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In this paper, based on the theoretical research of structural modal analysis, different types of phonon crystal modal structures are designed for the first time, and the characteristics and the generation mechanism of the bandgap were studied through theoretical calculations and experiments. According to the phenomenon in the experimental results, we can find that the vibration transmission characteristics of phonon crystal structure α3 are the best, and it is also superior to that of phonon crystal structure α10 (full period structure). Therefore, the comparison of theoretical analysis with experimental phenomena shows that the bandgap generation mechanism should be modal resonance instead of local resonance in the finite periodic structure. The profound reason lies in there is no separate Z direction local vibration mode of periodic structure in the vibration mode of finite structure, and the bandgap of finite structure is the mode superposition torsional resonance mechanism between scatterer and substrate mode.

High-power gears are widely used in various engineering fields. A gear transmission system is an extremely complex elastic system that produces complex vibrations under internal and external excitation. In this study, the excitation value in the gear was obtained based on the dynamic characteristics, stiffness, and error excitation, which were used as the input signals of the discrete element analysis. The dynamic model of the gear transmission system was established using the discrete element method. Meanwhile, the gear transmission energy was dissipated through the configuration of a particle damper in the gear. The continuous-discontinuous dynamic coupling method, which is the equivalent displacement mapping of gear contact loads from the discontinuous domain to the continuous element node, was realised, and the transformation of the local coordinates to the global coordinates was conducted. Finally, the effect of the particle restitution coefficient on the vibration reduction of gearboxes at various speeds was explored and verified through an experiment. At low rotating speeds, the best vibration reduction effect was achieved when the particle restitution coefficient was 0.2. At high rotating speeds, the best restitution coefficient was 0.7.

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Background: Postoperative sleep disturbance (PSD) is a common and uncomfortable experience for patients, which induces various negative clinical outcomes and increases the perioperative mortality. Thus, it is necessary to seek efficient methods to improve PSD. This study was designed to explore whether perioperative intravenous S-ketamine could improve sleep quality. Methods: Patients undergoing elective thoracoscopic surgery were recruited and assigned into two groups randomly. 0.5 mg/kg of S-ketamine was given to the individuals in the experimental group during the period of anesthesia induction followed by 0.1mg/kg/h intravenous infusion until 15 minutes before the completion of the procedure, while normal saline in the same protocol was performed in the control group. The primary outcomes included the salivary melatonin (MT) concentration on the first day after surgery, and the Richard Campbell Sleep Questionnaire (RSCQ) scores on the first three days postoperatively. The secondary outcomes were the rest and movement Visual Analogue Scale (VAS) score at 6, 12, 24, and 48 hours postoperatively, the level of serum IL-6 and IL-10 on the first day postoperatively, and the incidence of postoperative negative complications. Results: In the experimental group, the RSCQ scores on the first three days postoperatively and the level of MT on the first day after the procedure were significantly higher, and the rest and movement pain intensity at postoperative 6, 12 and 24 hours were statistically lower when compared with the control group, while the results at 48 hours postoperatively were comparable in both groups. In addition, the higher level of IL-6 and lower level of IL-10 postoperatively were noticed in the experimental group. In both groups, the incidence of negative outcomes was similar. Conclusion: S-ketaminecan effectively improve postoperative sleep quality, and reduce pain intensity and inflammation in patients undergoing thoracoscopic surgery.