基于可编程hash函数的短签名

数字签名中的短签名由于其签名长度的优势,特别适用于通信带宽受限的场合．现有的短签名方案大多是随机预言模型下可证明安全的,但是随机预言模型通常被认为过于理想化,现实中没有一种hash函数能够模拟随机预言模型,而少数标准模型下可证安全的短签名方案,一般被认为是低效的或者基于强困难假设,即攻击者被给于一定数量的随机的已解决问题实例,要求去解决一个它自己选择的实例．可编程hash函数fprogrammablehashflmctions,PHF）是一种能模拟随机预言的某些可编程特性的特殊hash函数．可编程hash函数可嵌入到签名的基本构造中,产生标准模型下的短签名．本文利用可编程hash函数设计了一个基于因子分解假设的短签名方案．它具有的优点是：1）签名长度短,只需要一个群上的元素和一个小整数;2）签名和验证计算量小,不需要在签名过程中进行生成素数的运算;3）不需要嵌入变色龙hash函数便可实现标准模型下可证明安全．     

某类解析函数的三阶Hankel行列式

令H表示形如$f(z)=z+a_2 z^2+a_3 z^3+\\cdots$且在$U=\\{z:|z|<1\\}$内解析的函数类,研究了在单位圆盘上的2类解析函数类$\\mathrm{ST}_{\\mathrm{s}}=\\left\\{f ? H: \\operatorname{Re} \\frac{2 z f^{\\prime}(z)}{f(z)-f(-z)}>0, z ? U\\right\\}$和$R\\left(\\frac{1}{2}\\right)=\\left\\{f ? H: \\operatorname{Re} \\frac{f(z)}{z}>\\frac{1}{2}, z ? U\\right\\}$的三阶Hankel行列式$\\left|H_{3, 1}(f)\\right|$的上界估计。

     

The bootstrapped artefact: a collectivist account of technological ontology, functions, and normativity

In 2006, this journal addressed the problem of technological artefacts, and through a series of articles aimed at tackling the ‘dual nature of technical artefacts’, posited an understanding of these as constituted by both a structural (physical) and a functional (intentional) component. This attempt to conceptualise artefacts established a series of important questions, concerning such aspects of material technologies as mechanisms, functions, human intentionality, and normativity. However, I believe that in establishing the ‘dual nature’ thesis, the authors within this issue focused too strongly on technological function. By positing function as the analytic axis of the ‘dual nature’ framework, the theorists did not sufficiently problematise what is ultimately a social phenomenon. Here I posit a complementary analytic approach to this problem; namely, I argue that by using the Strong Programme’s performative theory of social institutions, we can better understand the nature of material technologies. Drawing particularly from Martin Kusch’s work, I here argue that by conceptualising artefacts as artificial kinds, we can better examine technological ontology, functions, and normativity. Ultimately, a Strong Programme approach, constructivist and collectivist in nature, offers a useful elaboration upon the important question raised by the ‘dual nature’ theorists.     

Genetic and morphometric variation in the potamonautid river crab Potamonautes parvispina (Decapoda: Potamonautidae) from two Western Cape rivers,South Africa

Patterns of genetic and morphometric variation amongst five populations of Potamonautes parvispina from two rivers in the Western Cape, were examined. Genetic variation at 14 loci was investigated using protein gel electrophoresis. The results showed that the populations were genetically invariant within and between the two drainage systems. Discriminant functions analyses of seven carapace variables demonstrated regional differentiation between the population groups in the two drainage systems. Other morphometric characters exhibited a significant degree of variation within drainage systems. Morphometric data were highly variable and were discordant with the genetic data, which suggests that environmental factors may be responsible for the large degree of phenotypic plasticity. Results from the present study are discussed in terms of widespread gene flow and recent population divergence.     

广义Lupas-Baskakov算子关于导数为局部有界函数的点态逼近估计

得到了广义Lupas Baskakov算子一阶绝对矩量的渐近估计式,并结合区间分割技术和Bojanic Cheng方法研究了广义Lupas Baskakov算子关于导函数为局部有界函数的点态逼近估计.     

火箭风偏计算的格林函数法

本文全面揭示了垂直风对火箭主动段影响的物理本质,用格林函数法通过两种连续微扰动作用过程计算了垂直风所引起的攻角和偏角。     

离散大系统周期解的存在性

本文的目的在于综合运用比较原理和李雅普诺夫函数分解法来讨论离散大系统周期解的存在性问题.首先改进了文[2]中的一个充分条件(Th1).主要结果是分别运用标量和向量李雅普诺夫函数分解法给出了离散大系统(3.1)的T-周期的存在性的充分条件(Th2.Th 3.).作为标量法的例子考虑线性离散大系统(ρ),得到了(ρ)存在T一周期解的较文[7]更简单的条件(Th4.).     

盐酸在40Wt%DMSO—H_2O混合溶剂中热力学性质的研究

本文用emf法通过测定得到Pt,H_2(latm)Hcl(xm)+H_2O|AgCl—Ag及Pt,H_2(latm)I HCl(xm)+40Wt%DMSO+H_2O/AgCl—Ag两电池的标准电动势E°及其温度系数。求出盐酸从H_2O到40Wt%DMSO—H_2O混合溶剂的迁移自由能ΔGtr、迁移焓ΔHtr、迁移熵ΔStr及迁移活度系数~wγ~s。进而求出盐酸在40Wt%DMS0—H_2O混合溶剂中的标准生成自由能ΔfG°(298.15)。     

两对边简支单向变刚度矩形板的弯曲问题

本文通过做未知函数变换，将两对边简支单向变刚度矩形板在任意横向分布载荷作用下的弯曲问题归结为求解第二类的Ｖｏｌｔｅｒｒａ积分方程。对上述积分方程，建议了二次样条函数的近似解法，求得了问题的渐近解析解。为了检验方法的有效性并说明其应用，对线性变厚度的形做了数值计算，所得结果和精确解符合得很好。     

三阶变系数线性微分系统的二维向量Liapunov函数

在Ａ（ｔ）为三阶可微函数矩阵时,通过构造二维Ｌｉａｐｕｎｏｖ函数,给出了保证变系数线性系统＾．ｘ＝Ａ（ｔ）ｘ平凡解渐近稳定的判定准则。本文放弃了Ａ（ｔ）的特征值均有负实部的要求。