| 1. |
- Kari, Leif
(författare)
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Axially symmetric modes in finite cylinders - the wave guide solution
- 2002
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Ingår i: Wave motion. - 0165-2125 .- 1878-433X. ; 36:2, s. 169-184
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Tidskriftsartikel (refereegranskat)abstract
- The resonance frequencies and mode shapes for axially symmetric modes in elastic, finite, solid cylinders are examined via a wave guide model, where influences of higher order modes, structure-borne sound dispersion, cylinder diameter and length are investigated. Based on the dispersion relation for an infinite cylinder with boundary conditions at the lateral surfaces satisfied by mode matching, results are shown to converge properly. Comparisons with alternative and approximate approaches are made. The presented model agrees fully with three-dimensional models and simplified slender rod models while diverging from the latter for increased diameter-to-length ratios. To a great extent, the increased influences of higher order modes and dispersion explain the discrepancies reported for approximate approaches.
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| 2. |
- Andersson, L-E, et al.
(författare)
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Some fundamental transmission properties of impedance transitions
- 1984
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Ingår i: Wave motion. - : Elsevier BV. - 0165-2125 .- 1878-433X. ; 6:4, s. 389-406
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Tidskriftsartikel (refereegranskat)abstract
- Reflection and transmission of waves by impedance transitions from a constant input to a constant output characteristic impedence are considered. Several fundamental properties are explored, primarily for impedance transitions with piece-wise constant characteristic impedance in an arbitrary number N of intervals of equal length. For example, the following properties are shown: (i) The relative momentum transmission depends only on the ratio of output to input characteristic impedance. (ii) For a given impedance transition there are at most, and generally exactly, 2N different transitions, including the original one, with identical transmission properties. (iii) For monotoneous impedance transitions the efficiency of energy transmission is minimized by one with an abrupt change in characteristic impedance. (iv) There exists an optimal impedance transition, with a certain antisymmetry, which maximizes the efficiency of energy transmission for a given incident wave of finite duration and energy. Several of the results can be extended to more general classes of impedence transitions. Simple illustrative examples are given.
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| 3. |
- Gupta, Ram
(författare)
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Optimum design of wave transmitting joints
- 1982
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Ingår i: Wave motion. - : Elsevier BV. - 0165-2125 .- 1878-433X. ; 4:1, s. 75-83
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Tidskriftsartikel (refereegranskat)abstract
- Transmission of wave energy through a one-dimensional wave transmitting system (e.g. a nonuniform elastic rod) is considered. The wave transmitting system consists of an input section with constant impedence, a joint with variable impedance and an output section with constant impedance. A given incident wave is to be transmitted through a joint of given length and mass connecting the input and output sections of given (constant) impedances. The efficiency of energy transmission (defined as the ratio of transmitted to incident wave energy) is maximized by seeking the optimum impedance function for the joint, i.e., the optimum distribution of the joint mass over its length. Efficiencies corresponding to the optimum joints are compared with those obtained for joints with constant impedance and it is found that significant improvements in the efficiency can be achieved. For a case studied in detail, improvements of up to 30 per cent are obtained. The optimum joint shapes turn out to be consisting of segments with very large and very small impedances. Experiments are reported which confirm these results and support the validity of the one-dimensional model.
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| 4. |
- Hellsten, H., et al.
(författare)
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The spectrum of water waves produced by moving point sources, and a related inverse problem
- 2003
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Ingår i: Wave motion. - 0165-2125 .- 1878-433X. ; 38:4, s. 345-354
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Tidskriftsartikel (refereegranskat)abstract
- Parameters of moving sources on the sea surface are recovered by spectral analysis of the induced surface waves. The method can be an alternative to the standard way of seeing the ship directly, in particular, when the direct observation is impossible. © 2003 Elsevier B.V. All rights reserved.
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| 5. |
- Lundberg, Bengt, et al.
(författare)
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Optimum transmission of elastic waves through joints
- 1979
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Ingår i: Wave motion. - : Elsevier BV. - 0165-2125 .- 1878-433X. ; 1:3, s. 193-200
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Tidskriftsartikel (refereegranskat)abstract
- An elastic wave transmitting system (e.g. a nonuniform elastic rod) consisting of an input section with constant impedance, a joint with variable impedance, and an output section with constant impedance is considered. The efficiency of energy transmission (the ratio of transmitted to incident elastic wave energy) is determined and the following optimization problem is solved for two sample cases: Given the properties of the wave transmitting system and a limited duration of the incident wave, determine the shape of this wave such that the efficiency of energy transmission is maximized. In the first case (a joint with constant impedance) the optimization problem leads to a matrix eigenvalue problem. In the second case (a joint with concentrated mass) it leads to an eigenvalue problem for an integral equation. The efficiencies obtained for the optimum incident waves are compared with those obtained for rectagular incident waves an it is found that the differences are generally small. The results, which are discussed with particular reference to the transmission of elastic wave energy through drill rod joints, can also be interpreted for e.g. shallow water waves and electromagnetic waves in a transmission line.
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| 9. |
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| 10. |
- Dalarsson, Mariana, et al.
(författare)
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Two-dimensional boundary shape reconstructions in rectangular and coaxial waveguides
- 2016
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Ingår i: Wave motion. - : Elsevier BV. - 0165-2125 .- 1878-433X. ; 66, s. 10-20
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Tidskriftsartikel (refereegranskat)abstract
- We present a method for shape reconstruction of deformed metallic boundaries in rectangular and coaxial waveguides using microwave scattering. Our developed reconstruction method is a theoretical basis for a future on-line microwave-based monitoring system for power grid components. The bundle of winding conductors in the active part of a typical power grid component is modeled as a continuous metallic surface. Then, electromagnetic field perturbation theory in conjunction with inverse problem theory is used to reconstruct the shape parameters of this surface. We assume small perturbations of the boundaries, such that the scattering parameters of the waveguide in the first-order perturbation have linear dependencies of the continuous deformation function. Thus, the corresponding inverse problem can be linearized and we can employ direct inversion, without the need for optimization which requires a higher computational effort. Tikhonov regularization is used to regularize the arising ill-conditioned linear system. The reconstructions, performed with noisy synthetic measurement data, show a good agreement with the actual shapes of the studied two-dimensional localized shape deformations for both rectangular and coaxial waveguide boundaries.
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