eng
Shiraz University
Iranian Journal of Science and Technology (Sciences)
1028-6276
1028-6276
2008-02-17
32
1
1
5
10.22099/ijsts.2008.2234
2234
PULLBACK CROSSED MODULES OF ALGEBROIDS
M. ALP
malp@dumlupinar.edu.tr
1
Dumlupinar University, Art and Science Faculty, Mathematics Department, Turkey
In this paper, we present algebroids and crossed modules of algebroids. We also define pullbackcrossed module of algebroids.
http://ijsts.shirazu.ac.ir/article_2234_62c423d9a21fa541e8b88b608b5152fe.pdf
Crossed module
algebroids
pullback
action
eng
Shiraz University
Iranian Journal of Science and Technology (Sciences)
1028-6276
1028-6276
2008-02-17
32
1
7
16
10.22099/ijsts.2008.2235
2235
INVESTIGATION ON THE FLUX-BASED TORQUE-RIPPLE BEHAVIOR IN DTC BASED INDUCTION MOTOR DRIVES
Sh KABOLI
kaboli@sharif.edu
1
M. R. ZOLGHADRI
2
S. HAGHBIN
3
P. ESKANDARI
4
Electrical Engineering Department, Sharif University of Technology, Tehran, I. R. of Iran
Electrical Engineering Department, Sharif University of Technology, Tehran, I. R. of Iran
Electrical Engineering Department, Sharif University of Technology, Tehran, I. R. of Iran
Electrical Engineering Department, Sharif University of Technology, Tehran, I. R. of Iran
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.
http://ijsts.shirazu.ac.ir/article_2235_67e72585b39a8522188344db21f914fd.pdf
Induction motor drive
direct torque control
torque ripple
predictive controller
eng
Shiraz University
Iranian Journal of Science and Technology (Sciences)
1028-6276
1028-6276
2008-02-17
32
1
17
24
10.22099/ijsts.2008.2237
2237
CAPACITY ON FINSLER SPACES
B. BIDABAD
bidabad@aut.ac.ir
1
S. HEDAYATIAN
2
Faculty of Mathematics and Computer Sciences, Amirkabir University of Technology, 424 Hafez Ave, 15914 Tehran, I. R. of Iran
Faculty of Mathematics and Computer Sciences, Chamran University of Ahvaz, Golestan Bld, P.O. Box: 61355-83151 Ahvaz, I. R. of Iran
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.
http://ijsts.shirazu.ac.ir/article_2237_c853a94eb7e70ca1fcffe2b37e5b1eee.pdf
Capacity
conformal invariant
Finsler space
eng
Shiraz University
Iranian Journal of Science and Technology (Sciences)
1028-6276
1028-6276
2008-02-17
32
1
25
31
10.22099/ijsts.2008.2238
2238
INTEGRAL CHARACTERIZATIONS FOR TIMELIKE AND SPACELIKE CURVES ON THE LORENTZIAN SPHERE 3 S1
M. KAZAZ
mustafa.kazaz@bayar.edu.tr
1
H. H. UGURLU
2
A. OZDEMIR
3
Department of Mathematics, Faculty of Art and Sciences, University of Celal Bayar, Muradiye Campus, 45047, Manisa, Turkey
Gazi University, Gazi Faculty of Education, Department of Secondary Education, Science and Mathematics Teaching, Mathematics Teaching Program, Ankara, Turkey
Department of Mathematics, Faculty of Art and Sciences, University of Celal Bayar, Muradiye Campus, 45047, Manisa, Turkey
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
http://ijsts.shirazu.ac.ir/article_2238_9ccf89393e0c615c0234b48509b20d4e.pdf
Lorentzian 3-sphere
Timelike curve
spacelike curve
curvature
eng
Shiraz University
Iranian Journal of Science and Technology (Sciences)
1028-6276
1028-6276
2008-02-17
32
1
33
44
10.22099/ijsts.2008.2239
2239
DIRAC STRUCTURES
A. SHAFIEI DEH ABAD
shafiei@khayam.ut.ac.ir
1
School of Mathematics, Statistics and Computer Science, University of Tehran, Tehran, I. R. of Iran
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.
http://ijsts.shirazu.ac.ir/article_2239_ec8e645e2e54512fcf6f5038521f36fe.pdf
Dirac structure
Hermitian module
Hilbert module
vector bundle
eng
Shiraz University
Iranian Journal of Science and Technology (Sciences)
1028-6276
1028-6276
2008-02-17
32
1
45
51
10.22099/ijsts.2008.2240
2240
ON ENERGY DECAY OF AN N-DIMENSIONAL THERMOELASTICITY SYSTEM WITH A NONLINEAR WEAK DAMPING
F. TAHAMTANI
tahamtani@susc.ac.ir
1
Department of Mathematics, Shiraz University, Shiraz, I. R. of Iran
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.
http://ijsts.shirazu.ac.ir/article_2240_6be2e046e60631ea1bf828a2a5179ccd.pdf
Thermo-elasticity system
non-linear weak damping
energy decay rate
eng
Shiraz University
Iranian Journal of Science and Technology (Sciences)
1028-6276
1028-6276
2008-02-17
32
1
53
59
10.22099/ijsts.2008.2242
2242
CONFORMAL VECTOR FIELDS ON TANGENT BUNDLE WITH A SPECIAL LIFT FINSLER METRIC*
E. PEYGHAN
e-peyghan@araku.ac.ir,
1
A. RAZAVI
2
A. HEYDARI
3
Department of Mathematics, Faculty of Science, University of Arak, Arak, I. R. of Iran
Department of Mathematics and Computer Science, Amirkabir University, Tehran, I. R. of Iran
Faculty of Science, Tarbiatmodares University, Tehran, I. R. of Iran
On a Finsler manifold, we define conformal vector fields and their complete lifts and prove that incertain conditions they are homothetic.
http://ijsts.shirazu.ac.ir/article_2242_a7a4b6fb2c6283dfb292f9e29ed1cc7f.pdf
Conformal vector field
Complete lift
finsler manifold
lift metric
eng
Shiraz University
Iranian Journal of Science and Technology (Sciences)
1028-6276
1028-6276
2008-02-17
32
1
61
64
10.22099/ijsts.2008.2243
2243
THE STRUCTURE OF DERIVATIONS FROM A FULL MATRIX ALGEBRA INTO ITS DUAL
R. ALIZADEH
1
H. ESSLAMZADEH
esslamz@shirazu.ac.ir
2
Department of Mathematics, Shahed University, P. O. Box 18151-159, Tehran, I. R. of Iran
Department of Mathematics, Shiraz University, Shiraz 71454, I. R. of Iran
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∗
http://ijsts.shirazu.ac.ir/article_2243_75889e97656d745af5ba0a1ac3c67c89.pdf
derivation
full matrix algebra
dual space
eng
Shiraz University
Iranian Journal of Science and Technology (Sciences)
1028-6276
1028-6276
2008-02-17
32
1
65
70
10.22099/ijsts.2008.2244
2244
α − SEPARABLE AND O-TOPOLOGICAL GROUP
K. HAGHNEJAD AZAR
haghnejadmath@yahoo.com
1
A. RIAZI
2
Department of Mathematics, Mohghegh Ardabili University, Ardabil, I. R. of Iran
Faculty of Mathematics and Computer Science, Amir Kabir University Tehran, I. R. of Iran
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.
http://ijsts.shirazu.ac.ir/article_2244_96cf814894c4986d8503ec748d4bbf73.pdf
Topological group
O-topological group
α − separable space
α − first axiom and α − second axiom
eng
Shiraz University
Iranian Journal of Science and Technology (Sciences)
1028-6276
1028-6276
2008-02-17
32
1
71
78
10.22099/ijsts.2008.2245
2245
ON THE DISTRIBUTION OF Z-SCORES
J. BEHBOODIAN
behboodian@stat.susc.ac.ir,
1
A. ASGHARZADEH
2
Department of Mathematics, Islamic Azad University, Shiraz, I. R. of Iran
Department of Statistics, Faculty of Basic Sciences, Mazandaran University, Babolsar, I. R. of Iran
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.
http://ijsts.shirazu.ac.ir/article_2245_7c4086e2bf5cb1aaec28c2c0824b1b6e.pdf
Finite exchangeability
grading
outlier test
Quadratic Forms
Thompson's identity
Samuelson's
inequality
Slutsky's theorem