利用相位恢复波前传感技术检测球面镜面形

为了验证相位恢复波前传感器系统波前检测的能力,搭建了基于相位恢复测量方法的波前传感器检测球面镜面形的实验平台。该平台结构简单,抗震动,可以在对光路不进行任何改变的前提下,利用成像系统上已有的相机对整个光学系统进行在位检测。为了验证相位恢复波前传感器测量方法的准确性,将相位恢复波前传感器测量结果与ZYGO干涉仪测量结果进行比较,实验结果表明在面形误差分布及误差的峰谷值(PV)和方均根值(RMS)上,两者具有极大的相似性,所以利用相位恢复波前传感器技术能有效地检测出球面镜的面形误差。     

基于多项式Chirplet变换和变分模态分解的变转速工况轴向柱塞泵故障诊断

针对变转速工况轴向柱塞泵故障诊断时故障特征提取困难的问题,提出了基于多项式Chirplet变换和变分模态分解的诊断方法。首先使用多项式Chirplet变换估计瞬时频率;然后基于估计的瞬时频率重采样,将时域非平稳信号转化为角域平稳信号;最后对角域信号进行变分模态分解。根据峭度对所得的本征模态函数分量进行重构并作包络阶次谱分析,判断轴向柱塞泵中轴承的故障类型。实验结果表明,该方法有效提取了变转速工况轴向柱塞泵轴承的故障特征。     

基于并行处理的一种新型有效的网络架构 BSN-MOT

摘 要：结合BSN及MOT架构的双重优势,提出一种新型的双层架构体系BSN-MOT(mesh of tree),并研究了其上的拓扑性质及在并行处理中应用的基本的通信操作算法。算法包括行、列树广播、单向广播、数据求和、矩阵乘积、最短路径路由及多项式求根。最后,本文通过与其他2种有效的树形双层网络架构Multi-Mesh of trees(MMT)及OMULT比较说明,基于BSN-MOT架构的通信算法要比其他2种网络有着更小些的时间复杂度,且BSN-MOT是一种更具有竞争力的体系结构形式。     

新的基于变色龙的车载通信安全与隐私保护

在车载自组网（VANET）中许多服务和应用需要保护数据通信的安全,为提高驾驶的安全性和舒适性,一些与交通状况有关的信息就要被周期性地广播并分享给司机,如果用户的身份和信息没有隐私和安全的保证,攻击者就会通过收集和分析交通信息追踪他们感兴趣的车辆,因此,匿名消息身份验证是VANET中不可或缺的要求。另一方面,当车辆参与纠纷事件时,证书颁发机构能够恢复车辆的真实身份。为解决车载通信这一问题,郭等人在传统方案的基础上提出一种基于椭圆曲线的变色龙散列的隐私保护验证协议。虽然此方案较之前方案具有车辆身份可追踪性和高效率性,但分析表明此方案不满足匿名性。对郭等人的方案进行安全性分析并在此基础上做出改进。     

Novel computational methods for high‐dimensional stochastic sensitivity analysis

This paper presents three new computational methods for calculating design sensitivities of statistical moments and reliability of high‐dimensional complex systems subject to random input. The first method represents a novel integration of the polynomial dimensional decomposition (PDD) of a multivariate stochastic response function and score functions. Applied to the statistical moments, the method provides mean‐square convergent analytical expressions of design sensitivities of the first two moments of a stochastic response. The second and third methods, relevant to probability distribution or reliability analysis, exploit two distinct combinations built on PDD: the PDD‐saddlepoint approximation (SPA) or PDD‐SPA method, entailing SPA and score functions; and the PDD‐Monte Carlo simulation (MCS) or PDD‐MCS method, utilizing the embedded MCS of the PDD approximation and score functions. For all three methods developed, the statistical moments or failure probabilities and their design sensitivities are both determined concurrently from a single stochastic analysis or simulation. Numerical examples, including a 100‐dimensional mathematical problem, indicate that the new methods developed provide not only theoretically convergent or accurate design sensitivities, but also computationally efficient solutions. A practical example involving robust design optimization of a three‐hole bracket illustrates the usefulness of the proposed methods. Copyright © 2014 John Wiley & Sons, Ltd.     

Optimization of the fabrication of novel stealth PLA-based nanoparticles by dispersion polymerization using D-optimal mixture design

Purpose: Nanoparticle size is important in drug delivery. Clearance of nanoparticles by cells of the reticuloendothelial system has been reported to increase with increase in particle size. Further, nanoparticles should be small enough to avoid lung or spleen filtering effects. Endocytosis and accumulation in tumor tissue by the enhanced permeability and retention effect are also processes that are influenced by particle size. We present the results of studies designed to optimize cross-linked biodegradable stealth polymeric nanoparticles fabricated by dispersion polymerization.

Methods: Nanoparticles were fabricated using different amounts of macromonomer, initiators, crosslinking agent and stabilizer in a dioxane/DMSO/water solvent system. Confirmation of nanoparticle formation was by scanning electron microscopy (SEM). Particle size was measured by dynamic light scattering (DLS). D-optimal mixture statistical experimental design was used for the experimental runs, followed by model generation (Scheffe polynomial) and optimization with the aid of a computer software. Model verification was done by comparing particle size data of some suggested solutions to the predicted particle sizes.

Results and conclusion: Data showed that average particle sizes follow the same trend as predicted by the model. Negative terms in the model corresponding to the cross-linking agent and stabilizer indicate the important factors for minimizing particle size.     

斜视FMCW-SAR的四阶多项式插值波数域算法

FMCW-SAR因其体积小、重量轻、成本低和高分辨率等优点近年来发展迅速,在低成本的民事应用领域具有广阔的发展前景。FMCW-SAR 频率变标算法及其改进算法对距离-方位耦合相位项作了三阶近似,忽略二次和三次项的距离空变性,只能适用于窄测绘宽度、侧视及小斜视角情况。对中大斜视工作,文中提出了采用四阶多项式插值的波数域算法,给出了斜视下的距离徙动因子,考虑了二次距离压缩项的空变性和四次耦合项。利用典型参数,通过不同斜视角下误差相位的分析和点目标成像的仿真实验验证了所提算法的合理性和有效性。     

Identification and extraction of brain tumor from MRI using local statistics of Zernike moments

In this article, a novel method is proposed for the detection of brain tumor in magnetic resonance images (MRIs). The features of Zernike moments are used to analyze the MRIs. The image is divided into two parts from the center of the image based on the average value of the pixel located at the center boundary, and new image vectors are formed to extract the tumor. The local statistics values obtained from the low and high order Zernike moments are used to calculate the appropriate threshold value for efficient tumor extraction. The proposed method successfully analyzes the tumor part of the image on testing with different MRIs.     

基于多片ADSP的PPS雷达信号参数估计算法实现

采用四片ADSP-TS101S构成的雷达信号参数估计平台,实现了基于三次相位函数的多项式相位信号参数估计算法。该算法只需要通过二阶非线性变换即可实现PPS的参数估计。硬件实验表明,该算法可在低信噪比条件下准确地估计PPS参数,并且通过多片流水式的并行处理,最大限度地节省了估计时间。