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China's social work education dates back to the 1920s, but the profession disappeared for 36 years after the establishment of the People's Republic of China. Not until the late 1980s was social work education in China revived. At the turn of the new century, the Central Committee of the Chinese Communist Party and the State Council supported the urgent need for social work professionals to solve serious social problems to build what the government called a harmonious society. Since then, China's social work education has gone through rapid development. We examine the characteristics of China's social work education development since the economic reform of 1978 and present the challenges, opportunities, and future prospects for the profession.

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]

Fractional slot concentrated winding (FSCW) is a kind of winding structure with few‐slots/coils multi‐poles. FSCW has the potential value of high torque density due to its short end‐winding and high slot fill ratio and is widely used in low‐speed direct‐drive application situations. However, compared with integral slot winding (ISW), the back EMF coefficient of FSCW is smaller, which leads to smaller output torque under the same condition. To improve the back EMF coefficient of FSCW, equidirectional toroidal winding (ETW) is proposed and applied to the dual rotor slotless axial flux permanent magnet motor (AFPM), in which the unit structure is three slots/coils two poles, and the ideal back EMF coefficient is the same as that of ISW. In this paper, firstly, the structure of ETW is introduced and its operating principle is analyzed. Then, compared with the AFPM with ISW, the open circuit and load characteristics of the AFPM with ETW under two conditions of the same wire gauge and the same coil width are analyzed respectively. The back EMF coefficient and output torque of ETW‐AFPM are similar to that of ISW‐AFPM under the same coil width. The back EMF coefficient and output torque of ETW‐AFPM are a little lower than that of ISW‐AFPM under the same wire gauge. Finally, the experimental results also validate the feasibility of AFPM with ETW and the correctness of the analysis results. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

In this paper, a dual-rotor slotless axial-flux permanent magnet (AFPM) motor with equidirectional toroidal winding (ED-TW) is proposed and compared with the AFPM motor with traditional toroidal winding (T-TW) with the same dimensions, number of coils and poles. Different from the T-TW, only the positive sides of coils of the ED-TW are left on one side of the stator core, the return sides of the coils are all removed to the other side of the stator core. Firstly, the structure and operation principle of the two motors are introduced and analyzed. To clarify the features of the ED-TW, the synthetic electromotive force (EMF) vector and armature reaction field of the ED-TW and T-TW are studied. Secondly, the main size equations of the AFPM motors with toroidal windings are presented. Subsequently, the electromagnetic characteristics of the AFPM motors with ED-TW and T-TW are analyzed and compared based on the three-dimensional finite element method (3D-FEM). The comparison results indicate that the AFPM motor with ED-TW has superiority in torque density and efficiency. Finally, a prototype of the AFPM motor with ED-TW is manufactured and tested, which validates the feasibility of the proposed motor and the correctness of the analysis of the 3D-FEM. [ABSTRACT FROM AUTHOR]

In terms of the characteristics of multi‐objective and interactions among optimization objectives of the tubular permanent magnet linear generator with 120° phase belt toroidal winding (120°‐TPMLG), a multi‐objective optimization method is proposed to improve the generators performances, which is based on the combination of response surface method and the genetic algorithm. First, the sensitivity analysis of different structural parameters on the performances of the 120°‐TPMLG is conducted to pick out the sensitive structural parameters. Then develop those sensitive parameters as optimization variables to establish the response surface equation of the generator performances including output power (P), detent force (F), and the efficiency (η). Subsequently, based on the surface equation, the genetic algorithm (GA) fitness function is proposed to conducted the global optimization and the optimization results are finally obtained. To verify the effectiveness of the proposed optimization method, the performances of the optimal 120°‐TPMLG are analysed and compared with the initial one. The results show that the performances including the detent force and power density of the 120°‐TPMLG are greatly improved, which prove that the proposed multi‐objective optimization method is effective for the 120°‐TPMLG. [ABSTRACT FROM AUTHOR]

The three‐phase permanent magnet synchronous motor (three‐phase PMSM) has gained much popularity in many applications due to its various advantages. In addition, due to the good fault tolerance, simple inverter circuit structure and high torque density, the six‐phase PMSM has better prospects than three‐phase PMSM in biomedical devices, electric vehicles and other fields with high reliability requirements. In this study, a six‐phase axial‐flux PMSM inherently without cogging torque is proposed to improve torque density, which equips the 60° phase‐belt toroidal winding (60°TW) and slotless stator core. Based on the same effective volume, permanent magnet material, power grade and the other major motor parameters, two six‐phase PMSMs with 30° phase‐belt toroidal winding (30°TW) and 60°TW are designed, respectively. The armature reaction field, air gap magnetic density, back‐electromotive force, output torque, loss characteristic and torque‐speed characteristic are compared by using three‐dimensional (3D) finite‐element models in detail. Finally, the experimental test is carried out using the prototype of three‐phase PMSM with 120° phase‐belt toroidal winding. The experimental results indirectly verify the feasibility of 60° phase‐belt toroidal winding and correctness of 3D FEM. The 3D FEM analysis results are presented to show that torque density of the proposed six‐phase PMSM with 60°TW is improved in comparison to the six‐phase PMSM with 30°TW. Index Terms—60° phase‐belt toroidal winding, axial flux, six‐phase permanent magnet synchronous motor, torque density [ABSTRACT FROM AUTHOR]

Double-sided permanent magnet linear synchronous machine with 120° phase belt toroidal windings (120°-TWDSPMLSM) suffers from large detent force due to the end effect and slot effect. Many existing methods can reduce the detent force of the 120°-TWDSPMLSM effectively. But they also minimize the back electromotive force (back-EMF) and thrust simultaneously. To alleviate this problem, this paper adopts a method of combining slot-shift structure with rearranging the 120° phase belt toroidal windings (120°-TW) to suppress the detent force and improve the back-EMF and thrust of the 120°-TWDSPMLSM simultaneously. First, the slots on the two sides of the primary part are stagger by an optimal distance to reduce the detent force. The models of the detent force, including the end force and cogging force, is established theoretically, and then verified by finite-element analysis (FA). Then, the 120°-TW are rearranged to improve the back-EMF and average thrust. And the electromagnetic characteristics of the 120°-TWDSPMLSM under different shifted distances are analyzed and compared in detail. Finally, the result shows that the detent force of optimized machine is 70.19% lower than that of the original machine, and the thrust fluctuation reduces 19.21%. Besides, the back-EMF of optimized machine is 6.84% lower than that of the original machine, but 31.86 higher than the machine with shifting slots and without rearranging the 120°-TW. Therefore, the optimal method in this paper is available in the detent force reduction and thrust improvement of the 120°-DSPMLSM. [ABSTRACT FROM AUTHOR]

This article reviews China's social security system and its recent reforms from a macro perspective. The traditional "broad" social security model should be replaced by a new "narrow" social security model. If social security programs, eligibility, and responsibilities are adjusted according to the narrow model, urban and rural areas can be integrated into a single social security system. Reforms of the traditional system could thus redress the long practice of preferential policies for the cities and strive to reduce the disparities between urban and rural areas. [ABSTRACT FROM AUTHOR]