摘要:

This is a quantitative experimental study of the primary ionization of paraffin wax by beta‐radiation. Electrons emitted by uranium and carbon 14 were used. Interpretation, by means of a simple theory, of experimental data on the electrical conductivity permits evaluation of the ionic mobility in paraffin and the efficiency of ion‐pair production. Only small primary ions of relatively long mean life are detected by the conductivity method. Dipolar admixtures promote secondary reactions and lower the level of conductivities attained. No ionization was detected in two hydrocarbon polymers.

ISSN:0021-8979    

DOI:10.1063/1.1698249

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

The open two‐wire line is investigated as a measuring instrument and difficulties in its operation are overcome. These include, in particular, the problem of balance. The impedance of antennas is shown to depend on the nature of the driving structures. A comparison of measured impedances and corresponding theoretical values shows good agreement.

ISSN:0021-8979    

DOI:10.1063/1.1698250

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

The relation between elastic and plastic strains and the martensite transformation from face‐centered to body‐centered structure has been investigated in Fe‐Ni 71–29 alloy. Transformation begins at about −30°C and is of the martensite type except that it is not all completed instantaneously but continues at decreasing rate at constant temperature.It was found that (1) There is no anomalous decrease in elastic moduli as theMstemperature is approached, nor isMsaffected by applied elastic stresses. (2) Plastic deformation in a temperature range aboveMscauses partial transformation in amounts decreasing to zero at temperatureMd≈Ms+75°C, but stabilizes against further transformation by cooling. (3) Plastic yield stress increases sharply fromMdtoMsthen drops suddenly to a low value just belowMs. (4) TheMstemperature depends on grain size; a factor of ten increase in grain size reducesMsabout 30°C.These results are contrary to expectations on the basis of the usual homogeneous shear model for the transformation mechanism. They indicate that the martensite phase becomes thermodynamically stable atMdbut that transformation does not begin untilMsbecause of surface and strain energy considerations in growth of a martensite plate from a small nucleus.

ISSN:0021-8979    

DOI:10.1063/1.1698251

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

A high temperature precision x‐ray camera has been designed and constructed by modification of the familiar back‐reflection symmetrical focusing type of camera. The camera, specimen, and furnace are used within a vacuum chamber to avoid oxidation. The apparatus in its present form has been employed at temperatures up to 1000°C, but higher temperatures could be easily attained by making a few minor changes in the furnace materials.The lattice parameters of beryllium have been measured up to 1000°C. The derived coefficients of thermal expansion, both linear and bulk, are presented as a function of temperature. In addition, the data present strong evidence that the hexagonal close packed form of beryllium which exists at room temperature is stable up to at least 1000°C, contrary to several reports in the literature.

ISSN:0021-8979    

DOI:10.1063/1.1698252

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

At very high frequencies, the effect of losses in coupling devices makes itself felt in the determinations of the variousQ's and of the circuit efficiency of resonant systems. It is shown that the neglect of these losses (which appear in equivalent circuits in the form of series resistance), can lead to appreciable error. Formulas are derived and curves are plotted which permit an unambiguous determination of theQ's and of the circuit efficiency when the following items are known:1. the standing wave ratio at resonance,2. the standing wave ratio far from resonance, and3. knowledge as to whether the resonant system under study is ``under'' or ``overmatched'' to the external load.

ISSN:0021-8979    

DOI:10.1063/1.1698253

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

There are a number of important potential problems having axial symmetry and involving a conical boundary whose solutions require the use of zero‐order Legendre functions of real but non‐integral degree. The numerical evaluation of such problems is relatively simple once the zeros of these functions have been determined and when certain integrals have been evaluated. This paper presents tables and curves giving this information, together with a number of approximate expressions for these quantities. A number of potential distributions involving conducting cones, spheres, and rings are worked out to illustrate the application of these functions.

ISSN:0021-8979    

DOI:10.1063/1.1698254

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

An apparatus is described which produces homogeneous mists or clouds of solid particles of any desired size. As in Walton's original model liquid is sprayed by a Beams high speed air‐driven top, but an improved performance has been achieved by utilizing a property of high speed air films so that automatic extraction of unwanted satellite droplets, better running characteristics over a wider range, simplified construction, and low air consumption are obtained.

ISSN:0021-8979    

DOI:10.1063/1.1698255

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

The current and temperature distributions in a conductor are affected not only by the magnetic effect of the current, i.e., skin effect, but also by the variation of resistivity with temperature. Consequently the two are interdependent, and since the resistance change amounts to between three and four percent for every 10°C rise in temperature in metals, and is still greater in insulators, its effect can be quite appreciable. A complete solution for the steady state is given herewith.

ISSN:0021-8979    

DOI:10.1063/1.1698256

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

The formation of precipitates from the solid solutions of C and N in &agr;‐iron has been studied by means of the internal friction peak associated with the stress‐induced interstitial diffusion of the solute atoms. A transformation law has been found to fit the experimental data. The data are interpreted as showing the following: (1) Fe3C precipitates in the shape of spheres; (2) an intermediate phase in the precipitation of nitrogen forms in the shape of disks; and (3) within the experimental error there is indicated no continuous nucleation. Using the results of a derivation made by Zener, the mean distance between nuclei is calculated for Fe3C. For carbon concentrations of about 0.016 wt. percent, this distance is about 800, 2000, and 7000 Angstroms at 27°C, 102°C, and 312°C, respectively. With appropriate experimental conditions, the temperature dependence of the precipitation rate is found to be about the same as the temperature dependence of the diffusion rate of the solute atoms.

ISSN:0021-8979    

DOI:10.1063/1.1698257

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

The radius of a spherical precipitate particle growing in a solid solution of initially uniform composition may be shown to be equal to &agr;(Dt)½, whereDis the atomic diffusion coefficient,tthe time of growth, and &agr;, the growth coefficient, is a dimensionless function of the pertinent compositions. In this paper the precise dependence is found of this function upon the pertinent concentrations. A similar computation is made for the growth coefficient corresponding to the one‐dimensional growth of a plate.

ISSN:0021-8979    

DOI:10.1063/1.1698258

出版商:AIP    

年代:1949

数据来源: AIP