1,217 research outputs found

    Probably Unknown: Deep Inverse Sensor Modelling In Radar

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    Radar presents a promising alternative to lidar and vision in autonomous vehicle applications, able to detect objects at long range under a variety of weather conditions. However, distinguishing between occupied and free space from raw radar power returns is challenging due to complex interactions between sensor noise and occlusion. To counter this we propose to learn an Inverse Sensor Model (ISM) converting a raw radar scan to a grid map of occupancy probabilities using a deep neural network. Our network is self-supervised using partial occupancy labels generated by lidar, allowing a robot to learn about world occupancy from past experience without human supervision. We evaluate our approach on five hours of data recorded in a dynamic urban environment. By accounting for the scene context of each grid cell our model is able to successfully segment the world into occupied and free space, outperforming standard CFAR filtering approaches. Additionally by incorporating heteroscedastic uncertainty into our model formulation, we are able to quantify the variance in the uncertainty throughout the sensor observation. Through this mechanism we are able to successfully identify regions of space that are likely to be occluded.Comment: 6 full pages, 1 page of reference

    Distribution of macrobenthic invertebrates on the North Carolina continental shelf with consideration of sediment, hydrography and biogeography

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    The macrobenthic invertebrates of the North Carolina continental shelf in the vicinity of Cape Hatteras were sampled during four seasonal cruises, June 1977 to January 1978. Macrobenthos-sediment relationships were investigated in the area surrounding Diamond Shoals. Four benthic assemblages were recognized, each representative of specific sediment regimes. The results of multivariate analyses were interpreted as indicating that the percentages of very fine sand and silt and clay were of greatest biological significance. It is suggested that the importance of finer particles is due to their influence on sediment permeability and organic content. The degree of particle sorting was also important in accounting for some faunal differences with fossorial species predominating in the most well-sorted sediments. Thermal factors were found to be the dominating factor in species distributions on the shelf north of Cape Hatteras, an area occupied by a sharp thermal front between Gulf Stream and Virginia Shelf Water. The benthic community exposed to the greatest thermal variability within the front was more speciose than the benthos of more thermally stable areas, but otherwise demonstrated no unique characteristics. For several species the front represented a zoogeographic barrier. at mid-shelf depths the Cape Hatteras region was far more effective in limiting the northward distribution of southern species than in limiting the southward distribution of northern species. Biogeographic affinities, extent of geographic range, and ability to traverse the Cape Hatteras area were compared among the four most speciose groups, the Polychaeta, Amphipoda, Bivalvia and Gastropoda. The polychaetes and amphipods exhibited the broadest geographic distributions while the molluscs, particularly the gastropods, were the most narrowly distributed. These differences are related to the dispersal capabilities and comparative degree of eurytopy among the four macrofaunal groups considered. The present-day distributions and biogeographic affinities of the North Carolina macrofauna are also a function of the geologic history of the northwestern Atlantic and the evolutionary origin of the fauna

    Serological and Molecular Testing in Viral Hepatitis: An Update

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    The routine serological diagnoses of the three major forms of viral hepatitis - A, B and C - as well as delta hepatitis, are important in the evaluation of acute and chronic viral hepatitis. Increasingly, molecular virology is also being used to evaluate patients with chronic hepatitis C, with genotype and viral load testing to plan therapy

    Enhancement of reliability in condition monitoring techniques in wind turbines

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    The majority of electrical failures in wind turbines occur in the semiconductor components (IGBTs) of converters. To increase reliability and decrease the maintenance costs associated with this component, several health-monitoring methods have been proposed in the literature. Many laboratory-based tests have been conducted to detect the failure mechanisms of the IGBT in their early stages through monitoring the variations of thermo-sensitive electrical parameters. The methods are generally proposed and validated with a single-phase converter with an air-cored inductive or resistive load. However, limited work has been carried out considering limitations associated with measurement and processing of these parameters in a three-phase converter. Furthermore, looking at just variations of the module junction temperature will most likely lead to unreliable health monitoring as different failure mechanisms have their own individual effects on temperature variations of some, or all, of the electrical parameters. A reliable health monitoring system is necessary to determine whether the temperature variations are due to the presence of a premature failure or from normal converter operation. To address this issue, a temperature measurement approach should be independent from the failure mechanisms. In this paper, temperature is estimated by monitoring an electrical parameter particularly affected by different failure types. Early bond wire lift-off is detected by another electrical parameter that is sensitive to the progress of the failure. Considering two separate electrical parameters, one for estimation of temperature (switching off time) and another to detect the premature bond wire lift-off (collector emitter on-state voltage) enhance the reliability of an IGBT could increase the accuracy of the temperature estimation as well as premature failure detection

    Mirrors: \u27Bleeding\u27 the Creation of Alternative Organization through a Liberating Ideology of Transformative Humanism

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    In this paper, we propose a new way of explaining the everyday practices of communities who socially organize to create sustainable grass-roots engagement. We discuss how this collective engagement is based on principles and values of socio-economic engagement that are fundamentally different to those associated with capitalism. We theorise that these community engagements are sustained by an organizational ideology of \u27transformative humanism\u27 that is founded on an ongoing struggle for emancipation. Our perspective is constructed through a combination of Frantz Fanon\u27s ideas on humanism, Manfred Max-Neef\u27s barefoot economics, and Paulo Freire\u27s pedagogies of hope and transformation. We suggest that movements such as this embody alternative ways for disenfranchised individuals to shape grass-roots social transformation from within because they are based on an alternative system of beliefs. We present examples of grass-roots engagement in Argentina and South Africa to demonstrate how disenfranchised communities organize together through transformative humanism
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