A proton exchange membrane fuel cell (PEMFC), as an efficient energy conversion device, has many advantages, such as high energy conversion efficiency and environmentally friendly zero emissions, and is expected to have great potential for addressing the uneven distribution of global green energy. As a core component, the performance of the proton exchange membrane (PEM) directly affects the overall output of the fuel cell system. At present, Nafion membranes with good, comprehensive properties are the most widely used commercial proton exchange membrane materials. However, Nafion membranes demonstrate a great inadaptability with an increase in operating temperatures, such as a rapid decay in proton conductivity. Therefore, enhancing the overall performance of Nafion membranes under high temperatures and low relative humidity (RH) has become an urgent problem. Although many efforts have been made to solve this problem, it is difficult to find the balance point between high-temperature conductivity and overall stability for researchers. In this paper, we summarize the recent approaches to improving the operating temperature of Nafion membranes from the following two perspectives: (1) using different materials for the modification of Nafion membranes, and (2) applying different modification methods to the Nafion membranes. Based on the structural and functional characteristics of Nafion, the non-destructive targeted filling of fillers and the efficient synergy of the two-phase region are two vital research directions for the preparation of high-performance composite membranes.

In this study, RuT400(σ_b ≥ 500 MPa) was milled with different cutting speeds, feeding rates and cutting depths to construct cutting force and surface roughness prediction models via response surface method (RSM). The milling parameters were optimised via response surface, contour map and iterative algorithm. The results show that that feeding rate and cutting depth are factors that significantly affect the cutting force. Similarly, cutting speed and feeding rate were found to be significant in regards to surface roughness. The multivariate linear equations yield more accurate surface roughness and cutting force predictions than fitting the linearised multivariate non-linear equations. The cutting force prediction model is F = 60.823 − 0.020V + 149.489f + 41.932a; the surface roughness prediction model is Ra = 1.633 − 0.00161V + 1.803f + 0.0289a. The use of high-strength tools and a high-endurance manufacturing system for cutting force can greatly enhance the machining efficiency in a processing system with favourable rigidity.

To address the challenges of inefficient Camellia oleifera fruits harvesting in hilly and mountainous regions due to the difficulty of using large machinery, a handheld vibration harvesting device for Camellia oleifera fruits was designed. Based on the vibration-induced detachment process of Camellia oleifera fruits, a single-pendulum dynamic model of the “fruit-branch” system was established and solved to calculate the tangential acceleration required for fruit detachment. The key factors influencing harvesting efficiency were identified as vibration frequency, amplitude, height, and duration. Using ANSYS, modal response and harmonic response analyses were conducted on a 3D model of the Camellia oleifera tree to determine the operational parameters ensuring branch acceleration meets the fruit detachment. Furthermore, a rigid-flexible coupling simulation system integrating the harvesting device and Camellia oleifera tree was developed on the ADAMS. This analysis revealed the variation patterns of branch acceleration with respect to vibration frequency and clamping height, thereby validating the rationality of the dynamic model and the feasibility of the device. Finally, an orthogonal experiment was designed using Design-Expert 13, and multi-objective optimization analysis was performed on the device’s working parameters based on the experimental data. The aforementioned research identified the optimal working parameter combination and actual harvesting performance of the handheld vibration harvesting device: when the vibration frequency is 14 Hz, vibration height is 980 mm, and vibration duration is 13 s, the fruit picking rate reaches 95.22%. The harvesting efficiency of this device is significantly higher than manual picking methods, fully meeting the requirements for efficient Camellia oleifera fruit harvesting.

The white layer formed in hard cutting is widespread due to the intensive property of hardened steels and it also has important effects on machined surface integrity and service performance. In order to study the issue about the formation of white layer and concluding the relationship between the characteristics of white layer, tool flank temperature and the thermal conductivity, we used SCM415 (carburizing and quenching) as the object to carry out a series of high-speed dry cutting tests and observing the white layer by using optical microscope Axio Scope A1 in this paper. By analyzed these results we found that the temperature of tools is lower when the thermal conductivity of tool is higher and the greater the thermal conductivity of tool is, the more obvious the influence of the temperature change on the flank face is. When the flank temperature increased, the thickness of white layer increased. However, the white layer thickness is reduced, when the flank temperature are more than a certain range. Flank wear in a certain range can reduce the thickness of white layer and improve the surface quality.