The paper proposes mathematical models that make it possible to describe the electrical conductivity of a nanocomposite based on carbon nanotubes, taking into account the waviness effect and the dispersion index. The model takes into account the contribution of various parameters, such as the concentration of nanotubes, the length, diameter and orientation of the tubes, as well as the electrical properties of the nanocomposite matrix. Using the proposed model, numerical experiments were carried out to evaluate the effects of waviness and dispersion index on the electrical conductivity of the nanocomposite. Comparisons of model data with experimental data are presented, confirming the adequacy and accuracy of the model. The results obtained can be used to optimize the process of creating nanocomposites based on carbon nanoturbines, as well as to increase the efficiency of their use in various fields, including electronics and energy.
Keywords: mathematical modeling, software package, nanocomposites, electrical conductivity, carbon nanotubes, computational experiment
This article discusses the comparative calculation of solid-stage and three-layer tubular structures with an assessment of the reliability of their application. To do this, their stress-strain state is investigated when exposed to a pulsed load on the wall. Pipeline structures currently occupy important positions in the infrastructures of many countries. Every year new safety requirements are added to the reliability indicators of these structures. Such important strategic facilities fulfill the task of providing people with energy, without which it is difficult to imagine modern life. For a solid-stage pipe, displacements in the nodes of the pipe wall, as well as longitudinal stresses (Nx) and annular stresses (Ny) in the elements of the pipe wall are determined. In a three-layer pipe, the displacements are determined at the nodes of the pipe wall.
Keywords: three-layer tubular structure, solid-walled pipe, load-bearing layer, pulse load, filler, displacement, voltage
The article discusses a graphical notation using three-dimensional visualization for representing models of automated systems according to the Methodology of Automation of Intellectual Labor (MAIL). The research aims to enhance the efficiency of modeling automated systems by providing a more comprehensive representation of the models. Research methods employed include a systems approach. The study results in the formulation of descriptions and rules for creating the corresponding graphical notation for the initial and conceptual modeling stages of subject tasks in MAIL, as well as rules for forming representations for static and dynamic model structures and representing their interrelations. Additionally, rules for visually highlighting and concealing elements within the diagrams of the graphical notation are examined, rendering it suitable for implementation as a software module with a graphical interface for CASE tools, facilitating modeling according to MAIL. Such an approach enables the visualization of the model as a whole and enhances the efficiency of analysts conducting modeling following the methodology.
Keywords: methodology of Automation of Intellectual Labor, modeling of automated systems, conceptual modeling, graphical notation, three-dimensional visualization
Methods of computer formation of the equations of motion of multibody systems with a tree structure and algorithms for their reduction to the normal form of ordinary differential equations are considered. The equations of motion are written using Hamilton's formalism for an extended set of state variables of a mechanical system. The equations are presented in a compact visual form. Recursive formulas for determining all coefficients of equations are written out. Algorithms for reducing these equations to Hamilton equations in generalized coordinates and generalized momenta are presented. An algorithm for solving the obtained equations of motion for multibody systems using the LTDL-elimination is presented. Formulas are written that allow one to calculate the amount of arithmetic operations required to bring the equations of motion to normal form using the considered algorithms. On the basis of these formulas, a comparative analysis of the efficiency of algorithms for rigid bodies systems of various structures and with various types of connections between bodies is carried out. The results of the analysis are presented in the form of diagrams. The diagrams highlight areas in which the advantage of one or another method is manifested, depending on the type of mechanical system.
Keywords: multibody systems, equations of motion, dynamics, canonical momenta, mathematical modeling, computational efficiency
The article presents the prerequisites for the relevance of the processing and disposal of galvanic sludge generated from industrial enterprises, which in turn occupies numerous areas of land for storage, which harms the environment. An overview of the methods of processing and disposal of electroplating waste, including physical, chemical and biological processes. Experimental studies of galvanic sludge sediment are presented. The precipitate is a mixture of crystalline CaCO3, SiO2 and an amorphous phase, which is not determined by phase analysis. Modern advanced technologies for the processing and disposal of galvanic sludge are presented.
Keywords: galvanic sludge waste, automation, control, methods, sediment thermogram
The reconfigurable systems-on-a-chip (RSoC) includes hard and soft intellectual property cores (IP-cores). Hard IP-cores are placed on the specified positions on the chip and have a predetermined functionality. Soft IP-cores are developed using the logical blocks (LB) of a field programmable gate array (FPGA) on the RSoC. Both types of IP-cores have different features. Hard IP-cores have configurations that can be programmed. Soft IP-cores use the base RSoC specialized resources. All IP-cores features must be considered at various stages of the design flow of user circuits based on the RSoC. Any modes of the RSoC IP-cores should be extracted from the functional description of the user circuit during logical synthesis. The features of the base chip architecture and specialized routing resources must be considered during placement and routing. In this paper, a software-oriented set-theoretic model of IP-cores is presented. The model makes it possible to represent IP-cores in computer-aided design (CAD) system at different stages of design flow of user circuit based on RSoC and to map architecture-independent IP-cores of a user circuit to IP-cores on the base chip. The model combines formalized representations of the base chip components, architecture-independent and architecture-dependent parameterized IP-cores for the logical synthesis, as well as IP-cores for the layout synthesis. Also, the model has several distinctive features. The first feature is the availability of the relative coordinates of the soft IP-cores elements. These coordinates allow to take into account the RSoC architectural features at the placement stage. The second feature is that an information about specialized routing resources and interconnections of the user and base circuits. This information allows to establish a correspondence between IP-core and RSoC connections regardless of the routing resources type.
Keywords: reconfigurable system-on-a-chip, intellectual property core, field programmable gate array, computer-aided design system, set-theoretic model, formalization
The problem of flexible vibrations of a rectangular orthotorque plate clamped along the contour is considered. The general solution of the problem, which satisfies the vibartion equation identically, is constructed on the basis of the superposition method in the form of two Fourier series. Clamped boundary conditions lead to a homogeneous infinite system of linear algebraic equations with respect to unknown coefficients in the general solution. The uniqueness of a bounded non-trivial solution of an infinite system for the natural frequency is proved, the asymptotics of the unknowns are found, and an effective solution algorithm is constructed. Examples of the numerical implementation of the developed algorithm for calculating the natural frequencies and natural modes of the plate vibrations are given.
Keywords: plate, vibrations, natural frequencies, planar forces, superposition method, infinite system of linear equations, asymptotics
The construction and substantiation of a finite element model of the capillary tube running-in process, which was obtained by drawing on a fixed mandrel, are considered. The rolling rolls are cylindrical and absolutely rigid. The condition for performing the work is a comparison of the resulting gap between the pipe and the mandrel and the facet formed during deformation. The solid-state model of the process is described by an adaptive grid. Under these conditions, an informative model was obtained, which was used in parametric analysis.
Keywords: drawing with a mandrel, capillary tube, extraction, rolling, model construction, compression selection, pipe size tolerance
In the research the characteristic features of the historical appearance of the Vyritsa village on the base of its architectural and urban structure, features of the location of cultural heritage sites and precious landscape objects, on the base of which the stratеgy defining these main priorities, criteria and directions of protection of historical appearance are worked out . The concept of complex preserving of architectural and landscape environment of Vyritsa with creating of possibilities of effective using of these territories with the most display of its historical and cultural, memorial and museum potential.
Keywords: culture landscape, architectural and landscape revitalization, identity of settlement, sustainable development of the territory
In this work, an experimental model of a circuit diagram with pulsating circulation of a liquid coolant in a heated circuit of a plate heat exchanger was assembled and tested. As a result of hydraulic and energy calculations of the circuit, the optimal parameters for flow, pressure, and temperature of the coolant were selected at maximum efficiency of the impact unit. It has been established that with an increase in the operating frequency of the impact unit, the heat transfer coefficient of the heat exchanger first decreases and reaches a minimum of 452.47 W/(m2*0C) at a frequency of 0.5 Hz, and then begins to increase and reaches a maximum of 482.31 W/(m2* 0C) at a frequency of 2 Hz, after which it gradually decreases. It has also been experimentally established that the temperature at the outlet of the heat exchanger of the heated circuit increases with increasing frequency of the shock unit and reaches a maximum at a frequency of 2 Hz, after which it begins to gradually decrease. It has been established that the change in temperature at the outlet of the heat exchanger of the heated circuit exceeds the change in temperature at the outlet of the heat exchanger of the heating circuit at operating frequencies above 1 Hz, which is due to the stronger influence of cavitation at these frequencies.
Keywords: heat exchanger, heat transfer coefficient, impact unit, frequency, heat transfer
The article is devoted to the study of crowd behavior in public buildings during a fire. A method for evaluating the effectiveness of organizing the evacuation of people from a public building is proposed, which makes it possible to take into account the spread of panic among evacuees. The method is based on the development of an evacuation simulation model that takes into account the impact of certain factors on the degree of people's panic, which implements an agent-based approach. The proposed method allows, when describing the psycho-emotional behavior of each agent separately in the process of evacuation, to evaluate the effectiveness of organizing the evacuation of the crowd as a whole. The simulation results on the example of a shopping and entertainment center show that possible panic conditions of evacuees can affect the efficiency of evacuation.
Keywords: evacuation, panic, simulation model, efficiency assessment method, shopping and entertainment complex, agent-based approach
The article presents studies of a computer simulation statistical model between the characteristics of flows in terms of linear density and the proportion of components in a mixed flow. The results of evaluating the effect of the filling fraction of the component on the average and standard deviation of the fraction of the 1st component in the mixture are presented, the type of autocorrelation functions of the linear density of the mixed stream and the fraction of the 1st component in the mixed stream are determined, estimates of the spectral density of dispersion for the linear density of the mixed stream and the fraction of the 1st component in the mixed stream are shown.
Keywords: fiber mixing, linear density, component fraction, autocorrelation function, spectral density of dispersion, standard deviation
The work is aimed at modeling the control system of a slitting machine of a paper machine in order to improve the quality of products and eliminate defects in winding density. The developed automated system implements the functions of controlling the operating modes of the machine, distributing the loads of the bearing shafts, braking the roll and tensioning the paper web.
Keywords: slitting machine, paper machine, automated control system, rewinder, pressure roller, decoiler, reeler, accelerating shaft, deflecting shaft, cutting section
The article presents the results of a study of the rheological properties of cement compositions with a polycarboxylate-based plasticizer and stone flour from carbonate rocks of the Saratov region.
Keywords: cement, rheological matrix, powder-activated concrete, superplasticizer, hyperplasticizer, finely dispersed additive, stone crushing waste, stone flour, water-cement ratio, water-reducing effect
The influence of blast furnace ground granulated slag on the kinetics of strength gain of concrete prepared with a composite binder was revealed. The composite binder contained Portland cement in amounts of 70, 60 and 50%, and the rest was ground granulated slag. It has been established that at the early stage of strength development, concretes made with a composite binder have a strength lower than concrete prepared with Portland cement by 10-24%. However, at the age of 28 days, the strength of concrete using a composite binder corresponds to the strength of concrete using Portland cement. Using polycorboxylate hyperplasticizers, it was possible to obtain concrete with a W/C ratio of 0.25-0.35, which made it possible to obtain high early strength exceeding control compositions by 10-20%.
Keywords: portland cement, grn slag, grinding, composite binder, kinetics of strength gain, hyperplasticizer, kinetics of strength gain