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In order to solve the issue of pantograph arcing on trains passing through neutral sections caused by excessive pressure differentials between both ends of these sections, a safety concern for train operation, this paper presents a voltage control system for flexible neutral section passing based on the line-level energy management system (EMS). The system obtains voltage control commands to control the energy dispatching equipment (EDE) by collecting the status information of the traction network, thereby achieving voltage balance between both ends to ensure smooth passage of trains through neutral sections. This study explored the principle of voltage regulation. A model for EMS voltage regulation was built to simulate the AC power supply system of Chongqing Rail Transit (CRT) Line 15. The simulation revealed that voltage control based on EMS effectively maintained voltage balance by reducing the voltage difference across neutral section ends by more than 20%. This study finding substantiates the efficacy and feasibility of the proposed control system.

Train regenerative braking energy accounts about 10%~30% of the total traction energy, and its efficient utilization is of great importance to building green and low-carbon railway traction power supply system. Traditional railway traction power supply system consists of multiple independent sections, and energy cannot be transferred between sections. This restricts the utilization of regenerative energy in the traction power supply system. To solve this problem, this paper proposes a networked traction power supply system, where energy dispatching equipment is installed in the section post to connect adjacent sections. Topology of the networked traction power supply system and principles of the energy dispatching equipment are introduced in this paper, and energy dispatching equipment group's optimal strategy aimed for cost reduction is proposed too. The simulation result shows that compared with the traditional traction power supply system, the forward energy of networked traction power supply system can be reduced by 17.3%, and the maximum power of substation can be reduced by about 19.0%. The correctness and effectiveness of the networked traction power supply system's working principle and dispatching strategy are verified.

Polymer derived ceramics (PDCs) has been greatly developed over the past 40 years, due to its advantages of simple operation, low sintering temperature and strong design ability. The research progress of porous PDCs, including template method, foaming method, freeze casting technology, additive manufacturing technology and other preparation methods is reviewed in this paper. In addition, the molecular side chain design and synthesis of ceramic precursors such as polycarbosilane, polysiloxane and polysiloxane for adjusting the composition, microstructures and mechanical properties of porous PDCs are summarized. It is proposed that the design of ceramic precursors and the additive manufacturing method may be the future development direction in porous PDCs.

Escalators are now more and more widely used around the world. As escalator accidents occur from time to time, it is very important to analyze the structure and reliability of escalators. This paper studies the structure and reliability analysis methods of typical escalators. By applying parametric analysis methods, the efficiency and accuracy of escalator structure analysis are greatly improved. Because the failure of each structural member of the escalator truss system is dependent, this paper applies the dependent failure reliability modeling method and analyzes the reliability of the escalator truss system. The results show that the reliability analysis method of the truss system after considering the dependent failure is more reasonable. The above research work has certain reference significance for the design and analysis of escalators.

In order to meet the need of high thrust ratio aero engine working in long term thermal oxidation environment and the stealth requirement of key thermal structural components of aero engine, silicon carbide ceramic matrix composites are developed towards crack self-healing and structure-wave absorbing integration. In this paper, the design principles of silicon carbide ceramic matrix composites in strengthening and toughening, crack self-healing and electromagnetic wave absorption are introduced. The research progress in these three aspects is reviewed. The future development trend of structural and functional CMC-SiC is the combination of high strength and toughness, self-healing antioxidation and electromagnetic wave absorption.

Silicon carbide matrix composite reinforced by both SiC and carbon fibers [(SiC-C)/PyC/SiC] to alleviate the thermal residual stresses (TRS) between carbon fiber and SiC matrix, then reduce the microcracks in the SiC coating as well as in the matrix, was fabricated by chemical vapor infiltration (CVI) process. Compared with C/PyCHT/SiC composite in which PyC interphase was heat-treated at 1800°C in argon to lower the fracture energy of the interphase, the TRS in SiC matrix and SiC coating was reduced by 69.5% and 62.2%, respectively. Coating cracks density was 50 cracks/m for (SiC-C)/PyC/SiC composite, and 1090 cracks/m for C/PyCHT/SiC composite. Carbon phases could be protected in (SiC-C)/PyC/SiC composite when the composite was subjected to temperatures ranging from 700°C to 1300°C in air for 10 h. The residual strength of (SiC-C)/PyC/SiC composite was higher than those of C/PyCHT/SiC composite below 1200°C. The residual strength of (SiC-C)/PyC/SiC composite was lower than those of C/PyCHT/SiC composite at 1300°C because of the recession of SiC fiber.