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排序方式: 共有168条查询结果,搜索用时 31 毫秒
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Science China Mathematics - In this study, we propose nonparametric testing for heteroscedasticity in nonlinear regression models based on pairwise distances between points in a sample. The test... 相似文献
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以微观试验和流变性能试验为手段,分别研究零电场下和在电场作用下的电流变液体黏性变化规律.研究结果表明:零电场下电流变液体的黏性与Krieger-Dougherty公式具有很好的拟合效果,其中逾渗临界值强依赖于悬浮液体中固体颗粒的性质并随工作温度变化.在电场作用下,电流变悬浮液体的黏度随剪切速率的变化规律分为3个阶段:即呈线性的启动段、非线性的幂定律模型流动段和宾汉模型流动段.研究结果为电流变效应工程应用提供依据. 相似文献
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A silane‐modified mono‐lacunary Keggin‐type polyoxometalate (POM), (Bu4N)4[SiW11O39{(CH2?CH? Si)2O}] (SiW11? CH?CH2), was obtained by reaction of vinyltrimethoxysilane with K8(SiW11O39) in acidic MeCN/H2O mixed solutions. Then, the modified polyoxometalate was physically blended with the pyromellitic dianhydride (PMDA)‐4,4′‐oxydianiline (ODA) poly(amic acid) and the blends were thermally imidized to form polyimide/ polyoxometalate composites. The X‐ray diffraction (XRD) analysis indicates that the polyoxometalate clusters cannot form crystalline structures in the composite, suggesting that the blending leads to improved compatibility between the polymer matrix and the modified polyoxometalate. The EDS (W‐mapping) studies on the composite films reveal that the polyoxometalate clusters are well dispersed in the polyimide matrix. The physical incorporation of modified POM into polyimide remarkably reduced the dielectric constant of the latter from 3.29 to 2.05 when 20 wt% of SiW11? CH?CH2 was used. Besides, the addition of the modified POM into polyimide increased the storage modulus of polyimide without severely affecting its thermal properties. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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Shiheng Yin Dongxiao WuJi Yang Shumei LeiTongchun Kuang Bin Zhu 《Applied Surface Science》2011,257(20):8481-8485
Biomimic superhydrophobic surfaces with contact angle greater than 150° and low sliding angle on copper substrate were fabricated by means of a facile solution immersion and surface self-assembly method. The scanning electron microscopy showed a nanoneedle structure copper surface with sporadic flower-like aggregates after treatment with sodium hydroxide and potassium persulfate solution. X-ray photoelectron spectroscopy and X-ray diffraction results confirmed that the formed nanoneedles were crystallized Cu(OH)2. And the hydrophilic Cu(OH)2 surface can be further modified into superhydrophobic through surface self-assembly with dodecanoic acid. 相似文献
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Chromatographia - A capillary electrophoresis-indirect laser-induced fluorescence detection method was established for neomycin detection in fish. With rhodamine 6G as the background fluorescent... 相似文献
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Chen?Zong Duoduo?Zhang Hua?Yang Shumei?Wang Ming?Chu Ping?LiEmail author 《Mikrochimica acta》2017,184(9):3197-3204
The authors describe an array for chemiluminescence (CL) based determination of cardiac troponin T (cTnT), an important cardiovascular disease marker. The tracing tag consists of silver nanoparticles (AgNPs) loaded with guanine-rich DNA sequences and detection antibody in a high numerical ratio. The loaded AgNPs were then reacted with hemin to form a hemin/G-quadruplex DNAzyme. A disposable immunosensor array was fabricated by immobilizing capture antibody on corresponding sensing sites on a glass chip. Once a sandwich immunocomplex is formed on the array, the tracing tag catalyzes the CL reaction of the luminol-p-iodophenol and H2O2 system to produce a CL signal, which is collected by a CCD camera. An intuitive CL image is obtained containing all of the spots on the array. Under optimal conditions, the method shows a wide linear range over 4 orders of magnitude (from 0.003 to 270 ng·L?1), a detection limit down to 84 fg·L?1, and a throughput as high as 44 tests·h?1. The results obtained with serum samples are in acceptable agreement with reference values. The AgNP-based tracing tag as well as the immunoassay method shows a promising potential for point-of-care testing for the early clinical diagnosis of cardiovascular disease. 相似文献
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研究了外腔式PbWO4拉曼激光器在纳秒脉冲抽运下的输出特性。利用主动调Q的Nd:YAG激光器产生的脉冲宽度为31.4ns,最大输出能量为200mJ的1064nm激光作为抽运源。拉曼激光谐振腔采用的是平凹腔设计。测量了输出的拉曼光脉宽与抽运能量的关系,分析了输出的拉曼光脉冲波形图和光谱图,测量了输出的拉曼光脉冲能量与抽运能量的关系,计算了转换效率与抽运能量的关系。当注入抽运光能量达到42mJ时,得到了一阶斯托克斯光脉冲的最大能量和转换效率分别为10mJ和24%,获得外腔式PbWO4拉曼激光器的一阶斯托克斯光脉冲波长为1177.6nm,典型的一阶斯托克斯光脉冲脉宽为20ns。 相似文献
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破产概率受保费变化影响,保费随着准备金变化,在本文中考虑带有利率的风险模型;其索赔发生是Cox过程. 相似文献