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41.
This research intends to develop the classifiers for dealing with binary classification problems with interval data whose difficulty to be tackled has been well recognized, regardless of the field. The proposed classifiers involve using the ideas and techniques of both quantiles and data envelopment analysis (DEA), and are thus referred to as quantile–DEA classifiers. That is, the classifiers first use the concept of quantiles to generate a desired number of exact-data sets from a training-data set comprising interval data. Then, the classifiers adopt the concept and technique of an intersection-form production possibility set in the DEA framework to construct acceptance domains with each corresponding to an exact-data set and thus a quantile. Here, an intersection-form acceptance domain is actually represented by a linear inequality system, which enables the quantile–DEA classifiers to efficiently discover the groups to which large volumes of data belong. In addition, the quantile feature enables the proposed classifiers not only to help reveal patterns, but also to tell the user the value or significance of these patterns. 相似文献
42.
Martin M.F.Choi 《中国化学快报》2009,20(2):210-212
A novel mode-filtered light gas sensor has been reported.It was constructed by inserting an optical fiber deposited by a thin silicone cladding of cryptophane A into a fused-silica capillary.When different concentration of methane gas was introduced to the sensor,the phenomenon that mode-filtered light intensity decreased with the increasing concentration of methane was observed. And a linear relationship was obtained within the methane concentration range of 0.0-16.0%(v/v).The detection limit was 0.06% ... 相似文献
43.
44.
为更加准确地描述机械磨削表面的接触刚度,本文在现有统计分析理论的基础上,提出了一种新的粗糙表面接触模型。模型针对接触表面微凸体形貌,将原有的球体假设采用cos函数曲线回转体代替,在假设形貌的基础上重新解算了微凸体弹塑性变形的临界压入深度,推导出了接触区域真实接触压力与接触刚度关系表达式。通过数值仿真方法得到了不同塑性指数下平均距离、接触刚度与接触压力之间的变化关系。对比结果显示,随着塑性指数的增大,本文模型的平均距离与球形模型的平均距离之间的差值逐渐增大。在接触刚度方面,本文模型相比球形模型更加贴近实验结果,并且随着塑性指数的增加,球形模型与本文模型之间的差值越来越大。本文模型结果与实验数据的相对偏差能够控制在5%以内,从而验证了本文模型的正确性,为更加准确地描述磨削表面零件的接触行为提供理论基础。 相似文献
45.
In this paper we examine the conditions for surface topography evolution and crack growth/fracture during the cyclic actuation
of polysilicon microelectromechanical systems (MEMS) structures. The surface topography evolution that occurs during cyclic
fatigue is shown to be stressassisted and may be predicted by linear perturbation analyses. The conditions for crack growth
(due to pre-existing or nucleated cracks) are also examined within the framework of linear elastic fracture mechanics. Within
this framework, we consider pre-existing cracks in the topical SiO2 layer that forms on the Si substrate in the absence of passivation. The thickening of the SiO2 that is normally observed during cyclic actuation of Si MEMS structures is shown to increase the possibility of stable crack
growth by stress corrosion cracking prior to the onset of unstable crack growth in the SiO2 and Si layers. Finally, the implications of the results are discussed for the prediction of fatigue damage in silicon MEMS
structures. 相似文献
46.
Application of chromatography technology in the separation of active alkaloids from Hypecoum leptocarpum and their inhibitory effect on fatty acid synthase
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Qiulong Zhang Guangxiang Luan Tao Ma Na Hu Yourui Suo Xiaoyan Wang Xiaofeng Ma Chenxu Ding 《Journal of separation science》2015,38(23):4063-4070
A method that involved the combination of pH‐zone‐refining counter‐current chromatography and semipreparative reversed‐phase liquid chromatography has been established for the preparative separation of alkaloids from Hypecoum leptocarpum. From 1.2 g of crude sample, 31 mg N‐feruloyltyramine, 27 mg oxohydrastinine, 47 mg hydroprotopine, 25 mg leptopidine, and 18 mg hypecocarpine have been obtained. The structure of the new compound, hypecocarpine, is confirmed based on the analysis of spectroscopic data, including NMR, UV, and IR spectroscopy and positive electrospray ionization mass spectrometry. The known chemical structures were characterized on the basis of 1H and 13C NMR spectroscopy. The purities of the five alkaloids are all over 92.7% as determined by high‐performance liquid chromatography. The alkaloids’ cytotoxicity in breast cancer cells is assessed by using a Cell Counting Kit assay and their inhibitory effect on fatty acid synthase expression is assessed by a Western blot assay. These results suggest that leptopidine could suppress growth and induce cytotoxicity in breast cancer cells and that the cytotoxicity of leptopidine may be related to its inhibitory effect on fatty acid synthase expression. 相似文献
47.
Two Co(II) coordination polymers (CPs), namely [Co(L)(tp)] n (1) and [Co(L)0.5(tbip)·H2O] n (2), (L = 1,6-bis(2-methylbenzimidazolyl) hexane, H2tp = terephthalic acid, H2tbip = 5-tert-butyl isophthalic acid), were hydrothermally synthesized and characterized by physicochemical and spectroscopic methods. CP 1 possesses a 2D (4,4) corrugated layer structure, which further extends into a 3D supramolecular framework by π–π stacking interactions, while CP 2 has a 1D ladder-like chain structure and combines into a 2D layer via O–H?O hydrogen-bonding interactions. The thermal stabilities, luminescence and electrochemical properties of both CPs, as well as photocatalytic activities for the decomposition of methylene blue, were presented. The photocatalytic mechanism was investigated by introducing t-butyl alcohol, EDTA-2Na and benzoquinone as ?OH, (hole)+ and ·O2? scavengers, respectively. 相似文献
48.
Cellulose films were successfully prepared from NaOH/urea/zincate aqueous solution pre-cooled to −13 °C by coagulating with
5% H2SO4. The cellulose solution and regenerated cellulose films were characterized with dynamic rheology, ultraviolet–visible spectroscope,
scanning electron microscopy, wide angle X-ray diffraction, Fourier transform infrared (FT-IR) spectrometer, thermogravimetry
and tensile testing. The results indicated that at higher temperature (above 65 °C) or lower temperature (below −10 °C) or
for longer storage time, gels could form in the cellulose dope. However, the cellulose solution remained a liquid state for
a long time at 0–10 °C. Moreover, there was an irreversible gelation in the cellulose solution system. The films with cellulose
II exhibited better optical transmittance, high thermal stability and tensile strength than that prepared by NaOH/urea aqueous
solution without zincate. Therefore, the addition of zincate in the NaOH/urea aqueous system could enhance the cellulose solubility
and improve the structure and properties of the regenerated cellulose films. 相似文献
49.
为考察溶质浓度对三碳多元醇水溶液氢键作用以及不同物质玻璃态形成能力的影响,采用1H NMR外标法研究不同浓度的1-丙醇(NPA),2-丙醇(IPA),1,2-丙二醇(PG),1,3-丙二醇(PD)和丙三醇(glycerol)的水溶液在室温常压下质子化学位移.结果表明:具有CH3CH(OH)一基团的PG烷基质子的化学位移变化趋势与其他几种醇相比有较大差异.醇羟基质子与水分子的氧形成较强O-H…O氢键.相同摩尔分数下,羟基数的增加导致水质子和羟基质子的化学位移降低,而且羟基位置不同也会导致水质子和羟基质子化学位移差异.这几种三碳多元醇碱性强弱的顺序和降低冰的均相成核温度能力的顺序一致,即glycerol>PG>PD>IPA>NPA,1H NMR技术表明glycerol和PG更适合用作低温保护剂. 相似文献
50.
Effects of preparation conditions of Au/FeO_x /Al_2O_3 catalysts prepared by a modified two-step method on the stability for CO oxidation
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Composite oxide FeO x /Al 2 O 3 -supported gold catalysts were prepared by a modified two-step method. The effects of preparation conditions on the initial catalytic activity and long-time stability were studied for CO oxidation. XRD, XPS and in situ FTIR were employed to investigate the state of FeO x and the species on the catalyst surface. The results showed that Au/FeO x /Al 2 O 3 catalysts prepared by this method exhibited high activity and high stability in a wide pH value range. Calcination pretreatm... 相似文献