ISSN:0021-8979    

DOI:10.1063/1.1707653

出版商:AIP    

年代:1946

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1707654

出版商:AIP    

年代:1946

数据来源: AIP

摘要:

The indicial admittance of a simple mechanical system, a tourmaline crystal hydrophone, has been determined from its response to an underwater explosion wave. The indicial admittance is simply related to the observed response to the explosion wave—the observed response is just the indicial admittance ``wrapped around'' an exponential,e−t/&tgr;. The relative frequency calibration of two hydrophones obtained by Fourier analysis of their responses to the explosion wave is in good agreement with the direct continuous wave comparison. The peak pressure of the explosion wave is also determined from this Fourier analysis. It is suggested that the explosion wave can be used as a tool in acoustical ``circuit analysis'' in much the same way that a square wave generator is used in electrical circuit analysis.

ISSN:0021-8979    

DOI:10.1063/1.1707655

出版商:AIP    

年代:1946

数据来源: AIP

摘要:

When x‐rays are scattered from a thin crystalline surface film overlying a crystalline base material, diffraction lines are observed from both materials. Equations are developed for the general case of (1) a flat sample and (2) a cylindrical sample expressing the ratio of line intensities from the two materials as a function of film thickness. A usable range of 10−6cm to 5×10−2cm is indicated. Experimental confirmation is found in the range 10−4cm to 6×10−3cm.

ISSN:0021-8979    

DOI:10.1063/1.1707656

出版商:AIP    

年代:1946

数据来源: AIP

摘要:

A pure photo‐conductive effect was found in pyrolytically deposited and vaporized silicon films. An apparatus is described for making bridge type photo‐cells by reaction of silicon tetrachloride and hydrogen gases at ceramic or quartz surfaces at high temperatures. The maximum photo‐sensitivity occurs at 8400–8600A with considerable response in the visible region of the spectrum. The sensitivity of the cell appears about equivalent to that of the selenium bridge and its stability and speed of response are far better. For pyrolytic films on porcelain there are three distinct regions in the conductivity as a function of temperature. At low temperatures the electronic conductivity is given by the expression &sgr;=Af(T) exp−(E/2kT). At temperatures between 227°C and a higher temperature of 400–500°C &sgr;=Aexp−(E/2kT), whereElies between 0.3 and 0.8 ev; and at high temperatures &sgr;=Aexp−(E/2kT), whereE=1.12 ev. The value 1.12 ev represents the separation of the conducting and non‐conducting bands in silicon. The long wave limit of the optical absorption of silicon was found to lie at approximately 10,500A (1.18 ev). The data lead to the conclusion that the same electron bands are concerned in the photoelectric, optical, and thermal processes and that the low values of specific conductances found (1.8×10−5ohm−1cm−1) are caused by the high purity of the silicon rather than by its polycrystalline structure.

ISSN:0021-8979    

DOI:10.1063/1.1707657

出版商:AIP    

年代:1946

数据来源: AIP

摘要:

High centrifugal fields were produced by spinning small solid steel spherical rotors up to their bursting speeds. The rotors were supported magnetically in a vacuum by an improved method and spun by rotating magnetic fields. The peripheral velocities at which the rotors of various sizes, made of the same (flaw free) steel and having the same shapes, exploded, were roughly the same and of the order of 105cm/sec. A centrifugal field of 2.4×108times gravity was obtained with a .795‐mm spherical rotor which was the smallest diameter tried. Calculations indicate that in some cases plastic flow probably occurred in small regions near the centers of the spherical rotors somewhat below their bursting speed.

ISSN:0021-8979    

DOI:10.1063/1.1707658

出版商:AIP    

年代:1946

数据来源: AIP

摘要:

A cathode‐ray tube is described in which the screen of persistent phosphor is laid on a cylindrical portion of the glass. A stationary magnetic field bends the electron beam on to the screen, while rotation of the tube produces the time axis. When the beam is deflected and modulated, a continuous pattern may be viewed on the screen.

ISSN:0021-8979    

DOI:10.1063/1.1707659

出版商:AIP    

年代:1946

数据来源: AIP

摘要:

It was found that a considerable portion of the instability in the FP‐54 is caused by variations in emission from the thoriated tungsten filament. Operation of the filament at a current which neither activates nor deactivates was found to be a good criterion for adjusting the circuits employing these tubes. Large fluctuations were observed in emission immediately after activation of the filament. Greater stability was obtained by increasing the activation time from 8 to 40 minutes. Filament and shields improved the stability, showing that some rapid fluctuations in emission occur at the poorly activated end portions of the filaments. Long‐time drifts were not improved by end shields. Tubes with oxide‐coated filaments gave greater sensitivity and less grid current than tubes with thoriated tungsten filaments. These tubes, however, had a tendency to drift. A split type of FP‐54 was constructed with a common filament and space‐charge grid, but with twin control grids and plates. Both oxide‐coated and thoriated tungsten filaments were used. Operation of these tubes in a bridge type circuit eliminated long‐time drift and decreased the amplitude of rapid fluctuations.

ISSN:0021-8979    

DOI:10.1063/1.1707660

出版商:AIP    

年代:1946

数据来源: AIP

摘要:

A picturesque formation of MoO3on vacuum‐tube leads gains in interest and importance because of its close resemblance to a growth of W4O11on tungsten powder in the electron microscope.

ISSN:0021-8979    

DOI:10.1063/1.1707661

出版商:AIP    

年代:1946

数据来源: AIP

摘要:

Spectral energy distribution and luminous efficiency measurements of Zn2SiO4:Mn and of various samples of (Zn, Be)2SiO4:Mn are reported. Quantum efficiencies of these phosphors under 2537A excitation are calculated from this data. The introduction of beryllium into alphawillemite causes a decrease of the ``green'' luminescence band of this phosphor and the growth of a new emission band with a peak in the neighborhood of 6100A, the high quantum efficiency being preserved. The general role of manganese as an activator is considered, and the resulting picture used to explain the effect of beryllium and other substituents for Zn+2or Si+4on the spectral properties and on the luminescence decay of manganese‐activated materials.

ISSN:0021-8979    

DOI:10.1063/1.1707662

出版商:AIP    

年代:1946

数据来源: AIP