Optical analyzer

Another important method of determining the Gruneisen ratio in the shock state is the measurement of sound speed behind the shock front. The techniques employing optical analyzers (McQueen et al., 1982) piezoresistive (Chap-... 

McQueen et al. (1982) demonstrated that by placing a series of high-impedance transparent fluids (called optical analyzers) over the sample at a series of thicknesses less than d in the target that the overtaking rarefaction (sound) velocity can be accurately obtained. Arrival of rarefaction waves rapidly reduce the shock pressure. These wave arrivals could be very readily detected by the change in light radiance caused by the onset of a decrease in shock amplitude when the rarefaction wave caught up to the shock front. The... 

Zare and coworkers (2009) have recently discussed a continuous flow ring down spectroscopy system integrating chromatographic separation, a catalytic combuster, and an isotopic 13C/12C optical analyzer which conveniently yields 813C values at a precision nearing that for IRMS. A modification yields 8D and 815N values. 

Fiber Length Distribution, for industrial applications, the fiber length and length distribution are of primary importance because they are closely related to the performance of the fibers in matrix reinforcement. Representative distributions of fiber lengths and diameters can be obtained through measurement and statistical analysis of microphotographs fiber length distributions have also been obtained recently from automated optical analyzers. 

Below, a variety of designs of optical analyzers are presented. The designs are... 

Single-particle optical analyzers are especially useful for continuous measurement of particles of uniform physical properties. However, as discussed earlier, uncertainties develop in the measurement of particle clouds that are heterogeneous in composition because the refractive index may vary from particle to particle. Thus, in making atmospheric aerosol measurements, workers have assumed an average refractive index characteristic of the mixture to estimate a calibration curve or have reported data in terms of the equivalent particle diameter for a standard aerosol, such as suspended polystyrene latex spheres. 

An alternative is the use of an optical method to measure particulate concentrations and size distributions. This technique has the obvious advantage of having a negligible effect on the particulates since the equipment would be external to the exhaust system. An optical method also has the potential to be much simpler to use since it would eliminate the need for elaborate and cumbersome systems containing probes, stack samplers, flow development tunnels, filters, and heat exchangers. In addition, final data from an optical system could be immediately obtained electronically as opposed to weighing the various filters in a particle impactor by hand, and as such, the optical analyzer is a real time instrument capable of following exhaust gas fluctuations and other nonsteady effects. 

All of the systems described are now available with an incorporated differential thermal analyzer. DTA has been described in Section 16.2, so a few examples of the advantages of combining these systems will be presented. The incorporation of a DTA with one of the optical analyzers described requires the use of two thermocouples to measure the temperature difference between the sample and a reference standard (calcined kaolin or alumina). As noted, the optical noncontact instruments described are particularly useful in the glass and ceramics industries, so examples of evaluating raw materials from these industries will be described (from Paganelli and Venturelli). 

L Ouarterwave plate at 1.06 pm. S Spectrograph. A.O. j Optical analyzer (linear photodiode array). A.M. Multichannel analyzer. 

FIGURE 37.22 Optical analyzer as part of the modular sample conditioning platform. (Courtesy of Circor International, Inc., Burlington, MA.)... 

Whorlow (1992) published a book on rheological techniques that inctudes dynamic tests and wave propagation tests. In the appendix, he listed a number of rheologicat inves-tigahon equipment manufacturers. Some of the techniques appiy more to polymers and are not relevant to our discussion. Dynamic vibration tests have been extended to fresh concrete (Teixera et at., 1998). Concord and Tassin (1998) described a method to use rheo-ophcs for the study of thixotropy in synthetic clay suspensions. A rheometer optical analyzer was used on laponite, a synthetic hectorite clay. Laponite was mixed with water and tests were conducted at various intervals for up to 100 days. Rheo-ophcs seems to be... 

Conventional optical spectroscopy, i.e. techniques which use either incoherent line or broadband sources in conjunction with some form of optical analyzer or spectrograph, have of course contributed greatly to our understanding of optical properties in all phases. It is indeed through the findings of conventional optical spectroscopy that many of the advances in modern physical and chemical sciences find their foundation. It will be assumed that the reader is acquainted with the considerable background which has accumulated, for it provides the baseline for our discussion of the more refined and sophisticated laser based spectroscopies. For a pedagogical overview of conventional and other spectroscopic techniques, see for example Hollas (1982). 

Wu and Liu (2002) analyzed the mechanism of the pulse combustion spray drying of salt solution in an oscillating flow field produced by a Helmholtz-type pulse combustor with an external flapper valve. The solution was atomized directly by the pulsating flow in the combustor tailpipe, which reduced the average droplet diameter by about 50% in relation to conventional nozzle atomization. An optical analyzer was applied to measure the droplet size distribution in the spray in order to determine the initial conditions for the CFD model of the process. The results of CFD simulations enabled the average residence time of droplets in the drying chamber (ca. 0.1 s) and the... 

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