Springer Iranian Journal of Science 2731-8095 32 4 2008 12 12 PREDICTION ALGORITHM FOR TORQUE RIPPLE REDUCTION IN DTC-BASED DRIVES 343 355 2293 10.22099/ijsts.2008.2293 EN SH. KABOLI Electrical Engineering Department, Sharif University of Technology, Tehran, I. R. of Iran M. R. ZOLGHADRI Electrical Engineering Department, Sharif University of Technology, Tehran, I. R. of Iran P. ESKANDARI Electrical Engineering Department, Sharif University of Technology, Tehran, I. R. of Iran D. ROYE Polytechnic Institute of Grenoble, France Journal Article 2005 12 31 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.

https://ijsts.shirazu.ac.ir/article_2293_6c5b2a8ddd45315cdaa43ae301dfacd6.pdf

Springer Iranian Journal of Science 2731-8095 32 4 2008 12 12 (Aσ )Δ -DOUBLE SEQUENCE SPACES VIA ORLICZ FUNCTIONS AND DOUBLE STATISTICAL CONVERGENCE 357 367 2294 10.22099/ijsts.2008.2294 EN E. SAVAS Istanbul Ticaret University, Department of Mathematics, Uskudar, Istanbul, Turkey R. F. PATTERSON Department of Mathematics and Statistics, University of North Florida, Jacksonville, Florida 32224, USA Journal Article 2006 04 11 The aim of this paper is to introduce and study a new concept of strong double Δ ( A ) σ - convergence sequences with respect to an Orlicz function, and some properties of the resulting sequence spaces were also examined. In addition, we define the Δ ( A ) σ -statistical convergence and establish some connections between the spaces of strong double Δ ( A ) σ -convergence sequences and the space of double Δ ( A ) σ -statistical convergence.

https://ijsts.shirazu.ac.ir/article_2294_7b3faf5ebb8fb2aa2b49a4f784cc4981.pdf

Springer Iranian Journal of Science 2731-8095 32 4 2008 12 12 LINEAR PROGRAMMING PROBLEM WITH INTERVAL COEFFICIENTS AND AN INTERPRETATION FOR ITS CONSTRAINTS 369 390 2295 10.22099/ijsts.2008.2295 EN A. ABBASI MOLAI Faculty of Mathematics and Computer Science, Amirkabir University of Technology, Hafez Avenue, Tehran, I. R. of Iran E. KHORRAM Faculty of Mathematics and Computer Science, Amirkabir University of Technology, Hafez Avenue, Tehran, I. R. of Iran Journal Article 2006 09 16 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

https://ijsts.shirazu.ac.ir/article_2295_468f16722b798e7ccc781d7fd54c9b49.pdf

Springer Iranian Journal of Science 2731-8095 32 4 2008 12 12 AUTOCORRELATION FOR A CLASS OF POLYNOMIALS WITH COEFFICIENTS DEFINED ON T 391 396 2296 10.22099/ijsts.2008.2296 EN M. TAGHAVI Department of Mathematics, College of Sciences, Shiraz University, Shiraz, I. R. of Iran Journal Article 2006 03 15 In this work we deal with the coefficients of A (e it ) 2 , where A is in a class of polynomials having Unimodular coefficients. We first present a technique that calculates lower bounds for particular autocorrelations and then in a more general case we present an upper bound for their maximal order.

https://ijsts.shirazu.ac.ir/article_2296_56872c197938e0e404d49c7f95efc4cb.pdf

Springer Iranian Journal of Science 2731-8095 32 4 2008 12 12 DOSIMETRIC EVALUATION OF A NEWLY DEVELOPED RADIOCHROMIC FILM FOR RADIATION PROCESSING 397 401 2297 10.22099/ijsts.2008.2297 EN A. AKHAVAN Radiation Applications Research School, Nuclear Science and Technology Research Institute, P.O. Box 11365-3486 Tehran, I. R. of Iran M. SOHRABPOUR Department of Energy Engineering, Sharif University of Technology, Tehran, I. R. of Iran M. SHARIFZADEH Radiation Applications Research School, Nuclear Science and Technology Research Institute, P.O. Box 11365-3486 Tehran, I. R. of Iran Journal Article 2006 01 23 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

https://ijsts.shirazu.ac.ir/article_2297_7234ac0ffa0fca0d2f7bd6bc72de1224.pdf

Springer Iranian Journal of Science 2731-8095 32 4 2008 12 12 ON EINSTEIN (α,β )-METRICS 403 412 2298 10.22099/ijsts.2008.2298 EN B. REZAEI Department of Mathematics and Computer Science of Amir-Kabir University, Tehran, I. R. of Iran A. RAZAVI Department of Mathematics and Computer Science of Amir-Kabir University, Tehran, I. R. of Iran N. SADEGHZADEH Department of Mathematics and Computer Science of Amir-Kabir University, Tehran, I. R. of Iran Journal Article 2006 12 04 – In this paper we consider some (α ,β ) -metrics such as generalized Kropina, Matsumoto and F (α β )2 α = + metrics, and obtain necessary and sufficient conditions for them to be Einstein metrics when β is a constant Killing form. Then we prove with this assumption that the mentioned Einstein metrics must be Riemannian or Ricci flat.

https://ijsts.shirazu.ac.ir/article_2298_e9e30572a219839fc8b166c53a696227.pdf

Springer Iranian Journal of Science 2731-8095 32 4 2008 12 12 IONOSPHERIC ABSORPTION OF HF RADIO WAVE IN VERTICAL PROPAGATION 413 419 2299 10.22099/ijsts.2008.2299 EN I. UNAL Department of Science Teaching, Faculty of Education, Inonu Univ., 44280 Malatya, Turkey O. OZCAN Department of Physics, Faculty of Science and Arts, Firat Univ., 23169 Elazig, Turkey M. CANYILMAZ Department of Physics, Faculty of Science and Arts, Firat Univ., 23169 Elazig, Turkey Journal Article 2005 09 06 In this study, absorption of high frequency radio waves in the ionospheric plasma have been investigated. The wave equation was obtained in terms of ionospheric parameters. The numerical values of the absorption have been calculated for 4 MHz, 4.5 MHz and 5 MHz waves. The necessary parameters for calculation have been obtained using an International Reference Ionosphere (IRI) Model. The altitudinal, diurnal, seasonal and the variations of absorption with frequency have been examined. The calculations show that the highest absorption occurs in the D-region. The absorption is higher in summer than in other seasons and is maximum at daylight. In addition, absorption decreases with the increase of frequency.

https://ijsts.shirazu.ac.ir/article_2299_bf9f6139f8a03ab62b0f67f9b28d9c4d.pdf

Springer Iranian Journal of Science 2731-8095 32 4 2008 12 12 PROJECTIVELY RELATED EINSTEIN FINSLER SPACES 421 429 2300 10.22099/ijsts.2008.2300 EN N. SADEGH-ZADEH Department of Mathematics and Computer Science of Amir-Kabir University, Tehran, I. R. of Iran A. RAZAVI Department of Mathematics and Computer Science of Amir-Kabir University, Tehran, I. R. of Iran B. REZAEI Department of Mathematics and Computer Science of Amir-Kabir University, Tehran, I. R. of Iran Journal Article 2006 12 10 The main objective of this paper is to find the necessary and sufficient condition of a given Finsler metric to be Einstein in order to classify the Einstein Finsler metrics on a compact manifold. The considered Einstein Finsler metric in the study describes all different kinds of Einstein metrics which are pointwise projective to the given one. This study has resulted in the following theorem that needs the proof of three prepositions. Let F be a Finsler metric (n > 2) projectively related to an Einstein non-projectively flat Finsler metric F , then F is Einstein if and only if F = λ F whereλ is a constant. A Schur type lemma is also proved.

https://ijsts.shirazu.ac.ir/article_2300_1d2fa8ed46454558cc9c742c54cbf50f.pdf

Springer Iranian Journal of Science 2731-8095 32 4 2008 12 12 VELOCITIES OF DUAL HOMOTHETIC EXPONENTIAL MOTIONS IN D3* 431 434 2301 10.22099/ijsts.2008.2301 EN V. ASIL Department of Mathematics Faculty of Art and Science Fırat University, 23119 Elazıg, Turkey Journal Article 2005 01 09 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

https://ijsts.shirazu.ac.ir/article_2301_ddbd28d4f0af1df8d5fe9132a5dc9bd1.pdf

Springer Iranian Journal of Science 2731-8095 32 4 2008 12 12 BOUND STATE ENERGY OF DELTA-FUNCTION POTENTIAL: A NEW REGULARIZATION SCHEME 435 438 2302 10.22099/ijsts.2008.2302 EN A. JAHAN Department of Physics, Amirkabir University of Technology, P. O. Box 15875-4413, Tehran, I. R. of Iran M. JAFARI Islamic Azad University, Urmia branch, Urmia, I. R. of Iran Journal Article 2005 11 08 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.

https://ijsts.shirazu.ac.ir/article_2302_eb38ee6e1732a8150067147ff55416f4.pdf

Springer Iranian Journal of Science 2731-8095 32 4 2008 12 12 ON R-QUADRATIC FINSLER METRICS 439 443 2303 10.22099/ijsts.2008.2303 EN B. NAJAFI Department of Science, Shahed University, Tehran, I. R. of Iran B. BIDABAD Department of Mathematics and Computer Science, Amir Kabir University, Tehran, I. R. of Iran A. TAYEBI Department of Mathematics, Faculty of Science, The University of Qom, Qom, I. R. of Iran Journal Article 2006 09 27 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

https://ijsts.shirazu.ac.ir/article_2303_b1d104fd19fc0b74b7c8c77b82ef8f94.pdf