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951.
952.
K. Franke 《Surface science》2005,585(3):144-154
Polarization switching in scanning force microscopy (SFM) is influenced by both electric fields and stress, whereby the latter can arise inherently from Maxwell stress. We discuss the influence of electric charges and of the polarization asymmetry on the switching behaviour. For single crystallites of PZT(53/47) thin films, the sectors for ferroelectric, ferroelastoelectric and ferroelastic switching are represented in a field-stress map. The influence of stress on the second harmonic of the SFM is also discussed. 相似文献
953.
A germacalix‐crown, 25,27‐bis[1‐(3‐trimethylgermylpropyl)oxy]calix[4]arene‐crown‐6, 1,3‐alternate ( 1a ), and its carbon analog, 25,27‐bis‐[1‐(4,4‐dimethylpentyl)oxy]calix[4]arene‐crown‐6, 1,3‐alternate ( 1b ), were prepared and their structures were confirmed by elemental analysis and 1H and 13C NMR spectroscopy. A cation transport test indicated that both compounds exhibited much the same cation transport ability, so that the role of the germanium moiety in capturing and transporting counteranions is not yet clear. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
954.
采用制冷机直接冷却的低温超导磁体系统与传统液氮冷却方式相比,具有轻便紧凑、运行简单、维护方便、可长时间连续运行等优点;而脉管制冷由于冷端无运动部件,与传统的G-M制冷机相比,具有结构简单、运行可靠、振动小等优点.本文结合我们在液氮温区脉管制冷方面的技术,从漏热和经济性两方面探讨了将脉管制冷直接用于冷却一个5特斯拉NbTi低温超导磁体的可行性,为后期系统的搭建奠定基础. 相似文献
955.
P. A. Campbell L. J. Sinnamon C. E. Thompson D. G. Walmsley 《Surface science》1998,410(2-3):L768-L772
The unit cell height in the c-direction of muscovite mica is well established at 10 Å. However, we have observed steps much lower than this whilst imaging freshly cleaved mica surfaces in an atomic force microscope. The steps, 1.0±0.05 Å high, are unstable and disappear in a period of minutes after cleavage. We propose that they are due to the presence of domains of residual K+ ions that form two matching patchworks on the cleaved faces. Upon cleavage, they relax inwards from the bulk equilibrium position 1.6 Å above the oxygen atoms of the tetrahedral silicate. Possible mechanisms for the disappearance of the steps are discussed. 相似文献
956.
957.
An effective method is developed and used to investigate the antiplane problem of a rigid line in a confocal elliptic inhomogeneity
embedded in an infinite medium. The analytical solution is obtained. The proposed method is based upon the use of conformal
mapping and the theorem of analytic continuation. Special solutions which are verified by comparison with existing ones are
provided. Finally, the characteristics of stress singularity at the tip of the rigid line inhomogeneity are analyzed and the
extension forces for the crack and the rigid line inhomogeneity are derived.
The project supported by the National Natural Science Foundation of China, the State Education Commission Foundation and the
Failure Mechanics Lab of SEdC. 相似文献
958.
Dunshen Zhu Xingxian Shou Yixin Liu Erqiang Chen Stephen Zhengdi Cheng 《Frontiers of Chemistry in China》2007,2(2):174-177
The AFM-tip-induced crystallization of poly(ethylene oxide) (PEO) melt droplets was studied. The melt droplets with a height
of 50–100 nm and a lateral size of 2–3 μm were obtained by melting the PEO ultra-thin films on a mica surface. For the PEO
samples with average molecular weights (M
n) ranging from 1.0 × 103 g/mol to 1.0 × 104 g/mol, the lateral perturbation from the AFM tip in the hard-tapping or nanoscratch modes could not induce the growth of
the flat-on lamellae. In contrast, under AFM nanoindentation mode, the tip-induced crystallization occurred when a sufficiently
high vertical tip force was applied to the melt droplets of PEO with M
n ⩾ 1.0 × 104 g/mol. Moreover, the experimental results indicated that the AFM-tip-induced crystallization of PEO in the nanoindentation
process had molecular weight dependence.
Translated from Acta Polymerica Sinica, 2006, (4): 553–556 (in Chinese) 相似文献
959.
W. Richard Bowen Nidal Hilal Robert W. Lovitt Peter M. Williams 《Journal of membrane science》1996,110(2):233-238
Non-contact atomic force microscopy has been used to investigate the surface pore structure of Cyclopore and Anopore microfiltration membranes in air. Three Cyclopore membranes and three Anopore membranes of different pore sizes were studied. Excellent high resolution images were obtained. Analysis of the images gave quantitative information on the surface pore structure, in particular the pore size distribution. Non-contact AFM is an excellent means of obtaining such information for microfiltration membranes. 相似文献
960.
针尖 样品的距离控制系统是扫描近场红外显微镜的重要组成部分。切变力探测作为一种重要的近场距离控制手段而得到了广泛的应用。介绍了一种对切变力探测系统的改进方法 ,它可以有效地提高石英晶振音叉的品质因数 ,进而提高探测系统对切变力感应的灵敏度。给出了理论分析和实验验证结果 相似文献