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111.
Porous poly(vinyl alcohol) (PVA) membranes were prepared by a phase‐inversion method. The influence of chemical crosslinking and heat treatments on the swelling degree, resistance to compaction, mechanical strength, and morphology of porous PVA membranes was extensively studied. The crosslinking degree and crystallinity of the membranes, calculated from IR spectra, increased with the treatment time. The porosity, calculated on the basis of swelling experiments, showed a decreasing trend for heat‐treated membranes but remained almost at a constant value for crosslinked membranes. Such a change was further proved with scanning electron microscopy pictures. The behavior was explained by the rearrangement of PVA chains during the heat‐treatment process, which led to morphological changes in the membranes. The mechanical properties of the porous membranes in dry and wet states were measured, and a great difference was observed between crosslinked and heat‐treated membranes in the dry and wet states. The crosslinked membranes showed good mechanical properties in the dry state but became fragile in the wet state. On the contrary, the heat‐treated membranes were more flexible in the wet state than in the dry state. This change was explained by the turnaround of inner stress in the systems during the swelling process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
112.
以脱硅锆、轻烧氧化镁、消石灰为原料,进行了MgO-ZrO2-CaO系原料的合成,研究了化学组成(包括ZrO2含量、CaO/ZrO2比),烧成温度,杂质等对合成料性能和组织结构的影响。 相似文献
113.
114.
本文通过运用“生产函数法”、“增长速度方程”来定量分析技术进步在长城铝业公司水泥厂产出增长中的作用,从中找出该水泥厂生产经营过程中存在的问题及未来发展方向。 相似文献
115.
针对目前应用在UNIX系统中入侵检测知识库适应能力不足的问题.提出了一种适应于不同系统环境的知识库体系结构。检测规则按相应系统与服务类型以模块化形式存储,通过应用配制文件加载。实现了入侵检测知识库的可扩展性.提高了入侵检测知识库的通用性,并且可以提高检测规则的搜索效率。 相似文献
116.
This paper highlighted the use of X-ray diffraction, scanning electron microscopy and X-ray fluorescence spectroscopy to investigate the changes on the surface composition of high-sulfur coal and pyrite before and after ultrasonic conditioning. The results showed that ultrasonic conditioning resulted in a decrease in the contents of iron and sulfur in coal, an increase in the content of element carbon, and an increase in the purity of the coal. Conversely, ultrasonic conditioning led to an increase in the content of iron and sulfur in pyrite, a decrease in the impure content of calcium, and a relative increase in the purity of the pyrite after ultrasonic conditioning. This study verified that on the one hand, ultrasonic conditioning can promote the pyrite separation from the high-sulfur coal, with the separated pyrite taking the form of FeS; on the other hand, it can produce a cleaning effect on the surface of coal and pyrite with the consequent increase both in hydrophobicity of coal and hydrophilicity of pyrite. The paper introduced ultrasonic pre-treatment of the slurry and stepped froth removal tests of high-sulfur coal and the study on the yield, ash and sulfur content of clean coal in different phases. The results gave further evidence of the increases both in the rate and the selectivity of flotation. This study shows that ultrasonic conditioning can enhance the performance of de-sulphurization of high-sulfur coal flotation. 相似文献
117.
118.
Stock market forecasting has been a challenging financial research topic for decades. In the literature, there are numerous
results based on point methods. However, poor forecasting quality has been a continuous problem. Motivated by the fact that
financial data varies within intervals, we apply interval methods on a well known stock pricing model [3] to predict stock
market variability as intervals. Empirical results obtained with a few different approaches in this paper consistently suggest
that interval forecasts have better overall quality than traditional point forecasts. 相似文献
119.
分析了建筑陶瓷企业实施精益生产的条件和当前推行精益生产的主要障碍,对应用中存在的问题进行了分析并提出了相关建议。 相似文献
120.