SpringerIranian Journal of Science and Technology (Sciences)1028-627632120080217PULLBACK CROSSED MODULES OF ALGEBROIDS15223410.22099/ijsts.2008.2234ENM. ALPDumlupinar University, Art and Science Faculty, Mathematics Department, TurkeyJournal Article20061113In this paper, we present algebroids and crossed modules of algebroids. We also define pullback<br />crossed module of algebroids.SpringerIranian Journal of Science and Technology (Sciences)1028-627632120080217INVESTIGATION ON THE FLUX-BASED TORQUE-RIPPLE BEHAVIOR IN DTC BASED INDUCTION MOTOR DRIVES716223510.22099/ijsts.2008.2235ENSh KABOLIElectrical Engineering Department, Sharif University of Technology, Tehran, I. R. of IranM. R. ZOLGHADRIElectrical Engineering Department, Sharif University of Technology, Tehran, I. R. of IranS. HAGHBINElectrical Engineering Department, Sharif University of Technology, Tehran, I. R. of IranP. ESKANDARIElectrical Engineering Department, Sharif University of Technology, Tehran, I. R. of IranJournal Article20060108The efficiency of induction motors decreases at light loads. Efficiency optimizer control systems<br />adjust the motor flux value to achieve the best efficiency in a wide range of load variations. Reduced flux<br />operation has some other benefits such as power factor improvement and torque ripple reduction. The latter is<br />an important issue in a direct torque controlled induction motor drive. In this paper, the effect of flux<br />reference value on the torque ripple of a direct torque controlled induction motor is analyzed. The effect of<br />flux value on torque ripple in a wide range of speed variations is investigated. Simulation and the<br />experimental results presented justify the validity of the theoretical analysis about torque ripple.SpringerIranian Journal of Science and Technology (Sciences)1028-627632120080217CAPACITY ON FINSLER SPACES1724223710.22099/ijsts.2008.2237ENB. BIDABADFaculty of Mathematics and Computer Sciences, Amirkabir University of Technology,
424 Hafez Ave, 15914 Tehran, I. R. of IranS. HEDAYATIANFaculty of Mathematics and Computer Sciences, Chamran University of Ahvaz, Golestan Bld,
P.O. Box: 61355-83151 Ahvaz, I. R. of IranJournal Article20060924Here, the concept of electric capacity on Finsler spaces is introduced and the fundamental<br />conformal invariant property is proved, i.e. the capacity of a compact set on a connected non-compact Finsler<br />manifold is conformal invariant. This work enables mathematicians and theoretical physicists to become more<br />familiar with the global Finsler geometry and one of its new applications.SpringerIranian Journal of Science and Technology (Sciences)1028-627632120080217INTEGRAL CHARACTERIZATIONS FOR TIMELIKE AND SPACELIKE CURVES ON THE LORENTZIAN SPHERE 3 S12531223810.22099/ijsts.2008.2238ENM. KAZAZDepartment of Mathematics, Faculty of Art and Sciences, University of Celal Bayar,
Muradiye Campus, 45047, Manisa, TurkeyH. H. UGURLUGazi University, Gazi Faculty of Education, Department of Secondary Education, Science
and Mathematics Teaching, Mathematics Teaching Program, Ankara, TurkeyA. OZDEMIRDepartment of Mathematics, Faculty of Art and Sciences, University of Celal Bayar,
Muradiye Campus, 45047, Manisa, TurkeyJournal Article20060715V. Dannon showed that spherical curves in E4 can be given by Frenet-like equations, and he then<br />gave an integral characterization for spherical curves in E4 . In this paper, Lorentzian spherical timelike and<br />spacelike curves in the space time 4<br />1 R are shown to be given by Frenet-like equations of timelike and<br />spacelike curves in the Euclidean space E3 and the Minkowski 3-space 3<br />1 R . Thus, finding an integral<br />characterization for a Lorentzian spherical 4<br />1 R -timelike and spacelike curve is identical to finding it for E3<br />curves and 3<br />1 R -timelike and spacelike curves. In the case of E3 curves, the integral characterization<br />coincides with Dannon’s.<br />Let {T, N, B}be the moving Frenet frame along the curve α (s) in the Minkowski space 3<br />1 R . Let<br />α (s) be a unit speed C4 -timelike (or spacelike) curve in 3<br />1 R so that α '(s) = T . Then, α (s) is a Frenet<br />curve with curvature κ (s) and torsion τ (s) if and only if there are constant vectors a and b so that<br />(i) { [ ] } 0<br />'( ) ( ) 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,<br />(ii) { ( ) } 0<br />'( ) ( ) cosh ( ) ( ) ( ) ( ) s T s =κ s aeξ +be−ξ + ∫ ξ s −ξ δ T δ κ δ dδ , N is timelike,<br />where<br />0<br />( ) ( ) . s ξ s = ∫ τ δ dδSpringerIranian Journal of Science and Technology (Sciences)1028-627632120080217DIRAC STRUCTURES3344223910.22099/ijsts.2008.2239ENA. SHAFIEI DEH ABADSchool of Mathematics, Statistics and Computer Science, University of Tehran, Tehran, I. R. of IranJournal Article20070107In this paper we introduce the concept of Dirac structures on (Hermitian) modules and vector<br />bundles and deduce some of their properties. Among other things we prove that there is a one to one<br />correspondence between the set of all Dirac structures on a (Hermitian) module and the group of all<br />automorphisms of the module. This correspondence enables us to represent Dirac structures on (Hermitian)<br />modules and on vector bundles in a very suitable form and define induced Dirac structures in a natural way.SpringerIranian Journal of Science and Technology (Sciences)1028-627632120080217ON ENERGY DECAY OF AN N-DIMENSIONAL THERMOELASTICITY SYSTEM WITH A NONLINEAR WEAK DAMPING4551224010.22099/ijsts.2008.2240ENF. TAHAMTANIDepartment of Mathematics, Shiraz University, Shiraz, I. R. of IranJournal Article20070606We study the exponential decay of global solution for an n-dimensional thermo-elasticity system<br />in a bounded domain of ℜn . By using the multiplier technique and constructing an energy functional well<br />adapted to the system, the exponential decay is proved.SpringerIranian Journal of Science and Technology (Sciences)1028-627632120080217CONFORMAL VECTOR FIELDS ON TANGENT BUNDLE WITH A SPECIAL LIFT FINSLER METRIC*5359224210.22099/ijsts.2008.2242ENE. PEYGHANDepartment of Mathematics, Faculty of Science, University of Arak, Arak, I. R. of IranA. RAZAVIDepartment of Mathematics and Computer Science, Amirkabir University, Tehran, I. R. of IranA. HEYDARIFaculty of Science, Tarbiatmodares University, Tehran, I. R. of IranJournal Article20070414On a Finsler manifold, we define conformal vector fields and their complete lifts and prove that in<br />certain conditions they are homothetic.SpringerIranian Journal of Science and Technology (Sciences)1028-627632120080217THE STRUCTURE OF DERIVATIONS FROM A FULL MATRIX ALGEBRA INTO ITS DUAL6164224310.22099/ijsts.2008.2243ENR. ALIZADEHDepartment of Mathematics, Shahed University, P. O. Box 18151-159, Tehran, I. R. of IranH. ESSLAMZADEHDepartment of Mathematics, Shiraz University, Shiraz 71454, I. R. of IranJournal Article20070527Let A be a unital algebra over a field of characteristic zero. We show that every derivation from<br />( ) n M A into its dual ( ) n M A ∗ is the sum of an inner derivation and a derivation induced by a derivation<br />from A into A∗SpringerIranian Journal of Science and Technology (Sciences)1028-627632120080217α − SEPARABLE AND O-TOPOLOGICAL GROUP6570224410.22099/ijsts.2008.2244ENK. HAGHNEJAD AZARDepartment of Mathematics, Mohghegh Ardabili University, Ardabil, I. R. of IranA. RIAZIFaculty of Mathematics and Computer Science, Amir Kabir University Tehran, I. R. of IranJournal Article20070415We introduce some new concepts of topological spaces which say α − separable topological<br />space and O-topological group, α − first axiom, α − second axiom, and we find some relations between<br />them with some applications in normed spaces.SpringerIranian Journal of Science and Technology (Sciences)1028-627632120080217ON THE DISTRIBUTION OF Z-SCORES7178224510.22099/ijsts.2008.2245ENJ. BEHBOODIANDepartment of Mathematics, Islamic Azad University, Shiraz, I. R. of IranA. ASGHARZADEHDepartment of Statistics, Faculty of Basic Sciences, Mazandaran University, Babolsar, I. R. of IranJournal Article20061028Let X ,..., Xn 1 be a random sample from a distribution with sample mean X and sample<br />variance S 2. In this paper we consider certain very general properties of the so-called “Z-scores”<br />X X S i n i ( − )/ : = 1,...., . A representation theorem is then given for Z-scores obtained from an underlying<br />normal population, together with a theorem for their limiting distribution as the sample size tends to infinity.<br />Finally, two applications involving grading and testing for an outlier are presented.