An application of the maximization technique in the synthesis of polynomial adaptive algorithms for a posterior (retrospective) estimation of the change-point of the mean value of random sequences is presented. Statistical simulation shows a significant increase in the accuracy of polynomial estimates, which is achieved by taking into account the non-Gaussian character of statistical data.
Electrolytic capacitors are widely used in several power electronic systems. Their high energy density (J/cm³) features make them an attractive candidate for smoothing voltage ripple in supply circuitry. However, electrolytic capacitors have the shortest life span of components in power electronic circuits, usually due to their wear-out failure. The main wear-out mechanisms in electrolytic capacitors are the loss of the electrolyte by vapor diffusion trough the seals and the deterioration of the electrolyte. In this paper, a corrective model for reliability prediction is presented. This...
The paper deals with a theoretical analysis and a feasibility study on a method for measurement of temperature difference between two objects. An idea of distributed and self-powered system for indirect measurement of ?T is presented. It relies on two nodes consisting of thermoelectric modules (TEMs), instead of dedicated temperature sensors. Therefore, the essence of the method requires a wireless link to exchange data between two points (not necessarily to transfer measured data to a hub). Due to the Seebeck effect, the thermoelectric devices respond with output voltages proportional to...
In this paper some interesting and novel features of a four-terminal (4T) network are presented. A single DC current source is switched over and connected in turns to opposite arms of the four-element bridge circuit. This two-voltage-output circuit is called a double current bridge. The output voltages are dependent on the arm resistance increments and their values are given in absolute and relative units. The accuracy measures (limited errors and standard uncertainties) of two transfer functions are presented. A simple application with two sensors acting as strain gauges and RTD’s is...
The paper deals with eigenvalue and eigenmode analysis of a model of eddy current sensor over the testing object. This object is made of conducting materials without and with discontinuities. The mathematical model is defined by a Helmholtz equation, and it is the fundamental model to eigenmode analysis. It can be classified as a quasi-static problem in electromagnetics. With finite element method (FEM) the eigenvalues of systems are calculated and the distribution of magnetic flux density (mode) for the eigenvalue are presented.
During recent years the surface texture measurement and analysis has become one of the most important fields of interest in modern metrology. So, the development of the new filtering methods, enabling to separate surface’s components of different scale, should not be surprising. However, Gaussian linear filter, in spite of its significant drawbacks, remains the one and the only filter used by the vast majority of engineers in their professional performance. It is a result both of the chaos brought by the dozens of filtration algorithms proposed recently and the low consciousness of their...
Coal mine methane is a term given to the methane gas produced or emitted in association with coal mining activities either from the coal seam itself or from other gassy formations underground. The amount of methane generated at a specific operation depends on the productivity of the coal mine, the gassiness of the coal seam and any underlying and overlying formations, operational variables, and geological conditions. The primary reason for measuring methane is to improve the safety of the mines. In recent years, there have been many fatalities in underground coal mine explosions in which...
Modern railroad applications must fulfill proper reliability, availability, maintainability and safety (RAMS) specifications in compliance with the requirements of widely accepted international standards such as EN 50126-1:1999 and EN 50126-2:2007. In rolling stock two complementary hazards with potential critical consequences for passengers and personnel arise from the inability to determine if a vehicle is in motion and from the inability to detect if the operator driving the train is incapacitated. While the probability of occurrence of both events is remote, the level of risk of such...
Electric energy quality criteria relating to a DC supply system concerns the circuits from the rectifiers installed in traction substations till the vehicle's current collector. Energy Law and related implementing provisions unequivocally state that an electrified transport system as the energy recipient shall fulfil the requirements regarding energy consumption, which are defined in the agreement. It imposes certain requirements for the Department of Electrical Power Rail. Introduction into traffic of the traction vehicles that are equipped with converter power electronics drive systems...
The use of power electronics in modern drive systems that are used for traction purposes, makes it necessary to conduct EMC control regarding disturbances in operation of other devices of railway infrastructure that are caused by the vehicles, especially in traffic and signalling management systems. One of the investigated parameters is the value of input impedance of a vehicle. The article presents the results of works on analysis of traction vehicles input impedance as well as impedance measurements under laboratory conditions. The possibility of on-line measurements of impedance in...