15870104
Homomorphism Resolving of XPath Trees Based on Automata
As a query language for navigating XML trees and selecting a set of element nodes, XPath is ubiquitous in XML applications. One important issue of XPath queries is containment checking, which is known as a co-NP complete. The homomorphism relationship between two XPath trees, which is a PTIME problem, is a sufficient but not necessary condition for the containment relationship. We propose a new tree structure to depict XPath based on the level of the tree node and adopt a method of sharing the prefixes of multi-trees to construct incrementally the most effective automata, named XTHC (XPath Trees Homomorphism Checker). XTHC takes an XPath tree and produces the result of checking homomorphism relationship between an arbitrary tree in multi-trees and the input tree, thereinto the input tree is transformed into events which force the automata to run. Moreover, we consider and narrow the discrepancy between homomorphism relationship and containment relationship as possible as we can.
8620934
Certifying Concurrent Programs Using Transactional Memory
Transactional memory (TM) is a new promising concurrency-control mechanism that can avoid many of the pitfalls of the traditional lock-based techniques. TM systems handle data races between threads automatically so that programmers do not have to reason about the interaction of threads manually. TM provides a programming model that may make the development of multi-threaded programs easier. Much work has been done to explore the various implementation strategies of TM systems and to achieve better performance, but little has been done on how to formally reason about programs using TM and how to make sure that such reasoning is sound. In this paper, we focus on the semantics of transactional memory and present a proof-carrying code (PCC) system for reasoning about programs using TM. We formalize our reasoning with respect to the TM semantics, prove its soundness, and use examples to demonstrate its effectiveness.
17199895
An Active Storage System for High Performance Computing
Traditionally, active storage devices execute custom application code on large amounts of data by utilizing the unused processing power of the storage nodes. For computation-intensive applications, the performance might be quite low due to insufficient processing power on the storage devices. In this paper we present a reconfigurable computing solution that can provide flexible, high-performance processing capabilities for the storage nodes. We have made a change over the existing active storage framework for object-based storage device by off loading computation-intensive request-driven services to a reconfigurable hardware accelerator. In the experiment, we use two applications (AES encryption and FFT) as the case studies, and the results show that the reconfigurable computing-based system can dramatically increase the performance comparing with the traditional software-based active storage systems.
20139173
Muscle-driven modeling of wrinkles for 3D facial expressions
Facial expression animation considering wrinkle formation is an aspiring goal and a challenging task. This paper presents a new geometric wrinkle model that is defined according to facial muscle anatomy for efficient simulation of dynamic wrinkles within expressions. Our method is applied to an anatomy-based face model with a multi-layer structure of skin, muscles, and skull. The location and orientation of the wrinkles are automatically determined based on muscle contraction and its influence on the skin. Corresponding to two types of facial muscles, the geometric wrinkle model governs evolution of wrinkle amplitude in the local deformed face regions. It provides intuitive parameters for easy control over wrinkle characteristics by taking into account the properties of real wrinkles. Results show that this method enables realistic wrinkles synchronized with facial movements to be dynamically simulated and rendered at an interactive rate.
14113360
A Method Used To Dynamic Scene Management Based On Octree
At present the most important things on scene rendering in computer graphics are fidelity and efficiency. In order to achieve these goals, a considerable number of applications require a data structure like a tree to manage the entire scene. Searching the scene means to traversal the tree and moving objects in the scene means to recreate the tree, which are very costly but unavoidable process. In this paper, we establish an octree for managing the whole scene and encode the nodes in the tree. Through a simple process of calculation from one node's code, we can get this node's adjacent nodes' code. With the orderly structure of the octree, we have obtained the target that is searching the nodes in the octree and recreating part of the octree efficiently.
14242473
An Experimental Investigation of Wideband MIMO Channel Based on Indoor Hotspot NLOS Measurements at 2.35GHz
In this paper, measurement data from wideband multiple-input multiple-output (MIMO) channel measurements at 2.35 GHz are presented. Measurements were preformed in indoor hotspot scenario with no line of sight (NLOS). Space-alternating generalized expectation (SAGE) algorithm was utilized to estimate angular domain parameters and powers of multipath components (MPCs), which are then used to compute the circular angular spread (CAS) and to construct the power azimuth spectrum (PAS) of transmitter and receiver sides. It is found that PASs of both sides follow multi-cluster truncated Laplacian distribution. The spatial correlation, capacity and multiplexing gain are also presented. Due to rich scatters in the indoor hotspot environment, the correlation space is Q.2lambda and the multiplexing gain is 15, which indicate indoor hotspot MIMO channels facilitate multiplexing and could achieve high capacity. The results provide important basis for future channel modeling and technique evaluation.
18825124
A Trajectory Clustering Algorithm Based on Symmetric Neighborhood
Trajectory clustering is attractive for the task of class identification in spatial database. Existing trajectory clustering algorithm TRCLUS uses global parameters to discover common trajectories. However, it can not discover small and dense clusters and be sensitive to two input parameters. Based on the partition-and-group framework, we propose a simple but effective trajectory clustering algorithm based on symmetric neighborhood named BSNTC, which needs only one input parameter which eases the sensitivity of parameters in a certain extent. The proposed measure considers both neighbors and reverse neighbors of trajectories when estimating its density distribution. Also, we use an accumulator without calculating influence outlier of each trajectory to reduce the computation cost and corresponding storage cost. A comprehensive performance evaluation and analysis shows that our method is not only efficient in the computation but also effective in arbitrary shape and different densities trajectory databases.