UDC 621.372.061
Visualization of Surface Conductivity Distribution by Conductivity Zones Method / Sushko I.O., Rybin O.I. // Наукові вісті НТУУ “КПІ”. – 2014. – N 5. – P. 7–17.
The usage of modification method for direct EIT problem solving is substantiated. The voltages on phantom contour with known current approximation of surface conductivity distribution are calculated. The classical algorithm with Newton–Raphson method for inverse EIT problem solving is shown. That is “refinement” of surface conductivities by results of analysis. The conductivity zones method to reduce the order and time of calculations is described (transition from solution of the equation with 1000 order to 16 times solving the equations with 14 order). The regularization method by A.N. Tykhonov to solve the problem of ill-conditioned derivatives matrices from transfer resistances (nodal voltages) on surface zones conductivities solving the image reconstruction problem in EIT is considered. The algorithm of fast iterative updating regularization algorithm is given. It allows solving the problem by 10–20 steps instead of 1000–1000000 steps of classic algorithm. The expediency of classifier creating to assess the presence or absence of heterogeneity compared to uniform phantom is shown.
Keywords: Electrical Impedance Tomography, conductivity, conductivity zones, direct and inverse problem, image reconstruction, Newton–Raphson method, regularization by A.M. Tykhonov, phantom, inhomogeneity.
Fig. 4. Тabl. 4. Refs.: 32 titles.
UDC 621.577 + 697.1
The Efficiency of the Heat Pump in the Heating System Using Heat from Exhaust Gases after the Condensing Boiler Bezrodny M.K., Prytula N.O. – 4 – N 5 – P 18–23
The thermodynamic efficiency of heat pump hot water supply schemes using heat from exhaust gases after the condensing boiler was determined. It was established, that there is the optimum degree of cooling of the flue gases in the evaporator heat pump, which corresponds to the maximum specific useful effect received from the exhaust gases heat utilization by HP based on the cost to the heat pump compressor drive. The dependence of the optimum degree of cooling of the flue gases in the evaporator of heat pump has been calculated, water temperature at the inlet to the condenser of heat pump is in the range 10–35 °C and the temperature of water in the hot water supply is in the range 45–55°. The optimum degree of cooling of the flue gases in the evaporator heat pump allows you to get the maximum specific useful effect received from the exhaust gases heat utilization by HP based on the cost of the heat pump compressor drive.
Keywords: heat pump, hot water system, condensing boiler, exhaust gases, optimal temperature, maximum specific useful effect.
Fig 4 Refs.: 10 titles.
UDC 621.433
Comparative Analysis of Models of Heat Transfer in the Cylinder of Stationary Gas Engine 11GD100M / Marchenko A.P., Osetrov O.O., Kravchenko S.S. // Наукові вісті НТУУ “КПІ”. – 2014. – N 5. – P. 24–31.
Heat transfer process in the cylinder of a stationary gas engine pre-chamber – torch ignition of lean fuel-air mixtures and qualitative power regulation was studied and mathematically modelled. During the investigation of heat transfer in the cylinder of the gas engine the components obtained by the results of experimental research of internal thermal balance were analyzed. It was shown that heat transfer in the cylinder 11GD100M has distinctive features compared to the known petrol and diesel engines. The analysis of the temperature condition of the combustion chamber of the engine parts 11GD100M was carried out. According to the results of the experimental data, the empirical dependence of the average temperature of the cylinder wall of the geometrical and operational parameters was obtained. The empirical and semi-empirical models for determining the heat transfer coefficient were analyzed. According to the analysis of the internal heat balance, heat transfer model for application in a gas engine 11GD100M was chosen. It was shown that for the calculation of heat transfer in the test engine, the mathematical models of V. Annand and G. Rosenblit provide the most accurate results.
Keywords: gas engine pre-chamber-torch ignition, internal heat balance, the wall temperature, heat transfer, heat transfer coefficient.
Fig. 5. Тabl. 4. Refs.: 13 titles.
UDC 621.311
Identification of Low Frequency Oscillations Using Synchrophasor Measurements / Yandulskyy O.S., Matseyko V.V. // Наукові вісті НТУУ “КПІ”. – 2014. – N 5. – P. 32–38.
The actual questions of the study of low-frequency oscillations of power in the interconnected power system (IPS) of Ukraine in terms of introduction of modern Wide Area Measuring System (WAMS) are considered. The algorithm for identifying modes of oscillations by means of using recordings from the Phasor Measurement Units of a WAMS using spectral analysis and calculation of the main characteristics of identified fluctuations is developed. Reliability and adequacy of the algorithm is tested by comparing the results of calculations with traditional calculations of modal analysis of power system in DigSilent Power Factory. Several WAMS recordings in case of significant disturbances in the mainline power grids IPS of Ukraine were analyzed using an offered algorithm and results of analysis of frequency oscillations basic properties are presented. The level of danger of identified fluctuations in terms of under-damping of identified oscillations and a possible violation of the vibrational stability of the power system for the case of a cascade failure of Uglegorskaya TPP is clearly reflected in the article.
Keywords: low frequency oscillations, Wide Area Measuring System, spectral analysis, modal analysis, damping.
Fig. 4. Тabl. 2. Refs.: 10 titles.
UDC 519.8
Optimization Models and Algorithms for Network Problems of Resours’ Distribution / Alexandrova V.M., Kirik O.E. // Наукові вісті НТУУ “КПІ”. – 2014. – N 5. – P. 39–45.
The efficient algorithms for nonlinear programming problems for calculating networks have been offered, as well as the new network models to determine the optimal flows and distribution of resources have been constructed. The problems with nonlinear objective functions of general form and network structure of restrictions, which allow reaching quite a wide range of networks using common approach, were considered. For calculations the modifications of well-known methods of nonlinear programming were applied. The proposed methods of the first order is comparable by convergence rate with the methods of sequential quadratic programming through an efficient algorithm for the solution of the auxiliary quadratic problems and convenient procedure of step factor calculation. A series of models of resource distribution problems, taking into account the customers’ orders, the variable performance of sources and temporary storage of the product, was analyzed and numerically tested. The comparison of calculation results of applied problems using a standard package Solver and a specially designed computer program by the method of linearization of B.M. Pshenichniy demonstrated the possibility of reducing the number of iterations in the procedures of the same order by several times. The constructed models and algorithms of optimization of flow distribution allow creating effective information-analytical system for optimum control of functioning of the network distribution systems.
Keywords: problems of flow distribution, network models, methods of nonlinear programming, optimization algorithms.
Fig. 5. Refs.: 8 titles.
UDC 519.766.4
Optimization of Reinsurance Strategies Using DSS / Bidyuk P.I., Kozhukhivska O.A., Polishchuk V.Yu. // Наукові вісті НТУУ “КПІ”. – 2014. – N 5. – P. 46–54.
The basic purpose of the work is a study of existing approaches to reinsurance directed towards modeling of distribution and minimization of risk for an insurance portfolio, and forming a strategy for its optimal reinsurance using developed decision support system. A method for a search of optimal reinsurance strategy is proposed. For this purpose statistical models were selected that correspond to the structure and volume of portfolio losses as well as the number of these losses. The simulation model for the total insurance losses is developed. While finding an optimal reinsurance strategy it was taken into consideration the dependence of the load coefficient on a specific form of reinsurance. A numerical study of the dependence between optimal reinsurance strategy and the varying load coefficient has been performed. It was established that taking into consideration of the variable load coefficient for specific risk capital values for an insurance company the stop-loss strategy provides worse results than other forms considered. An architecture and the functional layout for decision support system are proposed, and appropriate software was developed in C#. The DSS functioning has been illustrated on simulated example. The system will provide a useful instrument for a business analytic to support decision making while selecting a strategy for insurance portfolio.
Keywords: modeling in reinsurance, optimization of reinsurance, load coefficient, decision support system, choice of reinsurance strategy.
Fig. 3. Refs.: 7 titles.
UDC 004.032.26:004.93
A 2-Layer Perceptron Performance Improvement in Classifying 26 Turned Monochrome 60-by-80-Images Via Training with Pixel-Distorted Turned Images / Romanuke V.V. // Наукові вісті НТУУ “КПІ”. – 2014. – № 5. – С. 55–62.
There is tried 2-layer perceptron in classifying turn-distorted objects at acceptable classification error percentage. The object model is a letter of English alphabet, which is monochrome 60-by-80-image. Neither training 2-layer perceptron with pixel-distorted images, nor with turn-distorted images makes it classify satisfactorily. Therefore in classifying turn-distorted images a 2-layer perceptron performance might be improved via training under distortion modification. The modified distorted images for the training set are suggested as mixture of turn-distorted and pixel-distorted images. Thus the training set is formed of pixel-distorted turned images on the 26 alphabet letters pattern. A performance improvement is revealed when there are passed much more training samples through 2-layer perceptron. This certainly increases traintime, but instead 2-layer perceptron can classify either of pixel-distorted images and pixel-distorted turned images. At that the trained 2-layer perceptron is about 35 times faster than neocognitron in classifying objects of the considered medium format.
Keywords: automatization, object classification, neocognitron, perceptron, monochrome images, pixel-distortion, rotation, turn-distortion, training set, classification error percentage.
Fig. 10. Refs.: 11 titles.
UDC 681.518.25
Adjustment of the Iterative Reclassification Method for Including the Rejected Applications into the Credit Scoring / Soloshenko O.M. // Наукові вісті НТУУ “КПІ”. – 2014. – N 5. – P. 63–69.
The objective of the research is the adjustment of the Iterative Reclassification Method for including the rejected applications into the credit scoring. The methodology of implementation uses partially classified data and the logistic regression generalization. The method of the adjustment the Weight Of Evidence and the Information Value indicators using the rejected loan applications is proposed at the first stage. The process of including the rejected applications into predictive power analysis of characteristics has been demonstrated, providing alternative and adjusted discretization process for the continuous variables. The method of including the adjusted Weight Of Evidence and the partially classified rejected applications into logistic regression procedure is proposed at the second stage. The general method of the Iterative Probability Recalculation is proposed at the final stage, using the adjusted logistic regression approach. The research results are the significant improvement of the Iterative Reclassification Method and the generalization of the logistic regression application. As a conclusion, the main advantages of the method are given in comparison with the classical Iterative Reclassification Method, for instance, the probabilistic duality of the rejected applications is mentioned here.
Keywords: credit scoring, reject inference, logistic regression, Weight Of Evidence, Information Value, partially classified data, data mining, binary classification, Iterative Reclassification Method.
Fig. 2. Refs.: 8 titles.
UDC 621.923.6:621.318.4:621.002.3
Effect of Diamond Honing Technological Factors for Parameters of Roughness and Exactness of Composite Sliding Bearings Surfaces for Printing Machines / Gavrish А.P., Кyrychok P.O., Roik Т.A., Vitsuk Yu.Yu. // Наукові вісті НТУУ “КПІ”. – 2014. – N 5. – P. 70–75.
In a paper the research results concerning an influence of honing process’ technological factors such as abrasive tool composition, cutting parameters, number of hones in honing head on surface roughness and surfaces’ exactness of new composite sliding bearings manufactured of new high-alloy composite alloys from tool steels wastes for high-speed printing machine have been presented. Results have shown, that quality parameters of surfaces roughness and exactness depend on structure of diamond tool, bond type of diamond tool, granularity of diamond hones, cutting parameters for fine honing technology process. Final quality of surfaces depends on value of cuttings section, interaction of force and temperature factors, which are formed at diamond grain cutting zone of honing tools. Recommendations were presented for choice of the diamond hones tools and cutting parameters for practical purposes to meet the quality requirements of high-speed bearings friction surfaces for printing machines.
Keywords: new composite alloys, quality surfaces, diamond tool, honing process, cutting parameter, printing machine.
Fig. 5. Tabl. 2. Refs.: 12 titles.
UDC 669.184.244.66.012.1
Control Oxygen-Converter Process in Closed Loop / Bogushevsky V.S., Zhuk S.V., Bondarenko E.K., Kapysnyak A.O. // Наукові вісті НТУУ “КПІ”. – 2014. – N 5. – P. 76–83.
The work was done in order to increase the efficiency of BOF smelting by constructing closed-loop control system. The creation of BOF melt models was based on the combined modeling method, which includes deterministic, probabilistic and heuristic approaches, methods of automatic classification and the positive experience of the previous administration. A closed-loop system including a static, dynamic and closed control model BOF steelmaking process was developed. Static model provides payment options to begin the process of melting, dynamic – decarbonization rate calculation, changes in temperature and burn-up rate during purging impurities. Developed a closed-loop control adaptation held under 160-tonnage converters PJSC “ArcelorMittal Kriviy Rih”. Economic effect of implementing a control system converter process is achieved through the issuance of heats on the specified steel grades, higher weight yield, improve product quality, saving time and materials. Closed-loop control provides settings for optimal process control.
Keywords: converter, purge, model, management, system..
Fig. 2. Refs.: 15 titles.
UDC 621.785
Diffusion Coatings with the Participation of Titanium, Aluminium and Silicon on Surface of the Steel 12X18H10T / Khyzhnyak V.H., Arshuk M.V., Datsyuk O.E. // Наукові вісті НТУУ “КПІ”. – 2014. – N 5. – P. 84–88.
Patterns of forming a multilayered diffusion coatings after complex saturation of titanium, aluminum and silicon to steel to improve heat resistance 12Cr18Ni10Ti were obtained and studied. The possibility of obtaining titanium-aluminum-silicon layers on steel 12Cr18Ni10Ti powder in containers with a gate in unpressurized conditions at temperature 1050 °C and with duration 4 hours was studied. As initial components powders of titanium, aluminum, silicon, aluminum oxide, ammonium chloride were used. The phase and chemical composition, structure and micro-hardness of the obtained coatings were investigated. For titanation and titanium-calorizing, coating phase composition consists of compounds zone Ti4Fe2O, Fe2Ti, TiS, the transition zone and for titanium-aluminum-silicon: Ti3(Al,Fe), (Fe,Al,Ni)2Ti, (Fe,Al,Ni)Ti, Ti(C,N,O) and the transition zone. In titanium-aluminum-silicon content in the coating zone Fe2Ti compounds in the layer is 1,5 % by weight, and in the transition zone at the boundary with the zone of connection – 1,2 % by weight. During oxidation of obtained coatings, degradation carries out in phase composition and structure. Heat-resistance of steel 12Cr18Ni10Ti with titanium aluminum siliconized coating increases 4,0 times in comparison with steel without coating.
Keywords: steel 12Cr18Ni10Ti, powder method, diffusion coatings, titanation, titanium calorizing, titanium-aluminum-silicon, microhardness, heat resistance, porosity.
Fig. 2. Tabl. 1. Refs.: 11 titles.
UDC 620.22:620.187.22:543.442.3
Formation of Structure and Phase Composition in Ecviatomic Alloys of Cu–Ni–Al–Fе–Cr System Synthesized by Mechanical Alloying / Yurkova A.I., Chernyavsky V.V., Kravchenko O.I., Kalian B.A. // Наукові вісті НТУУ “КПІ”. – 2014. – N 5. – P. 89–95.
Nanocrystalline equiatomic high-entropy alloys (HEAs) have been synthesized by mechanical alloying in Cu–Ni–Al–Fе–Cr system from the binary CuNi alloy to the quinary CuNiAlFeCr alloy. By using X-ray diffraction analysis structure and phase evolution during mechanical alloying (MA) in binary to quinary alloys selected from Cu, Ni, Al, Fe и Cr in sequence were investigated. Binary CuNi alloy formed solid solution with face-centered cubic crystal structure in nanocrystalline state. Ternary to quinary alloys (CuNiAl, CuNiAlFe CuNiAlFeCr) first formed solid solution with body-centered cubic crystal structure in nanocrystalline state and then transformed into XRD-amorphous phase at the end of MA. No precipitation of the second phase such as intermetallic phase was found. The alloying sequence for the present alloy system during MA is determined as CuNiAlFeCr in the order of decreasing alloying rate. The alloying rate is found to correlate with the melting temperature of the elements. This correlation is explained through the effect of melting temperature on solid diffusion.
Keywords: high entropy alloys, mechanical alloying, X-ray diffraction, structure, phase composition, diffusion.
Fig. 4. Tabl. 5. Refs.: 20 titles.
UDC 621.384.3
Improvement of Calculating Medical Thermovision Camera Minimum Resolvable Temperature Difference / Ahmed Malik Lazim Al-Mzirawi, Kolobrodov V.G., Mykytenko V.I. // Наукові вісті НТУУ “КПІ”. – 2014. – N 5. – P. 96–100.
The paper is devoted to improvement of the equation for calculating the minimum resolvable temperature difference (MRTD) of medical thermovision camera by means of more sophisticated models of thermal images visual perception. An MRTD calculating algorithm, which is based on a more reliable approximation of the visual system modulation transfer function by Schultz, is considered. We obtain new expression for the bandwidth of Schultz’s approximation, which does not depend on the angular size of the Foucault pattern bar. An improved equation for calculating the MRTD was obtained. Analysis of the equation has showed that it coincides with the well-known equations for Foucault pattern bar with appointed angular size. The limits of validity of this equation in the visual system spatial integration from 1 to 5,7 arc. minute were determined. An example calculation for Thermal Eye TSC Imager MRTD was fulfilled. There were received two differing analytical MRTD equations, which use Schultz and Lloyd approximations. It is shown that these equations coincide with each other when pixel angular size of microbolometer matrix is equal to 0,71 mrad.
Keywords: medical thermal imager, minimum resolvable temperature difference, modulation transfer function.
Fig. 4. Refs.: 6 titles.
UDC 577.169:611.814
Model of Plane Distribution of Heat Sources for Multi-Channel Matrix Oxygen Sensors / KotovskyiV.Y., DzhezheryaYu.I., DovzhenkoO.P., GrischukA.M. // Наукові вісті НТУУ “КПІ”. – 2014. – N 5. – P. 101–105.
Transcutaneous polarography is one of the most objective noninvasive assessment of the capillary blood flow and microcirculation by controlling the oxygen partial pressure in the subcutaneous tissue. The outcome of research is influenced by such common factors as the oxygen content in the ambient air, the adequacy of the central hemodynamics of the patient, the presence of violations of the transport function of the blood, the pathology of the pulmonary system and local factors (disturbance of the local microcirculation, tissue edema, marked capillary spasm, etc.). For research purposes single-channel analyzers are generally used. Increasing the informative value of biomedical research is possible due to the use multi-channel raster array of oxygen sensors as a primary sensor. The use of such matrices will provide information about the in vivo distribution of the partial pressure of oxygen from the surface of the human skin, to more complete assess of its functional state and dynamics to control the impact of possible therapeutic interventions. The paper analyzes the influence of heat sources on the distribution of temperature field of multi-channel raster array of oxygen sensors as the main component of its operation and determines the optimum configuration of such sources.
Keywords: partial pressure of oxygen, transcutaneous sensor, matrix oxygen sensors.
Fig. 3. Refs.: 12 titles.
UDC 615.84:615.472.03:615.847.8
Using of Thermal Imaging in the Study of the Temperature Distribution of Myocardial Danilova V.A., Shlykov V.V. – 4 – N 5 – P 106–111
Qualitative comparative analysis of thermal infarction was conducted using thermograph in the spectral range 8–14 microns. Quantitative assessment of myocardial temperature measurement accuracy is made depending on the ambient temperature. Based on the proposed approach to the analysis of thermal images infarction, researching area of temperature on the surface of the myocardium, which give a clear picture on the distribution of the internal temperature and the level of the microcirculation in the myocardium and vessels, were conducted. Development of method requires the use of infrared thermography (IRT), allowing to record the temperature of the heart and identify the interconnection between the electromechanical characteristics of the myocardium according to ECG and temperatures on the surface of the myocardium. Method for graphic representation of thermal image of the myocardium for open heart allows you to control the temperature of the operating area during operations on the heart. An integrated approach to distance control of temperature allows controlling uniformity of temperature protection, determine the level of cooling in different temperature zones, and significantly improves the security of the controlled cessation of blood circulation in vital organs.
Keywords: thermogram myocardium, temperature distribution, vascular pathology.
Fig. 7. Refs.: 11 titles.
UDC 535.241.62
Metrological Analysis of Integrating Sphere Photometers for LED Luminous Flux Measurement / Mikheenko L.A., Kovalenko A.V. // Наукові вісті НТУУ “КПІ”. – 2014. – N 5. – P. 112–118.
A comparative metrological analysis using mathematical models of three integrating sphere photometer schemes, for LED luminous flux measurement, was held. Each model takes into account the main design parameters of the photometer, typical values of which are used in the calculations. It's shown, that for given initial conditions, the greatest contribution to the total error for schemes with LED on the wall of sphere and in the center of sphere introduces instability of sphere reflectance coating, and for the scheme with LED in front of entrance aperture of sphere, for total luminous flux measurement, – instability of the distance to the diaphragm. In general, the highest accuracy for total luminous flux measurement have a scheme with LED in the center of the sphere, somewhat lower – a scheme with LED on the wall of sphere, and the lowest – a scheme with LED in front of input aperture of the sphere. The substantiated recommendations on the best practical application of each of the schemes are given. Also, for all schemes dependencies of the total relative error on the primary errors of basic design parameters, that can be used to select the optimal scheme of the photometer and selection of optimal values of design parameters are given.
Keywords: metrology, optical radiometry, photometry, LEDs flux measurements.
Fig. 5. Tabl. 3. Refs.: 12 titles.
UDC 681.758
Limiting Characteristics of Coherent Spectrum Analyzer / Tymchyk G.S., Nguyen Q.A., Kolobrodov M.S. // Наукові вісті НТУУ “КПІ”. – 2014. – N 5. – P. 119–123.
The influence of the component dimensions and parameters of a coherent optical spectrum analyzer on its performance was studied. One of the criteria for evaluating the performance of this instrument are the spatial resolution and the spatial bandwidth product. The purpose of this article is to study the dependence of the limiting characteristics on the changing of the component parameters of the coherent spectrum analyzer. It was considered, that the influence of the Fourier lens aberrations and the geometric dimensions of the CCD sensor on the spectral resolution and spatial bandwidth product in the schema of the analyzer, where the input transparency is located at the front focal plane of the Fourier lens. As the input transparency we used a circular aperture. The expressions, that show the dependence of the limiting characteristics on the size of the system components, were obtained in the case of using matrix sensor of a large resolution. The following example shows that the large size of the sensor allows obtaining the high spatial resolution and the large spatial bandwidth product of the device.
Keywords: coherent spectrum analyzer, spatial resolution, spatial bandwidth product, point spread function.
Fig. 2. Refs.: 5 titles.
UDC 546.18+54.183
Peculiarities of Sorbtion of Phosphates by Hydrous Oxides of the Elements of III and IV Groups Lesnichaya Т.V., Terikovskaya Т.Е., Visloguzova N.M., Kirillov S.А. – 4 – N 5 – P 124–129
Binary mixtures containing hydrous oxides of titanium, aluminum, lanthanum, and cerium with various ratio of ingredients have been synthesized by means of co-precipitation method from water solutions. The physical and chemical properties of the target materials have been characterized by X-ray diffraction, scanning electron microscopy, IR spectroscopy, porosity studies and pH titration. The sorption affinity of binary mixtures towards phosphate ions has been studied. The synthesized binary mixtures have a mezoporous structure with the pore size of 1–3,2 nm and the specific surface area of 242–432 m2/g. IR spectroscopy has shown that a mechanism of removal of phosphates with water solution by lanthanum containing materials is caused by the anion exchange process with participation of hydroxyl groups. рН titration has shown that binary mixtures are ampholytes. The mixture of Al(OH)3–La(OH)3 has the maximal exchange capacity of 9 mmol/g in acidic media and 6 mmol/g in alkaline media. Maximal exchange capacities towards phosphate ions are 522,5 mg/g (рН»» 2,5) for Al(OH)3–La(OH)3 and 294,5 mg/g (рН » 9) for Al(OH)3–Се(OH)4.
Keywords: sorption, phosphates, titanium (IV) hydroxide, lanthanum (III) hydroxide, aluminum (III) hydroxide, cerium (IV) hydroxide.
Fig. 9. Tabl. 1. Refs.: 10 titles.