摘要:

There are two types of crystal edges in the electron micrographs of oxide replicas of metals. The first type is characterized by the edges being more transparent than the facets in reprinted crystals. In the second type of reprinted crystal there were found the opaque edges of crystal. These characteristics of crystal edges were explained by the orientation of crystallites composing the replica films. It is proposed in the present study that the width of transparent edge of reprinted crystal might serve as a rough measure of microscopic magnification.

ISSN:0021-8979    

DOI:10.1063/1.1702353

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

The relation between the crystal size of barium‐strontium oxide and its thermionic emission was studied with the same vacuum tube. The crystal size was measured by an x‐ray diffraction method. The measurements were made in vacuum by using thin mica windows as the entrance and exit ports for the x‐ray beam. The emission was measured with pulse in order to avoid gas from the anode. Below 1050°C the crystal grows slowly, but above it crystal growth is rapid. It seemed that impurity activation is dominant at low temperatures, but heat activation is dominant at high temperatures.

ISSN:0021-8979    

DOI:10.1063/1.1702354

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

A new theory of turbulent diffusion is developed so as to describe the dynamics of particulate matter in fluid suspensions. In order that the statistical description be consistent with force equation dynamics of sedimentation, a new diffusion equation is derived from the postulates of a past‐future stochastic process.A steady‐state suspension of particles in a turbulent stream is treated like an atomosphere. Dimensional arguments are used to retain the most relevant physical entities in a linear theory. It is shown that the bed load and mid‐stream suspension of a muddy stream cannot be considered separately. Some experiments are discussed in this connection. A qualitative theory of sand rippling is explained in terms of the instability of a flat sandy bottom under certain turbulence conditions. A singular perturbation method is employed to obtain an asymptotic expansion of the solution of the equilibrium equation.Assumptions are discussed and criticized. The advantage of the theory is that all statistical coefficients are averages of familiar dynamical quantities.

ISSN:0021-8979    

DOI:10.1063/1.1702355

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

The radiation from an infinite dielectric slab fed by a line source has been calculated from a branch‐cut integral. The modal efficiency of the device as a wave guide is defined as the ratio of the power propagated in a mode to the sum of the modal and radiated powers. For a range of the parameters such that only one mode can be propagated, the modal efficiency has been plotted numerically. Except for extreme values of the parameters, the efficiency runs around 80 percent to 90 percent.The slab form is not one likely to be used in practice, but the efficiency of a cylinder would be expected to have about the same value.

ISSN:0021-8979    

DOI:10.1063/1.1702356

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

Silver from the vapor phase was diffused into thin gold wires and foils at 940°C. Measurements were made of the resulting dimensional changes which occurred normal and parallel to the direction of diffusion. The linear percentage expansion normal to the diffusion direction was always found to be only slightly less than the corresponding expansion parallel to the diffusion stream. The results are best explained by the creation of new lattice sites at dislocations and support both the vacancy and interstitial mechanisms of diffusion in substitutional solutions.

ISSN:0021-8979    

DOI:10.1063/1.1702357

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

A new device for metallic shadow‐casting by using the nozzle system is proposed, and an outline of the apparatus is given. The present device has a shutter, a nozzle, and a cover plate between specimen and filament in addition to the usual apparatus. The dimensions of the nozzle were chosen from the maximum of 3‐mm diam, 1.5‐mm diam, and 22 mm to the minimum 1.5‐mm diam, 0.7‐mm diam, and 38 mm as diameter at the entrance, diameter at the exit, and the length, respectively. It was found that this method was not only conspicuously effective in obtaining much more accurate shadows than that obtained by the usual method with the same shadowing material, but also brought into possible use metals, as shadowing materials, which could not be used for such a purpose by the usual method. Shadowing qualities of many kinds of evaporated metals are compared and a new rule for the order of aggregation of deposited metallic thin films is also proposed.

ISSN:0021-8979    

DOI:10.1063/1.1702358

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

The theory of Carlson and Heins and the extended theory of Lengyel has been verified experimentally for oblique angles of incidence. Both single surface and slab measurements were performed in the 3‐cm band. Single surface measurements were made by using tapered wooden wedges as absorbing materials to eliminate back surface reflections. The effect of plate thickness was studied for five different thicknesses. The phase and amplitude of the reflection coefficient of a metal‐plate slab were obtained for three angles of incidence, 10°, 25°, and 35°, and for values of 2a/&lgr; ranging from 1.10 to 1.30.

ISSN:0021-8979    

DOI:10.1063/1.1702359

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

Fundamentally, the method is closely related to one described by W. Weber in 1852 in hisElketrodynamische Maasbestimmungenand applied by him to the measurement of very small susceptibilities in cases in which it was desirable to exclude eddy currents from the specimens under examination. It is capable of being modified so as to measure magnetic moments and magnetic susceptibilities, large and small, under a great variety of conditions. The method has the advantage, for low permeabilities, over that of permeameters, that it measures precisely the (small)differencebetween the permeability of the specimen and that of air, and not theratioof the two. It determines the magnetic moment of the specimen and the susceptibilityk, from which the permeability &mgr; may be derived from the relation &mgr;=1+4&pgr;k.

ISSN:0021-8979    

DOI:10.1063/1.1702360

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

The equation log&eegr;=A+B/(T+C) is obtained as a simple modification of Andrade's viscosity equation by treating the activation energy as a function of temperature,A, B, andCbeing free parameters. This is shown statistically to express adequately the temperature dependence of viscosity over substantial ranges of temperature for all the liquids examined,viz., n‐heptane; n‐nonane; n‐undecane; n‐tridecane; n‐heptadecane; benzene; viscous mineral oil; ethanol; 1,2‐dibromopropane; water; mercury; molten gallium; potassium; sodium; sodium nitrate; silver bromide; lead chloride; bromine; 98–100 percent sulfuric acid.

ISSN:0021-8979    

DOI:10.1063/1.1702361

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

A method has been developed for determining the low temperature heat capacity of a cylindrical sample from heating and cooling curves. The effect of temperature gradient in the sample is included.

ISSN:0021-8979    

DOI:10.1063/1.1702362

出版商:AIP    

年代:1952

数据来源: AIP