Gabor小波目标特征提取和跟踪方法的研究

为了解决目标在发生旋转、尺度及平移等几何变形时的自动跟踪问题,提出 Sobel 边缘检测与 L-M 优化结合的 Gabor 小波目标提取与跟踪方法。该方法自动寻找目标的小波特征点,在跟踪过程中不断优化特征模板的旋转、尺度以及平移等几何变形参数,使得小波特征向量值在最小平方和意义上与初始值相匹配,实现目标跟踪。实验结果表明,该算法能够有效地提取目标特征,在目标尺度变化达到 50%,角度变化 10o,旋转 90o等不利条件下实现了可靠跟踪。     

A modelling and verification approach for soybean seed particles using the discrete element method

To build a discrete element method (DEM) model of soybean seed particles, the shape and size of soybean seed particles were measured and analysed. The results showed that the shape of a soybean seed particle could be approximated to an ellipsoid and that the dispersity in size could be approximated by a normal distribution. Additionally, a certain functional relationship between the primary dimension and secondary dimensions was determined. On this basis, an approach for modelling soybean seed particles based on the multi-sphere (MS) method was proposed. The soybean seed particle was simplified to an ellipsoid with the averaged size of one hundred randomly selected soybean seeds. The model of a single soybean seed particle was built by filling spheres within the ellipsoid. For modelling soybean seed assembly, the primary dimension was generated according to the normal distribution, and the other secondary dimensions were calculated based on their relationships with the primary dimension. In this way, the model of soybean seed assembly with different sizes and distributions was built. In this paper, four varieties of soybean seed were used. By comparing the simulated results and experimental results both in piling tests and “self-flow screening” tests, when the number of filling spheres was five, the simulated results were close to those obtained experimentally. Therefore, the feasibility and validity of the modelling method for soybean seed particles that we proposed were verified. Finally, an application case was employed to show how to use the soybean seed particle model and the discrete element method to analyse the discharging process of a silo.     

一种抑制EMD端点效应新方法及其在信号特征提取中的应用

经验模式分解(EMD)的端点效应一直是困扰其工程实用性的难点问题,结合端点效应产生机理和现有的研究成果,提出了一种基于端点优化对称延拓(End Optimization Symmetric Extension,EOSE)的抑制EMD端点效应新方法.通过对信号和其包络线的偏差评价函数的最小化计算,获取最佳的信号端点值,在此基础上延拓信号的上、下包络线将最大化地逼近原始信号两端点,在EMD后续"筛选"固有模态分量(IMF)过程中抛弃两端延拓的数据,将端点效应释放到原始信号的以外.将原EMD、基于EOSE改进EMD和基于时间序列建模(ARMA)改进EMD3种方法进行对比分析,仿真和实验结果表明,基于EOSE方法抑制EMD端点效应的效果最好,能够精确提取出旋转机械振动信号的典型故障特征,运算效率较高.     

A real‐time feature extraction method for PVC detection in bedside monitor

Abstract

This paper describes a fast and very efficient feature extraction method for discrimination of QRS and Premature Ventricular Contraction (PVC) beats in a microprocessor‐based bedside monitoring system. It converts each QRS and PVC beat into a positive‐pulse waveform by signal preprocessing. Two characteristic factors, the positive‐pulse and the pulse duration, are calculated when the onset and end points of each pulse have been detected by threshold detection. The prominent feature is extracted from a product of these two factors. This algorithm has been examined using 40 different patients’ electrocardiograph (ECG). The accuracy of QRS detection was 99.3 percent in the tests performed. The identification sensitivity of PVC was 81.2 percent with 18‐ different arrhythmia patients.     

一种自动提取IVUS图像血管包络的新方法

提取血管内超声(IVUS)图像的血管包络对冠状动脉疾病的诊断有一定的积极意义。本文综合考虑IVUS图像的灰度特征、序列时间特性、先验知识等三类信息,提出一种自动提取血管包络的方法。先由序列时间特性和先验知识减少噪声和伪像干扰,提取出第一帧图像的初始包络;然后用结合梯度、灰度方差、灰度均值信息的B样条GVFsnake对初始包络进行变形得到第一帧的最终包络;最后利用序列图像的时间特性提取后续帧的包络。通过实验表明:综合三类信息的包络自动提取方法在精度和鲁棒性等方面优于以往的方法。     

A neural feature extraction model for classification of firms and prediction of outsourcing success: advantage of using relational sources of information for new suppliers

Clustering is a family of classification techniques, often preceding further analysis or application in a number of fields like data analysis, strategy selection, supplier selection, etc. Data based neural techniques are gaining popularity in clustering applications due to flexibility and adaptability. Kohonen’s Self Organizing Map (SOM) is often used when the objects to be clustered have many attributes. In both supervised and un-supervised modes, Kohonen’s map exhibit good capability to extract a classification which assigns highest weight to the most important attribute. In this paper, we have applied SOM for classification of firms based on their sources of information for new suppliers/customers. Additional data regarding the outsourcing success of the firms’ is added to see if there is an association between a particular set of information sources and the probability of firms’ success to outsource to partner firms. Using data from World Bank BEEPS survey of German industries, we could produce three distinct clusters of industries. When successful outsourcing data were included, it still showed three clusters. The hits were obtained using specific support vector for identification of clusters. We found evidence of associations between relational sources and firms’ ability to outsource successfully.     

A new method for modelling cohesive cracks using finite elements

A model which allows the introduction of displacements jumps to conventional finite elements is developed. The path of the discontinuity is completely independent of the mesh structure. Unlike so‐called ‘embedded discontinuity’ models, which are based on incompatible strain modes, there is no restriction on the type of underlying solid finite element that can be used and displacement jumps are continuous across element boundaries. Using finite element shape functions as partitions of unity, the displacement jump across a crack is represented by extra degrees of freedom at existing nodes. To model fracture in quasi‐brittle heterogeneous materials, a cohesive crack model is used. Numerical simulations illustrate the ability of the method to objectively simulate fracture with unstructured meshes. Copyright © 2001 John Wiley & Sons, Ltd.     

A new method for evaluating powder flowability using constant-volume shear tester,

This is an article translated from the original version published in the Journal of the Society of Powder Technology, Japan. A new method for evaluating powder flowability is developed using a constant-volume shear tester; this tester measures the upper and lower normal stresses and the shear stress acting on a powder bed. A single shear test provides a series of characteristics, such as the powder yield locus (PYL), consolidation yield locus (CYL), critical state line (CSL), shear cohesion, stress relaxation ratio, stress transmission ratio, and void fraction. The values of shear stress as a function of the normal stress and void fraction are visualized in three-dimensional diagrams. Furthermore, powder flowability is evaluated using a flow function obtained from the PYL.     

A new method for measuring fluid densities using the Taylor dispersion experiment

The density of a pure fluid or a fluid mixture is of fundamental importance in the design of equipment for fluid processing and in the development of theory describing thermodynamic and transport properties of the liquid state. A new experimental technique for measuring fluid densities is presented, which is based on the well-known Taylor dispersion experiment for measuring mutual diffusion coefficients. The equipment and working equation are both simple, yet experimental results show that the method is accurate to at least 0.1%. An analysis of errors indicates that the accuracy could be improved to 0.01%. This new technique is of particular virtue since it can be used to obtain simultaneous measurements of the fluid density and diffusion coefficient of a solute in the fluid, using data from a single experiment.     

利用机械结构的振动加速度信号反算应变的新方法

针对结构紧凑的机械结构难以采用布置应变计的方法来测量应变的问题,从动力学角度出发,采用虚拟力技术建立了实际作用力的等效力。通过进行虚拟测点的计算,以解决实际测点不足的难题。提出了加速度响应信号与输入载荷的协调方程,利用运行状态下机械结构的加速度响应信号来反算结构应变的方法。并通过工程实例得以验证。研究结果对结构紧凑、不利于进行应变测试的部位,可采用该方法进行应变数据的分析,为进行疲劳寿命分析奠定基础。     

A new automated delineation method for SPECT lung scans using adaptive dual‐exponential thresholding

An accurate method for delineating lung contours in single photon emission computed tomography (SPECT) is critical to respiratory studies such as pulmonary embolism (PE) and respiratory aerosol deposition. Current delineation methods are not adaptive in nature and may require a priori information on lung volumes. We have developed a dual‐exponential thresholding method that solely requires SPECT scans, and is fast, accurate, and adaptive in nature. A dataset consisted of 90 patients was studied retrospectively. While most were suspected of PE, other pulmonary disorders were also present. SPECT ventilation scans were obtained after inhalation of ～40 MBq of 99mTc‐Technegas. Examination of the corresponding natural logarithmically transformed histograms revealed dual exponential functions like pattern. Adaptive thresholds were found as the intercept between the two exponential functions. 350 Monte Carlo simulations representative of normally‐ventilated scans with varying counts were used to quantitatively measure and evaluate the method. Our method correctly delineated lung volumes to above 97% agreement for 310 of the 350 Monte Carlo simulations with maximum count values greater than or equal to 31. The 40 low‐count simulations were included purely as extreme cases. For real patient scenario, an experienced physician was called upon to visually delineate a sample of 50 actual patient scans, and these delineated lung volumes were used as gold standard and compared with those delineated using our method. Our results had an average of 96% agreement. © 2007 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 17, 22–27, 2007