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981.
A rapid real-time polarization measurement system was designed and implemented in this paper. The system is centered round a computer running application developed for the purpose. The paper illustrates how to build such an excellent application with National Instruments’ graphical programming language LabVIEW, a synchronized high speed multi-channels data acquisition card and some photoelectric conversion module in detail. With simple and friendly user interface, the experimental result shows that the measurement system has high computational efficiency, high precision calibration matrix, which can be efficiently utilized in experiments relating to the measurement of polarization. 相似文献
982.
983.
984.
"文革"时期的期刊传播由于时代的特殊性而呈现与前后截然不同的传播范式,而在"文革"时期"如火如荼"的科学史研究,尤其是中国古代科学技术史的研究,是这个时代的"副产品"。虽然处于政治高压之下,"批林批孔"、批儒尊法是主要目的,但这一时期的科学史研究承上启下,为之后中国第二次科学史研究高潮的出现作了重要铺垫。 相似文献
985.
986.
An efficient strategy enabling the construction of polysubstituted 1,2-dihydroquinoline derivatives mediated by the commercially available, economical, and environmentally benign iodine (3 mol %) under mild conditions was developed. Various arylamines and α-ketoesters could participate in this cascade reaction, and the desired products were obtained in excellent yields up to 98%. 相似文献
987.
One new sesquiterpene lactone,1 α,8 α,9 α-trihydroxyeudesman-3(4),7(11)-dien-8 β,12-olide(1) and two new phenylpropanoidsubstituted catechin glycosides,glabraoside C(2) and glabraoside D(3) were isolated from the whole plant of Sarcandra glabra. Their structures were established by the analyses of spectral and chemical evidences. 相似文献
988.
The PdCl2-catalyzed allylation of heteroarenes is presented. Various heteroarenes including O-, N-, and S-based ones were allylated efficiently with a rich range of allylic acetates in the presence of only 2 mol % of PdCl2, without the need of bases/acids, additives, and external supporting ligands. In addition, the reactions were carried out under mild and simple conditions just by stirring the two reactants and catalyst in CH2Cl2 at 60 °C. Moreover, the by-product produced was non-toxic acetic acid. Thus, the method presented in this work provides a general, clean, and operationally simple approach for the functionalization of heteroarenes. Finally, a preliminary mechanistic study suggested that the Pd(II) may be reduced in situ by the heteroarenes to Pd(0), which serves as the active metal center to catalyze the following allylations of heteroarenes via a Tsuji–Trost pathway. 相似文献
989.
Zhonggang Zhang Danting Yue Changrong He Shuang Ye Weiguo Wang Jinliang Yuan 《Heat and Mass Transfer》2014,50(11):1575-1586
In this study, a three-dimensional computational fluid dynamics model has been developed for an anode-supported planar SOFC. The conservation equations of mass, momentum, species/charges and thermal energy are solved by finite volume method for a complete unit cell consisting of 13 parallel channels in both anode and cathode. The simulation results of the developed model are well in agreement with the experimental data obtained at same conditions. In this study, the co-flow arrangement with hydrogen utilization of 60 % and operating voltage of 0.7 V is used as the base case, and compared with the counter-flow arrangement. The predicted results reveals that the maximum temperature obtained in the counter-flow arrangement is about 10 °C lower than that of co-flow, but the counter-flow arrangement has a higher temperature gradient between the respective anodes and cathodes in a cross-section normal to the main flow direction, especially in the air inlet region of the cell (x = 0.04 m),which is very harmful to the lifetime of materials. The current density is very unevenly distributed along and normal to the flow direction for both the co- and counter-flow arrangements, and the maximum values occur at junctions of the electrodes, channels and ribs, which causes higher over-potentials and ohmic heating. 相似文献
990.
Ke Wang Zuyi Li Chengye Yuan 《Phosphorus, sulfur, and silicon and the related elements》2013,188(6-7):1797-1800
Bioreduction of 2-oxo-3-halo (or azido) alkanephosphonates and 4-ethoxy-4,2-dioxobutanephosphonates by baker's yeast afforded 3-substituted 2-hydroxyalkanephosphonates in moderate to good yields and ee value. Moreover, a regio- and stereoselective bioreduction of 2,3-dioxoalkanephosphonates and 2,4-dioxoalkanephosphonates by baker's yeast was studied also. The resulting chiral hydroxy compounds can be used as chirons for the stereoselective synthesis of biologically active molecules. 相似文献