ABSTRACTS OF TECHNICAL ARTICLES 1011 



Matthias, B. T./ and J. K. Hulm' 



Superconducting Properties of Cobalt DisiUcide, Phys. Rev., 89, 

 pp. 439-441, Jan. 15, 1953. 



A solid rod of cobalt disilicide was found to have a superconducting transition 

 temperature close to 1.4°K, a critical field gradient of 146 gauss per degree at 

 the transition point, an ice-point resistivity of 16.5 micro-ohm cm and a 

 residual resistivity of about 16 per cent of the ice-point value. 



Miller, R. L.^ 



Auditory Tests with Synthetic Vowels, J. Acoust. See. Am., 25, pp. 

 114-121, Jan., 1953. 



The results are given for a series of phonetic evaluation tests which were made 

 by means of synthetically produced vowel sounds. By employing synthetically 

 produced sounds, a number of the significant parameters could be varied in 

 an independent and systematic manner without encountering the uncertain- 

 ties and limitations of the human speech mechanism. The types of parameter 

 changes which were investigated by this means were those of fundamental 

 frequency or pitch, formant frequency and amphtude, and, finally, the num- 

 ber of formants important to a sound. The results of the tests indicate that 

 all of these parameters are important in the evaluation of the sound. In 

 particular, there is a shift in the phonetic evaluation which can be attributed 

 to pitch alone. 



Miller, S. E.,^ and A. C. Beck^ 

 Low-Loss Waveguide Transmission, I.R.E., Proc, 41, pp. 348-358 

 Mar., 1953 (Monograph 2080). 



The circular electric mode in round metallic tubing becomes increasingly more 

 attractive than the dominant mode from the standpoint of minimizing the 

 waveguide size at frequencies above about 10,000 mc for the loss criterion of 

 0.25 db/100 feet. The circular electric (TEoi) mode also makes available a 

 theoretical heat loss of 2 db/mile in waveguides less than 6 inches in diameter 

 at frequencies higher than about 5500 mc. Increased transmission bandwidth, 

 reduced delay distortion, and reduced waveguide size are factors favoring use 

 of the highest practical frequency of operation. An increased number of freely 

 propagating modes and smaller mechanical tolerances are the associated 

 penalties. Experimental work has been carried out in the 9000-mc region using 

 the TEoi mode in a pipe about 5 inches in diameter. Transmission of 0.1 -m sec 

 pulses had been observed over a distance of 40 miles. Mode conversion and 

 surface roughness of the tubing walls result in observed losses which average 

 about 50 per cent higher than the theoretical values for geometrically perfect, 

 smooth-walled tubing. There is included a brief discussion of several problems 

 unique to transmission in a multimode medium, including pure mode genera- 

 tion, mode filtering, the bend problem, and the effects of mode conversion on 

 transmission loss and signal fidelity. 



Bell Telephone Laboratories, Inc. 



