无线传感器网络中基于Convexhull的能量空洞避免路由算法

提供了一种绕过无线传感器网络"能量空洞"的方法(CHA方法),可以用来找到绕过能量空洞的最优节点路由路径。在数据包从源节点传递到目的节点的过程中,通过遇到能量空洞,先勾勒出空洞范围,再基于凸壳(Convex hull)找到绕过能量空洞的最优节点路由路径。仿真结果表明,该算法优化了能量空洞绕洞路由路径,有效提高了无线传感器网络传输效率,减少了无线传感器能量损耗和信息传递的延迟。

A new algorithm for computing the convex hull of a planar point set

When the edges of a convex polygon are traversed along one direction,the interior of the convex polygon is always on the same side of the edges. Based on this characteristic of convex polygons,a new algorithm for computing the convex hull of a simple polygon is proposed in this paper,which is then extended to a new algorithm for computing the convex hull of a planar point set. First,the extreme points of the planar point set are found,and the subsets of point candidate for vertex of the convex hull between extreme points are obtained. Then,the ordered convex hull point sequences between extreme points are constructed separately and concatenated by removing redundant extreme points to get the convex hull. The time complexity of the new planar convex hull algorithm is O(nlogh) ,which is equal to the time complexity of the best output-sensitive planar convex hull algorithms. Compared with the algorithm having the same complexity,the new algorithm is much faster.

A novel method for virtual clearance computation of high-speed train based on model integration and convex hull

The 3D clearance of a high-speed train(HST) is critical to ensure the safety of railway transportation. Many studies have been conducted on the inspection of the clearance profile in railway operation based on the vision system, but few researchers have focused on the computation of the 3D clearance in the design phase of an HST. This paper summarizes the virtual 3D clearance computation of an HST based on model integration and the convex hull method. First, both the aerodynamic and kinetic analysis models of the HST are constructed. The two models are then integrated according to the corresponding relationship map, and an array of transformation matrixes of the HST is created to drive the designed model simulating the physical railway motion. Furthermore, the convex hull method is adopted to compute the 3D envelope of the moving train. Finally, the Hausdorff metric is involved in the measurement of the minimum clearance model and the 3D envelope model. In addition, the color map of the Hausdorff distance is established to verify that the designed shape of the HST meets the national standards. This paper provides an effective method to accurately calculate the 3D clearance for the shape design of an HST, which greatly reduces the development cost by minimizing the physical prototype that must be built.

On Constructing Approximate Convex Hull

The algorithms of convex hull have been extensively studied in literature, principally because of their wide range of applications in different areas. This article presents an efficient algorithm to construct approximate convex hull from a set of n points in the plane in O(n+k) time, where k is the approximation error control parameter. The proposed algorithm is suitable for applications preferred to reduce the computation time in exchange of accuracy level such as animation and interaction in computer graphics where rapid and real-time graphics rendering is indispensable.

Group Target Tracking in WSN Based on Convex Hulls Merging

When a mass of individual targets move closely, it is unpractical or unnecessary to localize and track every specific target in wireless sensor networks (WSN). However, they can be tracked as a whole by view of group target. In order to decrease the amount of energy spent on active sensing and communications, a flexible boundary detecting model for group target tracking in WSN is proposed, in which, the number of sensors involved in target tracking is adjustable. Unlike traditional one or multiple individual targets, the group target usually occupies a large area. To obtain global estimated position of group target, a divide-merge algorithm using convex hull is designed. In this algorithm, group target’s boundary is divided into several small pieces, and each one is enclosed by a convex hull which is constructed by a cluster of boundary sensors. Then, the information of these small convex hulls is sent back to a sink. Finally, big convex hull merged from these small ones is considered as the group target’s contour. According to our metric of precision evaluation, the simulation experiments confirm the efficiency and accuracy of this algorithm.

Drug discrimination of Near Infrared spectroscopy based on the scaled convex hull classifier

Near Infrared spectroscopy(NIRS)has been widely used in the discrimination(classification)of pharmaceutical drugs.In real applications,however,the class imbalance of the drug samples,i.e.,the number of one drug sample may be much larger than the number of the other drugs,deceasesdrastically the discrimination performance of the classification models.To address this classimbalance problem,a new computational method--the scaled convex hull(SCH)-basedmaximum margin classifier is proposed in this paper.By a suitable selection of the reductionfactor of the SCHs generated by the two classes of drug samples,respectively,the maximalmargin classifier bet ween SCHs can be constructed which can obtain good classification per-formance.With an optimization of the parameters involved in the modeling by Cuckoo Search,a satisfied model is achieved for the classification of the drug.The experiments on spectra samplesproduced by a pharmaceutical company show that the proposed method is more effective androbust than the existing ones.

Secure planar convex hull protocol for large-scaled point sets in semi-honest model

Efficiency and scalability are still the bottleneck for secure multi-party computation geometry （SMCG）. In this work a secure planar convex hull （SPCH） protocol for large-scaled point sets in semi-honest model has been proposed efficiently to solve the above problems. Firstly, a novel priva- cy-preserving point-inclusion （PPPI） protocol is designed based on the classic homomorphic encryp- tion and secure cross product protocol, and it is demonstrated that the complexity of PPPI protocol is independent of the vertex size of the input convex hull. And then on the basis of the novel PPPI pro- tocol, an effective SPCH protocol is presented. Analysis shows that this SPCH protocol has a good performance for large-scaled point sets compared with previous solutions. Moreover, analysis finds that the complexity of our SPCH protocol relies on the size of the points on the outermost layer of the input point sets only.

A COUNTER－EXAMPLE TO A FAST ALGORITHM FOR FINDING THE CONVEX HULL OF A SIMPLE POLYGON

A linear-time algorithm was recently published (International Conference Proceedings ofPacific Graphics' 94/CADDM' 94, August 26-29 , 1994 , Beijing , China) for computing the convexhull of a simple polygon. In this note we present a counter-example to that algorithm by exhibiting afamily of polygons for which the algorithm discards vertices that are on the convex hull.

A NEW CONVEX HULL ALGORITHM FOR ANY POLYGON

A new algorithm for finding convex hull of a polygon is proposed. An example is given to show the effectiveness and the simplicity of the algorithm.

基于重构级别辨识的主配协同鲁棒供电恢复方法

传统配电网供电恢复策略大多先进行孤岛划分、后进行动态重构,缺少对二者的共同考虑,而全局重构又存在经济性差、操作难度大等问题。为此,提出基于重构级别辨识的主配协同鲁棒供电恢复方法。首先,根据配电系统的故障情况,按照局部自治、低级别优先重构的原则,快速确定主(变电站层级)、配(配电线路层级)多级重构需求。然后,对不同级别的区域进行孤岛划分与重构。接着,针对描述分布式光伏出力不确定性的凸包多面体集合存在放缩过程中保守性大的问题,采用超平面方法切割凸包集合并建立改进凸包集合模型。进一步,构建了配电网鲁棒供电恢复模型,并采用列与约束生成算法对鲁棒供电恢复模型进行求解。最后,通过改进的78节点系统进行仿真验证。结果表明,基于重构级别辨识的主配协同鲁棒供电恢复方法可以降低保守性,提高供电恢复结果的鲁棒性。

采用Hull树的贪婪地理位置路由算法的设计

地理位置路由算法是指借助节点获得的地理位置信息进行无线传感网络中的路由发现与数据转发工作。本文提出一种基于Hull树的贪婪地理位置路由算法——Greedy Hull Tree Geographic Routing(GHTGR)。通过图形学中凸包的概念,在网络初始阶段分布式地在各节点上建立Hull树以探查网络局部拓扑结构;同时在数据分组的路由转发阶段,通过Hull树内的搜索,寻找下一跳转发节点,完成数据分组的转发传输。通过仿真实验表明,与现有地理位置路由算法相比,该算法能够正确地寻找数据转发路径,有效地减少网络能耗,提高网络传输性能。

基于正常工作区的凝汽器多变量报警监测

凝汽器作为电厂的重要设备之一,保证凝汽器工作状态的稳定性对发电机组的安全经济运行具有重要意义,因此提出了一种基于正常工作区的凝汽器多变量报警监测方法。首先,根据凝汽器的热力特性搭建仿真模型,计算出模型中关联变量的解析解。然后,从历史数据中提取凝汽器真空及其关联变量的有效数据,利用遗传算法对模型的未知参数进行辨识。最后,以系统机理模型中多个关联变量的正常数据点为基础,建立相关关联变量的正常工作区。基于工业案例的测试结果验证了所提方法能够有效监测凝汽器系统,使操作人员提前发现异常情况,为火电机组的可靠运行提供了保障。

塞罕坝华北落叶松树冠投影面积模型构建

依据河北省塞罕坝国家森林公园华北落叶松纯林12块标准地4个不同林龄(10、15、20、25 a)数据,使用圆形、椭圆形、矩形和凸包结构,分别在4点位和8点位计算树冠投影面积,并分析不同计算方法和林龄之间的差异。通过绘制12个变量的散点图和相关性图,分析变量对树冠投影面积的影响。利用全子集法和刀切法构建树冠投影面积预测模型。结果表明,8点位的计算精度优于4点位,且15 a林龄的树冠投影面积存在显著变异趋势。最终,胸径(DBH)、单木竞争因子(BALD)、相对直径(RD)、冠长(CL)和冠幅(Crown)被纳入模型,除竞争因子外,其他变量与树冠投影面积呈显著正相关。

The Ellipsoidal Invariant Set of Fractional Order Systems Subject to Actuator Saturation:The Convex Combination Form

The domain of attraction of a class of fractional order systems subject to saturating actuators is investigated in this paper. We show the domain of attraction is the convex hull of a set of ellipsoids. In this paper, the Lyapunov direct approach and fractional order inequality are applied to estimating the domain of attraction for fractional order systems subject to actuator saturation. We demonstrate that the convex hull of ellipsoids can be made invariant for saturating actuators if each ellipsoid with a bounded control of the saturating actuators is invariant. The estimation on the contractively invariant ellipsoid and construction of the continuous feedback law are derived in terms of linear matrix inequalities (LMIs). Two numerical examples illustrate the effectiveness of the developed method. © 2014 Chinese Association of Automation.

Quickhull凸包算法在人体围度确定中的应用及改进

面向人体三维轮廓测量的凸包算法是确定服装截面围度尺寸的有效工具。为了减少耗时提高计算效率,引入了Quickhull凸包算法,根据人体具有20的凹凸对称性特征,在构建初始凸包前进行了对已知凹点直接删除的改进,并通过对女性最大胸围截面为例进行了说明,与Graham凸包算法精度和效率的比较,结果表明:采用Quickhull算法可获得与Graham算法相同的尺寸精度,但耗时明显减少,而通过对人体已知凹点的直接删除则可进一步减少计算的耗时。

基于机器视觉的芯片字符区域分割和定位算法

芯片表面的字符对分选具有重要意义,对字符的定位是分选工作的关键步骤。为了提高分选工作定位效率和定位精度,提出了一种基于改进的区域生长算法和凸包检测算法分割和定位芯片表面字符区域方法。首先,对采集图像进行预处理操作,利用改进的Canny算法获取无干扰图像边缘,将图像边缘作为区域生长法的种子点并以图像自适应阈值作为生长准则分割图像,使用最大内接矩形算法粗定位字符区域;其次,采用Harris角点检测算法获取字符角点分布位置;最后,筛选角点并提取关键点,利用一种改进的凸包检测算法定位字符区域。经过实验验证,所设计的算法能够完整的分割和定位芯片表面字符区域,定位精度和效率较原有方法提升5.3%和15.4%,满足实际工业生产的要求。

一种基于流形的机械臂动作构型知识压缩表达方法

针对在机械臂分拣任务中,存在物体形状各异、大小不一、训练神经网络成本过高的问题,提出一种基于流形空间的机械臂快速分拣方法。通过自主设计的一款简易实验装置模拟代替机械臂进行实验。对高维数据进行压缩,结合三维快速凸包求解算法,对体积大小不同的同类物体的流形空间进行分割,以凸包形式将稳定性较高的点集包裹起来。实验结果表明,体积大小不同的同类物体的高稳定流形子空间是一致的。该方法可以通过对一种物体的流形子结构进行尺度放缩,得到不同大小的同类物体的高稳定分拣区域,用于生成高效、可靠的机械臂分拣任务中的6D位姿构型,以提高分拣作业的工作效率。

基于灵活运行域的配-微电网协同优化调度方法

为了提高配电网与微电网间的协调能力,提出了基于灵活运行域的配-微电网协同优化调度方法。构建微电网灵活运行域(MGFOR)模型,准确刻画海量灵活性资源接入下微电网的灵活调节能力;采用基于MGFOR的凸包拟合表达式对微电网的灵活调节能力进行描述,并将其纳入配电网的优化决策过程中,以获取配-微电网协同过程中各微电网的基准运行点;微电网基于配电网优化决策给定的基准运行点进行灵活性分解,在保证配-微电网协同运行经济性和数据隐私的前提下获取各灵活性资源的具体调度策略。以修改的IEEE 33节点测试系统为算例进行仿真分析,验证所提方法能够准确刻画微电网的灵活调节能力,所提基于MGFOR的分解协同策略能够有效支撑配-微电网灵活经济调度。

基于凸包算法的极端运行方式提取方法

在电力系统规划与运行的安全稳定计算中,一般选择对安全稳定最不利的运行方式进行校验,但随着新能源渗透率的增加,电网越发复杂多变,人工选择场景主观性较强,针对此问题,提出了一种基于快速凸包算法的极端运行方式提取,从而满足场景选取进行安全校核需求。从电源规划、发输电协调规划两个角度,考虑发电充裕性、火电爬坡需求、网络传输安全3个方面,分析影响规划的极端运行方式;基于凸包算法分别从上述3个方面构建坐标系进行极端运行方式提取;采用中国西北地区电网为算例进行极端运行方式提取,并与基于K-means算法的极端场景提取做对比,结果表明:所提方法能为场景选取提供有效数据支撑,满足电网规划要求。

基于SPWVD-STFT的海面弱目标检测方法

为了进一步提升时频域特征检测海面弱目标的能力,提出一种平滑伪魏格纳-威利分布(smoothed pseudo Wigner-Ville distribution,SPWVD)-短时傅里叶变换(short-time Fourier transform,STFT)海面弱目标检测算法.首先,采用STFT对回波信号进行时频特征分析,优化SPWVD的时频特征分析结果,并引入K-medoids聚类算法对二者时频矩阵进行降噪处理.然后,提取时频域特征多普勒频率稳定度(Doppler frequency stability,DFS),利用快速凸包学习算法获得虚警可控的判决区域,从而判定海杂波与目标.最后,基于IPIX数据集中实测数据的实验结果表明所提出的检测算法在相同虚警率下比时频三特征检测器的平均检测概率高6.3%.