摘要:

ABSTRACTElectric field induced current saturation at room temperature is reported in low resistivity n-GaAs at fields much less than the threshold field for Gunn oscillations. In order to use the low resistivity crystal, surface-oriented devices were used, the fabrication technique of which is described. The apparent threshold field for the reported saturation corresponds to an electron drift velocity higher than the sound velocity in the crystal. Although no oscillation was detected, negative resistance was observed in the I-V characteristics, similar to those already observed at 77°K. Possible reasons for such saturation, based on the acoustoelectric effects in the crystal, are discussed.

ISSN:0377-2063    

DOI:10.1080/03772063.1967.11485495

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

ISSN:0377-2063    

DOI:10.1080/03772063.1967.11485496

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

ISSN:0377-2063    

DOI:10.1080/03772063.1967.11485497

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

ABSTRACTThe results of ionospheric absorption measurements at Ahmedabad (23°01'N, 72°36'E) on 2·6 Mc/s. by vertical pulse reflection method from May 1965 to April 1966 are presented in this paper.The following are the main conclusions:(1)The absorption rises after sunrise and reaches maximum at noon. From sunset to sunrise the absorption is very small, almost 10 per cent of the noon value.(2)The mean monthly mid-day values of absorption show seasonal variation: minimum in winter and maximum in summer. The summer maximum is broader than winter minimum.(3)The absorption is found to vary with cosχaccording to the relationThe value of n is 0·77 in summer, 0·70 in equinox and 0·66 in winter.(4)The overall absorption in 1965–66 was reduced to 34 per cent of the absorption in 1957–58.(5)The absorption values extrapolated for cosχ= l show a liner relation with sunspot number of the type L = L0(1 + bR), where0= 35 db., b = 0·006(6)During the solar eclipse, the absorption was significantly lower than that in the normal days.

ISSN:0377-2063    

DOI:10.1080/03772063.1967.11485498

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

ABSTRACTDynamic programming is studied as an optimizing technique in the synthesis of unequally spaced symmetrical antenna arrays. The criterion of optimization is to find an element combination which has the lowest value of the peak sidelobe level over a specified angular interval. A nine-element array is synthesized with aperture length 19λ0and spacing quantizationλ0/2 using an IBM 1620 computer. It is verified by considering all possible combinations of elements that the dynamic programming technique leads to truly optimum results.

ISSN:0377-2063    

DOI:10.1080/03772063.1967.11485499

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

ISSN:0377-2063    

DOI:10.1080/03772063.1967.11485500

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

ISSN:0377-2063    

DOI:10.1080/03772063.1967.11485501

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

ISSN:0377-2063    

DOI:10.1080/03772063.1967.11485502

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

ISSN:0377-2063    

DOI:10.1080/03772063.1967.11485504

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

ISSN:0377-2063    

DOI:10.1080/03772063.1967.11485505

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor