Abstracts of Technical Articles by Bell System Authors 



Weathering of Soft Vulcanized Rubber} James Crastree and A . R . Kemp. 

 Two separate and distinct processes are responsible for the breakdown of 

 soft vulcanized rubber when exposed to outdoor weathering — light-energized 

 oxidation and attack by atmospheric ozone. The former is independent of 

 stress and controllable to any marked extent only by incorporation of 

 opaquing fillers. The latter affects rubber only when under stress and is 

 checked to a considerable degree by addition of certain hydrocarbon waxes 

 as long as the stress is static. The conditions affecting these processes have 

 been investigated, and suggestions for accelerated aging are made on the 

 basis of the findings. 



A Note on a Simple Transmission Formula} Harald T. Friis. A simple 

 transmission formula for a radio circuit is derived. The utility of the 

 formula is emphasized and its limitations are discussed. 



Applicatio-ns of Thin Permalloy Tape in Wide-Band Telephone and Pulse 

 Transformers } A. G. Ganz. The properties and uses of thin permalloy 

 tapes ranging from two mils to as little as 1/8 mil thick in tape cores are 

 described. Typical applications covered are in transformers and non-linear 

 coils for radar and for telephone systems. Data are given on the steady 

 a-c. properties of thin tapes up to one megacycle. Pulse magnetization of 

 the tape is analyzed. The available flux density range with uni-directional 

 pulses and the effects of appropriate air gaps and of reverse magnetization 

 between pulses are illustrated. Equations are given for flux distribution, 

 effective permeability and loss, assuming linear magnetic properties, and 

 convenient graphs for these characteristics are included. Simple expressions 

 are developed for effective permeability and loss, which are approximations 

 for the high d-c. permeability and rapid transition to saturation which 

 characterize the permalloys. 



Derivation of the Lorentz Transformations.^ Herbert E. Ives. The 

 Lorentz transformations were obtained by Lorentz as a succession of ad hoc 

 inventions, to reconcile Maxwell's theor>' with the results of experiments on 

 moving bodies. By Einstein they were derived after a discussion of the 



1 Indus. & Engg. Chemistry, March 1946. 

 ^Proc. I.R.E., May 1946. 

 ^Elec. Engg., Trans. Sec, April 1946. 

 ■• Phil. Mag., June 1945. 



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