摘要:

Elastic resonances in NH4H2PO4(ADP) have been studied by an optical method which depends on the elasto‐optic effect. Displacement models of the overtone resonance modes have been inferred from the optical patterns. For a (zxt) 45° plate, the transmission patterns for the stronger resonances are consistent with the picture of two longitudinal standing waves traveling at right angles; the reduced frequency constants are independent of the mode numberm, and the sample resonates asm2Lame´ plates. For a (zxt) 0° plate, the greater part of the transmission patterns can be explained in terms of two shear standing waves traveling at right angles; the reduced frequency constants depend on the mode numbern, but they tend to become constant asnincreases. For both types of plate, the configuration of the electrodes is important in determining which modes are excited and to what extent.

ISSN:0021-8979    

DOI:10.1063/1.1713586

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

This paper describes a simple technique for determining the coefficient of kinetic friction for extremely small displacements. An attempt was made to obtain more information about the transition stage between the coefficients of static and kinetic friction. If the force of static friction persists over small distances before falling to the lower value of the kinetic friction, such distances in the case of steel on steel are probably smaller than 5×10−6cm. With the exception of very soft metals, higher values of the coefficient of static friction were obtained for impulsive forces than for slowly increasing tangential forces.

ISSN:0021-8979    

DOI:10.1063/1.1713587

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

Electrical conductivity measurements between 90° and 800°K have been performed on single crystals of uranium dioxide with compositions in the range UO2.000–UO2.007. The activation energy calculated from the ln&sgr;Tvs 1/Tcurves decreases from 0.34 to 0.19 eV with increasing excess oxygen content. Hall effect measurements by dc and ac techniques yielded no measurable response, and indicate that the Hall mobility is smaller than 0.015 cm2V−1sec−1at room temperature. This result and a consideration of the fundamental parameters determining the transport mechanism suggest an interpretation based on small polaron theory.

ISSN:0021-8979    

DOI:10.1063/1.1713588

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

The magnetic susceptibility of Eu2O3has been studied as a function of temperature between 300° and 1300°K. The results can be satisfactorily explained by the Van Vleck theory of paramagnetism with Judd's energy levels of free Eu3+ions.

ISSN:0021-8979    

DOI:10.1063/1.1713589

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

A spectrophotometric method for determining the concentration of chromium in oriented and unoriented single ruby crystals is described. It makes use of the absorption coefficients for the blue and green bands and for the red lines at ∼300°K. The coefficients are based on concentration data obtained by three independent methods.

ISSN:0021-8979    

DOI:10.1063/1.1713590

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

When Permalloy films are annealed, theHcandHkof the as‐deposited films are observed to decrease and &agr;, the dispersion angle, is seen to increase. Electron diffraction studies show the development of long‐range order in these films with annealing, as evidenced by the appearance of superlattice lines. The changes inHkand &agr; can be partly explained by this transition from short‐ to long‐range order, and a model is proposed.

ISSN:0021-8979    

DOI:10.1063/1.1713591

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

Two variable‐state methods have been developed which both offer the advantage of producing negligible thermal disturbance in a solid during measurement. The first is a curve‐fitting method. It makes use of the fact that the initial temperature rise, due to a constant flux plane heat source, at points within a certain region of a finite solid is essentially the same as that in an infinite solid. Temperature records obtained from such points thus can be analyzed with the assumption of linear heat flow, and used for calculating all thermal properties of the solid.The second is a pulse method. If a hot or cold pulse is applied to a plane surface of a specimen, the rise or drop of temperature at some distance from the surface will pass through a maximum; from the time of the maximum the thermal diffusivity can be calculated. The main advantage of this method is the ease of specimen preparation.

ISSN:0021-8979    

DOI:10.1063/1.1713592

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

An explanation of pressure‐induced polymorphic transitions from close‐packed structures to nonclose‐packed arrangements of atoms is attempted and compared with recent experimental data for ytterbium.

ISSN:0021-8979    

DOI:10.1063/1.1713593

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

The dynamic stress‐strain relation of aluminum was measured in compression to a stress of 22 kbar using plate impacts to induce uniaxial strain. The results were compared to a uniaxial strain curve constructed from elastic moduli and quasistatically determined stress‐strain curves. The dynamically determined stress‐strain relation was not unique in that it varied as a function of the magnitude of the induced stress and was offset from the quasistatic curve. These small deviations are attributed to strain rate effects. The rate effects were further demonstrated by observing the transmission of an elastic compression stress wave in aluminum after the aluminum was dynamically stressed beyond the yield point and held at constant strain for a period of approximately 2 &mgr;sec.The dynamic stress‐strain relation was measured upon the release of a shock induced compressive stress of 10.5 kbar to a tension of −9 kbar by observing the effects of tensile stress waves. The deviation of the unloading stress‐strain relation from that predicted by simple elastic‐plastic theory is attributed to strain rate and Bauschinger effects.

ISSN:0021-8979    

DOI:10.1063/1.1713594

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

A brief description of an Ampe`re electrodynamic experiment is given and some connection with it is indicated in such effects as those of: Wiedemann, Matteucci (MS), and Hall. Experimental arrangements and procedures in the MS study of ferromagnetics is described. The essential differences in the MS of different ferromagnetics are cited. An interpretation of the MS has been based on the well‐known effect of the exchange energy in ferromagnetic metals dependent on the interatomic distances instead of a phenomenological interpretation in terms of the magnetostriction.

ISSN:0021-8979    

DOI:10.1063/1.1713595

出版商:AIP    

年代:1964

数据来源: AIP