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Micromechanical investigation of granular ratcheting using a discrete model of polygonal particles

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Particuology 2008年第6期6卷 390-403页

作者： Fernando Alonso-Marroquín hans B. Mhlhaus hans j. Herrmann Earth Systems Science Computational Centre & School of Physical Sciences The University of Queensland Earth Systems Science Computational Centre The University of Queensland Institut fr Baustoffe ETH-HenggerbergZrich

We use a two-dimensional model of polygonal particles to investigate granular ratcheting. Ratcheting is a long-term response of granular materials under cyclic loading, where the same amount of permanent deformation is accumulated after each cycle. We report on ratcheting for low frequencies and extremely small loading amplitudes. The evolution of the sub-network of sliding contacts allows us to understand the micromechanics of ratcheting. We show that the contact network evolves almost periodically under cyclic loading as the sub-network of the sliding contacts reaches different stages of anisotropy in each cycle. Sliding contacts lead to a monotonic accumulation of permanent deformation per cycle in each particle. The distribution of these deformations appears to be correlated in form of vortices inside the granular assembly.

关键词： Granular systems Dynamics and kinematics of rigid bodies Molecular dynamics methods

Sol-gel derived nanocrystalline and mesoporous barium strontium titanate prepared at room temperature

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Particuology 2011年第3期9卷 235-242页

作者： Mohammad Reza Mohammadi derek j.Fray Department of Materials Science & Engineering Sharif University of Technology Department of Materials Science & Metallurgy University of Cambridge

Perovskite-type barium strontium titanate （BST） thin films and powders with nanocrystalline and mesoporous structure were prepared by a straightforward particulate sol-gel route at room temperature. The prepared sol had a narrow particle size distribution of about 20 nm. X-ray diffraction （XRD） revealed that phase composition and preferable orientation growth of BST depended upon the annealing temperature. Transmission electron microscope （TEM） images showed that the crystallite size of the powders decreased with increasing annealing temperature from 8 nm at 25 ℃ down to 5 nm at 800 ℃. Field emission scanning electron microscope （FE-SEM） analysis and atomic force microscope （AFM） images revealed that BST thin films had mesoporous and nanocrystafiine structure with average grain size of 3Onm at 600 ℃. Based on Brunauer-Emmett-Teller （BET） analysis, the synthesized BST showed mesoporous structure containing nnres with needle, and nlate shanes and BET surface area in the range of 49-32 m^2/g at 500-800℃

关键词： Barium strontium titanate Room temperature Sol-gel chemistry Nanostructure

Modeling slow deformation of polygonal particles using DEM

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Particuology 2008年第6期6卷 506-514页

作者： Andrés A. Pea Pedro G. Lind hans j. Herrmann Institute for Computational Physics Universitt Stuttgart Computational Physics IfB HIF E12 ETH Hnggerberg CH-8093 Zrich Switzerland Departamento de Física Universidade Federal do Ceará

We introduce two improvements in the numerical scheme to simulate collision and slow shearing of irregular particles. First, we propose an alternative approach based on simple relations to compute the frictional contact forces. The approach improves efficiency and accuracy of the Discrete Element Method （DEM） when modeling the dynamics of the granular packing. We determine the proper upper limit for the integration step in the standard numerical scheme using a wide range of material parameters. To this end, we study the kinetic energy decay in a stress controlled test between two particles. Second, we show that the usual way of defining the contact plane between two polygonal particles is, in general, not unique which leads to discontinuities in the direction of the contact plane while particles move. To solve this drawback, we introduce an accurate definition for the contact plane based on the shape of the overlap area between touching particles, which evolves continuously in time.

关键词： Granular media Discrete element method Slow deformation Contact forces

Enhancing Immune Responses for Cancer Therapy

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Cellular & Molecular Immunology 2007年第3期4卷 173-184页

作者： hans j.Stauss Department of Immunology and Molecular Pathology University College London Hampstead Campus Royal Free Hospital Rowland Hill Street London NW3 2PF United Kingdom

Although the immune system possesses the means to respond to cancer, it often fails to control the spread of malignancy. Nonetheless, equipping endogenous immunity to release a strong antitumor response has significant advantages over conventional therapies. This review explores some of the options available to accomplish this, focusing first on vaccinations with tumor antigens to stimulate the immune system and empower stronger antitumor responses. We then compare and contrast the so-far limited clinical success of vaccination with the well-documented curative potential of adoptive therapy using T lymphocytes transfer. Finally, we highlight novel approaches using T call receptor （TCR） gene transfer strategy to exploit allogeneic T cell repertoires in conj.nction with receptors selected in vitro for defined MHC/peptide combinations, as a basis for antigen-specific gene therapy of cancers. Cellular ＆ Molecular Immunology.

关键词： tumor antigen vaccination adoptive immunotherapy T cell receptor gene transfer TCR gene therapy

Evolution and stability of holographic soliton pairs

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Chinese Science Bulletin 2006年第10期51卷 1174-1179页

作者： LIU j.nsong WANG Cheng ZHANG Huilan hans j. Eichler State Key Laboratory of Laser Technology Huazhong University of Science and Technology Wuhan 430074 China Optisches Institut Technische Universitaet Berlin Strasse des 17. Juni 135 D-10623 Berlin Germany

The dynamical evolution and the stabiity property of both bright and dark holographic solton pairs have been investigated numerically. Resultshow that mutual trapping between two beams in pair is balanceable and both ... 详细信息

关键词：空间光孤子非线性光学稳定性全息光学

Anisotropic plastic deformation behavior of as-extruded ZK60 magnesium alloy at room temperature

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Science China(Technological Sciences) 2009年第1期52卷 161-165页

作者： hans j.R Department of Materials Science and Engineering Norwegian University of Science and Technology

The anisotropic plastic deformation behavior of as-extruded ZK60 magnesium alloy at room tempera-ture (RT) was investigated by compressive and tensile testing in different directions, i.e. the loading axis oriented at 0°, 45° and 90° to the extrusion direction. The relationship between texture and plastic deformation behavior were examined. The results show that the extruded ZK60 alloy exhibits a strong ring fiber texture. The mechanical properties are strongly orientation dependent. In tension testing, the 0° specimen exhibited higher yield strength and lower elongation. In compression testing, however, ZK60 alloy exhibited almost the same yield strength in three directions. The anisotropic plastic defor-mation behavior is due to strong fiber texture and the lower symmetry of the hexagonal close packed (hcp) structure of ZK60 alloy. The correlation between texture and mechanical behaviour offers the possibility to improve the mechanical properties of magnesium alloy by optimization of the material production process.

关键词： anisotropic plastic deformation behavior ZK60 Mg alloy texture mechanical property

Benoxacor is enantioselectively metabolized by microsomes and cytosol from the human liver

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Emerging Contaminants 2023年第1期9卷 10-19页

作者： derek Simonsen j.cob Heffelfinger David M.Cwiertny hans-j.achim Lehmler Department of Occupational and Environmental Health The University of IowaIowa CityIA52242United States Interdisciplinary Graduate Program in Human Toxicology The University of IowaIowa CityIA52242United States IIHR Hydroscience and Engineering The University of IowaIowa CityIA52242United States Department of Civil and Environmental Engineering The University of IowaIowa CityIA52242United States Center for Health Effects of Environmental Contamination The University of IowaIowa CityIA52242United States

Benoxacor is a safener added to current-use herbicide formulations to protect the target crop from herbicidal *** is an emerging environmental contaminant that has been detected in surface waters,raising the possibility of human exposure via drinking *** it is not subj.ct to the same regulations as active pesticide ingredients,its metabolism and toxicity in humans have not been *** we investigate the enantioselective metabolism of benoxacor in human subcellular *** human liver microsomes(pHLM)and cytosol(pHLC)were incubated with racemic benoxacor for up to *** chromatographic analyses were used to measure the enantioselective depletion of *** with and without nicotinamide adenine dinucleotide phosphate(NADPH,co-factor for cytochrome P450 enzymes[CYPs])and pHLC with glutathione(GSH,co-factor for glutathione Stransferases[GSTs])metabolized *** results demonstrate that microsomal CYPs,microsomal carboxylesterase(CESs),and cytosolic GSTs metabolize *** were predicted to have a higher clearance of benoxacor by GSTs than *** and female pHLM incubations with NADPH showed enrichment of the first eluting benoxacor enantiomer(E1-benoxacor).pHLM incubations without NADPH and pHLC incubations with GSH showed an enrichment of the second eluting enantiomer of benoxacor(E2-benoxacor).Our results indicate that human hepatic microsomal and cytosolic enzymes enantioselectively metabolize benoxacor,a fact that needs to be considered when investigating human exposures and toxicities of benoxacor.

关键词： cor metabolism depletion

Recycling of automotive aluminum

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Transactions of Nonferrous Metals Society of China 2010年第11期20卷 2057-2063页

作者： j.rang CUI hans j.ROVEN Department of Materials Science and Engineering Norwegian University of Science and Technology(NTNU)

With the global warming of concern,the secondary aluminum stream is becoming an even more important component of aluminum production and is attractive because of its economic and environmental *** this work,recycling of automotive aluminum is reviewed to highlight environmental benefits of aluminum recycling,use of aluminum alloys in automotive applications,automotive recycling process,and new technologies in aluminum scrap *** survey shows that newly developed techniques such as laser induced breakdown spectroscopy(LIBS) and solid state recycling provide promising alternatives in aluminum scrap *** with conventional remelting and subsequent refinement,solid state recycling utilizing compression and extrusion at room or moderate temperature can result in significant energy savings and higher metal yield.

关键词： recycling automotive aluminum sorting mechanical separation solid state recycling

Estimation of Pool Boiling Heat Transfer Coefficients of Ethanol-Water Mixtures

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Chinese j.urnal of Chemical Engineering 1999年第2期7卷 95-103页

作者：谷俊杰 hans-j.rgBart Lehrstuhl fur Thermische Verfahrenstechnik Universitat Kaiserslautern67653 KaiserslauternGermany

Based on the analysis of the principles of heat and mass transfer from the liquid bulk to bubble surface during nucleation, a new estimation method to predict the heat transfer of the nucleate pool boiling in binary mixtures is proposed in this paper by using the heat and mass transfer analogy (Colburn analogy) at the bubble surface transfer layers. With the use of Thome's concept of boiling range, an approximate method is derived to realize the calculation. The predicted results by this method are in good agreement with the experimental data from different sources.

关键词： heat transfer boiling water-ethanol mixture estimation