摘要:

A method is presented for the solution of the force‐free magnetic‐field boundary‐value problem in toroidal coordinates. An exact solution utilizing the Stokes' current function is given for the free space surrounding the toroid. The solution of the force‐free equations within the current‐carrying region of the toroid, however, requires the use of approximate methods. A suitable approximate method is developed which, also in accordance with physical considerations, exactly satisfies the requirement that the divergence of the current be zero. Galerkin's method is chosen for use in this approximation and use is made of the flexibility of this method to reduce the complexity of the approximation process. A sample calculation using this approximation method and the results of this calculation are described. This approximation method is found to give an accurate solution to the boundary‐value problem with a minimum of effort. An equation describing the forces still present on the surface of the toroid is developed and the limitation imposed by this equation on the reduction of these forces in the boundary‐value problem is noted.

ISSN:0021-8979    

DOI:10.1063/1.1714456

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Experiments with iron‐4% silicon wires containing preferred orientation with the ⟨110⟩ direction along the axis showed that under these conditions, extremely high magnetomechanical damping can be achieved at low strain levels in a torsion pendulum. The effect of crystallographic orientation on the damping was brought out by experiments on wires of square cross section of grain‐oriented commercial iron‐3% silicon alloy. Internal stress, produced by occluded hydrogen, markedly reduced the magnetomechanical damping in the iron‐4% silicon alloy but recovery began to take place after several days at room temperature. Changes in magnetic induction produced during the torsional oscillations by the inverse Wiedemann effect were measured to obtain an indication of the domain boundary movements. These latter experiments together with the damping experiments support the Summer and Entwistle model for the relationship between the magnetic field at maximum susceptibility, the saturation magnetization, the saturation magnetostriction, and the strain at which maximum damping occurs.

ISSN:0021-8979    

DOI:10.1063/1.1714457

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

This paper reports on simultaneous measurements of the reflectivity at normal incidence between 0.7 and 4.6 eV and the field effect of the surface conductance over a wide range of different surface conditions in germanium samples. In the wavelength region of direct interband transitions, the reflectivity is a function of the surface potential. It is concluded that the electric fields in the surface potential barrier are strong enough to change the optical properties of the surface region by Franz—Keldysh effect. A theoretical estimate based on this assumption reproduces the experimental results qualitatively. Since the effect is observed in reflection rather than in transmission, the influence of an electric field on interband transitions can be studied well above the fundamental absorption edge. It is shown that they are affected by an electric field in a way similar to the transitions which produce the fundamental absorption edge. It is further concluded that the field‐induced change in the absorption coefficient ``undercuts'' the field‐free absorption curve in the top portion of the fundamental absorption edge as predicted by the theory of the Franz—Keldysh effect.

ISSN:0021-8979    

DOI:10.1063/1.1714458

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

The general, linearized, coupled magnetoelastic equations for arbitrarily anisotropic, magnetically saturated insulators, which were derived in a previous paper, are specialized to the important case of a homogeneous, static biasing state. The equations applicable in the special case of a material in cubic classm3mare determined from the more general ones. Consideration of the material constants known for yttrium iron garnet allows the equations to be simplified considerably because many terms are negligible compared to a few which dominate. These latter equations are applied in the determination of the solution for the thickness vibrations of an infinite cubic plate, which is magnetized to saturation along a cube edge, for two special orientations of the magnetization direction relative to the surface of the plate. In both cases the driving field is normal to the magnetization direction, and it is shown that the fundamental solutions of the differential equations are coupled at the traction‐free and exchange‐torque‐free surfaces of the plate. However, when the fundamental solutions are circularly polarized, only those solutions which have the same sense of circular polarization are coupled. It is further shown, in both instances, that this boundary coupling disappears when the exchange interaction is neglected. In an Appendix, the procedure used to determine the influence of material symmetry on the equations is compared with a more accurate procedure.

ISSN:0021-8979    

DOI:10.1063/1.1714459

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

In the long‐wavelength limit, the current distribution in a thin‐film superconducting strip transmission line can be described by an inhomogeneous Fredholm equation of the second kind. By considering a fluxoid conservation derivation of this equation, physical insight into the structure of the kernel follows naturally. An approximate analytic solution to the integral equation is derived for a specified range of geometrical parameters commonly encountered in practice. The solution is obtained by making use of the Liouville—Neumann method of successive iterations and approximating the resulting series by a series involving powers of a defined coupling factor. It is shown that the critical current of the thin‐film superconducting strip transmission line, based on the calculations in the paper and a critical‐current‐density hypothesis, is underestimated by less than 10%.

ISSN:0021-8979    

DOI:10.1063/1.1714460

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

By rapid cooling from the melt, an amorphous phase has been obtained in palladium—silicon alloys containing 15 to 23 at.% Si. This phase is stable at room temperature and crystallization cannot be detected after one month at 250°C. With rates of heating greater than 20°C/min, rapid crystallization takes place at 400°C, with a heat release of approximately 1000 cal/mole. The electrical resistivity of an alloy containing 17 at.% Si at room temperature is 2.6 times that of the equilibrium alloy. The resistivity decreases linearly with decreasing temperature and is about 95% of the room‐temperature value at 2°K. Various factors involved in the retention of amorphous phases in rapidly quenched liquid alloys are discussed.

ISSN:0021-8979    

DOI:10.1063/1.1714461

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Drastic decreases in the thermal conductivity upon deformation similar to those reported by Sproull, Moss, and Weinstock have been found in NaCl, KCl, and NaF crystals. Unexpected differences in the frequency dependence of the phonon—defect relaxation times lead to an investigation of whether point defects, created during the deformation, might influence the phonon scattering. Studies of the recovery kinetics of the thermal conductivity paralleling those carried out on the mass density changes by Silverstone and Pratt on NaCl, and Vaughanet al.on KCl, seemed to exclude this. Experiments on bent LiF further supported the view of Sproullet al.that the thermal conductivity of deformed alkali halides is determined by coherent scattering of phonons off groups of dislocations.

ISSN:0021-8979    

DOI:10.1063/1.1714462

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

In the Ar II system transition probabilities are being calculated between states arising from the 3p44pand 3p44sconfigurations and between states of the 3p44sand 3p5configurations. We compare these calculations with previous theoretical and experimental work relating to the above‐mentioned transitions as well as to laser data. It is found that the various observed laser transition thresholds between the considered configurations are in reasonable agreement with the calculations. It appears that the various upper maser states are being pumped nonuniformly. It is also found that laser action should persist to rather high current densities. We estimate that, in 2‐mm‐diam tubes, output powers of at least 10 W/cm3of gas should be obtainable.

ISSN:0021-8979    

DOI:10.1063/1.1714463

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

The solubility of Ag in CdS has been measured under conditions of excess sulfur between 375° and 900°C. Also, the distribution coefficient of Ag between CdS and liquid Cd for dilute Ag concentrations has been measured between 500° and 900°C. In addition, the distribution coefficient has been measured at 800°C as a function of the composition of the Cd‐Ag alloy. These solubility measurements are interpreted to indicate at least two and probably three different forms of Ag in CdS. Diffusion profiles have been obtained between 300° and 500°C. The rate of diffusion of Ag shows a strong concentration dependence and is extremely rapid for dilute Ag concentrations. The profiles are discussed in terms of three independent steps in the incorporation of Ag in CdS.

ISSN:0021-8979    

DOI:10.1063/1.1714464

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Magnetostriction measurements, made with an interferometric dilatometer at room temperature, are reported for Bi, Sb, W, Nb, Mo, Ta, and V. The measurements were made using magnetic fields to 30 kG on high‐purity single crystals. The results for Bi agree qualitatively with those of Kapitza and Shoenberg. Generally, the Sb results were smaller. The values obtained for the transition elements were the smallest of those measured, but quantitative information on their magnetostrictive properties was obtained.

ISSN:0021-8979    

DOI:10.1063/1.1714465

出版商:AIP    

年代:1965

数据来源: AIP