Effects of Ca2+, Mg2+, Na+, and K+ substitutions on the microstructure and electrical properties of GdCoO3 ceramics

Journal of Electroceramics - GdCoO3-δ, Gd0.975Na0.025CoO3-δ, Gd0.98K0.02CoO3-δ, Gd0.98Ca0.02CoO3-δ, and GdCo0.99Mg0.01O3-δ ceramics were prepared via a solid-state reaction...     

改进遗传模拟退火算法在TSP优化中的应用

针对旅行商问题(TSP)优化中,遗传算法(GA)容易陷入局部最优、模拟退火算法(SA)收敛速度慢的问题,提出一种基于改进遗传模拟退火算法(IGSAA)的TSP优化算法.首先根据优化目标建立数学模型;然后对遗传算法部分中的适应度函数、交叉变异算子进行改进,使算法能够更加有效地避免陷入局部最优;最后根据旧种群和新种群每个对应个体的进化程度提出一种改进自适应的Metropolis准则,使模拟退火算法部分的染色体跳变更具有自适应性,利于算法寻优.对不同TSP实例的实验结果表明,与其他路径优化算法优化结果相比,所提出的IGSAA算法能够对不同TSP实例优化得到更优的旅行路径.     

The synthesis, spectroscopic properties and crystal structures of some rhodanine merocyanine dyes for optical recording with a blue diode laser

Six rhodanine merocyanine dyes were synthesized via both a conventional solvent method and a microwave method using rhodanine, 2-methylthio quaternary salts and 1H-indole-3-carbaldehyde as starting materials. The products were identified using UV-Vis, IR, MS, ¹H NMR and elemental analysis. The UV-Vis absorption spectra of the dyes in chloroform, DMSO, water, acetone, ethanol and methanol were investigated. The structures of two dyes (5a and 5b) were characterized and analyzed by X-ray diffraction as well. Crystallographic data revealed that dye 5a belonged to tetragonal, I4 (1)/a space group, while dye 5b belonged to monoclinic, P-1 space group. In the case of both dyes, intermolecular associations occurred by π-π stacking and intermolecular hydrogen bonds, which contributed to stabilize the crystal structure.     

Monomethine cyanine dyes with an indole nucleus: Microwave-assisted solvent-free synthesis,spectral properties and theoretical studies

Four asymmetric monomethine indocyanine dyes were rapidly synthesized by the condensation of indole quaternary salts with 2-methylthio quinoline quaternary salt in the presence of triethylamine under solvent-free, microwave irradiation. The effects of microwave power and irradiation time on yield were examined. The products were identified using elemental analysis, IR, MS, UV–Vis spectra, ¹H and ¹³C NMR. The absorption of the dyes was investigated both experimentally and theoretically. Calculations performed using a combination of the time-dependent density functional theory (TD-DFT) and the polarizable continuum model (PCM) reproduced the π → π¹ type absorption bands of the dyes. Multiple linear regression, applied to the theoretical absorption maxima in different solvents, fitted well with experimental data. Resonance frequency calculations were undertaken to study the IR spectra of the dyes and the calculated results were in good accordance with experimental values.     

Reinforcement of waste hemp fibres in aromatic diamine-based benzoxazine thermosets for the enhancement of mechanical and thermomechanical properties

Natural fibres (NFs) have been successfully reinforced in polymer matrices to strengthen the properties of the polymers. The polybenzoxazine thermosets are facing instable mechanical properties due to the high brittleness, herein, waste hemp fibres (WHF) reinforced polybenzoxazine composites are prepared. Effects of WHF volume % loading on curing, thermomechanical, mechanical, and thermal properties are studied. FTIR results confirmed that WHF rich in ?OH groups increased the ring-opening of oxazines and reduced curing temperature. In addition, an increase of 223%, 111%, 64%, and 253% in impact, tensile strength, flexural and Young's modulus, respectively, were recorded after loading optimum concentration (30 vol. %) in composites. Considerable enhancements were also seen in the thermomechanical properties on optimum loading, double stiffness and 26°C increase was recorded in the glass transition temperature. Nonetheless, the decline was observed in thermal stabilities, T_5% and Y_c were 24°C and 1.4 % lower, respectively, than neat poly(P-ddm).