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991.
Calcium carbonate (CaCO3) crystals with various shapes have been synthesized by aging calcium chloride and urea hybrid solution containing sodium dodecylsulfonate (SDSN) or sodium dodecylbenzenesulfonate (SDBS) in a 90 °C bath. The effects of SDSN and SDBS on the morphology and polymorph of precipitated CaCO3 are investigated with the help of scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectrometer and X-ray diffraction (XRD). Flower-like vaterite changes from monolayer to multilayer structure with the increase of SDSN concentration. While the crystal shape changes from plate-like, through rose-shaped, hat-like, to bicone-like as the concentration of SDBS is increased. 相似文献
992.
993.
Shaodian Shen Yan Deng Guibo Zhu Dongsen Mao Yuhong Wang Guishen Wu Jun Li XiaoZhen Liu Guanzhong Lu Dongyuan Zhao 《Journal of Materials Science》2007,42(17):7057-7061
Ti-SBA-16 mesoporous silica with a cubic Im3m structure has been successfully synthesized through prehydrolysis of a silica precursor in the presence of a tri-block copolymer
F127 under acidic condition. X-ray diffraction (XRD) shows that the highly ordered mesostructure was maintained even at the
high loading of titanium up to 5.5 (bulk molar ratio SiO2/TiO2). UV–vis and Raman spectroscopy reveal that the titanium species was highly dispersed in the silica framework with tetrahedral
coordinate and octahedral coordinate, respectively. N2-adsorption data exhibit that the BET surface, pore size and pore volume were maintained with an increase of titanium species
loading for this cubic Im3m mesoporous composite. SEM image shows its amorphous morphology. The synthesis of mesoporous TiO2-containing SBA-16 composite with a cubic Im3m structure will open new applications for catalysts. 相似文献
994.
Coning motion stability of wrap around fin rockets 总被引:1,自引:0,他引:1
MAO XueRui YANG ShuXing & XU Yong School of Mechatronic Engineering Beijing Institute of Technology Beijing China 《中国科学E辑(英文版)》2007,50(3):343-350
Both the asymptotical stability criterion and the bounded stability criterion of the coning motion for wrap around fin(WAF) rockets are proposed through the analy-sis of coning motion equations,which can be easily used to determine the exis-tence of the coning motion during the rocket design. The correctness of the crite-rions is verified by mathematical simulation examples of a WAF rocket with differ-ent setting angles. It is also found that the setting angle of WAF has great effects on the rolling moment and side moment of the rocket. 相似文献
995.
Ling Bai Xiaodong Mao Weiping Shen Changchun Ge 《北京科技大学学报(英文版)》2007,14(3):271-275
β-Si3N4 powders prepared by self-propagating high-temperature synthesis (SHS) with additions of Y2O3 and Al2O3 were sintered by spark plasma sintering (SPS). The densification, microstructure, and mechanical properties of Si3N4 ceramics prepared using this method were compared with those obtained by hot pressing process. Well densified Si3N4 ceramics with finer and homo- geneous microstructure and better mechanical properties were obtained in the case of the SPS technique at 200°C lower than that of hot pressing. The microhardness is 15.72 GPa, the bending strength is 716.46 MPa, and the fracture toughness is 7.03 MPa?m1/2. 相似文献
996.
997.
998.
提出了基于min-max Octree快速分类Shear-warp的交互式海量数据场体绘制算法.主要包括根据海量数据的特征,快速读入数据以及设计适当的不透明度传递函数;建立Summed-Area表与min-max Octree数据结构,并对体数据进行快速分类,然后,利用分类的结果进行快速体绘制.实验证明该方法不仅效率高,而且显示效果好. 相似文献
999.
1000.