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Magnetics, IEEE Transactions on

Issue 5 • Date May 2011

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Displaying Results 1 - 25 of 177
  • [Front cover]

    Publication Year: 2011 , Page(s): C1
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  • IEEE Transactions on Magnetics publication information

    Publication Year: 2011 , Page(s): C2
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  • Table of contents

    Publication Year: 2011 , Page(s): 849 - 861
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  • Message from the Editorial Board Chairman

    Publication Year: 2011 , Page(s): 862
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  • The 14th Biennial IEEE Conference on Electromagnetic Field Computation (IEEE CEFC 2010)

    Publication Year: 2011 , Page(s): 863
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  • Editorial Board

    Publication Year: 2011 , Page(s): 864 - 865
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  • Classification of Mental Task From EEG Signals Using Immune Feature Weighted Support Vector Machines

    Publication Year: 2011 , Page(s): 866 - 869
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (222 KB) |  | HTML iconHTML  

    The classification of mental tasks is one of key issues of EEG-based brain computer interface (BCI). Differentiating classes of mental tasks from EEG signals is challenging because EEG signals are nonstationary and nonlinear. Owing to its powerful capacity in solving nonlinearity problems, support vector machine (SVM) method has been widely used as a classification tool. Traditional SVMs, however, assume that each feature of a sample contributes equally to classification accuracy, which is not necessarily true in real applications. In addition, the parameters of SVM and the kernel function also affect classification accuracy. In this study, immune feature weighted SVM (IFWSVM) method was proposed. Immune algorithm (IA) was then introduced in searching for the optimal feature weights and the parameters simultaneously. IFWSVM was used to multiclassify five different mental tasks. Theoretical analysis and experimental results showed that IFWSVM has better performance than traditional SVM. View full abstract»

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  • 3-D Reconstruction of Encephalic Tissue in MR Images Using Immune Sphere-Shaped SVMs

    Publication Year: 2011 , Page(s): 870 - 873
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (309 KB) |  | HTML iconHTML  

    In the brain MR images, the boundary of each encephalic tissue is highly irregular. Traditional 3-D reconstruction algorithms are challenged. Owing to its powerful capacity in solving nonlinearity problems, the sphere-shaped support vector machines (SSSVMs) is applied in the 3-D reconstruction. Selecting parameters for SSSVM and the kernel function, however, is a complicated issue. Appropriate parameters can make the model more flexible and help to obtain more accurate data description. In this study, immune algorithm (IA) is used in searching for the optimal parameters. Immune SSSVM (ISSSVM) is proposed to reconstruct the 3-D encephalic tissues in MR images. As shown by the experiment of this study, each encephalic tissue can be reconstructed efficiently, and satisfied accuracy and visual effect can be obtained. View full abstract»

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  • EEG Inverse Problem Solution Using a Selection Procedure on a High Number of Electrodes With Minimal Influence of Conductivity

    Publication Year: 2011 , Page(s): 874 - 877
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (611 KB) |  | HTML iconHTML  

    The uncertain conductivity value of skull and brain tissue influences the accuracy of the electroencephalogram (EEG) inverse problem solution. Indeed, when the assumed conductivity in the numerical procedure is different from the actual conductivity then a source localization error is introduced. When using traditional least-squares minimization methods, the number of electrodes in the EEG cap does not influence the spatial resolution. A recently developed reduced conductivity dependence (RCD) methodology, based on the selection of electrodes, is able to increase the spatial resolution of the EEG inverse problem. This paper presents the implications of the RCD method when using a large number of electrodes in the EEG cap on the spatial resolution of the EEG inverse solutions. We show by means of numerical experiments that in contrast to traditional methods, the RCD method enables to increase the spatial resolution. The computations show that the EEG hardware should be modified with as large as possible electrodes. View full abstract»

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  • A Source Identification Problem for the Electrical Activity of Brain |During Hand Movement

    Publication Year: 2011 , Page(s): 878 - 881
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (265 KB) |  | HTML iconHTML  

    A field source reconstruction of the dipoles modeling the activated area of the brain, while a subject performs the task of the voluntary motion of the hand, is solved. Experimental data resulting from fMRI are used for constraining the position of the equivalent dipole. View full abstract»

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  • A Novel Array-Type Transcranial Direct Current Stimulation (tDCS) System for Accurate Focusing on Targeted Brain Areas

    Publication Year: 2011 , Page(s): 882 - 885
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (506 KB) |  | HTML iconHTML  

    In this paper, we propose a new array-type transcranial direct current stimulation (tDCS) system, which can modulate cortical excitability of human brain in a more effective manner. Once a target location inside a brain is determined, optimal injection current/potential at each electrode is calculated automatically by solving a constrained optimization problem. Current density distribution in a realistic head model was evaluated using the 3-D finite element method (FEM) adopting the superposition principle. Simulation results demonstrated that the proposed tDCS system enables effective and accurate field concentration on targeted brain areas. View full abstract»

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  • Domain Decomposition for Computing Extremely Low Frequency Induced Current in the Human Body

    Publication Year: 2011 , Page(s): 886 - 889
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (266 KB) |  | HTML iconHTML  

    Computation of electromagnetic fields in high resolution computational phantoms requires solving large linear systems. We present an application of Schwarz preconditioners with Krylov subspace methods for computing extremely low frequency induced fields in a phantom issued from the Visible Human. View full abstract»

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  • Modeling Deep Brain Stimulation Based on Current Steering Scheme

    Publication Year: 2011 , Page(s): 890 - 893
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (484 KB) |  | HTML iconHTML  

    The goal of this paper is to develop a quantitative understanding about the shape and the volume of tissue activated (VTA) and stimulation sites by deep brain stimulation (DBS) in deep brain area like subthalamic nucleus (STN) to improve neural stimulation. Monopolar current steering approach has been studied in cochlear implants and deep brain stimulation. In this paper, novel bipolar and tripolar current steering schemes are applied to deep brain stimulation. Finite-element models of deep brain stimulation are used to study the volume of tissue activated for monopolar, bipolar, and tripolar current steering configurations. View full abstract»

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  • Computation of Local Electromagnetic Force

    Publication Year: 2011 , Page(s): 894 - 897
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (246 KB) |  | HTML iconHTML  

    Total electromagnetic force on a body can be predicted by replacing the magnetization and polarization with appropriate equivalent currents and charges. Still, the equivalence of total force does not imply that the integrated densities have physical meaning. Instead of defining local electromagnetic force by using equivalent currents and charges we begin its determination from basic material elements. An example case illustrates how the approach can be used to compute magnetic force densities. View full abstract»

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  • Development of a Numerical Simulation Method for the Magnetic Separation of Magnetic Particles

    Publication Year: 2011 , Page(s): 898 - 901
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (478 KB) |  | HTML iconHTML  

    Magnetic separation is a very useful tool in medicine manufacturing and sludge disposal, and we have developed the magnetic chromatography system, which separates the magnetic particles or the ions from fluid due to its strong magnetic field gradients in the very small flow channel. There are many fine ferromagnetic wires on the wall of the developed magnetic column. A superconducting magnet applies a strong magnetic field to the magnetic column, and fine ferromagnetic wires make strong magnetic field gradients. It was, however, impossible to accurately evaluate the performance of the developed magnetic column due to the absence of a good simulation method. In order to enhance the accuracy of the simulation, it is necessary to couple the fluid dynamics simulation with the magnetic field simulation. Therefore, we have developed a simulation code dealing with the fluid dynamics, solving Navier-Stokes, control volume, and magnetic field equations simultaneously, and compared the simulation result to the experimental one to verify the validity. View full abstract»

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  • Demagnetizing Field in Micromagnetic Simulation Under Periodic Boundary Conditions

    Publication Year: 2011 , Page(s): 902 - 905
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (405 KB) |  | HTML iconHTML  

    The demagnetizing field in a micromagnetic simulation is studied under periodic boundary conditions. To evaluate the influence of the periodic structure, macroscopic demagnetizing factors are defined. A large demagnetizing field yields a linear magnetization where the susceptibility is given by the inverse of the macroscopic demagnetizing factor. The shape anisotropy induces rectangular hysteresis loops for which the coercive force is evaluated by the macroscopic demagnetizing factors. View full abstract»

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  • Hybrid Technique for Dynamic Modeling of the Performance of Linear Generators With Skewed Mounted Permanent Magnets

    Publication Year: 2011 , Page(s): 906 - 909
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (848 KB) |  | HTML iconHTML  

    This paper proposes a specific hybrid 2-D simulation model of magnetic field distribution accounting for magnet skew in the case of a linear permanent magnet generator (LPMG). The proposed methodology is based on a hybrid numerical technique implementing standard finite elements for the analysis of stator and rotor parts combined with an analytical solution in the Cartesian coordinate system in the air-gap area specified for magnet skew consideration. The developed technique has been incorporated in a coupled field-circuit model for the overall simulation of the performance of an electrical generating unit for sea-wave energy extraction using LPMG. The derived model has been implemented in the control subsystem aiming to tune the movement of the wave energy absorber to the system resonance frequency enabling to optimize its performance. Simulation results have been validated by measurements on a sea-wave energy extraction demonstration plant. View full abstract»

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  • An Extension of PEEC Method for Magnetic Materials Modeling in Frequency Domain

    Publication Year: 2011 , Page(s): 910 - 913
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (338 KB) |  | HTML iconHTML  

    An extension of the partial element equivalent circuit (PEEC) method for magnetic materials modeling in the frequency domain applied on toroidal magnetic inductors with rectangular cross section is presented in this paper. The extension is performed by coupling the PEEC method and the boundary element method (BEM). The influence of magnetic material is modeled by distributions of “fictitious magnetic currents and charges” existing on the surface of a magnetic body. To verify the developed 3-D PEEC model, calculated and measured impedances are compared for two winding arrangements employing a ferrite T38 core. A good agreement between the PEEC simulation and measurements is presented up to the first resonant frequency. The described PEEC modeling approach enables 3-D electromagnetic simulations with much less computational effort than given for existing finite element method (FEM) simulators. View full abstract»

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  • Coupled Field Synthesis in Magnetic Fluid Hyperthermia

    Publication Year: 2011 , Page(s): 914 - 917
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (242 KB) |  | HTML iconHTML  

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

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  • Multiphysics Modeling of Induction Hardening of Ring Gears for the Aerospace Industry

    Publication Year: 2011 , Page(s): 918 - 921
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (611 KB) |  | HTML iconHTML  

    Induction heating has been widely used for heat treating and especially surface hardening in a broad variety of applications, ranging from the automotive to the renewable energy market. However, the lack of precise knowledge about the interrelation between all the concurrent physical phenomena occurring within the part during the heating cycle has restricted its use to mass-production items (mostly gears). The benefits of this technology, which is clean, repeatable, and cost-effective, could boost its introduction into more conservative industry sectors, such as aerospace, where furnace-based treatments (e.g., carburizing) represent the golden standard. The major limitation is related to the optimization of the induction hardening process, which usually requires significant material know-how and can thus be very long and expensive. Computer simulation could provide a general tool for understanding and improving the critical aspects of each step of the process, thus speeding up the spreading of the induction technology into new markets. View full abstract»

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  • Semi-Analytical Magneto-Mechanic Coupling With Contact Analysis for MEMS/NEMS

    Publication Year: 2011 , Page(s): 922 - 925
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (429 KB) |  | HTML iconHTML  

    This paper presents a methodology and a tool for magnetic and mechanical deformation coupling using numerical and analytical modeling. An analytical magnetic model using Coulombian approach is used and coupled with a mechanical deformation model for a cantilever beam to evaluate contact size and contact force. Such a coupling is not available using numerical solution. This paper details the deformation and contact analysis, which is validated by finite element simulation and also details the coupling approach. Such a modeling is dedicated to an optimization process of magnetic MEMS/NEMS in general and to magnetic nano switch in particular. View full abstract»

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  • Numerical Modeling of Magnetic Properties of Ferromagnetic Shape Memory Materials Depending on Temperature and Stress

    Publication Year: 2011 , Page(s): 926 - 929
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (853 KB) |  | HTML iconHTML  

    This paper deals with a numerical modeling of nonlinear magnetic properties of ferromagnetic shape memory alloys (FSMAs). In order to design new magnetic actuators by using the FSMAs, it is necessary to develop an effective engineering modeling, which can represent the nonlinear magnetic properties depending on stress and temperature. This paper presents measured relationship among stress, temperature and magnetic properties of a Fe-based FSMA. On the basis of the measured result, we have developed a numerical modeling with an arc-tangent function. The modeling is applied to analyze a simple example for verification and the calculated results demonstrate its applicability in numerical simulations. View full abstract»

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  • Frequency-Dependent Coupled Field-Circuit Modeling of Armored Power Cables Using Finite Elements

    Publication Year: 2011 , Page(s): 930 - 933
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (487 KB) |  | HTML iconHTML  

    This paper proposes a frequency-dependent electromagnetic model for armored power cables using Coupled circuit-field method. The model parameters were obtained by conducting a series of coupled field-circuit studies at different frequencies. The cable capacitance matrix is calculated using an electrostatic FE analysis. The frequency response of the cable was obtained by coupling the cable FE domain model and external electric circuits. This technique allows the physical representation of the nonlinear magnetization behavior of the cable shell as well as the frequency dependence of the cable parameters. This frequency response was then fitted with rational function approximation. The resulting vector fitting (VF) rational function was then represented by an equivalent electrical network. This model represents the cable's high-frequency dynamic behavior to account for overvoltages or spikes in the current waveforms. View full abstract»

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  • Optimization of SPL and THD Performance of Microspeakers Considering Coupling Effects

    Publication Year: 2011 , Page(s): 934 - 937
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (638 KB) |  | HTML iconHTML  

    Mobile phones have become more versatile as a result of advances in mobile communication technology. The latest mobile phones are able to provide dazzling multimedia entertainment with portability. A microspeaker has become a generic electromechanical part of mobile phones that enables multimedia features. Therefore, the performance of the microspeaker must be improved in line with the increasing demand for high-quality sound produced by the phone. Sound pressure level (SPL) and total harmonic distortion (THD) are the two most common evaluation criteria that are used to quantify the performance of the microspeaker. Therefore, it is necessary to implement an analysis procedure that predicts and quantifies the SPL and THD characteristics. This manuscript suggests a multiphysics analysis procedure that comprehensively considers electromagnetic, mechanical, and acoustic coupling effects. The experimental results confirm the validity of the proposed analysis procedure. View full abstract»

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  • System Simulation of a PMSM Servo Drive Using Field-Circuit Coupling

    Publication Year: 2011 , Page(s): 938 - 941
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (232 KB) |  | HTML iconHTML  

    In the development process of electrical drive trains, consisting of a motor, the power electronics and the control scheme, it is difficult to predict the exact machine and control behavior in combination with the converter. Therefore, system simulations with analytical machine models embedded in a circuit simulation environment are performed. In order to increase accuracy by paying attention to parasitic machine effects caused by e.g. saturation or slot harmonics, a Finite Element model can be used instead of the analytical machine model. In this paper such a field-circuit coupling is applied to the simulation of a permanent magnet synchronous machine servo drive and the results are shown and discussed. View full abstract»

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Aims & Scope

IEEE Transactions on Magnetics publishes research in science and technology related to the basic physics and engineering of magnetism, magnetic materials, applied magnetics, magnetic devices, and magnetic data storage.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Pavel Kabos
National Institute of Standards and Technology