基于FPGA的基-16FFT模块的实现

阐述了采用Alter公司的StratixⅡ系列FPGA设计高速FFT处理器的实现方法及技巧;充分利用其芯片的硬件资源,减少复杂逻辑,采用流水方式对复数数据实现了FFT运算;整个设计采用流水与并行方式尽量避免“瓶颈”的出现,提高系统时钟频率,达到高速处理;实验表明,此处理器既有专用ASIC电路的快速性,又有DSP器件灵活性的特点,适合用于高速数字信号处理。     

一种基于分块大容量的LSB算法

信息隐藏的原理就是利用多媒体中存在很大的冗余信息来隐藏秘密信息。该文在传统的LSB算法基础上,结合人类视觉系统的掩蔽特性,对载体图像分成平滑区、边缘区和纹理区,相应地嵌入秘密信息;实验结果表明,用该算法进行信息隐藏具有较好的隐蔽性,且具有较大的隐藏容量。     

SAR image de-noising via grouping-based PCA and guided filter

A novel synthetic aperture radar(SAR)image de-noising method based on the local pixel grouping(LPG)principal component analysis(PCA)and guided filter is proposed.This method contains two steps.In the first step,we process the noisy image by coarse filters,which can suppress the speckle effectively.The original SAR image is transformed into the additive noise model by logarithmic transform with deviation correction.Then,we use the pixel and its nearest neighbors as a vector to select training samples from the local window by LPG based on the block similar matching.The LPG method ensures that only the similar sample patches are used in the local statistical calculation of PCA transform estimation,so that the local features of the image can be well preserved after coefficients shrinkage in the PCA domain.In the second step,we do the guided filtering which can effectively eliminate small artifacts left over from the coarse filtering.Experimental results of simulated and real SAR images show that the proposed method outstrips the state-of-the-art image de-noising methods in the peak signalto-noise ratio(PSNR),the structural similarity(SSIM)index and the equivalent number of looks(ENLs),and is of perceived image quality.     

基于分子动力学的P(VDF50-TrFE50)高电场极化仿真

P(VDF-TrFE)类共聚物具有优异的铁电性能,可用于制作柔性压电传感器。在试验研究中,通常采用高电场极化来增强其压电效应。为了研究该共聚物的传感特性,本文利用分子动力学模拟软件Materials Studio(MS)建立P(VDF₅₀-TrFE₅₀)的三维晶胞模型,模拟高电场极化过程,分析各项极化条件对其剩余极化的影响。结果显示：在高电场强度下,晶胞内的大部分铁电畴在极短时间内完成翻转;P(VDF₅₀-TrFE₅₀)的极化强度与外加电场强度正相关,但当电场强度高于5 V/nm后,极化强度增长减缓;晶胞在低温时保持铁电相而在高温时转变为顺电相;被充分极化的P(VDF₅₀-TrFE₅₀)晶胞的最高剩余极化强度为59.94 mC/m²。该研究表明MS软件具有模拟P(VDF-TrFE)聚合物材料压电特性的能力,可为后续试验研究及传感器制作提供仿真依据。     

Short-range clutter suppression method combining oblique projection and interpolation in airborne CFA radar

The airborne conformal array(CFA)radar's clutter ridges are range-modulated,which result in a bias in the estimation of the clutter covariance matrix(CCM)of the cell under test(CUT),further,reducing the clutter suppression performance of the airborne CFA radar.The clutter ridges can be effectively compensated by the space-time separation interpolation(STSINT)method,which costs less computation than the space-time interpolation(STINT)method,but the performance of interpolation algorithms is seriously affected by the short-range clutter,especially near the platform height.Location distributions of CFA are free,which yields serious impact that range spaces of steering vector matrices are non-orthogonal complement and even no longer disjoint.Further,a new method is proposed that the shortrange clutter is pre-processed by oblique projection with the intersected range spaces(OPIRS),and then clutter data after being pre-processed are compensated to the desired range bin through the STSINT method.The OPIRS also has good compatibility and can be used in combination with many existing methods.At the same time,oblique projectors of OPIRS can be obtained in advance,so the proposed method has almost the same computational load as the traditional compensation method.In addition,the proposed method can perform well when the channel error exists.Computer simulation results verify the effectiveness of the proposed method.     

一种改进的解相关LMS自适应算法

针对变步长LMS自适应滤波算法在输入信号高度相关时,收敛速度下降导致性能下降的问题,提出了一种改进的解相关LMS自适应算法,该算法引入解相关原理和归一化处理,用输入向量的正交分量来更新滤波器权系数,有效加快了算法的收敛速度,且稳态误差小,使得算法在有色输入和大范围的动态输入下都能保持良好性能.     

用于地月空间VLBI的加权全频谱信号合成技术

在我国探月工程四期嫦娥七号任务中,中继星将搭载一个4.2 m口径的X波段抛物面望远镜.该望远镜将与地基望远镜构成具有400000 km空地基线的月球轨道VLBI实验系统,实施地月空间VLBI实验.为尽可能提高空地VLBI基线灵敏度,提出了采用加权全频谱合成(FSC)技术增强地基信号.本文先理论推导了信号合成后的效果及两个望远镜信号合成时的最优加权系数比值.然后设计了VLBI加权全频谱合成算法,并基于实测信号利用网格搜索的方法找到最优加权系数,结果与理论推导相符.最后,利用“嫦娥四号”多组VLBI原始观测信号进行测试.结果表明,本文设计的信号合成算法可以大幅度提高VLBI基线射电源信号的信噪比.     

过渡金属修饰的杂原子掺杂多孔碳基氧还原和析氧催化剂的研究进展

高效且清洁的能源储存和转换装置对未来的社会发展至关重要.然而,金属空气电池、燃料电池、电解水制氢等设备中涉及的氧还原反应(ORR)迟缓的动力学和析氧反应(OER)较大的过电势限制了这些设备的能源效率和运行寿命.廉价、高效、稳定且环保的ORR和OER催化剂的制备是推动能源转换装置商用的关键环节.本文总结了过渡金属修饰的杂原子掺杂多孔碳基ORR和OER催化剂的最新研究进展,并重点评述了其结构与性能之间的关系.最后,从理论计算的角度讨论了活性位点的电子结构特性对碳基材料电化学性能的影响,并展望了该领域所面临的挑战和机遇.     

超高性能混凝土组合桥面板集群化短焊钉抗疲劳特性

进行4个单钉和2个群钉疲劳推出试验,将短焊钉疲劳寿命与国内外规范中的焊钉S-N曲线进行比较,并结合塑性损伤有限元模型展开分析。结果表明：短焊钉疲劳破坏表现为根部剪断和周围超高性能混凝土（UHPC）局部压溃;集群化短焊钉疲劳寿命较单钉减少26.9%,在疲劳加载过程中抗剪刚度退化显著快于单钉,当加载次数达到疲劳寿命的12.0%附近时,抗剪刚度比减小至16%左右;AASHTO规范有较大的安全储备,相比之下日本规范（JSCE）与试验结果最为接近,安全富余较少。此外,疲劳荷载下集群化短焊钉根部循环应变幅大于单钉,而且周边UHPC的塑性损伤累积分布更大。     

考虑员工移动成本的车缝生产线平衡问题

针对车缝生产线多品种小批量和自动化程度低等特点,提出了考虑员工多工序作业移动成本和为瓶颈工序增设适量设备的车缝生产线平衡问题。通过引入虚拟工作站和标准在制品（SWIP）库存概念,构建最大平衡率和最小生产节拍的双目标优化模型。最后,通过设计枚举算法和基于贪婪搜索策略的多目标遗传算法获取新增设备方案、标准在制品数量以及线平衡优化方案。车缝生产线实例计算结果表明,线平衡率及生产效率得到大幅提升,验证了模型和算法的合理性与有效性。