Add a useful package (from Source forge) for octave

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

diff --git a/octave_packages/secs1d-0.0.8/Utilities/Ubern.m b/octave_packages/secs1d-0.0.8/Utilities/Ubern.m
new file mode 100644 (file)
index 0000000..3111f08
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+++ b/octave_packages/secs1d-0.0.8/Utilities/Ubern.m
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+function [bp,bn]=Ubern(x)
+
+% [bp,bn]=Ubern(x)
+%
+% Bernoulli function
+% bp = B(x)=x/(exp(x)-1)
+% bn = B(-x)=x+B(x)
+
+
+ ## This file is part of 
+  ##
+  ## SECS1D - A 1-D Drift--Diffusion Semiconductor Device Simulator
+  ## -------------------------------------------------------------------
+  ## Copyright (C) 2004-2007  Carlo de Falco
+  ##
+  ##
+  ##
+  ##  SECS1D 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.
+  ##
+  ##  SECS1D 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 SECS1D; If not, see <http://www.gnu.org/licenses/>.
+
+     
+xlim=1e-2;
+ax=abs(x);
+
+%
+% Calcola la funz. di Bernoulli per x=0
+%
+
+if (ax == 0)
+   bp=1.;
+   bn=1.;
+   return
+end;
+
+%
+% Calcola la funz. di Bernoulli per valori
+% asintotici dell'argomento
+%
+
+if (ax > 80),
+   if (x >0),
+      bp=0.;
+      bn=x;
+      return
+   else
+      bp=-x;
+      bn=0.;
+      return
+   end;
+end;
+
+%
+% Calcola la funz. di Bernoulli per valori
+% intermedi dell'argomento
+%
+
+if (ax > xlim),
+   bp=x/(exp(x)-1);
+   bn=x+bp;
+   return
+else
+
+%
+% Calcola la funz. di Bernoulli per valori
+% piccoli dell'argomento mediante sviluppo
+% di Taylor troncato dell'esponenziale
+%
+   ii=1;
+   fp=1.;
+   fn=1.;
+   df=1.;
+   segno=1.;
+   while (abs(df) > eps),
+     ii=ii+1;
+     segno=-segno;
+     df=df*x/ii;
+     fp=fp+df;
+     fn=fn+segno*df;
+     bp=1./fp;
+     bn=1./fn;
+   end;
+   return
+end
+
+
+% Last Revision:
+% $Author: adb014 $
+% $Date: 2008-02-04 16:26:27 +0100 (man, 04 feb 2008) $