6,023 research outputs found

    RAFCON: a Graphical Tool for Task Programming and Mission Control

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    There are many application fields for robotic systems including service robotics, search and rescue missions, industry and space robotics. As the scenarios in these areas grow more and more complex, there is a high demand for powerful tools to efficiently program heterogeneous robotic systems. Therefore, we created RAFCON, a graphical tool to develop robotic tasks and to be used for mission control by remotely monitoring the execution of the tasks. To define the tasks, we use state machines which support hierarchies and concurrency. Together with a library concept, even complex scenarios can be handled gracefully. RAFCON supports sophisticated debugging functionality and tightly integrates error handling and recovery mechanisms. A GUI with a powerful state machine editor makes intuitive, visual programming and fast prototyping possible. We demonstrated the capabilities of our tool in the SpaceBotCamp national robotic competition, in which our mobile robot solved all exploration and assembly challenges fully autonomously. It is therefore also a promising tool for various RoboCup leagues.Comment: 8 pages, 5 figure

    From Interaction Overview Diagrams to Temporal Logic

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    In this paper, we use UML Interaction Overview Diagrams as the basis for a user-friendly, intuitive, modeling notation that is well-suited for the design of complex, heterogeneous, embedded systems developed by domain experts with little background on modeling software-based systems. To allow designers to precisely analyze models written with this notation, we provide (part of) it with a formal semantics based on temporal logic, upon which a fully automated, tool supported, verification technique is built. The modeling and verification technique is presented and discussed through the aid of an example system

    Asymptotically Unbiased Estimation of Exposure Odds Ratios in Complete Records Logistic Regression.

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    Missing data are a commonly occurring threat to the validity and efficiency of epidemiologic studies. Perhaps the most common approach to handling missing data is to simply drop those records with 1 or more missing values, in so-called "complete records" or "complete case" analysis. In this paper, we bring together earlier-derived yet perhaps now somewhat neglected results which show that a logistic regression complete records analysis can provide asymptotically unbiased estimates of the association of an exposure of interest with an outcome, adjusted for a number of confounders, under a surprisingly wide range of missing-data assumptions. We give detailed guidance describing how the observed data can be used to judge the plausibility of these assumptions. The results mean that in large epidemiologic studies which are affected by missing data and analyzed by logistic regression, exposure associations may be estimated without bias in a number of settings where researchers might otherwise assume that bias would occur

    Recovery From Monocular Deprivation Using Binocular Deprivation: Experimental Observations and Theoretical Analysis

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    Ocular dominance (OD) plasticity is a robust paradigm for examining the functional consequences of synaptic plasticity. Previous experimental and theoretical results have shown that OD plasticity can be accounted for by known synaptic plasticity mechanisms, using the assumption that deprivation by lid suture eliminates spatial structure in the deprived channel. Here we show that in the mouse, recovery from monocular lid suture can be obtained by subsequent binocular lid suture but not by dark rearing. This poses a significant challenge to previous theoretical results. We therefore performed simulations with a natural input environment appropriate for mouse visual cortex. In contrast to previous work we assume that lid suture causes degradation but not elimination of spatial structure, whereas dark rearing produces elimination of spatial structure. We present experimental evidence that supports this assumption, measuring responses through sutured lids in the mouse. The change in assumptions about the input environment is sufficient to account for new experimental observations, while still accounting for previous experimental results

    Narrative Dis/Repair: Interlinked Stories, Trauma, and Narrative Repair

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    This Ph.D. thesis is composed of two parts: a collection of interlinked stories and a critical study that investigates the same form. The story collection, Not That Far from Tel Aviv, entwines the autobiographical and the fictional, the realistic and the supernatural, the historical and the speculative. The stories involve themes such as life in Israel, home/homeland, war, the Shoa, and intergenerational trauma. With the creative part of my thesis deploying the form of interlinked stories, the critical research focuses on this literary form and, more specifically, its relationship with narratives of trauma. Looking at three collections of interlinked stories—Tim O’Brien’s The Things They Carried, Micheline Aharonian Marcom’s Three Apples Fell from Heaven, and Denis Johnson’s Jesus' Son—my study argues that this literary form reflects narratives of trauma and thus increases their impact and enables a resonant narrative repair. The question at the heart of this thesis, therefore, is: how does the form of interlinked stories enable the representation of trauma and enact a form of narrative repair? While the traditional realist novel provides details to create an environment in which the narrative unfolds, collections of interlinked stories often give only the minimally required details and are therefore better designed to deliver disjointed storytelling. I argue that the disjointed nature of interlinked stories reflects and augments the sense of chaos, crisis, and mental and physical breakdown that are typical of war, genocide, and addiction—the themes of the books examined in this study. Moreover, this literary form allows authors to entwine different time periods and merge a variety of styles and genres, which further highlights the disjointed nature of interlinked stories. Consistent across all three story collections is the narrative repair that concludes the books. Practices of storytelling complement processes of healing and of honoring the dead, allowing survivors and storytellers to find some sense of reparative community at last. Conducting the critical research and writing my story collection had a mutually beneficial effect. While my writing was influenced by my growing understanding of this literary form and its relationship with narratives of trauma, my analysis of the examined three books and the various critical thesis was at times informed by my creative journey

    Path-Fault-Tolerant Approximate Shortest-Path Trees

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    Let G=(V,E)G=(V,E) be an nn-nodes non-negatively real-weighted undirected graph. In this paper we show how to enrich a {\em single-source shortest-path tree} (SPT) of GG with a \emph{sparse} set of \emph{auxiliary} edges selected from EE, in order to create a structure which tolerates effectively a \emph{path failure} in the SPT. This consists of a simultaneous fault of a set FF of at most ff adjacent edges along a shortest path emanating from the source, and it is recognized as one of the most frequent disruption in an SPT. We show that, for any integer parameter k≄1k \geq 1, it is possible to provide a very sparse (i.e., of size O(kn⋅f1+1/k)O(kn\cdot f^{1+1/k})) auxiliary structure that carefully approximates (i.e., within a stretch factor of (2k−1)(2∣F∣+1)(2k-1)(2|F|+1)) the true shortest paths from the source during the lifetime of the failure. Moreover, we show that our construction can be further refined to get a stretch factor of 33 and a size of O(nlog⁥n)O(n \log n) for the special case f=2f=2, and that it can be converted into a very efficient \emph{approximate-distance sensitivity oracle}, that allows to quickly (even in optimal time, if k=1k=1) reconstruct the shortest paths (w.r.t. our structure) from the source after a path failure, thus permitting to perform promptly the needed rerouting operations. Our structure compares favorably with previous known solutions, as we discuss in the paper, and moreover it is also very effective in practice, as we assess through a large set of experiments.Comment: 21 pages, 3 figures, SIROCCO 201

    Emergent Dynamics of Thymocyte Development and Lineage Determination

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    Experiments have generated a plethora of data about the genes, molecules, and cells involved in thymocyte development. Here, we use a computer-driven simulation that uses data about thymocyte development to generate an integrated dynamic representation—a novel technology we have termed reactive animation (RA). RA reveals emergent properties in complex dynamic biological systems. We apply RA to thymocyte development by reproducing and extending the effects of known gene knockouts: CXCR4 and CCR9. RA simulation revealed a previously unidentified role of thymocyte competition for major histocompatability complex presentation. We now report that such competition is required for normal anatomical compartmentalization, can influence the rate of thymocyte velocities within chemokine gradients, and can account for the disproportion between single-positive CD4 and CD8 lineages developing from double-positive precursors
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