THE SUSTAINABILITY OF MANAGEMENT STRUCTURES IN BULGARIAN AGRICULTURE – LEVEL, FACTORS AND PROSPECTS

This paper assesses the sustainability of the farms in our country by applying the holistic approach. We first introduce the methods employed in our research and provide a general description of the farms included in it. Then we assess the integral, managerial, economic, social and environmental sustainability of farms in general as well as that of the different types of farms according to their size, specialization of production, environmental position and geographical location. Finally, we assess the factors for improving the sustainability of farms and present our conclusions about doing further research work and improving the assessment practice in the sector

Structure and mechanical properties of Al-Co-Cr-Fe-Mn-Ni-Si-V high-entropy films obtained by splat-quenching

The multicomponent films of Al-Co-Cr-Fe-Mn-Ni-Si-V high-entropy alloys obtained by splat-quenching from melt were investigated. Phase formation criteria for high-entropy alloys were considered. The films have a structure with body-centered cubic lattice. The value of lattice parameters of the investigated alloys suggests that the solid solutions are form on the base of Cr lattice, in view of its higher melting temperature. The positive influence of microstrains level and dislocation density on the microhardness values of splat-quenched high-entropy alloys has been established. Improved mechanical characteristics are ensured by the strong distortion of the crystal lattice due to the differences in atomic radii of the elements

The Physical Properties of the FeBiMo Films, Obtained by Ion-Plasma Sputtering

The paper presents the results of investigations of the phase composition and physical properties of the pure Bi, Mo and FeBiMo films, with thickness d~100-500 nm, obtained by three-electrode ion-plasma sput-tering. X-Ray analysis showed that in the as-deposited Bi films is formed a mixture of rhombohedral and cubic nanocrystalline Bi phases and traces of Bi2O3 oxide. Heat treatment at 650 K leads to the decay of the Bi non-equilibrium phase. In the Mo original films is formed a mixture of Mo cubic phase and MoO2, MoO3 oxides. As a result of heat treatment at the temperature of about 870 K phase composition and the grain size remains unchanged. FeBiMo films in the initial state is a mixture of rhombohedral and cubic Bi phases and the hexagonal Fe phase. In the Mo-doped films non-equilibrium Bi phase remains after heat treatment at 770 K. Construction of the temperature dependence of resistivity has revealed the reversible phase transition in the Bi films. A similar behavior of Bi properties is also manifested in FeBiMo films. The analysis of demagnetization curves of Bi films showed a manifestation of hysteresis properties, which is not typical for diamagnetic. This can be explained by the Bi2O3 phase presence. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3513

Phase Composition and Physical Properties of the MnBiCr Films, Obtained by Ion-Plasma Sputtering

The paper presents the results of investigations of phase composition and physical properties of the pure Mn, MnCr and MnBiCr films, thickness d 150-550 nm, obtained by a modernized three-electrode ion-plasma sputtering. X-ray analysis and estimation of the size (L) of coherent-scattering regions (CSR) showed that in the pure Mn as-deposited films is formed the nanocrystalline cubic phase of manganese, the size of the CSR which L 7,4 nm. There is a formation of solid solution nanocrystalline -Mn phase in the original MnCr films (L 7,5 nm). In the original state MnBiCr films is a mixture of rhombohedral Bi phase (L 10,5 nm) and Mn cubic, which decays by heat treatment at 703 K. Heat treatment of Mn and MnCr films at 773 K leads to the formation of MnO oxide. Analysis of displacement temperature of the initial phase transitions with increasing heating rate in the films allowed for the calculation of the activation energy (Ea) of phase transformations by the Kissinger method. For the MnCr films the activation energy is 3500-4800 K. In the MnBiCr films first phase transition ( 573 K) is related with melting of Bi, the second, probably due to the collapse of the cubic Mn ( 653 K, Ea 7000 K). When the film is heated above 673 K and subsequently cooling it, at a temperature of 423 K there is an abrupt increase in resistance of about two-fold. Analysis of the demagnetization curves of the MnBiCr films showed the manifestation of hard magnetic properties in a perpendicular field Hc 16 103 А/m. Study has shown that the addition of Cr in small amounts prevents oxidation of Mn and leads to an increase of the films thermal stability. Thus, the thermostable magnetically hard material in a film form was obtained. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3539

Influence of soaking time of modifier in melt on microstructure of Al-12%Si alloys

The influence of the soaking time of the silumin melt with a modifying nanopowder W on the microstructure and the impact toughness of the Al-12%Si silumin is studied in the paper. It was established that when introducing 0.1 mass. % of W and soaking it for 10 min, up to 30% of the inassimilable nanopowder W remains in the crucible after pouring. At that, the microstructure of castings is refined, and the impact toughness increases by 12 % compared to the initial alloy. It was established that the powder remaining in the crucible after melting consists of the remnants of metallic W, WO[3] and W[3]O. Nanopowder W is completely assimilated by the melt if the soaking time is increased by 120 min; in this case, the impact toughness reduces, which is connected with the increase of dendrites and silicon wafers sizes

A structure and physical properties of Ni films in metastabile ststes

There are presented the results of investigations of the influence of deposition rate and pressure of orifice gas on the structure, physical properties and thermal stability of nickel films obtained by the modified method of the three-electrode ion-plasmous sputtering (technique IPS). X-ray analysis and estimation of the size (L) of coherent-scattering regions (CSR)showed that in the as-deposited films which obtained with low energy of sputtered atoms and low deposition rate (~ 85 pm/s) there is formed a mixture of FCC Ni (L = 5 nm), traces of HCP nickel (L = 9 nm) and oxide of nickel NiO. Increase of energy of sputtered atoms by a decrease of pressure of orifice gas from 120 to 53 or 16 mPa leads to the formation at as-deposited films a mixture of phases FCC nickel and traces of oxides. Moreover, almost double increase of deposition rate leads to an increase the size of the CSR on ~20%. The heating of films of Ni with a mixture of FCC and HCP phases to 300-320 °C results in transformation of HCP in FCC. Freshly deposited films with the structure of FCC Ni are undergoing structural changes at heating above 350-450. These changes are linked obviously with the recrystallization. The size of the CSR for FCC Ni is increased almost in 2 times after heating. It is shown that energy of activating (EA) calculated by the method of Kissinger in the case of disintegration of HCP Ni exceeded from EA of beginning of recrystallization almost in three times and attains ~21000 K. In addition, it’s shown that increase of deposition rate brings to rise of activation energy of beginning recrystallization and indicates the formation of more stable structure in the films. Analysis of the demagnetization curves of the films of nickel showed anisotropy of magnetic properties. Hysteresis only is detected in a parallel field to the film of Ni. The coercive force does not exceed 200 A/m. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2078

Complexity of matrix problems

In representation theory, the problem of classifying pairs of matrices up to simultaneous similarity is used as a measure of complexity; classification problems containing it are called wild problems. We show in an explicit form that this problem contains all classification matrix problems given by quivers or posets. Then we prove that it does not contain (but is contained in) the problem of classifying three-valent tensors. Hence, all wild classification problems given by quivers or posets have the same complexity; moreover, a solution of any one of these problems implies a solution of each of the others. The problem of classifying three-valent tensors is more complicated.Comment: 24 page

Structural and electrical properties of CuAlMo thin films prepared by magnetron sputtering

The structural and electrical properties of a low resistivity CuAlMo thin film resistor material were investigated. The thin films were grown on Al2O3 and glass substrates by direct current (dc) magnetron sputtering. The key electrical properties of sheet resistance, temperature coefficient of resistance (TCR) and resistance stability were investigated as a function of sputtering pressure and post-deposition heat treatment time and temperature. A low sputtering pressure range of 0.13 to 0.40 Pa produced CuAlMo films with sheet resistance in the range 0.1 to 0.2 Ω/□ and resistance stability of 0.45 to 0.65% with a TCR of − 90 ppm/°C which could be shifted to zero following annealing in air at 425 °C. Films grown at higher sputtering pressures of 0.53 to 0.80 Pa had increased sheet resistance in the range 0.4 to 0.6 Ω/□ and inferior stability of 0.8 to 1.7% with a more negative TCR of − 110 to − 180 ppm/°C which could not be shifted to zero following annealing. The stability of the films grown at 0.13 and 0.40 Pa could be further improved to < 0.25% with heat treatment, due to the formation of a protective aluminium oxide layer. A minimum dwell time of 3 h at 425 °C was required to stabilise the films and set the electrical properties

Комплексный подход к прогнозированию клещевых нейроинфекций

Here, we propose a method of forecasting the development of the heavy forms of the tick-borne encephalitis using diagnostic tables. The method is based on evaluation of the patients with syndrome of endogenous intoxication using immunological and biochemical data along with evaluation of the clinical manifestations. We also propose an advanced form of the method that includes data based on the genotype of OAS1 — the gene, coding oligonucleotidesynthetase needed for immune response to RNA viruses. OAS1 genotype is an important risk factor since the differences in catalytic activity of OAS1 isoenzymes result in different susceptibility to the virus of the tick-borne encephalitis.В данной работе предлагается метод прогнозирования развития тяжелого течения очаговых форм клещевого энцефалита с помощью диагностической таблицы. Метод основан на оценке у больных синдрома эндогенной интоксикации с применением иммунологических и биохимических исследований, а также оценке клинических проявлений. Предлагается дополнение метода данными по генотипированию гена OAS1, кодирующего олигонуклеотидсинтетазу, необходимую для иммунного ответа на РНК-вирусы. Генотип OAS1 является важным фактором риска, так как различия в каталитической активности изоферментов OAS1 приводят к различиям в восприимчивости к вирусу клещевого энцефалита