摘要:

The theoretical distribution of velocity across a liquid (Newtonian) between two coaxial cylinders and the velocity gradient at the inner cylinder is calculated in a new way. The equation used for calculating the coefficient of viscosity of the liquid is also given. The theory agrees with experiment for all values of &thgr;0/&fgr;0≤1/2 (where &thgr;0is the amplitude of deflection of the inner cylinder and &fgr;0is the amplitude of the oscillations inexorably imposed on the outer cylinder).

ISSN:0021-8979    

DOI:10.1063/1.1702296

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

Measurements were made of the heat released during decay of the afterglow, the viscosity, and the free electron density in active nitrogen. Calorimeter measurements of the heat released during decay of the afterglow amounted to as much as 22.3 calories per gram of the gas, corresponding to an excitation of one part in 350 of the molecules present to an energy of 9.6 electron volts. The viscosity of the active nitrogen was found to be the same as that of the unactivated nitrogen within one‐half of one percent. Ionization in a stream of active nitrogen is shown to be incidental rather than essential to the production of the Lewis‐Rayleigh afterglow. Microwave measurements of the free electron density in a stream of active nitrogen indicated one free electron for each 2.3×108molecules in the stream. Contrary to Mitra's theory, probes in the stream were found to respond to carriers of negative sign rather than positive ions. Space discharges in an expanding stream of active nitrogen are attributed to free electrons moving with the stream. In the use of active nitrogen for studies of low density flow, by observation of the afterglow, disturbing effects will occur because of heating and ionization, but the disturbances appear not to be so large as to interfere with its use.

ISSN:0021-8979    

DOI:10.1063/1.1702297

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

The simplified theory of the Mach‐Zehnder interferometer developed by the latter author is tested. The reduction in the visibility of fringes formed by the interferometer due to an extended area light source is shown experimentally. This reduction is shown to be caused by the superposition of two separate effects which are characteristic of the two angular coordinates of the unit vector pointing from the center of the collimating lens toward each point in the plane of the area‐type source. The relation of each of the effects to that coordinate characterizing it is demonstrated experimentally to agree with the theory. The result of combining these two effects from all of the points of an area‐type source is experimentally seen to cause the ``focusing'' of the visible fringes and to limit them to a finite region of the intersecting beams determined by the size and shape of the source.

ISSN:0021-8979    

DOI:10.1063/1.1702298

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

A knowledge of the permittivity and loss tangent of snow and ice is essential in studying both radar echoes from snow‐covered terrain and the attenuation of microwave energy through snowstorms. To provide this information, a program was carried out at the National Research Council of Canada to measure the permittivity and loss tangent of ice and snow, and also to determine the reflection coefficients of snow‐covered surfaces, at a wavelength of 3.2 centimeters.As a result of these investigations values have been obtained for the permittivity and loss tangent of snow of varying density, temperature, and water content. Theoretical values of the reflection coefficients of snow‐covered surfaces, calculated from these data, are compared with the values obtained from the direct measurement of reflections from natural snow surfaces.

ISSN:0021-8979    

DOI:10.1063/1.1702299

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

The relativistic differential equations for the axial motion of an electron in a wave guide, excited by a progressive, sinusoidal, longitudinal, electric wave of constant speed less than that of light in vacuum, have been integrated. The first integral yields the results of J. C. Slater and gives the energy‐phase relationship, which is periodic. A second integration yields the phase distance relationship and thus completes the determination of the orbits. All separatrices are exactly integrable in terms of trigonometric and hyperbolic functions, while the general case requires elliptic integrals of the first and third kinds. The former are obtainable from tables, while the latter are evaluated by series expansions, or in the case of particles near the self‐crossing point of the separatrices where the convergence of the series expansion is slow, by the use of the addition theorem for elliptic integrals of the third kind.These results are applied to the case of the proposed new Purdue Linear Accelerator. Energy distribution of the particles coming out of the end of the first two sections of this accelerator is in this way obtained.

ISSN:0021-8979    

DOI:10.1063/1.1702300

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

The existing theories of the resistivity of mixtures assume regular arrangements of the two components, rather than random mixtures. A theory for a random mixture is given, based on the assumption that each crystal acts as if surrounded by a homogeneous medium whose properties are those of the mixture. Comparisons with experiment are made. The experimental data that have been examined fall roughly into two classes. One class consists of mixtures, where the variation of resistivity with composition disagrees violently with this theory, making it clear that the assumptions made are completely inapplicable. The remaining class consists of mixtures which generally agree well with the theory.

ISSN:0021-8979    

DOI:10.1063/1.1702301

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

In continuation of a previous study of grain boundary diffusion of silver in copper the grain boundary diffusion of zinc along grain boundaries of columnar copper has been investigated at various temperatures. The results confirm the influence of the angle between the grains on diffusion and indicate an angular dependence of the activation energy. The latter reaches very small or even negative values in a certain range of orientation in agreement with the proposed model.

ISSN:0021-8979    

DOI:10.1063/1.1702302

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

Radioactive tracers have been used in a study of evaporation of the alkaline earths, barium, strontium, and calcium from oxide coatings on passive nickel bases. Several percent of the total cathode Ba, Sr, and Ca leave a triple oxide cathode during processing and aging. The rates of transfer of these elements from the cathode during life tests of 118 hours at true cathode temperatures from 1175 to 1279°K obey equations of the form, logW=A−(B/T), whereWis the rate of transfer in g/cm2/sec,Tis the absolute temperature of the cathode,AandBare constants. The transfer of Ba from a BaO cathode obeys a similar law. The mass of Ba transferred in 118 hours of life from a triple oxide cathode at 1123°K true as 2.9×10−6g/cm2, and from a BaO cathode 1.4×10−5g/cm2. The masses of Sr and Ca transferred from a triple oxide cathode at the same temperature were 2.1×10−7and 1.2×10−8g/cm2, respectively.Bombardment of the anode by an electron beam during life tests decreased the quantity of Sr observed on the anode. Anode current densities of 5 to 10 ma/cm2at electron energies of approximately 100 volts produced a fiftyfold reduction in the quantity of Sr on the anode. Experiments indicated that this decrease was not due to heating of the anode. The quantity of Ba deposited on the anode was not decreased by electron bombardment.The very considerable transfer of Ba from the cathode during processing was greatly reduced by breaking down the carbonates and high temperature flashing the cathodes in the presence of a few mm pressure of argon gas.

ISSN:0021-8979    

DOI:10.1063/1.1702303

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

Conclusions important to the practice of electron microscopy are drawn from experiments. Particles of Dow Latex 580G are unstable under electron beams and best micrographed at low intensity. Two different effects of radiation are noted. At low intensity the mean diameter in the present work was 2890A, the standard deviation of the spherical particles was 60A. 580G is improved as an internal standard if recalibrated by some other suitable standard (not the reverse) each time before use. Fresh replicas of diffraction gratings are still the most practical standards, reproducing gratings to two percent. By an independent optical method (spectroscopy) one can measure the grating space of a replica when it is on an eighth‐inch, 200‐mesh specimen screen under exact calibration conditions for electron microscopes. Specific replicas, and from them specific preparations of 580G are checked easily and accurately by the spectroscopic method. Replica age or other factors which may affect accurate reproduction of an original grating are then no longer important in calibration. A reliable method of calibration using 580G is suggested.

ISSN:0021-8979    

DOI:10.1063/1.1702304

出版商:AIP    

年代:1952

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1702306

出版商:AIP    

年代:1952

数据来源: AIP