Małgorzata Rabiej

A hybrid immune–evolutionary strategy algorithm for the analysis of the wide‐angle X‐ray diffraction curves of semicrystalline polymers

Decomposition of wide-angle X-ray diffraction curves into crystalline peaks and amorphous components is one of the most difficult nonlinear optimization problems. For this reason, the elaboration of a reliable method that provides fast unambiguous solutions remains an important and topical task. This work presents a hybrid system dedicated to this aim, combining two methods of artificial intelligence – evolution strategies and an immune algorithm – with the classical method of Rosenbrock. A combination of the mechanisms of these three methods has given a very effective and convergent algorithm that performs very well a multicriterial optimization. Tests have shown that it is faster to converge and less ambiguous than the genetic algorithm.

Application of immune and genetic algorithms to the identification of a polymer based on its X-ray diffraction curve

This paper describes how a combination of two methods of artificial intelligence, an immune algorithm and a genetic algorithm, can be used to recognize a polymer by the shape of its X-ray diffraction curve. To this end, the hybrid algorithm uses a database which contains theoretical functions describing wide-angle X-ray diffraction curves of different polymers. These curves are compared by the algorithm with the experimental diffraction curve and the most similar are chosen. Such theoretical curves are kept in the immunological memory, and their parameters can be set as the starting ones in the optimization methods used for decomposition of the experimental curve into crystalline peaks and amorphous component. Using this algorithm, the preparation of the starting parameters is much easier and faster. Decomposition is the most important step in polymer crystallinity determination.

Application of the particle swarm optimization method for the analysis of wide-angle X-ray diffraction curves of semicrystalline polymers

The analysis of wide-angle X-ray diffraction curves of semicrystalline polymers is connected with a thorough decomposition of these curves into crystalline peaks and amorphous components. A reliable and unambiguous decomposition is the most important step in calculation of the crystallinity of polymers. This work presents a new algorithm dedicated to this aim, which is based on the particle swarm optimization (PSO) method. The PSO method is one of the most effective optimization techniques that employs a random choice as a tool for going through the solution space and searching for the global solution. The action of the PSO algorithm imitates the behaviour of a bird flock or a fish school. In the system elaborated in this work the original PSO algorithm has been equipped with several heuristics. The role of heuristics is performed by procedures which orient the search of the solution space using additional information. In this paper it is shown that this algorithm is faster to converge and more efficiently performs a multi-criterial optimization compared with other algorithms used for this purpose to date.

SAXS and WAXD, Time Resolved Investigations of the Morphology of Polyethylenes

This work shortly describes the morphology of polymers and presents the possibilities of SAXS method in the investigations of the structure of polymers referring to our studies on the structure of homogeneous copolymers ethylene-1-octene. Besides, we describe our computer program SAXSDAT designed for the analysis of SAXS curves of polymers.

A quantitative analysis of small- and wide-angle X-ray diffraction curves of homogeneous ethylene-1-octene copolymers

This paper presents a comparison of the results obtained with two methods employed in the analysis of small-angle X-ray scattering (SAXS) curves of isothermally crystallized homogeneous ethylene-1-octene copolymers: a method based on the calculation of the one-dimensional correlation function and a method based on model calculations and curve fitting. Data obtained from time-resolved SAXS investigations are supported by the results of simultaneous wide-angle X-ray diffraction (WAXD) measurements of crystallinity development during isothermal crystallization.

Modeling of Polymer Structure with the Use of SAXSDAT Computer Program

The most important structural parameters of semicrystalline polymers can be determined by modeling of their structure and best fitting of a theoretical intensity distribution calculated for the assumed model to the experimental SAXS curve. This paper presents a module of a computer program SAXSDAT dedicated to such calculations.

Digital Filtering and Shape Identification in the Analysis of WAXD Patterns of Semicrystalline Polymers

Most frequently, the degree of crystallinity of polymers is determined using Wide Angle X-ray Diffraction (WAXD) technique. The method consists in the resolution of WAXD diffraction curve of a polymer into individual crystalline peaks and amorphous halo. This work presents a procedure, which was elaborated to help in a quick determination of the angular positions of crystalline peaks present in the diffraction curve of investigated polymer. The positions of peaks are determined using numerical differentiation. Using these data the computer program WAXSFIT identifies investigated polymer and prepares a set of starting parameters which are used in the calculations of the degree of crystallinity.