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19995
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Bitiş tarihi: 1999 × WoS Q: Q1 ×

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Listeleniyor 1 - 5 / 5
  • Küçük Resim
    Yayın
    Design of optimum nyquist signals based on generalized sampling theory for data communications
    (IEEE, Piscataway, NJ, United States, 1999-06) Panayırcı, Erdal; Özuğur, Timuçin; Çağlar, Hakan
    A new method is given for the optimal design of bandlimited Nyquist-type signal shapes for data communications, which maximizes its energy in a given time interval. The method is based on the periodically nonuniform sampling (PNS) theory making use of the linear splines. The computation is straightforward, and the constraint for intersymbol interferrence is shown to be easy to include in the problem. A numerical example is given, and performance of the optimal signal shapes is compared with that resulting from the use of previously obtained signal shapes in the literature. It is also concluded that the optimal signal shapes thus obtained are almost immune to small offsets at the sampling instants.
  • Küçük Resim
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    Modulation of nonlinear waves in a thin elastic tube filled with a viscous fluid
    (Pergamon-Elsevier Science Ltd, 1999-11) Demiray, Hilmi
    In the present work, utilizing the nonlinear equations of a prestressed thin elastic tube filled with an incompressible viscous fluid the propagation of weakly nonlinear waves in such a medium is studied. Considering that the arteries are initially subjected to a large static transmural pressure P-0 and an axial stretch lambda(z) and, in the course of blood flow, a finite time dependent displacement is added to this initial field, the nonlinear equations governing the motion of the tube in the radial direction is obtained. Utilizing the reductive perturbation technique the amplitude modulation of weakly nonlinear and dissipative but strongly dispersive waves is examined. The localized travelling wave solution to the evolution equation is given and the stability condition is discussed.
  • Küçük Resim
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    Weakly nonlinear waves in a prestressed thin elastic tube containing a viscous fluid
    (Pergamon-Elsevier Science Ltd, 1999-11) Antar, Nalan; Demiray, Hilmi
    In this work, we studied the propagation of weakly nonlinear waves in a prestressed thin elastic tube filled with an incompressible viscous fluid. In order to include the geometrical and structural dispersion into analysis, the wall's inertial and sheer deformation are taken into account in determining the inner pressure-inner cross sectional area relation. Using the reductive perturbation technique, the propagation of weakly nonlinear waves, in the long-wave approximation, is shown to be governed by the Korteweg-de Vries-Burgers (KdVB) equation. Due to dependence of coefficients of the governing equation on the initial deformation, the material and viscosity parameters, the profile of the travelling wave solution to the KdVB equation changes with these parameters. These variations are calculated numerically for some elastic materials and the effects of initial deformation and the viscosity parameter on the propagation characteristics are discussed.
  • Küçük Resim
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    On the kinematic of a 3-DOF Stewart platform
    (John Wiley & Sons Inc, 1999-02) Bürüncük, Kadri; Tokad, Yılmaz
    The kinematic behavior of the Stewart platform has been discussed in the literature by many researchers. In the present article, a special form of the Stewart platform, namely, the 3-degrees of freedom platform with triangular shaped base and upper platforms, is considered by thoroughly deriving a new set of constraint equations which makes it possible to discover several new properties of the platform. Both the inverse and direct kinematic problems are discussed and a new approach for solution of the direct kinematic problem is described which gives all the real (physical) solutions.
  • Küçük Resim
    Yayın
    Propagation of weakly nonlinear waves in fluid-filled thick viscoelastic tubes
    (Elsevier Science Inc., 1999-10) Demiray, Hilmi
    In the present work, we studied the propagation of small-but-finite-amplitude waves in a prestressed thick walled viscoelastic tube filled with an incompressible inviscid fluid. In order to include the dispersion, the wall's inertial and shear effects are taken into account in determining the inner pressure-inner cross-sectional area relation. Using the reductive perturbation method, the propagation of weakly nonlinear waves in the long-wave approximation is investigated. After obtaining the general evolution equation in the long-wave approximation, by a proper scaling, it is shown that this general equation reduces to the well-known evolution equations such as the Burgers, Korteweg-de Vries (KdV), Koteweg-de Vries-Burgers (KdVB) and the generalized Burgers' equations. By proper re-scaling of the perturbation parameter, the modified form of the evolution equations is also obtained. The variations of the travelling wave profile with initial deformation and the viscosity coefficients are numerically evaluated and the results are illustrated in some figures.