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861.
862.
Hongtao Cui Minmin Wang Wanzhong Ren Yan Liu Yunan Zhao 《Journal of Sol-Gel Science and Technology》2013,66(3):512-517
Silica monoliths embedded with high concentration of γ-Fe2O3 or TiO2 nanoparticles were prepared by a sol–gel procedure designed according to the inherent properties of oxide colloids. In the first step, highly dispersible oxide nanoparticles were produced using an in situ modification sol–gel strategy. Then, these particles were re-dispersed in silicon alkoxide-containing solution to form a stable colloidal solution. The hydrolysis and condensation reactions of alkoxide were catalyzed by an organic base (morpholine). Due to the large molecule size of morpholine, the electric double layer on the surface of colloidal particles was not compressed by the ionized morpholine molecules. The colloidal solution thus remained stable during the gelation process. Through this procedure, oxide nanoparticles could be immobilized homogeneously in the pores of a silica matrix, forming highly transparent and crack-free monoliths. 相似文献
863.
Wenbo Wu Dr. Guohua Xu Prof. Conggang Li Prof. Gui Yu Prof. Yunqi Liu Prof. Cheng Ye Prof. Jingui Qin Prof. Zhen Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(21):6874-6888
Through the combination of the divergent and convergent approaches, coupled with the utilization of the powerful Sharpless “click‐chemistry” reaction, two series of sulfonyl‐based high‐generation NLO dendrimers were conveniently prepared with high purity and in satisfactory yields. Thanks to the perfect three‐dimensional (3D) spatial isolation from the highly branched structure and the isolation effect of the exterior benzene moieties and the interior triazole rings, these dendrimers exhibited large second harmonic generation coefficient (d33) values up to 181 pm V?1, which, to the best of our knowledge, is the highest value so far for polymers containing sulfonyl‐based chromophore moieties. Meanwhile, compared with the nitro‐chromophore‐based analogues, their optical transparency and NLO stability were improved in a large degree, due to the lower dipole moment (μ) and the special main‐chain structure of sulfonyl‐based chromophore in these dendrimers. 相似文献
864.
865.
Dr. Chao Xu Dr. Guoxin Tian Dr. Simon J. Teat Dr. Guokui Liu Dr. Linfeng Rao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(49):16690-16698
The complexation of NpO22+ and PuO22+ with dipicolinic acid (DPA) has been investigated in 0.1 M NaClO4 by spectrophotometry, microcalorimetry, and single crystal diffractometry. Formation of 1:1 and 1:2 (metal/ligand molar ratio) complexes of DPA with NpO22+ and PuO22+ were identified and the thermodynamic parameters were determined and compared with those of UO22+. All three hexavalent actinyl cations form strong 1:1 DPA complexes with slightly decreasing but comparable stability constants from UO22+ to PuO22+, whereas the stability constants of the 1:2 complexes (log β2) decrease substantially along the series (16.3 for UO2L22?, 15.17 for NpO2L22?, and 14.17 for PuO2L22? at 25 °C). The enthalpies of complexation for the 1:2 complexes become less exothermic from UO2L22? (?28.9 kJ mol?1), through NpO2L22? (?27.2 kJ mol?1), and to PuO2L22? (?22.7 kJ mol?1). The trends in the thermodynamic parameters are discussed in terms of the effective charge of the cations and the steric constraints in the structures of the complexes. In addition, the features of the absorption spectra, including the wavelength and intensity of the absorption bands, are related to the perturbation of the ligand field and the symmetry of the actinyl complexes. 相似文献
866.
Zheng Wang Shuai Luo Dr. Shoude Zhang Wu‐Lin Yang Yang‐Zi Liu Prof. Dr. Honglin Li Prof. Dr. Xiaoyan Luo Prof. Dr. Wei‐Ping Deng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(21):6739-6745
The first catalytic enantioselective 1,3‐dipolar cycloaddition of azomethine ylides to α‐aminoacrylate catalyzed by a AgOAc/ferrocenyl oxazolinylphosphine (FOXAP) system was developed, which exhibits excellent exo‐ and enantioselectivity (92–99 % ee). This process provides efficient access to useful 4‐aminopyrrolidine‐2,4‐dicarboxylic acid (APDC)‐like compounds containing a unique quaternary α‐amino acid unit. 相似文献
867.
常规驻极体传声器阵列成像系统存在数据采集系统复杂、体积大的问题,因而阵列传感器数量一般不超过60个,成像质量较差。为此,本文以数字式MEMS声传感器基础设计了260个传感器的声阵列,数据采集系统由FPGA控制,并嵌入到前端阵列中,后端是在另一个FPGA控制下的1个DSP芯片和2个PC104模块组成的集成系统,其中高速DSP芯片完成阵列信号处理以实现声成像功能。该系统能够实现对普通车间环境下机械设备噪声、气体泄漏噪声的现场成像测试,形成动态声像图。测试表明,该系统抗干扰能力强、声像分辨率高、成像速度快,实用效果良好。 相似文献
868.
砂尘浓度指标严重影响砂尘风洞试验效果;在大型砂尘风洞中准确的测量及有效的控制砂尘浓度是砂尘风洞设备研制中的两个关键问题;针对动态试验工况环境中浓度传感器标定的问题,分析了浓度测量时标定参数与风速和浓度的关系,使用模型树算法建立了三者之间的关系模型,以此模型来预测各种动态情况下的标定参数;针对复杂环境下浓度动态控制问题,采用专家PID算法,提出了多回路控制系统结构和专家规则;工程实践表明该测量和控制方法满足了动态试验环境的需求,取得了良好效果;模型树算法和专家PID系统能有效的解决动态工况下砂尘浓度的测量与控制问题。 相似文献
869.
870.