No abstract

In this paper, we study a one‐dimensional morphogenesis model considered by C. Stinner et al. (Math. Meth. Appl. Sci.2012;35: 445–465). Under homogeneous boundary conditions, we prove the existence of nonconstant positive steady states through local bifurcation theories. Then we rigorously study the stability of these nonconstant solutions when the sensitivity functions are chosen to be linear and logarithmic, respectively. Finally, we present numerical solutions to illustrate the formation of stable inhomogeneous spatial patterns. Our numerical simulations show that this model can develop very complicated and interesting structures even over one‐dimensional finite domains. Copyright © 2014 John Wiley & Sons, Ltd.

In order to effectively evaluate the acoustic vibration characteristics of viscoelastic sandwich composite cylindrical shell, based on FEM and BEM method, the vibration acoustic radiation of the viscoelastic sandwich panel and metal shell are calculated, and the results agree well with the experimental results. The dynamic mechanical parameters of viscoelastic core are obtained by dynamic thermodynamic experiments and the equivalent principle of temperature and frequency. The finite element method is used to simulate the coupling of water and shell. Finally, the indirect boundary method is used to calculate the radiated sound field under point excitation and the results show that the average and peak value of the acoustic power of the viscoelastic sandwich composite shell is 21.2dB and 46.4dB lower than that of the steel shell. In the range of low frequency,the radiation sound power is sensitive to the change of the layer angle,which is opposite in the range of high frequency. In the range of high frequency,the shear loss of the viscoelastic core is relatively obvious,which is opposite in the range of low frequency.

To study the influence of the opening process of a naval ship’s weapon launcher on the local strength of the impact-resistant structure, the load and inherent characteristics of the system were analyzed, a finite element dynamic model and theoretical Kelvin–Voigt single degree of the freedom system model were established, the dynamic response properties of the impact-resistant structure under an impact load were studied, and the impact spectrum of the system at different impact load durations was obtained. The results indicated that the first-order vibration period of the impact-resistant structure was much shorter than the impact load duration, and the dynamic amplification coefficient of the system was close to 1. Consequently, a theoretical model of a single degree of the freedom system was established, while the analytically derived displacement spectrum was consistent with the finite element calculation results. Therefore, the dynamic strength check of this impact-resistant structure could be treated as a static problem. According to the static calculation, the maximum stress of the structure occurred at the root of the base, which was 188.3 MPa, exceeds 0.3 times of the material yield stress specified in the military standard. To meet the military standard, a simplified collision model was established with the thickness of the rubber pad as the reference variable, the combined force on the bottom surface of the rubber pad was extracted, and the resulting equivalent displacement was calculated according to Hooke’s law. The range of the rubber pad thickness was determined as 11.6 mm  <  d <  12.5 mm to meet the military standard and not affect the normal firing of the weapon.

For the axial stretching fiber laser hydrophone, a fiber laser is often exposed to flexural interference. A theoretical model for the flexural vibration of a fiber laser was therefore constructed in this paper to explore the low frequency anti-interference mechanism for the frequency response of an axially tensioned fiber laser hydrophone (FLH). A specific packaging structure was used for finite element comparison and simulation. Packaged FLHs were tested for frequency response. The simulation and test results reveal that the flexible attachment at both ends of a fiber laser leads to lower amplitude of flexural vibration compared with rigid attachment, which therefore promotes a flat acoustic response curve of an FLH. The analysis given in this paper can be taken as a basis for improving the packaging technique.