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An experimental model is suggested and integrated with a numerical scheme for simultaneous identification of arbitrary shape particle size distribution (PSD) and its degree of non-sphericity present in a system. In this spectroscopic instrumentation, the transmittance intensity of light is measured by calculating the bulk absorption coefficient of randomly oriented arbitrarily shaped particles by adopting parameterized anomalous diffraction theory. The effects of reflection and refraction of arbitrary shapes of particles are also considered. Multi-wavelength transmittance signals (estimated and measured values) are used to fit the objective functions for the identification of target parameters. The unique feature of this simulation is the simultaneous identification of the joint function PSD and the shape perimeter of arbitrary particles using the joint log-normal distribution function. A probability-density-function-based ant colony optimization (PDF-ACO) algorithm is carried out for the inverse simulation. The parameters retrieved by the multi-wavelength transmittance signals show good agreement with the set original values of the target parameters. The robustness of the PDF-ACO algorithm could successfully keep the retrieval errors of the estimated parameters within the tolerable limit (error < 10%) even at high noise in the system.

An inverse estimation method and corresponding measurement system are developed to measure the apparent spectral directional emissivities of semitransparent materials. The normal spectral emissivity and transmissivity serve as input for the inverse analysis. Consequently, the refractive index and absorption coefficient of the semitransparent material could be retrieved by using the pseudo source adding method as the forward method and the stochastic particle swarm optimization algorithm as the inverse method. Finally, the arbitrary apparent spectral directional emissivity of semitransparent material is estimated by using the pseudo source adding method given the retrieval refractive index and absorption coefficient. The present system has the advantage of a simple experimental structure, high accuracy, and excellent capability to measure the emissivity in an arbitrary direction. Furthermore, the apparent spectral directional emissivity of sapphire at 773 K is measured by using this system in a spectral range of 3 μm–12 μm and a viewing range of 0°–90°. The present method paves the way for a new directional spectral emissivity measurement strategy.