Yukihisa Nanbu

A comparative study of the effective dielectric constant of a medium containing randomly distributed dielectric spheres embedded in a homogeneous background medium

Abstract The effective dielectric constant ∈eff of a medium containing randomly distributed dielectric particles has been analysed by conventional methods: Foldys approximation, the quasi-crystalline approximation (QCA) and the QCA with coherent potential. These conventional methods, however, have been indicated to become invalid for particles with a high dielectric constant; we have thus presented a new method that is valid for them. This paper compares ∈eff of our method with those of the conventional methods by changing the volume fraction and the dielectric constant of spheres. As a result, our method is shown to be more powerful for the analysis of ∈eff than the conventional methods.

Condition for random distribution of many dielectric spheres to be random for a coherent field

The condition for many dielectric spheres to be randomly distributed in view of expression of a coherent field is given in an analytic form. The condition is shown graphically for changing the parameters concerning spheres. The numerical results yield a quick computer simulation of a random distribution and may be useful for precise calculation of the effective wavenumber of a coherent field in a random distribution of dielectric spheres.

Analysis of depolarized electromagnetic waves propagated through random medium by using perturbation method

We have derived an integral equation using the dyadic Greens function on the assumption that there exists a random medium screen of which the dielectric constant is fluctuating randomly. On the integral equation, the depolarized EM wave has been analyzed by using a perturbation method, and we have shown the representation of the first order perturbation of the depolarized EM wave.

Numerical analysis of the effective propagation constant of a space where small spheres with high permittivity are randomly distributed

Numerical results are presented in detail for the effective propagation constant of a space where many small spheres with high permittivity are randomly distributed, on the basis of the multiple scattering theory. The results are valid also for the space where the results given by conventional methods become invalid.<<ETX>>

The effective permittivity of the discrete random medium composed of dielectric spheres and homogeneous space in the region of low to resonance frequencies

Presents the effective permittivity of the discrete random medium where dielectric spheres are randomly distributed for a coherent field, in the region of low to resonance frequencies. In addition, the authors have in part compared the results with those of the effective field approximation, the quasi-crystalline approximation and the quasi-crystalline approximation and coherent potential.

Depolarization of electromagnetic waves propagated through random media

In order to analyze the depolarization due to random medium quantitatively, we have derived an integral equation using the dyadic Greens function on the assumption that there exists a random medium layer of which the dielectric constant is fluctuating randomly. On the integral equation, the depolarized EM wave has been analyzed by using a perturbation method, and we have shown a far-field expression of the first order perturbed EM wave depolarized by random medium.

A comparative study of the effective propagation constant in a random medium containing coated dielectric particles

Studies of the propagation and scattering of waves in random media containing dielectric particles have previously been made with applications to remote sensing technology and material science. The particles in natural geophysical terrain and in composite materials consist of different constituents. Therefore it is important to have a medium model containing dielectric particles consisting of two layers with different materials. This model may be used to study waves propagating in media such as melting snow, wet snow, soil moisture and composite materials with coated granules. In this paper, we treat the medium model whose coated spherical particles are randomly distributed. The effective propagation constant (K/sub eff/) in a random medium containing coated dielectric particles has been analyzed by conventional methods: EFA (effective field approximation, Foldys approximation), QCA (quasicrystalline approximation) and QCA-CP (QCA with coherent potential). These methods, however, have been indicated to become invalid for particles coated with a material having high dielectric constant; we have thus presented a new method valid for them. This paper compares K/sub eff/ of our method with those of the conventional methods by changing the volume fraction and the structure of particles. As a result, our method is shown to be more powerful for the analysis of K/sub eff/.