function [ a, alpha, b, beta, dp, gamma, l, nx, omega, t0, w0, x ] = ...
  artery_parameters ( )

%*****************************************************************************80
%
%% artery_parameters returns parameter values for the artery PDE.
%
%  Licensing:
%
%    This code is distributed under the MIT license.
%
%  Modified:
%
%    21 December 2020
%
%  Author:
%
%    John Burkardt
%
%  Reference:
%
%    Alfio Quarteroni, Riccardo Sacco, Fausto Saleri,
%    Numerical Mathematics,
%    Second Edition,
%    Texts in Applied Mathematics, Volume 37,
%    Springer, 2007,
%    ISBN: 978-3-540-34658-6,
%
%  Output:
%
%    real A: used in the forcing term x*dp*(a+b*cos(omega*t)).
%
%    real ALPHA: a coefficient in the PDE.
%
%    real B: used in the forcing term x*dp*(a+b*cos(omega*t)).
%
%    real BETA: a coefficient in the PDE.
%    BETA = sqrt ( ALPHA ) -> stiff problem.
%    BETA = ALPHA, less stiffness.
%
%    real DP: used in the forcing term x*dp*(a+b*cos(omega*t)).
%
%    real GAMMA: a coefficient in the PDE.
%
%    real L: the length of the cylinder.
%
%    integer NX: the number of nodes between 0 and L.
%
%    real OMEGA: used in the forcing term x*dp*(a+b*cos(omega*t)).
%
%    real T0, W0(NX*2): the initial time, and initial condition.
%
%    real X(NX,1): the node coordinates.
%
%  Local:
%
%    real E: the Young modulus of the vascular tissue.
%
%    real H: thickness of the elastic tissue.
%
%    real R0: the unstressed arterial radius.
%
%    real RHO: the vascular wall density.
%
  a = 10.0 * 133.32;
  b = 133.32;
  dp = 0.25 * 133.32;
  e = 9.0e+05;
  h = 3.0e-04;
  l = 5.0e-02;
  nx = 51;
  omega = 2.0 * pi / 0.8;
  r0 = 5.0e-03;
  rho = 1000.0;

  alpha = e / rho / r0^2;
%
%  Quarteroni says beta=alpha is highly stiff,
%  beta=sqrt(alpha) not so bad.
%
  if ( true )
    beta = sqrt ( alpha );
  else
    beta = alpha;
  end
  gamma = 1.0 / rho / h;

  t0 = 0.0;
  w0 = zeros ( 1, nx * 2 );
  x = linspace ( 0.0, l, nx );
  x = x';

  return
end

