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  • 1
    Electronic Resource
    Electronic Resource
    Superconvergent patch recovery of finite-element solution and a posteriori L2 norm error estimate (1994)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 10 (1994), S. 313-320 
    Details
    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In the paper we present a superconvergent patch recovery technique for obtaining higher-order-accurate finite-element solutions and thus a postprocessed type of L2 norm error estimate. Two modifications make our procedure different from the one proposed by Zienkiewicz and Zhu (1992), in which higher-order-accurate derivatives of the finite-element solution at nodes are determined. Firstly, the recovery process is made for element, not for nodes. An ‘element patch’, which represents the union of an element under consideration and the surrounding elements, is introduced. Secondly, the local error estimate is calculated directly from the improved solution for this element. Numerical tests on both 1D and 2D model problems show that this method can provide an asymptotically exact a posteriori L2 norm error estimate if the used element possesses superconvergent points for the solutions.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cnm.1640100406
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    A simple local error estimator and an adaptive time-stepping procedure for direct integration method in dynamic analysis (1993)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 9 (1993), S. 273-292 
    Details
    ISSN: 1069-8299
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A simple a posteriori local error estimator for time discretization in structural dynamic analysis is presented. It is derived from the difference of the solutions between an ordinary integration method (the Newmark scheme) and another higher-order one which assumes that the derivatives of accelerations vary linearly within each time step. It may be obtained directly without resolving new equations, so the additional computational cost is small and the implementation is convenient. Furthermore, it is shown that this error estimator may also be obtained by Taylor expansion or by a post-processing technique. Accordingly, an adaptive time-stepping procedure, which automatically adjusts the time-step size so that the local error at each time step is within a prescribed accuracy, is described. Numerical examples, including two single-DOF problems, a two-DOF problem and a multi-DOF model, are presented. The results show that the presented local error estimator is simple, reliable and accurate.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cnm.1640090402
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    A postprocessed error estimate and an adaptive procedure for the semidiscrete finite element method in dynamic analysis (1994)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 37 (1994), S. 3585-3603 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In the paper we present a postprocessed type of a posteriori error estimate and a h-version adaptive procedure for the semidiscrete finite element method in dynamic analysis. In space the super-convergent patch recovery technique is used for determining higher-order accurate stresses and, thus, a spatial error estimate. In time a postprocessing technique is developed for obtaining a local error estimate for one step time integration schemes (the HHT-α method). Coupling the error estimate with a mesh generator, a h-version adaptive finite element procedure is presented for two-dimensional dynamic analysis. It updates the spatial mesh and time step automatically so that the discretization errors are controlled within specified tolerances. Numerical studies on different problems are presented for demonstrating the performances of the proposed adaptive procedure.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620372102
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    STRUCTURAL DYNAMIC ANALYSIS BY A TIME-DISCONTINUOUS GALERKIN FINITE ELEMENT METHOD (1996)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 39 (1996), S. 2131-2152 
    Details
    ISSN: 0029-5981
    Keywords: discontinuous Galerkin finite element method ; predictor-multicorrector ; adaptive time integration ; structural dynamics ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper studies a time-discontinuous Galerkin finite element method for structural dynamic problems, by which both displacements and velocities are approximated as piecewise linear functions in the time domain and may be discontinuous at the discrete time levels. A new iterative solution algorithm which involves only one factorization for each fixed time step size and a few iterations at each step is presented for solving the resulted system of coupled equations. By using the jumps of the displacements and the velocities in the total energy norm as error indicators, an adaptive time-stepping procedure for selecting the proper time step size is described. Numerical examples including both single-DOF and multi-DOF problems are used to illustrate the performance of these algorithms. Comparisons with the exact results and/or the results by the Newmark integration scheme are given. It is shown that the time-discontinuous Galerkin finite element method discussed in this study possesses good accuracy (third order) and stability properties, its numerical implementation is not difficult, and the higher computational cost needed in each time step is compensated by use of a larger time step size.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 5
    Electronic Resource
    Electronic Resource
    FINITE ELEMENT METHOD FOR GRADIENT PLASTICITY AT LARGE STRAINS (1996)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 39 (1996), S. 619-633 
    Details
    ISSN: 0029-5981
    Keywords: gradient plasticity ; strain localization ; mixed strain element method ; large strain ; consistent algorithm ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A finite element method for gradient elasto-plastic continuum in which the yield strength of strain hardening/softening materials not only depends on the effective plastic strain but also on its Laplacian is presented. The consistent integration algorithm to update the stress and the internal state variable at integration points and the consistent compliance matrix for the gradient plasticity are formulated in the non-local sense.The methodology to derive the finite element formulation for the gradient plasticity at large strains presented in this paper is applicable to general finite element analysis; the formulation in the context of the two-dimensional four-noded mixed finite element with one integration point and mean von Mises yield criterion is particularly derived.Numerical examples are tested to demonstrate the capability and performance of the present finite element method at large strain in solving for the strain localization problem.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 6
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    A Cluster-Randomized, Controlled Trial of a Simplified Multifaceted Management Program for Individuals at High Cardiovascular Risk (SimCard Trial) in Rural Tibet, China, and Haryana, India [Epidemiology and Prevention] (2015)
    American Heart Association (AHA)
    Details
    Publication Date: 2015-09-01
    Description: Background— In rural areas in China and India, the cardiovascular disease burden is high but economic and healthcare resources are limited. This study (the Simplified Cardiovascular Management Study [SimCard]) aims to develop and evaluate a simplified cardiovascular management program delivered by community health workers with the aid of a smartphone-based electronic decision support system. Methods and Results— The SimCard study was a yearlong cluster-randomized, controlled trial conducted in 47 villages (27 in China and 20 in India). Recruited for the study were 2086 individuals with high cardiovascular risk (aged ≥40 years with self-reported history of coronary heart disease, stroke, diabetes mellitus, and/or measured systolic blood pressure ≥160 mm Hg). Participants in the intervention villages were managed by community health workers through an Android-powered app on a monthly basis focusing on 2 medication use and 2 lifestyle modifications. In comparison with the control group, the intervention group had a 25.5% ( P 〈0.001) higher net increase in the primary outcome of the proportion of patient-reported antihypertensive medication use pre- and post-intervention. There were also significant differences in certain secondary outcomes: aspirin use (net difference: 17.1%; P 〈0.001) and systolic blood pressure (–2.7 mm Hg; P =0.04). However, no significant changes were observed in the lifestyle factors. The intervention was culturally tailored, and country-specific results revealed important differences between the regions. Conclusions— The results indicate that the simplified cardiovascular management program improved quality of primary care and clinical outcomes in resource-poor settings in China and India. Larger trials in more places are needed to ascertain the potential impacts on mortality and morbidity outcomes. Clinical Trial Registration— URL: http://www.clinicaltrials.gov . Unique identifier: NCT01503814.
    Keywords: Epidemiology
    Electronic ISSN: 1524-4539
    Topics: Medicine
    Published by American Heart Association (AHA)
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  • 7
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    Response to Letter Regarding Article "Temporal Trends in the Incidence and Prognosis of Aortic Stenosis: A Nationwide Study of the Swedish Population" [Correspondence] (2015)
    American Heart Association (AHA)
    Details
    Publication Date: 2015-11-17
    Keywords: Epidemiology
    Electronic ISSN: 1524-4539
    Topics: Medicine
    Published by American Heart Association (AHA)
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  • 8
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    A single mutation in the prM protein of Zika virus contributes to fetal microcephaly (2017)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2017-11-17
    Description: Zika virus (ZIKV) has evolved into a global health threat because of its unexpected causal link to microcephaly. Phylogenetic analysis reveals that contemporary epidemic strains have accumulated multiple substitutions from their Asian ancestor. Here we show that a single serine-to-asparagine substitution [Ser 139 -〉Asn 139 (S139N)] in the viral polyprotein substantially increased ZIKV infectivity in both human and mouse neural progenitor cells (NPCs) and led to more severe microcephaly in the mouse fetus, as well as higher mortality rates in neonatal mice. Evolutionary analysis indicates that the S139N substitution arose before the 2013 outbreak in French Polynesia and has been stably maintained during subsequent spread to the Americas. This functional adaption makes ZIKV more virulent to human NPCs, thus contributing to the increased incidence of microcephaly in recent ZIKV epidemics.
    Keywords: Epidemiology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 9
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    Temporal Trends in the Incidence and Prognosis of Aortic Stenosis: A Nationwide Study of the Swedish Population [Valvular Heart Disease] (2015)
    American Heart Association (AHA)
    Details
    Publication Date: 2015-03-17
    Description: Background— The aging of Western populations is expected to result in increasing occurrence of aortic stenosis (AS), but data are limited. Recent studies have reported declining incidence and mortality for other major heart diseases. We aimed to study temporal trends in the incidence and prognosis for AS in Sweden. Methods and Results— With the use of nationwide registers, all adult patients in the Swedish population with a first diagnosis of AS, heart failure, acute myocardial infarction, and aortic valve replacement for AS between 1989 and 2009 were identified and followed up until the end of 2010 for all-cause and cardiovascular-related mortality. The age-adjusted incidence of AS in Sweden declined from 15.0 to 11.4 in men and 9.8 to 7.1 in women per 100 000 between 1989 to 1991 and 2007 to 2009, and the median age at diagnosis increased by 4 years for both men and women. The age- and sex-adjusted relative risk of 1- and 3-year mortality in 2007 to 2009 was 0.58 (95% confidence interval, 0.53–0.63) and 0.60 (95% confidence interval, 0.56–0.65), respectively, compared with 1989 to 1991. Similar improvements were observed for heart failure and acute myocardial infarction. Findings were broadly consistent across subgroups. Postoperative mortality at 30 days declined despite increased median age at diagnosis. Conclusions— Incidence and mortality rates in AS in Sweden declined between 1989 and 2009 to an extent similar to that observed for heart failure and acute myocardial infarction. These findings could suggest that improved risk factor control and cardiovascular therapy, combined with increased use of aortic valve replacement in the elderly and reduced perioperative mortality in aortic valve replacement, have translated into favorable effects for AS.
    Keywords: Epidemiology
    Electronic ISSN: 1524-4539
    Topics: Medicine
    Published by American Heart Association (AHA)
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