Recent progress in the plastic methods of structural analysis

The techniques described in Part I of this paper for the calculation of plastic failure loads under proportional loading are further exemplified by indicating solutions for a rectangular building frame, a Vierendeel girder, and a shed-type portal frame. A method for estimating deflections of a frame just as the collapse load is attained is then described, with some indications as to its reliability. More general conditions of loading than proportional loading are next discussed, and generalized load and failure concepts are defined. The theorems and techniques for determining critical shakedown loads under variable, repeated loading are then described and illustrated. The relation of the elastic-plastic shakedown analysis to the much simpler analysis for failure under single load applications is discussed.     

Studies in the sensitivity of photographic materials

The sensitivity of photographic emulsions is not measured by the exposure necessary to produce an arbitrarily chosen density. It is measured by a definite value of DID…, which is given by the inflection point of the characteristic curve.For simple characteristic curves, the inertia point is quantitatively related to the inflection point.The most complete measurements of sensitivity are obtainable by a quantic analysis of the shape of the characteristic curve.