Detection of shorted-turns in the field winding ofturbine-generator rotors using novelty detectors-development and fieldtest

A method for detecting shorted windings in operational turbine-generators is described. The method is based on the traveling wave method described by El-Sharkawi, et. al. (1971). The method is extended in this paper to operational rotors by the application of a neural network feature extraction and novelty detection. The results of successful laboratory experiments are also reported     

Improving the accuracy of autotransformer and transformer alternating-current bridges

Variable-ratio and computational methods are described for improving the accuracy of autotransformer and transformer ac bridges that take into account and eliminate the additive and multiplicative components of the systematic error due to connecting leads and jumpers of the measuring circuit. Translated from Izmeritel'naya Tekhnika, No. 6, pp. 61–63, June, 1996.     

Specific heat of a marginal Fermi liquid

The temperature dependence of a marginal Fermi liquid has been calculated. We showed that the expectedT lnT correction is characteristic for the low-temperature domain. The high-temperature domain has a supplementary correction. The results are in agreement with the non-Fermi behavior of some metallic systems the in low-temperature domain.     

Effective index drift from molecular hydrogen diffusion inhydrogen-loaded optical fibres and its effect on Bragg gratingfabrication

When hydrogen loading is used to enhance the photosensitivity of silica-based optical waveguides and fibres, the presence of molecular hydrogen dissolved in the glass matrix changes the effective index of propagation of guided optical modes by as much as 0.05%. Real-time monitoring of the reflectivity spectrum of Bragg gratings written in such conditions shows that the centre wavelength follows the changes in hydrogen concentration due to diffusion and reaction with glass defects     

Accurate estimation of environment parameters from ultrasonic data

This paper describes a robust and accurate ultrasonic sensing system for a mobile robot. The system continuously updates a local map of the environment in which obstacles are represented by straight lines or points in a robot centered coordinate frame. The presented algorithms use a Kalman filter for the reduction of the noise in the ultrasonic data and use a systematical error correction (‘bundle correction’) to reduce the uncertainty in obstacle direction. Experiments are carried out in simulation and with a real mobile robot system. Results show that the accuracy with which line parameters can be estimated is in the order of 1 degree for the orientation and about 2 cm for the position. The effect of the bundle correction is significant and maximal when the robot approaches walls under a small angle.     

Gain control in reflex pathways

Summary form only given. A series of experiments was undertaken to determine the gain of the stretch reflex in decerebrate cats. Stretches are applied through a servo-controlled motor that receives length and velocity feedback which are adjusted so that it behaves like a spring of a particular stiffness. As the stiffness decreases the gain of the reflex increases until the stiffness is made much less than the intrinsic muscle stiffness. Under these conditions small brief pulses can elicit shortening of 1 mm or more and reflex forces that are larger than the force produced by the stretch itself. This suggests that the gain in the reflex is 1 or more at low frequencies. It is concluded that muscle control systems are adaptive and time-varying to accomplish the various tasks required by the organism. Although under some conditions the reflex gain is on the order of one, measurement of gain is compounded by a number of nonlinearities, and the value of these nonlinearities in various tasks remains to be determined     

An electrical network approach to the analysis of semiconductordevices

A simple electrical network is used to represent the five differential equations describing basic phenomena in one-dimensional semiconductor devices. Both standard and integrated approaches for solving transport equations are developed. Also, an electrical network equivalent for the nonlinear Poisson equation was derived. It allows students to better understand the physical phenomena and the process of computer simulation of such semiconductor devices