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1.
Mathematical Methods of Operations Research - 相似文献
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Alain-Yves LeRoux Marie-Noëlle LeRoux Jean-André Marti 《Comptes Rendus Mathematique》2004,339(4):313-316
The source waves are some particular solutions to genuinely non linear hyperbolic systems with a source term, whose propagation velocity is a constant determined by the roots of this source term. We propose a system of 2 equations on a 2 dimension space, which model the velocity field of the atmosphere near the ground. The source term is made of three parts: a given pressure gradient, a friction or aspiration effect and the Coriolis force. In the case where these parameters are constant, we build a solution which is a constant outside a circular crown. The internal circle represents the eye's wall of the hurricane and corresponds to a share shock wave. The external circle is a set generating the bifurcation which actually models the hurricane. To cite this article: A.-Y. LeRoux et al., C. R. Acad. Sci. Paris, Ser. I 339 (2004). 相似文献
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Urs Lang 《Mathematische Zeitschrift》1992,210(1):581-592
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Automatic segmentation and classification of color images is a problem of great practical interest in different areas. This
paper presents an algorithm for this purpose which is divided in three steps. Firstly, the regions of interest are isolated
from the rest of the image based on threshold functions defined in theYUV andYIQ color spaces, producing a set of connected components. Then, a set of features is computed to enable a quantitative evaluation
of the segmented objects. Finally, the image is classified by means of a decision rule based on the analysis of the differences
between the computed measures and a set of ideally segmented images, according to experts’ assessment. The algorithm was applied
to a decision support tool for estrus detection in cattle. This approach constitutes a valuable alternative to improve this
process, as it may replace the visual observation by the automatic analysis of pictures taken to cows in controlled environments.
Experimental results show that the segmentations obtained with this method are highly satisfactory and they allow a precise
classification of the images with low computational complexity. 相似文献
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H. K. Reimschuesel J. Marti N. S. Murthy 《Journal of polymer science. Part A, Polymer chemistry》1988,26(1):43-59
Copolymers of ethylene and chlorotrifluoroethylene that contain small amounts of units derived from perfluorohexylethylene show improved resistance of thermal stress cracking. This is a consequence of effects of these units on structural parameters of both the crystalline and amorphous phases. Those of the crystalline phase entail growth and organization of lamellae, whereas those of the amorphous phase are related to conformation and packing of polymer chains. The crystalline phase consists exclusively of alternately arranged units of ethylene and chlorotrifluoroethylene. The amorphous phase is characterized by chain segments composed of randomly distributed units derived from ethylene, chlorotrifluoroethylene, pairs of these two units, and units derived from perfluorohexylethylene. 相似文献
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Urs P. Wild Hans J. Griesser Vo Dinh Tuan Jean F.M. Oth 《Chemical physics letters》1976,41(3):450-455
The emission spectra of the second excited singlet state of [18] annulene and of monofluoro [18] annulene (in a 3-methylpentane glass at 4 K) are reported. The large energy gap between the first and second excited singlet states inhibits fast internal conversion and favours the appearance of S2 → S0 emission. In addition, fluorescence from the S1 state can be observed in monofluoro [13] annulene by exciting into the S2 or directly into the S1 absorption. 相似文献
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The photoelectron spectrum of tetrakis (methylidene)cyclobutane ( 1 , ‘[4]radialene’) is reported. The electronic states of 1 + are assigned on the basis of model calculations and with reference to related systems. Jahn-Teller activity in the degenerate states is discussed. A failure of the simple LCBO-model for the π(eg)-orbital of 1 is noted and traced to the fact that this orbital, though having a symmetry-equivalent π*-counterpart, does not interact with it. This feature is confined to [4n]radialenes; their total π-energies are therefore higher than those of the other members. It is shown that radialenes, in principle, do not constitute a class analogous to that of the linear polyenes as inferred earlier. 相似文献