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991.
介绍一种4.3m红外望远镜。它与2.16m望远镜用真空管道联机用于CCD照相和光干涉测量,可使集光能力达4.8m口径,分辨率达101m口径。 相似文献
992.
Kazumi Watanabe Robert G. Payton 《Journal of the mechanics and physics of solids》2002,50(11):2425-2439
Green's function for SH-waves in a cylindrically monoclinic material is considered for impulsive and time-harmonic sources. Closed form expressions for the Green's function are derived for a few limited values of anisotropic parameters. A very interesting time development of the wave front shape is illustrated and the wave front singularity is discussed for the transient SH-wave. Contours of the displacement amplitude for the time-harmonic wave are also shown. 相似文献
993.
F. Bontempi 《Nonlinear dynamics》1995,7(2):217-229
This paper deals with the dynamics of a truss structure, the Euler arch. The bars are made of elastic-plastic material, and the structure can exhibit large displacements. The aim of this paper is to give evidence of the possible chaotic behavior of this structure, even in the presence of a hardening plastic branch. The tools used are the diagrams of bifurcation, the measure of the dimension of the attractor, the Kolmogorov entropy, and the maximum Lyapunov exponent. This study emphasizes the sensitivity to the initial conditions by means of generalized basins of attraction. 相似文献
994.
The acrylamide‐based terpolymers (PADB) with 4‐butylstyrene (BST) as the hydrophobic monomer and dimethyldiallyammonium chloride (DMDAAC) were synthesized by the micellar free radical technique. The polymer was determined by UV, FT‐IR and 1HNMR, and the hydrophobic microblock structure of PADB was characterized successfully by the conventional DSC measurement. The use of DMDAAC improves the water solubility and intermolecular association of terpolymers. The feed amount of BST affects greatly the apparent viscosity of PADB solution. The polymer exhibits good viscosification property, salt resistance, temperature‐thickening, thixotropy, pseudoplastic behavior and shear‐thickening at low shear rate. The apparent viscosities of PADB solution remarkably increase by the addition of a small amount of surfactant. AFM measurements show that hydrophobic aggregates have been formed in 0.1 g dL?1 PADB aqueous solution, indicative of strong associations of hydrophobic groups, which are reinforced with increasing PADB concentration. The microstructures of PADB are disrupted by the addition of small amounts of salt, resulting in the decrease in solution viscosity. However, with increasing NaCl concentration, the tree‐like associating structures are formed, leading to the increase in the solution viscosity of PADB. The AFM results reveal that the solution properties of PADB are due to the associating structures in the aqueous solution and brine solution. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 826–839, 2007 相似文献
995.
本文依据工科数学第十卷(1994年8月)数学建模MCM—89问题A的数据,用Fisher判别方法建立数学模型,进行分类,识别新样品的类别,其结论与复杂的原解法一致,此方法一般本科生就可以去作,而且没有更多的假设。 相似文献
996.
采用拉曼光谱技术研究纳米锐钛矿到金红石的相转变 总被引:9,自引:4,他引:5
采用化学沉淀法制备出40nm的锐钛矿,并用拉曼光谱对纳米和块体锐钛矿到金红石的相转变过程进行了研究。实验结果表明:对于块体锐钛矿,在950℃保温1h,金红石的特征峰446cm^-1开始出现,随着温度的升高,金红石的特征峰446,610和231cm^-1继续增强,锐钛矿的特征峰639,515和397cm^-1逐渐减弱。在1100℃保温1h,锐钛矿转变为金红石;对于纳米锐钛矿,在900℃保温1h后几乎全部转变为金红石,比块体(微米级)锐钛矿到金红石的相转变温度降低了200℃。 相似文献
997.
Alexander A. Kaminskii Ludmila Li Andre V. Butashin Vladimir S. Mironov Alexsei A. Pavlyuk Sergey N. Bagayev Ken-ichi Ueda 《Optical Review》1997,4(2):309-315
Monoclinic KY(WO4)2:Pr3+, Tm3+:KY(WO4)2:Er3+, Yb3+ single crystals are grown by low-gradient Czochralski technique. Stimulated emission at 1.0223μm wavelength in the new lasing 1D2→3F3 channel of Pr3+ ions in KY(WO4)2 at room temperature under Xe-flashlamp pumping is excited. Full sets of Stark-level energies for Pr3+ ions in KY(WO4)2 and KGd(WO4)2 crystals at 77 K are determined. 4f2-4f2 intensity-transitions for the KY(WO4)2:Pr3+ are analyzed preliminarily. All observed at present and earlier one-micron Pr3+-ion, induced transitions in the 1D2→3F3 and 1D2→3F4 channels are identified. In yttrium and gadolinium sensitized-tungstates a two-micron (3H4→3H6) low-threshold generation of Tm3+ ions at cryogenic temperatures is achieved.All authors cooperate with the Joint Open Laboratory for Laser Crystals and Precise Laser Systems at the Institute of Crystallography and Institute of Laser Physics, Russian Academy of Sciences. 相似文献
998.
微重力条件下晶体生长过程的实时观察 总被引:1,自引:0,他引:1
从材料科学的微重力效应和晶体生长基本过程等两个方面出发,阐明了一种新的生长技术(晶体生长过程的光学实时观察法)的必要性,并介绍了空间高温实时观察装置的基本特性.在我国的科学技术探测卫星上,该装置进行了搭载实验,并首次清楚地观察到了空间溶质扩散效应和高温溶液的表面张力对流图像. 相似文献
999.
Thermoelastic stress analysis under nonadiabatic conditions 总被引:1,自引:0,他引:1
Thermoelastic stress analysis is a full-field stress measurement technique complementary to local techniques like strain gages.
Generally, the heat transfer inside the material is neglected with respect to the frequency of the cyclical loading. An adiabaticity
criterion is established to assert this simplification as a function of the thermal diffusion length and the spatial stress
gradients. Under nonadiabatic conditions, heat diffusion attenuates the spatial temperature gradients, which leads to an underestimation
of stress concentrations. Analytical and numerical considerations allow for the quantification of the spatial resolution.
Finally, several inverse techniques can restore the thermally attenuated contrasts. 相似文献
1000.
Investigators have viewed the stress rate in two different ways: the material (body-fixed) point of view and the Eulerian point of view. We discuss the Zaremba–Jaumann rate and Oldroyd’s rate from the material viewpoint and apply them to the material formulation of a theory of plasticity for materials undergoing anisotropic plastic deformation. Significant advantages of the material formulation are that the derivation of equations is straight forward, the distortion of yield surface can be easily accounted for, and the issue of self-consistent elastic equation does not arise. 相似文献