ISSN:0021-8979    

DOI:10.1063/1.1707314

出版商:AIP    

年代:1939

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1707315

出版商:AIP    

年代:1939

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1707316

出版商:AIP    

年代:1939

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1707317

出版商:AIP    

年代:1939

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1707318

出版商:AIP    

年代:1939

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1707319

出版商:AIP    

年代:1939

数据来源: AIP

摘要:

We show that suitably shaped objects made of a dielectric material can function as electrical resonators for high frequency oscillations. We develop the theory of such resonators very briefly and compute their resonant frequencies and losses in some very simple cases. The paper concludes with an observation on the behavior of dielectric wave guides.

ISSN:0021-8979    

DOI:10.1063/1.1707320

出版商:AIP    

年代:1939

数据来源: AIP

摘要:

The successive approximation theory for the thick film lubrication of flooded journal bearings and bearings with circumferential grooves is developed through the fourth approximation, that is, including the fifth power of the journal eccentricity. The analysis applies to bearings of arbitrary length, the boundary conditions at the ends of the bearings being satisfied rigorously. It is found that the journal eccentricities and friction coefficients, for fixed Sommerfeld variable, are greater for bearings of finite length than for that of infinite length, the difference increasing with decreasing bearing length. On the other hand the load‐carrying capacities, for fixed eccentricity, of the bearings of finite length are much less than that for the infinitely long bearing. The general theory for the bearing with a central circumferential groove is also developed and it is shown that the only hydrodynamic effect of such a groove is to cut the bearing into two separate end fed bearings, each of half the original bearing length. The load‐carrying and friction properties of these end fed bearings are identical with those of flooded bearings of the same length. The main advantages of such grooving must lie in the maintenance of the lubricant viscosity by the cooling effect of the lubricant flow and in overcoming the negative pressures and possible film rupture that would develop in a flooded bearing without internal lubricant sources.

ISSN:0021-8979    

DOI:10.1063/1.1707321

出版商:AIP    

年代:1939

数据来源: AIP

摘要:

At low contents of the manganese activator, the decay of phosphorescence takes place in two stages. The initial stage is exponential. It is complete in less than 0.1 second and is not affected by temperature. The second stage is at a much lower intensity level. It becomes noticeable after 0.03 second and persists for more than an hour. Its speed of decay increases with temperature. At − 196°C it is completely latent. A change in the intensity of the exciting light alters proportionally the luminescence caused by each stage of decay and has no effect upon the shape of the decay curves.About fifty times as many electrons are involved in the second stage of decay as in the first. It is assumed that the second stage is caused by the retention of electrons in a metastable state, probably one associated with the presence of lattice imperfections. The exponential decay of the first stage would result from the recombination of manganese ions, relatively in excess, with those free electrons which had not been captured in the potential cups of the metastable state.The decay of phosphors rich in manganese is always very abrupt and at a speed which rises rapidly with increase in temperature. The course of decay can be represented by the expressionp−x=a+btexcept at reduced temperatures where the two stages of decay characteristic of low manganese content are observable.

ISSN:0021-8979    

DOI:10.1063/1.1707322

出版商:AIP    

年代:1939

数据来源: AIP

摘要:

An investigation has been made of the reignition of short a.c. arcs in air at pressures from one to eight atmospheres, for currents less than 3.25 amperes (and with a resistance circuit). Pure graphite electrodes were used and were separated by a distance of 1 mm. The reignition voltage under these conditions increases with pressure and decreases as the current is increased. The characteristic of reignition potentialvs.current has been found to exhibit a discontinuity at a critical current. For this current the reignition potential decreases by about 1000 volts to a new characteristic typical of the higher currents. This critical current increases with the gas pressure to a maximum of 2.25 amp. As the r.m.s. current is increased from low values to values near the critical, the number of cycles during which the reignition potential has the value given by the higher characteristic decreases. For currents equal to, or greater than the critical value, only the low reignition potentials are obtained. This transition is accompanied by an increase in the burning voltage of the arc.

ISSN:0021-8979    

DOI:10.1063/1.1707323

出版商:AIP    

年代:1939

数据来源: AIP