摘要:

A detailed description of the preparation of silica replicas and substrates and their many and varied uses is presented with photographs and electron micrographs. A method of preparing silica replicas of specimens which cannot be subjected to the temperatures and pressures of the ordinary technique is described. It consists of applying a polystyrene lacquer to the specimen surface in place of the conventional molding. The question of ``up and down'' in stereo pictures of silica replicas is definitely settled by adding a metal oxide smoke (MgO) to the polystyrene replica before the silica evaporation. A successful powder dispersing technique consists of dispersing the powder in an ethyl cellulose lacquer and depositing upon a silica substrate. Several other techniques are also included.

ISSN:0021-8979    

DOI:10.1063/1.1697655

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

An application of the characteristics of infra‐red storage phosphors to radiography is described, whereby the expense and trouble of x‐ray film processing may be partially or completely eliminated. The properties of these materials to store x‐ray energy for periods of time and release that energy upon exposure to infra‐red radiation have proved practical for either temporary and permanent recording of the latent x‐ray image. One distinct feature of this method is the complete removal of harmful x‐radiation to the technician. The possibility of a new field of radiography in ``flash fluoroscopy'' is also suggested by the authors. Graphs and charts exhibiting the characteristic behavior of infra‐red phosphors to x‐ray energy are included as well as actual photographs and radiographs comparing radiography with phosphorography.

ISSN:0021-8979    

DOI:10.1063/1.1697656

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

In this report the flux plotting methods which have previously been applied to fields satisfying Laplace's and Poisson's equations are extended to fields satisfying Maxwell's equations. Application is made to the hole and slot, and vane types of magnetron tubes.

ISSN:0021-8979    

DOI:10.1063/1.1697657

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

Magnetron oscillators can provide very high frequency power for dielectric heating. Factors determining the choice of frequency for particular jobs are discussed. The design of a magnetron having 5 kw continuous output at 1050 megacycles is described, and performance data on the tube are given.

ISSN:0021-8979    

DOI:10.1063/1.1697658

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

In determining molecular weights with the ultracentrifuge by the equilibrium method, it is necessary to drive the rotor at relatively high speeds for very long periods of time. It would be a real advantage to be able to deduce molecular weights from the distribution of concentration within a cell placed in a rotor without waiting for equilibrium. The solution of a certain differential equation gives the theoretical distribution within the cell at any time, and a comparison of the experimentally determined concentrations with those deduced from theory should yield molecular weights without waiting for equilibrium. The exact solution of this differential equation is known, but it is not suitable for numerical work. The present paper presents an approximate solution from which numerical results can be obtained with ease.

ISSN:0021-8979    

DOI:10.1063/1.1697659

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

The elongations and natural frequencies of conically‐shaped coil springs are derived theoretically for several dynamic boundary conditions. Frequencies are verified experimentally on nickel and piano wire springs, attesting the reliability of the computations.

ISSN:0021-8979    

DOI:10.1063/1.1697660

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

The paper aims at introducing the reader to the principal theories of plasticity. Since a presentation of the general stress‐strain relations used in these theories would require too much space, the discussion is restricted to the mechanical behavior of plastic materials under shear. Theories of plastic deformation (Hencky, Nadai) and theories of plastic flow (Saint Venant‐Le´vy‐Mises, Prandtl‐Reuss, Prager) are illustrated by the example of a prismatic bar under torsion.

ISSN:0021-8979    

DOI:10.1063/1.1697661

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

For the video outputVof a receiver, consisting of an i‐f stage, a quadratic detector, and a video amplifier, the probability densityP(V) has been obtained for noise alone and for noise and signal. The results are expressed in terms of eigenvalues and eigenfunctions of the integral equation0∞K(t)&rgr;(s−t)f(t)dt=&lgr;f(s),where &rgr;(&tgr;) is the i‐f correlation function (i.e., the Fourier transform of the i‐f power spectrum) andK(t) is the response function of the video amplifier (i.e., the Fourier transform of the video amplitude spectrum). Two special cases are discussed in which the integral equation can be solved explicitly. Approximations for general amplifiers are given in the limiting cases of wide and narrow videos. Some applications of the method to other problems are shown in Sections 7B and 9.

ISSN:0021-8979    

DOI:10.1063/1.1697662

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

The analogy between thermal and electrical networks is used to obtain solutions to problems relating to the heating and cooling of air‐backed and solid‐backed bolometer elements exposed to radiation of periodically fluctuating intensity. From the equations derived, thermal response‐frequency characteristics are computed for ``typical'' bolometer elements. Features of these characteristics are discussed, and the physical influences of the various thermal properties of the bolometer material and of the backing material are pointed out.

ISSN:0021-8979    

DOI:10.1063/1.1697663

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

Brittle failure was produced in notched steel tensile specimens. The speed of propagation of the brittle crack was measured and found to be approximately 40,400 in./sec.

ISSN:0021-8979    

DOI:10.1063/1.1697664

出版商:AIP    

年代:1947

数据来源: AIP