فهرست مطالب

  • Volume:32 Issue:1, 2007
  • A1
  • تاریخ انتشار: 1386/02/15
  • تعداد عناوین: 10
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  • M. Alp Pages 1-5
  • Sh. Kaboli, M. R. Zolghadri, S. Haghbin, P. Eskandari Pages 7-16
    The efficiency of induction motors decreases at light loads. Efficiency optimizer control systems adjust the motor flux value to achieve the best efficiency in a wide range of load variations. Reduced flux operation has some other benefits such as power factor improvement and torque ripple reduction. The latter is an important issue in a direct torque controlled induction motor drive. In this paper, the effect of flux reference value on the torque ripple of a direct torque controlled induction motor is analyzed. The effect of flux value on torque ripple in a wide range of speed variations is investigated. Simulation and the experimental results presented justify the validity of the theoretical analysis about torque ripple.
    Keywords: Induction motor drive, direct torque control, torque ripple, predictive controller
  • B. Bidabad, S. Hedayatian Pages 17-24
    Here, the concept of electric capacity on Finsler spaces is introduced and the fundamental conformal invariant property is proved, i.e. the capacity of a compact set on a connected non-compact Finsler manifold is conformal invariant. This work enables mathematicians and theoretical physicists to become more familiar with the global Finsler geometry and one of its new applications.
    Keywords: Capacity, conformal invariant, Finsler space
  • M. Kazaz, H. H. Ugurlu, A. Ozdemir Pages 25-31
  • A. Shafiei Deh Abad Pages 33-44
    In this paper we introduce the concept of Dirac structures on (Hermitian) modules and vector bundles and deduce some of their properties. Among other things we prove that there is a one to one correspondence between the set of all Dirac structures on a (Hermitian) module and the group of all automorphisms 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.
    Keywords: Dirac structure, Hermitian module, Hilbert module, vector bundle
  • F. Tahamtani Pages 45-51
    We study the exponential decay of global solution for an n-dimensional thermo-elasticity system in a bounded domain of Rn. By using the multiplier technique and constructing an energy functional well adapted to the system, the exponential decay is proved.
    Keywords: Thermo, elasticity system, non, linear weak damping, energy decay rate
  • E. Peyghan, A. Razavi, A. Heydari Pages 53-59
  • R. Alizadeh, G. H. Esslamzadeh Pages 61-64
    Let be a unital algebra over a field of characteristic zero. We show that every derivation from Mn (A) into its dual Mn (A)* is the sum of an inner derivation and a derivation induced by a derivation from A into A*.
    Keywords: Derivation, full matrix algebra, dual space
  • K. Haghnejad Azar, A. Riazi Pages 65-70
    We introduce some new concepts of topological spaces which say α-separable topological space and O-topological group, α-first axiom, α-second axiom, and we find some relations between them with some applications in normed spaces.
    Keywords: Topological groupOtopological group, α separable space, α first axiom, α second axiom
  • J. Behboodian, A. Asgharzadeh Pages 71-78