摘要:

It is known that the configuration of the input driving system may be of importance to the impedance of antennas at high frequencies. In this paper, a region in the vicinity of the input is considered as a transducer between the TEM mode on the driving transmission line and the spherical nearly‐TEM mode on the antenna system, and the constants of this transducer are found both by calculation and measurement for a particular case. The calculation is based upon quasi‐static concepts, utilizing an electrostatic field map obtained from an electrolytic tank to give the approximate form of the electric field lines. The measurement is made by finding three input reactances corresponding to the input region closed by three spun aluminum hemispheres of different radii. The three sets of data, taken at each frequency, are sufficient to determine the constants of the transducer. They are expressed here as a pi‐network for comparison with calculated values.The main portion of the antenna is analyzed substantially as in Schelkunoff's approach, with the TM modes in space and in the antenna region expressed as a shunt admittance at the end of the antenna in the TEM mode equivalent circuit. This admittance is then transformed to the desired reference on the antenna by a perturbation calculation. From there it is transformed to a desired reference on the feed line by means of the input network constants. Values calculated in this way are compared with measured values over the range 200 to 1000 mc/sec. for the particular monopoles studied. Agreement is not perfect, but appears considerably better than without consideration of the specific input configuration.

ISSN:0021-8979    

DOI:10.1063/1.1699537

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

A resonant cavity method is described for the determination of the dielectric constant of polymeric solids in the form of fibers, films, and thin cylinders. Methods for investigating electrical anisotropy are outlined. In the case of fibers, for the electric field parallel to the fiber axis, the dielectric constant is determined directly. For the electric field perpendicular to the fiber axis, the problem arises of calculating the dielectric constant of the fiber from that of an air‐fiber mixture. For the latter purpose the Lichtenecker equation was found to be applicable. Illustrative measurements of the dielectric constant of wool, Nylon, and Cellophane are presented and discussed briefly.

ISSN:0021-8979    

DOI:10.1063/1.1699538

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

A theoretical procedure for the determination of the stresses of quenching origin in solid and concentric hollow cylinders has been derived. The method relies on interferometric data and the assumptions discussed in Section I, whose validity for the technically important case of glass is supported by a number of experimental investigations.The results should be of interest for the analysis of stresses in quenched glass cylinders, so great in magnitude that the usual cutting techniques are precluded, because of the explosive characteristics of highly stressed objects of this material.

ISSN:0021-8979    

DOI:10.1063/1.1699539

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

It was earlier established that the lens field between the cathode and crossover can be represented by a simple functionV=Asinhkz, so that the main properties of the paraxial ``crossover'' (or minimum section of the beam) can be determined as a first approximation in terms of ``A'' and ``k.'' The distance of the crossover works out at 8&pgr;/3k√3; its potential isAexp(8&pgr;/3√3); and the angle of the beam is simply proportional to ``k.'' The radius of the crossover is then 2/kexp[−(2&pgr;/3√3)]·tan&thgr; for electrons of initial velocity ``A,'' where &thgr; is the angle of emission within the paraxial limit. The differential analyzer was also used to obtain the correct solution for the trajectory equation from the field plots for different systems, and shows that the simple theory gives an adequate approximation for design purposes.

ISSN:0021-8979    

DOI:10.1063/1.1699540

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

Some surface structure characteristics of a metal single crystal are considered and the conclusions are applied to the preparation of single crystal plates of copper. A successful preparation is described as well as suitable methods for evaluating the effectiveness of the preparation. Using physical microadsorption isotherms of nitrogen at 78.1°K, electron diffraction, and x‐ray diffraction methods, the conclusion is tentatively asserted that the surfaces are essentially planar on a molecular scale, and that the surface atoms are arranged in an approximately undistorted lattice.

ISSN:0021-8979    

DOI:10.1063/1.1699541

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

Transient and steady state solutions of the parallel plane diode are obtained. The limitations on a single valued velocity theory are investigated. These general results are applied to the space charge limited diode with the a.c. components small compared to the d.c. Power consumption is discussed and it is shown that hitherto neglected terms are of importance.

ISSN:0021-8979    

DOI:10.1063/1.1699542

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

A simple theory of the lagging effect of the positive ions in neutralizing the space charge near the cathode of a gaseous diode is developed. By means of bridge measurement up to a frequency of 350 or 1000 kc per second, depending upon the type of tube used, the theory is checked experimentally in terms of the high frequency impedance of the diodes. Several constants of interest, such as the transit time and the lifetime of a positive ion, its effectiveness in neutralizing space charge, etc., can be deduced from the theoretical and experimental investigations.

ISSN:0021-8979    

DOI:10.1063/1.1699543

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

The stress wave caused by a longitudinal impact at the end of a cylindrical bar has been analyzed in the case where the impact velocity is large enough to produce plastic strain. The theory gives a method for computing the stress distribution along the bar at any instant during impact. It is shown that for a given material, there is a critical impact velocity such that when subjected to a tension impact with a velocity higher than the critical, the material should break near the impacted end with negligible plastic strain.An experimental investigation was made concurrently with the theoretical study. Some of the most significant experimental results are presented in this paper.

ISSN:0021-8979    

DOI:10.1063/1.1699544

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

This paper describes an experimental model of a combination Kerr cell camera and flash illumination unit designed specifically for the photography of projectiles under conditions of strong ambient illumination. Specific cases wherein such conditions are found are considered and the applicability of the Kerr cell as a secondary protecting shutter is described. A description is given of a pulse forming network—pulse transformer circuit designed to apply an operating voltage pulse to a Kerr cell of thirty‐six (36) kilovolts amplitude and one point nine (1.9) microseconds duration. Limitations inherent in the present equipment are considered together with proposals for overcoming these defects in future models. Typical results are presented, including (a) a picture taken with the unit showing a twenty‐millimeter shot at the time of emergence from the muzzle of a gun, and (b) a picture of a thirty‐seven millimeter shot taken shortly after penetration of a metal target plate.

ISSN:0021-8979    

DOI:10.1063/1.1699545

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

The field of a quarter‐wave‐length antenna above a circular conducting disk of zero thickness—the groundplane—is calculated theoretically by use of the wave functions of the oblate spheroid. Assuming a sinusoidal distribution of current on the antenna, we compute the currents on the groundplane, the radiation resistance and the radiation pattern of the system for various values of the radiusa. With these results the distortion of antenna radiation by finite groundplanes can be studied. We find good agreement with recent experimental data.

ISSN:0021-8979    

DOI:10.1063/1.1699432

出版商:AIP    

年代:1950

数据来源: AIP