ABSTRACIS OF TECHNICAL ARTICLES ()().") 



(Ireat Britain. Mini.stry of Supply. Symposium on Informal ion Tlu^ory. 

 Report of Proceedings held. . . Royal Soc, Burlinslon House, Loud., 

 Sept. 20-29, 1950. 



On Uir h'ddtion Between the Sound Fields Radiated and Dijfmeted bij 

 Plane Obstaeles. F. :M. Wiener'. ./. Aeoust. Soc. Am., 23, pp. ()97-700, 

 Nov., 1951. 



In the i)a8t, acoustic ditYiaction and radiation problems have often Ix'en 

 treated sei)anitely, although their intimate connection is clear from theory. 

 In the case of i)lane piston radiators and plane rifj;id scatterers exposed to a 

 perpendicularly incident plane wave, this connection becomes particulaily simple 

 and useful. It is easy to show that the radiated sound field is everywhere the 

 same as the field scattered (diffracted) in the diffraction case, except for a factor 

 of proportionality. It is also shown that the reaction of the medium on the ra- 

 diator, as expressed by the mechanical radiation impedance, is equal to the force 

 per unit incident pressure exerted on the same obstacle, held rij^id as a scatterer, 

 excei)t for a factor of proiK)rtionality. By way of illustration, the foregoing prin- 

 cijiles are applied to the important case of the circular disk. 



Magnetic Modulators. E. P. Felch\ V. E. Legg\ and F. G. Merrill\ 

 References. Electronics, 25, pp. 113-117, Feb., 1952. 



Conversion of low-level, low-frequency or dc signals to ac signals capable of 

 lieing amplified b\' conventional means is accomplished by magnetic-amplifier- 

 type device that combines higli efficiencj' and reliability with extreme rugged- 



ness. 



Conservation of Nickel. G. R. Gohn\ A.S.T.M., Bull., Xo. 179, p. 32, 

 Jan., 1952. 



The Mechanism of Electrolytic Rectification. H. E. HaringV Electro- 

 chem. Soc, JL, 99, pp. 30-37, Jan., 1952. (Monograph 1929). 



An electrochemical theory is proposed for rectification, as exemplified by the 

 tantalum (or aluminum) electrolytic rectifiei- and capacitor. A detailed con- 

 sideration of the mechanism of formation of the oxide film which constitutes 

 the rectification barrier leads to the conclusion that this barrier consists of an 

 electrolytic polarization, in the form of a concentration gradient of excess metal 

 ions, permanenth' fixed or "frozen" in position in an otherwise insulating matrix 

 of electrolytically-formed oxide. The phj'sical structure which has been de- 

 scribed functions as (a) a current-blocking ionic space chai'ge or (b) a current- 

 passing electronic semiconductor, de])ending solely upon the direction of the 

 applied voltage. The movement of electrons only is required. An exi)lanation 

 for breakdown of the l:)arriei' at excessively high voltages is suggested. This 

 explanation may be api)licable to dielectric breakdown of other kinds. 



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