基于IEEE 1588实现变电站过程总线采样值同步新技术

介绍并分析了网络测量和控制系统的精确时钟同步协议IEEE1588,通过与目前应用广泛的网络时间协议(NTP)相比较,指出其高精度时钟同步实现机制的特殊性。针对IEC61850所定义的过程总线上采样值高精度同步要求,提出了一种基于IEEE1588的合并单元同步实现的新方案。在此方案中,利用现场可编程门阵列(FPGA)对IEEE1588同步报文时标生成点进行精确确定,IEEE1588同步协议的实现利用微控制器完成。     

Reducing Symmetries to Generate Easier SAT Instances

Finding countermodels is an effective way of disproving false conjectures. In first-order predicate logic, model finding is an undecidable problem. But if a finite model exists, it can be found by exhaustive search. The finite model generation problem in the first-order logic can also be translated to the satisfiability problem in the propositional logic. But a direct translation may not be very efficient. This paper discusses how to take the symmetries into account so as to make the resulting problem easier. A static method for adding constraints is presented, which can be thought of as an approximation of the least number heuristic (LNH). Also described is a dynamic method, which asks a model searcher like SEM to generate a set of partial models, and then gives each partial model to a propositional prover. The two methods are analyzed, and compared with each other.     

Symmetry Breaking Constraints for Value Symmetries in Constraint Satisfaction

Constraint satisfaction problems (CSPs) sometimes contain both variable symmetries and value symmetries, causing adverse effects on CSP solvers based on tree search. As a remedy, symmetry breaking constraints are commonly used. While variable symmetry breaking constraints can be expressed easily and propagated efficiently using lexicographic ordering, value symmetry breaking constraints are often difficult to formulate. In this paper, we propose two methods of using symmetry breaking constraints to tackle value symmetries. First, we show theoretically when value symmetries in one CSP correspond to variable symmetries in another CSP of the same problem. We also show when variable symmetry breaking constraints in the two CSPs, combined using channeling constraints, are consistent. Such results allow us to tackle value symmetries efficiently using additional CSP variables and channeling constraints. Second, we introduce value precedence, a notion which can be used to break a common class of value symmetries, namely symmetries of indistinguishable values. While value precedence can be expressed using inefficient if-then constraints in existing CSP solvers, we propose efficient propagation algorithms for implementing global value precedence constraints. We also characterize several theoretical properties of the value precedence constraints. Extensive experiments are conducted to verify the feasibility and efficiency of the two proposals.     

基于信息论的连续属性离散化

使用信息论的方法进行连续属性的离散化，引入Hellinger偏差HD（Hellinger Divergence)作为每个区间对决策的信息量度量，从而定义切分点的信息熵，最终的离散化结果是使各区间的信息量尽可能平均，分析了HD度量在两种离散化方法中的作用，说明它在划分算法中运用比较理想，而在归并算法中则有局限。     

An efficient prototype merging strategy for the condensed 1-NN rule through class-conditional hierarchical clustering

A generalized prototype-based classification scheme founded on hierarchical clustering is proposed. The basic idea is to obtain a condensed 1-NN classification rule by merging the two same-class nearest clusters, provided that the set of cluster representatives correctly classifies all the original points. Apart from the quality of the obtained sets and its flexibility which comes from the fact that different intercluster measures and criteria can be used, the proposed scheme includes a very efficient four-stage procedure which conveniently exploits geometric cluster properties to decide about each possible merge. Empirical results demonstrate the merits of the proposed algorithm taking into account the size of the condensed sets of prototypes, the accuracy of the corresponding condensed 1-NN classification rule and the computing time.     

Nonlinearizable single-input control systems do not admit stationary symmetries

The main result of the paper states that almost any analytic single-input control system, which is truly nonlinear, that is not feedback linearizable, with controllable linearization at an equilibrium point, does not admit any symmetry preserving that point. By almost any system, we mean that we exclude a small class of odd systems, that admit just one nontrivial symmetry conjugated to minus identity. The obtained results are based on a recent classification of nonlinear single-input systems under formal feedback. We also describe symmetries of feedback linearizable systems.     

The Marching Intersections algorithm for merging range images

A new algorithm for the integration of partially overlapping range images into a triangular mesh is presented. The algorithm consists of three main steps: it locates the intersections between the range surfaces and a reference grid chosen by the user, then merges all nearly coincident and redundant intersections according to a proximity criterion, and, finally, reconstructs the merged surface(s) from the filtered intersection set. Compared with previous methods, which adopt a volumetric approach, our algorithm shows lower computational costs and improves the accuracy of the surfaces produced. It takes into account the quality of the input measurements and is able to patch small holes corresponding to the parts of the 3D scanned object that were not observed by the acquisition device. The algorithm has been tested on several datasets of range maps; graphical and numeric results are reported.     

CSCW中的对象同步与合并

为了满足响应时间以及可靠性的要求,协同应用通常采用全复制的体系结构．由此带来的一个巨大挑战就是如何保证复制在各个协作站点处的对象的一致性以及获得一个公共状态,总结了在线和离线两种协作模式下的不同需求,在此基础上给出了相应的控制机制——在线模式下的对象同步算法和离线模式下的对象合并算法．这些机制已经在协作支撑平台Cova系统中实现,实际的应用表明,这些措施与其他机制一起能够很好地满足协同应用数据一致性的要求。     

基于处理-分裂-合并的彩色图像自动分割系统

叙述一个基于处理-分裂-合并的彩色图像自动分割处理系统。其主要功能为：根据图像的区域特征将彩色图像自动分割成若干块并存储区域的边界特征，实现了地图的面查询，并可实现原图和分割出来的区域图的放大和缩小显示。采用适当的去噪、平滑方法使区域图像分割更精确。本系统采用面向对象的分析设计方法，在Windows平台上，进行编程开发实现。系统对GIS、图像数据库及其检索和图像及文字模式识别的研究有较重要的意义。