2018-10-24T09:29:02Z
http://ijsts.shirazu.ac.ir/?_action=export&rf=summon&issue=471
Iranian Journal of Science and Technology (Sciences)
Transaction A: Science
1028-6276
1028-6276
2008
32
4
PREDICTION ALGORITHM FOR TORQUE RIPPLE REDUCTION IN DTC-BASED DRIVES
SH.
KABOLI
M. R.
ZOLGHADRI
P.
ESKANDARI
D.
ROYE
In direct torque control, the selection of an applied voltage vector is based on the measured<br />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.
Induction motor drive
direct torque control
torque ripple
predictive controller
2008
12
12
343
355
http://ijsts.shirazu.ac.ir/article_2293_6c5b2a8ddd45315cdaa43ae301dfacd6.pdf
Iranian Journal of Science and Technology (Sciences)
Transaction A: Science
1028-6276
1028-6276
2008
32
4
(Aσ )Δ -DOUBLE SEQUENCE SPACES VIA ORLICZ FUNCTIONS AND DOUBLE STATISTICAL CONVERGENCE
E.
SAVAS
R. F.
PATTERSON
The aim of this paper is to introduce and study a new concept of strong double Δ ( A ) σ -<br />convergence sequences with respect to an Orlicz function, and some properties of the resulting sequence<br />spaces were also examined. In addition, we define the Δ ( A ) σ -statistical convergence and establish some<br />connections between the spaces of strong double Δ ( A ) σ -convergence sequences and the space of double<br />Δ ( A ) σ -statistical convergence.
Orlicz function
invariant means
almost convergence
double statistical convergence
2008
12
12
357
367
http://ijsts.shirazu.ac.ir/article_2294_7b3faf5ebb8fb2aa2b49a4f784cc4981.pdf
Iranian Journal of Science and Technology (Sciences)
Transaction A: Science
1028-6276
1028-6276
2008
32
4
LINEAR PROGRAMMING PROBLEM WITH INTERVAL COEFFICIENTS AND AN INTERPRETATION FOR ITS CONSTRAINTS
A.
ABBASI MOLAI
E.
KHORRAM
In this paper, we introduce a Satisfaction Function (SF) to compare interval values on the basis of<br />Tseng and Klein’s idea. The SF estimates the degree to which arithmetic comparisons between two interval<br />values are satisfied. Then, we define two other functions called Lower and Upper SF based on the SF. We<br />apply these functions in order to present a new interpretation of inequality constraints with interval<br />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
Interval number
inequality relation
equality relation
satisfaction function
interval linear programming
2008
12
12
369
390
http://ijsts.shirazu.ac.ir/article_2295_468f16722b798e7ccc781d7fd54c9b49.pdf
Iranian Journal of Science and Technology (Sciences)
Transaction A: Science
1028-6276
1028-6276
2008
32
4
AUTOCORRELATION FOR A CLASS OF POLYNOMIALS WITH COEFFICIENTS DEFINED ON T
M.
TAGHAVI
In this work we deal with the coefficients of A (e it ) 2 , where A is in a class of polynomials<br />having Unimodular coefficients. We first present a technique that calculates lower bounds for particular<br />autocorrelations and then in a more general case we present an upper bound for their maximal order.
Autocorrelation
frequency
Fouier coefficient
2008
12
12
391
396
http://ijsts.shirazu.ac.ir/article_2296_56872c197938e0e404d49c7f95efc4cb.pdf
Iranian Journal of Science and Technology (Sciences)
Transaction A: Science
1028-6276
1028-6276
2008
32
4
DOSIMETRIC EVALUATION OF A NEWLY DEVELOPED RADIOCHROMIC FILM FOR RADIATION PROCESSING
A.
AKHAVAN
M.
SOHRABPOUR
M.
SHARIFZADEH
In order to improve the performance of a newly developed radiochromic film, GIC-79, some<br />dosimetric characteristics of this film have been studied based on relevant standard practice. The present<br />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
Dosimetry
film dosimeter
radiochromic film
gamma radiation
electron beam
2008
12
12
397
401
http://ijsts.shirazu.ac.ir/article_2297_7234ac0ffa0fca0d2f7bd6bc72de1224.pdf
Iranian Journal of Science and Technology (Sciences)
Transaction A: Science
1028-6276
1028-6276
2008
32
4
ON EINSTEIN (α,β )-METRICS
B.
REZAEI
A.
RAZAVI
N.
SADEGHZADEH
– In this paper we consider some (α ,β ) -metrics such as generalized Kropina, Matsumoto and F (α β )2<br />α = + metrics, and obtain necessary and sufficient conditions for them to be Einstein metrics when β<br />is a constant Killing form. Then we prove with this assumption that the mentioned Einstein metrics must be<br />Riemannian or Ricci flat.
Einstein Finsler metrics
(α
β ) - metrics
Schur lemma
2008
12
12
403
412
http://ijsts.shirazu.ac.ir/article_2298_e9e30572a219839fc8b166c53a696227.pdf
Iranian Journal of Science and Technology (Sciences)
Transaction A: Science
1028-6276
1028-6276
2008
32
4
IONOSPHERIC ABSORPTION OF HF RADIO WAVE IN VERTICAL PROPAGATION
I.
UNAL
O.
OZCAN
M.
CANYILMAZ
In this study, absorption of high frequency radio waves in the ionospheric plasma have been<br />investigated. The wave equation was obtained in terms of ionospheric parameters. The numerical values of<br />the absorption have been calculated for 4 MHz, 4.5 MHz and 5 MHz waves. The necessary parameters for<br />calculation have been obtained using an International Reference Ionosphere (IRI) Model. The altitudinal,<br />diurnal, seasonal and the variations of absorption with frequency have been examined. The calculations show<br />that the highest absorption occurs in the D-region. The absorption is higher in summer than in other seasons<br />and is maximum at daylight. In addition, absorption decreases with the increase of frequency.
Ionosphere
HF wave
Absorption
2008
12
12
413
419
http://ijsts.shirazu.ac.ir/article_2299_bf9f6139f8a03ab62b0f67f9b28d9c4d.pdf
Iranian Journal of Science and Technology (Sciences)
Transaction A: Science
1028-6276
1028-6276
2008
32
4
PROJECTIVELY RELATED EINSTEIN FINSLER SPACES
N.
SADEGH-ZADEH
A.
RAZAVI
B.
REZAEI
The main objective of this paper is to find the necessary and sufficient condition of a given Finsler<br />metric to be Einstein in order to classify the Einstein Finsler metrics on a compact manifold. The considered<br />Einstein Finsler metric in the study describes all different kinds of Einstein metrics which are pointwise<br />projective to the given one. This study has resulted in the following theorem that needs the proof of three<br />prepositions. Let F be a Finsler metric (n > 2) projectively related to an Einstein non-projectively flat<br />Finsler metric F , then F is Einstein if and only if F = λ F whereλ is a constant. A Schur type lemma is<br />also proved.
Projectively related Finsler metrics
projectively flat
Einstein Finsler metric
2008
12
12
421
429
http://ijsts.shirazu.ac.ir/article_2300_1d2fa8ed46454558cc9c742c54cbf50f.pdf
Iranian Journal of Science and Technology (Sciences)
Transaction A: Science
1028-6276
1028-6276
2008
32
4
VELOCITIES OF DUAL HOMOTHETIC EXPONENTIAL MOTIONS IN D3*
V.
ASIL
In this paper the concept of Homothetic Dual Exponential Motions in D3 is discussed and their<br />velocities obtained. Due to the way in which the matter is presented, the paper gives some formula and facts<br />about dual exponential motions which are not generally known
Dual number
dual vector
homothetic motion
exponential transformation
2008
12
12
431
434
http://ijsts.shirazu.ac.ir/article_2301_ddbd28d4f0af1df8d5fe9132a5dc9bd1.pdf
Iranian Journal of Science and Technology (Sciences)
Transaction A: Science
1028-6276
1028-6276
2008
32
4
BOUND STATE ENERGY OF DELTA-FUNCTION POTENTIAL: A NEW REGULARIZATION SCHEME
A.
JAHAN
M.
JAFARI
In this letter we have proposed a new regularization scheme to deal with the divergent integrals<br />occurring in the quantum mechanical problem of calculating the bound state energy of the delta-function<br />potential in two and three dimensions. Based on the Schwinger parameterization technique we argue that<br />there are no infinities even in D dimensions. In this way we were able to compare our proposal with the<br />Schwinger regularization approch.
Delta-function potential
bound state energy
smeared propagators
2008
12
12
435
438
http://ijsts.shirazu.ac.ir/article_2302_eb38ee6e1732a8150067147ff55416f4.pdf
Iranian Journal of Science and Technology (Sciences)
Transaction A: Science
1028-6276
1028-6276
2008
32
4
ON R-QUADRATIC FINSLER METRICS
B.
NAJAFI
B.
BIDABAD
A.
TAYEBI
We prove that every R-quadratic metric of scalar flag curvature with a dimension greater than two<br />is of constant flag curvature. Then we show that generalized Douglas-Weyl metrics contain R-quadratic<br />metrics as a special case, but the class of R-quadratic metric is not closed under projective transformations
R-quadratic metric
Landsberg metric
generalized Douglas-Weyl metric
2008
12
12
439
443
http://ijsts.shirazu.ac.ir/article_2303_b1d104fd19fc0b74b7c8c77b82ef8f94.pdf