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Importance of initial buoyancy field on evolution of mantle thermal structure:Implications of surface boundary conditions

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Geoscience Frontiers 2015年第1期6卷 3-22页

作者： Petar gliovi Alessandro M.Forte GEOTOP Universite du Quebec a MontrealCP 8888Succursale Centre-Ville

Although there has been significant progress in the seismic imaging of mantle heterogeneity, the outstanding issue that remains to be resolved is the unknown distribution of mantle temperature anomalies in the distant geological past that give rise to the present-day anomalies inferred by global tomography models. To address this question, we present 3-D convection models in compressible and self-gravitating mantle initialised by different hypothetical temperature patterns. A notable feature of our forward convection modelling is the use of self-consistent coupling of the motion of surface tectonic plates to the underlying mantle flow, without imposing prescribed surface velocities （i.e., p/ate-like boundary condition）. As an approximation for the surface mechanical conditions before plate tectonics began to operate we employ the no-slip （rigid） boundary condition. A rigid boundary condition dem- onstrates that the initial thermally-dominated structure is preserved, and its geographical location is fixed during the evolution of mantle flow. Considering the impact of different assumed surface boundary conditions （rigid and plate-like） on the evolution of thermal heterogeneity in the mantle we suggest that the intrinsic buoyancy of seven superplumes is most-likely resolved in the tomographic images of present-day mantle thermal structure. Our convection simulations with a plate-like boundary condition reveal that the evolution of an initial cold anomaly beneath the Java-lndonesian trench system yields a long-term, stable pattern of thermal heterogeneity in the lowermost mantle that resembles the present- day Large Low Shear Velocity Provinces （LLSVPs）, especially below the Pacific. The evolution of sub- duction zones may be, however, influenced by the mantle-wide flow driven by deeply-rooted and long- lived superplumes since Archean times. These convection models also detect the intrinsic buoyancy of the Perm Anomaly that has been identified as a unique slow feature d

关键词： Dynamics: convection currents, and mantleplumes Hotspots Seismic tomography Planetary tectonics CMB topography Perm Anomaly

Influence of Cr, Mn and Mo Addition on Structure and Properties of V Microalloyed Medium Carbon Steels

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Journal of Materials Science & Technology 2012年第11期28卷 1053-1058页

作者： Abdunnaser Fadel Dragomir glii Nenad Radovi Djordje Drobnjak Department of Metallurgical Engineering Faculty of Technology and Metallurgy University of Belgrade

The effect of austenitizing temperature and Cr, Mo and Mn addition on microstructure and mechanical properties of V microalloyed medium carbon steel has been studied by means of metallography and mechanical testing. The addition of Cr, Mn and Mo leads to a decrease in yield strength （YS） by approximate 100 MPa in comparison to the base steel. It is assumed that Mn and Mo increase hardenability by promoting the formation of bainitic sheaves （BS）, i.e. by suppressing the formation of ferrite-pearlite and acicular ferrite （FP-AF）. Cr at the level used in this work is not that effective. Presence and packet size of bainitic sheaves decrease the Charpy V-notch impact energy at 20 ℃ （CVN20） in comparison to ferrite-pearlite and acicular ferrite microstructures.

关键词： Medium-carbon steels Chromium Molybdenum Manganese addition Bainite Acicular ferrite

Instability of equilibrium of nonholonomic systems with dissipation and circulatory forces

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Applied Mathematics and Mechanics(English Edition) 2011年第2期32卷 211-222页

作者： M.VESKovi V.ovi A.OBRADovi Faculty of Mechanical Engineering University of Kragujevac Faculty of Mechanical Engineering University of Belgrade

The paper discusses the equilibrium instability problem of the scleronomic nonholonomic systems acted upon by dissipative, conservative, and circulatory forces. The method is based on the existence of solutions to the differential equations of the motion which asymptotically tends to the equilibrium state of the system as t tends to negative infinity. It is assumed that the kinetic energy, the Rayleigh dissipation function, and the positional forces in the neighborhood of the equilibrium position are infinitely differentiable functions. The results obtained here are partially generalized the results obtained by Kozlov et al. （Kozlov, V. V. The asymptotic motions of systems with dissi- pation. Journal of Applied Mathematics and Mechanics, 58（5）, 787-792 （1994）. Merkin, D. R. Introduction to the Theory of the Stability of Motion （in Russian）, Nauka, Moscow （1987）. Thomson, W. and Tait, P. Treatise on Natural Philosophy, Part I, Cambridge University Press, Cambridge （1879））. The results are illustrated by an example.

关键词： nonholonomic constraint instability potential dissipative force

TEM and Raman scattering investigation of carbon in annealed Co/C soft X-ray multilayers

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Science China Mathematics 1997年第3期40卷 315-322页

作者：白海力姜恩永王存达 U.Bgli Department of Applied Physics Tianjin University Tianjin 300072 China

The structures of the carbon sublayers in the annealed Co/C soft X-ray multilayers fabricated by using a dual-facing-target sputtering system have been characterized by transmission electron microscopy (TEM) and Raman spectroscopy (RS). The results suggest that the structural variations in the carbon layers can be roughly divided into three stages, i e ordering, crystalline and grain growth stages. At the ordering stage with annealing temperatures below 400℃, the amorphous carbon layers change from ones of bond-angle disorder and fourfold-bonding only to ones of threefold-bonding. At the crystalline stage, the amorphous carbon layers in the as-deposited multilayers crystallize to graphite crystallites in the annealing temperature range of 500-600℃ At the grain growth stage, the specimens are annealed at temperatures higher than 700℃ A growth in the graphite crystallite dimensions is observed, which is consistent with the TEM results

关键词： soft X-ray multilayers thermal annealing graphitization.

On the stability of equilibria of nonholonomic systems with nonlinear constraints

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Applied Mathematics and Mechanics(English Edition) 2010年第6期31卷 751-760页

作者： V.ovi M. VESKovi D. DJURI A. OBRADovi Faculty of Mechanical Engineering University of Belgrade Faculty of Mechanical Engineering University of Kragujevac

Lyapunov＇s first method, extended by V. V. Kozlov to nonlinear mechani- cal systems, is applied to the study of the instability of the position of equilibrium of a mechanical system moving in the field of conservative and dissipative forces. The mo- tion of the system is limited by ideal nonlinear nonholonomic constraints. Five cases determined by the relationship between the degree of the first nontrivial polynomials in Maclaurin＇s series for the potential energy and the functions that can be generated from the equations of nonlinear nonholonomic constraints are analyzed. In the three eases, the theorem on the instability of the position of equilibrium of nonholonomic systems with linear homogeneous constraints （V. V. Kozlov （1986）） is generalized to the case of nonlin- ear nonhomogeneous constraints. In the other two cases, new theorems are set extending the result from V. V. Kozlov （1994） to nonholonomic systems with nonlinear constraints.

关键词： Lyapunov first method nonholonomic system instability of equilibrium

THE TEMPERATURE STRESS OF RC CONCRETE COMPONENT INDUCED BY LINEAR EXPENSION COEFFICIENT DIFFERENCE

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Journal of Wuhan University of Technology(Materials Science) 1999年第1期14卷 58-61页

作者： Wang, sr Mao, T Wuhan Univ Technol Coll Architecture Dept Engn Wuhan 430070 Peoples R China

The temperature stress of reinforced concrete component caused by different linear expension coefficient has been discussed in this paper from the point of view of composite materials, The temperature dress can reach about 22 to 45 percent of the tension strength for the concrete with low grade and high ratio of reinforcement which should be considered seriously.

关键词： reinforced concrete linear expension coefficient stress

A Theoretical Study of the Pressure for Liquid Metal Infiltration of a Fiber Preform

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Journal of Materials Science & Technology 1995年第1期11卷 75-78页

作者： YU, sr HE, ZM

A theoretical model has been established for calculating the infiltration pressure of metal melt into the preform of ceramic fibers according to the basic principle of hydromechanics. There are three forces acting on the infiltration process in the model, i.e. viscous friction, capillary force, and gravity. The effects of the volume fraction of fibers (V-f) and infiltrating depth on the infiltration pressure are discussed. the results show that the infiltration pressure increases with tile increase of fiber volume fraction and infiltration depth. There is a linear relationship between infiltration pressure and infiltration depth. The effect of gravity on the infiltration pressure can be ignored.

关键词： A Theoretical Study of the Pressure for Liquid Metal Infiltration of a Fiber Preform

Intracellular recording and morphology of tectal neurons activated by contralateral nucleus isthmi in toads

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Chinese Science Bulletin 1997年第19期42卷 1647-1651页

作者： Wang, sr Wu, GY Laboratory for Visual Information Processing Institute of Biophysics Chinese Academy of Sciences Beijing China

THE nucleus isthmi (NI) in lower vertebrates and its mammalian analogue, the nucleus para-bigeminalis, are all visual centres. They receive their tectal input ipsilaterally and project backipsilaterally in teleosts and birds, or bilaterally in amphibians and reptiles, as well as in mam-mals. It is well known that NI receives its visual excitation through the ipsilateral optic tec-tum (OT). NI mainly exerts inhibition on the ipsilateral OT in frogs.A recent study

关键词： nucleus isthmi tectum intracellular recording morphology toad

Multiple bilateral costo-chondral abscesses due to Mycobacterium tuberculosis

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Asian Pacific Journal of Tropical Medicine 2010年第11期3卷 922-924页

作者： Peter George Basti sr Joy AS Department of Medicine Yenepoya Medical CollegeUniversity RoadMangalore -575018KarnatakaIndia Department of Radio-diagnosis & Imaging Fr Muller Medical CollegeFr Muller RoadMangalore -575002KarnatakaIndia

Multiple abscesses of the costo-chondral junctions are very uncommon in *** this report we present the case of a 55 year old man who presented to us with chest pain and fever of few months *** imaging with ultrasound and CECT we were able to demonstrate multiple abscesses of costo-chondral junctions *** confirmed tuberculosis by FNAC and BACTEC cultures from abscesses.

关键词： Costo-chondral abscesses Multiple rib abscesses Tuberculosis