We report a controllable and scalable fabrication approach for the superhydrophobic hierarchical structures and demonstrate the excellent ability to harvest water energy when applied to water-solid contact triboelectric nanogenerator (TENG). A strategy combined with multiple photolithography and micromolding process was developed to accurately regulate the diameters and the center distances of the two-level micropillars. A variety of hierarchical structures were successfully fabricated and presented the advantages of structure control, large scale, high accuracy, and high consistency. The hydrophobic property characterizations were conducted, and the results indicated that the hierarchical structures showed a larger contact angle than the single-level structures and achieved superhydrophobicity. Then the hierarchical structures were applied to water-TENGs with flowing water continuously dripping on, and the effect of the structure parameter on the triboelectric output was analyzed. The hierarchical structures exhibited a superior ability to harvest water energy than the flat film and the single-level structures due to the enhanced friction area and superhydrophobic property. At a flowing velocity of 8 mL/s, the hierarchical structure generated the output voltage of approximately 34 V and the short-circuit current of around 5 μA. The water-TENG device exhibited a power density peak of 7.56 μW/cm² with a resistive load of 16.6 MΩ at a flowing velocity of 10 mL/s. These findings shed light on the potential applications of the hierarchical structures-based water-TENGs to water energy harvesting and self-powered sensor devices.

In this paper, a quasi-static angular contact ball bearing model, considering assembly accuracy is constructed, while a numerical solution method for bearing stiffness under bad assembly state is established. A 7014C angular contact ball bearing is used as the research object and five groups of different spacer inclinations are designed to imitate the installation error of the spindle bearing. The bearing stiffness performance was comparatively analyzed, according to the five spacers. The effect of preload and rotation speed on bearing stiffness are systematically investigated, considering different parallelism errors, as induced by the spacers. The influence mechanism of the badly assembled bearing on the respective stiffness anisotropy is studied based on the proposed model. The results show that the variations of the inclination between the inner and outer rings of the bearing exhibit a very weak effect on the axial stiffness, while the influence on the radial and angular stiffness is more significant.

Silicon carbide (SiC) is widely used in high-power, high-frequency, and high-temperature electronic devices due to its excellent physical and chemical properties. However, its high hardness and chemical inertness make it difficult to achieve efficient and damage-free ultra-smooth surface processing with traditional polishing methods. This paper proposes a novel ultrasonic-assistance microarc plasma polishing (UMPP) method for high-quality and high-efficiency polishing of 4H-SiC. This study introduces a novel Ultrasonic-assisted Microarc Plasma Polishing (UMPP) method for achieving high-efficiency, high-quality surface finishing of 4H-SiC. The technique innovatively combines ultrasonic vibration with microarc plasma oxidation in a neutral NaCl electrolyte to overcome the limitations of conventional polishing methods. The UMPP process first generates a soft, porous oxide layer (primarily SiO₂) on the SiC surface through plasma discharge, which is then gently removed using soft CeO₂ abrasives. The key finding is that ultrasonic assistance synergistically enhances the oxidation process, leading to a thicker and more porous oxide layer that is more easily removed. Experimental results demonstrate that UMPP achieves a remarkably high material removal rate (MRR) of 21.7 μm/h while simultaneously delivering an ultra-smooth surface with a roughness (Ra) of 0.54 nm. Compared to the process without ultrasonic assistance, UMPP provides a 21.9% increase in MRR and a 28% reduction in Ra. This work establishes UMPP as a highly promising and efficient polishing strategy for hard and inert materials like SiC, offering a superior combination of speed and surface quality that is difficult to achieve with existing techniques.

The machining mechanism and process parameters of ultra-high strength steel 16Co14Ni10Cr2Mo are still lack of complete understanding. By changing the milling condition, the influence of process parameters on cutting force, such as Radial milling depth, Axial milling depth, Feed per tooth and milling speed, is studied,and in the meanwhile that the surface morphology and hardness of 16Co14Ni10Cr2Mo after machining are analyzed. Indicating that the milling force increases with the increase of axial milling depth, feed rate and radial milling depth. With the increase of milling speed, the milling force reduces. The effect of axial cutting depth and radial cutting depth on cutting force is maximum. For 16Co14Ni10Cr2Mo ultra-high strength steel, it is suitable to use small cutting depth and high milling speed. On the surface of milling material, partial melting and partial oxidation of chips occur. When the milling speed and feed rate increased, the surface hardness of the material did not change significantly, and there was no work hardening.