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901.
Transport as a consequence of state-dependent diffusion 总被引:1,自引:0,他引:1
M. Büttiker 《Zeitschrift für Physik B Condensed Matter》1987,68(2-3):161-167
Overdamped particles subject to a drift in a force field with sinusoidal space dependence and also a sinusoidally modulated space-dependent diffusion, with the same period as the drift, experience a net driving force. The resulting current depends on the amplitude of the modulation of the diffusion and is a periodic function of the phase difference between the sinusoidal drift and the sinusoidal modulation of the diffusion. For small modulation amplitudes a particle subject to state-dependent noise behaves the same way as a particle subject to thermal noise but with a drift which, in addition to the sinusoidal term, contains a net force term.Dedicated to Professor Harry Thomas on the occasion of his 60th birthday 相似文献
902.
A narrow linewidth has been obtained in a new 1.5 ?m distributed feedback laser integrated monolithically with a tunable external cavity. The linewidth of 18 MHz has been achieved by tuning the current in the external cavity, and the FM response was flat from 100 kHz to 500 MHz. 相似文献
903.
Modeling and CW operation of a quasi-three-level 946 nm Nd: YAG laser 总被引:18,自引:0,他引:18
A model is developed for an end-pumped quasi-three-level laser with population in the lower laser level at equilibrium such as for transitions to the manifolds4I9/2 in Nd3+,4I15/2 in Er3+,5I8 in Ho3+and3H6 in Tm3+. It is shown that the effect of residual lower laser level population on laser operation can be treated as a saturable loss. Room temperature operation on the4F3/2 -4I9/2 transition in Nd:YAG under CW dye laser pumping has been demonstrated with a threshold as low as 11.5 mW incident power and a slope efficiency of 7 percent with 0.3 percent output coupling. Performance is limited by the low output coupling and diffraction loss. 相似文献
904.
High-resolution positive and negative photoresists were used to fabricate ?/4-phase-shifted corrugations by holographic exposure. To avoid mixing these photoresists, cyclised polyisoprene was used as a midlayer. The shape and depth of the corrugations on the positive and negative photoresist regions were almost the same. Single-mode operation at the Bragg wavelength was confirmed in lasers with the corrugation. 相似文献
905.
906.
A novel typed of hybrid-mode feed horn is presented. It comprises a hollow conical dielectric waveguide whose outer surface is metallized, and whose inner surface is coated with circumferentially oriented conducting strips. It may be designed to have mimimal cross polarization at two arbitrarily separated frequencies, as for a dual depth corrugated horn. Compared to the corrugated horn, it has the potential of lower weight and lower price. Small horns will have some cross polarization due to undesired radiation from the fields transmitted within the dielectric. 相似文献
907.
908.
A. I. Shtern 《Russian Journal of Mathematical Physics》2006,13(2):210-223
As was proved by van der Waerden in 1933, every finite-dimensional locally bounded representation of a semisimple compact
Lie group is continuous. This is the famous “van der Waerden continuity theorem,” and it motivated a vast literature. In particular,
relationships between the assertion of the theorem (and of the inverse, in a sense, to this theorem) and some properties of
the Bohr compactifications of topological groups were established, which led to the introduction and the study of certain
classes of the so-called van der Waerden groups and algebras. Until now, after more than 70 years have passed, the van der
Waerden theorem appears in monographs and surveys in diverse forms; new proofs were found and then simplified in important
special cases.
In this paper, we prove that the statement of the van der Waerden theorem remains valid for all (not necessarily compact)
real semisimple Lie groups, i.e., any given finite-dimensional representation of a real semisimple Lie group is continuous
if and only if this representation is locally bounded.
More subtle results are also obtained. The main theorem contains several conditions equivalent to the continuity condition
for a finite-dimensional representation. In particular, it is proved that every finite-dimensional representation of a real
semisimple Lie group is continuous if and only if the restriction of this representation to the “compact” part, to the Abelian
part, or to the nilpotent part of the Iwasawa decomposition is locally bounded, and the original van der Waerden theorem is
also somewhat refined. For instance, the following assertion holds: every finite-dimensional representation of a compact semisimple
Lie group is continuous if and only if the restriction of this representation to some maximal torus is locally bounded.
Dedicated to the memory of George Mackey (1916–2006)
Partially supported by the Russian Foundation for Basic Research under grant no. 02-01-00574, by the Program of Supporting
the Leading Scientific Schools under grant no. NSh 619.203.1, and by the INTAS grant. 相似文献
909.
Alcindo A. Dos Santos Renan S. Ferrarini Jefferson L. Princival João V. Comasseto 《Tetrahedron letters》2006,47(50):8933-8935
A masked lithium homoenolate, generated by tellurium/lithium exchange, was reacted with epoxides. The lithium compound was also converted into other organometallics such as Grignard, and cuprates and the reactivity of those organometallics with epoxides was evaluated. The same building block was employed in the synthesis of (+/−)-frontalin. 相似文献
910.
A. I. Nazarov 《Journal of Mathematical Sciences》2006,133(3):1314-1327
We find logarithmic small ball asymptotics for the L2-norm with respect to self-similar measures for a certain class of Gaussian processes including Brownian motion, Ornstein-Uhlenbeck
process, and their integrated counterparts. Bibliography: 46 titles.
__________
Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 311, 2004, pp. 190–213. 相似文献