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Re: [SCIRUN-USERS] apply fem voltage source description

Chronological Thread 
  • From: David Weinstein <>
  • To: "ashok kumar" <>
  • Cc:
  • 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/ 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.


On Jan 26, 2004, at 11:20 PM, ashok kumar wrote:


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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