The paper deals with mathematical modelling of dynamic response of the electric locomotive wheelset drive caused by short-circuit traction motor torque. The individual wheelset drive is composed of five subsystems - rotor of the traction motor with driving gear, driven gear, stator of the traction motor with gear housing, hollow graduated shaft with clutches and wheelset. The couplings between subsystems are linearized in dependence on longitudinal creepage and locomotive forward velocity before sudden short-circuit in the asynchronous traction motor. In comparison with previous models of the wheelset drives, the rotor of the electromotor is characterized by flexible shaft suppported on flexible rolling-element bearings. The sheet metal packjet of cylindrical shape is connected by parallel cooper bars with two short circuit rings. In conseqquence of strong excitation an interruption of gear mesh can be observed. This nonlinear effect and dynamic load of individual wheelset drive with large number of DOF is investigated using the condensed mathematical model created by model synthesis method. and Obsahuje seznam literatury
The paper deals with the mathematical modelling and the computer simulation of forced vibrations of the reactor core barrel excited by pressure pulsations generated by main circulation pumps. The modelling is focused on a possible core barrel flange slip along a pressure vessel flange. The slip in this internal reactor linkage is analysed providing the solid friction and the backlash between slip tongues of the pressure vessel flange and grooves in the core barrel flange. The impact motion can produce an excessive abrasive wear of the tongues and grooves. A guarantee of the fail-safe operation is achieved by calculated pre- stressing of toroidal tubes inserted between the upper flange of the core barrel and the pressure vessel cover. and Obsahuje seznam literatury
We model a market with multiple liquidity takers and a single market maker maximizing his discounted consumption while keeping a prescribed probability of bankruptcy. We show that, given this setting, spread and price bias (a difference between the midpoint- and the expected fair price) depend solely on the MM's inventory and his uncertainty concerning the fair price. Tested on ten-second data from ten US electronic markets, our model gives significant results with the price bias decreasing in the inventory and increasing in the uncertainty and with the spread mostly increasing in the uncertainty.
A topologically oriented neural network is very efficient in real-time path planning of a mobile robot in dynamic environments. Using a dynamic recurrent neural network to solve the partial differential equation of a potential field in a discrete manner, the problem of obstacle avoidance and path planning of a moving robot can be efficiently solved. A dimensional network used to represent the topology of the robot's workspace, where each network node represents a state associated with a local workspace point. In this paper, two approaches associated with different boundary conditions are proposed, namely, Dirichlet and Neumann conditions. The first approach relies on a field of attraction distributed around the moving target, acting as a unique local extreme in the local network space. The steepest gradients of the network state variables will aim towards the source of the potential field. The second approach considers two attractive and repulsive potential sources associated with the start and destination points. A dynamic neural mesh is used to model the robot workspace. A simulation package has been built and extensive computer experiments were conducted to demonstrate and validate the reliability of the presented approach.
We investigate the problem of power utility maximization considering risk management and strategy constraints. The aim of this paper is to obtain admissible dynamic portfolio strategies. In case the floor is guaranteed with probability one, we provide two admissible solutions, the option based portfolio insurance in the constrained model, and the alternative method and show that none of the solutions dominate the other. In case the floor is guaranteed partially, we provide one admissible solution, the portfolio insurance with spreads.
This paper is devoted to a new approach to the dynamic response of Soil-Structure System (SSS), the far field of which is meshed by decay or mapped elastodynamic infinite elements, based on scaling modified Bessel shape functions to be calculated. These elements are appropriate for Soil-Structure Interaction problems, solved in time or frequency domain and can be treated as a new form of the recently proposed elastodynamic infinite elements with united shape functions (EIEUSF) infinite elements. Here the time domain form of the equations of motion is demonstrated and used in the numerical example. In the paper only the formulation of 2D horizontal type infinite elements (HIE) is used, but by similar techniques 2D vertical (VIE) and 2D corner (CIE) infinite elements can also be added. Continuity along the artificial boundary (the line between finite and infinite elements) is discussed as well and the application of the proposed elastodynamical infinite elements in the Finite element method is explained in brief. A numerical example shows the computational efficiency and accuracy of the proposed infinite elements, baeed on scaling Bessel shape functions. and Obsahuje seznam literatury
The paper deals with the modelling of forced vibrations of reactor components excited by pressure pulsations generated by main circulation pumps. For the vibration analysis a new generalised model of the reactor with spatial localization of the nuclear fuel assemblies and protection tubes, continuously mass distribution of beam type components and more accurate model of the linear stepper drives for actuation of control cassettes was applied. Slightly different pump revolutions are sources of the heating which causes an amplification of vibration and possibility of the contact loss in internal linkages of the core barrel. and Obsahuje seznam literatury
The paper deals with the dynamic transmission error (ТЕ) measurements of a simple gear set at gearbox operational conditions that means under load and during rotation.
The analysis method is focused on the processing of impulse signals generated by incremental rotary encoders attached to the gears in mesh. The analysis technique benefits from demodulation of a phase-modulated signal. The theory is illustrated by experiments with a car gearbox and measurement errors are discussed. and Obsahuje seznam literatury
According to the present author´s results a following system of the galactic dynamical constants is proposed: local escape velocity, u = (520+30) km s^-1, local circular velocity, u = (230+30) km s^-1, local angular velocity of rotation, ω = (25+5) km s^-1 kpc^-1, local circular frequency of planar oscillations, κp = (40+10) km s^-1, local circlar frequency of vertical oscillations, κz = (70120) km^-1 kpc^-1. The value of (9+1), kpc is assumed fpar the galactocentric distance of the Sun. The latter three values yield (0.09±0.03) pc^-3 for the local matter density, a value very close to the density obtained by use of statistical methods. On the basis of the proposed value it is concluded that the dark matter should to present in the form of a large, rerefied, massive, spherical corona.
The dynamical evolution of short-period comets, and in particular of those belonging to the so-called Jupiter family, is reviewed. Encounters with Jupiter play a dominant role in determining the
dynamical fate of these objects, although, in some peculiar cases, also interactions with other planets may be important. Frequent although temporary librations around resonances with Jupiter are displayed by more than one third of short-period comets. Integrations of motion of observed comets, over a time span comparable with their lifetime as active objects, are compared with previous numerical investigations, to get insight into the non observed phases of the dynamical evolution of these objects.