Volume 16, Issue 2, 01 February 1945
Index of content:
16(1945); http://dx.doi.org/10.1063/1.1707558View Description Hide Description
The problems of airport and foundation engineering have become increasingly important in the war construction program. These problems frequently involve the consideration of stresses and settlements in layered soil deposits. The well‐known Boussinesq equations apply strictly only to homogeneous soil deposits. The general theory of stresses and displacements in a twolayer system is developed in order to provide the engineer with a useful tool which is more directly applicable to the analysis of actual conditions encountered in soil deposits. The basic equations of stresses and settlements are derived. The numerical evaluation of the surface settlement equation for the simplest case of Poisson's ratio equal to one‐half has been completed as the first of a series, and is presented in the form of influence curves for the analysis of practical problems.
16(1945); http://dx.doi.org/10.1063/1.1707559View Description Hide Description
Electron diffraction offers a solution to the problem of distinguishing between conducting and insulating surfacefilms on conducting objects. An electron beam striking an insulating surface behaves in a different manner than with a conducting surface because of a charging up of the insulating surface. This enables the observer to recognize an insulating film on the surface of a sample.
16(1945); http://dx.doi.org/10.1063/1.1707560View Description Hide Description
The observation of electron reflections in electron microscope images is reviewed and further data are presented. The observations of the reflected beams with the objective limiting diaphragm removed and the determination of the planes responsible for the reflections by this means are described. The results of the dynamical theory of electron diffraction are briefly discussed and the values of the ``characteristic'' crystal thickness D 0 are computed. These values of D 0 are compared with the experimental values and are in reasonably good agreement for the MgO (200) reflections at 60, 96, and 103 kv, MgO (220) reflections and CdO (200) reflections at 60 kv. The dynamical theory accounts satisfactorily for the intensity variations except as modified by inelastic scattering and the results may be considered as experimental verification of the theory.
16(1945); http://dx.doi.org/10.1063/1.1707553View Description Hide Description
This paper presents an experimental analysis of oscillatory current responses peculiar to certain types of non‐linear series circuits containing resistance,inductance, and capacitance. Methods of initiating the oscillations, and the effect of the boundary conditions necessary to sustain them, are summarized. This is followed by a discussion reviewing the effect of resistance and capacitance variation on sustained subharmonic response. For several values of capacitance, the effect of varying the inductor turns is presented in the form of curves. These curves are correlated in a plot of effective value of impressed voltage versus the product N 2 C 1.5 (N is the number of turns on the inductor core, and C is the capacitance). The voltage across the inductor appears to consist of only two sinusoidal components, when the circuit undergoes subharmonic oscillations.
16(1945); http://dx.doi.org/10.1063/1.1707554View Description Hide Description