Application of ESPI-method for strain analysis in thin wall cylinders

The Centre for Industrial and Engineering Optics, DIT, Ireland, have recently developed and applied new optical techniques for the measurement of mechanical strain, one of which was based on electronic speckle pattern interferometry (ESPI). The accuracy of this optical technique when used on flat surfaces is well established. In this research the technique is tested on curved surfaces, and results are compared with the theoretical hoop strain as predicted by the bi-axial strain equation modified for the thin cylinder, and by those obtained by electrical resistance strain gauge (ERSG) undoubtedly the principal method of measuring mechanical strain. For testing procedures, a special unit was designed and produced for holding and loading the thin cylinder. Also the basic equation for hoop strain by ESPI for flat surfaces was modified for applications on curved surfaces.Thin cylinder hoop strain obtained by ESPI and calculated by a modified equation show remarkably good correlation to the predicted theoretical value as well as to the results obtained by ERSG. Since the ESPI theory was originally developed for use on flat surfaces, there are reasonable grounds for further investigating this relationship especially where curved surfaces are involved.     

Two-dimensional phased arrays for application in surgery: Scanning by several focuses

Numerical simulation and comparative analysis of acoustic fields formed by two-dimensional phased arrays designed for ultrasonic surgery are conducted for the case of scanning by several focuses (in particular, by nine focuses arranged in a line and also by an array of nine focuses forming a 3×3 square grid). Calculations are performed for arrays with elements positioned at the surface both regularly (in square, ring, or hexagonal patterns) and randomly. Criteria for evaluating the “quality” of the intensity distributions in the field formed by the array in the case of scanning by several focuses are proposed. The quality of the intensity distributions for arrays containing 255 and 256 elements 5 mm in diameter arranged in regular patterns on the array’s surface (in square, ring, or hexagonal patterns) is inferior to that for arrays containing 256 randomly positioned elements. Among the regular arrays, the highest quality of intensity distributions is obtained for ring arrays, and the lowest quality is obtained for arrays with elements arranged in square or hexagonal patterns. The irregularity in the element positioning the array’s surface improves the quality of intensity distributions by reducing the secondary intensity peaks in the field formed by the array and, primarily, in the focal plane.     

铝锂合金样品的前处理及其Ag和Li的光谱分析

针对铝锂合金样品检测其Ag和Li,采用等离子体原子发射光谱法(ICP-OES)同时测定Ag和Li,火焰原子吸收光谱法(FAAS)分别测定Ag和Li,单宁酸分光光度法(VS)测Ag,对不同的光谱测定方法进行了比较,证明了ICP-OES检测铝锂合金中的Ag和Li具有较高的抗干扰性。对比了三种不同的样品消解方法,确定了FAAS测Li采用王水溶样最佳,ICP-OES,FAAS和VS测Ag采用HCl+H₂O₂体系溶样准确度更高。详细讨论了样品中共存元素Al, Mg, Zr, Ti, Cu的干扰及消除方法。用氨水沉淀消除共存元素Al,Ti,Zr,8-羟基喹啉沉淀分离Mg和Cu的方法消除原子吸收光度法测Ag的干扰;采用磷酸盐沉淀分离Ti而消除原子吸收光度法测Li的干扰;采用与原子吸收光度法测银相同的消除干扰方法,消除上述离子干扰,滤去干扰沉淀后,用硝酸赶盐酸解蔽Ag+离子,同时分解消除8-羟基喹啉的颜色,以消除分光光度法测银的干扰。对比消除干扰前后的结果发现准确度显著提高,证明消除干扰的方法切实有效。将选择的最佳消解体系和干扰消除方法应用于铝锂合金样品的测定,ICP-OES测Li和Ag回收率分别在100.39%～103.01%和100.42%～103.73%之间,FAAS测Li和Ag 回收率分别在95.91% ～99.98%和98.04%～103.67%之间,分光光度法测Ag回收率在98.00%～101.00%之间,测定结果满足分析要求。     

机械合金化致二元过渡金属非晶态合金形成规律的探讨

运用Ｍｉｅｄｅｍａ参数和尺寸因子Ｒ分别构成Ｍｉｅｄｅｍａ参数坐标和三维化学坐标成功地研究机械合金化二元过渡金属非晶合金的形成规律。基于实验事实所确定的机械合金化二元非晶的形成条件分别是见原文，以上两判据区分机械合金化非晶态合金形成与否的准确度分别为８０％和８８％。从微观原子的相互作用以及固态反应非晶化热力学和动力学的角度分析了以上参数在描述机械合金化二元过渡族合金体系非晶形成规律的内在物理涵义以及与固态反应非晶化实现所需条件的联系。 关键词：     

Determination of reduced thicknesses by means of the variable take-off angle technique

Reduced thicknesses can be determined by means of substrate, layer and ratio methods. All these methods require the determination of two unknown quantities — the reduced thickness and a proportional factor which is specific for the method applied. Experimental results can be evaluated by regression, employing equations derived for plane, smooth, homogeneous layers. The aim of this paper is to show how the measured data are influenced by surface roughness, by the energy-dependence of the mean free path of the photoelectrons, and by measurement errors. Moreover, a method is presented for applying the equations derived for ideal layers to results obtained from real structures, taking these influences into account. This evaluation procedure is demonstrated by two examples.     

A New Coherent States Approach to Semiclassics Which Gives Scott’s Correction

We introduce a new semiclassical calculus by generalizing the standard coherent states. This is applied to the semiclassical expansion for the sum of negative eigenvalues of Schrödinger operators which leads to a new proof of the Scott correction for non-relativistic molecules.Work partially supported by an EU TMR grant, by a grant from the Danish research council, and by MaPhySto – Centre for Mathematical Physics and Stochastics, funded by a grant from The Danish National Research Foundation. ©2003 by the authors. This article may be reproduced in its entirety for non-commercial purposes.     

Comments on the structures observed for atomic adsorption on (110) surfaces of face-centred cubic metals

The hybridisation model for face-centred cubic metals, proposed by Altmann, Coulson and Hume-Rothery, is used for analysing some aspects of the surface structures reported by LEED crystallography for S adsorbed on the (110) surfaces of nickel and rhodium, and for O adsorbed on the (110) surfaces of nickel and iridium. The main objectives are to rationalise the different adsorption sites adopted by S and O, and to assess the measured bond lengths. For the latter, use is made of a bond length-bond order relationship given by Pauling.     

Universal Bounds for Eigenvalues of a Buckling Problem

In this paper, we investigate an eigenvalue problem for a biharmonic operator on a bounded domain in an n-dimensional Euclidean space, which is also called a buckling problem. We introduce a new method to construct ``nice' trial functions and we derive a universal inequality for higher eigenvalues of the buckling problem by making use of the trial functions. Thus, we give an affirmative answer for the problem on universal bounds for eigenvalues of the buckling problem, which was proposed by Payne, Pólya and Weinberger in [14] and this problem has been mentioned again by Ashbaugh in [1]. Research partially supported by a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science. Research partially supported by SF of CAS     

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The cold pressure parameters of q and Q in the Born-Mayer(BM) model for fifty-seven metals equations were calculated by using the Hu-Jing(HJ) method based on isothermal bulk moduli of metal and measured data in shock wave experiments, and at the same time a trial method for computing them by combining Thomas-Fermi model at absolute zero-temperature with low pressure experiment data, is put forward for lack of the sufficient shock wave experiment data. By integrating the Faussurier model for electron thermal pressure, the Cowan model for ion thermal pressure and the above obtained cold pressure fitted formula, the Hugoniot curves of Be, Co and Pb are calculated and compared with experimental data, and then the discrepancies of q value and Q value obtained by HJ method and a comprehensive method are analyzed and interpreted. Furthermore, the precision for the cold pressure equation by HJ method is assessed by comparing the thermodynamic quantities on the Hugoniot curves of Sr, Ba, and Sm with the corresponding measured results and the calculated ones by other models.     

Spin squeezing in the presence of dissipation

The transfer of spin between photons and localized atomic levels, for a chain of two-level atoms, is studied. The Hamiltonian of the system is modelled by a radiation term and by atom-atom and radiation-atom interactions. Effects due to dissipation are accounted for by atom-photon exchange-interactions of complex strength. It is found that the spin-squeezing is suppressed by dissipation. Calculations are performed for arrays of Rb atoms excited by a GaAlAs laser.     

均聚物结晶与熔融化转变的稳态和亚稳态统计理论III. 分子分凝统计结晶动力学～熔体内结晶增长速率的一般化表征和它们对生长机制的依赖性

首先对微晶粒尺寸增长速率的表征进行总结.从微晶核和粒—高分子链组网络结构特点(高分子链组是微晶核和微晶粒同连接链段的复合体)同增长速率间的三个相关性的特征: ①晶核和晶粒加大同连接链段缩短的并存性; ②微晶核和粒表面上连接链段的缩短机制存有简并性; ③微晶粒内和粒表面上stem的反顺式构象共存性出发.建议了一种评估和计算微晶粒尺寸增长速率的新方法和原则,基于该种计算方法和原则用统计力学和动力学相结合法推导出了高分子熔体内几种不同结晶生长机制(近邻折叠、近邻伸直分凝和近邻折叠同近邻伸直分凝并存等生长方式)下微晶粒—高分子链组中微晶粒数增长速率和微晶粒尺寸增长速率动力学方程.     

Migration polarization in dielectrics and semiconductors

It is shown that during migration polarization the relaxation time is governed by the carrier lifetime in the bound state, by the thickness of the layer through which the migration occurs, and by the drift velocity. An equation is found for ion migration by generalizing the equation for ion-relaxation polarization. Experimental data found by the Ioffe method on the ion mobility in Al₂O₃ are reported and compared with the mobilities obtained by the method of this paper, on the basis of the equation for the relaxation time. Migration polarization must be taken into account in analyzing the mechanism for the excess noise and certain cases of current oscillations in semiconductors, dielectric loss of a relaxation nature, relaxation phenomena in film-type active devices, etc.     

Dielectric waveguide model for guided surface polaritons

Although surface polariton modes supported by finite-width interfaces can guide electromagnetic energy in three dimensions, we demonstrate for the first time to our knowledge that such modes can be modeled by the solutions of two-dimensional dielectric slab waveguides. An approximate model is derived by a ray-optics interpretation that is consistent with previous investigations of the Fresnel relations for surface polariton reflection. This model is compared with modal solutions for metal stripe waveguides obtained by full vectorial magnetic-field finite-difference methods. The field-symmetric modes of such waveguides are shown to be in agreement with the normalized dispersion relationship for analogous TE modes of dielectric slab waveguides. Lateral confinement is investigated by comparison of power-density profiles, and implications for the diffraction limit of guided polariton modes are discussed.     

Study of Solid Transparent Nanocomposite Organic/Inorganic Matrices and Thin Films by Time-Resolved Fluorescence Techniques

This work focuses on the study of nanocomposite organic/inorganic materials, particularly, those made by the sol-gel method, by using time-resolved fluorescence techniques. A model of stretched exponentials is presented and used to fit fluorescence (luminescence) decay profiles for fluorescence quenching reactions obtained by energy-transfer or by diffusion or both. Various types of information on both bulk and thin-film nanocomposite materials can be obtained by such analysis: for example, determination of the percolation threshold for the organic subphase, localization or mobility of incorporated molecular species, and extraction of structural parameters.     

Effect of ultrasonic separation on the structure and properties of diallyl phthalate prepolymer

The bulk polymerization of diallyl phthalate (DAP) was carried out at high temperature (190 degrees C) without using any initiator, and the reaction was stopped before the gelation point in order to get the prepolymer of DAP. The mixture for the prepolymer and the monomer was successfully separated by a novel ultrasonic method for the first time, and the separation efficiency for the new method was obviously higher than that for the traditional reprecipitation. The product obtained by ultrasonic separation was characterized by infrared spectroscopy (IR), gel permeation chromatography (GPC) and iodine number measurement. It was shown that the average molecular weight of the prepolymer got by the ultrasonic method was lower than that of the prepolymer got by the multi-precipitation, moreover, the molecular weight distribution of the prepolymer got by the ultrasonic separation was broader. Besides, the residual unsaturation degree of the prepolymer separated by ultrasonic was slightly higher than that of prepolymer separated by reprecipitation.     

Fidelity evaluation of metallic luster in six-band high-dynamic-range imaging

This paper presents subjective evaluation results for images reproducing metallic luster. The images were produced by a six-band high-dynamic-range imaging technique, which provides high color fidelity and the capability of various tone mapping operations. The preferences for images produced by four kinds of tone mapping operations were evaluated by means of a paired comparison method under the conditions that observers could or could not refer to real scenes. The evaluation results indicated that preferences for images depend on tone mapping operations, especially for objects that have the luster changing over a large area with moderately high intensity. In addition, when referring to a real scene, the spatially varying tone compression, which reproduces the color and complex characteristics of metallic luster, was significantly preferable to the tone mappings by other approaches. Without a real scene, the preference was also strong for images produced by simply saturating pixel values at highlights.     

Intensity distribution and coherence property for the broadband Gaussian Schell-model array beams in free space

The intensity distribution and the equal-time complex degree of coherence for the broadband Gaussian Schell-model array beams with different bandwidth propagating in free space are analyzed by the numerical calculation. Results show that the intensity distribution for the broadband Gaussian Schell-model array beams by uncorrelated superposition is rarely affected by the bandwidth; the intensity distribution in the far field for the broadband Gaussian Schell-model array beams by correlated superposition is affected by the bandwidth more obviously than that in the near field. With the increasing of the propagation distance, differences in the equal-time complex degree of coherence for the broadband Gaussian Schell-model array beams with different bandwidth become prominent.     

Control of the vortex flow in microchannel arrays produced in YBCO films by heavy-ion lithography

High-energy heavy-ion lithography is a powerful tool for tuning both structural and electromagnetic properties of high temperature superconductors by inducing nanometer scale defects confined in micron scale patterns. We show how the vortex dynamics in YBCO thin films patterned by heavy-ion lithography can be controlled and potentially exploited for device applications. Both local critical temperature and local critical currents are effectively tailored by the imposed irradiation geometry. The direct visualization of the real-time dynamics of the magnetic pattern is achieved by the magneto-optical imaging technique, while confined vortex flow is revealed by the simultaneous measurement of the electrical resistance both along and perpendicular (Hall resistance) to the direction of the applied current. It is shown that, for microchannel arrays inclined with respect to the transport current flow, the direction of vortex motion is solely determined by the imposed irradiation pattern geometry, in a well-defined temperature range, for a given applied current.     

Steering a multi-MeV positron beam with a curved crystal

We observe positron bending by a crystal lattice, presumably being guided by a channeling phenomenon, deflecting the beam by about 10 milliradian over a length of 1 mm of silicon. This technique may lead to the use of the channeling effect for steering particle beams at energies below 1 GeV, for the purpose of producing beams of low emittance with enhanced stability for medical and biological applications. The text was submitted by the authors in English.     

Infrared and microwave radiative properties of metal coated microfibres

Recent experimental investigations have shown that insulations containing metallised glass or polymer fibres are characterised by an extremely high extinction coefficient for infrared radiation and, as a result, by very good heat shielding properties. This may be explained by the unusual optical properties of single fibres. In this paper, the most general theoretical model for the radiation absorption and scattering by metallised fibres is employed. It is based on the rigorous theory of scattering by an arbitrary oriented two-layer cylinder and may be used for calculations in a wide spectral range. The accuracy of some simple models of metallised fibres is analysed. In particular, the range of applicability of the perfectly conducting cylinder approximation is determined. A comparison with published experimental data shows good agreement between the calculated and the experimental values of the equivalent specific extinction coefficients in the spectral range of 2.5 < λ < 27.5 μm. Computational data on the absorption and scattering of microwave radiation by metallised dielectric fibres are presented for the first time. High values of the absorption efficiency factor for single submicron fibres may be of interest for microwave applications.