High Precision Titrimetry,Ion Chromatography and ICP-Optical Emission Spectrometry for the Estimation of Inhomogeneities in Aqueous Calibration Solutions for Metrological Purposes

The homogeneity of samples intended for metrological intercomparison studies must be granted without ambiguity. This holds equally true for aqueous solutions for which the determination of between-bottle variations requires measurement techniques with extremely high precision. Therefore measurement series were designed for automated analysis techniques such as titrimetry, optical emission spectrometry and ion chromatography which offer very high precision of results. Between-bottle relative standard deviations (RSD) of at best 0.008% were obtained with titrimetry. With optical emission spectrometry and ion chromatography, between-bottle RSDs of 0.02% and 0.05% were obtained. The contributions from these measurements were included in a conservative approach to the uncertainty budgets of the gravimetrical reference values for the analytes in the samples.     

Embedded Digital Speckle Pattern Interferometry for Three-dimensional Strain Analysis

The extension of Digital Speckle Pattern Interferometry to three-dimensional cases poses new challenges from both the practical and the theoretical points of view. In the present research, a scattering surface was created within a transparent Plexiglas specimen with the aid of atomized aluminum particles, and strain was measured in the interior plane. Test specimen configurations included a beam in bending and a disc in diametral compression. The tests on the beam in bending showed excellent agreement between Embedded DSPI results and resistance strain gages. However, for the disc in compression, large discrepancies were found. The main source of errors was identified in the effect of the refractive index gradient. Based on the assumption that the index of refraction changes proportionally to the local dilatation, the error was calculated and the predicted results were ultimately in good agreement with the DSPI data. In conclusion, the Embedded DSPI technique was found to be a viable tool for direct experimental strain investigation of complex 3-D cases.     

Control of crankshaft finish by scattering technique

The paper describes a new sensor dedicated to measure and check the surface quality of mechanical products. The results were obtained comparing the light scattered from two different ranges of angles by means of 16 photodiodes. The device is designed for obtaining valid data from curved surfaces as that of a crankshaft. Experimental measurements show that the ratio between scattered and reflected light intensity increases with the surface roughness. This device was developed for the off-tolerance detection of mechanical pieces in industrial production. Results of surface quality on crankshaft supplied by Renault were carried out.     

Digital speckle correlation for strain measurement by image analysis

This paper is concerned with small strain measurement utilizing the numerical processing of digital images. The proposed method has its theoretical basis in digital signal analysis and, from a methodological point of view, it can be considered as an extension to digital images of the wellknown white light speckle photography technique. That conventional method is based on the analysis of photographic plates that are exposed twice (before and after the specimen deformation) with the image of a random speckle pattern that has been previously printed on the test piece surface. The digital speckle correlation advantages consist of requiring a very simple specimen preparation and, mainly, of allowing the strain field computation just by numerical elaboration of the acquired images. In this paper, the theoretical basis of the technique and some valuable improvements to the known analogous methodologies are presented. Finally, test results for an application of digital speckle correlation are shown and advantages and disadvantages of the technique are elaborated. In addition, further developments in this area are discussed.     

A Micromechanics Study of Lamellar TiAl

Microdeformation patterns of lamellar TiAl specimens with various grain sizes under uniaxial tension are mapped using the micro/nano experimental mechanics technique called SIEM (Speckle Interferometry w ith Electron Microscopy). The stress–strain relationships were obtained from deformations within decreasing areas ranging from mm² to μm². We found that the stress–strain relationship of the material depends on the size of strain measuring area in relation to the grain size. The stiffness at a grain boundary can be as large as 7–10 times more than that of the grain itself. From the data obtained so far, it seems that the traditional way of using PST (polysynthetically twinned) single crystal to predict polycrystalline behavior may not be appropriate.     

Effects of red blood cell aggregates dissociation on the estimation of ultrasound speckle image velocimetry

Ultrasound speckle image of blood is mainly attributed by red blood cells (RBCs) which tend to form RBC aggregates. RBC aggregates are separated into individual cells when the shear force is over a certain value. The dissociation of RBC aggregates has an influence on the performance of ultrasound speckle image velocimetry (SIV) technique in which a cross-correlation algorithm is applied to the speckle images to get the velocity field information. The present study aims to investigate the effect of the dissociation of RBC aggregates on the estimation quality of SIV technique. Ultrasound B-mode images were captured from the porcine blood circulating in a mock-up flow loop with varying flow rate. To verify the measurement performance of SIV technique, the centerline velocity measured by the SIV technique was compared with that measured by Doppler spectrograms. The dissociation of RBC aggregates was estimated by using decorrelation of speckle patterns in which the subsequent window was shifted as much as the speckle displacement to compensate decorrelation caused by in-plane loss of speckle patterns. The decorrelation of speckles is considerably increased according to shear rate. Its variations are different along the radial direction. Because the dissociation of RBC aggregates changes ultrasound speckles, the estimation quality of SIV technique is significantly correlated with the decorrelation of speckles. This degradation of measurement quality may be improved by increasing the data acquisition rate. This study would be useful for simultaneous measurement of hemodynamic and hemorheological information of blood flows using only speckle images.     

微型激光光学引擎中光学噪音的抑制

分析了微型激光投影引擎的两种主要光学噪音|干涉网格和激光散斑产生的基理|提出采用振动的随机位相板同时实现干涉网格和激光散斑抑制的方法并进行了理论分析|自行设计了微型激光投影引擎,利用微型电控马达带动随机位相板振动,用CCD相机在不同的F#及曝光时间下对投影图像进行了采集,并对图像的散斑对比度行了测试.结果表明,通过静止的随机位相板可以很好地抑制干涉网格噪音|通过使随机位相板以大于视觉暂留效应形成的融合频率进行振动,可以同时抑制干涉网格和激光散斑,使得散斑对比度小于5%,达到投影观察的要求.     

利用振动光纤减弱激光散斑的研究

在激光投影显示技术中,引入振动光纤的方法能够以较小的能量损失减弱激光散斑.本文利用广义范西特-泽尼克定理对激光投影显示中采用振动光纤抑制散斑做了理论分析.结果表明,散斑衬比度的大小取决于光纤的模式数和投影系统的光瞳大小,对于相同大小的像面,收集更多的光纤模式数和增大孔径均可减弱散斑衬比度.用两种不同的多模光纤所做的对比实验定性证实了这一结论.研究结果对光纤的选择和投影系统的设计有一定的指导意义.     

Phase retrieval in two-wavelength DSSI using a combined filtering method

Phase retrieval in two-wavelength DSSI (digital speckle shearing interferometry) using a combined filtering method is proposed for small deformation derivative measurement. A simultaneous two-wavelength illumination and 3-CCD camera are employed in the experimental setup. The proposed method, which uses a two-wavelength technique does not require the conventional spatial phase unwrapping and has the advantage of good noise suppression for phase retrieval. Experimental results obtained show that using the proposed combined filtering method sensitivity similar to the single wavelength technique can be achieved.     

MiC in Chemistry Curriculum at the University of Tartu: the current status

The introduction of MiC (Metrology in Chemistry) into the Chemistry Curriculum at the University of Tartu using a two-stage approach is described. As the first stage the topics of MiC are first touched at the beginning of the first analytical chemistry lecture course in the 3rd semester. The emphasis there is on the measurement uncertainty (MU) and its practical estimation (based on the ISO GUM approach). The main purpose of this is to make it clear from the beginning that MU is an integral part of any measurement and to enable the students to estimate MU in the laboratory courses of analytical chemistry (3rd and 4th semesters). As the second stage, MiC is treated in more detail in a dedicated course where also topics, such as reference materials, interlaboratory comparisons, standardization, quality management, accreditation, etc are covered. Received: 6 November 2001 Accepted: 6 December 2001