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121.
利用球形空腔膨胀理论的响应函数对靶板在弹体撞击下的侵彻进行分析,并基于量纲理论建立了侵彻相似律的一般形式.通过对侵彻混凝土靶的已有实验数据进行分析,得到了不同缩比因子下,无量纲侵彻深度曲线随侵彻速度不同而发生偏转和偏移.考虑到材料的应变率效应和损伤演化,认为几何相似律对混凝土等脆性材料在抗侵彻时不成立,有必要引入材料应变率效应和损伤演化对几何相似律的修正. 相似文献
122.
《代数通讯》2013,41(4):1669-1676
It has been previously shown by Lindner and Rodger that quasigroups associated with 2-perfect extended m-cycle systems can be equationally defined if and only if m ∈ {3, 5, 7}. In this paper we present a single identity for each such m which is equivalent to the identities given for these varieties. 相似文献
123.
David Kohel 《Journal of Number Theory》2011,131(5):894-919
The study of alternative models for elliptic curves has found recent interest from cryptographic applications, after it was recognized that such models provide more efficiently computable algorithms for the group law than the standard Weierstrass model. Examples of such models arise via symmetries induced by a rational torsion structure. We analyze the module structure of the space of sections of the addition morphisms, determine explicit dimension formulas for the spaces of sections and their eigenspaces under the action of torsion groups, and apply this to specific models of elliptic curves with parametrized torsion subgroups. 相似文献
124.
A modification of the material law associated with the well‐known Biot system as suggested by Murad and Cushman (Int. J. Eng. Sci. 1996; 34(3):313–338) and first investigated by Showalter (J. Math. Anal. Appl. 2000; 251(1):310–340) is reconsidered, generalized and analysed in the light of a new approach to a comprehensive class of evolutionary problems. The framework allows a uniform approach to problems involving general anisotropic, inhomogeneous, non‐smooth media thus covering, for example, transmission problems in layered materials. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
125.
We present a quick review of several reduction techniques for symplectic and Poisson manifolds using local and global symmetries compatible with these structures. Reduction based on the standard momentum map (symplectic or Marsden–Weinstein reduction) and on generalized distributions (the optimal momentum map and optimal reduction) is emphasized. Reduction of Poisson brackets is also discussed and it is shown how it defines induced Poisson structures on cosymplectic and coisotropic submanifolds. 相似文献
126.
127.
Anestis Antoniadis Andrey Feuerverger Paulo Gonçalves 《Annals of the Institute of Statistical Mathematics》2006,58(4):779-807
Stable distributions are characterized by four parameters which can be estimated via a number of methods, and although approximate
maximum likelihood estimation techniques have been proposed, they are computationally intensive and difficult to implement.
This article describes a fast, wavelet-based, regression-type method for estimating the parameters of a stable distribution.
Fourier domain representations, combined with a wavelet multiresolution approach, are shown to be effective and highly efficient
tools for inference in stable law families. Our procedures are illustrated and compared with other estimation methods using
simulated data, and an application to a real data example is explored. One novel aspect of this work is that here wavelets
are being used to solve a parametric problem, rather than a nonparametric one, which is the more typical context in wavelet
applications. 相似文献
128.
129.
The ageing of Paraloid® B72, an acrylic copolymer extensively used in conservation of works of art, has been investigated either under artificial irradiation (Xenon lamp) or in natural environment (external exposure) with the aim to correlate the results of the accelerate test with the real situation. For a better understanding of the involved mechanisms some acrylic homo-polymers were also subjected to the artificial ageing test. Molecular changes induced by ageing were followed by infrared spectroscopy (FT-IR) and size exclusion chromatography (SEC), while the efficiency of the treatment was checked by water capillary absorption test and colour determinations. The results obtained indicate that it is possible to discriminate, easily and within reasonable laboratory time experiment, between polymers that can be used in Conservation, and the macromolecules that should not be employed due to short efficacy life-times. 相似文献
130.
O. S. Klass O. Biham M. Levy O. Malcai S. Solomon 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(2):143-147
Statistical regularities at
the top end of the wealth distribution in the United States are
examined using the Forbes 400 lists of richest Americans,
published between 1988 and 2003.
It is found that the wealths are distributed according to a power-law
(Pareto) distribution.
This result is explained using a
simple stochastic model
of multiple investors that incorporates the
efficient market hypothesis
as well as the multiplicative nature of financial market fluctuations. 相似文献