复合材料层合开顶扁球壳在集中冲击下的非线性动力屈曲

研究了具有刚性中心的复合材料层合开顶扁球壳在中心集中冲击载荷作用下的非线性动力屈曲问题。通过增加横向转动惯量项得到中心集中冲击下复合材料层合开顶扁球壳非线性稳定性的控制方程，采用Galerkin方法得到以刚性中心位移表达的冲击动力响应方程，并用Runge-Kutta方法进行数值求解，应用Budiansky-Roth准则（简称B—R准则）确定冲击屈曲的临界荷载；讨论了壳体几何尺寸对复合材料层合开顶扁球壳冲击屈曲的影响。     

Ni-SiC脉冲电镀工艺对SiC共沉积量及镀层耐磨性的影响

采用脉冲电镀法制备了Ni-SiC复合镀层,考察了镀液中SiC质量浓度、脉冲平均电流密度、镀液pH值对复合镀层中SiC共沉积量及镀层耐磨性能的影响.结果表明:电镀工艺参数的改变影响镀层中SiC的共沉积量以及复合镀层的耐磨性.选择适当的工艺参数,可以制备出SiC共沉积量高、微粒弥散较均匀的耐磨复合镀层.复合镀层的抗磨性能不仅与硬质微粒的共沉积量有关,而且与微粒在镀层中分布的均匀性有很大关系,在共沉积量相同的情况下,微粒的分散性越好,镀层的抗磨损性能就越好.     

脉冲宽度对激光熔覆FeSiB涂层组织与硬度的影响

以FeSiB非晶带材为熔覆材料,采用激光熔覆在低碳钢表面制备高致密度涂层,利用光学显微镜(OM)、X射线衍射仪(XRD)、扫描电子显微镜(SEM)、显微硬度仪等研究不同脉冲宽度对激光熔覆涂层成形、组织特征及硬度的影响。结果表明:随脉冲宽度增大,涂层稀释率升高;裂纹倾向增加,裂纹源萌生由表面到界面处;晶化程度升高,结晶相为α-Fe,Fe_2B和Fe_3Si;熔合区宽度增大,柱状晶沿外延生长趋势更大;显微硬度先增加后减小。当脉冲宽度为3.2ms时,涂层结构致密,无孔洞缺陷,界面呈良好的冶金结合,稀释率低,为23.2%,涂层平均显微硬度达1192HV,约为基材的10倍。     

复合材料层合扁锥壳的冲击屈曲

研究了计及横向剪切的对称铺设正交异性复合材料层合扁锥壳在三角脉冲载荷作用下的非线性动力屈曲问题；通过在复合材料层合扁锥壳非线性稳定性的基本方程中增加横向转动惯量项并引入三角脉冲冲击力，得到了层合扁锥壳的冲击控制方程，采用Galerkin方法得到以顶点挠度表达的冲击响应方程，并用Runge—Kutta方法进行数值求解，应用B—R准则确定冲击屈曲的临界荷载；讨论了壳体几何参数、物理参数和边界条件对复合材料层合扁锥壳冲击屈曲的影响。     

Pseudo-Stokes Vector Correlation From Complex Signal Representation of a Speckle Pattern and Its Applications to Micro-Displacement Measurement

Abstract:  As an improvement of the intensity correlation used widely in conventional electronic speckle photography, we propose a new technique for displacement measurement based on correlating Stokes-like parameters derivatives for transformed speckle patterns. The method is based on a Riesz transform of the intensity speckle pattern, which converts the original real-valued signal into a complex signal. In closest analogy to the polarisation of a vector wave, the Stokes-like vector constructed from the spatial derivative of the generated complex signal has been applied for correlation. Experimental results are presented that demonstrate the validity and advantage of the proposed pseudo-Stokes vector correlation technique over conventional intensity correlation technique.     

脉冲管制冷机交变流动动态特性数值研究：第一部分;基本方程和数值方法

针对脉冲管制冷机的特点建立了数值模拟模型，采用改进的数值模拟方法对脉冲管制冷机的内部交变流动，换热以及制冷过程进行了详尽的数值研究，得到了脉冲管制冷机内部各参数的动态变化，并分析了各动态参数变化对制冷机整机性能的影响。数值模拟分析与实验结果符合良好。该模拟方法从基本流动换热微分方程出发，尽可能多地考虑实际制冷机工作过程中的各种不可逆因素，包括实际气体的物性变化，各部件的流动阻力和传热损失。     

基于声压幅度比的多声源分离定位决策研究

利用声压幅度比模型,提出了一种基于声压幅度比的多声源分离定位方法,该方法利用盲信号分离算法实现混合声源信号的分离,根据谱估计的相似度确定接收信号中各声源的分配情况,结合幅度差异因子获得传感器的声源信号分布,再通过单声源的声压幅度比模型确定声源位置,实现多声源定位。由于盲信号分离算法比较成熟,且实际中的声源信号大多为非高斯,因而满足盲信号分离条件。该方法具有实用强、应用性广等特点,对其它分离、定位问题也有借鉴作用。     

RS-LOD方法及其在旋转机械故障特征提取中的应用

局部波动特征分解(LOD)方法是一种新的自适应时频分析方法。该方法通过采用微分、坐标域变换、分段线性变换三种运算,可以高效地将信号自适应分解为一系列的单一波动分量(MOC),非常适合于处理多分量信号。然而,由于分段线性变换的使用,虽可以显著提高算法的计算效率,但会使MOC分量缺乏光滑性,从而导致失真。对此,将样条曲线形状可调可控的有理样条函数引入LOD方法替代分段线性变换,提出了基于有理样条函数的局部波动特征分解(RS-LOD)方法。在详细阐述RS-LOD分解原理的基础上,通过仿真信号将RS-LOD、LOD和经验模态分解(EMD)进行了对比分析,结果表明RS-LOD方法可以明显改善原LOD方法中MOC分量光滑度差的问题。此外,针对旋转机械故障振动信号的多分量调制特点,将RS-LOD方法应用于旋转机械的故障特征提取,对滚动轴承和齿轮箱故障振动信号的分析结果表明,RS-LOD方法可以有效地提取旋转机械振动信号的故障特征。     

流量测量中超声多普勒信号的频谱特点及其与管道中流速的关系

研究了工业测流的超声多普勒信号的频谱特点，并以此为依据分析了不同安装方式对多普勒频谱的影响，提出了不同测量环境下，应用多普勒频谱计算流速的公式及必要的修正，为提高检测准确度提供了理论依据。     

Tumor detection in T1, T2, FLAIR and MPR brain images using a combination of optimization and fuzzy clustering improved by seed‐based region growing algorithm

Tumor and Edema region present in Magnetic Resonance (MR) brain image can be segmented using Optimization and Clustering merged with seed‐based region growing algorithm. The proposed algorithm shows effectiveness in tumor detection in T1 ‐ w, T2 – w, Fluid Attenuated Inversion Recovery and Multiplanar Reconstruction type MR brain images. After an initial level segmentation exhibited by Modified Particle Swarm Optimization (MPSO) and Fuzzy C – Means (FCM) algorithm, the seed points are initialized using the region growing algorithm and based on these seed points; tumor detection in MR brain images is done. The parameters taken for comparison with the conventional techniques are Mean Square Error, Peak Signal to Noise Ratio, Jaccard (Tanimoto) index, Dice Overlap indices and Computational Time. These parameters prove the efficacy of the proposed algorithm. Heterogeneous type tumor regions present in the input MR brain images are segmented using the proposed algorithm. Furthermore, the algorithm shows augmentation in the process of brain tumor identification. Availability of gold standard images has led to the comparison of the suggested algorithm with MPSO‐based FCM and conventional Region Growing algorithm. Also, the algorithm recommended through this research is capable of producing Similarity Index value of 0.96, Overlap Fraction value of 0.97 and Extra Fraction value of 0.05, which are far better than the values articulated by MPSO‐based FCM and Region Growing algorithm. The proposed algorithm favors the segmentation of contrast enhanced images. © 2017 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 27, 33–45, 2017