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Physical Sciences and Mathematics Commons™

Open Access. Powered by Scholars. Published by Universities.®

2006

Computer Sciences

University of Nebraska - Lincoln

School of Computing: Faculty Publications

Articles 1 - 10 of 10

Full-Text Articles in Physical Sciences and Mathematics

Exploiting Geographical And Temporal Locality To Boost Search Efficiency In Peer-To-Peer Systems, Hailong Cai, Jun Wang Oct 2006

Exploiting Geographical And Temporal Locality To Boost Search Efficiency In Peer-To-Peer Systems, Hailong Cai, Jun Wang

School of Computing: Faculty Publications

As a hot research topic, many search algorithms have been presented and studied for unstructured peer-to-peer (P2P) systems during the past few years. Unfortunately, current approaches either cannot yield good lookup performance, or incur high search cost and system maintenance overhead. The poor search efficiency of these approaches may seriously limit the scalability of current unstructured P2P systems. In this paper, we propose to exploit two-dimensional locality to improve P2P system search efficiency. We present a locality-aware P2P system architecture called Foreseer, which explicitly exploits geographical locality and temporal locality by constructing a neighbor overlay and a friend overlay, respectively. …

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On The Use Of Mutation Faults In Empirical Assessments Of Test Case Prioritization Techniques, Hyunsook Do, Gregg Rothermel Sep 2006

On The Use Of Mutation Faults In Empirical Assessments Of Test Case Prioritization Techniques, Hyunsook Do, Gregg Rothermel

School of Computing: Faculty Publications

Regression testing is an important activity in the software life cycle, but it can also be very expensive. To reduce the cost of regression testing, software testers may prioritize their test cases so that those which are more important, by some measure, are run earlier in the regression testing process. One potential goal of test case prioritization techniques is to increase a test suite’s rate of fault detection (how quickly, in a run of its test cases, that test suite can detect faults). Previous work has shown that prioritization can improve a test suite’s rate of fault detection, but the …

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Image Interpolation By Two-Dimensional Parametric Cubic Convolution, Jiazheng Shi, Stephen E. Reichenbach Jul 2006

Image Interpolation By Two-Dimensional Parametric Cubic Convolution, Jiazheng Shi, Stephen E. Reichenbach

School of Computing: Faculty Publications

Cubic convolution is a popular method for image interpolation. Traditionally, the piecewise-cubic kernel has been derived in one dimension with one parameter and applied to two-dimensional (2-D) images in a separable fashion. However, images typically are statistically nonseparable, which motivates this investigation of nonseparable cubic convolution. This paper derives two new nonseparable, 2-D cubic-convolution kernels. The first kernel, with three parameters (designated 2D-3PCC), is the most general 2-D, piecewise-cubic interpolator defined on [-2, 2] x [-2, 2] with constraints for biaxial symmetry, diagonal (or 90 rotational) symmetry, continuity, and smoothness. The second kernel, with five parameters (designated 2D-5PCC), relaxes the …

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Interactive Fault Localization Techniques In A Spreadsheet Environment, Joseph R. Ruthruff, Margaret Burnett, Gregg Rothermel Apr 2006

Interactive Fault Localization Techniques In A Spreadsheet Environment, Joseph R. Ruthruff, Margaret Burnett, Gregg Rothermel

School of Computing: Faculty Publications

End-user programmers develop more software than any other group of programmers, using software authoring devices such as multimedia simulation builders, e-mail filtering editors, by-demonstration macro builders, and spreadsheet environments. Despite this, there has been only a little research on finding ways to help these programmers with the dependability of the software they create. We have been working to address this problem in several ways, one of which includes supporting end-user debugging activities through interactive fault localization techniques. This paper investigates fault localization techniques in the spreadsheet domain, the most common type of end-user programming environment. We investigate a technique previously …

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Implementing Cs1 With Embedded Instructional Research Design In Laboratories, Jeff Lang, Gwen C. Nugent, Ashok Samal, Leen-Kiat Soh Feb 2006

Implementing Cs1 With Embedded Instructional Research Design In Laboratories, Jeff Lang, Gwen C. Nugent, Ashok Samal, Leen-Kiat Soh

School of Computing: Faculty Publications

Closed laboratories are becoming an increasingly popular approach to teaching introductory computer science courses. Unlike open laboratories that tend to be an informal environment provided for students to practice their skills with attendance optional, closed laboratories are structured meeting times that support the lecture component of the course, and attendance is required. This paper reports on an integrated approach to designing, implementing, and assessing laboratories with an embedded instructional research design. The activities reported here are parts of a department-wide effort not only to improve student learning in computer science and computer engineering (CE) but also to improve the agility …

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Allocating Non-Real-Time And Soft Real-Time Jobs In Multiclusters, Ligang He, Stephen A. Jarvis, Daniel P. Spooner, Hong Jiang, Donna N. Dillenberger, Graham R. Nudd Feb 2006

Allocating Non-Real-Time And Soft Real-Time Jobs In Multiclusters, Ligang He, Stephen A. Jarvis, Daniel P. Spooner, Hong Jiang, Donna N. Dillenberger, Graham R. Nudd

School of Computing: Faculty Publications

This paper addresses workload allocation techniques for two types of sequential jobs that might be found in multicluster systems, namely, non-real-time jobs and soft real-time jobs. Two workload allocation strategies, the Optimized mean Response Time (ORT) and the Optimized mean Miss Rate (OMR), are developed by establishing and numerically solving two optimization equation sets. The ORT strategy achieves an optimized mean response time for non-real-time jobs, while the OMR strategy obtains an optimized mean miss rate for soft real-time jobs over multiple clusters. Both strategies take into account average system behaviors (such as the mean arrival rate of jobs) in …

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Ceft: A Cost-Effective, Fault-Tolerant Parallel Virtual File System, Yifeng Zhu, Hong Jiang Feb 2006

Ceft: A Cost-Effective, Fault-Tolerant Parallel Virtual File System, Yifeng Zhu, Hong Jiang

School of Computing: Faculty Publications

The vulnerability of computer nodes due to component failures is a critical issue for cluster-based file systems. This paper studies the development and deployment of mirroring in cluster-based parallel virtual file systems to provide fault tolerance and analyzes the tradeoffs between the performance and the reliability in the mirroring scheme. It presents the design and implementation of CEFT, a scalable RAID-10 style file system based on PVFS, and proposes four novel mirroring protocols depending on whether the mirroring operations are server-driven or client-driven, whether they are asynchronous or synchronous. The comparisons of their write performances, measured in a real cluster, …

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A Survey Of Security Issues In Wireless Sensor Networks, Yong Wang, Garhan Attebury, Byrav Ramamurthy Jan 2006

A Survey Of Security Issues In Wireless Sensor Networks, Yong Wang, Garhan Attebury, Byrav Ramamurthy

School of Computing: Faculty Publications

Wireless Sensor Networks (WSNs) are used in many applications in military, ecological, and health-related areas. These applications often include the monitoring of sensitive information such as enemy movement on the battlefield or the location of personnel in a building. Security is therefore important in WSNs. However, WSNs suffer from many constraints, including low computation capability, small memory, limited energy resources, susceptibility to physical capture, and the use of insecure wireless communication channels. These constraints make security in WSNs a challenge. In this article we present a survey of security issues in WSNs. First we outline the constraints, security requirements, and …

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Spatial Correlation-Based Collaborative Medium Access Control In Wireless Sensor Networks, Mehmet C. Vuran, Ian F. Akyildiz Jan 2006

Spatial Correlation-Based Collaborative Medium Access Control In Wireless Sensor Networks, Mehmet C. Vuran, Ian F. Akyildiz

School of Computing: Faculty Publications

Wireless Sensor Networks (WSN) are mainly characterized by dense deployment of sensor nodes which collectively transmit information about sensed events to the sink. Due to the spatial correlation between sensor nodes subject to observed events, it may not be necessary for every sensor node to transmit its data. This paper shows how the spatial correlation can be exploited on the Medium Access Control (MAC) layer. To the best of our knowledge, this is the first effort which exploits spatial correlation in WSN on the MAC layer. A theoretical framework is developed for transmission regulation of sensor nodes under a distortion …

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Exploiting Redundancy To Boost Performance In A Raid-10 Style Cluster-Based File System, Yifeng Zhu, Hong Jiang, Xiao Qin, Dan Feng, David Swanson Jan 2006

Exploiting Redundancy To Boost Performance In A Raid-10 Style Cluster-Based File System, Yifeng Zhu, Hong Jiang, Xiao Qin, Dan Feng, David Swanson

School of Computing: Faculty Publications

While aggregating the throughput of existing disks on cluster nodes is a cost-effective approach to alleviate the I/O bottleneck in cluster computing, this approach suffers from potential performance degradations due to contentions for shared resources on the same node between storage data processing and user task computation. This paper proposes to judiciously utilize the storage redundancy in the form of mirroring existed in a RAID-10 style file system to alleviate this performance degradation. More specifically, a heuristic scheduling algorithm is developed, motivated from the observations of a simple cluster configuration, to spatially schedule write operations on the nodes with less …

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