摘要:

Thermo‐optic effects have been studied with changing temperature of a part of the liquid crystal in a cell. The light transmission through the liquid crystal is subject to hysteresis. The experiments show that the mesophase barely coexists with the solid phase, and that there are transparent, semitransparent, and opaque states in the solid phase. Two new information display devices have been made in experiments on the basis of the display characteristics of the liquid crystal and the hysteresis phenomena in the thermo‐optic effects. The display device in which the mesophase and opaque solid phase are used shows three functions: memory of entry information; variations of the memory state corresponding to a linear analogue value; and temporary erasure of information. The display device in which the transparent and opaque solid phases are used shows such functions that entry and permanent erasure can be done alternately, and that linear analogue information can be stored.

ISSN:0021-8979    

DOI:10.1063/1.1663057

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

We have generated and detected surface elastic waves at a fundamental frequency of 15.5 MHz on high‐resistivity silicon. The generation process involved the Lorentz forces exerted by a static magnetic field on the current‐carrying elements of an evaporated aluminum meander line whose spatial periodicity matched that of the surface waves. The detection process involved the motional emf induced by the magnetic field in the vibrating elements of the receiver meander line. The generation‐detection signal amplitude shows aB2dependence and is a maximum when the magnetic field is parallel to the direction of propagation.

ISSN:0021-8979    

DOI:10.1063/1.1663058

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A model for the surface space‐charge layer in thin ionic films has been extended to include the effects of divalent cation impurities and the association of impurity‐cation vacancy complexes. The potential, electrostatic field, and defect distributions are shown to be dependent on film thickness. The fate of photogenerated electrons and holes is discussed relative to the field and defect distributions.

ISSN:0021-8979    

DOI:10.1063/1.1663059

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A number of recent papers have discussed the Hall effect in a material consisting of high‐conductivity grains surrounded by thin low‐conductivity layers. These discussions were based on a model in which the grains are identical parallel cubes and the layers are of uniform thickness. The effective Hall constant of this model is approximately equal to the Hall constant of the grains. To test the effect of grain geometry on the effective Hall constant, the present paper discusses the Hall effect in the ``composite sphere'' material in which the grains are spheres of various sizes and the intergranular layers are formed from spherical shells. In this model also the effective Hall constant is approximately equal to the Hall constant of the grains, suggesting that, in general, the effective Hall constant is not strongly dependent on the grain geometry.

ISSN:0021-8979    

DOI:10.1063/1.1663060

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The problem of nonlinear coupling of surface waves in an insulating piezoelectric to an adjacent but mechanically isolated semiconductor is treated theoretically. A perturbation approach is used with a small‐signal nonlinear field expansion to obtain nonlinear coupling equations in terms of the linear material parameters and geometry of the system. The limiting case of the linear solution is related to other linear coupling theories. The special case of the surface‐wave convolver is treated and compared to other convolver theories.

ISSN:0021-8979    

DOI:10.1063/1.1663061

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Measurements of the prebreakdown currents have been made for highly polished stainless‐steel electrodes in an ultrahigh vacuum (UHV) at 10−9Torr as a function of electrode separation in the range 0.5–3.81 mm. Three sets of electrodes are employed to investigate the dependence of the prebreakdown current on the radius of curvature of the electrodes and the electrodes‐insulator distance. The breakdown potential is measured in UHV gaps over the gap length range 0.25–4.57 mm and in hydrogen, in the pressure range 3 × 10−9−1.5 × 10−2Torr, over the gap length range 0.38–0.76 mm. It has been found that the breakdown voltage, the electric field enhancement factor, and the prebreakdown current are independent of electrode‐glass‐insulator distance in the range 1–12.65 mm for a fixed gap length and a fixed radius of curvature of the electrodes. On the other hand, increasing the radius of curvature of the edge of the flat electrodes, at a fixed gap length, results in (i) large increases in the prebreakdown currents, (ii) increase in the electric field enhancement factor at the cathode, and (iii) a decrease in the breakdown voltage. The addition of hydrogen causes an increase in both the prebreakdown currents and the field enhancement factor, at a fixed gap distance. The field enhancement factor at the cathode is determined from the Fowler‐Nordheim field emission theory and was found, in all cases, to increase initially with increasing gap length until saturation is reached, and therein it remains constant. The breakdown potential of vacuum gaps is found to follow a linear field‐emission dependence on gap separation up to 1 mm. At higher gaps a transition to the Cranberg clump mechanism is observed with a dependence law on distance to the power of 0.45. The critical electrical breakdown field at the cathode in high vaccum is determined to be (7.8 ± 1.3) × 109V m−1.

ISSN:0021-8979    

DOI:10.1063/1.1663062

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The scattering problem of a perfectly conducting rectangular box illuminated by a linearly polarized electromagnetic plane wave is numerically solved through consideration of the vector magnetic field integral equation. Because the scattering obstacle is three‐dimensional and possesses no rotational symmetry, the vector integral equations consist of coupled scalar integral equations, which are reduced by the method of moments. Numerical results are presented for broadside incidence where symmetry arguments are used to produce an eightfold reduction in matrix size. Calculated currents and radar cross sections for a square plate and a cube show good agreement with measurements found in the literature. Techniques for analyzing the case of arbitrary incidence are also included.

ISSN:0021-8979    

DOI:10.1063/1.1663063

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The complete solution of certain diffraction problems can be found in the form of a Sommerfeld integral. To obtain solutions in this form, a kernel must be obtained. There are no doubt, many different techniques for finding them. However, in solving the two‐dimensional problem in a wedge‐shaped region, Malyuzhinets demonstrates that the kernel (except for a periodic factor) is the solution to a difference equation. He gives conditions and proves theorems about this fact. For such problems as he treats, no immediate method is clearly discernible for obtaining the solution of this difference equation. This paper will fill that void.

ISSN:0021-8979    

DOI:10.1063/1.1663064

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A new type of plasma instability is described in an electron‐beam ionized discharge. This instability occurs in the form of current oscillations in gas mixtures in which the dissociative attachment rate increases strongly with electric field. It has been observed experimentally in He : H2O 74 : 2 and in He : CO21 : 1 and 9 : 1 mixtures. A theoretical analysis which describes the onset of instability is presented, and a physical explanation is given. The region of instability in parameter space of ionization source functionSand electric fieldEis presented for certain gas mixtures. The transient phenomena in this type of discharge appear to be controlled by electron attachment, and a theoretical explanation of the observed current overshoot has been provided.

ISSN:0021-8979    

DOI:10.1063/1.1663065

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The theoretical problem of the transient behavior of a plasma injected, at constant current, into a trap‐free semiconductor is solved exactly. Coincident with the arrival of the propagating injected‐plasma front at the collecting electrode there is a cusp in the time‐derivative‐of‐the‐voltage‐vs‐time profile. At any instant of time, the relative field‐intensity distribution within the injected plasma region is the same as in the steady state.

ISSN:0021-8979    

DOI:10.1063/1.1663066

出版商:AIP    

年代:1974

数据来源: AIP