Classes Caractéristiques de Fibrés Feuilletés, Holomorphes ou Algébriques

Résumé L'objet de cet article est de montrer comment laK-théorie multiplicative peut être utilisée pour définir de nouvelles classes caractéristiques secondaires de fibrés vectoriels munis de structures supplémentaires, dans des contextes géométriques variés. On y développe des exemples reliés à des travaux antérieurs divers.

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The purpose of this paper is to show how multiplicativeK-theory may be used to define new secondary characteristic classes for vector bundles with additional structures, in various geometrical contexts. Many examples are developed which are related to previous works.

     

Cyclic reduction and FACR methods for piecewise hermite bicubic orthogonal spline collocation

Cyclic reduction and Fourier analysis-cyclic reduction (FACR) methods are presented for the solution of the linear systems which arise when orthogonal spline collocation with piecewise Hermite bicubics is applied to boundary value problems for certain separable partial differential equations on a rectangle. On anN×N uniform partition, the cyclic reduction and Fourier analysis-cyclic reduction methods requireO(N ²log₂ N) andO(N ²log₂log₂ N) arithmetic operations, respectively.     

Note on the optimal transportation of distributions

We extend our work on the optimal mapping of distributions in three directions: (a) we consider any set-valued mapping, not just diffeomorphisms; (b) we distinguish between weak and strong optimality, and identify strong optimality with cyclic monotonicity; and (c) we prove that, under some restrictions, a weakly optimal mapping has the subgradient property.     

基于八面体理论的岩石循环加-卸载本构模型及修正

探究岩石的受力特点及破坏特性是研究岩石地下工程安全性的关键,诸多学者都期望能在岩石本构模型的研究上取得突破性进展。在此背景下,提出了一种能够描述循环加-卸载条件下岩石的本构模型。首先,假设岩石的微元强度服从八面体剪应力理论并且微元破坏服从Weibull概率公式,将岩石本构中的损伤变量以及岩石微元强度表达式里包含的损伤因子进行本构变换,得到关于应力、应变等其他表现加-卸载下岩石损伤本构模型的参数,表示出岩石微元强度和损伤变量,再将得到的岩石微元强度和损伤变量代入所提出的岩石本构模型中,并进行等式变换得到一个函数表达式。通过将其与实验数据进行拟合对比分析,得出修正后的拟合参数,将其代入函数式中,得到损伤本构模型的修正式。最后将拟合参数进行必要的敏感性分析,得出各拟合参数的实际物理意义。     

Catalytic properties of mesoporous materials supported heteropoly acids for Baeyer-Villiger oxidation of cyclic ketones

Three mesoporous molecular sieves loaded silicotungstic acids, named HSiW/SBA-15, HSiW/MCM-41, HSiW/MCM-48, were prepared and characterised by XRD, FT-IR, TEM and SEM. The catalytic performance of the prepared materials for the Baeyer-Villiger oxidation of cyclic ketones was carried out in the presence of 30%H₂O₂ under mild conditions. These loading materials were proved to be efficient and reusable catalysts, they all exhibited excellent catalytic performance for the Baeyer-Villiger oxidation of cyclic ketones with 30% H₂O₂ as oxidant. Many cyclic ketones were efficiently converted to the corresponding lactones with up to 90% conversions and high selectivities under the optimum reaction conditions.

Cyclic ketones were efficiently oxidised by mesoporous materials sopported silicotungstic acid to the corresponding lactones with 30%H₂O₂ as oxidant. All of the catalysts showed promising recyclability in the reactions.     

适于遥感图像实时压缩的小波基的选择

遥感图像相关性弱,纹理细节丰富,故对其采用基于小波变换的图像编码方法进行编码压缩,而在对图像进行小波变换时,小波基的选取是至关重要的,它直接影响到变换速度和编码效率。在详细分析小波基的基本性质及其与图像编码的关系的基础上,选出数种典型小波基进行实验比较。实验结果表明D5/3双正交小波基最适合于遥感图像实时压缩,最后经实验验证其选取是合理的。     

Three-Mode Cyclic Squeezed States Constructed via EPR Entangled State

We construct the three-mode cyclic squeezed states and analyze its squeezing property by using the technique of integration within an ordered product of operators and the natural representation of the two-mode squeezing operator in the Einstein-Podolsky-Rosen entangled state basis.     

[5‐(p‐alkoxy)phenyl‐10, 15, 20‐tri‐phenyl] porphyrin and their rare earth complex liquid crystalline

Three series of porphyrin liquid crystalline compounds, [5‐(p‐alkoxy)phenyl‐10, 15, 20‐tri‐phenyl] porphyrin and their rare earth complexes (Tb (III), Dy (III), Er (III), Yb (III)), with a hexagonal columnar discotic columnar(Col_h) phase have been synthesized. These compounds were characterized by elemental analysis, molar conductances, UV‐visible spectra, infrared spectra, luminescence spectra, and cyclic voltammetry. These compounds exhibit more than one mesophases, which transition points of temperature change from ?33.6 to 16.0 °C, and transition points of temperature for isotropic liquid also increase from 4.9 to 38.2 °C, with increasing chain length. Their surface photovoltage (SPV) response have also been investigated by the means of surface photovoltage spectroscopy (SPS) and field‐induced surface photovoltage spectroscopy (EFISPS). It was found that their SPV bands are analogous with the UV‐visible absorption spectra and derived from the same transition. Copyright © 2007 John Wiley & Sons, Ltd.     

Generation of attosecond pulses in molecular nitrogen

We investigate the carrier-envelope phase dependence of the total ionization yield for single and double ionization of xenon. We compare our results to theoretical calculations and to the phase dependent asymmetry in photoelectron emission. We observe that the phase dependence of the photoion yields, regardless if single or double ionization, is at least 2-3 orders of magnitude below the photoelectron emission signal. We conclude that total photoionization yields are only very weakly dependent on the carrier envelope phase, and that they are not a useful means for measurement of the phase. It seems possible that the broad bandwidth of few-cycle pulses facilitates multiphoton ionization, which leads to a randomization of strong field ionization phase dependencies. Besides, we observe that the spatial asymmetry in photoelectron emission appears to be useful as an indicator for the laser pulse duration in the few cycle regime.     

基于ROI编码的干涉超光谱图像近无损压缩

针对干涉超光谱成像仪所成图像的特点,提出了一种基于ROI（Region of Interest,感兴趣区域）编码的干涉超光谱图像序列压缩方法.利用帧内差值变换,结合矩形ROI编码,在提高遥感图像压缩比的同时,使压缩后的重建图像质量达到近无损的技术要求.实验结果表明,这种压缩方法在干涉超光谱图像压缩中当相对光谱二次误差为2.04％时,干涉图像的压缩比达到9.66∶1.