ISSN:0021-8979    

DOI:10.1063/1.1712722

出版商:AIP    

年代:1940

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1712723

出版商:AIP    

年代:1940

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1712724

出版商:AIP    

年代:1940

数据来源: AIP

摘要:

A mechanical model in the form of a gyroscope may be made to simulate the path of an electron in a uniform magnetic field acted upon by transverse electric fields. In using the model, one employs the following substitutions: The uniform magnetic field is replaced by the spin velocity of the gyroscope, the electric fields are replaced by magnetic fields which give the same field configuration, and the electron is replaced by one pole of a permanent magnet mounted on the axis of the gyroscope. The spin velocity may be arbitrarily chosen for convenient observation. Then, depending upon the value of the spin velocity, the dimensions of the gyroscope, the strength of the permanent magnet and the scale factor used in setting up the model, the strength of the magnetic field in the model is adjusted to correspond to the strength of the electric field in the actual case. The path described by the magnetic pole, under these conditions, corresponds to the actual path of the electron. Since the error involved in identifying the equations of motion of the gyroscope with those of the electron is of the order of &thgr;2, where &thgr; is the half‐angle of the cone through which the spin axis is allowed to move, the range of observations must be restricted accordingly. Some familiar structures for which electron paths have been observed and photographed are deflection plates in a uniform magnetic field, a diode in an axial magnetic field, and a split‐anode magnetron. By periodically reversing the current through the field magnets, it is possible to observe the effect of alternating electric fields. In one arrangement, in which the field was alternated in resonance with the revolution of the electron about the magnetic field lines, a path similar to that of charged particles in a cyclotron was obtained.

ISSN:0021-8979    

DOI:10.1063/1.1712725

出版商:AIP    

年代:1940

数据来源: AIP

摘要:

The ratio of watts to volt‐amperes does not give the power factor of long cables because of the resistance of the conductor and sheath. The error involved varies as the length squared and might be quite appreciable at lengths of 10,000 feet. Correction factors are given involving the use of an infinite series for exact results and a simple algebraic formula for approximate results.

ISSN:0021-8979    

DOI:10.1063/1.1712726

出版商:AIP    

年代:1940

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1712727

出版商:AIP    

年代:1940

数据来源: AIP

摘要:

This paper describes the results of an investigation and extension of the various proposed procedures and methods of analysis for the photoelastic determination of three‐dimensional states of stress. Two important limitations of the previous developments are removed. A true extension to three dimensions is given by the determination of the effect on retardation of appreciable variation in the orientation of the secondary principal stresses in planes perpendicular to the wave normal (such variation being the rule rather than the exception for general states of stress). Also, methods for the analysis of whole planes are presented, thus avoiding the cumbersome and tedious point by point procedures that have been advanced. In the particular case of plane stress, these methods reduce to a purely optical technique for determining the principal stresses themselves, or more easily their sum, for the entire model.

ISSN:0021-8979    

DOI:10.1063/1.1712728

出版商:AIP    

年代:1940

数据来源: AIP

摘要:

Laue photographs of aluminum‐rich aluminum‐silver crystals during aging at 20° and 150°C show more or less clearly defined streaks along certain zonal ellipses, in addition to the streaks caused by thermal agitation. These have been analyzed by stereographic and reciprocal lattice projections and are found to result from two‐dimensional gratings parallel to planes of the form {111}. The streaks with 20° aging are more diffuse than with 150° aging; no streaks were found with 200° aging. When the precipitate lattice is fully developed, it yields sharp spots along the streaks at positions predicted from earlier studies of the Widmansta¨tten structure; preceding this state there exist very thin plate‐like nuclei on randomly spaced {111} planes, which govern the orientation and shape of the fully developed precipitate. These may consist of (a) clusters of silver atoms or (b) imperfect lattices caused by (111) layers of atoms shifting parallel to themselves as required for the transformation from the face‐centered cubic to the hexagonal close‐packed lattice but with the shifting occurring on random planes, thus destroying the lattice periodicity normal to these planes.

ISSN:0021-8979    

DOI:10.1063/1.1712729

出版商:AIP    

年代:1940

数据来源: AIP

摘要:

The Reynolds theory is applied to the calculation of the lubrication properties of plane sliders—thrust bearings—of infinite width provided with lubricants whose viscosities increase exponentially with the pressure. The friction coefficient, minimum film thickness, and lubricant flow were calculated both for fixed wedge angle and pivoted sliders. The effect of the viscosity variation with pressure is determined by the magnitude of the dimensionless product of the viscosity‐pressure exponent and the bearing load per unit area. The analysis shows that for each choice of this product there will be a limiting position of the pivot line of the slider or of the equivalent Sommerfeld variable at which the film pressures and friction forces will become infinite, and beyond which it will be impossible to operate the slider. Moreover this product is shown to be limited by a maximum value equal to 2, which means that the absolute maximum load per unit area which can be carried by such slider systems is equal to twice the reciprocal of the viscosity‐pressure exponent. Specific calculations on the friction properties of bearings operating with lubricants of different viscosity pressure exponents give curves of friction coefficientvs.load or Sommerfeld variable quite similar to those observed in practical tests. At high loads or low values of the Sommerfeld variable the friction coefficient curves split and follow the behavior generally interpreted in terms of oiliness and boundary lubrication phenomena.

ISSN:0021-8979    

DOI:10.1063/1.1712730

出版商:AIP    

年代:1940

数据来源: AIP