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991.
R. López-Martens J. Mauritsson P. Johnsson K. Varjú A. L’Huillier W. Kornelis J. Biegert U. Keller M. Gaarde K. Schafer 《Applied physics. B, Lasers and optics》2004,78(7-8):835-840
We characterize the temporal structure of high-order harmonic radiation on both the femtosecond and attosecond time scales. The harmonic emission is characterized by mixed-color two-photon ionization with an infrared femtosecond laser using a Mach–Zehnder interferometer where both pump and probe arms travel completely separate paths. In a first experiment, we measure the duration and chirp of individual harmonics. In a second experiment, we resolve, for the first time with this type of setup, the attosecond beating of several harmonics generated under conditions similar to the first experiment. We suggest that the results of both measurements can be combined to determine the full attosecond time structure of the harmonic emission. PACS 32.80.Rm; 42.65.Ky 相似文献
992.
The magnetic and electric properties of the Sr2FeMoO6 compound produced under different preparation conditions were studied. Depending on the preparation condition, a strong variation in the nonmagnetic SrMoO4 impurity content was found, which in turn determined the metallic or semiconducting behavior of the resistivity of the Sr2FeMoO6 compound. There was also evidence that SrMoO4 played a crucial role in modifying the low magnetic field intergrain tunneling magnetoresistance in Sr2FeMoO6. In addition, we have established a simple method to prepare the single phase Sr2FeMoO6 polycrystals. 相似文献
993.
S. S. Stavitskaya N. T. Kartel’ N. N. Tsyba M. F. Kovtun T. P. Petrenko 《Russian Journal of Applied Chemistry》2007,80(3):379-385
The mineral and chemical compositions, as well as some structure-sorption characteristics were determined for clay minerals selected for examination. The integrated coefficients of contamination of bottom sediments with each of the toxicant metals (Fe, Ni, Co, Cu, Zn, Pb, Mn) were calculated. The minerals examined presumably can be used in medicine as efficient application materials, cosmetic agents, and sorbents (enterosorbents). 相似文献
994.
995.
Approximate method of calculating stresses in a rectangular plate locally loaded by a harmonic force
From double trigonometric series for bending moments the slowly converging components are picked out. When the loading facets are small compared with the width of the plate, they are approximately summed by the analytical method. This simplifies substantially the calculation of bending moments and stresses in the zone of small loading facets compared with the usual expansion with respect to the natural vibration forms.Translated from Teoreticheskaya i Prikladnaya Mekhanika, No. 20, pp. 84–88, 1989. 相似文献
996.
997.
998.
Tunnelling in periodically driven bistable symmetric potential wells is investigated in an analytical approximation in a domain where the driving frequency is large compared to the tunnelling frequency and only the four lowest lying levels contribute significantly. The influence of finite level widths is taken into account, and a smooth variation of the amplitude of the driving field is allowed for. 相似文献
999.
1000.
P. Recht 《Mathematical Methods of Operations Research》1992,36(3):201-210
In this paper we present a concept of the construction of generalized gradients by considering a development of directional derivatives into spherical harmonics. This leads to a derivation system as a system of generalized partial derivatives. Necessary conditions for local extrema for a broad class of not necessarily differentiable function can be given and a characterization of points of differentiability can be proved by using generalized gradients. 相似文献