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Stochastic subspace identification (SSI) and Bayesian methods are now the main representative approaches for high-performance system identification and uncertainty quantification. Both methods have been extensively used in engineering applications for the last 10 years despite them having quite different views in principle. However, no comparison has been carried out to inform which method is actually better for engineering applications in terms of modal identification accuracy, uncertainty quantification, and so forth. This paper therefore investigates the differences between these two quantifications of parameter uncertainty in system identification. Synthetic data for a six-degreeof-freedom spring-mass numerical system are first studied to compare their identification accuracy and applicable conditions. The investigation is then extended to field data from actual structures, which involves ambient modal testing of Heritage Court Tower in Canada, Canton Tower in China, and Ting Kau Bridge in Hong Kong. Results from the synthetic data show that, under white-noise excitation, identified modal parameters and quantified uncertainty for both methods are highly consistent with the values of frequentist statistics. However, when the excitation is not white noise, there may be some spurious modes identified via SSI, and the uncertainty quantified under colored-noise excitation via SSI is almost always larger than those under white noise, while the Bayesian method is not disturbed. Results for the structural field data indicate that in general applications under environmental excitation the identified modal parameters from both methods are almost identical; the quantified uncertainty of the SSI method is slightly larger than that of the Bayesian method, but they are of the same order of magnitude and can meet engineering requirements.

By creatively using R.F Magnetic sputtering technique , we have successfully prepared ZnSe polycrystalline thin films on glass substrates..The effect of different sputtering powers on the structural, morphological and optical properties of the as-deposited films were studied. The films were characterized by using X-ray diffraction, UV-VIS spectrometer ,scanning electrical microscope ,etc. The results indicate that :Under the pressure of o.8pa,with the diverse sputtering power varying from 60w to 100w,the intensities of XRD peaks of ZnSe thin films varied apparently ,while the morphological properties were almost the same. It should be noted here that the crystallinity of the ZnSe film, which was deposited with the power of 90W, showed a face-centered cubic phase. Besides, it showed relatively better performance: with strong [111] orientation ,smooth surface without obvious defects, comparatively large band gap and high transmission rate.

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This paper focuses on physical properties of ZnS thin films.ZnS thin films were successfully fabricated on Fluorine-Tin-Oxide(FTO) substrates(in a vacuum chamber maintained at 10-6Torr) at the substrate temperatures(Ts) of 150°Cand 200°Cby pulsed laser deposition(PLD),respectively.The structural properties of the ZnS films were analyzed with a X-ray diffraction(XRD) spectroscopy;The surface morphology of ZnS films was examined using scanning electron microscopy(SEM). With the increasing of the substrate temperature,the intensity of the (111) diffraction peak increases clearly and the surface of the ZnS films was more homogeneous and more compact.The main phase of the films deposited at 150°C and 200°C are both cubic-zinc-blende structure.The transmission spectra of the films was measured by UV-Vis spectrophotometer(UV,model a Perkin Elmer-Lambda 950),it shown that the films have the high transmittance in the spectrum of the visible light range,and the optical energy gaps were 3.48eV and 3.54eV,corresponding to the substrate temperatures of 150°C and 200°C.The results shown that the PLD technique can fabricate the better ZnS thin films.