官能化噻咯合成研究进展Ⅱ.交联法、取代法、硼化法与硅烷化法

官能化噻咯(silole音译)是一种重要的噻咯衍生物,不仅在有机金属合成领域占重要地位,也是建构新型π共轭体系的重要组成部分。本文介绍了官能化噻咯的几种重要合成方法,并对各种方法的特点及适用范围作了分析和总结。     

魅力型领导与团队学习:团队目标明确度的缓冲效应

本研究采用分组回归方法,以89支学生研究项目团队作为研究对象,考查魅力型领导与团队学习间的影响关系;并检验了团队目标的明确程度对魅力型领导和团队学习间关系所起的缓冲效应.结果表明,魅力型领导有助于团队学习;另一方面,当团队目标相对明确时,魅力型领导对团队学习的积极影响效应才较为显著;而当团队目标相对不明确时,魅力型领导...     

对一个群签名方案的分析与改进

分析了一个基于中国剩余定理的群签名方案,指出此方案并不安全：任何一个群成员或已被撤销的群成员都可以完全攻破此方案。针对该安全缺陷提出了一个改进的新方案。分析表明,该方案不仅可以在不改变其他群成员密钥的情况下有效地增加和撤销群成员,而且具有不可伪造性、防陷害攻击、抗联合攻击等性质。     

基于身份的认证群密钥协商协议

认证群密钥协商(AGKA)协议能为一群用户产生一个共享的会话密钥,使得群用户间能在公共数据网络进行安全通信.现有的大部分基于公钥技术的AGKAY协议分两类:第一类,认证部分是基于PKI/CA,会话密钥协商部分主要用模指数(或点乘)实现;第二类,认证部分是基于身份(ID)的公钥体制,会话密钥协商部分主要是用Weil对或Tate对实现.第一类AGKA协议存在一个较显著问题:公钥管理问题;第二类AGKA协议虽然有效地解决了公钥管理问题,但由于其会话密钥协商部分主要是用双线性对(即Weil对或Tate对)实现,与前者相比,计算量较大.针对这些不足,提出了一个新的AGKA协议,其认证部分是基于身份(ID)的公钥体制,会话密钥协商部分的运算主要用模指数实现;并在ROM,ECDH和BDH假设下证明了该AGKA协议的安全性.该协议与基于PKI/CA的相关AGKA协议相比,克服了后者在密钥管理上的困难;与其它基于身份的AGKA协议相比,在效率上具有一定的优势.     

Directed Evolution of Phi Class Glutathione Transferases Involved in Multiple-Herbicide Resistance of Grass Weeds and Crops

The extensive application of herbicides in crop cultivation has indisputably led to the emergence of weed populations characterized by multiple herbicide resistance (MHR). This phenomenon is associated with the enhanced metabolism and detoxifying ability of endogenous enzymes, such as phi class glutathione transferases (GSTFs). In the present work, a library of mutant GSTFs was created by in vitro directed evolution via DNA shuffling. Selected gstf genes from the weeds Alopecurus myosuroides and Lolium rigidum, and the cereal crops Triticum durum and Hordeum vulgare were recombined to forge a library of novel chimeric GSTFs. The library was activity screened and the best-performing enzyme variants were purified and characterized. The work allowed the identification of enzyme variants that exhibit an eight-fold improvement in their catalytic efficiency, higher thermal stability (8.3 °C) and three-times higher inhibition sensitivity towards the herbicide butachlor. The crystal structures of the best-performing enzyme variants were determined by X-ray crystallography. Structural analysis allowed the identification of specific structural elements that are responsible for k_cat regulation, thermal stability and inhibition potency. These improved novel enzymes hold the potential for utilization in biocatalysis and green biotechnology applications. The results of the present work contribute significantly to our knowledge of the structure and function of phi class plant GSTs and shed light on their involvement in the mechanisms of MHR.     

基于成组技术的电机制造CAPP系统

根据电机厂产品的特殊性及电机零件结构特点,自行设计了具有一定针对性的13位分类编码系统,通过工艺设计标准化、自动化过程,成功开发一套适合电机生产特点的DJ-1CAPP系统,解决电机生产过程中工艺设计的瓶颈问题。     

一种基于身份的群盲签名方案

基于身份和盲签名是当代密码学领域两个重要的概念,基于身份用来简化基于证书的公钥环境中的密钥管理;盲签名在实际应用中起着保护消息发送方隐私权的重要作用。本文将Paterson基于椭圆曲线的基于身份的签名方法与盲签名技术结合而提出一个新的基于身份的盲签名方案,并利用已有的转换方法,把我们提出的盲签名方案转换成一个群盲签名方案。分析表明,新的方案满足不可伪造性、匿名性、可追踪性及不可陷害性等安全特性;更重要的是,该群签名以及群公开密钥的长度都与群成员的个数无关,因此更适合群成员较多的大群。     

群签名方案的安全性分析及其改进

群签名允许群成员以匿名的方式代表整个群体对消息进行签名。发生争议时,群仲裁者能够识别出签名者,但对于非仲裁者来说是签名者匿名的。从匿名性方面分析了Ma等的基于双线性映射的群签名方案,利用双线性对的良好性质,提出了对这个群签名方案的4种攻击方法。为抵抗这4种攻击方法,提出了改进方案,改进后的方案在保持原方案安全性的同时,还能够抵抗这4种攻击方法。     

基于目的层预约的双子电梯群优化控制方法

针对双子电梯群控系统多目标性、不确定性的特点,提出了一种基于目的层预约的双子电梯群优化控制方法。在分析双子电梯结构特点的基础上,构造了适合双子电梯群的目标函数;在不同交通模式下,运用改进的遗传算法进行目的层预约系统下双子电梯群的优化控制仿真。仿真结果表明,控制方法能够适应双子电梯的运行特点,并能适应不同交通流模式,与传统电梯控制系统比较,平均候梯时间、长候梯时间发生率和电梯停靠次数明显减小,可为双子电梯群控系统的工程应用提供理论依据。     

GOMSS: A Simple Group Oriented (t,m, n) Multi-secret Sharing Scheme

In most (t,n)-Multi-secret sharing ((t,n)-MSS) schemes, an illegal participant, even without any valid share, may recover secrets when there are over t participants in secret reconstructions. To address this problem, the paper presents the notion of Group ori-ented (t,m,n)-multi-secret sharing (or (t,m,n)-GOMSS), in which recovering each secret requires all m (n ≥ m ≥ t) participants to have valid shares and actually participate in secret reconstruction. As an example, the paper then pro-poses a simple (t,m,n)-GOMSS scheme. In the scheme, every shareholder has only one share; to recover a secret, m shareholders construct a Polynomial-based randomized component (PRC) each with the share to form a tightly coupled group, which forces the secret to be recovered only with all m valid PRCs. As a result, the scheme can thwart the above illegal participant attack. The scheme is simple as well as flexible and does not depend on conventional hard problems or one way functions.