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A class of codes capable of correcting multiple errors is described. Some of these codes can be implemented with considerably less hardware than was needed for previous multiple error‐correcting codes. A general method is shown for constructing a code of redundancy 1/b that will correct error bursts of Kb or fewer digits (K and b integers). The logical design of the encoder and decoder, as well as the guard space requirement of good digits between bursts of errors, is described.

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP: 142.157.212.158 On: Sun, 07 Dec 2014 16:05:49 42 KERNOHAN, BILLINGTON, AND LEWIS calculation would indicate that for each pair of defects created approximately 30 beryllium atoms in the form of the intermetallic compound Ni-Be precipitate from the solid solution.The mechanism whereby the precipitation is enhanced is not yet understood, but it might be assumed that the additional vacancies and/or interstitials made available by the neutron bombardment are responsible for an increased diffusion rate. It is not believed that "thermal spikes" playa role, because of the temperature depend-ence of the process. That is, a momentary high temperature "spike" should induce effects that are independent of temperature. ACKNOWLEDGMENTS

A new method of suspending a molten zone is as follows: clamp a horizontal cylindrical ingot at both ends; apply a horizontal magnetic field normal to the ingot where the zone is to be suspended; and pass a direct current through the ingot, creating an upward force equal and opposite to the gravitational force, thereby permitting the zone to be melted and suspended. It is shown theoretically that such a zone will be stable in a uniform magnetic field if its length-to-diameter ratio is less than π and if its length is less than 0.17(γ/ρ)½, where γ and ρ denote surface tension and density, respectively, in cgs units. Some experimental results and practical considerations are discussed.

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