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In this paper we present an application of the grid method to the assessment of crack initiation and growth in brittle materials.
It is shown that a grid deposited on the surface of a structure can be utilized to characterize the crack location and opening.
Furthermore, one single picture only is required to carry out a control over a predefined area.
First, the principle of the method is introduced, showing that a periodical pattern encoding a cracked surface can be analyzed
by signal processing. The phase modulation of the grid can be calculated very accurately for any small deformation of the
structure. Discontinuities due to cracks are easily detected on the phase field and the crack width is proportional to the
amplitude of the discontinuity. Secondly, the performances of the method are presented, mainly depending on the spatial frequency
of both the pattern and the sampling. It is shown that good results can generally be obtained with few setting difficulties
and equipment investment. Finally, we sum up some basic recommendations for the practical use of the technique. 相似文献
105.
Precise measurement of the line width of the photoassociation spectra of ultracold molecules by using a frequency shifter 下载免费PDF全文
We propose a technique to precisely measure the line width of the photoassociation spectra of the excited cesium molecule by using a frequency shifter to generate two laser beams with a precise frequency difference. A series of photoassociation (PA) spectra are recorded with two laser beam induced molecular lines, whose peak separation serves as an accurate frequency ruler to measure the line width of the PA spectra. The full width half maximum line width was studied as a function of PA laser intensity. The extrapolated value at zero laser intensity is (34.84 ± 0.22) MHz. By analyzing other broadening mechanisms, a value of (32.02 ± 0.70) MHz was deduced. It is shown that this scheme is inexpensive, simple, robust, and is promising for applications in a variety of other atomic species. 相似文献
106.
M. Kleiber M. Bode R. Ravli N. Tezuka R. Wiesendanger 《Journal of magnetism and magnetic materials》2002,240(1-3):64-69
The magnetic properties of the Cr(0 0 1) surface have been studied by spin-polarized scanning tunneling spectroscopy (SP-STS). Spatially resolved mapping of the spectroscopic dI/dU signal at an energy close to the spin-polarized Cr(0 0 1) surface state allows the confirmation of the topological antiferromagnetic order of the Cr(0 0 1) surface. It is shown that the presence of screw dislocations leads to the formation of domain walls which exhibit a width of 120–170 nm. A long-period modulation of the SP-STS signal was not observed indicating that the bulk spin-density wave is modified at the surface due to symmetry breaking. 相似文献
107.
Recent developments in quantitative surface analysis by Auger (AES) and x-ray photoelectron (XPS) spectroscopies are reviewed and problems relating to a more accurate quantitative interpretation of AES/XPS experimental data are discussed. Special attention is paid to consideration of elementary physical processes involved and influence of multiple scattering effects on signal line intensities. In particular, the major features of core-shell ionization by electron impact, Auger transitions and photoionization are considered qualitatively and rigorous approaches used to calculate the respective transition probabilities are analysed. It is shown that, in amorphous and polycrystalline targets, incoherent scattering of primary and signal Auger and photoelectrons can be described by solving analytically a kinetic equation with appropriate boundary conditions. The analytical results for the angular and energy distribution, the mean escape depth, and the escape probability as a function of depth of origin of signal electrons as well as that for the backscattering factor in AES are in good agreement with the corresponding Mote Carlo simulation data. Methods for inelastic background subtraction, surface composition determination and depth-profile reconstructions by angle-resolved AES/XPS are discussed. Examples of novel techniques based on x-ray induced photoemission are considered. 相似文献
108.
R. Wadsworth I. RagnarssonB.G. Carlsson Hai-Liang Ma P.J. DaviesC. Andreoiu R.A.E. Austin M.P. CarpenterD. Dashdorj S.J. Freeman P.E. Garrett J. GreeneA. Görgen D.G. JenkinsF. Johnston-Theasby P. JoshiA.O. Macchiavelli F. MooreG. Mukherjee W. ReviolD.G. Sarantites D. SeweryniakC.E. Svensson J.J. Valiente-Dobón 《Physics letters. [Part B]》2011,701(3):306-312
Four previously known rotational bands in 76Rb have been extended to moderate spins using the Gammasphere and Microball γ ray and charged particle detector arrays and the 40Ca(40Ca, 3pn) reaction at a beam energy of 165 MeV. The properties of two of the negative-parity bands can only readily be interpreted in terms of the highly successful Cranked Nilsson-Strutinsky model calculations if they have the same configuration in terms of the number of g9/2 particles, but they result from different nuclear shapes (one near-oblate and the other near-prolate). These data appear to constitute a unique example of shape coexisting structures at medium spins. 相似文献
109.
用光学多通道分析仪系统作高分辨光谱测量的技术 总被引:1,自引:0,他引:1
通常的光多通道分析仪(OMA)存在着同时谱宽与分辨率的矛盾.本文所述方法,在不减小谱宽的前提下,可将该分析仪光谱分辨率提高1~2量级,使之可适用于高分辨率谱研究. 相似文献
110.
A study of the nucleation kinetics for a cooling crystallisation of paracetamol–ethanol solutions in a batch reactor is described in this paper. Metastable zone width (MSZW) experiments were conducted in order to estimate the nucleation kinetics of the system. Measured MSZWs can be affected by numerous process parameters, such as cooling rate, concentration, agitation rate, and working volume. Two theoretical approaches were employed to estimate the nucleation kinetics, the classical mass based approach of Nývlt, and a more recent approach by Kubota, which also considers number density. Both approaches were found to produce similar estimates for the nucleation rates of the paracetamol–ethanol solutions as a function of supersaturation for an assumed nucleus size of 10 μm. The theory of Kubota was found to predict satisfactory estimates for the induction time of the nucleation process from MSZW data. The induction time was observed to be independent of the solution temperature as suggested by Kubota’s theory. This is a novel finding and serves to validate the induction time theory of Kubota. In this investigation, MSZWs were observed to decrease with increased levels of agitation and found to be independent of working volume. 相似文献