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Machining slender workpiece is still a technical difficulty. This paper investigates the dynamic behavior of a slender shaft subject to constant feedrate moving cutting forces in twin-spindle turning process. The Euler-Bernoulli theory is used to model the rotating shaft. A dynamic cutting force model is formulated considering the flexibility of workpiece and rigid machine tool. The modal analysis method is employed to solve the dynamic response of the shaft. The parametric influence to the response and natural frequencies of shaft is discussed. Finally, the results are presented and compared between constant cutting forces and deflection-dependent force model introduced in this paper. It is found that there exists a stiffening effect due to the cutting process.

By comprehensive analysis and design optimization of barrier structure parameters, a new type of beam-and-post steel barrier was invented according to impact test condition and acceptance criteria of cross-sea bridge barrier. Full-scale impact tests and finite elements analysis were conducted to do safty evalution of the barrier. The results show that, ASI value is 1.62 for test and that is 1.67 for FEA, THIV is 30.7km/h for test and that is 31.2km/h for FEA. Working width is 0.88m for test and that is 0.62m for FEA. Occupant risk evaluation index can meet the requirements of level B and the working width can meet the requirements of level W3. Both of tracking and posture of vehicles are well. The study results above show that safety performance of cross-sea bridge barrier can meet or exceed the acceptance criteria. FEA results are consistent with Full-scale impact test, which validate the reliability of FEA. cross-sea bridge barrier can meet the highest test level for beam-and-post steel barrier, which can defend the out-of-control vehicles effectively and help to ensure the bridge safety.

In this paper, the stability and evolutionary trend of Hopf bifurcations are investigated thoroughly for the double-input SEPIC DC–DC converter with one-cycle control (OCC), which is widely used in hybrid power systems. By means of cycle-by-cycle simulations, the evolutionary trend of bifurcation behaviors is identified. The inherent mechanisms of two types of bidirectional Hopf bifurcations are uncovered based on the proposed averaged model. Moreover, stability boundaries in the parameter space are derived with the help of eigenvalue analysis to optimize the circuit design. Furthermore, some important indices with respect to coupling effects are evaluated to assess the coupling effects in the system. Finally, PSpice circuit experiments are performed to verify the bifurcation analysis.