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Naukovi visti NTUU “КPІ”. – 2017. – N 1



MODELING OF FLOODING IN THE CHANNEL OF CONTACT DEVICES // І.М. Kuzmenko, О.А. Gurzhij

Background. Contact economizers for recuperation of waste gases use hydraulic and aerodynamic flows and require a deeper understanding of their physical phenomena. So, the problem of hydrodynamics of common air flow and water film in channels of regular packing of contact economizers is important.

Objective. Finding dependencies between water film and air flow at critical modes of coolant flow in the contact heat mass transfer devices with a regular packing containing a system of vertical channels.

Methods. The goal is achieved by formulating and solving analytical model of stationary flowing of incompressible viscous liquids: water film and air. The model is described by the Navier–Stokes equation, reduced to a system of ordinary differential equations for viscous flow in a cylindrical coordinate system.

Results. It is shown that at the interface (for countercurrent movement of air and water film) there is air flow near water film that is moving down along with a water film. The thickness of the air-flow moving down near the interface (for countercurrent movement of air and water film), depends on the pressure gradient which prevents the gravitational running-off of the film. At a certain value of the pressure gradient the film stops at the interface of phases and the two-phase flow enters the mode of the film hanging. A further increasing of the pressure gradient at the film hanging mode causes the movement of the water film and air near the film layer vertically upwards. In this case, at the interface (for countercurrent movement) there is a film flow near the film layer moving in the direction of air flow.

Conclusions. Dimensionless values of the air velocity at movement flipping, film hanging, and flooding depending on the channel radius and Reynolds number values are established.

Keywords: countercurrent flow; interfacial surface; model; flooding; water film.

HEAT TRANSFER IN EVAPORATION ZONE OF AMMONIA ALUMINIUM HEAT PIPES // E.M. Pismennyi,  S.M. Khairnasov, B.M. Rassamakin

Background. There are no generalized correlations for the heat transfer intensity calculation in the evaporation zone of ammonia aluminum grooved heat pipe, which can be used in thermal stabilization systems of space satellites.

Objective. Development of calculation methods of the heat transfer coefficients in the evaporation zone of ammonia aluminium grooved heat pipes.

Methods. Experimental investigations, analysis and generalization of experimental data of heat transfer intensity in the evaporation zone of ammonia aluminum heat pipes, which were developed and manufactured in Igor Sikorsky KPI.

Results. Generalized formulas allow calculating heat transfer coefficients in the evaporation zone of ammonia aluminum heat pipes with outside diameters of 10.0, 12.5, 14.0 and 17.0 mm with the W-shaped longitudinal axial grooves in the heat flux density range of 0.1 to 7.0 W/cm2.

Conclusions. The experimental data were obtained with accuracy of correlation ±20 % with the calculated data in accordance with the proposed formulas.

Keywords: aluminium grooved heat pipes; capillary structure; heat transfer intensity; evaporation; boiling; space systems.

PREDICTIVE MODELING OF NONLINEAR NON-STATIONARY PROCESSES IN CROP PRODUCTION USING TOOLS OF SAS ENTERPRISE MINER // P.I. Bidyuk, O.M. Terentiev, T.I. Prosyankina-Zharova, V.V. Efendiev

Blackground. The issue of providing the increase of production of main agricultural crops in Ukraine under conditions of environmental management requires the use of modern scientific approaches. The complexity of solving this problem lies in the lack of practical experience of applying modern information-analytical systems, where different methods for analysis and modeling of nonlinear non-stationary processes in crop production would be implemented simultaneously. The proposed methodology has the advantage of using the tools of SAS Enterprise Miner – software where a wide range of techniques are implemented, that should be used for predictive modeling of main agricultural crops according to the performed research.

Objective. The goal of the study is in application of the integrated methods of analysis and predictive modeling of non-stationary processes for agricultural crop yield prediction using SAS Enterprise Miner tools.

Methods. To solve the problems stated the following approaches were used: systems analysis, regression analysis, gradient boosting, probabilistic modeling and decision trees. The methodology for developing of crop yield prediction under influence of various groups of factors was offered, and the possibility of their use in decision support systems in agriculture was substantiated.

Results. Based on the analysis of the works of domestic and foreign scientists it was proposed to improve methodology of development of yield prediction of main agricultural crops using integrated analysis methods, which were implemented in the system of SAS Enterprise Miner. The analysis of the obtained results was performed.

Conclusions. Winter wheat and corn yield prediction was performed for the Forest-Steppe Zone using the developed methodic. Different methods of construction of models for prediction of the non-stationary processes were applied; the choice of the worthiest one was reasonably proved. Advanced information technologies, including SAS Enterprise Miner, were used for automatization the process of selecting the optimal model for investigated crop yield prediction.

Keywords: non-stationary processes; regressive model; agricultural crop yield; prediction; decision support systems; SAS Enterprise Miner.

IDENTIFICATION AND ASSESSMENT OF ELECTROCARDIOGRAPHIC MARKERS OF CARDIAC ELECTRICAL INSTABILITY // K.O. Ivanko, N.G. Ivanushkina, Y.S. Karplyuk

Background. Development of the methods for identification and assessment of early signs of heart disorders makes it possible to catch the sight of disease at its initial stage. The article considers the methods of early diagnosis of the cardiovascular system using electrocardiographic markers of cardiac electrical instability.

Objective. The aim of the study is to identify low-amplitude components, which are inaccessible to standard procedures of electrocardiogram (ECG) evaluation by means of modern methods of registration, digital processing of electrocardiosignals and high resolution electrocardiography.

Methods. For detection of diagnostic symptoms associated with cardiac electrical instability, changes in real and simulated electrocardiosignals have been studied using different types of analysis: in time and frequency domains, scattergrams, cluster analysis, wavelet analysis and principal component analysis.

Results. The developed combined methods for analysis of low-amplitude components of electrocardiosignals allowed us to perform detection of late potentials, as well as T wave alternans, reflecting cardiac electrical instability.

Conclusions. Identification and evaluation of subtle manifestations of cardiac electrical activity are carried out. The use of the proposed method made it possible to distinguish the bursts of late potentials from the noise and to determine the temporal area of their localization.

Keywords: high-resolution electrocardiography; late potentials; T wave alternans; markers of cardiac electrical instability; clustering analysis; principal component analysis; eigenvectors basis; wavelet analysis.

G.V. Kriukova, S.P. Radchenko, O.O. Sudakov

ARTIFICIAL NEURAL NETWORK FOR MULTICLASS RECOGNITION AND ITS APPLICATION TO THE THYROID FUNCTIONAL STATE

Background. Development of automated diagnostic requires selection and improvement of appropriate machine learning methods, in particular multiclass recognition. Artificial Neural Networks (ANN) of various architecture are considered as an approach to the problem.

Objective. The goal is to analyze and compare performance of ANN-based classifiers on various datasets for further improvement of model selection strategy.

Methods. ANN-based models of the distribution of class labels in terms of predictor features are constructed, trained and validated for datasets of clinical records. Varying training algorithms for multi-layer perceptrons, Kohonen neural network, linear functional strategy with multi-parameters regularization are considered.

Results. Performance of the classifiers is compared in terms of accuracy, sensitivity, and specificity. Linear functional strategy classifier outperforms the other with more complex ANN-architecture and exhibits relative steadiness to overfitting. Performance of Kohonen neural network on large dataset exceeds 90 % in terms of specificity for each class, withal sensitivity for distinct classes is more than 95 %.

Conclusions. The understanding of the strengths and limitations of each method is crucial for careful choice of ANN-based classifier, particularly its architecture, regularization and training algorithm.

Keywords: artificial neural network; classification; ultrasound image processing; regularization; inverse problem.

THE  DISCRETE MODEL FOR THE SYSTEM OF THE MYOCARDIUM AND CORONARY VESSELS // V.B. Maksymenko, V.A. Danilova, V.V. Shlykov

Background. The numerical heat transfer model for a system of myocardium coronary vessels is considered.

Objective. The goal is to develop a discrete model for the physical system of myocardium and coronary vessels that would make it possible to explore the process of hypo- and hyperthermia with cardiopulmonary bypass.

Methods. To solve the differential equation of heat conduction in the MSC Sinda thermal system the network method (TNM – Thermal Network Method) is used, in which system of heat equations is presented in the form of cellular-centered nodes and resistances between the nodes using the finite difference method. In constructing the model of myocardial in the MSC Sinda system the thermal contact between three-dimensional bodies is implemented – the myocardium, coronary arteries, a liquid cooling of heart.

Results. Implementation of the model of heat exchange in the MSC Sinda system for infarction cooling process gives on the final process step in establishing the heat balance the temperature difference at the boundary between the myocardium and coronary vessels not more than 0,5 °C. However, in the areas of the myocardium that are removed from the coronary vessels the temperature difference exceeds 1,0 °C. The use of additional cooling for hearts allows for the cooling of myocardium with using of ice surface, that provides the unevenness reduction of the heart temperature during its cooling with cardiopulmonary bypass. This result allows exploring the dynamics of the process of hypo- and hyperthermia with cardiopulmonary bypass.

Conclusions. The discrete 3D-model of heat transfer in the layer structure of the myocardium and coronary vessels allows us to investigate the process of hypo- and hyperthermia with cardiopulmonary bypass. The simulation results also make it possible to perform the analysis of the temperature distribution on the surface of the myocardium provided free convection of heat between the layers.

Keywords: thermogram; myocardium; temperature distribution; vascular pathology.

QUANTITATIVE EVALUATION OF THE ABSOLUTE VALUE OF THE CEREBRAL BLOOD FLOW ACCORDING TO THE SCINTIGRAPHIC STUDIES WITH 99MTC-HMPAO // N.A. Nikolov, S.S. Makeyev, O.Yu. Yaroshenko, T.G. Novikova, M.V. Globa

Background. Represented by physical and mathematical model of cerebral hemodynamics, considered as a flow system.

Objective. Development of cerebral blood flow quantification procedure according to scintigraphy data with 99mTc-HMPAO.

Methods. Analytical, numerical and experimental study of the kinetics 99mTc-HMPAO in brain.

Results. For the purpose of quantitative assessment of volumetric cerebral blood flow according to the data of scintigraphy with 99mTc-HMPAO, it was suggested to view the brain as a flow system. This allows calculating volumetric cerebral blood flow after numerical determination of the model parameters according to the results of indirect angiography and establishment of effective blood dilution volume in brain using single-photon emission-computed tomography. In this case, the suggested blood flow calculation procedure does not require any a priori knowledge of hemodynamics in a certain reference area.

Conclusions. Preliminary clinical studies allow characterizing the suggested approach to calculation of volumetric cerebral blood flow absolute values as appropriate.

Keywords: brain; perfusion; cerebral blood flow; mathematical modeling; 99mTc-HMPAO; SPECT.

APPROPRIATE NUMBER AND ALLOCATION OF RELUS IN CONVOLUTIONAL NEURAL NETWORKS // V.V. Romanuke

Background. Due to that there is no common conception about whether each convolutional layer must be followed with a ReLU, the question on an appropriate number of ReLUs and their allocation is considered.

Objective. The goal is to find a law for ascertaining an appropriate number of ReLUs. If this number is less than the number of convolutional layers, then the law shall stand for an appropriate allocation of ReLUs.

Methods. A method of evaluating performance on the EEACL26 and CIFAR-10 datasets over various versions of ReLUs’ allocation is defined. The performance is evaluated through 4 and 8 epochs for EEACL26 and CIFAR-10, respectively, for each allocation version. The best scores of performance are extracted.

Results. In convolutional neural networks with 4 or 5 convolutional layers, the first three convolutional layers shall be followed with ReLUs, and the rest of convolutional layers shall not be ReLUed. It is plausible that appropriateness of ReLUs includes from-the-start compactness of allocating them, i. e. all ReLUs are allocated one by one from the very first convolutional layer. An appropriate number of ReLUs is an integer between a half of the convolutional layers’ number and the half increased by 1.

Conclusions. In some cases, the gain can grow up to 100 % and more. The gain for CIFAR-10, if any, is of roughly 10 to 20 %. Generally, as the training process goes on, the gain expectedly drops. Nevertheless, the stated appropriateness of number and allocation of ReLUs rationalizes the convolutional neural network architecture. Convolutional neural networks under the appropriate ReLUs’ allocation can be progressively optimized further on its other hyperparameters.

Keywords: convolutional neural network; ReLU; EEACL26; CIFAR-10.

QUANTIFICATION OF ANATOMICAL AND FLUID-DYNAMIC ANOMALIES IN FONTAN PATIENTS BASED ON MAGNETIC RESONANCE IMAGING // G. Signorini, S. Tirelli,  F. Piatti,  F. Pluchinotta,  S. Siryk,  E. Votta,  M. Lombardi, A.. Redaelli

Background. Univentricular diseases are lethal congenital diseases affecting about 2 % of newborns in the western world. Due to these pathologies, only one ventricle pumps blood into the circulatory bed, and arterial and venous blood are mixed, preventing from properly providing tissues and organs with oxygen. These pathologies are currently treated through the so-called Fontan procedure, which is a multi-step and complex surgical approach. The Fontan procedure aims at obtaining the anatomical separation between the systemic and pulmonary circulations, and hence between oxygenated and non-oxygenated blood. However, the only ventricle present in the heart remains the only pumping organ, and blood flow in the pulmonary circulation is merely passive. Also, and importantly, the post-surgical anatomy of the junction between systemic veins and pulmonary arteries is markedly non-physiological. As such, it is associated with altered blood fluid dynamics, undesired energy losses, and, ultimately, sub-optimal quality of life and short life expectancy.

Objective. On this basis, clinicians need tools to 1) quantify the post-surgical anatomical and fluid-dynamic alterations,                2) correlate these anatomies to the patients’ prognosis, and 3) identify criteria to improve Fontan surgery.

Methods. In order to support the pursue of these goals, we developed a computational tool for the processing of 4D flow data, i.e., phase contrast magnetic resonance images yielding information on the velocity of tissues within a 3D domain. The tool allows for reconstructing the 3D geometry of the surgically treated anatomical district and, through a semi-automated user-interface, extracting relevant geometrical scores, as well as quantifying flow rates in the different vessels, energy losses, and wall shear stresses. A numerical method based on the finite element approach was implemented to estimate relative pressures.

Results. The developed tool was preliminarily applied to the analysis of the datasets of six pediatric patients. The analysis of data obtained by two independent users highlighted a good repeatability of geometrical reconstructions, and hence of the quantification of geometrical scores. The method for the quantification of relative pressures was preliminarily tested in a simplified model of the thoracic aorta, with encouraging results.

Conclusions. The developed computational tool, which, to the best of our knowledge, is completely novel, helps clinicians to quantify the post-surgical anatomical and fluid-dynamic alterations. Ongoing activities include its application to the real datasets, and the extension of the analysis to a wider cohort of patients, so to check for correlations between the quantitative geometrical and fluid-dynamic indexes with the patients’ prognosis. Such possible correlations could help identifying criteria to improve Fontan surgery.

Keywords: magnetic resonance imaging; 4D flow; fluid dynamics; Fontan procedure.

WEAR BY FRICTION IN A PAIR WITH FIXED ABRASIVE COMPOSITE MATERIALS BASED ON IRON AND SELF-FLUXING ALLOY // A.A. Demidenko, A.N. Stepanchuk, A.A. Klekov

Background. Creation of theoretical and technological foundations of iron-based powder composite materials and self-fluxing alloys to work under the effect of abrasives is an urgent task that requires setting the dependence of the final product properties on the composition and the conditions of its obtaining.

Objective. The aim of the paper is to study the influence of the composition of composite materials based on iron-doped self-fluxing alloy and method for producing products from them in their resistance under abrasive wear.

Methods. The method of the study of frictional material wear process in contact with the fixed abrasive is developed. The investigation of density, structure and properties was carried out using modern methods and equipment for determining the mechanical characteristics, optical and electron microscopy and computer technologies.

Results. The analysis of the published data is carried out in order to establish promising materials for the manufacture of powder materials of tribological purpose for work in the conditions of action of abrasives. It is shown that the material may be powder compositions of iron and self-fluxing alloy which abrasion resistance may be significantly larger than existing content by SFA composition which has a relatively high hardness and wear resistance. It is found that the abrasion resistance under the influence of fixed abrasive material depends on the composition, method and technological parameters of its compaction. The increase of self-fluxing alloy content in the composite material, its porosity reduction, the presence of interaction between phase components increases its resistance to abrasion wear. It is shown that formation of self-fluxing alloy solid carcass in the material structure and its layer thickness increase improve the durability. According to the study results, the highest wear resistance got materials containing iron-based SFA of more than 30 %, obtained by pressing the blanks, and subsequent sintering and vacuum impregnation. The results are explained with the use of modern ideas about the mechanisms of deterioration when exposed to fixed abrasives.

Conclusions. The dependence of the resistance to abrasion when subjected fixed iron-based abrasive powder composite materials and self-fluxing alloys depending on their composition, the method and conditions of preparation, structure, and wear conditions was determined. It is shown that self-fluxing alloy content increase in the composite material, its porosity reduction, the presence of interaction between phase components increase its resistance to abrasion. It is shown that formation of self-fluxing alloy solid carcass in the material structure and its layer thickness increase improve the durability, in case if its content in the com-position is more than 20 %.

Keywords: composite material; iron; self-fluxing alloy; structure; abrasives; durability; pressing; sintering; hot stamping.

LASER TECHNOLOGY USE FEATURES IN THE CONDITIONS OF MODERN STATE OF UKRAINIAN INDUSTRY // V.P. Kotlyarov, A.N. Kiyaschenko

Background. The economic decline of Ukraine is mainly caused by the decrease of industry part with the high level of value-added in the wares in GDP. The ineffective use of modern equipment in modern technologies is related to the decrease of competence of engineering skilled workers and all-round violation of technological discipline of preproduction. Besides, most technological operations are executed on principle of “job shop” by small LTD or other with low production culture.

Objective. Creation of the simplified methodology of technological preparation of the most widespread laser treatment operations that does not require the special multicriterion researches.

Methods. The essence of the worked out methodology consists in the implementation of procedure in two stages: on the first one requirements to the object are covered, that can be taken into account as a result of the simplified decisions of thermal tasks of heating and destruction of material by a laser ray, are taken into account. The second stage of planning envisages implementation of other requirements to the results of technological operation due to modernization of treatment scheme and use of the created engineering facilities.

Results. For treatment of hardware (leaks, cups, scratch marks, collars, engraving and contour undercut) the simplified analytical decision of heat-conducting equalization that is adequate during the temporal and power stabilizing of procedure of irradiation is used. The contour undercut of wares of non-metals (wood, plastics) is designed on the worked out scheme with adaptive organization of technological operation. Implementation of this stage of planning envisages the use of the special backer-ups of operation. The observance of requirements to the indexes of quality of operations is realized on the second stage by perfection of irradiation procedure, with the use of lenses of special construction that promote its stability.

Conclusions. The executed developments allowed achieving the goals – operative technological providing of laser treatment operations – using the analytical design of treatment processes and additional perfection of operations by the use of the special engineering facilities.

Keywords: technology; laser; technological operation; engineering facilities; design of process; adaptive form of organization.

EFFECT OF THE LOCAL CROSS-STREAMLINED OBSTACLES ON THE VELOCITY AND PRESSURE FLUCTUATIONS // V.M. Turick, V.A. Voskoboinick, A.V. Voskoboinick

Background. Developing means to enhance the effectiveness of mass and heat transfer processes on streamlined surfaces and their hydroacoustic qualities in the objects of power, aerospace and marine engineering.

Objective. The purpose of the research is to determine the formation features and space-time characteristics of the velocity and wall-pressure fluctuation fields in flows above and on the streamlined surfaces with local obstacles as the cross-streamlined half-cylindrical trench on a flat surface and circular obstacle on the flexible longitudinal hydroacoustic antenna surface.

Methods. The research was carried out by means of hot-wire and hydroacoustic measuring in flows on streamlined obstacles and spectral analysis of statistical characteristics of the velocity and wall-pressure fluctuations in investigating systems.

Results. It has been determined experimentally the zones and conditions of vortices formation by various frequency ranges, the extremes of power spectrum densities of the velocity and wall-pressure fluctuations, vortex interaction, ejections and stalls near streamlined surfaces with local obstacles at rather wide Reynolds number ranges.

Conclusions. Basing on received space-time characteristics of the velocity and wall-pressure fluctuations and discovered typical features of their spectra the hydromechanical mechanisms of heat and mass exchange and hydroacoustic processes in the investigated systems have been determined. The results of the study can be used for designing of such systems and they reveal the perspective of directed control by mentioned processes for increase of their efficiency.

Keywords: half-cylindrical trench; circular obstacle; velocity fluctuation field; wall-pressure fluctuations; energy spectra; hydroacoustic measurements; heat and mass exchange.

EDUCATION THROUGH THE LIFE (TO 100TH BIRTH ANNIVERSARY OF G.G. YEFIMENKO)

The article dwells upon the 100th birth anniversary of G.G. Yefimenko.

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