接地故障中和器全补偿技术及应用

目前世界上普遍应用的配电系统消弧线圈接地方式在一定程度上保证了系统的供电可靠性,但仍然存在接地残流较大和高阻型故障检测难等问题。GFN(接地故障全中和器)具有消除接地电流、准确定位故障点,以及提升供电稳定性和可靠性的作用。介绍了瑞典GFN接地故障全补偿技术的基本原理、功能特点、应用实例和功能扩展等。实用情况表明GFN接地故障全补偿技术可以较为成功地减少特殊瞬时故障。     

德国中小城镇在国土开发中扮演的重要角色

与大多数欧洲城市相比,德国的城镇体系属于均衡发展的典范。地区的高度自治、联邦体制以及强有力的州政府使德国在两千多年的城市发展历程中,逐渐形成了大中小城市遍布全国的空间形态。这些城市都具有相似的生活质量、便捷的交通和便利的服务。基于对中小城镇的概括定义,本文将首先简要介绍城市均衡发展的历史渊源及小城镇在德国的重要作用,并举例分析一些进行中的都市化过程,随后将选取纽伦堡城市区域作为中小城镇的成功案例重点介绍,最后简要说明支持城镇发展的联邦政策规划。     

Quantification of Yttria in Stabilized Zirconia by Raman Spectroscopy

The relationship between Y₂O₃ content in tetragonal and cubic ZrO₂ phases and the shift of the Raman band at ～645/cm was investigated. With increasing Y₂O₃ content, the 645/cm Raman band position decreases to lower Raman shift values. A fit of x = Y₂O₃ content in wt% and y = Raman band position in per cm, was found to be valid for low Y₂O₃‐stabilized t‐ZrO₂, t′′‐ZrO₂ transition, and fully stabilized c‐ZrO₂. Modeling the change in lattice parameters due to the incorporation of Y₂O₃ in ZrO₂ as obtained from Rietveld‐refined XRD data confirms that the peculiar sigmoidal form of the band shift with Y₂O₃ content is mainly due to a variation of the amount of oxygen vacancies. The resultant method is highly attractive in fields of Y₂O₃ determination in ZrO₂ materials where a fast, spatially resolved, and nondestructive analysis is required.     

Structural characterization of octadecyl modified MCM-41 silica by NMR and FTIR

Mesoporous MCM-41 silica spheres were prepared via the pseudomorphic route, using commercial prontosil silica spheres. Surface modification offers a great opportunity to adjust both the pore structure and surface properties of MCM-41 type materials which results in materials of improved hydrothermal and mechanical stability to make them promising candidates for chromatographic applications. In the present context, the obtained MCM-41 silica spheres were surface modified with octadecyl (C₁₈) alkyl chains, by using direct grafting and surface polymerization methods, in order to vary the degree of surface hydrophobicity. The resulting materials were characterized before and after surface modification using various characterization techniques, with special emphasis on NMR and FTIR spectroscopies, for studying the attachment, mobility and the conformational order of the attached alkyl chains.     

Filler Wetting in Miscible ESBR/SSBR Blends and Its Effect on Mechanical Properties

The selective wetting behavior of silica in emulsion styrene butadiene rubber (ESBR)/solution styrene butadiene rubber (SSBR) blends is characterized by the wetting concept, which is further developed for filled blends based on miscible rubbers. It is found that not only the chemical rubber–filler affinity but also the topology of the filler surface significantly influences the selective filler wetting in rubber blends. The nanopore structure of the silica surface has been recognized as the main reason for the difference in the wetting behavior of the branched ESBR molecules and linear SSBR molecules. However, the effect of nanopore structure becomes more significant in the presence of silane. It is discussed that the adsorption of silane on silica surface constricts the nanopore to some extent that hinders effectively the space filling of the nanopores by the branched ESBR molecules but not by the linear SSBR molecules. As a result, in silanized ESBR/SSBR blends the dominant wetting of silica surface by the tightly bonded layer of SSBR molecules causes a low‐energy dissipation in the rubber–filler interphase. That imparts the low rolling resistance to the blends similar to that of a silica‐filled SSBR compound, while the ESBR‐rich matrix warrants the good tensile behavior, i.e., good abrasion and wear resistance of the blends.