An SVD-based image watermarking in wavelet domain using SVR and PSO

The paper presents a novel blind watermarking scheme for image copyright protection, which is developed in the discrete wavelet transform (DWT) and is based on the singular value decomposition (SVD) and the support vector regression (SVR). Its embedding algorithm hides a watermark bit in the low–low (LL) subband of a target non-overlap block of the host image by modifying a coefficient of U component on SVD version of the block. A blind watermark-extraction is designed using a trained SVR to estimate original coefficients. Subsequently, the watermark bit can be computed using the watermarked coefficient and its corresponding estimate coefficient. Additionally, the particle swarm optimization (PSO) is further utilized to optimize the proposed scheme. Experimental results show the proposed scheme possesses significant improvements in both transparency and robustness, and is superior to existing methods under consideration here.     

工艺参数对选择性激光烧结PS/SBS/纳米CaCO3制件弯曲强度影响

针对聚苯乙烯(PS)粉末选择性激光烧结(SLS)成型件强度较低的问题,采用机械混合法制备了PS/苯乙烯–丁二烯–苯乙烯嵌段共聚物(SBS)/纳米CaCO₃复合粉末,通过单因素实验分析了SLS工艺参数对成型件弯曲强度的影响,并通过正交试验和极差分析获得了最优工艺参数组合。实验结果表明,烧结件的弯曲强度随着激光功率的增大而升高,随着扫描速度、扫描间距和分层厚度的增大而降低;激光功率对PS/SBS/纳米CaCO₃复合粉末烧结件弯曲强度的影响最大,分层厚度对弯曲强度的影响最小,扫描速度和扫描间距的影响介于两者之间;最佳工艺参数组合为:激光功率27 W,扫描速度1300 mm/s,扫描间距0.24 mm,单层厚度0.22 mm。在此工艺参数组合下PS/SBS/纳米CaCO₃复合粉末烧结件的弯曲强度为13.38 MPa;改性纳米CaCO₃与PS和SBS的相容性较好,能有效起到增强的作用。     

自适应滤波语音增强算法改进及其DSP实现

为提高强噪声环境下语音信号的信噪比,增强语音通信的质量,以DSP为平台,构建一个基于自适应滤波技术的单通道语音增强系统。该系统以TMS320F2812为核心,结合其多通道缓冲串口(McBSP)与扩展音频接口芯片TLV320AIC23实现了语音信号的高速采集及输出;同时,利用箕舌线函数更新自适应滤波步长因子并引入解相关运算进行语音降噪处理,有效改善了传统算法适应性差,收敛速度慢,稳态误差大等问题。实验结果表明该算法降噪性能好,能明显提高语音清晰度,且系统稳定性强。     

随机图点覆盖1度顶点核化算法分析

将随机图引入参数计算领域,利用随机图统计和概率分布等特性,从全局和整体上研究参数化点覆盖问题1度点核化过程中问题的核及度分布演变的内在机制和变化规律,并得出关于随机图1度点核化强度与顶点平均度关系及随机图点覆盖问题的决策与度分布关系的两个重要推论.最后分别从MIPS和BIND提取数据进行1度核化实验和分析.初步结果表明,对随机图点覆盖问题的分析方法不仅具有理论上的意义,而且随着问题随机度的大小而对问题有不同程度的把握能力.     

基于子图的随机图点覆盖2度点核化研究

点覆盖问题虽然可以在参数计算理论的架构内求精确解,但是目前在理论及应用上有一定的局限性.根据不同度的顶点之间及顶点与边的关系,提出随机图参数化点覆盖问题的d-核化可决策性及2度点三角形予图的计数方法;通过研究子图对顶点的共享关系,分析2度顶点核化过程中核及度分布演变的动态过程,得出随机图2度点核化强度与2度点概率关系及2度点核化可决策性的两个推论:2度点核化算法对2度点分布概率约为0.75的随机图的核化强度最高;对顶点度概率分布为φ(χ)的随机图的参数化点覆盖问题(G,k),当k小于某一与φ(х)有关的值时,它是2-核化可决策的.仿真结果证实,该理论能够把握2度点核化的内在机制,提供随机图上这一NP完全问题的求解方法,也为参数计算在已知度分布的一类不确定问题中的应用提供了可能.     

天然气净化脱硫系统模拟与优化方案

针对陕北某天然气净化厂因靖边气田开发规模不断增大,致原料气中酸性组分含量较设计值高、生产系统故障频繁,本文选择Deshmukh-Mather方程作为理想的热力学模型和DESIGNⅡ软件全流程模拟MDEA溶液循环量提高后的脱硫系统,以确定需要核算的相关设备,最后利用FRI和HTRI等专业软件校核其优化前后的运行状况。结果表明,胺液吸收塔和再生塔的流体力学性能均符合要求,其工作点亦落在塔盘负荷性能图的中部适当位置;在现有浮头式胺液贫富液换热器的基础上,串联地增加1台同型号、同尺寸的换热器,并适当调整其换热管规格即可达到指定的换热要求,解决堵塞现象;用增加换热管管束、翅化换热管表面、提高热媒流率与进口温度等多种手段,均可提高胺液重沸器的换热效果。     

一种低成本光纤双向视频数据传输系统的设计

介绍利用波分复用技术（WDM）设计了一种低成本光纤双向视频和数据信号传输系统,实现了在一根单模光纤中传输数据信号和视频信号。视频信号传输采用基带直接强度调制（D-IM）技术,而数据信号传输利用频移键控（FSK）技术。该系统实现了无中继传输距离大于6km,适合中短距离视频、数据的传输,设计方案简易、成本低廉、图像质量良好成为该系统的主要特点。     

Formation and Height of the Interconnected Fractures Zone after Extraction of Thick Coal Seams with Weak Overburden in Western China

Formation of a zone of interconnected fractures during coal mining is a key factor in mine flooding. Coal mines in western China are characterized by thick coal seams with mechanically weak overburden. In situ studies including drill core analysis, drilling fluid loss measurement, and borehole video monitoring were used at the working face 101 in Shaanxi Jinjitan coal mine to explore the maximum height of the interconnected fractures zone (IFZ). Also, tests on a scaled physical model and numerical simulation based on the drilling data were used to study the formation of the fractured zone. By considering data from other mines with similar mining conditions, a logarithmic relationship was found between the maximum height of the IFZ and the thickness of coal excavation. The maximum height of the IFZ was found to be 27 times the thickness of the excavated coal seam, which is far more than in coal mining areas in eastern China. Also, the IFZ in overlying strata of the study area was arch-shaped, not saddle-shaped, as had been observed in previous studies.     

Berberine as an Environmental-Friendly Inhibitor for Hot-Dip Coated Steels in Diluted Hydrochloric Acid

The inhibition effect of an excellent environmental-friendly corrosion inhibitor-berberine on hot-dip coated steels in the diluted HCl has been investigated by using quantum chemistry analysis, mass-loss tests, electrochemical measurements and scanning electron microscopy (SEM) observation. Calculation results show that berberine has a nearly planar structure with a number of active centers. The value of Mulliken charge, and the distribution of the highest occupied molecular orbital (HOMO) and the lower unoccupied molecular orbital (LUMO) imply that berberine has a good ability of electron exchange with metal surface. The test results indicate that inhibition efficiency (IE%) increases with the inhibitor concentration and the highest IE can reach 99%. Adsorption of berberine on the coating surface follows Langmuir adsorption isotherm with a single molecular layer by chemisorption.     

致密WC增强铁基表面复合材料的原位制备与形成机理

利用铸渗复合-热处理工艺制备致密碳化钨增强铁基表面复合材料,研究了不同保温时间下复合材料的物相组成与微观组织.结果表明,不同保温时间下,复合材料表面均有致密碳化钨层生成,反应层厚度最大为148 μm.致密碳化钨层的显微硬度随保温时间无明显变化,均明显高于铁基体.铁基表面致密碳化钨的形成主要依赖于Fe-C-W体系中碳和钨原子的扩散与原位反应.