排序方式: 共有59条查询结果,搜索用时 15 毫秒
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基于结构方程(SEM)理论,以2008年统计数据为样本对影响城市现代化的测量指标进行了一阶、二阶验证性因素分析,得到了结构方程模型.并以测量指标在因子上的负荷、路径系数为基础构建权重,建立了城市现代化水平综合评价模型.对我国重要城市(直辖市、主要省会城市)现代化水平程度进行了相对评价,得到较为满意的结果. 相似文献
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Droplet aggregation is an important cause of instability in emulsions because it may, on one hand, lead to an increased creaming rate, resulting in fast separation of a concentrated emulsion phase (creamed layer). On the other hand, it may also lead to the formation of a stabilizing, droplet-based network. Early detection of instability is often difficult due to the high turbidity and viscosity of more concentrated food emulsions. The applicability of diffusing-wave spectroscopy (DWS) for monitoring droplet aggregation and creaming was studied using a model system consisting of a protein-stabilized emulsion, to which a soluble polymer ("thickener") was added. This addition leads to an increased solvent viscosity and may induce droplet aggregation. In addition, the redistribution process of emulsion droplets in aggregating concentrated emulsions was directly observed by confocal scanning laser microscopy (CSLM). By DWS the decrease of the droplet mobility caused by the viscosity increase of the continuous phase could be separated from the effect of droplet aggregation. Moreover, a distinction could be made between aggregation, leading to increased creaming rates and that leading to the formation of a stabilizing droplet network. The potential of DWS for in situ measurement of the stability of concentrated emulsions is discussed. Copyright 2000 Academic Press. 相似文献
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Raman spectra were obtained at temperatures 375–650 K and pressures up to 4 atm from GaCl3-NbCl5 and GaCl3-TaCl5 binary mixtures in the liquid and vapour state. The data indicate formation of NbGaCl8 and TaGaCl8 liquid and vapour dinuclear addition complexes. The spectra were interpreted in terms of a C2ν configuration for the MGaCl8 (M = Nb, Ta) molecules consisting of a MCl6 octahedron sharing an edge with a GaCl4 tetrahedron. A comparison of the spectral features of 1 : 1 GaCl3-NbCl5 and GaCl3-TaCl5 molten mixtures with the spectra of the corresponding polycrystalline samples indicates that the proposed identity for the complexes is maintained in all three phases. The NbGaCl8 and TaGaCl8 complexes exist in the liquid state in a wide temperature range beyond their melting points (125 and 150°C, respectively) and are shown to undergo dissociation to their components [Nb2Cl10(1)/NbCl5(1), Ga2Cl6(1) and Ta2Cl10(1)/TaCl5(1)] with increasing temperature. Both complex molecules are identified in the gaseous state in low percentages among the vapours of their components and are almost totally decomposed at temperatures higher than ca 325°C. The enthalpy of the reaction TaCl5(g) +1/2Ga2Cl6(g) TaGaCl8(g) was determined from accurate relative Raman intensity measurements as ΔH0 = −38±2 kJ mol−1. 相似文献
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Constantinos Tsitsilianis George A. Voyiatzis Joannis K. Kallitsis 《Macromolecular rapid communications》2000,21(16):1130-1135
A two step synthetic procedure towards model coil‐rod‐coil triblock copolymers was developed. In the first step, α,ω‐bromo‐functionalized oligophenylenes (rod part) were modified to anionic bifunctional initiators. In the second step, flexible chains were grown from both ends of the rod part by an anionic polymerization procedure leading to polystyrene‐rod‐polystyrene and/or poly(2‐vinyl pyridine)‐rod‐poly(2‐vinyl pyridine) triblock copolymers. Characterization of the final products by gel permeation chromatography, NMR spectroscopy, light scattering, Raman spectroscopy and differential scanning calorimetry demonstrated that well‐defined coil‐rod‐coilblock copolymers can be synthesized. 相似文献
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研究了铁(Ⅲ)和钼(Ⅵ)与邻苯二酚在pH 6.20 微酸性介质中反应生成的有色配合物与717型强碱性阴离子交换树脂的交换吸附,探讨了树脂相分光光度法同时测定铁(Ⅲ)和钼(Ⅵ)的实验条件。铁(Ⅲ)和钼(Ⅵ)树脂相有色配合物的最大吸收波长分别为520 nm 和400 nm ,表观摩尔吸光系数ε为4.1×104 L/(m ol·cm )和9.0×104 L/(m ol·cm ),符合Beer定律的范围为0~2.2 m g·L- 1和0~1.6 m g·L- 1。此法用于地下水中微量铁和钼的测定,相对标准偏差为3.3 % 和3.2 % 。 相似文献