In this study, we develop a numerical method for determining transient energy deposition in biological bodies exposed to electromagnetic (EM) pulses. We use a newly developed frequency-dependent finite-difference time-domain (FD2TD) method, which is combined with the fast inverse Laplace transform (FILT) and Prony method. The FILT and Prony method are utilized to transform the Cole-Cole model of biological media into a sum of multiple Debye relaxation terms. Parameters of Debye terms are then extracted by comparison with the time-domain impulse responses. The extracted parameters are used in an FDTD formulation, which is derived using the auxiliary differential equation method, and transient energy deposition into a biological medium is calculated by the equivalent circuit method. The validity of our proposed method is demonstrated by comparing numerical results and those derived from an analytical method. Finally, transient energy deposition into human heads of TARO and HANAKO models is then calculated using the proposed method and, physical insights into pulse exposures of the human heads are provided.

Magnetic fields are often utilized for position sensing of mobile devices. In typical sensing systems, multiple sensors are used to detect magnetic fields generated by target devices. To determine the positions of the devices, magnetic-field data detected by the sensors must be converted to device-position data. The data conversion is not trivial because it is a nonlinear inverse problem. In this study, we propose a machine-learning approach suitable for data conversion required in the magnetic-field-based position sensing of target devices. In our approach, two different sets of training data are used. One of the training datasets is composed of raw data of magnetic fields to be detected by sensors. The other set is composed of logarithmically represented data of the fields. We can obtain two different predictor functions by learning with these training datasets. Results show that the prediction accuracy of the target position improves when the two different predictor functions are used. Based on our simulation, the error of the target position estimated with the predictor functions is within 10cm in a 2m × 2m × 2m cubic space for 87% of all the cases of the target device states. The computational time required for predicting the positions of the target device is 4ms. As the prediction method is accurate and rapid, it can be utilized for the real-time tracking of moving objects and people.

To achieve smooth beam injection in operation of synchrotron radiation facilities, pulsed multipole magnet beam injectors are developed. It is found that the developed beam injector causes serious disturbance in the circulating storage beam in the Aichi synchrotron radiation center, and that such the unexpected disturbance of the storage beam may be caused by eddy current induced on thin titanium coating inside a beam duct. In this work, the induced eddy current on the titanium layer is evaluated quantitatively by numerical simulations and improvement for the developed beam injector is discussed based on the numerical simulation.

To realize a stable and efficient wireless power transfer (WPT) system that can be used in any environment, it is necessary to inspect the influence of environmental interference along the power transmission path of the WPT system. In this paper, attempts have been made to reduce the influence of the medium with a dielectric and conductive loss on the WPT system using spiral resonators for resonator-coupled type wireless power transfer (RC-WPT) system. An important element of the RC-WPT system is the resonators because they improve resonant characteristics by changing the shape or combination of spiral resonators to confine the electric field that mainly causes electrical loss in the system as much as possible inside the resonator. We proposed a novel dual-spiral resonator as a candidate and compared the basic characteristics of the RC-WPT system with conventional single-spiral and dual-spiral resonators. The parametric values of the spiral resonators, such as the quality factors and the coupling coefficients between resonators with and without a lossy medium in the power transmission path, were examined. For the lossy mediums, pure water or tap water filled with acryl bases was used. The maximum transmission efficiency of the RC-WPT system was then observed by tuning the matching condition of the system. Following that, the transmission efficiency of the system with and without lossy medium was investigated. These inspections revealed that the performance of the RC-WPT system with the lossy medium using the modified shape spiral resonator, which is the dual-spiral resonator proposed in our laboratory, outperformed the system using the conventional single-spiral resonator.

The growing threat of Hardware Trojans (HT) in the System-on-Chips (SoC) industry has given way to the embedded systems researchers to propose a series of detection methodologies to identify and detect the presence of Trojan circuits or logics inside a host design in the various stages of the chip design and manufacturing process. Many state of the art works propose different techniques for HT detection among which the popular choice remains the Side-Channel Analysis (SCA) based methods that perform differential analysis targeting the difference in consumption of power, change in electromagnetic emanation or the delay in propagation of logic in various paths of the circuit. Even though the effectiveness of these methods are well established, the evaluation is carried out on simplistic models such as AES coprocessors and the analytical approaches used for these methods are limited by some statistical metrics such as direct comparison of EM traces or the T-test coefficients. In this paper, we propose two new detection methodologies based on Machine Learning algorithms. The first method consists in applying the supervised Machine Learning (ML) algorithms on raw EM traces for the classification and detection of HT. It offers a detection rate close to 90% and false negative smaller than 5%. In the second method, we propose an outlier/novelty algorithms based approach. This method combined with the T-test based signal processing technique, when compared with state-of-the-art, offers a better performance with a detection rate close to 100% and a false positive smaller than 1%. In different experiments, the false negative is nearly the same level than the false positive and for that reason the authors only show the false positive value on the results. We have evaluated the performance of our method on a complex target design: RISC-V generic processor. Three HTs with their corresponding sizes: 0.53%, 0.27% and 0.09% of the RISC-V processors are inserted for the experimentation. In this paper we provide elaborative details of our tests and experimental process for reproducibility. The experimental results show that the inserted HTs, though minimalistic, can be successfully detected using our new methodology.

In this paper, an ultra-thin wave absorber using a resistive patch array closely-placed in front of a back-metal is designed. The positively large susceptance is required for the patch array to cancel out the negatively large input susceptance of the short-circuited ultra-thin spacer behind the array. It is found that the array needs the gap of 1mm, sheet resistance of less than 20Ω/sq. and patch width of more than 15mm to obtain the zero input susceptance of the absorber with the 1/30 wavelength spacer. Moreover, these parameters were designed considering the electromagnetic coupling between the array and back-metal, and the square patch array absorbers with the thickness from 1/30 to 1/150 wavelength were designed.

We review a new superconducting element, called “magnetic Josephson junctions” with a magnetic barrier instead of the insulating barrier of conventional Josephson junctions. We classify the three types of magnetic barrier, i.e., diluted alloy, conventional ferromagnet, and magnetic multilayer barriers, and introduce various new physics such as the π-state arising in magnetic Josephson junctions due to the interaction between superconductivity and magnetism.

In this letter, a method for the construction of polar codes based on the mutual information approximation (MIA) is proposed for the 4Tb/in2 two-dimensional inter-symbol interference (2D-ISI) channels, such as the bit-patterned magnetic recording (BPMR) and two-dimensional magnetic recording (TDMR). The basic idea is to exploit the MIA between the input and output of a 2D detector to establish a log-likelihood ratio (LLR) distribution model based on the MIA results, which compensates the gap caused by the 2D ISI channel. Consequently, the polar codes obtained by the optimization techniques previously developed for the additive white Gaussian noise (AWGN) channels can also have satisfactory performances over 2D-ISI channels. Simulated results show that the proposed polar codes can outperform the polar codes constructed by the traditional methods over 4Tb/in2 2D-ISI channels.

A non-volatile memory (NVM) employing MTJ has a lot of strong points such as read/write performance, best endurance and operating-voltage compatibility with standard CMOS. However, it consumes a lot of energy when writing the data. This becomes an obstacle when applying to battery-operated mobile devices. To solve this problem, we propose an approach to augment the capability of the precision scaling technique for the write operation in NVM. Precision scaling is an approximate computing technique to reduce the bit width of data (i.e. precision) for energy reduction. When writing image data to NVM with the precision scaling, the write energy and the image quality are changed according to the write time and the target bit range. We propose an energy-efficient approximate storing scheme for non-volatile flip-flops and a magnetic random-access memory (MRAM) that allows us to write the data by optimizing the bit positions to split the data and the write time for each bit range. By using the statistical model, we obtained optimal values for the write time and the targeted bit range under the trade-off between the write energy reduction and image quality degradation. Simulation results have demonstrated that by using these optimal values the write energy can be reduced up to 50% while maintaining the acceptable image quality. We also investigated the relationship between the input images and the output image quality when using this approach in detail. In addition, we evaluated the energy benefits when applying our approach to nine types of image processing including linear filters and edge detectors. Results showed that the write energy is reduced by further 12.5% at the maximum.

Electromagnetic scattering of an electromagnetic plane wave from a rectangular hole in a thick conducting screen is solved using the Kirchhoff approximation (KA). The scattering fields can be derived as field radiations from equivalent magnetic current sources on the aperture of the hole. Some numerical results are compared with those by the Kobayashi potential (KP) method. The proposed method can be found to be efficient to solve the diffraction problem for high frequency regime.

We propose a compact magnetic tunnel junction (MTJ) model for circuit simulation by de-facto standard SPICE in this paper. It is implemented by Verilog-A language which makes it easy to simulate MTJs with other standard devices. Based on the switching probability, we smoothly connect the adiabatic precessional model and the thermal activation model by using an interpolation technique based on the cubic spline method. We can predict the switching time after a current is applied. Meanwhile, we use appropriate physical models to describe other MTJ characteristics. Simulation results validate that the model is consistent with experimental data and effective for MTJ/CMOS hybrid circuit simulation.

Silver electrical contacts were separated at constant opening speed in a 200V-500VDC/10A resistive circuit. Break arcs were extinguished by magnetic blowing-out with transverse magnetic field of a permanent magnet. The permanent magnet was appropriately located to simplify the lengthened shape of the break arcs. Magnetic flux density of the transverse magnetic field was varied from 20 to 140mT. Images of the break arcs were observed from the horizontal and vertical directions using two high speed cameras simultaneously. Arc length just before extinction was analyzed from the observed images. It was shown that shapes of the break arcs were simple enough to trace the most part of paths of the break arcs for all experimental conditions owing to simplification of the shapes of the break arcs by appropriate arrangement of the magnet. The arc length increased with increasing supply voltage and decreased with increasing magnetic flux density. These results will be discussed in the view points of arc lengthening time and arc lengthening velocity.

Authors had proposed a hybrid electromagnetic field analysis method suitable for an airport surface so far. In this paper, the hybrid method is validated by measurements by using a 1/50 scale-model of an airport considering several layouts of the buildings and sloping ground. The measured power distributions agreed with the analyzed ones within 5 dB errors excepting null points and the null positions of the distribution is also estimated within one wavelength errors.

For actual multi-channel differential signaling system, the ideal balance or symmetrical topology cannot be established, and hence, an imbalance component is excited. However a theoretical analysis method of evaluating the voltage and current distribution on the differential-paired lines, which allows to anticipate EM radiation at the design stage and to study possible means for suppressing imbalance components, has not been implemented. To provide the basic considerations for electromagnetic (EM) radiation from practical asymmetrical differential-paired lines structure with equi-length routing used in high-speed board design, this paper newly proposes an analytical method for evaluating the voltage and current at any point on differential-paired lines by expressing the differential paired-lines with an equivalent source circuit and an equivalent load circuit. The proposed method can predict S-parameters, distributions of voltage and current and EM radiation with sufficient accuracy. In addition, the proposed method provides enough flexibility for different geometric parameters and can be used to develop physical insights and design guidelines. This study has successfully established a basic method to effectively predict signal integrity and EM interference issues on a differential-paired lines.

Magneto-optical (MO) switches operate with a dynamically applied magnetic field. The MO devices presented in this paper consist of microring resonators (MRRs) fabricated on amorphous silicon-on-garnet platform. Two types of MO switches with MRRs were developed. In the first type, the switching state is controlled by an external magnetic field component included in the device. By combination of MO and thermo-optic effects, wavelength tunable operation is possible without any additional heater, and broadband switching is achievable. The other type of switch is a self-holding optical switch integrated with an FeCoB thin-film magnet. The switching state is driven by the remanence of the integrated thin-film magnet, and the state is maintained without any power supply.

An effect of complex permeability of noise suppression sheets (NSS) on circuit parameters was investigated by a magnetic circuit analysis using cross-sectional size and material parameters. The series resistance and inductance of the coplanar waveguide (CPW) with a NSS considering the effect of the complex permeability of the NSS were quantitatively estimated. The result indicated that the imaginary and real part of the effective permeability affected the resistance and inductance, respectively. Furthermore, this analysis was applied to an 8-µm-wide CPW with a 0.5-µm-thick Co85Zr3Nb12 film for quantitative estimation of the resistance, the inductance and the characteristic impedance. The estimated parameters were almost similar to the measured values. These results showed that the frequency characteristics of the circuit parameters could be controlled by changing size and material parameters.

This paper proposes a single coil active shielding method of wireless unmanned aerial vehicle charger for leakage magnetic field reduction. A proposed shielding system eliminates the leakage magnetic field generated from the transmitting and receiving coils by generating the cancelling magnetic field. In order to enhance shielding effectiveness and preserve power transfer efficiency, shielding coil design parameters including radius and turns will analyze. Based on the analysis of coil design, shielding effectiveness and power transfer efficiency will estimate. In addition, shielding current control method corresponding to leakage magnetic field strength and phase will describe. A proposed shielding system has verified by simulations and experiments in terms of the total shielding effectiveness and power transfer efficiency measurements. The simulation and experimental results show that a proposed active shielding system has achieved 68.85% of average leakage magnetic field reduction with 1.92% of power transfer efficiency degradation. The shielding effectiveness and power transfer efficiency variation by coil design has been experimentally verified.

A planar electromagnetic field stirrer with periodically arranged metal patterns and diode switches is proposed for improving uneven heating of a heated object placed in a microwave oven. The reflection phase of the proposed stirrer changes by switching the states of diodes mounted on the stirrer and the electromagnetic field in the microwave oven is stirred. The temperature distribution of a heated object located in a microwave oven was simulated and measured using the stirrer in order to evaluate the improving effect of the uneven heating. As the result, the heated parts of the objects were changed with the diode states and the improving effect of the uneven heating was experimentally indicated.

The accurate calculation of the inductance is the most basic problem of the inductor design. In this paper, the core flux density distribution and leakage flux in core window and winding of core-type inductor are analyzed by finite element analysis (FEA) firstly. Based on it, an improved magnetic equivalent circuit with high accuracy flux density distribution (iMEC) is proposed for a single-phase core-type inductor. Depend on the geometric structure, two leakage paths of the core window are modeled. Furthermore, the iMEC divides the magnetomotive force of the winding into the corresponding core branch. It makes the core flux density distribution consistent with the FEA distribution to improve the accuracy of the inductance. In the iMEC, flux density of the core leg has an error less than 5.6% compared to FEA simulation at 150A. The maximum relative error of the inductance is less than 8.5% and the average relative error is less than 6% compared to the physical prototype test data. At the same time, due to the high computational efficiency of iMEC, it is very suitable for the population-based optimization design.

Wireless medical telemetry service (WMTS) is an important wireless communication system in healthcare facilities. Recently, the potential for electromagnetic interference by noise emitted by switching regulators installed in light-emitting diode (LED) lamps has been a serious problem. In this study, we evaluated the characteristics of the electromagnetic noise emitted from LED lamps and its effect on WMTS. Switching regulators generally emit wide band impulsive noise whose bandwidth reaches 400MHz in some instances owing to the switching operation, but this impulsive nature is difficult to identify in the reception of WMTS because the bandwidth of WMTS is much narrower than that of electromagnetic noise. Gaussian approximation (GA) can be adopted for band-limited electromagnetic noise whose characteristics have no repetitive variation. On the other hand, GA with the impulsive correction factor (ICF) can be adopted for band-limited electromagnetic noise that has repetitive variation. We investigate the minimum receiver sensitivity of WMTS for it to be affected by electromagnetic noise emitted from LED lamps. The required carrier-to-noise power ratio (CNR) of Gaussian noise and electromagnetic noise for which GA can be adopted was approximately 15dB, but the electromagnetic noise for which GA with the ICF can be adopted was 3 to 4dB worse. Moreover, the spatial distribution of electromagnetic noise surrounding an LED lamp installation was measured. Finally, we roughly estimated the offset distance between the receiving antenna of WMTS and LED lamps when a WMTS signal of a certain level was added in a clinical setting using our experimental result for the required CNR.