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排序方式: 共有732条查询结果,搜索用时 31 毫秒
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A novel cedar-like Au nanoparticles (AuNPs) coating was fabricated on an etched stainless steel (SS) wire by direct chemical deposition and used as an efficient and unbreakable solid phase microextraction (SPME) fiber. The etched SS wire offers a rough surface structure for subsequent growth of AuNPs in chloroauric acid solution. As a result, the uniform cedar-like AuNPs coating with larger surface area was tightly attached to the etched SS wire substrate. The AuNPs coated etched SS fiber (AuNPs/SS) was examined for SPME of ultraviolet (UV) filters, phthalate esters and aromatic hydrocarbons coupled to high-performance liquid chromatography with UV detection. The fabricated fiber exclusively exhibited excellent extraction efficiency and selectivity for some aromatic hydrocarbons. Influential parameters of extraction and desorption time, temperature, stirring rate and ionic strength were investigated and optimized. The limits of detection ranged from 0.008 μg L−1 to 0.037 μg L−1. The single fiber repeatability varied from 3.90% to 4.50% and the fiber-to-fiber reproducibility ranged from 5.15% to 6.87%. The recovery of aromatic hydrocarbons in real water samples spiked at 2.0 μg L−1 and 20 μg L−1 ranged from 94.38% to 106.2% with the relative standard deviations below 6.44%. Furthermore the growth of the cedar-like AuNPs coating can be performed in a highly reproducible manner. This fabricated fiber exhibits good stability and withstands at least 200 extraction and desorption replicates. 相似文献
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采用激光剥蚀电感耦合等离子体质谱法测定纯铝及铝丝中铁、硅、铜、锰、镁、钛、锌、铬和镍的含量。采用低功率等离子体,以27Al为内标。样品直径为0.5~3 mm时,直径粗细与元素的信号不相关。所有元素的分馏因子在0.94~1.13之间时,可以认为没有分馏效应;纯铝和铝合金的基体效应不明显,铸铝会影响基体效应。测定了块状和丝状标准物质,测定值与认定值基本吻合,纯铝板的测定值与直读光谱法测定结果相一致。受背景干扰的影响,测定值的相对标准偏差(n=5)在2.9%~32%之间。 相似文献
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A. P. Brylyakov G. M. Zharkova B. Yu. Zanin V. N. Kovrizhina D. S. Sboev 《Journal of Applied Mechanics and Technical Physics》2004,45(4):510-516
The flow structure behind wire grids is studied for flows with a low subsonic velocity, and the effect of grids on the boundarylayer flow structure is considered. It is shown that the meanvelocity inhomogeneity induced by the grid does not disappear until a distance of 925 calibers downstream of the grid is reached. Liquidcrystal thermography combined with hotwire measurements made it possible to find the source of steady largescale streamwise vortex structures in the boundary layer on a wedge and on an airfoil and to determine the parameters of these structures. 相似文献
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考虑铁基超导中能带间的相互作用和界面对每一个能带的散射作用, 利用推广的Blonder-Tinkham-Klapwijk模型, 并通过求解Bogoliubov-de Gennes 方程研究了具有不同类型双能隙系统的量子线/铁基超导隧道结中准粒子的输运系数和隧道谱. 研究表明: 1)在弹道极限时, 随着带间相互作用的增大, s± 波隧道谱中零偏压附近的平台演变成电导峰; s++ 波的平台演变成凹陷; p波的零偏压电导峰被压低. 2)界面对两个能带的散射作用不为零时, 随着带间相互作用的增大, s± 波和s++ 波两能隙处的峰值将降低, 而两峰间的凹陷值将变大; p波的零偏压电导峰被压低, 非零偏压电导增大. 3)界面对每个能带的散射, 可使其产生的电导峰变得更加尖锐, 但可压低和抹平另一个带产生的电导峰值. 这些结果对于澄清铁基超导体的能隙结构和区别不同类型铁基超导体有所帮助. 相似文献
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采用改进的线性组合算符和幺正变换相结合的方法研究了Rashba效应对抛物量子线中强耦合束缚磁极化子性质的影响.计算了抛物量子线中强耦合束缚磁极化子的有效质量和振动频率,对Rb Cl材料的数值计算结果表明:量子线中强耦合束缚磁极化子的振动频率随受限强度和回旋频率的增加而增大;有效质量与磁极化子的受限强度、回旋频率和电子面密度有关,在Rashba效应影响下有效质量随上述各量的变化曲线都发生了分裂. 相似文献
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Q.G. Meng H.Y. Fang J.G. Yang S.D. Ji 《Theoretical and Applied Fracture Mechanics》2005,44(2):178-186
By analyzing the shape of twin wire welding’s arcs and the track of droplets’ transition, the phenomenon that the twin wire welding’s fore arc and rear arc all deflect to the middle of the two arcs is found. Based on this the double ellipsoid heat source model is amended, and a heat source model which can apply to calculate the twin wire welding’s temperature field is put forward. This model is testified by actual experiment of temperature sampling. By comparing the temperature field of twin wire welding and single wire welding, the results show that twin wire welding has slender weld pool the end part of which is ellipsoid, and its HAZ is narrower than that of single wire welding. So, twin wire welding can not only reduce the Al alloy generating hot crack, but can also weaken the “overaging” softened phenomenon of heat treated strengthening Al alloy. In the end, the evolving rules of 2219 Al alloy’s longitudinal and transverse stress when welded with twin wire welding are analyzed. 相似文献
10.
《Physics letters. A》2019,383(17):2110-2113
The electron effective mass in GaAs quantum wires has been estimated by using a full dynamical random-phase approximation to examine its properties versus spin polarization, temperature, and carrier density. A decrease of mass with spin polarization is seen. The minority mass increases with the polarization while the majority mass decreases and this behaviour is seen for all densities. A maximal enhancement of mass at moderate temperature around 25 K is also presented. These calculations show a qualitative consistence with results in two-dimensional systems and help to control the electronic transport in quantum wires. 相似文献