ISSN:0021-8979    

DOI:10.1063/1.1707306

出版商:AIP    

年代:1939

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1707307

出版商:AIP    

年代:1939

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1707308

出版商:AIP    

年代:1939

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1707309

出版商:AIP    

年代:1939

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1707310

出版商:AIP    

年代:1939

数据来源: AIP

摘要:

A d.c. stream of cathode rays of constant current and speed is sent through a pair of grids between which is an oscillating electric field, parallel to the stream and of such strength as to change the speeds of the cathode rays by appreciable but not too large fractions of their initial speed. After passing these grids the electrons with increased speeds begin to overtake those with decreased speeds ahead of them. This motion groups the electrons into bunches separated by relatively empty spaces. At any point beyond the grids, therefore, the cathode‐ray current can be resolved into the original d.c. plus a nonsinusoidal a.c. A considerable fraction of its power can then be converted into power of high frequency oscillations by running the stream through a second pair of grids between which is an a.c. electric field such as to take energy away from the electrons in the bunches. These two a.c. fields are best obtained by making the grids form parts of the surfaces of resonators of the type described in this Journal by Hansen.

ISSN:0021-8979    

DOI:10.1063/1.1707311

出版商:AIP    

年代:1939

数据来源: AIP

摘要:

The experimental study of the lubrication of a complete journal bearing has been extended, emphasis being placed upon the role played by the position and strength of the lubricant source upon the coefficient of friction. As predicted theoretically, the friction on the bearing has been found to increase with increasing source strength and to be somewhat higher when the source is at the crown than when at the base (region of highest load) of the bearing. It has also been found that when the source is at the base, where it aids the journal rotation effects in supporting the load, the bearing may be successfully operated at much lower speeds and higher loads than when it is at the crown without encountering the usual thin film phenomena. Moreover, for this case, there exists a critical value of the source strength at which the journal and bearing are concentric and the coefficient of friction is given by the simple Petroff theory. The experimental results confirm qualitatively all the predictions of the hydrodynamic theory previously developed. Quantitatively, experiment and theory also agree for small values of the source strength and high values of the Sommerfeld variable, and especially when the source is at the base of the bearing, the discrepancies becoming marked in regions where the approximations of the theory are inherently inadequate.

ISSN:0021-8979    

DOI:10.1063/1.1707312

出版商:AIP    

年代:1939

数据来源: AIP

摘要:

The dynamic luminescence characteristics of five samples of commercial phosphors excited intermittently by electron bombardment have been studied. The decay of artificial willemite follows closely a simple exponential law, except for a rapid fall during the first three milliseconds after bombardment, the prominence of this component increasing with the current density. An attempt is made to correlate the observed dependence of build‐up rate on current density with the phenomenon of current‐saturation under continuous bombardment. A sample of calcium tungstate follows changes in the intensity of excitation within 100 microseconds, the resolving time of the apparatus. Two samples of ZnS·Ag and one sample of ZnS·CdS·Ag decay more rapidly the higher the intensity of excitation. The initial rate for ZnS·Ag is greater than would be predicted for a simple bimolecular reaction, and cannot plausibly be explained by non‐uniformity in the initial distribution of reactants in a bimolecular reaction. The ZnS·CdS·Ag decays initially according to a simple bimolecular law.

ISSN:0021-8979    

DOI:10.1063/1.1707313

出版商:AIP    

年代:1939

数据来源: AIP