摘要:

The variation of 1/fnoise in thin, single crystal germanium filaments was investigated by using gaseous ambients to change the surface potential of the sample. The noise samples, having a thickness of only 4 &mgr;, were extremely sensitive to variations in the surface potential and exhibited large fractional changes of the total sample conductance as a result of the surface conductance fluctuations which were interpreted as the 1/fnoise. These experimental results showed a definite noise minimum when the sample surface potential corresponded to the sample conductance minimum. The rms conductance fluctuation varied roughly linearly with &Dgr;G, where &Dgr;Gis the increase of the sample conductance with respect to the minimum value. The slope of the curve for the condition of an accumulation layer on the sample surface was an order of magnitude less than that for the inversion layer. The amplitude of the accumulation noise agreed (within a factor of two) with the prediction of McWhorter's majority carrier trapping effect, but the inversion noise was an order of magnitude greater.

ISSN:0021-8979    

DOI:10.1063/1.1728422

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Field configuration and resonant frequency are determined for the lowest azimuthally‐independent mode of a coaxial cavity surrounding a circular tube, Several values of the width of the coupling gap are considered, and the central problem consists in determining the tangential electric fieldEtin that gap. It was found that the fields near the axis of the accelerator are quite insensitive to the actual profile ofEt, and that satisfactory results are obtained by assumingEtto be constant. The problem is repeated for a parallel plane configuration, with the purpose of investigating the influence of the flattening of the cavity. Computations show that the two configurations yield fairly similar results.

ISSN:0021-8979    

DOI:10.1063/1.1728423

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

The previously reported three‐parameter stress function has been applied to natural rubbers similar to those used for engineering purposes. These rubbers were selected to cover a harness range from 30 to 80 British Standard Degrees. A suitable choice of values for the parametersA, B, and &bgr; was found to give a good description of the stress‐strain characteristics in pure shear, and positive and negative stretch squeeze. This agreement applied up to the maximum possible strains. Unique functional relationships were found to exist between the three parameters and rubber hardness. Theoretically, it would be possible to reduce the three‐parameter stress function to a single‐parameter stress function. As previously reported, this confirms and hence is indirectly confirmed by Blackwell's results [Trans. I. R. I.28, 75 (1952)].

ISSN:0021-8979    

DOI:10.1063/1.1728424

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

A model and resulting theory for the exoemission of electrons from metal surfaces are presented. The model states that the exoemission is governed by the diffusion of vacancies in the metal, vacancies created by the abrasion. A vacancy, upon diffusing to the surface, may give up its energy to an electron. However, when in the same event, a photon also transfers its energy to the electron, the electron may be emitted. Experiments performed show the exoemission decay to be composed of two exponential decays. Both exponential decay constants vary with temperature according to the equation:k=Fe−E/RT.Here,Fis a constant andEis an activation energy which, measured, approximates 5.6 kcal/mole. A comparison between experiment and theory give the theory corroboration.

ISSN:0021-8979    

DOI:10.1063/1.1728425

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

The effect of hydrostatic pressure on the energy gap of Bi2Te3has been investigated in the pressure range one to 30 000 atm. From resistivity measurements as a function of temperature and pressure, it has been determined that the energy gap decreases from 0.171 ev at one atmosphere to 0.104 ev at 30 000 atm, corresponding to ∂Eg(0)/∂p=−2×10−6ev/atm.

ISSN:0021-8979    

DOI:10.1063/1.1728426

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

The pairwise coupling of modes in distributed systems such as the traveling‐wave parametric electron‐beam amplifier and many other types is shown to permit only two types of interaction. One type, called &bgr; coupling, results in the periodic interchange of the signal between the modes, as typified in the Kompfner‐null coupler. The other, &ggr; coupling, results in the exponential growth of the mode, as in the TWT and in the pump section of a parametric amplifier. The nature of the resultant interaction is a direct consequence of the underlying relations contained in the conservation law that applies throughout the system, i.e., in the separate parts of the system and that is independent of the various coupling coefficients. The ``rank'' and ``signature'' of the metric that expresses this conservation law is sufficient to determine the type of behavior. The direction of flow of energy in the coupled modes imposes a duality on these relations. Where modes of opposite directionality are coupled, &bgr; coupling causes system amplification, while &ggr; coupling causes system interchange. These relations are generalizations of effects that have been studied in detail for many specific systems. They are not, however, consequences of the details of the system but are, rather, the only alternatives possible under assumptions that are broad in scope and generally applicable to devices of interest.

ISSN:0021-8979    

DOI:10.1063/1.1728427

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Thermorheological simplicity is available for the extrusion flow curves of polymers in a way similar to the case of creep or stress relaxation. The true consistency curves for acrylic resin which were obtained from the extrusion flow curves at various extrusion temperatures by the help of the end‐correction factor &xgr; are superimposed by shifting along the logDw′ (whereDw′ is apparent maximum shear rate at the die wall). Thus the consistency curves by extrusion which are useful for evaluating the viscoelastic behavior of amorphous linear polymers can easily be determined over a sufficiently wide range of shear rates by the change of extrusion temperature.

ISSN:0021-8979    

DOI:10.1063/1.1728428

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Electron‐transparent dislocation‐free platelets of cadmium were deformed in tension parallel to the basal plane, inside an electron microscope, in the temperature range from +25° to −150°C. At high strain rates the crystals twinned. At low strain rates (≲10−2sec−1) the glide system depended on &agr;, the angle between the tensile axis and a close‐packing direction. For 0≤&agr;≲20° pyramidal glide on the (112¯2) [1¯1¯23] system occurred. For 20°≲&agr;≤30° a new glide system, (101¯1) [12¯10], was identified which has not yet been observed in large cadmium crystals. Edge dislocations with a ⅓[12¯10] Burgers vector moved across the entire crystal on (101¯1) planes without multiplying or forming obstacles to further glide. Occasionally, at high strain, fracture occurred on a (101¯1) plane. The observations suggested that, in the temperature range studied, the flow stress for (101¯1) [12¯10] glide was considerably lower than that for prismatic glide on the (101¯0) [12¯10] system, slightly higher than that for (112¯2) [1¯1¯23] glide, and independent of strain for a given temperature.

ISSN:0021-8979    

DOI:10.1063/1.1728429

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

The (112¯2) [1¯1¯23] glide system was studied in thin, dislocation‐free cadmium platelets by transmission electron microscopy and compared with observations on zinc platelets. Screw dislocations with a ⅓<1¯1¯23> Burgers vector were formed at the edges of the crystal and moved primarily on {112¯2} planes. Elongated, sessile dislocation loops were formed on basal planes when screws developed large jogs during cross‐glide. Smaller numbers of secondary ⅓<1¯1¯20> dislocations were also formed and moved on basal planes. Observations in the temperature range −150° to +25°C showed that the behavior of the long loops and of the other dislocations in cadmium and zinc varied with temperature as follows: (1) At temperatures lower than ∼−120° in Cd and ∼−80° in Zn, the long loops were stable and practically no recovery took place. High densities of loops and networks of secondary dislocations were built up and hardened the crystal. (2) In the intermediate temperature range −120° to −40° for Cd and −80° to +10° for Zn, the long loops split up into rows of circular loops, which were then stable. The process involved the pipe‐diffusion of material around the long loops and required a lower activation energy than that for climb. Some of the circular loops were found to contain stacking faults. (3) At high temperature, above ∼−40° for Cd and ∼+10° for Zn, circular loops annealed out by climb with an activation energy ∼0.8 ev for Cd and ∼0.95 ev for Zn; secondary dislocation networks dispersed by climb; and the dislocation density, and therefore the work‐hardening, was small.At high beam intensities dislocation loops often grew by climb, probably as a result of the formation of point defects by ion bombardment, the ions being formed by the interaction between electrons and residual gas molecules.

ISSN:0021-8979    

DOI:10.1063/1.1728430

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Surface waves are defined as waves exponentially decreasing on both sides of a plane interface. It is shown how all such waves can be generated from a single Hertz vector perpendicular to the interface. The relations between the propagation parameters of the waves and the material constants are derived in a general case which includes media with different magnetic permeabilities. The condition for the existence of surface waves is derived.

ISSN:0021-8979    

DOI:10.1063/1.1728431

出版商:AIP    

年代:1961

数据来源: AIP