基于二维提升方案的可逆双正交小波变换在渐进性无损图像压缩中的应用

分析了一维(基于行、列分解和重构)提升方案的特点，从理论上指出了一维提升方案的不足之处，提出了二维(基于子带分解和重构)提升方案，并给出了CDF(1，3)双正交小波二维提升方案的具体形式，改进的提升方案弥补了一维提升方案的不足之处，不需作‘√2’因子和归一化处理，整个小波变换是可逆的、基于整数运算的、能量守恒的，减少了误差传递的机会，用该小波变换实现了快速的、渐进性的直至无损图像压缩。     

Shift visual cryptography scheme of two secret images

A new visual cryptography scheme of two secret images, which is named the shift visual cryptography of two secret images, is given. The compound function family of a general construction model is also introduced. The uniqueness and validity of this model are proved, and the minimum rows and columns for realizing the scheme are obtained. Compared with visual cryptography of one secret image, the shift visual cryptography scheme can share two secret images with the same size of pixels expansion without losing the contrast. It has randomness and various forms, and furthermore, we can also visually recover two secret images even if the two shares are different in form and color.     

Compact difference approximation with consistent boundary condition

For simulating multi-scale complex flow fields it should be noted that all the physical quantities we are interested in must be simulated well. With limitation of the computer resources it is preferred to use high order accurate difference schemes. Because of their high accuracy and small stencil of grid points computational fluid dynamics (CFD) workers pay more attention to compact schemes recently. For simulating the complex flow fields the treatment of boundary conditions at the far field boundary points and near far field boundary points is very important. According to authors' experience and published results some aspects of boundary condition treatment for far field boundary are presented, and the emphasis is on treatment of boundary conditions for the upwind compact schemes. The consistent treatment of boundary conditions at the near boundary points is also discussed. At the end of the paper are given some numerical examples. The computed results with presented method are satisfactory.     

科技期刊网络发布的一个解决方案

随着我国科学技术的发展，信息传递手段的进步，科技期刊的数字化、网络共享已是大势所趋。文章针对科技期刊的特征，提出了一个科技期刊网络发布的切实可行的方案。     

流域防洪系统调度的评价指标体系探讨

针对复杂的流域防洪系统调度方案评价决策问题，在已有研究成果的基础上，初步提出相应的防洪系统调度评价指标体系原型．该指标体系不仅考虑了防洪系统内各个防洪构件(如各个水库、分蓄洪区)的运行目标，而且考虑了整体防洪系统运行目标．     

杆振动方程的二级二阶显式辛格式及其稳定性

用PRK方法对四阶杆振动方程构造了二级二阶显式辛格式，并讨论了其稳定性．数值实验表明了理论分析的正确性．     

对流方程一族新的三层双参数高精度格式

对对流方程 ut=aux(其中 a为常数 ) ,构造一族新的含双参数高精度的三层差分格式 .当参数α=12 ,β=0时 ,得到一个双层格式 .这些格式对任意选取的非负参数都是绝对稳定的 ,其局部截断误差阶为 O((Δt) 2 (Δt) 2 (Δx) 2 (Δx) 6) .数值试验表明 ,所建立的差分格式是有效的 ,理论分析是正确的 .     

秘密分享密码体制进展

秘密分享是密码学研究中的一个热点问题,从中衍生的问题非常复杂 而就秘密分享密码体制、广义秘密分享密码体制和秘密分享的攻击欺诈行为以及防范手段,指出几个热点和研究发展的方向有重要意义     

基于仿射变换系的分形图形的交互式生成

提出了基于仿射变换系的分形图形的交互式生成分形图形方法，用此方法可以交互式地设计出各种形状分形图案。通过这些分形图案，可以加深对分形的理解。     

范德瓦耳斯方程研究

讨论了真实气体的状态方程，分析了范德瓦耳斯对其方程的推导过程，并根据统计物理学的系统理论，结合Ｍａｘｗｅｌｌ－Ｂｏｌｔｚｍａｎｎ分布，给出了建立范德瓦耳斯方程的一种新方法。还给出了真实气体修正系数ａ，ｂ的计算公式。