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991.
By expanding the hard-aperture function into a finite sum of complex Gaussian functions, we derive approximate analytical formulae for Lorentz and Lorentz-Gauss beams propagating through an apertured fractional Fourier transform (FRT) optical system. As an application example, properties of a Lorentz-Gauss beam in the FRT plane after propagating through a squarely or annularly apertured FRT optical system are studied numerically. The results obtained using the approximate analytical formula are in good agreement with those obtained using numerical integral calculation. The FRT optical system provides a convenient way for laser beam shaping. 相似文献
992.
Extracellular biosynthesis of monodispersed gold nanoparticles by a SAM capping route 总被引:1,自引:0,他引:1
Li Wen Zhonghua Lin Pingying Gu Jianzhang Zhou Bingxing Yao Guoliang Chen Jinkun Fu 《Journal of nanoparticle research》2009,11(2):279-288
Monodispersed gold nanoparticles capped with a self-assembled monolayer of dodecanethiol were biosynthesized extracellularly
by an efficient, simple, and environmental friendly procedure, which involved the use of Bacillus megatherium D01 as the reducing agent and the use of dodecanethiol as the capping ligand at 26 °C. The kinetics of gold nanoparticle
formation was followed by transmission electron microscope (TEM) and UV-vis spectroscopy. It was shown that reaction time
was an important parameter in controlling the morphology of gold nanoparticles. The effect of thiol on the shape, size, and
dispersity of gold nanoparticles was also studied. The results showed that the presence of thiol during the biosynthesis could
induce the formation of small size gold nanoparticles (<2.5 nm), hold the shape of spherical nanoparticles, and promote the
monodispersity of nanoparticles. Through the modulation of reaction time and the use of thiol, monodispersed spherical gold
nanoparticles capped with thiol of 1.9 ± 0.8 nm size were formed by using Bacillus megatherium D01. 相似文献
993.
994.
Xiubo Jiang Yi Shi Wen Zhu Yongming Chen Fu Xi 《Journal of polymer science. Part A, Polymer chemistry》2012,50(20):4239-4245
Well‐defined mikto‐topology star polystyrene composed of one cyclic arm and four linear arms was synthesized by a combination of atom transfer radical polymerization (ATRP) and Cu‐catalyzed azide‐alkyne cycloaddition (CuAAC) click reaction. First, the bromine‐alkyne α,ω‐linear polystyrenes containing four hydroxyl groups protected with acetone‐based ketal groups were synthesized by ATRP of styrene using a designed initiator. Then, the bromine end‐group was converted to the azide and the linear polystyrene was cyclized intra‐molecularly by the CuAAC reaction. The four hydroxyl groups were released by deprotection and then esterified with 2‐bromoisobutyryl bromide to produce a cyclic polymer bearing four ATRP initiating units. By subsequent ATRP of styrene to grow linear polymers with the cyclic polystyrene as a macroinitiator, the mikto‐topology star polymers were prepared. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
995.
<正>SnO_2 nanorods were deposited on the Si substrates in an aqueous solution containing both SnCl_4 and CO(NH_2)_2.It is found that different self-assembled patterns of SnO_2 nanorods can be obtained by changing the deposition conditions such as the molar ratio of CO(NH_2)_2 to SnCl_4 and the pretreatment of the substrate.Scattered SnO_2 nanorods,for example,can be changed into flower-like patterns when the molar ratio of CO(NH_2)_2 to SnCl_4 is raised,and well-aligned nanorod arrays can be formed when the pretreatment of the substrate is changed.In addition,some interesting patterns,e.g.tree-like patterns,can also be observed. 相似文献
996.
A series of novel ruthenium-manganese oxide (denoted as RunMn1−nOx) has been formed by oxidative co-precipitating. The precursor was obtained by mixing Mn(VII) (potassium permanganate), Mn(II) (manganese acetate) and Ru(III) (ruthenium chloride) in neutral aqueous solution at room temperature. The powder of RunMn1−nOx was obtained by calcinating the precursor at appropriate temperature. The crystalline structure and electrochemical performance of the powder have been studied as a function of the calcination temperature. At appropriate calcination temperature (e.g. 170 °C), the powder is in hydrous amorphous phase with a high specific capacitance. When the calcination temperature reaches up to 350 °C, the crystal form of α-MnO2 is formed, but the ruthenium oxide still keeps amorphous structure, which will lead to the decrease of specific capacitance of the composite electrode materials. The X-ray photoelectron spectroscopy (XPS) analysis shows that the powder of RunMn1−nOx prepared in this study belongs to the composite of RuO2-MnO2. The results from cyclic voltammetry (CV), chronopotentiometry and electrochemical impedance spectroscopy (EIS) indicate that the ruthenium weight density of 9 wt% in RunMn1−nOx can improve the cost-performance of ruthenium-manganese composite electrode. 相似文献
997.
This study extends the upstream flux‐splitting finite‐volume (UFF) scheme to shallow water equations with source terms. Coupling the hydrostatic reconstruction method (HRM) with the UFF scheme achieves a resultant numerical scheme that adequately balances flux gradients and source terms. The proposed scheme is validated in three benchmark problems and applied to flood flows in the natural/irregular river with bridge pier obstructions. The results of the simulations are in satisfactory agreement with the available analytical solutions, experimental data and field measurements. Comparisons of the present results with those obtained by the surface gradient method (SGM) demonstrate the superior stability and higher accuracy of the HRM. The stability test results also show that the HRM requires less CPU time (up to 60%) than the SGM. The proposed well‐balanced UFF scheme is accurate, stable and efficient to solve flow problems involving irregular bed topography. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
998.
999.
1000.
Yuan Xu ShiXiang Peng HaiTao Ren JiaMei Wen AiLin Zhang Tao Zhang JingFeng Zhang WenBin Wu ZhiYu Guo JiaEr Chen 《中国科学:物理学 力学 天文学(英文版)》2017,60(6):060021
<正>Multiple charge ions (MCIs) are necessary for increasing the output energy of particles in accelerators. In general, MCI beams are largely produced by electron beam ion source (EBIS) [1], laser ion source (LIS) [2], or high-frequency (mostly 5 GHz) electron cyclotron resonance (ECR) ion source [3]. Among these, only ECR ion source can operate in the continuous wave (CW) mode, while EBIS and LIS only support pulses. In addition, ECR ion source with lower frequency (mostly 2.45 GHz) are required primarily for generating single charge state ions, because the corresponding ECR field (875 Gs) is not sufficiently strong for MCI generation [4]. 相似文献