电子商务中的PKI、SSL与SET的技术分析

PKI是目前在电子商务中安全传输方案，SSL和SET两种安全的电子交易协议，在网上交易中有着广泛地应用，是大多数在线支付所采用的支付协议。这里在探讨PKI、SSL、SET技术原理的基础上，对它们各自的作用、技术实现、工作漉程等进行了描述；对它们之间的联系、区别、应用范围进行了深入的分析。     

Mutual information-based analysis of JPEG2000 contexts.

Context-based arithmetic coding has been widely adopted in image and video compression and is a key component of the new JPEG2000 image compression standard. In this paper, the contexts used in JPEG2000 are analyzed using the mutual information, which is closely related to the compression performance. We first show that, when combining the contexts, the mutual information between the contexts and the encoded data will decrease unless the conditional probability distributions of the combined contexts are the same. Given I, the initial number of contexts, and F, the final desired number of contexts, there are S(I, F) possible context classification schemes where S(I, F) is called the Stirling number of the second kind. The optimal classification scheme is the one that gives the maximum mutual information. Instead of using an exhaustive search, the optimal classification scheme can be obtained through a modified generalized Lloyd algorithm with the relative entropy as the distortion metric. For binary arithmetic coding, the search complexity can be reduced by using dynamic programming. Our experimental results show that the JPEG2000 contexts capture the correlations among the wavelet coefficients very well. At the same time, the number of contexts used as part of the standard can be reduced without loss in the coding performance.     

Preparation and Compressive Stress Effect of Polymer Matrix RE-Fe Giant Magnetostrictive Composite

Polymer matrix RE-Fe giant magnetostrictire composite （GMPC） was prepared using bonding and magnetic field forming technique, and magnetostriction of samples was measured for different compressive stress. The experimental results show thai there is certain compressive effect in GMPC. And the influence of compressive stress on magnetostriction of sample was investigated. It offers essential reference for application and device design of GMPC.     

一种前馈型全摆幅恒跨导准恒增益CMOS运放设计

设计了一种适合在低电源电压下工作的前馈型输入级放大结构，在全摆幅的动态工作范围内，输入级跨导保持不变，采用负载电流补偿以保证增益近似恒定，输出采用前馈型AB类输结构，实现全摆幅输出。     

以寻呼区分析为基础的PHS网络优化方法

通过分析PHS网络中各寻呼区的统计指标,剖析指标劣化的根本原因,采取修改相应的参数配置、移站、调整天线等措施进行网络优化,优化实施后再次收集统计指标做对比分析,总结经验。     

各向异性损伤理论与复合材料层板损伤的实验研究(一)-各向异性损伤理论

本文讨论了各向异性损伤力学的基本概念并介绍了以应变等效性假设为基础的Lemaitre模型和以能量等效性假设为基础的Cordebois模型.在此基础上作者导出了两种损伤模型的损伤能释放率的表达式.文中作者定义了一维损伤时弹性材料板单元的一些损伤定义,并导出了两种模型在一维损伤时损伤能释放率Y₂的简单表达式,从而为复合材料层板损伤测量的实验研究提供了理论基础,     

Preparation and characterization of cuprous iodide nanoparticles

A new technique for the preparation of CuI nanoparticles from CuSO₄ and KI ethanol solutions has been developed. Preparation conditions were optimized through a series of experiments. Under these conditions, the yield of CuI reached 95.39%. The product was characterized and the reaction kinetics was studied. The results show that the product takes a roughly spherical shape with an average particle size of less then 50 nm. The activation energy of the formation of CuI is found to be E _a = 0.58 × 10² kJ/mol, and the preexponential factor in the Arrhenius equation is k ₀ = 7.43 × 10¹⁶ mol/(l s). The text was submitted by the authors in English.     

基于奇异值分解和神经网络的个性化信息模式识别

随着信息资源的持续增长，信息获取系统为特定用户提供特定信息服务的需求越来越重要。该文提出了基于奇异值分解和神经网络的个性化信息模式识别的方法，可以方便地获取用户信息需求的特征，并且利用这些特征信息完成个性化的信息识别和匹配，即实现个性化信息的模式识别，进而实现信息的个性化获取和管理。该文中的算法实现简单，可以方便地应用到目前的一些信息管理、服务系统中。