摘要:

A definition sufficient to define a function of frequency &rgr;(t,f) which could be regarded as the instantaneous power spectrum was given by Page. This function is not unique, since it may have added to it a complementary function of frequency &rgr;c(t,f) satisfying−∞∞&rgr;c(T,f)df=0without changing the original signal in any way.It is shown that when a signal is observed by different observers, starting their observations at different times, they will not derive the same ``instantaneous power spectral function,'' and the differences between their results will be complementary functions as defined above.It is well known that the Fourier transform of the autocorrelation function is equal to the square of the magnitude of the spectral function. Analogously, a ``running autocorrelation function'' is defined and it is shown that the Fourier transform of its partial differential coefficient with respect to time is an instantaneous power spectral function.

ISSN:0021-8979    

DOI:10.1063/1.1721565

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

Formulas for the backscattering and total scattering cross sections for dielectric coating spheres of arbitrary size were developed following the methods of Hansen and of Aden and Kerker. Calculations based on the resultant formulas were made in the region of the first resonance (outside dimension of the concentric spheres is approximately 0.4 wavelength). It was found that certain choices of coating thickness and dielectric constant can lead to increases in the scattering cross sections of more than 100 percent relative to a solid metal sphere of the same outside diameter. A number of calculated and measured curves are presented, and they show the variation of the backscattering and total scattering cross sections as functions of coating thickness, coating permittivity, and outside diameter of the coating. Where both calculations and measurements were made for the same conditions, the values agree to ±2 percent.

ISSN:0021-8979    

DOI:10.1063/1.1721566

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

In order to compute the spectral response of a quadratic device to noise, a fourth‐order momentPof the input noise is sufficient,Pbeing a function of three independent time delays. The functionP1by which this fourth moment for a non‐Gaussian noise differs from the corresponding moment for a Gaussian noise having the same spectrum is examined. The Fourier transform of this function isQ1, a function of three frequencies.Q1is capable of an interpretation in terms of nonlinear correlations between noise components at different frequencies. A specialization ofQ1leads toE, a function of two frequencies which is a measure of the correlation between the squares of the envelopes associated with those frequencies.Several networks involving quadratic nonlinear elements are examined to illustrate the theory. It is shown that while the functionPmakes it possible to compute the complete spectral response of the network, the functionE(together with the spectrum of the input) is sufficient in order to find the spectral density at zero frequency. Finally, for three examples of non‐Gaussian processes, the correspondingP1,Q1andEfunctions are computed.

ISSN:0021-8979    

DOI:10.1063/1.1721567

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

Measurements of the electron emission from Mg, Al, Fe, Ni, Au, and Pb surfaces bombarded by atomic (H1+) and molecular (H2+) hydrogen ions with energies from 0.7 to 2.0 Mev showed a diminishing emission with ion energy and little dependence on either atomic number or on the field intensity at the metal surface. Measurements of this type are of interest in connection with the mechanism of high voltage discharges in vacuum. The expected variation of secondary emission with angle of incidence and with conditioning was found. The emission ratios are compared with measurements by others at lower ion energies.

ISSN:0021-8979    

DOI:10.1063/1.1721568

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

Schnadt‐type impact specimens of SAE 1019 steel were irradiated with 18.6‐Mev deuterons for the purpose of studying the influence of radiation on the brittle property as measured by the change in transition temperature. The effect was compared with that of two, five, and ten percent strain hardening. Microhardness studies were made to determine the extent and location of the radiation effect. An integrated flux of 29.6 microampere‐hr per cm2shifted the transition temperature from −1°C to 18°C. The embrittling action was not a linear function of dose. Hardness was increased from 180 to 380 Knoop numbers. It was found to depend on the depth of penetration as well as the integrated flux. While radiation caused an effect similar to strain hardening, the nature of this effect was different. Annealing studies showed recovery of the irradiated material occurred between 260°C and 480°C. An interstitial vacancy diffusion process was indicated. Activation energies increased as recovery progressed. Recovery of the five percent strain hardened material occurred between 315°C and 371°C and would appear to be relaxation of internal stresses by the movement of dislocations.

ISSN:0021-8979    

DOI:10.1063/1.1721569

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

The density‐function method is applied to the one‐dimensional model of the traveling‐wave tube to determine the effect of velocity distribution on traveling‐wave tube performance. For narrow velocity spreads, a term is introduced into the root equation for the incremental propagation constants which is like the space charge term 4QCand directly added thereto. This term is proportional to the ratio of the variance of the distribution to the square of the gain parameterC. For a typical tube, thermal velocities are found to reduce the gain by less than one part in 104. In a tube employing confined magnetic focusing, and employing a high perveance beam, the velocity spread resulting from space charge lowers the gain by about 1 percent.

ISSN:0021-8979    

DOI:10.1063/1.1721570

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

Formal relationships defining the regions of the diffusion zone where porosity tends to form during the Kirkendall effect are developed. The surfaces at which the intrinsic diffusional flux of each component reaches a maximum are also considered. The results are applicable to diffusion systems subject to the usual boundary conditions where the solutionN1=N(x/√t) holds. The results are discussed in relation to presently available experimental findings.

ISSN:0021-8979    

DOI:10.1063/1.1721571

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

A report is made of a calibration of a nickel (A)versusmolybdenum thermocouple up to 2242°F (50 mv).

ISSN:0021-8979    

DOI:10.1063/1.1721572

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

A thermodynamic derivation is given for the representation of a system having viscoelastic or relaxation properties by means of a potential and dissipation function familiar in Lagrangian mechanics. This leads to modes of relaxation which are used as normal coordinates to derive general expressions for operational tensors relating stress and strain. A large variety of phenomena involving interaction of diffusion, chemical reaction, heat transfer, mechanical deformation, etc., is included in this theory.

ISSN:0021-8979    

DOI:10.1063/1.1721573

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

Electrical noise pulses have been observed at elevated temperatures in polarized dielectrics (electrets) made of carnauba wax and of a vinyl acetate polymer. Pulse rateversustime was observed for electrets heated at a uniform rate and the results differ from those previously reported by others. Experiments devised to determine the origin of the pulses indicate that they are associated with the decay of volume polarization rather than with real surface charge. The total charge associated with the pulses from carnauba wax electrets is at least 5 percent of the maximum electret charge.

ISSN:0021-8979    

DOI:10.1063/1.1721574

出版商:AIP    

年代:1954

数据来源: AIP