scholarly journals Propagation of non-stationary antisymmetric kinematic perturbations from a spherical cavity in Cosserat medium

2020 ◽  
pp. 201-210
Author(s):  
D. V Tarlakovskii ◽  
Van Lam Nguyen
Keyword(s):  
Laplace Transform ◽  
Spherical Cavity ◽  
Bessel Functions ◽  
Initial Conditions ◽  
Displacement Vector ◽  
Elementary Functions ◽  
Linear Combinations ◽  
Spherical Coordinate ◽  
Cosserat Medium ◽  
The Laplace Transform

We consider a space filled with a linearly elastic Cosserat medium with a spherical cavity under given nonstationary antisymmetric surface perturbations, which are understood as the corresponding analogue of classical antiplane deformations. The motion of a medium is described by a system of three equations with respect to nonzero components of the displacement vector and potentials of the rotation field, written in a spherical coordinate system with the origin at its center of the cavity. The initial conditions are assumed to be zero. To solve the problem, we use decomposition of functions to Legendre and Gegenbauer polynomials, as well as the Laplace transform in time. As a result, the problem is reduced to independent systems of ordinary differential equations with the Laplace operator for the coefficients of the series. A statement about the structure of the general solution of this system is formulated. Images of the series coefficients are presented in the form of linear combinations of boundary conditions with coefficients - transformants of surface influence functions, the explicit formulas for which include the Bessel functions of a half-integer index. Due to the complexity of these expressions, to determine the originals in the linear approximation, the method of a small parameter is used, which is taken as a coefficient characterizing the relationship between the displacement and rotation fields. Then, taking into account the connection between the Bessel functions and elementary functions, the images are written in the form of linear combinations of exponentials with coefficients - rational functions of the transformation parameter. The further procedure for inverting the Laplace transform is carried out using residues. It is shown that there are three wave fronts corresponding to a shear wave modified with allowance for free rotation and two rotation waves. Examples of calculations for a granular composite of aluminum shot in an epoxy matrix are presented.

Initial conditions and the Laplace transform

1965 ◽  
Vol 11 (11) ◽  
pp. 385
Author(s):  
J.H. Brodie ◽  
C. Jones ◽  
S.E. Tweedy ◽  
E. Besag
Keyword(s):  
Laplace Transform ◽  
Initial Conditions ◽  
The Laplace Transform

Asymptotic solution of the Vlasov and Poisson equations for an inhomogeneous plasma

1991 ◽  
Vol 45 (1) ◽  
pp. 59-70 ◽  
Author(s):  
Riccardo Croci
Keyword(s):  
Magnetic Field ◽  
Laplace Transform ◽  
Integral Equations ◽  
Initial Conditions ◽  
Inhomogeneous Plasma ◽  
Algebraic Equations ◽  
Poisson Equations ◽  
The Laplace Transform ◽  
Eigenvalue Parameter ◽  
The Fourier Transform

The purpose of this paper is to derive the asymptotic solutions to a class of inhomogeneous integral equations that reduce to algebraic equations when a parameter ε goes to zero (the kernel becoming proportional to a Dirac δ function). This class includes the integral equations obtained from the system of Vlasov and Poisson equations for the Fourier transform in space and the Laplace transform in time of the electrostatic potential, when the equilibrium magnetic field is uniform and the equilibrium plasma density depends on εx, with the co-ordinate z being the direction of the magnetic field. In this case the inhomogeneous term is given by the initial conditions and possibly by sources, and the Laplace-transform variable ω is the eigenvalue parameter.

Initial conditions and the Laplace transform

1965 ◽  
Vol 11 (10) ◽  
pp. 349
Author(s):  
G.K. Steel ◽  
D.J. Storey ◽  
H.M. Power
Keyword(s):  
Laplace Transform ◽  
Initial Conditions ◽  
The Laplace Transform

scholarly journals On generalized thermoelastic disturbances in an elastic solid with a spherical cavity

1991 ◽  
Vol 4 (3) ◽  
pp. 225-240 ◽  
Author(s):  
Basudeb Mukhopadhyay ◽  
Rasajit Bera ◽  
Lokenath Debnath
Keyword(s):  
Laplace Transform ◽  
Classical Theory ◽  
Spherical Cavity ◽  
Dynamic Pressure ◽  
Elastic Solid ◽  
Dynamical Theory ◽  
The Laplace Transform ◽  
Generalized Thermoelastic ◽  
Short Time ◽  
The Waves

In this paper, a generalized dynamical theory of thermoelasticity is employed to study disturbances in an infinite elastic solid containing a spherical cavity which is subjected to step rise in temperature in its inner boundary and an impulsive dynamic pressure on its surface. The problem is solved by the use of the Laplace transform on time. The short time approximations for the stress, displacement and temperature are obtained to examine their discontinuities at the respective wavefronts. It is shown that the instantaneous change in pressure and temperature at the cavity wall gives rise to elastic and thermal disturbances which travel with finite velocities v1 and v2(>v1) respectively. The stress, displacement and temperature are found to experience discontinuities at the respective wavefronts. One of the significant findings of the present analysis is that there is no diffusive nature of the waves as found in classical theory.

scholarly journals The Laplace transform as an alternative general method for solving linear ordinary differential equations

2021 ◽  
Vol 1 (4) ◽  
pp. 309
Author(s):  
William Guo
Keyword(s):  
General Solution ◽  
Differential Equations ◽  
Laplace Transform ◽  
Ordinary Differential Equations ◽  
Case Studies ◽  
Initial Conditions ◽  
Linear Ordinary Differential Equations ◽  
The Laplace Transform ◽  
Linear Odes ◽  
General Method

<p style='text-indent:20px;'>The Laplace transform is a popular approach in solving ordinary differential equations (ODEs), particularly solving initial value problems (IVPs) of ODEs. Such stereotype may confuse students when they face a task of solving ODEs without explicit initial condition(s). In this paper, four case studies of solving ODEs by the Laplace transform are used to demonstrate that, firstly, how much influence of the stereotype of the Laplace transform was on student's perception of utilizing this method to solve ODEs under different initial conditions; secondly, how the generalization of the Laplace transform for solving linear ODEs with generic initial conditions can not only break down the stereotype but also broaden the applicability of the Laplace transform for solving constant-coefficient linear ODEs. These case studies also show that the Laplace transform is even more robust for obtaining the specific solutions directly from the general solution once the initial values are assigned later. This implies that the generic initial conditions in the general solution obtained by the Laplace transform could be used as a point of control for some dynamic systems.</p>

Dirichlet Random Walks

2014 ◽  
Vol 51 (04) ◽  
pp. 1081-1099 ◽  
Author(s):  
Gérard Letac ◽  
Mauro Piccioni
Keyword(s):  
Random Walk ◽  
Laplace Transform ◽  
Dirichlet Process ◽  
Hypergeometric Functions ◽  
Bessel Functions ◽  
Random Variable ◽  
Infinite Divisibility ◽  
Stieltjes Transform ◽  
The Laplace Transform ◽  
Infinite Divisible Distributions

This paper provides tools for the study of the Dirichlet random walk inRd. We compute explicitly, for a number of cases, the distribution of the random variableWusing a form of Stieltjes transform ofWinstead of the Laplace transform, replacing the Bessel functions with hypergeometric functions. This enables us to simplify some existing results, in particular, some of the proofs by Le Caër (2010), (2011). We extend our results to the study of the limits of the Dirichlet random walk when the number of added terms goes to ∞, interpreting the results in terms of an integral by a Dirichlet process. We introduce the ideas of Dirichlet semigroups and Dirichlet infinite divisibility and characterize these infinite divisible distributions in the sense of Dirichlet when they are concentrated on the unit sphere ofRd.

scholarly journals Laplace transform of certain functions with applications

2000 ◽  
Vol 23 (2) ◽  
pp. 99-102
Author(s):  
M. Aslam Chaudhry
Keyword(s):  
Laplace Transform ◽  
Bessel Functions ◽  
Whittaker Functions ◽  
Special Cases ◽  
The Laplace Transform ◽  
Special Case

The Laplace transform of the functionstν(1+t)β,Reν>−1, is expressed in terms of Whittaker functions. This expression is exploited to evaluate infinite integrals involving products of Bessel functions, powers, exponentials, and Whittaker functions. Some special cases of the result are discussed. It is also demonstrated that the famous identity∫0∞sin (ax)/x dx=π/2is a special case of our main result.

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