Purpose: The best treatment strategy for primary spontaneous pneumothorax is controversial and varies widely in practice.Methods: Literatures were searched from databases till 24 August 2021. A Bayesian network meta-analysis was conducted to compare the outcomes of various treatments with the following endpoints: recurrence rate, postoperative chest tube duration, postoperative air leakage duration, length of hospital stay, and complications rate.Results: In all, 7210 patients of 20 randomized controlled trials and 17 cohort studies were included. Surgery had a significantly lower recurrence rate compared to other treatments. Besides, bullectomy (BT) combined with chemical pleurodesis (CP), mechanical pleurodesis, or staple line coverage (SLC) can reduce the recurrence rate compared to BT alone, but none of them were statistically significant. In terms of reducing chest tube duration, BT with tubular Neoveil outperformed BT + pleural abrasion (mean difference [MD], 95% confidence interval [CI]: −2.5 [−4.63, −0.35]) and BT + apical pleurectomy (MD, 95% CI: −2.72 [−5.16, −0.27]).Conclusions: Surgical methods were superior to manual aspiration (MA), chest tube drainage (CTD), and conservative treatment in terms of recurrence reduction. There was no significant difference between MA and CTD in reducing the recurrence rate. Among surgical methods, CP is more effective than mechanical pleurodesis and SLC among the additional procedures based on BT.

The failure of the key parts, such as gears, in cutter head driving system of tunneling boring machine has not been properly solved under the interaction of driving motors asynchronously and wave tunneling torque load. A dynamic model of multi-gear driving system is established considering the inertia effects of driving mechanism and cutter head as well as the bending-torsional coupling. By taking into account the nonlinear coupling factors between ring gear and multiple pinions, the influence for meshing angle by bending-torsional coupling and the dynamic load-sharing characteristic of multiple pinions driving are analyzed. Load-sharing coefficients at different rotating cutter head speeds and input torques are presented. Numerical results indicate that the load-sharing coefficients can reach up to 1.2–1.3. A simulated experimental platform of the multiple pinions driving is carried out and the torque distributions under the step load in driving shaft of pinions are measured. The imbalance of torque distribution of pinions is verified and the load-sharing coefficients in each pinion can reach 1.262. The results of simulation and test are similar, which shows the correctness of theoretical model. A loop coupling control method is put forward based on current torque master slave control method. The imbalance of the multiple pinions driving in cutter head driving system of tunneling boring machine can be greatly decreased and the load-sharing coefficients can be reduced to 1.051 by using the loop coupling control method. The proposed research provides an effective solution to the imbalance of torque distribution and synchronous control method for multiple pinions driving of TBM.