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Grafting nanomaterials on the carbon fiber (CF) surface is considered an effective strategy for enhancing the interfacial properties of CF-reinforced polymer composites (CFRPs). However, the mechanical properties of the CFs are often compromised during treatment. A new method for in situ growing silver nanoparticles (AgNPs) on the CF surface is proposed in this study. The CFs are first immersed in a low-viscosity silver nitrate solution to form a thin liquid film on the surface. Subsequently, using the abundant active particles in the plasma, the silver ions are reduced to silver atoms and grown into AgNPs on the CF surface. The tensile strength of CF@Ag was 38.74% greater than that of untreated CF, potentially due to the reparative action of AgNPs on defects in CF. The CF showed an evident improvement in surface wettability because of the AgNPs. Furthermore, the interfacial properties were noticeably improved, with the interfacial shear strength of CF@Ag increasing to 91.59 MPa, which was about twice that of pristine CF. Thus, the mechanical properties of composites are significantly improved (flexural strength increased by 190.74%). This study presents a non-destructive and convenient method for growing nanoparticles onto CF to establish a robust interface in CFRPs. [ABSTRACT FROM AUTHOR]

Lithium–ion batteries are key elements of electric vehicles and energy storage systems, and their accurate State of Charge (SOC) estimation is momentous for battery energy management, safe operation, and extended service life. In this paper, the Multi-Kernel Relevance Vector Machine (MKRVM) and Whale Optimization Algorithm (WOA) are used to estimate the SOC of lithium–ion batteries under different operating conditions. In order to better learn and estimate the battery SOC, MKRVM is used to establish a model to estimate lithium–ion battery SOC. WOA is used to automatically adjust and optimize weights and kernel parameters of MKRVM to improve estimation accuracy. The proposed model is validated with three lithium–ion batteries under different operating conditions. In contrast to other optimization algorithms, WOA has a better optimization effect and can estimate the SOC more accurately. In contrast to the single kernel function, the proposed multi-kernel function greatly improves the precision of the SOC estimation model. In contrast to the traditional method, the WOA-MKRVM has a higher precision of SOC estimation. [ABSTRACT FROM AUTHOR]

Thermal defects widely occur in electrical equipment and affect its stable operation. This paper proposes a novel detection method based on derivatives for thermal defects of electrical equipment. First, the equivalent models of the equipment are established to analyze the surface temperature formed by different defects. Second, the theoretical foundation of the derivative-based detection method is described, and numerical calculations on thermal defect detection based on derivative characteristic curves are carried out. The results show that the method can detect the position effectively and calculate the depth with an error of 1.6%. Then, the thermal defects in different situations are analyzed, and the results indicate that the method is effective in all cases. Finally, the experiment is conducted by artificially preparing samples with thermal defects, and the achieved calculation error of the experimental results is within 3.3%, which indicates the validity of this method. [ABSTRACT FROM AUTHOR]

As the unique power entrance, the pantograph–catenary plays a vital role in providing traction power for high-speed railways. Along with the operational velocity of trains constantly increasing, the poor contact between the contact wire and the pantograph strip happens frequently due to the "rigid point" existing on the contact wire, forming the "off-line" phenomenon. The off-line phenomenon is normally accompanied by the pantograph–catenary arc occurring, which seriously threatens the safety of the power supply for the high-speed train. Nowadays, as some railways have been built in remote places at high altitude, the motion characteristics of the pantograph–catenary arc under the sub-atmospheric pressure with strong airflow are extremely different from the case under normal pressure. Herein, a pantograph–catenary arc experimental platform is built for observing the evolutionary process of the arc under the sub-atmospheric pressure strong-airflow condition. The impact brought from different air pressures and airflows on the arc is analyzed, as the experimental results show that the pantograph–catenary arc has different motion characteristics when the arcing process is at different stages. To further explore the reason resulting in the varying motion characteristics of the arc, a multi-stress coupled force analysis model is established, with the consideration of the influence of air pressure, wind load, thermal buoyancy, air resistance, arc self-magnetism, etc. From the perspective of force acting on the arc, the arc formation mechanism at the development evolutionary stages is investigated under sub-atmospheric pressure strong-airflow conditions, which lays a theoretical foundation for effectively restraining the pantograph–catenary arc. [ABSTRACT FROM AUTHOR]

In this paper, a surface discharge test was conducted on a silicone rubber insulating sheet, an epoxy resin insulating sheet, a porcelain insulating sheet, and a glass insulating sheet by using an independently constructed test platform of insulating media to study the discharge characteristics along the surface of insulating media under low air pressure and strong airflow environment. Experiments were conducted to obtain the variation in the discharge characteristics along the surface of the four kinds of insulation media with respect to airflow velocity at different air pressures. The discharge voltage characteristics and discharge morphology characteristics along the surface of the insulating media in a strong airflow environment at low air pressure are elucidated. This paper provides theoretical support for the selection of insulation materials and insulation protection design for a low air pressure and strong airflow environment. [ABSTRACT FROM AUTHOR]

Cold atmospheric-pressure plasma is used widely for treating material surfaces and can be considered for modifying insulation paper (IP) to improve its surface performance. However, the mechanism for interaction between reactive oxygen species (ROS), which are the dominant components of such plasma, and IP is important for setting experimental parameter values but is difficult to observe experimentally. In this paper, reactive force field molecular simulation technology is used to study the mechanism for interaction between ROS (O atoms, OH radicals, and H2O2 molecules) and cellulose, which is the main component of IP. The results show that the ROS can abstract H atoms, and the H2O2 molecules can also abstract hydroxyl groups from a cellulose chain, resulting in changes to the cellulose chain structure, such as reductions of the hydroxyl groups and pyran rings and formations of aldehyde and vinyl groups. The three types of ROS exhibit different reactivities when reacting with the cellulose chain, and the difficulty of breaking different bonds therein also differs, which influences how the chemical groups change the cellulose chain. This study provides basic insight into the mechanism for interaction between ROS and IP at the atomic level as well as offering some guidance for practical experiments. [ABSTRACT FROM AUTHOR]

The induced airflow velocity level and the mechanical efficiency are the significant issues for the surface DBD flow control application. In this paper, the effects of optical characteristics, electrical performances and mechanical properties of surface DBD with composite dielectric glass/PI film are investigated. The current, discharge plasma morphology, electrical power consumption, and induced airflow velocity are analyzed at applied voltage 17-23 kV with working frequency 9.15 kHz. The experiment results indicate that with the addition of PI film, the discharge just occurs near the exposed electrode and is suppressed obviously in the negative half cycle of current. Though the induced airflow velocity decreases slightly about 0.1-0.2 m/s at each voltage level, the mechanical efficiency substantially improves. The maximum mechanical efficiency increases by 25.12% under the 23 kV. [ABSTRACT FROM AUTHOR]

Contact wire is an essential part of traction power supply system in the electrified railway, which on the one hand transmits the electrical energy, and on the other hand plays as a smooth track for the current collection strip. In the daily operation of the electrified train maintenance, the contact wire suffers from the arcing ablation during the pantograph lowering process. Potential contact wire breakdown might take place. In this paper, the surface erosion of the contact wire by the pantograph arcing was studied numerically. A multi-physical model dedicated to the contact wire erosion issues was established, with the process of heat transfer, phase transition, and liquid metal flow taken into account. Characteristics of the surface erosion, the temperature field as well as the flow field under different current conditions were studied respectively. Particularly, the Marangoni effects on molten pool evolutions were examined, which could have a significant influence on the final erosion characteristics. This work might be helpful for the further understanding of the basic physical process of the contact wire erosion by the pantograph arcing, and as well as providing a meaningful reference for the performance improvement of the current collection system. [ABSTRACT FROM AUTHOR]