UDC 621.317.3
Selection of Stabilitrons and Modes of the Power Supplies of Reference High-Voltage Installations of the Direct Current Brzhezytskyy V.O., Vendychanskyy R.V., Garan Y.O., Desiatov O.M. Naukovi visti NTUU P – 4 – N 1 – P 7–13
The problem of stabilitrons selecting for use in reference high-voltage installations of a direct current, calculation of a high voltage pulsations are observed at various modes of operation of such installations and definitions of methods of their amplitude decreasing. Problems of support of the stable power supplies of reference installation depending on characteristics of an alternating voltage source selection and the circuit design of this voltage transformation are analyzed. Researches of modes of the power supplies of reference installation over the operating voltage range from 1 to 180 kV are performed. It was found that the amplitude and character of voltage pulsations can have an effect on accuracy of scale high voltage transformation, and factor of pulsations ∆p essentially depends on operating conditions of reference installation. The obtained results have shown that increasing of resistance value of the filter is almost proportional to the decreasing of pulsations amplitude. Provisions for pulsations amplitude decreasing and raise of demands to stability of separate elements of reference installations are offered.
Keywords: the standard of a high voltage of a direct current, the stabilitron, voltage ripple, stability of the power supplies.
Fig 7 Тabl. 1. Refs 7 titles.
UDC 621.317.789
New Metod of Measuring of Symmetric Sequences of Three-Phase Voltage Makov D.K. Naukovi visti NTUU P – 4 – N 1 – P 14–19
This article concerns the digital determination of three-phase quality indexes of electric power – coefficient of asymmetry on a negative sequence, rejection and oscillation of fundamental frequency voltage. These indexes are characterized by voltages of negative (VNS) and direct (VDS) sequences of fundamental frequency. For determination of VNS (after analog-digital transformation with tuning of frequency of measuring of instantaneous values of linear voltages) it is possible to take advantage of two linear operations – selection of linear voltages of fundamental frequency and selection of measureable sequence. Traditional approach of VNS measuring uses just the same sequence of implementation of operations. Thus, accuracy requirements of selection of linear voltages of fundamental frequency are very high. And in obtained codes of linear voltages codes of VDS of fundamental frequency are dominant and inconclusive. Fundamental frequency is obtained further using complicated algorithm with the multi-bits calculations. Crushing down dominant and inconclusive VNS using addition of codes of instantaneous values of linear voltages after analog-digital transformation is proposed for determination of VNS of fundamental frequency. An algorithm is thus simplified in 20–50 times, accuracy requirements of subsequent selection of voltage of fundamental frequency decrease, VDS of most ultraharmonics disappears almost completely. VNS of fundamental frequency increases in 3 times as compared to its in linear voltages. VNS of fundamental frequency is further distinguished. The offered method of determination of voltage of symmetric constituents is characterized by simplicity and increased accuracy.
Keywords: indexes of quality of electric power, coefficient of asymmetry, symmetric systems of voltage of positive, zero, negative sequences.
Fig 2 Refs 8 titles
UDC 621.311.003.13
Selecting of Mathematical Models for Determination of Energy Production Facilities “Standards” on the Basis of a Multi-Criteria Approach Nakhodov V.F., Borychenko O.V., Ivanko D.О. Naukovi visti NTUU “КPІ”. – 4 – N 1 – P 2 –28
The necessity of improvement of approaches monitoring energy resources consumption efficiency, which are applicable today in Ukraine and are based on a system of rationing of specific expenses of fuel and energy, is analyzed. For this purpose the possibility of application of the operational management of fuel and energy resources consumption efficiency, which represent set of so-called systems of planning and control of energy consumption was shown. Some methods of energy resources consumption mathematical modeling which can be applied to establishment “standards” of power consumption in operative control systems of fuel and energy use efficiency are considered. Approach to a choice of the mathematical model for use on a number of quantitative criteria of their adequacy taking into account additional “qualitative” criteria allowing to take into account other advantages and disadvantages of the considered models is offered. The technique of numerical values determination of “qualitative” criteria by means of mathematical apparatus of fuzzy logic is given. For the purpose of choice problem solution of the method of modeling by several criteria at the same time possibility of technique application of criteria “importance” ranging, and also a method of the environment functioning analysis (DEA the analysis, Data Envelopment Analysis) is considered.
Keywords: operational control system of energy efficiency, “standard” of energy consumption, criteria of adequacy of mathematical models, fuzzy logic, technique of criteria “importance” ranging, DEA (Data Envelopment Analysis) analysis.
Fig 2 Тabl. 7. Refs 14 titles
UDC 66.041.491
Features of Shale Gas in rotary kilns Building Materials Industry Shcherbyna V.Yu. Naukovi visti NTUU “КPІ”. – 4 – N 1 – P 29–34
The possibility of shale gas usage in existing kilns of building materials industry is analyzed. The questions considering determination of thermal performance conditions of kilns for burning cement using nature and shale are studied. For a more complete modeling a mathematical model, compared with the known, taking into account such additional factors as the temperature of the exhaust gases and the conditions refractory lining wear during operation was applied. Conclusions are drawn about the possibility of structural elements furnace using shale gas: 1) significantly increases the amount of fuel requiring the installation of two or even three burners in the furnace unit; 2) low gas flow in the furnace is increased to ~ 300 °C requiring the selection of an appropriate type of refractory; 3) the temperature of the furnace body is increased to 35 °C–45 °C; 4) using the shale gas reduces the amount of secondary air, so it does not display significant impact on reducing fuel consumption. Hence there is the need for re-adjustment of the refrigerator, fans and ductwork used in the flowsheet. Thus, the direct application of shale requires replacement devices or nodes in the design of machines. Another option is to create a combined gas with a defined chemical composition by mixing oil shale and natural gas.
Keywords: shale gas, rotary kiln, temperature, the flow gases, heat transfer, mathematical model.
Fig 7 Refs 7 titles
UDC 519.766.4
Adaptive Short-Term Forecasting of Selected Financial Processes Bidyuk P.I., Konovalyuk M.M., Kuznetsova N.V., Pudlo I.V. Naukovi visti NTUU “КPІ”. – 4 – N 1 – P 35–41
A computer based system is proposed for adaptive modeling and forecasting of financial and economic processes, that is constructed with application of system analysis principles. A hierarchical structure of decision making process during forecasts estimation was taken into consideration and the methods were used for describing uncertainties of structural, parametric and statistical nature. To estimate model structure and parameters several mutually supporting estimation techniques were used as well as optimal state estimation procedure for dynamic systems that allowed take into consideration some types of structural and statistical uncertainties. Probabilistic modeling methods make it possible to consider uncertainties of probabilistic type. The problem of short term forecasting for gold price is considered as an example using a set of constructed regression models and Kalman filter for generating optimal estimates of states. The best forecasting results were achieved with optimal filter and autoregression models with trends. Also the models were constructed for conditional variance that provided acceptable quality forecasts for variance (volatility) that could be used for constructing decision making rules in trading operations.
Keywords: adaptive forecasting, system approach, nonlinear nonstationary processes, model structure and parameters estimation, complex criterion.
Fig 1 Тabl. 3. Refs 7 titles
UDC 669.184
Investigation of the Economic Efficiency of Automation Bof Production Bogyshevskiy V.S., Sukhenko V.Yu., Kadyhrob S.V., Shulga A.O. Naukovi visti NTUU “КPІ”. – 4 – N 1 – P 42–46
The influence of technological and human factors on the cost of steel, the improvement of the process and the organization of production were investigated. Technological factors include the basicity of slag, lining life, rate of oxygen input, changes in nitrogen content in the metal, clean of blowing, conditions of slag formation. Statistical relationship between the lining life and the basicity of slag was obtained. Found that the most important factors that affect the resistance lining this is a temperature in bath, chemical composition of the slag, duration of blowing time and idle time. Statistical relationship the action of average number turndown converter for melting on lining life was obtained. The study found that the control system can realize the basic provisions to reduce the cost of BOF steel, which is associated with an increase of scrap, lining life of the unit and weight yield, reduced material consumption, improve the process and the organization of production, reducing the duration of blowing and melting in general. The indicators received from the first turndown of the main parameters of melting – the carbon content and the temperature of the bath, and the simultaneous achievement of these parameters were presented.
Keywords: BOF, parameters of melting, cost of steel, APCS.
Fig 6 Refs 9 titles
UDC 669.715 ¢721¢782¢74–143/–126.4::669.017.16
Natural Aging of AlMg5Si2Mn Casting Alloy Boyko V.V., Prach O.L., Trudonoshyn O.I., Mykhalenkov K.V. Naukovi visti NTUU “КPІ”. – 4 – N 1 – P 47–53
The as-cast and heat treated structure of permanent mould and high pressure die castings of the AlMg5Si2Mn alloy has been investigated by differential scanning calorimetry, microhardness measurements, transmission electron microscopy and energy dispersive X-ray analysis. Curved plate-like precipitates were detected for both alloys inside the a-Al grains. Examination of these precipitates revealed a number of features, such as: 1) the composition of the precipitates is very close to the stoichiometric Mg2Si compound; 2) precipitates are aligned along dislocations; 3) the precipitate density is much higher for the high pressure die castings where the a-Al matrix contains more dislocations than in permanent mould castings; 4) precipitates lie inside the a-Al grains where they are randomly distributed. The Mg2Si lamellas were not observed between precipitates; 5) homogenization of the alloy results in complete dissolution of the precipitates and during artificial aging new needle-shaped precipitates are formed.
Keywords: aluminum casting alloy, precipitates, element distribution, natural hardening.
Fig 5 Таbl. 3. Refs 10 titles
УДК 621.923.6:621.318.4:621.002.1
Мгновенные контактные температуры при тонком алмазном шлифовании деталей из композитных материалов на основе отходов инструментальных сталей / Gavrish А.P., Roik Т.A., Кyrychok P.O., Vitsuk Yu.Yu. // Naukovi visti NTUU “КPІ”. – 2014. – N 1. – P. 54–57.
The results of experimental researches of momentary contact temperatures which appear on the end of diamond grain’ cutting edge at fine grinding of friction pieces of new composite materials on the base of utilized and regenerated grinding alloy tool steels’ wastes of 86Х6НФТ, 5Х3В3МФС and 7ХГ2ВМФ with solid lubricant CaF2 additives have been presented in this article. It was studied that the influence of abrasives composition and cutting parameters on temperatures value. It was shown the type grains material of diamond composition tool, granulosity of tools and abrasive disc’s material of bond have essential influence on the temperature field at fine grinding process. It was demonstrated that the for formation of high quality parameters of working surfaces of details made from new composites it is necessary to apply the diamond discs on the base of synthetic diamonds with granulosity 14–20 mm on elastic bond. The experiments showed the decrease in ~2,0–2,5 times of diamond disc granulosity reduces the momentary contact temperatures value. The minimization of temperature field in processing zone at fine diamond grinding of new composite alloys on the base of grinding wastes of tool steels takes place at using the fine-grain diamond tools.
Keywords: composite alloys, momentary contact temperatures, diamond tools, grinding parameters.
Тabl. 4. Refs.: 11 titles
UDC 621.791.763
Estimation of Mechanical Properties of Welded Joints Produced by Resistance Spot Welding with Electromagnetic Stirring / Kochubei V.V., Ryzhov R.M., Sydorenko P.Yu. // Naukovi visti NTUU “КPІ”. – 2014. – N 1. – P. 58–63.
The paper reveals investigation results of effect of external electromagnetic fields on mechanical properties of welded joints produced by resistance spot welding. Results of research of external electromagnetic fields effect on the mechanical properties of constructive and stainless steels and joints made from different materials were presented. Samples which are suitable for performing static-load tests of spot welding for the minimization of data misrepresentation were proposed and the analysis was performed. The results of shear and peel tests for different thickness samples made from structural steel St3, stainless steel 12X18Н10T were presented as well as those for different joints made from these materials. The tendencies of changes of mechanical properties for joints made from structural and stainless steels and for those made from different metals for different thicknesses and for different values of the external magnetic field induction were presented. Basing on the analysis of data obtained during the static-load tests the range of values of the external magnetic field was determined which allows producing the welded joints with the highest effect on their mechanical properties. The application of external electromagnetic fields in the spot welding with the optimal value of magnetic field induction of constructive and stainless steels and joints made from materials with different thickness allows increasing shear strength up to 10 % and tear strength – up to 50 %.
Keywords: resistance spot welding, external electromagnetic fields, static load tests, mechanical properties of the joints.
Fig. 5. Тabl. 1. Refs.: 6 titles.
UDC 621.6.078
Flows Features in the Internal Channels of Involute External Gear Pumps Stryczek J., Kostiuk D.V., Yakhno O.M. Naukovi visti NTUU “КPІ”. – 4 – N 1 – P 64–7
Results of investigations of external gear pump with involute tooth profile which goal was to obtain the flow patterns in the suction and discharge chambers, and in meshing region and examining the effect on them of operating parameters of the pump were presented. Flow patterns were obtained by visualisation of fluid flow with a high-speed video recording of working process of the pump with a lid made of a transparent material. As result of video analysis appearance of cavities in the fluid closed in trapped volume was found. Process of the emergence of a cavitation bubble, its growth and collapse was reviewed. The calculation dependencies that link up dimensions of cavitation bubbles and the pressure in the surrounding liquid were shown. The change of the trapped volume dimensions for given pump and type of pressure changes inside were determined. Using p-theorem dependencies in dimensionless form were obtained, criterion analysis of the results was performed showing the dependence of the pressure in the trapped volume from a number of complexes, such as centrifugal Reynolds number. It was revealed that in the trapped volume compression of fluid and cavitation occur; intensity depends on the operating conditions of the pump.
Keywords: gear pump, flow visualisation, trapped volume, cavitation.
Fig. 8 Тabl. 1. Refs. 7 titles.
UDC 535.51; 537.5
Polarization Characteristics of Electroluminiscence, that Accompanies Electric Breakdown of p–n-Structures on Silicon Carbide Genkin A.M., Genkina V.K., Germash L.P. Naukovi visti NTUU “КPІ”. – 4 – N 1 – P 71–78
Spectral dependence of the linear polarization extent of electroluminicsence, which accompanies the electric breakdown of alloyed p–n-structures, made on the base of SiC–4Н, 6Н, 15R polytypes, and аlso cubic silicon carbide in the range of 1,4–3,8 еВ have been obtained for the first time. The structures have been placed on the crystal faces, which are parallel and perpendicular to the crystallographic axis С. The luminescence was lead out from the side of thin р-region perpendicularly, and also at the sharp angle to the operating crystal face. The components of luminescence which are polarized linearly in the parallel and perpendicular to the crystallographic axis С (Е||С, Е^С) plane, and also parallel to the vector F of electric field tensity in the p–n-junction (Е||F) have been revealed. Spectral location and intensity of the component, connected with direction of the axis С, have essential differences in different polytypes. Common feature for all polytypes is the presence of polarization (with the level of 0,3–0,4) in the plane Е||С in the region of fundamental absorption and in the adjoining region. Accordance of polarization characteristic of luminicsence to the date on optical absorption takes place only in the separate cases. Polarization Е||F reaches the level 0,5 and tends to increase in the side of increasing of photon energy.
Keywords: silicon carbide, electric breakdown, breakdown electroluminiscence, linear polarisation.
Fig. 7 Refs. 11 titles.
UDC 528.7:629.78
The Theory of Forming the Illumination Field on the Inner Surface of an Integrating Sphere of Photometer for Luminous Flux Measurement of the LEDs Mikheenko L.A., Kovalenko A.V. Naukovi visti NTUU “КPІ”. – 4 – N 1 – P 79–84
Simplified mathematical models of the formation of the illumination field on the inner surface of the spherical photometer for three common schemes of constructive placement of the LED were proposed. The models are based on a combination of the method of successive reflections with the integration of illumination of rings around elementary segment symmetrically illuminated by LED. Each model takes into account the main design parameters of the photometer, which affect the level of light reflectance of the inner coating, and spatial orientation of the indicatrix of LED sources. Comparative analysis of calculations of the schemes with typical parameters shows highly informative results. It is shown that the value of the reflection coefficient of more than 0,98 and the sphere diameter less than 0,6 m significantly increases impact of the volatility of these parameters on the overall error of the photometer. If the total indicatrix of LED is narrowing, the total illumination decreases when placing it on the wall of the sphere, and increases – when placed in the center. The results of calculations can be used to select the optimal photometer scheme for the given parameters of LED, and select the optimal parameters values of its design.
Keywords: metrology, optical radiometry, photometry, flux measurements of LEDs.
Fig. 7 Refs. 7 titles
UDC 615.47
The Biooperated Magnetophonotherapy System on the Basis of an Estimation of Physiological Indicators of the Man Rudyk V.U., Tereshchenko M.F., Tymchik G.S. Naukovi visti NTUU “КPІ”. – 4 – N 1 – P 85–92
At the present stage of development of medical instrument-making working out magnetotherapy apparatus with feedback automatically correcting parameters of medical influence according to physiological parameters of patients during a magnetotherapy session obtains an actual value. The purpose of this study was to research an influence of a magnetic field on change of physiological indicators of the man for working out magnetophonotherapy system with control algorithm of parameters of magnetic field influence and ultrasound on a biological tissue. Modern clinical researches of man’s change of physiological indicators were analyzed. The experimental researches of pulse change, degree of oxygenating of hemoglobin (saturation), arterial pressure, temperature were performed before, during and after completion of a session of a magnetotherapy of the overhead extremities. Adaptive possibilities of formation of adequate influences of magnetophonotherapy system on the basis of the analysis of controllable physiological indicators of the patient and regulation of magnetic field parameters are considered. The construction principles of automated multipurpose magnetophonotherapy apparatus with algorithm of control of influence of a magnetic field and ultrasound on a biological tissue were offered.
Keywords: magnetic field, magnetotherapy, the magnetophonotherapy apparatus.
Fig. 4 Тabl. 1. Refs. 21 titles
UDC 535(075)
The Method for Evaluating Ametropia and the Depth of Focus of the Eye / Chyzh I.G., Golembovskiyi O.O. // Naukovi visti NTUU “КPІ”. – 2014. – N 1. – P. 93–98.
The need is established for measuring pseudo-accommodation (the depth of focus of the eye) when a standard artificial or accommodative lens is implanted into the eye. It is specified the need for analyzing the impact of aberrations of a measuring device’s elements as well as the pupil’s diameter onto the accuracy of ametropia and pseudo-accommodation measurements by the method, proposed by the authors. In this study, a computer simulation is applied for an optical system of the measuring device and an ametropic eye with a diffuse-scattering retina. The optical system was simulated using paraxial and real aberrational components. The results of simulation have confirmed an insignificant effect of aberrations of the device’s actual components on ametropia measurement errors. The length of the focal region was estimated by using RMS spot diagrams of light microspots at the retina, formed by the optical system of the eye in the reverse ray path. The influence of reverse ray path on measurement errors of the eye’s ametropia and pseudo-accommodation has been found as negligible. It is also shown the dependence of a pseudo-accommodation volume on the pupil diameter for the eye having no accommodation function.
Keywords: Depth of the focus, pseudo-accommodation volume.
Fig. 5. Тabl. 2. Refs.: 8 titles
UDC 615-65
Application of Modified Hooke–Jeeves Method for Multi-Objective Optimization Branovitskaya S.V., Bondarenko S.G., Danilkovich A.G., Sanginova O.V., Chervinsky V.O. Naukovi visti NTUU “КPІ”. 4 N 1 P 99 105
The task of multi-objective constrained optimization of chrome tanning of semi-finished leather applying the Hooke–Jeeves method is solved. The optimality criterion is formulated in the form of a generalized additive objective function. Local criteria for the objective function are normalized and nondimensionalized. The weighting parameters are obtained on the basis of professional assessments. The algorithm of the modified Hooke–Jeeves method is the basis for the software module, which is implemented using object-oriented programming language Visual Basic for Application. The possibility to work with explicit and implicit constraints in the software module is provided. The developed software module is used to find the optimal values of the generalized objective function. For a low-waste technology of chrome tanning of semi-finished leather with dry chrome tanning agent its mathematical description is obtained and its constraints on the technological parameters of the process are determined. The optimization problem of the dry chrome tanning of semi-finished leather process is solved and the optimal values of the parameters of the tanning process are determined.
Keywords: optimum task, objective function, algorithm, semi-finished leather, tanning.
Fig. 2 Тabl. 2. Refs. 12 titles
UDC 546.18+54.183
Sorption of Phosphates by Iron (III) Oxyhydrates with Various Crystalline Structures Lesnichaya Т.V., Terikovskaya Т.Е., Zykova О.P., Khodakovskaya Т.А., Visloguzova N.M., Kirillov S.А. Naukovi visti NTUU “КPІ”. 4 N 1 P
By means of precipitation method FeOOH (amorphous ferric oxyhydrate), a-FeOOH (goethite) and g-FeOOH (lepidocrocite) have been synthesized. Physical-and-chemical parameters of the synthesized compounds have been characterized using X-ray diffraction, porosity studies, pH titration. With the aid of XRD it was found that a-FeOOH and g-FeOOH have crystalline structure, while FeOOH is amorphous. The sorption affinity of ferric oxyhydrates of various crystalline structure towards phosphate ions has been studied. The synthesized oxyhydrates have a mezoporous structure with the pore size of 2 nm for FeOOH (amorphous), g-FeOOH and 16 nm for a-FeOOH . рН titration has shown that FeOOH (amorphous) is an ampholite with the maximal exchange capacity of 3 mmol/g in acidic media and 3,5 mmol/g in alkaline media. The comparison of the sorption affinity of the ferric oxyhydrates with various crystalline structures towards phosphate ions shows that FeOOH (amorphous) has the best parameters, and its sorption capacity reaches 237,5 mg/g in acidic media and 104,5 mg/g in alkaline media.
Keywords: sorption, phosphates, precipitation, iron (III) oxyhydrate.
Fig. 5 Тabl. 1. Refs. 10 titles