共查询到20条相似文献,搜索用时 844 毫秒
1.
介绍了离散余弦变换的系数特征,提出了一种基于离散余弦变换的彩色图像置乱数字水印算法。算法是将数字水印置乱加密后微小的扰动原始彩色图像经离散余弦变换后的对应系数,从而达到数字水印嵌入的目的。仿真实验表明算法简单高效,原图像与嵌入水印后图像差异小,水印提取准确,能较好的保证数字水印不可感知性,在对嵌入水印图像进行各种加噪、裁剪、旋转、锐化等处理后,水印仍有较强的鲁棒性。 相似文献
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提出了一种基于离散余弦变换的彩色图像数字水印算法.首先原始彩色图像的绿色分量进行8 x 8分块DCT变换.计算每块的噪声阈值,相应调整每块选取的两个中频系数的大小,把经过Arnold置乱加密的二值水印图像嵌入.水印提取时,不需要原始图像.实验结果表明,该算法能有效抵抗JPEG压缩、裁剪、加噪、图像增强等攻击,具有良好的透明性和较强的稳健性. 相似文献
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提出了一种基于整数小波变换的视频水印技术.算法首先对水印进行混沌加密和Arnold置乱处理和借助密钥选取r帧视频;其次对选取视频帧的每一通道进行互不重叠的8×8分块和对选取的每一分块进行1级整数小波变换;最后根据视觉掩蔽特性来自适应调整两相邻块对应高频子带均值之间的大小关系以嵌入水印.实验表明,该算法实现简单,具有较好的透明性和鲁棒性. 相似文献
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音频作品被非法篡改会导致作者利益受到侵害,因此音频水印嵌入提取算法的研究在数字产品版权保护中具有重要的研究价值。针对音频水印的特性及评价进行分析,分别基于离散小波变换、离散余弦变换以及DWT-DCT-SVD等算法,重点研究音频水印评价标准中透明性和鲁棒性问题。考虑相同音频及水印,针对不同的嵌入提取算法从透明性及鲁棒性两方面进行对比分析。结果表明,DWT-DCT-SVD算法在透明性及鲁棒性方面更具优势,为数字产品版权保护中音频水印算法的选择、应用及优化提供了重要的理论及应用依据。 相似文献
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一种基于离散余弦变换与奇异值分解的数字图像水印算法 总被引:2,自引:1,他引:2
结合奇异值分解(SVD)和离散余弦变换(OCT)的特点,提出了一种基于离散余弦交换与奇异值分解的数字图像水印算法.该算法能够很好地解决透明性和鲁棒性之间的矛盾.算法中采用经过置乱变换的灰度图作为水印,不仅增加了嵌入的信息量,而且提高了水印的安全性.实验结果表明,该算法不仅具有较好的透明性,而且对常见攻击如:叠加噪声、JPEG压缩、滤波以及几何攻击等具有较好的鲁棒性. 相似文献
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基于离散四元数余弦变换的彩色图像数字水印技术 总被引:1,自引:0,他引:1
将离散四元数余弦变换(DQCT)应用于彩色图像的数字水印技术中,提出了一种在彩色图像中嵌入水印的新技术。应用四元数理论把彩色图像作为一整体进行余弦变换,在彩色宿主图像的DQCT域中实现彩色水印图像的嵌入。实验表明,该方法具有较好的抗压缩能力,对高斯噪声、椒盐噪声和缩放攻击具有较好的鲁棒性。 相似文献
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基于Arnold置乱和DCT变换的图像水印算法 总被引:3,自引:2,他引:1
采用灰度图像为水印信息,对基本离散余弦变换域图像数字水印算法进行改进,为保证信息的安全性,在嵌入宿主图像之前结合Arnold变换进行加密。通过在图像块离散余弦变换域中修改中频区来嵌入不同强度的水印。实验结果证明该算法提高了水印检测的准确性,并且该算法具有较好的不可见性和鲁棒性。 相似文献
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GU Min-fen LIANG Zhong-cheng WANG Ren-zhou DONG Xiang-mei ZHANG Pei-ming CHEN Jia-bi 《光电子快报》2008,4(2):150-152
Waveguide multilayer optical card (WMOC) is a novel storage device of three-dimensional optical information. An advanced readout system fitting for the WMOC is introduced in this paper. The hardware mainly consists of the light source for reading, WMOC, motorized stages addressing unit, microscope imaging unit, CCD detecting unit and PC controlling & processing unit. The movement of the precision motorized stage is controlled by the computer through Visual Basic (VB) language in software. A control panel is also designed to get the layer address and the page address through which the position of the motorized stages can be changed. The WMOC readout system is easy to manage and the readout result is directly displayed on computer monitor. 相似文献
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R.Pelzer P.Lindner T.Glinsner B.Vratzov C.Gourgon S.Landis P Kettner C.Schaefer 《半导体技术》2004,29(7):86-91
IntroductionNanoimprint Lithography is a well-acknowl-edged low cost, high resolution, large area pattern-ing process. It includes the most promising methods,high-pressure hot embossing lithography (HEL) [2],UV-cured imprinting (UV-NIL) [3] and micro contactprinting (m-CP, MCP) [4]. Curing of the imprintedstructures is either done by subsequent UV-lightexposure in the case of UV-NIL or by cooling downbelow the glass transition temperature of the ther-moplastic material in case of HEL… 相似文献
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The collinearly phase-matching condition of terahertz-wave generation via difference frequency mixed in GaAs and InP is theoretically studied. In collinear phase-matching, the optimum phase-matching wave hands of these two crystals are calculated. The optimum phase-matching wave bands in GaAs and lnP are 0.95-1.38μm and 0.7-0.96μm respectively. The influence of the wavelength choice of the pump wave on the coherent length in THz-wave tuning is also discussed. The influence of the temperature alteration on the phase-matching and the temperature tuning properties in GaAs crystal are calculated and analyzed. It can serve for the following experiments as a theoretical evidence and a reference as well. 相似文献
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Composition dependence of bulk and surface phonon-polaritons in ternary mixed crystals are studied in the framework of the modified random-element-isodisplacement model and the Bom-Huang approximation. The numerical results for Several Ⅱ - Ⅵ and Ⅲ- Ⅴ compound systems are performed, and the polariton frequencies as functions of the compositions for ternary mixed crystals AlxGa1-xAs, GaPxAS1-x, ZnSxSe1-x, GaAsxSb1-x, GaxIn1-xP, and ZnxCd1-xS as examples are given and discussed. The results show that the dependence of the energies of two branches of bulk phonon-polaritons which have phonon-like characteristics, and surface phonon-polaritons on the compositions of ternary mixed crystals are nonlinear and different from those of the corresponding binary systems. 相似文献
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A doping system consisting of NPB and PVK is employed as a composite hole transporting layer (CHTL). By adjusting the component ratio of the doping system, a series of devices with different concentration proportion of PVK : NPB are constracted. The result shows that doping concentration of NPB enhances the competence of hole transporting ability, and modifies the recombination region of charge as well as affects the surface morphology of doped film. Optimum device with a maximum brightness of 7852 cd/m^2 and a power efficiency of 1.75 lm/W has been obtained by choosing a concentration proportion of PVK : NPB at 1:3. 相似文献
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An insert layer structure organic electroluminescent device(OLED) based on a new luminescent material (Zn(salen)) is fabricated. The configuration of the device is ITO/CuPc/NPD/Zn(salen)/Liq/LiF/A1/CuPc/NPD/Zn(salen)/Liq/LiF/A1. Effective insert electrode layers comprising LiF(1nm)/Al(5 nm) are used as a single semitransparent mirror, and bilayer cathode LiF(1 nm)/A1(100 nm) is used as a reflecting mirror. The two mirrors form a Fabry-Perot microcavity and two emissive units. The maximum brightness and luminous efficiency reach 674 cd/m^2 and 2.652 cd/A, respectively, which are 2.1 and 3.7 times higher than the conventional device, respectively. The superior brightness and luminous efficiency over conventional single-unit devices are attributed to microcavity effect. 相似文献
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Due to variable symbol length of digital pulse interval modulation(DPIM), it is difficult to analyze the error performances of Turbo coded DPIM. To solve this problem, a fixed-length digital pulse interval modulation(FDPIM) method is provided. The FDPIM modulation structure is introduced. The packet error rates of uncoded FDPIM are analyzed and compared with that of DPIM. Bit error rates of Turbo coded FDPIM are simulated based on three kinds of analytical models under weak turbulence channel. The results show that packet error rate of uncoded FDPIM is inferior to that of uncoded DPIM. However, FDPIM is easy to be implemented and easy to be combined, with Turbo code for soft-decision because of its fixed length. Besides, the introduction of Turbo code in this modulation can decrease the average power about 10 dBm, which means that it can improve the error performance of the system effectively. 相似文献
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It is a key problem to accurately calculate beam spots' center of measuring the warp by using a collimated laser. A new method, named double geometrical center method (DGCM), is put forward for the first time. In this method, a plane wave perpendicularly irradiates an aperture stop, and a charge couple device (CCD) is employed to receive the diffraction-beam spots, then the geometrical centers of the fast and the second diffraction-beam spots are calculated respectively, and their mean value is regarded as the center of datum beam. In face of such adverse instances as laser intension distributing defectively, part of the image being saturated, this method can still work well. What's more, this method can detect whether an unacceptable error exits in the courses of image receiving, processing and calculating. The experimental results indicate the precision of this method is high. 相似文献
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Thomas M.Trexler 《半导体技术》2004,29(5)
From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test. 相似文献
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The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high. 相似文献