سال:1388 | دوره: | شماره: |تعداد مقالات:9

Brushless DC (BLDC) motor is attracting much interest due to its high efficiency, good performance and ease of control for many applications. Moreover, reducing of the drive components is more attractive for low cost applications. This paper presents the design and implementation of a reduced-parts BLDC motor drive using the TMS320LF2407A digital signal processor (DSP). Part reducing is achieved by elimination of three Hall Effect position sensors and reducing the number of power switches. The performance of the proposed reduced parts BLDC motor drive is verified via some simulations. Then, hardware and software details of the system are explored. Finally, an experimental system including a BLDC motor, DSP control board, inverter, and rectifier is set up to validate the theoretical results.

A novel method for ferroresonance detection is presented in this paper. Using this method ferroresonance can be discriminate from other transients such as capacitor switching, load switching, transformer switching. Wavelet transform is used for decomposition of signals and Multi Layer Perceptron (MLP) neural network used for classification. Ferroresonance data and other transients are obtained by simulation using EMTP program. Results show that the MLPNN trained with the Levenberg–Marquardt algorithm is effective for discriminating Ferroresonance from other transients.

In this paper, Brent method is proposed to solve dynamic economic dispatch (DED) problem with transmission losses. The proposed algorithm involves the selection of the values of incremental fuel costs (lambda) and then the evaluation of optimal lambda is done by Brent method. The constraint of ramp rate limits distinguishes the DED problem from traditional static economic dispatch (ED) problem. The DED problem divides the entire dispatch period into a number of small time intervals and then static economic dispatch problem is solved in each interval by incorporating the ramp rate limits. The proposed method has been tested on 6- and 15- units. The simulation results of the proposed method are compared with conventional lambda iterative method. The simulation results show that the proposed method achieves qualitative solution with less computational time than the conventional lambda iterative method.

In this paper, we introduce a new constellation scheme to have better performance (in terms of BER) with respect to the conventional rectangular QAM constellation. We compared the new one and two new kinds of circular constellations with QAM. They were chosen so that they have the same average power. Also we compared the effects of using FHT and FFT for all constellations. Based on the results, the new constellations to provide slightly better performance in channels which have maximum SNR=20 dB. Also it is shown that the new constellation has better performance for the noisy channels (AWGN and burst) with ISI and low SNR. Also we have shown the effect of channel length with respect to cyclic prefix in this system.

This paper describes a methodology for obtaining minimum load-shed at selected buses from voltage stability margin viewpoint. The buses for load-shed have been selected based on line voltage stability index and its sensitivities at operating point. Computational algorithms for minimum load-shed have been developed using conventional particle swarm optimization (PSO) and coordinated aggregation based particle swarm optimization (CAPSO) one of its variant. Using these two algorithms load-shed results for two sample test systems have been obtained and compared.

Wealth distribution based classic sugarscape model was studied. The results showed high rate of mortality in agents and high rate of increase in social inequality. Classic sugarscape model was developed by employing the parameters of receiving/ utilizing one fifth of wealth for the poor through the experience. The results showed the decrease in Gini coefficient, i.e. an increase in social equality and more welfare of agents, then it leads to decrease in mortality rate, and increase in survival of agents. It was concluded that by employing the mechanism of receiving/ utilizing one fifth of agent’s wealth, mortality is decreased and wealth adjustment is improved.

The performance of speaker identification is almost perfect in the neutral environment. However, the performance is significantly deteriorated in emotional environments. In this work, three different and separate models have been used, tested and compared to identify speakers in each of the neutral and emotional environments (completely two separate environments). Our emotional environments in this work consist of five emotions. These emotions are: angry, sad, happy, disgust and fear. The three models are: Hidden Markov Models (HMMs), Second-Order Circular Hidden Markov Models (CHMM2s) and Suprasegmental Hidden Markov Models (SPHMMs). Our results show that the three models perform extremely well for speaker identification in the neutral environment. In emotional environments, the average speaker identification performance based on HMMs, CHMM2s and SPHMMs is 61.4%, 66.4% and 69.1%, respectively. Our results in this work are better than those obtained in subjective evaluation by human judges.

Smell detection is the idea of improving the quality of software by finding and fixing the problems (bad smells) in the source code. The same idea is applicable at the design level. Early detection of the problems in UML design models helps designers produce high quality software.In this paper, we present a process called Sign/Criteria/Repair (SCR) for detecting and fixing the smells in the application of a pattern language in a UML design. We investigate how the SCR process can be implemented in three different environments, ArgoUML, Epsilon, and OCLE, and how these tools can help the designer improve a UML model.

High-pressure mercury (HPM) lamps use a phosphor on their outer envelope for the sake of improvement of efficacy and color rendition. Although this is basically a rare earth phosphor, if its composition is changed in part, the lumen maintenance ratio of the lamp is improved by about 5% for 8000 hours of lighting. Factors in the lumen maintenance ratio are not the phosphor alone, but the influence of variation in amount on lamp characteristics have not been reported so far. In the current study, we attempted to determine the influence of these phosphors on various characteristics of a standard 400W lamp. With regard to lumen maintenance ratio of a lamp designed for about twice the life, the phosphor involved is identified as one of the components, and the optimum amount of change is verified from the practical application viewpoint. Results obtained indicate that an improvement of as much as about 20% is feasible. This provides a new finding useful for energy saving and reliability improvement.