摘要:

This paper presents a closed expansion of the convolution integral, which is useful in approximating the response of a linear time invariant system to an arbitrary forcing function. In a sense it is a generalization of the well known error coefficient expansion frequently discussed in connection with servomechanisms. This expansion is helpful when the response of the system cannot be evaluated exactly (i.e., the input function is specified graphically or input function cannot be transformed conveniently). This expansion differs from the error coefficient expansion in that it is valid for an arbitrary forcing function and is in a closed form accounting for the entire response of the system, rather than in an open form of Taylor's series that either neglects or simply bounds a portion of the total response.

ISSN:0021-8979    

DOI:10.1063/1.1721863

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

Electrical polarization in thin, dielectric sheet material induced by handling or other means is not readily observed because the external field from a dipole charge layer is very weak compared with the field from net charges that are usually present. A method is described for measuring polarization in the presence of net charges by placing the dielectric sheet in contact with a grounded metal backing plate and by placing a field meter at a short distance in front of the dielectric. The grounded metal backing plate has the effect of almost completely annulling the external field of any net charge by induction, and of doubling the external field of a dipole charge layer of polarization.

ISSN:0021-8979    

DOI:10.1063/1.1721864

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

Extensive calculations have been performed with an electronic calculator to evaluate a problem in elasticity that simulates the effect of a cylindrical charge of high explosive detonated in intimate contact with a steel plate. The general method of calculation has been described in detail. Although elastic theory has been extrapolated into a regime where it is known not to apply, insight of a valuable general nature has been obtained on the nature of the negative component of the pulse.

ISSN:0021-8979    

DOI:10.1063/1.1721865

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

Under certain conditions the usual gas‐discharge circuit was found to give rise to relaxation oscillations. The relaxation oscillations produce a series of very narrow pulses with random pulse repetition interval, which appear as noise. The amount of noise was found to depend upon the gas, the cathode electrode material, the power supply voltage, and the external circuit configuration. It seems that this mechanism may be responsible for most of the high level noise usually reported from gas discharges. The pulsed nature of the apparently continuous discharge appears to be a fundamental property of the low‐current, cold‐cathode arc which has not been considered previously.

ISSN:0021-8979    

DOI:10.1063/1.1721866

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

The problem of armor penetration of thin plates is considered from a quasi‐dynamical approach. Equations are derived for the energy dissipation due to plastic deformation and for heating of the projectile target interface. Both the conical and the ogival head are considered in the application of the general equations.

ISSN:0021-8979    

DOI:10.1063/1.1721868

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

For the study of high‐temperature gas dynamics, shock‐tube techniques have been developed earlier to produce shock waves strong enough to heat gases to high and accurately known enthalpy (for argon up to 18 000°K or 40 percent ionization at equilibrium). This paper reports a study of the visible radiation from the highly luminous argon following strong shock waves.Preliminary spectrograms showed a strong continuum and that the prominent argon lines were broadened and shifted to the red. Correlation of the frequency shifts with theoretical treatments permitted an evaluation of the ion density in the gas. Development of a drum camera spectrograph (film speed 700 ft/sec) in which time effects could be resolved to about 1 &mgr;sec indicated that equilibrium ion density was reached rapidly, and provided a rough measurement of the rate of decline of ion density due to cooling.Absolute photoelectric spectrophotometric measurements of the continuum radiation were made and correlated with theoretical expectations. Confirmation of the expected variation of continuum intensity with wavelength and temperature was obtained and an undetermined factor on the theoretical intensity was evaluated. Determinations of the cooling rate of the high‐temperature argon from time variation of the continuum intensity, the line shift, and the electrical conductivity (by others) are in agreement and show that continuum radiation was the dominant heat loss.

ISSN:0021-8979    

DOI:10.1063/1.1721869

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

Shock tube techniques for the production of shock waves up to Mach number 20 have been developed and reported previously by Resler, Lin, and Kantrowitz, J. Appl. Phys.23, 1390 (1952). These techniques can produce high temperature gas with accurately known enthalpy (e.g., in argon 25 percent ionization has been produced following an incident shock). Spectroscopic studies of high temperature argon produced this way by Petscheck, Rose, Glick, Kane, and Kantrowitz, ``Spectroscopic studies of highly ionized argon produced by shock waves,'' J. Appl. Phys.26, 83 (1955), showed that equilibrium ionization can be reached in the time available in these experiments (of the order of 100 microseconds). This paper reports a study of the electrical conductivity of high temperature argon produced by shock waves.At low degrees of ionization (less than 10−3for argon), the diffusivity of electrons and thus the gas conductivity is determined by the cross section for electron‐atom collisions which has been measured by mobility and by scattering techniques. At high degrees of ionization (larger than 10−3for argon) the diffusion of electrons is primarily limited by long range Coulomb interaction with positive ions and thus is independent of the chemical nature of the gas. Theoretical treatments of this case have been given by Chapman and Cowling, Cowling, and by Spitzer and Ha¨rm. At intermediate degrees of ionization additive effects of both of these resistivity mechanisms would be expected.Preliminary measurements with electrodes indicated large surface resistances. These effects were avoided by the development of an electrodeless technique in which the moving ionized gas deflected a magnetic field. Resultant voltages induced in a search coil were related to the conductivity distribution in the gas following the shock wave. At temperatures greater than 8000–10 000°K (depending on the gas density) the gas conductivity quickly reached a maximum value (up to 80 mhos/cm). The maximum conductivity obtained at these high temperatures agreed within 10 percent with theoretical expectations. It also agreed well with measurement of electrical resistivity in the cesium discharge by F. L. Mohler, Bur. Standards J. Research21, 873 (1938). At lower temperatures the oscillograms indicated that the conductivity was still rising at the end of the hot region. Under these conditions maximum conductivities reached were much lower than the theoretical values. The ionization rate obtained varied considerably with the gas density.At the highest temperatures the conductivity declined quickly from the maximum value and the rate of decline could be correlated with the expected cooling due to recombination radiation. Indications of a high conductivity associated with luminous shock fronts were obtained.

ISSN:0021-8979    

DOI:10.1063/1.1721870

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

The ``superstate'' in a magnetic ion source has been investigated experimentally and theoretically. The space‐charge density is approximately constant throughout the source. The radial plasma density does not differ significantly from a Gaussian distribution. The radial distribution of space potential is approximately parabolic. The theoretical results have been tested by probe measurements, and good agreement has been found.

ISSN:0021-8979    

DOI:10.1063/1.1721844

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

Experimental results are presented of shock wave and contact front velocity measurements, in air, obtained in a 3 in.×3 in. wave interaction tube. A diaphragm pressure ratio range up to 10 000 was employed, while the distance was varied simultaneously from the origin to 142 in. beyond.It is shown that when shock‐wave attenuation occurs, it consists of two portions; (a) a decrement due to formation, and (b) a further attenuation due to the distance traversed by the shock wave.Concurrently with the attenuation phenomenon, the contact region spreads with time and its front boundary accelerates. The increase in velocity consists of two portions; (a) an increment due to formation, and (b) a further rise in velocity with the distance travelled by the contact front.A satisfactory empirical relation is developed for the total shock‐wave attenuation.A Rayleigh‐type incompressible ``pipe''‐flow analysis applied to the experimental results overestimates the attenuation for stronger shock waves.

ISSN:0021-8979    

DOI:10.1063/1.1721845

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

Alloyed germaniump‐njunctions of 0.1 to 0.2 mm diameter or less have been alloyed upon crystals of roughly ten times greater linear dimensions such that when these units are suitably electrolytically etched, ring formations (both scattered rings and tracks of overlapping rings) occur on the crystal faces in the neighborhoods of the junctions. Best current evidence indicates that the observed effects are etch produced. An explanation of this is given in terms of the action of bubbles accompanying the etching procedure.

ISSN:0021-8979    

DOI:10.1063/1.1721846

出版商:AIP    

年代:1955

数据来源: AIP