Local histogram based geometric invariant image watermarking

Compared with other existing methods, the feature point-based image watermarking schemes can resist to global geometric attacks and local geometric attacks, especially cropping and random bending attacks (RBAs), by binding watermark synchronization with salient image characteristics. However, the watermark detection rate remains low in the current feature point-based watermarking schemes. The main reason is that both of feature point extraction and watermark embedding are more or less related to the pixel position, which is seriously distorted by the interpolation error and the shift problem during geometric attacks. In view of these facts, this paper proposes a geometrically robust image watermarking scheme based on local histogram. Our scheme mainly consists of three components: (1) feature points extraction and local circular regions (LCRs) construction are conducted by using Harris-Laplace detector; (2) a mechanism of grapy theoretical clustering-based feature selection is used to choose a set of non-overlapped LCRs, then geometrically invariant LCRs are completely formed through dominant orientation normalization; and (3) the histogram and mean statistically independent of the pixel position are calculated over the selected LCRs and utilized to embed watermarks. Experimental results demonstrate that the proposed scheme can provide sufficient robustness against geometric attacks as well as common image processing operations. (C) 2010 Elsevier B.V. All rights reserved.

模糊免疫非线性PID控制的优化设计

在深入分析生物免疫系统中T细胞对B细胞辅助调节作用的基础上,提出了免疫反馈原理。针对非最小相位极点系统控制的难点,借鉴免疫反馈原理,结合积分控制的规律,提出了一种模糊免疫非线性PID控制方法。由于该方法中的参数确定比较复杂,利用免疫进化算法进行参数优化设计,实现了控制参数的合理设计。仿真结果表明,该方法在非最小相位极点系统控制中可行且有效,优于PID控制方法,具有更好的响应特性和抗干扰性能。

理性遗传算法及其在多机器人运动协调中的应用

面对传统遗传算法在解决一些复杂问题时所存在的收敛慢或早熟等困难 ,基于仿人理性决策原则 ,提出一种具有更丰富进化含义的进化算法——理性遗传算法 .其通过遗传信息的反馈或理性规则的建立来指导遗传操作的进行 ,从而将种群内部知识与经验的继承和学习更有效地结合在遗传算法之中 .相对于传统遗传算法 ,较好地解决了多机器人确知环境下协调运动规划问题 .理论分析和仿真实验结果都是令人鼓舞的 .

成批生产计划调度的集成建模与优化

针对多品种批量生产类型,建立了调度约束的生产计划与调度集成优化模型。模型的目标函数是使总调整费用、库存费用及生产费用之和最小,约束函数包括库存平衡约束和生产能力约束,同时考虑了调度约束,即工序顺序约束和工件在单机上的加工能力约束,保证了计划可行性。该模型为两层混合整数规划模型,对其求解综合运用了遗传算法和启发式规则,提出了混合启发式求解算法。最后,针对某机床厂多品种批量生产类型车间进行了实例应用,对车间零件月份作业计划进行分解,得到各工段单元零件周作业计划,确定了零件各周生产批量与投产顺序。

Coherent enhancement of broadband frequency up-conversion in BBO crystal by shaping femtosecond laser pulses

An optimal feedback control of broadband frequency up-conversion in BBO crystal is experimentally demonstrated by shaping femto-second laser pulses based on genetic algorithm, and the frequency up-conversion efficiency can be enhanced by similar to 16%. SPIDER results show that the optimal laser pulses have shorter pulse-width with the little negative chirp than the original pulse with the little positive chirp. By modulating the fundamental spectral phase with periodic square distribution on SLM-256, the frequency up-conversion can be effectively controlled by the factor of about 17%. The experimental results indicate that the broadband frequency up-conversion efficiency is related to both of second harmonic generation (SHG) and sum frequency generation (SFG), where the former depends on the fundamental pulse intensity, and the latter depends on not only the fundamental pulse intensity but also the fundamental pulse spectral phase. (c) 2006 Elsevier B.V. All rights reserved.

强外加电场与大调制度下光折变动力学光栅形成研究

强外加电场与大调制度在光折变效应的研究中已经得到了广泛应用。采用PDECOL算法, 严格求解光折变带输运方程, 得到外加电场时不同调制度下光折变晶体中随时间变化的空间电荷场、载流子浓度, 并讨论了外加电场对它们的影响。通过将物质方程与耦合波方程联立数值求解, 可得到光折变光栅形成过程中两波耦合增益系数以及光束条纹相位的变化。模拟结果表明, 在强外加电场作用下, 两束记录光之间的光强与相位耦合都得到了增强, 而原有的解析式忽视了强外加电场与大调制度对空间电荷场相位耦合的影响, 此时不再适用。同时发现折射率光

Far-field spot compression without energy loss in main lob in wireless laser communication

Far-field spot compression without energy loss in main lob is of great significance to wireless laser communication. In this letter, we propose two schemes to obtain far-field spot compression without energy loss in main lob. One scheme is based on the simulated annealing (SA) algorithm. Using SA algorithm, we design the phase profile of the diffractive phase element (DPE). Using the designed DPE, far-field spot compression without energy loss in main lob is achieved. The other scheme is based on YG algorithm. By means of YG algorithm, we appropriately designed the DPE in the emitting plane. Using the DPE, far-field spot compression without energy loss in main lob is obtained. (c) 2007 Elsevier GmbH. All rights reserved.

Characterization of TRPC2, an Essential Genetic Component of VNS Chemoreception, Provides Insights into the Evolution of Pheromonal Olfaction in Secondary-Adapted Marine Mammals

Pheromones are chemical cues released and sensed by individuals of the same species, which are of major importance in regulating reproductive and social behaviors of mammals. Generally, they are detected by the vomeronasal system (VNS). Here, we first investigated and compared an essential genetic component of vomeronasal chemoreception, that is, TRPC2 gene, of four marine mammals varying the degree of aquatic specialization and related terrestrial species in order to provide insights into the evolution of pheromonal olfaction in the mammalian transition from land to water. Our results based on sequence characterizations and evolutionary analyses, for the first time, show the evidence for the ancestral impairment of vomeronasal pheromone signal transduction pathway in fully aquatic cetaceans, supporting a reduced or absent dependence on olfaction as a result of the complete adaptation to the marine habitat, whereas the amphibious California sea lion was found to have a putatively functional TRPC2 gene, which is still under strong selective pressures, reflecting the reliance of terrestrial environment on chemical recognition among the semiadapted marine mammals. Interestingly, our study found that, unlike that of the California sea lion, TRPC2 genes of the harbor seal and the river otter, both of which are also semiaquatic, are pseudogenes. Our data suggest that other unknown selective pressures or sensory modalities might have promoted the independent absence of a functional VNS in these two species. In this respect, the evolution of pheromonal olfaction in marine mammals appears to be more complex and confusing than has been previously thought. Our study makes a useful contribution to the current understanding of the evolution of pheromone perception of mammals in response to selective pressures from an aquatic environment.

Gene duplication in the genome of parasitic Giardia lamblia

Background: Giardia are a group of widespread intestinal protozoan parasites in a number of vertebrates. Much evidence from G. lamblia indicated they might be the most primitive extant eukaryotes. When and how such a group of the earliest branching unicellular eukaryotes developed the ability to successfully parasitize the latest branching higher eukaryotes (vertebrates) is an intriguing question. Gene duplication has long been thought to be the most common mechanism in the production of primary resources for the origin of evolutionary novelties. In order to parse the evolutionary trajectory of Giardia parasitic lifestyle, here we carried out a genome-wide analysis about gene duplication patterns in G. lamblia. Results: Although genomic comparison showed that in G. lamblia the contents of many fundamental biologic pathways are simplified and the whole genome is very compact, in our study 40% of its genes were identified as duplicated genes. Evolutionary distance analyses of these duplicated genes indicated two rounds of large scale duplication events had occurred in G. lamblia genome. Functional annotation of them further showed that the majority of recent duplicated genes are VSPs (Variant-specific Surface Proteins), which are essential for the successful parasitic life of Giardia in hosts. Based on evolutionary comparison with their hosts, it was found that the rapid expansion of VSPs in G. lamblia is consistent with the evolutionary radiation of placental mammals. Conclusions: Based on the genome-wide analysis of duplicated genes in G. lamblia, we found that gene duplication was essential for the origin and evolution of Giardia parasitic lifestyle. The recent expansion of VSPs uniquely occurring in G. lamblia is consistent with the increment of its hosts. Therefore we proposed a hypothesis that the increment of Giradia hosts might be the driving force for the rapid expansion of VSPs.

一种空间飞行器编队重组的轨道优化方法

现有的空间飞行器编队重组的轨道规划方法在求解能量最优策略时,都预先给定了变轨花费的时间,但没有说明给定的时间是怎么选择的。将空间飞行器主从编队重组的轨道规划视为一个多目标优化问题,提出了一种小生境进化算法。该方法通过使用特定的染色体表示方法和进化算子,能有效的搜索到飞行器编队重组轨道规划问题的时间-能量前沿,并引入等值分享法保证优秀个体具有较大的选中概率和前沿的多样性。该方法能同时提供多种变轨方案,编队飞行的任务制定者从而可以根据实际应用情况选择最合适的方案。仿真结果表明了该方法的正确性。

基于Rete算法的多Agent的实时协同推理

1 引言多Agent系统是由若干具有一个或多个目标的Agent按照一定的信息关系和控制关系以及问题求解能力的分布模式组成的系统,它主要研究一组在逻辑上或物理上分离的Agent之间行为的协调。目前,多Agent系统已应用于诸如空中交通控制、电子商务、通讯网络管理和作业调度等生产实际领域。Agent技术应用到实际领域时映射的对象一般有

基于半监督学习的P2P协议识别

随着P2P技术的发展,网络上充满了大量的P2P应用。协议加密技术的发展,使得P2P应用的识别和管理变得非常困难。描述了如何运用半监督的机器学习理论,根据传输层的特征,用聚类算法训练数据并建立一个高效的在线协议识别器,用于在内核协议层对协议特别是P2P协议进行识别,并对BitComet和Emule进行了实验,得到了很高的识别准确率(80%)。研究并解决了将选取好的特征用于聚类并高效地实现最后的协议识别器。

基于libMini的动态地形实时渲染算法

为了减少地形动态变化时的地形计算时间,满足动态地形实时可视化的需要,在地形渲染库libMini的基础上,依据地形动态变化的局部性特点,以及库中LOD(Level ofDetail)算法的具体实现方式,运用局部更新的思想,提出了一种动态地形实时计算和渲染算法.算法避免了在地形动态变化时进行大量重复计算,使得在地形动态变化时所需的计算量大大减少,达到实时渲染要求.实验表明,算法使得局部地形动态变化时地形计算和渲染的时间从秒级降低到毫秒级,可以满足实时渲染要求.