Chemical vapor deposition (CVD) on Cu foils emerged as an important method for preparing high-quality and large-area graphene films for practical applications. However, to date it remains challenging to rapidly identify the structural features, especially the layer numbers, of CVD-graphene directly on Cu substrate. Herein, we report an O 2 -plasma-assisted approach for identifying the coverage, wrinkles, domain size, and layer number of large-area graphene films on Cu foils by optical microscopy. The wrinkles and grain boundaries of five-layer graphene can be observed with a grayscale increment of ∼23.4% per one graphene layer after O 2 -plasma treatment for only 15 s, which allows for checking graphene on Cu foils with a sample size of 17 cm × 20 cm in a few minutes. The Raman spectroscopy and X-ray photoelectron spectroscopy presents a strong layer number dependence of both the plasma induced graphene defects and Cu oxides, which, as indicated by molecular dynamic simulation, is responsible for the improved image contrast as a result of the interaction between O-ions and graphene with different layer numbers. We expect that this O 2 -plasma-assisted method would be applied to meter-scale samples if atmospheric-pressure plasma is used and therefore will be beneficial for the fast evaluation of CVD-graphene in both laboratory and industry.
A three-dimensional modelling approach is used to study the effects of operating and ambient conditions on the thermal behaviour of the spiral wound supercapacitor. The transient temperature distribution during cycling is obtained by using the finite element method with an implicit predictor-multicorrector algorithm. At the constant current of 2A, the results show that the maximum temperature appears in core area. After 5 cycles, the maximum temperature is 34.5°C, while in steady state, it’s up to 42.5°C. This paper further studies the relationship between the maximum temperature and charge-discharge current. The maximum temperature will be more than 60°C after 5 cycles at the current of 4A, and cooling measurements should be taken at that time. It can provide thoughts on inner temperature field distribution and structure design of the spiral wound supercapacitor in working process.
Direct-Driving Automated Mechanical Transmission (DAMT) gearshift actuator is a kind of electromagnetic linear actuator. In practical application, the actual gearshift force in each steady states is significantly different from the electromagnetic force model. For the optimization of gear shifting actuator with undetermined volume constraint, this paper presents a variable weight coefficient optimization method of electromagnetic linear actuator which equates the output forces under different steady states in the fitness function. These are intended to adjust the relationships among the optimized objects by using the fitness function to improve the overall optimization effect. In order to obtain the fitness value of each combination parameter accurately, finite element analysis (FEA) is adopted in this paper, to improve the efficiency of the algorithm, and a more efficient simulated annealing-particle swarm optimization algorithm (SA-PSO) is used by the proposed optimization method. Finally, experiment is carried out based on prototype of gearshift actuator to verify the optimization results. The results show that the maximum electromagnetic force and terminal electromagnetic force are both increased by more than 20%, and the volatility of gearshift force is reduced 26.4%, which ensures the structure compactness and fast response. The proposed method decreases the volatility by 27.5% compared with the constant weight coefficients and improves the gearshift force in each stage. INDEX TERMS DAMT, gearshift actuator, variable weight coefficient optimization, experiment.
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