Research Bulletin of the National Technical University of Ukraine "Kyiv Politechnic Institute"

Microwave Filters Based on the Structures with Resonators in Parallel Channels as Metamaterial Cells

2019-01-15T15:28:19+02:00

Background. Many of the properties of metamaterials are similar to those found in filters with mutually detuned by frequency unrelated resonators. The bridge filters are used as a low-frequency prototypes of such microwave filters. For further development and design of new types of metamaterials it is necessary to establish an analogy between metamaterials and filters with mutually detuned by frequency unrelated resonators.

Objective. Creating a model of metamaterials based on the bandstop microwave filters with mutually detuned resonators and on the low-frequency prototypes.

Methods. Checking the equivalence of metamaterials characteristics and microwave filters with mutually detuned resonators, identifying their inherent laws (oscillation types in parallel channels, location of the attenuation poles above or below the bandwidth), which appear regardless of the types of resonators, studying the possibility of using prototype bridge filters for modeling of metamaterials.

Results. The basic model of an 8-pole network with resonators in parallel channels has been studied in detail. Analytical expressions are obtained for the transmission and reflection coefficients for all inputs of an 8-pole network. The 4-pole networks implemented on the basis of the aforementioned basic model are investigated. Experimental studies are performed that confirm the adequacy of analytical models. An analogy between metamaterials and microwave filters with mutually detuned resonators is established, the possibility of the use as a low-frequency prototype bridge bandpass filters is shown.

Conclusions. Microwave filters with mutually detuned resonators can be used for modeling of metamaterials, and bridge bandpass filters – as low-frequency prototypes, which design techniques are well developed.

Efficiency of a Heat Pump Recuperative Heating and Ventilation System with Use of Heat of Ventilation and Atmospheric Air

2019-01-15T15:28:25+02:00

Background. Modern technological progress of mankind leads to an increase in demand for energy whether it is heat or electricity. Most of this energy is obtained by burning minerals, which reserves are rapidly decreasing. Energy saving in all sectors of the economy is a global problem of our time.

Objective. The search for effective ways to reduce the energy capacity of heat and power equipment is a pressing issue. One of such ways is the use of alternative low-potential energy sources such as air heat pumps, which are widely used due to low capital investments compared to other energy sources, unlimited and affordable heat source. However, their significant disadvantage is the loss of power and efficiency with a decrease in air temperature. The aim of the study is to find a solution to this drawback.

Methods. The article describes a method for analysing the effectiveness of a heat pump recuperative heating and ventilation system with use of heat of ventilation and atmospheric air. A theoretical model of this system has been designed, and a numerical analysis of its thermodynamic efficiency has been performed.

Results. It is seen that the use of this system allows reducing the total relative costs of external energy for heating and ventilation as compared to the system without using ventilation air at any values of the recovery coefficient and relative heat flow for ventilation. Graphic dependencies for unknown parameters at system nodes were obtained. Ratios for determining the total unit cost of external energy in the scheme under study are obtained.

Conclusions. It was determined that when using this system at the design stage of the heat pump heating and ventilation system, it is possible to significantly reduce capital and operating costs. The use of the obtained dependencies in the development of heat pump heating and ventilation systems will ensure maximum energy efficiency of their work.

Practical Aspects of Recognition of Electric Type Defects on the Analysis Results of Gases Dissolved in Oil

2019-01-15T15:28:36+02:00

Background. Recognition of the type of defects in high-voltage oil-filled equipment, based on the analysis of gases dissolved in oil, using the values of the criteria that are regulated by the normative document in force in Ukraine, doesn’t always allow us to establish the correct diagnosis. Given that misdiagnosis can lead to accidental damage, ways to improve the reliability of defect type recognition are considered.

Objective. The aim of the paper is to increase the reliability of recognition of the type of defects in high-voltage oil-filled equipment, based on the analysis of gases dissolved in oil using the normative document in force in Ukraine.

Methods. A comparative analysis of the values of the ratios of gases and graphical images, for 31 types of electrical defects, for 808 units of oil-filled equipment was performed. A brief description and values of the ratios of gases and graphic images for defects, the recognition of which causes difficulties with the use of the normative document in force in Ukraine, is given.

Results. It is established that in real operation conditions the values of the diagnostic criteria used to recognize the type of defects can significantly differ from the values regulated by the normative documents in force both in Ukraine and abroad. Moreover, for some defects, the values of the gas ratios simultaneously correspond to different defects, and the reference graphic images are absent, which considerably complicates the procedure for their recognition. To eliminate these drawbacks, graphical images and ranges of values of gas ratios are offered, which allow us to recognize a greater number of varieties of defects, compared to the normative document in force in Ukraine, 31 instead of 6.

Conclusions. The ranges of values of gas ratios obtained and given in the work and the graphic images of defects are a diagnostic scheme, the practical use of which makes it possible to significantly expand the range of defects recognized by the analysis of gases dissolved in oil and thereby improve the operational reliability of high-voltage oil-filled equipment.

Logical Operations in Algebraic System of Aggregates for Multimodal Data Representation and Processing

2019-01-15T15:28:40+02:00

Background. The range of computer software applications which operate with multimodal data becomes wider and wider. To develop efficient algorithms for data processing, the representation of multimodal data as complex structures is required. Existing approaches are mostly oriented to independent data sets representation and they are not efficient for complex representation of multimodal data.

Objective. The development of a mathematical approach which can be used for complex multimodal data representation and processing in computer systems.

Methods. The Algebraic System of Aggregates is developed for enabling complex representation of multimodal data. There are logical, ordering and arithmetical operations in the Algebraic System of Aggregates. Logical operations can be used for preparing complex data representations in a form of aggregates which are supposed to be a subject of further data analysis. The precondition for such representation is that data sequences are of different modalities and they are recorded with respect to time.

Results. The logical operations on aggregates are proposed and described. They allow to construct different compositions of multimodal data what in its turn enables complex data representation for compound description of objects and processes in different areas including healthcare. The multi-image concept which enables overall description of an object, a subject, or a process of observation carried out in the course of time is also proposed and discussed.

Conclusions. The Algebraic System of Aggregates is a tool for complex data representation. It enables multimodal data processing by using a range of operations and relations. The key difference in the fulfilment of logical operations in the Algebraic System of Aggregates and logical operations on sets is that an aggregate is a form of complex representation of data sequences where the order of data in each sequence of each type is important and influences on the order of data in the result of a certain logical operation.

Program of Simplification of High-Level Polynomial at the Example of Simplification of Wilson’s Formula

2019-01-15T15:28:43+02:00

Background. Since many formulas have the form of high-level polynomials and their use leads to a large number of computations, which slows down the speed of obtaining results, the technology of simplification of high-level polynomials is considered.

Objective. The aim of the paper is to obtain a technology for the simplification of high-level polynomials based on the application of the theory of experiment planning to the Wilson’s formula.

Methods. To simplify high-level polynomials, combination and consistent application of experiment planning and least squares methods are proposed. For the field of input values, matrix of rotatable central composite plan Box of second order for three factors is constructed. To the constructed matrix the least squares method was applied, by which the coefficients of the simplified formula can be found. The resulting simplified formula will have the form of a polynomial of the 2nd degree.

Results. The Wilson’s formula, which has the form of a polynomial of degree 4, is simplified to the form of a polynomial of degree 2. Having broken down the entire definition domain for Wilson's formula on the parts and constructed a simplified formula for a particular part, we obtained a result that, using the simplified formula, one can calculate the speed of sound almost 25 times faster than using the Wilson's formula, with only a slight deviation in the results.

Conclusions. When simplifying polynomials of high degree, the reduction of the ranges of input parameters is decisive for obtaining a satisfactory deviation between the calculated values. The proposed approach to simplifying the formulas worked quite well on the example of Wilson's formula. It can also be used to simplify other formulas that have the form of high-level polynomials. One of the options for further use of the results of this work is the creation of a technology that would enable the parallel calculation of the sound speed based on the simplified formulas obtained for each of the parts to which the definition area for the Wilson's formula is divided.

Analysis of Air Heating in Winter in Underground Heat Exchangers and in Water Bodies During Water Freezing on Submerged Pipes

2019-01-15T15:28:46+02:00

Background. Air heating in winter in the ambient temperatures range below -5 °С is possible both by the heat of the soil and by the heat of the phase transition of water to ice. Heated air reduces energy consumption in ventilation systems and heat pumps such as air–water and air–air during peak loads on the heating system, which reduces the installed capacity of the heat-generating equipment.

Objective. The aim of the paper is determination of the influence of air velocity (flow rate) on the desired length of pipes at a constant value of the diameter of the channel with air, as well as determination of thermal resistances and linear heat flux density with a comparison of the processes of soil cooling and water crystallization.

Methods. Air with a temperature below -5 °С is passed through elements of the natural environment for use in ventilation systems, heat pumps, and in the buffer zones of buildings during the frost period. The lower the air temperature, the greater the economic and energy efficiency.

Results. The calculated analysis of the effect of air velocity (flow rate) on the required length of pipes embedded in the ground and submerged in water subject to a phase transition of water to ice was carried out. It is shown that the required length of the ground heat exchanger is strongly influenced by the mode of operation (continuous operation without interruptions or operation with interruptions). To heat the air from -10 to -3 °С, depending on the air speed in the ground heat exchangers, the needed length of the pipes should be 1.5–2 times longer because the thermal resistance of the soil is greater than that of ice and the ice thickness is lower than that of the cooled soil, due to the high heat value of water crystallization. At high speeds, the linear density of the heat flux reaches 40–60 W/m².

Conclusions. When placing a channel in the form of a pipe in the ground or in water, it is possible to pre-heat the frosty air during peak loads on heating systems, which makes it possible to reduce the installed power of the heat-generating equipment. The technology of water freezing during air heating has significant advantages, especially when operating in annual mode.

Modulation Transfer Function of the Remote Sensing System when the Line of Sight Deviates From the Nadir

2019-01-15T15:28:49+02:00

Background. Today, one of the main requirements, which relates to space optical-electronic viewing systems (OEVS) is shooting by a spacecraft (SC) of a requisite area at different angles of sighting. When the line of sight deviates from the nadir, the image quality gets worse. Primarily, the deformation of the projection of pixels on the Earth's surface (ES) and changing of the velocity and direction of vector of movement of the sub-satellite point of SC affect the image quality. Generally, the resulting image quality is estimated by the modulation transfer function (MTF) of OEVS. The evaluation of the MTF of OEVS by only two components, such as the MTF of a lens and detector is insufficient, since there is a high probability that the image will have significantly lower quality compared to theoretically calculated one. Therefore, it is necessary to take into account in the resulting MTF the effect of additional factors such as vibration, movement velocity of the sub-satellite point, detector reading frequency, height instability and position of the line of sight, the atmosphere, to name a few.

Objective. The aim of the paper is to develop physico-mathematical model for determining MTF of space OEVS, that takes into account the deformation of the projection of pixels, the variation of velocity and movement vector direction of the SC sub-satellite point and the influence of additional factors at the different angles of sighting.

Methods. In the basis of physico-mathematical model is proposed to use a Sun-synchronous orbit trajectory and to calculate the resulting MTF of OEVS in the direction and transverse to the direction of flight.

Results. Practical results of the calculations confirm that the deformation of the projection of the pixels and the mentioned additional factors significantly affect the resulting MTF of space OEVS and also depending on the angles of sighting the MTF in the direction and transverse to the direction of flight differ.

Conclusions. The analysis of the proposed physico-mathematical model for MTF calculation of the OEVS showed that when a scanner with a large number of pixels is deviated at the significant angles of sighting, heterogeneity appears on sensitive matrix of detector. Attention is drawn to the fact that when scanner deviates at the angles of sighting, the affect of the reading frequency of detector should also be reduced by negotiating it with the image movement velocity in the focal plane. In the process of the research, it was discovered that when use the slight additional turn of yaw angle it is possible to improve the MTF and reduce the difference between the MTF of in the direction and transverse to the direction of flight affecting the image perception efficiency.

Factors of Microdrift of Piece Surfaces in Mechanical Processing

2019-01-15T15:28:53+02:00

Background. The article considers the aspects of an actual problem of research of factors of accuracy loss of exact piece manufacturing by mechanical processing in conditions of serial and mass production, in particular occurrence of a piece surface microdrift during processing that leads to the accuracy control function loss of shaping parameters.

Objective. The aim of the paper is to create an analytical model for controlling the dimensions of a batch of pieces, which can be the basis for recommendations for the further development of instrumentation for operation in mass production.

Methods. A model for changing the technological process parameters referring turning machining) is proposed, which can be regarded as a single discrete sample with a single piece taken. It is shown that the geometric dimensions have a parallel transfer in time from one piece to another. This approach allows us to consider a single discrete sample with respect to the piece in question, as a completed definite function for a separate study.

Results. It is proved that with this approach to the process consideration the main components that influence the formation of the required dimension are taken into account. The components that influence piece dimensions are shown. A model for the appearance of a temperature drift of the piece surface and the effect on the accuracy of working out the surface coordinate is proposed.

Conclusions. The model for taking into account the piece surface microdrift is proposed, which arises from the difference between the absolute and local coordinates of the object. Further studies should be aimed at identifying the design features of the measuring transducers, which also allow for the presence of the surface microdrift of the technological object. Thus, the principles of constructing the basic types of the design of measuring heads will be justified taking into account the location of process objects in the working space of the metalworking machine in measuring the physical properties of certain specific local area of the workpiece surface (or finished part).