No abstract

-Contacts between pantograph and catenary are the most critical parts in the transmission of electrical energy for modern high-speed trains. Contact wire oscillations change combined force between pantograph and catenary, and the contact may even get lost. Therefore special pantographs and catenaries have been developed and further constructive changes are under development. A design criterion includes the permanent contact of pantograph head and contact wire at high speed and the reduction of both aero acoustic noise and wear. Because of complicated dynamic behaviour and very high costs for prototypes, all modifications and new design concepts for the pantograph/catenary system are essentially based on dynamical simulation. Traditional approaches focus on the catenary, which is modelled as set of coupled strings and/or beams, whereas simplified lumped mass models are used to describe the pantograph. Nowadays increased computer power allows considering applications with more refined pantograph modes (e.g. the elasticity of the pantograph) and active control components in innovative pantograph concepts.Keywords -interaction pantograph-catenary, mechanical multibody system, high performance computing in MATLAB

Abstract. An analytical solution has been obtained for a problem on magnetohydrodynamic flow in a rectangular duct with perfectly conducting Hartmann walls and side walls of finite conductivity. The slip boundary conditions for velocity were applied to the duct side walls. The exact analytical solution of the problem has been obtained in the form of convergent series. On the base of the obtained analytical solution the velocity field of the flow has been studied numerically.Keywords: MHD duct flow, slip boundary condition. IntroductionA flow of electrically conducting fluid in the presence of external magnetic field produces a variety of new effects, which are not realizable in usual hydrodynamics. These effects are studied by magnetohydrodynamics (MHD), the discipline combining the classical fluid mechanics and electrodynamics.Electromagnetic methods of action on electrically conducting medium are widely exploited in industrial processes in metallurgy, material processing, chemical industry, industrial power engineering and nuclear engineering in order to control and manipulate various conducting materials. Besides, the MHD effects are exploited in technical devices such as MHD pumps, flow meters, MHD generators and accelerators, where channels with electrically conducting fluids are their common parts. Thus, investigation of MHD phenomena in channels with conducting fluids is quite important.In magnetohydrodynamics the number of exact analytical solutions is limited due to the nonlinearity of the Navier-Stokes equations. Therefore, numerical methods are widely used for solving these problems, although analytical solutions still do not lose their importance (even if these solutions are often obtained for simplified flows). The present analytical study was motivated by the recent publication [2], in which three classical MHD problems were considered, but the applied boundary condition at the interface between the electrically conducting fluid and the insulating solid walls was the hydrodynamic slip condition. Despite the no-slip boundary condition is usually applied for the majority of flows of viscous fluids, there exist situations when no-slip boundary conditions lead to unrealistic behaviour, for example, if viscous effects at the wall are negligible, then the slip boundary condition must be applied (see [1; 2]). This paper presents an exact analytical solution obtained for a new problem on a MHD flow in the rectangular duct with perfectly conducting Hartmann walls and the side walls of finite conductivity. The boundary condition applied to the Hartmann walls of the duct is the Dirichlet (no-slip) boundary condition, which is the simplest boundary condition for the velocity of viscous fluid, while the boundary condition applied to the side walls is the 3rd kind (slip) boundary condition. This solution seems absent in literature. Some numerical results for the velocity of the flow calculated on the base of the obtained analytical solution are also presented. It is to be noted that the study of the present prob...

No abstract

-This article continues research on the pantographcatenary system started in the previous papers [1], [2].The main purpose of the study is to use a computer of highspeed train to optimize the pantograph-catenary system by reducing power consumption when basic parameters of pantograph and catenary (contact network) change over time randomly.A linear model of pantograph-catenary system is considered where the upper and lower blocks of pantograph and catenary are modelled using lumped masses, springs and shock absorbers.The input and output system signals are measured when the train moves. These signals are processed by parametric identification algorithms to determine current values of system matrices. State matrices are used in Riccati equation to calculate controller coefficients. Adaptive controller provides dynamic stability of the system when its parameters change over time, and the system is subject to random external perturbations.