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54th AIAA Aerospace sciences Meeting, 2016

作者： Roberts, David A. Stokes, Neil P. Quinn, Mark K. Coppin, Joe H. Birch, Trevor J. Aircraft Research Association Manton Lane BedfordMK41 7PF United Kingdom The University of Manchester George Begg Building Sackville Street ManchesterM1 3NJ United Kingdom Platform Systems Division Defence Science and Technology Laboratory DSTL FarehamPO17 6AD United Kingdom

ISBN: (数字)9781624103933

ISBN: (纸本)9781624103933

This study has investigated the use of Dynamic Pressure-Sensitive Paint (DPSP) to analyse the complex multi-dimensional flow-field within a generic small-scale rectangular planform cavity. The analysis and understanding of cavity flows have received renewed interest due to the low-observability requirements for modern military aircraft and Unmanned Combat Aerial Vehicles (UCAVs). This study has demonstrated the use of DPSP to provide unsteady pressure data, from the full model surface coverage of a model-scale cavity ceiling in a transonic Mach number range of 0.70 ≤ M ≤ 0.95. These results were compared against traditional point transducer measurements and also compared with numerical simulations of the cavity flow-field. These comparisons demonstrate that DPSP represents a very useful tool for the validation of numerical data as well as for flow-diagnostic investigations, where point measurements from transducers would provide spatially limited data. Further analysis of the transducer and DPSP data has also demonstrated temporal intermittency of the widely known Rossiter modes within the cavity acoustic signature. This instability has been previously linked to mode switching and a breakdown in the modal generation feedback process within the cavity flowfield. © 2016, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

关键词： Flow fields

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Virtual simulation-based scene modeling of helicopter earthquake search and rescue

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AIP Conference Proceedings 2017年第1期1839卷

作者： Xue Sun Hu Liu Chenguang Yang Ning Wang 1State Key Laboratory of Virtual Reality Technology and Systems School of Aeronautic Science and Engineering Beihang University Beijing 100191 China 2School of Sino-French Engineer Beihang University Beijing 100191 China

The characteristics of helicopter earthquake search and rescue (HESAR) oriented virtual simulation scene are summarized to guide the modeling of virtual simulation scene. Then a method of scene modeling which can satisfy the simulation requirements and simplify the modeling is proposed. The seismic influence field is first determined by inversion to get the distribution of buildings with different damage grades. And then, the division of different levels of detail (LOD) regions where the intricacy requirements of modeling are different is obtained to simplify the modeling. Besides, Unity3D is used for the three-dimensional terrain construction and scene rendering. Finally, a sample case was shown to verify the effectiveness of the proposed method.

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Impact and damage of an armour composite

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AIP Conference Proceedings 2017年第1期1793卷

作者： A. D. Resnyansky S. Parry N. K. Bourne D. Townsend B. James 1Weapons and Combat Systems Division Defence Science and Technology Group Edinburgh SA 5111 Australia 2Centre for Matter under Extreme Conditions School of Materials University of Manchester Research Complex at Harwell Rutherford Appleton Laboratory Didcot Oxfordshire OX11 0FA United Kingdom 3Structural Dynamics Group Defence Science and Technology Laboratory (DSTL) Porton Down Salisbury Wiltshire Oxfordshire SP40JQ United Kingdom

The current study assesses the application of the Taylor Test to validate hydrocode modelling of composite materials. 0° in-plane and through-thickness rods were cut from a 25 mm thick composite panel, made from autoclave cured 0°, 90° uni-directional carbon/epoxy prepreg. The rods were fired against a semi-infinite steel anvil and high-speed video imaging was used to capture the difference in rod shape and damage patterns during the experiments. Results of simulation with a rate sensitive, transversely isotropic composite material model implemented in the CTH hydrocode were compared with the present experiments. The model showed good correlation with global deformation of the rods, and was used to qualitatively assess some of the asymmetric deformation features in the material. As the present model implementation did not account for damage at this stage, it did not predict inter-ply delamination normal to the impact face for the in-plane 0° rods and that parallel to the impact face in the through-thickness samples.

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Enhancing Discovery of Genetic Variants for Posttraumatic Stress Disorder Through Integration of Quantitative Phenotypes and Trauma Exposure Information (vol 91, pg 626, 2022)

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BIOLOGICAL PSYCHIATRY 2022年第7期91卷 690-690页

作者： Maihofer, Adam X. Vinkers, Christiaan H. Department of Psychiatry University of California San Diego La Jolla California Department of Family Medicine and Public Health University of California San Diego La Jolla California Center of Excellence for Stress and Mental Health Veterans Affairs Healthcare System San Diego California. Electronic address: amaihofer@health.ucsd.edu. Department of Epidemiology Harvard T.H. Chan School of Public Health Boston Massachusetts Department of Psychiatry Massachusetts General Hospital Boston Massachusetts. Social Genetic and Developmental Psychiatry Centre Institute of Psychiatry Psychology and Neuroscience King's College London London United Kingdom National Institute of Health Research Maudsley Biomedical Research Centre King's College London London United Kingdom. Department of Psychiatry Harvard Medical School Boston Massachusetts Stanley Center for Psychiatric Research Broad Institute of MIT and Harvard Cambridge Massachusetts Center of Excellence in Depression and Anxiety Disorders Belmont Massachusetts. Department of Epidemiology Harvard T.H. Chan School of Public Health Boston Massachusetts Stanley Center for Psychiatric Research Broad Institute of MIT and Harvard Cambridge Massachusetts. Department of Psychiatry University of California San Diego La Jolla California Center of Excellence for Stress and Mental Health Veterans Affairs Healthcare System San Diego California Research Service Veterans Affairs Healthcare System San Diego California. Duke Molecular Physiology Institute Duke University School of Medicine Durham North Carolina. Department of Psychiatry Veterans Affairs Connecticut Healthcare System West Haven Connecticut Department of Psychiatry Yale University School of Medicine New Haven Connecticut. Department of Epidemiology Harvard T.H. Chan School of Public Health Boston Massachusetts Department of Epidemiology Columbia University Mailman School of Public Health New York. Division of Mental Health Atlanta Veterans Affairs Medical Center

BACKGROUND: Posttraumatic stress disorder (PTSD) is heritable and a potential consequence of exposure to traumatic stress. Evidence suggests that a quantitative approach to PTSD phenotype measurement and incorporation of lifetime trauma exposure (LTE) information could enhance the discovery power of PTSD genome-wide association studies (GWASs). METHODS: A GWAS on PTSD symptoms was performed in 51 cohorts followed by a fixed-effects meta-analysis (N = 182,199 European ancestry participants). A GWAS of LTE burden was performed in the UK Biobank cohort (N = 132,988). Genetic correlations were evaluated with linkage disequilibrium score regression. Multivariate analysis was performed using Multi-Trait Analysis of GWAS. Functional mapping and annotation of leading loci was performed with FUMA. Replication was evaluated using the Million Veteran Program GWAS of PTSD total symptoms. RESULTS: GWASs of PTSD symptoms and LTE burden identified 5 and 6 independent genome-wide significant loci, respectively. There was a 72% genetic correlation between PTSD and LTE. PTSD and LTE showed largely similar patterns of genetic correlation with other traits, albeit with some distinctions. Adjusting PTSD for LTE reduced PTSD heritability by 31%. Multivariate analysis of PTSD and LTE increased the effective sample size of the PTSD GWAS by 20% and identified 4 additional loci. Four of these 9 PTSD loci were independently replicated in the Million Veteran Program. CONCLUSIONS: Through using a quantitative trait measure of PTSD, we identified novel risk loci not previously identified using prior case-control analyses. PTSD and LTE have a high genetic overlap that can be leveraged to increase discovery power through multivariate methods.

关键词： GWAS Genetics Heritability PTSD PheWAS Trauma

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Robust parameter estimation for periodic point process signals using circular statistics 8

Robust parameter estimation for periodic point process signa...

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8th European Signal Processing Conference, EUSIPCO 1996

作者： Elton, Stephen D. Slocumb, Benjamin J. Electronics and Surveillance Research Laboratory Defence Science and Technology Organisation Cooperative Research Centre for Robust and Adaptive Systems P.O. Box 1500 SalisburySA5108 Australia Electronic Systems Laboratory Georgia Tech Research Institute Georgia Institute of Technology AtlantaGA30332-0840 United States

We discuss the application of signal parameter estimators for periodic point process signals with missing data. The proposed estimation techniques operate on the observed event arrival time sequence of a pulse train signal and have application to pulse train signal classification and signal reconstruction. The methods we describe are based on the use of circular statistics and are shown to offer considerable robustness to a pulse train time series corrupted by missing pulses. © 2015 European Signal Processing Conference, EUSIPCO. All rights reserved.

关键词： Signal reconstruction

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Aggregation Encoding: Reducing Network Traffic for Big Data Erasure-Coded Storages

Aggregation Encoding: Reducing Network Traffic for Big Data ...

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International Conference on Cyber-Enabled Distributed Computing and Knowledge Discovery, CyberC

作者： Jing Zhang Shanshan Li Xiangke Liao Xiaodong Liu School of Computer Science and Technology National University of Defence Technology Changsha China Science and Technology on Complex Aviation Systems Simulation Laboratory Beijing China

ISBN: (纸本)9781467392013

Erasure-coded storages provide data reliability for big data archiving and backup with high storage efficiency. However, erasure code generates a large amount of data transmission traffic in both encoding (write) and decoding (repair) which costs substantial bandwidth in the network. Most of the existing work focus on the decoding cost due to the importance of data repair, but unfortunately overlooks the encoding cost. In this paper, we propose Aggregation Encoding for reducing the bandwidth cost of the encoding phase in erasure-coded storages. Aggregation Encoding takes inspiration from network coding to enforce encoding through data transmission, which reduces redundant information transmitting. The extensive analysis and experimental results demonstrate that Aggregation Encoding reduces bandwidth cost by 20% in average.

关键词： Encoding Bandwidth Routing Vegetation Network topology Topology Approximation methods

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Numerical study of blunt leading edge separation on a 53 degree swept diamond wing (STO AVT-183) using the edge and cobalt flow solver 53

Numerical study of blunt leading edge separation on a 53 deg...

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53rd AIAA Aerospace sciences Meeting, 2015

作者： Edefur, Henrik Tormalm, Magnus Coppin, Joe Birch, Trevor Nangia, Raj Department of Information and Aeronautical Systems StockholmSE-164 90 Sweden Defence Science and Technology Laboratory Air and Weapons Systems Department FarehamPO17 6AD United Kingdom Nangia Aero Research Associates BristolBS9 2DA United Kingdom

ISBN: (数字)9781624103438

ISBN: (纸本)9781624103438

This paper presents numerical results for a diamond wing test case using the FOI developed flow solver Edge and the commercial flow solver Cobalt. The results show the effect of grid resolution, turbulence modelling and temporal accuracy using RANS, URANS and hybrid RANS-LES methods on structured and unstructured meshes. The sensitivity of the solution to the free-stream Mach number, incidence and Reynolds number is also presented. The computed wing pressure distributions have been post-processed to give spanwise and chordwise distributions of the axial, normal and side forces which give an indication of the flow progression as incidence changes as well as showing the limits to attached flow on this wing. To verify the calculations, the results have been compared with wind tunnel test results. Wind tunnel corrections are also derived in order to compare the results provided with the free air numerical predictions. This paper concludes that when modelling this case with CFD, the details of the flow separation on the leading edge are extremely sensitive to the modelling approach taken. A large spread of results has been obtained although in some cases the results (both forces and pressures) match the experiment very well. There are also unresolved issues regarding what assumptions can be made about the experiment when conducting the CFD modelling, particularly regarding lift interference. © 2015 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

关键词： Cobalt

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An approximation of surprise index as a measure of confidence

An approximation of surprise index as a measure of confidenc...

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AAAI 2015 Fall Symposium

作者： Zagorecki, Adam Kozniewski, Marcin Druzdzel, Marek J. Center for Simulation and Analytics Cranfield University Defence Academy of United Kingdom ShrivenhamSN6 8LA United Kingdom Decision Systems Laboratory School of Information Sciences University of Pittsburgh PittsburghPA15260 United States Faculty of Computer Science Bialystok University of Technology Wiejska 45A Bialystok15-351 Poland

ISBN: (纸本)9781577357513

Probabilistic graphical models, such as Bayesian networks, are intuitive and theoretically sound tools for modeling uncertainty. A major problem with applying Bayesian networks in practice is that it is hard to judge whether a model fits well a case that it is supposed to solve. One way of expressing a possible dissonance between a model and a case is the surprise index, proposed by Habbema, which expresses the degree of surprise by the evidence given the model. While this measure reflects the intuition that the probability of a case should be judged in the context of a model, it is computationally intractable. In this paper, we propose an efficient way of approximating the surprise index. © Copyright 2015, Association for the Advancement of Artificial Intelligence (***). All rights reserved.

关键词： Bayesian networks

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How enterprise architecture formative critical success facets might affect enterprise architecture success: A literature analysis 15

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15th IFIP WG 8.1 International Conference on Informatics and Semiotics in Organisations, ICISO 2014

作者： Wan, Haining Luo, Aimin Luo, Xueshan Science and Technology on Information Systems Engineering Laboratory National University of Defence Technology Changsha410072 China

ISBN: (纸本)9783642553547

Though Enterprise Architecture (EA) is getting increasing attentions from both academics and practitioners, EA research around EA success factors remains modest and immature. This study explores how EA formative critical success facets/factors would affect the achievement of EA success. This research highlights the importance of four mediators, i.e., (I) Real and mature business needs;(II) Real and continuous commitment;(III) Actionable EA programs;and (IV) Well-controlled execution of EA programs. This study deepens our understanding of EA success and would be of explanatory contribution to EA value development and action-guiding contribution to EA adoption and implementation. © IFIP International Federation for Information Processing 2014.

关键词： Information systems

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Adaptive Control with Nonlinear Reference systems

Adaptive Control with Nonlinear Reference Systems

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American Control Conference

作者： Tansel Yucelen Benjamin Gruenwald Jonathan A. Muse Gerardo De La Torre Mechanical and Aerospace Engineering Department and the Director of the Advanced Systems Research Laboratory at the Missouri University of Science and Technology Rolla MO 65409 USA Graduate Research Assistant of the Mechanical and Aerospace Engineering Department and a member of the Advanced Systems Research Laboratory at the Missouri University of Science and Technology Rolla MO 65409 USA Research Aerospace Engineer of the Autonomous Control Branch at the Air Force Research Laboratory WPAFB OH 45433 USA Graduate Research Assistant of the School of Aerospace Engineering at the Georgia Institute of Technology Atlanta GA 30332 USA

ISBN: (纸本)9781479917730

Although reference systems with linear dynamics are common in the adaptive control literature, they can lead to limitations on the achievable closed-loop dynamical system performance. This is due to the fact that linear reference systems can only approximate the desired closed-loop behavior of nonlinear dynamical systems in narrow regions of the state-space. In this paper, we study a new adaptive control architecture for uncertain dynamical systems based on a nonlinear reference system. It is shown that the system error between the uncertain dynamical system and the nonlinear reference system asymptotically vanishes in steady-state, and its performance is guaranteed during the transient-time. Two illustrative numerical examples are provided to demonstrate the efficacy of the proposed methodology.

关键词： reference system adaptive control Systematic errors DYNAMICAL systems Nonlinear dynamical systems nonlinearity

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