scholarly journals Huygens' Principle geometric derivation and elimination of the wake and backward wave

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Forrest L. Anderson
Keyword(s):  
Wave Propagation ◽  
Wave Front ◽  
Propagation Speed ◽  
New Wave ◽  
Forward Wave ◽  
Wave Fronts ◽  
Propagation Analysis ◽  
Backward Wave ◽  
Tangential Surface ◽  
Huygens Principle

AbstractHuygens' Principle (1678) implies that every point on a wave front serves as a source of secondary wavelets, and the new wave front is the tangential surface to all the secondary wavelets. But two problems arise: portions of wavelets that exist outside of the new wave front combine to form a wake. Also there are two tangential surfaces so wave fronts are propagated in both the forward and backward directions. These problems have not previously been resolved by using a geometrical theory with impulsive wavelets that are in harmony with Huygens' geometrical description. Doing so would provide deeper understanding of and greater intuition into wave propagation, in addition to providing a new model for wave propagation analysis. The interpretation, developed here, of Huygens' geometrical construction shows Huygens' Principle to be correct: as for the wake, the Huygens' wavelets disappear when combined except where they contact their common tangent surfaces, the new propagating wave fronts. As for the backward wave, a source propagates both a forward wave and a backward wave when it is stationary, but it propagates only the forward wave front when it is advancing with a speed equal to the propagation speed of the wave fronts.

Meandering and unstable reentrant wave fronts induced by acetylcholine in isolated canine right atrium

1997 ◽  
Vol 273 (1) ◽  
pp. H356-H370 ◽  
Author(s):  
T. Ikeda ◽  
T. J. Wu ◽  
T. Uchida ◽  
D. Hough ◽  
M. C. Fishbein ◽  
...  
Keyword(s):  
Wave Front ◽  
Current Strength ◽  
Right Atrial ◽  
New Wave ◽  
Wave Fronts ◽  
Bipolar Electrodes ◽  
Upper Limit Of Vulnerability ◽  
Before And After ◽  
Simultaneous Decrease ◽  
Front Dynamics

The mechanism(s) by which acetylcholine (ACh) increases atrial vulnerability to reentry and maintains its activity for longer durations remains poorly defined. In the present study we used high-resolution activation maps to test the hypothesis that ACh promotes meandering of atrial reentrant wave fronts, resulting in breakup and the generation of new wave fronts that sustain the activity. Reentry was induced in 11 isolated canine right atrial tissues (3.8 x 3.2 cm) by a premature point stimulus (S2) before and after superfusion with ACh (15 x 10(-6) M). Endocardial isochronal activation maps were constructed with the use of 509 bipolar electrodes (1.6-mm spatial resolution), and the dynamics of the activation wave fronts were visualized with animation. A vulnerable period was found during which an S2 current strength > 4.4 +/- 2.5 mA [lower limit of vulnerability (LLV)] and < 26 +/- 13 mA [upper limit of vulnerability (ULV)] induced a single stationary reentrant wave front that lasted 3 +/- 2.5 s with a period of 159 +/- 17 ms (16 episodes). AC shortened the refractory period from 100 +/- 12 to 59 +/- 9 ms (P < 0.001) and increased vulnerability to reentry induction by simultaneous decrease in the LLV (0.7 +/- 0.2 mA, P < 0.001) and an increase in the ULV (82 +/- 24 mA, P < 0.01). ACh accelerated the rate (period of 110 +/- 16 ms, P < 0.001) and converted the stationary reentrant wave front to a nonstationary (meandering) reentrant wave front showing polymorphic electrograms, i.e., “fibrillation-like” activity (22 episodes). Rapid meandering of the reentry tip led to wave front breakup (18 episodes) and the generation of new wave fronts (19 episodes). These wave front dynamics also led to sustained (76 +/- 224 s, P < 0.001) fibrillation-like electrograms. We conclude that ACh increases the ULV and promotes meandering of a single reentrant wave front, leading to breakup and the generation of new wave fronts. Single meandering and complex wave front dynamics cause fibrillation-like activity and sustain the activity for longer duration.

On Wave Propagation in Thermoplastic Media

1966 ◽  
Vol 33 (3) ◽  
pp. 514-520 ◽  
Author(s):  
A. D. Fine ◽  
H. Kraus
Keyword(s):  
Wave Propagation ◽  
Closed Form ◽  
Wave Front ◽  
Dynamic Behavior ◽  
Static Analysis ◽  
Equations Of Motion ◽  
Normal Velocity ◽  
Wave Fronts ◽  
Closed Form Solutions ◽  
Infinite Region

The dynamic behavior of a medium, according to the uncoupled thermoplastic theory, is presented and is compared to the behavior that would be obtained from an uncoupled quasi-static analysis. Since the inertia terms are retained in the equations of motion, wave fronts (or surfaces of discontinuity) are produced in the medium. The normal velocity of the wave front separating the elastic and plastic regions is determined. General closed-form solutions of the displacement (according to both the dynamic and the quasi-static approaches) are obtained; their unique forms are found for the semi-infinite region, and an illustrative numerical example is then presented.

The structure and propagation of ionizing wave fronts

1968 ◽  
Vol 2 (2) ◽  
pp. 145-155 ◽  
Author(s):  
D. L. Turcotte ◽  
R. S. B. Ong
Keyword(s):  
Wave Propagation ◽  
Lower Bound ◽  
Charge Separation ◽  
Propagation Speed ◽  
Critical Value ◽  
Propagation Mechanism ◽  
Linear Wave ◽  
Wave Fronts ◽  
Ionization Fronts ◽  
Linear Wave Propagation

A non-linear wave propagation mechanism is found for ionization fronts. The fronts propagate due to ionizing collisions between electrons and neutrals. A parameter is obtained which specifies the amount of electrical interaction. For small electrical interaction, charge separation may occur and the front can propagate at any speed greater than a critical value. For large electrical interaction, the number densities of ions and electrons are nearly equal and a lower bound on the propagation speed is also found.

Influence of the applied pressure of the transducer on the propagation speed of the ultrasonic wave in wood

Holzforschung ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Edgar V.M. Carrasco ◽  
Rejane C. Alves ◽  
Mônica A. Smits ◽  
Vinnicius D. Pizzol ◽  
Ana Lucia C. Oliveira ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Applied Pressure ◽  
Pressure Gauge ◽  
Eucalyptus Grandis ◽  
Propagation Speed ◽  
Ultrasonic Waves ◽  
Ultrasonic Speed ◽  
Wave Propagation Speed ◽  
Propagation Technique ◽  
Non Destructive

Abstract The non-destructive wave propagation technique is used to estimate the wood’s modulus of elasticity. The propagation speed of ultrasonic waves is influenced by some factors, among them: the type of transducer used in the test, the form of coupling and the sensitivity of the transducers. The objective of the study was to evaluate the influence of the contact pressure of the transducers on the ultrasonic speed. Ninety-eight tests were carried out on specimens of the species Eucalyptus grandis, with dimensions of 120 × 120 × 50 mm. The calibration of the pressure exerted by the transducer was controlled by a pressure gauge using a previously calibrated load cell. The robust statistical analysis allowed to validate the experimental results and to obtain consistent conclusions. The results showed that the wave propagation speed is not influenced by the pressure exerted by the transducer.

scholarly journals Wave Fronts in a Causality-Violating Gödel-Type Metric

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Thomas P. Kling ◽  
Faizuddin Ahmed ◽  
Megan Lalumiere
Keyword(s):  
Wave Front ◽  
Space Time ◽  
Wave Fronts ◽  
Light Rays ◽  
Synchronized Clocks

The light rays and wave fronts in a linear class of the Gödel-type metric are examined to reveal the causality-violating features of the space-time. Noncausal features demonstrated by the development of unusual wave front singularities are shown to be related to the nonmonotonic advance of time along the light rays, as measured by a system of observers at rest with respect to one another with synchronized clocks.

Electro-magneto wave propagation analysis of viscoelastic sandwich nanoplates considering surface effects

2016 ◽  
Vol 231 (2) ◽  
pp. 387-403 ◽  
Author(s):  
A Ghorbanpour Arani ◽  
M Jamali ◽  
AH Ghorbanpour-Arani ◽  
R Kolahchi ◽  
M Mosayyebi
Keyword(s):  
Zinc Oxide ◽  
Wave Propagation ◽  
Feedback Control ◽  
Graphene Sheet ◽  
Surface Effects ◽  
Structural Damping ◽  
Sensors And Actuators ◽  
Velocity Feedback ◽  
Oxide Layers ◽  
Propagation Analysis

The original formulation of the quasi-3D sinusoidal shear deformation plate theory (SSDPT) is here extended to the wave propagation analysis of viscoelastic sandwich nanoplates considering surface effects. The sandwich structure contains a single layered graphene sheet as core integrated with zinc oxide layers as sensors and actuators. The single layered graphene sheet and zinc oxide layers are subjected, respectively, to 2D magnetic and 3D electric fields. Structural damping and surface effects are assumed using Kelvin–Voigt and Gurtin–Murdoch theories, respectively. The system is rested on an elastic medium which is simulated with a novel model namely as orthotropic visco-Pasternak foundation. An exact solution is applied in order to obtain the frequency, cut-off and escape frequencies. A displacement and velocity feedback control algorithm is applied for the active control of the frequency through a closed-loop control with bonded distributed zinc oxide sensors and actuators. The detailed parametric study is conducted, focusing on the combined effects of the nonlocal parameter, magnetic field, viscoelastic foundation, surface stress, applied voltage, velocity feedback control gain and structural damping on the wave propagation behavior of nanostructure. Results depict that with increasing the structural damping coefficient, frequency significantly decreases.

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