摘要:

Ultrasonic propagation in piezoelectric crystals as a function of conductivity and electric field has been theoretically described by White. Deviations from the theory are frequently encountered in materials such as CdS, and explanations in terms of trapping, transducer misalignment, dielectric relaxation effects, and nonuniformities in conductivity have been invoked. In this paper the effects of conductivity variations along (longitudinal) and perpendicular (transverse) to the direction of sound propagation on ultrasonic attenuation and amplification characteristics are considered. It is assumed that White's theory is valid locally. The effects of conductivity inhomogeneities are shown to be significant even for relatively small departures from uniformity. Longitudinal variations are especially important, because the electric field required to produce zero attenuation, which is frequently used for determining drift mobilities, shows a considerable variation with measured sample conductivity. A discussion in terms of experimental observations is presented.

ISSN:0021-8979    

DOI:10.1063/1.1709967

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A summary of the results of experiments to determine the magnetic aging characteristics of ``Chainstore'' memory elements as a function of time, temperature, and electrical exercise is presented. A phenomenological theory of anisotropy kinetics is constructed which provides an account of aging in magnetic films in agreement with the ``Chainstore'' experiments. The theory, which is capable of simple geometric representation, describes the kinetics by which the uniaxial anisotropy constant and skew angle change when a device is subjected to magnetic annealing at an elevated temperature. Conclusions are also drawn in regard to the phenomena of angle and amplitude dispersion.

ISSN:0021-8979    

DOI:10.1063/1.1709968

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Parametric coupling between ion and electron waves is studied by means of coupled‐mode theory. The coupling coefficients are determined. Two examples of parametric coupling are considered. One results in amplifying waves and the other in an absolute instability. The growth rate is calculated.

ISSN:0021-8979    

DOI:10.1063/1.1709969

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

An experimental study has been carried out to determine how the behavior of an elastic pulse produced by step‐function pressure loading of a single‐crystal lead bar, depends on the orientation of the crystal relative to the axis of the bar. It was observed that the strain‐time records had the same general characteristics as in the case of an isotropic bar. The effect of varying the crystal orientation was to change the velocity of the pulse, the amount by which it disperses, and its amplitude. For lead, the velocity and amount of dispersion can be changed by a factor of approximately two and the amplitude by a factor of five. Reasonable predictions of this behavior result from an approximate equation of motion developed on the same assumptions as used by Love for an isotropic bar.

ISSN:0021-8979    

DOI:10.1063/1.1709970

出版商:AIP    

年代:1967

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1709971

出版商:AIP    

年代:1967

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1709972

出版商:AIP    

年代:1967

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1709974

出版商:AIP    

年代:1967

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1709975

出版商:AIP    

年代:1967

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1709976

出版商:AIP    

年代:1967

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1709977

出版商:AIP    

年代:1967

数据来源: AIP