Characterization of the effectiveness of silica anti-scalants

The presence of silica in brackish water greatly complicates the reverse osmosis desalting process. Threshold limits of silica scale precipitation are difficult to predict and there are no reliable techniques for evaluating the performance of silica anti-scalants (AS) used to extend water recovery limits. The aim of the present work is to illustrate a fundamentally oriented procedure for assessing the relative effectiveness of various anti-scalants. Rigorous analysis of inhibition data obtained in comparative tests of four commercial anti-scalants, dosed at the recommended dosage levels, revealed that there was no significant difference in their inhibitory effectiveness. The mitigating effect provided by all AS tested was increase of the threshold limit for the onset of scaling from a membrane surface supersaturation (s/s) level of 1.7-1.9 in the absence of an AS, to the level of 2.1-2.3, in the presence of the AS.     

基于Simulink连续系统仿真驱动噪声生成

对噪声驱动的连续系统仿真,由于连续系统往往含有积分运算,不能直接输入通常的噪声信号,必须产生适合的输入信号.针对这种情况,研究了噪声驱动的连续系统仿真时的噪声生成问题,得到了输入噪声信号表达式;分析了Simulink中噪声源模块产生的数据,提出利用Simulink白噪声模块构成的等效带限白噪声模型来产生连续系统仿真需要的典型噪声;通过分析比较认为,Simulink带限白噪声模块和等效带限白噪声模型的参数意义不同但两种方法等价,能够产生连续系统仿真需要的输入信号,为噪声驱动的连续系统仿真研究奠定了基础.     

Silicon-based oxynitride and nitride phosphors for white LEDs—A review

As a novel class of inorganic phosphors, oxynitride and nitride luminescent materials have received considerable attention because of their potential applications in solid-state lightings and displays. In this review we focus on recent developments in the preparation, crystal structure, luminescence and applications of silicon-based oxynitride and nitride phosphors for white light-emitting diodes (LEDs). The structures of silicon-based oxynitrides and nitrides (i.e., nitridosilicates, nitridoaluminosilicates, oxonitridosilicates, oxonitridoaluminosilicates, and sialons) are generally built up of networks of crosslinking SiN₄ tetrahedra. This is anticipated to significantly lower the excited state of the 5d electrons of doped rare-earth elements due to large crystal-field splitting and a strong nephelauxetic effect. This enables the silicon-based oxynitride and nitride phosphors to have a broad excitation band extending from the ultraviolet to visible-light range, and thus strongly absorb blue-to-green light. The structural versatility of oxynitride and nitride phosphors makes it possible to attain all the emission colors of blue, green, yellow, and red; thus, they are suitable for use in white LEDs. This novel class of phosphors has demonstrated its superior suitability for use in white LEDs and can be used in bichromatic or multichromatic LEDs with excellent properties of high luminous efficacy, high chromatic stability, a wide range of white light with adjustable correlated color temperatures (CCTs), and brilliant color-rendering properties.     

温度场对冻藏环境下速冻白芦笋脱水的影响

模拟冻藏环境下稳定温度场和周期波动的非稳定温度场，在其中对未解冻、半解冻和严重解冻的速冻白芦笋分别进行脱水实验。理论分析和实验结果证实，温度场的存在是造成冻藏局部小环境水分浓度不平衡而引发速冻白芦笋脱水危害的根本原因。可以通过冻结物冷藏库设计的改进和操作管理的改进来防止速冻食品脱水的措施。     

Control of wall thickness in the formation of ordered mesoporous silica films

Ordered mesoporous silica thin films using block copolymer have drawn an attention for low-k application due to its ordered pore structure. From the respect of dielectric and mechanical properties of the film, there is trade-off between pore size and wall thickness. In this work, factors for increase of wall thickness were investigated. It was found that body-centered cubic structure was maintained irrespective of the concentration of catalytic acid. The catalytic acid thickens the framework wall because counterion reduces the repulsion force between silicic acids. The highly ordered mesoporous silica films were obtained although high concentration of acid was added to the silica sol. However, wormlike micelle exists more with high HCl concentration due to fast gellation rate. And excess water, which has the role similar to the humid atmosphere, also increases the thickness of silica wall. However, large amount of excess water at the micelle interface disrupts organic-inorganic electrostatic interaction. As a conclusion, optimization of HCl concentration in the silica sol and control of humidity during spin coating can simultaneously increase the framework thickness while maintaining the pore periodicity.     

Facile route for preparation of silica-silver heterogeneous nanocomposite particles using alcohol reduction method

Silica-silver heterogeneous nanocomposite particles were successfully prepared by facile route including alcohol reduction method. Thiol groups were employed as a chemical protocol to make a binding between silver nanoparticle and silica surface. After the reaction for 10 min, a large number of quasi-spherical silver nanoparticles with an average size of 6.9 nm in diameter were homogeneously formed on the surface of silica particles. The immobilized silver nanoparticles grew to large ones with an average size of 10.6 nm in diameter after additional reaction for 2 h. The resulting nanocomposite particles were characterized by transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), UV-vis spectrophotometer, and X-ray diffraction (XRD) analysis.     

Synthesis and luminescence properties of europium doped silica thin film

Mixture of europium oxide (Eu₂O₃) nanoparticles and spin-on glass (SOG) solution without annealing exhibited a strong room temperature photoluminescence (PL) at 610 nm. We developed a one-step synthesis to incorporate europium ions in silica thin film by mixing the Eu₂O₃ nanoparticles with the SOG solution and found that the weight ratio of the nanoparticles and the SOG solution was 1:5 for maximum PL. We also studied the temperature effect on the light emission of the europium doped thin film by time-of-flight secondary ion mass spectrometry (SIMS). The PL intensity of the thin film doubled after annealing. SIMS study confirmed the reduction of hydroxyl groups and explained the PL enhancement in the annealed europium doped silica thin film.