Free-surface phenomena under low- and zero-gravity conditions

A free surface experiment using a liquid doped with a fluorescent dye under sheet illumination is summarized. The work includes the selection of a CCD camera for use during the design stages of the experiment as well as a preliminary demonstration of this technique in the production of a contour map of a liquid-liquid interface with better than 0.1 mm resolution. With a different data sampling and storage procedure, the image processing is reduced to a simple thresholding procedure which can be done in hardware

Propagation of weak shocks through a random medium

The propagation of weak shock waves (M_s = 1.007, 1.03 and 1.1) through a statistically uniform random medium has been investigated experimentally in a shock tube. The wave-from geometry, rise time and amplitude of initially plane shocks which have propagated through a random mixture of helium and refrigerant 12 are measured. The effect of shock propagation on the properties of the random medium is visualized with schlieren and shadow photography. The pressure histories of the distorted shock waves reflecting from a normal end wall are observed to be both peaked and rounded. In the rounded case the perturbed shock is found to be made up of a succession of weak, slightly curved fronts with a total effective rise time orders of magnitude greater than the classical Taylor thickness. The radius of curvature of the weakest shocks after propagating through the random medium is inferred from observations at two downstream stations to be about 7 times the integral scale of the gas inhomogeneities. It is concluded that the observed distortions of the wave fronts can best be explained in terms of random focusing and defocusing of the front by the inhomogeneities in the medium. A ray-tracing calculation has been used to interpret the experimental observations. It is found that geometrical considerations are sufficient to account for many of the effects observed on the shocks

High speed optical tomography for flow visualization

A novel optical architecture (based on holographic optical elements) for making high speed tomographic measurements is presented. The system is designed for making density or species concentration measurements in a nonsteady fluid or combustion flow. Performance evaluations of the optical system are discussed, and a test phase object was successfully reconstructed using this optical arrangement

Optical memory: introduction by the feature editors

The contributions to this feature issue represent a wide range of topics in optical memory

Mystery Shopping: In-depth measurement of customer satisfaction

This paper will discuss the phenomenon Mystery Shopping in the fieldof customer satisfaction measurement techniques. By using theliterature about Mystery Shopping definitions and restrictions of thisinstrument will be presented. Also, possible ways to present and usethe gathered data will be shown. After the literature part of thepaper some practical research will be presented. A Dutch Flexcompanyintroduced the instrument Mystery Shopping in addition to the alreadyused measurement methods like customer satisfaction measurement withuse of questionnaires. Some of the first results of the MysteryShopping visits will be presented.customer satisfaction;mystery guest;service quality