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2015

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Articles 31 - 60 of 2510

Full-Text Articles in Computer Sciences

Low Delay Marking For Tcp In Wireless Ad Hoc Networks, Choong-Soo Lee, Mingzhe Li, Emmanuel Agu, Mark Claypool, Robert Kinicki Dec 2015

Low Delay Marking For Tcp In Wireless Ad Hoc Networks, Choong-Soo Lee, Mingzhe Li, Emmanuel Agu, Mark Claypool, Robert Kinicki

Emmanuel O. Agu

End-hosts on wireless ad hoc networks typically use TCP as their transport layer protocol. Being designed for wired networks, TCP can perform poorly over wireless networks. Work that has proposed ways to improve TCP performance over wireless networks has concentrated primarily on improving TCP throughput only. Emerging applications, such as interactive multimedia and network games, require reduced delay at least as much as increased throughput. In this paper, we propose LDM1, an IP layer queue marking mechanism that estimates the number of hops and flows at each wireless node to computes the optimal marking probability. We present simulation results and …

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Time-Partitioned Index Design For Adaptive Multi-Route Data Stream Systems Utilizing Heavy Hitter Algorithms, Karen Works, Elke Rundensteiner, Emmanuel Agu Dec 2015

Time-Partitioned Index Design For Adaptive Multi-Route Data Stream Systems Utilizing Heavy Hitter Algorithms, Karen Works, Elke Rundensteiner, Emmanuel Agu

Emmanuel O. Agu

Adaptive multi-route query processing (AMR) is a recently emerging paradigm for processing stream queries in highly fluctuating environments. AMR dynamically routes batches of tuples to operators in the query network based on routing criteria and up-to-date system statistics. In the context of AMR systems, indexing, a core technology for efficient stream processing, has received little attention. Indexing in AMR systems is demanding as indices must adapt to serve continuously evolving query paths while maintaining index content under high volumes of data. Our proposed Adaptive Multi-Route Index (AMRI) employs a bitmap time-partitioned design that while being versatile in serving a diverse …

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Performance Enhancement Of Tfrc In Wireless Networks, Mingzhe Li, Emmanuel Agu, Mark Claypool, Robert Kinicki Dec 2015

Performance Enhancement Of Tfrc In Wireless Networks, Mingzhe Li, Emmanuel Agu, Mark Claypool, Robert Kinicki

Emmanuel O. Agu

The TCP-Friendly Rate Control (TFRC) is used as a streaming media transport protocol. Using the TCP congestion response function and current network conditions, TFRC adjusts its transmission rate to yield the maximum TCP-Friendly throughput when sharing capacity with TCP flows. Since TFRC was designed for wired networks, it does not achieve the maximum TCP-Friendly throughput in multihop ad hoc wireless networks. The reduced wireless spatial channel reuse due to hidden terminals in multihop wireless networks induces TFRC throughput reductions. Specifically, TFRC is unaware of MAC layer transmission delays due to collisions, retransmissions and MAC layer congestion. This paper illustrates that …

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Discovering A Research Agenda For Using Design Rationale In Software Maintenance, Janet Burge, David Brown Dec 2015

Discovering A Research Agenda For Using Design Rationale In Software Maintenance, Janet Burge, David Brown

David C. Brown

Design Rationale consists of the reasons behind decisions made while designing. This information would be particularly useful during software maintenance. In this paper, we describe a study performed to investigate the content, structure, and use of design rationale during maintenance. The major goal of this study was to discover an agenda for further research into the use of design rationale for software maintenance.

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Measuring The Performance Gains From Directional Antennas In An Unplanned 802.11b Mesh Network, Jason Wilson, Patrick Gemme, Emmanuel Agu Dec 2015

Measuring The Performance Gains From Directional Antennas In An Unplanned 802.11b Mesh Network, Jason Wilson, Patrick Gemme, Emmanuel Agu

Emmanuel O. Agu

Wireless mesh networks are becoming increasingly popular. Most proposed mesh algorithms are evaluated using simulation. Simulations frequently oversimplify real world scenarios and can lead to results that are significantly different. Thus, although it is more difficult to run controlled experiments in already deployed real-world networks, it is important to understand how proposed improvements perform under these realistic scenarios. Several authors have suggested the use of directional antennas, but their merits have only comprehensively evaluated in simulators. Roofnet is an unplanned 802.11b wireless mesh network deployed by MIT and is constructed primarily of omni-directional antennas. We use measurements to evaluate performance …

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Inferring Unobservable Learning Variables From Students’ Help Seeking Behavior, Ivon Arroyo Dec 2015

Inferring Unobservable Learning Variables From Students’ Help Seeking Behavior, Ivon Arroyo

Ivon Arroyo

Results of an evaluation of students’ attitudes and their relationship to student behaviors within a tutoring system are presented. Starting from a correlation analysis that integrates survey-collected student attitudes, learning variables, and behaviors while using the tutor, we constructed a Bayesian Network that infers attitudes and perceptions towards help and the tutoring system.

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Web-Based Intelligent Multimedia Tutoring For High Stakes Achievement Tests, Ivon Arroyo Dec 2015

Web-Based Intelligent Multimedia Tutoring For High Stakes Achievement Tests, Ivon Arroyo

Ivon Arroyo

We describe Wayang Outpost, a web-based ITS for the Math section of the Scholastic Aptitude Test (SAT). It has several distinctive features: help with multimedia animations and sound, problems embedded in narrative and fantasy contexts, alternative teaching strategies for students of different mental rotation abilities and memory retrieval speeds. Our work on adding intelligence for adaptivity is described. Evaluations prove that students learn with the tutor, but learning depends on the interaction of teaching strategies and cognitive abilities. A new adaptive tutor is being built based on evaluation results; surveys results and students’ log files analyses.

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Reasoning With Design Rationale, Janet Burge, David Brown Dec 2015

Reasoning With Design Rationale, Janet Burge, David Brown

David C. Brown

Design Rationale (DR) consists of the decisions made during the design process and the reasons behind them. Because it offers more than just a “snapshot” of the final design decisions, DR is invaluable as an aid for revising, maintaining, documenting, evaluating, and learning the design. Much work has been performed on how DR can be captured and represented but not as much on how it can be used. In this paper, we investigate the use of DR by building InfoRat, a system that inferences over a design’s rationale in order to detect inconsistencies and to assess the impact of changes.

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Tradeoffs Between Energy And Security In Wireless Networks, Fernando Colón Osorio, Emmanuel Agu, Kerry Mckay Dec 2015

Tradeoffs Between Energy And Security In Wireless Networks, Fernando Colón Osorio, Emmanuel Agu, Kerry Mckay

Emmanuel O. Agu

In recent years, several researchers have studied the vulnerabilities present in the encryption protocols and authentication mechanisms associated with 802.11-based networks. This research has led to the creation of protocol extensions and replacement proposals such as WPA, 802.11i, and 802.1X. In addition, Denial of Service attacks that can be launched against 802.11-based networks, with relative ease and impunity, have been studied. Simultaneously, researchers studying the limitations of wireless networks have turned their attention to one of the inherent limitation of wireless devices, namely, power consumption. Research in this area has been focused in understanding the impact of the network interface …

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Characterizing The Performance And Behaviors Of Runners Using Twitter, Qian He, Emmanuel Agu, Diane Strong, Bengisu Tulu, Peder Pedersen Dec 2015

Characterizing The Performance And Behaviors Of Runners Using Twitter, Qian He, Emmanuel Agu, Diane Strong, Bengisu Tulu, Peder Pedersen

Emmanuel O. Agu

Running is a popular physical activity that improves physical and mental wellbeing. Unfortunately, up-to- date information about runners’ performance and psychological wellbeing is limited. Many questions remain unanswered, such as how far and how fast runners typically run, their preferred running times and frequencies, how long new runners persist before dropping out, and what factors cause runners to quit. Without hard data, establishing patterns of runner behavior and mitigating the challenges they face are difficult. Collecting data manually from large numbers of runners for research studies is costly and time consuming. Emerging Social Networking Services (SNS) and fitness tracking devices …

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Mapping Nominal Values To Numbers For Effective Visualization, Geraldine Rosario, Elke Rundensteiner, David Brown, Matthew Ward Dec 2015

Mapping Nominal Values To Numbers For Effective Visualization, Geraldine Rosario, Elke Rundensteiner, David Brown, Matthew Ward

David C. Brown

Data sets with a large number of nominal variables, some with high cardinality, are becoming increasingly common and need to be explored. Unfortunately, most existing visual exploration displays are designed to handle numeric variables only. When importing data sets with nominal values into such visualization tools, most solutions to date are rather simplistic. Often, techniques that map nominal values to numbers do not assign order or spacing among the values in a manner that conveys semantic relationships. Moreover, displays designed for nominal variables usually cannot handle high cardinality variables well. This paper addresses the problem of how to display nominal …

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All Your Sessions Are Belong To Us: Investigating Authenticator Leakage Through Backup Channels On Android, Guangdong Bai, Jun Sun, Jianliang Wu, Quanqi Ye, Li Li, Jin Song Dong, Shanqing Guo Dec 2015

All Your Sessions Are Belong To Us: Investigating Authenticator Leakage Through Backup Channels On Android, Guangdong Bai, Jun Sun, Jianliang Wu, Quanqi Ye, Li Li, Jin Song Dong, Shanqing Guo

Research Collection School Of Computing and Information Systems

Security of authentication protocols heavily relies on the confidentiality of credentials (or authenticators) like passwords and session IDs. However, unlike browser-based web applications for which highly evolved browsers manage the authenticators, Android apps have to construct their own management. We find that most apps simply locate their authenticators into the persistent storage and entrust underlying Android OS for mediation. Consequently, these authenticators can be leaked through compromised backup channels. In this work, we conduct the first systematic investigation on this previously overlooked attack vector. We find that nearly all backup apps on Google Play inadvertently expose backup data to any …

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Gpu Accelerated On-The-Fly Reachability Checking, Zhimin Wu, Yang Liu, Jun Sun, Jianqi Shi, Shengchao Qin Dec 2015

Gpu Accelerated On-The-Fly Reachability Checking, Zhimin Wu, Yang Liu, Jun Sun, Jianqi Shi, Shengchao Qin

Research Collection School Of Computing and Information Systems

Model checking suffers from the infamous state space explosion problem. In this paper, we propose an approach, named GPURC, to utilize the Graphics Processing Units (GPUs) to speed up the reachability verification. The key idea is to achieve a dynamic load balancing so that the many cores in GPUs are fully utilized during the state space exploration.To this end, we firstly construct a compact data encoding of the input transition systems to reduce the memory cost and fit the calculation in GPUs. To support a large number of concurrent components, we propose a multi-integer encoding with conflict-release accessing approach. We …

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Implicit Interest Indicators, Mark Claypool, Phong Le, Makoto Waseda, David Brown Dec 2015

Implicit Interest Indicators, Mark Claypool, Phong Le, Makoto Waseda, David Brown

David C. Brown

Recommender systems provide personalized suggestions about items that users will find interesting. Typically, recommender systems require a user interface that can "intelligently" determine the interest of a user and use this information to make suggestions. The common solution, "explicit ratings", where users tell the system what they think about a piece of information, is well-understood and fairly precise. However, having to stop to enter explicit ratings can alter normal patterns of browsing and reading. A more "intelligent" method is to use implicit ratings, where a rating is obtained by a method other than obtaining it directly from the users. These …

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Expectation Formation In Multi-Agent Design Systems, Dan Grecu, David Brown Dec 2015

Expectation Formation In Multi-Agent Design Systems, Dan Grecu, David Brown

David C. Brown

No abstract provided.

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Some Reactions To Presentations At The 2007 Computational Creativity Workshop, David Brown Dec 2015

Some Reactions To Presentations At The 2007 Computational Creativity Workshop, David Brown

David C. Brown

No abstract provided.

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Detection Of Diabetic Foot Ulcers Using Svm Based Classification, Lei Wang, Peder Pedersen, Diane Strong, Bengisu Tulu, Emmanuel Agu, Qian He, Ronald Ignotz, Raymond Dunn, David Harlan, Sherry Pagoto Dec 2015

Detection Of Diabetic Foot Ulcers Using Svm Based Classification, Lei Wang, Peder Pedersen, Diane Strong, Bengisu Tulu, Emmanuel Agu, Qian He, Ronald Ignotz, Raymond Dunn, David Harlan, Sherry Pagoto

Emmanuel O. Agu

Diabetic foot ulcers represent a significant health issue, for both patients’ quality of life and healthcare system costs. Currently, wound care is mainly based on visual assessment of wound size, which suffers from lack of accuracy and consistency. Hence, a more quantitative and computer-based method is needed. Supervised machine learning based object recognition is an attractive option, using training sample images with boundaries labeled by experienced clinicians. We use forty sample images collected from the UMASS Wound Clinic by tracking 8 subjects over 6 months with a smartphone camera. To maintain a consistent imaging environment and facilitate the capture process …

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A Context-Aware Activity Recommendation Smartphone Application To Mitigate Sedentary Lifestyles, Qian He, Emmanuel Agu Dec 2015

A Context-Aware Activity Recommendation Smartphone Application To Mitigate Sedentary Lifestyles, Qian He, Emmanuel Agu

Emmanuel O. Agu

A sedentary lifestyle involves irregular or no physical activity. In this kind of lifestyle, people’s activities do not increase their energy expenditure substantially above resting levels. Long periods of sitting, lying, watching television, playing video games, and using the computer are typical examples. Energy expenditures at 1.0-1.5 Metabolic Equivalent Units (METs) are considered sedentary behaviors. A recent study of sedentary lifestyles found that the length of sedentary times is associated with an increased risk of diabetes, cardiovascular disease, and cardiovascular and all-cause mortality. In this study, we developed a smartphone application called “On11”, which continuously tracks and informs the user …

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The Effects Of Loss And Latency On User Performance In Unreal Tournament 2003, Tom Beigbeder, Rory Coughlan, Corey Lusher, John Plunkett, Emmanuel Agu, Mark Claypool Dec 2015

The Effects Of Loss And Latency On User Performance In Unreal Tournament 2003, Tom Beigbeder, Rory Coughlan, Corey Lusher, John Plunkett, Emmanuel Agu, Mark Claypool

Emmanuel O. Agu

With the growth in interactive network games comes an increased importance in a better understanding of the effects of latency on user performance. While previous work has studied the tolerance game players have for high latencies and has studied the effects of latency on user performance in real-time strategy games, to the best of our knowledge, there has been no systematic study of the effects of loss and latency on user performance. In this paper we study user performance for Unreal Tournament 2003 (UT2003), a popular FPS game, under varying amounts of latency and packet loss. First, we deduced typical …

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New Potentials For Data-Driven Intelligent Tutoring System Development And Optimization, Kenneth Koedinger, Emma Brunskill, Ryan Baker, Elizabeth Mclaughlin, John Stamper Dec 2015

New Potentials For Data-Driven Intelligent Tutoring System Development And Optimization, Kenneth Koedinger, Emma Brunskill, Ryan Baker, Elizabeth Mclaughlin, John Stamper

Ryan S.J.d. Baker

Increasing widespread use of educational technologies is producing vast amounts of data. Such data can be used to help advance our understanding of student learning and enable more intelligent, interactive, engaging, and effective education. In this article, we discuss the status and prospects of this new and powerful opportunity for data-driven development and optimization of educational technologies, focusing on intelligent tutoring systems We provide examples of use of a variety of techniques to develop or optimize the select, evaluate, suggest, and update functions of intelligent tutors, including probabilistic grammar learning, rule induction, Markov decision process, classification, and integrations of symbolic …

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Nfrs: Fact Or Fiction, Janet Burge, David Brown Dec 2015

Nfrs: Fact Or Fiction, Janet Burge, David Brown

David C. Brown

No abstract provided.

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Robust Distributed Scheduling Via Time Period Aggregation, Shih-Fen Cheng, John Tajan, Hoong Chuin Lau Dec 2015

Robust Distributed Scheduling Via Time Period Aggregation, Shih-Fen Cheng, John Tajan, Hoong Chuin Lau

Shih-Fen Cheng

In this paper, we evaluate whether the robustness of a market mechanism that allocates complementary resources could be improved through the aggregation of time periods in which resources are consumed. In particular, we study a multi-round combinatorial auction that is built on a general equilibrium framework. We adopt the general equilibrium framework and the particular combinatorial auction design from the literature, and we investigate the benefits and the limitation of time-period aggregation when demand-side uncertainties are introduced. By using simulation experiments on a real-life resource allocation problem from a container port, we show that, under stochastic conditions, the performance variation …

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Robust Distributed Scheduling Via Time Period Aggregation, Shih-Fen Cheng, John Tajan, Hoong Chuin Lau Dec 2015

Robust Distributed Scheduling Via Time Period Aggregation, Shih-Fen Cheng, John Tajan, Hoong Chuin Lau

Shih-Fen Cheng

In this paper, we evaluate whether the robustness of a market mechanism that allocates complementary resources could be improved through the aggregation of time periods in which resources are consumed. In particular, we study a multi-round combinatorial auction that is built on a general equilibrium framework. We adopt the general equilibrium framework and the particular combinatorial auction design from the literature, and we investigate the benefits and the limitation of time-period aggregation when demand-side uncertainties are introduced. By using simulation experiments on a real-life resource allocation problem from a container port, we show that, under stochastic conditions, the performance variation …

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Robust Distributed Scheduling Via Time Period Aggregation, Shih-Fen Cheng, John Tajan, Hoong Chuin Lau Dec 2015

Robust Distributed Scheduling Via Time Period Aggregation, Shih-Fen Cheng, John Tajan, Hoong Chuin Lau

Shih-Fen CHENG

In this paper, we evaluate whether the robustness of a market mechanism that allocates complementary resources could be improved through the aggregation of time periods in which resources are consumed. In particular, we study a multi-round combinatorial auction that is built on a general equilibrium framework. We adopt the general equilibrium framework and the particular combinatorial auction design from the literature, and we investigate the benefits and the limitation of time-period aggregation when demand-side uncertainties are introduced. By using simulation experiments on a real-life resource allocation problem from a container port, we show that, under stochastic conditions, the performance variation …

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Mapping The Organizational Relations Within Physical Security’S Body Of Knowledge: A Management Heuristic Of Sound Theory And Best Practice, Richard Coole, David J. Brooks Dec 2015

Mapping The Organizational Relations Within Physical Security’S Body Of Knowledge: A Management Heuristic Of Sound Theory And Best Practice, Richard Coole, David J. Brooks

David J Brooks Dr.

Security Science education at university levels is still in its infancy, with little agreement towards knowledge, curriculum and competency. Therefore, it is essential that educators draw on relevant literature highlighting means of efficient and effective knowledge transfer for tertiary students within the Security Science domain. Such knowledge transfer will reduce the gap between academic knowledge (explicit) and professional competency (tacit knowledge). This paper presents phase one of a multiphase study. A qualitative “systems based knowledge structure” of security domain categories has been conceptually mapped as a domain heuristic. The heuristic drew on research highlighting that experts have both richer depths …

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Mapping The Organizational Relations Within Physical Security’S Body Of Knowledge: A Management Heuristic Of Sound Theory And Best Practice, Richard Coole, David J. Brooks Dec 2015

Mapping The Organizational Relations Within Physical Security’S Body Of Knowledge: A Management Heuristic Of Sound Theory And Best Practice, Richard Coole, David J. Brooks

David J Brooks Dr.

Security Science education at university levels is still in its infancy, with little agreement towards knowledge, curriculum and competency. Therefore, it is essential that educators draw on relevant literature highlighting means of efficient and effective knowledge transfer for tertiary students within the Security Science domain. Such knowledge transfer will reduce the gap between academic knowledge (explicit) and professional competency (tacit knowledge). This paper presents phase one of a multiphase study. A qualitative “systems based knowledge structure” of security domain categories has been conceptually mapped as a domain heuristic. The heuristic drew on research highlighting that experts have both richer depths …

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Describing Images Using A Multilayer Framework Based On Qualitative Spatial Models, Tao Wang, Hui Shi Dec 2015

Describing Images Using A Multilayer Framework Based On Qualitative Spatial Models, Tao Wang, Hui Shi

Baltic International Yearbook of Cognition, Logic and Communication

To date most research in image processing has been based on quantitative representations of image features using pixel values, however, humans often use abstract and semantic knowledge to describe and analyze images. To enhance cognitive adequacy and tractability, we here present a multilayer framework based on qualitative spatial models. The layout features of segmented images are defined by qualitative spatial models which we introduce, and represented as a set of qualitative spatial constraints. Assigned different semantic and context knowledge, the image segments and the qualitative spatial constraints are interpreted from different perspectives. Finally, the knowledge layer of the framework enables …

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Bm3d Image Denoising Using Learning-Based Adaptive Hard Thresholding, Farhan Bashar Dec 2015

Bm3d Image Denoising Using Learning-Based Adaptive Hard Thresholding, Farhan Bashar

Electronic Thesis and Dissertation Repository

Image denoising is an important pre-processing step in most imaging applications. Block Matching and 3D Filtering (BM3D) is considered to be the current state-of-art algorithm for additive image denoising. But this algorithm uses a fixed hard thresholding scheme to attenuate noise from a 3D block. Experiments show that this fixed hard thresholding deteriorates the performance of BM3D because it does not consider the context of corresponding blocks. In this thesis, we propose a learning based adaptive hard thresholding method to solve this issue. Also, BM3D algorithm requires as an input the value of the noise level in the input image. …

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Predicting Energy Demand Peak Using M5 Model Trees, Sara S. Abdelkader, Katarina Grolinger, Miriam Am Capretz Dec 2015

Predicting Energy Demand Peak Using M5 Model Trees, Sara S. Abdelkader, Katarina Grolinger, Miriam Am Capretz

Electrical and Computer Engineering Publications

Predicting energy demand peak is a key factor for reducing energy demand and electricity bills for commercial customers. Features influencing energy demand are many and complex, such as occupant behaviours and temperature. Feature selection can decrease prediction model complexity without sacrificing performance. In this paper, features were selected based on their multiple linear regression correlation coefficients. This paper discusses the capabilities of M5 model trees in energy demand prediction for commercial buildings. M5 model trees are similar to regression trees; however they are more suitable for continuous prediction problems. The M5 model tree prediction was developed based on a selected …

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Ramping Down Chinese Commercial Cyber Espionage, Emilio Iasiello Dec 2015

Ramping Down Chinese Commercial Cyber Espionage, Emilio Iasiello

Emilio Iasiello

While detractors believe that commercial cyber espionage hasn’t really stopped, recent Chinese efforts show a government trying to get a handle on its large spying apparatus that could include hired and independent contractors acting autonomously in addition to its other resources. While complete cessation may never occur, significant timely reduction demonstrates Beijing’s willingness to work with the United States as a partner and not a pariah, and provides a foundation from which the two governments can move forward on other cyber security areas where incongruity persists.

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