ISSN:0021-8979    

DOI:10.1063/1.1699720

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

Theory and design equations are presented for the conversion of a microwave, narrow‐band f‐m signal into very nearly a pure a‐m signal within an ordinary wave guide of specified dimensions. Frequency relationships and guide dimensions are arranged so that the f‐m side bands are shifted with respect to the carrier until they become a‐m side bands at the guide output. A complex intelligence signal may be transmitted with negligible distortion if it is used to amplitude modulate an intermediate carrier which frequency modulates the microwave carrier.

ISSN:0021-8979    

DOI:10.1063/1.1699721

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

A new method dispensing with the use of radioactive tracers has been developed for measurement of volume self‐diffusion. The method is based upon the relationship of the rate of sintering of metallic wires to the coefficients of self‐diffusion. The values of the self‐diffusion coefficients for silver as measured by this method are in good agreement with those obtained by the radioactive tracers method.

ISSN:0021-8979    

DOI:10.1063/1.1699722

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

Analytical computation of the detailed lobe structure of an elevated meter or centimeter band antenna for a standard atmosphere is quite tedious. In case there are discontinuities in the gradient of refractive index the analysis becomes hopelessly involved.This paper presents a straightforward method of graphical analysis for the optical region, equally applicable to a standard or stratified atmosphere.

ISSN:0021-8979    

DOI:10.1063/1.1699723

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

Starting with the differential equation relating the output and the input of a linear varying‐parameter network, it is shown that the impulsive response of the system is related to a Green's function associated with the system through a linear operator which is the adjoint of the right‐hand operator in the given differential equation. A perturbation procedure for the determination of the impulsive response of a slowly varying network is outlined. Use of the method is illustrated by a simple example involving a band width‐modulatedRChalf‐section.

ISSN:0021-8979    

DOI:10.1063/1.1699724

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

The theory of prediction described in this paper is essentially an extension of Wiener's theory. It differs from the latter in the following respects.1. The signal (message) component of the given time series is assumed to consist of two parts, (a) a non‐random function of time which is representable as a polynomial of degree not greater than a specified numbernand about which no information other thannis available; and (b) a stationary random function of time which is described statistically by a given correlation function. (In Wiener's theory, the signal may not contain a non‐random part except when such a part is a known function of time.)2. The impulsive response of the predictor or, in other words, the weighting function used in the process of prediction is required to vanish outside of a specified time interval 0≤t≤T. (In Wiener's theoryTis assumed to be infinite.)The theory developed in this paper is applicable to a broader and more practical class of problems than that covered in Wiener's theory. As in Wiener's theory, the determination of the optimum predictor reduces to the solution of an integral equation which, however, is a modified form of the Wiener‐Hopf equation. A simple method of solution of the equation is developed. This method can also be applied with advantage to the solution of the particular case considered by Wiener. The use of the theory is illustrated by several examples of practical interest.

ISSN:0021-8979    

DOI:10.1063/1.1699725

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

A theoretical analysis of the effect of the spaces between drain tube units as used in the artificial drainage of soil is given. The problem is one of potential flow; therefore, the results are applicable to heat flow, etc. The basic problem solved is that for axially symmetric flow from an external cylindrical boundary at constant potential to a series of equal, equally spaced openings at a lower potential, all located axially on, and comprising a part of, the otherwise impervious drain tube. The radii of the open sections and impermeable sections of the drain tube are equal. The basic problem is extended to obtain the solution to the practical problem—the seepage of ground water into drain tubes beneath a horizontal water table. The exact solution of the basic problem is not suitable for numerical work. Accordingly, approximate solutions of specified uncertainty are derived and are utilized for tabulation of numerical results. As an example, the analysis shows, in the case of 6 in. diameter drain tubes having 1 ft. long impermeable sections and buried 4 ft. deep in uniformly permeable soil, that increasing the openings from132in. width to ¼ in. width will increase the flow 36 percent; while embedding the tubes in gravel, to make the132in. openings of effectively infinite width, will increase the flow 180 percent.

ISSN:0021-8979    

DOI:10.1063/1.1699726

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

This paper presents the results of measurements of the signal strength and phase of 3.2‐centimeter radio waves for a 26.5‐mile path over the Gulf of Mexico under a variety of meteorological conditions. The radio data are used to determine the modified index‐of‐refraction as a function of height and the associated attenuation factor. The modified index‐of‐refraction curves are compared to those measured meteorologically.

ISSN:0021-8979    

DOI:10.1063/1.1699727

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

A three‐dimensional array of thin conducting disks has found special application as an artificial refracting medium at microwave frequencies. Treatment of these refractive properties at oblique incidence requires specification of the dielectric and permeability coefficients of the medium.When an alternating magnetic field is parallel to the disk faces, the field is undisturbed and the relative permeability coefficient is unity. When the alternating magnetic field is normal to the disk faces, circulating currents are induced on them. The boundary value problem of determining the current distribution on a single perfectly conducting disk is carried out in detail for the case where the disk diameter is small compared to the wave‐length. This current distribution is found to be representable by a magnetic dipole. If the disks in an array are far enough apart to neglect interaction, a simple summation of the dipole moments shows the array to have a diamagnetic susceptibility in the direction normal to the disk faces.Combining this result with an expression for the dielectric coefficient, which was developed earlier by Kock, the constants of the anisotropic array are completely specified.

ISSN:0021-8979    

DOI:10.1063/1.1699728

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

Mathematical methods of stress analysis are presented for linear, compressible, viscoelastic, or anelastic, materials such as metals at high temperatures or high polymers with small strains. For such materials stress, strain and their time derivatives of all orders are related by linear equations with coefficients which are material constants. Fourier integral methods are used to show that static elasticity solutions can be used to determine the time dependent stresses in viscoelastic bodies with any form of boundary conditions.If stress and double refraction and their time derivatives are also linearly related, the standard photoelastic techniques can be used to determine the directions and difference in magnitude of the time dependent principal stresses, even though the principal stress axes do not coincide with the polarizing axes and both vary with time. When viscoelastic models are used in photoelastic studies, the time variation of the stress distribution in the model represents a first approximation to the dependence of the stress in the elastic prototype on Poisson's ratio.

ISSN:0021-8979    

DOI:10.1063/1.1699729

出版商:AIP    

年代:1950

数据来源: AIP