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The chemical equilibrium and reaction kinetic behavior in the synthesis of polyoxymethylene dimethyl ethers(DMMn) were investigated over sulfated titania in order to reveal the decisive factor controlling the reaction. The results showed that the molar ratio of adjacent DMMn products in equilibrium solution had the same value, which depended absolutely on the reaction temperature. Meanwhile, the reactions had the same DMMn products distributions under varied reaction conditions. The equilibrium constants of the related step-wise reactions for DMMn formation were equal, which were calculated based on the bulk compositions of the reaction solution. And thus, the selectivity to DMMn was mainly controlled by the chemical equilibrium, i.e., thermodynamic control. In brief, the present results provide some guidance for future synthesis of DMMn. 相似文献
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脉冲激光离子源飞行时间质谱计的设计与研制 总被引:1,自引:0,他引:1
目前国内外的飞行时间质谱计,大多采用双电场加速的方式改善其质谱分辨率。通过较详尽的计算,讨论了双电场飞行时间质谱计中各参数对质谱分辨率和灵敏度的影响及其选择的方向,并在此基础上选定了仪器的主要参量,为飞行时间质谱计的设计与改进提供了依据。还介绍了在此基础上设计与建立的脉冲激光离子源飞行时间质谱计。 相似文献
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在本文中,以电声子机制超导电性理论为基础,用电负性均衡原理研究了由于超导材料的各向异性引起的电子态密度分布的不均匀性,晶格稳定性的差异性及超导材料中元素成键特征对超导转变温度影响的特征,提出了在各向异性的超导材料中电声子机制可以产生高的超导转变温度Tc. 相似文献
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陈蔚 《数学物理学报(B辑英文版)》2003,23(3)
The transient behavior of a semiconductor device consists of a Poisson equa-tion for the electric potential and of two nonlinear parabolic equations for the electrondensity and hole density.The electric potential equation is discretized by a mixed finiteelement method. The electron and hole density equations are treated by implicit-explicitmultistep finite element methods. The schemes are very efficient. The optimal order errorestimates both in time and space are derived. 相似文献
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The Preparation of Perovskite Nano Powder by Sol-gel from DTPA and the Mechanism of Thermal Decomposition 总被引:2,自引:0,他引:2
ZunLiMO HongCHEN KunJieWANG ZhengHaiSHI HeJunLI 《中国化学快报》2004,15(6):721-724
Dy0.8Sr0.2FeO3 nano powder, a synthetic oxide, is made by sol-gel method from metal nitrate and diethylenetriaminepentaaeetic acid (DTPA), and the processing parameters are optimized.The process of the preparation, thermal decomposition and the property of the powder are studied by TG-DTA, IR, TEM, and XRD. The diameter of the average grain is about 70 nm. This new technique can be used in the preparation and the studying of ha‘no materials in the complex oxide system. 相似文献
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In the present paper, we define sensitive pairs via Furstenberg families and discuss the relation of three definitions: sensitivity, F -sensitivity and F -sensitive pairs, see Theorem 1. For transitive systems, we give some sufficient conditions to ensure the existence of F -sensitive pairs. In particular, each non-minimal E system (M system, P system) has positive lower density ( Fs , Fr resp.)-sensitive pairs almost everywhere. Moreover, each non-minimal M system is Fts -sensitive. Finally, by some exampl... 相似文献
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V.?M.?AkhmedovEmail author N.?E.?Melnikova I.?D.?Akhmedov 《Russian Chemical Bulletin》2017,66(5):782-807
The results of theoretical and experimental studies of the structure and properties of poly-meric carbon nitrides are reviewed. Various routes of the synthesis of these compounds using nitrogen-rich precursors, viz., cyanamide, dicyandiamide, carbamide, melamine, etc., are described. Particular attention is paid to the catalytic properties of graphite-like carbon nitrides and methods of their texture and chemical modification. The main trends for the synthesis of meso- and nanostructured materials based on graphite-like carbon nitrides are considered. Prospects of their practical application as efficient photo-, electro-, and heterogeneous metal-free catalysts are discussed. 相似文献
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