摘要:

Periodic domain patterns have been generated by surface ultrasonic waves in a nematic liquid crystal film. Rotational vortex motion of the fluid due to acoustic streaming and the resultant shear flow alignment of the director are believed to be responsible for the observation.

ISSN:0003-6951    

DOI:10.1063/1.88847

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

The acoustic‐surface‐wave filter for the use of video intermediate frequency at 58 MHz was fabricated using an rf‐sputtered ZnO film overlying the interdigital electrodes and the wave path on a glass substrate, and its fundamental properties for practical application were studied. The average and easily reproducible insertion loss characteristics are as follows: 16 dB at the minimum, 5(+16) dB at chromatic and picture signal carrier frequencies, 15(+16) dB at sound signal carrier frequency, more than 55(+16) dB at trap frequencies for adjacent channels, and 35(+16) dB at the maximum side lobe. The triple transit echo suppression is more than 30 dB. The temperature coefficient of the frequency characteristic is 30 ppm/°C. 400 days of aging has shown no significant change in the filter.

ISSN:0003-6951    

DOI:10.1063/1.88848

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

In this paper we show that a large amount of information can be stored in a sample of piezoelectric powders. The technique used to write and read the information is based on the principle of phonon echos. It is demonstrated that the frequency can serve as an address of a memory and that a word can be written into each address by selecting an appropriate writing pulse sequence. It is also shown that the information contained in one address can be read out quickly and nondestructively.

ISSN:0003-6951    

DOI:10.1063/1.88849

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Redox dopants are used to improve the dc dynamic scattering (DS) characteristics of phenyl benzoate liquid crystals as compared to the use of salt‐type conductive dopants. The redox dopants are selected by their electrochemical properties so that they react preferentially and reversibly at the electrodes, thus providing the current carriers for the dc‐DS effect. Low‐threshold voltages (∼2 V), high scattering efficiency (99% at 20 V), and long dc‐DS lifetimes (up to 18 000 h) are obtained with an ester liquid crystal containing a redox dopant pair consisting of di‐n‐butyl‐ferrocene and (2,4,7‐trinitro‐9‐fluorenylidene) malononitrile.

ISSN:0003-6951    

DOI:10.1063/1.88850

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

By utilizing a discharge caused between electrodes (specimens) in a high vacuum (≃2×10−5Torr) and without inert gas, the evaporation of high‐melting‐temperature materials (W, Ta, and C) has been successfully achieved. The main part of the instrument was composed of two electrodes (0.8–1.5 mm&fgr;) and a helical filament (0.8–1 mm&fgr;, 10 turns). An alternating voltage was supplied between electrodes (sparking gap: 0.5–2 mm), and in order to get sparking easily, the electrodes were preheated by bombarding with electrons (emission: 500 &mgr;A) from the filament. After starting, the high voltage was lowered to a range of 1–2 kV and the filament fell in disuse. Then the discharge was maintained stably. The structure of 600‐A˚‐thick W films deposited by this method was mostly of the ordered W3W.

ISSN:0003-6951    

DOI:10.1063/1.88827

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

It is demonstrated that the efficiency of the electromagnetic generation of ultrasonic surface waves in ferrous metals is strongly influenced by superimposed elastic strains. A graph of efficiency versus applied magnetic field has many features, and the changes of these in Armco iron and 1018 Steel are reported for the strain range −3×10−3<&Dgr;l/l<3×10−3(‖calculated stress‖<620 MN/m2or 90 KSI). Striking changes are observed, particularly for fields below 200 Oe. The results are interpreted in terms of the strain dependence of the magnetostrictive properties of the material. Possible applications of the effect to nondestructively measure residual stress are considered.

ISSN:0003-6951    

DOI:10.1063/1.88852

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A heavy ion beam probe has been used to obtain spatially resolved instability measurements in an energetic magnetically confined plasma. The amplitude and phase of both density and space potential fluctuations associated with a coherent 70‐kHz oscillation have been measured in a hollow cathode discharge. The measurements are made simultaneously from the same point in the plasma, are continuous in time, and have a spatial resolution element of <5 mm.

ISSN:0003-6951    

DOI:10.1063/1.88853

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Recent monochromator measurements of the photon emission and volume photoionization produced by a simple spark source within the laser gas environment are presented. Nitrogen gas is seen to dominate the ultraviolet radiation generated while carbon dioxide is shown to control the photon transmittance in the laser volume. The data clearly identify two narrow photon bands as the only useful portions, of the spark emission spectrum, in the production of volume ionization.

ISSN:0003-6951    

DOI:10.1063/1.88854

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

The effects of electrically inactive ion implantation inn‐type GaAs1−xPx(x≃0.38) on photoluminescence intensity have been studied. Improvement of the photoluminescence efficiency for the near‐band‐gap transition was achieved by a group‐III element (B and Ga) ion implantation at 1013cm−2. Group‐V element (As) ion implantation led to deterioration of the efficiency to the same degree or more than group‐VIII element (Ar) ion implantation. The results suggest that the efficiency improvement is attributed to a decrease in the concentration of the ’’killer’’ center, probably associated with the Ga vacancy included in the as‐grown GaAsP crystals.

ISSN:0003-6951    

DOI:10.1063/1.88855

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Photodiodes have been produced by recoil implantation of Al and Ga into Si, using inert‐gas‐ion bombardment. Yields as large as 40 implanted Ga atoms per incoming Xe ion have been observed. The diodes were characterized by optical‐window thicknesses from 0.14 to ∼1 &mgr;m.

ISSN:0003-6951    

DOI:10.1063/1.88828

出版商:AIP    

年代:1976

数据来源: AIP