GPS接收信号中线性扫频干扰的抑制

研究了阵列接收的GPS接收信号中线性扫频(LFM)干扰的抑制问题。LFM信号瞬时频率的估计是抑制干扰的关键,而要准确估计信号瞬时频率,必须抑制接收信号时频分布中交叉项干扰。本文对接收信号矢量进行白化,得到信号矢量白化后的空时频分布(STFD)矩阵。文中推出一个与传统方法获得的判决变量不同的判决变量,用该判决变量可以更加清晰地选出LFM信号在时频分布中的自项。根据时频脊点的分布估计LFM信号频率参数以及信号瞬时频率,之后即可根据瞬时频率构建陷波器滤除干扰。仿真表明该方法能够将受交叉项严重干扰的接收信号时频分布映射为清晰的接收信号自项的时频分布,在数据快拍数满足一定要求时可以很好地抑制掉LFM干扰。     

结合流形滤波的矩阵信息几何检测器

针对小样本、非均匀杂波下的信号检测问题,提出一种基于流形滤波的矩阵信息几何检测器,将信号检测问题转化为矩阵流形上的几何问题。将每一个样本的相关性数据建模为一个托普利兹正定矩阵,在此基础上,利用每一个样本数据的邻近矩阵进行加权平滑滤波,去除一部分杂波能量,提升目标与杂波间的区分性。计算了辅助样本数据对应矩阵的几何均值,通过比较待检测样本数据矩阵与几何均值矩阵之间的距离与检测门限的大小,以实现信号检测。实验结果表明,与自适应匹配滤波相比,本文方法在小样本、非均匀杂波下具有明显的性能优势。     

Investigation of the mechanical and ballistic properties of hybrid carbon/ aramid woven laminates

High-performance ballistic fibers, such as aramid fiber and ultra-high-molecular-weight polyethylene (UHMWPE), are commonly used in anti-ballistic structures due to their low density, high tensile strength and high specific modulus. However, their low modulus in the thickness direction and insufficient shear strength limits their application in certain ballistic structure. In contrast, carbon fiber reinforced epoxy resin matrix composites (CFRP) have the characteristics of high modulus in the thickness direction and high shear resistance. However, carbon fibers are rarely used and applied for protection purposes. A hybridization with aramid fiber reinforced epoxy resin matrix composites (AFRP) and CFRP has the potential to improve the stiffness and the ballistic property of the typical ballistic fiber composites. The hybrid effects on the flexural property and ballistic performance of the hybrid CFRP/AFRP laminates were investigated. Through conducting mechanical property tests and ballistic tests, two sets of reliable simulation parameters for AFRP and CFRP were established using LS-DYNA software, respectively. The experimental results suggested that by increasing the content of CFRP that the flexural properties of hybrid CFRP/AFRP laminates were enhanced. The ballistic tests’ results and the simulation illustrated that the specific energy absorption by the perforation method of CFRP achieved 77.7% of AFRP. When CFRP was on the striking face, the shear resistance of the laminates and the resistance force to the projectiles was promoted at the initial penetration stage. The proportion of fiber tensile failures in the AFRP layers was also enhanced with the addition of CFRP during the penetration process. These improvements resulted in the ballistic performance of hybrid CFRP/AFRP laminates was better than AFRP when the CFRP content was 20 wt% and 30 wt%.     

钢丝增强复合条带抗弹性能数值分析

为研究钢丝增强聚合物基复合条带的抗弹性能,基于冲击动力学理论分析其抗弹机理,再借助ANSYS/LS-DYNA软件和LS-PrePost前后处理器模拟有无增强钢丝2种工况下,条带对7.62 mm弹体的冲击响应。分析表明：条带的弹性模量、剪切模量和面密度会影响其能量吸收性能,能量吸收量随三者的增大而增大;由于聚合物基体的正交各向异性,应力云图显示出扁平椭圆状是合理的;在聚合物基复合条带中嵌入增强钢丝对条带整体的抗弹性能有积极的影响,但嵌入过量的钢丝会导致重量和成本的增加,因此需要对合理的钢丝配比率作进一步研究。研究结果可为钢丝增强聚合物基复合条带在野战防护结构中的应用提供参考。     

热塑性互穿聚合物网络研究综述

概述了热塑性互穿聚合物网络（ＴＩＰＮ）的研究进展及其结构特点、制各方法和熔体的流动性,并对ＴＩＰＮ的前景作了简要的分析。     

一类复三次样条的保凸条件

本文研究了一类定义在实轴区间上亏数为１的复三次样条的保凸条件,推广了文［２］Ｃ￣２连续的实三次多项式样条的相应结果。     

用矩阵法FTA 进行非单调关联系统的早期不交化

本文针对带有重复事件的非单调关联系统故障树,定义了非单调关联系统的割集矩阵及不交化最小割集矩阵,利用矩阵变换实现故障树的早期不交化,从而为求解复杂非单调关联系统,解决其ＮＰ困难问题,提供了一条新途径     

点阵图形的二次压缩法

基于YH-1巨型机,本文详细介绍了一种计算机图形的二次压缩法。该方法已经在YHHT 图形软件上成功地实现,应用结果证明这种方法是高效的。     

Approximation methods for the analysis of a multicomponent,multiproduct assemble‐to‐order system

In this article, we consider the performance evaluation of a multicomponent, multiproduct assemble‐to‐order (ATO) system. Each component is managed independently using a base‐stock policy at a supply facility with limited production capacity and an infinite buffer. The arrivals of demands follow a multivariate Poisson process and unfilled demands are backlogged. Because exact analysis of the proposed system is not feasible, we propose two approximation methods which provide upper and lower bounds for various performance measures such as fill rate, average waiting time, and average number of backorders of the proposed system. Our computational experiments demonstrate the effectiveness of the two approximation methods under various system settings. © 2011 Wiley Periodicals, Inc. Naval Research Logistics, 2011     

多核数字信号处理器并行矩阵转置算法优化

矩阵转置是矩阵运算的基本操作,广泛应用于信号处理、科学计算以及深度学习等各种领域。随着国防科技大学自主研制的飞腾异构多核数字信号处理器(digital signal processor, DSP)在各种领域中的推广应用,对高性能矩阵转置实现提出了强烈需求。针对飞腾异构多核DSP的体系结构特征与矩阵转置操作的特点,提出了一种适配不同数据位宽(8 B、4 B以及2 B)矩阵的并行矩阵转置算法ftmMT。该算法基于DSP中向量处理单元的Load/Store部件实现了向量化,同时基于矩阵分块实现了多个DSP核的并行处理,通过隐式乒乓设计实现了片上向量化转置与片外访存的重叠以及访存性能的大幅提升。实验结果表明,ftmMT能够显著加快矩阵转置操作,与CPU上的开源转置库HPTT相比,可获得高达8.99倍的性能加速。