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.     

电视胸腔镜下微创脊柱侧弯前路松解术的初期临床结果

探讨电视胸腔镜在严重脊柱侧弯前路松解中的应用价值,并对其初期临床结果进行分析.2001年11月-2002年8月,共11例严重脊柱侧弯患者接受电视胸腔镜下前路松解,均为女性,特发性胸椎脊柱侧弯,年龄14～17岁.冠状面Cobb角90°～100°,Risser征+++～++++,松解范围T5～T12,松解节段5～7.术后行牵引二周再行后路TSRH矫形内固定术.术中出血量为100～150mL,手术时间180～220min,术后引流量520～650mL,引流时间48～96h,二期后路手术矫正率平均为58%.电视胸腔镜下脊柱侧弯的前路松解在不影响矫形手术效果的同时,能减少组织损伤,降低感染可能,减轻术后疼痛,缩短病人的康复时间.     

M_2Cl_4(PH_3)_4(M=Cr、Mo、W)分子的DFT计算

采用密度泛函理论(DFT)研究M_2Cl_4(PH_3)_4(M=Cr、Mo、W)分子,在D_(2d)对称约束下进行结构优化和能量解析,三种化合物的M—M键长分别是C—Cr1.737A,Mo—Mo2.157A,W—W2.286A.能量解析表明:E_(Cr—Cr)相似文献   

民族生态审美场论

与相应的审美氛围、审美风范双向对生并走向整生的民族审美活动循环圈 ,构成民族生态审美场。民族生态审美场是民族生态审美学的整体对象 ,它的逻辑结构统观化整生化展开 ,构成当代民族生态审美学的理论体系     

高科技企业竞争的网络特征及其对策

本文从提高我国高科技企业持续创新能力的现实需要出发 ,在对高科技产业核心资源和市场特性分析的基础上 ,从网络效应角度具体分析了其竞争的网络特征 ,最后从培育核心能力 ,实施网络作战等方面提出了在网络竞争环境下 ,提升高科技企业竞争优势的具体对策。     

Triassic U-Pb age for zircon from granites in the Tonghua area and its response to the Dabie-Sulu ultrahigh-pressure collisional orogenesis

Single-grain zircon U-Pb dating was carried out to constrain the emplacement timing of granitic plutons at Chaxinzi, Xiaoweishahe and Longtou in the Tonghua area, south of Jilin Province. The results show that these plutons formed in the Triassic with ages of 203—217 Ma. Geological and geochemical characteristics indicate that the plutons are composed of quartz diorite and granite. The former was derived from partial melting of mafic lower crust, whereas the latter originated from thickened crust with garnet as the residue in the source. It appears that protoliths of these two types of granitits are different although they have the same emplacement age. Considering that these plutons are petrologically different from the coeval granites in the Xingmeng (Xing‘an-Mongolian) to Jihei (Jilin-Heilongjiang) orogenic belt in the north, it is suggested that their formation was related to the Dabie-Sulu ultrahigh-pressure collisional orogenesis since their ages are only 10—20 Ma younger than timing of the ultrahigh-pressure metamorphism, but comparable to that of the first rapid exhumation of the ultra-high-pressure metamorphic rocks and the emplacement of the post-collisional granites.     

对"过氧化氢碘化钾催化分解"催化概念的质疑

在过氧化氢中加入碘化钾溶液，过氧化氢的分解速率显著加快．国内外文献普遍认为这是碘化钾在起催化剂作用．我们发现反应过程中溶液颜色变黄．进一步的实验表明，溶液中碘离子浓度降低、溶液的电导率增大、pH值升高，而且溶液中生成了单质碘．根据对上述实验研究结果，我们对碘化钾作为过氧化氢分解反应的催化剂的概念提出了质疑。并证实发生了过氧化氢氧化碘化钾的化学反应．     

多跨连续梁桥横桥向抗震的概念设计

连续梁桥是具有较好抗震性能的桥型之一.针对某桥梁工程进行抗震分析,利用连续梁桥等效模型的简化分析,并结合反应谱理论探讨桥墩刚度的分布对横桥向抗震性能的影响.提出对于坚实的地基,应采取在独柱墩上设置纵向竖缝的方案调整刚度分布;而针对软土地基则应采取改变制动墩或伸缩缝的位置,并在关键点将独柱墩分解为双柱墩的方案,以改善受力.2种方案的目的都是要尽量减小转动位移,从而提高横桥向抗震性能.并利用SAP2000进行了横桥向反应谱分析与验证.研究结果可应用于地震区连续梁桥的概念设计中.     

发动机怠速稳定性控制方法的分析研究

从提高发动机经济性和降低有害排放物质的角度出发，讨论了发动机怠速控制方法，对用PID控制，模糊控制，模糊－PID控制方法进行深入分析研究，并给出3种控制方法的仿真结果，模糊控制完全可用于发动机ECU的怠速控制。     

崇明东滩鸟类自然保护区被子植物区系研究

报道了崇明东滩鸟类自然保护区被子植物名录、植物区系组成成分及特点，并将其与奉贤地区滩涂和九段沙湿地的植物区系进行了比较，分析讨论了东滩植物区系的形成原因及其影响因子。为保护区的生物多样性研究及其保护提供了基础资料。