数字水印的应用及攻击类型

随着多媒体技术的应用,在多媒体数据中嵌入隐蔽标记的数字水印技术,因其保真性、安全性和鲁棒性,在票据防伪、拷贝控制及广播监视等领域得到了探索性的应用.同时针对水印系统的攻击也越来越多,影响了水印的安全性.针对水印系统的攻击主要分为三大类:未经授权的删除、未经授权的嵌入、未经授权的检测.本文从水印系统的特性、应用、攻击三个方面对数字水印技术进行论述.     

利用温度梯度法合成硫化物

以金属镁、钛、锆和钨以及升华硫为原料，通过温度梯度法合成了硫化镁、硫化钛、硫化锆和硫化钨，并利用X射线衍射分析了合成物的矿物组成，研究了合成体系内升华硫的蒸发量与合成体系容积大小、合成温度以及合成体系抗压强度等参数间的关系．研究结果表明，在本实验条件下，合成体系内的最大升华硫蒸发量应为1．15g，并根据此硫蒸发量控制合成体系内的温度梯度和升温速度，安全且大量地合成了硫化镁、硫化钛、硫化锆和硫化钨，其质量分别为56．37，112．00，155．36和247．97g．     

Crocin Synthesis Mechanism in Crocus sativus

Saffron （Crocus sativus） cells can synthesize crocin, crocetin digentiobiosyl ester, in suspension cultures. The crocin family biosynthesis mechanism was studied using high pressure liquid chromatography （HPLC） to determinate the glucosyltransferase activity and to develop a method for synthesizing medicine from saffron cells. Previous studies indicated that two glucosyltransferases might be involved in the formation of crocetin glucosyl- and gentiobiosyl-esters. GTasel formed an ester bond between crocetin carboxyl groups and glucose moieties while GTase2 catalyzed the formation of glucosidic bonds with glucosyl ester groups at both ends of the molecule. These enzymes can catalyze the formation of crocetin glucosides in vitro. GTasel activity is higher during the first four days of crocin glucosides biosynthesis, but decreases after four days. The formation and accumulation of crocin increase during the first six days and stabilized on the eighth day.     

Simulation of a compartment fire using a zone model

This paper presents the zone modeling analysis of a single compartment flashover fire. Two criteria are applied in the model to judge the onset of ignition for different combustibles. By calculating the total received energy through radiation or the surface temperature of the combustible, the fire growth can be quantitatively determined. The improved zone fire model shows the influence of different combustibles upon the fire growth. This model is better than the traditional zone model because the common criteria of flashover, i.e. an upper layer temperature of 600℃ and the heat radiation intensity received by the floor of 20 kW/m^2, have not been applied in it.     

我国体育产业市场的现状及其发展策略

在市场经济大潮下．体育市场正逐渐发展成一个日益重要的消费市场。这个市场在新世纪市场经济发展中发挥着强大的推动作用。为了加快体育消费市场的市场化程度．让体育市场催生出日益繁荣的体育产业．对我国体育产业的现状与特点进行分析．提出我国体育产业市场发展策略．以期有助于我国体育产业市场的规范化发展。     

模糊层次分析法在地基处理方案优选中的应用

简要介绍了模糊层次分析法的基本原理和分析问题的步骤。基于模糊层次分析法的软土地基处理方案优选，结果表明选择结果与实际相符合。     

The Recent Advances in Plant Protection Researches of China

There are eight examples briefly given in this paper, namely, (1) Polymyxa graminis and the cereal viruses it transmits; (2) the geographical types and facultative migration of cotton bollworm as well as the safety of Bt transgenic cotton; (3) development of crop near-isogenic lines with resistance to diseases; (4) molecular-biological researches induced resistance of rice by infection of blast fungus;(5) to use cytological and molecular-biological techniques for breeding wheat varieties resistant to barley yellow dwarf virus; (6) mass rearing and field releasing of Microplitis mediator for cotton bollworm control; (7) identification and recombination of insecticidal crystal genes of Bacillus thuringiensis; and (8) interplanting of diverse resistance rice varieties for sustainable control of blast disease; which reflect the general situation of recent advances in plant protection researches of China.     

基于高斯矢量场的多尺度水平集图像分割算法

针对主动轮廓模型的弱边界和运算复杂度高等缺点,提出一种有效的解决算法,该算法引入高斯矢量场(GVF),扩大边界力的作用范围,同时综合区域信息,有效解决弱边界问题;并运用多尺度LevelSet方法提高算法的运算速度.实验表明,所提出算法不仅分割效果好,而且具有抗噪性能强和运算速度快的特点.     

超高射频火炮射击实验及内弹道过程仿真

该文进行了超高射频火炮膛内串联排列的3发弹丸的射击实验，建立了膛内过程的经典内弹道模型，并进行了数值模拟。计算结果和实验结果很接近，表明该模型用于模拟超高射频火炮高频连发的膛内过程是可行的。利用该模型分析了射击频率对最大膛压和初速的影响，计算结果表明：超高射频火炮的射击频率应该有一上限，就是在上一发弹出炮口并且膛内压力下降到一定压力时再击发下一发弹，才能避免各弹丸之间的相互影响，使初速散布减小。     

基于风压线形叠加法张拉膜结构风荷载与风振响应分析

综合分析了几种现有的张拉膜结构风荷载分析的方法,在此基础上提出了用风压线形叠加法进行风荷载计算的新方法,并給出一个工程算例进行了风振响应分析。该方法采用平均风压与脉动风压线性组合叠加的办法,生成风压时程函数,既保证了作用于结构上的风荷载随时间变化,而且还能保证结构所受的力是围绕着静力风压上下波动。这种算法可为膜结构的抗风设计提供参考。