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Phase-field modeling of fracture for quasi-brittle materials

Underground space 2019年第1期4卷 10-21页

作者： Jacinto Ulloa Patricio Rodríguez Cristóbal samaniego Esteban samaniego Department of Civil Engineering Katholieke Universiteit LeuvenB-3001 LeuvenBelgium Departamento de Recursos Hídricos y Ciencias Ambientales Universidad de CuencaCuenca 010151Ecuador Universidad de cuenca Cuenca 010151Ecuador Institut für Kontinuumsmechanik Leibniz Universität HannoverHannover 30167Germany Inria Bordeaux-sud-Ouest Research Center 200 Avenue de la Vieille TourTalence 33405France Facultad de Ingeniería Universidad de CuencaEcuador

This paper addresses the modeling of fracture in quasi-brittle materials using a phase-field approach to the description of crack *** the computational mechanics community,several studies have treated the issue of modeling fracture using phase *** of these studies have used an approach that implies the lack of a damage *** herein explore an alternative model that includes a damage threshold and study how it compares with the most popular *** formulation is systematically explained within a rigorous variational ***,we present the corresponding three-dimensional finite element discretization that leads to a straightforward numerical *** simulations in two dimensions and three dimensions are then *** results show that while an elastic stage and a damage threshold are ensured by the present model,good agreement with the results reported in the literature can be obtained,where such features are generally absent.

关键词： Quasi-brittle materials Fracture Variational formulation Phase fields Gradient damage

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A Multifunctional Borate ester/Amide for Engine Oils

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润滑油 2010年第2期25卷 25-29页

作者： carl Esche Glenn Mazzamaro steven Donnelly R.T.Vanderbilt Company Inc.

Global economic and pollution concerns are having a major impact on how modern engine oils are being *** engine oil specifications mandate reduced levels of phosphorus and sulfur to protect the efficacy of pollution control *** addition,modern engine oil must also be more fuel efficient than earlier generations to reduce greenhouse gas emissions and the impact of high priced gasoline and diesel fuel to the *** the same time,oxidation,wear,and corrosion performance of the oil must not be *** additives are useful formulation tools that help formulators meet these tough new *** such additive is the organo-borate ester/*** conceived as an organic friction modifier,this patented technology is really a multifunctional additive that addresses the global economic and pollution *** the addition of boron,this unique commercial organic friction modifier also imparts antioxidancy,antiwear and anticorrosion properties to engine *** addition,the organo-borate ester/amide is compatible with pollution control devices because it does not contain sulfur or *** is on going to uncover additional beneficial properties of this chemistry.

关键词： borate ester friction modifier antioxidant antiwear engine oil

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Induced Deactivation of Genes Encoding Chlorophyll Biosynthesis Enzymes Disentangles Tetrapyrrole- Mediated Retrograde signaling

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Molecular Plant 2014年第7期7卷 1211-1227页

作者： Hagen schlicke Annabel salinas Hartwig Vivien Firtzlaff Andreas s. Richter , Christine Glasser Klaus Maier Iris Finkemeier Bernhard Grimm Institute of Biology/Plant Physiology Humboldt University Berlin Philippstr. 13 Building 12 D 10115 Berlin Germany Helmholtz Zentrum Monchen Deutsches Forschungszentrum for Gesundheit und Umwelt (GmbH) Ingolstadter Landstr. 1 85764 Neuherberg Germany Max-Planck-lnstitute for Plant Breeding Research. Plant Proteomics and Mass spectrometry Group Carl-von-Linne Weg 10 50829 Cologne Germany

In photosynthetic organisms, tetrapyrrole-mediated retrograde signals are proposed to contribute to a bal- anced nuclear gene expression （NGE） in response to metabolic activity in chloroplasts. We followed an experimental short- term approach that allowed the assessment of modified NGE during the first hours of specifically modified enzymatic steps of the Mg branch of tetrapyrrole biosynthesis, when pleiotropic effects of other signals can be avoided. In response to 24-h-induced silencing of CHLH, CHLM, and CHL27 encoding the CHLH subunit of Mg chelatase, the Mg protoporphyrin methyltransferase and Mg protoporphyrin monomethylester cyclase, respectively, deactivated gene expression rapidly led to reduced activity of the corresponding enzymes and altered Mg porphyrin levels. But NGE was not substantially altered. When these three genes were continuously inactivated for up to 4 d, changes of transcript levels of nuclear genes were determined. CHL27 silencing for more than 24h results in necrotic leaf lesions and modulated transcript levels of oxidative stress-responsive and photosynthesis-associated nuclear genes （PhANGs）. The prolonged deactivation of CHLH and CHLM results in slightly elevated transcript levels of PhANGs and tetrapyrrole-associated genes. These time-resolved studies indicate a complex scenario for the contribution of tetrapyrrole biosynthesis on NGE mediated by IO2-induced signaling and feedback-regulated ALA synthesis.

关键词： plastid signal transcription analysis retrograde signal tetrapyrrole metabolism Mg protoporphyrin.

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