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This research paper focuses on evaluating the log piling technique as a sustainable, cost-effective, and environmentally friendly solution for reducing soil liquefaction risks during earthquakes. Although this method has been used extensively in Japan, mainly aiming for complete soil layer penetration, its economic viability is questionable in cases requiring very deep soil improvements. The study highlights that shallow ground improvement can notably enhance the seismic behavior of the soil-improvementstructure system, as evidenced by the reduced total and penetration settlements caused by liquefaction. The paper presents a methodology for determining the optimal dimensions of the modified ground zone using both small and medium-scale 1-g shaking table tests. The small-scale tests involve a detailed parametric study, examining variables like improvement width, pile spacing, and the depth-to-thickness ratio of the improved layer. Medium-scale tests, on the other hand, are geared towards identifying the minimum effective pile length. This approach provides a practical guideline for engineers to implement log piling for small residential buildings. Additionally, the paper utilizes finite element method (FEM) effective stress analysis, incorporating a PLAXIS 2Dbased constitutive model (PM4Sand) calibrated with laboratory undrained cyclic torsional tests. This model accounts for the changes in effective stress during seismic activities. Finally, the study correlates its numerical findings with the results from the 1-g shaking table experiments, offering a well-rounded perspective on the effectiveness of log piling in mitigating liquefaction risks during seismic events. [ABSTRACT FROM AUTHOR]

SF6 is a greenhouse gas. Finding an alternative gas for SF6 has become an urgent problem in the switch field. In order to explore the feasibility of replacing SF6 gas with dry air directly, CO2 and C4F7N/CO2 mixed gas, based on the KYN28‐12 medium voltage switchgear, the finite element method was used to solve the three‐dimensional coupled multi‐physics of the switchgear in this paper. From the angle of the temperature field and flow field, the temperature rise characteristics under different operation conditions were analyzed. The results showed that the temperature field and flow field distribution under the four gases were similar. Among them, the temperature rise of SF6 gas was the smallest, followed by the C4F7N/CO2 mixed gas, CO2 and dry air. The flow rate of SF6 gas was the lowest, about 0.11 m/s. The flow velocities of other gases were relatively close. When the switchgear was filled with the same gas, as the inflation pressure increased, the temperature rise of the switchgear decreased and the gas flow rate also dropped to a certain extent. The temperature field and flow field of the switchgear under the C4F7N/CO2 mixed gas at 0.2 Mpa were similar to those under the 0.1 Mpa SF6 gas. Under the C4F7N/CO2 mixed gas, the contact failure of the plum contact made the temperature rise of the switchgear increase overall. The maximum temperature rise point transferred to the contact failure. The temperature rise further rose with the increase of the contact failure degree. The gas flow rate also greatly increased with the failure degree elevated. From the perspective of temperature rise, the C4F7N/CO2 mixed gas has the possibility of being applied in the electrical equipment under the premise of meeting the insulation conditions. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

The low‐speed and high‐torque modular fault‐tolerant permanent magnet motor has the strong fault‐tolerant ability, and can make the motor output torque act on the load directly, and the system has the highest transmission efficiency, which is especially suitable for ship propulsion. In the electric ship direct‐drive propulsion system, the motor is the core of the power system. Because the motor is directly connected with the load, the intermediate buffer mechanism is canceled, so the smooth operation of the motor is put forward to higher requirements. Especially in some fault‐tolerant operations, the unbalanced radial force generated by the asymmetric operation may cause the motor to vibrate greatly, which will reduce the operational life of the motor and even bring new faults. In serious cases, the whole transmission system will be damaged. Therefore, it is necessary to study the vibration of the fault‐tolerant motor under different operating conditions. In this paper, the module combined stator fault‐tolerant permanent magnetic synchronous motor for ship direct‐drive propulsion is taken as the research object. Based on the Maxwell tensor method, the radial force wave expressions of the motor during regular operation and fault‐tolerant operation are derived, and the harmonic order and frequency, which have a significant influence on vibration are summarized. The radial force of the motor under different operating conditions with different control strategies is calculated by the finite element method, and the harmonic components are analyzed by the two‐dimensional Fourier transform. On this basis, the vibration of the motor and the mechanical strength of the rotor support frame are analyzed. The research results of this paper provide some reference for the subsequent vibration reduction strategies of fault‐tolerant motors. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

This paper presents a designed experimental simulation scheme for dynamic air gap eccentricity (DAGE) faults in permanent magnet synchronous generator (PMSG), along with the testing of their electromechanical characteristics. Unlike previous studies, this paper proposes and applies an experimental device setting scheme that enables accurate and convenient calibration of the DAGE fault degree, offering a novel solution for practical DAGE simulation. The experimental unit measures the electromechanical characteristics of the PMSG before and after the DAGE fault, taking into account the influence of load. The mechanical parameter considered is the stator vibration, while the electrical parameter is the circulating current parallel branches (CCPB) inside the stator winding. The characteristic frequencies of stator vibration and CCPB under the DAGE fault are analyzed based on the experimental results and verified through theoretical calculations and finite element analysis (FEA). The findings demonstrate the effectiveness of the proposed DAGE experimental device. Moreover, DAGE failure increases the strength of stator vibration and introduces new frequency components, namely fr and 2f ± fr. Under normal operation, the PMSG exhibits no CCPB. However, DAGE faults cause CCPB with frequency components of f ± fr. Moreover, the severity of the fault degree positively correlates with larger root‐mean‐square (RMS) values and characteristic frequency amplitudes of stator vibration and CCPB. Furthermore, the amplitude of stator vibration and CCPB decreases with increasing load. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

In order to improve the reliability of the traditional doubly salient electro‐magnetic generators (DSEG) and realize the isolation of interphase magnetic circuit, a U‐shaped rotor stator excitation generator (UR‐SEG) for vehicle applications is proposed in this paper. The machine has the interphase physical isolation and short flux path structure because of the U‐shaped rotors. According to the theoretical analysis of the fault‐tolerant characteristics of this UR‐SEG, the characteristic of the phase electromotive force (EMF) of the UR‐SEG completely overlaps with the EMF of front and rear phase in the entire power generation stage is revealed. Then the flux linkage, EMF, output voltage of both normal and faulty states are comparative investigated using the two‐dimensional finite element method (FEM). The output characteristics of the normal state and four faulty states of the machine with different exciting currents are researched, and the influence rules of fault on output characteristics are obtained. Finally, the outstanding fault‐tolerant characteristics of the UR‐SEG were verified by the experimental results. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

This study proposed a probabilistic generic transformation model between two rock mass properties, specific fracture energy, Ev, and P-wave velocity, VP. To build the transformation model, 12 pairwise data sets of Ev and VP were collected from six different construction sites involving construction of mountain tunnels in Japan. This database is labeled as "RockMass/2/350". A probabilistic transformation model was built based on a bivariate standard normal distribution with these 350 data points. The model is generic, because it is based on a variety of sites. The performance of the constructed transformation model was evaluated through a cross-validation. It was found that 98.2% of the validation data fell within the computed 95% confidence interval of the model estimation, and this result provides a preliminary validation of the probabilistic transformation model. Unlike existing deterministic transformation models for estimating VP from Ev, the proposed model can explicitly evaluate the transformation uncertainty with a quantitative metric such as a percentile. For practical application, a 3D model of the spatial distribution for Young's modulus, E, was visualized based on the proposed transformation model. Since the proposed model is probabilistic, it can provide the spatial distribution for percentiles of E values. The constructed 3D model presented in this paper can be directly used as an input data for finite element or finite difference analysis, and probabilistic evaluation of excavation simulation is feasible based on the proposed probabilistic model. The quantitative information on such uncertainty can be useful in decision-making for tunnel constructions, such as selection of a cautious characteristic value. [ABSTRACT FROM AUTHOR]

Because the magnetic circuits of homopolar inductor machines (HIMs) are three‐dimensional (3‐D), a 3‐D finite element model (FEM) is usually built to accurately compute the cogging torque in HIMs, but the drawback is very time‐consuming in modeling and computing. Therefore, a two‐dimensional (2‐D) FEM of HIMs is needed to simplify the computation of the 3‐D FEM. However, the existing odd harmonic 2‐D FEM cannot accurately predict the cogging torque in HIMs. To address this problem, this paper proposes a full‐order harmonic 2‐D FEM. First, the analytical expressions of HIM cogging torque are derived by the combination of energy method and air‐gap field modulation principle. Based on the obtained analytical expressions, the equivalent principles between the 3‐D and 2‐D FEMs are analyzed. According to the above equivalent principles and taking a 48‐slot/4‐tooth (48S4T) permanent magnet (PM) HIM as an example, a full‐order harmonic 2‐D FEM of the example machine excited by a field winding is proposed. The structure of the full‐order harmonic 2‐D FEM is described in detail. The turn number of field winding and field current amplitude of the proposed 2‐D FEM are investigated. The differences between the odd harmonic 2‐D and full‐order harmonic 2‐D FEMs are also analyzed. Finally, the cogging torque in the 48S4T PM HIM with distinct rotor tooth‐arc to tooth‐pitch ratios is computed by 3‐D, odd harmonic 2‐D and full‐order harmonic 2‐D FEMs of the machine, respectively. The results illustrate that compared with the odd harmonic 2‐D FEM, the full‐order harmonic 2‐D FEM can shorten the calculation time and has the similar computation accuracy as the 3‐D FEM. Moreover, the experimental validation is performed on a prototype of the 48S4T PM HIM. The error between the maximum cogging torque obtained by the full‐order harmonic 2‐D FEM and experiments is only 2.12%. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Brushless doubly‐fed generator (BDFG) is a most promising candidate for the wind turbine due to its simple structure, high reliability, and low converter capacity. To improve space utilization and achieve higher power density, this paper proposes a new dual‐stator BDFG (DS‐BDFG), which provides two separated windings, namely, the power winding (PW) placed in the outer stator and the control winding (CW) placed in the inner stator. A cup‐shaped rotor sandwiched between the inner and outer stators consists of the short‐circuited coil and the salient‐pole core. The coupling between the PW and the CW is realized via the rotor based on the general airgap magnetic field modulation theory for electrical machines. A prototype of the DS‐BDFG with rated PW power of 7.2 kW is designed and optimized. The keys of this paper are the power equation derivation, the determination of pole/slot combinations, and the rotor optimization. The electromagnetic characteristics and unbalanced magnetic force of the DS‐BDFG are analyzed by 2D finite element analysis to verify the reasonableness of the proposed model. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

This paper proposes a novel consequent‐pole dual‐stator linear permanent magnet vernier machine (DS‐LPMVM) with PM in the mover slot opening, which has a bi‐directional flux modulation effect. The novelty of the proposed machine consists of consequent‐pole double‐sided topology with toroidal windings placed in the mover slot, as well as PMs both on the stator and mover slot to improve the air gap magnetic field. The dual‐stator adopts misalignment structure to suppress detent force and produce steady thrust. The electromagnetic parameters of the proposed DS‐LPMVM are evaluated and quantitatively compared with the conventional linear permanent magnet vernier machine (C‐LPMVM) in terms of air‐gap flux density, no‐load back EMF, inductance, and thrust. The geometrical parameters are designed to reduce the detent force. By analyzing the optimized structure parameters of the two machines, the good electromagnetic performances of the proposed machine are verified by the finite element method (FEM) and semi‐analytical method, and both results of the two methods are basically the same. It is found that the amount of PMs for the proposed machine is reduced by 20% compared to the C‐LPMVM, but the average thrust is increased by 20.7% and the thrust ripple is reduced to 4.04%. The results show that the proposed DS‐LPMVM has better flux modulation effect and thrust characteristics than C‐LPMCM. Finally, a 12‐slot, 10‐pole pairs prototype was manufactured and tested. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

A novel asymmetric interior permanent magnet (AIPM) machine is proposed in this paper. The machine's rotor consists of asymmetric poles and auxiliary flux barriers. The torque ripple of the machine is weakened by the asymmetric design of the left and right sides of the magnetic poles. The magnetic‐field‐shifting (MFS) effect improves the electromagnetic torque after adding the auxiliary flux barrier to shift the magnetic axis. The influence of critical geometrical parameters on the electromagnetic performance of the machine is investigated under the condition that the stator and permanent magnet volume remain unchanged. The relevant geometrical parameters of the machine are optimized and designed through the improved Taguchi method. The performance of the AIPM machine and the conventional machine under no‐load and load conditions are further compared by simulation analysis with finite elements, verifying the increase in electromagnetic torque and the reduction in torque ripple. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

The axial flux permanent magnet (AFPM) machines with the parallel magnetic circuit (PMC) rotor can effectively improve its torque density. The PMC rotor consists of two sub‐rotors, radial Halbach array permanent magnet (PM) and tangential PM. The magnetic fields generated by two sub‐rotors are not in the same 2‐D analytical planes. In this paper, an equivalent analytical model of PMC‐AFPM machines is proposed to solve this problem. The radial Halbach array PM rotor is equated to the axial Halbach array PM rotor based on the equivalent transformation principle. The exact subdomain models of equivalent axial Halbach array PM rotor and tangential PM rotor are built respectively and then superimposed to obtain the magnetic field distribution. The electromagnetic characteristics of the PMC‐AFPM machine under no‐load and load conditions are calculated by the proposed analytical model and compared with calculations of the finite element model (FEM). The results verify the accuracy of the equivalent analytical model. The comparative analysis of the AFPM machines with PMC rotor and tangential PM rotor verifies the advantage of PMC rotor configuration to improve the torque density. © 2024 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Packaging and die bonding of conventional micro‐electro‐mechanical‐systems (MEMS) and semiconductor devices include separate dispensing, mounting and heating curing. A novel die bonder's work stage and temperature control method are proposed so that dispensing, mounting and heating curing can be completed at the same station. This paper introduces the working principle of the thermopile sensor and the requirements for temperature change during die bonding, analyses the main structure and working process of the novel die bonding stage, and uses commercial finite element analysis software to evaluate the temperature field of the novel die bonding stage and devices during the process of heating, holding and cooling to provide process guidance for accurate temperature control of die bonding. Dispensing, mounting and heating curing are integrated in the same station, avoiding the position error of devices when transferring, reducing the number of equipment and floor area, and effectively saving production costs. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

The dual‐stator permanent magnet (PM) machine has the advantages of high torque density, high efficiency, and compact size, which makes it suitable for low‐speed high‐torque applications. A dual‐stator low‐speed high‐torque permanent magnet drive machine (DLHPMDM) is discussed and studied in this paper, which is applied to the ball mill application. First, in order to meet the requirements of high efficiency and high reliability, a DLHPMDM with the inner and outer windings connected in parallel is obtained through the designs carried out in terms of the magnetic circuit structure, structural size, and the pole‐slot number combination. However, for the DLHPMDM with the inner and outer windings connected in parallel, the power allocation between the inner and outer machines is a critical problem that needs to be accurately analyzed, and the circulating current between the two sets of windings is also a particular issue that merit attention. Therefore, a new modeling method is proposed for the DLHPMDM to solve such cases more accurately. The proposed new method combines the advantages of the rapidity of the finite element analysis (FEA) with current excitations and the accuracy of the FEA with voltage excitations. Finally, a prototype of the DLHPMDM is manufactured and tested. The feasibility of the design theory and the validity of the proposed modeling method is verified by both the tested and simulated results. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Intrinsic localized mode (ILM) can be generated in multiple mass‐spring systems using nonlinear springs, and ILM has attracted a lot of attention due to its special vibration modes that are not found in linear systems. However, the difficulty of creating nonlinearity remains a barrier to ILM research. In this paper, we propose a rotating magnetic spring based on magnetic nonlinearity. The nonlinear restoring properties of the proposed magnetic spring are confirmed by finite element method (FEA). Finally, using the restoring properties obtained from FEA, it is shown that ILM can be excited by MATLAB numerical analysis. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

The fractional slot concentrated winding structure effectively solves the difficulty of low‐speed and high‐torque permanent magnet (PM) machines with a large number of poles and slots, but it also brings a wealth of magnetomotive force (MMF) harmonic. The winding function method is used to compare and analyze the stator MMF distribution and harmonic content of the fractional slot PM machines with different pole and slot combinations, and the cogging torque waveform and torque ripple are calculated by the finite element method. The influence of pole and slot combination on radial force and vibration modes of fractional slot PM machines is studied. The main vibration mode can be determined from the lowest order of radial force harmonics. The results show that in a fractional slot PM motor, the radial force is the main cause of noise and vibration, rather than the cogging torque and torque ripple. The dominant radial force is mainly produced by the interaction of rotor field harmonics and armature reaction field harmonics, and the vibration and noise will significantly increase with the decrease of the dominant vibration mode order, which largely depends on the pole and slot combination. This paper provides a certain reference for the selection of pole and slot combination in the electromagnetic design process of low speed high torque fractional slot PM motors. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

After the Fukushima nuclear accident in Japan, whether the structural safety of the nuclear power plant (NPP) can be guaranteed under an earthquake has been of wide concern. Automatic seismic trip systems (ASTS) have been deployed in NPPs. There are generally two units or more double units on the one NPP site, and the vibration energy of the structure can certainly affect its adjacent structures through the soil, and there is energy transfer and conversion between adjacent structures. At present, the distance between two reactors of NPPs of different reactor types is generally 100–200 m (this distance is referring to the distance between the centers of two reactors, which is slightly different for different reactor types). In the past, seismic instruments were used in the ASTS and the setting of shutdown threshold, so the impact of only one unit was considered in the structural analysis of NPPs, and the interaction of two reactors through site conditions was not considered. In addition, as the site conditions of NPPs become more and more complex, it is necessary to consider the impact of one reactor structure on another reactor structure through the soil on the same site under an earthquake. In order to analyze the influence of structure–soil–structure interaction (SSSI), a three-dimensional refined finite element model of NPPs is established in this paper. The soil–structure interaction (SSI) is considered by using viscoelastic boundary. The seismic responses of different positions of the raft foundation and NPP structure, under the conditions of considering SSI effect (one reactor) and SSSI effect (two reactors), are compared. The influence of SSSI effect on the seismic responses of the raft foundation and NPP structure is revealed. It is proposed that SSSI effect should be reasonably considered according to the site conditions for the structural analysis of NPPs for the NPP ASTS. [ABSTRACT FROM AUTHOR]

This paper describes a study on the responses analyses of a seismically isolated multi-span highway bridge recorded during the 2011 Great East Japan (Tohoku) earthquake and assessment of isolation bearing condition based on the responses. During the earthquake, lateral pounding and locking between the side-stoppers and the upper steel plate of the isolation bearings were observed of several piers. Finite element model was employed to analyze the problem and scenarios of locked bearing on the piers were simulated. The study also presents a wavelet-based technique to detect the presence and location of locked bearing. Instantaneous frequency of continuous wavelet transform of girder and piers accelerations were employed to evaluate isolation bearing condition by identifying the occurrence of high-frequency filtering effect. Afterwards, bearing condition was characterized via statistical clustering technique. Accuracy and efficacy of the technique were verified in simulations using three-dimensional finite element model of the bridge. Results of simulations demonstrate that wavelet-based features can effectively characterize isolation bearings condition directly from seismic responses of girder and piers. [ABSTRACT FROM AUTHOR]

The double‐sided permanent magnet linear synchronous motor (DS‐PMLSM) is widely used in the industrial field with high precision and long strokes due to simple construction, high instantaneous thrust and high controllability. However, parasitic issues, such as unavoidable manufacturing tolerances, might cause the symmetrical position deviation of primary or secondary components, which results in an asymmetrical air‐gap between components, affecting the motor's electromagnetic characteristics further. In this paper, it is taken into account secondary torsional or offset conditions (the secondary component is displaced sideways from a symmetrical position), and investigates the variations of electromagnetic characteristics on the 12‐solt 14‐pole short‐primary DS‐PMLSM. Based on the finite element method (FEM), the effects of secondary torsion or offset on the air‐gap flux density, the back‐EMF, the detent force, the thrust force, and the normal force are investigated and compared respectively. In addition, the analytical results of the back‐EMF considering lower secondary torsion are verified on a lower secondary torsional prototype. From the analytical results of electromagnetic characteristics, it is revealed that with the torsional angle or offset distance rising, the normal force and detent force in the Y‐axis gradually increase, while the thrust force and the back‐EMF decrease. These theoretical researches can play an important role in the operation and assembly process of the DS‐PMLSM. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

In order to reduce the thrust ripple caused by the detent force and improve the thrust capacity of the permanent magnet linear synchronous motor (PMLSM), a flat‐type PMLSM is taken as the study object to globally optimize the motor parameters. Firstly, an analytical model for PMLSM is established. The end effect force based on the virtual displacement principle and the cogging force using the equivalent air gap length are considered when analyzing the model. The detent force is found that closely related to the relative position of the primary and secondary, the end air gap volume and the equivalent air gap length. Then, a motor structure optimization method based on parameter classification is proposed in this paper. By sensitivity analysis, the parameters are divided into two types. For parameters with high sensitivity, the response surface methodology (RSM) is used to establish the second‐order regression equation between parameters and response, and then these parameters are optimized by the multi‐population genetic algorithm (MPGA) to improve thrust capacity and reduce thrust ripple. The optimal values of parameters with low sensitivity are obtained by the parametric search. Finally, the optimized motor is used to predict its thrust performance by the finite element method (FEM). The prediction results show that the optimized motor not only performs better but also improves the design efficiency through parameter classification. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

With the wide use of new energy vehicles, the research and development of high‐performance generators become more important. The claw pole machine is very suitable to be used as an automobile generator because of its unique characteristics. However, its development is limited by the disadvantage of abundant harmonic content, especially when used with fractional slot concentrated winding layout. A novel dual‐direction hybrid excitation generator (DDHEG) is proposed in this paper. It has dual 3‐phase winding layout to reduce spatial subharmonic magnet motive force (MMF). Also, it uses dual 3‐phase rectifier bridge circuit to reduce armature current, so as to reduce copper loss. It uses rotor sleeve to reduce the eddy current loss in the rotor and permanent magnets (PMs) caused by higher order harmonics. It has hybrid excitation from both directions to improve the efficiency and terminal voltage. The basic characteristics of DDHEG are analyzed by finite element analysis (FEA) method. The highlights of the proposed DDHEG are illustrated. The simulation results and experimental results reveal that the proposed DDHEG can effectively adjust the terminal voltage at different loads and reduce the harmonics and loss to a satisfied degree. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Hybrid excited machine (HEM) is a novel type of machine which has attracted much attention as it is able to adjust the flux linkage flexibly and ensure the wide speed range operation. In this paper, a novel brushless HEM with permanent magnet (PM) located in rotor is further researched. By supplying specific armature currents, the sub‐harmonic component magnetomotive force (MMF) in stator MMF would be generated and utilized to realize the brushless hybrid excited operation. Firstly, the generation principle of the sub‐harmonic component is derived analytically. Secondly, during the brushless hybrid excited operation, the influence of the stator current amplitude ratio m$$ m $$ is quantitatively studied. Thirdly, based on 2D finite element analysis (FEA), the electromagnetic performance of the brushless HEM is analyzed under different operation statuses over a wide speed range. At last, the experiment is performed based on a 6 kW brushless HEM prototype machine, and the correctness of the theoretical analysis and FEA results are validated by the test. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

In‐wheel motors (IWMs) are one of the most important key technologies to be used by electric vehicles, hybrid electric vehicles, and fuel cell vehicles. To meet the limitations of the space within the wheel rim, unsprung mass, and drive without a multispeed transmission, IWMs need to be designed to simultaneously have high torque per volume and power per mass and wide high‐efficiency operation region. In addition, it is obligatory to meet the requirements of torque output capacity, speed capacity, torque ripple, peak efficiency, power output capacity, etc. In this paper, a direct‐drive surface‐mounted permanent magnet in‐wheel motor (DSPMIWM) is synthetically optimized. Above design demands are accounted for simultaneously by selecting some of them as the design objectives and setting the others as constraints. Firstly, simplified design equations of the DSPMIWM, which can reduce the number of design variables, are established. The size parameters of the DSPMIWM are classified by constants, indirect design parameters, and direct design parameters. The direct design parameters are selected as optimal design variables. Then, a synthetically optimal design of the DSPMIWM is executed by employing the Kriging method combined with the Latin Hypercube sampling and Genetic Algorithm. Compared with an existing mature design, the torque per volume, power per mass, and high‐efficiency operation region of the studied IWM are still improved while all constraints are met. Finally, the effectiveness of the proposed synthetically optimal design procedure is verified by finite element analysis. © 2020 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

Cogging torque can affect the performance of permanent magnet (PM) homopolar inductor machines (HIMs). In order to find the reduction methods of the PM HIM cogging torque, it is necessary to investigate its production mechanism and analytical model. In this paper, the production mechanism of the PM HIM cogging torque is revealed from the perspective of air‐gap field modulation principle. It is found that the air‐gap permeance of PM HIMs can modulate their air‐gap magneto‐motive force (MMF) and then a large number of modulated air‐gap magnetic fields are generated. These magnetic fields with identical production condition but different rotation speeds or rotation directions can interact with each other, hence the production of the PM HIM cogging torque. By the combination of energy method and air‐gap field modulation principle, the cogging torque analytical model of PM HIMs is derived. Based on the obtained analytical model, the methods for reducing the PM HIM cogging torque are further analyzed. Finally, a 48‐slot/4‐pole (48S4P) PM HIM is designed and exampled. The air‐gap flux density of the 48S4P PM HIM is simulated by three‐dimensional (3‐D) finite element analysis (FEA). Based on the harmonic analysis for the simulated results, the correctness of the proposed cogging torque production mechanism is validated. In addition, a prototype of the 48S4P PM HIM is manufactured. The cogging torque in the prototype is obtained by the analytical model, 3‐D FEA and experiments, respectively. The simulation and measurement results verify the correctness of the cogging torque analytical model. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

In this paper, a novel differential dual‐rotor contra‐rotating axial‐flux PM (DDC‐AFPM) motor with equidirectional toroidal winding (EDTW) applied to electric propulsion of ships is proposed. Different from the conventional AFPM motor with contra‐rotating rotors (CR), the rotors of the proposed motor on both sides of the stator rotate oppositely at different speeds. The structure of the proposed motor is introduced and the operation principle is clarified. Initial parameters of the proposed motor are given, and the correctness of the simulation results is indirectly verified through the prototype of the AFPM motor with dual‐rotor and EDTW. In order to further improve the electromagnetic performance of the proposed motor, parameters of the motor are preliminarily improved. Finally, the electromagnetic characteristics including armature field, no‐load and on‐load characteristics of the proposed motor are analyzed based on three‐dimensional finite element method (3D‐FEM). The simulation results show that the proposed motor has good electromagnetic characteristics and is suitable for ship propulsion. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Since huge earthquakes are expected along plate subduction zones such as the Japan Trench and Nankai Trough, the estimation of coseismic slip and interseismic slip deficit is essential for immediate response and preliminary measures to reduce damage. Recently, analysis considering the complex topography and underground structure of the plate subduction zone has been performed for improving the estimation performance. However, the three-dimensional (3D) crustal structural model needs to be improved continuously. In this paper, we obtained Green's functions for 3D crustal structural models with ambiguity by 3D crustal deformation analysis, and the coseismic slip and interseismic slip deficit were estimated. Here we enabled the calculation of many Green's functions with different physical properties of the 3D crustal structure by utilizing a GPU-based 3D crustal deformation analysis method that significantly reduces the analysis cost. The physical properties on the upper plate's side, which are located above the plate boundary fault, were changed. We found no significant difference in the estimation performance, except for the upper crust, which most of the fault slip area is in contact with, in the case of coseismic slip estimation. In contrast, the coseismic slip estimation when the properties of the upper crust was changed had a significant error, and a negative slip was estimated at the deep part of the plate boundary where no slip was originally given. [ABSTRACT FROM AUTHOR]

In this paper, the three‐dimensional fluid field‐temperature field coupled model of air core reactor is established, the detailed temperature field distributions of reactor can be obtained, and the reason about the temperature rise of reactor is significant increased when adding the rain cover is given by analyzing the flow velocity of fluid in the air ducts. Considering the natural air cooling no longer meets the temperature rise requirement of the reactor, the forced air cooling is performed by installing ventilation duct and fan at the bottom of the reactor, combined with the finite element method and central composite experimental design method (CCD), the influence of structure parameters of rain cover and ventilation duct on the temperature rise of reactor are analyzed, meanwhile, the response surface model is established, which reflects the relationship between the temperature of reactor and the structure parameter of rain cover and ventilation duct, and the optimal design parameters can be obtained based on the quantum genetic algorithm, the maximum temperature of the reactor is only 59.3°C, the difference between the prediction of response surface and simulation result is only 0.1°C, and the correctness of the optimization method is validated, which provides an important guiding significance for the safe and stable operation of reactor in the system. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

This paper deduces an exact model of analytical calculation for the multilayer rotor eddy current losses of high‐speed permanent magnet machines based on the subdomain method. The analytical calculation model solution domain is divided into six parts of subdomains, including permanent magnet, shielding layer, metal retaining sleeve, air gap, slot openings, and windings. The Laplace equation of the air subdomain and the diffusion equation of the eddy current subdomain and the windings subdomain are established with the vector magnetic potential as the independent variable. The eddy current losses of the permanent magnet, shielding layer, and retaining sleeve of the multilayer rotor are calculated considering the slots effect and eddy current reaction. This analytical model is used to study the interfering factors of the multilayer rotor eddy current losses including the shielding layer thickness, carrier ratio, and modulation ratio. Finally, the correctness and regularity of the analytical calculation model are proved by finite element analysis and machine experiment analysis. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

The magnetically coupled three‐phase dual‐active‐bridge (DAB3) DC‐DC converter is highly suitable for high‐power applications. Although the converter has many advantages, the structure, working mode and electromagnetic effect of its key magnetic component—high‐power medium‐frequency three‐phase transformer (MFT3) is more complex, and the capacity, frequency, loss, temperature rise and leakage inductance restrict each other, forming a complex and systematic design problem. This paper focuses on the overall design method and performance of high‐power MFT3. Based on the analysis of steady‐state voltage and current waveforms of DAB3 converter, the expression of harmonic current is derived by using fundamental wave analysis, and the analytical calculation method of copper loss is proposed. According to the piecewise linear flux density waveform excited by six‐step voltage wave, the modified IGSE method is proposed to calculate the core loss. For MFT3 with three‐phase five column core topology, a lumped parameter thermal network model with 14 temperature nodes is established to obtain the temperature rise. The influence of winding arrangement on leakage inductance is analyzed, and the analytical expression of leakage inductance is presented. On this basis, the design method of high‐power MFT3 is proposed based on the free parameter scanning method. A 5 kHz, 15 kW MFT3 model with the nanocrystalline core material is made, and the leakage inductance, core loss, copper loss and temperature rise are extracted by finite element method (FEM) and experiment. The effectiveness of the proposed method is verified by comparing the design results with the FEM simulation and experimental results. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

This paper investigates the influence of the loss distribution and magnetic saturation on the efficiency performance, which includes the location of maximum efficiency point, the size of high‐efficiency region and the value of maximum efficiency, for an interior permanent magnet synchronous motor (IPMSM). The loss expressions considering magnetic saturation are first proposed and then the efficiency‐losses function model of the IPMSM is constructed. The efficiency performance of the motor is analyzed quantitatively. The general principle is summarized including adjusting the location of maximum efficiency point, expanding the size of high‐efficiency zone and improving the maximum value of efficiency from the perspective of loss distribution and magnetic saturation. Two IPMSMs with different magnetic circuit characteristics are designed to verify the correctness of the analytical method by finite‐element analysis (FEA). Finally, prototypes are manufactured for the experiment and measurement results are given for validations. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

In the field of ship propulsion, highly reliable propulsion motor is one of the key factors for the stable operation of the drive system. This paper proposes a new modular stator low‐speed high‐torque fault‐tolerant permanent magnet motor (MCS‐PMFTSM) for the direct‐drive ship propulsion system. The unequal‐span winding is used for enhanced fault‐tolerant as well as modular operation of the motor. Each module is isolated electrically and mechanically, while the maintenance procedure is greatly simplified by the structure that uses external radiation installation. Introducing the new structure and operating principle of the MCS‐PMFTSM, the basic size equation of the motor is derived followed by the analysis for the selection of the number of poles and slots. The rotor structure of the motor is then optimized using the genetic algorithm. The finite element method is used to analyze the motor performance under normal and various fault‐tolerant conditions. In addition, the electromagnetic vibration of the proposed motor is also examined under different operating conditions. Finally, a 12 kW 100 r/min 3 × 3 modular prototype is developed to experimentally validate the excellent performance of the proposed motor under both normal and fault‐tolerant operating conditions. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

In this paper, according to the parameters of the dry type air core smoothing reactor, the stress‐sound field and fluid‐temperature field coupling simulation model is established, the detailed temperature field and sound field distribution are obtained, and the influence law of sound arrester on the sound pressure level and temperature rise are analyzed. It can be found that the temperature rise of encapsulation coils are significantly increased when adding the sound arrester, and the reasons are given by analyzing the fluid velocity in the air ducts. Meanwhile, the optimization design method about sound arrester is proposed based on the orthogonal experiment design and finite element method. The influence curve and contribution rate of sound arrester on the pressure level and temperature rise are analyzed, and the optimal structural parameters of the sound arrester are obtained. The results show that the optimization method can significantly reduce the temperature rise and sound pressure level simultaneously, and improving the operational reliability of the smoothing reactor. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Feed screws are used in various industrial machines and robots to convert rotational motions into linear motions. Mechanical screws, such as ball screws and slide screws, transmit force via frictional contacts through which noise and heat are being generated; thus, the drive efficiency is decreased. To address these problems, we have proposed some types of magnetic lead screws (MLSs) without spiral permanent magnets. The design has no spiral permanent magnets and comprises relatively few components. However, the differences in the thrust density and productivity due to the structural differences have not been reported. This paper investigates and discusses the performance and productivity of the MLSs without spiral permanent magnets based on a magnetic field analysis using a three‐dimensional finite element method. The MLSs are designed under the same size and basic design parameters. The analysis results of the thrust and torque characteristics of the MLSs are shown and compared, and their productivity is evaluated by the number of components. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

On the basis of existing studies presented in literature on optimizing permanent magnet (PM) shaping with third harmonic for the tile‐shaped magnetic poles under radial magnetization, this paper proposes a method for PM shape optimization using third harmonic for bread‐shaped magnetic pole under parallel magnetization. Furthermore, the optimal value of third harmonic that should be injected for achieving maximum torque output of a surface‐mounted permanent‐magnet (SPM) motor under parallel magnetization is obtained. The accuracy of the analytical calculation is verified using the finite element method. Furthermore, electromagnetic properties, including back‐EMF waveform, cogging torque, average torque, and torque ripple of the SPM motor obtained under different PM shaping conditions, i.e., without PM shaping, sinusoidal PM shaping, and sinusoidal PM shaping with third harmonic are compared. The comparison results indicate that injecting the optimal value of third harmonic into the PM being subject to sinusoidal shaping can greatly improve the average torque and power density of the SPM motor without increasing the torque ripple. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

This paper presents a new pole‐changing method with multiple three‐phase inverters. Since the number of controllable current phases is much larger than that in conventional methods, a higher winding factor can be obtained in both high‐ and low‐pole driving modes. To evaluate the magnetic characteristics of the proposed method, magnetomotive force analysis is conducted based on Fourier series expansion and finite element method (FEM). Moreover, mutual inductance is compared between high‐ and low‐pole drives using FEM. To validate the effectiveness, an efficiency map is evaluated by using a prototype induction motor. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

The line start permanent magnet synchronous motor (LSPMSM) can be used for direct‐on‐line (DOL) starting, so it is easily affected by voltage unbalance. Based on the finite element method (FEM) and analytical method, the influence of voltage unbalance on the steady‐state performance of LSPMSM is studied in this paper. A two‐dimensional finite element model is built, and the armature current, losses and torque ripple as a function of the phase voltage unbalance rate (PVUR) are obtained. The influence mechanism of voltage unbalance on the steady‐state performance of a motor is demonstrated. Finally, a prototype of LSPMSM is manufactured and tested. By comparing the experimental data with the simulation data, the accuracy of the calculation model is verified, and the correctness of the research is proved. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

In Japan, plain concrete piers with no reinforcing bars are still in service, and their damages have been reported in past earthquakes. The typical failure is the damage to the concrete edge below the cold joint, and no damage has occurred to the concrete above the joint. To prevent damage in future earthquakes, it is essential to clarify the failure mechanism and clarify whether the concrete above the joint can also fail. In this paper, the finite element analysis of the plain concrete pier under two sinusoidal wave inputs with different frequencies was performed, and the failure mechanism was investigated. The results revealed that tensile failure is caused by friction force at the joint, and the direction of friction force changes depending on the input frequency. The friction force causes tensile stress at the concrete below the joint when the input frequency is low. Past earthquake damages to the concrete below the joint correspond to the case with the low input frequency. It was also found that the friction force causes tensile stress at the concrete above the joint when the input frequency is high. Therefore, it was found that the concrete above the joint can fail when a large earthquake with high frequency occurs. Finally, a shaking table test was conducted using a miniature model made of styrene foam, and the mechanism revealed by the finite element analysis was confirmed. [ABSTRACT FROM AUTHOR]

Background: This work investigated the differences in the biomechanical properties of open reduction and internal fixation (ORIF) and percutaneous minimally invasive fixation (PMIF) for the fixation of calcaneal fractures (Sanders type II and III calcaneal fractures as examples) through finite element analysis. Methods: Based on CT images of the human foot and ankle, according to the principle of three-point fixation, namely the sustentaculum tali, the anterior process and the calcaneal tuberosity were fixed. Three-dimensional finite element models of Sanders type II and III calcaneal fractures fixed by ORIF and PMIF were established. The proximal surfaces of the tibia, fibula and soft tissue were constrained, and ground reaction force and Achilles tendon force loads were added to simulate balanced standing. Results: The maximum stress was 80.54, 211.59 and 113.88 MPa for the calcaneus, screws and plates in the ORIF group and 70.02 and 209.46 MPa for the calcaneus and screws in the PMIF group, respectively; the maximum displacement was 0.26, 0.21 and 0.12 mm for the calcaneus, screws and plates in the ORIF group and 0.20 and 0.14 mm for the calcaneus and screws in the PMIF group, respectively. The values obtained from the simulation were within the permissible stress and elastic deformation range of the materials used in the model, and there was no significant stress concentration. The maximum stress and displacement of the calcaneus and implants were slightly lower in the PMIF group than in the ORIF group when fixing Sanders type II and III calcaneal fractures. Conclusions: This study may provide a reference for optimising the design of implants, the development of individualised preoperative plans and the choice of clinical surgical approach. [ABSTRACT FROM AUTHOR]

Combining Schwarz–Christoffel transformation, magnetic field reconstruction method, and Maxwell stress tensor method, the calculation model of cogging torque of a dual‐stator axial flux permanent magnet machine is established. The end effect and slotting effect are both been taken into account. The results are verified by finite element method. And with the proposed method, calculation time can be significantly reduced compared with finite element method. Three measures to reduce the cogging torque of dual‐stator axial flux permanent magnet machines are discussed based on which the cogging torque is optimized by genetic algorithm. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

The structure of the reluctance electromagnetic launcher (REML) is equivalent to an inductor with a movable iron core. The dynamic current in the launching process is easy to be measured by instruments, but the data such as the position, velocity of the projectile and the equivalent inductance are not only difficult to solve by analytical methods, but also difficult to measure by instruments, which seriously hinders the development of the control technology. To solve this problem, referring to the method of introducing the inductance matrix into the motor algorithm model to realize semi‐analytic calculation, a special algorithm model is proposed to calculate the launch process data of REML based on the current data. According to the working characteristics of the reluctance coil transmitter, it is pointed out that its inductance matrix should be specifically expressed as a three‐dimensional data table rather than a traditional two‐dimensional table. The current can be obtained by closed‐loop calculation according to the proposed algorithm block diagram when the circuit parameters are known, or measured by instruments when the circuit parameters are unknown, and then the launch process data is obtained indirectly through calculation. In this study, an experimental platform was built, and the algorithm model was established using MATLAB/Simulink. The comparison of the dynamic launch process data of the finite element method (FEM) showed that the method was feasible. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Earthquake is a threat to all kinds of structures including underground structures. Before the 1995 Hyogoken-Nanbu Japan earthquake, however, it was considered that underground structures are at minimum seismic risk in comparison to above-ground structures unless they are crossing the active faults. The collapse of Daikai station in the Kobe subway system during the 1995 Hyogoken-Nanbu earthquake exhibited that underground structures are at high risk of earthquake with shallow overburden. Though researches have been done on this issue, it is still necessary to investigate further the mechanical behavior of underground structure during an earthquake and corresponding efficient seismic enhancement. In this paper, in order to find out an optimum ground-improvement pattern for a rectangular-shaped box culvert constructed in soft ground that does not meet the present seismic requirement, numerical tests with nonlinear 2D/3D dynamic FEM are conducted. Different patterns of the ground improvement for the box curvet constructed with cut-and-cover method are investigated to find out an optimum pattern that can reduce the impact of earthquake in the most effective way. In the 2D/3D dynamic finite element analysis, the ground is Toyoura sand, typical clean sand, and its nonlinear mechanical behavior is described by Cyclic Mobility model. Validity of the proposed numerical method is firstly confirmed with 1 g shaking table test and then numerical tests are conducted to find out the optimum pattern for the ground improvement. Finally, an effective pattern of ground improvement for existing box culvert is proposed by the numerical analysis. [ABSTRACT FROM AUTHOR]

The multi-directional site response of a well-documented downhole array in Japan is numerically investigated with three directional (3-D) dynamic hydro-mechanically (HM) coupled Finite Element (FE) analysis. The paper discusses the challenges that 3-D modelling poses in the calibration of a cyclic nonlinear model, giving particular emphasis on the independent simulation of the shear and volumetric deformation mechanisms. The employed FE model is validated by comparing the predicted site response against the recorded motions obtained from the KiK-net downhole array monitoring system in Japan. The results show that, by employing the appropriate numerical model, a good agreement can be achieved between the numerical results and the monitored acceleration response in all three directions simultaneously. Furthermore, the comparison with the recorded response highlights the significance of the independent modelling of the shear and volumetric deformation mechanisms to the improvement of the numerical predictions of multi-directional site response. [ABSTRACT FROM AUTHOR]

Background: The Japanese invasion of the Korean peninsula lasted from 1592 to 1598, where Japan had the upper hand in infantry warfare based on superior firepower. The representative portable personal firepower weapons were the Japanese Tanegashima (matchlock musket) and the Korean Seungja-Chongtong (hand cannon). Objective: To provide an engineering aspect and explanation for the firepower difference in infantry warfare, this work aims to evaluate the lethality of the two weapons using projectile penetration and mass drop experiments. Methods: The projectile penetration experiment was conducted by firing the weapons at ballistic gelatin blocks and capturing the images of the projectiles using a high-speed camera. The mass drop experiment was conducted by dropping impactors on wooden specimens to obtain data on impact force values. Analyses were conducted using the captured projectile images and impact force data to compare the diameters of temporary cavities formed in gelatin blocks, shooting ranges, and projectile energies of the two weapons. Additionally, finite element method (FEM)-based simulations using ANSYS Workbench Explicit Dynamics were performed to further investigate the degree of injuries caused by the two weapons. Results: From the experiments, it was found that the Tanegashima is more lethal compared to the Seungja-Chongtong in terms of wounding potential, shooting range, and energy value. Simulation revealed that more energy is transferred from the projectile to impacted object when Tanegashima is utilized. Conclusions: The results allow the lethality evaluation of the main weapons used by the two countries. They also demonstrate the engineering aspect of Japanese dominance in infantry warfare at the time of the invasion. [ABSTRACT FROM AUTHOR]

Due to high power density, favorable permanent magnet cooling capability, and essentially sinusoidal electromotive‐force (EMF) waveform, the flux‐switching permanent magnet (FSPM) machine has aroused wide interest around the world. In this article, to obtain a better topology of the FSPM machine, three FSPM machines, namely 12/10 C‐shaped core, 12/10 E‐shaped core, and 24/10 E‐shaped core FSPM machines, are investigated and compared. First, based on magnetic field modulation theory, the air‐gap modulation magnetic fields as well as their harmonic distribution of the three FSPM machines are modeled and investigated based on magnetic field modulation theory. Then, the optimal rotor tooth widths of the three FSPM machines are determined by finite element analysis. Finally, under the same conditions such as main dimensions, current density, and slot full ratio, the main performances including cogging torque, back‐EMF, output torque, overload capacity, and loss of the above three FSPM machines are predicted and compared, resulting in that the 12/10 E‐shaped core FSPM machine is capable of the best performance under rated condition. In addition, experiment verification on a 12/10 C‐shaped core FSPM prototype machine is conducted. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Arimatsu Narumi Shibori (thread-tying), which is a traditional craft, has a history of more than 400 years and has been handed down to artisans in Japan. Recently, the shortage of successors to artisans has emphasized the maintenance of this thread-tying technique. To achieve this, Arimatsu Narumi Shibori needs to be elucidated based on scientific knowledge using numerical analysis techniques, which has not been achieved so far. In this technique, the fabric is complexly deformed, and complex wrinkles are formed in it. One possible approach for modeling this fabric is the use of a shell element that does not have an element volume. As the tensile and bending stiffnesses of the shell element are evaluated using a single Young's modulus, the bending stiffness increases with the tensile stiffness. Therefore, unlike the deformation achieved by the actual fabric-tying, this fabric analysis model cannot achieve large deformation of the fabric. In this study, a tying analysis method is proposed to elucidate Arimatsu Narumi Shibori. In this method, the fabric is modeled using three layers of shell elements to reproduce the fabric behavior. The material properties of the three-layer structure are presented based on the tensile test, the bending test and the friction test. Using the proposed method, we could visualize the stress distribution and wrinkles in the fabric-tying and elucidate its breaking condition. [ABSTRACT FROM AUTHOR]

The electromagnetic vibration and noise level of ultra‐high‐speed bearingless permanent magnet synchronous motor (UBPMSM) for air compressors used in the fuel‐cell vehicle (FCV) is an important evaluation. A 10 kW, 100 k r/min UBPMSM is adopted as the object of study in this research. The expression of radial electromagnetic force of UBPMSM is derived through theoretical analysis, and the order and frequency characteristics of radial electromagnetic force harmonics are summarized. Through the two‐dimensional (2D) Fourier decomposition of radial electromagnetic force by finite element analysis (FEA), the main sources of radial electromagnetic force causing the electromagnetic vibration and noise are studied. The correctness of the mathematical model is verified by FEA. In addition, the three‐dimensional (3D) finite element model of the motor is established to calculate the radial modal, natural frequency, and electromagnetic vibration and noise of UBPMSM. The research shows that the spatial order of radial electromagnetic force of UBPMSM is kN and kN ± 1 (N = GCD [2p, Z], k = 1, 2, 3, ...), and the noise change of UBPMSM caused by the addition of suspension windings could be ignored compared with ordinary motor. It provides reference values for the design and optimization of UBPMSM. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

The present study assessed the Bailey Bridge's condition and investigated its adaptation as a permanent structure, targeted the Acrow Bailey Bridge in Japan. Field diagnostic loading experiments were performed under various loading conditions, such as dynamic and static loading tests. The onsite data were obtained using a transducer, friction strain gauge, target measurements for the image processing approach, and accelerometer. From the field measurements, the deflection and stresses of the bridge were found to operate within the linear elastic region. The bridge was then accurately modeled based on the in situ geometric configuration of the bridge, and Finite Element Analysis was performed. The model's accuracy was validated with the onsite data under the linear elastic domain. The model was deployed to check for resistance of critical members. A nonlinear analysis based on the linear and nonlinear buckling method was performed to determine the subject bridge's Serviceability Limit State and Ultimate Limit State. The results showed that the first out-of-plane eigenvalue buckling analysis could monolithically assess bridge members. Further, the study established digital twin models resolve for historical data through in situ modeling measurements. Therefore, the findings obtained in this study highlight the bridge's Structural Health Condition, bearing capacity, and propose a framework for adaptation as a permanent structure. [ABSTRACT FROM AUTHOR]

The voltage across a 77‐kV‐class transmission line surge arrester (TLSA) and the heat in the TLSA have been computed using the finite‐difference time‐domain (FDTD) method for a lightning current having a magnitude of 50 kA, a risetime of 1 μs, and a half‐peak width of about 100 μs. The TLSA is represented with series‐connected‐nine ZnO elements, each of which has a length of 36 mm and a diameter of 32 mm. The ZnO element is represented with many 2 × 2 × 2 mm cubic cells, each of which has a nonlinear resistivity in each of the x‐, y‐, and z‐directions dependent on the electric field in each direction and the temperature in each cell. From the spatial and temporal distributions of FDTD‐computed heat in the TLSA, the spatial and temporal distributions of thermal stress in the TLSA have been computed using the finite‐element method. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

A limited number of studies have explored drum brake noise with uncertainty. Therefore, a new method for the robust design of drum brakes is presented herein on the basis of complex modal analysis and Taguchi's robust design. Based on the finite element method, complex modal analysis is used to predict drum brake noise. Taguchi's robust design is adopted to reduce drum brake noise and improve system robustness. In this method, the Young's moduli of the brake drum, brake shoes, and friction lining are considered as control factors, the friction coefficient and brake pressure are taken as noise factors, and the weighted instability tendency coefficient is regarded as the objective function. When the proposed method is applied to drum brake design, drum brake noise is significantly reduced and system robustness is increased. Specifically, the signal‐to‐noise ratio increases by 62.94%, and the average value of the weighted instability tendency coefficient decreases by 91.7%. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Precast prestressed high‐strength spun concrete (PHC) piles are one of the common types of piles used in Japan due to its high bearing capacity. These piles have been utilized as an industrial standard since the 1970s as part of earthquake‐resilient foundation systems. The focus of this research is to examine the shear performance of PHC piles subjected to large earthquake loads. Three hollow‐section PHC pile specimens were tested under constant compressive or tensile axial load along with quasi‐static antisymmetric lateral load. An investigation using finite element analysis was carried out to reproduce the damage that occurred during the experiment. Comparison between experimental and analytical results were presented in terms of global and local behaviors of the piles. The finite element models were able to simulate axial splitting cracks that occurred for specimens under axial compression load. In addition, a parametric study was conducted to observe the influence of axial load ratio and shear span to diameter ratio on the shear capacity and failure mode of PHC piles. The study results along with the results from a PHC pile database are compared to the shear design equation proposed in the guidelines for PHC piles from the Architectural Institute of Japan (AIJ). [ABSTRACT FROM AUTHOR]

Around the world, and especially in Japan, the tearing down of social infrastructure, including civil engineering structures, has been increasing due to the aging of these constructions, which were built during a period of high economic growth, and a decrease in their utilization caused by a recent drop in the population. The number of existing pile foundations being pulled out has gradually risen to a higher number than that of pile foundations being newly installed. However, after the pulling-out of a pile foundation, the mechanical characteristics of the surrounding ground are of great concern due to the existence of the holes that form when the existing piles are removed (extraction holes). In this study, a three-dimensional elasto-plastic consolidation analysis was performed to examine the effect of the extraction holes of removed piles on the static properties of the surrounding ground. As examples of the results of the analysis, if an extraction hole of a removed pile is left as it is, large ground subsidence will occur near the extraction hole of removed pile, especially at the lower part of the clay layer near the hole. The greater the number of extraction holes of removed piles, the greater the compressive stress acting on the extraction holes after the pile removal. Therefore, the filler should exhibit strength early as the number of extraction holes of removed piles increases. [ABSTRACT FROM AUTHOR]