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Energy transfer in solid-state dye lasers based on methyl methacrylate co-doped with sulforhodamine B and crystal violet

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Chinese Physics B 2013年第11期22卷 319-324页

作者： R.G.Geethu mani m.Basheer Ahamed Department of Physics KCG College of Technology Research Centre Bharathiar University Department of Physics B.S. Abdur Rahman University

Laser action in methyl methacrylate （mmA） co-doped with sulforhodamine B and crystal violet dyes was investi- gated. The dye mixture was incorporated into a solid polymeric matrix and was pumped by a 532-nm Nd：YAG laser. Distributed feedback dye laser （DFDL） action was induced in the dye mixture using a prism arrangement both in the donor and acceptor regions by an energy transfer mechanism. Theoretically, the characteristics of acceptor and donor DFDLs, and the dependence of their pulse widths and output powers on acceptor-donor concentrations and pump power, were studied. Experimentally, the output energy of DFDL was measured at the emission peaks of donor and acceptor dyes for different pump powers and different acceptor-donor concentrations. Tuning of the output wavelength was achieved by varying the period of the gain modulation of the laser medium. The laser wavelength showed continuous tunability from 563 nm to 648 nm.

关键词： sulforhodamine B crystal violet distributed feedback dye laser solid state distributed feedbackdye laser

Effect of Process Parameters on Tensile Strength of Friction Stir Welded Cast Lm6 Aluminium Alloy Joints

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Journal of materials Science & Technology 2009年第5期25卷 655-664页

作者： m.Jayaraman R.Sivasubramanian V.Balasubramanian Department of mechatronics Engineering Kongu Engineering CollegeErodeTamil NaduIndia Department of mechanical Engineering Coimbatore Institute of TechnologyCoimbatoreTamil NaduIndia Centre for materials Joining&Research(CEmAJOR) Department of Manufacturing EngineeringAnnamalai UniversityAnnamalainagarTamil NaduIndia

This paper reports the effect of friction stir welding （FSW） process parameters on tensile strength of cast Lm6 aluminium alloy. Joints were made by using different combinations of tool rotation speed, welding speed and axial force each at four levels. The quality of weld zone was investigated using macrostructure and microstructure analysis. Tensile strength of the joints were evaluated and correlated with the weld zone hardness and microstructure. The joint fabricated using a rotational speed of 900 r/min, a welding speed of 75 mm/min and an axial force of 3 kN showed superior tensile strength compared with other joints. The tensile strength and microhardness of the welded joints for the optimum conditions were 166 mPa and 64.8 Hv respectively.

关键词： Lm6 aluminium alloy Friction stir welding Tool rotation speed Welding speed Axial force Tensile strength

Influence of organic and inorganic properties of coal-shale on spontaneous combustion liability

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International Journal of mining Science and Technology 2019年第6期29卷 851-857页

作者： m.Onifade B.Genc N.Wagner The School of mining Engineering University of the WitwatersrandJohannesburg 2050South Africa Department of Geology University of JohannesburgJohannesburg 2092South Africa

Coal and coal-shale undergo low-temperature oxidation when exposed to air,potentially leading to spontaneous ***-shale found in association with coal seams vary considerably in their intrinsic properties and spontaneous combustion liability *** coal-shale samples collected from four different coal mines in Witbank Coalfield,South Africa,were experimentally *** influence of coal-shale intrinsic properties and spontaneous combustion liability indices(determined by the WitsEhac Index and the Wits-CT Index)were *** liability indices indicate relationships with the intrinsic factors and thus,identifying the major intrinsic factors affecting liability toward spontaneous combustion in these coal-shale *** XRF analysis indicated that the coal-shale samples are rich in Si O2,Al2O3 and Fe2O3,while the XRD showed that same coal-shale samples are generally dominated with kaolinite and *** coal-shale occurred in association with medium Rank C bituminous coal and contained varying proportion of *** Wits-Ehac Index was unable to reliably determine liability indices of some coal-shale samples,and hence the Wits-CT Index was *** results obtained from the characterisation tests may be used as a tool to predict the spontaneous combustion liability in carbonaceous material and may serve as a reference when comparing coal-shale from different coal mines.

关键词： Wits-Ehac Index Wits-CT Inde Witbank Coalfield and self-heating

Wash Waves Generated by High Speed Displacement Ships

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China Ocean Engineering 2015年第5期29卷 757-770页

作者：周利兰高高 R.H.m.Huijsmans Key Laboratory of High Performance Ship Technology ministry of Education Wuhan University of Technology School of Transportation Wuhan University of Technology Delft University of Technology

It is difficult to compute far-field waves in a relative large area by using one wave generation model when a large calculation domain is needed because of large dimensions of the waterway and long distance of the required computing points. Variation of waterway bathymetry and nonlinearity in the far field cannot be included in a ship fixed process either. A coupled method combining a wave generation model and wave propagation model is then used in this paper to simulate the wash waves generated by the passing ship. A NURBS-based higher order panel method is adopted as the stationary wave generation model; a wave spectrum method and Boussinesq-type equation wave model are used as the wave propagation model for the constant water depth condition and variable water depth condition, respectively. The waves calculated by the NURBS-based higher order panel method in the near field are used as the input for the wave spectrum method and the Boussinesq-type equation wave model to obtain the far-field waves. With this approach it is possible to simulate the ship wash waves including the effects of water depth and waterway bathymetry. Parts of the calculated results are validated experimentally, and the agreement is demonstrated. The effects of ship wash waves on the moored ship are discussed by using a diffraction theory method. The results indicate that the prediction of the ship induced waves by coupling models is feasible.

关键词： wash waves wave generation model wave spectrum method Boussinesq type equation wave model motions of moored ship

An Event Horizon Imager(EHI) mission Concept Utilizing medium Earth Orbit Sub-mm Interferometry

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空间科学学报 2021年第2期41卷 211-233页

作者： KUDRIASHOV V mARTIN-NEIRA m ROELOFS F FALCKE H BRINKERINK C BARYSHEV A HOGERHEIJDE m YOUNG A POURSHAGHAGHI H KLEIN-WOLT m mOSCIBRODZKA m DAVELAAR J BARAT I DUESmANN B VALENTA V PERDIGUES ARmENGOL J m DE WILDE D mARTIN IGLESIAS P ALAGHA N VAN DER VORST m Department of Astrophysics/ImAPP Radboud University NijmegenP.O.Box 90106500 GL Nijmegenthe Netherlands ESTEC/ESA Keplerlaan 12201 A2 Noordurigkthe Netherlands mar Planck Institute for Radio Astrorny Auf dem Higel 69D-53121 Bon(Endenich)Germany University of Groningen Landleven 129747 AD Groningenthe Netherlands Leiden Observatory Leiden UniversityPO Box 95132300 RALeidenthe Netherlands Anton Pannekoek Institute for Astronomy University of AmsterdamScience Park 9041098 XHAmsterdamthe Netherlands Center for Computational Astrophysics Flatiron Institute162 Fifth AvenueNew YorkNY 10010USA

Submillimeter interferometry has the potential to image supermassive black holes on event horizon scales,providing tests of the theory of general relativity and increasing our understanding of black hole accretion *** Event Horizon Telescope(EHT) performs these observations from the ground,and its main imaging targets are Sagittarius A~* in the Galactic Center and the black hole at the center of the m87 ***,the EHT is fundamentally limited in its performance by atmospheric effects and sparse terrestrial(u,v)-coverage(Fourier sampling of the image).The scientific interest in quantitative studies of the horizon size and shape of these black holes has motivated studies into using space interferometry which is free of these *** resolution considerations and interstellar scattering effects push the desired observing frequency to bands above 500 *** paper presents the requirements for meeting these science goals,describes the concept of interferometry from Polar or Equatorial medium Earth Orbits(PECmEO) which we dub the Event Horizon Imager(EHI),and utilizes suitable space technology *** this concept,two or three satellites orbit at slightly different orbital radii,resulting in a dense and uniform spiral-shaped(u,v)-coverage over *** local oscillator signals are shared via an inter-satellite link,and the data streams are correlated on-board before final processing on the ***-satellite metrology and satellite positioning are extensively employed to facilitate the knowledge of the instrument position vector,and its time *** European space heritage usable for both the front ends and the antenna technology of such an instrument is *** and future sensors for the required inter-satellite metrology are *** performance estimates and simulation results are given.

关键词： Instrumentation Space VLBI Radio Telescopes

Interaction of TbCl_3 and lanthanide complexes with poly(N-vinylpyrrolidone)

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Journal of Rare Earths 2014年第3期32卷 282-287页

作者： m.Karbowiak J.Cichos K.Buczko Faculty of Chemistry University of Wroc?aw

The interaction of TbC13 and lanthanide（Ⅲ） β-diketonate complexes with poly（N-vinylpyrrolidone）（PVP） polymer was studied using fluorescence spectroscopy. In the presence of PVP the emission of Tb3＋ in cthanolic solution of TbCl3 significantly in- creased owing to the excitation energy transfer from PVP to Tb3＋ ions, which was more efficient as compared to a direct excitation of the Tb3＋ 4f75d1 levels. In contrast, emission of NEt4Tb（hfa）4 and NEt4Eu（hfa）4 complexes was almost completely quenched in solu- tion containing PVP. The PVP bound both Ln3＋ ions and hfa ligands which caused decomposition of Ln-hfa complexes and switched off the excitation energy transfer from the ligand to the emitting Ln3＋ ion. The important role of hydrogen bonds in stabilization of in- teraction ofhfa ligands with PVP was indicated.

关键词： poly(N-vinylpyrrolidone) PVP lanthanide(Ⅲ) TbCl3 emission quenching rare earths

Slip effects on shearing flows in a porous medium

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Acta mechanica Sinica 2008年第1期24卷 51-59页

作者： m.Khan T.Hayat Y.Wang Department of mathematics Quaid-i-Azam University Islamabad 44000 Pakistan Chair of Fluid Dynamics Department of Mechanical Engineering Darmstadt University of TechnologyHochschulstrasse 164289 Darmstadt Germany

This paper deals with the magnetohydrodynamic （mHD） flow of an Oldroyd 8-constant fluid in a porous medium when no-slip condition is no longer valid. modified Darcy＇s law is used in the flow modelling. The non-linear differential equation with non-linear boundary conditions is solved numerically using finite difference scheme in combination with an iterative technique. Numerical results are obtained for the Couette, Poiseuille and generalized Couette flows. The effects of slip parameters on the velocity profile are discussed.

关键词： Porous medium. magnetohydrodynamic flow Slip effect

Solid fraction evolution characteristics of semi-solid A356 alloy and in-situ A356–TiB_2 composites investigated by differential thermal analysis

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International Journal of minerals,metallurgy and materials 2015年第4期22卷 389-394页

作者： S.Deepak Kumar A.mandal m.Chakraborty School of mechanical Sciences Indian Institute of Technology Bhubaneswar School of minerals Metallurgical and Materials Engineering Indian Institute of Technology Bhubaneswar

The key factor in semi-solid metal processing is the solid fraction at the forming temperature because it affects the microstructure and mechanical properties of the thixoformed components. Though an enormous amount of data exists on the solid fraction-temperature re- lationship in A356 alloy, information regarding the solid fraction evolution characteristics of A356-TiB2 composites is scarce. The present article establishes the temperature-solid fraction correlation in A356 alloy and A356-xTiB2 （x = 2.5wt% and 5wt%） composites using dif- ferential thermal analysis （DTA）. The DTA results indicate that the solidification characteristics of the composites exhibited a variation of 2℃ and 3℃ in liquidus temperatures and a variation of 3℃ and 5℃ in solidus temperatures with respect to the base alloy. moreover, the eutectic growth temperature and the solid fraction（fs） vs. temperature characteristics of the composites were found to be higher than those of the base alloy. The investigation revealed that in-situ formed TiB2 particles in the molten metal introduced more nucleation sites and reduced undercooling.

关键词： particle reinforced composites aluminum alloys titanium boride casting solid fraction differential thermal analysis

Current and near-term advances in Earth observation for ecological applications

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Ecological Processes 2021年第1期10卷 1-57页

作者： Susan L.Ustin Elizabeth m.middleton John muir Institute of the Environment University of CaliforniaDavisCA 95616USA NASA/Goddard Space Flight Center(Emerita) GreenbeltMD 20771USA.

There is an unprecedented array of new satellite technologies with capabilities for advancing our understanding of ecological processes and the changing composition of the Earth’s biosphere at scales from local plots to the whole *** identified 48 instruments and 13 platforms with multiple instruments that are of broad interest to the environmental sciences that either collected data in the 2000s,were recently launched,or are planned for launch in this *** have restricted our review to instruments that primarily observe terrestrial landscapes or coastal margins and are available under free and open data *** focused on imagers that passively measure wavelengths in the reflected solar and emitted thermal *** suite of instruments we describe measure land surface characteristics,including land cover,but provide a more detailed monitoring of ecosystems,plant communities,and even some species then possible from historic *** newer instruments have potential to greatly improve our understanding of ecosystem functional relationships among plant traits like leaf mass area(LmA),total nitrogen content,and leaf area index(LAI).They provide new information on physiological processes related to photosynthesis,transpiration and respiration,and stress detection,including capabilities to measure key plant and soil biophysical *** include canopy and soil temperature and emissivity,chlorophyll fluorescence,and biogeochemical contents like photosynthetic pigments(e.g.,chlorophylls,carotenoids,and phycobiliproteins from cyanobacteria),water,cellulose,lignin,and nitrogen in foliar *** data will enable us to quantify and characterize various soil properties such as iron content,several types of soil clays,organic matter,and other *** of these satellites are in low Earth orbit(LEO),but we include a few in geostationary orbit(GEO)because of their potential to measure plant physiological traits over diurnal periods,impro

关键词： Terrestrial ecosystems Earth Observing Satellites Ecosystem processes Physiological functions multispectral Hyperspectral Thermal LiDAR Radar imagers Biochemistry Soil properties Species mapping Change detection 3D canopy structure Topography