Search

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.

Droughts or floods are usually attributed to precipitation deficits or surpluses, both of which may become more frequent and severe under continued global warming. Concurring large-scale droughts in the Southwest and flooding in the Southeast of China in recent decades have attracted considerable attention, but their causes and interrelations are not well understood. Here, we examine spatiotemporal changes in hydrometeorological variables and investigate the mechanism underlying contrasting soil dryness/wetness patterns over a 54-year period (1965–2018) across a representative mega-watershed in South China—the West River Basin. We demonstrate that increasing rainfall intensity leads to severe drying upstream with decreases in soil water storage, water yield, and baseflow, versus increases therein downstream. Our study highlights a simultaneous occurrence of increased drought and flooding risks due to contrasting interactions between rainfall intensification and topography across the river basin, implying increasingly vulnerable water and food security under continued climate change. Increasing rainfall intensity produces opposite hydrological effects across a large river basin in South China (drying in the uplands vs. wetting in the lowlands) due to spatially contrasting interactions between rainfall intensification and topography. [ABSTRACT FROM AUTHOR]

As a surface peening technique, shot peening introduces residual compressive stresses to the surface of the part, which effectively increases the fatigue life of the structure and material. However, when structures are subjected to alternating loads, this can lead to stress relaxation on the material surface, weakening the effectiveness of the shot peening process. In addition, reasonable shot peening parameters are essential. In this paper, the effects of shot peening pressure and shot coverage on the fatigue life of materials during shot peening were investigated, followed by fatigue tests on 20CrMnTi specimens using a high-frequency fatigue testing machine to study the effects of shot peening and re-shot peening on the fatigue life of shot-peened materials after different load cycles. The results show that a reasonable shot peening pressure and coverage rate can significantly improve the fatigue life of the material, while a shot peening pressure higher than 0.4 MPa will reduce the fatigue life of the material 20CrMnTi. Coverage rates of 100% and 200% can both improve the fatigue life of the material, while a 200% coverage rate has a better strengthening effect. Re-shot peening removes the residual compressive stress relaxation on the surface of the material caused by cyclic loading and improves the fatigue life of the material. The maximum value of the residual compressive stress on the surface of the test material after shot peening is 443 MPa, and after a certain number of fatigue loads, the residual compressive stress on the surface is reduced to 203 MPa, which is subjected to secondary shot peening, and the residual compressive stress is restored to 415 MPa, and the fatigue life is significantly increased. When the second shot peening time is taken as 25% of the fatigue life of the initial shot blasting of the material, the shot peening effect is better. [ABSTRACT FROM AUTHOR]

High-speed trains have a large amount of ancillary equipment, which is suspended from the underside of the train by means of a suspension structure. Due to the large mass of the ancillary equipment, the suspension structure is subjected to various loads during train operation and there is a risk of fatigue failure. In this paper, the stress distribution at the suspension point and the lo-cation of the maximum stress point under load are investigated in detail based on actual test loads at the suspension point and finite element simulation analysis. In order to further investigate the fracture failure of the suspension points, experimental studies were carried out. Firstly, static strength tests were carried out to obtain the load–displacement curves of the structural members and to determine the fracture strength of the structure based on the displacement sensors, and secondly, fatigue tests at different stress levels were carried out to obtain the load–life curves of the structural members and to investigate the probabilistic load–life curves at different reliability levels. The test results show that the structural component has a high fracture strength of 65kN, while the conditional fatigue strength is relatively low, corresponding to a load level of 12.5kN at a median life of 106 cycles. The above research work provides the necessary basis for the design, optimization and reliability assessment of the suspension structures of high-speed trains. [ABSTRACT FROM AUTHOR]

Older adults tend to rate unfamiliar faces higher on trustworthiness than do their younger counterparts. Although the saying goes "look before you leap", it is still unknown whether such a strategy could also apply to facial trustworthiness perception, and our understanding of the time course in facial trustworthiness perception also remains unclear. Here, we have argued that a cognitive controlled process suggested by "socioemotional selectivity theory" could potentially lead to such biased trustworthiness perception. Two experiments were conducted to test the association between viewing time and trustworthiness perception. The first study used hierarchical linear modeling in a sample of younger (N = 30, Mage = 20.53, SD = 1.61, 50% female) and older (N = 30, Mage = 63.27, SD = 3.14, 43% female) adults, and found that viewing time and trustworthiness evaluation were positively associated. Using the same stimuli, our second study further manipulated viewing time by two levels (500 ms vs. 3000 ms) and compared younger (N = 28, Mage = 23.93, SD = 2.68, 50% female) and older (N = 30, Mage = 64.47, SD = 4.32, 50% female) adults' facial trustworthiness evaluation. As expected, a significant three‐way interaction revealed that viewing time only impacted older adults' facial trustworthiness evaluation, and only when given shorter viewing time did older adults show similar facial trustworthiness ratings as younger adults. The present study is the first to directly investigate the relationship between older adults' viewing time on unfamiliar faces and their perception of facial trustworthiness. Findings suggested that a second thought in facial perception may not benefit older adults' trustworthiness evaluation. [ABSTRACT FROM AUTHOR]