摘要:

Measurements of dielectric constant and power loss were made from 1 to 90 kc/sec and from 20°C to 400°C. The dielectric constant parallel to the optic axis for all frequencies shows a sharp rise, which occurs at successively higher temperatures for higher frequencies. The loss at a given frequency has a temperature maximum which is higher, the higher the frequency. The results are partially explained by assuming that ions are present in ``tunnels'' parallel to the optic axis. The density and mobility of these ions are obtained. The density is temperature dependent in such a way as to lead to an activation energy of 17.7 kcal per mole. Lithium ions were introduced into the crystals, and the effects caused by these ions were at least compatible with the assumption that lithium ions were originally present. Perpendicular to the optic axis none of the above effects exist.

ISSN:0021-8979    

DOI:10.1063/1.1721922

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

Electron emission from a cathode surface produced by an applied fieldEis enhanced by the presence of projections on the emitter surface which cause a local increase inE. The nature of this enhancement factor &mgr;(z), which is a function of the distancezfrom the cathode, is discussed more fully than hitherto and its magnitude is calculated for certain ideal but realistic geometries. Although such a factor may be large on the surface (z=0), it decreases rapidly aszincreases so that the mean field magnification&mgr;¯(z), which is required in the Schottky thermionic emission theory, is unlikely to be >2 and is probably near to unity even for fields as great as 5×105v/cm. This fact will mean that the Fowler‐Nordheim theory frequently used to explain emission results at these fields is not applicable and that a Schottky theory should be used.It is also shown that&mgr;¯(z)is itself field dependent and produces departures from the Schottky law in such a way that the slope of the currentvs E½plot increases rapidly forE<103v/cm, remains approximately constant for 103<E<104v/cm, and then increases again at higher fields. A similar reasoning shows that deviations from the Fowler‐Nordheim law for fields >106v/cm can also be expected.Finally, the assumption of a constant emitting area for rough cathodes is also shown to give departures from the emission laws in such a manner that the estimated current density at high fields is appreciably less than the expected values.These deductions help to explain some of the anomalous results frequently found in many conduction experiments in gases and liquids.

ISSN:0021-8979    

DOI:10.1063/1.1721923

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

A new multistable element is described, and the conditions under which it may operate are discussed. It is found that a bistable element (flip‐flop) with reasonable resolving time may be achieved, though it might be necessary to operate it at low temperatures. A tristable element is found to be possible, but not practical. A slowly operating model is described.

ISSN:0021-8979    

DOI:10.1063/1.1721924

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

Electron microscopy of etched and nascent surfaces of single ice crystals shows a characteristic microstructure of elongated, hexagonal prisms. The small hexagonal units vary greatly in size with an expected width of the order of 3 microns and a length of 6 microns. The coordination among microcrystalline units characterizes a particular single crystal, the size of which may be determined by processes of freezing and subsequent history, but the sizes of the microcrystalline units of which they are composed appear to be independent of the rates of freezing. The etched surfaces show that the center of the hexagonal unit etches to a greater depth than does the outer area, indicating a higher degree of crystal disorder along the axis of symmetry.Ice surfaces in process of growing from the melt also appear to consist of hexagonal pyramidal pits which are built up by concentric steps around theC‐axis. This structure appears to be consistent with that of the etched surfaces. Observations of growing‐ice surfaces formed from cesium fluoride solutions reveal that the fluoride impurity tends to reduce the prominence of the pyramidal microstructure in a manner dependent upon concentrations such that the structure disappears for concentrations greater than 10−3M.

ISSN:0021-8979    

DOI:10.1063/1.1721925

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

The space‐charge distribution in a static magnetron was investigated by a method involving measurement of the radiation intensity from excited gas atoms at low pressure. Results of the measurements show that space charge extends to the anode under all conditions. Evidence is presented to show that a considerable fraction of the space charge consists of electrons that are trapped for exceedingly long times within the interaction space.

ISSN:0021-8979    

DOI:10.1063/1.1721926

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

Application of the engravement method to the study of particle velocity distribution in the wall of a thick‐walled metal cylinder internally loaded with an explosive charge is described. Tests were conducted with this method on modified cylinders of annealed low‐carbon steel and of brass. Even though each of the modified cylinders broke into a number of fragments, the engravements were well enough preserved to furnish considerable data. Many measurements were obtained from each cylinder by using a large number of pellets of several thicknesses. Particle velocity data were obtained to within716inch from the metalexplosive interface. Temporal particle velocity distribution curves are presented for each of the cylinders.

ISSN:0021-8979    

DOI:10.1063/1.1721927

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

Equations governing thickness‐shear and flexural vibrations of crystal plates are solved for the infinite plate, the simply‐supported rectangular plate and the rectangular plate with one pair of parallel edges free and the other pair simply‐supported. The equations permit three types of sinusoidal waves, with sinusoidal crests, in an infinite plate. Each of these undergoes a simple reflection upon normal incidence at a simply‐supported straight edge, so that the frequency spectrum of a simply‐supported rectangular plate has a relatively simple character. The results of a typical computation are given for the AT‐cut of quartz. At a free edge each type of incident wave gives rise, in general, to all three types of reflected wave. Consequently, the frequency spectrum of a plate with a pair of parallel, free edges exhibits an intricate coupling of three infinite systems of modes. The development of the coupling is traced continuously by means of a solution involving elastically supported edges.

ISSN:0021-8979    

DOI:10.1063/1.1721928

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

The problem of space‐charge waves propagating along a neutralized electron stream moving in a medium pervaded by crossed static electric and magnetic fields is discussed. From energy considerations it is shown that gain can be realized either by conversion of the electron kinetic or potential energy into electromagnetic energy. A small signal analysis shows that for the first case theTEandTMmodes are coupled in general. However, when the electron velocity is much smaller than the velocity of light the coupling coefficients are negligible and the gain realized is identical with that of the conventional traveling‐wave tube. A similar analysis for the second case, which is that of the traveling‐wave magnetron tube, yields the interesting result that theTEandTMmodes separate even when the electron velocity is comparable with the velocity of light.

ISSN:0021-8979    

DOI:10.1063/1.1721929

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

The theory of Debye and Bueche for the scattering of light by an amorphous solid is extended to the case where fluctuations in anisotropy as well as density are considered. A generalized correlation function is defined, which gives the probability of a simultaneous occurrence of fluctuations in polarizability in two volume elements a distancerapart. The fluctuations are specified by the magnitudes of the polarizabilities and the directions of the optic axes. The correlation function is assumed to depend onr, on the angle between the axes of the fluctuations, and on the angle giving the position of the second element with respect to the optic axis of the first. The intensities of the horizontal and vertical components of the scattered light are expressed as integrals over the correlation function of explicit functions ofrand the two angles. From the initial slopes and intercepts of the intensities plotted against sin2(&thgr;/2) where &thgr; is the scattering angle, one can obtain average values and average dimensions of the fluctuations, and a measure of the extent to which fluctuations in density and anisotropy are correlated. The theory is applicable to glasses, gels, and liquid crystals.

ISSN:0021-8979    

DOI:10.1063/1.1721930

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

A capillary viscometer is described for the study of the flow behavior of non‐Newtonian fluids at shear stresses of 0.06–20 dynes/cm2. The all‐glass instrument consists of two units connected by a ball joint, one unit of which contains the capillary while the second is essentially a manometer. As the test fluid moves through the capillary, the rate of rise of the fluid in the manometer is observed. This measurement of the column height as a function of time allows calculation of both pressure drop and rate of flow. Different combinations of capillary and manometer units can be employed interchangeably to study liquids of widely varying viscosities. Data and methods are presented which show that the instrument can be used to determine the absolute viscosities of Newtonian liquids and the flow curves of non‐Newtonian fluids over the indicated shear stress region.

ISSN:0021-8979    

DOI:10.1063/1.1721931

出版商:AIP    

年代:1955

数据来源: AIP