Visible photoluminescence (PL) from ZnO has been found to be tunable in a wide range from blue to green and orange through chemical doping and annealing. Mg-doped, (Al, Li)-doped, and undoped ZnO thin films were deposited on glass substrates by a metal-organic decomposition method at temperatures around 600°C. The films were annealed under different atmospheres, including air, oxygen, nitrogen, and hydrogen/nitrogen. X-ray diffraction analysis and field-emission scanning electron microscope observations revealed that the films consisted of large ZnO grains 50-100 nm in size. When the Mg-doped ZnO films were annealed in nitrogen or hydrogen/nitrogen, unusual blue or bluish-white PL, respectively, was observed in response to an ultraviolet light excitation. We confirmed the band-gap broadening (approximately 0.25 eV) of the Mg-doped ZnO films as compared to that of the undoped films through observation of the absorption edge. The blue-related PL therefore appeared to be caused by energetic shifts of the valence band and/or the conduction band of ZnO. Films annealed in the oxidizing atmospheres, on the other hand, showed yellow/ orange PL. We ascribed this PL to electronic transitions between shallow and deep defect levels. Yellow PL was also observed in the (Al, Li)-doped ZnO films, suggesting that shallow donor/acceptor levels due to extrinsic defects also contributed to the yellow PL.

Neutral ethylene glycol (EG) molecules have been intercalated into zinc hydroxide layers to produce a new hybrid material in which only one kind of metal ion is included. Initially, layered basic zinc acetate (LBZA, Zn(5)(OH)(8)(CH(3)COO)(2).2H(2)O) was prepared from a methanolic zinc acetate dihydrate solution. The immersion of LBZA in EG resulted in its intercalation, which was accompanied by an interlayer expansion of 7.12 A, as revealed by X-ray diffractometry. A Fourier transform infrared spectroscopic study indicated that the new compound contained both the acetate groups and the EG molecules. Together with thermogravimetry-differential thermal analysis, a composition of the new compound was estimated to be Zn(5)(OH)(8)(CH(3)COO)(2)(HOC(2)H(4)OH)(2).2H(2)O. The EG intercalation was found to increase the dehydration temperature of the zinc hydroxide layers from 130 to 180 degrees C. So the thermally stable material is then promising as a new class of precursors in creating organic-inorganic nanocomposites.

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A simplified seismic design procedure for steel portal frame piers installed with hysteretic dampers is proposed, which falls into the scope of performance-based design philosophy. The fundamental goal of this approach is to design a suite of hysteretic damping devices for existing and new bridge piers, which will assure a pre-defined target performance against future severe earthquakes. The proposed procedure is applicable to multi-degree-of-freedom systems, utilizing an equivalent single-degree-offreedom methodology with nonlinear response spectra (referred to as strength-demanded spectra) and a set of formulae of close-form expressions for the distribution of strength and stiffness produced in the structure by the designed hysteretic damping devices. As an illustrative example, the proposed procedure is applied to a design of a simple steel bridge pier of portal frame type with buckling-restrained braces (one of several types of hysteretic dampers). For the steel portal frame piers, an attempt is made to utilize not only the displacement-based index but also the strain-based index as pre-determined target performance at the beginning of design. To validate this procedure, dynamic inelastic time-history analyses are performed using the general-purpose finite element program ABAQUS. The results confirm that the proposed simplified design procedure attains the expected performance level as specified by both displacement-based and strain-based indices with sufficient accuracy. SIMPLIFIED SEISMIC DESIGN APPROACH 553 Figure 6. Finite element models and member sections: (a) single-deck piers; (b) double-deck piers; (c) pier section; (d) girder section; and (e) details of strengthened parts. and { } is [0.48, 0.52] T . {} is then used to establish the ESDOF system, and the computed properties are presented in Table V. Considering the inherent simplification of the method, it is worth noting that, for the pier presented, a linear variation of the deformations along the pier height could be used instead of {}, at least in the first design trials. The global displacement demand of the ESDOF system, * max , is 0.475m. * max can be transformed to max using Equation (3). It is found that max (= 0.569 m) of the original portal frame pier exceeds its ultimate capacity, u (= 0.518 m). Therefore, damping devices need to be employed to reduce structural damage in the case of a strong earthquake.

Luminescence D 6540 Tunable Visible Photoluminescence from ZnO Thin Films Through Mg-Doping and Annealing. -Visible photoluminescence from ZnO thin films is tunable in a wide wavelength range. Mg-doped ZnO films, annealed in H2/N2 and air, exhibit strong blue and orange emissions upon UV excitation, respectively. Yellow photoluminescence is observed in (Al, Li)-doped ZnO films. -(FUJIHARA*, S.; OGAWA, Y.; KASAI, A.; Chem.