Thermal conductivity vs depth profiling using the hot disk technique-Analysis of anisotropic, inhomogeneous structures

A recently developed method for analyzing the thermal conductivity vs depth variation near a sample surface has been extended to include inhomogeneous samples with anisotropy. If not considered, the anisotropy ratio in the sample structure can distort the depth-position data of the original test method. The anisotropy ratio is introduced in the original computational scheme in order to improve the depth-position estimations for inhomogeneous structures with anisotropy. The proposed approach has been tested in experiments and shown to improve depth position mapping

A Reconfigurable Motor for Experimental Emulation of Stator Winding Inter-Turn and Broken Bar Faults in Polyphase Induction Machines (Journal article)

The benefits and drawbacks of a 5-hp reconfigurable induction motor, which was designed for experimental emulation of stator winding interturn and broken rotor bar faults, are presented in this paper. It was perceived that this motor had the potential of quick and easy reconfiguration to produce the desired stator and rotor faults in a variety of different fault combinations. Hence, this motor was anticipated to make a useful test bed for evaluation of the efficacy of existing and new motor fault diagnostics techniques and not the study of insulation failure mechanisms. Accordingly, it was anticipated that this reconfigurable motor would eliminate the need to permanently destroy machine components such as stator windings or rotor bars when acquiring data from a faulty machine for fault diagnostic purposes. Experimental results under healthy and various faulty conditions are presented in this paper, including issues associated with rotor bar-end ring contact resistances that showed the drawbacks of this motor in so far as emulation of rotor bar breakages. However, emulation of stator-turn fault scenarios was successfully accomplished

Energy spectrum, density of states and optical transitions in strongly biased narrow-gap quantum wells

We study theoretically the effect of an electric field on the electron states and far-infrared optical properties in narrow-gap lead salt quantum wells. The electron states are described by a two-band Hamiltonian. An application of a strong electric field across the well allows the control of the energy gap between the two-dimensional (2D) states in a wide range. A sufficiently strong electric field transforms the narrow-gap quantum well to a nearly gapless 2D system, whose electron energy spectrum is described by linear dispersion relations \epsilon_{\sigma} (k) ~\pm (k-k_{\sigma}), where k_{\sigma} are the field-dependent 2D momenta corresponding to the minimum energy gaps for the states with spin numbers \sigma. Due to the field-induced shift of the 2D subband extrema away from k=0 the density of states has inverse-square-root divergencies at the edges. This property may result in a considerable increase of the magnitude of the optical absorption and in the efficiency of the electrooptical effect.Comment: Text 18 pages in Latex/Revtex format, 7 Postscript figure

Impact of rotor design on interior permanent-magnet machines with concentrated and distributed windings for signal injection-based sensorless control and power conversion

© 1972-2012 IEEE. This paper examines the relationship between rotor design, saliency-based signal injection sensorless control, and power conversion properties for four industrially relevant interior permanent-magnet machine configurations: a 36-slot 6-pole stator with v bar rotor, a 36-slot 6-pole stator with flat bar rotor, a 9-slot 6-pole stator with v bar rotor, and a 9-slot 6-pole stator with flat bar rotor. The influence of rotor geometric design variables over the range of current densities at the maximum torque per ampere angle was found using a design of experiments\u27 methodology and standardized regression coefficients. Tradeoffs between sensorless control and power conversion properties are found using a Monte Carlo methodology. Power conversion and sensorless control properties were analyzed using hybrid static and time-stepping finite-element simulations

A Reconfigurable Motor for Experimental Emulation of Stator Winding Inter-Turn and Broken Bar Faults in Polyphase Induction Machines (Conference Proceedings)

The advantages and demerits of a 5-hp reconfigurable induction motor, which was designed for experimental emulation of stator winding inter-turn and broken rotor bar faults, are presented in this paper. It was perceived that this motor has the potential of quick and easy reconfiguration to produce the desired stator and rotor faults in a variety of different fault combinations. Accordingly, this would eliminate the need to permanently destroy machine components such as stator windings or rotor bars when acquiring data from a faulty machine for fault diagnostic purposes. Experimental results under healthy and various faulty conditions will be presented in this paper, including issues associated with rotor bar-end ring contact resistances, to demonstrate the benefits and drawbacks of this motor for acquiring large amounts of fault signature data

Study of School Child Motor Activity Using Individual Wearable Devices - Fitness-trackers

They presented the results of qualitative and quantitative indicator study concerning the motor activity of schoolchildren of both sexes, obtained by using individual wearable devices-fitness trackers. It was found that 8.2% of students, regardless of gender and age, are characterized by low values ​​of this indicator; 3.4% demonstrate high values ​​of the indicator relative to the hygiene norm