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排序方式: 共有563条查询结果,搜索用时 125 毫秒
1.
《Ceramics International》2021,47(23):32963-32968
Effects of carbon source in single-source ZrC-based liquid precursors on the properties of the precursors and precursor-derived nano ZrC powders were investigated. The liquid precursors were prepared by directly blending and heating zirconium n-butoxide with either 2,4-pentanedione, benzoyl acetone or 1,3-diphenyl-1,3-propanedione additives which have the same chemical composition and structure except for the number of benzene rings (0, 1 and 2, respectively) in order to control the carbon content in the precursors. The ceramic yield of the precursor decreased as the number of benzene rings in the precursors increased. The stability of the precursors in air and the carbon content of the ceramic powder increased when using 1,3-diphenyl-1,3-propanedione additive. X-ray pure nano zirconium carbide powders with ultra-fine size (30 nm), isotropic shape and homogeneous particle size distribution were synthesized from the liquid precursors containing two benzene rings in the structure. Compared with ZrC powders derived from the precursors containing zero or one benzene ring, the powder from the precursor containing two benzene rings was finer and more homogeneous in size distribution. 相似文献
2.
Kenichiro Masaoka Fu Jiang Mark D. Fairchild Rodney L. Heckaman 《Journal of the Society for Information Display》2020,28(3):273-286
There are claims that multi‐chromatic displays can achieve a wider color gamut by the use of additional highly saturated secondary color channels. However, there are other claims that these displays lose lightness and/or color saturation at brighter levels. These apparently divergent views have led to some controversy in the display industry and at standard setting organizations. This study examines the color gamut volume for a variety of simulated and measured multi‐chromatic (sometimes incorrectly referred to as “multi‐primary”) displays using combinations of white and/or secondary color channels, such as cyan, magenta, and yellow. Furthermore, a two‐dimensional gamut representation, referred to as “gamut rings,” is introduced to illustrate that the addition of nonprimary optical color channels to a trichromatic (RGB) display can result in a significant decrease in the chroma at higher lightness levels. The additional saturated color channels can increase the gamut volume only around their hues at darker levels. The results also confirm the validity of comparing the color light output and white light output for revealing the design trade‐offs between the high‐peak white and the color‐image brightness for multi‐chromatic displays. 相似文献
3.
在开展结冰试验时,结冰风洞风扇叶片前缘有结冰风险,影响风洞安全运行。针对大型旋转叶片结冰问题,提出了旋转叶片电加热防冰系统设计方法,研制了大型结冰风洞旋转叶片电加热防冰系统。首先,研制了内置电加热单元和温度反馈的防冰叶片。针对叶片复杂的工作环境,提出一种新的旋转叶片电加热防冰功率计算方法,通过精确测量和方案优化,设计了基于特殊环境的分半式、大尺寸、高线速度、碳刷自动移开/压紧的导电滑环。最后,采用变结构分级温度闭环和试验参数连锁防冰控制策略解决了旋转叶片结冰问题。该系统已应用于大型结冰风洞,运行中加热电流和叶片温度反馈信号传输连续,所有旋转叶片前缘快速加热且温度分布均匀,防冰效果好。 相似文献
4.
AbstractCryptographic attacks are typically constructed by black-box methods and combinations of simpler properties, for example in [Generalised] Linear Cryptanalysis. In this article, we work with a more recent white-box algebraic-constructive methodology. Polynomial invariant attacks on a block cipher are constructed explicitly through the study of the space of Boolean polynomials which does not have a unique factorisation and solving the so-called Fundamental Equation (FE). Some recent invariant attacks are quite symmetric and exhibit some sort of clear structure, or work only when the Boolean function is degenerate. As a proof of concept, we construct an attack where a highly irregular product of seven polynomials is an invariant for any number of rounds for T-310 under certain conditions on the long term key and for any key and any IV. A key feature of our attack is that it works for any Boolean function which satisfies a specific annihilation property. We evaluate very precisely the probability that our attack works when the Boolean function is chosen uniformly at random. 相似文献
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针对薄壁圆环类零件钻孔时不易找正中心、加工效率低、加工精度很难得到保证的难题,设计一种用于薄壁圆环类零件的钻模。给出钻模的整体设计,列出钻模结构图,指出钻模的使用方法及注意事项,论述其产生的经济效益。结果表明:该方法简单、实用,避免了零件在加工过程中的变形,很好地保证了零件的加工精度,提高了加工效率,降低了加工成本。 相似文献
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我国古村落数量大,历史悠久,历史和艺术价值不容忽视,但当今社会快速发展,人们生活方式发生巨大变革,原始古村落难以满足现代人生活需求,古村落发展和保护面临许多现实问题,该文以张家口市西古堡为例,探讨古村落的保护和发展问题。 相似文献
9.
《Journal of Industrial and Engineering Chemistry》2014,20(2):372-378
A series of new bis (imidazolium) cation-based ionic liquids, wherein two imidazole rings are tethered by alkyl ether chains (oxygen numbers) of different lengths, were prepared, and their coal dissolution and dispersion properties were studied. It was found these ionic liquids can be used to fragment, disperse, and partially dissolve micrometer-size coal particles by simply mixing ionic liquid/coal dispersions. Dissolution performances and light hydrocarbon production were found to be sensitively increased by increasing the lengths of alkyl ether chains between imidazolium rings. 相似文献
10.
The development of the scientific theory on the stability of vaulted structures was driven mainly during the 18th century based on applying the laws of Mechanics and the knowledge of the properties of materials. In the specific case of structures such as domes, the development of the theory is closely related to the theory of arches and vaults. Still, the main contributions are made in technical reports on the construction, stability, and repair of domes, such as the dome of Saint Peter's in Rome and Sainte-Geneviève or Pantheon in Paris. This article, therefore, analyses the relationship between theory and practice and the development achieved in the specific subject of masonry domes during the 18th century from the point of view of the Limit Analysis of Masonry Structures. In a more general sense, the objective of this research is to study in greater depth the theory of Limit Analysis itself, that is, to learn from the work carried out in the 18th century by mathematicians, architects, and engineers, who, although unaware of the existence of the theoretical framework of Limit Analysis as such, moved within it. 相似文献