The electric field mill in our underground observation room detected a co-seismic electromagnetic signal in the vertical electrostatic field ca. 8 s after the origin time of the Niigataken Chuetsu-oki Earthquake in 2007, but ca. 30 s before the arrival time of the P-waves.

A simple analytical model to predict the DC MOSFET behavior under electromagnetic interference (EMI) is presented. The model is able to describe the MOSFET performance in the linear and saturation regions under EMI disturbance applied to the gate. The model consists of a unique simple equivalent circuit based on a voltage dependent current source and a reduced number of parameters which can accurately predict the drift on the drain current due to the EMI source. The analytical approach has been validated by means of electric simulation and measurements and can be easily introduced in circuit simulators. The proposed modeling technique combined with the nth-power law model of the MOSFET without EMI, significantly improves its accuracy in comparison with the n-th power law directly applied to a MOSFET under EMI impact.

When contact failure occurs in a connector in a coaxial high-frequency (HF) signal transmission line, it is well known that common-mode (CM) radiation occurs on the line. We focus on contact conditions in a connector causing such CM radiation. Experiments and simulations verify that CM radiation increases as the contact resistance increases. While the CM current strongly depends on the distribution pattern of contact resistances at a low resistance, the CM current does not depend on these pattern at a high resistance. Our results indicate that it is important to maintain a symmetrical distribution of contact spots whenever the number of such spots is four or more.

Recently, photovoltaic power systems and electric vehicles have been commonly used. Therefore, the importance of DC (direct current) switching is expected to increase in the near future. The authors have been examining a method of evaluating the electrode loss of AgNi contacts for an electromagnetic contactor with a medium DC load current at a resistive circuit. In this study, the arc energy and electrode mass changes were investigated in more detail. We carried out experiments of 100,000 operations for an electromagnetic contactor at a load current of 5 A constant with a source voltage change from 100 to 160 V. The arc duration, contact resistance, arc energy, and electrode mass changes were measured. As a result, the arc duration was found out increase with the source voltage. In addition, the stationary cathode mass change (loss) increased proportion only to the total arc energy. However, the stationary cathode loss per unit arc energy decreased at the highest source voltage.

In this paper, we propose a new method to estimate and effectively reduce the effect of thermal asperity (TA) in the perpendicular magnetic recording (PMR) channels with the state trellis. The TA is estimated from the state trellis, then its average is used to modify the equalized signal entering the Viterbi detector. For the partial response (PR) targets with DC component, the proposed method with a maximum-likelihood detector can improve the bit error rate performance by more than an order of magnitude when TA occurs and degrades when the giant magneto-resistive (GMR) nonlinearity and base line wander (BLW) effects are present. Unlike the previous studies, this method allows the use of PR targets with DC component under the presence of TA.

Silver electrical contacts are separated to generate break arcs in a DC48 V/6-24 A resistive circuit. The transverse magnetic field formed by a permanent magnet is applied to the break arcs. A series of experiments are carried out for two different experimental conditions. One condition is a constant contact separating speed while the magnetic flux density is changed to investigate the shortening effect of the arc duration. Another condition is a constant magnetic flux density while the contact separating speed is changed to investigate the changes in the arc duration and the contact gap when the break arc is extinguished. As a result, with constant separating speed, it is confirmed that the duration of break arcs is shortened by the transverse magnetic field and the break arcs are extinguished when the arc length reaches a certain value L. Under the condition of constant transverse magnetic field, (i) the arc duration is shortened by increasing the separation speed; (ii) the contact gap when the break arc is extinguished is almost constant when the separating speed v is sufficiently faster than 5 mm/s.

In this paper, we performed six human movement simulation by a commercial software (Poser7). We performed FDTD simulations for body area network propagation with one transmitter and six receivers. Received amplitudes were calculated for every time frame of 1/30 s interval. We also demonstrated a polarization diversity effectiveness for dynamic wearable body area network propagation.

We propose an active noise control (ANC) system for reducing periodic noise generated in a high magnetic field such as noise generated from magnetic resonance imaging (MRI) devices (MR noise). The proposed ANC system utilizes optical microphones and piezoelectric loudspeakers, because specific acoustic equipment is required to overcome the high-field problem, and consists of a head-mounted structure to control noise near the user's ears and to compensate for the low output of the piezoelectric loudspeaker. Moreover, internal model control (IMC)-based feedback ANC is employed because the MR noise includes some periodic components and is predictable. Our experimental results demonstrate that the proposed ANC system (head-mounted structure) can significantly reduce MR noise by approximately 30 dB in a high field in an actual MRI room even if the imaging mode changes frequently.

A sensor network consisting of a number of palm-sized nodes with small electric and magnetic sensors has been proposed to monitor local electromagnetic activities in space plasmas. In the present study, a compact loop antenna system is designed and fabricated for use in sensor nodes that can capture magnetic vector fields from ELF to MF frequencies. The performance of the developed system is shown to be sufficient to allow measurement of the magnetic field activity around artificial structures in addition to intense natural plasma waves in geospace.

Owing to the concerns about electromagnetic interference (EMI) from wireless local area networks (WLAN), an investigation into its impact on medical equipment is carried out. The results indicate that there is no evidence of 802.11 Wireless LAN systems being unsafe for installation inside hospital premises and only one piece of equipment was found to be susceptible to IEEE 802.11b standard.

This paper presents various types of iterative progressive numerical methods (IPNMs) for the computation of electromagnetic (EM) wave scattering from many objects and reports comparatively the performance of these methods. The original IPNM is similar to the Jacobi method which is one of the classical linear iterative solvers. Then the modified IPNMs are based on other classical solvers like the Gauss-Seidel (GS), the relaxed Jacobi, the successive overrelaxation (SOR), and the symmetric SOR (SSOR) methods. In the original and modified IPNMs, we repeatedly solve linear systems of equations by using a nonstationary iterative solver. An initial guess and a stopping criterion are discussed in order to realize a fast computation. We treat EM wave scattering from 27 perfectly electric conducting (PEC) spheres and evaluate the performance of the IPNMs. However, the SOR- and SSOR-type IPNMs are not subject to the above numerical test in this paper because an optimal relaxation parameter is not possible to determine in advance. The evaluation reveals that the IPNMs converge much faster than a standard BEM computation. The relaxed Jacobi-type IPNM is better than the other types in terms of the net computation time and the application range for the distance between objects.

A novel computational method is proposed to investigate electromagnetic scattering problems. It is error controllable and reliable simulation in time domain can be performed. We apply the proposed method to analysis of transient scattering from open-ended structures and discuss scattering mechanisms.

This letter presents the field uniformity characteristics of a triangular prism reverberation chamber. A reverberation chamber that generally uses a stirrer to create a uniform electric field inside is an alternative to the semi-anechoic chamber for an electromagnetic compatibility test. To overcome the size and maintenance problems of a stirrer, we propose to replace it with a Quadratic Residue Diffuser which is commonly used in acoustics. To confirm that the diffuser is a valid alternative to the stirrer, a diffuser and an equilateral triangular prism reverberation chamber are designed and fabricated for 2.3-3.0 GHz operation. To investigate the field uniformity characteristics by varying the location of the transmitting antenna, both simulation and measurement in the triangular prism reverberation chamber were also done at its two positions, respectively. A commercial program XFDTD 6.2, engaging the finite difference time domain (FDTD), is used for simulation and a cumulative probability distribution, which the IEC 61000-4-21 recommends, is used to evaluate the field uniformity. Both simulation and measurement results show that the field uniformity in the chamber satisfies the international standard requirement of 6 dB tolerance and 3dB standard deviation, which means that a diffuser can be substituted for a stirrer.

A fast calculation tool for state-dependent capacitance of power distribution network is proposed. The proposed method achieves linear time-complexity, which can be more than four orders magnitude faster than a conventional SPICE-based capacitance calculation. Large circuits that have been unanalyzable with the conventional method become analyzable for more comprehensive exploration of capacitance variation. The capacitance obtained with the proposed method agrees SPICE-based method completely (up to 5 digits), and time-linearity is confirmed through numerical experiments on various circuits. The maximum and minimum capacitances are also calculated using average and variance estimation. Calculation times are linear time-complexity, too. The proposed tool facilitates to build an accurate macro model of an LSI.

This paper presents a method of expanding the operating frequency band of a Reverberating TEM Cell (RTC) for electromagnetic compatibility (EMC) testing. To expand the operating frequency band of an RTC, this paper places a wire septum inside the cell instead of a solid septum. The maximum usable frequency (MUF) for TEM cell operation and the lowest usable frequency (LUF) for reverberating chamber operation with the wire septum are studied and compared with a conventional solid septum. The E field strengths inside the RTC are measured and evaluated. The measurement results show that the RTC with the wire septum have similar MUF to the RTC with a solid septum at TEM mode, but have much lower LUF at a reverberating mode, which proves that the operating frequency band of the RTC can be expanded by using the wire septum.

In this paper, we consider the behavior of an autoregressive (AR) detector for partial-response (PR) signaling against offtrack interference (OTI) environment in perpendicular magnetic recording. Based on the behavior, we derive the optimum branch metric to construct the detector by the Viterbi algorithm. We propose an optimum AR detector for OTI that considers an optimum branch metric calculation and an estimation of noise power due to OTI in order to calculate an accurate branch metric. To evaluate the reliability of soft-output likelihood values calculated by our proposed AR detector, we demonstrate a bit error rate performance (BER) of low-density parity-check (LDPC) codes under OTI existing channel by computer simulation. Our simulation results show the proposed AR detector can achieve a better LDPC-coded BER performance than the conventional AR detector. We also show the BER performance of our proposal can keep within 0.5 dB of the case that perfect channel state information regarding OTI is used in the detector. In addition, we show that the partial-response maximum-likelihood (PRML) detector is robust against OTI even if OTI is not handled by the detector.

A characteristic-based constrained interpolation profile (CIP) method for solving three-dimensional, time-dependent Maxwell's equations is successfully developed. It is utilized to solve one-dimensional wave equations in the formulation of the Maxwell's equations. Calculation procedure of the CIP method for three-dimensional scattering analysis is described in details. Update equations for boundary conditions of a perfectly conducting (PEC) interface and a dielectric interface are formulated and obtained in explicit forms. Numerical analyses of electromagnetic scatterings of PEC sphere, dielectric sphere and PEC cube are performed and the scattering coefficient is calculated and compared with the Mie's analytic results. As a result, the scattering coefficients show good agreement with the Mie's results, which demonstrates the validity of the CIP method and the formulated update equations. It is also shown that the phase of the scattering coefficients determined by the CIP method are slightly more accurate than that of the FDTD method.

An algorithm is formulated for reconstructing a dielectric cylinder with the use of the T-matrix and the singular value decomposition (SVD) and is discussed through numerical examples under noisy conditions. The algorithm consists of two stages. At the first stage the measured data of scattered waves is transformed into the T-matrix. At the second stage we reconstruct the cylinder from the T-matrix. The singular value decomposition is applied in order to separate the radiating and the nonradiating currents, and the radiating current is directly obtained from the T-matrix. The nonradiating current and the object are reconstructed by decreasing a residual error of the current in the least square approximation, where linear equations are solved repeatedly. Some techniques are used in order to reduce the calculation time and to reduce the effects of noise. Numerical examples show us that the presented approach is simple and numerically feasible, and enables us to reconstruct a large object in a short time.

The dynamic characteristics are the key issues in the optimum design of a permanent magnetic actuator (PMA). A new approach to forecast the dynamic characteristics of the multilink PMA is proposed. By carrying out further developments of ADAMS and ANSOFT, a mathematic calculation model describing the coupling of mechanical movement, electric circuit and magnetic field considering eddy current effect, is constructed. With this model, the dynamic characteristics of the multilink PMA are calculated and compared with the experimental results. Factors that affect the opening time of the multilink PMA are analyzed with the model as well. The method is capable of providing a reference for the design of the PMA.

Adjustability is an important function of the magnetic release for modern molded case circuit breakers. Based on virtual prototype technology, an automatic prediction method is proposed to design reasonable reactive spring parameters for this kind of magnetic release. 3-D finite element method is adopted to calculate the static characteristics of the magnetic release. Then the dynamic characteristics of the magnetic release can be simulated taking into account the variation of the spring parameters with multi-dynamics method. The calculation results have been verified by the relevant experiments. It demonstrates that the proposed method is feasible to perform the design task.