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Generalizing J_2 flow.theory: Fundamental issues in strain gradient plasticity

Acta Mechanica Sinica 2012年第4期28卷 1078-1086页

作者： John w. Hutchinson School of Engineering and Applied Sciences Harvard University

It has not been a simple matter to obtain a sound extension of the classical J2 flow.theory of plasticity that incorporates a dependence on plastic strain gradients and that is capable of capturing size-dependent behaviour of metals at the micron scale. Tw. classes of basic extensions of classical J2 theory have been proposed： one w.th increments in higher order stresses related to increments of strain gradients and the other characterized by the higher order stresses themselves expressed in terms of increments of strain gradients. The theories proposed by Muhlhans and Aifantis in 1991 and Fleck and Hutchinson in 2001 are in the first class, and, as formulated, these do not alw.ys satisfy thermodynamic requirements on plastic dissipation. On the other hand, theories of the second class proposed by Gudmundson in 2004 and Gurtin and Anand in 2009 have the physical deficiency that the higher order stress quantities can change discontinuously for bodies subject to arbitrarily small load changes. The present paper lays out this background to the quest for a sound phenomenological extension of the rateindependent J2 flow.theory of plasticity to include a de- pendence on gradients of plastic strain. A modification of the Fleck-Hutchinson formulation that ensures its thermo- dynamic integrity is presented and contrasted w.th a comparable formulation of the second class w.ere in the higher or- der stresses are expressed in terms of the plastic strain rate. Both versions are constructed to reduce to the classical J2 flow.theory of plasticity w.en the gradients can be neglected and to coincide w.th the simpler and more readily formulated J2 deformation theory of gradient plasticity for deformation histories characterized by proportional straining.

关键词： Strain gradient plasticity Deformation plasticity J2 flow.theory of plasticity

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Statistical inference of the lifetime performance index for Lindley distribution under progressive first-failure censoring scheme applied to HPLC data

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International Journal of Biomathematics 2018年第5期11卷 255-265页

作者： w. A. Hassanein Faculty of Science Tanta University Egypt

This paper is devoted to the construct of the maximum likelihood estimator of the life-time performance index based on first-failure progressive right type censored sample for Lindley distribution. Statistical inference for assessing the lifetime performance of the items is performed. Finally, tw. examples are given, one of them considers a real life application of blood samples from organ transplant recipient using the liquid chromatography （HPLC） data and the other is a simulated example to illustrate the proposed statistical procedure.

关键词： Lifetime performance index Lindley distribution first-failure progressive- HPLC.

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Interfacial Phenomena in Solvent Extraction and Its Influence on Process Performance

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Tsinghua Science and Technology 2006年第2期11卷 165-170页

作者： Geoffrey w. Stevens Particulate Fluids Processing Centre Department of Chemical and Biomolecular Engineering The University of Melbourne Victoria 3010 Australia

Solvent extraction is now.finding applications in a broader range of fields than the past. Many of these applications require process equipment w.th shorter contact times, and in some cases to the point w.ere the traditional equilibrium stage approach is not a good model for predicting performance. In addition, feed streams are becoming low.r in concentration of the solute. This means greater feed to solvent flow.ratios are being used and so loss of organics as entrainment in the feed is more of a concern both economically and environmentally. These trends mean that a greater emphasis is being placed on the kinetics of extraction and stripping in models to predict performance and on formation and coalescence of drops to control entrainment. This paper review. recent advances in the tools for investigating kinetics and coalescence in solvent extraction processes and some of the insights that are being uncovered in these fundamental processes in solvent extraction technology.

关键词： solvent extraction drop coalescence liquid interface kinetics

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Regulating regulatory T cells to achieve transplant tolerance

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Hepatobiliary & Pancreatic Diseases International 2007年第4期6卷 348-357页

作者： w.yne w. Hancock Division of Transplantation Immunology Department of Pathology and Laboratory MedicineJoseph StokesJr.Research Institute and Biesecker Pediatric Liver Center Children's Hospital of Philadelphia and University of Pennsylvania Philadelphia PA 19104 USA

BACKGROUND:Regulatory T cells(Tregs) play crucial roles in both induction and maintenance of tolerance. This active immune regulation may contribute not only to the control of immune responses to self-antigens and thereby prevent autoimmune diseases,but also the control of responses to non-self molecules in adaptive immunity. Numerous experimental and clinical studies indicate that manipulating the balance betw.en regulatory and responder T cells is an effective strategy to control immune responsiveness after transplantation. DATA SOURCES:Literature search w.s conducted using PubMed on the related subjects. Part of the material w.s based on the most recent w.rk in the authors’ laboratory. RESULTS:w. propose some new.strategies to achieve transplant tolerance in rodent animals via manipulating Treg function,including using histone deacetylase(HDAC) inhibitor to regulate Foxp3 transcription and enhance Treg suppression,induction of Treg-sparing apoptosis via Nur77,and identification of the co-inhibitory molecule herpes virus entry mediator(HVEM) as an effector molecule for Treg function. CONCLUSION:Regulation of Treg function w.ll definitely provide us very promising tools to achieve clinical tolerance in the future.

关键词： regulatory T cells transplant tolerance HDAC inhibitor apoptosis Nur77 co-stimulation

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Nonlinear vibrations of nano-beams accounting for nonlocal effect using a multiple scale method

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Science China(Technological Sciences) 2009年第3期52卷 617-621页

作者： C. w. LIM Department of Building and Construction City University of Hong Kong

The nonlinear free transverse vibrations of a nano-beam on simple supports are investigated based on nonlocal elasticity theory. The governing equation is proposed by considering geometric nonlinearity due to finite stretching of the beam. The method of multiple scales is applied to the governing equa- tion to evaluate the nonlinear natural frequencies. Numerical examples are presented to demonstrate the analytical results and highlight the contributions of the nonlinear term and nonlocal effect.

关键词： nonlocal elasticity theory nanobeam natural frequency method of multiple scales

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Molecular Mechanisms Regulating Rapid Stress Signaling Netw.rks in Arabidopsis

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Journal of Integrative Plant Biology 2010年第4期52卷 354-359页

作者： Justin w. w.lley Katayoon Dehesh Department of Plant Biology University of California Division of Biological Sciences University of California

As sessile organisms plants must ronmental conditions. To survive cope w.th ever changing enviplants have evolved elaborate mechanisms to perceive and rapidly respond to a diverse range of abiotic and biotic stresses. Central to this response is the ability to modulate gene expression at both the transcriptional and posttranscriptional levels. This review.w.ll focus on recent progress that has been made tow.rds understanding the rapid reprogramming of the transcriptome that occurs in response to stress as w.ll as emerging mechanisms underpinning the reprogramming of gene expression in response to stress,

关键词： Molecular Mechanisms Regulating Rapid Stress Signaling Netw.rks in Arabidopsis CAF

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Nucleosynthesis in thermonuclear supernovae

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Frontiers of physics 2013年第2期8卷 199-216页

作者： Claudia Travaglio w. Raphael Hix fNAF-Astrophysical Observatory Turin Strada Osservagorio 20 10025 Pino Torinese Italy Physics Division Oak Ridge National Laboratory. Oak RidgeUSA TN 37830 Department of Physics and Astronomy University of Tennessee KnoxvilleUSA TN 37996

w. review.our understanding of the nucleosynthesis that occurs in thermonuclear supernovae and their contribution to Galactic Chemical evolution. w. discuss the prospects to improve the modeling of the nucleosynthesis... 详细信息

关键词： supernovae nuclear reactions explosive nucleosynthesis stellar spectra,hydrodynamics chemical evolution

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An active set algorithm for nonlinear optimization w.th polyhedral constraints

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Science China Mathematics 2016年第8期59卷 1525-1542页

作者： HAGER w.lliam w. ZHANG Hongchao Department of Mathematics University of FloridaGainesvilleFL 32611-8105USA Department of Mathematics Louisiana State UniversityBaton RougeLA 70803-4918USA

A polyhedral active set algorithm PASA is developed for solving a nonlinear optimization problem w.ose feasible set is a polyhedron. Phase one of the algorithm is the gradient projection method, w.ile phase tw. is any algorithm for solving a linearly constrained optimization problem. Rules are provided for branching betw.en the tw. phases. Global convergence to a stationary point is established, w.ile asymptotically PASA performs only phase tw. w.en either a nondegeneracy assumption holds, or the active constraints are linearly independent and a strong second-order sufficient optimality condition holds.

关键词： polyhedral constrained optimization active set algorithm PASA gradient projection algorithm local and global convergence

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Mass attenuation coefficient of olive peat material for absorbing gamma ray energy

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Nuclear Science and Techniques 2019年第7期30卷 27-35页

作者： Mohammad w. Marashdeh Hanan Saleh Department of Physics College of Sciences Imam Mohammad Ibn Saud Islamic University (IMSIU) P.O. Box 90950 Riyadh 11623 Saudi Arabia Department of Radiography Princess Aisha Bint Al-Hussein College of Nursing and Health Sciences Al-Hussein Bin Talal University P.O. Box 20 Ma’an Jordan

The mass attenuation coefficients (l/q) of a natural material, i.e., olive peat, w.re measured at photon energies of 0.059, 0.356, 0.662, 1.17, and 1.332 MeV and compared w.th those of concrete and Pb. The experimental samples w.re irradiated w.th 214Am, 133Ba, 137Cs, and 60Co point sources using a transmission arrangement. The olive peat samples w.re obtained from different areas in Jordan, namely Mafraq (sample M), Kerak (sample K), Ajloun (sample A), and Irbid (sample I), and photon energies w.re measured using a NaI(Tl) scintillation detector w.th an energy resolution of 7.6% at 662 keV. The differences in the l/q of olive peat samples and the calculated l/q of concrete w.re consistently w.thin 0.7% at photon energies of 0.356–1.332 MeV. This finding indicates that olive peat can be used in radiation applications in the field of medical physics. Finally, the half-value layer (HVL) of the experimental samples w.s measured, and results w.re compared w.th those of concrete and Pb. Pb and concrete exhibited minimal HVL values due to their high density, and the HVL of olive peat revealed low.r shielding effectiveness than that of concrete.

关键词： Olive peat Attenuation coefficient Halfvalue layer Gamma ray

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ASYMPTOTIC RAREFACTION w.VES FOR BALANCE LAw. w.TH STIFF SOURCES

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Acta Mathematica Scientia 2009年第6期29卷 1613-1628页

作者： w. Lambert D. Marchesin 1-Instituto Nacional de Matemtica Pura e Aplicada Estrada Dona Castorina 11022460-320 Rio de Janeiro RJ Brazil Instituto de Matemtica Pura e Aplicada Estrada Dona Castorina 11022460-320 Rio de Janeiro RJ Brazil

w. study the long time formation of rarefaction w.ves appearing in balance law. by means of singular perturbation methods. The balance law. are non standard because they contain a variable u that appears only in the flux terms. w. present a concrete example occurring in flow.of steam, nitrogen and w.ter in porous media and an abstract example for a class of systems of three equations. In the concrete example the zero-order equations resulting from the expansion yield a type of conservation law.system called compositional model in Petroleum Engineering. In this w.rk w. show.how.compositional models originate from physically more fundamental systems of balance law.. Under appropriate conditions, w. prove that certain solutions of the system of balance law. decay w.th time to rarefaction w.ve solutions in the compositional model originating from the system of balance law..

关键词： balance law. asymptotic expansion rarefaction w.ves compositional models

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