Free-space measurement of bi-axial anisotropic materials
This paper presents an extension of the free-space method for measurement of bi-axial anisotropic material at microwave frequencies. In this method, four complex transverse constitutive parameters are directly computed from the reflection and transmission coefficients of a planar sample in free space for a normally incident plane wave with two polarizations. By using the measured amplitudes of the reflection and transmission coefficients of a planar sample at six incident angles with two polarizations, two complex longitudinal constitutive parameters are obtained by finding the solution to minimize the properly designed objective function under the suitable judging criterion. The numerical trials are carried out for a high-loss material by joining random errors to simulate the real measurement condition, which verifies the validity of this method.
A new free-wave method for ferrite measurement at millimeter wavelengths
It is shown that by measurement of the complex Fresnel reflection coefficients of a thick slab of ferrite for both parallel and perpendicular polarization, the complex permittivity and permeability of the ferrite can be found. In case the reflection coefficients are too small to be measured accurately, it is also shown that a slab of arbitrary but known thickness, backed by a metal plate, may be used. The necessary formulas are given for both cases. They are simple and explicit and do not involve the solution of transcendental equations, as might have been expected in the case of the second method proposed.
Radiation exposure reduction by use of Kevlar cassettes in the neonatal nursery.
A study was performed to determine whether the use of Kevlar cassettes in the neonatal intensive care nursery would reduce radiation exposure to patients. The radiation dose to the neonates was measured by using thermoluminescent dosimeters. In addition, the attenuation of the Kevlar cassettes and the sensitivity of the film-screen combination were compared with the previously used system. The greatest radiation reduction using a mobile X-ray unit was 27%; based on sensitivity measurements, the theoretical reduction averaged 38%. The reduction in radiation exposure resulted from reduced attenuation by the Kevlar cassette.