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Bearings are pivotal components in mechanical systems, providing crucial support to rotating bodies. However, traditional bearings are susceptible to failure caused by friction and wear. This vulnerability is particularly pronounced in scenarios involving ultrahigh speeds and extreme conditions, necessitating the minimization of bearing losses and the enhancement of performance. Magnetic bearings, distinguished by their frictionless operation, absence of lubrication requirements, and high-speed capabilities, offer a promising solution to mitigate bearing failure attributable to friction. Nevertheless, a comprehensive review of magnetic bearings, encompassing their structural attributes, modeling mechanisms, and control strategies, is currently lacking in the literature. This paper aims to address this gap by conducting an exhaustive literature review on magnetic bearings. The objective is to provide scientists with a profound understanding of the structural characteristics, operational mechanisms, control performance, and future development trajectories of this technology. The paper begins by categorizing various magnetic bearings and conducting an in-depth analysis of their properties and characteristics, focusing on their magnetic circuit structures. Subsequently, it delves into the working principles and performance of mathematical models for magnetic bearings with different configurations, outlining the modeling procedures and optimization approaches. Additionally, the paper highlights the impact of control strategies on the performance of magnetic bearings. Modern control theory has demonstrated a remarkable 50% improvement in position accuracy and adjustment time compared to traditional PID control. Finally, the paper offers a glimpse into the future of magnetic bearing design, modeling mechanisms, and control strategies, presenting prospective directions for further advancements in this field.

This study focuses on designing and optimizing Permanent Magnet Synchronous Motors (PMSMs) using hybrid rare earth and ferrite materials. Two distinctive rotor topologies of the Hybrid-Type Permanent Magnet Motor (HTPMM) are proposed: series and parallel magnetic circuits. Initially, the rotor topology and magnetic circuit principles of both the prototype and the designed HTPMM are introduced. Subsequently, a multi-objective genetic algorithm is employed to optimize the two HTPMMs, determining the final optimized parameters. Thise study further analyzes the cost advantage of HTPMMs from the perspective of permanent magnet materials, and detailed finite element analysis is conducted to evaluate the electromagnetic performance, including the air-gap flux density, no-load back electromotive force, cogging torque, load torque characteristics, and demagnetization properties. A comparative analysis of the prototype and two designed motors reveals that the HTPMM exhibits similar performance to the prototype, effectively reducing the usage of rare earth materials and significantly lowering the manufacturing costs. This research validates the feasibility of reducing rare earth material usage while maintaining a similar performance and provides a new perspective for the design of permanent magnet motors.

Advanced Encryption Standard (AES) key expansion unit is usually implemented by chain structure with a long critical path length. That makes key expansion unit become the bottleneck of high-speed AES implementations. In this paper, a design method of low-delay AES key expansion unit is proposed. The proposed design method is based on a delay-drive binary tree (DDBT) structure, which has been proven that it has the shortest critical path length. Based on the proposed design method, a low-delay AES encryption key expansion unit and a low-delay AES encryption/decryption unified key expansion unit are designed in this paper. Both hardware complexity analysis and integrated circuit synthesis indicate that our DDBT-structure-based designs can reduce the delay greatly compared to traditional chain structures. Furthermore, compared to previous works, our designs can achieve the largest throughput.

In this study, a novel buck–boost DC/DC converter is presented. The circuit structure of the proposed converter consists of a single power switch, two diodes and some energy storage elements. Employing only a single power switch reduces the implementation cost and switching power losses. The proposed converter has higher voltage gain in step-up mode in comparison with conventional buck–boost and Cuk converter. In addition, this converter expands the continuous conduction mode (CCM) operational region. The presented converter has three operation modes in CCM. The second mode reduces the voltage stresses across the capacitors. Therefore the current stresses on diodes are also reduced. To verify the operation of the proposed converter, the experimental results are provided using a hardware prototype.

A three-dimensional frequency selective surface (3D-FSS) that provides stability for an angle of incidence and miniaturised unit cell size is presented. The proposed 3D-FSS is easy to fabricate and is implemented using via holes in a multilayer printed circuit board structure. Frequency transmission characteristics for different angles of both TE and TM polarisations are presented through simulations. The proposed structure was fabricated so as to verify the simulation results. The comparisons between the simulation and the measured results show good agreement. The results also show that the proposed 3D-FSS can provide better frequency stability for different incidence angles and polarisations as well as miniaturised unit cell size.

Previous studies on reconfigurable intelligent metasurface (RIS) design have primarily relied on full-wave electromagnetic simulation software, which often incurs high computational costs and lacks clear design direction. The design of multi-bit RIS remains challenging and there is currently no suitable systematic method for selecting the corresponding tuning devices. To overcome these limitations, this article proposes a novel equivalent circuit-based approach to RIS design. In contrast to the conventional approach, where the equivalent circuit model is derived from post-design evaluation of the scattering properties of RIS, our work is entirely driven by the equivalent circuit model from the outset to accomplish the unit cell design. A complete workflow as well as details of each constituent step are presented for the topology design of RIS based on equivalent circuit topology. Building on this circuit topology, a 3-bit reflective phase reconfigurable unit cell is developed based on a tunable band-stop filter circuit. We conducted adjustable phase verification experiments and beam deflection experiments. The consistency between the experimental results and circuit theory demonstrates the feasibility and practicality of the equivalent circuit method of RIS design. This circuit-to-structure methodology provides a physically interpretable and systematic framework for designing RIS with arbitrary electromagnetic responses, offering new insights into RIS design.

In order to compare the performance difference of the permanent magnet synchronous motors (PMSM) with different rotor structure, two kinds of rotor magnetic circuit structure with surface-mounted radial excitation and tangential excitation are designed respectively. By comparing and analyzing the results, the difference of the motor performance was determined. Firstly, based on the finite element method (FEM), the motor electromagnetic field performance was studied, and the magnetic field distribution of the different magnetic circuit structure was obtained. The influence mechanism of the different magnetic circuit structure on the air gap flux density was obtained by using the Fourier theory. Secondly, the cogging torque, output torque and overload capacity of the PMSM with different rotor structure were studied. The effect mechanism of the different rotor structure on the motor output property difference was obtained. The motor prototype with two kinds of rotor structure was manufactured, and the experimental study was carried out. By comparing the experimental data and simulation data, the correctness of the research is verified. This paper lays a foundation for the research on the performance of the PMSM with different magnetic circuit structure.

The attribute-based encryption (ABE) scheme is suitable for access control of ciphertext in cloud computing. Kowalczyk and Wee proposed an adaptively secure attribute-based encryption scheme that supports NC 1 circuits. However, the ciphertext length increases rapidly with the depth of the circuit, resulting in an increase of the computational complexity of the encryption and decryption algorithms. In this paper, to overcome this challenge, a ciphertext-policy ABE scheme that supports circuits with fan-in n is proposed. First, we design new pebble rules for secret sharing in circuits with fan-in n, improving the compactness of the security reduction. Then, the new secret sharing scheme is embedded in the encryption algorithm, which is the key to improving efficiency. Moreover, we prove the adaptive security of the scheme by using a piecewise guessing framework and dual-system encryption. Finally, by comparison analysis, this scheme exhibits a better performance.

Characterised with more integrated topology, simpler manipulations, less component count, and comparative higher efficiency, multiple-input converters (MICs) become an attractive candidate in renewable energy hybrid systems (REHSs). To seamlessly and smoothly transit from one operating mode to another is one of the critical issues that the energy management strategy should concern about. Normally, the mode transition (MT) design is usually required for the auxiliary circuits and components, which runs opposite to the MIC's intrinsic advantages and may cause potential problems for the system's reliability and stability. The subproportion control (SPC) approach presented in this study combines two operating modes into a sole control algorithm module without any hardware assistance. The so-called subproportion (SP) term is an additional control variable served as a certain proportion of the voltage-regulation duty cycle, dv. The product of SP and dv composes the duty cycle for current limitation of the first power source, beyond which, a seamless and smooth MT can be automatically and spontaneously implemented. The small-signal modelling for the three most-commonly-used topologies in the MIC family showed SPC's universal applicability. It was employed onto a 1 kW double-input-buck-converter-based fuel cells/battery REHS prototype for the verification of its control performance and auto-MT capability.

The inverse and direct piezoelectric and circuit coupling are widely observed in advanced electro-mechanical systems such as piezoelectric energy harvesters. Existing strongly coupled analysis methods based on direct numerical modeling for this phenomenon can be classified into partitioned or monolithic formulations. Each formulation has its advantages and disadvantages, and the choice depends on the characteristics of each coupled problem. This study proposes a new option: a coupled analysis strategy that combines the best features of the existing formulations, namely, the hybrid partitioned-monolithic method. The analysis of inverse piezoelectricity and the monolithic analysis of direct piezoelectric and circuit interaction are strongly coupled using a partitioned iterative hierarchical algorithm. In a typical benchmark problem of a piezoelectric energy harvester, this research compares the results from the proposed method to those from the conventional strongly coupled partitioned iterative method, discussing the accuracy, stability, and computational cost. The proposed hybrid concept is effective for coupled multi-physics problems, including various coupling conditions.