With zinc acetate and butyl titanate as raw materials, pure ZnO and ZnTiO₃/ZnO composite photocatalysts were synthesized by a sol–gel method and calcined at 550 °C. The crystal structure, morphology, surface area, optical property, and element valence states of samples were characterized and the photocatalytic activity of the prepared photocatalysts were assessed by the degradation of rhodamine B. Results show that the crystal structure of ZnO is a hexagonal wurtzite phase with a band gap of 3.20 eV. When the Zn/Ti molar ratio reaches 0.2, ZnTiO₃ phase appears and ZnTiO₃/ZnO composite forms, which advances the transfer of photogenerated charges. ZnTiO₃/ZnO (Ti/Zn = 0.2) exhibits the highest photocatalytic activity, and the degradation degree of RhB reaches 99% after 60 min, which is higher than that of pure ZnO (90%). An exorbitant Ti/Zn molar ratio will reduce the crystallinity and form more amorphous components, which is not conducive to photocatalytic performance. Therefore, when the Ti/Zn molar ratio exceeds 0.2, the photocatalytic activities of ZnTiO₃/ZnO composites decrease.

Using butyl titanate and absolute ethanol as raw materials, TiO₂ was prepared by a hydrothermal method with different hydrothermal times, and the influences of hydrothermal time on the structure and photocatalytic performance of TiO₂ were investigated. The obtained samples were characterized by XRD, SEM, TEM, BET, PL and DRS, separately. The results show that TiO₂ forms anatase when the hydrothermal time is 12 h, forms a mixed crystal composed of anatase and rutile when the hydrothermal time is 24 h, and forms rutile when the hydrothermal time is 36 h. With the extension of hydrothermal time, anatase gradually transforms into rutile and the surface area decreases. Although TiO₂-24 h and TiO₂-36 h show lower photoinduced charge recombination and higher light source utilization, TiO₂-12 h exhibits the highest photocatalytic activity owing to its largest surface area (145.3 m²/g). The degradation degree of rhodamine B and tetracycline hydrochloride reach 99.6% and 90.0% after 45 min.

The anatase/rutile mixed crystal TiO₂ was prepared and modified with Ag decoration and SnO₂ coupling to construct a Ag@SnO₂/anatase/rutile composite photocatalytic material. The crystal structure, morphology, element valence, optical properties and surface area were characterized, and the effects of Ag decoration and SnO₂ coupling on the structure and photocatalytic properties of TiO₂ were studied. Ag decoration and SnO₂ coupling are beneficial to reduce the recombination of photogenerated electrons and holes. When the two modification are combined, a synergistic effect is produced in suppressing the photogenerated charge recombination, making Ag@SnO₂/TiO₂ exhibits the highest quantum utilization. After 30 min of illumination, the degradation degree of tetracycline hydrochloride (TC) by pure TiO₂ increased from 63.3% to 83.1% with Ag@SnO₂/TiO₂.

Tooth surface wear is an essential factor that affects gear transmission system dynamic characteristics and must be considered in monitoring the health status of gear systems. In this study, a coupled bending and torsion dynamic model is first established. The internal excitation changes under the influence of tooth surface wear and geometric errors, including the time‐varying meshing stiffness and comprehensive meshing error, are calculated using the method proposed by the authors in a previously published paper. Subsequently, a quasi‐static wear model of a tooth surface is established based on the Archard wear formula. The two proposed models are combined to simulate the changes in the wear area and depth of involute gear pairs and to investigate the influence of tooth surface wear on gear system dynamic characteristics. Several sets of simulation results are used to demonstrate the relationship between the tooth surface wear and gear system dynamic characteristics. The coupled analysis method and findings presented in this study are of great significance for the fault diagnosis and health monitoring of gear transmission systems.

Reliability assessment of multi-component systems under competing degradation and random shocks has been intensively investigated in recent years. In most cases, the parameters associated with competing degradation and random shocks are represented by crisp values. However, due to insufficient data and vague judgments from experts, it may produce epistemic uncertainty with those parameters and they are befitting to be described as fuzzy numbers. In this article, the internal degradation is treated as a continuous monotonically increasing random process with respect to operating time, whereas the amount of cumulative damage produced by each external random shock is modeled by a geometric process. As components in a system suffer the same environmental condition, an external random shock will produce different amounts of cumulative damage to each component simultaneously. Each component fails when either the internal degradation or cumulative damage from the random shocks, whichever comes first, exceeds its corresponding random thresholds. Moreover, the parameters associated with the internal degradation and the random shocks are represented by triangular fuzzy numbers. The fuzzy reliability functions of components and the entire system are evaluated by a set of optimization models. A multi-component system, together with some comparative results, is presented to illustrate the implementation of the proposed method.