摘要:

Two methods of cancelling the surface reflections of dielectric lenses are described in this paper. The first utilizes a simulated quarter‐wave matching layer, and the second a reactive wall embedded within the dielectric. The reactive wall may take a variety of physical forms, such as arrays of thin conducting disks which have a capacitive reactance, or arrays of thin wires which have an inductive reactance. Surface matching is obtained when the disks are placed approximately ⅜ wavelength inside the lens, or the wires ⅛ wavelength. Curves are presented that show how the reflections at the air and dielectric boundary are reduced for various angles of incidence and polarization when quarter‐wave layer and reactive‐wall matching are employed.The reactance of the array of disks for waves incident at various angles and polarizations is computed by means of Bethe's small aperture theory, and Babinet's principle. Measurements in wave guide of the reactance of an array of circular disks for various angles of incidence and for bothE‐ andH‐plane polarization show close agreement with the theory.

ISSN:0021-8979    

DOI:10.1063/1.1722017

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

A derivation is given for the electromagnetic field produced by an arbitrary slot cut in the surface of an elliptic cylinder of perfect conductivity and infinite length. The electric field tangential to the slot is assumed to be a prescribed function. The integrals in the formal solution are evaluated by the saddle point method for the far zone fields which when specialized to thin transverse or axial slots agree with known results. As illustrative examples, patterns of thin axial and transverse slots on a strip are computed.

ISSN:0021-8979    

DOI:10.1063/1.1722018

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

Experimental techniques are described by which one can observe the separation of a shock wave in a metal into an elastic wave and a slower plastic wave. The plastic‐wave velocity was about 15 percent less in steel and 10 percent less in tungsten than the elastic‐wave velocity, at pressures imparted by Composition B explosive. Elastic‐wave velocities were the same, within experimental error, as the measured sound velocities. The pressure in the elastic wave in SAE 1020 steel, deduced from the material and wave velocities, is independent of the plastic‐wave pressure within experimental accuracy, and is about 12 kilobars. SAE 1040 steel, however, does not exhibit a single characteristic elastic‐wave pressure. The pressure initially is about 6 kilobars, and increases to about 12 kilobars before the arrival of the plastic wave.

ISSN:0021-8979    

DOI:10.1063/1.1722019

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

The effect of crystal orientation on the electrical resistivity of high‐purity magnesium at 24°C may be represented by the equation:&rgr;(&phgr;)=4.60−0.75cos2&phgr;, (in microhms/cm3),where &thgr; is the angle between the hexagonal axis and the direction of current flow. The effect of temperature on the electrical resistivity for varying orientations shows temperature coefficients of 0.00390 and 0.00408/°C obtained perpendicular and parallel to the hexagonal axis, respectively, for the temperature range of 24° to 200°C. Magnesium shows rotational symmetry about the hexagonal axis with respect to electrical resistivity. Grain size has little or no effect on the electrical resistivity of magnesium.

ISSN:0021-8979    

DOI:10.1063/1.1722020

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

A theoretical analysis of the cubic to orthorhombic transformation is presented which predicts for a partly transformed crystal, the interface plane, orientation relationships, and macroscopic distortions from a knowledge only of the lattice parameters of the initial and final phases. Arguments are advanced to show that in order to minimize the strain energy associated with the transformation, the interface plane must be one of zero average distortion. This leads directly to considerations of an inhomogeneous product phase. Experimental studies on an AuCd alloy are described and the observed crystallographic features of the transformation compared with values calculated using the theory. The agreement between calculated and observed results for this alloy system as well as others is strong evidence for the theory of diffusionless phase transformations presented.

ISSN:0021-8979    

DOI:10.1063/1.1722021

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

It is shown that a system with discontinuously varying damping and spring coefficients transfers arbitrary inputs well, if the change of the coefficients from one constant value to another is controlled by the deviation between input and output.

ISSN:0021-8979    

DOI:10.1063/1.1722022

出版商:AIP    

年代:1955

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1722024

出版商:AIP    

年代:1955

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1722025

出版商:AIP    

年代:1955

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1722026

出版商:AIP    

年代:1955

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1722027

出版商:AIP    

年代:1955

数据来源: AIP