A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

Fringe projection techniques: Whither we are?

To improve the performance of particle image velocimetry in measuring instantaneous velocity fields, direct cross-correlation of image fields can be used in place of auto-correlation methods of interrogation of double- or multiple-exposure recordings. With improved speed of photographic recording and increased resolution of video array detectors, cross-correlation methods of interrogation of successive single-exposure frames can be used to measure the separation of pairs of particle images between successive frames. By knowing the extent of image shifting used in a multiple-exposure and by a priori knowledge of the mean flow-field, the cross-correlation of different sized interrogation spots with known separation can be optimized in terms of spatial resolution, detection rate, accuracy and reliability.

Theory of cross-correlation analysis of PIV images : Image analysis as measuring technique in flows

In recent years, both industrial and academic world are focussing their attention toward the development of sustainable composites, reinforced with natural fibres. In particular, among the natural fibres (i.e. animal, vegetable or mineral) that can be used as reinforcement, the basalt ones represent the most interesting for their properties. The aim of this review is to illustrate the results of research on this topical subject. In the introduction, mechanical, thermal and chemical properties of basalt fibre have been reviewed. Moreover, its main manufacturing technologies have been described. Then, the effect of using this mineral fibre as reinforcement of different matrices as polymer (both thermoplastic and thermoset), metal and concrete has been presented. Furthermore, an overview on the application of this fibre in biodegradable matrix composites and in hybrid composites has been provided. Finally, the studies on the industrial applications of basalt fibre reinforced composites have been reviewed.

A review on basalt fibre and its composites

http://eia.udg.es/~qsalvi/papers/2010-PR.pdf

A state of the art in structured light patterns for surface profilometry

Reference IMAC-CONF-2010-001doi:10.1063/1.3426097 URL: http://link.aip.org/link/?APCPCS/1236/124/1 Record created on 2010-02-19, modified on 2016-08-08

Enhancing Accuracy and Sensitivity of Temperature Gradient Measurements in DOE Schardin Schlieren ♯2 Using Windowed Fourier Transform Method

In studying hydrodynamic instabilities between two miscible fluid mixtures one often faces the problem of assigning a reliable value to very small diffusion coefficients. As for diffusion between two binary mixtures such as water and glycerin, water and salt, etc., no complete data are available in the literature. In order to measure small diffusion coefficients of miscible fluids, in this paper we propose an improved version of digital projection moire. The system uses a fringe generator realized with a diffractive optical element (DOE). The fringe patterns are projected on the bottom of a ground glass plate. The phase object (diffusion cell) is placed in front of the ground glass (in other words, in front of the fringe pattern), which is imaged by a digital video camera. Grating patterns, during the evolution of diffusion phenomena, are captured by a CCD camera and stored in a computer at different times. With the aid of Fast Fourier Transform (FFT) and signal demodulating techniques, the images are processed to obtain the diffusion coefficients. The theoretical basis of the device is presented. Furthermore, we report some experiments conducted for demonstrating the usefulness of the system.

Diffractive optical element based sensor to measure small diffusion coefficients

Today, the vibration analysis of laminated structures represents an important field in engineering metrology. To perform non-invasive vibration measurements in industrial environments, optical methods are a preferable choice. Electronic Speckle Pattern Interferometry is a method, which permits full field and non-contacting displacement or deformation measurements. The experimental measurement of the resonant frequencies for the piezoceramic material is generally performed by impedance analysis. In this work, Electronic Speckle Pattern Interferometry (ESPI) technique is proposed for studying vibration of piezoceramic/nickel circular laminated plates. The circular membrane is a composite made of a nickel alloy disk with thickness 0. 1 mm and diameter 32 mm, to which a piezoceramic disk, with the same thickness and a smaller diameter (24 mm) is bonded. The time average frame subtraction technique is improved by subtracting two Bessel fringe patterns at two different amplitude levels. A brief analysis of the techniques and some preliminary experimental tests are presented.

Vibration analysis of layered structures by optoelectronics methods

Optical techniques have a long tradition in flow visualization, allowing both qualitative and quantitative analysis. In particular, speckle photography, introduced in 1968, has been extensively used. The aim of this work is to discuss speckle-based deflection techniques in the investigation of diffusion phenomena in liquids.

Speckle-Based Deflection Techniques in Diffusivity Measurements

This paper describes an instrument developed for the semi-continuous measurement of aerosol mass and its categorization into three classes. These classes have been chosen to evaluate the health hazards of the inhalable particles. The instrument performs sampling through three probes, each providing different cut-points (~15, ~4 and ~2 µm) and collecting airborne particles on circular membrane filters. The increase in weight is measured with the beta-rays attenuation method.

Domenica Paoletti

Papers

Enhancing Accuracy and Sensitivity of Temperature Gradient Measurements in DOE Schardin Schlieren ♯2 Using Windowed Fourier Transform Method

Diffractive optical element based sensor to measure small diffusion coefficients

Vibration analysis of layered structures by optoelectronics methods

Speckle-Based Deflection Techniques in Diffusivity Measurements

Automatic system for three fractions sampling of aerosol particles in outdoor environments