فهرست مطالب

  • No. 3104, 2007
  • A4
  • تاریخ انتشار: 1385/11/15
  • تعداد عناوین: 11
|
  • Sh. Kaboli, M. R. Zolghadri, P. Eskandari, D. Roye Pages 343-355
    In direct torque control, the selection of an applied voltage vector is based on the measured parameters at the beginning of the sampling period. The delay between the measurement and the application of the voltage vector is the origin of an extra torque ripple. In this paper, a new predictive controller is proposed for compensating this delay and reducing the torque ripple. The stator current is measured twice in each sampling period and its expected value at the end of the period is predicted according to a linear extrapolation algorithm. Therefore, none of the machine parameters are used in the prediction, and consequently, the algorithm is quite robust against machine parameter variations. The calculation of the electromagnetic torque is performed using the predicted value of the stator current. Therefore, the selection of the voltage vector is more realistic and prevents extra torque ripple. This controller is quite suitable for high power drives where the sampling frequency is low, and there is enough time for the extra measurements. Simulation and experimental results which confirm the ability of this method to considerably reduce the torque ripple are presented.
    Keywords: Induction motor drive, direct torque control, torque ripple, predictive controller
  • E. Savas, R. F. Patterson Pages 357-367
  • A. Abbasi Molai, E. Khorram Pages 369-390
    In this paper, we introduce a Satisfaction Function (SF) to compare interval values on the basis of Tseng and Klein’s idea. The SF estimates the degree to which arithmetic comparisons between two interval values are satisfied. Then, we define two other functions called Lower and Upper SF based on the SF. We apply these functions in order to present a new interpretation of inequality constraints with interval coefficients in an interval linear programming problem. This problem is as an extension of the classical linear programming problem to an inexact environment. On the basis of definitions of the SF, the lower and upper SF and their properties, we reduce the inequality constraints with interval coefficients in their satisfactory crisp equivalent forms and define a satisfactory solution to the problem. Finally, a numerical example is given and its results are compared with other approaches.
    Keywords: Interval number, inequality relation, equality relation, satisfaction function, interval linear programming
  • A. Akhavan, M. Sohrabpour, M. Sharifzadeh Pages 397-401
    In order to improve the performance of a newly developed radiochromic film, GIC-79, some dosimetric characteristics of this film have been studied based on relevant standard practice. The present study describes some parameters that may affect the dosimeter response before, during, and after irradiation. The effect of absorbed dose rate on dosimeter response was determined by irradiating dosimeters at low absorbed dose rates with gamma rays. Calibration irradiations of dosimeters were performed with both gamma rays and also electrons to determine the effect of large difference absorbed dose rates on dosimeter response. In addition, post irradiation stability was obtained and also the temperature and humidity effects on the dosimeter response during the storage time prior to irradiation and post irradiation have been investigated.
    Keywords: Dosimetry, film dosimeter, radiochromic film, gamma radiation, electron beam
  • B. Rezaei, A. Razavi, N. Sadeghzadeh Pages 403-412
  • I. Unal, O. Ozcan, M. Canyilmaz Pages 413-419
  • N. Sadegh, Zadeh, A. Razavi, B. Rezaei Pages 421-429
  • V. Asil Pages 431-434
    In this paper the concept of Homothetic Dual Exponential Motions in D3 is discussed and their velocities obtained. Due to the way in which the matter is presented, the paper gives some formula and facts about dual exponential motions which are not generally known.
    Keywords: Dual number, dual vector, homothetic motion, exponential transformation
  • A. Jahan, M. Jafari Pages 435-438
    In this letter we have proposed a new regularization scheme to deal with the divergent integrals occurring in the quantum mechanical problem of calculating the bound state energy of the delta-function potential in two and three dimensions. Based on the Schwinger parameterization technique we argue that there are no infinities even in D dimensions. In this way we were able to compare our proposal with the Schwinger regularization approch.
    Keywords: Delta, function potential, bound state energy, smeared propagators
  • B. Najafi, B. Bidabad, A. Tayebi Pages 439-443
    We prove that every R-quadratic metric of scalar flag curvature with a dimension greater than two is of constant flag curvature. Then we show that generalized Douglas-Weyl metrics contain R-quadratic metrics as a special case, but the class of R-quadratic metric is not closed under projective transformations.
    Keywords: R, quadratic metric, Landsberg metric, generalized Douglas, Weyl metric