4,777 research outputs found
Trust-Based Techniques for Collective Intelligence in Social Search Systems.
A key-issue for the effectiveness of collaborative decision support systems is the problem of the trustworthiness of the entities involved in the process. Trust has been always used by humans as a form of collective intelligence to support effective decision making process. Computational trust models are becoming now a popular technique across many applications such as cloud computing, p2p networks, wikis, e-commerce sites, social network. The chapter provides an overview of the current landscape of computational models of trust and reputation, and it presents an experimental study case in the domain of social search, where we show how trust techniques can be applied to enhance the quality of social search engine predictions
High Peformance and Low Power On-Die Interconnect Fabrics.
Increasing power density with technology scaling has caused stagnation in operating frequency of modern day microprocessors. This has led designers to prefer multicore architectures over complex monolithic processors to keep up with the demand for rising computing throughput. Although processing units are getting smaller and simpler, the dramatic rise of their count on a single die has made the fabric that connects these processing units increasingly complex. These interconnect fabrics have become a bottleneck in improving overall system effciency. As a result, the design paradigm for multi-core chips is gradually shifting from a core-centric architecture towards an interconnect-centric architecture, where system efficiency is limited by the fabric rather than the processing ability of any individual core. This dissertation introduces three novel and synergistic circuit techniques to improve scalability of switch fabrics to make on-die integration of hundreds to thousands of cores feasible. 1) A matrix topology is proposed for designing a fully connected switch fabric that re-uses output buses for programming, and stores shue congurations at cross points. This significantly reduces routing congestion, lowers area/power, and improves per-
formance. Silicon measurements demonstrate 47% energy savings in a 64-lane SIMD processor fabricated in 65nm CMOS over a conventional implementation. 2) A novel approach to handle high radix arbitration along with data routing is proposed. It optimally uses existing cross-bar interconnect resources without requiring any additional overhead. Bandwidth exceeding 2Tb/s is recorded in a test prototype fabricated in 65nm. 3) Building on the later, a new circuit topology to manage and update priority adaptively within the switch fabric without incurring additional delay or area is then proposed. Several assist circuit techniques, such as a thyristor based sense amplifier and self regenerating bi-directional repeaters are proposed for high speed energy efficient signaling to and from the switch fabric to improve overall routing efficiency.
Using these techniques a 64 x 64 switch fabric with 128b data bus fabricated in 45nm achieves a throughput of 4.5Tb/s at single cycle latency while operating at 559MHz.Ph.D.Electrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/91506/1/sudhirks_1.pd
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SenseMap: Supporting Browser-based Online Sensemaking through Analytic Provenance
Sensemaking is described as the process in which people collect, organize and create representations of information, all centered around some problem they need to understand. People often get lost when solving complicated tasks using big datasets over long periods of exploration and analysis. They may forget what they have done, are unaware of where they are in the context of the overall task, and are unsure where to continue. In this paper, we introduce a tool, SenseMap, to address these issues in the context of browser-based online sensemaking. We conducted a semistructured interview with nine participants to explore their behaviors in online sensemaking with existing browser functionality. A simplified sensemaking model based on Pirolli and Card’s model is derived to better represent the behaviors we found: users iteratively collect information sources relevant to the task, curate them in a way that makes sense, and finally communicate their findings to others. SenseMap automatically captures provenance of user sensemaking actions and provides multi-linked views to visualize the collected information and enable users to curate and communicate their findings. To explore how SenseMap is used, we conducted a user study in a naturalistic work setting with five participants completing the same sensemaking task related to their daily work activities. All participants found the visual representation and interaction of the tool intuitive to use. Three of them engaged with the tool and produced successful outcomes. It helped them to organize information sources, to quickly find and navigate to the sources they wanted, and to effectively communicate their findings
Modeling and Experimental Verification of Adaptive 100% Stator Ground Fault Protection Schemes for Synchronous Generators
Salient pole synchronous generators as the main component of an electricity generation station should be carefully maintained and their operation has to be monitored such that any damage on them is avoided. Otherwise, the generating station might experience frequent shut downs which results in electricity generation interruptions and high costs associated with repairing and compensation of lack of energy. In this sense, many protective schemes focusing on a variety of synchronous generator faults have already been proposed and are still modified and developed to further enhance the quality of protection.
In this thesis, synchronous generator stator windings to ground fault is studied as one of the most common and crucial faults in these machines. Numerous methods of stator winding to ground fault protection schemes are also reported in the literature. Third harmonic differential voltage and sub-harmonic schemes are studied in this research. A novel adaptive scheme for both methods is modelled and implemented in a comprehensive lab scale set-up where a real generation unit is scaled down including all different components and apparatus. The simulation model is also established based on simultaneous finite element analysis (FEA) and coupled magnetic circuit to assist with system configuration design and parameter selections.
The adaptive scheme is proved to be capable of detecting stator windings to ground faults based on actual experimental data. Finally, the proposed adaptive scheme is compared against other available non-adaptive protection schemes currently used in industrial relays. Several important performance evaluation criteria in protection schemes such as sensitivity and security of operation referred to as reliability are considered. It is shown that the adaptive scheme offers higher reliability than other schemes which emphasizes its credibility and applicability
Facilitating Mobile Music Sharing and Social Interaction with Push!Music
Push!Music is a novel mobile music listening and
sharing system, where users automatically receive
songs that have autonomously recommended
themselves from nearby players depending on similar
listening behaviour and music history. Push!Music
also enables users to wirelessly send songs between
each other as personal recommendations. We
conducted a two-week preliminary user study of
Push!Music, where a group of five friends used the
application in their everyday life. We learned for
example that the shared music in Push!Music became
a start for social interaction and that received songs in
general were highly appreciated and could be looked
upon as ‘treats’
Replacement bearing for Rocketdyne SSME HPOTPs using alternate self-lubricating retainer materials
Research was conducted to develop replacement bearings for the Rocketdyne Space Shuttle main engine (SSME) high pressure oxidizer turbopumps (HPOTPs). The replacement bearings consisted of standard balls and races with a special Battelle Self-Lubricating Insert Configuration (BASIC) retainer. The BASIC retainer consists of a phosphor bronze housing with inserts consisting of a polytetrafluoretheylene (PTFE) and bronze compound. The PTFE contacts the balls and the land guiding surface on the outer race. A PTFE transfer film is formed on balls and races, which lubricates the critical interfaces. The BASIC retainer is a one-to-one replacement for the current Armalon retainer, but has superior lubricating properties and is stronger over the broad temperature range anticipated for the HPOTP bearings. As a part of the project 40 sets of balls and races (two sizes) and 52 BASIC retainers were shipped to NASA/MSFC
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