Neutron diffraction and Mössbauer spectroscopic measurements have been performed on four series of ternary alkali stannosilicate glasses of nominal composition (SnO0.5-x
(M2
O)x
(SiO2
)0.5
with 0
x
0.2, where the modifier cations were M = Li, Na, K and Rb. The data show that the tin is predominantly three co-ordinate and that the length of the Sn-O bond and the O-Sn-O angle decrease with increasing modifier concentration x
. This reduction increases with increasing size of the modifier cation, and is opposite in sign to the macroscopic molar volume which increases with modifier content. The 119
Sn Mössbauer spectra of these samples showed that most of the tin is in the Sn2+
state and that the isomer shift and quadrupole splitting vary approximately linearly with the Sn-O bond length and O-Sn-O bond angle for each series. This is consistent with a contraction of the 5p electron orbitals of the tin atoms and an increase in the symmetry of the ligand environment as modifier ions are added.
IN1RODUCTIONEddy current NDE has been used for many years to effectively detect defects in conducting materials [1]. However, a major limitation associated with the technique is that imaging techniques are generally qualitative classification schemes which rely on calibration procedures. This is because eddy current phenomena are governed by diffusion, and as such, quantitative inversion/imaging schemes which rely on properties of wave propagation such as diffraction, scattering, and time-of-flight are not applicable. 1his paper will examine the possibility of using phase shifts associated with time-harmonic eddy current phenomena to solve quantitative inverse problems in the same manner that phase shifts of wave propagation are used.The governing equation for the electric field associated with eddy current NDE is given by 2-which is a parabolic partial differential equation describing diffusion [2]. The time-harmonic counterpart of (1) is an elliptic equation given by 2--On the other hand the electromagnetic wave phenomena underlying millimeter and microwave NDE are described by
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