The orifices in thick microperforated panels (MPPs) are normally straight holes. Although the increase in thickness extends application field of MPPs, the eventually change of acoustic impedance leads to the decline of absorption coefficient. One way to improve this deterioration is to have variable axial section in thick MPPs. In this paper, varying section MPP molded by tapered and step-shaped molding core were prepared by using epoxide resin, and their acoustic characters were measured. Results showed expansion of absorption band in varying section MPP. Compared with conventional straight hole MPP, the absorption frequency range extended from 300~700Hz to 310~830Hz, and average absorption increased from 0.45 to 0.54 for tapered section MPP.

Independent fault diagnosis for orbited spacecraft in real time is always the bottleneck in the development of aerospace engineering. In this paper, the empirical mode decomposition (EMD) is employed for fault diagnosis of moving component parts of spacecrafts. The stepout fault characteristic is extracted effectively and the base frequency is obtained. This method provides with the basis for fault diagnosis of orbited spacecrafts under the blackbox condition. In addition, in comparison with FFT and wavelet analysis, it is found that the EMD method is more efficient and advanced in the fault diagnosis of moving component parts of spacecrafts.

Thick microperforated panels (MPP) usually do not have such a good sound absorption feature as the thin panels do because of their high resistance and/or reactance. In order to improve the thick MPPs acoustical performance, thin stainlesssteel fibers are inserted into the orifices of the thick MPP, and their sound absorption coefficients are measured. Results show that the thin stainlesssteel fibers can widen the frequency band for sound absorption of the thick MPP effectively. When the insertion rate of the fibers reaches 50% and the usage of fibers reaches 0.75mg per orifice, the frequency band of sound absorption is 3921168Hz for the absorption coefficient larger than 0.5. While for the MPP without fiber insertion the frequency band for sound absorption is only 5301076Hz.

The transfer matrices of the axial, flexible and torsional modes of fluidconveying elbow pipe are deduced considering fluidstructure interaction between pipe and fluid. Calculate the modal frequency and shape of a “U” shape pipe with Transfer Matrix Method and ANSYS software respectively. The results indicate that Transfer Matrix Method is an effective way to analyze fluidconveying pipe. The effect of fluidstructure interaction can not be ignored which will depress the modal frequency of the pipe.