This paper aims at improving the performance of tracked ambulance nonlinear vibration reduction system by the structure optimization design. The structure optimization focuses on the stretcher base. Two structure optimization schemes are proposed based on the mechanism of dynamic vibration absorber (DVA), namely, the linear and nonlinear structure optimization schemes. The linear structure optimization scheme is finally adopted by comparison of two schemes under random vibration, and the performance of linear scheme is also validated under shock vibration. Then the global sensitivity analysis method is applied to calculate the parameter sensitivity of nonlinear vibration reduction system. At last, the nondominated sorting genetic algorithm II (NSGA-II) is used to optimize the performance of the nonlinear vibration reduction system. It shows the vibration energy of the supine human body on stretcher is reduced after above studies, which proves the validity and feasibility of the structure optimization schemes proposed, and the optimization studies applied in this paper.

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In this paper, we investigate the existence, multiplicity and asymptotic property of positive solutions for a Kirchhoff type problem with indefinite conditions. The existence, multiplicity of positive solutions are obtained by using variational method and the critical point theory, and then combing with some analytical techniques, we have the asymptotic property of positive solutions when k approach 0.

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