543 research outputs found

    Eigen-AD: Algorithmic Differentiation of the Eigen Library

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    In this work we present useful techniques and possible enhancements when applying an Algorithmic Differentiation (AD) tool to the linear algebra library Eigen using our in-house AD by overloading (AD-O) tool dco/c++ as a case study. After outlining performance and feasibility issues when calculating derivatives for the official Eigen release, we propose Eigen-AD, which enables different optimization options for an AD-O tool by providing add-on modules for Eigen. The range of features includes a better handling of expression templates for general performance improvements, as well as implementations of symbolically derived expressions for calculating derivatives of certain core operations. The software design allows an AD-O tool to provide specializations to automatically include symbolic operations and thereby keep the look and feel of plain AD by overloading. As a showcase, dco/c++ is provided with such a module and its significant performance improvements are validated by benchmarks.Comment: Updated with accepted version for ICCS 2020 conference proceedings. The final authenticated publication is available online at https://doi.org/10.1007/978-3-030-50371-0_51. See v1 for the original, extended preprint. 14 pages, 7 figure

    Application of quasi-Monte Carlo methods to PDEs with random coefficients -- an overview and tutorial

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    This article provides a high-level overview of some recent works on the application of quasi-Monte Carlo (QMC) methods to PDEs with random coefficients. It is based on an in-depth survey of a similar title by the same authors, with an accompanying software package which is also briefly discussed here. Embedded in this article is a step-by-step tutorial of the required analysis for the setting known as the uniform case with first order QMC rules. The aim of this article is to provide an easy entry point for QMC experts wanting to start research in this direction and for PDE analysts and practitioners wanting to tap into contemporary QMC theory and methods.Comment: arXiv admin note: text overlap with arXiv:1606.0661

    Hot new directions for quasi-Monte Carlo research in step with applications

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    This article provides an overview of some interfaces between the theory of quasi-Monte Carlo (QMC) methods and applications. We summarize three QMC theoretical settings: first order QMC methods in the unit cube [0,1]s[0,1]^s and in Rs\mathbb{R}^s, and higher order QMC methods in the unit cube. One important feature is that their error bounds can be independent of the dimension ss under appropriate conditions on the function spaces. Another important feature is that good parameters for these QMC methods can be obtained by fast efficient algorithms even when ss is large. We outline three different applications and explain how they can tap into the different QMC theory. We also discuss three cost saving strategies that can be combined with QMC in these applications. Many of these recent QMC theory and methods are developed not in isolation, but in close connection with applications

    Ageing Intensifies the Care Needs of Adults Living with Parkinson ’s Disease and their Carers

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    Parkinson’s disease (PD) is the second most common neurological disorder in Australia typically affecting people over the age of 65. Few studies of people living with Parkinson’s disease have estimated current hours of home support and unmet needs. In addition no studies have been found that estimate hours of unmet need in terms of functioning or care arrangements or examined whether these estimates differ depending on the viewpoints of carers and the people living with PD whom they care for. In 2007, we surveyed the home care support needs of adults diagnosed with Parkinson’s disease in Western Australia (WA). The survey revealed that adults living with Parkinson’s disease prefer, and can be supported with, home care support services in lieu of residential care placement. As expected, required services increased as functioning decreased. In addition, unmet needs were found to be greater for those with carers irrespective of their level of functional dependency. Unmet needs for weekly services, for people that require home support services, are estimated at 38, 33, 55 and 47 min for personal care, cleaning, social support, and gardening and home maintenance, respectively. The survey also found that most carers and people living with PD agreed that current levels of different types of home care support including nursing were either adequate or insufficient; some carers preferred more services even if the people living with PD were satisfied and some people living with PD wanted more services even if their carers reported needing no extra help. Respite was used by 29 % of people living with PD with carers with two thirds wanting more opportunities for respite. Of the 71 % of people living with PD with carers who had not used respite, less than half stated that they would like to use respite. The 2007 survey was followed by interviews with a sample of survey respondents at different stages of their disorder. In the interviews, most of the people living with Parkinson’s disease commented that continuing to remain at home depended on the rate of degeneration of their disorder as well as the ability of their carers to continue to care. Most of these people and their careers were living day-to-day with a hope that enough support would be made available if and when they need it. As vocal Baby Boomers age, policymakers would do well to acknowledge the diversity of care needs for people with Parkinson’s disease and address the quantum and type of support to meet these needs

    Synthesis of an ordered mesoporous carbon with graphitic characteristics and its application for dye adsorption

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    An ordered mesoporous carbon (OMC) was prepared by a chemical vapor deposition technique using liquid petroleum gas (LPG) as the carbon source. During synthesis, LPG was effectively adsorbed in the ordered mesopores of SBA-15 silica and converted to a graphitic carbon at 800 °C. X-ray diffraction and nitrogen adsorption/desorption data and high-resolution transmission electron microscopy (HRTEM) of the OMC confirmed its ordered mesoporous structure. The OMC was utilized as an adsorbent in the removal of dyes from aqueous solution. A commercial powder activated carbon (AC) was also investigated to obtain comparative data. The efficiency of the OMC for dye adsorption was tested using acidic dye acid orange 8 (AO8) and basic dyes methylene blue (MB) and rhodamine B (RB). The results show that adsorption was affected by the molecular size of the dye, the textural properties of carbon adsorbent and surface-dye interactions. The adsorption capacities of the OMC for acid orange 8 (AO8), methylene blue (MB) and rhodamine B (RB) were determined to be 222, 833, and 233 mg/g, respectively. The adsorption capacities of the AC for AO8, MB, and RB were determined to be 141, 313, and 185 mg/ g, respectively. The OMC demonstrated to be an excellent adsorbent for the removal of MB from wastewater.Web of Scienc

    Dust in brown dwarfs and extra-solar planets IV. Assessing TiO2 and SiO nucleation for cloud formation modeling

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    Clouds form in atmospheres of brown dwarfs and planets. The cloud particle formation processes are similar to the dust formation process studied in circumstellar shells of AGB stars and in Supernovae. Cloud formation modelling in substellar objects requires gravitational settling and element replenishment in addition to element depletion. All processes depend on the local conditions, and a simultaneous treatment is required. We apply new material data in order to assess our cloud formation model results regarding the treatment of the formation of condensation seeds. We re-address the question of the primary nucleation species in view of new (TiO2)_N-cluster data and new SiO vapour pressure data. We apply the density functional theory using the computational chemistry package Gaussian 09 to derive updated thermodynamical data for (TiO2)_N-clusters as input for our TiO2 seed formation model. We test different nucleation treatments and their effect on the overall cloud structure by solving a system of dust moment equations and element conservation or a pre-scribed Drift-Phoenix atmosphere structure. Updated Gibbs free energies for the (TiO2)_N-clusters are presented, and a slightly temperature dependent surface tension for T=500 ... 2000K with an average value of sigma_infty = 480.6 erg 1/cm2. The TiO2-seed formation rate changes only slightly with the updated cluster data. A considerably larger effect on the rate of seed formation, and hence on grain size and dust number density, results from a switch to SiO-nucleation. Despite the higher abundance of SiO over TiO2 in the gas phase, TiO2 remains considerably more efficient in forming condensation seeds by homogeneous nucleation followed by heterogeneous grain growth. The paper discussed the effect on the cloud structure in more detail.Comment: accepted for publication in A&A (abstract abridged

    The role of receptivity in the courtship behavior of Podocnemis erythrocephala in captivity

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    The courtship behavior of Podocnemis erythrocephala (Red-headed Amazon River Turtle) in captivity was studied to examine female receptivity and male response to female rejection. We observed 20 females and 39 males in 150 sessions (3–6 h/day for a total of 450 h). In 36% of the trials, there was no interaction between males and females, and 20% of the trials resulted in copulations. All males introduced into tanks approached females, and eventually there was aggression among the males. In 48% of the experiments, females also searched for or approached males. When males initially approached females, they either accepted the male’s advances (14%), rejected the male passively (38%), or rejected the male aggressively (48%). In 86% of the cases where males were rejected, 4% attempted to approach females again, and in 51% they were ultimately successful
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