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- From: David Weinstein <dmw@sci.utah.edu>
- To: "ashok kumar" <spruceupak@hotmail.com>
- Cc: scirun-users@sci.utah.edu
- Subject: Re: [SCIRUN-USERS] apply fem voltage source description
- Date: Tue, 27 Jan 2004 11:17:54 -0700
Hello Ashok,
The difference between these two modules is that the
ApplyFEMCurrentSource module is used for applying Neumann boundary
conditions (known values related to the first spatial derivative of the
potential, e.g. flux, current density, dipoles), whereas the
ApplyFEMVoltageSource module is used for applying Dirichlet boundary
conditions (known values for the potential at specific locations). In
both cases these boundary conditions affect the right-hand side of the
linear system (which is why both modules take an optional RHS
ColumnMatrix as input, and produce a modified RHS ColumnMatrix as
output), and in the case of a Dirichlet BC, the stiffness matrix must
also be modified (which is why ApplyFEMVoltageSource requires the
stiffness matrix as input, and produces a modified stiffness matrix as
output).
Typically, the ApplyFEMCurrentSource takes two Fields as input -- a
TetVolField that specifies the geometry and conductivity information
for the volume (e.g. brain-eg-mesh.tvt.fld), and a collection of dipole
sources (PointCloudField<Vector>). This is the case for the
forward-fem network described in the BioPSE tutorial. It is also
possible to pass in current densities instead, as demonstrated in the
SCIRun/src/Packages/BioPSE/nets/current-sources.net network.
In contrast, the ApplyFEMVoltageSource applies Dirichlet condition at
location in the mesh where potentials are know. Note, unlike
ApplyFEMCurrentSource, the ApplyFEMVoltageSource requires a second
upstream module in order for it to work correctly. Specifically, an
InsertVoltageSource module is required. The user passes the
TetVolField of conductivity (e.g. brain-eg-mesh.tvt.fld) into the first
Field input port of InsertVoltageSource, and a PointCloudField<double>
specifying the positions and voltages of the known potentials into the
second Field input port. The module identifies which nodes of the
mesh those Dirichlet conditions will be applied to and stores that
information with the output TetVolField. The output TetVolField (which
now has the Dirichlet BC info stored as a Property of the Field) is
passed into the first input port of ApplyFEMVoltageSource.
Cheers,
Dave
On Jan 26, 2004, at 11:20 PM, ashok kumar wrote:
sir
the descriptions for both the applyfemcurrentsource and
applyfemvoltagesources are given the same one .
may i know the right description for applyfemvoltagesource module.
i am in urgent need of it sir please help.
yours sincerely
ashok kumar
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