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31.
报道了既不连续又不可逆一维映象中出现的一种具有新特征的激发(crisis)模式。这一新型激发产生于不连续性与不可逆性相互作用所导致的“映孔”与混沌吸引子的碰撞。映孔的出现可使迭代过程逃逸原来吸引子所占据的相空间区域,从而发生吸引子的突然扩张。数值计算结果表明,激发的特征时间<τ>与外控参量距其临界值距离的依赖关系为<τ>∝exp(U_0—U_(0c))~(-1/2),τ的不变分布P(τ)随τ增长呈现指数衰减关系。这种产生机制及主要特征与三种常见的激发相比均有新的特点。
关键词: 相似文献
32.
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Summary. We use the integral equation approach to study electromagnetic scattering by perfectly conducting (non-orientable) Lipschitz
screens. The well-posedness of the electric field integral equation is derived. The Galerkin method for this problem is analysed
in a general setting and optimal error bounds are proved for conforming finite elements in natural norms.
Received September 7, 2001 / Revised version received May 15, 2002 Published online October 29, 2002
Mathematics Subject Classification (1991): 65R20
Work of the second author was sponsored by Thales Airborne Systems. 相似文献
34.
C. Thomsen P. Wiggers H. Ring-Larsen E. Christiansen J. Dalh j O. Henriksen P. Christoffersen 《Magnetic resonance imaging》1992,10(6):867-879
A total of 4302 healthy blood donors were screened for elevated serum ferritin and transferrin saturation. Fifteen had increased serum ferritin at a follow-up examination. Five relatives of these donors also entered the study. Eleven patients had elevated liver iron concentrations, while five had normal liver iron concentrations. The R2 relaxation rate in the liver was first measured with a conventional multi-spin-echo imaging sequence, and then by a volume-selective spectroscopic multi-spin-echo sequence, in order to achieve a minimum echo time of 4 msec. No correlation was found between the relaxation rate R2 and the liver iron concentration, when R2 was calculated from the imaging data. Multi-exponential transverse relaxation could be resolved when the spectroscopic sequence was used. A strong correlation between the initial slope of the relaxation curve and the liver iron concentration was found (r = 0.90, p < 0.001). Signal intensity ratios between liver and muscle were calculated from the first three echoes in the multi-echo imaging sequence, and from a gradient echo sequence. A strong correlation between the logarithm of the signal intensity ratios and the liver iron concentration was found. Although both spectroscopic T2 relaxation time measurements and signal intensity ratios could be used to quantify liver iron concentration, the gradient echo imaging seemed to be the best choice. Gradient echo imaging could be performed during a single breath hold, so motion artifacts could be avoided. The accuracy of liver iron concentration estimates from signal intensity ratios in the gradient echo images was about 35%. 相似文献
35.
Jürgen Vogt Manfred Winnewisser Jørn Johs. Christiansen 《Journal of Molecular Spectroscopy》1984,103(1):95-104
The rotational a-type spectra of isotopically enriched diazirine isotopomers, H212C14N15N and H212C15N2, have been recorded in the region between 8 and 300 GHZ; the latter isotopomer has been observed for the first time. Using Watson's A-reduced Hamiltonian, the rotational constants and the quartic and some sextic centrifugal distortion constants have been determined for the ground vibrational states. 相似文献
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J. Christiansen N. Lieser W. Rath W. Steudtner K. Rózsa M. Jánossy P. Apai P. Mezei 《Optics Communications》1985,56(1):39-40
Pulsed laser oscillation at the 488.0 and 514.5 nm transitions of Ar II was observed in an Ar-He pseudospark discharge. The time delay between current rise and laser pulse of the 488.0 nm line was 2.5 μs. 相似文献
38.
We show that for a positive linear operator acting in ℓ2 and defined from
anxn+1+bnxn+an-1xn-1