摘要:

The shock‐wave equation of state for a commerically available alumina‐filled epoxy has been determined in the stress range from 0.4 to 3.7 GPa via gas‐gun‐impact experiments. A linear fit to the shock‐velocity–particle‐velocity data yieldsU=2.78+1.63u. This curve lies between theU‐ucurves for an unfilled epoxy and for an alumina‐filled epoxy of higher density.

ISSN:0021-8979    

DOI:10.1063/1.325055

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A current‐noise equation has been derived as a function of resistor geometry under some assumptions which are acceptable in usual cases. This equation is described by the integral formula. We can estimate the magnitude of current noise of an arbitrarily shaped planar resistor by integrating the square value of current density with current and field potentials. Application of numerical integration of the equation to an L‐shaped resistor is described for instance.

ISSN:0021-8979    

DOI:10.1063/1.325056

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The effects of bimolecular (Langevin) recombination of charge carriers on the photocurrent in the constant‐voltage mode and on the surface potential decay in the open‐circuit (or xerographic) mode are studied. By solving the charge‐carrier transport equations numerically, it is possible to treat cases of practical interest, e.g., transport with recombination of more than 1CV’s worth of charge carriers, field‐dependent mobilities, and nonuniform generation of charge‐carrier pairs. The calculation of photocurrent in the constant‐voltage mode justifies Hughes’s use of the small‐signal formula in the interpretation of the large‐signal data. In the open‐circuit mode, the difference between the small‐signal formula and the calculation taking into account the space‐charge effects becomes more significant. The natures of the contrast potential and the reciprocity relation are examined.

ISSN:0021-8979    

DOI:10.1063/1.325057

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The anisotropy in the carrier mobility due to the presence of dislocations in III‐V compounds is determined using a method based on the equivalence of scattering energy loss and Joule heat created in the crystal. It is found that the mobility is a maximum perpendicular to the slip planes of 60° and 90° dislocations of both the &agr; and &bgr; types of dislocations. Screw dislocations do not cause any scattering and consequently do not affect the mobility through this mechanism.

ISSN:0021-8979    

DOI:10.1063/1.325058

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Using Bube’s formulation of the sensitization process in photoconductors a particular exchange mechanism is proposed that associates a shallow trap (excited state) and a recombination level (fundamental state). Expressions are deduced describing the photocurrent behavior as a function of temperature and illumination on both sides of the continuous thermal quenching zone; explicit formulations are also deduced for the upper and lower break points in the lux‐ampere characteristics. Such a phenomenological model is applied to photoconduction data on stannic oxide high‐resistivity samples. Optical quenching and pulsed photoconductivity are also emphasized in order to propose a consistent scheme for the localized levels in the forbidden energy band. It is shown from this work that localized transitions occur between three possible recombination states and a common excited state working with the conduction band as a shallow trap; associated lifetimes are measured.

ISSN:0021-8979    

DOI:10.1063/1.324709

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A rapid initial brightness slump and occasional subsequent recovery observed for the zinc‐doped zinc oxide phosphor undergoing cathodoluminescence is shown to depend on the surface work function. A quantitative model leads to an explanation of the dependence on surface potential in terms of field‐aided or retarded surface recombination. Evidence is given that temporarily recovered surfaces result from dynamic surface adsorption of barium.

ISSN:0021-8979    

DOI:10.1063/1.325059

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Superconducting transition temperatures of noncrystalline and partially crystalline Be‐Nb‐Zr alloys obtained by liquid quenching are reported. An increase of the transition temperatureTcto about 7 K from about 3 K was achieved in a partially crystalline Be20Nb15Zr65alloy. The enhancement ofTcis attributed to a proximity effect in a glassy Be‐Zr base matrix containing superconducting crystalline particles.

ISSN:0021-8979    

DOI:10.1063/1.325060

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

We present experiments on photon‐assisted tunneling and ac Josephson effect using microwaves in an energy range 1.05<h&ngr;<2.2 meV of the same order of magnitude as the superconducting gap 0.6<2&Dgr;<4 meV. We show that, whereas the photon‐assisted tunneling shows no anomaly in this region, the amplitude of the Josephson steps is strongly affected by the Riedel anomaly. Furthermore, the results under strong irradiations show an indirect evidence of a decrease of the gap value by the creation of quasiparticles.

ISSN:0021-8979    

DOI:10.1063/1.325007

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Amorphous rare‐earth RE(Gd, Tb, Dy, Ho, Er) ‐Fe films prepared by cosputtering were studied. The compositional analysis was obtained from known deposition profiles, x‐ray microanalysis, and the stripe‐width measurements. The structural variation with composition change was investigated by electron diffraction and dark‐field microscopy. The Curie temperatureTc, the compensation temperatureTcomp, the coercive forceHc, the uniaxial anisotropy energyKuand the static domain properties such as the stripe widthWs, the wall energy &sgr;w, and the exchange stiffness constantAwere investigated. The systematic variation ofTcandTcompassociated with a variation of composition and RE species could be described by the Heimanetal. model. The static domain properties could be interpreted in terms of the wall energy model and the mean field approximation of the exchange stiffness constantA.

ISSN:0021-8979    

DOI:10.1063/1.325008

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The application (or removal) of a magnetic field to the ferromagnetic Gd metal near its Curie point (293 K) will produce adiabatic heating (or cooling) of 14 K or isothermal expulsion (or absorption) of 32 kJ of heat per liter of Gd metal. A refrigerator and a heat engine are described for which porous Gd metal forms the rim of a wheel rotating into and out of a magnetic field region. Fluid forced to flow through the porous metal exchanges heat; the field and flow configurations are such that the metal executes a magnetic Stirling cycle allowing a very wide temperature span (many times 14 K) while maintaining the 32‐kJ/l capacity. Efficiencies approaching that of Carnot are expected at 1‐Hz rotation rates, resulting in 32‐kW/l refrigeration or heating capacity.

ISSN:0021-8979    

DOI:10.1063/1.325009

出版商:AIP    

年代:1978

数据来源: AIP