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Using an integrodifferential approach to steady‐state skin effect problems, the current density distribution in straight flat conductors is solved by the finite‐element method. The approach takes into account a combination of one‐dimensional finite elements corresponding to the flat conductors and triangular finite elements for the remaining domain outside conductors. The results obtained for a flat conductor placed inside a ferromagnetic medium are compared with analytical solutions provided by finite Fourier transforms. As a final output, besides current density distribution, one can calculate parameters useful to designers such a a.c. resistance and reactance of the straight flat conductors.

The paper presents an extension to previous work on modelling AC losses in high‐temperature superconducting tapes as a highly non‐linear diffusion process. Following successful formulation for a bulk superconductor the presence of silver in a tape has now been included, using a “sandwich” model, to represent more realistically the practical arrangement. The results of the extended 1‐D model are included and a new 2‐D scheme is described using finite difference formulation. Effects of non‐linearity are emphasised.

This paper develops a plausible software availability model for operational use. In particular, we consider two kinds of restoration scenarios; one involves the debugging activity and the other does not involve the debugging activity. The time‐dependent behavior of the software system during the operation phase is described by a Markov process. Several stochastic quantities for software availability measurement are derived from this model. Finally, numerical examples are shown to illustrate software availability analyses.

AIRSCREW data for performance estimation, in practical form, is generally acceptable in the design office, and the present charts and notes have been found useful and convenient in use.

The dyadic Green's function for a horizontally stratified dielectric medium is computed. The general electric field integral equation describing the scattering from an arbitrary dielectric scatterer embedded in one of the layers is formulated using the dyadic Green's function of the respective layer. For the numerical solution of the equation the method of moments is used. Numerical results are given for the case of a cylinder buried in the middle of a five‐layer space for various cases of plane wave excitation.

(i) The Position of the Vertical Asymptotes Vertical asymptotes of the (X, y) curve are given by those values of X which make y infinite. Taking the curve in the form given by Eq. (10), viz.:

A general method of element testing is presented. The method applies to any shape of element with any number of nodes. The shape parameters for a quadrilateral are shown to be contained within the Jacobian matrix and it is also shown that the determinant of this matrix can be expressed in terms of the shape parameters.

Two sets of dual magnetodynamic and magnetostatic finite element formulations taking thin conducting magnetic shells into account are proposed. The abstraction of the thin region from the computational domain is performed by an appropriate treatment of the surface integral terms arising in the weak formulations. Results are presented for two three‐dimensional test‐problems.

An examination is made of the way in which the ground resonance properties of a helicopter depend on the fuselage damping, blade damping, drag hinge offset, inter‐blade spring stiffness, blade mass and angular velocity of the rotor as specified by the parameters λƒ, λβ, Λ1, Λ2, Λ3 and Ω respectively. A direct method of drawing stability boundaries in the (Ω, λβ) plane is developed, and the geometry of these boundaries as the remaining parameters vary is studied theoretically at length. Arising out of the geometry, the validity of Coleman's criterion for stability is examined, and it is shown that the requirement that the product λƒ,λβ should have a certain minimum value is not itself sufficient to ensure stability for all Ω. The condition can be made sufficient by a proper and unique choice of the individual values of ?f and ??, and these values are found in terms of Λ1, Λ2, and Λ3. All other cases of stability require a larger value of the product λƒ, λβ. An alternative criterion for stability is developed which gives the minimum value of λƒ capable of ensuring stability for all Ω. This, and the preceding criterion, are mathematically exact, and follow from Coleman's equations of motion as applied to the case of a helicopter on isotropic supports. A brief account is also given of the case of a rotor having inter‐blade friction damping as against the viscous damping previously assumed.

Ceramic superconductors experience losses when carrying alternating currents. A first step in an attempt to macroscopically model the loss mechanism is to consider the ac transport current in a ribbon that has a cross‐section of width much greater than thickness. To some extent high‐temperature superconductors behave in a way similar to type II superconductors in which the loss mechanism is described by the critical state model, where the current is assumed to flow with a constant critical density Jc and is independent of the magnetic flux density B and ∂B/∂t. The dominant mechanism is the irreversible motion of fluxoids due to their interaction with the pinning sites, resulting in a form of hysteretic loss that can be represented in macroscopic terms (in a system with only one component of magnetic field) as proportional to ∫HsdBa/T over a complete cycle of period T, where Hs is the surface magnetic field strength and Ba is the space average value of flux density. However, it is found that the high‐temperature materials exhibit strong flux creep effects, and so the critical state model may not provide a sufficient description. To find an alternative formulation it is necessary to consider the flux creep E‐J characteristic of the ceramic material. If a highly nonlinear expression for the resistivity ? can be found, it may be possible to model the flux and current behaviour as a diffusion process.