一类存在特权集的门限群签名方案

针对冯登国提出的“存在特权集的门限群签名”问题，旨在分析现有解决方案的安全缺陷并给出新的解决方案．首先基于有限域理论分析指出石怡等人给出的一种实现方案存在不足和安全隐患．然后推广了利用单签名构造群签名的思想，提出了具有4个变形的一类EIGamal类型门限群签名方案，从而解决了以上问题．这类方案还具有消息恢复、签名长度短等许多良好性质．最后，基于单签名的安全性假设，证明以上方案是安全的。

原子核多重碎裂中同位旋相分比的产生机理研究

利用非对称核物质状态方程及同位旋相关的量子分子动力学 (IQMD)模型对中能重离子碰撞中的同位旋相分比 (isospinfractionation)现象进行了研究 .给出了同位旋相分比现象的一种静态解释 .并详细分析了各种动力学因素对同位旋相分比的影响 .同时 ,也讨论了同位旋相分比的同位旋效应

Strangeness production process pp -> nK(+)Sigma(+) within resonance model

We explore production mechanism and final state interaction in the pp -> nK(+)Sigma(+) channel based on the inconsistent experimental data published respectively by COSY-11 and COSY-ANKE. The scattering parameter a > 0 for n Sigma(+) interaction is favoured by large near-threshold cross section within a nonrelativistic parametrization investigation, and a strong n Sigma(+) interaction comparable to pp interaction is also indicated. Based on this analysis we calculate the contribution from resonance Delta*(1920) through pi(+) exchange within resonance model, and the numerical result suggests a rather small near-threshold total cross section, which is consistent with the COSY-ANKE data. With an additional sub-threshold resonance Delta*(1620), the model gives a much better description to the rather large near-threshold total cross section published by COSY-11

Phenomenological analysis of the double-pion production in nucleon-nucleon collisions up to 2.2 GeV

With an effective Lagrangian approach, we analyze several NN -> NN pi pi channels by including various resonances with mass up to 1.72 GeV. For the channels with the pion pair of isospin zero, we confirm the dominance of N*(1440) -> N sigma in the near-threshold region. At higher energies and for channels with the final pion pair of isospin one, we find large contributions from N*(1440) -> Delta pi, double-Delta, Delta(1600) -> N*(1440)pi, Delta(1600) -> Delta pi and Delta(1620) -> Delta pi. There are also sizable contributions from Delta -> Delta pi, Delta -> N pi, N -> Delta pi, and nucleon pole at energies close to the threshold. We give a good reproduction to the total cross sections up to beam energies of 2.2 GeV except for the pp -> pp pi(0)pi(0) channel at energies around 1.1 GeV and our results agree with the existing data of differential cross sections of pp -> pp pi(+)p pi(-), pp -> nn pi(+)pi(+), and pp -> pp pi(0)pi(0) which are measured at CELSIUS and COSY.