Effect of anionic surfactant on vaterite CaCO3

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.     

高灵敏度CMOS光电集成接收机设计

设计了一个由调节型级联跨阻抗放大器(TIA)和双光电二极管(DPD)构成的CMOS光电集成(OEIC)接收机.具体分析了这个光电集成接收机的噪声和灵敏度及其相互关系.接收机中的噪声主要是电路中电阻的热噪声和MOS器件的闪烁噪声.提出了优化接收机灵敏度的方法.通过低成本的CSMC 0.6μm CMOS工艺流片并对芯片进行了测试.从测试眼图可知,该CMOS光电集成接收机可工作在1.25GB/s的传输速率下,灵敏度为-12dBm.     

PMD补偿器和PMD补偿接收机的特性

以介绍ITU—TG．666建议主要内容的方式，讨论了有关PMD补偿器和PMD补偿接收机的特性。     

Synthesis and characterization of Ti-SBA-16 ordered mesoporous silica composite

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.     

Coning motion stability of wrap around fin rockets

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.     

Comparative study of β-Si3N4 powders prepared by SHS sintered by spark plasma sintering and hot pressing

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.     

换流站直流刀闸发热改造

就两起换流站直流刀闸发热的问题进行技术分析,从技术、经济及工程施工难易程度方面进行方案比较,在回路电阻计算的基础上提出了增加旁路导电带的改造方案.实施改造后在实际运行中测量结果表明改造结果良好.     

大功率立式电机转子有限元结构分析与优化

基于Pro/Engineer建立了某型号的大功率电机转子的实体模型和虚拟样机模型,在MSC.PATTERN/NASTRAN环境下,利用有限元方法进行了电机转子的动力学仿真、应力位移仿真,得到了转子两端轴承的力学状态、转子的应力、位移等参数值.根据仿真结果,进行了转子的强度和刚度校核,分析了转子的主要破坏形式和危险位置.结果表明现有电机转子的结构基本满足设计要求,并在此基础上优化转子外径和支承结构,减小电机振动,优化工艺,为同类产品的开发和改进提供了参考.     

RTD/HEMT串联型共振隧穿三极管的设计与研制

对RTD/HEMT串联型共振隧穿三极管进行了设计和研制.测量结果表明:最大电流峰谷比为17.6∶1,棚压对峰值电压调控能力在1.5～7.7范围内,-3dB截止频率为4GHz,此种器件可与HEMT在结构和工艺上兼容,可应用于HEMT高速电路.     

Bézier样条曲线改进的近似弧长参数化方法

提出了Bézier样条曲线利用分割技术近似弧长参数化的一种方法，并给出了相应的算法。通过求出曲线上所谓的‘最坏点’并在相应点处进行分割。可得到两条Bézier样条曲线。让这两条Bézier样条曲线具有与它们的近似弧长成比例的权，并对所得到的新的Bézier样条曲线进行同样的工作最终可得到一条由多条Bézier样条曲线所构成的新曲线。将这多条Bézier样条曲线合并成为一条Bézier样条曲线并通过节点插入技术将所得Bézier样条曲线转化为B一样条曲线的形式可得到全局参数域，其中各条Bézier曲线在全局参数域中所占子区间的长度与它们的权成比例，这样使得到了一条近似弧长参数化曲线。