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# "rough draft" of updated version

- To: femm@yahoogroups.com
- Subject: "rough draft" of updated version
- From: "David Meeker" <dcm3c@aol.com>
- Date: Fri, 03 Aug 2001 16:19:00 -0000
- User-agent: eGroups-EW/0.82

    All-

    I've posted sort of a "rough draft" of a new femm release in the
    Files section of the femm yahoo groups site at:
    http://groups.yahoo.com/group/femm/files/
    If you have trouble getting into the files section, the same files
    are also mirrored at:
    http://members.aol.com/_ht_a/gmagnetics/roughdraft
    Both the executable and source have been posted.

    If you download this release and you see it do anything "weird", let
    me know.

    This version isn't monumentally different from the version currently
    available on the femm website, but it does have a number of minor
    fixes and additions:

    Robin Cornelius' lua extensions have been included into this latest
    version. I've also included a file called "coilgun.zip" that shows a
    relatively simple example of the kind of thing that you can do with
    the lua scripting. This particular case considers the force on a
    small steel ball, stepping the position of the ball in small
    increments, evaluating the force, and writing the force to a file.
    Since the "gun" is just an air-cored coil, I evaluate force in this
    example by computing the Lorentz force on the coil and infer that the
    force on the ball should be of equal magnitude and opposite direction.

    Both femme and femmview now have a "preferences" selection off of the
    "Edit" selection of the main menu. These preferences allow the user
    to set a number of default behaviors, colors, etc. This was a
    suprisingly difficult addition to make, because I kept running into
    instances in which the preferences were not getting applied in a
    consistent way. I think I've rooted most of these instances out, but
    if you find any, let me know.

    The font sizes have been increased, both in the status bar and in the
    point properties window of femmview.

    The documentation has been (more or less) updated to reflect the
    features in the current version. Probably some more editing is
    required, however....

    I've included a pdf version of Ian Stokes-Rees' "Introduction to FEA
    with FEMM" tutorial in the standard distribution. Since the original
    version of this tutorial had some stuff that was specific to the 2.1a
    version of the program, I've updated it a bit to conform to the
    present release.

    I made a mild change in the way that the program interpolates B-H
    curves. Now, the program fits a cubic spline to the data points and
    tests to see if the resulting fit is single-valued. If not, the B-H
    curve is smoothed using a 3-point moving average filter, and the
    process is repeated until a single-valued curve is obtained. In
    contrast, the previous version smoothed every B-H curve initially and
    then fit cubic spline to the smoothed data. If the B-H points
    weren't relatively carefully chosen, the result could be a B-H curve
    that is not single valued. A B-H curve that isn't single-valued can
    cause convergence problems.

    Bug fixes were made to both the fast point location algorithm as well
    as the B-field smoothing algorithm to accommodate some sort of
    obscure but pathological geometries.

    Dave.

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