We introduce a novel method to optimize field decomposition for a mode matching technique. Using our method, expanded mode numbers can be minimized to achieve the desired digits of computational accuracy.

Error analysis of the multilevel fast multipole algorithm is studied for electromagnetic scattering problems. We propose novel error prediction and control methods and verify that the computational error for scattering problems with over one million unknowns can be precisely controlled under desired digits of accuracy. Optimum selection of truncation numbers to minimize computational error also will be discussed.

This paper presents the iterative progressive numerical methods (IPNMs) based on the induced dimension reduction (IDR) theorem. The IDR theorem is mainly utilized for the development of new nonstationary linear iterative solvers. On the other hand, the use of the IDR theorem enables to revise the classical linear iterative solvers like the Jacobi, the Gauss-Seidel (GS), the relaxed Jacobi, the successive overrelaxation (SOR), and the symmetric SOR (SSOR) methods. The new IPNMs are based on the revised solvers because the original one is similar to the Jacobi method. In the new IPNMs, namely the IDR-based IPNMs, we repeatedly solve linear systems of equations by using a nonstationary linear iterative solver. An initial guess and a stopping criterion are discussed in order to realize a fast computation. We treat electromagnetic wave scattering from 27 perfectly electric conducting spheres and reports comparatively the performance of the IDR-based IPNMs. However, the IDR-based SOR- and the IDR-based SSOR-type IPNMs are not subject to the above numerical test in this paper because of the problem with an optimal relaxation parameter. The performance evaluation reveals that the IDR-based IPNMs are better than the conventional ones in terms of the net computation time and the application range for the distance between objects. The IDR-based GS-type IPNM is the best among the conventional and the IDR-based IPNMs and converges 5 times faster than a standard computation by way of the boundary element method.

An iterative inter-track interference (ITI) cancelling scheme is described for multi-track signal detection in nonbinary (NB)-LDPC-coded two-dimensional magnetic recording. The multi-track iterative ITI canceller that we propose consists of multi-track soft interference cancellers (SICs), two-dimensional partial response (TDPR) filters, noise-predictive max-log-MAP detectors, and an NB-LDPC decoder. TDPR filters using an ITI-suppressing tap-weight vector mitigate ITI in the first iteration. Multi-track SICs and TDPR filters adjusted to the residual two-dimensional ISI signals efficiently detect multi-track signals in the latter iterations. The simulation results demonstrated that our proposed iterative multi-track ITI canceller achieves frame error rates close to those obtained in a non-ITI case in media-noise-dominant environments when the both-side off-track ratio is up to 50%.

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.

An adaptive and iterative intertrack-interference (ITI) cancelling scheme is described for multi-track signal detection in inter-track asynchronous shingled write magnetic recording. There is write-clock frequency drift in asynchronous recording systems. Read-back signals obtained with a wide read head scanning narrow tracks thus suffer from not only intersymbol interference (ISI) but also time-variant ITI. To efficiently cope with static ISI and time-variant ITI, multi-track soft interference cancellers and two-dimensional partial-response filters are incorporated based on per-survivor processing into each trellis state defined in a one-dimensional/two-dimensional trellis-switching max-log-MAP detector. In addition, the computational complexity can be reduced based on channel interpolation and intermittent TDPR-filter control by allowing small degradation in signal detection. Computer simulation results in media-noise-dominant environments demonstrate that the proposed adaptive and iterative ITI canceller achieves bit error rates close to those obtained in a non-ITI case when the read-head off-track ratio is up to 50% in write-clock frequency difference of 0.02%.

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.

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 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.

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.

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.

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.

Break arcs are rotated with the radial magnetic field formed by a magnet embedded in the fixed contact. They are generated in a DC42 V resistive circuit. The circuit current when the contacts are closed varies from 5 A to 21 A. The strength of a radial magnetic field for rotating break arcs changes. Arc duration is investigated. Then rotational frequency, arc length and Lorentz force when the periodic rotation of break arcs starts are analyzed to investigate the conditions required to rotate break arcs. The following results are obtained. The arc length L when the rotational motion of the break arc starts is almost constant at a constant magnetic flux density with an increase in circuit current. The arc length L decreases with an increase in the magnetic flux density of the radial magnetic field. The rotational motion of break arcs starts when the arc length L reaches a certain value determined by magnetic flux density. Rotational frequency and Lorentz force increase linearly with an increase in circuit current.

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.

This study demonstrates the ability of a portable X-band Doppler weather radar (XDR) to measure Doppler velocity (Vd). Existing portable X-band weather radars are housed in a container and hence have to be carried by a truck. Therefore they have limitations in their installation places. For installations at small areas where the existing X-band weather radars cannot be installed (e.g., rooftop area of small building), XDR is designed to be carried by a cart. Components of the outdoor unit (a parabolic antenna with a diameter of 1.2 m, magnetron transmitter, and radio frequency (RF) and intermediate frequency (IF) analog components) are housed in a compact body with a weight less than 300 kg. The radar operation, IF digital processing, and data storage are carried out by a desktop computer having a commercial IF digital receiver. In order to attain the required portability and reduced purchase and running costs, XDR uses a magnetron transmitter. Because XDR is the first that utilizes an IF digital receiver for the signal processing specific to magnetron transmitters (i.e., the phase correction of received signals due to the randomness of the transmitted pulse phase), Vd measured by XDR (hereafter VdXDR) was assessed. Using the dataset collected from 25 to 26 October 2009 at the Shigaraki MU Observatory (3451'N, 13606'E), the equivalent radar reflectivity factor (Ze) and VdXDR were assessed using Ze and Vd measured by a Micro Rain Radar and a L-band Doppler radar named LQ-7. The results using correlation coefficients and regression lines demonstrate that XDR measured Ze and Vd accurately. The results also show that IF digital receivers are useful for providing magnetron weather radars with the function of Vd measurement, and further suggest that a combination of IF digital receiver and magnetron transmitter contributes to future development of Doppler weather radars, because high cost performance is strongly required for a precipitation monitoring radar network.

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.