摘要:

A study of shock‐loaded Armco iron has been made using a flash radiographic technique. Oblique shock waves were produced in iron samples by the collision of an explosively loaded driver. Details in the radiograph were compared qualitatively with the shock configuration to be expected from the Hugoniot curve of iron. The double shock structure of iron and the rarefaction shock were observed.

ISSN:0021-8979    

DOI:10.1063/1.1702591

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

The ion‐drag pumping problem is re‐examined. New theoretical results are presented for both the static and dynamic cases: in particular, the phenomena of ``cut‐in'' voltage and hydrodynamic instability are shown to behave in a fashion different from that previously believed. The predictions of the theory are evaluated in the light of the published experimental evidence.

ISSN:0021-8979    

DOI:10.1063/1.1702592

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

The problem of the electrical pumping of a dielectric liquid along lines of the applied field is considered experimentally. The pressure generated by typical pumps are studied in detail, often in novel fashions; e.g., by varying the liquid flow velocity, the electrode spacing, or the liquid temperature while the applied field is held constant. It is shown that the experimental data are consistent with an ion emission model of the phenomenon, but that the emission is not necessarily space‐charge‐limited; photomicrographs are presented to show the effects of the emission process on the electrodes.

ISSN:0021-8979    

DOI:10.1063/1.1702593

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Tunnel field emission is here proposed as a model for rectification in rutile diodes. This model has been previously applied by Mead [C. A. Mead, J. Appl. Phys.23, 646 (1961)] to rectification phenomena observed with tantalum and aluminum oxides. In the case of rutile diodes it was found that the forward characteristics were explained by the tunnel field emission mechanism.

ISSN:0021-8979    

DOI:10.1063/1.1702594

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

In two previous papers the stress‐strain‐time relations with respect to variables of temperature, concentration, andpH were given for attapulgite suspension in water, in terms of rheopexy (dilatancy) and thixotropy. Stress relaxation and scriptS‐like curves showing both thixotropy and rheopexy were determined at various temperatures. Yield‐point viscosities for the rheopectic and thixotropic curves showed activation energies of about 1 and 2 kcal, respectively. In the present paper Eyring's rate theory of viscosity is briefly discussed in terms of the well known generalized‐viscosity equation&eegr;=i=1iXi&bgr;i&agr;isinh−1&bgr;is˙&bgr;is˙, which is applied successfully to given flow curves. A new method for determining the parameter &bgr;iis discussed.

ISSN:0021-8979    

DOI:10.1063/1.1702595

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

The ultrasonic attenuation in SAE 4150 steel has been measured from 5 to 100 Mc at various stages in its heat treatment. The attenuation is changed by changes in grain diameter and anisotropy. The anisotropy of grains transformed to martensite is lower than pearlite, while martensite itself becomes less anisotropic upon tempering. The dependence of the attenuation upon frequencyf, grain diameterD, and anisotropy &mgr; agrees well with the theory of Lifshits and Parkhomovskii, who predict Rayleigh scattering proportional to &mgr;2D3f4for &lgr; > 2&pgr;Dand another type proportional to &mgr;2Df2for &lgr;<2&pgr;D. The anisotropy factor &mgr;2is lower by a factor of 10 for hardened, tempered steel than for iron.

ISSN:0021-8979    

DOI:10.1063/1.1702596

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Critical current densitiesJcfor restoration of detectable resistance have been measured for super‐conducting Ti‐Mo alloys at 1.2°K in steady magnetic fields up to 30 kG, and for approximate Mo concentrations of 6, 9, and 16 at. %. Cold‐rolling is observed to increase theJcvalues considerably and, in the case of Ti‐16 at. % Mo, to result in a marked ``anisotropy'' ofJcsimilar to that observed in many other cold‐rolled alloy superconductors: at high fieldsJcis essentially a maximum or minimum when the applied transverse magnetic field (H⊥J) is, respectively, parallel or perpendicular to the rolling plane, apparently independent of specimen geometry. This suggests thatJcis very sensitive to the relative orientation of the field and an anisotropic defect structure normally introduced during cold‐rolling. TheJcanisotropy does not appear to be critically dependent upon the angle between the current and the rolling direction for current directions in the rolling plane and can apparently be suppressed by martensitic transformation during cold‐rolling. Although an explanation ofJcanisotropy in cold‐worked alloys does not fall within the scope of homogeneous alloy‐negative surface energy theories, the ``upper'' resistive critical fields [Hr(J=1A/cm2)] for these alloys, ranging from 26.5 to 64 kG, are in fair agreement with predictions of the Ginzburg‐Landau‐Gor'kov‐Abrikosov theory.

ISSN:0021-8979    

DOI:10.1063/1.1702597

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Cathode emission was studied at over 1 atmosphere pressure into He and A plasmas at 100‐ to 500‐A total current. The cathode spot temperature and current density were measured by a high speed photometric method developed for this purpose. A low vacuum thermionic work function was found to be a most important criterion for long cathode life. Emission current densities of the order of 100 to 200 A/mm2were found to be independent of total current; surface temperature, typically, increased 300°C for the 5‐fold increase in current and was approximately 2500°C in argon for a thoriated W cathode. Calcium‐barium‐aluminate‐impregnated W cathodes operated well in such an arc, remaining at very low temperatures, confirming the results obtained with the thoriated W.

ISSN:0021-8979    

DOI:10.1063/1.1702598

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

A connection between some ferroelectric switching functions and the Sievert integral is established. Switching functions of Landaueret al.and of Franklin are computed and discussed.

ISSN:0021-8979    

DOI:10.1063/1.1702599

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Electrical resistivity of polycrystalline scandium has been studied between 1.38° and 358.8°K. The measurements show a step‐type anomaly in the resistivity between 4 and 5°K and possibly a very small minimum at 9.5°K. Considerable hysteresis in the electrical resistivity exists at low temperatures, depending upon the previous thermal history of the sample. It is very likely that these anomalies may be associated with a super‐conductive substructure resulting from the presence of small amounts of tantalum as an impurity. However, the possibility that the anomalous behavior is due to the occurrence of some cooperative magnetic states at low temperatures cannot be completely eliminated at the present time. Between about 80° and 360°K the intrinsic resistivity of scandium is describable by the Bloch‐Gru¨neisen formula with Debye &thgr; of 275°K. At lower temperatures the temperature dependence of the intrinsic resistivity is consistent with expectations derived from the interband electron‐phonon scattering. Ziman's reduced electrical resistivity at 300°K is calculated to be 50.8.

ISSN:0021-8979    

DOI:10.1063/1.1702600

出版商:AIP    

年代:1963

数据来源: AIP