774 THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1951 



hanced by a factor of 10 by soldering a solid brass ''horn," tapered exponen- 

 tial, to the end of the barium titanate cylinder. If the large end of the horn, 

 which is soldered to the cylinder, is 10 times the diameter of the small end, 

 the horn acts as a transformer to increase the particle motion by a factor of 

 10. Hence, a 1.5-mil motion is possible with this combination at 18 kilo- 

 cycles. This structure has been made the basis of several instruments used for 

 testing wear, for measuring magnetic flux, for testing adhesion of films, and 

 for boring odd-shaped holes. A feedback amplifier system with a diode 

 limiting element is used to keep the amplitude constant. 



Transmission-Line Equivalent of Electronic Traveling-Wave Systems * W. 

 E. Mathews^ References. Jl. Applied Phys., v. 22, pp. 310-316, Mar., 

 1951. 



Abstract — It is well known that the small-signal behavior of long elec- 

 tron beams may be analyzed in terms of propagating space-charge waves 

 suggesting an equivalence between such beams and longitudinally moving 

 transmission lines. This in turn suggests the analysis of such electronic 

 devices as the traveling-wave amplifier, double-stream or electron-wave 

 amplifier, and multicavity magnetron, in terms of coupled distributed- 

 parameter transmission lines moving relative to each other. It is shown that 

 this approach is equivalent to a rigorous field-theory analysis in certain 

 cases of particular interest, and the procedure for calculating the significant 

 distributed parameters is indicated. Final results for the idealized helix and 

 thin cylindrical electron beam are presented. 



Electronic Music for Four. L. A. Meacham^ Electronics, v. 24, pp. 76-79, 

 Feb., 1951. 



Thickness-Shear and Flexural Vibrations of Crystal Plates. R. D. Mindlin^ 

 References. Jl. Applied Phys., v. 22, pp. 316-323, Mar., 1951. 



Abstract — ^The theory of flexural motions of elastic plates, including the 

 effects of rotatory inertia and shear, is extended to crystal plates. The 

 equations are solved approximately for the case of rectangular plates excited 

 by thickness-shear deformation parallel to one edge. Results of computations 

 of resonant frequencies of rectangular, AT-cut, quartz plates are shown and 

 compared with experimental data. Simple algebraic formulas are obtained 

 relating frequency, dimensions, and crystal properties for resonances of 

 special interest in design. 



Television Transmission in Local Telephone Exchange Areas. L. W. 

 Morrison^. S.M.P.E., JL, v. 56, pp. 280-294, Mar., 1951. 



Abstract — The functions of a video transmission system in a local ex- 

 change area in providing mobility for the pickup camera and interconnection 



* A reprint of this article may be obtained on request. 

 > B. T. L. 



