Subjects -> MATHEMATICS (Total: 1117 journals)
    - APPLIED MATHEMATICS (92 journals)
    - GEOMETRY AND TOPOLOGY (23 journals)
    - MATHEMATICS (818 journals)
    - MATHEMATICS (GENERAL) (45 journals)
    - NUMERICAL ANALYSIS (26 journals)
    - PROBABILITIES AND MATH STATISTICS (113 journals)

MATHEMATICS (818 journals)            First | 1 2 3 4 5     

Showing 401 - 538 of 538 Journals sorted alphabetically
Journal of Computational Physics     Hybrid Journal   (Followers: 71)
Journal of Computational Physics : X     Open Access   (Followers: 1)
Journal of Computer Engineering, System and Science (CESS)     Open Access  
Journal of Contemporary Mathematical Analysis     Hybrid Journal  
Journal of Cryptology     Hybrid Journal   (Followers: 6)
Journal of Difference Equations and Applications     Hybrid Journal  
Journal of Differential Equations     Full-text available via subscription   (Followers: 1)
Journal of Discrete Algorithms     Hybrid Journal   (Followers: 4)
Journal of Discrete Mathematics     Open Access   (Followers: 1)
Journal of Dynamics and Differential Equations     Hybrid Journal  
Journal of Engineering Mathematics     Hybrid Journal   (Followers: 2)
Journal of Evolution Equations     Hybrid Journal  
Journal of Experimental Algorithmics     Full-text available via subscription   (Followers: 1)
Journal of Flood Risk Management     Hybrid Journal   (Followers: 15)
Journal of Formalized Reasoning     Open Access   (Followers: 2)
Journal of Function Spaces     Open Access  
Journal of Functional Analysis     Full-text available via subscription   (Followers: 2)
Journal of Geochemical Exploration     Hybrid Journal   (Followers: 3)
Journal of Geological Research     Open Access   (Followers: 1)
Journal of Geovisualization and Spatial Analysis     Hybrid Journal  
Journal of Global Optimization     Hybrid Journal   (Followers: 7)
Journal of Global Research in Mathematical Archives     Open Access   (Followers: 1)
Journal of Group Theory     Hybrid Journal   (Followers: 2)
Journal of Homotopy and Related Structures     Hybrid Journal  
Journal of Honai Math     Open Access  
Journal of Humanistic Mathematics     Open Access   (Followers: 1)
Journal of Hyperbolic Differential Equations     Hybrid Journal  
Journal of Indian Council of Philosophical Research     Hybrid Journal  
Journal of Industrial Mathematics     Open Access   (Followers: 2)
Journal of Inequalities and Applications     Open Access  
Journal of Infrared, Millimeter and Terahertz Waves     Hybrid Journal   (Followers: 3)
Journal of Integrable Systems     Open Access   (Followers: 1)
Journal of K-Theory     Full-text available via subscription  
Journal of Knot Theory and Its Ramifications     Hybrid Journal   (Followers: 1)
Journal of Liquid Chromatography & Related Technologies     Hybrid Journal   (Followers: 7)
Journal of Logical and Algebraic Methods in Programming     Hybrid Journal  
Journal of Manufacturing Systems     Full-text available via subscription   (Followers: 4)
Journal of Mathematical Analysis and Applications     Full-text available via subscription   (Followers: 5)
Journal of mathematical and computational science     Open Access   (Followers: 7)
Journal of Mathematical and Fundamental Sciences     Open Access  
Journal of Mathematical Behavior     Hybrid Journal   (Followers: 3)
Journal of Mathematical Chemistry     Hybrid Journal   (Followers: 4)
Journal of Mathematical Cryptology     Hybrid Journal   (Followers: 1)
Journal of Mathematical Extension     Open Access   (Followers: 3)
Journal of Mathematical Finance     Open Access   (Followers: 9)
Journal of Mathematical Imaging and Vision     Hybrid Journal   (Followers: 6)
Journal of Mathematical Logic     Hybrid Journal   (Followers: 3)
Journal of Mathematical Modelling and Algorithms     Hybrid Journal   (Followers: 1)
Journal of Mathematical Neuroscience     Open Access   (Followers: 10)
Journal of Mathematical Sciences     Hybrid Journal  
Journal of Mathematical Sciences and Applications     Open Access   (Followers: 3)
Journal of Mathematical Sociology     Hybrid Journal   (Followers: 3)
Journal of Mathematics     Open Access  
Journal of Mathematics and Statistics     Open Access   (Followers: 8)
Journal of Mathematics and Statistics Studies     Open Access   (Followers: 3)
Journal of Mathematics and the Arts     Hybrid Journal   (Followers: 2)
Journal of Mathematics Education at Teachers College     Open Access   (Followers: 3)
Journal of Mathematics in Industry     Open Access  
Journal of Mathematics Research     Open Access   (Followers: 6)
Journal of Metallurgy     Open Access   (Followers: 8)
Journal of Modern Mathematics Frontier     Open Access  
Journal of Multidisciplinary Modeling and Optimization     Open Access  
Journal of Multivariate Analysis     Hybrid Journal   (Followers: 13)
Journal of Natural Sciences and Mathematics Research     Open Access  
Journal of Nonlinear Analysis and Optimization : Theory & Applications     Open Access   (Followers: 4)
Journal of Nonlinear Mathematical Physics     Hybrid Journal   (Followers: 1)
Journal of Nonlinear Science     Hybrid Journal   (Followers: 1)
Journal of Numerical Cognition     Open Access   (Followers: 1)
Journal of Numerical Mathematics     Hybrid Journal   (Followers: 2)
Journal of Optimization     Open Access   (Followers: 5)
Journal of Peridynamics and Nonlocal Modeling     Hybrid Journal  
Journal of Problem Solving     Open Access   (Followers: 2)
Journal of Progressive Research in Mathematics     Open Access   (Followers: 5)
Journal of Pseudo-Differential Operators and Applications     Hybrid Journal  
Journal of Pure and Applied Algebra     Full-text available via subscription   (Followers: 4)
Journal of Quantitative Analysis in Sports     Hybrid Journal   (Followers: 9)
Journal of Quantitative Linguistics     Hybrid Journal   (Followers: 6)
Journal of Scientific Computing     Hybrid Journal   (Followers: 18)
Journal of Scientific Research     Open Access  
Journal of Symbolic Computation     Hybrid Journal   (Followers: 1)
Journal of the Australian Mathematical Society     Full-text available via subscription  
Journal of the Egyptian Mathematical Society     Open Access  
Journal of the European Mathematical Society     Full-text available via subscription   (Followers: 1)
Journal of the Indian Mathematical Society     Hybrid Journal   (Followers: 1)
Journal of the Institute of Mathematics of Jussieu     Hybrid Journal  
Journal of the London Mathematical Society     Hybrid Journal   (Followers: 2)
Journal of the Nigerian Mathematical Society     Open Access   (Followers: 1)
Journal of Theoretical and Applied Physics     Open Access   (Followers: 8)
Journal of Topology and Analysis     Hybrid Journal  
Journal of Transport and Supply Chain Management     Open Access   (Followers: 16)
Journal of Turbulence     Hybrid Journal   (Followers: 9)
Journal of Uncertainty Analysis and Applications     Open Access   (Followers: 1)
Journal of Universal Mathematics     Open Access  
Journal of Urban Regeneration & Renewal     Full-text available via subscription   (Followers: 11)
JRAMathEdu : Journal of Research and Advances in Mathematics Education     Open Access   (Followers: 6)
JUMLAHKU : Jurnal Matematika Ilmiah STKIP Muhammadiyah Kuningan     Open Access   (Followers: 2)
JURING (Journal for Research in Mathematics Learning)     Open Access   (Followers: 1)
Jurnal Ilmiah AdMathEdu     Open Access  
Jurnal Matematika     Open Access   (Followers: 1)
Jurnal Matematika Integratif     Open Access  
Jurnal Matematika, Sains, Dan Teknologi     Open Access  
Jurnal Natural     Open Access  
Jurnal Pendidikan Matematika Raflesia     Open Access  
Jurnal Penelitian Pembelajaran Matematika Sekolah     Open Access  
Jurnal Penelitian Sains (JPS)     Open Access  
Jurnal Riset Pendidikan Matematika     Open Access  
Jurnal Sains Matematika dan Statistika     Open Access  
Jurnal Tadris Matematika     Open Access  
Jurnal Teknologi dan Sistem Komputer     Open Access  
Kontinu : Jurnal Penelitian Didaktik Matematika     Open Access   (Followers: 2)
Kreano, Jurnal Matematika Kreatif-Inovatif     Open Access   (Followers: 6)
Le Matematiche     Open Access  
Learning and Teaching Mathematics     Full-text available via subscription   (Followers: 7)
Lettera Matematica     Hybrid Journal  
Lietuvos Matematikos Rinkinys     Open Access   (Followers: 3)
Limits : Journal of Mathematics and Its Applications     Open Access   (Followers: 1)
Linear Algebra and its Applications     Full-text available via subscription   (Followers: 23)
Linear and Multilinear Algebra     Hybrid Journal   (Followers: 8)
Lithuanian Mathematical Journal     Hybrid Journal  
LMS Journal of Computation and Mathematics     Free  
Lobachevskii Journal of Mathematics     Open Access  
Logic and Analysis     Hybrid Journal   (Followers: 1)
Logic Journal of the IGPL     Hybrid Journal   (Followers: 1)
Logica Universalis     Hybrid Journal  
manuscripta mathematica     Hybrid Journal  
MaPan : Jurnal Matematika dan Pembelajaran     Open Access  
Marine Genomics     Hybrid Journal   (Followers: 2)
Matemáticas, Educación y Sociedad     Open Access  
Matematicheskie Zametki     Full-text available via subscription  
Matematychni Studii     Open Access  
Mathematica Eterna     Open Access  
Mathematica Scandinavica     Full-text available via subscription   (Followers: 1)
Mathematica Slovaca     Hybrid Journal   (Followers: 1)
Mathematical Analysis and its Contemporary Applications     Open Access   (Followers: 1)
Mathematical and Computational Forestry & Natural-Resource Sciences     Free  
Mathematical Communications     Open Access  
Mathematical Computation     Open Access   (Followers: 1)
Mathematical Geosciences     Hybrid Journal   (Followers: 4)
Mathematical Journal of Interdisciplinary Sciences     Open Access   (Followers: 1)
Mathematical Medicine and Biology: A Journal of the IMA     Hybrid Journal   (Followers: 2)
Mathematical Methods in the Applied Sciences     Hybrid Journal   (Followers: 4)
Mathematical Methods of Statistics     Hybrid Journal   (Followers: 4)
Mathematical Modelling and Analysis     Open Access   (Followers: 1)
Mathematical Modelling in Civil Engineering     Open Access   (Followers: 5)
Mathematical Modelling of Natural Phenomena     Open Access   (Followers: 2)
Mathematical Models and Methods in Applied Sciences     Hybrid Journal   (Followers: 2)
Mathematical Models in Engineering     Open Access   (Followers: 1)
Mathematical Notes     Hybrid Journal  
Mathematical Proceedings of the Cambridge Philosophical Society     Full-text available via subscription   (Followers: 2)
Mathematical Programming Computation     Hybrid Journal   (Followers: 3)
Mathematical Sciences     Open Access  
Mathematical Social Sciences     Hybrid Journal   (Followers: 1)
Mathematical Theory and Modeling     Open Access   (Followers: 13)
Mathematical Thinking and Learning     Hybrid Journal   (Followers: 4)
Mathematics and Statistics     Open Access   (Followers: 5)
Mathematics Education Forum Chitwan     Open Access   (Followers: 2)
Mathematics Education Journal     Open Access   (Followers: 3)
Mathematics Education Research Journal     Partially Free   (Followers: 20)
Mathematics in Science and Engineering     Full-text available via subscription  
Mathematics of Control, Signals, and Systems (MCSS)     Hybrid Journal   (Followers: 5)
Mathematics of Quantum and Nano Technologies     Open Access  
Mathématiques et sciences humaines     Open Access   (Followers: 6)
Mathematische Annalen     Hybrid Journal   (Followers: 1)
Mathematische Nachrichten     Hybrid Journal   (Followers: 1)
Mathematische Semesterberichte     Hybrid Journal  
Mathematische Zeitschrift     Hybrid Journal   (Followers: 1)
MathLAB Journal     Open Access   (Followers: 5)
MATICS     Open Access   (Followers: 2)
Matrix Science Mathematic     Open Access   (Followers: 1)
Measurement Science Review     Open Access   (Followers: 3)
Mediterranean Journal of Mathematics     Hybrid Journal  
Memetic Computing     Hybrid Journal  
Mendel : Soft Computing Journal     Open Access  
Metaheuristics     Hybrid Journal  
Metals and Materials International     Hybrid Journal  
Metascience     Hybrid Journal   (Followers: 1)
Metrology and Instruments / Метрологія та прилади     Open Access   (Followers: 1)
Milan Journal of Mathematics     Hybrid Journal  
Mitteilungen der DMV     Hybrid Journal  
MLQ- Mathematical Logic Quarterly     Hybrid Journal   (Followers: 1)
MONA : Matematik- og Naturfagsdidaktik     Hybrid Journal   (Followers: 4)
Monatshefte fur Mathematik     Hybrid Journal  
Moroccan Journal of Pure and Applied Analysis     Open Access   (Followers: 4)
Moscow University Mathematics Bulletin     Hybrid Journal  
MSOR Connections     Open Access   (Followers: 1)
Multiscale Modeling and Simulation     Hybrid Journal   (Followers: 3)
MUST : Journal of Mathematics Education, Science and Technology     Open Access   (Followers: 3)
Nagoya Mathematical Journal     Hybrid Journal  
Nano Research     Hybrid Journal   (Followers: 4)
Nanotechnologies in Russia     Hybrid Journal   (Followers: 1)
Natural Resource Modeling     Hybrid Journal   (Followers: 1)
New Mathematics and Natural Computation     Hybrid Journal  
Nonlinear Analysis : Modelling and Control     Open Access   (Followers: 1)
Nonlinear Analysis : Theory, Methods & Applications     Hybrid Journal   (Followers: 1)
Nonlinear Analysis: Hybrid Systems     Hybrid Journal  
Nonlinear Analysis: Real World Applications     Hybrid Journal   (Followers: 2)
Nonlinear Differential Equations and Applications NoDEA     Hybrid Journal  
Nonlinear Engineering     Open Access  
Nonlinear Oscillations     Hybrid Journal   (Followers: 1)
North Carolina Journal of Mathematics and Statistics     Open Access  

  First | 1 2 3 4 5     

Similar Journals
Journal Cover
Metrology and Instruments / Метрологія та прилади
Number of Followers: 1  

  This is an Open Access Journal Open Access journal
ISSN (Print) 2307-2180 - ISSN (Online) 2663-9564
Published by Kharkiv National University of Radio Electronics Homepage  [1 journal]
  • State Primary Standard of Gas Volume and Flow Rate Units for the Pressure
           Range of 1 MPa to 5 MPa (PVTt-15)

    • Authors: M. S. Rozhnov, Yu. V. Kuzmenko, D. M. Melnyk, O. S. Levbarg, A. M. Rak, V. I. Pashun, L. M. Pohribna
      Pages: 3 - 12
      Abstract: For the first time in Ukraine a primary measurement standard of gas volume and flow rate units in a pressure range of 1 MPa to 5 MPa has been created. The standard is based on realisation of the units by PVTt principle and units dissemination using critical Venturi nozzles. Gas passing through the nozzle during its calibration fills an evacuated collection tank located downstream the nozzle, and the respective time interval is measured. Mass flow rate is calculated by multiplying the volume of the collection tank by the gas density change and dividing by the tank filling time. Density values are determined by the equation of state and the measured initial and final pressure and temperature values. The structural and functional scheme of the measurement standard is shown in Figure 3. The standard consists of two units. The first unit is intended to realise, keep and transfer the units of gas volume and flow rate. The general view of the block is shown in Figure 4. The unit contains high pressure collection tank, precision water thermostat, vacuum pump, piston gas pressure gauge, flow switch, fine filter, a set of seven Venturi nozzles with diameters from 0.1 mm to 3.0 mm. The second unit is designed to form a stationary gas flow and provide a critical gas flow rate (at the speed of sound) at the nozzle throat. In the case of an elementary reversible adiabatic (isoentropic) process at a critical velocity, the mass flow rate of gas passing through the nozzle is maximally possible. The unit consists of equipment for reducing the pressure from 150 bar to 70 bar and from 70 bar to 10 bar, the heat exchanger and the instruments measuring the pressure and temperature of the gas flow. The created measurement standard will assure metrological traceability of the measurements of gas volume and volume flow rate at high pressures for the flow rate up to 100 m3/h and calibration of the primary reference nozzles with a throat diameter from 0.1 mm to 3 mm.
      PubDate: 2020-05-21
      DOI: 10.33955/2307-2180(2)2020.3-12
       
  • Automated Unit for Magnetization of Strong Magnets of Electromagnetic
           Drives

    • Authors: M. M. Sirenko, B. M. Gorkunov, S. G. Lvov, V. V. Lysenko
      Pages: 13 - 21
      Abstract: The paper is about the development of an automated unit with optimum energy and mass-dimensional parameters for high-quality magnetization of magnets of electromagnetic drives, while preser­ving the integrity of their windings. The authors develop an approach for calculating amplitude and width of magnetization pulse. The authors than estimate the rise time of leading edge of the pulse, with respect to conditions of complete magnetization of the electromagnetic drive’s magnetic conductor and preservation of its excitation winding integrity. For the formation of the magnetization pulse with given para­me­ters, the authors propose an electronic device, which feedbacks bitween the drive winding and the pulse current source, which provides power to the inductor winding. The authors propose a method of the inductor magnetic system synthesis by criteria of: given magnetic field strength in inductor’s operating volume; power supply unit minimal dimensions and it power consumption while magnetizing. The final result is obtaining cross-section profile of the inductor electrical coil with certain dimensions and number of winding’s turns of a wire of certain diameter. In order to optimize the mass, size, magnetic and energy para­meters of the inductor, the authors solve a problem of synthesizing its magnetic system in way of calculating the parameters of the magnetic field for operating volume of the inductor. It is determined by the characteristic overall dimensions of the NZTB type electromagnetic drives (brakes, 0.2 m in diameter), which were subject to magnetization in a field with strength of at least 400 A/m. The result is the determination of geometrical parameters and the cross-section profile of the inductor electrical coil. This profile ensures the uniformity of the magnetic field when magnetizing the electromagnetic drive of given overall dimensions. On the basis of all these results, the authors develop the functional scheme of the automated unit and propose a structure of a pa­nel for monitoring and management of devices and units involved.
      PubDate: 2020-05-21
      DOI: 10.33955/2307-2180(2)2020.13-21
       
  • Measuring System for Non-Destructive Testing of Metal Rods

    • Authors: D. P. Ornatsky, O. O. Krivokulska, O. O. Burbela, O. D. Bliznyuk
      Pages: 22 - 24
      Abstract: The control parameters of metal products using the eddy current method of nondestructive testing based on electromagnetic induction law is now widespread. Due to the high sensitivity over a wide frequency range of the ability to control the mechanical properties , uniformity of material, both magnetic and non-magnetic materials, beskonechnosti, high reliability, automation, process control, etc. The object of study is the process of interaction of external electromagnetic fields with defects in heterogeneity of structure in metal rod, causing a deformation of microtubuli currents and, accordingly, their influence on the inductance coil of the sensor. So, according to the law of electromagnetic induction eddy currents induced by an external electromagnetic field will be asking a private field that will oppose the external field that will lead to a change in inductance of the sensor coil. Therefore, the most informative parameter in this case is the relative change in inductance of the sensor. In the known designs use differential transformer sensors, transmission type, which differ in complexity of implementation, but have high sensitivity. In existing works not enough attention on improving of the metrological characteristics . Modern means of microstraava flaw detectors in the overwhelming number are for scientific research, but little attention is paid to tools that can be used in industrial processes, through a complex measurement process in the existing funds and the large volume of the software during automatic processing of information. In the presented work there is a system for nondestructive testing of metal bars with deprivation of the above-mentioned disadvantages, which would provide high metrological characteristics in a wide frequency range, separate measurement of impedance components of the sensor, which allows the reduction of methodological errors of determination of the main characteristics of the output signal of microstraava sensors. The scientific result is created sambalanco pavement system based on electronic dharamtala model of a vortex sensor with high metrological characteristics, which allows you to create real-time signal proportional to the amount of damage that will give you the opportunity to increase productivity in the quality control bar of metal products in a production environment.
      PubDate: 2020-05-21
      DOI: 10.33955/2307-2180(2)2020.22-24
       
  • Investigating the Additional Components of Uncertainty of Measurment
           Result of Unsteady Flow

    • Authors: I. V. Kostyk, F. D. Matiko, V. I. Roman
      Pages: 25 - 33
      Abstract: The additional components of uncertainty of measurement result of unsteady flow by means of pressure differential flowmeter are investigated in the article. In particular, the authors considered in detail the technique for estimating the additional component of uncertainty, caused by the nonlinearity of the flowrate dependence on the pressure drop on the standard primary device, as well as the additional component, which is related to the absence of the inertial term in the root expression of the quasi-steady flow equation. On the example of four differential pressure signals that reproduce the pulsating and unsteady flow modes of the fluid, the estimating the named components is carried out and the dependence of these components of uncertainty on the basic characteristics of the differential pressure signal (root mean square amplitude of pulsations and the maximum relative deviation) is demonstrated. It is shown that the increase of these signal characteristics leads to an increase in the corresponding components of the uncertainty and, consequently, in the resulting additional uncertainty of the measured value of flowrate. Particularly, for the investigated pressure drop signals for which the root mean square amplitude does not exceed 20% of the mean pressure drop, the resulting additional uncertainty of the measured flowrate reaches 0.5%. Since the additional uncertainty caused by unsteady flow is systematic and has a positive sign, it is possible to determine the correction coefficient based on this additional uncertainty and to correct the measured value of the flowrate by considering the correction factor in the flow equation. However, the authors propose to correct the measured value of the flowrate only if it is impossible to identify the causes of unsteady flow and to eliminate their impact on the flowrate.
      PubDate: 2020-05-21
      DOI: 10.33955/2307-2180(2)2020.25-33
       
  • THE ARTICLE IS ELLIMINATED

    • Authors: Editorial Board
      Pages: 34 - 39
      Abstract: As the result of the article V. U. Ihnatkin, Yu. L. Zabulonov, Yu. M. Tuz, O. V. Farrakhov «Calculation and Estimation of the Uncertainty of Pollution Emissions in the Environment» revision for borrowings from third parties work this article had been elliminated according to the policy of anti-plgiarism as such, that contains, in fact, the complete plagiarism with the similar article published by «Measurement Technics» journal, Russia, N 2, 2009
      PubDate: 2020-05-21
       
  • Metrological Activity At the Enterprise

    • Authors: O. M. Dziabenko
      Pages: 40 - 43
      Abstract: When organizing metrological activity at an enterprise, the question arises of the need to organize verification (metrological confirmation) of measuring equipment that is not used in the field of legislatively regulated. In the international standards «Quality Management Systems» (ISO 9001, EN 9100, AQAP-2110), to ensure that the requirements of Section 7.1.5 «Resources for Monitoring and Measurement» are met, the requirement is established that all measuring equipment, as part of a measurement management system, must have metrological confirmation in accordance with the requirements of ISO 10012. Metrological confirmation provides for the calibration and verification of measuring equipment. Laboratory specialists who carry out metrological confirmation of measuring instruments, establish a relationship between the values of the values that provide the standards, and the result of measuring this quantity using measuring instruments (carry out calibration), based on this ratio establish the conformity / non-compliance of the measuring instruments with the established requirements (carry out verification) and draw up the corresponding supporting document. After comparing the concepts of metrological confirmation and verification of measuring instruments, we can conclude that metrological confirmation (calibration and verification) of measuring equipment is essentially nothing more than verification of measuring instruments. Metrological activities to ensure the uniformity of measurements in enterprises should comply with the requirements of ISO 10012: 2003. This standard establishes general requirements and contains recommendations for the management of measurement processes and metrological confirmation of the suitability of measuring equipment, which is used to maintain and demonstrate compliance with metrological requirements. Compliance with the requirements set forth in the ISO 10012 standard makes it possible to ensure compliance with the measurement requirements and the management of measurement processes established by the international standards «Quality Management Systems».
      PubDate: 2020-05-21
      DOI: 10.33955/2307-2180(2)2020.40-43
       
  • Research of the Influence of Temperature Factor on Express Control of
           Natural Gas Combustion Heat

    • Authors: O. E. Seredyuk, N. M. Malisevich
      Pages: 44 - 50
      Abstract: The article is devoted to the study of the influence of the qualitative and quantitative composition of gas environments on the flame temperature of the combusted gas at different values of gas flow rate and changes volume ratio gas-air in its combustion. The functional scheme of the developed labo­ratory stand (Fig. 1), which provides temperature measurement during combustion of natural gas or propane-butane mixture, is considered. The design of the developed burner is described and the expe­rimental researches are carried out when measuring the flame temperature of the combusted gas during the operation of the laboratory stand. The opera­ting conditions of different thermocouples in measuring the temperature of the flared gas are investigated (Fig. 2). The temperature instability in the lower and upper flames was experimentally determined (Fig. 3) and its difference from the reference data [12, 13]. The measurement of the flame temperature with a uncased thermocouple and two thermocouples of different types with protective housings is reali­zed. Methodical error of temperature measurement by different thermocouples was estimated (Fig. 5). An algorithm for the implementation of measurement control in determining the heat of combustion of natural gas according to the patented method is outlined [11]. Experimental studies of temperature changes of combusted gas mixtures at different gas flow rates and different ratios with air, which is additionally supplied for gas combustion, were carried out (Figs. 4, 7). The computer simulation (Figs. 6, 8) of the change in the flame temperature was performed on the basis of the experimental data, which allowed to obtain approximate equations of the functional dependence of the flame temperature on the gas flow rate and the ratio of the additional air and gas consumption. The possibility of realization of the device of express control of the heating value of natural gas by measuring the combustion temperature of the investigated gases, which is based on the expe­rimentally confirmed increase in the flame temperature of the investigated gases with increasing their calorific value, is substantiated (Fig. 9). The necessity of further investigation of the optimization design characteristics of the burner and the operating conditions of combustion of the gases under rapid cont­rol of their combustion heat was established (Fig. 9).
      PubDate: 2020-05-21
      DOI: 10.33955/2307-2180(2)2020.44-50
       
  • A Computer Model of the Dynamics of a Heterogeneous Liquid-Solid Medium in
           a Technological Apparatus with Bubbling

    • Authors: O. Yu. Oliynyk, Yu. K. Taranenko
      Pages: 51 - 56
      Abstract: The article is devoted to the development of a computer model of the dynamics of a heterogeneous liquid-solid medium in a technological apparatus with bubbling. In a heterogeneous bubbler medium, the known methods of environmental control are difficult to implement and practically unsuitable for control in the flow of the medium; therefore, new approaches to the implementation of the software and hardware complex of information systems are necessary. Existing mathematical not take into account the change in the concentration of the liquid due to the formation of solid suspensions included in the bubbling of the liquid by flue gases and the dyna­mics of the behavior of gas bubbles in the vibration field of the apparatus. Vibration measuring instruments could solve the problem by taking into account changes in the density and viscosity of the components of the medium. The developed mathematical model of a heterogeneous liquid-solid medium, which ensures the accuracy of information in information systems, is based on the model of vibration frequency me­thods for monitoring the concentration of the solid fraction of suspensions, based on the use of the behavior of the solid phase of the suspension in a vibration field. Based on the equation of motion of a particle in a vibratio­nal field for the case of a spherical shape of the particle, which is in free conditions under a laminar regime of motion, taking into account the dependence of the density of the suspension on the density of the solid phase and liquid, the viscosity of the suspension on the viscosity of the liquid and density of the solid phase, a new differential equation is obtained. The obtained equation of dynamics of a heterogeneous li­quid-solid medium in a technological apparatus with bubbling is solved by a software solution in the Python environment, with the introduction of the sympy library using complex Conjugation and simplification. Relations are obtained for controlling the concentration of the suspension formed in the technological apparatus after bubbling flue gases through a liquid layer. The presented results of the software implementation of the model confirm that with an increase in the frequency of the vibrational field, the relative amplitude of the solid phase decreases, and therefore its effective mass participating in the vibrations of the medium.
      PubDate: 2020-05-21
      DOI: 10.33955/2307-2180(2)2020.51-56
       
  • Femtosecond Optical Tomography

    • Authors: O. A. Kalnaya, Yu. S. Kurskoy
      Pages: 57 - 60
      Abstract: The aim of the work is development of medical optical tomo­graphy technologies. The physical principles, tasks, and boundary possibilities of the optical tomography systems are considered. The autors propose to use the femtosecond lasers, operating in the «optical comb» mode, as a lught source in optical tomography system. The advantages of this source uses were analyzed and reso­lution power of femtosecond optical tomographs was calculated in the artical.
      PubDate: 2020-05-21
      DOI: 10.33955/2307-2180(2)2020.57-60
       
  • Eloboration of Methods for Determination on Content of the Oxygen,
           Nitrogen, Hydrogen Admixtures in Titanium Aluminides

    • Authors: M. M. Kalyniuk, Ya. P. Gritskiv, L. M. Kahitanchuk
      Pages: 61 - 67
      Abstract: Titanium intermetalides (TiAl and Ti3 Al) and alloys on theirs bases applies in air — and spacetechnology and automobile industry. Physical and mechanical properties there alloys is better, then at classical Ti — or Ni — alloys, that are utilized in aeroplanes and rocets. Alloys, based on TiAl and Ti3Al, are made with utilization vacuum — arc, plasma — arc, induction- garnisage, magnetoperating electroslag melting, electron — beam melting with intermediate capacity, electroslag melting in inert atmosphere under «active» fluxes with metallic calcium, induction melting in muchsectional crystallizator and cold crucible, argon — arc melting with unexpended tungsten electrode in copper watercooling crucible. For connection of the details, that were made from these alloys, there were used welding by pressure, contact, electron — beam, diffusion welding. Alloys, based on titanium aluminide, have essential defects — high brittleness and low plasticity, viscosity and resistance thermal impact strength. Autors a lot of articles explaines these descriptions by structural special features of titanium aluminides and alloys on their bases, but does not consider possibilities of the influence by oxygen nitrogen, hydrogen admixtures. In literature information about methods of determination gaseous admixtures (O, N, H) contents in titanium aluminides and alloys on their bases are absented. Methods of determination oxygen, nitrogen, hyd­rogen contents in titanium aluminides on ana­lysers TC436, RO316, TN114, RH402 are created. Parameters of these methods are described in this article (temperatures of heating on graphite crucibles, times, masses of analytical samples).
      PubDate: 2020-05-21
      DOI: 10.33955/2307-2180(2)2020.61-67
       
  • Definition and Analysis of the Main Requirements for Laboratory Competence

    • Authors: О. А. Nykytyuk, V. М. Novikov
      Pages: 68 - 71
      Abstract: The work is devoted to the study of the actual issue of technical regulation and metrology — determination of criteria of competence of laboratories. The results of the worldwide accreditation work are subjective in nature and therefore require continuous improvement in the assessment methods used to determine the compliance of laboratories with standard competency requirements. The analysis of the main elements of the management system, which, in accordance with the Paretto principle, mainly form the competence of laboratories in its accreditation in the national body was held. For the first time, the authors, with the involvement of all stakeholders, have analyzed and identified major competency requirements for laboratories across a wide range of DSTU ISO / IEC 17025: 2017 requirements. Also, for the first time, the technology of peer review was applied to the analysis of the criteria of competence of laboratories. The recommendations of ILAC, EA and EUROLAB international organizations for the criteria of competence of laboratories are analyzed in detail. Particular attention is given to the introduction of specific requirements for staff competence and accreditation criteria, which are in one way or another related to the competence of the laboratory staff. It has been established experimentally (by the method of expert evaluation) that such elements of the management system as risk management, personnel management, internal audit, intralaboratory control and interlaboratory comparisons are considered today to be the most important in confirming the competence of a laboratory.
      PubDate: 2020-05-21
      DOI: 10.33955/2307-2180(2)2020.68-71
       
 
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