摘要:

A process is described whereby the complex wave equation is transformed into an integro‐differential equation in a single real dependent variable. This makes possible a technique for obtaining wave functions, which is believed to offer definite advantages in some instances where the more standard methods are difficult to handle, e.g., in regions where the complex index is varying rapidly. The index may be entered in a tabulated form, and its exact analytical expression is not required.The technique is then demonstrated by computing the reflection coefficient associated with an extremely critical region, that which one encounters at the ``fourth reflection condition,'' where the refractive index goes through a sharp peak (see reference 3).

ISSN:0021-8979    

DOI:10.1063/1.1701997

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

The output of a low pass filter preceded by a nonlinear device excited by a noise source is given in terms of an integral equation. The first three central moments of the probability density of the output signal are obtained from the integral equation and the approach of these moments to those of a Gaussian or normal density is demonstrated.

ISSN:0021-8979    

DOI:10.1063/1.1701998

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

Barium sulfide has been prepared in a form suitable as a cathode emitter as well as in the form of compressed pills. It has a work function of 2.1 ev with a wide variation possible in activation. The most active materials had an emission at temperatures of 900°K and greater comparable to that from pure BaO. Pure nickel and platinum only were used as base metals. An equimolar mixture of BaS‐SrS had a work function of 2.6 ev, and x‐ray analysis indicated solid solution formation. The electrical conductivity of BaS was found to vary between wide limits depending on the degree of activation and the denseness of the specimen but was much less than for BaO. At 1000°K the specific conductivity of a compressed pill was 10−5ohm−1cm−1. The thermoelectric power was found to be constant with temperature although it decreased with increase in the activity of the specimen. The warmer electrode was always positive. Pure BaS had a thermoelectric power of 2.5 mv per degree between 970° and 1270°K. The effect of added impurities of iron on the electrical characteristics was studied. By mass‐spectrometer studies, the evaporation rate of BaS was found to be much less than that of BaO, indicating a vapor pressure of the sulfide about 100 times less than that of the oxide. The heat of sublimation was found to be 104 kcal/mole.

ISSN:0021-8979    

DOI:10.1063/1.1701999

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

First‐order perturbation theory is used to evaluate the scattered power at a receiver resulting from random inhomogeneities in the propagating medium. The integral expression for this scattered power is equivalent to the expressions as used by Pekeris and Booker and Gordon. However, it is shown that it is not appropriate to use a space correlation function of refractive index as defined by the above authors. Instead, this paper defines a time correlation function of refractive index which permits formal evaluation of the time average scattered power. It is also shown that, whereas a space correlation function of refractive index is not amenable to direct experimental evaluation, the time correlation function as defined in this paper is directly measurable. Finally, it is shown that for so‐called small‐scale turbulence the average scattered power does not depend appreciably on any particular model of atmospheric turbulence, whereas for large‐scale turbulence the frequency and scattering angle dependence of the scattered energy is affected greatly by the particular time correlation function chosen or by the assumption that scattering is the result of randomly located spheres.

ISSN:0021-8979    

DOI:10.1063/1.1702000

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

Gaseous phenomena induced by short‐duration sparks at atmospheric pressure have been photographed during the first microseconds of their existence by a flash‐schlieren technique. The growth of the heated gas domain (kernel) expanding from the spark discharge has been observed for air and argon. The kernel continues to expand rapidly, but subsonically, after the spark current ceases and after the shock wave separates. It develops further into a torus about the spark electrodes and eventually decays. The development of flame from a heated gas kernel in a flammable mixture is illustrated. Energy relationships for the expanding argon kernel are discussed.

ISSN:0021-8979    

DOI:10.1063/1.1702001

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

General formulas are derived for the shift in x‐ray diffraction maxima due to small distortions in simple cubic crystals. The special case of radial distortions due to lattice defects is considered in detail; it is found that the relative change in lattice constant computed from the shift in diffraction maxima is of the order of magnitude of the defect concentration and larger by as much as 100 percent than the linear expansion when the concentration of defects is of the order of one percent or less. A comparison is made of lattice constant, linear expansion, and density expected in crystals containing Frenkel defects, Schottky defects, orFcenters.

ISSN:0021-8979    

DOI:10.1063/1.1702002

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

Unsupported films of nitrocellulose of 0.25 micron and less in thickness bonded immediately and spontaneously in air to solid surfaces which they were made to touch. Bond strength increased with diminishing film thickness. Similar behavior was shown by films of gold, regenerated cellulose, polymethyl methacrylate, and gelatin. This bonding power of nitrocellulose films, which was apparently not attributable to static electricity or to mechanical joint formation, was lost while immersed in water, benzene, or hexane, but was regained upon removal and drying.

ISSN:0021-8979    

DOI:10.1063/1.1702011

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

Complete and quantitatively accurate solutions of the properties of electrically short transmitting and receiving antennas (of length 2hsuch that 2&pgr;h/&lgr;0≦1) are obtained by determining the distributions of current that actually satisfy the integral equations. Components of current in phase and in phase‐quadrature with the driving voltage or the incident electric field are evaluated together with the impedance, the effective length, and the gain. It is shown that when the King‐Middleton method of solving Halle´n's integral equation by iteration is applied correctly, quite accurate results are obtained even in a first‐order solution. The greatest error in the first‐order formulas is shown to be in the resistance, a small quantity of higher order compared with the reactance. The newly determined values are combined with the King‐Middleton second‐order results to obtain more complete and more accurate impedances and effective lengths in the range of 0≦2&pgr;h/&lgr;≦1.4.

ISSN:0021-8979    

DOI:10.1063/1.1702023

出版商:AIP    

年代:1952

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1702026

出版商:AIP    

年代:1952

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1702027

出版商:AIP    

年代:1952

数据来源: AIP