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Carbon isotopes of graphite:Implications on fluid history

Geoscience frontiers 2012年第2期3卷 197-207页

作者： f.j.Luque E.Crespo-feo j.f.barrenechea L.Ortega Departamento de Cristalografía y Mineralogía facultad de Geología Universidad Complutense de Madrid 28040 MadridSpain Instituto de Geociencias(UCM-CSIC) Jos Antonio Novais 228040 MadridSpain Departamento de Cristalografia y Mineralogia facultad de Geología Universidad Complutense de Madrid28040 MadridSpain Departamento de Cristalografía y Mineralogía facultad de Geología Universidad Complutense de Madrid28040 MadridSpain

Stable carbon isotope geochemistry provides important information for the recognition of funda- mental isotope exchange processes related to the movement of carbon in the lithosphere and permits the elab- oration of models for the global carbon cycle. Carbon isotope ratios in fluid-deposited graphite are powerful tools for unravelling the ultimate origin of carbon （organic matter, mantle, or carbonates） and help to constrain the fluid history and the mechanisms involved in graphite deposition. Graphite precipitation in fluid-deposited occurrences results from C02- and/or CH4-bearing aqueous fluids. fluid flow can be considered as both a closed （without replenishment of the fluid） or an open system （with renewal of the fluid by successive fluid batches）. In closed systems, carbon isotope systematics in graphite is mainly governed by Rayleigh precipi- tation and/or by changes in temperature affecting the fractionation factor between fluid and graphite. Such processes result in zoned graphite crystals or in successive graphite generations showing, in both cases, isotopic variation towards progressive 13C or 12C enrichment （depending upon the dominant carbon phase in the fluid, C02 or CH4, respectively）. In open systems, in which carbon is episodically introduced along the fracture systems, the carbon systematics is more complex and individual graphite crystals may display oscillatory zoning because of Rayleigh precipitation or heterogeneous variations of 613C values when mixing of fluids or changes in the composition of the fluids are the mechanisms responsible for graphite precipitation.

关键词： Graphite Carbon isotopes Crust C-O-H fluids

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Investigation on the influence of the initial RDX crystal size on the performance of shaped charge warheads

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Defence Technology（防务技术） 2019年第5期15卷 802-807页

作者： f.Majiet f.j.Mostert Rheinmetall Denel Munition Somerset WestSouth Africa Centre for Scientific&Industrial Research PretoriaSouth Africa

Copper lined wave shaped shaped charges of particular design and liner metallurgy were used to investigate the effect of explosive crystal size on the resultant shaped charge jet *** A3 with RDX of three different average crystal sizes,i.e.30μm,100μm and 300μm were used in the *** other parameters in the charge were kept constant and in particular,care was given to obtain consistent dimensional quality and liner microstructure,in order to prohibit the variation of other *** flash-X-ray diagnostics were used in field tests to obtain the jet parameters from multiple firings of similar *** is found that the varying crystal size of the RDX has a marginal influence in the total jet length of the ***,it is also found that there is less variation between firings in the jet parameters for jets from the charges loaded with the crystal size of 100 μm.

关键词： shaped size crystal

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Implementation of a Roughness Element to Trip Transition in Large-eddy Simulation

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journal of Thermal Science 2015年第1期24卷 30-36页

作者： j.Boudet j.-f.Monier f.Gao LMfA Ecole Centrale de Lyon Université de Lyon–UMR CNRS 5509 69134 Ecully Cedex France PhD.Candidate Université de Lyon–UMR CNRS 5509 69134 Ecully Cedex France

In aerodynamics, the laminar or turbulent regime of a boundary layer has a strong influence on friction or heat transfer. In practical applications, it is sometimes necessary to trip the transition to turbulent, and a common way is by use of a roughness element （e.g. a step） on the wall. The present paper is concerned with the numerical im- plementation of such a trip in large-eddy simulations. The study is carried out on a flat-plate boundary layer con- figuration, with Reynolds number Rex=l.3x 106. first, this work brings the opportunity to introduce a practical methodology to assess convergence in large-eddy simulations. Second, concerning the trip implementation, a volume source term is proposed and is shown to yield a smoother and faster transition than a grid step. Moreover, it is easier to implement and more adaptable. finally, two subgrid-scale models are tested： the WALE model of Nic0ud and Ducros （flow Turbul. Combust., vol. 62, 1999） and the shear-improved Smagorinsky model of Ldv^que et al. （j. fluid Mech., vol. 570, 2007）. Both models allow transition, but the former appears to yield a faster transition and a better prediction of friction in the turbulent regime.

关键词： large-eddy simulation boundary layer roughness element transition tripping

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Surface morphology and impurity distribution of electron beam recrystallized silicon films on low cost substrates for solar cell absorber

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Rare Metals 2006年第Z1期25卷 195-200页

作者： GROMBALL f MüLLER j Department of Mikrosystemtechnik Technische Universitt Hamburg-Harburg Hamburg 21073 Germany

A line shaped electron beam recrystallised polycrystalline silicon film on the low cost substrate was investigated for the use of the solar cell absorber. The applied EB energy density strongly influences the surface morphology of the film system. Lower EB energy density results in droplet morphology and the rougher SiO2 capping layer due to the low fluidity. With the energy increasing, the capping layer becomes smooth and continuous and less and small pinholes form in the silicon film. Tungstendisilicide (WSi2) is formed at the interface tungsten/silicon but also at the grain boundaries of the silicon. Because of the fast melting and cooling of the silicon film, the eutectic of silicon and tungstendisilicide mainly forms at the grain boundary of the primary silicon dendrites. The SEM-EDX analysis shows that there are no chlorine and hydrogen in the area surrounding a pinhole after recrystallization because of outgassing during the solidification.

关键词： polycrystalline silicon film solar cell recrystallization energy surface morphology outgassing

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Characterization of Phases in an As-cast Copper-Manganese-Aluminum Alloy

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journal of Materials Science & Technology 2006年第6期22卷 779-784页

作者： j.Iqbal f.Hasan f.Ahmad Department of Metallurgical and Materials Engineering University of Engineering and TechnologyLahorePakistan

Copper-manganese-aluminum （CMA） alloys, containing small additions of fe, Ni, and Si, exhibit good strength and remarkable corrosion resistance against sea water. The alloys are used in as-cast condition, and their microstructure can show wide variations. The morphology, crystallography and composition of the phases presented in an as-cast （CMA） alloy of nominal composition Cu-14%Mn-8%Al-3%fe-2%Ni were investigated using optical, electron optical, and microprobe analytical techniques. The as-cast microstructure consisted of the grains of fcc α and bcc β-phases alongwith intermetallic precipitates of various morphologies. The room temperature microstructure exhibited four different types of precipitates inside the α-grains： the ＇large＇ dendritic-shaped particles and the cuboid-shaped precipitates, which were rich in fe and Mn and had an fcc structure, while the ＇small＇ dendritic-shaped particles and the globular precipitates were based on feaAI and had DO3 structure. These four different morphologies of intermetallic precipitates exhibited discrete orientation-relationships with the α-matrix. The β-grains only contained very small cuboid shaped precipitates, which could only be resolved through transmission electron microscopy. These precipitates were found to be based on fe3Al and had the DO3 structure.

关键词： Orientation relationship DO3 structure Intermetallic phases

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ＯＮＴＨＥＨＹＰＥＲＢＯＬＩＣＯＢＳＴＡＣＬＥＰＲＯＢＬＥＭＯＦＦＩＲＳＴＯＲＤＥＲ

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Chinese Annals of Mathematics,Series B 2002年第2期23卷 253-266页

作者： j.f.RODRIGUES CMAf/Universidade

This paper presents new results for strong solutions and their coincidence sets of the obstacle problem for linear hyperbolic operators of first order. An inequality similar to the LewyStampacchia ones for elliptic and parabolic problems is shown. Under nondegeneracy conditions the stability of the coincidence set is shown with respect to the variation of the data and with respect to approximation by semilinear hyperbolic problems. These results are applied to the asymptotic stability of the evolution problem with respect to the stationary coercive problem with obstacle.

关键词： Hyperbolic obstacle problem Linear hyperbolic operator Strong solution

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Laser induced photo-detachment of O2 in DC discharge

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Plasma Science and Technology 2018年第7期20卷 98-105页

作者： j r legorreta j l patiNo f b yousif Centro de Investigacion en Ciencias Universidad Autonoma del Estado de Morelos.Av.UniversidadNo.1001 Col.Chamilpa Cuemavaca MorelosMexico

Determination of the negative ion number density of O2 and O in a DC discharge of oxygen plasma was made employing Langmuir probe in conjunction with eclipse laser photo- detachment technique. The temporal evolution of the extra electrons resulting from the photo- detachment of O2- and O- were used to evaluate the negative ion number density. The ratio of O2 number density to O varied from 0.03 to 0.22. Number density of both O~ and O increased with increasing power and decreased as the pressure was increased. Electron number density was evaluated from the electron energy distribution function （EEDf） using the I-V recorded characteristic curves. Electron temperature between 2 and 2.7 eV were obtained. Influence of the 02（al△g） metastable state is discussed.

关键词： electronegative plasma electron temperature Langmuir probe negative ion number density

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Improving weld formability by a novel dual-rotation bobbin tool friction stir welding

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journal of Materials Science & Technology 2018年第1期34卷 135-139页

作者： f.f.Wang W.Y.Li j.Shen Q.Wen j.f.dos Santos State Key Laboratory of Solidification Processing Shaanxi Key Laboratory of Friction Welding Technologies Northwestern Polytechnical University Helmholtz-Zentrum Geesthacht Institute of Materials Research Materials Mechanics China Academy of Launch Vehicle Technology Beijing Institute of Astronautical Systems Engineering

A novel dual-rotation bobbin tool friction stir welding （DBT-fSW） was developed, in which the upper shoulder （US） and lower shoulder （LS） have different rotational speeds. This process was tried to weld 3.2 mm thick alunlinum-lithium alloy sheets. The metallographic analysis and torque measurement were carried out to characterize the weld formabiliW. Experimental results show that compared to conven- tional bobbin tool friction stir welding, the DBT-fSW has an excellent process stability, and can produce the defect-free joints in a wider range of welding parameters. These can be attributed to the significant improvement of material flow caused by the formation of a staggered layer structure and the unbalanced force between the US and LS during the DBT-fSW process.

关键词： Bobbin tool friction stir welding Dual rotation Material flow Microstructure Microhardness

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STUDY Of EXPLOSIVE VAPORIZATION Of LD11R ALUMINUMALLOY DURING ELECTRON BEAM DEEP PENETRATION

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Acta Metallurgica Sinica(English Letters) 2000年第6期13卷 1119-1124页

作者： Wang, Y.j. jia, S.j. Liu, f.j. Chen, X.f. NKL of EDB process. Technol. Beijing 100024 China

High-power-density electron beam with single pulse was performed on the LD11R aluminum alloy. The electron beam was focused on three typical positions. for each case, the distribution of the solute concentration at the cavity bottom solid-liquid interface was investigated by using the 'rapidly fixing' method. The interaction of the beam and solute atoms was analyzed. A new mechanism of explosive vaporization was proposed based on the present results. The occurrence of this explosive vaporization source was discussed.

关键词： Electron beam welding Vaporization

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Comeld^TM joints: A Novel Technique for Bonding Composites and Metal

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稀有金属材料与工程 2009年第A3期38卷 134-141页

作者： Tu W Guild f j Hogg P j Queen Mary University of London Imperial College London South Kensington Campus University of Manchester PO Box 88

Current and future structural applications for composite laminates frequently involve design solutions combining composite laminates and metal; the materials must be joined. Two conventional means of joining are available mechanical joining and adhesive bonding. Both methods have critical disadvantages. A novel surface treatment for metals developed at TWI, Surfi-Sculpt, leads to the formation of surface protrusions on metal surfaces. These protrusions are typically 1.0 mm high and 0.6 mm in diameter. The surface modified metal can be bonded with composite laminates to form a Comeld～TM joint. These joints can be described as a combination of mechanical fastening and adhesive bonding. This paper describes our current work using finite element modelling to optimize the protrusions in respect to their geometry and distribution. The simulations require multi-scale modelling techniques to transfer results between the global model of the whole joint and the unit cell models containing a protrusion. Results from the simulations show critical effects on stress distributions arising from changing protrusion geometry. These joints show significant advantages over conventional adhesive joining technologies and their application would allow improved performance for combinations of metal and composite laminates.

关键词：复合材料金属表面处理技术物理性能

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