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Naukovi visti NTUU “КPІ”. – 2017. – N 2



E.N. Pis’mennyi, S.A. Reva, A.M. Terekh, O.V. Baraniuk

HEAT-AERODINAMIC EFFICIENCY OF HELICAL TUBES

Background. Research and development of new highly efficient heat exchange surfaces.

Objective. Determination of the heat-aerodynamic efficiency of the new equally developed surfaces in the form of helical tubes packets.

Methods. Experimental and numerical study of heat transfer and aerodynamics of helical tubes chess packages.

Results. The specific heat flux which is taken away from packages of helical tubes is 30–65 % bigger than a specific heat flux which is taken away from the corresponding (respective) packages of smooth tubes at equal costs for pumping the heat transfer agent. The maximal sizes are reached for packages of type 3 tubes at  σ2=1,46

Conclusion. Application of helical tubes allows increasing the intensity of heat exchange with moderate growth of an aerodynamic drag therefore it is possible to improve mass-dimensional characteristics of heat exchange devices significantly.

Keywords: helical tubes; equaldeveloped surface; chess packages; efficiency.

A.O. Danilchenko, S.M. Kravchenko

MODIFICATION OF THE ANT COLONY OPTIMIZATION ALGORITHM FOR SOLVING THE MATCHING PROBLEM WITH VANISHING ARCS

Background. The applied problem of making out the optimal schedule of reception of manipulation treatments can be reduced to the extended mathematical problem of search of maximal matchings in the dicotyledonous graph. The basic challenge of solving this problem is the necessity of taking into account the limits on the acceptance of procedures.

Objective. The aim of the paper is modification of the ant colony algorithm for solution of the problem of matching with the vanishing arcs.

Methods. The initial population forming method and modified method of analysis of way of ants are proposed.

Results. The carried out studies proved the possibility of receipt of feasible optimal solution of the problem of matching with the vanishing arcs at the use of the modified ant colony algorithm.

Conclusions. The proposed method can be used for development and application of the scheduling systems and operative management in a direct care as well as at the development of control systems by flexible CASS for enterprises with discrete type of production.

Keywords: matchings; dicotyledonous graph; ant colony optimization algorithm.

V.J. Kotovskyi, V.V. Shlykov, V.A. Danilova

NON-INVASIVE MONITORING OF TEMPERATURE IN THE HEART HYPO- AND HYPERTHERMIA WITH CARDIOPULMONARY BYPASS

Background. The implementation of the method of non-invasive control of heart temperature based on the model of heat exchange in the myocardium during extracorporeal circulation is considered.

Objective. The purpose of the research is the use of numerical simulation methods in the MSC Sinda system to estimate the temperature gradient that is observed on the surface of the myocardium during hypo- and hyperthermia in the conditions of artificial circulation.

Methods. To obtain the original data in the cardiopulmonary bypass loop temperature sensor system in arterial, venous, and cardioplegic lines is used. When assessing the temperature gradient applied of thermal diagnostics methods and analysis of thermograp in the infrared spectrum that allow getting data for the simulation of heat transfer process between the myocardium and coronary vessels in the MSC Sinda system.

Results. As a result of numerical modeling 2D-model of heat exchange in the myocardium was proposed and the comparative analysis of thermal images of open heart with hypo- and hyperthermia with cardiopulmonary bypass was carried out. Carrying out non-invasive temperature measurement and simulation results of heat transfer on the surface of the myocardium allow more accurately adjust the speed of warming (hyperthermia) of venous blood in the heat exchanger.

Conclusions. The simulation results allow supplementing the qualitative indications of system sensors for cardiopulmonary bypass. Application of thermal diagnostics methods and imaging analysis of thermograms for the monitoring of venous return temperature cardiopulmonary bypass circuit that allows you to adjust the flow of blood to the hollow veins with using venous occlusion line change with the clamp or a special device.

Keywords: thermogram; myocardium; model; temperature distribution; MSC Sinda.

O.V. Koval, V.A. Kuzminykh, D.V. Khaustov

USING STO­CHASTIC AUTOMATON IN SELECTING FOR DATA CONSO­LI­DATION

Background. Development of methods and algorithms for efficient search of relevant information on demand. The article deals with the consolidation of data for subsequent use in the information and analytical systems.

Objective. The aim of the paper is to identify capabilities and build relevant information search algorithms from disparate sources by analyzing the probability information identifying the possible presence of relevant documents in these sources.

Methods. To find the relevant information for search queries the approach based on the use of probability estimates of relevant documents available in the sources of further increasing the number of selected documents from these sources to analyze their relevance to the query is used.

Results. A stochastic programmable automaton structure to ensure selection of the most possible information sources by relevance parameters and information retrieval algorithm based on the use of stochastic automaton were developed.

Conclusions. The described algorithm using stochastic automaton for data consolidation allows developing a set of software tools, provides plenty full and holistic data consolidation problem-solving for diverse systems which search for information from information sources different in composition and presentation type.

Keywords: open data sources; data consolidation; information-analytical systems; information retrieval systems; probabilistic models; relevance; big data tasks.

I. Nesteruk, A. Redaelli, I. Kudybyn, F. Piatti, F. Sturla

GLOBAL AND LOCAL CHARACTERISTICS OF THE BLOOD FLOW IN LARGE VESSELS BASED ON 4D MRI DATA

Background. Magnetic resonance imaging (MRI) using three-dimensional velocity encoding phase contrast (PC) methods offers the opportunity to quantify time-resolved 3D flow patterns in vivo. This technique can have a breakthrough impact on the evaluation, risk stratification and surgical planning in hemodynamic-related pathologies, e.g., cardiac valve diseases, arterial stenos or insufficiency, aortic dilation, dissection or coartaction. However, its applicability in clinics is limited due to the complex post-processing required to extract the information and the difficulty to synthesize the obtained data into clinical useful parameters.

Objective. In this work, a software tool is presented which analyzes the row data and provides information along the whole vessel, between two selected cross-sections and in the vicinity of the selected points.

Methods. A fully automatic algorithm based on the properties of the steady Hagen–Poiseuille flow was developed which in few minutes segments the vessel shape, visualize the blood flow and calculates its characteristics. Since the time and space resolutions of the data are limited, we avoid the differentiation of the velocity field.

Results. The algorithm has been tested on datasets of patients with bicuspid aortic valve and healthy volunteers. Results are provided both as maximum and time-averaged values in aorta, pulmonary artery, left and right ventricles.

Conclusions. The results demonstrate that the presented approach could be useful for medical doctors in order to classify and stratify different valve and/or vessel pathologies.

Keywords: 4D flow; MRI; bicuspid valve; aortic flow; vessel pathologies.

F. Rigoldi, L. Spero, A.D. Vedove, A. Redaelli, E. Parisini, A. Gautieri

MOLECULAR DYNAMICS SIMULATIONS PROVIDE INSIGHTS INTO STRUCTURE AND FUNCTION OF AMADORIASE ENZYMES

Background. Enzymatic assays based on Fructosyl Amino Acid Oxidases (FAOX) represent a potential, rapid and economical strategy to measure glycated hemoglobin (HbA1c), which is in turn a reliable method to monitor the insurgence and the development of diabetes mellitus. However, the engineering of naturally occurring FAOX to specifically recognize fructosyl-valine (the glycated N-terminal residue of HbA1c) has been hindered by the paucity of information on the tridimensional structures and catalytic residues of the different FAOX that exist in nature, and in general on the molecular mechanisms that regulate specificity in this class of enzymes.

Objective. In this study, we use molecular dynamics simulations and advanced modeling techniques to investigate five different relevant wild-type FAOX (Amadoriase I, Amadoriase II, PnFPOX, FPOX-E and N1-1-FAOD) in order to elucidate the molecular mecha­nisms that drive their specificity towards polar and nonpolar substrates. Specifically, we compare these five different FAOX in terms of overall folding, ligand entry tunnel, ligand binding residues and ligand binding energies.

Methods. We used a combination of homology modeling and molecular dynamics simulations to provide insights into the structural difference between the five enzymes of the FAOX family.

Results. We first predicted the structure of the N1-1-FAOD and PnFPOX enzymes using homology modelling. Then, we used these models and the experimental crystal structures of Amadoriase I, Amadoriase II and FPOX-E to run extensive molecular dynamics simu­lations in order to compare the structures of these FAOX enzymes and assess their relevant interactions with two relevant ligands, f-val and f-lys.

Conclusions. Our work will contribute to future enzyme structure modifications aimed at the rational design of novel biosensors for the monitoring of blood glucose levels.

Keywords: fructosyl amino acid oxidase; amadoriases; deglycating enzymes; molecular dynamics simulation; enzyme specificity; bind­ing interactions; HbA1c monitoring; diabetes monitoring; glycated haemoglobin.

Ie.V. Verbytskyi, M. Münter, C. Buj, R. Brinkmann

A PROBLEM OF A DISPLACEMENT CALCULATION OF TISSUE SUR­FACE IN NON-CONTACT PHOTOACOUSTIC TOMOGRAPHY

Background. Photoacoustic tomography (PAT) is a relatively new imaging modality,which allows e.g. visualizing the vascular network in biological tissue noninvasively. This tomographic method has an advantage in comparison to pure optical/acoustical methods due to high optical contrast and low acoustic scattering in deep tissue. The common PAT methodology, based on measurements of the acoustic pressure by piezoelectric sensors placed on the tissue surface, limits its practical versatility. A novel, completely non-contact and full-field PAT system is described. In noncontact PAT the measurement of surface displacement induced by the acoustic pressure at the tissue/air border is researched.

Objective. To solve a simulation problem of the displacement calculation based on the medium pressure, which consists in deriving a formula for recalculating the pressure in the surface displacement based on the momentum conservation law, developing a simulation technique, and comparing the error of the proposed technique with the earlier used one.

Methods. Comparing the experimental data with simulated pressure data in the k-Wave toolbox. The criterion of comparison is the relative quadratic error.

Results. The simulation results of the displacement based on a new approach are more consistent with the experimental data than previous. The quadratic error numerical value of the new approach is 18% and the previous is 71%.

Conclusions. The theoretical features of the surface displacement simulation are investigated and the solution of this problem is proposed based on momentum conservation law. The implementation of the proposed methodology has a four times smaller simulation error compared to the previous technique, so it can be implemented in the non-contact PAT. The residual error can be caused by the properties of the tissue, which are not taken into account in the model, which requires further research.

Keywords: non-contact photoacoustic tomography; displacement; calculation error.

Ia.V. Zagumennyi

MODELING OF MOLECULAR DIFFUSION IN NON-HOMOGENEOUS MEDIA

Background. Due to combined effects of medium inhomogeneity and action of external forces, i.e. Earth’s gravitation, electro-magnetic forces, global rotation, etc., a number of specific fluid motions appear in the environmental and life systems even in absence of pure mechanical reasons. Among them are so called diffusion-induced flows which always exist around obstacles with arbitrary geometry due to breaking of natural molecular flux of a stratifying agent on an impermeable surface.

Objective. The aim of the paper is to analyze numerically a diffusion induced flow structure and dynamics around motionless obstacles immersed into a stably stratified medium, including a sloping plate, a wedge-shaped obstacle, a disc, and a circular cylinder. The numerical results obtained are compared with the available analytical and experimental data.

Methods. The problem is solved numerically using two different algorithms based on the finite difference and finite volume methods. The first approach is implemented in the specially developed Fortran program codes, and the second one is based on the open source package OpenFOAM with the use of C++ programming language for developing special own solvers, libraries, and utilities, which enable solving the problems under consideration.

Results. The numerical simulation reveals a complex multi-level vortex system of compensatory circulating flows around a motionless obstacle, which structure is strongly dependent on its position relative to the horizon. The most intensive and extended high-gradient horizontal interfaces attached to sharp edges or poles of obstacles are clearly observed in the numerical computations and laboratory experiments. Diffusion-induced flows form intensive pressure deficiency zones around an obstacle, which may lead to generation of propulsion mechanism resulting in self-movement of neutral buoyancy bodies in a continuously stratified fluid, e.g. horizontal movement of a wedge, rotation of a sloping plate, etc.

Conclusions. Diffusion-induced flows are a wide-spread phenomenon in biology, medicine, and environmental systems, since such flows inevitably occur in any inhomogeneous media, including different solutions, suspensions, mixtures, etc. A complex multilevel vortex structure of diffusion-induced flows on an obstacle becomes even more compli­­cated due to self-motion of the obstacle itself and displacement of various admixtures, suspended particles, additives, etc., which are always present in the real systems.

Keywords: molecular diffusion; stratified fluid; diffusion-induced flow; propulsion mechanism; finite volume method.

I.I. Pukhovyi

WATER DISPERSION BY HITTING THE RIBBED AND ROUNDED SURFACES AT THE LOW-HEAD OUTFLOW THROUGH A SMALL HOLE

Background. Low-pressure water spray by impact on a hard surface is convenient for crystallization of water on vertical surfaces and horizontal nozzles with icicles. In the previous works of the author, it was noticed the effect of an impact surface roughness on spray flow hydrodynamics, therefore, in this paper we investigate the effect of surface topography on the dispersion impact characteristics. The direction of drops movement along and across significantly affects the scattering drops parameters on the ribbed surfaces. This fact can be used in the irrigation of surfaces.

Objective. The work aims to investigate the effect of an impact surface topography and shape on the spray droplets flow hydrodynamics after the impact.

Methods. The experiments were conducted at a constant geometric height in the vessel 250–260 w.c. with the distance change from the impact surface to the hole from which water jet discharged at a cost in the range of 0.46–of 2.75 g/s. The height and the maximum radius of the droplets dispersion after impact were measured according to the evidence of the drops on a paper.

Results. We carried out the experimental studies of the drops dispersion characteristics: of the primary drops (after the discharge from small diameter holes) and of the secondary ones – after hitting the ribbed surfaces (flat, round, a roof), the convex and concave segment surfaces of sphere and cylinder. The drops scatter in 1.5–3 times further in the direction along the rib than in the perpendicular direction. We see farthest flying drops when using the ribbed roof. Impact on the surface with small ribs at low water flow rates and low heights of the jet fall does not give the desired results. The maximal height of the drops rising upward across the ribs is at a smaller distance from the impact center. The linear dependence of water flow on the pressure for the hole of 1.6 mm diameter in the investigated range of water pressures was confirmed.

Conclusions. Under nozzles irrigation, there is a possibility of atomized flow distribution in the directions that allows ensuring the devices design requirements, for example, with pipes irrigation the ribs are placed along the edges of the pipes. Adjacent holes for the water flow are placed at a distance less than the maximum radius of the secondary droplets dispersion, given the lower irrigation density with increasing radius. If the vertical surfaces are irrigated, the distance from the impact center to the surface is selected depending on the irrigation density requirements and on the irrigation elementary point over the impact surface.

Keywords: spray impact; radius and height of spray drops; ribbed and rounded impact surfaces; nozzles irrigation for the icicles formation; heat and mass transfer devices.

A.I. Yurkova, V.V. Chernyavsky, F.N. Matveev, S.Y. Gandzyuk 

MULTICOMPONENT AlSiNiCoFeCr AND AlSiNiCoFeCrTi HIGH-ENTROPY COATINGS ON STEEL

Background. In many situations, only the contact surface properties are important in determining performance of the component in practical applications. Therefore, the use of a coating from materials with high physical and mechanical characteristics, such as high-entropy alloys (HEA), has several attractive advantages. HEAs have been found to have novel microstructures and unique properties. Considering HEA’s tendency to form simple structures, fabricating HEA coating by electron beam welding process is of great significance and potential for extensive use. Until now this novel method for preparing HEA coatings has just been reported by any organizations.

Objective. The purpose of this work is to study the features of microstructure, phase and chemical composition, and microhardness of HEA coatings, produced by electron-beam welding on steel substrate of 6 and 7-component powder equiatomic mixtures of the system Al–Si–Ni–Со–Fe–Cr–Ti.

Methods. The coatings were obtained by electron-beam welding. The microstructure, chemical composition, and constituent phases of the synthesized coatings were characterized by SEM, EDX, and XRD analysis, respectively. Microhardness was also evaluated.

Results. Experimental results demonstrate that the AlSiNiСоFeCr and AlSiNiСоFeCrTi HEA coatings are composed of only three substitutional solid solutions with body-centered cubic (BCC) structure and different lattice parameter due to different component concentration. The coatings exhibit dendritic microstructure with different size and morphology. The Vickers’s hardness of AlSiNiСоFeCr and AlSiNiСоFeCrTi HEA coatings has been found to be HV = 9.2 ± 0.2 and HV = 11.25 ± 0.3 GPa, respectively, and is much higher than that of the similar alloys prepared by laser cladding technique.

Conclusions. Evidence from multicomponent powder mixtures of the Al–Si–Ni–Со–Fe–Cr–Ti system, it is possible to form HEA coatings consisting of solid substitution solutions with a BCC structure and all initial components by electron-beam welding method. Through the strong crystal lattice distortion of solid solutions at the mutual dissolving of dissimilar atoms of AlSiNiCoFeCr and AlSiNiCoFeCrTi, HEA coatings have a high microhardness that is much higher than the hardness of the initial components.

Keywords: high-entropy alloy; electron beam welding; coating; structure; phase composition; microhardness.

V.G. Kolobrodov, D.V. Pozdnyakov, V.M. Tiagur

INFLUENCE OF GEOMETRICAL PARAMETERS OF REDUCTION ON THE DEFORMATION OF WORKING SURFACE OF THE OFF-AXIS SEGMENTS OF AXISYMMETRIC MIRRORS

Background. Weight reduction of mirrors is an important issue in the development of space-based optical systems. However, the study of the influence of weight reduction on the deformation of the mirror surface of the off-axis segments of axially symmetric mirrors and methods of its calculation is given little attention.

Objective. Development of the algorithm for calculating the deformation of the working surface of the off-axis segments of axisymmetric mirrors, and analysis of the impact of different types of weight reduction and geometrical parameters on deformation of the working surface of the off-axis segments of axially symmetric mirror by gravity, using the algorithm developed.

Methods. Four work stages of the developed algorithm are described and the influence of the geometric parameters of weight reduction on the deformation of working surface of the off-axis segments of axially symmetric mirrors is studied.

Results. It was determined that the developed algorithm can be used to determine the deformation of any of the optical surfaces, the ratio at which related parties are less to more is greater 0.3. The influence of geometrical dimensions on deformation of the working surface of the off-axis segments of axially symmetric mirrors was analyzed by developed algorithm and recommendations on the use of various types of weight reduction was given.

Conclusions. In the process, an algorithm for determining the deformation of the working surfaces of optical components was proposed and the influence of the geometric parameters of weight reduction on the working surface of the off-axis segments of axially symmetric mirrors was studied.

Keywords: Zernike coefficients; weight reduction of mirrors.

S.M. Matvienko, S.P. Vysloukh, K.G. Filonenko

THERMAL CONDUCTIVITY MEASUREMENT OF SOLID MATERIALS BY THERMISTOR DIRECT HEATING METHOD

Background. This work addresses the development of an experimental device and increasing the accuracy of determining the thermal conductivity of solid materials by thermistor direct heating method.

Objective. The aim of the paper is to create the installation, conduct experimental studies to determine the value of the thermal conductivity of solid materials by thermistor direct heating method and to research destabilizing factors that affect the measurement error, and to suggest ways to increase the accuracy of measurements.

Methods. Experimental device has been created, which work is based on the direct heating method of the thermistor and necessary researches have been carried out. The results of the measurement are given by setting the thermal conductivity coefficients of various materials, which make it possible to expand the scope of the method.

Results. Rational operating modes and design of probes for measuring the thermal conductivity of solid materials depending on their TPC are proposed and justified. Ways to reduce the measurement error by thermistor direct heating method are presented. Investigation of destabilizing factors influencing the measurement error made it possible to determine means of reducing their influence on the results of determining the thermal conductivity of solid materials and to suggest ways to increase the accuracy of measurements.

Conclusions. The experimental device has been tested experimentally and implemented in the research and production activities of “VIRCOM” and in the educational process of the Department of Instrumentation Design and Engineering of the National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”.

Keywords: thermal conductivity; thermistor direct heating method; experimental device; thermophysical characteristics of solid ma­terials.

A.N. Sapegin, N.V. Norenko

STRAPDOWN INERTIAL ATTITUDE SYSTEM BASED ON RING LASER GYRO ALGORITHM

Background. The paper is dedicated to improving the accuracy of strapdown inertial systems by improving the algorithmic software.

Objective. The aim of the paper is the development and analysis of the accuracy of a strapdown inertial orientation system algorithms.

Methods. Construction of a strapdown attitude reference system algorithms based on kinematic equation of Poisson and quaternions. The input data for the orientation algorithms are signals from the real laser gyroscopes installed in the system. Orientation equation integration is performed using the Runge–Kutta methods.

Results. The attitude system errors, depending of the different vehicle motions are determined.

Conclusions. Research of selected orientation algorithms and numerical integration showed their high accuracy. They may be used in the design of precision strapdown inertial systems.

Keywords: ring laser gyro; Poisson equation; quaternion; math modeling; strapdown inertial attitude system.

S.I. Cheberiachko, V.Yu. Frundіn, Yu.I. Cheberiachko, D.I. Radchuk

RESEARCH ON FILTER BOXES DESIGNS EFFICIENCY

Background. Filtering respirators are widely used in various industries to protect workers from dust, so studies aimed at improving ergonomic parameters of personal respiratory protection are relevant.

Objective. The aim of the paper is the filter box design influence on respirator breathing resistance.

Methods. The distribution of the air flow rate and the pressure drop across the filter was determined in accordance with the requirements of the DSTU EN 143: 2002. To do this, in the back wall of the filter box housing 5 mm holes were drilled, in which every 10 mm a Pitot tube was installed, connected to an electronic manometer Testo 512.

Results. It is established that the designs of filter boxes affect the pressure drop of the respirator, due to the failure to use a significant surface of the filters (the formation of dead zones in which air does not move) what affects the efficiency of their performance.

Conclusions. The designs of filter boxes for modern respirators require appropriate modification to reduce the resistance to breathing, to increase the duration of protection and dust load, due to uniform flow around the filter surface by air flow throughout the area.

Keywords: respirator; filter; filter box; pressure drop.

O.V. Lysak

TARIFF RATE FOR ELECTRICAL THERMAL STORAGE FOR HEATING, VENTILATION, AND AIR CONDITIONING SYSTEMS

Background. The most efficient use of available electricity capacity during the hours of consumption decline is very important problem in Ukraine. This article provides an analysis of the actual tariff policy and the use of electricity during the hours of the low tariff for heating, ventilation and air conditioning systems.

Objective. The aim of the paper is to analyze the set validity periods of the reduced prices for electrical energy. Priority attention is paid to the tariff policy differences for the cost of electricity in Ukraine and abroad and how these differences affect possible storage system cost and, thus, payback period.

Methods. The general feasibility of using electricity as the heat source is presented, different energy sources as a generator of heat are compared, the possibility of strengthening cooperation between producers and consumers of electricity in order to achieve optimal modes of generation and consumption of heat is stated, the tariff plans for electricity in Ukraine and abroad are provided.

Results. As a result of the work it was made the comparison of tariff policy in Ukraine and three other countries: the UK, Canada and Spain. It is shown that overseas tariff rates are more flexible than in Ukraine, and promotes more effective relationships between the power generating companies and consumers in both economic and technological aspects. It was also shown that additional day charging can significantly reduce a necessary amount of heat storage material as well as the set power of the system.

Conclusions. At the current level of technological development, the actual policy for determining electricity tariffs should be based on innovative technologies, for example, on the dynamic determination of the electricity cost. It becomes relevant with the growth of the share of renewable energy sources in general electricity generation.

Keywords: renewable energy; electricity tariffs; electric storage heating.

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