Shiraz University
Iranian Journal of Science and Technology (Sciences)
1028-6276
32
1
2008
02
17
PULLBACK CROSSED MODULES OF ALGEBROIDS
1
5
EN
M.
ALP
Dumlupinar University, Art and Science Faculty, Mathematics Department, Turkey
malp@dumlupinar.edu.tr
10.22099/ijsts.2008.2234
In this paper, we present algebroids and crossed modules of algebroids. We also define pullbackcrossed module of algebroids.
Crossed module,algebroids,pullback,action
http://ijsts.shirazu.ac.ir/article_2234.html
http://ijsts.shirazu.ac.ir/article_2234_62c423d9a21fa541e8b88b608b5152fe.pdf
Shiraz University
Iranian Journal of Science and Technology (Sciences)
1028-6276
32
1
2008
02
17
INVESTIGATION ON THE FLUX-BASED TORQUE-RIPPLE BEHAVIOR IN DTC BASED INDUCTION MOTOR DRIVES
7
16
EN
Sh
KABOLI
Electrical Engineering Department, Sharif University of Technology, Tehran, I. R. of Iran
kaboli@sharif.edu
M. R.
ZOLGHADRI
Electrical Engineering Department, Sharif University of Technology, Tehran, I. R. of Iran
S.
HAGHBIN
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
10.22099/ijsts.2008.2235
The efficiency of induction motors decreases at light loads. Efficiency optimizer control systemsadjust the motor flux value to achieve the best efficiency in a wide range of load variations. Reduced fluxoperation has some other benefits such as power factor improvement and torque ripple reduction. The latter isan important issue in a direct torque controlled induction motor drive. In this paper, the effect of fluxreference value on the torque ripple of a direct torque controlled induction motor is analyzed. The effect offlux value on torque ripple in a wide range of speed variations is investigated. Simulation and theexperimental results presented justify the validity of the theoretical analysis about torque ripple.
Induction motor drive,direct torque control,torque ripple,predictive controller
http://ijsts.shirazu.ac.ir/article_2235.html
http://ijsts.shirazu.ac.ir/article_2235_67e72585b39a8522188344db21f914fd.pdf
Shiraz University
Iranian Journal of Science and Technology (Sciences)
1028-6276
32
1
2008
02
17
CAPACITY ON FINSLER SPACES
17
24
EN
B.
BIDABAD
Faculty of Mathematics and Computer Sciences, Amirkabir University of Technology,
424 Hafez Ave, 15914 Tehran, I. R. of Iran
bidabad@aut.ac.ir
S.
HEDAYATIAN
Faculty of Mathematics and Computer Sciences, Chamran University of Ahvaz, Golestan Bld,
P.O. Box: 61355-83151 Ahvaz, I. R. of Iran
10.22099/ijsts.2008.2237
Here, the concept of electric capacity on Finsler spaces is introduced and the fundamentalconformal invariant property is proved, i.e. the capacity of a compact set on a connected non-compact Finslermanifold is conformal invariant. This work enables mathematicians and theoretical physicists to become morefamiliar with the global Finsler geometry and one of its new applications.
Capacity,conformal invariant,Finsler space
http://ijsts.shirazu.ac.ir/article_2237.html
http://ijsts.shirazu.ac.ir/article_2237_c853a94eb7e70ca1fcffe2b37e5b1eee.pdf
Shiraz University
Iranian Journal of Science and Technology (Sciences)
1028-6276
32
1
2008
02
17
INTEGRAL CHARACTERIZATIONS FOR TIMELIKE AND SPACELIKE CURVES ON THE LORENTZIAN SPHERE 3 S1
25
31
EN
M.
KAZAZ
Department of Mathematics, Faculty of Art and Sciences, University of Celal Bayar,
Muradiye Campus, 45047, Manisa, Turkey
mustafa.kazaz@bayar.edu.tr
H. H.
UGURLU
Gazi University, Gazi Faculty of Education, Department of Secondary Education, Science
and Mathematics Teaching, Mathematics Teaching Program, Ankara, Turkey
A.
OZDEMIR
Department of Mathematics, Faculty of Art and Sciences, University of Celal Bayar,
Muradiye Campus, 45047, Manisa, Turkey
10.22099/ijsts.2008.2238
V. Dannon showed that spherical curves in E4 can be given by Frenet-like equations, and he thengave an integral characterization for spherical curves in E4 . In this paper, Lorentzian spherical timelike andspacelike curves in the space time 41 R are shown to be given by Frenet-like equations of timelike andspacelike curves in the Euclidean space E3 and the Minkowski 3-space 31 R . Thus, finding an integralcharacterization for a Lorentzian spherical 41 R -timelike and spacelike curve is identical to finding it for E3curves and 31 R -timelike and spacelike curves. In the case of E3 curves, the integral characterizationcoincides with Dannon’s.Let {T, N, B}be the moving Frenet frame along the curve α (s) in the Minkowski space 31 R . Letα (s) be a unit speed C4 -timelike (or spacelike) curve in 31 R so that α '(s) = T . Then, α (s) is a Frenetcurve with curvature κ (s) and torsion τ (s) if and only if there are constant vectors a and b so that(i) { [ ] } 0'( ) ( ) cos ( ) sin ( ) cos ( ) ( ) ( ) ( ) , s T s =κ s a ξ s + b ξ s + ∫ ξ s −ξ δ T δ κ δ dδ T is timelike,(ii) { ( ) } 0'( ) ( ) cosh ( ) ( ) ( ) ( ) s T s =κ s aeξ +be−ξ + ∫ ξ s −ξ δ T δ κ δ dδ , N is timelike,where0( ) ( ) . s ξ s = ∫ τ δ dδ
Lorentzian 3-sphere,Timelike curve,spacelike curve,curvature
http://ijsts.shirazu.ac.ir/article_2238.html
http://ijsts.shirazu.ac.ir/article_2238_9ccf89393e0c615c0234b48509b20d4e.pdf
Shiraz University
Iranian Journal of Science and Technology (Sciences)
1028-6276
32
1
2008
02
17
DIRAC STRUCTURES
33
44
EN
A.
SHAFIEI DEH ABAD
School of Mathematics, Statistics and Computer Science, University of Tehran, Tehran, I. R. of Iran
shafiei@khayam.ut.ac.ir
10.22099/ijsts.2008.2239
In this paper we introduce the concept of Dirac structures on (Hermitian) modules and vectorbundles and deduce some of their properties. Among other things we prove that there is a one to onecorrespondence between the set of all Dirac structures on a (Hermitian) module and the group of allautomorphisms of the module. This correspondence enables us to represent Dirac structures on (Hermitian)modules and on vector bundles in a very suitable form and define induced Dirac structures in a natural way.
Dirac structure,Hermitian module,Hilbert module,vector bundle
http://ijsts.shirazu.ac.ir/article_2239.html
http://ijsts.shirazu.ac.ir/article_2239_ec8e645e2e54512fcf6f5038521f36fe.pdf
Shiraz University
Iranian Journal of Science and Technology (Sciences)
1028-6276
32
1
2008
02
17
ON ENERGY DECAY OF AN N-DIMENSIONAL THERMOELASTICITY SYSTEM WITH A NONLINEAR WEAK DAMPING
45
51
EN
F.
TAHAMTANI
Department of Mathematics, Shiraz University, Shiraz, I. R. of Iran
tahamtani@susc.ac.ir
10.22099/ijsts.2008.2240
We study the exponential decay of global solution for an n-dimensional thermo-elasticity systemin a bounded domain of ℜn . By using the multiplier technique and constructing an energy functional welladapted to the system, the exponential decay is proved.
Thermo-elasticity system,non-linear weak damping,energy decay rate
http://ijsts.shirazu.ac.ir/article_2240.html
http://ijsts.shirazu.ac.ir/article_2240_6be2e046e60631ea1bf828a2a5179ccd.pdf
Shiraz University
Iranian Journal of Science and Technology (Sciences)
1028-6276
32
1
2008
02
17
CONFORMAL VECTOR FIELDS ON TANGENT BUNDLE WITH A SPECIAL LIFT FINSLER METRIC*
53
59
EN
E.
PEYGHAN
Department of Mathematics, Faculty of Science, University of Arak, Arak, I. R. of Iran
e-peyghan@araku.ac.ir,
A.
RAZAVI
Department of Mathematics and Computer Science, Amirkabir University, Tehran, I. R. of Iran
A.
HEYDARI
Faculty of Science, Tarbiatmodares University, Tehran, I. R. of Iran
10.22099/ijsts.2008.2242
On a Finsler manifold, we define conformal vector fields and their complete lifts and prove that incertain conditions they are homothetic.
Conformal vector field,Complete lift,finsler manifold,lift metric
http://ijsts.shirazu.ac.ir/article_2242.html
http://ijsts.shirazu.ac.ir/article_2242_a7a4b6fb2c6283dfb292f9e29ed1cc7f.pdf
Shiraz University
Iranian Journal of Science and Technology (Sciences)
1028-6276
32
1
2008
02
17
THE STRUCTURE OF DERIVATIONS FROM A FULL MATRIX ALGEBRA INTO ITS DUAL
61
64
EN
R.
ALIZADEH
Department of Mathematics, Shahed University, P. O. Box 18151-159, Tehran, I. R. of Iran
H.
ESSLAMZADEH
Department of Mathematics, Shiraz University, Shiraz 71454, I. R. of Iran
esslamz@shirazu.ac.ir
10.22099/ijsts.2008.2243
Let A be a unital algebra over a field of characteristic zero. We show that every derivation from( ) n M A into its dual ( ) n M A ∗ is the sum of an inner derivation and a derivation induced by a derivationfrom A into A∗
derivation,full matrix algebra,dual space
http://ijsts.shirazu.ac.ir/article_2243.html
http://ijsts.shirazu.ac.ir/article_2243_75889e97656d745af5ba0a1ac3c67c89.pdf
Shiraz University
Iranian Journal of Science and Technology (Sciences)
1028-6276
32
1
2008
02
17
α − SEPARABLE AND O-TOPOLOGICAL GROUP
65
70
EN
K.
HAGHNEJAD AZAR
Department of Mathematics, Mohghegh Ardabili University, Ardabil, I. R. of Iran
haghnejadmath@yahoo.com
A.
RIAZI
Faculty of Mathematics and Computer Science, Amir Kabir University Tehran, I. R. of Iran
10.22099/ijsts.2008.2244
We introduce some new concepts of topological spaces which say α − separable topologicalspace and O-topological group, α − first axiom, α − second axiom, and we find some relations betweenthem with some applications in normed spaces.
Topological group,O-topological group,α − separable space,α − first axiom and α − second axiom
http://ijsts.shirazu.ac.ir/article_2244.html
http://ijsts.shirazu.ac.ir/article_2244_96cf814894c4986d8503ec748d4bbf73.pdf
Shiraz University
Iranian Journal of Science and Technology (Sciences)
1028-6276
32
1
2008
02
17
ON THE DISTRIBUTION OF Z-SCORES
71
78
EN
J.
BEHBOODIAN
Department of Mathematics, Islamic Azad University, Shiraz, I. R. of Iran
behboodian@stat.susc.ac.ir,
A.
ASGHARZADEH
Department of Statistics, Faculty of Basic Sciences, Mazandaran University, Babolsar, I. R. of Iran
10.22099/ijsts.2008.2245
Let X ,..., Xn 1 be a random sample from a distribution with sample mean X and samplevariance S 2. In this paper we consider certain very general properties of the so-called “Z-scores”X X S i n i ( − )/ : = 1,...., . A representation theorem is then given for Z-scores obtained from an underlyingnormal population, together with a theorem for their limiting distribution as the sample size tends to infinity.Finally, two applications involving grading and testing for an outlier are presented.
Finite exchangeability,grading,outlier test,Quadratic Forms,Thompson's identity,Samuelson's
inequality,Slutsky's theorem
http://ijsts.shirazu.ac.ir/article_2245.html
http://ijsts.shirazu.ac.ir/article_2245_7c4086e2bf5cb1aaec28c2c0824b1b6e.pdf