D.J. Tylavsky et al. (see ibid., vol.74, no.9, p.1290-1292, 1986) formulate the boundary value problem of an electric line source eccentrically located in a cylindrical cavity. Their solution is consistent with the full-wave solution for a similar problem arising in electrical geophysics. The commenter claims that, in reducing their solution to a simpler form, the authors make some physical approximations which are questionable. In replying, Tylavsky et al. agree with Wait's comments that the application of a planar image model to the case of a conductor eccentrically located in a cylindrical dielectric is indeed a nontrivial problem.>

The two-dimensional Fourier transform is used to derive an expression for the electric field and impedance associated with a transmission line with a multilayered earth return. The expressions are based on a model of the earth which includes arbitrary horizontal stratification with differing resistivities and permeabilities. A method is proposed to extend the applicability of these results to conductors over multilayered media with varying permitivities such as semiconductor devices.

A new factorization technique, known as Quadrant Interlocking Factorization (QIF), has recently been shown to exhibit a degree of inherent parallelism which is superior to that of L-U factorization. It is shown here that the QIF method may be derived more simply using block L-U factorization (BLUF) techniques.

A generalized form of the matrix inversion lemma is shown which allows particular forms of this lemma to be derived simply. The relationships between this direct method for solving linear matrix equations, lower-diagonal-upper decomposition, and iterative methods such as point-Jacobi and Hotelling's method are established. The generalized form is used to derive a new factorization scheme and a new matrix inversion algorithm with a high degree of parallelism.