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71.
72.
Stopband phenomena are reported in the passband of left-handed metamaterials. The samples with linear defect are designed by removing one layer of split ring resonators (SRRs). It is shown that the left-handed transmission peaks have a distinct transform with the relative deviation of the SRRs centre from the wire centre 8, from a single left-handed peak, double left-handed peaks with different magnitude to no transmission peak, i.e. left-handed properties of metamaterials disappear. Numerical simulation shows that the change of 8 makes the effective permeability shift at a frequency range, where stopband occurs. It is thought that the stopband in left-handed passband is due to the symmetry breaking between SRRs and wires in the metamaterials. 相似文献
73.
KBA显微镜是一种非轴对称、非共轴的掠入射成像系统。其结构复杂,调节精度要求很高,在实际成像实验操作中难以掌握其成像特性。利用光学设计软件模拟其成像,对系统的调节和成像分析提供有益的参考。利用光学设计软件ZEMAX模拟了KBA显微镜对点源的成像过程,给出了KBA显微镜成像系统的焦深约为1 mm,景深为50 mm左右。并且由模拟可知,掠入射角对成像的影响很大。对像素尺寸约10μm的探测设备,模拟得出KBA成像系统的空间分辨力上限为3μm左右。基于星光Ⅱ装置对周期为20μm的网格靶成像,获得了KBA显微镜较为清晰的X光图像。该项工作为进一步开展掠入射成像系统的研究奠定了基础。 相似文献
74.
Pu-Kun Liu Zhong-Hai Yang Shang-Jie Qian Sheng-Gang Liu 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1995,23(2):156-162
Using the Laplace transformation, the kinetic theory of the high-relativistic electron cyclotron maser having a novel open-resonator-the axisymmetrical quasioptical cavity of oblique rotation at arbitrary angle, is carried out within the framework of the linearized Vlasov-Maxwell equations. The beam-wave interaction power, starting current and frequency shift have been derived and numerically calculated. The influence of rotation angle on the beam-wave interaction is also studied. A series of important conclusions obtained reveal the characteristics of this novel quasioptical electron cyclotron maser 相似文献
75.
本文介绍了我们研制的“运动粒子瞬态激光全息测试仪”电子线路.该电路经严格的逻辑设计及计算,采用了10MHz时钟电路,并将1MHz的时钟信号巧妙地引入门控电路中,同时在技术上采用了行之有效的措施,消除了可能产生0.1μs的随机误差,时间间隔达到了(1~9)±0.1μs的精度,所输出的激光双脉冲能量接近,整机抗干抗能力强,一次性试验成功率高,可精确地测量雾化粒子场中的微粒的速度、形状、大小及其分布,收到了良好的使用效果. 相似文献
76.
77.
In this paper we prove that
(1<p<+∞), give the characteristics of xo and the optimal subspace for n-width dn in space X=l
n
N
. Where dn in the n-width, in the sense of Kolmogorov, ofD in X, dn is the n-width ofD with respect to X, in the sense of Gel'fand, δ is the linear n-width ofD with respect to X. 相似文献
78.
79.
Xu ZK Dai QW Wu J Huang XJ Yang Q 《Langmuir : the ACS journal of surfaces and colloids》2004,20(4):1481-1488
A novel method for the surface modification of a microporous polypropylene membrane by tethering phospholipid analogous polymers (PAPs) is given, which includes the photoinduced graft polymerization of N,N-dimethylaminoethyl methacrylate (DMAEMA) and the ring-opening reaction of grafted poly-(DMAEMA) with 2-alkyloxy-2-oxo-1,3,2-dioxaphospholanes. Five 2-alkyloxy-2-oxo-1,3,2-dioxaphospholanes, containing octyloxy, dodecyloxy, tetradecyloxy, hexadecyloxy, and octadecyloxy groups in the molecular structure, were used to fabricate the PAP-modified polypropylene membranes. The attenuated total reflectance FT-IR spectra of the original, poly(DMAEMA)-grafted, and PAP-modified membranes confirmed the chemical changes on the membrane surface. Scanning electron microscope pictures showed that, compared with the original membrane, the surface porosities ofpoly(DMAEMA)-grafted and PAP-modified membranes were somewhat reduced. Water contact angles measured by the sessile drop method on PAP-modified membranes were slightly lower than that on the original polypropylene membrane, but higher than those on poly(DMAEMA)-grafted membranes with the exception of octyloxy-containing PAP-modified membranes. However, BSA adsorption experiments indicated that the five PAP-modified membranes had a much better protein-resistant property than the original polypropylene membrane and the poly(DMAEMA)-grafted membranes. For hexadecyloxy- and octadecyloxy-containing PAP-modified membranes, almost no protein adsorption was observed when the grafting degree was above 6 wt %. It was also found that the platelet adhesion was remarkably suppressed on the PAP-modified membranes. All these results demonstrate that the described approach is an effective way to improve the surface biocompatibility for polymeric membranes. 相似文献
80.
Seven transition metal molybdovanadoarsenic heteropoly compounds have been synthesized and characterized using IR, UV, TG-DTA, pH potential titration techniques. The molecular formulae of these compounds are pro-posed to be HxMyAsMO10V2O40·zH2O(x=1~3, y=1,2, M=Cr, Mn, Fe, Co, Ni, Cu, Zn).They are all keggin structure. Surface nature of these compounds have been investigated by temperature programmed desorption and temperature programmed reduction techniques. NH3-TPD results show that in TPD profiles of the compounds there are two desorption peaks corresponding to weak acid sites of desorption, respectively. Desorbing activativon energy and preexponential factor of weak acid site of desorption for compounds have been calculated. H2-TPR re-sults show that introducting transtion metal to molybdovanarsenic acid, the reduction peak temperatures of H2-TPR shift regularly with increasing d electron numbers of transition metals. In addition, Zn and Cu heteropoly com-pounds have yet apparent effect of hydrogen spill over. 相似文献