Model Representations on Introduction of Rare-Earth Dopants (Eu and Y) in Nanocrystalline Silicon
P. 5–9. Fig. 2. Refs.: 7 titles.
In this paper, we reveal model representations on the nature of RE dopant centers in nanocrystalline silicon films. Using the results of chemical composition analysis and temperature measurements of resistance, we compare theoretical and experimental data. Crucially, we determine that the nature of dopant centers changes depending on the conditions of films processing (temperature deposition) and dopants concentration.
A Contactless Method of Measuring Charge Carriers Recombination Parameters in Semiconductors
P. 10–16. Fig. 6. Refs.: 22 titles.
The present study proposes the contactless optical method of measuring surface recombination rate (s) and diffusion length (L) of charge carriers. This method is based on the analysis of dependence of excess thermal emission (TE) of a semiconductor sample in the long wavelength spectral range (hν < Eg)on the wavelength of excitation light in the range of fundamental absorption (hν > Eg). The procedure is tested on a monocrystal silicon plate with different surface treatment that allows changing s from 400 tо 105 сm/s. The measurements are taken in 400–600 К temperature range. The results obtained correlate well with the classic method of photoconductivity spectral dependence and literary sources. The advantages of this new method are well-grounded by comparing it with existing ones.
Influence of the Quality of Electrical Energy and Technical Conditions of Induction Motors on their Static Stability
P. 17–21. Fig. 3. Tabl. 1. Refs.: 7 titles.
The paper provides insights into the research of static stability of induction motors at a low-quality supply voltage and an unsatisfactory technical condition of the motor. The dP/ds criterion of static stability of the induction motor was used to assess its static stability. The results obtained show that a non-symmetric voltage has a negative influence on the static stability of the induction motor by decreasing the component of a positive-sequence voltage. The non-symmetric voltage is considered the most dangerous when the induction motor operates in the mode, close to the margin of a static stability loss.
Litvinchuk M.Yu., Shilovich I.L.
A Simplified Mechanical Model of a Chain of Granulated Material Elements
P. 22–25. Fig. 4. Refs.: 8 titles.
Our study focuses on a simplified mechanical model of the separate part of a granulated material layer. This layer is represented as a chain of two kinds of elastic elements (elastic element, interlayer). The intensity of compression stress changing considerably decreases in the chain with elastic elements and interlayers at a certain quantity of elements. The influence of the compression stress on a contact resistance can be neglected starting from this quantity.
Shcherbyna V.Yu., Sakharov O.S., Samilenko Yu.M., Bobah V.V.
Research into thermal tension in rotary kilns with Vortex Heat Exchangers
P. 26–33. Fig. 7. Refs.: 6 titles.
We develop the mathematical model and algorithms to determine the stress-strain state of a rotary kiln, taking into account mass forces and heat loads. We study operating conditions of the vortex heat exchanger in a furnace size 4´60m, determine stress and analyze the calculation results on design elements of the heat exchanger and the furnace.
An Optimal Decision Theory in the Problems of Choice of Imperfect Inspection Strategies
Refs.: 28 titles.
The paper deals with the decision rule for applying imperfect inspection strategies based on the associated penalty costs and feasibility of successful detecting of the existing failure. We take this approach to determine whether the imperfect inspection policy is efficient. To that end, we present necessary and sufficient conditions for a certain failure distribution function in explicit form, as well as sufficient conditions for the increasing failure rate. By using the imperfect inspection strategies, we consider the probabilistic behavior of high-quality and defective in-process units in the multistage production process. We show the joint distribution of the state variables at each stage for binomial processing and imperfect inspection. This joint distribution is the product of two independent binomial distributions. Through experiments conducted, it turns out that our null hypotheses on inspection policy, processing losses and additional information don’t completely hold true. As a result, we propose a modified form of the joint binomial distributions.
A Multicriterion Transport Problem on Combinatorial Sets and the Method of its Solving
P. 44–50. Refs.: 12 titles.
The present paper aims to study a multicriterion transport problem on the combinatorial construction of transpositions. We introduce the approach to its solving in case of one, two and more criteria. We also prove the specificity of finding a lot of effective solutions given that there are two and more criteria. Finally, we develop the mathematical models of the applied tasks which reduce to the multicriterion transport problems.
Optimization of Pedestrian Behavior in Cellular Automata Models of Crowd Movement
P. 51–60. Fig. 7. Refs.: 5 titles.
The issue under consideration is optimization of pedestrian movement rules within cellular automata models of crowd movement. This approach can minimize the evacuation time from premises of arbitrary geometry by taking into account pedestrians’ mental states such as anticipation – an ability to adjust the behavior to the anticipated situation in some neighborhood. We also demonstrate the results of computational experiments that prove the validity of the proposed approach. In addition, we suggest perspectives for future research.
On Development of the Structured Knowledge Base for Solving Tasks of Technology Forecasting
P. 61–68. Fig. 7. Refs.: 8 titles.
In this paper, we provide insights into the knowledge model taking into account the specificity of methodology of technology forecasting. We also demonstrate the architecture of knowledge field and the algorithm for constructing the structured knowledge base in the form of frame network.
Artiukh Ya.Yu., Minakova R.V., Grechaniuk I.M., Grechaniuk V.G.
The Structure and Physico-Chemical Properties of (Cu-Cr)-Mo Composite Materials Obtained by Electron Beam Evaporation and Condensation in Vacuum
P. 69–74. Fig. 7. Tabl. 2. Refs.: 8 titles.
We show the research results of the structure, mechanical properties and corrosion resistance of (Cu-Cr) Mo composite materials in order to determine the optimal composition of tracks for application of these materials in the electrical industry. We determine that the introduction of molybdenum in small quantities (up to 12 %) don’t significantly change the electrical conductivity and corrosion resistance.
Bogushevsky V.S., Sergeieva K.O.
Control of the Temperature Mode of BOF Process
P. 75–80. Fig. 2. Refs.: 10 titles.
We analyze the existing methods of the bath temperature control. We study direct and indirect methods of controlling the temperature in the course of purging. We define the dependence between the output parameters of converter melting and the bath temperature. Finally, we elucidate the results obtained by implementing the dependencies in the algorithms of control of the BOF process.
Kotlyarov V.P., Vahdatinia I., Mollabashi H.Haji
Technological Problems of Stents Laser Undercut
P. 81–87. Fig. 7. Refs.: 11 titles.
The analysis of the laser cutting stents operations enables to reveal the specificity of processing results by different duration impulses, as well as to determine the cause of substantial differences in quality, productivity and prime price of these operations. We consider and provide a technological basis for the most effective (in our opinion) operations carried out with the impulses of millisecond duration by the method of choice of the processing modes and technological rigging.
Kylinich А.A., Ryabinina O.O., Kotlyar S.M.
The Structure and Mechanical Properties of Al-6 % Mg-2 % Zn-0,5 % Fe-0,5 % Alloys with Additions of Manganese after Different Modes of Annealing
P. 88–92. Fig. 3. Tabl. 2. Refs.: 8 titles.
This paper discusses the influence of up to 0,7 percent of manganese and various modes of annealing on the phase composition, the structure and a level of mechanical properties of Al-6 % Mg-2 % Zn-0,5 % Fe-0,5 % Si alloy. More compact (Fe, Mn)Al6 phase is formed instead of FeAl3 phase at Mn/Fe = (0,4–0,5) optimal correlation. Thus alloy plasticity rises by 40–50 % at the insignificant increase of durability. The application of a two-stage annealing mode with optimal temperature-time parameters allows boosting the plasticity of the alloy under study which additionally contains 0,25 percent of manganese in 2,5 time.
Loskutova T.V., Khizhnyak V.G., Pogrebova I.S., Bobina M.М., Degula A.I.
Heat-Tolerance of Carbide Coverages Obtained at a Successive Satiation of U8А Steel by Chrome and Titan
P. 93–97. Fig. 5. Tabl. 1. Refs.: 8 titles.
In this paper, we study the structure and properties of carbide coverages based on titan and chrome carbides on U8A steel. We discuss possible reactions of the interaction between chrome and titan carbides with oxygen and determine the chemism of coverages oxidization. Finally, we show the advantage of complex two-component coverages as compared to single-component ones.
Makogon Yu. M., Sidorenko S.I., Pavlova O.P., Verbitska T.I.
The Solid-State Reactions in Ti(200 nm)/Cu(200 nm)/Ti(100 nm)/SiO2(370 nm) Film Composition on the Monocrystalline Silicon (001)
P. 98–103. Fig. 4. Refs.: 10 titles.
By employing the methods of X-ray diffraction, transmission electron microscopy of cross-sections, scanning electron microscopy and resistometry measurements, we examine the solid-state reactions in the Ti(200 nm)/Cu(200nm)/Ti(10nm)/SiO2(370nm) film composition on the monocrystaline silicon of (001) orientation. The film composition under study is obtained by consecutive electron-beam deposition of elements layers in a vacuum of about 10-4 Pa without breaking a vacuum on the substrate of silicon with an oxide layer on the surface. The vacuum annealing of specimens is carried out in the 670–1170 K temperature range for 1 hour. We establish that the first Cu15Si4 silicide copper phase is formed after annealing at 970 K for 1 hour. Annealing at 1070 K is accompanied by formation of ternary CuTiSi compound and TiSi2.
Calculation of Trajectory and Speed of Growth of Curvilinear Fatigue Cracks in the Piece-Homogeneous Plate
P. 104–110. Fig. 4. Tabl. 2. Refs.: 8 titles.
By using the tracing method, we investigate the trajectories of fatigue cracks growth near the border of the section in the piece-homogeneous plates in the cyclic loading process. We describe the form of a crack by means of cubic splines. We also employ the method of boundary integral equations to study the tense state near the cracks. The power fracture criterion is used to detect the change of direction of tops extension. Moreover, we suggest some calculation examples of the trajectories motion of the crack tops in plates with various mechanical properties.
Rybak V.M., Chernega D.F.
A Refinement Technology of Foundry Aluminium Alloys
P. 111–115. Fig. 4. Tabl. 2. Refs.: 11 titles.
Using carbamide, we develop the refinement technology of foundry aluminium alloys from gases and nonmetallic inclusions. We study the influence of carbamide on physical and mechanical properties of the final alloys and crystallization parameters. The comparative analysis of the developed technology with other technologies is conducted. Finally, we verify that processing of the foundry aluminium alloys by carbamide allows enhancing physical and mechanical properties of final alloys and reducing the refinement cost.
Shysha T.O., Chyzh I.G.
Simulation of Aberrations of an Optical System of the Human Eye. Chapter 2. Technological errors of a doublet physical eye model with aberrations
P. 116–123. Fig. 2. Tabl. 2. Refs.: 6 titles.
The present study considers the influence of technological errors of construction parameters of the optical system of the human eye model on the errors of a simulated wave aberration. We verify the technological possibility of manufacturing the model with an accuracy of wave aberration simulation, sufficient for examining ophthalmic aberrometers.
Maksymiv N.L., Starchevsky V.L.
Specificity of Ultrasound Influence on bacterial Agglomerates Destruction in Aqueous Suspension
P. 124–127. Fig. 7. Refs.: 6 titles.
Sonication has two main effects on bacterial suspensions. The first effect is bacterial declumping which breaks up agglomerates into a large number of individual bacteria in a suspension and the second one is bacterial inactivation which depends on reducing of individual ability of cells’ reproduction. The general effect of applying ultrasound is connected with the sonication time.
Ilchenko M.Yu., Gorobets O.Yu., Bondar I.A., Gaponov A.M.
Influence of External Magnetic Field on the Etching of a Steel Ball in an Aqueous Solution of Nitric Acid
P. 128–133. Fig. 8. Tabl. 1. Refs.: 6 titles.
This paper reveals the effect of the change of a steel ball shape as a result of its etching in an aqueous solution of nitric acid under the influence of an external magnetic field. The elongation of a ferromagnetic ball was observed along the direction of an external magnetic field. The steel ball etching in a magnetic field is characterized by formation of three cylindrically symmetric regions with different etching rates and surface structures, divided from each other by clear borders, namely, the pole, equator and transition regions.
Research into Equilibrium States of a Spherical Pendulum with Non-Ideal Excitation
P. 134–141. Fig. 3. Refs.: 5 titles.
The present paper studies the equilibrium states of a dynamic system, formed by a spherical pendulum, whose point of suspension is excited in a vertical plane by the power-constrained electromotor. We identify that in the phase space of the system there is a singular surface, whose all points are the equilibrium states. Furthermore, sufficient conditions of asymptotic stability are obtained for one of equilibrium states and relevant domains of stability in the space of parameters’ system are constructed.
Preparation of Sensitive Substrates for Surface-Enhanced Raman Spectroscopy on the Basis of Ag/Si Nanoisland Films
P. 142–147. Fig. 6. Refs.: 17 titles.
The paper aims to examine nanostructured silver films prepared by a thermal deposition on silicon and to investigate their properties as substrates for surface-enhanced Raman spectroscopy (SERS). To that end, we establish the optimal conditions of the post-growth annealing of the substrates. The study of dispersion by atomic force microscopy reveals that the silver films with relatively dense and homogeneous arrays of 60–80 nm high pyramidal nanoislands are the most efficient for SERS of both organic dye and inorganic nanoparticles analytes.
Recurrent Relations with the Generalized Legendre Functions
Refs.: 8 titles.
This paper considers τ-generalized (by Wright) τ Ρμν(z) Legendre functions. By using the known properties of τ-generalized (by Wright) τ2F1(a,b;c;ξ) Gauss hypergeometric function and the relation betweenτΡνμ and τ2Fτ functions, the theorem of recurrent relations, as well as the theorem of differentiation formulas for these functions are formulated and proved.