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EMTM

Effective Medium Theory Materials (EMTM©)

Effective Medium Theory Materials (EMTM©) is a computer code that calculates the effective permittivity of a material comprising a substrate or matrix that is randomly loaded with general ellipsoidal particles or inclusions.

EMTM© (Effective Medium Theory Materials) is a computer code which calculates the effective permittivity of a material comprised of a substrate or matrix which is randomly loaded with general ellipsoidal particles or inclusions. The program is capable of handling both lossy matrix materials and lossy particles. Inclusion shapes include both prolate (fiber-like) and oblate (disk-like) ellipsoids as well as spheres. Spheres may be comprised of as many as ten concentric shells or coatings. The user can choose from various distributions for particle shape, including a simple distribution in which the relative numbers of each type of particle are given as input, a flat distribution in which the relative numbers of particles are equal over a specified range, or a Gaussian distribution in which the relative particle numbers are calculated given the mean and standard deviation of one of the particle dimensions.

The properties of the constituent materials must be provided on input. The permittivity of the matrix material is given in terms of its (measured) real and imaginary parts. The shape (type of ellipsoid) of the inclusions and their dimensions must also be provided. The permittivity of the inclusions is supplied in terms of bulk material properties. The imaginary part of the inclusion dielectric is calculated from its resistivity. Clumping of inclusion particles can be handled by using an appropriate distribution of clump sizes within the finished material. For a given volume loading of particles, the effect of clumping is to reduce the effective particle loading, leading to lower permittivity values. Maxwell-Garnet theory is used to calculate the effective permittivity. Note that this theory is valid for low densities of inclusion particles. The validity of the theory used is checked for each case after all data is input.


Applications

EMTM is used on targets that are prolate (fiber-like) and oblate (disk-like) shaped ellipsoids as well as spheres for 1D RCS prediction.


Features

  • Controlled dispersion of particles
  • Prolates (fiber-like), oblates (disk-like) ellipsoids, multi-layered spheres
  • Maxwell-Garnet theory
  • Relates external field to internal w/ perturbations caused by inclusions
  • Various distributions options
  • Simple distribution
  • Flat distribution
  • Gaussian distribution

Benefits

  • EMTM is capable of handling both lossy matrix materials and lossy particles.
  • EMTM allows the user to choose various distributions for particle shape such as simple, flat, or Gaussian.
  • It automatically checks the validity of the theory used for each case after all data are input.

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