HalfEllipsoid:

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   Compute volume, surf area, centroid and specific MOI of half-ellipsoid
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   Form:
   [V,S,cSld,cShl,inrSld,inrShl] = HalfEllipsoid( a, b );
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   Inputs
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   a          (1)   Length along axis of rotation
   b          (2)   Radius at max cross-section
                       Note: a==b is a hemisphere


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   Outputs
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   V          (1)   Volume
   S          (1)   Surface Area
   cSld       (1)   Centroid of solid
   cShl       (1)   Centroid of shell
   inrSld     (1)   Specific inertia of solid, multiply by density for I
   inrShl     (1)   Specific inertia of shell, multiply by density for I

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