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Background: To evaluate the methodological quality, report quality, and evidence quality of meta-analysis (MA) and systematic review (SR) on the efficacy of probiotics in the treatment of rheumatoid arthritis (RA). Methods: Databases were used to identify eligible SRs/MAs until February 12, 2024. The methodological quality of the studies was assessed using AMSTAR-2 tool, the quality of the literature reports was scored using PRISMA checklists, and the quality of the evidence was graded using GRADE system. Methods: Databases were used to identify eligible SRs/MAs until February 12, 2024. The methodological quality of the studies was assessed using AMSTAR-2 tool, the quality of the literature reports was scored using PRISMA checklists, and the quality of the evidence was graded using GRADE system. Conclusions: Probiotics may have a therapeutic effect on RA, based on the evidence provided by the SRs/MAs in this overview. Nevertheless, there is still a lack of conclusive evidence due to methodological limitations in the included research. To make trustworthy judgments regarding the efficacy of probiotics in the treatment of RA, more large-scale, high-quality randomized controlled trials are still required. [ABSTRACT FROM AUTHOR]

The unbalance current issue of the high-speed railway is the most prominent power quality of the traction power supply systems. Bullet trains can generate energy feedback when they brake, which should not be neglected. In this study, the effects of energy feedback on the unbalance issue are analysed, under different operating conditions of the trains. A collaborative unbalance compensation method (CUCM) for the high-speed railway is proposed in this work to lower the compensation capacity of the expensive power electronics compensation devices. To ensure that the CUCM works well, a further analysis of the two compensation principles, the railway power conditioner principle and Steinmetz principle, was carried out. The analysis results showed that the two compensation principles have different implementation methods and compensation current expressions, but the compensation essences were the same. According to the principle analysis results, a collaborative strategy was used. A capacity analysis of the CUCM, based on the actual operating situations of the bullet trains, was also completely done in this study. The simulation and experimental results showed that the proposed CUCM could adequately compensate the unbalance current of the high-speed railway power systems well with a low cost, in both traction and energy feedback situations. [ABSTRACT FROM AUTHOR]

In this paper, numerical techniques for simulation of magnetic domain structures of ferromagnetic materials using micromagnetics with large cells are investigated to save the computation cost. The exchange energy is modified to be applicable to large cells considering the angle between two neighboring cells. The demagnetizing energy is also modified to take account of erroneous magnetic surface charges which appear around the domain walls as a result of discretization. The method is then applied to a simple model and the result shows that an ideal vortex magnetic domain structure and domain wall motion can be represented [ABSTRACT FROM AUTHOR]

To solve power quality problem in V/V traction power supply system, a novel electrical magnetic hybrid power quality compensation system based on railway power conditioner (RPC) and magnetic static var compensator (MSVC) is proposed in this study. The RPC is only used to transfer active power and suppressing harmonics. The MSVC is used to compensate reactive power and suppress 3rd and 5th harmonic currents. The proposed hybrid compensation system will reduce the capacity as well as the DC-link voltage of RPC. The principle of negative, reactive and harmonic currents compensation is analysed first. And then, a collaborative control strategy is proposed to make the compensation system have a fast respond speed. At last the simulation and experiment results have verified the proposed structure and its control strategy effectively. [ABSTRACT FROM AUTHOR]

In this paper, an immune algorithm (IA)-based dead-time elimination PWM control strategy is proposed. For existing dead-time elimination applications, one of the major problems is the dead-time control around the zero-current-crossing points. To deal with this problem, this paper proposes a different PWM control method which first restricts the control sequence to a specified level around the zero-crossing zone. Also, the proposed method can improve the current waveform quality by using the IA approach and three-level control strategy. Compared with conventional dead-time elimination methods, this technique has the features of simple hardware requirement and adaptive control. Moreover, this control strategy effectively eliminates the effect of dead-time, while at the same time significantly reducing the total harmonic distortion of output current and improving the amplitude of output RMS value in different modulation indexes and loads conditions. To verify the analysis, an experimental platform based on DSP and field-programmable gate array is built. The simulation and experimental results are given to demonstrate the effectiveness and feasibility of this new method. [ABSTRACT FROM AUTHOR]

This paper focuses on analysis and suppression of circulating harmonic currents in a modular multilevel converter (MMC) considering the impact of dead time in medium-voltage applications. A continuous equivalent model of the MMC containing two ideal transformer models is presented. Using this model, the impact of a harmonic voltage upon the dc side is analyzed and the production mechanism of circulating harmonic currents is elucidated. At the same time, the impact of dead time and insulated gate bipolar transistor (IGBT) voltage drop (DTVD) is studied, which indicates that capacitor voltages, output harmonics, and circulating harmonic currents are influenced. Based on this analysis, an open-loop control strategy to suppressing circulating harmonic currents caused by the output current and DTVD is presented. Finally, all these conclusions are verified using a simulation platform with 14 modules per arm fed by a 14-kV dc voltage source and a downscaled experimental platform with four modules per arm fed by a 560-V dc voltage source. [ABSTRACT FROM AUTHOR]