Iranian Journal of Electrical and Electronic Engineering
Volume:6 Issue: 1, Mar 2010

The aim of this study is to address a new feature extraction method in the area of the heart arrhythmia classification based on a metric with simple mathematical calculation called Curve-Length Method (CLM). In the presented method, curve length of the under study excerpted segment of signal is considered as an informative feature in which the effect of important geometric parameters of the original signal can be found. To show merits of the presented method, first the original electrocardiogram (ECG) in lead I is pre-processed by removing its baseline wander then by scaling it in the [-1,1] interval. In the next step, using a trous method, discrete wavelet scales 23 and 24 and smoothing function scale 22 are extracted. Afterwards, segments including samples of the QRS complex, P and T waves are estimated via an approximation criterion and CLM is implemented to extract corresponding features from aforementioned scales, smoothing function and also from each original segment. The resulted feature vector (including 12 components) is used to tune an Adaptive Network Fuzzy Inference System (ANFIS) classifier. The presented strategy is applied to classify four categories found in the MIT-BIH Arrhythmia Database namely as Atrial Premature Beat (APB), Left Bundle Branch Block (LBBB), Right Bundle Branch Block (RBBB) and Premature Ventricular Contraction (PVC) and average values of Se = 99.81%, P+ = 99.80%, Sp = 99.81% and Acc = 99.72% are obtained for sensitivity, positive predictivity, specifity and accuracy respectively showing marginal improvement of the heart arrhythmia classification performance.

When a detector sensitive to the target plume IR seeker is used for tracking airborne targets, the seeker tends to follow the target hot point which is a point farther away from the target exhaust and its fuselage. In order to increase the missile effectiveness, it is necessary to modify the guidance law by adding a lead bias command. The resulting guidance is known as target adaptive guidance (TAG). First, the pure proportional navigation guidance (PPNG) in 3-dimensional state is explained in a new point of view. The main idea is based on the distinction between angular rate vector and rotation vector conceptions. The current innovation is based on selection of line of sight (LOS) coordinates. A comparison between two available choices for LOS coordinates system is proposed. An improvement is made by adding two additional terms. First term includes a cross range compensator which is used to provide and enhance path observability, and obtain convergent estimates of state variables. The second term is new concept lead bias term, which has been calculated by assuming an equivalent acceleration along the target longitudinal axis. Simulation results indicate that the lead bias term properly provides terminal conditions for accurate target interception.

The air-gap of electrical machines may become non-uniform due to low accuracy of the manufacturing machinery, in assembling processes, or by aging. Detection and monitoring of this phenomenon is very important and of interest. There are several methods to model non-uniform air-gaps and to detect them by monitoring systems. One of the most widely used methods is by the analysis of the line currents. In this paper a new, simple and comprehensive method is presented to model and detect non-uniform air-gaps in synchronous generators with skewed rotors. The influence of non-uniform air-gaps on the harmonics of the induced voltage of the stator is investigated by the proposed method. Simulations are performed for three cases: uniform air-gap, static rotor eccentricity, and stator ovality in a two phase generator. The experimental results are also presented. The good correspondence between the simulation and the experimental results clearly validates the theoretical findings put forward in this paper.

Congestion management in electricity markets is traditionally done using deterministic values of power system parameters considering a fixed network configuration. In this paper, a stochastic programming framework is proposed for congestion management considering the power system uncertainties. The uncertainty sources that are modeled in the proposed stochastic framework consist of contingencies of generating units and branches as well as load forecast errors. The Forced Outage Rate of equipment and the normal distribution function to model load forecast errors are employed in the stochastic programming. Using the roulette wheel mechanism and Monte-Carlo analysis, possible scenarios of power system operating states are generated and a probability is assigned to each scenario. Scenario reduction is adopted as a tradeoff between computation time and solution accuracy. After scenario reduction, stochastic congestion management solution is extracted by aggregation of solutions obtained from feasible scenarios. Congestion management using the proposed stochastic framework provides a more realistic solution compared with the deterministic solution by a reasonable uncertainty cost. Results of testing the proposed stochastic congestion management on the 24-bus reliability test system indicate the efficiency of the proposed framework.

In the present work, an integrated method of pole shape design optimization for reduction of torque pulsation components in permanent magnet synchronous motors is developed. A progressive design process is presented to find feasible optimal shapes. This method is applied on the pole shape optimization of two prototype permanent magnet synchronous motors, i.e., 4-poles/6-slots and 4-poles-12slots.

The application of electric field theory to widely different aspects of electrical insulation has led to more understanding the phenomena. Electric fields may be considered as the main reason for insulation failure. The purpose of this paper is to modify importance of analyzing electric field in insulation design. The SF6 circuit breaker is chosen as case study that encounters critical situations during its application. The other phenomena affects insulation is the presence of polar species in a non-polar molecular material locally modifies the polarization energy, thus creating local states (traps) on neighboring molecules. Results of calculations carried out for arrays of spatially connected dipoles indicating that local states of a considerable density may be created, modifying the density-of-states function, and therefore influencing the effective mobility of charge carriers. The main result of polarization during application in circuit breaker is loss of life. In this paper the reduction of negative effects of electric field and polarization by choosing a suitable insulation structure in a 33 kV SF6 circuit breaker according to calculation in critical areas is investigated that can also be studied in other types of circuit breakers.

Stray magnetic field is one of the main issues in design of transformers, since it causes non-ideal behavior of transformers. One of the techniques is usually adopted to mitigate the unwanted stray magnetic field is the use of auxiliary windings creating a magnetic field opposite to the incident one giving rise to the reduction of the total magnetic fields. This paper presents a new mathematical proof for optimized parameters such as connection resistance and leakage inductance of the auxiliary windings based on state equations. Some numerical examples for various types of practical transformers are given to demonstrate the validity of the presented mathematical proof and a comparison is made with the results of transformers behavior which is obtained with the help of finite element method. The proposed method is successfully implemented on three different types of transformers: current injection transformer, pulse transformer and superconductor transformers.