对一种新型代理签名方案的分析与改进

Gu-Zhang-Yang(2005)提出了一个不需要可信第三方参与的匿名代理签名方案,由于该方案的签名验证数据中没有回避孤悬因子这一现象,因此并不满足强不可伪造性,原始签名人可以伪造一个有效的代理签名通过验证,并成功地在代理签名者身份揭示阶段向公众证明该伪造的代理签名是由合法的代理签名者产生的。本文在分析该方案安全性的基础上提出了改进的匿名代理签名方案,克服了原方案的不足。     

一种新的图像去噪混合滤波方法

为了去除图像中混入的脉冲噪声和高斯噪声,提出了一种基于自适应中值滤波和模糊加权均值滤波的混合滤波方法.该方法首先进行噪声检测把受高斯型噪声污染的像素和受脉冲型噪声污染的像素区别开来,然后对受高斯噪声污染的像素采用模糊加权均值滤波算法,而对受脉冲噪声污染的像素则采用改进的中值滤波算法进行去噪.仿真结果证明,该方法更具有实用性和有效性.     

利用非双曲时距校正快速抽取CCP道集

转换波CCP道集的抽取及其速度分析是CCP叠加成像的重点和难点。本文提出一种快速抽取CCP道集的方法,该方法基于精确成像的转换波时距曲线公式,利用面元分割方法,快速抽取CCP道集。针对CCP道集的非对称性,利用设置虚拟震源和虚拟接收点的方法校正非双曲CCP道集。在非双曲校正后得到具有双曲时距特征的CCP道集,因此可用常规纵波处理系统完成转换波速度的分析和动校正及叠加。分别利用模型数据和实际数据抽取CCP道集和测试非双曲校正。结果表明,新方法获得的CCP道集速度谱能量团更加集中,且校正后的CCP道集同相轴更加水平,证明了本文方法的正确性,且精度更高。     

沧东凹陷孔二段细粒沉积岩致密油甜点预测

针对孔二段细粒沉积岩致密油储层薄、岩性复杂、纵横向变化快、地震资料分辨率低、常规手段预测难度大的问题,应用“逐级剥离”的方法预测甜点。首先通过单井岩电特征及模型正演分析明确了不同甜点段的地震响应特征,通过井震结合分析了不同岩相的振幅、频率特性,并构建振幅、频率融合属性预测岩性;然后通过优选敏感特征曲线反演预测甜点,预测出孔二段细粒沉积岩致密油甜点区的分布,有效指导了细粒沉积岩致密油勘探的选区,提高了钻探的成功率。通过逐级剥离的方法,预测出小集地区、官西高斜坡区、孔西低斜坡区等三个Ek₂¹细粒沉积岩致密油甜点区,合计面积达185km²。展示了沧东凹陷孔二段致密油勘探的良好前景,同时证实了文中的致密油甜点预测方法具有一定的实用性。     

Si上Si1-xGex:C 缓冲层的载流子分布

用化学气相淀积方法在Si(100)衬底上生长了Ge组分渐变的Si1-xGex:C合金缓冲层.研究表明,较高温度下生长的Si1-xGex:C缓冲层中Ge的平均含量较高,其晶体质量要优于较低温度下生长的外延薄膜.载流子浓度沿衬底至表面方向逐渐上升且Si1-xGex:C缓冲层总体呈p型导电,存在一局域n型导电区,本文对其导电分布特性进行了分析研究.     

4H-SiC MESFET器件工艺

介绍了制作4H-SiC MESFET器件的关键工艺.通过改进工艺,采用半绝缘衬底的国产SiC三层外延片,制造出总栅宽为1mm,2GHz连续波下输出功率大于4W,小信号增益大于10dB的SiC MESFET.     

四棱镜系统压缩LD端泵Yb:YAG皮秒脉冲的实验研究

设计了一种结构简单、易于调节、能够有效压缩皮秒脉冲的超短脉冲激光器.采用半导体端面泵浦Yb:YAG晶体,利用半导体可饱和吸收体(SESAM)产生皮秒脉冲,腔型为直腔.在上述基础上产生了稳定的皮秒脉冲(脉冲宽度＜10 ps),在腔内插入四棱镜系统优化腔内色散补偿,调节棱镜对后输出稳定的皮秒脉冲列,经过自相关仪测量,压缩后的脉冲宽度为4 ps.通过紧凑型四棱镜系统,可以适当压缩Yb:YAG超短脉冲,而不用再进行脉冲展宽.对设计全固态小型化超短脉冲激光器具有现实指导意义.     

Substituent Effects on Crosslike Packing of 2′,7′‐Diaryl‐ spiro(cyclopropane‐1,9′‐fluorene) Derivatives: Synthesis and Crystallographic,Optical, and Thermal Properties

A series of 2′,7′‐diarylspiro(cyclopropane‐1,9′‐fluorene) derivatives are efficiently synthesized and characterized to determine the reason for the “green‐light” emission of these compounds. These compounds exhibit bright‐violet to blue photoluminescence (PL) (λ^PL_max = 353–419 nm) with excellent PL quantum efficiencies (Φ_PL = 83–100 %) in solution and show high thermal stabilities (T_d = 267–474 °C). The variation of the optical properties of these molecules in the solid state depends on the different stacking modes of these compounds containing different substituents, which are revealed by crystallographic analysis. CH…π hydrogen bonds instead of intermolecular π–π interactions act as the driving force between adjacent fluorenes, even though a very small dialkyl group (cyclopropane) is introduced at the C‐9 position of fluorene. The crosslike molecular stacking efficiently reduces the energy transfer between the herring‐like aggregates and therefore results in the absence of a “green‐light” emission tail. In order to determine the cause of the “green‐light” emission tails, the fluorescence spectra of the films annealed in N₂ or in air are recorded. Broad green‐light emission tails were observed for the films annealed in air, which might be caused by fluorenone defects generated during processing or during the course of the photophysical analysis by reaction with residual oxygen.     

The revisit of QoS routing based on non‐linear Lagrange relaxation

The development of efficient quality of service (QoS) routing algorithms in a high‐speed networking or the next generation IP networking environment is a very important and at the same time very difficult task due to the need to provide divergent services with multiple QoS requirements. Recently, a heuristic algorithm H_MCOP, which is based on a non‐linear Lagrange relaxation (NLR) technique, has been proposed to resolve the contradiction between the time complexity and the quality of solution. Even though H_MCOP has demonstrated outstanding capability of finding feasible solutions to the multi‐path constrained (MCP) problem, it has not exploited the full capability that an NLR‐based technique could offer. In this paper, we propose a new NLR‐based heuristic called NLR_MCP, in which the search process is interpreted from a probability's perspective. Simulation results indicate that NLR_MCP can achieve a higher probability of finding feasible solutions than H_MCOP. We also verify that the performance improvement of a MCP heuristic has a tremendous impact on the performance of a higher level heuristic that uses a MCP heuristic as the basic step. Copyright © 2006 John Wiley & Sons, Ltd.     

渐变巴伦馈电的超宽带天线单元及阵列研究

为了满足超宽带电子系统对天线的需求, 研究了强互耦超宽带天线单元及阵列.首先设计了能够满足强耦合线极化的天线单元, 然后研究了超宽带相控阵天线阵, 设计了10×10天线单元组成的阵列.以此为基础, 利用高频电磁场仿真软件在二维周期环境中模拟了无限大周期阵列.结果表明, 在满足尺寸约束的前提下实现了二维周期边界下超宽带阵列的功能要求, 同时, 解决了强互耦效应下超宽带无限大偶极子相控阵进行全阵列仿真耗时极多、难度极大的问题.为了解决阵列单元如何有效馈电的问题, 在分析了天线单元结构设计的基础上, 研究了渐变结构巴伦的馈电特性, 并将这种馈电结构与上述强耦合超宽带天线单元相结合, 对单元结构和馈电方式进行了优化, 实现了超宽带馈电的效果.加工了天线阵列并在微波暗室中对不同频点进行了测试, 测试结果与仿真结果吻合.从测试结果可以看出, 主平面辐射方向图在不同频点内的最大扫描角波束峰值增益均大于5 dBi, 最大达到20 dBi, 满足设计要求.说明所设计的阵列天线能够应用于实际微波系统中.