Phase velocity measurement of dispersive wave modes by Gaussian peak-tracing in the f-k transform domain

Author(s):  
Bikash Ghose ◽  
Rabi Sankar Panda ◽  
Krishnan Balasubramaniam
1991 ◽  
Vol 46 (9) ◽  
pp. 746-758 ◽  
Author(s):  
F. Winterberg

AbstractIt is hypothesized that the collapse of the wave function is a real physical phenomenon caused by vacuum fluctuations near the Planck scale. The hypothesis is suggested by a recently proposed model (Planck aether model) according to which the fundamental kinematic symmetry is the Galilei-group with the Lorentz invariance as a derived dynamic symmetry. The proposed model has the goal to derive all fields and their interactions from an exactly nonrelativistic operator field equation, resembling Heisenberg's relativistic spinor field equation. In this model the groundstate of the vacuum is a superfluid consisting of an equal number of positive and negative Planck masses interacting via delta function potentials and making the cosmological constant equal to zero. Gauge bosons come from transverse waves propagating in a lattice of quantized vortices, and spinors are explained in this model as exciton-like quasiparticles held together by gauge bosons. Because vector gauge bosons move in the model with the velocity of light, objects held together by the forcc fields of these bosons obey Lorentz invariance as a dynamic symmetry. With the longitudinal wave modes moving with a superluminal phase velocity at energies near the Planck scale, it is conjectured that the quantum mechanical wave function is real and that its collapse results from the entrapment of the wave function by these longitudinal superluminal wave modes. Because these modes occur near the Planck scale their very large zero point fluctuations might therefore trigger the collapse even through dense matter. But because the fluctuations are finite, and because the wave modes have a finite albeit very large phase velocity, the quantum mechanical correlations would be broken above a ccrtain finite length. In the limit of a vanishing Planck length, and hence vanishing gravitational constant G, the phase velocity would become infinite, and the same would be true for the length above which the correlations are broken. One therefore may say that in the limit G = 0 the collapse is infinitely fast and that in this limit the correlations are not broken even over arbitrarily large distances


2020 ◽  
Vol 10 (23) ◽  
pp. 8397
Author(s):  
Anurup Guha ◽  
Michael Aynardi ◽  
Parisa Shokouhi ◽  
Cliff J. Lissenden

The hollow long bones of the human appendicular skeleton are known to support the propagation of ultrasonic guided waves, whose potential for diagnosing bone health is being investigated. In this study, ultrasonic guided waves propagating in the diaphysis of human tibia are characterized experimentally and numerically in the frequency range around 200 kHz. The experiment involves a unique combination of omni-directional shear transducer-based excitation and detection using a 1D laser Doppler vibrometer. The cluster of phase velocities obtained from a linear array of time-history data using space-time Fourier transform is found to be in the non-dispersive low-phase velocity region of the dispersion curves obtained for a tibial cross-section. Time-domain finite element analysis revealed that the displacement components normal to the surface are significant, even though the loading is from a shear transducer. Furthermore, semi-analytical finite element analysis revealed that the wave structures of the wave modes contained within the cluster of low-phase velocity modes are consistent with the displacement profiles obtained from the time-domain analysis. The experimental results show that the low-phase velocity mode cluster has sufficient intensity to propagate axially at least 85 mm in the mid-diaphyseal region.


1995 ◽  
Vol 42 (3) ◽  
pp. 381-386 ◽  
Author(s):  
K. Yamanaka ◽  
Y. Nagata ◽  
S. Nakano ◽  
T. Koda ◽  
H. Nishino ◽  
...  

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