Volume 11, Issue 2, 01 February 1940
Index of content:
11(1940); http://dx.doi.org/10.1063/1.1712742View Description Hide Description
A chimney or column is considered as a rigid rod, initially in a vertical position, and hinged at its base. The internal forces and stresses which are developed as the rod falls freely from the vertical position are calculated. It is shown that the inertial reaction forces produce a bending moment which results in a tension on the leading side and a compression in the trailing side of the rod. This tension in the leading side has its maximum value at roughly 0.3 to 0.5 the height of the rod, depending upon its shape and the angle of inclination from the vertical. This tension usually produces a transverse rupture in large falling chimneys or columns, though not always. These transverse ruptures should occur at the point of maximum tension.
It is shown that in very tall columns or chimneys the vertical shear stress near the base is sufficient to produce a tension rupture there—and usually does. The positions of these latter ruptures cannot be predicted accurately in actual cases because of the greatly variable conditions which may exist at the point of support after dynamiting.
Calculations are given for the cases of solid columns of uniform cross section, solid columns of uniformly tapered cross section, and uniformly tapered chimneys of constant wall thickness. Photographs of actual falling chimneys are presented to check the theory.
An Investigation into the Gettering Powers of Various Metals for the Gases Hydrogen, Oxygen, Nitrogen, Carbon Dioxide and Air11(1940); http://dx.doi.org/10.1063/1.1712744View Description Hide Description
Measurements of the ``gettering'' or clean‐up ability of aluminum,magnesium,thorium,uranium, misch metal, zirconium and barium for the common gases were made. In most cases the measurements were quantitative and represent gettering powers unassisted by an electric discharge or other source of ions. The effect of temperature conditions on the gettering and keeping properties of several of the getters is given. The superior gettering powers of the diffuse layers produced by vaporizing the getters in the presence of a gas, as compared to those of the bright getter deposits produced in a high vacuum were confirmed. Barium and misch metal were found to be the most active of the materials tried, and the convenient forms which barium is now commercially obtainable would seem to make it first choice for most work, though it is not effective in the presence of Hg vapor. Magnesium and aluminum showed little activity without the presence of a discharge. Thorium and uranium showed considerable activity for H2 and O2, but the high temperatures needed for flashing, make them rather inconvenient to use.
11(1940); http://dx.doi.org/10.1063/1.1712745View Description Hide Description
The transmission of thin films of the following materials has been measured between 400 cm−1 and 3000 cm−1: Cellophane, ethyl cellulose, cellulose acetate, Duco household cement, polystyrene, glyptal, Pliofilm, rubber, Plexiglas, methyl methacrylate polymer, XYSG Vinylite, and Shawinigan V‐15 resin. The possibility of using these materials for windows in spectroscopic experiments is discussed.
11(1940); http://dx.doi.org/10.1063/1.1712746View Description Hide Description
An electrolytic model of a full journal bearing having a ratio of journal displacement to radial clearance of 0.1 has been constructed. The reliability of the model was established by comparing the results observed for the infinitely wide bearing with those predicted by the theory of Reynolds. The results obtained for models of journal bearings of finite width, bearings with circumferential grooves, and bearings with sources of lubricant are also in agreement with hydrodynamic theory.
11(1940); http://dx.doi.org/10.1063/1.1712747View Description Hide Description
Under scanning conditions in a specially designed tube, it was found that a willemite screen not only deviates from the potential of the accelerating electrode, but also shows potential variations on the surface. These potential variations are functions of scanning frequency and current density and may become of the order of several thousand volts. Light measurements were also taken. The dependence of the light intensity on voltage can be represented by a power law.
- LETTERS TO THE EDITOR
11(1940); http://dx.doi.org/10.1063/1.1712748View Description Hide Description