Quantum computing is a technology that uses features of quantum mechanics to compute certain problems much faster than conventional computers and has recently received a great deal of interest. Although the expectations are high, the world will not change right away with the current state of quantum computing due to limited computational performance caused by noise in quantum circuits. Because of this situation, conventional computing techniques called quantum inspired, where the essential quantum phenomena that provide the speedup are emulated by conventional algorithm, are also attracting attention. In this presentation, the quantum computing technologies that NEC is working on as well as technical trends in this field are introduced.

Magnetic permeability perturbation testing (MPPT) owns the advantage of high sensitivity for deep buried defects steel pipes. The local wall thickness of pipes will change under complex working conditions, making it difficult to evaluate defects. The effects of uneven variation of wall thickness on magnetic permeability perturbation (MPP) is analyzed in the theoretical model. The magnetic field distribution in the case of thickening, thinning and normal thickness of the steel plate is studied in the simulation. The simulation and experiment results both show that the detection signal increases in case of thickness thinning while it decreases in case of thickness thickening. This study will contribute to the quantitative evaluation of defects in MPPT method.

The total focusing method (TFM) based on full matrix capture (FMC) is one of the hot spots in the research and application of ultrasonic testing. Compared with the traditional phased array method, the TFM can reduce the structural noise in ultrasonic testing for materials with inhomogeneity and anisotropy. In order to solve the problems of weak detection ability and low signal-to-noise ratio (SNR) in such materials, a new ultrasonic testing method that combines pulse compression technology with TFM is established in this work. First, the feasibility of this method is verified by numerical simulations based on the finite element method (FEM). Then, a TFM Ultrasonic testing system based on pulse compression technology is built and applied to the detection of defects in inhomogeneous and anisotropic materials. By comparing with traditional detection methods, it was verified that the Enhanced TFM with pulse compression technology of Encoding Modulation can effectively improve the detection ability and SNR of detection.

In this paper, the mode conversion of a single-mode ultrasonic beam is studied when passing across cracks of different depths in an aluminum plate. The single S0 mode is obtained using a wedge-angle beam probe. According to the aluminum properties and the plate thickness, the chosen operation frequency is sufficiently low to only permit the propagation of the A0 and S0 modes. Time signals along the propagation line path were acquired using a digital oscilloscope and a 2D Fast Fourier Transform was applied to the space-time map, and the wavenumber frequency map is obtained.

Eddy current testing can detect defects of carbon fibers in CFRP thanks to their conductive properties. In this study, the electric conductivity model of unidirectional laminated CFRP is investigated. The directional coil is sensitive to the fiber orientation, and the angular dependency of coil impedance over unidirectional laminated CFRP is studied. The conductivity model is developed based on the electromagnetic response of the directive coil.

In this paper, a permanent magnet levitation system is introduced, and the ADRC controller is designed to enhance its control performance. Firstly, the variable flux path mechanism and mechatronic system structure are introduced, and the mathematical model of the system is established. Then, the ADRC controller is designed, and the control system simulation is performed. Finally, the levitation experiments are executed using a prototype, and the time-domain responses are analyzed. The results show that the control performance of the system with ADRC is significantly enhanced compared with PID.

In steel plate production lines at steel mills, steel plates are conveyed by rollers, which causes problems such as deterioration of surface quality due to contact. By installing electromagnets on the side of steel plates on the conveying path, this research group was able to obtain high inductive performance in experiments. However, the shape of the steel plate has not yet been obtained analytically. Therefore, focusing on multi-body dynamics, we are studying the optimal placement position of electromagnets. In this study, the behavior of steel plates when the damping coefficient is varied is analyzed using multi-body dynamics. The results showed that the behavior was close to that of actual free vibration experiments.

Permanent magnet elastomer particle using in this study is spherical particles dispersing neodymium fine particles in an elastomer. Damper force of a separated dual-chamber single-rod type damper using permanent magnet elastomer particles was investigated by experiments and numerical simulations. The effects of applying magnetic field were examined. The dependency of damper force on the frequency and stroke were also investigated. Behavior of magnetic elastomer particles inside the damper was simulated by using the discrete particle method.

Magnetic levitation is expected to transport thin steel plate without contact, however magnetic levitation is difficult because thin steel plate bend due to their flexibility. In addition, elastic vibration occurs in the steel plate during magnetic levitation. In order to improve the levitation stability, it is necessary to suppress the vibration of the steel plate. For this purpose, it is necessary to grasp the vibration of the steel plate, but it is difficult to experimentally grasp the vibration of the whole steel plate. Therefore, the vibration of the steel plate during magnetic levitation is clarified by numerical analysis. In this report, the usefulness of the proposed analysis method is clarified by com-paring the experimental results and analytical results.

We developed a new optimization program to design a solar cavity for a solar-pumped laser. The software is based on ray tracing, and it calculates the optimal shape of the solar cavity to maximize total absorbed power into a laser medium. Results changing the co-doped density of Cr3+ in the laser medium of Cr/Nd:YAG ceramics are discussed. Although the maximum absorption efficiency of the laser medium is 0.65 when the traditional cone-shaped solar cavity and 1% of Nd3+ doped Nd:YAG is used, the optimized solar cavity with the same laser medium is expected to have 0.82 of absorption efficiency.

Reconfigurable intelligent surfaces (RISs) are widely investigated as promising candidates to control and process the environment in modern high-frequency telecommunication applications. In many cases RISs are built as metasurfaces that contain concentrated parameter elements, helping with one can change the geometry of the metasurface to modify the electromagnetic (EM) wave environment according to the requirements. In this paper we present the analysis of a simple two-dimensional RIS that is able to reflect the incident EM wave in wide range of reflection angles. The analysis method used here is recently developed by the authors for the fast calculation of the EM field of metasurfaces. The applied procedure can be used for the fast evaluation of the many possible states of investigated RISs.

A W-band low-noise amplifier (LNA) of four stages of common source topology is proposed in this paper. The chip was fabricated by using 90-nm CMOS process technology. It adopted parallel-coupled transmission lines between the gate terminal and the source terminal of the NMOS. Such structure was applied for optimizing among the noise, input matching and the gain. The measured results showed a peak gain of 13.15 dB at 73 GHz; a minimum noise figure of 4.83 dB at 77.5 GHz; an input P1dB of –7.3 dBm at 78 GHz, and an IIP3 of –1.1 dBm. The chip area is 0.730x0.588 mm^2, and the total power consumption is 28.14 mW under 1.2-V supply.

A ridge regression with initial values (RR) is proposed to improve the strain measurement accuracy of Digital Volume Correlation (DVC) for full-gradient strain field. It is a combination of the advantage of power window weighted digital volume correlation (PW-DVC) and widely used pointwise least square (PLS) methods. The calculation examples of synthetic images indicate that, for image with large strain gradient, PW-DIC+RR can reduce the minimum strain error by 20.3% compared with PW-DIC+PLS, but only increase the minimum strain error by 2 microstrains compared with PW-DIC. For image with small strain gradient, PW-DIC+RR can reduce the minimum strain error by 56.7% compared with PW-DIC, but only increase the minimum strain error by 44.7 microstrains compared with PW-DIC+PLS.

The multi-layer structure of GFRPs can result in layered defects during production and service, which can significantly impact the integrity and safety of equipment. To achieve precise quantitative characterization of delamination defects in GFRPs, a novel method is proposed to detect the depth and thickness of defects. We establish a mathematical relationship between the depth and thickness of the defect and amplitude of the echo signal. Employing the verified mathematical model, we successfully solve for the depth and thickness of the defect by analyzing amplitude of the echo signal based on least square method. According to our findings, the proposed method demonstrates the capability to simultaneously measure the depth and thickness of defects. Notably, the method exhibits outstanding accuracy, with the detected thickness error being within 0.01 mm and the depth error within 0.1 mm.

The debonding defect is one of the critical flaws that have been posing a severe threat to structural integrity of Glass Fibre Reinforced Polymer (GFRP). In this paper, a sweep-frequency microwave testing method based on Cross-polarization Microwave Reflectometry (CMR) is proposed for detection and imaging of debonding defects in a unidirectional GFRP. Simulations and experiments are carried out to investigate the feasibility and applicability of the proposed method. The characteristics regarding the testing signal in Ka band (26.5GHz~40GHz) is scrutinized along with the correlation of the signal feature with the defect sizing parameters. In experiments a direct wave suppression method is proposed for enhancement of the defect image quality. The debonding area is subsequently assessed by using an edge-recognition algorithm.

Thermal barrier coating (TBC) is a key component of the heavy duty gas turbine blade to protect the substrate material from high working temperature. Thinning of the top coating and the thermally grown oxide (TGO) layer formed between TC and BC cause TBC thickness reduction, which may significantly affect the in-service performance of TBC. High frequency eddy current testing (HF ECT) is considered as an efficient technique for nondestructive evaluation of the TBC thickness but its measurement accuracy is not satisfied up to now. Aiming to realize a high precision TBC thickness evaluation with HF ECT signals, a numerical method for simulating HF ECT of TBC was developed and implemented with consideration of the dielectric properties of TC and TGO material. It was found that the thickness of the TC layer can be evaluated with a 10 μm accuracy for the plate TBC specimens, which reveals the HF ECT method and new ECT probe are suitable for sizing of TBC thickness.

In this paper, a ferrite-cored funnel-shaped probe of pulse-modulation eddy current (PMEC) is proposed for quantitative screening of pitting corrosion in conductive heterostructures. Closed-form expressions of field quantities regarding the proposed probe are formulated via the semi-analytical modelling. Results from theoretical simulations reveal good characteristics of the probe particularly in terms of high-sensitivity testing of the pitting corrosion buried in the conductor and capability of balancing the defect detection depth and spatial resolution. Experiments are being conducted to further investigate the imaging and evaluation of pitting corrosion via PMEC, which alongside the theoretical investigation would confirm the superiority of the proposed probe.

In eddy current testing, lift-off signals are often larger than crack signals; therefore, post signal processing and/or probe design are used to suppress lift-off signals in surface inspection. We have proposed a differential tangential eddy current probe with dual induction. The dual induction is induction in which self and mutual inductions are performed simultaneously. In simulation using the finite element method, it is confirmed that lift-off signals of the self and mutual inductions have an anti-phase property, and the proposed probe suppresses lift-off signals by 80 - 90% when adjusting the mutual induction excitation current.

Thickness of thermal barrier coating (TBC) is one of the key parameters of its thermal insulation ability. It is very essential to evaluate the thickness of TBC nondestructively. There is still a lack of a nondestructive evaluation technique to efficiently measure the thickness of TBC of a large area. In this paper, two spots pulse laser thermography methods, i.e., the array spots laser thermography and the scanning spots laser thermography, were adopted to measure the thickness of TBC by using the time at the minimum 2nd derivative of the falling edge of the temperature evolution curve. Both numerical simulation and experimental results show that the laser spot methods are feasible for the thickness measurement of TBC specimen prepared by using the atmospheric plasma spraying technique.

This study evaluates the effect of how currents are injected on the accuracy of electrical impedance tomography using the monotonicity-based inverse analysis algorithm. Electrical Impedance Tomography (EIT) is a technique to evaluate the distribution of electrical impedance inside a target from the voltage on the surface of the target. One of the largest problems associated with EIT is that the inverse problem it deals with is significantly ill-posed because there is no clear mathematical background that assures the uniqueness of the solution, unlike X-ray computed tomography.The results revealed the importance of choosing a proper condition, such as the number of electrodes and the current pattern, to evaluate the impedance inside the target.

This study evaluated the effect of current injection pattern on the accuracy of EIT results obtained using algorithm which is based on the monotonicity principle. The results obtained revealed that a proper condition, such as the number of electrodes and the current injection pattern, depends on the target.

Magnetic field has been playing an important role in many key fields. Measuring magnetic field is quite important for us to understand and make better use of it. Magnetic field measuring sensors are important components to transform information of invisible magnetic field into visual information. In this study, we proposed a novel sensor based on the magneto-thermal effect of the magnetic nanoparticles. We used the sensor to measure the magnetic field distribution of different alternating magnetic fields, by taking the temperature rise rate of the sensing unit to characterize the magnetic field intensity, converting magnetic information into infrared temperature images. The effectiveness of the sensor was also verified through both simulation calculations and comparative experiments. It is found that the proposed novel sensor can be flexible, arrayed, passive and wireless, and it breaks through the measurement of high frequency magnetic field.

This study estimated the profiles of a fatigue crack from eddy current signals probabilistically based on Bayesian estimation. Artificial rectangular slits and fatigue cracks were measured by eddy current testing to obtain the likelihood functions and test data, respectively. Numerical simulation was also conducted by the 3-dimensional finite element method. Experiment and numerical signals were used to estimate the profiles of the fatigue crack.

Rectangular wave eddy current testing is a technique that can simultaneously acquire both low- and high-frequency information, thus allowing detection of surface and backside flaws. During flaw detection, the excitation field affects the accuracy of the detected signal. Therefore, a compensation coil is employed to compensate for the direct magnetic field from the excitation magnetic field. A 12 mm-thick aluminum plate with flat-bottom drilled holes on its backside is used as a specimen. The diameter of the holes is 3 mm, and the depths of the holes are 2, 4, and 6 mm. Results show that flaw signals of 4 and 6 mm are successfully detected.

The bidirectional radiation pattern of conventional shear vertical wave electromagnetic acoustic transducers(SV-EMAT) reduces the signal energy and makes it difficult to locate the scatterer. In this work, we propose a new unidirectional SV wave EMAT with an oblique bias magnetic field(OMF-EMAT). Oblique magnetization changes the distribution of the ultrasonic field over the two obliquely incident SV waves and improves the unidirectionality and signal amplitude. Firstly, the magnetic circuit superposition approach is selected to generate oblique magnetic fields; Then, the OMF-EMAT is designed and the corresponding time-domain simulation model is established to further analyze the effect of the oblique magnetic field on the unidirectionality of the ultrasonic beam. It is found that when the magnetic field oblique angle is in the range of 45°, the unidirectionality of the acoustic beam gradually increases with the increase of the magnetic field oblique angle, and the signal amplitude shows a trend of first increase and then decrease.

Electromagnetic thermography detection technology holds significant importance in the field of non-destructive detect, necessitating further research. Recent years have witnessed substantial advancements in electromagnetic thermography detection. The theoretical investigations focused on the analysis of uniform detection regions that facilitate the amplification of thermal contrast for the detection of subtle signals. In terms of sensor coil design, a novel L-shaped electromagnetic sensor capable of generating a uniform magnetic field was proposed, yielding significant improvements in the detectability and thermal contrast of omnidirectional micro fatigue cracks. A multi-physical structure, integrating eddy current detection and electromagnetic thermography, was proposed for defect diagnosis in dynamic experiments. Building upon these results, an electromagnetic thermography detection system employing a long return-loop three-turn coil was developed, enabling defect detection experiments on an actual calibrated line under the conditions of a 30mm lift-off and an 80 km/h detection speed. Remarkably, 11 calibration wounds of varying depths were successfully detected.

Terahertz (THz) nondestructive testing has been considered as a promising method for measuring the thickness of thermal barrier coatings. However, there are few reports concerning the online evaluation of the results without destructing specimens. Thus, a physics-based transfer learning framework is presented to build the relationship between the residual signals and errors of thickness measurements. To decrease the training cost, the source domain and target domain are simulated and experimental residual signals, respectively, but the differences between these two types of data cannot be ignored due to the THz dispersion. A physical constraint layer is proposed to improve their similarity for decreasing the errors. The results show that our method evaluates the thickness measurements of the actual specimens with an accuracy of 95.2%.

Metal structures are widely used in industrial fields, for which various composite defects are probably produced from manufacture to service. For example, both the surface and bottom of structures emerge defects. Facing the composite defects, a single electromagnetic nondestructive testing (ENDT) method usually cannot meet all needs. However, two or more targeted ENDT methods have the problems of low efficiency. To solve this problem, a novel pulsed eddy current and electromagnetic ultrasonic (PECT-EMAT) hybrid testing method is developed. For this developed method, the surface defects and bottom defects can been detected synchronously only by one set of testing system and probe based on the demodulated electromagnetic components and ultrasonic components. In addition, as a novel ENDT method, it is necessary to evaluate the detection capability of the PECT-EMAT hybrid testing method. Therefore, a reliability evaluation method based on probability of detection (POD) is developed.

One of the plasma-facing unit design options for the divertor in a nuclear fusion reactor is a tungsten mono-block with a screw pipe that has grooves on the inner wall for high heat removal capability. To develop a non-destructive inspection method for the cooling pipe, this study evaluates the applicability of high-frequency ultrasonic tests to inspect the interface between the pipe and mono-block. Samples with grooved surfaces were prepared and inspected by an ultrasonic microscope. The results indicate that defect detection performance is reduced due to ultrasonic scattering from the screwed inner wall.

In this paper, a numerical scheme for simulation of infrared thermography images under ultrasonic excitation is proposed and validated. A FEM code is updated at first to calculate the vibration of the inspection object with internal cracks excited by body ultrasonic wave. The relative displacement at the crack interface and contact force are subsequently extracted to find the strength of inner heating flux. Using the obtained pulsed inner heating source, the temperature field is calculated by treating the ultrasonic heating flux as a quasi-static equivalent heating source. The numerical scheme is finally validated by comparison its results with that using commercial software.

In service pipelines are prone to various defects such as corrosion and cracks on the inner and outer surfaces under complex working conditions. Magnetic permeability perturbation testing (MPPT) owns the advantage of high sensitivity for both inner and outer surfaces defects in ferromagnetic pipes. A method of distinguishing internal and external defects based on layered magnetization with variable pole shoe thickness is proposed. The effects of pole shoe thickness on the magnetization are analyzed by FEA model. The simulation and experiment results show that the method performance well for distinguishing internal and external defects.

A method is proposed to estimate the radiation source distribution inside the fuel debris storage canister from the γ-ray energy spectrum detected by NaI crystals placed outside the storage canister. This method is a combination of a particle transport Monte Carlo simulation and a neural network for machine learning. It was shown that the estimation accuracy for simple physical models was high.

The paper reports on the development of a new EMAT sensor using a configuration based on Halbach magnet to detect defects in long metallic plates, up to 3.5 meters. Optimizations of the EMAT sensor, related to Halbach magnet configuration and others, enable greatly increase the signal-to-noise ratio of the defects. The defects are located on the opposite side of the surface from the EMAT sensor position, with depths up to 20% of plate thickness and at much greater distances (meters) from the sensor, in a frequency range below 1 MHz. Experimental measurements confirm the feasibility of the method, and the new EMAT opens up the possibility of faraway detection of defects in the meter range, as compared with the standard EMAT method until now limited to a 0.1~0.4 m applicability in metallic plates.

Engineering structures are prone to damages from stress and environmental factors. An effective way of monitoring structural health of these structures is by using the ultrasonic nondestructive evaluation (NDE) technique. In general, ultrasonic techniques are contact methods requiring use of a couplant to couple the energy into the test object. To address this problem, Electromagnetic Acoustic Transducer (EMAT) techniques were introduced which use Lorentz force acting on induced currents to generate an elastic wave. EMAT’s are effective on conductive or ferromagnetic samples. This paper presents a novel EMAT for use with non-conductive samples. Numerical model and simulation results are presented to demonstrate the feasibility of generating an elastic wave in the non-conductive sample.

Non-contact immobilization of macromolecules, cells, and other bioparticles plays an important role in life science and clinical diagnostics. State of the art acoustofluidics typically treat bio-particles in a multi-wavelength range due to the scale limitations of the established ultrasound field. Here, the theory and method of spatiotemporal modulation of the multiple physical fields for SAW microfluidics is proposed. We report several selective acoustofluidic devices that allow trapping and heating bio-particles in a wavelength scale. We also show that the temperature field of a droplet on the path of a travelling surface wave can be regulated by modulating the heat source distribution and thermal conduction inside the target. Through proof-of-concept experiments, the proposed acoustofluidic devices show potential applications in on-chip biological and chemical analyses, where localized handing and heating is required.

Thermal error has an adverse effect on the operating accuracy of the machine tool. Therefore, reducing the thermal error is very important to improve the machining accuracy. In this paper, in order to realize real-time compensation, taking a three-axis machine tool as an example and a method for robust modeling and predicting thermally induced positional error is proposed. First of all, the number of temperature measuring points required in thermal error’s model was reduced based on the rough set theory, which greatly reduced variable searching and modeling time. Then through grey relation theory, systematic analysis of the similarity degree between thermal error and temperature data was carried out to select sensitive temperature measuring points. which eliminated the coupling problems. The thermal error prediction model of LSTM（ Long Short Term Memory） neural network is established by using temperature change and error data as input samples. The results show that the prediction accuracy of the proposed thermally induced position error model is reliable.

The vibration and noise of transformer core under DC bias are studied in this paper. Firstly, the 30ZH120 silicon steel sheet is tested for B-H and B-λ. The test results in electromagnetic and magnetostrictive characteristics of electrical steel sheet under different DC bias conditions are given. Secondly, based on the Preisach model, the hysteresis model of electrical steel sheet under DC bias is derived. This model is based on the classical Preisach model and describes the influence of DC component on hysteresis model. Thirdly, the vibration and noise of transformer under DC bias are simulated by FEM. The calculation results under different DC bias conditions are obtained. Finally, the vibration noise of transformer is studied experimentally, and the accuracy of simulation results is verified. This work supplements the derivation of Preisach model under DC bias and provides a basis for designers to understand the vibration and noise characteristics of transformer under DC bias.

To increase the areal density in heat assisted magnetic recording (HAMR), a split pole head with integrated nano coil was investigated using numerical simulations. The unique head design realized a preferable head field distribution. LLG micromagnetic recording simulations showed that the head field distribution was effective at reducing the transition curvature.

The classical Jiles-Atherton model is a typical magnetic hysteresis model. However, there are some deviations between actual magnetization curve and the modeled one, especially in the case of unsaturated magnetization curve which is important as a factor the increases hysteresis loss in actual components of electromagnetic equipment. The hybrid modified Jiles-Atherton model is proposed to avoid such deviations. In this paper, we applied the HJA model to symmetric and asymmetric magnetic hysteresis loops. And, Ni, which has stable composition and magnetic properties, is adopts as the material.

As a result, it is shown that the symmetric and asymmetric hysteresis loops of Ni under several applied magnetic field conditions can be expressed by HJA model with good accuracy. And this result also shows that the HJA model could be applied to describing hysteresis loops of various materials.

Flexoelectricity is an electro-mechanical coupling effect between electric polarization and mechanical strain gradient. Dielectric materials, such as ceramics, rubber, plastics, etc., have a flexoelectric effect, and bending or twisting to them will generate electricity, but not when applying pressure or tension, which greatly limits its application, because in fact tension and pressure loads are the easiest to obtain. In this work, we establish a theoretical model and asymmetric structure in polymer elatomers, in which complex asymmetric structures can exhibit flexoelectric effects under any load due to their local structural asymmetry compared to traditional structures. By comparing a series of parameters of the asymmetric structure, we design a structure in elastomer, as a result, its equivalent piezoelectric coefficient is much larger than the material flexoelectric coefficient. The results show that the polymer elastomers with asymmetric structure can be widely used in the energy harvesting, sensing and mechanical actuating with high flexoelectric effect.

In space optical applications, the piezoelectric-actuated fast steering mirror (FSM) is one of the pivotal components for high-precision beam capturing and trajectory tracking. The FSM is restrained in small-angle scanning applications due to the short actuation stroke of the incorporated piezoelectric materials. This study introduces a dual-axis sub-radian stroke FSM with high precision and self-sensing capability, based on cascading structures for displacement amplification. Experimental results reveal that both axes can rotate 148.67 mrad, comparable to existing electromagnetic FSMs.

Bridge arm reactors are subjected to composite current of AC and DC in operation. Aiming to study the differences in temperature rise, current and loss calculations are performed according to electromagnetism and heat transfer theories. Considering the influence of metal accessories, the temperature distribution of the reactor and its influencing factors are analyzed. The results show that the loss of metal accessories accounts for 1.02% and the collector ring is prone to local overheating. The maximum temperature rise of the encapsulation shows a nonlinear decrease with the increase of the flow rate and the decrease of the ambient temperature. The maximum temperature rise is increased by 14.6℃ after considering the sound insulation device. Finally, the error is 5.72% when comparing the results of AC and DC temperature rise tests, which verifies the correctness of the simulation model. The research results can provide reference for the design of temperature rise of reactors under AC-DC compound high current in actual engineering.

Physics-informed neural networks (PINNs), which is a powerful approach for solving partial differential equations with deep learning, has been recently applied to modeling of electrodynamic interaction problems including a relativistic beam in charged particle accelerators. In the present study, the transfer learning (TL) is applied to the PINNs based on the total-field (TF) formulation. It is shown that TL can accelerate significantly the training process of the TF-PINNs in the simulation of the beam impedance of an infinitely long beam pipe of circular cross section.

To address the inconvenience and the maintenance cost of conventional batteries in the development of large-scale low-power wireless sensors, radio frequency (RF) energy harvesting (EH) technology has gained significant tractions since RF energy offers advantages such as abundant availability and resilience to environmental conditions. In this study, we propose and optimize a novel topology for a quad-band and polarization-insensitive metasurface (MS) absorber. The MS unit employs four spoof-local-surface-plasmons (SLSPs) resonators arranged using a sequentially-rotation technique, enabling a polarization insensitivity and facilitating a post-stage power accumulation. We then develop an optimization methodology by combining a hybrid algorithm and finite element method simulations to calculate the performance parameters. The methodology is applied to a prototype design, demonstrating exceptional results.

Millmeter wave band electromagnetic waves are used in 5G communication systems. They have a wide frequency range for wireless communication, however their short wavelength makes them susceptible to relatively small obstacles such as robots and people. In this study, we use machine learning to estimate the wave propagation of electromagnetic waves in the 28 GHz band in order to estimate the effect of obstacles. The ray tracing method was used as the teacher data for the machine learning. Comparison of the machine learning estimation results with the experimental results shows good agreement.

We synthesize non-spherical magnetic particles and evaluate their heat generation efficiency under an ac magnetic field. Ferrocene is dissolved in ethanol and the solution is heated up to reach a supercritical state. Spherical, dendritic and flower-shaped magnetic particles are synthesized under the supercritical condition and their production rates change depending on the heating time. We show that the non-spherical magnetic particles exhibit higher heat generation efficiency under an ac magnetic field as compared to the spherical ones.

Recently, more and more researchers are contributing their efforts to developing electrification to achieve a carbon-neutral society. Besides as an indispensable part of electrification, the development of electric motors plays an important role. Among them, a permanent magnet synchronous motor (PMSM) is applied in most fields due to its high-power density and compactness. However, most permanent magnets are brittle materials that cannot withstand centrifugal force caused by high-speed operation. Besides, the rotor steel rib also suffers from centrifugal force. Those make PMSM a disadvantage in mechanical strength. Therefore, we focus on a simpler structure motor called flux reversal motor (FRM) as a research target and propose a new shape FRM with a cross-pole shape to improve its performance. This paper describes eddy current loss reduction in permanent magnets by the cross-pole shape using a three-dimensional finite element method (3D-FEM).

In this paper, a tunable magnetorheological elastomers (MREs) metasurface composed of MREs and three-dimensional (3D) printing material polylactic acid (PLA) is proposed to steer the propagation of incident flexural waves arbitrarily. Based on the Generalized Snell’s Law, MREs metasurfaces with different refraction angles are designed by adjusting the applied magnetic field, including positive refraction and negative refraction. In addition, wave focusing and self-bending beam effects are also investigated. Different focal spots and self-bending beam paths can be realized by adjusting the applied magnetic field. A wave focusing experiment is conducted to verify the simulation results, The simulated and experimental results of the elastic wave focusing effect are in good agreement.

This paper presents a wave energy converter based on stochastic resonance and its numerical simulation method. Numerical simulations show that the proposed converter has wide operational frequency range thanks to the nonlinearity of the proposed converter. Moreover, it is also shown that the frequency response of the proposed converter can be controlled by the field current to adapt various ocean wave conditions.

The present paper demonstrates the manufacturing of a “wireless” microvalve composed of magnetic-nanoparticle-embedded thermoresponsive hydrogels via a photolithography process. The microvalve was remotely actuated using the alternating-magnetic-field application. The field application caused the microgel to shrink and thus “microvalve-open.” The microvalve completely closed when the field was turned off. In addition, we confirmed the valve opening/closing behavior was consistent with magnetic-field switching. Although the spontaneous repetition of shrinking and swelling of microvalves was observed when the magnetic field application was kept, the repetition could be reduced by increasing the strength of the magnetic field.

This study proposes a numerical model to predict pipe failure based on periodic non-destructive inspections using electromagnetic acoustic resonance (EMAR). A total of 176 artificially corroded samples were measured using EMAR to quantify the uncertainty in pipe wall thickness evaluation. Pipe failure probability in the future was evaluated based on the results of EMAR measurements with the aid of the Bayes theorem. Whereas this study considered only pipe rupture, the results of numerical simulations supported the validity of the model.

The evolution of the power system is reviewed in the context of massive penetration of variable renewable energy sources. Some issues seem underexplored to enforce the stability, the adequacy and the decarbonation of the power system in a context of migration towards electricity.

In this paper we use a micromagnetic model to preview the switching behavior of very small ferromagnetic elements deposited on a nonmagnetic substrate. These elements present a rectangular shape and very small dimensions. A regular pattern of the magnetization inside each element is expected. The micromagnetic model is based on the calculation of the energies involved for a given applied external magnetic field. To obtain the different components of the energy each element was divided into smaller finite cubes. The magnetization is assumed as a uniform-magnitude vector inside each element, with equal magnitude, but different direction.

This paper proposes a surrogate-assisted evolutionary algorithm based on an artificial neural network (ANN) for computationally expensive multi-objective optimization problems of electromagnetic devices. The training data of ANN are selected from the current population according to the Pareto rank and the crowding distances of individuals to learn cumulative knowledge from the searched solutions in the evolution. Reproduction of the offspring is implemented by the trained ANN instead of the traditional genetic operators. Finally, the performance of the proposed algorithm is tested on the team workshop problem 35.

This study extends the application of Monte Carlo tree search (MCTS) to the comprehensive design of three-dimensional (3D) inductors with nonlinear characteristics. Specifically, configuration settings of inductors are determined by MCTS, and the finite element method is employed for the simulation. This research demonstrates the effectiveness of MCTS in achieving desired performance of inductors, such as attaining a target value of inductance, and meeting the requirement of minimum saturated current.

A structural dynamics model updating method based on a novel particle swarm optimization algorithm with Lévy flight and orthogonal learning (LOPSO) is proposed and successfully applied to the updating of the finite element (FE) model of a typical complex multi-component structure. The LOPSO is designed to overcome premature convergence and better solve inverse problems such as parameter identification and model updating. The LOPSO method is used to update the equivalent stiffness and damping parameters of shafting bearings. It is proved that the new algorithm has higher accuracy. After updating, the errors of the parameters were reduced to less than 1%. The accuracy of the FE model was significantly improved, verifying the effectiveness of the proposed method and its applicability to engineering problems.

For a proper application of the Kirchhoff migration technique for imaging small anomaly, complete element of the scattering matrix must be collected. However, it is very hard to measure the diagonal element of scattering matrix in real-world microwave imaging. Here, we set the diagonal elements as a constant, apply the KM for anomaly imaging, and show that zero constant choice guarantees good imaging results.

The concept and advantages of physics-based Digital Twins are presented. A Digital Twin is a virtual representation of real-world entities and processes, synchronized at a specified frequency and fidelity. The approach based on the physics-based simulations which can predict the physical values enables to achieve the predictive maintenance and optimal operations on Digital Twin systems for industrial equipment. Key technologies for the physics-based twin models with machine learning technologies are discussed.

In this paper, we review some of the most significant contributions of the Authors in the field of real-time soft-field tomography and electromagnetic material design, together with a discussion on new research directions.

Specifically, we present (i) the imaging methods based on the Monotonicity Principle, combining excellent performances, real-time operations and capability to handle the presence of nonlinear materials, (ii) a new non-iterative inversion method for Electrical Resistance Tomography, the Kernel Method and (iii) a new material design paradigm in the framework of electromagnetic fields.

Flexible steel plates have been widely used for industrial products. Since flexible steel plates are currently conveyed by roller conveyance, which causes fine scratches, a method is required to convey the steel plate non-contact by magnetic levitation to prevent quality deterioration. The levitation method performed by the authors utilizes the attractive force from electromagnets.

In this paper, we design a novel snap-fit mechanical metamaterial. Compared with traditional energy-absorbing structures, the snap-fit structure has the characteristics of repeatability and recoverability. We reveal the energy absorption characteristics by theoretical analysis and numerical simulation, and we analyze the influence of related parameters on the energy absorption effect. The results show that the energy absorption effect of the structure is mainly affected by the elastic deformation of the material and the friction energy dissipation between the components. The study provides important support for the future design of energy-absorbing mechanical metamaterials.

The magnetic bearing of the total artificial heart is investigated to reduce the device size. The attractive force production performance of the double-bias hybrid magnetic bearing, DHMB, and the single-bias hybrid magnetic bearing, SHMB, is investigated using three-dimensional finite element method analysis. The thickness of the MB may be reduced by 1 mm, which is 20 % of total thickness, with the SHMB with keeping the magnetic bearing performance.

A finite element model is established to study the mechanism of out-of-tolerance of the liquid-filled tank in this work. The out-of-tolerance phenomenon refers to the difference between the expected applied load and the actual measured load during vibration testing of nonlinear structures. It is very meaningful for effective vibration testing of such structures by using of the electromagnetic vibtaion table. The simulation model is established in Abaqus which can provide the smoothed particle hydrodynamics method to solve the transient motion of liquid. The simulation results are consistent with the experimental results, which demostrates the correctness of the numerical method. The influence of the amplitude of the external excitation and the height of the liquid level on the out-of-tolerance situation are also analyzed.

The optically pumped magnetometer (OPM) operating in spin exchange relaxation-free (SERF) regime is a kind of magnetic sensor with ultra-high sensitivity, which attracts widespread attentions for biomagnetism measurements in recent years. SERF OPMs need to operate in a zero magnetic field environment, otherwise the sensors will have reduced sensitivity. In many applications, multi-channel OPMs should be utilized to inversely localize and quantify the magnetic source, in which case the magnetic fields of the OPMs interfere with each other. This paper proposes an array OPMs magnetic field compensation method based on an artificial neural network (ANN) algorithm. The transfer function between the compensation currents and the observed signals are derived, based on which a nonlinear multiparameter optimization problem is abstracted. Then, an ANN model is employed to optimize the compensation currents of the OPMs with the objective function minimizing the magnetic field at each sensor location. This method can effectively reduce the effect of the magnetic field crosstalk of multi-channel OPMs.

Aiming at real-time control of a powered prosthetic hand, this paper studies the real-time classification of intended hand motions from tactile feature patterns on the forearm surface caused by muscle contraction. Two sheets of Plyvynylidene Fluoride (PVDF) film were used as tactile sensors to detect the tactile features on the forearm caused by intended hand motions. Machine learning was applied to the classification of hand motion intentions using the tactile feature patterns. In this paper, we further studied the real-time motion classification methods in an online environment. We found that average classification accuracy for the 6 types of motion in 6 experiment participants was 82.8 %, showing that real-time motion classification is possible by using the support vector machine with simple training for several minutes.

The decrease in radiofrequency wavelengths poses a challenge of B1-field inhomogeneity for ultra-high-field MRI. This study introduces a novel solution—a planar metamaterial with a unique hybrid structure that is specifically designed for integration with a birdcage coil at 7T. Simulations have demonstrated that this new structure greatly enhances the transmit efficiency.

Humans perceive tactile sensations to discriminate objects’ properties and manipulate them. While tactile sensation has been attempted to be used in robot sensing and tactile presentation in Virtual Reality, the mechanism of tactile sensation is not clarified. Hardness is one of the tactile senses, and it is generally perceived when an object is deformed. Moreover, in previous research, it was shown that an object’s surface properties also change the hardness sensation. However, the cause of this change has not been identified. The purpose of this study is to investigate how the hardness sensation changes depending on the surface properties of an object, and what factors cause the difference in hardness sensation. In this study, a sensory evaluation of the hardness feeling and measurement of the contact state were conducted by using samples with five different roughnesses.

To enhance the acceleration performance of a superconducting linear accelerator (SLA) system used for fuel pellet injection in fusion reactors, a numerical investigation was carried out. For this purpose, a numerical code based on the finite element method (FEM) was developed to analyze the simultaneous behavior of shielding current density and dynamic motion of the high-temperature superconducting thin film. To optimize the current profile in the electromagnets, a method combining the normalized Gaussian network approach with a genetic algorithm was implemented in the code. The computational results demonstrated that the optimized current distribution resulted in a narrower profile compared to the uniform distribution. As a result, it was possible to increase the size of the thin film, leading to a significant reduction in the acceleration time required to reach the desired speed, approximately 2.9 times faster.

In this paper, non-ideal superconductors with crack defects are considered and two-dimensional partial differential control equations are presented based on the H-method. A coupled electric-magnetic-thermal multi-field of non-ideal HTSLS was analyzed employing the PDE module and heat transfer module of the finite element software COMSOL. The temperature distribution and AC losses variation of the non-ideal HTSLS under alternating magnetic fields were investigated. The simulation results indicate that the presence of cracks aggravates the AC losses of the system. The AC losses of the HTSLS increase with the increasing of the crack opening angle of the bulk, and show a linear increasing relationship with the amplitude of the applied magnetic field. The temperature distribution interior to the ideal superconductor propagates from the edges towards the inside, with the highest temperature rise effect occurring at the edges. The temperature distribution of ideal HTSLS displays an axisymmetric bimodal law. However the non-ideal HTSLS with cracks defects shows a unimodal distribution.

Ultra-high magnetic field high-temperature superconducting (HTS) magnets beyond 20 T are under development all over the world. Electromagnetic forces strong enough to deteriorate the specifications of HTS work for such ultra-high field magnets. In recent years, several simulation methods to simultaneously consider the electromagnetic and the mechanical behaviors were proposed. In this paper, we propose a correct inductive voltage formulation and an acceleration method to compute the inductances with a fast multipole method. As the result, we can report a phenomenon that the turn-to-turn contact resistance which is an important factor for no-insulation HTS coils increases, because some gaps appear between coil turns.

In high-field applications, mechanical and electromagnetic properties are crucial components of high-temperature superconducting (HTS) magnets. In this research, to predict the multi-field behaviors of conductors on the round core (CORC) cable during the excitation and cool-down, the coupled mechanical-electromagnetic model is constructed with consideration of the strain and magnetic field dependences of the critical current. 3D modeling is used to enhance the irreversible strain limit of HTS tape, which also allows for reducing magnetization losses. The result shows that smaller winding angles are still the optimal choice regarding resistance to deformation, critical current degradation, and magnetic shielding. The conclusions drawn in this paper will guide the design of future CORC cables.

The H-matrix-based preconditioning has been improved, and the performance of the ICCGH incorpo- rated with the proposed preconditioning has been investigated numerically. The result of computations shows that the modified ICCGH is faster than the conventional one.

In inductors driven by the inverter using GaN devices, the ringing phenomenon, which occurs due to the multi-resonances during the short rising and falling time, increases noise and loss. To clarify the mechanism of the multi-resonances, the high frequency behaviors of a ring core inductor in frequency domain are simulated by using the 2D electromagnetic field finite element analysis taking account of the stray capacitance. Moreover, to explain this phenomenon, a distributed-element circuit model including the stray capacitance is proposed based on the simulated results. It is shown that the proposed finite element and circuit models can represent the measured HF behaviors of the ring core inductor.

This paper presents mechanism and calculation of multipoint grounding current of converter transformer core. Firstly, the core multipoint grounding equivalent circuit and the circuit impedance calculation method are given and the analytical calculation under harmonic and DC bias is carried out. Secondly, the anisotropic resistivity matrix based on the homogenization modeling theory is given and the FEM calculation under harmonic and DC bias is carried out. Then, the core multi-point grounding test based on the converter transformer model was carried out under harmonic and DC bias is carried out. Finally, the mechanism of multipoint grounding current of core is given, and correctness of the calculation method is verified.

To clarify the mechanism of the excess loss in a Non-Oriented (NO) electrical steel sheet, a modeling of excess loss taking account of the variation of grain orientation is proposed in this paper. In the proposed method, the NO steel sheet is modeled by grains with random orientations, then an uniaxial anisotropic magnetic characteristic is considered in each grain. The nonlinear eddy current analysis of a simple model composed of cubic grains with different easy axes is carried out by using the initial anisotropic BH curves of a Grain-Oriented steel sheet. Then, the calculated eddy current loss is compared with the measured values of an actual NO steel sheet. It is shown that the proposed model can represent the excess loss in low flux density region, but not in high flux density region.

Transformer bushing is an important part of transmission engineering, its structure safety is very important. In this paper, the failure of the conductor rod of the high voltage bushing of a 750kV transformer is analyzed. The high voltage bushing of this transformer is made of oil paper capacitive structure. The conductor rod used to transport the current inside the high voltage bushing bears the current and the tension from the pressing spring. Based on the finite element simulation and experimental research, this paper analyzes the fault cause is the insufficient strength of the conductive rod connector, and gives the operation and maintenance suggestions.

In recent years, wearable devices have become increasingly important in improving quality of life. Wireless power delivery to such devices is a promising technology for the miniaturization. Magnetic resonant wireless power transmission is a suitable method for such applications. The operating frequency should be varied corresponding to change the coupling coefficient. Recently, use of power oscillators in the transmission circuit is investigated for such cases. An LC power oscillator is one of the candidates for such applications because of the high efficiency and the simple circuit configuration. In this paper, an improved LC power oscillator suitable to wireless power transmission was proposed and the power efficiencies between the parallel and series configuration for the receiver circuit were compared.

The novel preprocessing method to improve the prediction accuracy of deep learning (DL) has been proposed. In the proposed method, the Empirical Mode Decomposition (EMD), one of the frequency decomposition methods, is applied to the gap magnetic flux density distribution, the input data of DL. The method is applied to DL to predict motor characteristics.

In semiconductor manufacturing, the process of manufacturing various components and wiring on silicon wafers requires high cleanliness. Although traditional magnetic levitation slider devices can eliminate mechanical contact and suppress dust, suspension devices, and propulsion devices are usually used separately. The actuator using a linear motor generates about 10 times the suction force in the upward direction compared to the driving force. Applying it to upward buoyancy can improve energy utilization and simplify the structure [1]. This study used four sets of E-type electromagnets to design a linear slider that can simultaneously utilize buoyancy and propulsion forces. By using an E-type iron core, the electromagnet can be miniaturized. Replace the torque in the rotating electric motor with propulsion force, and replace the bearing support force with buoyancy force. Through suspension and disturbance experiments, the device was subjected to a 1N impact and returned to stability after 3 seconds. The experimental results proved that the device has good response characteristics.

this paper investigates the dynamic modeling and optimization of a V-type energy harvester. The research of energy harvester pays more and more attention to practicality. Therefore, an new energy harvester is designed, which can be placed under the soles of people’s shoes. Firstly, the model of V-type energy harvester is designed, and the mechanical model is established to analysis the natural frequency. Two V-type energy harvesters are combined into one Z-type energy harvester. Secondly, the finite element analysis of V-type and Z-type energy harvesters are carried out, and the displacement, stress, strain are pointed out. Furthermore, the natural frequency is compared with the theoretical value, and the maximum strain position is pointed out. The results show that the modeling method and analysis results are correct.

A magnetic-geared motor (MGM) with permanent magnets only in its stator is proposed. The MGM can control the maximum transmission torque utilizing DC currents. In addition, low-speed rotor torque due to coil currents is larger compared with conventional MGMs. Therefore, the dynamic characteristics of the proposed MGM are different from that of conventional MGMs. In this paper, firstly, a mathematical model of the proposed MGM is created. Secondary, the electric circuit equation of the proposed MGM is described, and physical quantity maps are introduced. Finally, the simulated relationship between the phase angle difference of the rotors and load is compared with finite element analysis under vector control.

An investigation into the impact of atmospheric fine particles on the ionic mobility is presented. A measurement apparatus was designed using direct current corona discharge at room temperature. Positive and negative ionic mobilities were extracted from the electric field and ion current density measured in the apparatus. With the presence of fine particles, equivalent ionic mobility was found to decrease exponentially with the mass concentration of the fine particles. Distributions of the electric field and space charge density, and the contributions to the charge density from small ions and charged fine particles were also calculated.

This paper presents a new optimal design method for a PM motor based on loading separation. Using the relationship between the loadings of the power equation and the motor’s geometries, it is revealed that the arbitrary selection of four variables p, Dg, Lstk and gm provides a unique motor with the required output power. Consequently, the optimal design is determined through characteristic evaluation and comparison of the motors designed with a myriad combination of four independent variables. To verify the validity of the proposed method, an optimal design is performed for a 5 kW SPMSM and the performances are analyzed.

This paper investigates one of the key equipment in UHVDC transmission, which is the converter transformer. The harmonic current generated by the converter can cause localized overheating in the transformer windings. Finite element models of the magnetic field and thermal field of the core winding are established based on experimental data. Finite element simulation results are provided for sine excitation, rated excitation, and variations in winding conductivity with temperature. Finally, the hot spot temperature of the winding is verified using analytical and the experimental scaling model, confirming the necessity of considering harmonic current and variations in winding conductivity with temperature.

To aim to achieve portable, low cost and low power consumption high-performance computing (HPC) in practical use of neural network (NN), this paper presents a conceptual design study of dedicated computer for the NN processing. Then, dataflow architecture is adopted to develop the dedicated computer to be extremely high-performance by highly parallel processing. The topology of the NN and signal flow in the forward process are suitable for hardware acceleration, and it seems to readily construct the hardware circuit of the NN. In particular, dataflow architecture hardware circuits for both of the forward process and backward propagation process are considered in this work.

This paper presents a numerical investigation of the thermal interruption capability for the gas circuit breaker (GCB) adopting CO2/O2 mixture. The ohmic loss of the insulation gas is calculated from current continuity equation, and is utilized as a heat source for thermal fluid analysis. In order to accurately estimate the thermal interruption capability of a GCB adopting CO2/O2 mixture, we proposed an electric arc plasma model combining electric model and thermal fluid dynamics model. The validity of the proposed electric arc plasma model is verified by comparing it with experimental data. Subsequently, interruption indices are predicted using the calculated parameters to estimate the thermal interruption capability.

A surface integral equation method for modeling inductors in a wide frequency range is presented.

The unknowns are surface current and surface charge densities on the conductor surfaces. In the dielectric medium, a full-wave formulation is used, whereas in the conductor, a magneto-quasistatic model is considered. The full-wave formulation ensures that the model correctly takes into account high-frequency effects, such as resonance or radiation. The magneto-quasistatic model within the conductor yields accurate results for the real part of the impedance, i.e., the ohmic loss, starting from very small frequencies, where the 0th order surface impedance boundary condition is no longer valid due to the large skin-depth.

The electrical contact impedance at stiff interfaces is essential to the development of touch sensors for in-situ force and pressure measurements. This work examines systematically the relationship between the electrical contact impedance and the applied normal contact load between two spheres of silicon carbide. Through the combination of numerical simulations and experimental measurements, we meaningfully locate the linearity between the electrical contact impedance and the contact load, for various measurement conditions. Results indicate that the electrical contact impedance, for slight normal compression, is strongly affected by voltage amplitude, measurement time, and the generally existing surface roughness at the submicron scale, presenting significant nonlinearity and nonrepeatability. However, these dependencies vanish as the normal compression increases. This study advances our understanding of electro-mechanical mechanisms at conductive interfaces, providing insights into the development of touch sensors for in-situ force and pressure measurements.

The output performance of stick-slip piezoelectric actuators is comprehensively determined by the electro-mechanical responses of the driving unit, control strategy, and the contact status between the driving unit and the slider. Most previously developed inertial piezoelectric actuators face the problems of frequency dependence, motion speed, excessive volume, step resolution as well as loading capacity. To exhaustively improve actuation performance while maintaining low power consumption, we propose a compact bi-directional piezoelectric-based rotary actuator incorporating the rhombic amplification mechanism, adjustable preload, and simulation method based on by LuGre friction model for comparison. A prototype is fabricated and examined, which accomplishes the maximum load torques of 27.78 and 30.87 Nmm in clockwise and anticlockwise directions, respectively, at the highest rotational velocity of 0.4720 rad/s, which is almost equal in two directions. Compared with previously reported inertial actuators, the performance of the proposed actuator is significantly enhanced, promising in applications requiring nanometer resolution, long stroke, large holding and driving forces.

Atomic magnetometers are among the most sensitive technologies for detecting and characterizing magnetic fields, making them ideal for many applications. A compact atomic magnetometer utilizes a built-in laser diode to generate light at the specified frequency. The stability of the diode significantly affects the sensor’s performance. This paper proposes a novel method of stabilizing the laser diode output by a regulated double feedbacks control setting. The control coefficients are regulated dynamically according to the operating state of the atomic magnetometer. The method does not need any additional component and performs better than the conventional approach in a long-time operation. A compact atomic magnetometer with sensitivity 14 fT/Hz1/2 @10 Hz is developed and tested, which demonstrates the feasibility of the proposed method.

The detection of small defects that are buried in ferromagnetic steel is still a challenging problem for electromagnetic non-destructive testing. This paper presents a probe with high-resolution high-sensitivity tunneling magnetoresistance (TMR) sensors for buried defects inspection. The operation principle of the probe is based on eddy current testing (ECT) and magnetic flux leakage effects, which does not need a strong magnetic field to saturately magnetize the sample. The excitation frequency is optimized, in which way the eddy current field can penetrate through the sample. Experimental results show that the probe can detect a defect with dimensions of 5 mm (length)* 1 mm (width)* 1 mm (depth) buried in a 3 mm thick carbon steel plate. The proposed probe can be widely used for ferromagnetic materials inspection.

This paper proposes a new multi-degree-of-freedom (DOF) vibration system using electropermanent magnet (EPM) to achieve wide band frequency response of the system. A five-DOF system with four EPMs can operate with 16 different frequency response curves. Numerical calculation reveals that the proposed system significantly broadens its operational range by using the MAX function.

The lift-off effect is a main challenge for the eddy current testing (ECT)-based rail detections. The non-coaxial transmitter-receiver (TR) probes are considered as promising structures, however, the research focused on the transmitter-receiver coil distance optimization is limited. In this study, this coil distance is optimized for the Tx-Rx probe with varying lift-offs in rail inspections. Analytical simulations under different conditions show that the optimized coil distance can reduce the lift-off effect. The proposed method provides an optimization method for coil parameter design.

This paper compares 6-phase switched reluctance motors (SRMs) with 24 stator slots. A 24-slot-20-pole (24/20) SRM has a small torque ripple compared with a conventional 24/16 3-phase SRM. However, the iron loss of a 24/20 SRM is larger than that of a 24/16 SRM because the number of rotor poles is large. In order to decrease the iron loss of a 6-phase SRM, 24/14 and 24/10 SRMs are firstly proposed in this paper. Next, the torque and iron loss characteristics of these 6-phase SRMs are compared. Finally, the effectiveness of the proposed 24/14 and 24/10 SRMs are discussed.

Electrical and mechanical energy type converts around the nature. Among electromechanical coupling effects and materials, electrets are widely applied on microphones, earphones, and air filters. Stretchable electrets have been developed with elastomeric bases and nano-particle electrets to behave its mechanical stretchability and electrical activity simultaneously, and its electromechanical properties has been expanded on multiple applications such as mechanical sensing, energy harvesting and actuation. The electromechanical coupling properties of this energy-active material are analyzed in this work by four types of mechanical procedures: compression, vertical motion, stretch extension, and vertical pricking between electrode setup. It is found that the vertical pricking onto electret films induces ultra-high effective piezoelectric coefficients according to its mechanical-induced deformations. The electromechanical applications of mechanical sensing, energy harvesting and actuation with this mechanical procedure are demonstrated with this pricking type, showing its advantages of electromechanical coupling capabilities.

This paper proposes a new method of pulsed eddy current thickness measurement based on a new characteristic quantity to address the problem that the pulsed eddy current detection signal can be affected by lift-off, resulting in inaccurate thickness measurements. Firstly, the principle of pulsed eddy current detection is introduced, the simulation model of Tx-Rx (Transmitter-Receiver) sensor is established, the differential signal characteristics of ferromagnetic materials are studied, and the relationship between the time and amplitude of the gradient minima time and the lift-off is discussed. Secondly, an experimental system is built and it is found that the gradient minima time is less affected by the lift-off and increases with the thickness of the differential specimen. Finally, a method of thickness measurement of ferromagnetic materials based on gradient minima is proposed.

In this study, we evaluated the magnetic properties of ring-shaped laminated cores manufactured by laser machining, which are used in prototype motor development. As a result, it was found that the magnetic properties of the specimens manufactured by laser machining were degraded due to the distortion of the B-H loop caused by the thermal stress generated during the machining process. It was also found that hysteresis loss increased by about 113% when the excitation frequency was 50 Hz and the magnetic flux density was 1.0 T.

An active seat suspension was proposed to improve ride comfort of the ultra-compact vehicle. Discomfort vibration for vehicle occupants was reduced by active control of the seat suspension. In this study, a control system that directly feedback the absolute acceleration measured on the seat was proposed. To investigate the performance of vibration control, vibration response of this control system was measured using the experimental apparatus assumed the active seat suspension. In acceleration feedback control, improving the ride comfort by selecting proper feedback gain because characteristics of frequency was changed by gain.

Obtaining real-time force and displacement states of piezoelectric actuators is a necessary condition for accurate control. Self-sensing methods that utilize the piezoelectric actuator itself as the sensor have attracted much attention due to low cost and portability. However, researches on the self-sensing of piezoelectric actuators mostly focuses on phenomenological models, and reports on fundamental physics are infrequent. In this work, theoretical calculations and experimental measurements were combined to expose the physical mechanism of self-sensing. Taking the widely used barium titanate (BaTiO3) piezoelectric materials as an example, the influence of intrinsic and extrinsic contributions on the capacitance under mechanical-electrical coupling were systematically studied. The data obtained from material and electrical characterizations were used to quantify the contributions of various parts in piezoelectric materials to capacitance, and the obtained theoretical formula is in good agreement with experimental measurements. This study will further promote the applications of self-sensing in piezoelectric actuators.

There are many situations in the operation of mechanical products that require linear motion. In most cases, the conversion from rotational to linear motion is performed through various mechanisms. However, there is concern that such a method may be subject to the mechanical effects of each mechanism. Although there are some cases in which the motion pattern can be varied by installing a variable mechanism, such mechanisms are rarely used in general products because they complicate the system. Therefore, our laboratory has been continuously studying linear actuators that enable high-speed and high-precision linear motion. In this report, a linear actuator with a dual Halbach array of permanent magnets in the stator was designed to further improve the thrust of the linear actuator. The effect of the geometry of the permanent magnets on the thrust characteristics was investigated using electromagnetic field analysis based on the finite element method.

Hybrid vehicles have multiple power sources and are energy efficient; this improves both their fuel efficiency and dynamic performance. Therefore, hybrid vehicles have recently been used as competition vehicles, which require high powertrain performance. The system of hybrid vehicle consists of two power resources: an internal combustion engine and motor, each of which requires precise control. Controlling the output of an internal combustion engine is difficult. In this study, the dynamic response of an actuator to an electronic throttle system is investigated. The experimental results indicate that the optimized parameters improve the dynamic response.

Linear motion in a machine is converted from rotational motion by the mechanism. The performance of linear motion by a mechanism depends on the geometry of the mechanism. In addition, energy loss occurs by using mechanisms. However, by replacing these mechanisms with linear actuators that use Lorentz force and have a simple structure, direct drive can be realized and highly efficient linear motion can be achieved. In this study, a prototype actuator in which the magnetic flux is concentrated in the coil by the arrangement of magnets was fabricated, and the thrust characteristics in the reciprocating motion of the mover were evaluated.

In conventional elevators, vibration and cable twisting are major problems when the cable is long. Therefore, we are considering an elevator that omits the counterweight and uses a single cable with fixed ends to move the actuator. However, there are problems such as reduced efficiency due to cable contact and damage. Therefore, we propose a vertical transfer system that uses a cylindrical linear induction motor (LIM) as an actuator to move the actuator in a non-contact manner over a long uniform conductor cable. By placing the cylindrical LIM on top of a reaction plate, which is a cylindrical shell-shaped conductor, the advantage is that the magnetic force acts uniformly on the reaction plate and vibration in the gap direction is suppressed. So, we built an analytical model in which the cylindrical LIM is driven vertically and analyzed the electromagnetic field using the finite element method.

This paper deals with the design optimization of a mechanical fast switch for DC circuit breaker (DCCB) using the response surface method (RSM). The dynamic characteristics such as transient current, electromagnetic force, velocity, and movement of repulsive plate are calculated using a coupled electric circuit, magnetic, and mechanical analysis based on the finite element method (FEM). In order to verify the validity of coupled analysis model, the calculated dynamic characteristics are compared with the experimental values. Subsequently, in order to improve the action completion time of the mechanical fast switch, an optimal thomson coil model(TCA) is designed using the RSM.

In this paper, the devices of PECT and ECT were set up, and the performance of PECT and ECT was compared in thickness measurement. The experimental results indicated that although the exciting current of PECT was higher than ECT, PECT cannot evaluate 1 mm plate. Using the amplitude of ECT signal, ECT cannot evaluate 10 mm plate. Using the phase of ECT signal, all four plates can be evaluated. Traditional ECT has better performance than PECT in the thickness evaluation of current plates.

This paper presents a planar microwave sensor sensitive to complex permittivity changes in polymer materials. Characterization of permittivity changes in polymers is measured and correlated with heat caused degradation. To track minute permittivity changes, a highly sensitive design is developed, and tested with different polymers, The main advantage of the proposed sensor is its design, allowing ease of fabrication, while combining a dual band operation principle, with differential sensing, providing sensitivity to the difference between two materials at multiple frequencies. The proposed differential sensor possesses a high sensitivity of (360MHz) in terms of absolute sensitivity.

Magnetic incremental permeability (MIP) method is an efficient Non-Destructive Testing (NDT) method for characterizing metallurgical treatments (carburization, shoot-peening). Still, the conventional experimental setup is limited by inherent properties mostly due to the flat coil Eddy Current Testing (ECT) sensor (lift-off, etc.). In this study, direct electrical contacts derived from the magnetic needle probe (MNP) stand in place of the conventional sensor. This alternative “MNP-MIP” method provides directional measurement and solves multiple issues of the current process as applied to material surface treatment inspection.

The eddy current magnetic signature (EC-MS) method has a high ability to evaluate residual stress in carbon steels with high sensitivity. In this study, an electromagnetic model for the EC-MS method is developed to quantitatively evaluate the amplitude and profile of residual stresses in steels. For this purpose, in-situ measurement of EC-MS signals is carried out during the compression test of carbon steel specimens. The experimental signals are compared with simulated signals based on electromagnetic field analysis considering the constitutive relationship of dynamic magnetization.

Metal additive manufacturing (AM) methods are increasingly being employed due to their ability to create complex parts that are sometimes very difficult to manufacture using conventional methods and often with fewer flaws. Typically, metal additive manufacturing involves fusing layers of powder using an energy source, such as a laser to first melt the metal powder to form a melt pool. The dynamics of melt-pool influences the microstructure and resultant properties of the AM parts. If the process is not controlled precisely, flaws result due to what is known as keyholing. This paper investigates the feasibility of minimizing the possibility of keyholing by actively controlling the dynamics of melt-pool by employing rotating magnetic fields to churn the melt pool. Simulation results showing our ability to churn the melt-pool will be presented.

Magnetic fluids are nanofluids in which 10 nm-sized magnetic particles are stably dispersed in a carrier liquid such as water. The magnetic fluids are expected as phase change material to develop the thermal storage system. In the present study, we clarified the thermophysical properties of magnetic fluids during the melting and solidification process using differential scanning calorimetry (DSC). As a result, it was found that the magnetic fluid has a lower melting point than purified water and that the heat flow changes differently.

In this paper, a magnetic flux concentrator plate is used to heat a non-oriented electrical steel sheet, and the inductances before and after the heat treatment were compared and investigated. It was clear that the temperature at the center of the sample increased the most when using the magnetic flux concentrator plate. It was clarified that the inductance distributions differed upon heating with the magnetic flux concentrator plate.

This paper presents a new type of cable-driven variable stiffness robot elbow joint based on permanent magnet spring, pulley block and planetary gear train structure, which increases the range of motion and variable stiffness range of elbow joint. It expounds the principle and overall structural design of elbow joint, and gives the changing law of joint stiffness. The position control characteristics and stiffness controllability of this new type of variable stiffness elbow joint are verified by the decoupling verification experiment of stiffness and position of variable stiffness joint.

Structural health monitoring involves periodic observations to monitor material and geometrical variations in constructions and structures. For reliable measurements, instrumentation must be set in perfect reproducible conditions. Printing sensors directly on the part to be controlled is the solution promoted in this study. This method solves the reproducibility issue, limits the Human factor influence, and leads to sensors that can be used in confined or hazardous environments.

This work was intentionally limited to eddy current testing sensors. Still, the printed-developed techniques and the conclusions are transposable to other non-destructive testing methods (ultrasounds, electromagnetic acoustic transducer, etc.).

In this paper, a cylindrical energy harvester, which combines an anti-vibration rubber and PVDF, and its characteristics evaluation method is presented. A forced vibration test using a hydraulic servo dynamic testing machine was conducted to determine the power generation characteristics. As a method to evaluate the power generation performance, a characteristic evaluation method was developed based on the governing equation of longitudinal vibration of the bar, and the results were compared with the experimental results to confirm the validity of the characteristic evaluation method.

A mesh deformation technique based on affine transformation is proposed to avoid re-meshing in this paper. To promote the speed of mesh generation, an improved mesh smoothing method is proposed in the initial mesh generation. An affine transformation is used to realize the mesh deformation. Magnetic field calculation of an induction motor is used to test the proposed method. The numerical results demonstrate that the proposed method can obtain a qualified mesh without re-meshing in small deformation.

In order to prototype a waveguide bandpass filter (BPF) using a 3D printer and plating, we proposed a new window structure and used μGA (micro Genetic Algorithm) for its design. From the design results, it was confirmed that the proposed structure can also obtain filter characteristics.

A permanent magnet elastomer is a magnetized elastomer in which particles of a hard magnetic material such as neodymium particles are dispersed. The permanent magnet elastomer reacts against an applied magnetic field. In this study, sound absorption properties of a permanent magnet elastomer membrane were investigated experimentally by using an acoustic tube which can be able to apply magnetic field. The permanent magnet elastomer membrane is deformed by applied magnetic field and the sound absorption properties can be controlled by changing the direction of applied magnetic field.

Flexible steel plates are used in the manufacturing process of household electrical products. Since flexible steel plates are transported by rollers, surface deterioration of the plates is problem. One method to solve this problem is non-contact gripping and conveyance using magnetic levitation technology. The proposed magnetic levitation method is a two-degree-of-freedom active control system that controls vertical and horizontal motion. In this study, experiments were conducted under different steady current using the control system.

The optically pumped magnetometer (OPM) is one of the most sensitive magnetic field sensors, which is widely used for ultra-weak magnetic field measurement. To localize and quantify the magnetic source, array OPMs are needed to work simultaneously in a small area. However, an OPM typically employs a modulation magnetic field. In the presence of multiple sensors, the modulation fields of the OPMs interference with each other, resulting in reduced measurement accuracy and sensitivity. This paper proposes a novel array OPMs setting to eliminate the mutual interference of the modulation magnetic field, where the OPMs are modulated by a specially designed coil. The coil is optimized based on the numerical calculation and it generates an almost uniform magnetic field in the sensor area. The operating principle of the method is analyzed by solving the Bloch equation. Then, the feasibility of the method is demonstrated experimentally with compact OPMs and the magnetocardiography signal of human body is measured.

Flexible steel plates have problems with the transport method. Flexible steel plates are transported by rollers. However, the contact between the roller and steel plate degrades the surface quality. To solve this problem, non-contact transportation for steel plates using electromagnetic force has been proposed. In this study, a magnetic levitation system that suppresses deflection using gravity. In this report, the characteristics of the system under vertical disturbance were investigated.

This work introduces a novel electromagnetic active vibration isolator that employs a displacement amplification mechanism and fuzzy PID control. The integration of a ring-shaped permanent magnet and an electromagnetic coil within the central part of the rhombic displacement amplification mechanism leads to a substantial enhancement in the electromagnetic force stroke. Consequently, the effectiveness of vibration isolation is significantly improved. Firstly, the vibration isolation principle of the isolator is presented. Subsequently, a multi-node theoretical model is developed for the vibration isolator. Finally, the vibration isolation performance of the isolator is simulated and analyzed using fuzzy PID control.

The optical loads on high-resolution satellites are very sensitive to vibration. Therefore, it is crucial to meet the pointing accuracy and micro-vibration suppression for the optical loads. In this work, a parallel platform with new nine legs is designed for integrated micro-vibration and pointing control. The legs include three voice coil and six piezoelelctric actuators. Combining the decoupling of micro-vibration and attitude motion, a joint control model is built in Matlab/Simulink. The simulation result shows that the new platform can achieve good performance in both micro-vibration suppression and precision pointing control.

In the centrifuge shaking table composite environmental test system, the centrifuge arm is a typical beam-like structure. When regarded as a rigid body, the dynamic characteristics of the composite system cannot be accurately reflected. An original finite volume approach is used to model the centrifuge arm, along with a multi-rigid body model of the shaking table. Simulation results show non-negligible coupling of the composite system.

This paper proposes a noise level calculation formula based on vibration velocity from the mechanism of bridge arm reactor noise generation. The evaluation method first calculates the equivalent flux density value. Then, the deformation displacement is solved according to the mechanical relationship of the thin-walled ring and the vibration velocity sum of the multilayer encapsulations is obtained from the displacement to time derivative. The noise level is calculated by the sound pressure level equation, and the error is 6.1% when comparing the sound level measurement test results. Finally, the sensitivity calculation of the analytical formula is performed to obtain the influence of structural and material parameters on the sound pressure level.

The evolution of aerodynamic devices has improved the performance of competition vehicles.On the other hand, suspension systems have become stiffer to maintain a constant distance between the vehicle body and the road surface in order to maximise the performance of aerodynamic devices. Stiffer suspensions tend to reduce the static displacement of the vehicle spring against aerodynamic forces, while ground load fluctuations tend to increase. Therefore, a basic study of two methods was conducted to develop an active suspension system that optimises aerodynamic performance and load fluctuations to improve vehicle dynamics: simulation and a vibration test system that verifies the dynamic behaviour of a scale car by vibrating it.

Deformation and vibration of thin-walled structures exist simultaneously under fast maneuvering environment, which affects the accuracy and safety of structures seriously. In this paper, the plate’s dynamic control equation under time-varying environment is established, which includes four coupling factors: rigid body motion coupling, deformation coupling，rigid body motion and deformation coupling, electromechanical coupling. MFC actuator and sliding mode control algorithm are employed to control the elastic deformation and vibration of the plate induced by the time-varying motion. The results show that dynamic model established and control strategy optimized can be used for deformation and vibration control of plate undergoing overall motion with 6 degrees of freedom effectively.

In thin steel sheet production lines, contact conveying by rollers is used, which sometimes results in scratches and plating defects on the steel sheet surface. To solve this problem, non-contact conveyance by magnetic levitation is expected. When thin steel plates are magnetically levitated, magnetic levitation control becomes difficult due to deflection caused by the flexibility of the plate. Therefore, we have proposed a curved magnetic levitation system that improves the levitation stability by curving the steel plate for magnetic levitation. However, the dynamic behavior of thin steel plates during bending magnetic levitation have not been clarified. In this report, we performed a levitation experiments of bending steel plate, and input disturbance to the bending levitation device. From the measured response of levitated and oscillated steel plate, it was confirmed that the bending thin steel plate was in rigid body motion due to the disturbance.

A novel vibration control device based on the piezoelectric shunt damping technology is proposed and successfully applied to a single DOF system. This proposed absorber is composed of a butterfly-shaped steel frame and a piezoelectric stack. This butterfly-shaped structure is designed to protect the piezoelectric stack during the vibration reduction process and maximize the force transmitted to the stack for a better reduction effect. The optimal geometric parameters of the butterfly steel frame are obtained by utilizing the PSO algorithm for structural optimization and parameter analysis. The excellent vibration reduction performance of the optimal-designed absorber is verified by the numerical simulation and experiment.

Ultra-compact mobility has been proposed as a new means of transportation in consideration of short-distance travel and environmental considerations in tourist destinations and urban areas. Since these vehicles are small and lightweight, it is expected that the ride quality will be uncomfortable due to vibration and the driver's discomfort will increase. Therefore, our research group proposes to improve the ride quality by mounting the active seat suspension on the seat. In this study, we conducted a basic study on ride comfort estimation considering the psychological state.

The sustainability of Information and Communication Technologies (ICT) is discussed in a thermodynamic framework regarding the end of Moore's and Koomey's laws and in a context of data deluge. Magnetism is expected to provide a few orders of magnitude for the efficiency of ICT towards the thermodynamic maturity.

Magnetic resonance imaging (MRI) has been widely used as gold standard of many clinical diagnostics. However, traditional MRI systems have high demands on facility settings and are often costly. Recently, portable low-field MRI systems have shown promising compatibility to different conditions. In this work, we obtained image on two portable low-field MRI systems, using an open-source MRI control system called MaRCoS.

Steady-state visual evoked fields (SSVEF) signals have a wide range of applications in brain-computer interface (BCI). An SSVEF system commonly uses multi-channel sensors to measure the signals simultaneously, which reduces the portability and increases the cost of the system. This paper studies the distribution of the human brain visually evoked magnetic field experimentally and then presents an SSVEF system based on a single optically pumped magnetometer (OPM). The sensor is placed at the position with maximum magnetic signal amplitude. A BCI system employing a magnetic field compensation system to suppress the low-frequency magnetic field fluctuation and the power line interference is developed and tested, where the subject under test can control the movement of an object in a game to avoid objects based on the SSVEF measurement. This system can potentially be used to develop BCI games and medical aid instruments.

In this report, an antenna for wireless power feeding systems using sewing technology was described. The reflection loss of the antenna was -8 dB in a simulation and -11 dB The difference between the values in the simulation and measurement can be resulted from the dielectric material to support the antenna.

Litz wire has flexibility and low loss due to skin effect. Flexible coils can be fabricated by sewing or stitching the wire into cloth. Magnetic field resonant power transmission with those coils has been researched. In the magnetic resonant power transmission, it is important to increase the Q value of the coil. To increase the Q value of the coil, it is necessary to reduce the coil loss. Coil losses include DC loss, proximity effect, skin effect, and loss due to stray capacitance. In this study, we evaluated the losses in sewn coils in the frequency range from 1 to 15 MHz in terms of proximity effect and stray capacitance. As a result, the loss due to stray capacitance is significant for the loss between coils.

This paper describes the transmission efficiencies of fractal antennas using sewing technology for efficient wireless power transmission to implantable devices such as artificial hearts. Since the use of percutaneous power sources can cause infections, contactless power transmission is considered a safer option. The Vicsec fractal pattern antennas fabricated with a sewing technique were proposed. The size of the antennal can be reduced by using the pattern. The transmission efficiencies of a fabricated antenna were around -30 to -40 dB at a designed frequency.

In recent years, wireless power transmission has attracted attention as a method of supplying power to medical devices in the body. This study proposes magnetic field resonance wireless power transmission using an auxiliary coil sewn into clothing and a coil to match the impedance of the circuit. The system is designed to supply power to implantable medical devices while the patient is lying in bed, with the auxiliary coil sewn into the garment and the matching coil placed on the power transmission coil side. The auxiliary coil is used as a repeater to improve the coupling coefficient between the transmitter and receiver. The matching coil is installed to prevent reflection of electricity due to impedance mismatch. The conditions for efficient power transmission were investigated using a simulation software.

We develop a PCR method utilizing carbon-coated iron (Fe@C) nanoparticles. The outer carbon layers of the particles absorb near-infrared (NIR) light and release energy as heat. We carry out PCR performing thermal cycling via the on/off operation of NIR irradiation to the particles. We show that the total time of PCR is shortened compared to the conventional method thanks to rapid, efficient heating by Fe@C nanoparticles. We also show that the total amount of by-products is smaller than the conventional case, which may be attributed to the rapid thermal cycling.

Recently, wireless power transmission has been attracting attention as a method of supplying power to medical devices inside the body. Wireless power transmission using electromagnetic waves has been studied for long-distance transmission. In this report, a three-antenna system with a sewn auxiliary antenna is proposed. The auxiliary antenna sewn into clothing such as a shirt is worked as a repeater between power transmitting antennas and a receiving antenna inside the body. As a first step, the transmission characteristics between the auxiliary antenna and the power receiving antenna were evaluated.

One of the leading causes of critical current degradation in (RE)BCO tapes is the micro-cracks produced by mechanical slitting. In this paper, a tape model with multiple edge cracks is established. Under tensile loading, the effects of the Poisson ratio, crack length, crack angle, and geometric mutation between cracks on the stress intensity factor are investigated using the extended finite element method (XFEM). The stress intensity factor exhibits an evident jump characteristic when a geometric mutation occurs. The jump level strongly depends on the geometric difference. The jump location is the initiation site for crack propagation, which is consistent with the experiment results. The impact of cracks on the critical current degradation of the tape is also discussed.

In this study, the restoring force generated by the superconducting pinning phenomenon was examined in terms of the characteristic change caused by the concave-stage arrangement of the two superconductors. By analyzing the restoring force characteristics in each direction of a superconducting magnetic bearing created using two superconductors, we verified whether the restoring force characteristics change. As a result of the experiment, it was confirmed that the restoring force in each direction is increased by arranging the superconductor with a stepped shape. Experiments have shown the usefulness of applying a concave step arrangement to superconductors.

A method to design a magnetorheological damper with large damping force in a limited space is proposed, and a nonlinear model at high velocity is established. First, a magnetorheological damper with radial damping gap is designed and fabricated in this paper. The maximum damping force exceeds 24kN. Secondly, the dynamic characteristics of the designed magnetorheological damper at low velocity and high velocity are tested respectively. The results show that the controllable damping force dominates due to the increase of current at low velocity. When the velocity increases to a certain range, the damping force increases nonlinearly, and the non-controllable damping force is the main component. The damping force calculation model of the magnetorheological damper with radial damping gap at high velocity is obtained. Finally, by comparing the model with the experimental results, the accuracy of the damping force calculation model at high velocity is verified.

Stereolithography apparatus (SLA), a standard 3D printing technology, suffers from post-processing burrs and the use of extra material for support legs. To solve the problem, we propose a novel SLA approach that utilizes a magnetically levitated fluid, enabling the fabrication of desired objects through photocuring and layering processes. The key requirement for the fluid is its good responsiveness to magnetic fields while being curable under specific wavelengths of light. To fulfill the requirement, we developed and evaluated a new magnetic photocurable resin (mPCR) fluid with both magnetic responsiveness and photocurability. Additionally, we designed and implemented a prototype SLA system that incorporates the magnetic levitation technique.

Influence of channel height, magnetic fluid concentration, Reynolds number and magnetic field intensity on heat transfer of magnetic fluid flow in a mini-channel was investigated experimentally. Two mini-channels which has 1 mm and 5 mm of channel height and 1.6 vol% and 3.2 vol% of magnetic fluid are prepared in this study. Reynolds numbers are set to 100, 200 and 300, and magnetic field intensity is varied 100, 300 and 500 mT. The results show that heat transfer is enhanced for 5 mm of channel height by applying strong magnetic field, while heat transfer is slightly suppressed for 1 mm of channel height.

A continuous steel plate production line in steelworks is several kilometers long; over this distance, steel plates suffer from problems such as vibration, friction, distortion, and surface quality degradation, which are caused by contact with rollers. To solve this problem, our research group investigates noncontact guidance control that suppresses the vibration of continuous steel plates by applying an electromagnetic force near the edge of the plates. We analyze and experience the vibration characteristics of steel plates by changing the positions of the electromagnets used in the magnetic guideway for the plates, which are stationary.

In order to control the magnetic field adjusted electrical behaviors in composite piezomagnetic-piezoelectric semiconductor structure, non-uniform piezomagnteic layers are designed. After establishing the mathematical model, the effects of the non-uniform piezomagnetic layers on the electrical field quantities are investigated thoroughly. This work could be the guidance designing magneto-electric devices.

X-ray CT scans were employed to visualize and track the movement of NdFeB particles dispersing permanent magnet urethane elastomer (PMUE) during the compression process. The particle translation and rotation were quantified by analyzing the data obtained from the CT scans. The findings revealed that particles closer to the compression plane exhibited larger translation distances while the amount of rotation remained unaffected by the initial position. Furthermore, it was observed that most particles did not undergo significant rotations beyond 45 degrees.

We have developed a connection system that automatically connects modular robots to each other. For automatic connection, the magnetic flux density was used for connection position estimation using the magnet and the Hall effect IC. The relationship between the relative position and the magnet flux density was identified, and the threshold value was set to determine contact.

In recent years, robot hands using soft materials have been studied. By using a soft material, you can easily grab fragile or various-shaped objects. Many of these soft grippers are pneumatically driven. However, it is required to use an air compressor which is not favorable for agricultural robots or field robots. Therefore, we propose a gripper that uses a magnetically functional fluid for the fingertip and investigated the characteristics. Furthermore, we also employed image processing techniques with the visual sensual camera to extract the contour of objects. This enables us to obtain information such as shapes, centroid, area…which we can use to perform Object detecion using the Raspberry Pi. And in conjunction with the Arduino, we can conduct the automatic grasping for the flexible fingertip robot system.

To realize multi-DOF motions for miniature robots, complex structures and driving mechanisms are usually implemented. This study develops a novel stick-slip robot driven by a single electromagnetic coil, which can accomplish forward, backward, and turning motions. The proposed structure includes four driving legs, a single electromagnetic coil rotatable around the main supporting body, which can switch between two statuses corresponding to linear and rotational modes. By adjusting the coil positions, the driving legs undergo asymmetric deformation. The robot motion is then realized by this system asymmetry, which varies reaction forces at four driving legs during the vibrations caused by the electromagnetic coil. This study proposes a model based on stick-slip frictions to elucidate the operating principles of the developed crawling robot, and examines the structure characteristics and driving capabilities for a 3D-printed prototype.

This paper presents our proposed frequency sweeping excitation and spectrogram method (FSES method) by magnetic sensor for non-destructive evaluation of yield strength on low carbon steels. This method can evaluate the magnetic properties of low carbon steels whose yield strength were changed by induction heating. It was examined by our proposed method that the degrees of yield strength on low carbon steels were varied depending on conditions of induction heating.

For magnetic flux leakage testing, various variants of the same-diameter steel wire rope were developed respectively, and the simulation results show that different modeling structures of wire rope result in different distributions of internal magnetic field and defect leakage magnetic field. Therefore, a comprehensive study on the magnetic field transmission and defect leakage magnetic field characteristics of steel wire rope is required.

This paper aims to present the effectiveness of the new nondestructive method dedicated to detection of the rebar-concrete debonding. The Magnetic Force-Induced Vibration Evaluation (M5) method is designed to detect changes caused by corrosion. The method's concept is to directly induce rebars' vibrations (not a whole structure), measure them, and analyze the frequency spectrum changes. The presented in the paper experiments show that the structure condition correlates with its response to electromagnetic excitation at different frequencies. In the purpose to avoid the damping of the mechanical wave by the concrete cover, a magnetic coupling was implemented. Such a solution allowed to increase the sensitivity and reproducibility of measurements significantly. The work presents the principle of operation of the M5 method as well as the results of the most critical tests.

We investigated an influence of surface condition of steel specimen on nondestructive testing to detect small defects using magnetic flux leakage with highly sensitive magnetic field sensor. When the defect diameter becomes smaller, the leakage flux distribution caused by the defect becomes equal to the background magnetic field distribution, which makes defect detection difficult. The background noise is not attributed to environmental magnetic noise or electrical noise, and reflects some magnetic characteristics of the specimen.

Discretization of a boundary-value problem with the eXtended Element-Free Galerkin (X-EFG) method yields an asymmetric EFG-type Saddle-Point (EFG-SP) problem that is difficult to solve numerically. As high-performance solvers for the problem, four types of the Asymmetric-version improved Variable-Reduction Methods (AiVRMs) are formulated. A numerical code is developed for solving asymmetric EFG-SP problems with four types of AiVRMs and, by means of the code, performances of the four methods are investigated numerically.

The multifunctional magnetically controlled transformer (MCT) organically integrates the magnetically controlled reactor with the distribution transformer. It has the advantages of fast and smooth adjustment of reactive power, and small overall floor area. Because of the topology of MCT is complex and affected by DC current, the analysis of electromagnetic loss characteristics on MCT iron cores is rather necessary. Firstly, this paper studied the structure and operating principle of MCT through the circuit analysis; Then, established the instantaneous core loss calculation model; Finally, quantitatively calculated the electromagnetic losses of MCT via finite element analysis (FEA), providing reference for its parameter design and heating verification.

The paper reports the progress to obtain accurate simulations of amplitude of EMAT signal from defects in metallic plates by means of FEM simulations. The simulations results are applied to a FEM model based on a two-dimensional coupled eddy-current (ECT) and ultrasound (UT) formulation, by using various numerical integration methods as Crank-Nicolson, Backward Euler and Newmark-beta method. The paper presents the methodology to acquire convergence of the large variation in the EMAT signal from a defect to the same final EMAT signal, not only in the defect amplitude but also in the shape of the time transient EMAT signal when using different methods. Accurate EMAT signals can be obtained by means of the combination of high order finite elements (FEM) and advanced numerical time integration, to reach the converged EMAT signal in the shortest time, opening the way to simulate accurate signals form faraway defects.

This paper presents a shape optimization of power inductor using actor-critic approach which is one of the reinforcement learning. The performance of the actor-critic (AC) approach is compared with that of the genetic algorithm. Comparing to GA, AC is more stably converged to an optimal solution with lower computational cost.

Living matters transmit signals via ions, while machines transmit signals via electrons. Ions and electrons couple at the life-machine interfaces. Such a coupling has long been developed for applications in electrophysiology, neural stimulation, and neural recording. Central to merging life and machine is the transduction between ions and electrons. Here an approach to noncontact transduction between ions and electrons using a time-varying magnetic field is described. The magnetic field induces an electric field in an ionic conductor, driving ions to move. This ionomagnetic induction is studied through a combination of experiment, theory, and calculation. The ionomagnetic induction enables ionotronic transformer, noncontact power transmission, and noncontact motion detection. It is hoped that this work will guide the development of bioelectronics, ionotronic devices, and life-machine interface.

This paper proposed a new method for topology optimization using combination of Digital Annealer (DA) and Genetic Algorithm (GA), eliminating the need for manual formulation based on expert knowledge. The proposed method was successful in optimizing the shape of the magnetic shield, as the quick search of DA on the approximate model and the global search of GA combined enhanced optimization performance.

The high-pressure hydrogen storage tank used in vehicles is in a high-pressure state for a long time, so the inner surface of its aluminum liner is prone to corrosion, cracks, and other defects, leading to the failure of the hydrogen cylinder. Due to the small volume and narrow mouth of hydrogen storage bottles used in vehicles, it poses significant engineering difficulties for traditional detection methods. Therefore, there is an urgent need for a fast scanning system suitable for the hydrogen cylinders. In this paper, an array eddy current scanning system for detecting surface defects on the aluminum inner liner of hydrogen cylinders is designed. The comprehensive scanning of the aluminum inner liner is completed with the scanning system.

Reducing the power consumption of electromagnetic actuators even by 0.1% is significant in lowering environmental impact. When the actuator’s plunger is attracted to a fixed iron core, the magnetic properties of the iron core greatly influence of the plunger’s electromagnetic force due to the small air gap of the magnetic path. Thus, understanding and utilizing the magnetic properties of the iron core is critical. The manufacturing process deteriorates the magnetic properties, hence their behavior under stress has been studied. However, the effect of the bending process, frequently used in iron cores manufacturing, on magnetic properties has not been studied well. This paper clarifies the influence of magnetic properties of the bent part in an electromagnetic actuator. The magnetic properties of the bent part are estimated from a flat and a bent ring core. The magnetic permeability of the bent part decreases by one-third, leading to a 2.5% decrease in the electromagnetic force of the actuator as shown in our analysis.

A parallel Newmark-β algorithm for dynamic differential equations based on GPU has been proposed, whose reliability and acceleration performance has been varified with a cantilever beam. The results show that when the degree of freedom of model reaches 20000, the calculation speed of the algorithm is 12.99 times that of Newmark-β algorithm based on CPU, and shows a good trend with the increase of the degree of freedom. Furthermore, the proposed algorithm has been used to solve the dynamic differential equation of the rocket sled system, the result shows that despite the frequent data transmission between CPU and GPU in the solution of nonlinear time-varying differential equations, the algorithm proposed can still reduce the calculation time by 62%.

Ultra-compact mobility has been proposed as a new means of transportation in consideration of short-distance travel and environmental considerations in tourist destinations and urban areas. Since these vehicles are small and lightweight, it is expected that the ride quality will be uncomfortable due to vibration and the driver's discomfort will increase. Therefore, our research group proposes to improve the ride quality by mounting the active seat suspension on the seat. In this study, we conducted a basic study on ride comfort estimation considering the psychological state.

Noncontact magnetic levitation conveyance of thin steel plates using the attractive force of electromagnets has been proposed. In this study, magnetic levitation experiments were conducted on steel plates using the optimum arrangement of permanent magnets for each condition obtained by the genetic algorithm, and the stability of levitation was experimentally investigated. The results confirmed that the levitation performance of the steel plates was different for each gap and distance between horizontal electromagnets.

This study is being conducted to construct an active steering wheel system that provides an appropriate steering reaction torque for each driver. We conducted load experiments and confirmed that the results were consistent with the amount of steering burden, and found that the steering burden can be evaluated quantitatively.

During the hypersonic flight of the vehicle, the intense aerodynamic heating causes the temperature within the shock layer to rise sharply. Complex physicochemical reactions occur in the gas mixture accompanied by excitation of species in different energy modes, forming a plasma ionized flow. Applying a magnetic field to the flow can push the shock wave away from the body, producing good thermal protection and some reduction in resistance. However, the effect of the Lorentz force causes more additional drag, which makes the drag environment harsher. To achieve better heat shield and minimal drag growth of magnetohydrodynamics (MHD) flow control, researches on the drag and heat characteristics under a uniform and dipole magnetic field are carried out for several typical geometrical bodies. We obtained the influence of body’s shapes and magnetic field layouts on the aerodynamic characteristics of vehicles, which can help us to extend the application of MHD flow control.

To isolate low frequency vibration, this study proposed a magnetic high-static-low-dynamic

stiffness vibration isolator (MHSLDs-VI), which is composed of a spiral flexure spring (SFS) and

a magnetic negative stiffness spring (MNSS) based on variable reluctance stress. Theoretical study

and simulation of the MNSS stiffness-displacement relationship shows that an approximate linear

high negative stiffness is generated under small working air gap by employing the variable

reluctance stress. Comparing with existing single mover configuration, the negative stiffness of the

proposed double mover configuration increase two times. Besides, the optimization of the location

of the non-working air gap effectively improves the negative stiffness density. The axial positive

stiffness of SFS is analyzed by finite element method (FEM) and then the MHSLDs-VI is designed.

The dynamic model of the proposed isolator is established and the derived transmissibility

demonstrates that the isolation band is expanded towards low frequency. Therefore, the proposed

MHSLDs-VI can isolate low frequency vibration with high load-capacity and small size.

In production lines for thin steel sheets, which are often used in industrial products, contact conveyance by rollers is used. However, quality deterioration due to contact has become a problem. Therefore, non-contact magnetic levitation conveyance of thin steel sheets using the attractive force of electromagnets has been proposed. In this report, the effect of horizontal electromagnets on levitation performance is experimentally investigated.

One of the problems with ultra-compact vehicle is the resultant ride quality by vibrations in the vertical and pitch directions. Therefore, active seat suspension system using voice coil motor was proposed. Active seat suspension is mounted under the seat and directly suppresses vibrations transmitted to the occupant. In this report, the vibration suppression effect of using a voice coil motor was investigated.

Design a novel High-Static-Low-Dynamic Stiffness (HSLDS) magnetic spring consisting of permanent magnet and electromagnetic coil. Establishes the mathematical model and dynamic model of magnetic spring stiffness. Without adjusting the structural parameters, the initial vibration isolation frequency and peak transmissibility can be reduced by changing the magnitude and direction of current in the coil, thereby broaden the effective vibration isolation frequency band.

In this paper, a new permanent magnetic levitation system is proposed, which achieves stable levitation by controlling the magnetic force generated by the rotation of two permanent magnetic sticks acting on the iron ball below. We firstly design the structure and dimensions of this magnetic levitation system. Secondly, we determine the optimal rotation angle of the two permanent magnet sticks when the iron ball is in different positions. Finally, the control system of the magnetic levitation system is designed by using LQR (Linear Quadratic Regulator) control method. The simulation results show that the magnetic levitation system has good dynamic performance and can effectively realize the stable levitation of the iron ball.

In this paper, we proposed a novel piezoelectric damper which is designed for multi-mode vibration control of mechanical structures. This damper is composed of three butterfly-shaped energy converters, in which the piezoelectric stacks are embedded. Each energy converter is connected with a shunt circuit. For realizing the multi-mode vibration control of mechanical systems, these circuits’ electric resonant frequencies should be tuned to the structure’s targeted modal frequencies in one-to-one correspondence. To validate the proposed damper, the numerical simulation is carried out. In the presented numerical example, the damper is placed at three quarters of a hinged-hinged beam, and a point force with sweep sinusoidal frequency is applied at one quarter of that beam. Simulation results show that the proposed damper can significantly suppress the targeted modal vibrations.

As a fundamental study to improve the cornering performance of a yaw moment control system that assists the self-spinning motion of a competition vehicle, a quasi-static analysis of a vehicle subjected to electric motor drive torque and brake torque using an actuator was conducted. As a result of the analysis, the vehicle cornering performance with and without the system was evaluated, and the torque of the electric motor and the force of the actuator were calculated to satisfy the requirements for the amount of yaw moment change due to the system.

Deterioration of surface quality of steel plates due to conveyance by rollers has been a problem. As a solution, a technology for non-contact gripping and conveyance using electromagnetic force has been proposed. In this study, as a consideration of electromagnet units in magnetic levitation systems, the characteristics of magnetic field was investigated when the electromagnets are tilted.

In this paper, a novel purely data-driven modal parameter identification approach for time-varying structural systems based on dynamic mode decomposition with sliding-window recursive mechanism is presented, which can address the drawbacks of parameterized modeling methods. The effectiveness of proposed method is illustrated through representative numerical simulations with time-varying dynamic behaviours, exhibiting a good engineering application prospect.

Quasi-zero stiffness isolators have a broad application prospect in effectively suppressing low-frequency vibration, but most quasi-zero stiffness isolators for low-frequency vibration isolation are only applicable to rated loads. Considering the strong nonlinearity and structural complexity of quasi-zero stiffness vibration isolators, small changes in system parameters may lead to dramatic deterioration of vibration isolation performance in an undesired direction.In this paper, the dynamics model of the vibration isolator under force excitation and displacement excitation is established, and the effects of the three uncertainties of damping, stiffness and excitation amplitude acting individually and coupled on the steady-state displacement response of the quasi-zero stiffness vibration isolator are analyzed by using the chaotic polynomial expansion method. By post-processing the coefficients of the established chaotic polynomial model, the Sobol` global sensitivity indices of each uncertainty parameter at different frequency bands under the coupling action are investigated.

In engineering, the adjustment of large hoop truss mesh antennas (LHTMA) reflector relies on manual labor. The adjustment method is usually complex, time-consuming, and often difficult to achieve high accuracy. The paper proposes an active adjustment method for LHTMA based on inertial actuators. Firstly, the driving method of inertial actuators based on piezoelectric ceramics was studied. Then, optimization methods were used to study the active adjustment algorithm for LHTMA, and genetic algorithms were used to solve the optimization problem. Finally, the feasibility of the active adjustment method was demonstrated through a simulation example of LHTMA with 8m aperture.

This paper proposes a topology optimization method for permanent magnet (PM) motors using the Gabor filter, which is widely used in image processing. In the proposed optimization, we maximize the average torque and minimize the torque ripple simultaneously. The proposed method leads to a PM motor with slit-shaped magnetic cores, which is difficult to obtain conventional approaches. It is shown that the proposed optimization results in PM motors with slit-shaped magnetic cores, which have better torque performance than a conventional model.

This study focuses on the topology optimization of the iron yoke used in Nuclear Magnetic Resonance (NMR) logging sensors for logging-while-drilling applications. A novel structure is designed to maximize the field strength and linearity of the static field for NMR logging sensors using topology optimization method based on NGnet-method.

Engineering structures subjected to stationary random loads tend to have a large impact on the stability of the structure, and the load environment during its operation must be accurately identified to ensure the safe operation of the structure. In this work, a stationary random load identification method based on ensemble empirical modal decomposition (EEMD) and deep recurrent neural network (RNN) is proposed. The method designs a deep RNN model with one gated recurrent unit (GRU) layer, one bi-directional long short-term memory (Bi-LSTM) layer, two long short-term memory (LSTM) layers and two feedforward layers in sequence, and uses decomposed load and response data as the output and input of the network. The effectiveness of the proposed method is verified by simulation data of a three-degree-of-freedom linear system and experimental data of a clamped beam.The results show that the proposed method is with higher accuracy than using only deep recurrent neural network. Further, the proposed method is also effective under undefined conditions.

This paper presents a topology optimization of a rotor core for asymmetric interior permanent magnet (IPM) motors. In the proposed optimization, the rotor structure is represented by a linear combination of normalized Gaussian functions to improve the average torque and torque ripple of an asymmetric IPM motor simultaneously. It is shown that the optimized asymmetric IPM motor, which improves the reluctance torque effectively, has higher average torque than the optimized symmetric one.

Sparse regularization methods have been extensively used in impact force identification to accurately determine the time history and locations of the impact force. However, in the context of impact forces, especially in structural health monitoring, accurate impact localization is far more critical than reconstruction time history. Furthermore, increasing the number of monitoring points to enhance force localization accuracy leads to a significant increase in the dimensionality of the transmission matrix. In this paper, a reduced iteratively reweighted l1-norm minimization algorithm (rIRI1) is proposed, which combines the reweighted lp-norm regularization with reduced control equation method. By taking into account the sparsity of impact force, the reduced transfer matrix is reconstructed to alleviate computational difficulty. Several simulations and experiments are conducted on an edge-fixed plate to compare the performance of IRL1 and rIRI1 under different underdetermined systems with varying numbers of monitoring points. The numerical and experimental results demonstrate the proposed method a substantial enhancement in computational efficiency compared to IRL1.

In order to improve the identification method of impact load using transient statistical energy analysis, which requires the known point mobility of excited subsystem to compute load, an identification method employing the basis vectors is proposed. The subsystem applied with impact load is firstly identified using the average kinetic energy of all subsystems based on the established transient statistical energy model of complex structure. On this basis, the basis vector is defined according to the distribution position, signal energy of impact load and its arrival time to sensor installed on the subsystem, so as to identify the specific position of impact load and obtain the impact signal of impact position. The time history is ultimately reconstructed by combining the identified input energy of impact load and the impact waveform. The method provides an effective way to identify the impact load of complex structures through improving the shortcomings of existing methods.

A robust optimization method, that can obtain a solution with high robustness in practical

settings with unpredictable fluctuation, for quadratic unconstrained binary optimization problems is proposed. The proposed method is applied to the optimal permanent magnet (PM) design problem of an electronic magnetic device. Even in the case of occurrence of a fluctuation of material property of the PM, it is possible to obtain a robust PM structure in which a value close to the target magnitude of magnetic flux density can be obtained.

In this paper, a fast inversion method for reconstructing the vibration loads of pipeline structures based on a dynamic transfer matrix method was proposed. The method involves a scheme to calculate the harmonic vibration responses as well as the dynamic transfer matrices of the pipeline structures with the finite element model, and an inverse algorithm to recover the unknown loads from vibration information at limited measuring points. Pipeline vibration experiments were also conducted to validate the numerical model and the proposed reconstruction method. Based on the simulated and measured vibration signals, the validity and efficiency of the proposed method were confirmed in regard to the inversion of vibration loads on pipeline structures from vibration signals at limited measuring points.

It is demanding to optimize the cable ampacity to make full use of the cluster. Since the optimization of the cable ampacity in a cable cluster is a hard constrained global optimization problem, and the final solution may be located on the constrained boundary, the existing optimization methodology will incur deficiencies in solving such a problem. In this respect, a hybrid optimizer of an improved genetic algorithm (IGA) and a local search adaptive tabu search (ATS) is proposed to optimize the ampacity in a cable cluster. The proposed optimizer uses a dual population strategy in IGA to exploit promising infeasible solutions effectively during the evolutionary process. A new neighborhood structure is proposed in ATS to generate neighborhood solutions directionally, helping local searches near constraint boundaries. The superiorities of the proposed method are confirmed by the optimization results of a test function and a cable cluster.

The number and location of nodes is crucial for the accuracy of radial basis function (RBF) meshless method. To promote the accuracy of electromagnetic numerical calculations, an adaptive refinement algorithm based on an error threshold in RBF meshless method is proposed. To identify the exact area where new nodes need to be generated, an error threshold is proposed and a hybrid node generation method is developed to promote the efficiency of node generation. A metal box example is used to test the proposed method. The results demonstrate the proposed method have the ability to improve the calculation accuracy of RBF collocation meshless method.

Our research group has developed a machine-learning method to estimate the radiation source distribution from γ-ray spectra in a space. In the previous study, we estimated radiation sources distributed in a 2D plane and achieved a high estimation rate. This paper extends the method to 3D space and discusses the estimation methods and results. In the 3D extension, it is examined that the estimation accuracy depends on the number of detection planes of the γ-ray spectrum used for estimation, and the effectiveness of estimation in 3D space is revealed.

Large-scale optimization has become the hot spot of practical engineering problems due to the complex structure of modern system. An improved fireworks algorithm (FWA) is proposed to solve the large scale optimization problem. To promote the ability of jumping out of the local optimal solution, differential sparks generation mechanism and a novel reinitialization mechanism are developed. To speed up the convergence, a dual-channel selection mechanism is proposed. CEC2013 test suite is used to test the performance of the proposed method. The numerical results demonstrate that the proposed method has better performance among the FWA variants.

“Tie” constraint is commonly used to establish the link relation of structural finite element model (FEM) in engineering. In this paper, the confined area is taken as the updated object, and modal test data is used to update the structural finite element model. Artificial neural network (ANN) is used to describe the nonlinear relationship between the natural frequency and the confined area of the structure. Training the network with FEM calculation results, and updating the FEM by test natural frequency. The results show that the error of natural frequency between the modal test and modal analysis of FEM is small, so the model has high precision.

As the modern antenna developing towards systematization and multi-function, antenna optimizations are often involved with large scale of variables. Fireworks algorithm (FWA) based on differential grouping is proposed to solve these high dimensional antenna designs. To search the variable space efficiently in a vast variable space, differential grouping method is introduced to identify the dependent variables and divide the optimization into sub-domains. To cooperate the evolutions in variable sub-domains, an information exchange and a monitor strategy is developed. An UWB antenna is proposed test the effectiveness and efficiency of the proposed method.

A novel data-DRNN method is proposed for time-domain load identification of a cylindrical structure subjected to random base excitation of electromagnetic shaker. The data-DRNN model comprises two Long Short-Term Memory (LSTM) layers and one Bidirectional LSTM (BLSTM) layer, trained using a large dataset of measured acceleration. The effectiveness and accuracy of the proposed method are validated under various temperature conditions using quartz lamp heater. Furthermore, the model's generalization capability is evaluated by different Power Spectral Density (PSD) target spectrums of excitation. The results indicate that data-DRNN has great accuracy and generalization ability, making it a promising choice for load identification of complex structures.

Research on the use of limited sensor measurement information to identify modal parameters in underdetermined situation has important engineering application values. This paper proposes an underdetermined modal parameters identification method based on block term decomposition. By transforming the underdetermined modal parameters identification problem into tensor uniqueness decomposition problem, the connection between modal parameters identification and tensor decomposition is established, and the algorithm is optimized to solve the problem of uncertain sequence of source signals after decomposition. Finally, through a numerical simulation example and an experiment of a certain type of solid rocket motor structure, the ability of the proposed method in dealing with the identification of underdetermined modal parameters is verified, demonstrating good engineering application prospects.

Currently, analytical methods used to analyze the internal magnetic fields of pipelines seldom consider the leakage flux generated during magnetization. This paper uses the magnetic field segmentation method to establish pipeline axial equivalent magnetic circuit model that considers edge effect magnetic resistance of the detection area.

An electromagnetic pulse-induced acoustic testing (EPAT) method was investigated for length sizing of a debonding between rebar and concrete of reinforced concrete. In EAPT, a pulsed electromagnetic field is applied to vibrate a rebar inside a reinforced concrete and excite elastic waves on a rebar. The elastic wave signal is detected by an acoustic emission sensor to evaluate the properties and condition of the material. By comparing the signal reach time of the elastic waves between specimens with and without a debonding, it was clarified that EPAT can be used as a length sizing method of rebar debonding.

In visualizing inner structures in constructional materials to maintain buildings, it is important to know the size and position of the foreign objects precisely. Spatial resolutions of conductivity distributions obtained using two algorithms for electrical impedance tomography (EIT), one of the simplest and lowest cost methods for non-destructive visualization, were evaluated in terms of the position and size of foreign objects in the specimens. From theoretical and experimental aspects, we obtained that the machine learning-assisted method is more suitable for the EIT algorithm.

In recent years, remanent magnetization after non-destructive inspection using magnetization and after transfer by electromagnet type magnets has become a problem. The influence of external magnetic fields and the demand for demagnetization accuracy in industry will be presented. Therefore, we propose a new demagnetization method and report basic demagnetization experiments and application examples of demagnetization of steel plates.

Silicon steel sheets are widely used as electromagnetic yoke materials in electric motors and generators. These yoke materials have various shapes and are sheared by die presses, etc., but residual stress is generated on the sheared surface. It is known that the magnetic permeability of ferromagnetic materials generally decreases in the residual stress area, and electrical equipment using sheared silicon steel sheets may not produce the designed output. Generally, X-ray test equipment is used to measure the residual stress in the processed part, but a simpler test method is required. In this research, a DC magnetic field is applied to a silicon steel plate, and leakage magnetic flux is generated from the sheared surface. In this paper, a magnetic measurement method is proposed to evaluate the magnetic properties of the sheared surface machined part from the distribution of the leakage magnetic flux. The usefulness of this proposed method is examined by three-dimensional nonlinear magnetic field FEM analysis and verification experiments.

The remote field eddy current testing (ECT) method is known to be effective in detecting external surface defects in ferromagnetic pipes used in petrochemical and steel industries. In previous research, it is clarified that the detection signal is decreased because of the phase angle difference between flux density due to the excitation current and eddy current approaches 180 degrees and cancels each other out. In this paper, an improved remote field ECT probe with ferromagnetic cores inserted inside the excitation and search coils is proposed to deviate phase angle to 180 degrees. The measured sensitivity of the proposed probe is increased by 15% compared with the conventional one. The mechanism is analysed in detail by using 3D nonlinear eddy current analysis using finite element method.

Carburizing and quenching is a type of surface hardening method used to improve durability, such as wear resistance. In carburizing and quenching, only the surface part of the steel material is carburized, making it possible to create a steel material with a hard surface and high toughness inside the steel material. It is important for quality control to measure the hardening layer depth of this carburized material. There is a difference in the hysteresis magnetization curve and electrical conductivity between the carburized layer and the non-carburized layer. Therefore, an electromagnetic inspection method is proposed to measure the depth of the carburized layer by detecting these electromagnetic property differences. In this paper, the usefulness of the proposed method is demonstrated through 3D nonlinear FEM analysis using the play model method, which considers the hysteresis magnetization curves and conductivity of carburized and non-carburized layers. In addition, the Verification experiment is also be conducted.

Nondestructive evaluation (NDE) of Fiber reinforced plastics (FRP) is essential, but challenging owing to the presence of interlaminar interfaces and anisotropy of material properties. The present paper provides for a dual-mode concentrical sensor which may be used for flaw detection in FRP composites using eddy current testing (ECT) and capacitive imaging (CI). Combining ECT and CI techniques provides necessary synergy to detect different types of flaws in electrically conductive and insulating FRP. The proposed sensor consists of a central pancake coil and an outer ring coil. Both coils are printed on a multi-layered flexible PCB such that the windings in each layer provide the same direction of current flow. ECT and CI inspection modalities are realized by establishing proper electrical connections between the coils. Validation of the sensing technique is provided on carbon FRP and glass FRP samples with simulated flaws such as fiber breakage and interlaminar delaminations.

The magnetic Barkhausen noise (MBN) effect, caused by the jumps of the magnetic domains, is demonstrated sensitive to the microstructure of ferromagnetic materials, which makes it a valuable tool for evaluating the micro damage and monitoring the magnetic domain motion. This paper presents a novel 3D numerical model for MBN problem by simulating the motion of magnetic domains during magnetization evolution procedure in the applied magnetic field. The model incorporates the pinning effect of micro damage by spatially randomly distributed barriers, and characterizes the discontinuous domain jumping by comparing the barrier potential and 3D magnetic field simulated with equivalent magnetic polarization method. The proposed model exhibits potential to investigate the MBN phenomenon under complex load and damage conditions and can aid in the optimization of MBN testing devices.

Thermal barrier coating (TBC) is widely used for the purposes of heat insulation and protection in high-temperature structural component such as aero-engine and heavy-duty gas turbine. Aiming at the difficulty of TBC measurement with conventional nondestructive testing method, a new method of surface acoustic wave spectrum analysis based on grating laser generation is proposed for both thickness measurement and delamination defect inspection of TBC. Firstly, the dispersion curve of surface acoustic waves in thermal barrier coating is obtained. Numerical simulation of grating laser acoustic signal and spectrum is then performed. Finally, both thickness measurement and debonding defect inspection of TBC with the proposed method is validated experimentally.

The surface state of metal material is closely related to its service life. Electromagnetic acoustic transducers (EMATs) can realize the nondestructive evaluation of the surface of metal materials because of its non-contact detection characteristics. However, EMAT relies on the principle of electromagnetic induction when exciting ultrasonic waves, so it has the disadvantage of low energy conversion efficiency. In this study, a new design is proposed, and the amplitude of signal is improved by combining linear frequency modulation (LFM) signal with variable-pitch meander coil. The finite element method is used to compare the conventional EMAT with the new designed ultrasonic surface wave EMAT. The numerical analysis results show that the combination of LFM signal and variable-pitch meander coil can greatly improve the amplitude of ultrasonic surface wave.

The detection of cracks with any orientations is a main challenge for the eddy current testing (ECT). In this paper, we propose a flexible printed circuit board (FPCB) probe based on "EIGHT" shape transmitter coils (Tx coils) to solve this problem. Firstly, the detection principle of the probe is given. Secondly, the angle of the Tx coils is designed through experiments, results shows that Tx coils with an angle of 60 is better. Finally, the probe is used for cracks with different orientations. Results show that the probe can detect both 0 - and 90-degree cracks.

The carbon fiber reinforced plastic (CFRP) material is a lightweight, high-strength material that combines carbon fiber and resin and takes advantage of the characteristics of each. This material is widely used in parts that require high strength, such as aircraft, automobiles, and hydrogen tanks. Although this material has high strength, if it is subjected to a large impact, it may cause internal delamination or internal defects. The detecting of these delamination and defects is important for strength and quality assurance of CFRP materials. In this research, the inspection method for detecting backside defects in CFRP plate is proposed from the measurement of the vibration intensity of electromagnetic force vibration. When the proposed measurement method was applied to a CFRP plate with a backside defect, the signal output was large at the defect site, indicating that this measurement method is effective.

This study monitored the Barkhausen noise, the incremental permeability, and the flux density in the same experimental conditions to evaluate the tensile elastic stress influence on magnetic behaviors. Hysteresis loops were reconstructed for all these measurements and used to define common indicators to establish correlations with elastic stress. Simulation tests based on the Jiles-Atherton-Sablik theory were run in parallel to confirm the relations between the elastic stress and assist in investigating the magnetization mechanisms.

In a bid to simultaneously exploit the advantages of pulsed eddy current and pulsed remote-field eddy current for evaluation of buried defects in layered conductors, in this paper, the near- and remote-field pulsed eddy current integrated testing (NRPEC) alongside an axi-symmetric probe has been proposed. Simulations are conducted to reveal the field characteristics underlying the proposed method and analyse the signal response to hidden flaws. In parallel, an NRPEC system has been built up. Based on the images of near-field and remote-field signal features, a fusion algorithm is proposed to fuse the signal features of near-field and remote-field signals for defect testing with the enhanced signal-to-noise ratio. Results from simulations and experiments indicate that based on the fused signal feature, high-accuracy imaging of hidden defects in a double-layer conductor can be achieved via NRPEC with the improved signal-to-noise ratio.

This study evaluates the applicability of using eddy current testing to detect the cracks that appear on the surface of full-tungsten divertor monoblocks. Tungsten blocks with artificial slits were inspected by a differential plus point probe. The results reveal that deep cracks away from the edge can be confirmed well and confirming the amplitude of signals due to an edge would be effective to detect a crack near the edge.

Flow-accelerated corrosion thins the pipe wall and makes a periodic rough surface on the inner pipe wall. The objective of this study is to develop a non-destructive evaluation method of the inner rough surface. To evaluate the roughness of the inner rough surface, a reflected wave from the surface with periodic flaws is acquired, and a frequency spectrum is calculated from the reflected wave. When the flaws are periodic, the spectrum decreases at a specific frequency. This effect on the spectrum is verified by experimental and simulation data, and a method for evaluating roughness is discussed.

The nuclear power equipment contains a large number of dissimilar metal welded structures, which are easy to be damaged, therefore need to be inspected. Detection of defects in dissimilar metal welds can be carried out using non-coaxial Transmitter-Receiver (Tx-Rx) PECT (pulsed eddy current testing) probes. However, considering the diverse materials and complex structure, the detection method needs to be further studied. In this paper, firstly, a simulation model is established to discuss the effects of the material distribution and the position of the excitation coil on the eddy current distribution in the dissimilar metal welded specimens. It is used for probe design. Secondly, the experimental platform is established to verify the simulation results, and the peak value of differential signal is used to analyze weld defects quantitatively.

Incremental permeability measurement is one of the electromagnetic non-destructive tests (NDT) used to characterise industrial parts and evaluate cementation depth, hardness, or residual stresses. Residual stresses are a determining factor for the performance, integrity, and service life of structural steels. A precise assessment of internal stresses makes it possible to anticipate possible breakdown and degradation with disastrous consequences. The first part of the study explores the dependence of the magnetic incremental permeability of a Grain-Oriented Iron-Silicon steel on the amplitude and orientation of applied uniaxial stresses. The second part proposes a model to predict this magnetic signature.

This work presents the Analytical Model(AM) of H-type linear permanent magnet eddy current brakes(H-type LPMECB). In the presented paper, firstly, the AM of the H-type LPMECB was established using the equivalent magnetic circuit method. Secondly, the braking performance of the H-type LPMECB was simulated with the Finite Element Model(FEM) and the AM, respectively. The AM performance results are consistent with those of the FEM, which validates the AM. Hereafter, the nonlinear relationship between the Iron Foils (IF) number of the H-type LPMECB and the braking force was found by the AM and the FEM, which provides a guide for the IF number selection in future work. Finally, the experimental results are in agreement with the results obtained from the simulations, which also proves the AM and the simulation results.

Multivariate Empirical Mode Decomposition (MEMD) is a powerful tool to analyze nonlinear properties but it is very computationally time-consuming. The purpose of this study is to parallelize and accelerate MEMD, and to apply the accelerated MEMD to the analysis of electromagnetic wave propagation in photonic crystals, to improve the efficiency of generation of a demultiplexer. In the proposed method, part of the procedures which do not depend on channels of input signal were parallelized. Speedup which is based on 24 threads of 5.12 times is achieved when 192 threads are adopted.

In this study, electromagnetic field simulation using the FDTD method is performed to reproduce the electromagnetic shielding effect, and frequency analysis using the Hilbert-Huang Transform (HHT) is performed on the obtained results. Fourier analysis is generally adopted when performing electromagnetic field frequency analysis. However, since Fourier analysis is a technique that decomposes signals linearly, it is difficult to fully analyze phenomena of nonlinear signals. On the other hand, HHT is an analysis method that decomposes signals into a nonlinear frequency components, so it can be said that it is an analysis method suitable for analysis of complex and nonlinear phenomena.

Spoke PM topology has been applied to the PM vernier machine to enhance the airgap flux density and the back EMF. However, the problem of magnetic potential oscillation is found in the isolated core pieces, which greatly limits the advantage of spoke PM vernier machines. Spoke PM vernier machine with alternate bridges is then adopted to avoid this problem. The alternate bridge has been proven effective, but the contribution is yet to be identified quantitatively. Therefore, this paper presents a more precise analytical equation to determine the role of alternate bridges. The analytically obtained results are verified through FEM simulations. Furthermore, using the obtained equations, the bridge can be designed properly.

The DC bias of a power transformer will increase the noise level and additional losses of the transformer. It thus is essential to calculate the transient electromagnetic fields of a power transformer under DC Bias. In this respect, the time period finite element method (TPFEM) is a feasible solution. However, the standard constant time step TPFEM will encounter deficiencies in solving a field problem with a sharp change occurring in a relatively small interval. In this point of view, an improved adaptive time step TPFEM is proposed and validated in this paper.

The conductor rod is a crucial component of a high-voltage casing, and any breakage can trigger line protection actions and result in significant economic losses. Therefore, this paper investigates the stress and deformation of the conductor rod in a 750kV HV casing under service conditions that consider creep characteristics. Firstly, a finite element model of the rod connector that considers creep characteristics is established. Secondly, stress and deformation tests of the rod connectors are conducted, considering the effect of creep characteristics. Lastly, the experimental results are compared with the simulation results to verify the accuracy of the simulation.

This paper explores the influence of rotor containment sleeves on the comprehensive performance of high-speed PM generator. In this respect, the electromagnetic loss and temperature fields distribution under different material fabricated sleeves are compared and analyzed by electromagnetic field and three dimensional coupled fluid-thermal field analysis. The numerical results show that a carbon fiber sleeve performs better than a copper-embedded composite one.

The application of a rotating magnetic field has been posited to contribute to the functionalization of materials. The quadrupole magnet previously developed, although functional, presents installation challenges for attached parts due to spatial restrictions, as it is enclosed on all four sides. To avoid these issues, we utilized a triple-pole magnet that affords larger space. A three-dimensional finite integration technique simulation was conducted to assess the alterations in magnetic orientations when a current was applied to each pole. It was observed that the magnetic directions could be steered to any angle within a 4 × 4 mm2 range. Moreover, the magnetic field strength can be kept constant by adjusting the maximum current value.

According to statistics, short circuit faults in transformer windings account for 70% to 80% of the total faults. Therefore, the study of the short circuit withstand capability of transformers holds significant importance. This paper focuses on investigating the winding deformation and short circuit strength of a 2kV/0.4kV/160kVA single-phase four-column transformer under secondary side load short circuit conditions. The influence of pads and struts offset on various aspects of windings is considered during the implementation. The paper presents the distributions of magnetic leakage field, current, winding deformation displacement, and electromagnetic forces under transformer short circuit conditions. This provides a novel approach for the verification of short circuit strength in large-scale transformer windings.

Several studies have implemented edge elements into meshless methods to suppress spurious solutions. However, all of these methods are subject to some limitations, which detract from the advantages of the meshless method. This study proposed a meshless method that implements the idea of edge elements but does not impose any restrictions on the nodal arrangement. Accuracy was also evaluated by adapting it to modal analysis.

The existing coil electromagnetic launcher such as coil guns are designed with tubular coil structures,which is inefficient in filling ammunition. In this paper, a continuously acceleration propulsion system based on opening electromagnetic launcher is proposed. The opening electromagnetic launcher with certain electromagnetic energy is obtained by "opening" the traditional spiral coil. On the basis of single-stage electromagnetic launcher, the segmented structure design of 90 mm multi-stage coil is carried out. Then, the electromagnetic launcher motion model is established to analyze the force and motion speed of the projectile during the motion. Finally, its feasibility is verified by simulation.

The 3-D stray loss of the upgraded TEAM P21e with the two-sided excitation (ADH2) under the harmonic and DC-biased magnetization is analyzed by the 3-D fixed-point harmonic-balanced finite element method considering the anisotropic properties. First, the measured results of the leakage flux density and the stray loss obtained by the TEAM P21e experiment platform are compared to the calculated results for validation and characteristic analysis. Then, the efficiency of the harmonic-balanced method with parallel computing is analyzed in detail.

The mechanical properties of transformer winding components have an important influence on the winding deformation during short circuit. In this paper, an analysis method of winding dynamic deformation under different working conditions of transformer considering the influence of different pre-pressure and pressing force on the mechanical characteristics of winding components is proposed. The relationship between elastic modulus, yield strength, displacement and fracture times of winding components and different pre-pressure and pressing force was tested by universal material testing machine. Using this method, the instantaneous dynamic response of the deformation of the winding component of the 750kV power transformer under different working conditions is obtained, including the short-circuit dynamic force, displacement and stress of the winding component.

Recently, ultra-compact electric vehicles (EVs) are beginning to replace general vehicles installed with gasoline engines. However, the outer plate of an ultra-compact EV has low rigidity; hence road and wind noise is transmitted to the inside of the vehicle. Therefore, we propose an active noise control (ANC) system using wall vibration generated by a giant magnetostrictive actuator (GMA). In this study, we developed a model of the GMA and analyzed, by electromagnetic field analysis, output performance due to differences in properties of the GMA material.