An Eu2+-activated AlN phosphor was synthesized by firing the powder mixture of AlN, α-Si3N4, and Eu2O3 at 2050°C for 4h under 1.0MPa N2. This nitride phosphor emits a strong blue color with the chromaticity coordinates of x=0.139 and y=0.106 at an accelerating voltage of 3kV. The cathodoluminescence properties of AlN:Eu2+ was evaluated by utilizing it in the Spindt-type field emission display panel. It shows that the nitride phosphor exhibits higher brightness, higher color purity, lower saturation, and longer lifetime than the currently used Y2SiO5:Ce3+, indicative of the suitability of the AlN:Eu2+ blue phosphor in field emission displays.

An Eu2+-activated AlN phosphor was synthesized by firing the powder mixture of AlN, α-Si3N4, and Eu2O3 at 1500−2050 °C for 4 h under 1.0 MPa N2. The phase purity, photoluminescent properties, thermal quenching, and quantum efficiency of the fired samples were investigated. A single AlN wurtzite phase was formed at low doping concentrations of Eu2+ (≤0.1 mol %) and Si (≤2.2 mol %). The introduction of Si is essential for the solubility of Eu2+ in the AlN lattice. Intense blue luminescence with a peak emission wavelength of 465 nm was observed in AlN:Eu2+, when Si was doped simultaneously. This blue phosphor shows a small thermal quenching, retaining the luminance of 90% at 150 °C. The absorption and external quantum efficiencies of AlN:Eu2+ are 63%μ and 46% upon 365 nm excitation, respectively. These results indicate that AlN:Eu2+ has great potential as a blue phosphor for white light-emitting diodes (LEDs) utilizing UV chips as the light source.

The crystal structure of nylon 12 prepared by polymerization of dodecalactam has been determined by x‐ray diffraction. Nylon 12 fiber exhibits only the γ form as its stable crystal structure. The unit cell of nylon 12 was determined with the aid of the x‐ray diffraction pattern of a doubly oriented specimen. The unit cell is monoclinic with a = 9.38 Å, b = 32.2 Å (fiber axis), c = 4.87 Å and β = 121.5° and contains four repeating monomer units. The chain is planar zigzag for the most part but is twisted at the position of amide groups, forming hydrogen bonds between neighboring parallel chains. The chain conformation is similar to that of the γ form of nylon 6 proposed by Arimoto. It was deduced from the calculations that there are two chain conformations statistically coexistent according to the direction of twisting. In each conformation, hydrogen bonds are formed between parallel chains to make pleated sheetlike structures. The sheets are nearly parallel to (200) and in the sheet the directions of the neighboring chains are antiparallel, as is the case with nylon 6.

SUMMARYThis paper presents a generic frame (GF) model useful for the simulation of earthquake responses of steel moment frames. Adopting the assumption that all rotations at joints lying at each oor level are identical, the model requires the solution of signiÿcantly fewer degrees of freedom than models with member-by-member representation. Procedures to construct a GF model that represents a multi-storey, multi-span frame are detailed. The model can allow for panel zone behaviour as well. The accuracy of the GF model in predicting maximum storey drifts and member plastic rotations is calibrated for two example frames against a variety of ground motions. Errors associated with the model are found to be negligible in light of the variability of responses attached to randomness and uncertainties of earthquake ground motions. The GF model is e ective in conducting extensive numerical analyses needed for the identiÿcation and characterization of primary structural parameters that control the earthquake responses of steel moment frames, thereby contributing to further advancement of performance-based design.

The luminescence properties of Si,Eu-codoped AlN phosphors were investigated by means of cathodoluminescence. The concentration of Eu was kept constant, while that of Si was varied from 0 to 9.0 at.% using two different Si-source starting powders, Si 3 N 4 and SiC. The luminescence of Eu 21 in AlN is only observed for samples doped with Si. On the other hand, a concentration quenching is observed for samples doped with high amount of Si from Si 3 N 4 while not for those doped from SiC. These results show the importance of Si in the luminescence properties of Eu 21 -doped AlN.