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The increasing interest in all-electric, low-Earth orbit satellite constellations has stimulated the rapid development of electric propulsion technology, particularly low-power Hall thrusters. In this study, the difficulties in magnetic field design were analyzed in low-power Hall thrusters, and a new and efficient hybrid production technique is proposed. Hybrid production combines the advantages of coil and permanent magnet production; the main magnetic field is generated by permanent magnets, and the regulating magnetic field is generated by coils in parallel. Accordingly, a prototype of a 600-W hybrid-produced magnetic field Hall thruster, HPHT-600, was designed and tested. The HPHT-600 has a small size (channel outer diameter 54 mm), light weight (1.2 kg), low area–volume ratio (0.148), and low magnetic power. In addition, it exhibits a power envelope of 300–1000 W and a total efficiency of 53.5 % at the discharge voltage of 300 V, anode volume flow rate of 35 sccm, and total specific impulse of 1900 s at 500 V and 20 sccm. • A hybrid-produced magnetic-field hall thruster, combining the advantages of coil and permanent magnet production, is proposed. • The hybrid-produced magnetic-field thruster has great advantages in size and weight. • The performance of the hybrid-produced magnetic-field thruster reaches the level of the state of art Hall thrusters. [ABSTRACT FROM AUTHOR]

• Mismatched functions of electromagnetic performance and temperature rise performance may deteriorate the performance of air conditioning system. • Electromagnetic field and temperature field produced by the coil are dynamic feedback coupling fields. • Accuracy of magnetic circuit calculation is to consider all possible magnetic flux leakage as much as possible. • Performance algorithm based on the combination of magnetic circuit splitting method and dynamic feedback. • Larger electromagnetic force and lower temperature rise are two contradictory parameters. Four-way valves are commonly used in air conditioning system for switching the cooling mode or the heating mode, and the mismatched functions of electromagnetic performance and temperature rise performance may deteriorate the performance of air conditioning system. The purpose of this paper is to develop a new design method of four-way valve by coupling electromagnetic performance and temperature rise performance based on the principle of magnetic circuit splitting method and dynamic feedback. In this method, the mathematical relationship between the electric and magnetic fields is established based on the principle of electromagnetic induction firstly; then the electromagnetic forces are further related to the structure of the coil, temperature, and other parameters to establish a dynamic equation; lastly, a mathematical model of the magnetic circuit generated by the coil was developed on the basis of the existing four-way valve structure by means of the magnetic field partitioning method. A prototype of the four-way directional valve is developed and the electromagnetic performance and temperature performance of the four-way directional valve under specific operating conditions are verified by the experimental method. The results of temperature performance experiments shown that the relative error between the prototype experiment and the simulation is 18.89%. The results of electromagnetic performance experiments shown that the RMSE (Root Mean Square Error) between the experimental and simulation results was 0.277 and the MAPE (Mean Absolute Percentage Error) between the experimental and simulation results was 3.74%. Taking into account the resistance variation with temperature and the manufacturing error of the machinery, the experimental results are within the error tolerance, further verifying the validity of the design method. Both the simulation and experimental results shown that the method proposed in this paper provides a new way of thinking for the design of AC four-way reversing valve solenoids. [ABSTRACT FROM AUTHOR]

Using permanent magnet linear synchronous machines for transportation tasks offers a higher flexibility in production plants compared to conventional conveyor solutions. In this context, passive transportation devices (shuttles) with permanent magnets are commonly used. When multiple shuttles are operated in close vicinity, disturbances due to magnetic interaction can occur. To allow for high-speed operation of the motor with high position control accuracy, these coupling effects must be considered. This paper presents a model-based control strategy that is based on a magnetic equivalent circuit model which is able to describe the nonlinear magnetic behavior at low computational costs. A framework is derived for the model calibration based on measurements. An optimal control scheme for the multi-shuttle operation is derived that allows to accurately track the desired tractive forces of the shuttles while minimizing the ohmic losses at the same time. The control concept is experimentally validated on a test bench and compared to a state-of-the-art field-oriented control concept typically used in industry. • Magnetic equivalent circuit (MEC) model for multiple shuttles. • Calibration framework for MEC model using test data. • Current optimization based on MEC model and optimal force controller for multiple shuttle operation. • Improved efficiency and suppression of magnetic interference between shuttles. [ABSTRACT FROM AUTHOR]

The traditional electromagnetic force calculation method does not consider the non-linear magnetization characteristics of the ferromagnetic material or the magnetic resistance in full circuit, resulting in large calculation errors when the electromagnet operation state is far from the rated state, and causing the dynamics simulation results to diverge from the actual situation. A more accurate analytical formula for electromagnetic force is derived based on the full circuit magnetic resistance modification and considering the non-linear magnetization characteristics of ferromagnetic materials. Then combined with the finite element simulation analysis, the magnetic resistance modification (MRM) method is proposed for calculating electromagnetic levitation force and guiding force. This MRM method greatly improves the accuracy of electromagnetic force calculations and provides greater accuracy for EMS maglev vehicle dynamics simulations. • Proposing a modified method for calculating two-dimensional electromagnetic forces. • Improving accuracy of electromagnetic force calculation greatly. • The method can be applied to maglev vehicle system dynamics simulation directly. [ABSTRACT FROM AUTHOR]

The effects of different particle space distributions on the magnetism and the high-frequency power loss are studied and analyzed. The parallel arrangement of the easy-plane FeSi 3.5 particles along the x-y plane can make hysteresis loops of composite in the x-y plane obtain extremely large slopes, and make the composite more easily magnetize in the x-y plane. The composite can obtain an extremely small demagnetization factor in the x-y plane due to the parallel arrangement of the easy-plane FeSi 3.5 particles with the x-y plane, leading to a significant increase of the real part of complex permeability. In addition, the parallel arrangement of the easy-plane FeSi 3.5 particles along the x-y plane can effectively decrease the hysteresis loss and the excess loss. The parallel arrangement of the easy-plane FeSi 3.5 particles with the x-y plane reduces the angle between the magnetic moment and the magnetic circuit, making the energy that magnetizes the magnetic moment to the direction of the magnetic circuit decrease. Meanwhile, this makes the composite obtain a more homogeneous arrangement of magnetic domains and a larger number of activated domain walls along the direction of the magnetic circuit. It is important for the study of the magnetism and power loss of composites in the MHz frequency band. • The parallel arrangement of the particles can effectively improve magnetism and high-frequency power loss of composite. • This parallel arrangement can make the composite more easily magnetize in the x-y plane. • This parallel arrangement can make the composite obtain an extremely small demagnetization factor and high permeability. • This parallel arrangement can reduce the energy that magnetizes the magnetic moment to the direction of the magnetic circuit decrease. • This parallel arrangement can makes the composite obtain a more homogeneous arrangement of magnetic domains and a larger number of activated domain walls along the direction of the magnetic circuit. [ABSTRACT FROM AUTHOR]

Time-varying output characteristics of high-power giant magnetostrictive actuators (GMA) are determined by magnetic-thermal-mechanical coupling field effect. However, the influence of non-uniform magnetic field and temperature distribution on the output displacement of GMA is often ignored in the present researches. Therefore, a comprehensive model under multi-physics effects is established in this paper. Firstly, the leakage flux and eddy current effects are taken into account, and the non-uniform magnetic circuit model (MCM) is built. Then, the uneven power losses of heat source in GMA are analyzed according to the MCM results. A three-dimensional time-domain thermal circuit is developed based on the heat transfer equation and the "T" equivalent thermal circuit model. Finally, the time-varying displacement is calculated on the basis of multi-degree-of-freedom dynamics theory, so as to build the entire model. Compared with the traditional lumped parameter model and the steady-state thermal field researches, the proposed model is more accurate in analyzing temperature distribution and output characteristics of GMA under different working conditions. Furthermore, the proposed model can also provide a guidance for the temperature management methods and the optimal designing scheme of GMA in various application scenarios. The accuracy and effectiveness of the proposed model have been verified by experiments. [Display omitted] • A magneto-thermo-mechanical coupling model considering non-uniform flux distribution is built in this paper. • The multi-temperature node thermal circuit could calculate time-varying characteristics of GMA accurately. • Compared with existing literatures, this paper focuses on the time-varying output of the GMA due to temperature rise. • The magnetic field distribution is uneven in GMM, thus affecting the temperature and output characteristics of GMA. • As the temperature increases, the output displacement of the transducer decreases, by more than half at most. [ABSTRACT FROM AUTHOR]

• Accurate transformer equivalent circuit for PDP simulation under DC bias is proposed in this study. The main contributions of this paper include: • The proposed π equivalent circuit is derived from the principle of duality. The two excitation branches correspond to the two magnetic circuits of the core. In the PDP circuit simulation, the operation and restraint currents have a specific physical meaning. • The three-segment component saturation inductance is proposed. The non-uniform deep saturation phenomenon of the transformer core under DC bias can be accurately simulated by the excitation inductances of the two excitation branches, respectively. Percentage differential protection (PDP) is one of the main protections of the transformer. The traditional transformer T equivalent circuit is insufficient to simulate the uneven saturation characteristics of the core for PDP under DC bias. Therefore, the transformer π equivalent circuit with three-segment component saturation is proposed for transformer PDP circuit simulation. FEM simulation is carried out to analyze the performance of transformer. The simulation and the experiment on PDP operation and restraint currents are conducted. Compared to the experiment, the errors of operation and restraint currents are significantly reduced using the proposed circuit under DC bias. The circuit simulations of transformer internal and external faults are implemented. The electromagnetic field analysis verifies the limitation of T equivalent circuit for PDP. The proposed method can achieve better performance in both transformer internal and external fault circuit simulation than the traditional method. [ABSTRACT FROM AUTHOR]

• Uses 3D simulations to explore how orifice slot parameters affect VVT solenoid valves. • Investigates key structural parameters and their impact on electromagnetic force. • Shows that orifice slot adjustments affect average electromagnetic force and variability. • Provides insights to improve solenoid valve performance while reducing costs. • Advances understanding of solenoid valve behavior in variable valve timing systems. This paper investigates the impact of structural modifications in solenoid valves on the electromagnetic force characteristics crucial for efficient Variable Valve Timing (VVT) system operation. Utilizing finite element analysis, various hole and slot configurations within solenoid valve components were examined to determine their effect on the electromagnetic forces generated during valve operation. The study focused on base and spool structural parameters, such as the diameter and number of oil drain holes, the size and position of steel ball slots, and variations in structural dimensions. Results from empirical and simulation data reveal significant findings: larger diameters and an increased number of holes tend to reduce electromagnetic forces, while specific configurations can stabilize or enhance these forces. These findings offer critical insights for optimizing solenoid valve designs in VVT systems with the aim of improving performance and reliability. The study establishes a robust theoretical foundation for further empirical research on the multifactorial effects of valve structure on solenoid performance, paving the way for more refined VVT system designs in the automotive industry. [ABSTRACT FROM AUTHOR]

This paper presents an electromechanical height adjustment system for vehicles. The proposed design acts on the spring holder of the automotive suspension by means of a reversible ball-screw transmission. This actuator falls within the load-leveling category of suspensions, which becomes relevant in instances where the vehicle enters different terrains, driving conditions, or travel speeds. Furthermore, it could ease accessibility for passengers and goods. To provide reversibility, the actuation system relies on a ball-screw mechanism. It increases the overall efficiency of the actuator, which in turn, implies faster actuation times and lower power consumption. To avoid back-drivability when not needed, a highly integrated and compact locking clutch is engaged. This component provides a fail-safe feature to the suspension, even in the absence of electricity. The clutch is controlled by means of an electromagnet, which is also used to estimate its locking state by measuring the inductance of its magnetic circuit. The proposed solution is compared to a very similar irreversible configuration, where the ball-screw is replaced by a power screw with trapezoidal profile. Experiments demonstrate the benefits of the reversible ball-screw transmission in terms of actuation time (two times faster) and average efficiency (three times more efficient) when compared to the irreversible alternative. The functionality and state estimation of the locking clutch is also validated. • A height adjustment system for vehicle suspensions is presented. • High efficiency is provided by a reversible ball-screw transmission. • A highly integrated electromagnetic clutch guarantees position locking. • Experiments are used to compare reversible and irreversible actuators. • The reversible actuator is faster than the irreversible one and draws less power. [ABSTRACT FROM AUTHOR]

• A fast excitation structure has been proposed that can reduce the transient time of MCR from 400 ms to 37 ms. • The new structure proposed in the article can simultaneously reduce the time required for the excitation and demagnetization stages. • The fast excitation structure proposed in this article does not require additional circuit structures and retains the reliability of the original MCR. • The fast excitation structure proposed in this article has been verified through both simulation and experimental verification. With the increasing proportion of renewable energy usage, the randomness and volatility of renewable energy have led to a corresponding increase in the demand for reactive power regulation in the power system. Magnetic controlled reactor (MCR) is one of the technical and economic means used to solve problems such as reactive power compensation and voltage regulation in the power system. However, the transient time of traditional MCR is relatively long compared to other reactive power compensation devices, which limits the further application of MCR. At present, most methods for optimizing the dynamic response time of MCR are to add additional circuits or change control strategies, which will increase the difficulty of MCR control and reduce stability. Therefore, without adding additional circuit structure and control difficulty, this paper proposes a three-phase MCR fast excitation structure that changes the winding connection method, which can improve the DC voltage in the control circuit and reduce the transient time of the MCR. A magnetic circuit model in the MCR core under the fast excitation structure is built and analyzed, based on which, the transient time of the MCR is mathematically calculated. A fast excitation MCR simulation model was constructed based on MATLAB/Simulink platform for dynamic response test simulation. Compared with typical MCR simulation results, the transient time was reduced from 400 ms to 37.1 ms. Dynamic response tests were conducted on a three-phase MCR prototype of 35 kV/18 Mvar, and drop test indicates that the fast excitation structure could reduce the transient time of the three-phase MCR prototype to 36.6 ms, which substantiate the precision of mathematical and simulation results and the efficacy of the fast excitation structure. [ABSTRACT FROM AUTHOR]

Magnetorheological (MR) dampers are widely used as semi-active energy-dissipation devices in structural vibration control. Traditional MR dampers, particularly their working mode, often struggle to achieve a high damping force output and sometimes fail to meet the needs of practical engineering. Therefore, it is necessary to study MR dampers that can provide a high damping force. This study proposes an MR damper that combines a built-in shear valve with various working modes of shear extrusion. The damper generates a higher damping force by applying a current to the coils at different positions and altering its working mode. First, the ANSYS Maxwell software simulates the internal magnetic circuit of the damper to assess whether the magnetic field intensity distribution and circuit direction meet the design requirements. Analysis revealed that the internal magnetic circuit distribution was reasonable and satisfied the operating requirements of the damper. Furthermore, the mechanical models of the two working modes were derived based on the Bingham and double-viscous models. Finally, the accuracies of the mechanical models were verified experimentally. The experimental results showed that the simulation values closely matched the experimental values under all the working conditions. Therefore, the proposed mechanical models are reasonable, and can provide significant reference values for practical engineering applications. • A magnetorheological damper based on the combination of shear built-in valve mode and extrusion mode is proposed, which has a stronger damping force output range. • The mechanical models of two different working modes under this MR damper are proposed. • The internal magnetic circuit of the MR damper is simulated and analyzed to verify the rationality of the internal structure of the proposed damper. • The mechanical properties of the MR damper were tested to verify the accuracy and rationality of the proposed mechanical model. [ABSTRACT FROM AUTHOR]

Linear transverse flux permanent magnet machines (LTFPMs) are categorized as high force density topologies, which are suitable candidates for direct drive and low-speed applications. This paper introduces a novel LTFPM topology, which also proposes advantages of the flux-switching machines. This proposed linear transverse flux switching PM machine (LTFSPM) has two long passive translators located at the armature's top and bottom sides. The topology offers a high value of force density, and also, it is a cost-effective topology due to its double-sided passive translator. Furthermore, the PMs are fully utilized in the magnetic circuit, the end winding length is negligible, and the iron cores can be laminated easily. In this paper, the operation principle of the topology is explained and its magnetic circuit is discussed. To reduce the computational time of optimization procedure, a double-layer method is adopted, which provides high robustness, low computational time, and high precision. Results of the finite element method indicate that the proposed machine can be considered a potential candidate for linear motion applications especially direct drive wave energy conversion systems, which require high force density values. [ABSTRACT FROM AUTHOR]

Ultrafast optical spin control allows gate operations to be performed within picosecond time scale, orders of magnitude faster than microwave or electrical control. Here, using high-level quantum chemical computations, we suggest several two-qubit logic gates based on the optically induced ultrafast spin-flip and spin-transfer processes on rhombic graphene nanoflakes (Co 4 -GNF). It is demonstrated that Co atoms chemisorbed on π -conjugated C atoms can significantly influence the spin properties of the system. The spin density of different energy levels is distributed on different Co atoms, thus opening channels for successful spin-transfer processes between the Co atoms. Reversible local spin-flip processes on each Co atom as well as global spin-transfer processes between the Co atoms are realized. By carefully combining the various spin-dynamics processes achieved in our Co 4 -GNF structure, both classical (OR, AND, NAND) and quantum (CNOT, SWAP) binary logic gates are constructed. All spin manipulation processes finish at the subpicosecond time scale with fidelities above 96%. This theoretical design, which is exclusively based on laser-induced ultrafast spin dynamics, represents a novel implementation of qubit manipulation and can thus pave the way towards the construction of nano magnetic logic circuits and spintronic devices. [Display omitted] [ABSTRACT FROM AUTHOR]

• An improved non-destructive magnetic-based steel bar corrosion detection with simple structure and high accuracy. • Equivalent numerical model to quantify the corrosion degrees and impacts of frame internal structural parameters. • Sensitivity coefficient changes linearly with the diameter of steel rods. • Increase in frame width and foot length are beneficial to growth of sensitivity coefficient. • Adding extra calibration magnetic circuits leads to reduction in sensitivity coefficient. Steel-bar corrosion can not only induce corrosion cracking, but also cause the bearing capacity decline of concrete structures. This contribution reported an improved magnetic-based steel bar corrosion detection apparatus with simple structure and high accuracy. Accelerated corrosion tests on steel rebar were carried out to calibrate the accuracy of the magnetic-based corrosion detection apparatus. A parameter of sensitivity coefficient, k , was proposed to evaluate the corrosion detection sensitivity of the apparatus. An equivalent numerical model was established based on multi-physical simulation to quantify the corrosion degrees and explore the impacts of the frame internal structural parameters. Results show that k is stable and changes linearly with the diameter of steel rods tested. Increasing frame width and foot length can increase k , and adding extra calibration magnetic circuits leads to reduction in k. Overall, the modified magnetic-based apparatus provides a simple, reliable, accurate and non-destructive method for steel corrosion detection. [ABSTRACT FROM AUTHOR]

The tensile response of ultra-high performance fibre-reinforced composites (UHPFRC) is decisive in many applications and depends on the steel fibre content and orientation. These vary troughout the structural element and may differ from those in the laboratory specimens used to characterize the material behaviour. This work presents the developments on a non-destructive test method based on the measurement of the magnetic inductance, substantiating its use for the determination of the fibre content and orientation in thin UHPFRC elements and allowing the estimation of the directionally dependent post-cracking tensile strength of the material in the structure. Starting from a probabilistic description of the fibre orientation, an existing physical model of the magnetic circuit composed of a U-shaped inductor and the composite is generalized and is used to derive the relations between the magnetic inductance measurements, the fibre volumetric fraction and the fibre orientation factor. A second-order tensor approximation of the relative magnetic permeability of the composite is proposed to determine the in-plane fibre orientation factor along any direction based on any three non-collinear measurements. Experimental evidence is presented supporting the theoretical developments. The factors that may affect the measurements are experimentally quantified. The paper concludes with an application example. [ABSTRACT FROM AUTHOR]

The harmonic distortion in a ferromagnetic plate is studied both experimentally and using numerical simulations. The electromagnetic field inside the specimen is excited by a couple of air-cored coils, and the field is measured at a specific location using a set of Hall sensors. The considered material is a typical structural steel of an intermediate mechanical and magnetic hardness. The comparison of the numerical results with carefully conducted measurements demonstrates the importance of an accurate and physically consistent hysteresis model. The absence of magnetic circuit reduces the number of the setup uncertainties thereby simplifying the characterisation procedure and making this particular configuration a good benchmark candidate for the validation of numerical codes dealing with the hysteresis problem. [ABSTRACT FROM AUTHOR]

Open-circuit (OC) faults in electric machines cause deviations from the desired torque and result in undesired radial forces, which cause vibrations and noise. Multiphase permanent magnet synchronous machines (PMSM) provide additional degrees of freedom (DOFs) for the control of the machine, which allows to (partially) mitigate the impact of OC faults. Therefore, in this paper, an optimal fault-tolerant control (FTC) strategy with radial force compensation is developed for multiphase PMSMs under multiple OC faults. It minimizes the torque tracking error, power losses, and radial forces. Optimized reference currents are generated based on a magnetic equivalent circuit (MEC) model, ensuring a high control accuracy even for motors with significant non-fundamental wave behavior and magnetic saturation. The paper proposes a control strategy that consists of a nonlinear feedforward term, a PI-based feedback controller, and an iterative learning control (ILC) concept. Measurements validate the effectiveness of the proposed FTC strategy on a test stand for multiple OC fault cases. The proposed FTC strategy is applied to a twelve-phase PMSM with a single-star multiphase system (1 × 12 configuration) and a multiple three-phase system (4 × 3 configuration). The advantages of the proposed approach are demonstrated by experimental results in comparison with a proportional integral resonant (PIR) control strategy as the scientific state of the art in the literature. • Optimized fault-tolerant control strategy for arbitrary multiple open-circuit faults. • Systematic exploitation of available degrees of freedom for additional control goals. • Performance comparison of n-phase and multiple three-phase systems under OC faults. • Reduced noise and vibration, preventing further damage via radial force compensation. • Multiphase PMSM modeling with magnetic saturation and non-fundamental wave BEMF. [ABSTRACT FROM AUTHOR]

• 1. A novel dual-magnetic circuit actuated fast-switching valve (DAFV) is designed. • 2. A multi-stage excitation control algorithm (MSEC) is proposed. • 3. The mathematical model of DAFV is established in detail. • 4. The key influence parameters of the DAFV characteristics are obtained. • 5. The DAFV and MSEC are verified to improve flow accuracy and reduce power consumption. Solenoid type fast-switching valve is the commonly used control element in digital hydraulics, and its magnetic circuit is completely composed of soft magnetic materials. The current research primarily focuses on reducing the response time of the valve, but it neglects the influence of the relationship between the opening and closing response times on the control accuracy. However, it faces the issue of opening and closing processes asymmetry aggravated by coil severe heating and various operating pressures, which would lead to flow errors and restrict control accuracy. Hence, this paper proposed a novel dual-magnetic circuit actuated fast-switching valve (DAFV) with a multi-stage excitation control algorithm (MSEC). The DAFV utilizes a permanent magnet (PM) to maintain the open state without electrical, avoiding large temperature rises. The variable excitation control of MSEC is achieved by precisely adjusting the duty cycle of both the delay and movement stages, ensuring stability and symmetry in response time. Among in, the duty cycles are set online for each stage to adapt to the operating pressure and target response time. The experiment shows that the response times of opening and closing almost remain the same at approximately 1.16 ms under different operating pressures. The relative flow error is reduced to within 4.1 %, while the maximum temperature rise is 15 ℃. [ABSTRACT FROM AUTHOR]

• An FNB optimization method based on FEM surrogate model and BWO is proposed to reduce time costs while maintaining MRD optimized performance. • A novel NM architecture is proposed to develop the surrogate model, comprising NLSTM and MHA with improved input and output modes. • Extensive ablation and contrast experiments affirm the improvements of the NM surrogate model. • FNB demonstrates better theoretical optimization efficacy and lower time costs, and has good extendibility. • Practical experiments indicate that FNB sample exhibits the best ultimate performance under various vibration condition. An accurate and efficient optimization method is required to design magnetorheological dampers (MRDs). To solve the contradiction between calculation accuracy and efficiency in the existing method, an FNB optimization method comprising the finite element method (FEM) surrogate model built upon a novel NM neural network architecture and alternating stacked beluga whale optimization (BWO) algorithm was proposed. A high-fidelity approximation of FEM results with lower time costs was achieved. The corresponding dataset was obtained based on the optimization objective simplified by the multi-physics coupling FEM, and the optimized surrogate model was obtained by the first layer BWO. Extensive ablation and contrast experiments indicated the improvement effectiveness of the proposed surrogate model, which was further utilized by the second layer BWO to optimize the MRD structural parameters. The final results were corrected by FEM to further reduce the approximation error of the surrogate model. Moreover, compared to the optimization results obtained by simple scanning FEM and refined magnetic circuit modelling algorithm, the optimization efficiency and effect of FNB were better improved from a theoretical perspective, and extensive experiments further indicated that the overall relative improvements amounted to 5.819% and 7.137% on peak damping force. [Display omitted] [ABSTRACT FROM AUTHOR]

• Dynamic trajectory of a magnetic particle around a film of magnetic disk in a rotating uniform magnetic field is analyzed by employing the immersed-boundary-lattice Boltzmann method (IB-LBM). • There are three motion regimes: phased-locked, phase-slipping and phase-insulated regimes. • Capability of IB-LBM to simulate the three dynamic regimes and motion patterns of the magnetic bead is analyzed, and also the critical frequencies of the rotating magnetic field are identified according to the pervious experimental studies. • The influences of the magnet bead size are analyzed on the dynamic regimes. The capability and accuracy of the immersed boundary-lattice Boltzmann method (IB-LBM) for simulating a precise manipulation of an individual magnetic bead on the edge of a magnetic disk (magnetophoretic circuits approach) are investigated. Also, the influences of the magnetic bead diameter on its dynamic responses are analyzed, for the first time. The dynamic behavior and motion patterns of the magnetic bead in an external magnetic field, using the IB-LBM model, are studied. The high accuracy of the model is determined after gaining the true dynamic regimes of the magnetic bead in a wide range of applied frequencies and the strength of the magnetic field, validated with experimental results. Employing different sizes of magnetic beads or magnetically labeled objects (cells) effectively changes the dynamic regimes and motion patterns due to the variation of drag force and inertia. Single-cell analysis is one of the most important and valuable application of this magnetic platform, where the magnetic disks trap and separate single magnetic objects for further purposes. The necessity of the proposed model is in the efficient designing of the magnetophoretic circuits composed of serially connected magnetic disks. [ABSTRACT FROM AUTHOR]

Soft Magnetic Composite (SMC) materials show a high potential for growth in the electrification of several industrial sectors for two main reasons: the reduced eddy current losses and the 3D magnetic path which allows to redesign magnetic circuits without geometrical constraints. On the other hand, some material limitations and process restrictions limit the use of SMC on a large scale; this contribution aims to overcome such constraints through a novel surface approach using a Layer-by-Layer (LbL) technique that allows to coat each particle with a nanostructured layer, providing electrical insulation enhanced mechanical strength and withstanding higher treatment temperatures. Four SMCs encompassing the developed innovative multi-functional layers have been prepared and deeply analyzed with a characterization campaign through the study of the surface morphology with a Scanning Electron Microscope (SEM), the magnetic properties with a Single Sheet Tester (SST) and the mechanical strength through the "Transverse Rupture Strength" (or TRS) test. The discussion on the results has to be considered a starting point for future investigations, as each of the four different systems represents a partial solution to a specific SMC problem. Also, some considerations on the possible application are proposed. [ABSTRACT FROM AUTHOR]

Due to the inspection demand of curved permeable metal walls, such as large ships, a wall-climbing robot that can adapt to various curvatures of metal walls is built to solve the problems of unstable adsorption and poor adaptability of rigidly-connected wall-climbing robots. Two relatively independent passive adaptive moving devices are designed using the five-link mechanism to fit active wheels to both convex and concave surfaces. It can also make the two driving wheels fit onto convex surfaces with different curvatures. Static and dynamic models are developed to obtain the minimum adsorption force and torque required for the robot to move stably on the wall. A permanent magnet wheel is designed and the magnitude of the adsorption force generated when it is rotated at different thicknesses of the wall is analyzed. Three different magnetic circuit models of the gap-type permanent magnet adsorption device are proposed and parametrically simulated to analyze the effect of gap variation on the adsorption force. And experimental verification was conducted on three models. Finally, the prototype is built, and the motion performance experiments are conducted. The results show that the 5-bar mechanism improves the adaptability of the robot by adjusting its posture so that the driving wheels can fit the wall completely. The permanent magnet wheels can provide a large adsorption force, which enhances the stability of the robot. It provides a basis for the intelligent development of shipbuilding enterprises. • Design a novel passive adaptive wall-climbing robot based on 5-bar mechanisms. • The adaptive mechanism improves the fit between the driving wheel and the surface by increasing degrees of freedom. • Propose a novel permanent magnet wheel combines the advantages of high magnetic force and coefficient of friction. • Three magnetic circuit designs of the adsorption structure are analyzed. [ABSTRACT FROM AUTHOR]

• A comb-type brake disc structure that simultaneously uses magnetic field enhancement and increases the contact area of magnetorheological fluid is proposed. • The effects of brake disc working radius, brake gap, coil turns and current on brake magnetic field strength and braking torque are investigated by simulation. • Structural optimisation of comb-type disc magnetorheological brake using PSO particle swarm algorithm with brake torque and mass as optimisation objectives. • A braking experimental platform was designed to achieve the effect of continuous braking by increasing the flywheel set. • The effects of temperature on braking performance and the stability of braking torque output under different braking initial speeds were analysed. The magnetic circuit method was adopted in this paper to design a comb-type disc magnetorheological brake for electric vehicles, aiming to solve the problem of the existing magnetorheological brake with large volume and limited braking torque. A mathematical model of braking torque was established. The effects of different structural dimensions on the performance of the brake were investigated through electromagnetic field simulation. The brake structure was optimized using PSO, which reduced the mass by 19.17 % and increased the torque by 6.58 %, and its performance was experimentally verified. The results showed that the brake produced a braking torque of 334 N·m at a saturated current of 3.6 A, with a response time ranging from 134 to 275 ms. After 10 braking cycles, the maximum braking torque remained above 94.5 % of the initial value. The source of heat was mainly located at the comb teeth portion of the brake disc. [ABSTRACT FROM AUTHOR]

• Novel AMR/magnet, flow control and cabinet/heat exchanger systems are presented. • A detailed performance assessment of the magnetic refrigerator is carried out. • The system was able to control the temperature of a 31-bottle retrofit cabinet. • In a temperature pull-down test, the cabinet air reached 13 o C in 1h 37 min. • For cabinet/ambient temperatures of 12.5/25 o C, the COP and η 2nd were 0.38 and 1.6. This work presents the design and performance evaluation of a novel magnetic refrigeration unit capable of controlling the temperature of a 31-bottle wine cooler cabinet. The main components of the system are: an active magnetic regenerator composed of eight porous beds of Gd/Gd-Y spheres, a two-pole magnetic circuit responsible for the magnetic field changes, a set of solenoid valves for flow control, and fan-supplied finned tube heat exchangers on the cold and hot sides of the wine cooler apparatus. Synchronization of the magnetic field variation and fluid flow processes was performed using real-time magnetic field measurements. The system was capable of reaching a mean temperature of 10.8 o C inside the retrofitted wine cooler cabinet by generating 27.9 W of cooling capacity for an ambient temperature of 25 o C. The coefficient of performance and second-law efficiency for this operating point were estimated as 0.21 and 1.0%, respectively. When operating at a cabinet temperature of 12.5 o C, the coefficient of performance and second-law efficiency achieved by the magnetic system were 0.38 and 1.6%. [ABSTRACT FROM AUTHOR]

To overcome the inherent limitation of existing nanopositioning stages running in hundreds of micrometres, a novel normal-stressed electromagnetic actuator is developed to construct a direct drive XY nanopositioning stage, which features a contactless dual-axial actuation with a relatively high force density, a loosely-constrained stroke, and a monolithic magnetic circuit. Assisted by the established model, the mechanical-electromagnetic parameters for the stage are determined with a further verification through both finite element analyses and experimental tests. By combining a PID-based and a parallel resonant controller, the control system for the stage is constructed, which is then demonstrated by ultra-precisely tracking a Lissajous trajectory. [ABSTRACT FROM AUTHOR]

This paper proposes a Magnetic Equivalent Circuit (MEC) method to model the Ladder-Secondary-Linear Induction Machines (LS-LIMs), where the model accuracy can be determined as desired. This method makes it much easier to change parameters of motor include poles and slots number as well as its dimension than the Finite Element Method (FEM). The end-effect phenomenon is considered in the model by two virtual zones with arbitrary length at the both exit and entrance ends of the primary for saturable LS-LIMs. The proposed MEC method also makes it possible to investigate the motor performance under different secondary structures (two types), bars material and their width. Finally, FEM and experimental results are given to evaluate the accuracy of the proposed method, and simulation time is compared with 2D-FEM. In a general overview, modeling the end-effect and saturation phenomena, analyzing the impacts of different secondary structures and bars width on the performance of motor are studied by the suggested MEC method in the present work. • A flexible MEC-based method for Ladder secondary Linear Machine based on MEC method. • Determining the accuracy level of model as desired. • Performance analysis under various secondary sheets. • Performance analysis under various secondary bars width. • Performance analysis under various secondary bars material. [ABSTRACT FROM AUTHOR]

A novel full circumferential reluctance maglev coupling (FCRMC) is proposed in this paper, which not only meets the requirements of force transmission and valve position feedback of two-dimensional (2D) valve but also has the advantages of closed-loop magnetic circuit and high magnetic energy utilization rate. To investigate the torque-displacement characteristic of FCRMC, a detailed analytical model based on the equivalent magnetic circuit method is formulated, which considers the leakage flux effect, edge effect, and magnetic permeability nonlinearity. The effects of the inclination angle, width, air gap, and number of teeth on the torque are explored by the analytical model, and appropriate structural parameters are selected to design and manufacture the prototype. A dedicated test bench is built and the static/dynamic characteristics of FCRMC are tested. The experimental results show that the FCRMC prototype has a step velocity of 20.8 × 10−3 mm/ms, a torque-volume ratio of 8.47 × 10−3 N m/cm3, a torque-permanent magnets(PMs) volume ratio of 0.050 N m/cm3, and a step velocity-PMs volume ratio of 2.63 × 10−3 mm/ms·cm3. Finally, to verify the feasibility of the FCRMC in real work situations, the FCRMC is applied to a 2D electro-hydraulic proportional flow valve. The experimental results show that, at 15 MPa, the no-load flow of the valve is 82.4L/min, with a hysteresis of 3.8 %, a step velocity of 17.5 × 10−3 mm/ms, and amplitude and phase frequency widths of 22.4 Hz and 26.5 Hz. • The highlights of this paper are as follows: since rare earth permanent magnet is a non-renewable strategic resource, the study on rare earth permanent magnet effective utilization of maglev coupling is substantially important. Therefore, a novel FCRMC for 2D valves is proposed, which not only meets the requirements of force transmission and valve position feedback of 2D valves but also has the advantages of closed-loop magnetic circuit and high magnetic energy utilization rate. [ABSTRACT FROM AUTHOR]

To improve the adaptive motion performance of traditional wall-climbing robots on variable-curvature facades, a crawler-type wall-climbing robot suitable for ship wall features is proposed by utilizing the advantages of passive mechanisms in realizing autonomous robots. The robot consists of two passive adaptive crawler mechanisms and a connecting module. Each track structure contains multiple permanent magnets that can passively adapt to concave and convex facades of different curvatures. A static failure model is established according to the characteristics of the triangular distributed load, and the minimum adsorption force required for the robot to achieve safe motion is determined. The Halbach Array magnetic circuit design method was used to construct a gap-type permanent magnet adsorption model for lightweight design. The influence of wall thickness and air gap distance on the adsorption force is analyzed by parametric simulation. The prototype platform test shows that the robot can realize adaptive variable curvature motion through passive adjustment of the mobile mechanism attitude and has a certain load capacity. [ABSTRACT FROM AUTHOR]

• An electromagnetic transient model of the Sen Transformer (ST) with inter-turn fault (ITF) is proposed. • The hysteresis effects are considered as it affect the accuracy of the analytical results of the proposed model. • The current variation of the ST in the event of an ITF is analyzed. • The effects of number of fault turns and fault locations on the current of the ST with ITF are presented. In order to analyze the electromagnetic characteristics of the Sen Transformer (ST) in the event of an inter-turn fault (ITF), an electromagnetic transient model of the ST with ITF based on reluctance is proposed in this paper. Firstly, the magnetic equivalent circuit model of the ST with ITF is established based on the magnetic coupling relationship among the internal windings of the ST with ITF. Secondly, the electrical analytical model for the current in each winding of the ST with ITF is derived from the electrical connection established the ST with ITF and the external system. Finally, the electromagnetic transient model of the ST with ITF can be obtained by combining the magnetic equivalent circuit model with the electrical analytical model. The J-A hysteresis model is employed for representing the saturation characteristics of the iron core and the hysteresis effects. Meanwhile, an energy method is used to calculate the leakage reluctance between the windings. Three case studies have been conducted with the assistance of MATLAB and ANSYS/Maxwell. The results of the analytical calculations are compared with the time-domain simulation to verify the validity of the model. Furthermore, the growth of the current in the fault phase is significant after an ITF occurs in the ST, while the growths of the currents in the non-fault phases are very small. Moreover, the effects of the number of fault turns and the fault location on the current in the ST with ITF are further analyzed. [ABSTRACT FROM AUTHOR]

• In this paper, an amorphous alloy with oriented silicon steel double-layer composite wound core (DCWC) structure is proposed. • In order to calculate the flux density distribution in the DCWC, an equivalent dual nonlinear electric circuit and magnetic circuit coupling model is established which considers the differential permeability difference of the two ferromagnetic materials. • The structure optimization design method of the DCWC is proposed with the percentage of oriented silicon steel and structure parameters as the free variables. • Based on the structure optimization design results, the experimental prototype of the DCWC is manufactured, and its magneto-mechanical characteristics are analyzed based on theoretical calculation and experimental measurement. Three-dimensional wound cores are widely used in three-phase distribution transformer due to the symmetrical magnetic circuit structure. Amorphous alloy and oriented silicon steel are two kinds of ferromagnetic materials commonly used to make distribution transformer cores, each has own advantages and disadvantages in magnetic and mechanical characteristics. The amorphous alloy and oriented silicon steel composite core can synthesize the advantages of both. In this paper, a double-layer composite wound core (DCWC) structure is proposed and the corresponding dual nonlinear electric circuit and magnetic circuit coupling model is established. A structure optimization design method for the DCWC based on the free parameter scanning method is proposed by taking the percentage of oriented silicon steel in the composite core and the structure parameters as free variables. Based on the proposed optimization design method, a DCWC is designed and the experimental prototypes are manufactured. Further, the flux density distribution, core loss and mechanical vibration displacement of the DCWC are analyzed, and the effectiveness of the proposed method is verified by comparing with the measured results. [ABSTRACT FROM AUTHOR]

• A novel axial magnetic bearing without thrust disk. • The proposed RTMB is composed of staggered teeth structure. • The RTMB is analyzed by air–gap ratio permeance method and FEA. • The influence of slot effect is analyzed and displacement stiffness of RTMB is modified. • Static test device of RTMB is manufactured and proved the correctness of theoretical analysis. Conventional thrust magnetic bearing (TMB) uses large thrust disk to generate axial levitation force. However, due to the existence of thrust disk, it will lead to many problems in assembling and dynamic balance. Moreover, it will even limit rotational speed. In order to solve these shortcomings, a novel TMB with uniform teeth on the stator and rotor is proposed. It replaces the conventional thrust disk with staggered teeth structure between the stator and rotor. This paper obtains analytical expressions of levitation force, current stiffness and displacement stiffness of the novel TMB by equivalent magnetic circuit method and method of air–gap ratio permeance. Considering slot effect between the teeth of stator and rotor, its influence is analyzed by finite-element analysis (FEA) and the expression of displacement stiffness has been modified. The simulation and experiment results show that the proposed TMB can ensure enough bearing capacity by reasonably designing the staggered distance between the teeth of stator and rotor. In addition, under the reasonable tooth structure, TMB can achieve self-recovery ability by utilizing the influence of slot effect on levitation force. Compared with conventional TMB, the proposed TMB has greater advantages in assembly, dynamic balance and high speed. It will be conducive to its application in medical, aerospace and other fields. [ABSTRACT FROM AUTHOR]

This study presents a novel two-way microspeaker design (SPK) aimed at improving the mid-frequency sound pressure level (SPL) without compromising the overall dimensions. This innovative approach includes a new magnetic circuit design, new diaphragm structures, and electromagnetic-mechanical-acoustic (E-M-A) coupling analysis of two microspeakers (SPKs). First, the E-M-A coupling method is validated on the prototype SPK, which forms the basis for subsequent design iterations. Four types of SPKs, with strategically reduced magnet numbers, are introduced and enhance the force factor of microspeakers. A new diaphragm structure that uses two side diaphragms with varying hardness levels effectively controls the resonance frequencies for each SPK. The SPL results demonstrate that Type 4 with new diaphragm structure exhibits a significant 0.94 dB increase in the mid-frequency SPL compared with the prototype, with minor reduction in the low-frequency SPL. The conclusion turns out the two-way SPKs can be uses as a good approach to improve the mid- frequency SPL. [Display omitted] • Designed novel two-way microspeaker for improved mid-frequency sound pressure level. • Adopted innovative designs: a new magnetic circuit, and new diaphragm structures. • Two-side diaphragm with various hardness levels controls resonance frequency. • Enhanced mid-frequency sound pressure level while maintaining compact form factor. • Verified E-M-A coupling method on prototype microspeaker. [ABSTRACT FROM AUTHOR]

• A novel twin-tube MR damper with meandering channel is proposed. • The maximum dynamic range of the proposed MR damper is 10.76 when I = 0.5 A. • Temperature characteristics and damping characteristics of the proposed MR damper are experimental studied. • The damping force of the proposed MR damper reaches 4523 N when I = 0.5 A, f = 2.0 Hz, and A = 8 mm. A twin-tube magnetorheological (MR) damper with meandering channel is proposed in this paper. The proposed MR damper has a longer damping channel than conventional MR dampers due to the structure of twin-tube and the design of meandering channel. The magnetic circuit model and the damping force model of the proposed MR damper are established and finite element analysis is conducted. In addition, experimental research is conducted on the temperature characteristics and damping characteristics of the proposed MR damper. Results demonstrate that the theoretical and experimental maximum damping forces of the proposed MR damper are in good agreement. The temperature of the coil surface changes very little under a current of 0.5 A. The maximum damping force of the proposed MR damper can reach 4523 N and the maximum dynamic range is 10.76 at the current of 0.5A. Furthermore, the maximum dynamic range of the proposed MR damper is larger than that of other conventional MR dampers in references. [ABSTRACT FROM AUTHOR]

• Switched Reluctance Machine sensorless for position control. • Presentation of an active method for indirect measurement of shaft angular position. • Active method based on frequency modulation. • Experimental results studying the influence of temperature, speed and magnetic circuit. This paper presents a study of a system to detect the angular position of the shaft of an 8/6 Switched Reluctance Machine (SRM) for position control. The detection system is independent of the machine circuits and is based on the indirect measurement of the induction coefficient, using a diagnostic coil. This induction coefficient, variable with the angular position, is the variable element of an oscillator, producing a frequency modulation. The intrinsic problems that this indirect position measurement system presents, particularly related with position control, are explained. The influence of the machine temperature, of the rotor speed and of the magnetic circuit saturation are also discussed. [ABSTRACT FROM AUTHOR]

• Magnetic-Equivalent-Circuit proposal for the partitioned stator flux-switching permanent magnet machine. • New method is presented for saturation effect model which is presented for first time. • Dynamic simulation of the modeled machine has been presented for first time. This paper presents a novel technique for modeling Partitioned Stator Flux-Switching Permanent Magnet (PS-FSPM) machine by Magnetic Equivalent Circuit (MEC) method which provides adjustable accuracy for the modeling of the machine. The machine geometry is divided into 13 zones, where the number of flux tubes in the core and air parts can be selected. Considering multiple flux tubes in the teeth and slots regions, the flux distribution can be accurately obtained. The saturation effect of the core elements are also taken into account by nonlinear reluctances. A novel method for saturation effect is proposed, where the B-H curve can be tuned by selectable parameters. The proposed model is capable of modeling PS-FSPMs with various poles-teeth combination. Finally, the results of the proposed method are compared with finite element method (FEM) in terms of accuracy and processing time. [ABSTRACT FROM AUTHOR]

Abstract Transverse Flux Permanent Magnet Motor (TFPMM) has received extensive attention in the field of electric vehicles. The magnetic circuit of TFPMM is three-dimensional and non-linear, which leads to the high nonlinearity of electromagnetic torque. Although the three-dimensional finite element method (3DFEM) could be used to estimate torque, it is very time-consuming. Instead of it, this study adopts a kind of machine learning method—Gaussian process regression (GPR). For the hyper-parameters optimization of GPR, most previous studies used single-objective algorithms for improving the regression accuracy. However, GPR is an algorithm of probability prediction and it could not guarantee to have the satisfactory confidence interval characteristic simultaneously while the regression precision achieves optimal. Therefore this paper proposes a variable parameters fuzzy dominance genetic algorithm (VPFDGA) which is suitable for the multi-objective optimization, including the optimization of regression precision, confidence interval reliability, confidence interval width and skill score. By combining GPR with VPFDGA, the electromagnetic torque of a building-block transverse flux permanent magnet motor (B-TFPMM) is estimated by VPFDGA-GPR (GPR based on variable parameters fuzzy dominance genetic algorithm). Besides, two other GPRs based multi-objective optimization, three GPRs based on single-objective optimization and a GPR based on weighted sum method that is the classic multi-objective optimization algorithm are all implemented to compare with VPFDGA-GPR. The results of comparison show that VPFDGA-GPR has the better performances including the higher regression precision, more powerful ability of probability prediction, higher stability, less convergence time and so on. [ABSTRACT FROM AUTHOR]

Abstract In this paper, we aim to improve the optical properties of magnetic lenses in transmission electron microscope(TEM). First, the mathematical model of the magnetic field is established, and the formula of the reluctance of the magnetic lens at the corner of the magnetic circuit is deduced. The calculation results of the reluctance are obtained by the numerical analysis method. Then, we find that the corner reluctance affects the density distribution of the magnetic flux lines at the corner. Therefore, the structural shape of the corner of the magnetic lens is optimized. The magnetic flux density on optical axis and the corresponding electron optical parameters are obtained by calculations and simulations. The optical properties of the magnetic lens are improved after the optimization. [ABSTRACT FROM AUTHOR]

• A multi-stage hysteresis (MSH) model is proposed for magnetorheological dampers. • Steady-state and transient finite element methods are combined. • An equivalent weighted mean magnetic field hypothesis is proposed and validated. • The MSH model effectively predicts the behaviour of magnetorheological dampers. • The MSH model has a smooth transition in different stages. An accurate theoretical model is the basis for the structural design and parameter optimisation of magnetorheological dampers (MRDs). Owing to the inability of existing models to accurately describe the motion characteristics of MRDs in the entire region, a multi-stage hysteresis (MSH) model for low-frequency conditions was proposed. The MSH model comprised a magnetic chain model and Bi-Viscous model to describe the characteristics of the pre-yield and yield flow stages, respectively. The local loss and inertia effect were considered in the MSH model. Steady-state and transient finite element methods were combined to analyse the magnetic field distribution during MRD motion, and an equivalent weighted mean magnetic field hypothesis was proposed to reduce the quantisation error and time consumption. The experimental results demonstrate the prediction effectiveness of the MSH model. Moreover, the quantitative evaluation parameters of the flow and hysteresis regions were obtained and the variation trend of the MRD main design indices with the magnetic circuit parameters was analysed. The obtained velocity distribution parameters indicate a smooth transition of the stages in the MSH model from a qualitative perspective. The mixed mode incorporates the physical properties of the shear and flow modes, but cannot simply be regarded as a linear superposition of these two modes. [Display omitted] [ABSTRACT FROM AUTHOR]

Wireless coupling can offer significant advantages for in-reactor applications. For instance, wireless signal couplings can avoid electrical feedthroughs penetrating fuel cladding or other high-temperature pressure barriers in fuel performance testing. This paper presents a feasibility study of a wireless coupling technology for the linear variable differential transducer (LVDT), as LVDTs have been successfully demonstrated in reactor applications and can be used to measure a variety of physical parameters. The coupling technology utilizes mutual inductance at a low frequency to transfer power into and signal out of a stainless steel pressure barrier. Using Kirchhoff's law and magnetic circuit analysis, a theoretical model is developed, including the LVDT, wireless power coupling parts, and wireless signal coupling parts. The LVDT is assumed to have a constant inductance of the primary coil and the sum of two secondary coils. An experimental system is built to test and verify the performance of the technology with a commercial LVDT. The experimental setup has an input voltage limitation to prevent the excessive heating. The non-linearity of the commercial LVDT is ±0.77% as measured in the lab. After coupling the LVDT with the wireless system, the measurement non-linearity is increased to ±1.26%, which shows the wireless power and signal transfer can be applied with LVDTs with limited additional measurement uncertainty. The theoretical model prediction agrees with the experiment results, with the maximum discrepancy of 1.5% between prediction and experiment. The model and experimental results of this study can be directly used to guide the design and optimization of wireless LVDT measurement systems for future in-reactor experiments. • This work develops a wireless coupling technology for nuclear reactor experiments. • The technology can simplify the reactor experiment design and improve safety. • The measurement uncertainty caused by the technology can be less than 1%. [ABSTRACT FROM AUTHOR]

Magnetic fluid seals are contact-free rotary seals widely used to seal gas and vacuum. However, their effectiveness declines when utilized to seal liquids due to the inherent incompatibility and instability at the interface between the two liquids. The underlying mechanism for this premature failure remains incompletely comprehended, posing a significant challenge to their widespread use for sealing liquids. Here we demonstrate a novel pole structure featuring a non-magnetic shaft, which creates a closed magnetic circuit without requiring the magnetic circuit to pass through the rotating shaft. This innovative approach enables the observation of the failure processes of the seal through a hollow transparent shaft, utilizing an endoscope. The results show that the static seal failure occurrs in two stages: extrusion, infiltration, and magnetic fluid barrier rupture. In the first stage, a leakage channel opens cyclically, whereas in the second stage, the seal leaks completely once the critical pressure is surpassed. Dynamic failure arises from the intricate interplay between dissolution, extrusion, and interface instability. Upon attaining the critical speed, the flow at the interface transitions from laminar to turbulent, leading to apparent delamination fluctuations. At this point, the magnetic fluid film becomes unstable and instantly leaks from the seal upon exceeding the critical speed. This research has unveiled crucial inducing factors for seal failure that have significant implications for the design of liquid seals. The intricate and complex nature of the failure mechanism emphasizes the need for a comprehensive understanding of the interplay between the seal design, magnetic fluid properties, and operating conditions to develop efficient liquid seals with superior performance. [ABSTRACT FROM AUTHOR]

Magnetite nanoparticles were prepared in a weakly basic solution at the low reaction temperature by the co-precipitation method. As a comparison, the oxidative precipitation method was also applied in this study. The structure, morphology, and other properties of the obtained samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), transmission electron microscope (TEM), and thermogravimetric analysis (TGA). The above characterization data indicate that small size and narrow size distribution are found for magnetite nanoparticles prepared by the co-precipitation method. Further magnetic property and Zeta potential results illuminate that magnetite nanoparticles prepared by this method display a quasi-superparamagnetic property and a good dispersion in the aqueous solution. Based on the investigation results, the magnetite nanoparticles with a quasi-superparamagnetic property and a fine dispersion can be facilely prepared in a weakly basic solution at the low reaction temperature by the co-precipitation method. [ABSTRACT FROM AUTHOR]

Hydrogen fuel cells are one of the important directions of development of the global energy. Hydrogen fuel cells are being actively implemented in the aviation systems, for example in Airbus A320. Boeing and Airbus announced creation of an auxiliary power unit fuel cell with capacity up to 200 kW in 2017–2018. In the automotive industry hydrogen fuel cells are also widely used. But the efficient use of hydrogen fuel cells is not possible without establishment of effective systems related to their operation. Therefore, our article proposes a new topology of high-speed motor for compressor of the hydrogen fuel cell. An original solution to raise the energy efficiency of high-speed motor presented in our article, the novelty of which is the use of amorphous alloys. Research of the new design methods of computer modeling in Ansys Maxwell was conducted; optimal geometric dimensions of the high-speed motor with two-pole and four-pole magnetic system were obtained in this article. In the modeling losses on eddy currents in permanent magnets and iron of the rotor for two-pole and four-pole magnetic systems were taken into account. All the theoretical results have been experimentally verified. For this purpose the layout of the high-speed motor with the perforated winding was created. Design of the experimental model is also described in this article. The high-speed motor testing and analysis of test data take a special place in this article. In the experimental tests was found that the efficiency of our topology is 92.8% and the power density of our high-speed motor is 0.21 kg/kW with air cooling. These experimental tests prove the effectiveness of our topology compared to the known world analogues. Also in the article was proven that the use of our topology allows minimizing the mass of a hydrogen fuel cell with improved energy efficiency. This is especially important for the aerospace applications and automotive industry. [ABSTRACT FROM AUTHOR]

As is well known, the armature current will be ahead of the back electromotive force (back-EMF) under load condition of the interior permanent magnet (PM) machine. This kind of advanced armature current will produce a demagnetizing field, which may make irreversible demagnetization appeared in PMs easily. To estimate the working points of PMs more accurately and take demagnetization under consideration in the early design stage of a machine, an improved equivalent magnetic network model is established in this paper. Each PM under each magnetic pole is segmented, and the networks in the rotor pole shoe are refined, which makes a more precise model of the flux path in the rotor pole shoe possible. The working point of each PM under each magnetic pole can be calculated accurately by the established improved equivalent magnetic network model. Meanwhile, the calculated results are compared with those calculated by FEM. And the effects of d-axis component and q-axis component of armature current, air–gap length and flux barrier size on working points of PMs are analyzed by the improved equivalent magnetic network model. [ABSTRACT FROM AUTHOR]

In this paper a new superconducting inductor topology intended for synchronous machine is presented. The studied machine has a standard 3-phase armature and a new kind of 2-poles inductor (claw-pole structure) excited by two coaxial superconducting coils. The air-gap spatial variation of the radial flux density is obtained by inserting a superconducting bulk, which deviates the magnetic field due to the coils. The complex geometry of this inductor usually needs 3D finite elements (FEM) for its analysis. However, to avoid a long computational time inherent to 3D FEM, we propose in this work an alternative modeling, which uses a 3D meshed reluctance network. The results obtained with the developed model are compared to 3D FEM computations as well as to measurements carried out on a laboratory prototype. Finally, a 3D FEM study of the shielding properties of the superconducting screen demonstrates the suitability of using a diamagnetic-like model of the superconducting screen. [ABSTRACT FROM AUTHOR]

A packaged angle sensor consisting of four PZT/FeGa/PZT magnetoelectric (ME) laminate composites, four magnetic accumulation arcs, a magnetic accumulation (MA) ring, a multi-polar magnetic ring (MPMR), a shaft, and necessary shells is fabricated and characterized. The ME laminate composite with a slim shape is placed between the MA arc and the MA ring. The MPMR fixed on the shaft is used to apply a magnetic field associated with angle information to the ME laminate composites. Under the role the MA parts, the magnetic field applied to the ME laminate composites can be enhanced about 7 times. With the increasing of the rotational speed, the frequency of the sensor’s output signal is increased linearity, which can be used to measure the rotational speed. The amplitude of the output signal is increased as well and finally reached a stable value of 45.3 Vpp. In order to realize static test without the participation of an excitation coil, one of the ME laminate composites has been used as a piezoelectric transformer. In experimental, a resolution of 0.2° and a favorable stability with a standard deviation in population of ∼40 μVpp are achieved from this sensor. These characteristics show that the packaged sensor can be successfully used in rotational parameters testing and has the potential to establish self-powered wireless angle-sensing devices. [ABSTRACT FROM AUTHOR]

• The SEQZS VI has an extensive negative stiffness tunable range by applying a newly designed "8"-shaped equivalent magnetic circuit negative stiffness mechanism (NSM). • The SEQZS VI with electrical eddy-current damping (EED) can significantly suppress the resonance amplitude and nonlinearity. • The SEQZS VI possesses ultra-low resonant frequency and can be tuned by coil current. • A prototype of the proposed SEQZS VI is fabricated and tested. A semi-active electromagnetic quasi-zero-stiffness (QZS) vibration isolator (VI) (SEQZS VI) is proposed to broaden the frequency bandwidth for low or ultra-low frequency vibration isolation. The electromagnetic negative stiffness mechanism (NSM) applies a newly designed "8"-shaped electromagnetic equivalent magnetic circuit and has a more extensive tunable range of negative stiffness (NS) than previous studies. Moreover, theoretical formulations for the SEQZS VI in static and dynamic analyses under harmonic excitations were derived in detail and the parameter analysis is carried out to provide a reference for the design. Furthermore, a prototype is fabricated and tested to validate the design concept of SEQZS VI. The experimental results validate the present formulation and show that the vibration isolation performance of the proposed SEQZS VI is much better than that of the corresponding linear isolator. Moreover, the present SEQZS VI can have lower stiffness in a wider region and lower transmissibility at the resonance frequency. [Display omitted] [ABSTRACT FROM AUTHOR]

• A giant magnetostrictive transducer was simulated and calculated using magneto-mechanical coupling in COMSOL Multiphysics, the influence of the thickness of the magnetic cylinder and the magnetic block on the performance of the transducer was investigated. • The temperature rise of the two transducers during the operation was simulated and experimentally tested. • The finite element calculations of the output amplitude and temperature rise of the transducer agreed with the experimental test values. It can be used as a simulation method to optimize the design of the magnetic circuit structure of the giant magnetostrictive transducer and improve its vibration performance. A giant magnetostrictive transducer was studied. The dynamic simulation analysis of the transducer was carried out, the influence of the magnetic block and the magnetic cylinder on the vibration performance of the transducer was studied, and the temperature rise of the transducer during the operation was simulated and calculated. The impedance and output amplitude of the developed transducer were tested experimentally. The results show that the axial magnetic field intensity of the Terfenol-D rod increased and then decreased, and the output amplitude increased and then decreased slightly with the increase of the thickness of the magnetic cylinder. As the thickness of the magnetic block increased, the axial magnetic field intensity of the rod increased, and the output amplitude of the transducer also increased. Compared with the transducer without magnetic cylinder, the transducer with magnetic cylinder has larger electromechanical conversion coefficient, and output amplitude, but the temperature was higher after working for the same time. [ABSTRACT FROM AUTHOR]