ISSN:0021-8979    

DOI:10.1063/1.1712731

出版商:AIP    

年代:1940

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1712732

出版商:AIP    

年代:1940

数据来源: AIP

摘要:

The values of the constant in the equation which relates permeability of a porous medium to the porosity and specific surface of the medium are determined for three cases. These experimental values are found to be consistent with the theoretical indications of Fowler and Hertel.

ISSN:0021-8979    

DOI:10.1063/1.1712733

出版商:AIP    

年代:1940

数据来源: AIP

摘要:

Short spark gaps (order of one mm) in air at atmospheric pressure, unless specially radiated, show large spark lag when tested at little above the sparking potential. In engineering literature this property is measured by the impulse ratio, i.e., the ratio of the voltage at which breakdown occurs under a voltage surge rising at a specified rate (about 50 kilovolts per microsecond), to the voltage at which breakdown occurs with slowly increasing impressed 60‐cycle voltage. The spark lag shows statistical variations, and its mean has been shown to be nearly equal to the mean time for emission of an electron from the cathode, prior to the spark. The electron current from the cathode prior to the spark is greatly increased by the presence of a pointed projection on the cathode, so that the mean spark lag at a given voltage is greatly reduced. However, if a single pointed projection is used, of sufficient size to reduce the spark lag at a given voltage, it also reduces the 60‐cycle sparking potential, so that the impulse ratio, which is the quantity important in engineering applications, is not reduced. By using a very large number of extremely small pointed projections on the cathode, the spark lag can be reduced without appreciable lowering of the 60‐cycle sparking potentials. Thus impulse ratios little greater than unity can be obtained. Small particles of carborundum, rutile, alumina and porcelain, of various sizes were attached to the cathodes of spark gaps, and the impulse ratios tested. Minimum impulse ratios were obtained when the particle linear dimensions were between 2×10−3and 15×10−3cm.

ISSN:0021-8979    

DOI:10.1063/1.1712734

出版商:AIP    

年代:1940

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1712735

出版商:AIP    

年代:1940

数据来源: AIP

摘要:

The temperature dependence (298°K to 80°K) of the absorption spectrum of Ag, Cu, Cd, Al, Sn, Sb, Pb, and Ni has been studied. Only Pb and Ni showed a relative change; Pb films transmit more ultraviolet light at 80°K than at 298°K, Ni films transmit less visible light at 80°K than at 298°K.

ISSN:0021-8979    

DOI:10.1063/1.1712736

出版商:AIP    

年代:1940

数据来源: AIP

摘要:

The processes of formation of the initial ions in the cyclotron are reviewed, after which the various processes by which the ions are lost from resonance are considered. A theory of the loss of ions by collision or by electron capture is given and is compared with measurements made on the variation of the high energy beam current with gas pressure: satisfactory agreement is found. The inhomogeneity of the magnetic field of the 60‐inch Berkeley cyclotron has been measured, and an analysis of the electric and magnetic focusing in that cyclotron is made. Rose's work on the loss of ions resulting from their getting out of phase with the radiofrequency voltage is applied to the calculation ofV0, the voltage necessary to apply to the dees just to get a beam. As an example, the value ofV0is computed for the 60‐inch cyclotron, and is found to be in good agreement with the directly measured value. The wandering of the ion paths is reviewed and is applied to the calculation of the inhomogeneity of the energy of emergent beam. Measurements made on the homogeneity of the energy of the protons from the 37‐inch cyclotron are compared to the calculations. Finally, the question of shimming the magnetic field of a cyclotron is considered. It is suggested that the magnetic field be made to decrease from the center with a constantdH/dr. For this shape of magnetic field, analytic expressions are derived for the magnitudes ofdH/drandV0, and methods for attaining such a field are suggested.

ISSN:0021-8979    

DOI:10.1063/1.1712737

出版商:AIP    

年代:1940

数据来源: AIP

摘要:

From the assumptions underlying the diffusion theory of electrolytic polishing two quantitative current‐time relations are deduced and compared with the behavior of a copper‐orthophosphoric acid cell. One equation relates the current through the cell to the time required for the growth of the concentration layer necessary for polishing. The other equation describes the fall in limiting current once the layer is formed. Both equations are in accord with the results of some simple experiments designed to test them. The present study removes some of the mystery in electrolytic polishing and permits a more intelligent use of it to be made.

ISSN:0021-8979    

DOI:10.1063/1.1712738

出版商:AIP    

年代:1940

数据来源: AIP

摘要:

A simple method by which the proper radiation or combination of radiations may be selected for the precision determination of hexagonal, rhombohedral, and tetragonal lattice constants is described and illustrated in detail. The method involves the use of specially prepared charts. With a knowledge of the approximate lattice constants, positions of diffraction lines with &thgr;>60°; i.e., back‐reflection lines, can be predicted directly from the charts for any common radiation. From the number, distribution, and indices of back‐reflection lines, a suitable target may be chosen for an accurate determination of lattice constants. Furthermore, the charts are useful for predicting positions of beta‐lines, and for indexing without calculation back‐reflection lines in powder x‐ray photograms of hexagonal, rhombohedral, or tetragonal lattices.

ISSN:0021-8979    

DOI:10.1063/1.1712739

出版商:AIP    

年代:1940

数据来源: AIP

摘要:

Deviations from isochronism for the system of hairspring and balance wheel are treated by a method due to Haag. The results are given a geometrical interpretation. It is shown that the deviations are related to the displacement of the end point of the hairspring in a set‐up in which this end point is free to move keeping its tangent constant in direction. Such an arrangement can be realized with Bouasse's pendulum. For the so‐called ``helical'' spring a more accurate solution than Phillips' has been found for the shape of the terminals. Extensive numerical calculations have been made for flat spiral springs, and a new simple terminal has been designed.

ISSN:0021-8979    

DOI:10.1063/1.1712740

出版商:AIP    

年代:1940

数据来源: AIP