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The paper presents the results of an analysis of the development of mobile traction and power means in agriculture: in most cases, a tractor is used in conjunction with agricultural machines and implements to perform technological operations; in order to increase labor productivity, there is a tendency to increase the power of the tractors used, and therefore the weight of tractors and machines connected to them increases, which leads to an increase in pressure on the soil and its over-compaction; When forming wide-cut units consisting of several agricultural machines with energy-saturated tractors, there is a need to use additional devices - couplers equipped with several support wheels, creating additional resistance to the movement of the unit, which increases the energy costs for performing the technological operation, reduces maneuverability, complicates the design and increases the metal consumption of the unit being formed. An analysis of the flow of scientific publications, including the Scopus database, showed that the interest of the scientific community in the research of robotic systems, including the development of agricultural unmanned vehicles, is growing every year. The article discusses the results of creating an unmanned traction-energy module and the method of its aggregation with agricultural machines. The use of the invention will simplify the design of traction and power equipment for agricultural purposes and agricultural machines, reduce their metal consumption, increase the productivity of agricultural units, reduce energy consumption and the cost of performing technological operations, and increase the level of unification of traction and power equipment for agricultural purposes and agricultural machines. [ABSTRACT FROM AUTHOR]

The existing equipment for electrofusion welding of polyethylene pipes does not allow obtaining a high-quality connection at air temperatures below minus 10°C. It is proposed to additionally preheat the heat-affected zone of the welded joint with a built-in heater and control its cooling when welding under ambient conditions in the temperature range from minus 50 to plus 40°C. The results of calculations are presented that confirm the effectiveness of the proposed method for controlling the thermal welding process at low temperatures. [ABSTRACT FROM AUTHOR]

It is proposed to approximate data from differential scanning calorimeter (DSC) at different rates of temperature change by two-dimensional cubic splines to consider distribution evolution of crystallinity degree of polymer material when modeling thermal process of welding polymer pipes. Formulas are obtained for determining the change in time of crystallinity degree at each point of test compound according to function of DSC heat flux for variable rate of temperature change. Results of calculations of thermal regime of polyethylene pipes welding are presented. [ABSTRACT FROM AUTHOR]

The method of thermal diagnostics of friction (TDF) has been developed in detail for radial sliding bearings with rotary motion of the shaft, which makes it possible to determine the friction force from temperature data.The possibility of determining the frictional moment by measuring the temperature is theoretically shown in the case of the swinging motion of the shaft using a two-dimensional mathematical model of the thermal process. The use of a two-dimensional model limits the use of the TDF method for solving practical problems. In this paper a three-dimensional model of the thermal process is proposed, taking into account the rotating speed of the shaft for a sliding bearing operating in a reciprocating-rotational mode. Taking into account the speed of the shaft movement leads to a significant increase in the calculation time, which is not always desirable for TDF based on solving the inverse problem of heat transfer. Determining the conditions under which it is possible to disregard the speed of the shaft in the thermal process model is an urgent problem. The method for determining the kinematic conditions for accounting for the speed of the shaft in the mathematical model of the thermal process is proposed on the basis of a numerical analysis of the unsteady three-dimensional temperature field in a radial self-lubricating sliding bearing. The results obtained can be used for TDF in real sliding bearings. [ABSTRACT FROM AUTHOR]

The article examines the issues of aeration modelling (organized natural air exchange) in quarries using guiding devices. The simulation was carried out in a wind tunnel, which makes it possible to study the aerodynamics of air currents in the goaf and evaluate the effectiveness of the use of the guiding device. The design of a closed-circuit wind tunnel and the modelling technique are considered. [ABSTRACT FROM AUTHOR]

The paper considers the problem of determining non-stationary temperature field during welding tapping saddles to polyethylene gas pipeline at low temperatures during repair and restoration operations in pipeline with gas pressure. Technology for welding tapping saddle to polyethylene pipe at low temperatures in conditions of gas movement with negative temperature inside the pipe is proposed based on calculations. Results of determining technological parameters of welding are given. [ABSTRACT FROM AUTHOR]

In this work dynamics of temperature fields of the weld obtained at low air temperatures at various durations of keeping pipe ends in warm shelter is investigated, based on mathematical modeling of the thermal process. Calculations have shown that with insufficient heating of pipes in shelter, the dynamics of temperature fields during welding deviates from the dynamics of standard welding. Calculations show the boundaries of the melt under various welding conditions. Recommendations for welding polyethylene pipes at low temperatures using shelters are given. [ABSTRACT FROM AUTHOR]

The paper focuses on the stage of heating the welded ends of a polyethylene pipe and a coupling with special replaceable nozzles for subsequent welding at low temperatures. The thermal process is simulated in a polyethylene pipe in contact with a replaceable nozzle, the base of which is kept at a constant temperature by means of a heating plate with a set temperature. The results of calculations demonstrate a temperature distribution close to homogeneous in a pipe wall, which was obtained by heating with a replaceable packing followed by free cooling to equalize the temperatures. [ABSTRACT FROM AUTHOR]

The present paper introduces a technique for determining technological parameters for welding polyethylene pipes into a socket at low temperatures on the basis of mathematical modeling of the thermal process according to the regularities corresponding to the temperature change during welding under conditions of air temperatures acceptable for welding. The calculation of the technological parameters of welding is performed with account taken of a two-phase zone in which the substance is in both solid and liquid states. [ABSTRACT FROM AUTHOR]

Distinctive features of the stress-strain state of a welded joint depending on the ambient air temperature are investigated by comparative analysis of temperature fields, stress fields and displacements during the heating and cooling processes of welding. The results reveal that the pressure between the pipe and the coupling during the formation of a welded joint is lower when welding is performed at low temperatures than when it is performed at an acceptable temperature. The calculations explain the low strength of the coupling welds produced at low temperatures. [ABSTRACT FROM AUTHOR]

A method of thermal diagnostics of friction in a system of polymeric sliding bearings at low shaft rotation speeds is developed. The efficiency of the method is checked by comparing the values of the moments of friction obtained by solving the inverse problem and by measuring with an inductive sensor of a serial friction machine. It is established that the agreement of the values of the total moments of friction obtained by fundamentally different methods is in the range between 10 and 15%. [ABSTRACT FROM AUTHOR]

The thermal process of electrofusion welding of polyethylene gas pipelines at air temperatures below the standard is investigated. The mathematical model used in the research takes into account the heat of the phase transition in the temperature interval. Computational experiments show the possibility of regulating the temperature regime for welding at low ambient air temperatures and providing the same temperature field variation in the thermal zone as with the permissible air temperatures. [ABSTRACT FROM AUTHOR]

The present paper outlines a procedure for determination of dynamics of the temperature field during the welding of the branch saddle to the polyethylene gas pipeline at ambient temperatures below the normative. The analysis is accomplished by the finite element method with the heat of the phase transition taken into account. Methods of the visualization of data sets reveal the possibility of controlling the thermal process by preheating and thermal insulation during welding of the branch saddle to the pipe at low temperatures and the possibility of obtaining the dynamics of the temperature field at which a high-quality welded joint is formed. [ABSTRACT FROM AUTHOR]

The thermal process of welding a saddle branch to a polyethylene pipe is considered with the heat of the phase transition taken into account. The corresponding three-dimensional nonlinear equation of thermal conductivity is solved by the finite element method in a complex domain. The technological operations necessary for welding the saddle branch to the polyethylene pipe at air temperatures below standard are defined based on the study of the dynamics of the temperature field during welding at various ambient temperatures. [ABSTRACT FROM AUTHOR]

A technique is developed for calculating the width of the contact edge of the roller-heater in a unit for thermo-adhesive extraction of diamond grains from a concentrate based on an analysis of the temperature field dynamics in the "heating element-diamond-thermo-adhesive substance" system. The developed technique will increase the efficiency and productivity of the plant. [ABSTRACT FROM AUTHOR]

On the basis of computing experiments on thermal process modeling, it is shown that preheating with a gradient distribution of temperature for welding polypropylene pipes into the socket at low temperatures allows receiving more homogeneous distribution of temperature at the time of crystallization of a weld seam in comparison with welding at admissible temperatures. [ABSTRACT FROM AUTHOR]

The thermal process of welding polyethylene pipes for gas pipelines at temperatures below standard is theoretically studied. The used mathematical model considers the heat of the phase change within the temperature range and the heat effect formed at burr setting. Computing experiments indicate the possibility of regulation by temperature conditions when welding at low ambient air temperature and the possibility of providing the same change of the temperature field as at admissible air temperature in the heat-affected zone. [ABSTRACT FROM AUTHOR]

The bench and field testing of friction units of machines and mechanisms reveal inability to measure the frictional force with existing devices, and this significantly reduces the information content of these tests and the accuracy of the diagnostic methods of the technical condition of the test tribounit. This paper presents the development of a method of heat friction diagnostics determining the function of frictional heat and, therefore, the friction torque in a bearing system taking into account the movement of the shaft. The principle of the method is as follows: temperature measurements by time are made in the contact zone of the sleeves. This allows constructing a mathematical model of the thermal process in the friction unit. The solution of the boundary inverse problem detects frictional heat correlated with the friction torque.. [ABSTRACT FROM AUTHOR]

This paper proposes a method for the determination of the duration of heating polyethylene pipes in coils by heated air during the installation and laying works in the construction of gas pipelines under the conditions of low temperatures. The mathematical model of thermal process of heating polyethylene pipes by heated air is considered. Calculation results on the heating duration of a polyethylene pipe are given in the range of external air temperatures at a known flow rate of heated air supplied inside the pipe. [ABSTRACT FROM AUTHOR]

Non-isothermal evaporation of sessile liquid drops is analyzed. For temperature and concentration distributions the analytical formulae are derived as functions of the system and ambient parameters. Non-uniform temperature distribution on drop surface results in Marangonni force. Extremes of surface temperature cause Marangonni force to change its direction in stagnation points. Critical values of system parameters, at which stagnation points take place, are found. Position of these points is derived as function of thermal properties of substrate, liquid and gas and contact angle. [ABSTRACT FROM AUTHOR]

Reliable modeling of multiphase pipe flows demand the development of fast and robust numerical techniques. The presented in this paper study proposes a multi-fluid model and its implementation using the Jacobian-Free Newton-Krylov (JFNK) method. The fully implicit formulation framework described in this paper will enable to efficiently solve governing fluid flow equations. A reduction of a multi-fluid model in zones of phase disappearance based on the phase state distribution over the cells is considered within the numerical method where the single phase cells and multiphase cells are distinguished by solving reduced set of governing equations for single phase cells. Current algorithm for slug flows simulations and further perspectives are proposed and discussed in this paper. [ABSTRACT FROM AUTHOR]

The two-fluid two-pressure model for 1D gas-liquid pipe flows is considered. The system of governing equations is hyperbolic and can be formulated in a conservative form. The model is implemented numerically using a Godunov-type scheme with GFORCE numerical flux. Two simulationcases are presented: water faucet test to validate the numerical scheme and air-water flow in a V-tube to demonstrateslug capturing technology in the frame of the approach considered. [ABSTRACT FROM AUTHOR]

We propose an approach for generalization of 1D transient model for multiphase flows. It allows to combine an arbitrary number of phases with interaction defined by multi-fluid and drift-flux models. Commonly a fluid carries a number of components. The model is based on a graph of fluids and components, where on higher level the flow of several fluids is governed by the multi-fluid approach, while on lower level the relative motion of components within each fluid is described by drift-flux relations. The proposed model is applied to flows in oil and gas wells. The model is implemented numerically using a SIMPLE-like iterative scheme with the geometry conservation based algorithm (GCBA). The numerical realization of the algorithm for an arbitrary number of fluids and components is presented. For illustration, particular cases are considered which are relevant to wellbore flows in oil and gas applications. The introduction of drift-flux correlations into the numerical implementation is discussed. The code is validated against experimental flow patterns and stability study of stratified flows. The typical graphs for gas/liquid transport are discussed. The simulation of phase segregation in a vertical pipe demonstrates the flexibility of model. [ABSTRACT FROM AUTHOR]

We present the results of developing a multi-fluid model for a transient multiphase flow in a pipe with application to oil and gas well cleanup after drilling or hydraulic fracturing. The model is an extension of the earlier work on multi-fluid models for near-horizontal pipes to cover any inclination angle and include additional phases. The 1D multi-fluid model governs a transient isothermal flow of three compressible fluids in a horizontal, deviated, or a vertical pipe. The multi-fluid model research code is based on well-known SIMPLE schemes, and features implementation of either a geometry or a mass conservation based algorithms. The multi-fluid model is able to predict the flow regimes with a single interface between gas and liquid mixture: stratified flow, flow with rolling waves, and flow with slugs. The code is validated against an analytical solutions and flow pattern maps. Agreement with theory is found in predicting the transition between the regimes. The final application of the model will be in transient wellbore dynamics with flow regime transitions. [ABSTRACT FROM AUTHOR]

We discuss the physics case for a new experimental setup that consists of the Crystal Ball multiphoton spectrometer and the CLAS12 forward detector installed at the tagged photon beam of Hall-B at JLab. The proposed apparatus will provide nearly 4π sr coverage and good energy and angular resolution for photons and protons allowing a detailed high statistics investigation of the reactions with multiple photons. Such setup can be used to investigate the spectrum of doubly-strange Ξ via their neutral decays, test C, CP, and T invariance in the neutral and charged decays of η and η′ perform precise measurements of the Dalitz and double Dalitz decays of pseudoscaler and vector mesons, etc. Such data may also shed new light on the existence and the properties of the earlier claimed light exotic mesons. [ABSTRACT FROM AUTHOR]

Equilibrium rate constants of inelastic processes in dense media have been studied with taking account the quantum corrections to the particle momentum distribution function (PMDF). These corrections arise at high medium pressure and relatively low temperature and can be treated as a manifestation of the time-energy uncertainty relation for particles colliding elastically at a high rate ν, so that the characteristic energy hν becomes comparable with the temperature. The main problem in evaluation of the rate constants of inelastic processes as well as PMDF relates to finding the scattering amplitude out of the energy shell. This problem is resolved within the frame of the approach developed based on the asymptotic representation of the wave function of scattering particles. The explicit solution has been obtained for the problem of vibrational relaxation of diatomic molecules. The specific calculations performed for low temperature atmospheric pressure relaxation of nitrogen result in a reasonable agreement with existing experimental data. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

The paper is devoted to studying the dusty plasma created by the injection of dust particles into the atmospheric pressure gas ionized by an electron beam of 85–120 keV energy. The beam current density was varied within 0.1–1.0 mA/cm2. The electron gun operated in the stationary regime. The behavior of dusty particles lighted by a laser “knife” was observed with a digital video camera. Stable plate-like structures were observed in the cathode sheath of non-self-sustained discharge. Numerical simulation was performed by using the non-local model of the non-self-sustained discharge. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

The detailed derivation of hydrogen weakly-nonideal plasmas EOS is presented. For the model hydrogen plasmas the values of computed sound velocity and adiabatic exponent along the Sun trajectory are presented. In our computations the relativistic corrections, degeneracy of electrons, radiation pressure in plasma, Coulomb interaction in Debye-Hückel approximation together with diffraction and exchange corrections, and the contribution of bound and scattering states are taken into account. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

A thermodynamic model SAHA-S for solar plasma is presented. Effects of Coulomb interaction, exchange and diffraction effects, free electron degeneracy, relativistic corrections, radiation pressure contributions are taken into account. Contribution of bound states of atoms and ions is corrected in comparison with Plank-Brillouin-Larkin formula. Calculations of equation of state of solar plasma with different element composition are carried out. Contribution of various plasma effects and chemical element abundance to thermodynamic functions and in particular Γ1 is discussed. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

We present solar models computed with a newly developed equation of state (EOS) of solar plasma, SAHA-S. SAHA-S is a solar version of the SAHA-* family of EOS designed for various states of matter. It incorporates modern state-of-the-art features such as arbitrary degenerated and slightly relativistic electron gas, improved formalism for Debye correction and generalized Planck-Larkin function which refines bound states contributions. We discuss standard solar models computed with SAHA-S and two versions of OPAL. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

As it was experimentally shown earlier, there is an intense IR radiation in purely thermal emission spectra of dense sodium vapors. Based on the assumption that the wing profile is formed by buffer gas quasistatic broadening in nearest neighbor approximation, a theoretical model for the far wing of sodium D-lines was developed. The model described the experimental results within an order of magnitude, unlike to the standard theory of radiation transfer. However, the validity of this approximation at large detunings is not evident. Thus, the problem of the intense IR emission of dense vapors remains open. Its origin was also assigned to the influence of sodium clusters. In order to verify this hypothesis an investigation of absorption spectra of dense sodium vapors in a wide spectral range (0.35 - 1.1 µm) was carried out. For verification of the validity of the nearest neighbor approximation at large detunings, numerical calculations of the distribution function of ionic microfields in dense plasma were carried out. [ABSTRACT FROM AUTHOR]