281 research outputs found

    Performance Degradation Based on Importance Change and Application in Dissimilar Redundancy Actuation System

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    The importance measure is a crucial method to identify and evaluate the system weak link. It is widely used in the optimization design and maintenance decision of aviation, aerospace, nuclear energy and other systems. The dissimilar redundancy actuation system (DRAS) is a key aircraft control subsystem which performs aircraft attitude and flight trajectory control. Its performance and reliability directly affect the aircraft flight quality and flight safety. This paper considers the influence of the Birnbaum importance measure (BIM) and integrated importance measure (IIM) on the reliability changes of key components in DRAS. The differences of physical fault characteristics of different components due to performance degradation and power mismatch, are first considered. The reliability of each component in the system is then estimated by assuming that the stochastic degradation process of the DRAS components follows an inverse Gaussian (IG) process. Finally, the weak links of the system are identified using BIM and IIM, so that the resources can be reasonably allocated to the weak links during the maintenance period. The proposed method can provide a technical support for personnel maintenance, in order to improve the system reliability with a minimal lifecycle cost

    Data-Driven Audiogram Classification for Mobile Audiometry

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    Recent mobile and automated audiometry technologies have allowed for the democratization of hearing healthcare and enables non-experts to deliver hearing tests. The problem remains that a large number of such users are not trained to interpret audiograms. In this work, we outline the development of a data-driven audiogram classification system designed specifically for the purpose of concisely describing audiograms. More specifically, we present how a training dataset was assembled and the development of the classification system leveraging supervised learning techniques. We show that three practicing audiologists had high intra- and inter-rater agreement over audiogram classification tasks pertaining to audiogram configuration, symmetry and severity. The system proposed here achieves a performance comparable to the state of the art, but is signific

    Exploring Cosmic Origins with CORE: The Instrument

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    We describe a space-borne, multi-band, multi-beam polarimeter aiming at aprecise and accurate measurement of the polarization of the Cosmic MicrowaveBackground. The instrument is optimized to be compatible with the strict budgetrequirements of a medium-size space mission within the Cosmic Vision Programmeof the European Space Agency. The instrument has no moving parts, and usesarrays of diffraction-limited Kinetic Inductance Detectors to cover thefrequency range from 60 GHz to 600 GHz in 19 wide bands, in the focal plane ofa 1.2 m aperture telescope cooled at 40 K, allowing for an accurate extractionof the CMB signal from polarized foreground emission. The projected CMBpolarization survey sensitivity of this instrument, after foregrounds removal,is 1.7 {\mu}Kâ‹…\cdotarcmin. The design is robust enough to allow, if needed, adownscoped version of the instrument covering the 100 GHz to 600 GHz range witha 0.8 m aperture telescope cooled at 85 K, with a projected CMB polarizationsurvey sensitivity of 3.2 {\mu}Kâ‹…\cdotarcmin

    Exploring cosmic origins with CORE : The instrument

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    We describe a space-borne, multi-band, multi-beam polarimeter aiming at a precise and accurate measurement of the polarization of the Cosmic Microwave Background. The instrument is optimized to be compatible with the strict budget requirements of a medium size space mission within the Cosmic Vision Programme of the European Space Agency. The instrument has no moving parts, and uses arrays of diffraction-limited Kinetic Inductance Detectors to cover the frequency range from 60 GHz to 600 GHz in 19 wide bands, in the focal plane of a 1.2 m aperture telescope cooled at 40K, allowing for an accurate extraction of the CMB signal from polarized foreground emission. The projected CMB polarization survey sensitivity of this instrument, after foregrounds removal, is 1.7 mu K.arcmin. The design is robust enough to allow, if needed, a downscoped version of the instrument covering the 100 GHz to 600 GHz range with a 0.8 m aperture telescope cooled at 85K, with a projected CMB polarization survey sensitivity of 3.2 mu K.arcmin.Peer reviewe

    Imitating Human Responses via a Dual-Process Model Approach

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    Human-autonomous system teaming is becoming more prevalent in the Air Force and in society. Often, the concept of a shared mental model is discussed as a means to enhance collaborative work arrangements between a human and an autonomous system. The idea being that when the models are aligned, the team is more productive due to an increase in trust, predictability, and apparent understanding. This research presents the Dual-Process Model using multivariate normal probability density functions (DPM-MN), which is a cognitive architecture algorithm based on the psychological dual-process theory. The dual-process theory proposes a bipartite decision-making process in people. It labels the intuitive mode as “System 1” and the reflective mode as “System 2”. The current research suggests by leveraging an agent which forms decisions based on a dual-process model, an agent in a human-machine team can maintain a better shared mental model with the user. Evaluation of DPM-MN in a game called Space Navigator shows that DPM-MN presents a successful dual-process theory motivated model

    Evolutionary games on graphs

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    Game theory is one of the key paradigms behind many scientific disciplines from biology to behavioral sciences to economics. In its evolutionary form and especially when the interacting agents are linked in a specific social network the underlying solution concepts and methods are very similar to those applied in non-equilibrium statistical physics. This review gives a tutorial-type overview of the field for physicists. The first three sections introduce the necessary background in classical and evolutionary game theory from the basic definitions to the most important results. The fourth section surveys the topological complications implied by non-mean-field-type social network structures in general. The last three sections discuss in detail the dynamic behavior of three prominent classes of models: the Prisoner's Dilemma, the Rock-Scissors-Paper game, and Competing Associations. The major theme of the review is in what sense and how the graph structure of interactions can modify and enrich the picture of long term behavioral patterns emerging in evolutionary games.Comment: Review, final version, 133 pages, 65 figure

    Trace gases in Antarctic and Greenland firn and ice: a record of carbonyl sulphide and the isotopologues of chlorofluorocarbons

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    Through the industrial revolution of the last 250 years, trace gases have had a significant impact on the climate. Of particular relevance to this work are species which facilitate the destruction of stratospheric ozone. In this thesis, I focus on four of these species. Understanding the release, reaction and transport pathways of the man-made chlorofluorocarbons (CFCs) could help us to mitigate their destructive effect. Previous studies have found that both source and sink processes significantly alter the isotopic composition of trace gases (e.g. N2O and CFC-12). Measuring these changes can be used to better constrain the interaction of these gases with the atmosphere. Atmospheric histories of δ(37Cl) and δ(13C) in CFC-11, CFC-12 and CFC-113 are presented, covering the last 20 – 60 years. Air samples came from Greenland (NEEM) and Antarctic (Fletcher Promontory) polar firn, with additional samples taken from an archive of Southern Hemispheric background air (Cape Grim, Tasmania). This study extends the novel approach to measuring trace gas isotope ratios in small air volumes (200 – 600 ml), using a single-collector gas chromatography-mass spectrometry system. Carbonyl sulphide (COS) is the principal source of sulphur in the stratosphere, where it breaks down into sulphate aerosol which catalyses the destruction of ozone. Air was extracted from Greenland (NEEM) and Antarctic (DE08, DML (BAS) and DSS) ice core samples and analysed for COS and a range of other trace gas mole fractions. The COS measurements were affected by a previously unknown post-extraction growth effect, leading to higher than expected values. This study also presents new COS measurements in firn air from NEEM and the Southern Hemisphere (EDML, Antarctica). The observed increase and subsequent decrease largely reflects changes in anthropogenic emissions during the 20th century. These measurements also indicate that regional and site-specific effects have a significant influence on the recorded atmospheric history of COS
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