From d’Alembert to Bloch and back: A semi-analytical solution of 1D boundary value problems governed by the wave equation in periodic media

2022 ◽  
Vol 234-235 ◽  
pp. 111239
Author(s):  
Daniel P. Shahraki ◽  
Bojan B. Guzina
Author(s):  
John F. Ahner ◽  
John S. Lowndes

AbstractAlgorithms are developed by means of which certain connected pairs of Fredholm integral equations of the first and second kinds can be converted into Fredholm integral equations of the second kind. The methods are then used to obtain the solutions of two different sets of triple integral equations tht occur in mixed boundary value problems involving Laplace' equation and the wave equation respectively.


2004 ◽  
Vol 14 (01) ◽  
pp. 47-78 ◽  
Author(s):  
MUSTAPHA MOKHTAR-KHARROUBI

This paper deals with boundary value problems and spectral problems for neutron transport equations involving locally periodic (in space) collision frequencies and collision operators. We show strong convergence results to the solution of homogenized problems when the period goes to zero. The mathematical analysis relies mainly on smoothing effects of velocity averages.


2020 ◽  
Vol 18 (4) ◽  
pp. 676-680
Author(s):  
Olga Egorova ◽  
Ko Ye

Research in the field of unsteady interaction of shock waves propagating in continuous media with various deformable barriers are of considerable scientific interest, since so far there are only a few scientific works dealing with solving problems of this class only for the simplest special cases. In this work, on the basis of analytical solution, we study the inverse non-stationary boundary-value problem of diffraction of plain pressure wave on convex surface in form of parabolic cylinder immersed in liquid and exposed to plane acoustic pressure wave. The purpose of the work is to construct approximate models for the interaction of an acoustic wave in an ideal fluid with an undeformable obstacle, which may allow obtaining fundamental solutions in a closed form, formulating initial-boundary value problems of the motion of elastic shells taking into account the influence of external environment in form of integral relationships based on the constructed fundamental solutions, and developing methods for their solutions. The inverse boundary problem for determining the pressure jump (amplitude pressure) was also solved. In the inverse problem, the amplitude pressure is determined from the measured pressure in reflected and incident waves on the surface of the body using the least squares method. The experimental technique described in this work can be used to study diffraction by complex obstacles. Such measurements can be beneficial, for example, for monitoring the results of numerical simulations.


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