Studies of aspen and birch wood interaction with pulsed exposure to microwave energy have been carried out. A method for determining the effect of microwave energy on the temperature inside the test ...specimen has been developed. It includes experimental setup for studying heat and mass transfer during drying and heat treatment of wood with microwave energy. Moisture content inside wood specimens has been determined by a new method using a laboratory installation for studying the mechanical properties of wood under the influence of microwave energy. This energy influences on the drying speed of the tested wood specimens. The research enables to select the optimal mode of wood heating by pulsed exposure to microwave energy. The results of wood tests for strength and hardness, obtained under the influence of microwave energy, have revealed the effect of wood hardening. The research has shown that microwave treatment of specimens reduces drying time of aspen and birch wood by five times in comparison with convective treatment.
Modeling the Structure of an Oxide Solar Cell Saenko, A. V.; Klimin, V. S.; Rozhko, A. A. ...
Journal of communications technology & electronics,
12/2022, Letnik:
67, Številka:
Suppl 1
Journal Article
Recenzirano
The article discusses numerical simulation of an oxide solar cell based on a Cu
2
O/TiO
2
p
–
n
heterojunction that was carried out to optimize its structure and increase the efficiency of energy ...conversion. The influence of layer thicknesses, concentrations of acceptors and donors in Cu
2
O and TiO
2
layers, as well as the work function of the back contact material on the photoelectric parameters of the solar cell is studied. It was found that the optimal thickness of Cu
2
O and TiO
2
layers is 1.5 µm and 100 nm, respectively. It is shown that to obtain a high efficiency of a solar cell, the concentration of acceptors in the Cu
2
O layer should be 10
16
cm
–3
, and the concentration of donors in the TiO
2
layer should be 10
19
cm
–3
. It has been found that the work function of the back contact material must be at least 4.9–5 eV in order to achieve high efficiency values. The most suitable contact materials for Cu
2
O are Ni, C and Cu. For a solar cell based on a Cu
2
O/TiO
2
p
–
n
heterojunction, a maximum efficiency of 10.21% was obtained (short circuit current density 9.89 mA/cm
2
, open circuit voltage 1.38 V, fill factor 74.81%). The results can be used in the development and formation of heterostructures of inexpensive oxide solar cells.
Forest fires are studied and developed in all countries with forest resources. However, despite large number of studies, the problem is still far from being resolved and fires still cause great ...damage to forests. The article deals with research on the influence of the screw drum parameters on the quality of removing the surface soil layer from combustible materials and on the performance of the forest fires soil-sweeping machine. The geometric parameters of the screw drum of the forest fires soil-sweeping machine were optimized. As a result of optimization, the optimal values of the screw channel depth in the range of 7.5-8.7 cm and the screw pitch of 23-40 cm were obtained. At these optimal values, the ground cover content in the thrown soil stream will be less than 15 %, the productivity of the forest fires soil-sweeping machine will be more than 40 kg/s, and the power consumption will be less than 12 kW.
Abstract
A variant of the electromechanical transmission scheme for mobile platforms of small mass, designed primarily for operation in an organized artificial environment under the conditions of ...dimensional restrictions, is proposed. Typical examples of such environments are greenhouses, gardens and parks. Distinctive features of the proposed transmission are the use of a single traction motor and a power distribution mechanism that allows the use of two modes of side turn: in the range from a given minimum radius to infinity and turning around the center of gravity. The transmission scheme, with some changes, can be extended to mobile chassis of a larger mass - tractors of various traction classes, forestry machines, loaders, mobile robots, etc.
Magnetron sputtering in the medium frequency (MF) mode was used to obtain ITO films on glass substrates at room temperature in an oxygen-free environment. The effect of the magnetron sputtering power ...on the electrophysical properties and surface morphology of ITO films is studied. It is shown that the ITO film deposition rate depends linearly on the power of magnetron sputtering in the MF mode. It is found that ITO films have a predominantly nanocrystalline structure at a magnetron sputtering power of more than 100 W. Increasing the sputtering power leads to an increase in surface roughness from 13.5 to 24.6 nm and grain size from 11.7 to 27.5 nm in the ITO film. The minimum resistivity of the ITO films is 6.82 × 10
–4
Ω cm at the concentration and mobility of charge carriers of 2.48 × 10
20
cm
–3
and 36.8 cm
2
/V s, which corresponds to the optimum power of magnetron sputtering of 200 W. The results obtained correspond to a high level of surface resistance values for ITO films (34.1 Ω/□), which can be used to form transparent conducting electrodes in solar cells and memristors, both on glass and flexible substrates.
One of the main difficulties in combating forest fires with conventional water-based methods is the difficult topography and the fact that there are usually no accessible roads to bring firefighting ...techniques closer to the fire site. Today, a large number of scientific teams are working on the topic of extinguishing the edge of a forest fire with soil. The aim of the study is to increase the efficiency of forest fire prevention and extinguishing by ground-throwing machines by removing the upper combustible layer of forest soil, the formation of a loosened soil shaft from the mineralized layers of forest soil and throwing soil into the edge of a forest ground fire. The paper briefly describes the technical means for extinguishing forest fires using soil. The analysis of the structures of soil-throwing machines has been carried out. The promising directions for improving the technology and working bodies of fire-fighting ground launchers are described, the advantages and disadvantages of its designs are revealed, and ways of further improvement are outlined. A promising design of a strip-laying soil gun with a hydraulic drive of working bodies for preventing and extinguishing forest fires is presented. A distinctive feature of the developed design of the strip-laying soil launcher is the use of an auger to remove the upper fire-hazardous cover, consisting of plant residues, and cut spherical discs to improve the quality of loosening the soil shaft. As a result of the conducted studies of the working process of the strip-laying machine, it was found that the share of the soil covers with combustible materials in the soil flow decreased from 40 to 7%, and the quality of soil shaft loosening increased by 17%, due to which the average distance of soil ejection increased from 10 to 15 m and the power consumption of the rotor-thrower is reduced from 12 to 10 kW.
This paper provides an overview and analysis of existing tools and machinery for fighting ground forest fires. The paper examines theoretical issues of applying soil-thrower machine to extinguish ...forest fires. In the paper, the information database on the usage of existing technology in modern conditions is studied in order to evaluate the effectiveness of the usage of new technology. The design of the presented machine makes it a universal one, replacing two technological units and thereby reducing the material consumption of technological process of extinguishing fire with soil and laying firebreaks; it increases the amount of ground to extinguish the fire, increasing efficiency in the fight against fire, as well as the traveling speed of the unit and its performance.
This research summarizes the analytical and experimental results of heat-transfer processes influence on defects formation during sapphire crystal growth by horizontal directed crystallization method ...(HDC). The shape of solid-melt interface significantly influences the process of sapphire crystals growth by this method. We receive the Stefan problem solution for sapphire crystals growth. It allows investigating the crystal growth process and the related factors (thermal stresses on different stages of growth process), their influence on defects formation. We investigate the main reasons for the formation of defective structures of the solid phase of sapphire crystals and the influence of thermal unit construction, the crystal geometry on the quality of the resulting sapphire crystal. We study the structure formation process, impurity distribution, and the nature of the defects in the crystal during it growth.
Abstract
The article describes the use of mulcher technology in forestry for the care of forest crops, removal of overgrowth under power lines, in the right-of-way of gas and oil pipelines, railways ...and highways. With the help of mulchers, they create fire strips in the forest, make clearings. Mulchers clean fallen trees after fires, floods and hurricanes. They are involved in landscaping and agricultural work. The article examines the work of the PT-400 self-propelled tillage mulcher for the surface crushing of logging waste on the utilized poplar plantations of the Oryakhovsky state forestry in Bulgaria. The work of the Rotor Ferri S stump grinder was studied when crushing poplar stumps with a diameter of up to 50 cm. The hourly productivity of these machines at various operations was determined, and also the process of crushing stumps and felling residues by fractional composition was studied. The work of the mulcher was compared with the bulldozer technology and the mounted tractor stump grinder Rotor Ferri S. It was concluded that the mounted stump grinder Rotor Ferri S is the most suitable machine for grinding poplar stumps of any diameter, since its productivity significantly exceeds that of the PT-400 mulcher/tiller. The load on the tractor is minimal, which saves energy. At the same time, mulching technology is very effective and in demand.
We study the surface structure of titanium oxide (TiO2) film on sapphire substrate obtained by laser annealing (wavelength of 1064 nm). The film was studied by powder x-ray diffractometry. The ...obtained TiO2 films can be used as a sensitive material for gas sensors.
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