Free vibration of polar orthotropic circular plates with elastic growth stresses and drying stresses

This study was performed to analyze effect of transverse growth stresses and drying stresses on natural frequencies of transverse free vibration of thin tree disk with free boundary condition. Using Rayleigh-Ritz method and finite element method, explicit closed form expression was derived for homogeneous orthotropic circular plates with internal stresses, which enables to predict both the effects of growth stresses, drying stresses, and combined growth and drying stresses on the natural frequency changes. This model can be used for predicting growth stresses from known natural frequencies. The same approach can also be undertaken to validate models visco-elastic drying stresses.     

High Emittance Electron Beam Source Coupled to Slab Loaded Accelerating Structure

High power line source emitter assembly was coupled to a twin symmetric H-plane slab loaded accelerating structure for beam acceleration. Closed form field analysis of the accelerating structure that includes guideline information regarding modal hierarchy, mode nomenclature, propagation plane, cut-off plane and dispersion relations is presented. Furthermore it was confirmed that by using symmetrically loaded dielectric accelerating structures with one rotated through 90° results in exerting a uniform acceleration impact on a travelling beam passing through the structure.     

基于各向异性扩散的红外图像噪声滤波算法

抑制红外焦平面阵列探测器噪声时,为了有效保持边缘细节,在塔基(Tukey)扩散模型的基础上,提出了一种基于各向异性扩散的滤波算法.算法由微分法提取边界点集,利用信号和噪声的空间分布特性对图像进行预处理,从而改善了Perona-Malik(P-M)方程的病态性.建立了新的扩散系数且该系数在理论上满足Charbonnier等人构造准则.通过给定边界条件实现了有利于保持边缘的目的.该算法已在基于DSP FPGA的硬件平台上实时运行,较好地抑制了噪声,又有效地保持了边缘,处理后的图像具有良好的视觉效果.     

Analytical solutions for some defect problems in 1D hexagonal and 2D octagonal quasicrystals

We study some typical defect problems in one-dimensional (1D) hexagonal and two-dimensional (2D) octagonal quasicrystals. The first part of this investigation addresses in detail a uniformly moving screw dislocation in a 1D hexagonal piezoelectric quasicrystal with point group 6mm. A general solution is derived in terms of two functions φ ₁, φ ₂, which satisfy wave equations, and another harmonic function φ ₃. Elementary expressions for the phonon and phason displacements, strains, stresses, electric potential, electric fields and electric displacements induced by the moving screw dislocation are then arrived at by employing the obtained general solution. The derived solution is verified by comparison with existing solutions. Also obtained in this part of the investigation is the total energy of the moving screw dislocation. The second part of this investigation is devoted to the study of the interaction of a straight dislocation with a semi-infinite crack in an octagonal quasicrystal. Here the crack penetrates through the solid along the period direction and the dislocation line is parallel to the period direction. We first derive a general solution in terms of four analytic functions for plane strain problem in octagonal quasicrystals by means of differential operator theory and the complex variable method. All the phonon and phason displacements and stresses can be expressed in terms of the four analytic functions. Then we derive the exact solution for a straight dislocation near a semi-infinite crack in an octagonal quasicrystal, and also present the phonon and phason stress intensity factors induced by the straight dislocation and remote loads.      

The effect of magnetic field heat treatment on magnetostriction of Terfenol-D 2-2 composites

Based on the analysis of the magnetostriction for Terfenol-D composites, Terfenol-D 2-2 magnetostrictive composites have been prepared with laminations perpendicular to [1 1 2] axes. Then one of the samples was annealed in the vacuum at 423 K for 15 min at the magnetic field of 240 kA/m, which is along the direction of laminations and vertical to the [1 1 2] axes of the specimen. The static magnetostriction λ and dynamic magnetostrictive coefficient d₃₃ of samples were measured under the compressive stress of 0, 2, 4, 6 and 8 MPa. Effects of the compressive stress and the magnetic field heat treatment on the magnetostriction λ have been investigated. It is found that the magnetostriction of 2-2 composites can be improved under the compressive stress when the magnetic field is larger than 20 kA/m. The magnetostriction of 2-2 composites with the magnetic field heat treatment increases under compressive stress, and it can reach 1390×10⁻⁶ at the magnetic field of 200 kA/m and under the compressive stress of 4 MPa, much larger than the value of 860×10⁻⁶ without the magnetic field heat treatment. The highest magnetostriction of the 2-2 composite with the magnetic field heat treatment can reach 1530×10⁻⁶. The dynamic magnetostrictive coefficient d₃₃ of 2-2 composites with the magnetic field heat treatment have been improved, compared with that without magnetic field heat treatment. The maximum value of d₃₃ of the sample with magnetic field heat treatment is 71% larger than that without magnetic field heat treatment.     

High concentration trans form unsaturated lipids detected in a HeLa cell by Raman microspectroscopy

High concentration trans form unsaturated lipids have been found in a HeLa cell by Raman microspectroscopy. Two CC stretch bands are observed simultaneously at 1669 cm⁻¹ (trans form) and at 1656 cm⁻¹ (cis form) in a Raman spectrum obtained from a small area (1 µm in diameter) in a HeLa cell. The intensity ratio 1669/1656 indicates that the concentration of the trans form is as high as that of the cis. It is demonstrated that Raman microspectroscopy provides a powerful and unique means for in situ and noninvasive structural characterization of unsaturated lipids in a living cell. Copyright © 2008 John Wiley & Sons, Ltd.     

Theory and experiment of large numerical aperture objective Raman microscopy: application to the stress‐tensor determination in strained cubic materials

We present the theory underlying the large numerical aperture objective micro‐Raman backscattering experiment and apply it to the elaboration of a characterization methodology for the determination of the stress tensor in strained cubic semiconductor structures. The presented stress characterization technique consists in monitoring the variations of the stress‐sensitive optical phonon peak position and linewidth while rotating stepwise the sample about its normal. The practical application of the technique is illustrated on a silicon‐on‐insulator (SOI) microelectronic structure demonstrating a plane stress‐tensor determination. Copyright © 2008 John Wiley & Sons, Ltd.     

The Goodmanham plane: Raman spectroscopic analysis of a Roman ivory artefact

Raman spectroscopy has been applied to the study of the exceptional ivory stock of an archaeological discovery of great importance for the history of woodworking tools: a virtually complete Roman plane that was found in a late fourth century A.D. context in North Yorkshire, UK, in A.D. 2000. An assessment has been made of the viability of Raman spectroscopy for the identification of ivories from archaeological excavations and comparisons made with similar studies of modern specimens. All of the attributed ivory specimens studied have suffered from deterioration in their burial environment, and severe degradation of their proteinaceous component was observed. In addition, spectral quality was affected through the absorption of fluorescent materials from their environment, and from the presence of emergency conservation procedures undertaken to preserve the integrity of very fragile specimens. The spectra of ivories dating from about 2000 years ago varied considerably because some specimens had experienced an almost complete leaching‐out of collagen, whereas in others, the degraded protein was still substantially identifiable. Generally, however, the protocols used successfully for the identification of modern ivories and for an assignment of their mammalian species were not transferable into archaeological ivory identification and classification because of the collagen degradation and decreased spectral quality. Copyright © 2008 John Wiley & Sons, Ltd.