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<DIV><FONT face=Arial>Hi,</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>I post the problem abou itk::fem several times, but no any
reply. I need your help very much and any reply will be
appreciated!</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>1. may be a bug in the itk::fem::applyBC</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>The extracted code from the
code\numerics\fem\femsolver.cxx is shown below:</FONT></DIV>
<DIV><FONT face=Arial size=2><FONT face=Arial></FONT> </DIV>
<DIV><FONT size=3></FONT> </DIV>
<DIV><FONT size=3> // Step over each nonzero matrix element in a
row<BR> for(LinearSystemWrapper::ColumnArray::iterator c=cols.begin();
c!=cols.end(); c++)<BR> {<BR> // Get value from the
stiffness matrix<BR><STRONG> Float
d=this->m_ls->GetMatrixValue(fdof, *c, matrix);</STRONG></FONT></DIV>
<DIV><FONT size=3></FONT> </DIV>
<DIV><FONT size=3> // Store the appropriate value in bc
correction vector (-K12*u2)<BR> //<BR> //
See </FONT><A
href="http://titan.colorado.edu/courses.d/IFEM.d/IFEM.Ch04.d/IFEM.Ch04.pdf"><FONT
size=3>http://titan.colorado.edu/courses.d/IFEM.d/IFEM.Ch04.d/IFEM.Ch04.pdf</FONT></A><BR><FONT
size=3> // chapter 4.1.3 (Matrix Forms of DBC Application
Methods) for more info.<BR>
this->m_ls->AddVectorValue(*c,-d*fixedvalue,1);<BR> }</FONT></DIV>
<DIV><FONT size=3><BR></FONT> </DIV>
<DIV><FONT size=3>the method which itk use to apply BC is in the </FONT><A
href="http://titan.colorado.edu/courses.d/IFEM.d/IFEM.Ch04.d/IFEM.Ch04.pdf"><FONT
size=3>http://titan.colorado.edu/courses.d/IFEM.d/IFEM.Ch04.d/IFEM.Ch04.pdf</FONT></A><FONT
size=3> </FONT></DIV>
<DIV><FONT size=3>However, the code in the Bold format may be wrong. It should
be :</FONT></DIV>
<DIV><STRONG><FONT size=3>Float
d=this->m_ls->GetMatrixValue(*c,fdof, matrix);</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=3></FONT></STRONG> </DIV>
<DIV><FONT size=3>I need your affirmation!</FONT></DIV>
<DIV><FONT size=3></FONT> </DIV>
<DIV><FONT size=3></FONT> </DIV>
<DIV><FONT size=3>2. I fix some DOFs with specific values when applying the BC,
however, the solution of the linear system is different at DOF which
I fix with the specific value. </FONT></DIV>
<DIV><FONT size=3></FONT> </DIV>
<DIV><FONT size=3></FONT> </DIV>
<DIV><FONT size=3>Thank you in advance!</FONT></DIV>
<DIV><FONT size=3></FONT> </DIV>
<DIV><FONT size=3>Regards,</FONT></DIV>
<DIV><FONT size=3></FONT> </DIV>
<DIV><FONT size=3>Yixun Liu</FONT></DIV>
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