摘要:

The application of preferential etching techniques to the study of crystalline imperfection in photographic emulsion grains is described. Both chemical etching and halogen evolution by print‐out exposure in the absence of gelatin form well‐defined pits in most cases. The concentration of chemical etch pits is dependent on the solvent used but is not sensitive to concentration or etch time over the range investigated. A general increase in etching on certain faces is found after intentionally straining the grains, but the effect is not sufficiently strong to establish a one‐to‐one relationship between etch pits and dislocations. In both silver bromide and silver bromoiodide grains, no evidence is found for the existence of any type of polycrystalline substructure. Experiments on pitting by print‐out exposure indicate that iodide ions provide internal hole traps or recombination centers.

ISSN:0021-8979    

DOI:10.1063/1.1723287

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

Expressions are developed for the average power radiated by a high‐energy electron moving in a circular orbit. The instantaneous electron energyE(t) is assumed to vary with the time in accordance withE(t)Emsin2(&pgr;t/2T). Spectral distributions are obtained corresponding to the radiation emitted over a partial or full acceleration interval. The numerical results predicted from the general relations are examined for a particular value of the peak energyEm=6.0 Bev and the orbital radiusR=86.14 ft. In the case of these parameters, the continuous spectrum attains a peak at 0.36 A. Other numerical calculations, related to the case where the radiation is collected only over the low‐energy portion of the acceleration interval, indicate that it is feasible to utilize the continuum as a source for measurements in problems of interest to astrophysics and solid state spectroscopy.

ISSN:0021-8979    

DOI:10.1063/1.1723288

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

The mechanisms for bulk viscosity are different between associated and nonassociated liquids. Here, a new mechanism for bulk viscosity is proposed from the standpoint of the hole theory of liquids and the rate process theory. This mechanism can explain the temperature and pressure dependencies of acoustic absorption for associated liquids and very viscous nonassociated liquids.

ISSN:0021-8979    

DOI:10.1063/1.1723290

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

An x‐ray method has been worked out for the detection of screw dislocations in whiskers and has been proved satisfactory on &agr;‐Al2O3whiskers in which the screw dislocation is identified by an axial pore and the twist independently measured by optical methods.

ISSN:0021-8979    

DOI:10.1063/1.1723291

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

Glass breakage experiments were made which indicate two different mechanisms of fracture. The breaking process is dependent on the widths as well as the depth of the origin flaws. When the fracture is of the large, open type, the reciprocal of the breaking stress is a linear function of the depth of flaw; when the flaw is minute, the reciprocal of the breaking stress is a linear function of the square root of fracture depth.A pronounced strength increase was observed in cuts formed under various liquids and aged for various lengths of time. This increase took place about one hour after cutting and was interpreted as a rehealing phenomenon. Cuts made in air did not show the rapid strength increase.Cycle fatigue tests were also made on laths of glass and it was observed that there was an initial decrease in strength followed by an increase. This was interpreted as rehealing effect in the minute type of flaw.

ISSN:0021-8979    

DOI:10.1063/1.1723292

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

Application is made of the semi‐asymptotic method of Spencer to the penetration and slowing down of neutrons in infinite media. This method can handle complete numerical input data, and is not restricted in distance. Calculations are carried out for the ideal constant cross section case, and a 1‐kev point source in air. Complete flux spectra for the 1‐kev point source are given for distances out to 100 mean free paths (mfp).

ISSN:0021-8979    

DOI:10.1063/1.1723293

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

A simple procedure for determining the ``instantaneous'' absolute evaporation rate of barium from dispenser cathodes is presented. The method entails exposing a clean tungsten wire to a stream of barium and noting the time required to reach maximum emission. The sensitivity of the wire as a detector of total barium is established on an absolute basis by chemical calibration. It has been found that the wire sensitivity is a function of the barium oxide content of the evaporant stream. This fact may be employed to determine the oxide composition of the evaporant from wire emission‐time measurements and a single chemical analysis. It is also possible to obtain approximate, instantaneous values of total barium and the fraction BaO at any time during tube life from wire emission‐time measurements only. Calibration data are presented for almost the full range of Ba&sngbnd;BaO compositions.

ISSN:0021-8979    

DOI:10.1063/1.1723294

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

Positive‐ion effects have been observed in pulsed electron beams of short duration (0.5 to 5 microseconds), under conditions of operation normally encountered in high‐power microwave tubes. Three different aspects of ion effects were studied; (1) beam focusing, (2) ion oscillations, and (3) ion trapping at scallop minima. Experimental results are given and correlated with previous work on ion effects by other authors.

ISSN:0021-8979    

DOI:10.1063/1.1723295

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

Diffusion rates of tungsten in single crystal and polycrystalline nickel were measured at temperatures between 1100°C and 1275°C by using radioactive tungsten185and a sectioning technique. Grain boundary diffusion was observed by use of radioautographs. A simple vacancy mechanism accounts for nearly all of the diffusion; some refinement is required for the transport observed at greater depths.The rate of reaction of polycrystalline 4.9% tungsten‐nickel alloy with SrO was measured by the hydrogen evolution technique at temperatures between 830°C and 1280°C. The rate indicates that the production of Sr in amounts up to 200 &mgr;g cm−2is not limited by diffusion of tungsten in the nickel core.

ISSN:0021-8979    

DOI:10.1063/1.1723296

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

A magnetic memory can be interrogated nondestructively by applying a perturbing field normal to the direction of remanent magnetization, and, at the same time, observing the sign of the reversible flux change. However, there may be a considerable irreversible flux change during the first few interrogations following magnetization. This irreversible component can be reduced by introducing magnetic anisotropy in a direction parallel to the direction of magnetization which is used to store binary information. The characteristics of the ideal memory is analyzed by means of domain theory. In an experimental memory a steel wire under tension was used for the memory material. A small solenoid was used to magnetize the wire locally and also to observe the flux change which was produced by an interrogative current pulsed through the wire itself. The general predictions of the theory were confirmed by experiment. Interrogation is non‐destructive and is completed in less than 1 &mgr;sec. The output is proportional to the square of the wire current, and discrimination is a matter of observing its polarity. A single bit can be written into a memory array by a coincidence of a wire current and a solenoid current. The wire current can be the same as that used for interrogation. A number of bits can be carried on one wire and interrogated simultaneously. The factors affecting the design of a memory array are discussed.

ISSN:0021-8979    

DOI:10.1063/1.1723297

出版商:AIP    

年代:1958

数据来源: AIP