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891.
The free vibration of a functionally graded material hollow sphere submerged in a compressible fluid medium is exactly analyzed.
The sphere is assumed to be spherically isotropic with material constants being inhomogeneous along the radial direction.
By employing a separation technique as well as the spherical harmonics expansion method, the governing equations are simplified
to an uncoupled second-order ordinary differential equation, and a coupled system of two such equations. Solutions to these
equations are given when the elastic constants and the mass density are power functions of the radial coordinate. Numerical
examples are finally given to show the effect of the material gradient on the natural frequencies.
The project is supported by the National Natural Sciences Foundation of China(No. 19872060). 相似文献
892.
893.
Bo Zheng Yiquan Liu Huihui Li Yunhua Ye Xingming Gao Gu Yuan 《Journal of mass spectrometry : JMS》2009,44(10):1478-1481
In this research, the characteristic ions' abundance ratio between two isomers A and B in MS/MS mass spectra was defined as a parameter for discriminating diastereomers. Through this ratio, the discrimination of four pairs of cyclic peptide (CP) diastereomers was successfully achieved. Furthermore, in the analysis of diastereomers' mixtures, both calibration curve and calculational methods were substantiated to have high precision and accuracy. The average absolute errors of the two methods were 2.0 and 2.5% in the 48 measurements of 16 samples, respectively. This research provided a promising approach for the analysis of the CP diastereomers in the fields of asymmetrical synthesis, chiral natural products and structural biology by ESI‐MS/MS. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
894.
β-淀粉样肽的结构、合成与性质及其与老年痴呆症的关系 总被引:3,自引:0,他引:3
β-淀粉样肽是β-淀粉样前体蛋白的剪切产物,分别由39-43个氨基酸残基组成。本文介绍了β-淀粉样肽的化学结构、化学合成及β-淀粉样肽与老年痴呆症的关系。 相似文献
895.
N. N. Il’ichev A. V. Kir’yanov V. P. Shapkin S. A. Nasibov S. Ye. Mosaleva 《Applied physics. B, Lasers and optics》2005,81(1):83-91
An experimental study and theoretical modeling of the nonlinear change in refractive index of a Co2 +: ZnSe crystal at the short-pulse single-beam probing at the wavelength 1.54 μm is reported. In the experimental conditions of negligible contributions in the index non-linearity stemming from the Kerr-effect and inhomogeneous heating, the nonlinear change in refractive index in Co2 +:ZnSe is shown to be caused by the resonant Co2 + population-perturbation effect (i.e., by the Co2 + ground-state absorption saturation). The Z-scan single-beam technique and novel theoretical approach addressing the resonant nonlinear refraction in a saturable doped medium are used, respectively, for an experimental and theoretical inspection of the phenomenon. For a set of Co2 +:ZnSe samples with different concentrations of Co2 + ions at the short-pulse (200 ns) mJ-range probing, we show that the maximal nonlinear change in refractive index is about of units of 10− 4 at the chosen wavelength. 相似文献
896.
Ye.V. Visitskii A.G. Petrov M.M. Shunderyuk 《Journal of Applied Mathematics and Mechanics》2009,73(5):548-557
The sedimentation of a heavy solid spherical particle from a state of rest in an incompressible viscous fluid in a vessel with a vibrating bottom is investigated. Taking the Basset force into account, the problem is reduced to solving a Cauchy problem for a linear integro-differential equation. An exact solution of this problem and simple asymptotic formulae are obtained and a complete analysis of the effect of the Basset force on the oscillations and sedimentation of the particles is carried out. It is shown that a consideration of the Basset force introduces a considerable correction to the classical amplitude-frequency relation, reducing its value and also considerably slowing the arrival of the amplitude at a constant value. When there are no vibrations, it follows from the solution of the problem that there is a slow establishment of the limiting velocity (inversely proportional to the square root of the time), which differs considerably from the case of the sedimentation of particles in accordance with Stokes's law (the establishment of the limiting velocity occurs exponentially). 相似文献
897.
898.
对于广义 Eady 模型, 分别讨论了密度函数是常数函数与指数函数两种情形, 利用变分原理, 考虑到动量守恒的约束条件, 得到了优化的 Poincaré不等式, 从而得到了新的非线性稳定性定理, 并且得到了在径向长度分别不大于纬向长度的0.84402倍 及 0.86068 倍时(这对于地球的实际情况是成立的), 非线性稳定性判据与线性稳定性判据是一致的. 相似文献
899.
The first phytochemical investigation on stems of Mitrephora thorelii led to the isolation of three new lignanamides, thoreliamides A–C ( 1 – 3 ), and a new sesquiterpenoid, thorelinin ( 4 ), together with ten known compounds. The structures of the new compounds were established on the basis of extensive spectroscopic analyses. Thoreliamide C is the first trimer derived from cinnamic acid amide units. 相似文献
900.