The mechanical performance and failure mechanism of a retard-bonded (RB) type prestressed concrete (PC) girder in different curing periods are investigated through four-point loading experiments. Six RB-type PC girder specimens with three RB prestressed tendons (PTs) along the longitudinal direction were fabricated. The measurements include the following: the retard-bonded agent ages versus the load-carrying capacity of the girder, the deflection of girder, the strain distribution at key cross sections through the girder, the pressure at PT tensile and anchoring ends, crack distribution, and so on. The experimental results indicate that when stretching the PT within proper tensile period, the retarder curing ages have less impact on the cracking load and a greater impact on the ultimate bending strength; the ultimate bending strength of the RB-type PC girder increased with increased retarder curing. Nonetheless, stretching the PT after excessive retarder curing (after the retarder had solidified completely), the cracks in the PC girder’s pure bending segment are wider and less numerous, the ultimate bending strength of the girder is lower, and its ductility is poor.
Titanium oxide (TiO 2 ) thin films were prepared by electronbeam evaporation (EBE) method on crystal silicon, and were thermally treated by rapid thermal annealing (RTA) process. X-ray diffraction (XRD) and variable angle spectroscopic ellipsometry (VASE) were used to analyze the crystal structure, band gap, and optical constants evolution of the investigated films. The strongest diffraction peaks in XRD patterns were found to shift to higher 2u angle with an increase of film thickness. The lattice spacing decreases and the average grain size increases, indicating the improvement of crystal quality by increasing film thickness. The band gap from well-fitted Forouhi-Bloomer (FB) dispersion model in VASE decreases with an increase of thickness, and one-dimensional quantum confinement effect and disorder effect have been introduced to explain this relation. The refractive indices of TiO 2 thin film decrease monotonically with an increase in film thickness in the spectral range from 230 to 800 nm, which can be attributed to the contribution of compressive stress effect.
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