摘要:

A method is presented to evaluate quantitatively the operation of the invertron, a recently developed device for measuring directly the lifetimes of quantized systems lying in the nanosecond range. The device consists of two electrodes in cylindrical geometry, the inner positive‐grid electrode being 45% transparent to electrons while the outer is an rf‐heated cathode.

ISSN:0021-8979    

DOI:10.1063/1.1658141

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Using the London theory we investigate the inductance of a system consisting of a long straight conductor of uniform cross section situated parallel to a nearby superconducting plate. Explicit formulas are derived for the particular cases of conductors having cylindrical, rectangular, and thin‐film cross sections and the limitations of the theory are discussed. The conclusions indicate that measurements of the inductance of such a system can be used to determine the penetration depth of a superconductor.

ISSN:0021-8979    

DOI:10.1063/1.1658142

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The eddy‐current method for measuring electrical resistivity is extended to situations in which the resistivity is anisotropic. It is shown that in most cases of interest in practice, one can obtain the full resistivity tensor from eddy‐current measurements.

ISSN:0021-8979    

DOI:10.1063/1.1658143

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Measurements of internal friction and Young's modulus between −210° and 700°C have been carried out at frequencies 130–185 kHz on U4O9single crystals. Two pronounced internal friction peaks were observed, one at 60° and the other at −175°C. The peak at the higher temperature seems to be due to a phase transition of U4O9. The factors affecting the peak suggest that it is not caused by a relaxation process. It is suggested that some cooperative movements of interstitial oxygen ions in some lattice planes cause such a transition. The peak at the lower temperature is due to a relaxation effect. A rough calculation of the activation energy gave 0.034 eV. In addition, the results of the electrical conductivity measurements at low temperatures (25°–−160°C) gave the activation energy of 0.057 eV, in an approximate agreement with the one derived from the internal friction measurements. This indicates that the relaxation process involves activated charge transfer between U5+and U4+ions (hopping motion of electronic holes). It is tentatively proposed that stress‐induced ordering of a defect complex involving U5+ion and some oxygen ion(s), which produces a ⟨111⟩ elastic distortion in the lattice, gives rise to the relaxation effect.

ISSN:0021-8979    

DOI:10.1063/1.1658144

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The long‐range interaction between localized defects in an infinite elastically isotropic solid is derived. It is shown that when the defect has cubic symmetry the interaction energy is proportional to the inverse fifth power of the separation, in agreement with the result previously obtained from discrete lattice theory. The difference in magnitude of the interaction derived by the two methods is attributed to phonon dispersion.

ISSN:0021-8979    

DOI:10.1063/1.1658145

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The generation of misfit dislocations has been investigated on epitaxial silicon wafers with boron‐doped substrates, as a function of the film thickness and the misfit resulting from the difference in lattice parameters between the film and the substrate. Critical values of the film thicknesshcand of the misfitfcrequired to form misfit dislocations were found to behc=2.4–‐2.9 &mgr; for the interfacial misfit of 0.019% andfc=0.003–0.006% for relatively large film thickness, where the interfacial energy approaches that of infinitely thick film. These results were analyzed in terms of van der Merwe's theory and a good agreement was found between the experiment and the theory. The density of misfit dislocations was observed to increase with the interfacial misfit or with the film thickness. The relation between bending of the specimens associated with the misfit and the film thickness was studied. Some properties of misfit dislocations are described.

ISSN:0021-8979    

DOI:10.1063/1.1658146

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

An analysis of the behavior of concentric circular dislocation glide loops of opposite sign lying on parallel slip planes has been performed by numerical methods. At large loop radii, a critical stress exists above which the loops may pass one another. This stress decreases as the slip plane spacing between the loops increases or as the loop radii increase. Below the critical passing stress the loops become coupled. In the absence of a lattice friction stress the coupled loops continuously shrink and ultimately vanish. If, on the other hand, such a friction stress exists, there also exists a critical loop radius above which the coupled loops remain permanently stuck within the crystal.

ISSN:0021-8979    

DOI:10.1063/1.1658147

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A mathematical analysis for the accumulation of tracer as diffused through a thin metallic slab by grain‐boundary diffusion is presented. Boundary conditions on the side where the tracer is deposited consist of a small depletable source, and the grain‐boundary concentration is enhanced by surface diffusion. Due to the mathematical difficulty associated with boundary conditions for combined grain‐boundary and surface diffusion, two cases are studied: No accelerated surface diffusion and infinite surface diffusivity along with finite grain‐boundary diffusivity. The difference between the accumulated tracer for the two cases is similar to the contribution from lattice diffusion only. Thus, for a relatively short diffusion time, grain‐boundary diffusion analyses without surface diffusion complications are correct.

ISSN:0021-8979    

DOI:10.1063/1.1658148

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Results are presented of a study of the (normalized) complex dielectric coefficient, and related parameters, of unidirectionally frozen artificial sea ice having salinities from 4 to 20‰. The frequency dispersion was investigated between 20 Hz and 100 MHz at temperatures from −35° to −12.5°C. An unusual measurement cell, which becomes incorporated into the ice as it forms, is described and justification offered for its use. The frequency dispersion of the real part of the dielectric coefficient may be considered in three parts. Large values (105to 106at −15°C, and 103to 104at −35°C) were observed at 20 Hz, falling slightly more rapidly than (frequency)−1up to 5 kHz. Between 5 and 500 KHz most curves exhibited a distinct downward concavity (which was more prominent at lower temperatures), values dropping from between 103and 104to the order of 102over this range. At higher frequencies the rate of decrease was smaller, values of 10 or less being observed at 100 MHz. Loss factors (values at 20 Hz: 106to 107at −15°C, and 104to 105at −35°C) in most cases decreased approximately as (frequency)−1over most of the frequency range. Loss tangents, which were slightly larger at higher temperatures, were of order 10 below 1 MHz, dropping to less than 1 above 10 MHz. The curves for this parameter exhibited two temperature‐dependent maxima. The electrical properties changed most rapidly with temperatures near −23°C, the NaCl deposition temperature.

ISSN:0021-8979    

DOI:10.1063/1.1658149

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The temperature and pressure dependence of the dielectric constant &egr;′ of CdF2has been measured forT=4°−300° K (at atmospheric pressure) andP=1–2000 bar (at room temperature). The frequency dependence of the real and imaginary parts (&egr;′ and &egr;″) has been investigated up to 100 MHz.

ISSN:0021-8979    

DOI:10.1063/1.1658150

出版商:AIP    

年代:1969

数据来源: AIP