Origin of Violet‐Blue Emission in Ti‐Doped Gahnite

ZnAl₂O₄ doped with Ti⁴⁺ (2%) was synthesized by the hydrothermal method at 220°C at pressure of 25 bars. An average grain size of the as‐prepared sample was 3 nm, the samples with biggest grain size were obtained after annealing at 300°C, 500°C, 600°C, 700°C, and 900°C, diameter of the latter was about 33 nm. IR spectroscopy indicated that ZnAl₂O₄ was partially inverted. The degree of the inversion decreases with increase in the annealing temperature but increases with increasing Ti⁴⁺ content. Absorption and emission spectra as well as emission decay profiles were recorded at 300 and 77 K. The observed spectra are due to charge‐transfer O^2??Ti⁴⁺ transitions. Color of the emission depends on the nanocrystal size and with increase in its diameter changes from violet to blue, accordingly the absorption bands exhibit redshift. The calculations based on Density Functional Theory confirmed the experimental results. 3d electrons of titanium ions form the bottom of the ZnAl₂O₄:Ti⁴⁺ conduction band, oxygen, aluminum or zinc vacancies create additional levels in the gahnite energy band gap. It was also found that in ZnAl₂O₄ aluminum or zinc vacancy induces magnetism with relatively high magnetic moment close to 1 μ_B per vacancy.     

The solution behavior of hydrophobically associating zwitterionic polymer in salt water

The acrylamide‐based hydrophobically associating zwitterionic polymer was prepared, which was composed of dimethyl‐dodecyl‐allyl ammonium chloride as hydrophobic group and carboxyl betaine 2‐(4‐acrylamido‐propyl‐dimethyl ammonic)‐sodium acetate as functional group. Hydrophobically associating polyacrylamide (HAPAM) was also prepared for comparative study. The behaviors of polymers in pure water and salt solutions were investigated by the means of apparent viscosity test, laser light scattering, atomic force microscope, and fluorescence experiments. The viscosities of polymer solution increased with the increasing of salt concentration, which indicated that the addition of salt resulted in significant antipolyelectrolyte effect in the zwitterionic polymer solution. The results of dynamic laser light scattering experiment also showed that the average hydrodynamic diameters of the zwitterionic polymer molecules increased with the increasing of salt concentration. The network structures had been observed by atomic force microscope and the addition of salt strengthened the formation of network structures. The results of fluorescence experiment showed that the addition of salt could enhance the association of hyrophobically zwitterionic polymer. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39707.     

Physicochemical Properties Improvement of Soy Protein Using Divalent Ions During a Two-Step Fractionation Process

This study proposed a two-step fractionation (TSF) method with the addition of divalent ions to produce a soy protein with lower contents of lipophilic proteins and polar lipids (less-LP SPI). Flavor volatiles profiles and some functional properties of less-LP SPI were compared with soy protein prepared from conventional acid precipitated methods (APP). Protein composition and thermal behavior analysis indicated that less-LP SPI prepared with the addition of 10 mM Ca²⁺ during TSF process contained less lipophilic proteins and less denatured proteins. Gas chromatography–mass spectrometry analysis showed that the flavor volatiles content of less-LP SPI was significantly lower than that of APP (p < 0.05). The emulsifying stability of less-LP SPI was improved in comparison to that of APP (p < 0.05), as indicated by a less significant change in the creaming index and particle size (after 14 and 30 days of storage) of the emulsion prepared with the former than with the latter. Less-LP SPI had a similar or slightly lower water solubility compared to APP, but it possessed a higher protein content and a lower lipid level. These improvements in the properties of less-LP SPI might be due to the removal of lipophilic proteins and polar lipids by the divalent ions during the TSF process.     

一种索支撑柔性结构轨迹跟踪控制方法

大型射电望远镜馈源支撑结构采用六根柔索驱动馈源舱完成大范围高精度扫描跟踪的创新设计方案.针对该柔性结构非线性、大滞后、多变量耦合的特点,提出了一种双模糊控制和干扰观测器相结合的控制算法来实现馈源轨迹跟踪策略.这种新方法通过构造干扰观测器来观测柔性结构的各种干扰,并根据观测到的干扰信息进行补偿以抑制干扰对系统的影响;同时引入带有比例积分校正环节的双模糊控制器来实现馈源舱轨迹跟踪,通过调整因子来优化控制规则.仿真结果表明,该控制算法不仅能满足对轨迹跟踪精度要求,而且具有较强的鲁棒性.     

基于DSP温度PID-NN控制系统设计

针对低噪声单元(LNB)温度控制系统的非线性,时变性,大滞后等特点,采用PID NN控制策略来实现温度控制,并且给出了DSP控制实现的具体方案。实验结果表明,该电路简单可靠,运行稳定;对于低噪声单元的温度控制,与普通PID控制器相比,PID NN参数自适应算法具有较好的控制性能和较强的鲁棒性。     

桁架结构损伤识别的最小秩方法

在结构损伤的早期阶段,损伤往往集中发生在少数单元,损伤前后总体刚度矩阵差的秩较小。本文给出一种基于矩阵最小秩理论的计算方法,对损伤结构的模态力余量方程进行求解,反演得到总体刚度矩阵的变化量。数值试验表明,该方法对桁架结构的损伤可进行精确的定位和标定。     

一种聚类挖掘结果的可视化方法

简要介绍了数据挖掘、聚类分析及多维数据可视化,提出将Kmeans算法输出的多维结果集通过主分量分析转换为3D空间点坐标,实现数据挖掘结果的可视化。     

基于SyncML协议的异构数据源同步方法

移动计算环境下各个同步设备上存储的数据元结构不尽相同,这给移动计算环境下的数据同步带来了挑战。提出了基于SyncML协议的异构数据源同步方法,该方法可以在不改变SyncML协议的基础上方便地完成异构数据源之间的同步。     

一种基于安全芯片的CA方案设计和实现

以符合可信计算联盟标准的安全芯片为基础,提出一种基于安全芯片的CA方案,它不仅解决了CA抵抗外部攻击,而且也解决了CA抵抗内部攻击的问题,同时该方案具有较高的性能和较低的成本。     

Hydrostatic pressure influence on electric relaxation response of bismuth manganite ceramics

Electrical impedance of bismuth manganite ceramics was studied under ambient and high hydrostatic pressure. Local disorder of crystal lattice was confirmed using XRD and DSC. Two relaxation processes were discerned. One was attributed to small polarons, which showed a changeover from variable range hopping features related to Fermi glass and structural disorder to the nearest neighbor hopping behavior in higher temperature range related to uniform distribution of energy levels. Hydrostatic pressure shortened relaxation times that would be interesting for applications. The second process, which was assigned to the nearest neighbor hopping of polarons, also exhibited a changeover to glassy features in a high-temperature range.