3,418 research outputs found

    Online Primal-Dual Algorithms with Configuration Linear Programs

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    In this paper, we present primal-dual algorithms for online problems with non-convex objectives. Problems with convex objectives have been extensively studied in recent years where the analyses rely crucially on the convexity and the Fenchel duality. However, problems with non-convex objectives resist against current approaches and non-convexity represents a strong barrier in optimization in general and in the design of online algorithms in particular. In our approach, we consider configuration linear programs with the multilinear extension of the objectives. We follow the multiplicative weight update framework in which a novel point is that the primal update is defined based on the gradient of the multilinear extension. We introduce new notions, namely (local) smoothness, in order to characterize the competitive ratios of our algorithms. The approach leads to competitive algorithms for several problems with convex/non-convex objectives

    Effects of Leading-Edge Tubercles on Wing Flutter Speeds

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    The dynamic aeroelastic effects on wings modified with bio-inspired leading-edge (LE) tubercles are examined in this study. We adopt a state-space aeroelastic model via the coupling of unsteady vortex-lattice method and a composite beam to evaluate stability margins as a result of LE tubercles on a generic wing. The unsteady aerodynamics and spanwise mass variations due to LE tubercles have counteracting effects on stability margins with the former having dominant influence. When coupled, flutter speed is observed to be 5% higher, and this is accompanied by close to 6% decrease in reduced frequencies as an indication of lower structural stiffness requirements for wings with LE tubercles. Both tubercle amplitude and wavelength have similar influences over the change in flutter speeds, and such modifications to the LE would have minimal effect on stability margins when concentrated inboard of the wing. Lastly, when used in sweptback wings, LE tubercles are observed to have smaller impacts on stability margins as the sweep angle is increased

    Saliva continine levels of babies and mothers living with smoking fathers under different housing types in Hong Kong: a cross-sectional study

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    Paper Session 15 - The Challenge of Second-Hand Smoke: PA15-3BACKGROUND: After the Smoking Ordinance enacted in HK since 1/2007, shifting of smoking from outdoor to home was found, home becomes a major source of secondhand smoke (SHS) exposure of nonsmokers. OBJECTIVES: It aimed to assess the SHS exposure of babies and mothers living with smoking fathers of two housing types by using a biomarker. METHODS: Trios of smoking father, non-smoking mother and a baby under 18-months were recruited from Maternal and Child Health Centres (MCHCs) from 6/2008 to 10/2009. Consented couples completed the baseline survey including demographic data, fathers’ household smoking behaviors and mothers’ actions in protecting babies from household SHS exposure. Saliva samples from baby and mother were collected and then sent to the National University of Singapore for cotinine analyses. Log-transformations were used for the saliva cotinine due to skewed data. There were 2 housing types (public/private) and father was asked if they smoked at home (yes/no). MANOVA was used to compare the babies’ and mothers’ cotinine levels when fathers smoked at home under the 2 housing types. RESULTS: 1,158 trios were consented. 1,142 mothers’ and 1,058 babies’ samples were assayed. The mean age of the fathers and mothers was 35.5(±7.0) and 31.2(±4.9). The mean mothers’ cotinine level was 12.15ng/ml (±61.20) while babies’ was 2.38ng/ml (±6.01). 606 and 501 trios were living in public and private housing. Fathers’ smoked at home led to higher mothers’ and babies’ saliva cotininary (mean log of mothers’ cotininary: 0.14±0.62 vs. 0.05±0.55, p=0.06; babies: 0.16±0.38 vs. 0.07±0.34, p=0.003). Housing types influenced babies’ cotinine level (public: 0.17±0.37; private: 0.10±0.36, p=0.01). MANOVA showed that fathers smoked at home (Λ=0.99, p=0.01) and housing types (Λ=0.99, p=0.01) were positively related to the saliva cotinine levels. CONCLUSIONS: Father smoked at home and the housing types have greater impact on babies’ saliva cotininary, showing that they were highly exposed at home and in public housing environment. HK government should promote smoke-free homes and to provide more smoking cessation services to minimize the household SHS exposure to babiespublished_or_final_versio

    Spectral and morphological analysis of the remnant of Supernova 1987A with ALMA & ATCA

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    We present a comprehensive spectral and morphological analysis of the remnant of Supernova (SN) 1987A with the Australia Telescope Compact Array (ATCA) and the Atacama Large Millimeter/submillimeter Array (ALMA). The non-thermal and thermal components of the radio emission are investigated in images from 94 to 672 GHz (λ\lambda 3.2 mm to 450 μ\mum), with the assistance of a high-resolution 44 GHz synchrotron template from the ATCA, and a dust template from ALMA observations at 672 GHz. An analysis of the emission distribution over the equatorial ring in images from 44 to 345 GHz highlights a gradual decrease of the east-to-west asymmetry ratio with frequency. We attribute this to the shorter synchrotron lifetime at high frequencies. Across the transition from radio to far infrared, both the synchrotron/dust-subtracted images and the spectral energy distribution (SED) suggest additional emission beside the main synchrotron component (Sνν0.73S_{\nu}\propto\nu^{-0.73}) and the thermal component originating from dust grains at T22T\sim22 K. This excess could be due to free-free flux or emission from grains of colder dust. However, a second flat-spectrum synchrotron component appears to better fit the SED, implying that the emission could be attributed to a pulsar wind nebula (PWN). The residual emission is mainly localised west of the SN site, as the spectral analysis yields 0.4α0.1-0.4\lesssim\alpha\lesssim-0.1 across the western regions, with α0\alpha\sim0 around the central region. If there is a PWN in the remnant interior, these data suggest that the pulsar may be offset westward from the SN position.Comment: ApJ accepted. 21 pages, emulateapj. References update

    Oscillations and interactions of dark and dark-bright solitons in Bose-Einstein condensates

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    Solitons are among the most distinguishing fundamental excitations in a wide range of non-linear systems such as water in narrow channels, high speed optical communication, molecular biology and astrophysics. Stabilized by a balance between spreading and focusing, solitons are wavepackets, which share some exceptional generic features like form-stability and particle-like properties. Ultra-cold quantum gases represent very pure and well-controlled non-linear systems, therefore offering unique possibilities to study soliton dynamics. Here we report on the first observation of long-lived dark and dark-bright solitons with lifetimes of up to several seconds as well as their dynamics in highly stable optically trapped 87^{87}Rb Bose-Einstein condensates. In particular, our detailed studies of dark and dark-bright soliton oscillations reveal the particle-like nature of these collective excitations for the first time. In addition, we discuss the collision between these two types of solitary excitations in Bose-Einstein condensates.Comment: 9 pages, 4 figure

    Multicompartment and cross-species monitoring of contaminants of emerging concern in an estuarine habitat

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    Supplementary data to this article can be found online athttps://doi.org/10.1016/j.envpol.2020.116300.Biotechnologyand Biological Sciences Research Council (BBSRC) iNVERTOX proj-ect (Reference BB/P005187/1); Universityof Essex

    Anderson impurity model at finite Coulomb interaction U: generalized Non-crossing Approximation

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    We present an extension of the non-crossing approximation (NCA), which is widely used to calculate properties of Anderson impurity models in the limit of infinite Coulomb repulsion UU\to\infty, to the case of finite UU. A self-consistent conserving pseudo-particle representation is derived by symmetrizing the usual NCA diagrams with respect to empty and doubly occupied local states. This requires an infinite summation of skeleton diagrams in the generating functional thus defining the ``Symmetrized finite-U NCA'' (SUNCA). We show that within SUNCA the low energy scale TKT_K (Kondo temperature) is correctly obtained, in contrast to other simpler approximations discussed in the literature.Comment: 7 pages, 6 figure
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