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排序方式: 共有853条查询结果,搜索用时 31 毫秒
91.
Y. Y. Lau K. R. Chu L. R. Barnett V. L. Granatstein 《International Journal of Infrared and Millimeter Waves》1981,2(3):373-393
The operation of the gyrotron travelling wave amplifier is based on the convective cyclotron maser instability. It is found that this convective instability may become absolute (nonconvective) at a sufficiently high current level, resulting in oscillation instead of amplification. This threshold current for the transition depends sensitively on the applied magnetic field. The axial wavelength and the characteristic frequency of oscillation at the onset of absolute instability are given. It is found that momentum spread has virtually no effect on the threshold current. A small amount of resistive wall loss, however, raises the threshold current significantly. Oscillations due to partial reflection at the ends of the system are also examined. Preliminary experimental results on both types of oscillations are reported and are found to be in good agreement with the theory. 相似文献
92.
Barteld Braaksma 《Journal of Dynamics and Differential Equations》1992,4(3):485-513
We study a system which may serve as a prototype model for excitability. Its long-term behavior is governed by a globally attracting fixed point, but it has the interesting property that an appropriate small perturbation of the equilibrium situation elicits a large (transient) response. Using singular perturbation techniques, the threshold for excitation is determined. Asymptotic expansions for the threshold are given and their validity is proved. An associated system is studied, which yields further quantitative information on the position of the threshold. 相似文献
93.
一年以前 ,人们惊奇地发现 :在相当弱的磁场中 ,并不太强的微波辐照就可以使二维半导体的磁阻产生强烈的振荡 ,振幅的最大值可超过无辐照磁阻值的十几倍 ,最小值可以一直降到零 .全世界众多的凝聚态物理学家争相聚焦到这个领域 ,进行了许多实验和理论研究 ,企图弄清这一意外发现的机理 .经过一年多的努力 ,人们已经掌握了这个现象更多的细节 ,对其物理机制也有了初步了解 .但深入的实验和理论探索可能还要继续相当一段时间 .文章将对这个物理现象及相关的理论模型 ,尤其是目前得到较多赞同的光子辅助磁输运模型 ,作一简单的介绍 . 相似文献
94.
In this paper we give the explicit form of the solutions of the singular integral equations associated with some models of gas dynamics and plasma physics which are extensively investigated in the existing literature. In particular, we deal with equations on infinite and semi-infinite contours, where the data are assumed to be meromorphic functions. In this context we rederive some published results and present some new results which show how our method can be successfully used to obtain the explicit form of the solutions in much more general cases than those found in the literature. 相似文献
95.
96.
The study of transient behaviour of a pulse pumped solid state laser system has assumed importance on account of SLM generation
by self-seeding with the pre-lase signal. This paper reports on the observations of seed pulses for two different Nd: YAG
laser rods, one with anti-reflection coating (AR) on end faces and the other without. The latter displays single longitudinal
mode behaviour in each of the relaxation pulse train while the former displays multimode behaviour. Our observations are well
explained by the ‘active etalon concept’ introduced earlier. 相似文献
97.
G.Ya. Slepyan S.A. Maksimenko A.V. Magyarov A. Hoffmann D. Bimberg 《Superlattices and Microstructures》2004,36(4-6):773
The influence of local fields on the excitonic Rabi oscillations in an isolated, arbitrary shaped quantum dot (QD) has been theoretically investigated. QD interaction with both a classical electromagnetic field and quantum light has been considered. In the classical light, time harmonic and ultrashort pulse excitations are analyzed. The general formalism has been formulated for quantum light and applied to the case of a Fock qubit. Noticeable modification of the Rabi oscillation dynamics induced by the local fields is predicted to be observable in QDs exposed to both classical and quantum light. In particular, the bifurcation and anharmonism in the Rabi oscillations have been revealed under time harmonic excitation and a dependence of the Rabi oscillation period on the QD depolarization has been obtained. 相似文献
98.
99.
100.
B. Meadows 《中国物理 C》2010,34(6):780-787
Studies in which BABAR data have shown evidence for mixing in the neutral charm meson system are presented. A new measurement of the lifetime difference parameter ycp = (1.16±0.22±0.18)% is described. Results are also presented from a systematic study of DK and D*K invariant mass distributions from a 470 fb^-1 sample of asymmetric e^+e^- interactions recorded by the BABAR detector at the PEP-Ⅱ storage rings. A new charmed-strange meson has been observed with mass [3044 ± 8stat (-5^+30 )syst] MeV/c^2 and width [239± 35stat (-42^+46)syst]MeV/c^2. 相似文献