vb_dipole_pot

 Dipole electric potential field 
   P0 = vb_dipole_pot(J0,x0,Vs)  
 三角面内点上の双極子ポテンシャル 
 P0 = 2*(xd*J0)/|xd|^3 , xd = Vs - x0

 2004-02-06 Taku Yoshioka
 2004-12-26 M. Sato modified

 Copyright (C) 2011, ATR All Rights Reserved.
 License : New BSD License(see VBMEG_LICENSE.txt)

0001 function    P0 = vb_dipole_pot(J0,x0,Vs)  
0002 % Dipole electric potential field
0003 %   P0 = vb_dipole_pot(J0,x0,Vs)
0004 % 三角面内点上の双極子ポテンシャル
0005 % P0 = 2*(xd*J0)/|xd|^3 , xd = Vs - x0
0006 %
0007 % 2004-02-06 Taku Yoshioka
0008 % 2004-12-26 M. Sato modified
0009 %
0010 % Copyright (C) 2011, ATR All Rights Reserved.
0011 % License : New BSD License(see VBMEG_LICENSE.txt)
0012 
0013 xd = [Vs(:,1)-x0(1), Vs(:,2)-x0(2), Vs(:,3)-x0(3)];
0014 dd = sum( xd.^2, 2 );
0015 rx = sqrt(dd).*dd;
0016 P0 = 2*(xd*J0')./rx;