Viscoelastic properties of polystyrene–polycarbonate blends in melt

Viscoelastic properties of polymer blend melts of polystyrene–polycarbonate were investigated in a wide range of temperatures, frequencies, and compositions. It was established that the more essential changes in viscoelastic characteristics took place at small concentrations of one of the components and at low frequencies, probably because of a putting down of the slow relaxation processes. The marked decrease in the viscosity of the melts takes place in the region of phase separation due to thermodynamic incompatibility of the components and is in a good correlation with the appearance of excess free volume in the system.     

Electroarc Synthesis and Cleaning from Carbon Impurities of Cubic Silicon Carbide in the Air Atmosphere

The method is presented of producing a cubic phase of the silicon carbide β-SiC by anneling in the air a powder product of the electroarc synthesis, which consists of β-SiC, graphite and a small amount of silicon. Due to its high resistance of β-SiC to the oxidation in the air we succeeded in the purification of it during the process of combustion of the graphite phase burning in the temperature interval of ~ 700–900°C. According to the X-ray diffractometry, the obtained powder material contains β-SiC with the content close to 99% (by volume). In this case according to the results of the scanning electron microscopy, β-SiC is characterized by a wide (from ~ 0.1 to ~10 μm) distribution of particles by size and typical shape for this phase crystals. The method of the electroarc synthesis of β-SiC and its subsequent purification to the commercial purity for the first time is realized in the air without the use of protective inert gases.     

Optimal image compression via block-based adaptive colour reduction with minimal contour effect

Current image acquisition devices require tremendous amounts of storage for saving the data returned. This paper overcomes the latter drawback through proposing a colour reduction technique which first subdivides the image into patches, and then makes use of fuzzy c-means and fuzzy-logic-based inference systems, in order to cluster and reduce the number of the unique colours present in each patch, iteratively. The colours available in each patch are quantised, and the emergence of false edges is checked for, by means of the Sobel edge detection algorithm, so as to minimise the contour effect. At the compression stage, a methodology taking advantage of block-based singular value decomposition and wavelet difference reduction is adopted. Considering 35000 sample images from various databases, the proposed method outperforms centre cut, moment-preserving threshold, inter-colour correlation, generic K-means and quantisation by dimensionality reduction.

     

To a method of evaluating ontologies

The problem of evaluating the quality of ontologies is addressed. A classification of the existing methods of evaluating ontologies is given and a model for evaluating the human perception of ontologies from the cognitive point of view is proposed. In addition, a methodology of application of the proposed model is presented, as well as an example of comparison of two ontologies in the field of artificial intelligence by the given method.