International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

The article is devoted to the problem of comprehensive evaluation of the efficiency of the use of various alternative fuels obtained from natural gas (NG) in a total life cycle (TLC). Despite the fact that all types of motor fuel under consideration are produced from NG, the energy and environmental consequences of their use may vary significantly. Goals of this research are: developing TLC mathematical models of a power unit operating on motor fuels obtained from NG (compressed NG, liquefied NG, methanol, dimethyl ether, synthetic diesel fuel and hydrogen) and conducting a simulation in order to determine energy and environmental indicators for the use of the considered fuel types. The results of simulation allow to choose the most promising types of alternative fuels according to the criteria of energy efficiency and a level of environmental pollution by harmful substances and greenhouse gases.

An approach for creation of biophysically based models for the steady state current of cyclic processes is investigated. When the process (like chemical reactions) can be described by a system of linear ordinary differential equations, an analytic expression for its steady state exists. The analytic expression is especially simple for the current of single cycle processes. In biologic context, concentrations of many substances change in a very restricted (patho)physiological range. This allows neglecting some terms of the analytic expression and thus obtaining biophysically based models that are both simple and adequate for description of currents produced by enzymes, pumps or transporters. The approximations obtained could be reduced to the existing empirical models. A clear way of expanding a specific empirical model for obtaining the desired quality and range of validity is also represented. The described approach is general and can be useful for creating biophysically based models of other types of processes.

This paper focuses on designing mathematical model a integrated bioethanol supply chain (IBSC) that will account for economic and environmental aspects of sustainability. A mixed integer linear programming model is proposed to design an optimal IBSC. Bioethanol production from renewable biomass has experienced increased interest in order to reduce Bulgarian dependence on imported oil and reduce carbon emissions. Concerns regarding cost efficiency and environmental problems result in significant challenges that hinder the increased bioethanol production from renewable biomass. The model considers key supply chain activities including biomass harvesting/processing and transportation. The model uses the delivered feedstock cost, energy consumption, and GHG emissions as system performance criteria. The utility of the supply chain simulation model is demonstrated by considering a biomass supply chain for a biofuel facility in Bulgarian scale. The results show that the model is a useful tool for supply chain management, including selection of the optimal bioethanol facility location, logistics design, inventory management, and information exchange.

The paper proposes a mathematical model for describing the dynamics of multicomponent emulsions, based on ideas and methods of the kinetic theory of gases. The methodological basis of the proposed theory is the ideas and methods of the theory of integral kinetic equations.

The efficient operation of the harvesting transport complex (grain harvester – transport aggregate) depends on the organization of the transport service and the identification of the necessary means of transport is a probable task.

An economically viable ratio counts combines, service vehicles for which minimizes the target function:

Overview of pre-selection – transport complex as a mass service system.

When machines are operating in a group, service requests are continually being carried out on a grain harrow filled grain hopper and after unloading the hopper, the combine is restarted and is a potential source of new orders.

Thus, the "harvester-car" system is considered a mass service system in which a service request per unit time arises on average. We assume that the stream of queries is a simple (Poisson) stream that is ordinarily, stationary, and without consequences.

The proposed model is certified with real data for agricultural cooperative in Yambol and the results show that for 5 CLAAS combine harvesters, is optimally served by three cars working in a group.

Based on the analysis of the mathematical model of the motor grader movement in the process of implementation of working operations, the factors that have the greatest influence on formation of the machine’s motion path are identified. It is proved that some of the factors characterizing the parameters of the machine and technological process have a destabilizing impact on the formation of the grader motion path, while the rest of them have a stabilizing impact. The analytical research enables developing practical recommendations to ensure the movement of the machine along a predetermined path without deviations.

This paper presents the process of developing and studying of a complete mathematical model of the spatial movement of drones. The model synthesized is used in their automatic control systems.

A major part of working operations performed by a motor-grader is accompanied by asymmetric action of the resultant vector of external resistance forces applied to the main blade. The eccentrically applied horizontal loads together with additional lateral forces affect the parameters of the machine road-holding ability resulting in deviation of its actual trajectory from the planned one. In the presented work on the basis of the developed model there have been analyzed the impact of operational characteristics of the working process on the indicators of the machine road-holding ability.

Paper deals with the dynamic behavior of pump unit electric drive. The electric motor, subject of development, is a new standard efficiency induction motor with squirrel cage rotor, designed to operate in continuous operation. The determination of operating characteristics of induction motor in dynamic modes is necessary to establish the properties of the machine in specific conditions. In some industrial areas can occur very often sags with a depth of between 10% and 15% of the rated voltage as a result of switching electrical loads on systems of users. As a result of simulation studies the influences of the supply voltage and total torque of inertia of the electric drive have been assessed on arising impact torques and currents and electric energy losses of electric drive for pump unit. The results obtained are in addition to experimental studies of the same motor. Some of the study results have been presented graphically. An analysis and conclusions from the results obtained have been done

In the present article, a mathematical model is developed to describe the motion of solid particles of micro- and nano-size in a gaseous medium. The model is represented by certain integro-differential equation with appropriate initial and boundary conditions. A probabilistic interpretation of the model is provided and its solvability is studied. We find that unique solution exists at certain sufficient condition. It is shown that the Fokker-Planck equation can be obtained from the integro-differential equation. Finally, a generalization to the 2D case is performed.

In this paper, we propose a physico- mathematical 3D model to study some of the basic features of the interaction of radiation with solid materials ( metals, semiconductors , insulators ) under the action of femtosecond laser pulses. The constructed model is a parametric model that, in particular, takes into account the dependence of the physical and chemical characteristics of the periodic nano- surface structures controlled laser irradiation parameters the polarization, angle of incidence, the energy density, wavelength, etc. The developed model is meant for the excitation of periodic nano-surface structures by electric waves which are in the process of irradiation and periodically amplified and attenuated, i.e. it holds periodic interference.

The oil products remain the main contaminant of the Black Sea, as well as of the entire world’s oceans. A main amount of oil is transported by tankers and reloaded in port terminals. 12 per cent of overall marine pollution is the share of transportation, oil congestion and accidents losses. At the Caspian-Black Sea-Mediterranean area there are actively used the Black Sea ports of Batumi, Poti and Kulevi.
A huge damage to the nature is doing by oil spills on the surface of the oceans and seas owing to transportation oil by tankers. These spills are associated with loading and unloading operations as well as with tankers accidents. In this case, the oil spreads as a spot on the surface of the sea.

Problems associated with environmental pollution from the oil spill in the sea, made necessity to develop mathematical models that describe the transportation and transformation processes of oil spills. The proposed mathematical model can be used for prediction of the spread of an oil spill during the process of spreading of oil products on the water surface, and it also enables to take into account the reduction of the area of spill due to the action of sea-surface winds and turbulence of the water surface.