摘要:

In this paper, we examine the coupled electromechanical responses of transversely isotropic linear piezoelectric materials. In particular, we consider the boundary–initial‐value problem which is consistent with the transverse‐ or normal‐mode experiment and evaluate the effects of lateral boundary conditions on the electrical output of a rectangular specimen of such a material. The solution of the problem entails the simultaneous solution of the wave equation and the circuit equation. This is accomplished via numerical methods. Our results show that the electrical output of the specimen depends markedly on the lateral boundary conditions in that its value and its duration can either be enhanced or degraded without having to alter the mechanical loading. These observations are of importance, particularly in design considerations and in the interpretation of experimental information.

ISSN:0021-8979    

DOI:10.1063/1.324622

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A new method for measurements of ultralow currents in the audio‐frequency range (from dc up to over 104Hz) has been developed. The combined use of a ferromagnetic current transformer and of a superconducting flux transformer together with a rf‐biased SQUID allows measurements of currents as low as 10−14A. A detailed circuital analysis and considerations on the input impedance of the device are presented. The agreement between predictions and experiments is quite good. The measured noise level beyond the low‐frequency region keeps at values typical of commercial SQUID’s.

ISSN:0021-8979    

DOI:10.1063/1.324623

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A lower bound is derived for the length of an autoresonant accelerator designed to produce relativistic positive ions of a given energy. The ion kinetic energy is found to scale as the 2/3 power of the distance along the accelerator in the nonrelativistic limit and as the 1/3 power in the ultrarelativistic limit. For protons trapped in a negative‐energy Doppler‐shifted cyclotron wave that enters the accelerator with a phase velocity of 0.05c, we estimate that GeV energies can be attained only if the accelerator length exceeds 75 m, which is roughly 10 times greater than previous estimates made by the authors of this collective acceleration scheme.

ISSN:0021-8979    

DOI:10.1063/1.324624

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Type‐IIb diamonds are partially compensatedp‐type semiconductors at room temperature. Radiation damage makes such diamonds highly insulating. This effect can be exploited to make a fast radiation detector which is sensitive both to light and charged particles. This is done by confining the radiation damage to a narrow band within the crystal. The decay time is less than 3×10−10s after illumination with photons of energy 3.68 eV (337 nm). The fact that ’’counting diamonds’’ can now be manufactured from the relatively abundant type‐IIb diamonds, both natural and synthetic, will be of some interest, since natural counting diamonds are very rare.

ISSN:0021-8979    

DOI:10.1063/1.324625

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

We show how the characteristics (index and thickness) of an optical step index waveguide can be determined very easily, no calculations being necessary. The method is compared to some results published in the literature, and the agreement is found to be better than 5×10−3with other methods.

ISSN:0021-8979    

DOI:10.1063/1.324626

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The kinetics of the O+2first‐negative band laser due to near‐resonance charge exchange between He+2and O2are presented. It can be excited in the afterglow of a discharge in a high‐pressure He and O2mixture (He≫O2). Gain calculation, however, is presented for discharges due to high‐energy proton beams advocating their use for high‐pressure gas lasers. In addition, a comment is made on the disappearance of 3914 laser lines with increasing N2density in the He+2+N2charge exchange laser.

ISSN:0021-8979    

DOI:10.1063/1.324627

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The short‐range shrinking of a laser beam in a solid by relativistic self‐focusing generates intensities which accelerate highly charged ions to MeV energies in agreement with experiments. Limitations at higher energies due to ionization, relativistic limits, and Debye length are given.

ISSN:0021-8979    

DOI:10.1063/1.324628

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

This paper presents a study of the dispersion relation for propagation in the TM0mmode along a dielectric‐rod waveguide immersed in collisionless plasma with a strong static magnetic field in the direction of the rod axis. Dispersion characteristics, covering all plasma densities, are plotted for a typical value of the dielectric constant (&egr;d) of the rod. A discussion of how the characteristics would change if &egr;dis varied is also presented. In particular, the special case in which &egr;d=1 and the dielectric rod is replaced by a vacuum channel is investigated in detail.

ISSN:0021-8979    

DOI:10.1063/1.324629

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Thin films of Al, Pb, Bi, and Sn representing a range of bulk crystal structures and low‐melting‐point metals were vacuum‐vapor deposited onto air‐cleaved (001) NaCl substrates in the presence of dc electric fields applied in the plane of the deposit (using detached electrodes) ranging between 102and 103V/cm even considering displacement current effects during evaporation. Such experiments, conducted at room temperature (25 °C) within short vaporization periods in order to avoid thermal‐induced enhancement of bulk and surface conductivities in the NaCl substrate, and time‐dependent gradient losses, showed no significant or detectable effects on residual microstructures or crystal structure upon examination and comparison of representative film samples that have an approximate thickness of 1200 A by transmission electron microscopy.

ISSN:0021-8979    

DOI:10.1063/1.324630

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Measurements on the Hall and the magnetoresistive effect in Fe‐Si amorphous films are described. The spontaneous Hall constantRsincreases as the Si content increases. A sensitive irreversible change ofRswas observed by annealing.Rsincreases by crystallization. The magnetoresistive effect &Dgr;&rgr;/&rgr; is low but &Dgr;&rgr; is comparable to those of Fe‐Ni crystalline alloys.

ISSN:0021-8979    

DOI:10.1063/1.324631

出版商:AIP    

年代:1978

数据来源: AIP