指纹奇异点精确定位新方法

针对指纹图像奇异点快速精确定位的难题,提出一种简单实用算法。对指纹图像预处理,计算方向场并归域化,接着选出奇异点候选区,并以Poincare Index（PI）算法从中提取奇异点候选点集。对候选奇异点集去伪并精确定位。采用FVC2004指纹库进行实验验证,结果与PI算法对比,该算法鲁棒性更好,定位更精确,漏检率和误检率分别降低5.86%、6.8%,平均速度提高了3.71~9.38倍,基本满足高精度高速度的指纹奇异点定位要求。     

一种类四次三角样条曲线的奇拐点分析

根据移动一个控制顶点而固定其他控制顶点的方法, 分析一种类四次三角样条曲线的形状。在一类控制多边形下,利用控制顶点之间距离的关系,分别得到了对应的四次三角样条曲线含有尖点、二重点以及拐点的判别条件。     

Splitting iteration method for simple singular points and simple bifurcation points

A splitting iteration method is introduced to compute the simple singular points and the simple bifurcation points of nonlinear problems. It needs little computational work and converges with an adjustable rate. Numerical examples are presented.     

The facility and transfer points location problem

In this paper, we investigate the location of a facility and several transfer points to serve as collector points for customers who need the services of the facility. For example, demand for emergency services is generated at a set of demand points that need the services of a central facility (such as a hospital). Patients are transferred to a helicopter pad (transfer point) at normal speed, and from there they are transferred to the facility at increased speed. The model involves the location of multiple transfer points and one facility. Locating one transfer point when the set of demand points and the location of the facility are known was investigated in Berman et al. (2004a). Location of several transfer points when the location of the facility is given is investigated in Berman et al. (2004b). In this paper, we propose heuristic approaches for the solution of this problem and report computational experiments on a test set of 40 problems.     

一种有效的指纹奇异点提取方法

在指纹方向场分割的基础上提出了一种称之为方向丰富度的特征,并据此形成了一种有效的指纹奇异点提取方法。该方法首先将指纹方向场分割为一系列互不重叠的同质区域;然后通过同质区域边缘检测及边缘端点提取实现了奇异点快速定位;最后依据已定位点的poincare index值确定奇异点类型。与目前占据绝对主流的poincare index方法在FVC2002指纹库上的对比实验表明:在准确性方面,两者各有优、缺点,该文方法的误检率明显低于后者,漏检率略高于后者;在简单实用性方面,该文算法的平均提取速度是后者的14.2倍,具有明显优势。     

平面非规则曲线的一种快速识别与匹配算法

平面非规则曲线的识别与匹配主要用于图像识别、物体匹配等领域。文章在综合研究比较国内外的研究成果后,提出了一种新的快速提取特征进行筛选而后进行细节比对进行匹配的方法。该方法首先通过提取构成平面非规则曲线的一系列离散点的关键特征进行快速筛选,而后逐步比对细节特征,分析其变化趋势,对平面非规则曲线的匹配有着较为满意的匹配效果。该方法相比现有的匹配方法,具有识别与匹配速度快,准确率高,适应性强等优点。     

Combining singular points and orientation image information for fingerprint classification

Fingerprint classification is crucial to reduce the processing time in a large-scale database. Two popular features used are the singularities and orientation information and they are complementary. Therefore, an algorithm based on the interactive validation of singular points and the constrained nonlinear orientation model is proposed. The final features used for classification comprises the coefficients of the orientation model and the singularity information. This resulted in very compact feature vector which is used as input to an SVM classifier to perform the classification. The experiments conducted on the NIST database 4 show the effectiveness of the proposed method in producing good classification result.     

平面点集Delaunay三角剖分的分治算法

为发展图形网格化技术,研究了平面点集的三角剖分算法.根据经典算法中在实际应用中遇到的共性问题,提炼了3个工具算法;为了更好地表示平面区域划分的拓扑信息,引入了双链接边表(DCEL)的数据结构.在此基础上,设计并实现了平面集Delaunay三角剖分分治算法,并对特殊退化情况进行了处理,通过计算表明了该算法时间复杂度为0(N* logN).实验数据结果验证了该算法的正确性、健壮性.     

Rapid location of mount points

‘Mount points’ allow more storage to be grafted into tree-structured hierarchical file systems. Administrative tasks use their locations, which are tabulated in a file. In our System V Unix environment, this file was occasionally removed. Getmnt was written to recover the information. Getmnt has had three significant versions. The original version (getmnt1) was a highly optimized naive tree traversal. Getmnt3 improved the real time performance by a mean factor of 7 by pruning unnecessary branches from the traversal. Getmnt3 doubled getmnt2's speed, with a change from depth-first to breadth-first search. On our development system, getmnt1 required 647.6 s to run, whereas getmnt3 required 42.53 s.     

基于兴趣点定位的局部方向模式人脸识别方法

为了解决局部方向模式（LDP）在人脸特征提取过程中采用固定的平均分块方式,不能自适应突出不同样本特征的这一问题,提出一种基于兴趣点定位的改进LDP人脸特征提取方法。兴趣点所在位置特征信息丰富,其根据不同图像自动分布,可以突出不同图像的不同特点。首先定位人脸图像的加速鲁棒特征（SURF）特征点,并通过K-means聚类算法优化兴趣点的数量,确定兴趣点位置;之后以每个兴趣点作为中心建立LDP特征提取窗口,计算其4方向LDP编码,得出图像的特征向量;最后,采用支持向量机（SVM）对人脸进行识别分类。使用该改进算法分别在FERET和Yale数据库中进行实验,并与原始LDP、4方向的LDP方法（4-LDP）、融合PCA与LDP的特征提取算法（PCA-LDP）进行了比较,实验结果表明,所提出的特征提取方法在保证系统实时性的同时,可以有效提高人脸识别的准确率与稳定性。     

Algorithms for determining planar area properties from peripheral points

The determination of planar properties—cross sectional areas, centroids, moments of inertia, and so forth—plays a central role in the solution of many diverse engineering problems. Despite the increasing availability of computational power to engineers and students alike in recent years with the advent of small desktop computers, however, the traditionally laborious and error-prone methods of making these determinations, involving area decomposition or strip integration, are still being taught to the present generation of engineering students, mostly due to a lack of suitable alternative techniques. These classical methods are found to be particularly difficult to adapt to general computational algorithms. This work presents a novel approach, requiring only the peripheral points of any planar area as inputs, and is ideally suited for numerical methods. It is shown that all planar properties of technical interest can be generated, once and for all, with straightforward algorithms that are readily programmed in any scientific computing language, or adapted to typical spreadsheet formats. These algorithms are fully general and require no decision-making on the part of the user. Various worked examples are presented.     

Average curve of n smooth planar curves

We define the Average Curve (AC) of a compatible set of two or more smooth and planar, Jordan curves. It is independent of their order and representation. We compare two variants: the valley AC (vAC), defined in terms of the valley of the field that sums the squared distances to the input curves, and the zero AC (zAC), defined as the zero set of the field that sums the signed distances to the input curves. Our formulation provides an orthogonal projection homeomorphism from the AC to each input curve. We use it to define compatibility. We propose a fast tracing algorithm for computing a polygonal approximation (PAC) of the AC and for testing compatibility. We provide a linear-cost implementation for tracing the PAC of polygonal approximations of smooth input curves. We also define the inflation of the AC and use it to visualize the local variability in the set of input curves. We argue that the AC and its inflation form a natural extension of the Medial Axis Transform to an arbitrary number of curves. We propose extensions to open curves and to weighted averages of curves, which can be used to design animations.     

Measuring linearity of open planar curve segments

In this paper we define a new linearity measure for open planar curve segments. We start with the integral of the squared distances between all the pairs of points belonging to the measured curve segment, and show that, for curves of a fixed length, such an integral reaches its maximum for straight line segments. We exploit this nice property to define a new linearity measure for open curve segments. The new measure ranges over the interval (0, 1], and produces the value 1 if and only if the measured open line is a straight line segment. The new linearity measure is invariant with respect to translations, rotations and scaling transformations. Furthermore, it can be efficiently and simply computed using line moments. Several experimental results are provided in order to illustrate the behaviour of the new measure.     

Optimal location of sampling points for river pollution control

Common methods of controlling river pollution include establishing water pollution monitoring stations located along the length of the river. The point where each station is located (sampling point) is of crucial importance and, obviously, depends on the reasons for the sample. Collecting data about pollution at selected points along the river is not the only objective; must also be extrapolated to know the characteristics of the pollution in the entire river. In this work we will deal with the optimal location of sampling points. A mathematical formulation for this problem as well as an efficient algorithm to solve it will be given. Finally, in last sections, we will present numerical results obtained by using this algorithm when applied to a realistic situation in a river mouth.     

On the All-Farthest-Segments problem for a planar set of points

In this note, we outline a very simple algorithm for the following problem: Given a set S of n points p₁,p₂,p₃,…,pn in the plane, we have O(n²) segments implicitly defined on pairs of these n points. For each point pi, find a segment from this set of implicitly defined segments that is farthest from pi. The time complexity of our algorithm is in O(nh+nlogn), where n is the number of input points, and h is the number of vertices on the convex hull of S.     

A hierarchical algorithm for the planar single-facility location routing problem

Location routing problem (LRP) is an important logistical problem that comprises two of the main logistical drivers namely facility location and vehicle routing. In this paper, we focus on the planar single-facility LRP with Euclidean distance where the location of the facility can be anywhere in the space and not restricted to a given set of potential sites only as in the discrete case. A hierarchical heuristic-based method is put forward which continuously takes into account the information from the routing results while systematically improving the location using the end-points of the obtained routes. In addition, some enhancement schemes that include a set of local searches as well as diversification and intensification mechanisms are also incorporated into the search. The proposed method outperformed the existing approaches when tested on the data sets taken from the literature. Our approach produced nine new best results out of the fifteen in the literature besides being relatively robust when compared to the existing methods.     

计算点到平面NURBS曲线的最小距离

提出了一种利用控制顶点投影法计算点到平面NURBS曲线最小距离的算法。将控制顶点投影到平面NURBS曲线上,投影点将平面NURBS曲线分割成若干曲线段;计算点到各曲线段的最小距离,通过比较这些最小距离值,找出点到平面NURBS曲线的最小距离。该算法实现简单,计算精度较高,具有重要的实用价值。     

A numerical method for quasilinear singular perturbation problems with turning points

In this paper we consider a quasilinear singular perturbation problem with turning points. First derivatives of the exact solution are estimated. Then an approximate problem is constructed. Finally we give an algorithm whose accuracy is good for arbitrary ?>0.