Photovoltaic Power Supply Unit for the Basic Stations of Cellular Companies

The data on the use of solar photovoltaic plants (PVPs) for providing a reliable and guaranteed power supply to telecommunication systems and cellular communication systems in the conditions prevalent in Uzbekistan are given. The research-based structures developed by OOO MIR SOLAR and the selection of PVP elements ensuring their reliable operation are described. The main influencing factors are discussed, and the use of effective combinations of different types of panels (from monocrystalline and polycrystalline silicon) and a specially developed controller are considered.     

Study of the Thermal Technical Characteristics of a Combined Solar Desalination and Drying Plant

The paper presents the results of calculated research on determining the thermal technical indicators of a combined solar desalinization and drying plant. The structure of the plant is developed and proposed. A mathematical model is developed that describes the thermal processes occurring in the plant based on heat-balance equations solved using the Laplace method.     

Design and synthesis of foam glasses from recycled materials

Recycling has emerged as an environmental key point due to the diminishing of natural resources and the generation of ever-increasing amounts of industrial solid wastes. Glass wastes are among the materials that attract great interest in the recycling concept. This work presents the results of foams production from four series of compositions. The first series comprises powders of a sodium-calcium-silicate sheet glass cullet as the main component, an alkali-earth aluminosilicate glass as an additive, and a reagent grade silicon carbide (SiC) powder as gassing agent. In the second series, the glass cullet was used in combination with fly ashes (FLA) as main components, while SiC waste from abrasive paper served as foaming agent. In the third and fourth series, carbonates (calcite and dolomite) were used for foaming powder mixtures composed of sheet glass cullet and FLA, and powdered cathode ray tube panel glasses, respectively. All the processing parameters, including the main components, the nature and content of foaming agents are shown to play a crucial role on the foaming ability and final properties of the glass foams.     

Structural stability of ternary D8m–Ti5Sb2X (X=Al,Ga, In,Si, Ge,Sn) compounds

The crystal and electronic structures of Ti₅Sb₂X (X=Al, Ga, In, Si, Ge, Sn) ternary compounds in the Nb₅Sn₂Si-type structure (ternary-D8_m) have been investigated by means of first principles calculations. The calculated structural parameters are in good agreement with the experimental data. The total electronic densities of states as well as the Bader charges of the atoms have been computed. Both electronic and size effects allow to explain the stability of the Ti₅Sb₂X (X=Al, Ga, In, Si, Ge, Sn) ternary compounds in the ternary D8_m structure. The enthalpies of formation of the ternary D8_m compounds have been obtained. The off-stoichiometry domains of D8_m–Ti₅Sb₂Ga and D8_m–Ti₅Sb₂Si are discussed.     

Synthesis and in vitro bioactivity assessment of injectable bioglass−organic pastes for bone tissue repair

The aim of this work was to study the bioactivity of systems based on a clinically tested bioactive glass (BG) particulates (mol%: 4.33 Na₂O−30.30 CaO−12.99 MgO−45.45 SiO₂−2.60 P₂O₅−4.33 CaF₂) and organic carriers. The cohesiveness of injectable bone graft products is of high relevance when filling complex volumetric bone defects. With this motivation behind, BG particulates with mean sizes within 11−14 μm were mixed in different proportions with glycerol (G) and polyethylene glycol (PEG) as organic carriers and the mixtures were fully injectable exhibiting Newtonian flow behaviors. The apatite forming ability was investigated using X-ray diffraction and field emission scanning electron microscopy under secondary electron mode after immersion of samples in simulated body fluid (SBF) for time durations varying between 12 h and 7 days. The results obtained revealed that in spite of the good adhesion of glycerol and PEG carriers to glass particles during preparation stage, they did not hinder the exposure of bioactive glass particulates to the direct contact with SBF solution. The results confirmed the excellent bioactivity in vitro for all compositions expressed by high biomineralization rates with the formation of crystalline hydroxyapatite being identified by XRD after 12 h of immersion in SBF solution.     

Structural Features and Tribological Properties of Multilayer Coatings Based on Refractory Metals

A comparative analysis of the structural features and tribological properties of multilayer coatings based on refractory metal compounds has been conducted in this review. Features of formation of the electronic structure of the synthesized coatings have been discussed, and the effect of methods and conditions of deposition on changes in the physicomechanical characteristics of nanocrystalline structures based on transition metal nitrides has been shown. Dependences of antifriction properties, corrosion resistance, and thermal stability on the modulation period (Λ) and the number of bilayers in the studied multilayer coatings have been determined. A decrease in the modulation period of individual layers in a coating positively affects the oxidation resistance of the coating, while an increase in the number of interfaces between the layers slows down the diffusion of oxygen atoms deep into the coating and, thereby, increases the protective properties of the multilayer system as a whole. The effect of the droplet component in cathodic-arc coatings on corrosion development mechanisms in corrosive media has been shown. A class of multifunctional multilayer coatings with an adaptive friction mechanism, which is characterized by a change in the properties and structure during tribological tests, has been discussed separately.     

Strengthening and toughening of a multi-component lithium disilicate glass-ceramic by ion-exchange

A multi-component lithium disilicate (LD) glass-ceramic with interlocking microstructure consisting of rod-like LD crystals and glassy matrix was ion-exchanged over wide temperature and time ranges in pure NaNO₃ or mixed NaNO₃ and KNO₃ baths below the glass transition temperature. Treatment temperature, time and salt bath dependences of surface characteristics and mechanical properties for the ion-exchanged glass-ceramic were investigated. It was found that the glass-ceramic with limited glassy matrix could be remarkably strengthened and toughened in NaNO₃ bath by adjusting the treatment temperature to a moderate level, at which Li⁺/Na⁺ exchange between the glassy matrix and the salt bath could form an ion-exchanged layer with larger depth and less stress relaxation. Furthermore, by using the mixed salt bath, the undesirable exchange of K⁺/Na⁺ in pure NaNO₃ bath could be limited; further enhanced strengthening effect was achieved. The results might renew the interest on strengthening LD glass-ceramics by traditional ion-exchange process.