Topology preservation of template-based 6-subiteration reduction operations

Generally, a reduction operation (e.g., thinning and shrinking) on 3D binary images can be represented as a set of reduction templates where every object voxel of the image satisfying any template is turned to a background voxel. Generally, it is rather difficult, error-prone and time-consuming for verifying the topological soundness of a 3D parallel reduction operation. This paper proposes sufficient conditions of time complexity O(n) for verifying the topological soundness of 3D parallel 6-subiteration reduction operations of n templates where such a kind of 3D reduction operations is performed alternatively from the six orthogonal directions to turn object voxels to background voxels. By such sufficient conditions, the topology soundness of a 3D 6-subiteration parallel reduction operation can be verified by checking each and every of its templates.     

手背静脉图像分割及细化算法研究

手背静脉识别技术通常基于静脉纹路的细节特征点对个人身份进行验证。为了准确地提取出手背静脉纹路中的细节特征点,提取手背静脉图像中的有效区域并对其进行归一化、增强和去噪处理．分别采用局部最大类间方差法（OSTU）、阈值图像法和NiBlack法对图像进行分割,分别采用Hilditch算法、快速细化算法、Zhang＆Suen算法和OPTA算法对分割后得到的二值图像进行细化以获取静脉纹路。实验结果表明,基于合理的参数,NiBlack法和Hilditch算法分别取得较好的分割与细化处理结果。     

New method for determination of the pose of the grinding wheel for thinning drill points

Traditionally, twist drills are reconditioned by thinning the web so the correct chisel edge length is restored. Recently, thinning has been included in the original design of drills so as to reduce torque and tool force. Because the International Standards Organization (ISO) has a system which can comprehensively model conventional twist drills but cannot model thinning specifications, this paper presents a system for precise mathematical modeling and CNC control of a 6-axis grinding workstation for drill thinning. The presented method determines the position and orientation of the grinding wheel based on the evaluated rake and clearance angles of ISO standards for 2-flute twist drills. The mathematical model and background are discussed. For verification and demonstration, two experimental drills are produced to the identical ISO standard except that one is thinned. The modeling herein is of value to industry and research if incorporated into computer software for drill design and manufacture. It is suitable for linear notch-type cutting with controlled variable rake angle along the secondary cutting edge for purposes of thinning, notching, dubbing and advanced drill research.     

基于扩充的GIX/M/1/N排队系统的主动队列管理算法性能评价模型

为了评价主动队列管理(AQM Active Queue Management)算法的性能,通过在标准的排队系统GIX/M/1/N中嵌入主动队列管理(AQM)算法的方法,建立了一个扩充的GIX/M/1/N排队系统。利用该扩充的GIX/M/1/N排队系统和Internet业务流量自相似性的特征,提出了一种评价AQM算法在非响应业务流量下的性能的分析方法,并据此评价了TD,RED,GRED和Adaptive RED等4个经典的AQM算法。为了验证该分析方法的合理性,利用NS2进行了一系列的仿真实验。结果表明,该分析方法所得结果与仿真实验所得结果一致,因此该分析方法能用于评价AQM算法的性能。     

一种快速的扫描铅笔稿图细化算法

二维动画计算机输助制作系统中,在对扫描铅笔稿图进行矢量化后,可以大大提高描线上色的效率,并且能够提取线条和闭包,对便于自动上色和中间帧生成等更高级功能的实现。扫描铅笔搞图的细化是矢量化的第一步,在比较了大量现存的图象细化算法后,提出了一种非迭代线跟踪细化算法,该算法效率较高,只需对图象进行一遍扫描加两遍轮廓跟踪,就能较好地满足二维动画计算机辅助制作系统对细化效率的要求。该文还对算法的时间复杂性进行     

Real-time building of a thinning-based topological map

An accurate and compact map is essential to an autonomous mobile robot system. A topological map, one of the most popular map types, can be used to represent the environment in terms of discrete nodes with edges connecting them. It is usually constructed by Voronoi-like graphs, but in this paper the topological map is incrementally built based on the local grid map by using a thinning algorithm. This algorithm, when combined with the application of the C-obstacle, can easily extract only the meaningful topological information in real-time and is robust to environment change, because this map is extracted from a local grid map generated based on the Bayesian update formula. In this paper, position probability is defined to evaluate the quantitative reliability of the end node extracted by the thinning process. Since the thinning process builds only local topological maps, a global topological map should be constructed by merging local topological maps according to nodes with high position probability. For real and complex environments, experiments showed that the proposed map building method based on the thinning process can accurately build a local topological map in real-time, with which an accurate global topological map can be incrementally constructed.     

Thinned-ECOC ensemble based on sequential code shrinking

Error-correcting output coding (ECOC) is a strategy to create classifier ensembles which reduces a multi-class problem into some binary sub-problems. A key issue in designing any ECOC classifier refers to defining optimal codematrix having maximum discrimination power and minimum number of columns. This paper proposes a heuristic method for application-dependent design of optimal ECOC matrix based on a thinning algorithm. The main idea of the proposed Thinned-ECOC method is to successively remove some redundant and unnecessary columns of any initial codematrix based on a metric defined for each column. As a result, computational cost of the ensemble is reduced while preserving its accuracy. Proposed method has been validated using the UCI machine learning database and further applied to a couple of real-world pattern recognition problems (the face recognition and gene expression based cancer classification). Experimental results emphasize the robustness of Thinned-ECOC in comparison with existing state-of-the-art code generation methods.     

Micro-roll forming of stainless steel bipolar plates for fuel cells

Stainless steel bipolar plates for use in proton exchange membrane (PEM) fuel cells have been identified as a lighter and cheaper alternative to graphite plates. Current manufacturing of metal bipolar plates by hydroforming or micro-stamping leads to excessive stretching of the material and therefore limits the channel depths that can be formed. Low channel depths for the bipolar plates will result in low overall fuel cell efficiency. In comparison, the bending-dominated deformation mode present in roll forming provides the potential to form metal bipolar plates with less thinning and to greater channel depths. In this work, the roll forming process is employed for the first time to form thin stainless steel sheets to micro-scale channel sections of the kind required for bipolar plates. This paper describes the process and machine design as well as the establishment of the forming methodology. Experimental trials are performed and the final part quality is evaluated in terms of material thinning, longitudinal bow and cross-sectional shape. The process was numerically analysed to understand the causes of the forming problems and shape defects observed in the experimental trials. The results of this work show that roll forming of micro-scale corrugated bipolar sheets is feasible. Furthermore, the findings provide a summary of both the practical difficulties and the possible advantages of using micro-roll forming to manufacture improved thin metal micro-corrugations for bipolar plates.     

Stability of Polymer Electrolyte Membranes In Fuel Cells: Initial Attempts To Bridge Physical And Chemical Degradation Modes

In recent years, research on coupled degradation of Nafion^® membrane in polymer electrolyte fuel cell has generated huge interest among the scientific community. The coupled phenomenon behind the premature failure of fuel cell membranes in terms of its degradation is not well established. As the researches on this are in its adolescence, we try to provide some significant answers to the degradation phenomenon in terms of mechanically stimulated chemical degradation of the membrane. While the basic concept heavily relies on accurately modeling the membrane for its mechanical response to obtain molecular chain stretch, the results are utilized by the modified chemical rate equation for unzipping degradation mechanism. This article addresses significant degradation issues such as localized membrane thinning and pinhole formation, and inhomogeneous damage patterns in membrane electrode assembly in terms of mechanically induced accelerated chemical degradation of the membrane.     

基于边缘细化的角点提取算法

图像的角点提取在计算机视觉领域中具有重要的应用价值。本文基于角点一定是边缘点且是两条边缘或多条边缘交点的这一几何特性,提出了一种基于边缘细化的角点提取算法。算法先用Canny算子提取图像的边缘,然后进行细化并填充边界线上的断点,再利用角点的几何特性来确定角点的位置。实验结果表明,这种算法提高了角点提取的正确率、定位精确、实用性强。