Broken rotor bar detection in induction machines with transient operating speeds

Previous work on condition monitoring of induction machines has focused on steady-state speed operation. Here, a new concept is introduced based on an analysis of transient machine currents. The technique centers around the extraction and removal of the fundamental component of the current and analyzing the residual current using wavelets. Test results of induction machines operating both as a motor and a generator shows the ability of the algorithm to detect broken rotor bars.     

On the equivalence of three independently developed phase-locked loops

Three independent research groups have proposed three apparently different architectures for an improved phase-locked loop (PLL) structure through three entirely different approaches. It is shown that all three PLLs are structurally and mathematically the same. A linear analysis is performed and concludes that the available theory for the design of conventional PLLs can be leveraged into the design of the new class of PLLs.     

Galerkin's method and the variational procedure

Galerkin's method and the variational procedure, when applied to most practical problems in electromagnetics, lead to matrix equations of the same form. Variational procedures for self-adjoint and nonself-adjoint operators also result in the same form of matrix equations for a large subclass of problems. However, the three cases may yield different matrix equations in general. This paper examines the subclass of problems for which these methods result in the same matrix equation and provides systematic ways for classification of problems for which two or all three of the cases lead to the same matrix equation. It also describes properties of the coefficient matrix in the matrix equation     

A molecular dynamics study of perturbed Poiseuille flow in a nanochannel

This paper reports the results from a nonequilibrium molecular dynamics (NEMD) simulation and analytical solution of Poiseuille flow through a nanochannel. Two kinds of external perturbing forces, sinusoidal and step pulse, have been applied on the flow passing through a nanochannel. A total number of 2,000 particles of simple fluid interacting with one another, according to the Week–Chandler–Anderson (WCA) potential model between two parallel plates, has been considered in this study. The flow is bounded by horizontal walls in one direction and periodic boundary conditions are imposed in the other two directions. The velocity profile predicted by molecular dynamics is a second-order polynomial and is in good agreement with the analytical solution based on the Navier–Stokes equations. The temperature profile obtained from the molecular dynamics simulation also conforms to the overall continuum predictions of a fourth-order polynomial energy equation. Moreover, in the vicinity of the boundaries, a jump in temperature profile has been observed.     

Performance characterization of a non‐linear system as both an adaptive notch filter and a phase‐locked loop

The behaviour of a non‐linear dynamical system is described. The system may be characterized as an adaptive notch filter, or alternatively, as a phase‐locked loop. Either way, the system has the inherent capability of directly providing estimates of the parameters of the extracted sinusoidal component of its input signal, namely its amplitude, phase and frequency. The structure and mathematical properties of the system are presented for two cases of fixed‐frequency and varying‐frequency operation. The effects of parameter setting of the system on its performance are studied in detail using computer simulations. Transient and steady‐state behaviour of the system are studied in the presence of noise. Simplicity of structure, high noise immunity and robustness and the capability of direct estimation of amplitude, phase and frequency are the salient features of the system when envisaged as an adaptive notch filter or a phase‐locked loop. Copyright © 2004 John Wiley & Sons, Ltd.     

Serendipity in Recommender Systems: A Systematic Literature Review

A recommender system is employed to accurately recommend items,which are expected to attract the user's attention.The over-emphasis on the accuracy of the recommendations can cause information over-specialization and make recommendations boring and even predictable.Novelty and diversity are two partly useful solutions to these problems.However,novel and diverse recommendations cannot merely ensure that users are attracted since such recommendations may not be relevant to the user's interests.Hence,it is necessary to consider other criteria,such as unexpectedness and relevance.Serendipity is a criterion for making appealing and useful recommendations.The usefulness of serendipitous recommendations is the main superiority of this criterion over novelty and diversity.The bulk of studies of recommender systems have focused on serendipity in recent years.Thus,a systematic literature review is conducted in this paper on previous studies of serendipity-oriented recommender systems.Accordingly,this paper focuses on the contextual convergence of serendipity definitions,datasets,serendipitous recommendation methods,and their evaluation techniques.Finally,the trends and existing potentials of the serendipity-oriented recommender systems are discussed for future studies.The results of the systematic literature review present that the quality and the quantity of articles in the serendipity-oriented recommender systems are progressing.     

A novel adaptive flicker measurement technique

An adaptive measurement method is presented for the estimation of interharmonic components causing light flicker. The method provides an alternative technique for the estimation of sinusoidal components of unknown frequency, where well-known methods of processing of stationary signals such as the DFT-based techniques may fail. The proposed technique is based on a recently developed sinusoid-tracking algorithm that is capable of tracking time-variations of the parameters of a nonstationary signal such as its frequency and amplitude. The preliminary stages of demodulation and bandpass filtering combined with dynamic adjustment of the parameters of the sinusoid-tracking algorithm allow for effective estimation of the components that may cause light flicker. The structure of the proposed flicker measurement technique is composed of two parallel branches, each finding the amplitude and frequency of an interharmonic component. Presented computer simulations demonstrate its performance while laboratory experiments verify its in situ functionality. Given the low complexity of the proposed technique, it is well-suited for real-time applications.     

A nonlinear adaptive method of elimination of power line interference in ECG signals

A new method of elimination of power line noise in electrocardiogram signals is presented. The proposed method employs, as its main building block, a recently developed signal processing algorithm capable of extracting a specified component of a signal and tracking its variations over time. Design considerations and performance of the proposed method are presented with the aid of computer simulations. Superior performance is observed in terms of effective elimination of noise under conditions of varying powerline interference frequency. The proposed method presents a simple and robust structure which complies with practical constraints involved in the problem such as low computational resource availability and low sampling frequency.     

A novel method of estimation of DPOAE signals

A new method of measurement of distortion product otoacoustic emission (DPOAE) signal level based on a recently introduced nonlinear adaptive method of extraction of nonstationary sinusoids is presented. Essentially, three units of such an algorithm are employed to extract and measure the two stimuli and the DPOAE signal. Each unit has the capability of locking on a specified sinusoidal component of the input signal and tracking its variations over time. Performance of the proposed method is demonstrated with the aid of computer simulations and is verified in laboratory using recorded clinical data. Comparison is made between the proposed technique and existing methods. The proposed method features structural simplicity which renders it particularly attractive for implementation on both software and hardware platforms. It offers a high degree of immunity with regard to background noise and parameter variations. Compared to conventional methods, the proposed method offers a shorter measurement time which is of significant value in clinical examinations.     

Elimination of Power Line Interference on Telephone Cables Under Frequency-Varying Conditions

A new method for the elimination of power line interference of potentially time-varying frequency, phase, and amplitude on telephone loops is presented. The proposed method is based on adaptive estimation, and subsequent elimination, of the fundamental and individual harmonic components of the induced power signal and tracking their variations over time. The structure and mathematical formulation of the proposed technique are presented, and its performance is demonstrated in a variety of scenarios. Superior performance of the proposed method over existing techniques is observed throughout all experiments. The proposed algorithm presents a simple and efficient method of elimination of narrowband interference of a potentially nonstationary nature that is suitable for real-time applications due to its structural simplicity.