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953: Error: Singular Matrix

What does the error message "Singular Matrix" mean? The problem is that the stiffness matrix of the linear system is singular and the linear solver cannot invert it. Examples of practical modeling situations where...
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952: Avoiding negative concentrations

Why do I get negative values of the concentration in my diffusion, convection and reaction model? Why do I see values that go below, or above, their lowest, or highest, possible values based upon the boundary...
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933: Troubleshooting graphics issues

Chances are that there is a graphics rendering problem if any of these symptoms show up: The graphics window is black It is not possible to mouse-select objects in the graphics window The COMSOL application crashes...
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913: Computing Time and Space Integrals

How do I compute integrals over space or time? What if I want to use the result of these integrals elsewhere in my model? The COMSOL Multiphysics architecture allows you to evaluate integrals in both space and time in...
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905: Modeling of step transitions

You may want to define loads, material properties, or boundary conditions that vary abruptly with respect to the solution, or with respect to time. This can, however, lead to a solution which is discontinuous in space...
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903: Could not obtain license for COMSOL Multiphysics GUI

Any of the following errors can appear for example if the COMSOL application has problems communicating with the license manager: License error: -15. Cannot connect to license server system. License error:...
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878: Should I use the RMS, the peak, or the instantaneous value to...

Should I use the RMS, the peak, or the instantaneous value to specify sources for electromagnetic fields? How can I specify the phase angle? The COMSOL Multiphysics formulation uses complex fields when solving...
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875: What does degrees of freedom (DOFs) mean in COMSOL Multiphysics?

What does degrees of freedom (DOFs) mean in COMSOL Multiphysics? The solution time and memory requirements are strongly related to the number of degrees of freedom in the model. It is often desirable to be able to...
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866: What hardware do you recommend for COMSOL Multiphysics®?

I am going to buy a new dedicated computer for running COMSOL Multiphysics®. What hardware do you recommend? Due to the wide range of different problem types that COMSOL Multiphysics® solves, the rapid pace of...
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838: Can COMSOL import topological data, meshes and images?

Can COMSOL Multiphysics import meshes, topological data, and images? Importing Meshes Mimics and ScanIP can export volumetric meshes on COMSOL's own mesh format created from 3D scans, that can be directly imported...
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