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81.
82.
合成并表征了{4-[2-(4-氟苯基)-乙烯基]-苯基}-二甲基胺(DPVF).结果表明,DPVF(10.0 μmol·L-1)的水∶乙醇=1∶1(体积比)溶液的紫外可见吸收强度对pH值(7.02~2.22)变化灵敏,荧光强度对pH值(7.02~1.66)变化灵敏.荧光增强阶段是氟原子质子化,荧光减弱阶段是氟原子与氮原子同时质子化,氮原子与氟原子都是pH功能基.该化合物显示了"开-关"荧光发射性能,可应用于荧光分子开关;同时又是一个很好的pH荧光探针,检测pH值范围为7.02~1.66,pH值检测最高灵敏度为ΔpH=0.04. 相似文献
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In membrane filtration, solution environment factors such as pH and solvent density are important in controlling the filtration
rate and the rejection of the particles and/or the macromolecules. The filtration rate and the rejection in membrane filtration
have been investigated from physicochemical aspects. It was shown that the properties of the filter cake formed on the membrane
surface play a vital role in determining the filtration rate in mem-brane filtration. It was clearly demonstrated that such
filtration behaviors as the filtration rate and the rejection are highly dependent on the electrical nature of the particles
and/or the macromolecules. Furthermore, it was shown that the solvent density ρ has a large effect on the steady filtration
rate in upward ultrafiltration. 相似文献
87.
By means of contact angle measurements on dry layers of electrostatically neutral dextran with pure water (pH 6.1), water acidified with HCl (to pH 1.94) and water made alkaline with NaOH (to pH 12.8), it could be shown that there was essentially no change as a function of pH in the ratio of γ+/γ- of water as compared with the aqueous acid and alkaline solutions. (Here γ+ is the Lewis acid parameter of the polar surface tension component of water and γ- is its Lewis base parameter). In contrast, with contact angles measured with the same liquids on negatively charged clean glass, a significant decrease in contact angle was observed with water at pH 12.8, which was caused by the fact that at this alkaline pH an increase in surface hydrophilicity took place. This is because surfaces that have a given surface electrical potential at neutral pH generally acquire an even higher surface potential under more alkaline conditions which, concomitantly, also gives rise to an increase in surface hydrophilicity, and thus to lower contact angles with water. Finally, contact angles with acid water, pure water, and alkaline water, deposited on hydrophobic Parafilm surfaces, were exactly the same. 相似文献
88.
Equilibrium exchange isotherms were determined for the exchange of Cu2+ with NaZSM-5 at varying Cu(Ac)2 concentrations in solutions of constant volume and zeolite weight. At low Cu2+ levels the solid scavenged all the copper ions. When copper could be detected in the equilibrated solutions, overexchange was observed. The extent of overexchange was higher at pH 6 than at pH 4. These results were analyzed in relation to catalytic activity.On leave from the Central Institute for Chemistry, Hungarian Academy of Sciences, H1525 Budapest, Hungary. 相似文献
89.
《Journal of Process Control》2014,24(7):1023-1037
In this research the use of a feedback PID-like fuzzy controller scheme for pH control is presented to deal with instability problems near the equivalence point in neutralization processes. State space analysis of the titration curves and a fuzzy clustering algorithm based on calculating a measure of potential derived from the square distance of the pH data are complementary applied to define the membership structure and the fuzzy sets of the controller. To test the performance of the controller, both simulated and experimental runs were used. The fuzzy controller was tested for compensating step-change perturbations of propionic acidic flow rates, propionic acid concentration, and buffering conditions. Stationary cycling behavior has been observed for large loads of acidic flow rates. It was found that though the rejection time was strongly dependent on the mean residence time of the liquid solutions, the proposed controller keep the neutralization process operating close to the specified set point of pH = 7. 相似文献
90.
基于CARS变量筛选的固态发酵pH值近红外检测 总被引:2,自引:0,他引:2
为了提高近红外光谱技术快速检测固态发酵过程中pH值的精度和稳定性,提出了采用竞争自适应重加权采样(competitive adaptive reweighted sampling,CARS)法筛选出与pH相关的波长变量建立PLS预测模型,对验证集样本进行预测的方法。并与2种常见的变量筛选法GA-PLS和蒙特卡罗无信息变量消除法(MC-UVE)相比较.实验结果表明:CARS方法能有效筛选有用波长26个变量建立PLS模型,其校正集交互验证均方根误差(RMSECV)以及交互验证相关系数(Rc)分别为0.0368和0.9950;验证集的预测均方根误差(RMSEP)以及预测相关系数(Rp)分别为0.0589和0.9895。 相似文献