Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / secs1d-0.0.8 / Utilities / Uscharfettergummel.m

diff --git a/octave_packages/secs1d-0.0.8/Utilities/Uscharfettergummel.m b/octave_packages/secs1d-0.0.8/Utilities/Uscharfettergummel.m
new file mode 100644 (file)
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+++ b/octave_packages/secs1d-0.0.8/Utilities/Uscharfettergummel.m
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+function A=Uscharfettergummel(nodes,Nnodes,elements,Nelements,acoeff,bcoeff,v)
+  
+%A=Uscharfettergummel(nodes,Nnodes,elements,Nelements,acoeff,bcoeff,v)
+%
+% Builds the Scharfetter-Gummel  matrix for the 
+% the discretization of the LHS 
+% of the Drift-Diffusion equation:
+%
+% $ -(a(x) (u' - b v'(x) u))'= f $
+%
+% where a(x) is piecewise constant
+% and v(x) is piecewise linear, so that 
+% v'(x) is still piecewise constant
+% b is a constant independent of x
+% and u is the unknown
+%
+
+  ## This file is part of 
+  ##
+  ## SECS1D - A 1-D Drift--Diffusion Semiconductor Device Simulator
+  ## -------------------------------------------------------------------
+  ## Copyright (C) 2004-2007  Carlo de Falco
+  ##
+  ##
+  ##
+  ##  SECS2D is free software; you can redistribute it and/or modify
+  ##  it under the terms of the GNU General Public License as published by
+  ##  the Free Software Foundation; either version 2 of the License, or
+  ##  (at your option) any later version.
+  ##
+  ##  SECS2D is distributed in the hope that it will be useful,
+  ##  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  ##  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  ##  GNU General Public License for more details.
+  ##
+  ##  You should have received a copy of the GNU General Public License
+  ##  along with SECS2D; If not, see <http://www.gnu.org/licenses/>.
+
+  h=nodes(elements(:,2))-nodes(elements(:,1));
+  
+  c=acoeff./h;
+  Bneg=Ubernoulli(-(v(2:Nnodes)-v(1:Nnodes-1))*bcoeff,1);
+  Bpos=Ubernoulli( (v(2:Nnodes)-v(1:Nnodes-1))*bcoeff,1);
+  
+  
+  d0    = [c(1).*Bneg(1); c(1:end-1).*Bpos(1:end-1)+c(2:end).*Bneg(2:end); c(end)*Bpos(end)];
+  d1    = [1000;-c.* Bpos];
+  dm1   = [-c.* Bneg;1000];
+  
+  A = spdiags([dm1 d0 d1],-1:1,Nnodes,Nnodes);
+  
+  % Last Revision:
+  % $Author: adb014 $
+  % $Date: 2008-02-04 16:26:27 +0100 (man, 04 feb 2008) $