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992.
Dario VenegoniPhilippe Serp Roselyne FeurerYolande Kihn Constantin VahlasPhilippe Kalck 《Carbon》2002,40(10):1799-1807
Multiwalled carbon nanotubes have been produced from H2-C2H4 mixtures on Fe-SiO2 catalysts by a fluidized bed catalytic chemical vapor deposition process. Various parameters such as the catalyst preparation, the residence time, the run duration, the temperature, the H2:C2H4 ratio, the amount of metal deposited on the support have been examined. The influence of these parameters on the deposited carbon yield is reported, together with observations of the produced material. This process allows an homogeneously distributed deposition of nanotubes (10-20 nm diameter), that remain anchored to the support. 相似文献
993.
针对目前用户在使用搜索引擎过程中,检索结果冗余、效率低下等问题,本文在对文献垂直搜索系统中Lucene.Net的索引算法研究基础上,结合用户实际专业检索需求,改变其算法中的激励因子,实验结果证明该方法确能提高搜索结果的相关度. 相似文献
994.
随着电子商务,个人博客,社交网站和微博的蓬勃发展,互联网进入了一个崭新的时代,而在线评论的情感分类关系到个人决策、企业管理甚至社会安全.提出了一种基于区间直觉模糊的情感分类模型,采用了区间直觉模糊算子来计算特征词的区间直觉模糊数,利用区间直觉模糊集的隶属度、非隶属度和犹豫度分别定量地描述特征词,通过情感合成确定文本的情感倾向,从而获得准确率较高的情感倾向性分析结果.最后通过相同语料库的比较实验证明该分类模型的可行性、正确性和较高的分类性能. 相似文献
995.
Walking tracks of Colorado potato beetles,Leptinotarsa decemlineata Say, were recorded on a locomotion-compensator in response to wind, odors of host plantsSolanum tuberosum L. and nonhost plantsLycopersicon hirsutum f.glabratum C.H. Mull, and to mixtures of these plant species. Host-plant odor induced positive anemotactic responses in starved females, whereas odor of the nonhostL. hirsutum was neither repellent nor attractive. The attractiveness of host-plant odor, however, was neutralized in the odor blend of plant species. Masking the attractive host-plant odor will hinder the beetle's searching for host-plant patches, and this principle may be exploited in pest control by mixed cropping.The locomotion-compensator was constructed with financial support from the Foundation for Fundamental Biological Research (BION), which is subsidized by the Netherlands Organization for the Advancement of Pure Research (ZWO), grant 14-02-02. The first author was supported by a grant from the French Ministry of Industry and Research. 相似文献
996.
The variable property grain model, including the effect of grain diffusion resistance, has been applied to experimental results from the reaction of hydrogen sulfide with zinc oxide. Grain radius is assumed to vary under the combined effects of sintering and extent of reaction. Property variations are correlated by the specific surface area, an easily measured quantity. All model parameters with the exception of the grain diffusion coefficient have been evaluated by literature correlations or independent experimental measurements. Significant improvement in the match with experimental data, as compared to the constant property grain model, has been achieved. 相似文献
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Polysiloxane loaded with SiC as inert filler, and Al as active filler, was pyrolyzed in nitrogen to fabricate SiOC composites, and the processing and properties of the filled SiOC composites were investigated. Adding SiC fillers could reduce the linear shrinkage of filler-free cured polysiloxane in order to obtain monolithic SiC/SiOC composites. The flexural strength of SiC/SiOC composites reached 201.3 MPa at a SiC filler content of 27.6 vol.%. However, SiC/SiOC composites exhibited poor oxidation resistance, thermal shock resistance and high temperature resistance. Al fillers could react with hydrocarbon generated during polysiloxane pyrolysis at 600 °C and N2 at 800 °C to form Al4C3 and AlN, respectively. The volume expansions resulting from these two reactions were in favor of the reduction in linear shrinkage and the improvement in flexural strength of SiC/SiOC composites. The flexural strength of Al-containing SiC/SiOC composites was 1.36 times that of SiC/SiOC composites without Al at an Al filler content of 20 vol.%. The addition of Al fillers remarkably improved the high temperature resistance and oxidation resistance of SiC/SiOC composites, but not thermal shock resistance. 相似文献
1000.