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1
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Surface True and Leaky Waves in Subsonic and Supersonic Regions. Explicit Solution of a Simple Model

100%
Trzupek D., Zieliński P.
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issue 4
570-573
EN
A simple model of a surface of a 2D continuum is shown to exhibit subsonic and supersonic surface resonances (leaky waves, pseudosurface waves), i.e. finite-lived excitations, along with usual surface waves (true subsonic surface waves). The physical meaning, controversial in the existing literature, of the surface leaky waves in both regions is discussed by a thought experiment in which a stimulus adjusted to the resonance parameters is applied to the surface. The infinite displacement-stimulus ratio in the long-time limit then is shown to be in power in all the cases of surface states and a finite amplitude of the leaky waves is demonstrated despite an apparent divergence suggested by their algebraic form.
2
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Stress Induced Phononic Properties and Surface Waves in 2D Model of Auxetic Crystal

81%
Trzupek D., Twaróg D., Zieliński P.
Acta Physica Polonica A
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2009
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vol. 115
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issue 2
576-578
EN
Elastic stiffness parameters are determined in a 2D model system of rigid rods interacting by harmonic force constants. Any positive ("normal" crystal) or negative (auxetic crystal) Poisson ratio can be obtained in this model as a function of the external stress. Conditions for opening an absolute stop band (phononic crystal) and for various kinds of surface waves are obtained.
3
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Surface Dynamics and Phononic Properties of 2D Field Tunable Auxetic Crystal

81%
Twaróg D., Trzupek D., Zieliński P.
Acta Physica Polonica A
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2009
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vol. 115
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issue 2
579-582
EN
The lattice in-plane dynamics is studied as a function of external field in a model of auxetic crystal consisting of rigid polar rods and of elastic springs. The phase speed of the transverse acoustic wave propagating parallel to the polar rods is shown to be higher than the speed of the longitudinal wave at strong fields. An absolute stop band for the lattice waves opens in the whole Brillouin zone with increasing field. The surface waves and resonances at a surface parallel to the rods are studied. Infinitely narrow resonances called exceptional surface waves are found within bulk bands at certain specific values of the parameters characterizing the surface. Generally, the surface layer should be significantly heavier and stiffer than the substrate for the phenomenon to occur.
4
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Impulse and Resonant Response in Systems Showing Secular and Leaky Excitations

81%
Sobieszczyk P., Gałązka M., Trzupek D., Zieliński P.
Acta Physica Polonica A
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2013
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vol. 124
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issue 6
1020-1024
EN
A model consisting of a string embedded in an elastic medium and terminated by a harmonic oscillator has been studied in the frequency and time domains to elucidate the physical effects of supersonic and subsonic leaky waves as well as that of true surface waves. A supersonic leaky wave manifests itself by a resonant maximum of the local density of states within the band of bulk waves and by an anomalous dispersion of the real part of the frequency dependent response function. The time domain impulse response then contains mainly resonant contribution from the poles of the response function in analogy to ordinary resonances. True surface waves show generally analogous behaviour. Here, however, the phenomenon is governed by dissipation mechanisms different from the radiation into the bulk. An important difference is that the impulse response contains equilibrated contributions due to the poles and due to the stop frequency gap in the case of true surface waves. The main manifestation of a subsonic leaky wave, i.e. a surface resonance with the frequency situated in the stop gap, is a sharp peak of the real part of the frequency-dependent response function just at the bottom of the bulk waves band. This is in certain analogy with a large reactive power in electric circuits. A strong destructive interference of the resonant part of the impulse response with the part due to the gap makes the time domain response fast attenuated.
5
Content available remote

On Surface Waves in Materials with Negative Poisson Ratio

81%
Zieliński P., Twaróg D., Trzupek D.
Acta Physica Polonica A
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2009
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vol. 115
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issue 2
513-515
EN
True surface wave, i.e. a resonance with infinite lifetime is found within a bulk band in a model of thin planar layer coating a continuous auxetic substrate. Conditions for the existence of this wave are given.
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