摘要:

The effectiveness of acoustic absorbing wall materials in delaying the onset of detonation in gases is explored. Experiments are reported for stoichiometric H2&sngbnd;O2mixtures in two‐inch diameter cylindrical tubes. The results show that the detonation induction distance may be increased by as much as a factor of two by making the walls of the tube of porous sintered bronze.

ISSN:0021-8979    

DOI:10.1063/1.1722162

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

Radial distribution functions of the microcrystalline particles in fibers are derived from the x‐ray scattering at small angles. Particle distribution functions are obtained by application of the method of Fourier synthesis to the x‐ray data, by inversion of the intensity scattered under conditions where interparticle interference plays a part.Different distribution curves are obtained with different fibers, investigated under the same conditions.The distribution curves obtained with the same fiber investigated under different conditions of swelling, are consistent with the wider separation of the particles at higher degrees of swelling. A quantitative explanation is thus given of the differences between the scattered intensities at different degrees of swelling.The degree of crystallinity is calculated from the distribution curves, so obtained, in combination with the particle sizes determined in preceding papers.

ISSN:0021-8979    

DOI:10.1063/1.1722163

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

The general utility of an approximate expression for the first Townsend coefficient of a gas, derived several years ago by Druyvesteyn and Penning, has been tested by introducing into the theoretical treatment somewhat more realistic assumptions regarding the relevant scattering cross sections of the gas molecule. It has been demonstrated by numerical calculations that the functional dependence of the Townsend &agr; upon the electric field and the gas pressure is, within certain limits, insensitive to the assumed energy dependence of the elastic and inelastic cross sections. The functional form of the inelastic cross section does, however, influence the way in which the ionization energy of the gas molecule enters in the exponential part of the expression.

ISSN:0021-8979    

DOI:10.1063/1.1722164

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

Experimental techniques for measuring the magnetic susceptibility tensor components in microwave cavities are described. General expressions for the perturbation of microwave cavities by the magnetic properties of ferrites are developed. Experimental results are given for Ferramic 1331 measured at 9165 Mcps. Since these results indicate that both the real and imaginary parts of the tensor components &khgr; and &kgr; are approximately equal to each other in the resonance region, only measurement of the diagonal components may suffice to specify the complete tensor. However, whenever the small differences between &khgr; and &kgr; are desired, measurement of the tensor susceptibility in a degenerate cavity will be necessary. An attempt has been made to compare the experimental results with the Bloch‐Bloembergen magnetic resonance theory as applied to circularly polarized excitation.

ISSN:0021-8979    

DOI:10.1063/1.1722165

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

A theory is presented for the tensile strength of rubbery plastics under dynamic test conditions. It is found that a nearly universal curve may be plotted relating the tensile strength of rubbers to the time of application of the load in a simple creep test or to the shear rate in a conventional type tensile test. The dependence on chain length, degree of cross linking, and temperature is also predicted.Experimental results for the tensile strength of poly butyl methacrylate in the range 30–95°C are presented. These are shown to agree with the theory within the experimental error. The experimental testing scale extends over a range of eight decades when use is made of a temperature—time superposition principle predicted by the theory.By comparing the tensile creep and tensile strength curves for poly butyl methacrylate, it is possible to find the size of a segment as defined in the theory of viscoelasticity. One segment is found to contain about six monomer units.

ISSN:0021-8979    

DOI:10.1063/1.1722166

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

A light microscope study of etched germanium crystals has shown the dislocation distribution in them. The dislocations form a network in the crystal.The formation of small angle grain boundaries is discussed.Screw dislocations with large Burgers vectors have been found in some germanium crystals.

ISSN:0021-8979    

DOI:10.1063/1.1722167

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

The effect of plates of nitrides on the coercive force of iron has been determined. A pronounced particle size effect was observed. The maximum effect on the coercive force was produced by particles whose largest dimension was of the order of the domain wall thickness, &dgr;. For particles much larger than &dgr;, an expression given by Ne´el for the effect of inclusions is found to be valid. The results of this study are in good agreement with earlier results reported for the effect of carbides on the coercive force of iron.

ISSN:0021-8979    

DOI:10.1063/1.1722168

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

A new construction for an electromechanical transducer makes use of the Wiedemann effect to produce a magnetostrictive coupling between an input and an output winding, which are orthogonally disposed so that there is no direct inductive coupling between them. A first‐order theory of the operation of the transducer is given, and is used to derive an equivalent electrical circuit. The more important characteristics of the transducer are discussed in terms of the equivalent circuit, and are shown to be verified by experimental models. A method for deriving the equivalent circuit components by experiment is outlined, and the performance of a representative model is presented.

ISSN:0021-8979    

DOI:10.1063/1.1722169

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

In electron tubes utilizing long electron beams ionization of residual gases can produce a positive space charge which can partially or wholly neutralize the negative space charge of the beam. Such neutralization has, under special conditions, been successfully utilized in focusing electron beams. In certain electron devices requiring long electron beams, this type of focusing is inadequate and an axial magnetic field is employed to focus the electron beam. However, when magnetic focusing is used, the assumption is usually made that the electronic space‐charge fields of the beam are not neutralized by positive ions. Measurements have been made on a magnetically focused electron beam yielding information on (a) the longitudinal drainage of positive ions from the electron beam and (b) the degree of positive‐ion neutralization of the electron beam. It is pointed out that localized ion traps may be present in the beam if the beam diameter varies periodically along its length because of the applied magnetic field.

ISSN:0021-8979    

DOI:10.1063/1.1722170

出版商:AIP    

年代:1955

数据来源: AIP

摘要:

A new cathode is described consisting of an oxide‐impregnated nickel matrix. A sintered nickel matrix of controllable porosity is prepared and impregnated with solutions which precipitate a mixed carbonate within the matrix. The resulting cathode is a dispenser type with a minimum of surface coating. The cathodes can be activated by schedules which approximate those of a normal oxide‐coated cathode. Pulse‐emission tests of these cathodes show properties intermediate between the oxide‐coated cathode and theL‐cathode, and of the same order as the molded cathode described by McNair, Lynch, and Hannay.

ISSN:0021-8979    

DOI:10.1063/1.1722171

出版商:AIP    

年代:1955

数据来源: AIP