relation is modeled by means of three parameters, suitable for describing low fields magnetization curve. A FEM-BEM approach is used to solve the forward problem whilst the inverse problem is tackled with a genetic algorithm application. Results of the reconstruction are presented.

In this paper, we present two feature extraction techniques for the classification of ultrasonic NDE signals acquired from weld inspection regions of boiling water reactor piping of nuclear power plants. The classification system consists of a pre-processing block that extracts features from the incoming patterns, and of an artificial neural network that assigns the computed features to a particular class of defect present on the inspected pipe. The two techniques are respectively based on the discrete Gabor transform(DGT) and on the discrete wavelet transform (DWT); a third feature extraction technique, based on the clustering of the wavelet coefficients, is also presented. The results carried out by artificial neural networks trained and tested using the described feature extraction techniques, demonstrate the usefulness of the clustered DWT method with respect to the well known techniques of DGT and DWT.

A study on non-destructive technique for creep damage of type304 stainless steel was performed. In this study, we concentrated on the magnetic field change with creep damage. This technique has a possibility that the damage before crack initiation is detected. We report that the results on the magnetic field change during creep damage progress, in order to examine the applicability of this technique based on magnetic field change to time-dependent damage. Though type304 stainless steel is a paramagnetic material, the leakage flux density of creep damaged specimen changes obviously, as compared with that of aged specimen.

A wide range of pressurized systems in the field of chemical and power-plant techniques are made of austenitic material because of its special corrosion and temperature stability. Concerning safety components like pressure vessels and pipe systems, the quality of these components has to be controlled during production, and their condition during use has to be inspected in defined intervals. Especially for nuclear power plants, the detection of defects as well as the early recognition of material phase transformations in austenitic material is an important contribution to the assurance of the system integrity. Inside this paper, the results of the qualitative and quantitative non-destructive evaluation of this phenomenon will be presented. Therefore, material physics, FEM-calculations and applied advanced electromagnetic testing techniques will be explained.

The present study investigates a method for the non-destructive detection of damage in an austenitic stainless steel SUS 304 by the use of martensitic transformation. Volume fraction of α' martensite transformed in uniformly stretched SUS304 plates was measured and expressed as a function of the applied strain levelε. The distributions of α' phase in the plastic wake regions produced around fatigue cracks were then electromagnetically measured in fatigued SUS 304 plate specimens. The results were compared with the distributions of magnetic flux density B_{z} above the fatigue cracks in the specimens magnetized by a strong magnetic field higher than 0.4 T. It was revealed that the B_{z} distributions reflected the α" phase distributions in the wake regions: i.e., the distance between the points where B_{z} reached the minimum and the maximum had a high correlation with the fatigue crack length, and the minimum and the maximum values of B_{z} showed a linear relationship with the applied stress intensity factor range ΔK. These results imply that not only the crack length but also the fatigue damage can be detected effectively in an electromagnetic non-destructive way.

We performed magnetic nondestructive evaluation of degradation of nuclear pressure vessel steels due to mechanical loading as a fundamental research. We measured magnetic properties of low alloy steel samples, which were degraded due to tensile and cyclic loads. Magnetic hysteresis curves change depending on the loading conditions. The changes of the coercive force, residual magnetic flux density and permeability were obtained and analyzed in details as a function of the residual strain. Based on the above results, we performed the sensitivity analysis of magnetic property changes for the mechanical load. Finally we concluded that the incremental permeability at H = 0 is the most sensitive index for early degradation due to the mechanical loads. The feasibility of application of this magnetic technique to the evaluation of degradation due to neutron mechanical and thermal loading is now under consideration.

This paper has investigated the possibility of applying nondestructive evaluation technique for finding the defects in electroplated materials. Planar meander and mesh type magnetic sensors have been considered and their relative performance have been compared based on a single criterion that the effective area of the material surface covered by each type of sensor is same.

The component of ITER facing directly to plasma is called the first wall. The first wall is composed of DSCu/SS316 HIP bonded structure. In addition to residual stress due to the HIP bonding process the electromagnetic force is loaded on the first wall during plasma disruption. In this study, we assume an initial crack in the first wall. Stress induced by the electromagnetic force at the crack tip is estimated by finite element method taking the residual stress into consideration. From a viewpoint of fracture mechanics, stress intensity factor K is evaluated to make sure the structural integrity of the DSCu/SS316 HIP bonded structure. As a result of analyses, the stress intensity factor K is not so large for all of the assumed cracks. Therefore, there is no possibility of fracture due to the crack growth during the lifetime of the first wall.

This paper introduces a novel approach of visualization for electromagnetic fields. Our approach is one of the image analysis methodologies based on the classical field theory, which has versatile capability for image processing, compressing, visualizing, identifying, and animating. A key idea is that each of the pixels representing a digital image is regarded as a kind of potentials in vector fields. Gradient or curl operation of the vector calculus to the image data yields image field vector distribution. Any kinds of images can be represented by well-known partial differential equations. The Poisson and Helmholtz types of equations are possible to represent the static and dynamic images, respectively. In this paper, visualized electromagnetic field images are analyzed based on our image differential equations. The image Poisson equation is possible to reconstruct the original electromagnetic fields with high spatial resolution. The image Helmholtz equation enables us extr action of the parameters characterizing the electromagnetic phenomena.

We have been proposing the image processing methodology where the human voice signals are transformed into the three-dimensional image data by means of the three-dimensional Lissajous diagram [1]. In this paper, we apply the image cognition technology to the cognition of the magnetic sensor signals. At first, the time domain signals are converted into the three-dimensional images, which construct the database system. Secondly, when we measure a time domain signal, this signal is also converted into a three-dimensional image. This three-dimensional image becomes an input vector of a least squares means. Least squares solution gives a composite signal as a linearly combined database signals. Extracting the most dominant term from the least squares solution reveals the cognized signal. Thus, we have succeeded in the time domain magnetic sensor signal cognition by means of the image cognitive technology [2].

In the present paper, we propose a method of analysis for the magnetic sensor signals. Based on the physical characteristic value such as a time constant of the electric circuits, our methodology tries to work out an equivalent characteristic value reflecting the physical property of the target metallic material [1,2,3]. Our smart magnetic sensor developing is to recognize a datum from the signal database. This is applied to the space domain signal cognition. As a result, this paper reports that the equivalent characteristic value is an extremely useful quantity in order to examine the physical nature of the target.

Any of the numerical methods for electromagnetic field analysis essentially require a subdivision of a problem region. By notifying this subdivision, we have previously proposed a new methodology by applying the analytical solution to each of the discretized parts. The first trial of this semi-analytical electromagnetic filed computational methodology has made it possible to simulate the complex electromagnetic field distributions not obtainable by the conventional numerical schemes, such as finite and boundary elements means. However, our semi-analytical method encounters some difficulty when analyzing the high frequency electromagnetic field distributions because of the displacement currents.In the present paper, we propose a new semi-analytical approach taking the displacement currents into account to overcome this difficulty.

A new computer-aided method, based on Saito's Fourier-wavelet theory, is used to extract the facial expressions that appear and disappear in less than one-fifth of a second, i.e. expressions that reveal the true emotions of a human being. The new method consists of two major steps. The first step is the application of the Fourier transform to reduce the spatial phase differences between the reference and test images. The second is the application of the wavelet transform to extract the local discontinuous differences. This method is applied to the moving images in the interview scene. Using this method, the difference between the two facial expressions has been extracted, even though both images differ in their size and reference position.

In the present paper, we propose the methodologies in order to realize the desired magnetic field distributions by using single-sided exciting coils. As a result, it is revealed that a combination of the least squares and the generalized vector sampled pattern matching method suggests the practically realizable exciting coil layout.

When reading a novel by EKUNI Kaori, reader's world in the brain has been clarified by means of the discrete wavelet analysis. According to the analysis, reader's world in the brain has been classified into two layers. One is the world in the book and the other is the existing real world. Major target of this paper is to visualize the transition states between two layers. As a result of our analysis, it has been revealed that the wavelet multi-resolution analysis has made it possible to visualize the transition states as well as to clarify the composing methodology of the novel.

In order to design an optimal planar inductor, this paper carries out several axisymmetrical magnetic field simulations fully taking the magnetic hysteretic properties of ferromagnetic core materials as well as open boundary condition into account. Finite element method is applied to evaluating the magnetic fields, reactive and dissipative energies in a planar inductor. Because of the nature of magnetic fields, it is essentially taken into account the open boundary effects to evaluate the exact characteristics of planar inductor. Since the finite elements is one of the methodologies to solving for the partial differential equations, and then it has been difficult to take the open boundary effects into account. However, this paper removes this difficulty by employing the strategic dual image (SDI, in short) method [1,2]. Another difficulty is caused by the hysteretic magnetization characteristics of magnetic core materials. Applying the Chua type magnetization model to represent the hysteretic property also removes this difficulty. As a result, it is revealed that the frequency characteristic of core magnetic materials as well as shape dominate major characteristics of the magnetic fields, reactive and dissipative energies in the inductors.

Our motive of this study is to develop an application of the wavelet packet to PIV image compression processing in order to improve the spatial resolution and reliability furthermore. It was found that the reconstructed PIV image with a lower compression ratio might emphasize particle edges at a relatively high spatial resolution. The reconstructed PIV image with a higher compression ratio may display the large-scale motion of particles and may deduce noisy. In this study, the relative error of the wavelet packet image compression technique was lower than that of the standard wavelet image compression technique. The higher compression ratio of 64:1 can be realized without losing significant flow information in PIV processing. It could say that the wavelet packet could provide a better compression performance than the standard wavelet image compression technique when compressing PIV images.

The vector wavelet multi-resolution technique based on the orthogonal wavelet transform was used to analyze the velocity vector data that were simultaneously obtained by sixteen X-wires in the turbulent near-wake of a circular cylinder at different streamwise positions. The instantaneous velocity vector field is decomposed into the multi-scale structures, and its sectional streamline of various scales is displayed. The large-scale structures in the plane of mean shear are consistent with the well-known Kármán vortices. The structures that correspond to the saddle region between Kármán vortices are identified with the rib-like structures. Even smaller scale structures are also observed. As increasing x/d, the decay of vortical structure and rib-like structure are observed. The topologies of Reynolds stress and RMS vorticity associated with the multi-scale structures are discussed at different downstream positions. It is found that the most significant contribution to Reynolds stress comes from the frequency components of f ≤ 219 Hz at x/d = 20. However, the contribution to Reynolds stress coming from the intermediate-scale structure becomes weak at x/d = 40. The RMS vorticity components of f = 875 Hz is the largest among all components.

The purpose of this article is to apply an inverse approach for image reconstruction during electromagnetic field visualization. The reconstruction of the images is formulated as an inverse problem. For the image color model, the Poisson equation with open boundary condition is imposed. The color source densities have been evaluated from the color distributions for electromagnetic field data set. The Generalized Vector Sampled Pattern Matching method is applied to solve an ill posed linear system of equations for the corresponding inverse problem. The new color distributions are generated and visualized using the obtained color source densities. With the proposed inverse approach the dark parts of the images can be reduced or completely removed. This article collects several examples for electromagnetic field visualization of the most commonly used sensor coil.

This paper proposes a visualizing methodology of iron loss generation in a magnetic material using its visualized domain images, i.e., SEM, Kerr and Faraday effects. Based on the differential equations for dynamic image, the material behavior is visualized. The state transition matrix of the Helmholtz equation, for which is derived from a series of distinct visualized domain images representing magnetized state. This makes it possible to visualize the magnetizing mechanism as well as iron loss generation. In the present paper, visualization of iron loss generation on a grain-oriented electrical steel sheet is worked out using a set of SEM images. As a result of our image analysis, magnetization curves at the particular points can be estimated.

A new interactive visualization system for education and design purposes in 2D electromagnetics is proposed. The proposed system using numerically computational results for several typical model configurations can display interactively electromagnetic field phenomena for any other model configuration bounded with the previously computed ones. It uses simple bilinear interpolation techniques in order to provide fast interactive display. This visualization system can be used for design purposes of problems with different model configurations and as an educational tool for teaching electromagnetics.

A concept to extract a feature of solid-air two-phase flow in a pipeline has been launched with a combination of a capacitance-computed tomography and wavelets transform. With this concept, particle distribution images obtained by CT are transformed with discrete wavelets multiresolution. As a result, in the case of low open area ratios of the pipe cross-section, high particle densities are shown in secondary dominant levels as well as a substantial space level. The high value in the secondary level resulted from inhomogeneous density due to collision between particles.

In developing a visual prosthesis, it is essential for us to determine its specifications which meet the minimal needs in daily lives of patients. For that purpose, we have proposed a prosthetic vision simulator which enables us to experience prosthetic vision in the virtual space. This time, we applied this system to quantitative evaluation of the reading ability. Experimental results suggested that the electric current intensity in stimulation has small effects to the reading ability.

As is well known, conventional magnetic circuit theory makes it possible to analyze the three-dimensional magnetic fields, even though its theoretical background is based on the engineering experiences. On the other side, finite elements have a firm theoretical background but it is too expensive to implement the three-dimensional analysis. In order to carry out the three-dimensional magnetic field analysis in a most efficient manner, we propose the theory of modern magnet circuit based on finite elements. This makes it possible to implement the three-dimensional magnetic field computation in a quite efficient manner. A simple example demonstrates not only the usefulness but also efficiency of our new methodology.