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Recent Submissions

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    Proportional contact representations of planar graphs
    (University of Waterloo, 2011-03-04) Alam, Md. J.; Biedl, T.; Felsner, S.; Kaufmann, M.; Kobourov, S. G.
    We study contact representations for planar graphs, with vertices represented by simple polygons and adjacencies represented by a point-contact or a side-contact between the corresponding polygons. Specifically, we consider proportional contact representations, where given vertex weights are represented by the areas of the corresponding polygons. Several natural optimization goals for such representations include minimizing the complexity of the polygons, the cartographic error, and the unused area. We describe optimal (with respect to complexity) constructive algorithms for proportional contact representations for general planar graphs and planar 2-segment graphs, which include maximal outerplanar graphs and partial 2-trees. Specifically, we show that: (a) 4-sided polygons are necessary and sufficient for a point-contact proportional representation for any planar graph; (b) triangles are necessary and sufficient for point-contact proportional representation of partial 2-trees; (c) trapezoids are necessary and sufficient for side-contact proportional representation of partial 2-trees; (d) convex quadrilaterals are necessary and sufficient for hole-free side-contact proportional representation for maximal outer-planar graphs.
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    Improving health care with a virtual human sleep coach
    (University of Waterloo, 2011-03-01) Ribeiro, Cristina; Mehrotra, Gaurav; Vey, Gregory; Alhothali, Areej; DiMarco, Chrysanne
    Persuasive technology can have a significant effect on people's health. The sleep coach application is a persuasive technology that raises student's awareness and attitudes toward getting a full night's sleep (6-9 hours) to be more positive. Students using the application to attempt changing their sleep patterns as a direct result of the application. NOTE: We will have the results of this research by the final camera-ready paper deadline. We are currently in the process of conducting the experiment.
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    Overcoming adversaries in sensor networks: A survey of theoretical models and algorithmic approaches for tolerating malicious interference
    (University of Waterloo, 2011-02-28) Young, Maxwell; Boutaba, Raouf
    Interference is an unavoidable property of the wireless communication medium and, in sensor networks, such interference is exacerbated due to the power-starved nature of the network devices themselves. In the presence of antagonistic interference, reliable communication in sensor networks becomes an extremely challenging problem that, in recent years, has attracted significant attention from the research community. This survey present the current state of affairs in the formulation of theoretical models for adversarial interference in sensor networks and the different algorithmic remedies developed by the research community. there is a particular focus on jamming adversaries and Byzantine faults as these capture a wide range of benign faults as well as malicious attacks. The models in the literature are examined and contrasted with the aim of discerning the underlying assumptions that dictate analytical bounds with regards to feasibility and a number of performance metrics such as communication complexity, latency, and energy efficiency. Limitations are also highlighted with a focus on how various results impact real world applications and, conversely, how the current sensor network technology informs newer models. Finally, directions for future research are discussed.
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    Faster optimal algorithms for segmentMinimization with small maximal value*
    (University of Waterloo, 2011-02-21) Biedl, Therese; Durocher, Stephane; Engelbeen, Celine; Fiorini, Samuel; Young, Maxwell
    The segment minimization problem consists of finding the smallest set of integer matrices (segments) that sum to a given intensity matrix, such that each summand has only one non-zero value (the segment-value), and the non-zeroes in each row are consecutive. This has direct applications in intensity-modulated radiation therapy, an effective form of cancer treatment. We study here the special case when the largest value H in the intensity matrix is small. We show that for an intensity matrix with one row, this problem is fixed-parameter tractable (FPT) in H; our algorithm obtains a significant asymptotic speedup over the previous best FPT algorithm. We also show how to solve the full-matrix problem faster than all previously known algorithms. Finally, we address a closely related problem that deals with minimizing the number of segments subject to a minimum beam-on-time, defined as the sum of the segment-values. Here, we obtain an almost-quadratic speedup over the previous best algorithm.
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    SMURFEN: A knowledge sharing intrusion detection network
    (University of Waterloo, 2011-02-11) Fung, Carol; Zhu, Quanyan; Boutaba, Raouf; Basar, Tamar
    The problem of Internet intrusions has become a world-wide security concern. To protect computer users from malicious attacks, Intrusion Detection Systems (IDSs) are designed to monitor network traffic and computer activities in order to alert users about suspicious intrusions. Collaboration among IDSs allows users to benefit from the collective knowledge and information from their collaborators and achieve more accurate intrusion detection. However, most existing collaborative intrusion detection networks rely on the exchange of intrusion data which raises the privacy concern of participants. To overcome this problem, we propose SMURFEN: a knowledge-based intrusion detection network, which provides a platform for IDS users to effectively share their customized detection knowledge in an IDS community. An automatic knowledge propagation mechanism is proposed based on a decentralized two-level optimization problem formulation, leading to a Nash equilibrium solution which is proved to be scalable, incentive compatible, fair, efficient and robust. We evaluate our rule sharing mechanism through simulations and compare our results to existing knowledge sharing methods such as random gossiping and fixed neighbours sharing schemes.