Selection of Descriptors for Particle Shape Characterization

Abstract

Conventional shape descriptors, formed from a ratio of two particle size measurements, are among the simplest of the many methods used for quantitative particle shape characterization. However, a significant limitation of using one of these shape descriptors is that its value is often not unique to a specific shape. Use of several different shape descriptors may circumvent this problem but, as particle size can be defined in a large number of ways, a similarly large number of shape descriptors can be defined. While some differ substantially, others are only subtly different, conveying similar information. Thus, it is not obvious which of the many possible descriptors should be utilized. In this paper, two-dimensional particle shape descriptors obtained by image analysis of six different commercially sourced powders were considered. Techniques of cluster and correlation analysis were applied to assist in identifying redundant descriptors for shape characterization of these powder particles, allowing for efficient description of shape using a reduced set. It was found that at least two descriptors are required: aspect ratio and the square root of form factor. Significantly, each descriptor is most sensitive to a different attribute of shape: elongation and ruggedness, respectively.

Collection strategy, inner morphology, and size distribution of dust particles in ASDEX Upgrade

“…The aspect ratio is defined as the ratio between length to breadth of the circumferential rectangle with minimal area [52,55,56]. The separation into sub-sets of spheroids and non-spherical, irregularly shaped particles by other criteria does not strongly vary, i.e., roundness threshold of >0.75 (>0.85) and aspect ratio threshold of <1.18 (<1.07) leads to about the same sub-sets of particles.…”

Particle shape characterisation and classification using automated microscopy and shape descriptors in batch manufacture of particulate solids

“…The shapes of particles of different materials produced in laboratorial and industrial scales are often regarded as being arbitrary. Despite this degree of arbitrariness, previous research has demonstrated that the ratios of various particle size measurements can be used to derive shape descriptors of different orders (Hentschel & Page, 2003;Pourghahramani & Forssberg, 2005). However, the challenge lies in determining the combinations of size measurements that best provide the relevant morphological information of a sample or some samples.…”

“…Each of such combinations is sensitive to a specific attribute of shape according to the size measurements selected. Based on this principle, the size measurements obtained by the PVS 830 were combined as follows to create 85 new shape descriptors (Hentschel & Page, 2003):…”

“…Alternative shape description techniques have been investigated in the last two decades, for example, using spectral or functional mathematical approaches such as the Fourier descriptors (Bernard-Michel, Rohani, Pons, Vivier, & Hundal, 1997;Hentschel & Page, 2003;Jarvis, Jefferson, & Parsons, 2005; N. Laitinen, Antikainen, Rantanen, & Yliruusi, 2004;N Laitinen, Osmo, & Yliruusi, 2003;Podczeck, 1997;Pons, Vivier, Delcour, Authelin, & Pailleres-Hubert, 2002;Pourghahramani & Forssberg, 2005;Raj & Cannon, 1999). The main goals are to express or describe as accurate as possible the arbitrary and complex shapes of objects particularly for the purpose of classification, characterization, automated recognition and shape reconstruction.…”

2D Shape Measures for Computer Vision

“…It should also be noted that, while there are many possible shape measures already available in the literature, and many more that can be designed, they are not all independent. Some analysis on this topic was carried out by Hentschel and Page [23] who computed the correlations between many similar measures as well as determining the most effective for the specific task of powder particle analysis.…”