Image Steganography by Pixel-Value Differencing Using General Quantization Ranges

A new steganographic method by pixel-value differencing(PVD)using general quantization ranges of pixel pairs’difference values is proposed.The objective of this method is to provide a data embedding technique with a range table with range widths not limited to powers of 2,extending PVD-based methods to enhance their flexibility and data-embedding rates without changing their capabilities to resist security attacks.Specifically,the conventional PVD technique partitions a grayscale image into 1×2 non-overlapping blocks.The entire range[0,255]of all possible absolute values of the pixel pairs’grayscale differences in the blocks is divided into multiple quantization ranges.The width of each quantization range is a power of two to facilitate the direct embedding of the bit information with high embedding rates.Without using power-of-two range widths,the embedding rates can drop using conventional embedding techniques.In contrast,the proposed method uses general quantization range widths,and a multiple-based number conversion mechanism is employed skillfully to implement the use of nonpower-of-two range widths,with each pixel pair being employed to embed a digit in the multiple-based number.All the message bits are converted into a big multiple-based number whose digits can be embedded into the pixel pairs with a higher embedding rate.Good experimental results showed the feasibility of the proposed method and its resistance to security attacks.In addition,implementation examples are provided,where the proposed method adopts non-power-of-two range widths and employsmultiple-based number conversion to expand the data-hiding and steganalysis-resisting capabilities of other PVD methods.

基于差分非平稳Transformer的液压支架立柱压力预测

液压支架立柱压力预测是回采工艺决策的重要依据,也是确保围岩稳定的基础信息之一。然而,液压支架立柱压力虽然具有一定的规律性,却无法用简单的数学模型进行预测;且在回采过程中,支架不接顶、顶板破碎、传感器检测误差等带来大量的随机噪声,使得压力数据劣化为非平稳时间序列,给压力的预测带来的很大的困难。本文在Transformer基础上,提出一种差分非平稳Transformer模型,在Transformer的编码器和解码器中分别引入差分归一化和反归一化操作,以提升序列的平稳性。同时,在Transformer中采用去平稳注意力机制,计算序列元素之间的关联关系,以增强模型的预测能力。在真实的煤矿支架立柱数据集上的对比实验表明,本文提出的差分非平稳Transformer的预测效果达到0.674,表现明显优于LSTM、Transformer和非平稳Transformer模型。

顾及系统误差影响的智能手机GNSS观测值质量分析

针对现有智能手机观测值质量分析大多直接从原始观测值出发,未能顾及系统误差影响的问题,文中提出质量分析方法利用星间与历元间差分消除部分系统误差,再分别对智能手机伪距与载波进行质量分析。通过分析经预处理后的观测值以及原始观测值综合分析手机观测值质量。实验结果表明,智能手机在不同GNSS系统伪距质量不同,伪距标准差最大为2.115 m;手机载波质量较高,不同系统载波质量差异较小,其中载波标准差最大为0.1962 m;BDS的伪距质量优于其他系统,GPS载波质量优于BDS与Galileo。

基于FPGA的动态目标检测与防御躲避系统设计

针对传统动态目标检测实时性差、功耗高及精度低等问题,提出了一种基于FPGA芯片的高精度、低功耗动态目标检测与防御躲避系统。该系统采集OV5640摄像头像素信息,经DDR4高速缓存后,依次对图像进行多步预处理,包括灰度化、自适应快速中值滤波、改进型三帧间差分、形态学运算及包围盒检测等,在HDMI液晶屏上实时显示目标检测结果。系统根据计算出的动态目标中心坐标,驱动电机控制摄像头进行精准的对角躲避。硬件测试结果表明,该系统在50 MHz的时钟频率下,视频帧率达到60 FPS,具有较高的实时性和鲁棒性,能够清晰并准确检测出动态目标,且防御躲避设计可行,功耗仅为0.969 W。

基于TDCP历元间位置变化量的GNSS地质灾害快速变形识别

提出一种基于GNSS载波相位历元间差分(TDCP)位置变化量的地质灾害监测快速变形识别方法。通过TDCP解算历元间坐标变化量,识别监测体历元间显著位移,据此对卡尔曼滤波的过程噪声进行实时调节,使相对定位滤波结果能及时准确地反映监测体的快速变形。模拟实验结果表明,该方法既可以及时准确地反映监测体历元间大于1 cm的快速变形,同时又能保持mm级监测精度。

融合两帧差分法的改进视觉背景提取算法

针对视觉背景提取(visual background extractor,ViBe)算法在运动目标检测过程中容易受到噪声干扰的问题,将两帧差分法融入ViBe的前景检测阶段,提出一种融合两帧差分信息的改进ViBe算法(ViBe with two-frame differencing,ViBe-TD)。首先,设计单阈值形ViBe(single-threshold form of ViBe,S-ViBe)检测,为信息融合做准备;其次,基于逻辑斯蒂(logistic)回归模型,实现像素点上两帧差分和S-ViBe检测信息的融合;最后,综合两类检测信息完成前景像素点的判定。实验结果表明,ViBe-TD算法在4种不同场景视频上的检测效果达到了0.932的平均精确率,0.785的平均召回率以及0.842的平均F 1值。与原算法相比,ViBe-TD算法的各项指标平均有0.158的提高,具有良好的检测效果。

基于内部通道参考的时间失配误差校正方法

为了提升TIADC系统采样率,解决时间失配误差校正的主流方法参考通道法限制采样率提升的问题,在对时间失配误差的估计中以系统内部通道作为参考通道,提出一种基于内部通道参考的时间失配误差校正方法。采用内部通道参考方法估计出时间失配误差参数,中心求导法求得目标信号导数,利用时间失配误差参数和目标信号导数对时间失配误差进行重构并完成误差补偿。仿真结果表明,所提出的方法可以在后台、自适应、无额外限制的情况下,实现30 dB左右的无杂散动态范围提升,5位左右的有效位数提升。对误差的压制能力接近参考通道法。

Multi-channel differencing adaptive noise cancellation with multi-kernel method

Although a various of existing techniques are able to improve the performance of detection of the weak interesting sig- nal, how to adaptively and efficiently attenuate the intricate noises especially in the case of no available reference noise signal is still the bottleneck to be overcome. According to the characteristics of sonar arrays, a multi-channel differencing method is presented to provide the prerequisite reference noise. However, the ingre- dient of obtained reference noise is too complicated to be used to effectively reduce the interference noise only using the clas- sical linear cancellation methods. Hence, a novel adaptive noise cancellation method based on the multi-kernel normalized least- mean-square algorithm consisting of weighted linear and Gaussian kernel functions is proposed, which allows to simultaneously con- sider the cancellation of linear and nonlinear components in the reference noise. The simulation results demonstrate that the out- put signal-to-noise ratio （SNR） of the novel multi-kernel adaptive filtering method outperforms the conventional linear normalized least-mean-square method and the mono-kernel normalized least- mean-square method using the realistic noise data measured in the lake experiment.

Voltage-Mode Universal Biquad Filter Employing Single Voltage Differencing Differential Input Buffered Amplifier

A new multi function voltage-mode universal biquadratic filter using single Voltage Differencing Differential Input Buffered Amplifier (VD-DIBA), two capacitors and one resistor is proposed. The proposed configuration has four inputs and one output and can realize all the five standard filters from the same circuit configuration. The presented biquad filter offers low active and passive sensitivities. The validity of proposed universal biquadratic filter has been verified by SPICE simulation using 0.35 μm MIETEC technology.

New Predictor-Corrector Methods Based on Exponential Time Differencing forSystems of Nonlinear Differential Equations

We present the new predictor-corrector methods for systems of nonlinear differential equations, based on the method of exponential time differencing. We compare the present schemes with the explicit multistep exponential time differencing and Adams–Bashforth–Moulton method. The numerical results show that the schemes are more accurate and more efficient than Adams predictor-corrector method. The exponential time differencing method has been developed and perfected by the present studies.

Block-Based Steganographic Algorithm Using Modulus Function and Pixel-Value Differencing

The main purpose in developing the steganographic algorithms lies in achieving most of the steganographic objectives which comprise the embedding capacity, imperceptibility, security, robustness and complexity. In this paper, we propose a high quality steganographic algorithm using new block structure which makes a good use of both modulus function and pixel-value differencing, namely, MF-PVD. We have made many experiments with various test images from several galleries, such as USC-SIPI and UWATERLOO-LINK. The performance of our proposed algorithm is verified using three different performance metrics which include peak signal-to-noise ratio (PSNR), structural similarity index measure (SSIM), and embedding capacity (EC). Experimental results and comparisons with six pertinent state-of-art algorithms are given to prove the validation and efficiency of the proposed algorithm.

Exponential time differencing based efficient SC-PML for RCS simulation

To efficiently simulate and calculate the radar cross section(RCS) related electromagnetic problems by employing the finite-difference time-domain(FDTD) algorithm, an efficient stretched coordinate perfectly matched layer(ESC-PML) based upon the exponential time differencing(ETD) method is proposed.The proposed implementation can not only reduce the number of auxiliary variables in the SC-PML regions but also maintain the ability of the original SC-PML in terms of the absorbing performance. Compared with the other existed algorithms, the ETDFDTD method shows the least memory consumption resulting in the computational efficiency. The effectiveness and efficiency of the proposed ESC-PML scheme is verified through the RCS relevant problems including the perfect E conductor(PEC) sphere model and the patch antenna model. The results indicate that the proposed scheme has the advantages of the ETD-FDTD method and ESC-PML scheme in terms of high computational efficiency and considerable computational accuracy.

A Homogenized Function to Recover Wave Source by Solving a Small Scale Linear System of Differencing Equations

In order to recover unknown space-dependent function G(x)or unknown time-dependent function H(t)in the wave source F(x;t)=G(x)H(t),we develop a technique of homogenized function and differencing equations,which can significantly reduce the difficulty in the inverse wave source recovery problem,only needing to solve a few equations in the problem domain,since the initial condition/boundary conditions and a supplementary final time condition are satisfied automatically.As a consequence,the eigenfunctions are used to expand the trial solutions,and then a small scale linear system is solved to determine the expansion coefficients from the differencing equations.Because the ill-posedness of the inverse wave source problem is greatly reduced,the present method is accurate and stable against a large noise up to 50%,of which the numerical tests confirm the observation.

New Voltage Mode Sinusoidal Oscillator Using Voltage Differencing Transconductance Amplifiers (VDTAs)

The purpose of this paper is to introduce a new electronically controlled voltage mode sinusoidal oscillator (VMSO) using Voltage Differencing Transconductance Amplifiers (VDTA). The proposed circuit provides electronic control of ω0 and independent condition of oscillation (CO). It is found that the oscillator works very satisfactorily and pure sinusoidal waveforms are available at the outputs. The PSPICE simulation confirms the theoretical results. The proposed oscillator circuit employs only two VDTAs, along with two grounded capacitor and single grounded resistor. The circuit exhibits low active and passive sensitivities for ω0. Simulation results are obtained by using PSPICE software with TSMC CMOS 0.18 um process parameters.

Note on Filon-type integration for higher order exponential time differencing methods in stiff systems

The Filon-type quadrature is efficient for highly oscillatory functions - Fourier transforms. Based on Cox and Matthews' ETD schemes, the higher order single step exponential time differencing schemes are presented based on the Filon-type integration and the A-stability of the two-order Adams-Bashforth exponential time differencing scheme is considered. The effectiveness and accuracy of the schemes is tested.

励磁绕组短路下关键运行参数差异对汽轮发电机转子动力学特性的影响

分析了励磁绕组短路下,关键运行参数差异对汽轮发电机转子动力学特性的影响。关键运行参数包括短路程度、短路位置,以及电机负载率;转子动力学特性包括转子不平衡磁拉力激励特性、径向振动响应特性,以及转子铁芯动力学响应规律。基于柔性转子不平衡磁拉力激励与振动响应的理论分析、有限元仿真计算,以及动模试验来探索不同运行参数造成动力学特性差异的规律。结果表明:正常情况下转子不平衡磁拉力趋于零,转子振动以常规基频和定子传递过来的各偶次倍频为主;励磁绕组匝间短路下,转子不平衡磁拉力及其振动响应将产生新的奇次倍频成分,且通频振动幅值增大。随着短路程度或负载的增加,转子不平衡磁拉力与振动响应的基频将增大;短路位置越靠近大齿处,转子不平衡磁拉力与振动幅值越大;转子铁芯大齿的外表面和内槽表面边沿为动力学响应的危险位置。

国家生态文明试验区对省域绿色全要素生产率的影响及溢出效应研究

绿色全要素生产率是测度我国生态文明建设的重要抓手,其效果的评估对于凝聚改革合力、增添绿色发展动能、探索生态文明建设模式具有重要意义。基于Super-SBM和GML指数测算出我国内地30个省、市、自治区(除西藏外)2010~2020的绿色全要素生产率,运用双重差分法及其扩展的空间形式将国家生态文明试验区的政策作为一项准自然试验,考察其政策效果及溢出效应。研究结果表明:国家生态文明试验区政策显著提高了试点省份的绿色全要素生产率,且具有明显的空间溢出效应;该结论在动态时间窗、安慰剂等一系列检验下仍具有稳健性;渠道分析表明降低能源强度、优化产业结构、创新低碳技术和发展绿色信贷是国家生态文明试验区政策促进绿色全要素生产率提高的重要路径;异质性检验结果显示,生态基础较差和经济发展水平较好的地区,绿色全要素生产率的提升更加明显。本文的研究为评估国家生态文明试验区的政策效果提供了分析视角、总结了有效经验,也为我国生态文明建设的推广与应用提供了政策参考。

Multifunction Filter Employing Current Differencing Buffered Amplifier

This paper proposes a new filter biquad circuit, which utilizes three Current Differencing Buffered Amplifiers (CDBA), two capacitors and five resistors, and operates in the trans-resistance mode. This multi-input and single-output multifunction filter uses only grounded capacitors. All the employed resistors are either grounded or virtually grounded, which is an important parameter for its implementation as an integrated circuit. The circuit enjoys independent tunability of angular frequency and bandwidth. The 0.5 μm technology process parameters have been utilized to test and verify the performance characteristics of the circuit using PSPICE. The non-ideal analysis and sensitivity analysis, transient response, Monte-Carlo analysis and calculations of total harmonic distortion have also been shown.

混合时间差分和非差分载波相位的无人机精密单点定位

针对精密单点定位(PPP)在载波相位模糊度估计值收敛之前,定位精度波动较大,这一阶段对于传统PPP技术来说需要几十分钟的时间,难以满足快速无人机作业需求,且时间差分载波相位(TDCP)技术可以消除模糊度等常值变量,计算得到的历元间位置变化量精度较高,但是受系统误差影响较大且增加了数据的相关性,误差会随着时间积累等问题,提出一种PPP和TDCP相结合的无人机定位算法:基于20Hz高采样固定翼无人机实际观测数据,对比分析基于传统PPP、TDCP、混合TDCP与非差观测PPP 3种方法的无人机定位性能。结果表明,混合TDCP和传统非差观测的无人机PPP定位算法的精度较传统PPP方法提高71.5%。

交通可达性与制造业出口升级——基于空间溢出效应视角的经验分析

构建了能够客观反映城市交通基础设施发展的交通可达性指标,从理论和实证层面分析验证了交通改善影响城市制造业出口升级的传导机制与渠道,并通过构造外生冲击检验以及选取合宜的工具变量对内生性问题进行了良好处理,同时重点探讨了交通可达性提升对地区制造业出口升级的多维空间溢出效应。研究发现:交通可达性提升不仅能够显著促进城市制造业出口升级,还能够对邻接地区制造业出口升级产生正向空间溢出效应;交通可达性提升对城市制造业出口的溢出效应符合地理距离衰减规律,其溢出效应在300km以内最为稳定且强烈,之后逐渐衰减,并在900km处出现半衰期;高铁开通的外生冲击检验以及工具变量估计同样验证了交通可达性提升对城市制造业出口升级的促进作用。但对高铁开通溢出效应的进一步分解表明,高铁开通对城市制造业出口升级的空间溢出效应存在不对称性,其外溢效应仅表现为高铁城市间的组内溢出效应,而高铁开通城市对未开通高铁城市的组间溢出效应并不显著。进一步的机制分析表明,交通可达性提升主要通过优化城市资本要素错配、促进产业多样化集聚、强化知识技术溢出以及缓解劳动力市场分割进而促进城市制造业出口升级。