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In this work, the thermal stability of annealed Ag/Nb multilayers was investigated as the individual layer thickness (h) varies from 1 nm to 100 nm. The lamellar structures remain unchanged after annealing at 500 °C for 1 h, and the hardness at all scales remains undiminished after annealing. The results show that two low energy interfaces are responsible for the superior thermal stabilities. The coherent interface is formed when h < 20 nm, and the amorphous interface is formed when h ≥ 20 nm, respectively. The evolution of interfacial structures and the process of solid state amorphization are discussed accordingly. [ABSTRACT FROM AUTHOR]

We study the optical properties of amorphous GaAs1-xNx films grown by radio frequency magnetron sputtering method with different N2 partial pressures. The surface morphology, the optical absorption, the Raman spectra, and optical constants of the films with different N2 partial pressures are reported. The appearance of the Raman peak at 245 cm-1 of “GaAslike” and a shoulder at about 750 cm-1 related to GaN indicates the formation of GaN clusters in GaAs matrix. The roughness decreases and the optical band gap of amorphous GaAs1-xNx films moves to short wavelength with increasing N2 partial pressure. The refractive index and the extinction coefficient of the films decrease with increasing N2 partial pressure, and it has been found that the amorphous GaAs1-xNx films with nonzero N2 partial pressure are transparent in red and near infrared wavelength regions. [ABSTRACT FROM AUTHOR]

Measurements of flow noise produced by strip spoilers in the air duct of a ventilation system and radiated from an open exhaust termination unit into a reverberation chamber have been made. The results agree with the previous work of Nelson and Morfey [J. Sound Vib. 79, 263-289 (1981)]. Prediction of flow noise produced by multiple spoilers requires the values of the ratio of the mean drag forces that act on the spoilers, the phase relationship between the fluctuating drag forces that act on the spoilers, and the coherence function of the noise sources. The latter is empirically derived from the measured results, where the predicted results agree well with the experimental results within 3 dB at most frequencies except for very high frequencies.