基于DCT的大容量二值水印嵌入新算法

传统的基于DCT变换的二值水印嵌入算法通常是在分块系数矩阵中选择一对中频系数实现1bit水印信息的嵌入,水印嵌入容量有限,为提高载体图像的安全性,提出了一种新的基于DCT的大容量二值水印嵌入算法.本算法首先对二值水印图像进行Arnold置乱加密处理,其次对所选取的载体图像进行分块DCT变换,然后选择4个中频系数进行排序,充分利用两两之间的3个差值关系实现水印的嵌入.若待嵌入水印位为0,通过改变系数值使得差值大于或等于阈值A,若待嵌入水印位为1,通过改变系数值使得差值等于阈值B,最终使得每块选择4个系数值实现了3bit二值水印信息的嵌入,水印嵌入容量大大优于传统方法.仿真实验表明,本算法实现了大容量水印的嵌入与提取且抵抗图像裁剪、图像加噪、JPEG压缩等攻击效果较好.     

Enhancing Resistive Switching Performance and Ambient Stability of Hybrid Perovskite Single Crystals via Embedding Colloidal Quantum Dots

Hybrid organic‐inorganic halide perovskites are actively pursued for optoelectronic technologies, but the poor stability is the Achilles’ heel of these materials that hinders their applications. Very recently, it has been shown that lead sulfide (PbS) quantum dots (QDs) can form epitaxial interfaces with the perovskite matrix and enhance the overall stability. In this work, it is demonstrated that embedding QDs can significantly modify the transport property of pristine perovskite single crystals, endowing them with new functionalities besides being structurally robust and free from grain boundaries. Resistive switching memory devices are constructed using solution‐processed CH₃NH₃PbBr₃ (MAPbBr₃) perovskite single crystals and the QD‐embedded counterparts. It is found that QDs could significantly enhance the charge transport and reduce the current–voltage hysteresis. The pristine singe crystal device exhibits negative differential resistance, while the QD‐embedded crystals are featured with filament‐type switching behavior and much improved device stability. This study underscores the potential of QD‐embedded hybrid perovskites as a new media for advanced electronic devices.     

Analysis of blind data hiding using discrete cosine transform phase modulation

This paper presents an analysis for data embedding in two-dimensional signals based on DCT phase modulation. A communication system model for this data embedding scheme is developed. Closed form expressions for estimating the number of bits that can be embedded given a specific distortion measure and the probability of bit error are developed. The data embedding process is viewed as transmitting data through a binary symmetric channel with crossover error probabilities, which depends only on the power in the selected coefficients and the noise created by the signal processing operations undergone by the image.     

Boosting up the data hiding rate through multi cycle embedment process

Prediction error based multi-layer data embedment schemes conceal secrets into several high frequency errors by modifying their prediction error histogram (PEH). It is investigated that k-times data embedment into n/k errors of PEH produces higher embedding payload, while maintaining better stego-image quality compared to those for embedding into n distinct errors for a single time only. This paper proposes a novel multi-cycle embedment scheme in which data is embedded into the errors of a defined range in each of its k cycles. Experiments were conducted to examine the performance of the proposed scheme comparing the multi-layer vs. multi-cycle embedding schemes individually and jointly. The scheme explores the points at which significantly better payloads can be obtained at the lower image distortions. Substantial improved performance were obtained during investigations, especially while large volume data embedment. The proposed scheme can embed massive and hybrid data of type text, numeric, image and audio.     

A sequentially self-seeded Fabry-Perot laser for two-dimensional encoding/decoding of optical pulses

Multiwavelength optical pulse trains with variable two-dimensional (2-D) code patterns formed by a single encoder have been generated from a self-seeded gain-switched Fabry-Perot (F-P) laser for the first time. Mechanically tunable cascaded fiber Bragg gratings (FBG) are used to construct the reconfigurable encoder, which acts as a discrete nonlinear dispersive component in the subharmonically pulse-gated external cavity of the laser to generate multiwavelength pulse trains with a variable 2-D code pattern defined by the settings of the FBG string. Four distinct repetitive patterns (corresponding to four different 2-D codes) of optical pulse trains, each made up of up to four pulses generated sequentially with different wavelengths, have been produced at a repetition rate of 250 MHz. The output pulses obtained by this method are much more intense and stable than those obtained from a free-running F-P laser. Furthermore, the different pulse patterns obtained show that the scheme can allow easy switching among different 2-D codes by simply reconfiguring the FBG string. Hence this laser with the embedded reconfigurable encoder should be a viable optical source for incoherent 2-D fiber-optic code-division multiple access (FO-CDMA) applications. Near-error-free transmission of data at 250 Mbit/s employing this laser/encoder over 9.5 km standard single mode fiber has been successfully demonstrated, thus confirming its performance and viability for FO-CDMA.     

一种小波域自适应鲁棒闭环数字盲水印技术

本文提出了一种基于小波域的闭环自适应图像鲁棒数字盲水印技术.水印的嵌入过程是一个闭环过程,且其嵌入的位置及强度均与原始图像有关.水印嵌入的初始强度由小波域图像压缩的量化因子决定,并根据检测要求不断的进行调整,从而达到水印的最佳嵌入.本文证明了这种闭环系统的收敛性,并且给出了水印检测过程中正确检测概率和虚警检测概率的求解公式,可用于闭环系统的检测性能判决条件.水印的检测过程中不需要任何原始图像和原始水印信号的信息,采用独立分量分析实现对水印信号的盲检测.检测过程中不仅可以检测到水印的存在,而且可以提取出嵌入到图像中的多个水印信号.实验结果证实了本文提出的闭环自适应数字盲水印技术优于传统的自适应水印技术,水印检测过程中在不需要考虑水印图像所经历的攻击类型及攻击参数的情况下可以正确的提取水印信号.本文提出的水印算法对通用水印测试软件Stirmark具有很好的鲁棒性.     

EFFECT OF PERIODIC DEFECTS ON ELECTROMAGENTIC SCATTERING BY THE TWO-DIMENSIONAL PHOTONIC CRYSTALS

Electromagnetic scattering from two-dimensional photonic crystals with two-dimensionally periodic defects is analyzed using a model of multilayered periodic arrays of parallel circular cylinders. The reflectance of the photonic crystals of finite thickness, which are free-standing or embedded in a dielectric slab, is obtained in terms of the lattice-sums, the T-matrix of a circular cylinder, and the generalized reflection matrix for a layered system. Numerical examples demonstrate that the refection and transmission bands of the crystals are reformed by introducing the periodic defects and their band natures are very sensitive to the polarization of excitation and the relative position of the defect element within a unit cell.     

话音通信中的数据自适应隐藏算法

基于话音通信的PCM量化编码,导出了数据嵌入强度因子的选取准则,给出了两种自适应选取的实现策略,进而提出了根据载体信号的幅度以及信道的噪声强度自适应调整的数据隐藏算法.隐藏信息为二进制比特数据时,仿真实验结果表明该自适应隐藏方法具有良好的隐蔽信息传输性能.     

一种DCT域的闭环数字水印技术

本文提出了一种DCT域的闭环数字水印技术，水印的嵌入是一个闭环过程。水印嵌入的初始强度由视觉系统结合JPEG量化表确定，并根据性能分析的结果不断调整水印的嵌入，如果性能分析结果满足某种检测要求或者水印的嵌入已经影响了图像的显示质量，相应调整水印嵌入的强度，以实现水印的最佳嵌入。本文证明了所提出的闭环水印过程具有收敛性，还对检测过程中的似然函数的分布规律进行了分析，得到正确检测率和错误检测概率的表达式，可作为闭环系统的判决条件。实验结果证明这种闭环水印技术比传统DCT域的水印技术性能好。     

矢量变换域内灰度级数字水印嵌入算法

本文提出了一种新的数字静止图像的水印嵌入算法,该算法将含有丰富细节信息的灰度级图像作为水印,水印嵌入过程不是在传统的标量变换域(如离散余弦变换域等)内进行,而是在矢量变换域实现.实验结果表明该算法具有很好的稳健性.     

An Authentication Technique for Image/Legal Document (ATILD)

The paper presents an image/legal-document authentication and secures message transmission technique by embedding message/image/message-digest into color images. Image authentication is done by embedding message/image within the image pixels of source image. Legal document authentication is done by embedding the authenticating image and self generated message digest (generated from signed document part) into the image part of the legal document. The position of insertion is chosen within each byte of source image using XOR operation between upper three bits of each source byte and k where k is any number from 0 to 7. Three bits of authenticating message/image/message-digest are embedded in each byte of source image. Fabrication process starts with the dimension of authenticating image followed by message digest (MD) and ends by embedding the content of authenticating message/image. To enhance the security further a layer has also been fabricated by XOR operation of the embedded image with another self generated MD key obtained from the source image. The decoding is done by applying the reverse algorithm. Experimental results are tested with the aid of Histogram analysis, noise analysis, standard deviation computation and PSNR, IF, MSE analysis of the source and embedded image and has been compared with popular existing steganographic algorithms like S-Tools where the proposed ATILD is capable to hide large volume of data than S-Tools and shows better performance. The proposed ATILD technique also shows high amount of sustainability against various attacks.     

基于图像插值的大容量可逆水印算法

提出一种基于图像插值的大容量可逆水印算法 。首先,对输入图像进行下采样 处理,利用某种图像插值方法对下采样生成的图像进行插值放大,得到待嵌入水印信号的载 体图像;然后,对载体 图像进行分块,得到每一分块4个基准像素的最大值和最小值,之后计算每一个非基准像素 分别与最大值和最小值 差值的绝对值,根据自适应选定的差值,计算每一个非基准像素能嵌入的最大水印位数;最 后,从待嵌入的水印信 号中将每一个非基准像素能嵌入的位数转换为十进制数,并将此数修改像素值,完成水印 信号的嵌入。大量的仿 真实验结果表明,本文算法不会出现像素值溢出现象,能实现可逆数据隐藏;与相似的基于 图像插值的可逆水印算法 相比,该算法的嵌入率(ER,embedding rate)更高;在相同 的ER条件下,本文算法的性能更好。     

一个利用双线性对和部分盲签名的电子现金支付方案

论文基于双线性对和部分肓签名构造了个电子现金支付方案。双线性对构造的签名方案具有签字短、安全、高效等特点,并将部分盲签名加入其中,既有效保护消息发送方的隐私权,又能够通过加入签名方的信息来提高存款时银行的处理效率。     

Dual-frequency slotted rectangular microstrip antenna

By embedding a pair of properly-bent narrow slots close to the non-radiating edges of a rectangular microstrip patch, a novel dual-frequency operation of microstrip antennas using a single probe feed is proposed and experimentally studied. The two operating frequencies have parallel polarisation planes and similar broadside radiation patterns, and the frequency ratio of the two frequencies is controlled by the bent angle of the embedded slots. Details of the obtained dual-frequency performance are presented and discussed     

适合光镜和电镜诊断肾小球疾病的固定剂选择

目的：为了使已经石蜡包埋的肾穿组织脱蜡后进行电镜观察,关键是选择适当的固定剂。方法：在石蜡包埋前,肾穿组织分别用甲醛、戊二醛及戊二醛、锇酸双固定。根据光镜和电镜观察结果,选择能兼顾光镜和电镜的固定剂。结果：甲醛固定不能有效保存肾穿组织的超微结构,锇酸的固定能有效地保存超微结构,但严重影响了光镜切片的染色;而戊二醛与甲醛相比,较好地保存了肾穿组织的超微结构,同时又不影响光镜切片的染色。结论：在石蜡包     

Radiation from a Line Source Placed in Two-dimensional Photonic Crystals

A novel formulation of radiation from a localized line source placed in two-dimensional photonic crystals consisting of layered periodic arrays of parallel circular cylinders is presented. The method employs the spectral domain approach. The spectral response of the photonic crystals to the line source excitation is calculated using the lattice sums, the T-matrix of a circular cylinder, and the generalized reflection and transmission matrices of the layered system. The far-zone radiated field is obtained using the conventional asymptotic method to the spectral response. The radiation patterns of the localized line source sandwiched by two photonic crystals are numerically studied.     

A High Capacity Steganographic Method Based on Quantization Table Modification and F5 Algorithm

This paper presents a steganographic method based on quantization table modification and the F5 algorithm. This method has a larger embedded secret message capacity and improves the embedding strategy to avoid “shrinkage” due to the use of the F5 algorithm. The experimental results show that, in comparison with the F5 algorithm and other methods, the proposed method has a higher steganographic capacity and an improved embedding efficiency. In terms of the structural similarity as well as PSNR for assessing image quality, the stego-image has better image quality and the proposed method has better anti-attack capability.     

Considering the reconstruction loop for data hiding of intra- and inter-frames of H.264/AVC

This paper presents and analyzes a new approach to data hiding that embeds in both the intra- and inter-frames from the H.264/AVC video codec. Most of the current video data hiding algorithms take into account only the intra-frames for message embedding. This may be attributed to the perception that inter-frames are highly compressed due to the motion compensation, and any embedding message inside these may adversely affect the compression efficiency significantly. Payload of the inter-frames is also thought to be less, compared with the intra-frames, because of the lesser residual data. We analyze data hiding in both intra- and inter-frames over a wide range of QP values and observe that the payload of the inter is comparable with that of the intra-frames. Message embedding, in only those non-zero quantized transform coefficients (QTCs) which are above a specific threshold, enables us to detect and extract the message on the decoding side. There is no significant effect on the overall bitrate and PSNR of the video bitstream because instead of embedding message in the compressed bitstream, we have embedded it during the encoding process by taking into account the reconstruction loop. For the non-zero QTCs, in the case of intra-frames, we benefit from the spatial masking, while in the case of inter-frames, we exploit the motion and texture masking. We can notice that the data hiding is done during the compression process and the proposed scheme takes into account the reconstruction loop. The proposed scheme does not target robustness and the obtained payload is higher, with a better trade-off in terms of quality and bitrate, as compared with previous works.     

Real structure of partially ordered crystals

Partial order in crystals is a frequently observed phenomenon in minerals and synthetic materials. The partially ordered structures are characterized by low-dimensional order of the real structure. In the case of 1D structures, the ordered units can be described as rods; 2D structures contain ordered layers. The disorder of the real structures is indicated by prominent diffuse scattering in the diffraction patterns of single crystals. No simple method for the quantitative analysis of the diffuse scattering exists, therefore the determination of essential characteristics of the structures is complicated. However, the determination can be facilitated using a combination of different methods, including electron microscopy, computation and X-ray diffraction.     

Embedded Test Decompressor to Reduce the Required Channels and Vector Memory of Tester for Complex Processor Circuit

An embedded test stimulus decompressor is presented for the test patterns decompression, which can reduce the required channels and vector memory of automatic test equipment (ATE) for complex processor circuit. The proposed decompressor mainly consists of a periodically alterable MUX network which has multiple configurations to decode the input information flexibly and efficiently. In order to reduce the number of test patterns and configurations, a test patterns compaction algorithm, using CI-Graph merging, is proposed. With the proposed periodically alterable MUX network and the patterns compaction algorithm, smaller test data volume and required external pins can be achieved as compared to previous techniques