8294856
Clustering moving objects
Due to the advances in positioning technologies, the real time information of moving objects becomes increasingly available, which has posed new challenges to the database research. As a long-standing technique to identify overall distribution patterns in data, clustering has achieved brilliant successes in analyzing static datasets. In this paper, we study the problem of clustering moving objects, which could catch interesting pattern changes during the motion process and provide better insight into the essence of the mobile data points. In order to catch the spatial-temporal regularities of moving objects and handle large amounts of data, micro-clustering [20] is employed. Efficient techniques are proposed to keep the moving micro-clusters geographically small. Important events such as the collisions among moving micro-clusters are also identified. In this way, high quality moving micro-clusters are dynamically maintained, which leads to fast and competitive clustering result at any given time instance. We validate our approaches with a through experimental evaluation, where orders of magnitude improvement on running time is observed over normal K-Means clustering method [14].
1498767
Clustering by pattern similarity in large data sets
Clustering is the process of grouping a set of objects into classes of similar objects. Although definitions of similarity vary from one clustering model to another, in most of these models the concept of similarity is based on distances, e.g., Euclidean distance or cosine distance. In other words, similar objects are required to have close values on at least a set of dimensions. In this paper, we explore a more general type of similarity. Under the pCluster model we proposed, two objects are similar if they exhibit a coherent pattern on a subset of dimensions. For instance, in DNA microarray analysis, the expression levels of two genes may rise and fall synchronously in response to a set of environmental stimuli. Although the magnitude of their expression levels may not be close, the patterns they exhibit can be very much alike. Discovery of such clusters of genes is essential in revealing significant connections in gene regulatory networks. E-commerce applications, such as collaborative filtering, can also benefit from the new model, which captures not only the closeness of values of certain leading indicators but also the closeness of (purchasing, browsing, etc.) patterns exhibited by the customers. Our paper introduces an effective algorithm to detect such clusters, and we perform tests on several real and synthetic data sets to show its effectiveness.
32059093
A Genetic Algorithm for Physical Mapping Problems
In this paper, we study a genetic algorithm for solving physical mapping problem. First, the physical mapping problem is transferred to an optimization problem by incorporating biological knowledge and limitations into the objective function. Based on the idea of genetic algorithms, the proposed approach integrates Edge Assembly Crossover (EAX) and Inver-over genetic operators to get the optimal solution. We analyze essential components of the proposed approach as well as implementation details. Our approach is then applied to some widely used test sets and simulated data, real data of this problem. Experimental results indicate that the new approach performs efficiently and precisely to solve physical mapping problem.
3829528
Dynamically inferring temporal properties
Model checking requires a specification of the target system's desirable properties, some of which are temporal. Formulating a temporal property of the system based on either its abstract model or implementation requires a deep understanding of its behavior and sophisticated knowledge of the chosen formalism. This has been a major impediment to documenting and verifying temporal properties. We propose a dynamic approach to automatically infer a program's temporal properties based on a set of property pattern templates. We describe a preliminary implementation of this approach, and report on our experience using it to discover interesting temporal properties of a small program.
24960929
3D Image Segmentation of Deformable Objects with Shape-Appearance Joint Prior Models
We propose a novel method for 3D image segmentation, where a Bayesian formulation, based on joint prior knowledge of the shape and the image gray levels, along with information derived from the input image, is employed. Our method is motivated by the observation that the shape of the object and the gray level variation in an image have consistent relations that provide configurations and context that aid in segmentation. We define a Maximum A Posteriori(MAP) estimation model using the joint prior information of the shape and image gray levels to realize image segmentation. We introduce a representation for the joint density function of the object and the image gray level values, and define joint probability distribution over the variations of object shape and the gray levels contained in a set of training images. By estimating the MAP shape of the object, we formulate the shape-appearance model in terms of level set function as opposed to landmark points of the shape. We found the algorithm to be robust to noise, able to handle multidimensional data, and avoiding the need for point correspondences during the training phase. Results and validation from various experiments on 2D/3D medical images are demonstrated.
23948133
Building Domain Ontology Based on Web Data and Generic Ontology
The automatic or semi-automatic construction of ontology has become a research topic of interest in recent years. This paper describes a mechanism for constructing domain specific ontologies automatically based on web data and generic ontology. Firstly, we employ the hierarchical agglomerative clustering(HAC) algorithm, clustering web pages hierarchically and resulting in a binary tree. Then an algorithm is proposed, which selectd from the binary tree the significative nodes as topics implying concepts of domain interests. Lastly, the Chinese generic ontology, HowNet, is introduced to evolve the topics (together with their hierarchical structures) into domain ontology. We experiment our method in the field of computer hardware based on web pages collected from Chinese BtoC web sites. An in-depth discussion on the experiment results is also given.
154630
Dual Labeling: Answering Graph Reachability Queries in Constant Time
Graph reachability is fundamental to a wide range of applications, including XML indexing, geographic navigation, Internet routing, ontology queries based on RDF/OWL, etc. Many applications involve huge graphs and require fast answering of reachability queries. Several reachability labeling methods have been proposed for this purpose. They assign labels to the vertices, such that the reachability between any two vertices may be decided using their labels only. For sparse graphs, 2-hop based reachability labeling schemes answer reachability queries efficiently using relatively small label space. However, the labeling process itself is often too time consuming to be practical for large graphs. In this paper, we propose a novel labeling scheme for sparse graphs. Our scheme ensures that graph reachability queries can be answered in constant time. Furthermore, for sparse graphs, the complexity of the labeling process is almost linear, which makes our algorithm applicable to massive datasets. Analytical and experimental results show that our approach is much more efficient than stateof- the-art approaches. Furthermore, our labeling method also provides an alternative scheme to tradeoff query time for label space, which further benefits applications that use tree-like graphs.