Cascade Structure of Digital Predistorter for Power Amplifier Linearization

In this paper, a cascade structure of nonlinear digital predistorter (DPD) synthesized by the direct learning adaptive algorithm is represented. DPD is used for linearization of power amplifier (PA) characteristic, namely for compensation of PA nonlinear distortion. Blocks of the cascade DPD are described by different models: the functional link artificial neural network (FLANN), the polynomial perceptron network (PPN) and the radially pruned Volterra model (RPVM). At synthesis of the cascade DPD there is possibility to overcome the ill conditionality problem due to reducing the dimension of DPD nonlinear operator approximation. Results of compensating nonlinear distortion in Wiener–Hammerstein model of PA at the GSM–signal with four carriers are shown. The highest accuracy of PA linearization is produced by the cascade DPD containing PPN and RPVM

Chemical activation of aspenwood components in the production of thermomechanical pulp

The article represents the results of researches that allow to establish the appropriateness of usage of aspenwood modified by sodium monosulphite as a raw material for thermomechanical pulp (TMP) in newsprint production. Replacement of 30% of sprucewood by aspen using 1% consumption of sodium sulphite permits to achieve strength of samples of unbleached TMP 4510 m, which ensures the highest demands to newsprint. In this case the process of wood grinding accelerates and the reactivity of hemicelluloses and lignin increases

Chemically modified mechanical pulp of wood chips of different breeds

The results of studies that allow to establish the feasibility of using a modified aspen wood as a raw material for thermomechanical pulp (TMP) in the production of newsprint. Modification of wood chips can increase the proportion of aspen wood in combination with spruce up to 30% without reducing the strength of quality newsprint. When this process is accelerated and the grinding timber increases reactivity of hemicelluloses and lignin, but also leads to lower energy consumption

Technology features of fuel pellets from deciduous wood

The present researches are aimed at studying the physical and mechanical properties of pellets produced from hardwood. For the experiment black alder and birch widespread on the territory of the Republic of Belarus hardwood timber has been chosen. It is stated that the use of wood in an unaltered form is impractical because the pellets derived from them have a low mechanical strength. The technological solution of this problem was the treatment of crushed wood raw material by saturated steam. The results of industrial tests confirmed that wood particles activation of hardwood fuel pellets gives the required quality standard. Technical feature of the technology is the use of a matrix with the length of the pressing channel 33 mm

Influence of the substrate-induced strain and irradiation disorder on the Peierls transition in TTF-TCNQ microdomains

The influence of the combined effects of substrate-induced strain, finite size and electron irradiation-induced defects have been studied on individual micron-sized domains of the organic charge transfer compound tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) by temperature-dependent conductivity and current-voltage measurements. The individual domains have been isolated by focused ion beam etching and electrically contacted by focused ion and electron beam induced deposition of metallic contacts. The temperature-dependent conductivity follows a variable range hopping behavior which shows a crossover of the exponent as the Peierls transition is approached. The low temperature behavior is analyzed within the segmented rod model of Fogler, Teber and Shklowskii, as originally developed for a charge-ordered quasi one-dimensional electron crystal. The results are compared with data obtained on as-grown and electron irradiated epitaxial TTF-TCNQ thin films of the two-domain type

Clusters of galaxies : observational properties of the diffuse radio emission

Clusters of galaxies, as the largest virialized systems in the Universe, are ideal laboratories to study the formation and evolution of cosmic structures...(abridged)... Most of the detailed knowledge of galaxy clusters has been obtained in recent years from the study of ICM through X-ray Astronomy. At the same time, radio observations have proved that the ICM is mixed with non-thermal components, i.e. highly relativistic particles and large-scale magnetic fields, detected through their synchrotron emission. The knowledge of the properties of these non-thermal ICM components has increased significantly, owing to sensitive radio images and to the development of theoretical models. Diffuse synchrotron radio emission in the central and peripheral cluster regions has been found in many clusters. Moreover large-scale magnetic fields appear to be present in all galaxy clusters, as derived from Rotation Measure (RM) studies. Non-thermal components are linked to the cluster X-ray properties, and to the cluster evolutionary stage, and are crucial for a comprehensive physical description of the intracluster medium. They play an important role in the cluster formation and evolution. We review here the observational properties of diffuse non-thermal sources detected in galaxy clusters: halos, relics and mini-halos. We discuss their classification and properties. We report published results up to date and obtain and discuss statistical properties. We present the properties of large-scale magnetic fields in clusters and in even larger structures: filaments connecting galaxy clusters. We summarize the current models of the origin of these cluster components, and outline the improvements that are expected in this area from future developments thanks to the new generation of radio telescopes.Comment: Accepted for the publication in The Astronomy and Astrophysics Review. 58 pages, 26 figure