Illuminating formulations

In integrated photoelasticity it is impossible to achieve a complete reconstruction of stresses in samples by only illuminating a system of parallel planes and using equilibrium equations of the elasticity theory. Theory of the fictitious temperature field allows one to formulate a boundary-value problem which permits to determine all components of the stress tensor field in some cases. If the stress gradient in the axial direction is smooth enough, then perturbation method can be used for the solution of the inverse problem. As an example, distribution of stresses in a bow tie type fiber preforms is shown in Fig. 2 [2]. 

When Munsell devised his color space, he did so on the basis of minimum observable color perception steps. But the problem with the Munsell System was one of reproducibility, which the CIE Standard Observer cured. In formulating a color match, one wants to be able to predict the correct concentration of colorants required, whose scattering and absorption properties are known, i.e.- the lightness, so as to match the sample submitted, starting with their spectrophotometric curves. In practice, this is not so simple, since two colors must have identical spectrophotometric curves to be exactly equal. It turns out that the human eye will identify the two colors to be equal if their spectrophotometric reflectances are reasonably close. Two colors may appear to be equal under Daylight illumination, but quite different under incandescent lamp illumination. These colors are known zus "metamers" and the phenomenon "metamerism". 

As an example of this work, the reflectance spectra of tablets formulated with FD C Blue No. 1 and exposed to various light intensities are shown in Fig. 3. Under normal illumination (45 foot-candles), the decomposition kinetics are modest. When exposed to higher levels of illumination (550 foot-candles), complicated kinetics characterized by at least three different reaction pathways were observed [15]. 

Fig. 3 Reflectance spectra of tablets formulated with FD C Blue No. 1 and expose to ordinary illumination for various time periods. Full spectra are shown in the upper bo for tablets (A) as initially prepared, and after (B) 42 days and (C) 84 days of illuminatior The dependence of dye absorbance on elapsed time is shown in the lower box. (Dal adapted from Ref. 14.)...

Other workers have used the tristimulus parameters to study the kinetics of decomposition reactions. The fading of tablet colorants was shown to follow first-order reaction kinetics, with the source of the illumination energy apparently not affecting the kinetics [49]. The effect of excipients on the discoloration of ascorbic acid in tablet formulations has also been followed through determination of color changes [50]. In this latter work, it was established that lactose and Emdex influenced color changes less than did sorbitol. 

For monochromatic illumination of constant intensity, the rate of Fe(II)aq production can be formulated as ... 

It should be noted that the MTF expresses the modulation in the image plane of a sinusoidal object and is useful only for incoherent illumination. Under practical conditions for large features (> 3.0 m), the sinusoidal object (mask) is not a good choice when what is really relevant is a binary object. However, as the mask features approach 1.0 pm, the light intensity through the mask becomes sinusoidal and the mathematical formulation for MTF becomes relevant. 

Salvador [100] introduced a non-equilibrium thermodynamic approach taking entropy into account, which is not present in the conventional Gerischer model, formulating a dependence between the charge transfer mechanism at a semiconductor-electrolyte interface under illumination and the physical properties thermodynamically defining the irreversible photoelectrochemical system properties. The force of the resulting photoelectrochemical reactions are described in terms of photocurrent intensity, photoelectochemical activity, and interfacial charge transfer... 

The catecholamine hypothesis brought several pharmacological findings together in an illuminating relationship but contradicted a number of clinical observations, in particular the delayed onset of action of antidepressant drugs. This also applies to the serotonin hypothesis, which was formulated at about the same time. 

Colored illuminating mixtures may also be used, but they do not produce light of such intensity as do white lights. Several new formulations were developed at Picatinny Arsenal before and after WWII... 

In a nutshell, Mg and Al are the most commonly used pyrotechnic fuels to create heat and light. Both have been used in the development of radiation effect. While Mg is the fuel of choice for most illuminating and tracer formulations, Al is still the main ingredient of photoflash and thermite formulations. The pyrotechnic behavior of Mg is due to its low melting and boiling points in comparison to most... 

Basically, an illuminating formulation is a mixture of a metallic fuel and an oxidizer besides some additives in order to modify the burning rate and radiation output and to enhance safety in handling. The Mg-sodium nitrate binder system appears to be a universal choice for illuminating formulations. The main reaction of the Mg-sodium nitrate binary system is (Equation 5.1) ... 

The performance of an illuminating formulation mainly depends on the factors ... 

Many investigators have studied the effect of binders and their percentages on the efficiency of illuminating formulations. In general, the luminosity and luminous efficiency increase to a maximum at =4—6% of the binder and thereafter decrease. It has also been reported that binders with high oxygen content, such as unsaturated polyesters and epoxy resins, improve the efficiency... 

The performance of the illuminating formulations is assessed by various parameters such as burning rate, luminosity and luminous efficiency. In addition to performance, some other important characteristics such as sensitivity to impact and friction, ignition temperature, mechanical properties and luminosity are also... 

Some pyrotechnic formulations are used for photographic purposes and the main requirement of such formulations is that they should produce a very powerful illumination for a short duration. Such pyrotechnic formulations are known as photoflash formulations and are used in photoflash cartridges, photoflash bombs and dust bombs. 

With the advancement of polymer chemistry, a wide range of polymers are now available for use as binders for HEMs. The extensive use of polymers such as unsaturated polyesters, epoxy resins, epoxy-PS blends and VAARs as binders for illuminating formulations has been reported in the literature. The chemistry of unsaturated polyesters and epoxy resins has already been discussed in Chapter 4 on propellants. Some salient features of liquid PS and its blends with epoxy resin and VAARs are given in this section. 

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