On the Relative Efficiencies of Context-free Grammar Recognizers


Book Description

A number of diverse recognition procedures that have been proposed for parsing sentences with respect to a context-free grammar are described in this paper by means of a common device. Each procedure is defined by giving an algorithm for obtaining a nondeterministic Turing Machine recognizer that is equivalent to a given context-free grammar. The formalization of the Turing Machine has been chosen to make possible particularly simple descriptions of the parsing procedures considered.




Machine-aided Design of Context-free Grammars


Book Description

The following paper represents work to date on the deformation method for quadratic programming and thus may be regarded as a sequel to Zahl, S. (1964) A Deformation Method for Quadratic Programming, Research Note AFCRL-63-132. It gives an explanation of a modified Iverson programming language and uses this to give a detailed algorithm for the Zahl Deformation Method of Quadratic Programming.




A Study of Band Edge Distortion in Heavily Doped Germanium


Book Description

Details of the energy band structure of degenerate n-type germanium were determined by analysis of fine structure in the 4.2K volt-ampere characteristic of germanium tunnel diodes. No shift in the relative energy of the conduction band minima was observed. The band edge is found to be exponentially distributed with 1/e energies of the order of 10 MeV. There appears to be an ordering mechanism among the group V impurity atoms used as substrate dopants. (Author).




Experimental Study of Zone Refining of the Binary System Triphenyl Antimony-benzoic Acid


Book Description

An experimental study on the zone refining of the binary system triphenyl antimony-benzoic acid is described. The isotope Sb124, which is a strong gamma emitter, was employed as a tracer; this allowed a rapid in situ nondestructive analysis, closely spaced experimental points, and the opportunity to study distribution as a function of varying experimental conditions. With the aid of computers (IBM 7090 and IBM 7044) apparent k's were calculated and the experimental data compared with those predicted from various mathematical models. (Author).







Earth-to-space Communications at Millimeter Wavelengths


Book Description

It is expected that with the exploration of outer space, a requirement for high data rate earth-to-space communication channels will arise. A program to investigate the feasibility of using the millimeter-wave region of the spectrum for this application is presented. The theory of atmospheric attenuation resulting from losses due to absorption, scattering and refraction processes is reviewed and used to estimate propagation losses produced by atmospheric gases, clouds and precipitation. Curves of total atmospheric attenuation and noise level as a function of meteorological parameters and antenna elevation angle are also presented. A series of experiments designed to obtain as much information as possible on the limitations imposed by the atmosphere on millimeter-wave propagation is considered. Although experiments using natural celestial bodies such as the sun, moon, planets and galaxies as radio sources are emphasized, those which would utilize aircraft, rockets and satellites are also mentioned. Finally, the characteristics of a recently installed precision 29-ft antenna designed to operate at 35 Gc (wavelength = 8.6 mm) with a traveling-wave maser as a preamplifier for the radiometer are outlined along with the specific experiments for which this antenna system will be used. (Author).