Volume 16, Issue 9, 01 September 1945
Index of content:
16(1945); http://dx.doi.org/10.1063/1.1707620View Description Hide Description
The x‐ray diffraction tool in most common use is the powdercamera, yet it is usually ill‐designed. This paper presents constructive criticisms of current powdercamera design, and describes briefly a series of instruments having desirable features. Among the issues discussed are: adjustments, recovery of adjustments, desirable diameters, important recording ranges, film arrangements, fitting the film to cylindrical form, design of direct beam systems, elimination of air‐scatter, specimen attachment and adjustment, and scanning. The following special instruments are also discussed: high temperaturecameras, large spacing cameras, and film cutters and punches.
16(1945); http://dx.doi.org/10.1063/1.1707621View Description Hide Description
The object of this paper is to extend to tapered beams and conical shells (membranes) the conventional formulas of the beam theory. This extension is made for two conditions: the plane tapered beam and the thin conical shell. The method of solution and the results obtained in the two cases are essentially different. The general analysis of the conical shell leads to solutions which are more complex than the corresponding solutions for cylindrical shells. However, in the case of applied stress analysis, simplifications are possible, which lead to solutions of the same type as for cylindrical shells.
16(1945); http://dx.doi.org/10.1063/1.1707622View Description Hide Description
By introducing an electrostatic problem analogous to the impedance function problem it is found possible to prove that, under simple and quite broad assumptions, the maximum possible gain‐band width products for two‐terminal coupling, four‐terminal low‐pass coupling and four‐terminal band‐pass coupling are, respectively, 1, 2.47, and 2.53 times g/πC. The first result was conjectured by Wheeler long ago, and it and the second have recently been proved by Bode. The last result covers a case more general than those considered by Bode.
16(1945); http://dx.doi.org/10.1063/1.1707623View Description Hide Description
The purpose of this paper is to present the development of a ``power function,'' P, such that Lagrangian generalized forces, Fqr , which stem from a wide variety of forces (as, externally applied, conservative, dissipative forces proportional to the nth power of speed, etc.) can be obtained from the simple relation:The value of this easily obtained function lies in the fact that it places the task of determining almost all generalized forces which occur in practice on the same basis as that of determining conservative forces from a potential‐energy function. Moreover, it is equally applicable to mechanical, electrical, and electro‐mechanical systems. Since it is believed that the function has wide applications, several of its most useful forms are listed. Two specific examples are given.
16(1945); http://dx.doi.org/10.1063/1.1707624View Description Hide Description
A theory of flow orientation was developed which is based on a relation giving the change in entropy accompanying molecular orientation under the influence of a stress field, and on the applicability of the Eyring theory of viscousflow. The proposed theory predicts the ratio of the viscosity at attainment of complete orientation to the viscosity of ``normal'' i.e., random flow to be equal to the ratio of the average length v ⅓ to the actual length of the (fully stretched) molecule. The thermodynamics of a flow‐oriented system are outlined, predicting the temperature changes, accompanying adiabatic orientation and disorientation. It is also suggested that the relaxation times in viscous media are large enough to prevent observation of flow orientation in capillary viscosimeters in many cases.
16(1945); http://dx.doi.org/10.1063/1.1707625View Description Hide Description
Boundary value problems in regions with rectangular symmetry can be treated by means of the finite Fourier Transform. Transforms of vector point functions and their divergence and curl are obtained. The transforms of Maxwell's equations take a particularly simple form; the resonator problem is discussed as an example.