Mingge Wu

A well-designed flow field structure can effectively reduce mass transport losses in Proton Exchange Membrane Fuel Cell (PEMFC) under high current densities. Most optimization designs focus on two-dimensional equidistant-depth flow fields, while research on nonequidistant-depth three-dimensional flow fields remains limited. This study introduces a novel nonequidistant-depth 3D flow field and utilizes rapid laser ablation technology to fabricate metal bipolar plates. Numerical simulations are performed to analyze gas flow velocity, reactant distribution, and fuel cell performance across flow field structures with varying inclinations and trapezoidal block heights. Results indicate that optimal fuel cell performance is achieved with a flow field where the channel tilt height and trapezoidal block height are both 0.3 mm. Compared to the parallel flow field, the proposed design significantly enhances flow velocity at the Channel-GDL interface and ensures a higher, more uniform reactant concentration at the GDL-CL interface. The maximum power density reaches 1.551 W/cm², representing a 39.48% increase, with only a 10.79% rise in water content, highlighting effective water management.

The Ring Main Unit (RMU) is a critical device in power distribution systems used for connecting and distributing electricity. However, due to its compact ... Jove

Hydroponic lettuce was prone to pest and disease problems after transplantation. Manual identification of the current growth status of each hydroponic lettuce not only consumed time and was prone to errors but also failed to meet the requirements of high-quality and efficient lettuce cultivation. In response to this issue, this paper proposed a method called YOLO-EfficientNet for identifying the growth status of hydroponic lettuce. Firstly, the video data of hydroponic lettuce were processed to obtain individual frame images. And 2240 images were selected from these frames as the image dataset A. Secondly, the YOLO-v8n object detection model was trained using image dataset A to detect the position of each hydroponic lettuce in the video data. After selecting the targets based on the predicted bounding boxes, 12,000 individual lettuce images were obtained by cropping, which served as image dataset B. Finally, the EfficientNet-v2s object classification model was trained using image dataset B to identify three growth statuses (Healthy, Diseases, and Pests) of hydroponic lettuce. The results showed that, after training image dataset A using the YOLO-v8n model, the accuracy and recall were consistently around 99%. After training image dataset B using the EfficientNet-v2s model, it achieved excellent scores of 95.78 for Val-acc, 94.68 for Test-acc, 96.02 for Recall, 96.32 for Precision, and 96.18 for F1-score. Thus, the method proposed in this paper had potential in the agricultural application of identifying and classifying the growth status in hydroponic lettuce.

In order to address the time-consuming and labor-intensive challenges as well as the suboptimal operational quality encountered in the conventional processes of fruit bagging within expansive orchards, an innovative end-of-bagging actuator is proposed, which can be installed on a fruit-production robot. Due to the excessive power sources required to complete the bagging operation, while also taking into account the quality and cost of the end effector, we have implemented a clutch transmission system to control individual motors, thereby achieving efficient bag-opening and collection actions. Through kinematic analysis of the bagging end effector, the optimal bag opening size is determined to be 40.3372 mm, with a deviation of 0.1428 mm from the design target and an error rate of 0.35%. This ensures the desired bag size for bagging juvenile fruits. Moreover, a dynamic simulation model comprising rigid drive components and a flexible clutch was developed. The simulation results demonstrate the system’s stable performance. However, it is evident that the gear speed falls below that of the flexible clutch, resulting in insufficient bag opening and bag gathering compared to the intended design target. The observed phenomenon is a result of the characteristics exhibited by the flexible clutch. Specifically, the demands for bagging and stretching can be accommodated by modifying the stiffness and geometric configuration of the flexible clutch, alongside the level of operational force. To conclude, the suggested end effector can successfully simulate the implementation of the manual bagging process. By taking into account the quality and cost of the end effector, a clutch drive system was utilized to regulate a single motor, resulting in efficient bag-opening and collection actions. This approach offers a more integrated and efficient solution compared to manual bagging and semi-automatic mechanically assisted bagging methods.

When cleaning the surface of a glass greenhouse, the washing machine often encounters slippery tracks or strong winds, in which case the washing machine is very likely to deviate from the axis of the greenhouse. In order to improve the stability and reliability of the glass greenhouse cleaner under different working conditions, this paper studies the controller of the glass greenhouse cleaner and puts forward a fuzzy PID control scheme optimized by the PSO algorithm. Using Adams and Matlab to jointly simulate the machine model, the results show that the particle swarm fuzzy PID controller has the best control effect and can make the cleaner adaptable to a variety of working conditions. The system overshoot was reduced by up to 35.5%, the response time by up to 3 s, and the difference between left and right wheel speeds by up to 0.086 deg/s.

The internal structure of the Ring Main Unit is compact, the gap between the components is limited, and the heat dissipation performance is poor. Working in a high temperature environment for a long time will lead to structural deformation and aging, which will affect the service life and insulation performance, and may even lead to electrical accidents. In order to better solve such problems, this study uses the finite element multi-physics coupling simulation model. According to the characteristics of the Ring Main Unit, the internal components and the body are simplified, the calculation amount is reduced and the simulation accuracy is improved. In ANSYS Workbench, through the coupling calculation of steady-state heat and transient heat, the temperature distribution of the Ring Main Unit circuit under the condition of external temperature is obtained. The temperature change and distribution are further used for the thermal stress and strain analysis of the structural field to obtain the thermal strain distribution map of the conductive circuit under the influence of temperature, which provides theoretical support for the internal structure design of the new Ring Main Unit.

To address the issues of the existing dry granulation process, which mostly relies on manual adjustments based on empirical experience and lacks the analysis of theoretical data, a simplified model of tablet pressing based on a modified Drucker–Prager Cap (DPC) material constitutive model was proposed to simulate and analyze the forming process of tablets, and study the impacts of the feeding speed, roller speed, friction coefficient and roller clearance on the density distribution of the pressed tablets via ABAQUS. The results show that the roller speed significantly impacts the density of tablets, and a lower roller speed and a higher friction coefficient are beneficial to the formation of tablets. As the roller clearance decreases, the average density at the clearance increases, and the unevenness of the lateral density distribution of the tablets increases, showing a distribution trend of larger density at the center and smaller density on both sides.

In this paper, a method to improve the performance of PEMFCs using porous material as a flow channel baffle is proposed. The results show that PEMFCs with four porous baffles flow channels have better performance at high current density compared with the traditional flow channel. The structural parameters of the flow channel explored in this study include porosity, the thickness of the baffle and the number of baffles, and their influence on the performance of PEMFCs. Sensitivity analysis results show that the performance of the PEMFCs with the porous baffle channel is the most sensitive to baffle thickness, and the thickness and baffle could be appropriately adjusted. The number of plates and porosity of the baffle are adjusted to improve the performance of the PEMFCs.