Catalyst development for oxidative methane coupling

The heterogeneously catalyzed oxidative coupling of methane has been investigated for several catalysts. A Ce/Li/MgO system was found to be the most attractive catalyst. The regeneration of the active sites seems to play a major role in the radical generating mechanism. The influence of the operating conditions on the conversion/selectivity has been studied, in order to find conditions for an optimal yield of C₂₊ - hydrocarbons. It is demonstrated that it is unrewarding to compare different types of catalysts only under selected standard conditions.     

Identification of Boolean symmetries in spectral domain ofReed-Muller transform

Spectral information from the Reed-Muller transform is used to identify four types of Boolean symmetry. The results show that for most of the symmetries only a part of the Reed-Muller spectrum is needed     

Application of monosaccharides derivatives in colloidal processing of aluminum oxide

Obtaining highly loaded, time-stable and relatively low viscosity suspensions approaches colloidal processing to be very convenient and effective route of shaping of nanopowders. In order to obtain well dispersed, homogenous ceramic slurries, certain additives are given. Saccharides, particularly monosaccharides, as well as their derivatives, were found to be a group of effectively working processing agents in case of alumina, which has been used as a solid phase of highly loaded nanosuspensions. This class of chemical compounds can be described by a series of advantages – they are non-toxic, water-soluble, inexpensive, etc. In this paper suspensions of nano- and submicro-alumina powders with addition of d-fructose, 1-O-methyl-d-fructose, d-glucose and 3-O-acrylic-d-glucose have been studied in terms of their rheological properties, moreover the properties of as-received green bodies have been presented.     

How does carotid artery stenosis increase?

In 25 patients with carotid artery stenosis equal or higher than 40% colour doppler examinations were performed 105 times. The aim of this study was estimate the dynamics of progress of carotid artery stenosis. The mean time of observation was 22.5 months. In 11 (44%) patients there was no progress of stenosis, in 6 (24%) a leap progress over 30% of arterial lumen, and in 8 (32%) patients the progress of carotid artery stenosis were gradual and slow. The leap progress of carotid artery stenosis was usually caused by eruption or dissection of atherosclerotic plaque located in carotid bifurcation and this situation poses especially high risk of stroke.     

Family of generalised multi-polarity complex Hadamard transforms

A family of generalised complex Hadamard transforms using the concept of polarity is introduced. Forward and inverse transformation kernels and methods of recursive generation of transform matrices using Kronecker products of elementary matrices are shown. Mutual relationships among transform matrices and spectra for arbitrary polarities are presented. Efficient ways of calculating spectra for logic functions through decision diagrams are also shown. The half-spectrum property is used to reduce further the computational requirements for both fast transforms and decision diagram based calculations     

Family of fast linearly independent ternary arithmetic transforms

In this paper, the family of fast linearly independent ternary arithmetic (LITA) transforms, which possesses fast forward and inverse butterfly diagrams, has been identified. This family is recursively defined and has consistent formulas relating forward and inverse transform matrices. The LITA transforms, which require horizontal or vertical permutations to have fast transforms are also discussed. Computational costs of the calculation for presented transforms are also discussed and compared with multipolarity ternary arithmetic transform for ternary benchmark functions.     

Effect of the sintering temperature on microstructure and properties of Al2O3–Cu–Ni hybrid composites obtained by PPS

In the present research, the influence of sintering temperature on the microstructure and properties of Al₂O₃–Cu–Ni hybrid composites prepared by the Pulse Plasma Sintering (PPS) technique were described. In this research, three temperatures have been selected: 1250°C, 1300°C, and 1350°C. SEM observations were carried out to determine the distribution of the metallic phase in the composite depending on the sintering temperature. The conducted experiments and microscopic observations enabled a better understanding of the phenomena occurring between the ceramic matrix and metallic phase in the obtained materials. The mechanical properties like a hardness and fracture toughness were measured. The technology applied allowed us to obtain ceramic-metal composites with a homogeneous microstructure. It was found that the sintering temperature influences the selected physical and mechanical properties of the composites produced. It was found that samples produced at 1300°C are characterized by the highest relative density and the mechanical properties.     

Influence of core-shell structure on the cure depth in photopolymerizable alumina dispersion

The heterogeneous nucleation-and-growth processing was used to obtain core-shell particles based on alpha alumina core with silica layer. Presence of silica shell was confirmed by transmission electron microscopy (TEM) and zeta potential measurement. The coverage of aluminum oxide surface by SiO₂ improved a cure of the depth of photopolymerizable ceramic dispersion around 20%. The proposed surface modification enables the production of thicker cured layer which is favorable for additive manufacturing methods such as stereolithography. Thus, the number of layers that have to be printed to form the 3D object might significantly decrease, thereby reducing time and costs of fabrication.