摘要:

The changes that occur in the magnetic properties of iron‐cobalt‐nickel alloys when they are annealed in a magnetic field, have been investigated for a series of these alloys. The maximum change for the iron‐nickel alloys occurs between 65 and 70 percent nickel and is evidenced by a large increase in maximum permeability and a hysteresis loop of rectangular shape. All of the alloys with Curie points above 500°C and with no phase transformation have their properties similarly changed. Thorough preliminary annealing enhances the effect. With an extreme preliminary anneal of 1400°C for 18 hours specimens of 65 permalloy have been obtained with the record value of maximum permeability of 600,000. The magnetic characteristics of materials treated in this way are relatively insensitive to stress. These magnetic characteristics are, however, highly anisotropic; the maximum permeability in one direction is as much as 150 times as large as that at right angles.

ISSN:0021-8979    

DOI:10.1063/1.1745332

出版商:AIP    

年代:1935

数据来源: AIP

摘要:

The magnetization of two alloys, as affected by heat treatment in a magnetic field at various temperatures, is examined in some detail in order to elucidate the nature of the accompanying changes which result in some cases in a 30‐fold increase in maximum permeability. Theexperimentsshow that these alloys (one containing approximately 35 percent iron and 65 percent nickel, the other 20 percent iron, 60 percent cobalt and 20 percent nickel) can be effectively heat treated in a magnetic field of 10 oersteds if the temperature is above 400°C and below the Curie point of the alloy. The time during which the magnetic properties change has been measured at different temperatures and is found to vary according to the equation &tgr;=AeW/kT. The experiments areinterpretedin terms of the domain theory of ferromagnetism. The changes which occur are due to the relief of magnetostrictive stresses which arise when the material becomes ferromagnetic upon cooling through the Curie point or when an external magnetic field is applied, and the relief comes about by plastic flow or diffusion in the separate domains. The values ofA(about 10−12second) andW(2.1 electron volts) are the same as those determined by Bragg and Williams for the above equation which also gives the time necessary for the establishment of a superstructure in alloys. The relation between the two processes, establishment of superstructure and the relief of magnetostrictive strains, is pointed out.

ISSN:0021-8979    

DOI:10.1063/1.1745333

出版商:AIP    

年代:1935

数据来源: AIP

摘要:

A general solution is presented for the displacements induced in any piezoelectric medium by static electric fields which are constant throughout the medium. This solution is then specialized to the case of &agr;‐quartz. The solutions for &agr;‐quartz have been used by the second writer in an accurate remeasurement of its piezoelectric moduli. The piezoelectric behavior of &agr;‐quartz is found to be closely predicted by these solutions.

ISSN:0021-8979    

DOI:10.1063/1.1745334

出版商:AIP    

年代:1935

数据来源: AIP

摘要:

Certain metals projecting through a mercury surface are known to have the property of ``anchoring'' the cathode spot. A variety of metals have been examined for this ability and it has been found to exist for all of them tried, Fe, Pd, Zr, Pt, Cr, Cb, Ir, Mo, Ta, W. The property depends upon wetting of the metal by the mercury, and this in turn depends upon having a clean metallic surface. The spot lengthens into a fine bright cathode line (C.L.) at the meniscus edge. These metals differ in the ease of cleaning and of maintaining cleanliness. Electrolysis, hydrogen firing, vacuum firing and ion bombardment were used in different cases. The first five show attack by the cathode spot, the Mo shows slight disintegration. Besides the bright line spectrum, the C.L. has also a strong, continuous spectrum from red into ultraviolet which is quite different from hot body radiation. The C.L. consists of a multitude of small emitting areas which are in constant rapid and chaotic motion. The details as shown by moving film photographs differed with the anchor. Cb showed the most clear‐cut phenomena. Its individual spots passed 0.22 amp. each and they moved with a predominant velocity of 46 cm/sec. They oscillated in intensity with a period of the order of 10−4sec. Their current density was ∼9000 amp./cm2. The behavior of the C.L. under different kinds of varying current has been observed, and the change in C.L. length with current plotted. Increasing the arc current while maintaining the length of C.L. fixed resulted in a lowering of the C.L. even to below the pool level and to the formation of a trough in the liquid outside the C.L. This helps explain the mechanism of spot freeing at large current densities and gave the upper limit for a circular anchored spot at about 40 amp./cm.

ISSN:0021-8979    

DOI:10.1063/1.1745335

出版商:AIP    

年代:1935

数据来源: AIP

摘要:

The most suitable characteristics for steady deflection and electrometer use are discussed separately. For the former case it is shown that the mutual conductance may be increased three times the recognized value. When the tube is used as an electrometer a grid current as low as 10−17ampere may be obtained with a voltage sensitivity of 10−4volt/division. The capacity of the grid system being only 3×10−12farad a highly satisfactory electrometer results.

ISSN:0021-8979    

DOI:10.1063/1.1745336

出版商:AIP    

年代:1935

数据来源: AIP

摘要:

In continuation of a previous paper, the equation of propagation of a nerve impulse is studied now under more general assumptions about the physical mechanism of excitation. Instead of H. A. Blair's excitation formula, used previously, a more general formula, proposed by the author elsewhere and having several advantages, is considered. It is found in this case, that the velocity of propagation is notstrictlyconstant, but tends asymptotically to a constant value. This asymptotic value is reached practically within 10−3sec. after the propagation of the impulse begins, and the initial velocity is only slightly different from the asymptotic value. The expression for this asymptotic value is in the first approximation identical with the expression deduced previously, and inasmuch as the latter was found to agree with experimental data, the same remains in the present case.

ISSN:0021-8979    

DOI:10.1063/1.1745337

出版商:AIP    

年代:1935

数据来源: AIP