227 research outputs found

    Automating Vehicles by Deep Reinforcement Learning using Task Separation with Hill Climbing

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    Within the context of autonomous driving a model-based reinforcement learning algorithm is proposed for the design of neural network-parameterized controllers. Classical model-based control methods, which include sampling- and lattice-based algorithms and model predictive control, suffer from the trade-off between model complexity and computational burden required for the online solution of expensive optimization or search problems at every short sampling time. To circumvent this trade-off, a 2-step procedure is motivated: first learning of a controller during offline training based on an arbitrarily complicated mathematical system model, before online fast feedforward evaluation of the trained controller. The contribution of this paper is the proposition of a simple gradient-free and model-based algorithm for deep reinforcement learning using task separation with hill climbing (TSHC). In particular, (i) simultaneous training on separate deterministic tasks with the purpose of encoding many motion primitives in a neural network, and (ii) the employment of maximally sparse rewards in combination with virtual velocity constraints (VVCs) in setpoint proximity are advocated.Comment: 10 pages, 6 figures, 1 tabl

    Annual Greenland accumulation rates (2009–2012) from airborne snow radar

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    Contemporary climate warming over the Arctic is accelerating mass loss from the Greenland Ice Sheet through increasing surface melt, emphasizing the need to closely monitor its surface mass balance in order to improve sea-level rise predictions. Snow accumulation is the largest component of the ice sheet's surface mass balance, but in situ observations thereof are inherently sparse and models are difficult to evaluate at large scales. Here, we quantify recent Greenland accumulation rates using ultra-wideband (2–6.5 GHz) airborne snow radar data collected as part of NASA's Operation IceBridge between 2009 and 2012. We use a semiautomated method to trace the observed radiostratigraphy and then derive annual net accumulation rates for 2009–2012. The uncertainty in these radar-derived accumulation rates is on average 14 %. A comparison of the radar-derived accumulation rates and contemporaneous ice cores shows that snow radar captures both the annual and long-term mean accumulation rate accurately. A comparison with outputs from a regional climate model (MAR) shows that this model matches radar-derived accumulation rates in the ice sheet interior but produces higher values over southeastern Greenland. Our results demonstrate that snow radar can efficiently and accurately map patterns of snow accumulation across an ice sheet and that it is valuable for evaluating the accuracy of surface mass balance models

    1951: Abilene Christian College Bible Lectures - Full Text

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    Delivered in the Auditorium of Abilene Christian College Abilene, Texas February 18-22, 1951 Price, $3.00 FIRM FOUNDATION PUBLISHING HOUSE Austin, Texa

    Comparing Skill Acquisition Under Varying Onsets of Differential Reinforcement: A Preliminary Analysis

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    The purpose of the current study was to evaluate the effect of implementing differential reinforcement at different times relative to the onset of teaching new skills to learners with autism spectrum disorder. Specifically, we first determined the most efficient differential reinforcement arrangement for each participant. Using the most efficient arrangement, we evaluated if differential reinforcement from the immediate onset, early onset, or late onset is the most efficient for learners to acquire a new skill. Three children diagnosed with autism spectrum disorder who have a history of receiving intervention based on the principles of applied behavior analysis participated in this study. The immediate onset of differential reinforcement resulted in the most efficient instruction in 6 of 7 comparisons. The results are discussed in light of previous studies and suggestions for future research are provided

    Utopianism and social change: materialism, conflict and pluralism

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    This article discusses criticisms that utopia and utopianism undermine social change. It outlines two types of utopia, future and current. It argues against claims that utopianism is idealist and steps aside from material and conflictual dimensions of society and so undermines change, proposing that utopias are material and conflictual and contribute to change. Against liberal and pluralist criticisms that utopianism is end-ist and totalitarian and terminates diversity and change it argues that utopianism can encompass liberal and pluralist dimensions and be dynamic rather than static. It is proposed that criticisms create false conflations and dichotomies. Critical perspectives, rather than being rejected, are answered on their own terms. Utopianism, it is argued, is part of change, materially, now and in the future

    Metal Complexes as Antifungals? From a Crowd-Sourced Compound Library to the First InVivo{In Vivo} Experiments

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    There are currently fewer than 10 antifungal drugs in clinical development, but new fungal strains that are resistant to most current antifungals are spreading rapidly across the world. To prevent a second resistance crisis, new classes of antifungal drugs are urgently needed. Metal complexes have proven to be promising candidates for novel antibiotics, but so far, few compounds have been explored for their potential application as antifungal agents. In this work, we report the evaluation of 1039 metal-containing compounds that were screened by the Community for Open Antimicrobial Drug Discovery (CO-ADD). We show that 20.9% of all metal compounds tested have antimicrobial activity against two representative Candida and Cryptococcus strains compared with only 1.1% of the >300,000 purely organic molecules tested through CO-ADD. We identified 90 metal compounds (8.7%) that show antifungal activity while not displaying any cytotoxicity against mammalian cell lines or hemolytic properties at similar concentrations. The structures of 21 metal complexes that display high antifungal activity (MIC ≀1.25 ÎŒM) are discussed and evaluated further against a broad panel of yeasts. Most of these have not been previously tested for antifungal activity. Eleven of these metal complexes were tested for toxicity in the Galleria mellonella moth larva model, revealing that only one compound showed signs of toxicity at the highest injected concentration. Lastly, we demonstrated that the organo-Pt(II) cyclooctadiene complex Pt1\textbf{Pt1} significantly reduces fungal load in an in vivoG. mellonella infection model. These findings showcase that the structural and chemical diversity of metal-based compounds can be an invaluable tool in the development of new drugs against infectious diseases

    1954: Abilene Christian College Bible Lectures - Full Text

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    Preface The 1954 Abilene Christian College Lectureship was one of the best attended and most successful in the history of the school. Considerable interest was manifested in the timely theme, “Overcoming Dangerous Tendencies,” and in the two special topics, “Ways and Means of Doing Mission Work,” and “Caring For Widows and Orphans.” The reports from the mission fields were highly stimulating, and all in all, the speeches were unusually high caliber. The Panel Discussions were also on timely subjects and well presented. They received a warm response, as did also the thirty classes that were conducted each day. These classes were taught by persons expert in their particular fields, and covered a wide range of interests to the faithful, working Christian. We at Abilene Christian College predict for this book of Lectures a wide and hearty reception, and believe that its reading will issue in profit to the individual and to the church at large. J. D. Thomas Lectureship Directo

    A Reconciled Estimate of Ice-Sheet Mass Balance

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    We combined an ensemble of satellite altimetry, interferometry, and gravimetry data sets using common geographical regions, time intervals, and models of surface mass balance and glacial isostatic adjustment to estimate the mass balance of Earth's polar ice sheets. We find that there is good agreement between different satellite methods-especially in Greenland and West Antarctica-and that combining satellite data sets leads to greater certainty. Between 1992 and 2011, the ice sheets of Greenland, East Antarctica, West Antarctica, and the Antarctic Peninsula changed in mass by -142 plus or minus 49, +14 plus or minus 43, -65 plus or minus 26, and -20 plus or minus 14 gigatonnes year(sup 1), respectively. Since 1992, the polar ice sheets have contributed, on average, 0.59 plus or minus 0.20 millimeter year(sup 1) to the rate of global sea-level rise
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