云计算在RSA密码体制分析中的应用

RSA是著名的公钥密码体制之一,其安全性是基于大整数因子分解困难性假设的,求解RSA问题的最直接方法是分解RSA的模数.由于云计算的大规模分布式计算能力,一些使用分布式计算模型MapReduce的大整数分解手段已经实现,针对大整数因子分解的问题,提出了给定范围内搜索因子的新方法,并对相应的实验数据和结果进行了分析.结果表明,在云中的分布式计算的运行时间远小于单台机器.     

面向不确定需求租户集的云服务智能匹配模型

为了解决云计算环境下由海量租户集和资源集间的不确定性因素引起的高质量云服务获取困难的问题,提出了一种描述动态异构租户集不确定性需求的方法.在此基础上,构建属性权重完全未知情况下的云服务智能匹配模型,排除了租户提交权值造成的偏差.神经网络以属性区间计算的相离度作为输入,服务满意度为输出来动态模拟租户集的不确定需求,运用萤火虫算法求解模型获取最优服务组合.最后,实例验证了神经网络的可靠性以及算法的有效性.实验结果表明,模型能有效获取高质量的云服务组合,优于传统的匹配方法.     

Chiral and water‐soluble poly(2‐oxazoline)s

We describe the synthesis and characterization of the first water‐soluble and chiral poly(2,4‐disubstituted‐2‐oxazoline)s. While poly(2,4‐dimethyl‐2‐oxazoline)s are water soluble up to 100 °C, aqueous solutions of poly(2‐ethyl‐4‐methly‐2‐oxazoline) exhibit a lower critical solution temperature. This is discussed in context with its constitutional isomers poly(2‐oxazoline)s and poly(2‐oxazine)s. Circular dichroism spectroscopy revealed strong Cotton effects, which are also responsive to temperature in aqueous solution. It is therefore hypothesized that structures, comparable to polyproline helices, are formed in aqueous solution. In contrast to polyproline, poly(2,4‐disubstituted‐2‐oxazoline)s are highly water soluble and therefore represent very interesting pseudo‐polypeptides that may be useful to develop responsive biomimetic biomaterials. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Thermal multifragmentation in p + Au interactions at 2.16, 3.6 and 8.1 GeV incident energies

Multiple emission of intermediate-mass fragments has been studied for the collisions p + Au at 2.16, 3.6 and 8.1 GeV with the FASA setup. The mean IMF multiplicities for events with at least one IMF are equal to 1.7, 1.9 and 2.1 (±0.2) respectively. The multiplicity, charge distributions and kinetic energy spectra of IMF are described in the framework of a intranuclear cascade model followed by the statistical multifragmentation model. However, between the two parts of the calculation the excitation energies and the residual masses and charges are modified to take into account the losses during expansion. The results support a scenario of true thermal multifragmentation of a hot and expanded target spectator. Received: 15 December 1997 / Revised version: 24 April 1998     

Entry of Material into an Arc Discharge in the Case of a Diffusion Mechanism of Impurity Exit to the Surface of a Small-Weight Sample

The process of formation of a radiating discharge cloud in the case of a diffusion mechanism of impurity exit to the surface of a molten small-weight sample is considered. An analytical expression describing the behavior of the relative rate of impurity entry into a discharge is obtained.     

Meshfree Thinning of 3D Point Clouds

An efficient data reduction scheme for the simplification of a surface given by a large set X of 3D point-samples is proposed. The data reduction relies on a recursive point removal algorithm, termed thinning, which outputs a data hierarchy of point-samples for multiresolution surface approximation. The thinning algorithm works with a point removal criterion, which measures the significances of the points in their local neighbourhoods, and which removes a least significant point at each step. For any point x in the current point set Y⊂X, its significance reflects the approximation quality of a local surface reconstructed from neighbouring points in Y. The local surface reconstruction is done over an estimated tangent plane at x by using radial basis functions. The approximation quality of the surface reconstruction around x is measured by using its maximal deviation from the given point-samples X in a local neighbourhood of x. The resulting thinning algorithm is meshfree, i.e., its performance is solely based upon the geometry of the input 3D surface point-samples, and so it does not require any further topological information, such as point connectivities. Computational details of the thinning algorithm and the required data structures for efficient implementation are explained and its complexity is discussed. Two examples are presented for illustration. This paper is dedicated to Arieh Iserles on the occasion of his 60th anniversary.     

在具有伸缩子的QCD势模型中的重介子

从伸缩子–胶子有效耦合理论得到的重夸克–反夸克势模型出发,计算了重介子的自旋平均能谱及轻子衰变和辐射跃迁宽度,并与Cornell势模型所得到的相应结果作了比较.结果表明,新的重夸克势的计算结果与重介子的实验数据更好地符合,而且估计的伸缩子质量5?7MeV很好地位于有关伸缩子质量的其他理论途径所估计的范围之内.     

Cavitation-induced shock wave behaviour in different liquids

This paper follows our earlier work where a strong high frequency pressure peak has been observed as a consequence of the formation of shock waves due to the collapse of cavitation bubbles in water, excited by an ultrasonic source at 24 kHz. We study here the effects of liquid physical properties on the shock wave characteristics by replacing water as the medium successively with ethanol, glycerol and finally a 1:1 ethanol–water solution. The pressure frequency spectra obtained in our experiments (from more than 1.5 million cavitation collapsing events) show that the expected prominent shockwave pressure peak was barely detected for ethanol and glycerol, particularly at low input powers, but was consistently observed for the 1:1 ethanol–water solution as well as in water, with a slight shift in peak frequency for the solution. We also report two distinct features of shock waves in raising the frequency peak at MHz (inherent) and contributing to the raising of sub-harmonics (periodic). Empirically constructed acoustic pressure maps revealed significantly higher overall pressure amplitudes for the ethanol–water solution than for other liquids. Furthermore, a qualitative analysis revealed that mist-like patterns are developed in ethanol–water solution leading to higher pressures.     

Analysis of the interaction between the ? meson and nucleus

In this study, we systematically investigate the ? meson and nucleus interaction by analyzing and fitting the cross sections of \begin{document}$ \gamma N $\end{document}\begin{document}$ \rightarrow \phi $\end{document}N reactions near the threshold, where N represents the nucleus. Using the vector meson dominant model, the distribution of the ?-N scattering length is presented as a function of energy, and the results show that there is a slight increase in scattering length with increasing energy. Based on this, the average scattering length of a ?-proton is obtained as\begin{document}$ 0.10\pm0.01 $\end{document} fm by combining experimental data and theoretical models. Moreover, the average scattering length of the ?-deuteron interaction is derived to be \begin{document}$ 0.014\pm0.002 $\end{document} fm for the first time. Furthermore, the effect of the momentum transfer \begin{document}$|t_{{\rm min}}|$\end{document} on the ?-N scattering length at the threshold is discussed. The obtained results not only provide important theoretical information for a more comprehensive and accurate study of the ?-N scattering length, but also a basis for future experimental measurements of ? meson production.     

Insights into the nature of X(3872) through B meson decays

We study the \begin{document}$ B_{c,u,d}\to X(3872)P $\end{document} decays in the perturbative QCD (PQCD) approach, involving the puzzling resonance \begin{document}$ X(3872) $\end{document}, where P represents a light pseudoscalar meson (K or π). Assuming \begin{document}$ X(3872) $\end{document} to be a \begin{document}$ 1^{++} $\end{document} charmonium state, we obtain the following results. (a) The branching ratios of the \begin{document}$ B^+_c\to X(3872)\pi^+ $\end{document} and \begin{document}$ B^+_c\to X(3872) K^+ $\end{document} decays are consistent with the results predicted by the covariant light-front approach within errors; however, they are larger than those given by the generalized factorization approach. (b) The branching ratio of the \begin{document}$ B^+\to X(3872)K^+ $\end{document} decay is predicted as \begin{document}$ (3.8^{+1.1}_{-1.0})\times10^{-4} $\end{document}, which is smaller than the previous PQCD calculation result but still slightly larger than the upper limits set by Belle and BaBar. Hence, we suggest that the\begin{document}$ B^{0,+}\to X(3872)K^{0,+} $\end{document} decays should be precisely measured by the LHCb and Belle II experiments to help probe the inner structure of \begin{document}$ X(3872) $\end{document}. (c) Compared with the \begin{document}$ B_{u,d}\to X(3872)K $\end{document}decays, the \begin{document}$ B_{u,d}\to X(3872)\pi $\end{document} decays have significantly smaller branching ratios, which drop to values as low as \begin{document}$ 10^{-6} $\end{document}. (d) The direct CP violations of these considered decays are small (\begin{document}$ 10^{-3}\sim 10^{-2} $\end{document}) because the penguin contributions are loop suppressed compared to the tree contributions. The mixing-induced CP violation of the \begin{document}$ B\to X(3872)K^0_S $\end{document} decay is highly consistent with the current world average value \begin{document}$ \sin2\beta=(69.9\pm1.7)$\end{document}%. Experimentally testing the results for the branching ratios and CP violations, including the implicit \begin{document}$S U(3)$\end{document} and isospin symmetries of these decays, helps probe the nature of \begin{document}$ X(3872) $\end{document}.