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Effect of extrusion on properties of Al-based composite

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Transactions of Nonferrous Metals society of China 2010年第12期20卷 2229-2233页

作者： R.dasGUPTA s.das s.CHATURVEDI A.K.JHA Advanced Materials and Processes Research Institute CSIR Bhopal 462064Madhya PradeshIndia

An aluminium alloy and its composite with dispersed siC particles made by liquid metallurgy route were extruded under optimized *** properties were characterized in terms of microstructure,hardness and sliding wear behaviour and then compared between the extruded and cast alloys and composites,in order to understand the benefits of composite and extrusion on the *** was observed that composites drastically increased the hardness and the extruded composites further increased this *** advantage of composites was realized in sliding wear tests.

关键词： extrusion Al-alloy composites microstructure wear

Characterization of electrical properties of AlGaN/GaN interface using coupled schrodinger and Poisson equation

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Journal of semiconductors 2012年第11期33卷 16-23页

作者： s.das A.K.Panda G.N.dash National Institute of science and Technology Palur HillsBerhampurOdisha761008India

The electrical characterization of AlGaN/GaN interface is *** dependence of two-dimensional electron gas（2-DEG） density at the interface on the Al mole fraction and thickness of AIGaN layer as well as on the thickness of GaN cap layer is *** information can be used to design and fabricate AlGaN/GaN based MODFET（modulation doped field effect transistor） for optimum DC and RF characteristics.

关键词： MODFET 2-DEG polarization critical thickness self-heating

Entropy analysis of unsteady magneto-nanofluid flow past accelerating stretching sheet with convective boundary condition

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Applied Mathematics and Mechanics(English Edition) 2015年第12期36卷 1593-1610页

作者： s.das s.CHAKRABORTY R.N.JANA O.D.MAKINDE Department of Mathematics University of Gour Banga Department of Applied Mathematics Vidyasagar University Faculty of Military science Stellenbosch University

The unsteady laminar magnetohydrodynamics （MHD） boundary layer flow and heat transfer of nanofluids over an accelerating convectively heated stretching sheet are numerically studied in the presence of a transverse magnetic field with heat source/sink The unsteady governing equations are solved by a shooting method with the Runge-Kutta- Fehlberg scheme. Three different types of water based nanofluids, containing copper, aluminium oxide, and titanium dioxide, are taken into consideration. The effects of the pertinent parameters on the fluid velocity, the temperature, the entropy generation num- ber, the Bejan number, the shear stress, and the heat transfer rate at the sheet surface are graphically and quantitatively discussed in detail. A comparison of the entropy generation due to the heat transfer and the fluid friction is made with the help of the Bejan number. It is observed that the presence of the metallic nanoparticles creates more entropy in the nanofluid flow than in the regular fluid flow.

关键词： unsteady MHD flow nanofluid heat source/sink entropy generation Bejan number

Powder mixed electrochemical discharge process for micro machining of C103 niobium alloy

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Defence Technology（防务技术） 2023年第8期26卷 84-101页

作者： niladri Mandal Nitesh Kumar Alok Kumar das Defence Research&Development Laboratory(DRDL)-DRDO HyderabadIndia Department of Mechanical Engineering Indian Institute of Technology(ISM)DhanbadIndia

This work demonstrates the viability of the powder-mixed micro-electrochemical discharge machining(PMECDM) process to fabricate micro-holes on C103 niobium-based alloy for high temperature *** processes are involved simultaneously *** erosion,chemical etching,and abrasive grinding for removal of material while the classical electrochemical discharge machining process involves double actions *** erosion,and chemical *** powder-mixed electrolyte process resulted in rapid material removal along with a better surface finish as compared to the classical microelectrochemical discharge machining(MECDM).Further,the results are optimized through a multiobjective optimization approach and study of the surface topography of the hole wall surface obtained at optimized *** the selected range of experimental parameters,PMECDM shows a higher material removal rate(MRR) and lower surface roughness(R_(a))(MRR:2.8 mg/min and R_(a) of 0.61 μm) as compared to the MECDM process(MRR:2.01 mg/min and corresponding Raof 1.11 μm).A detailed analysis of the results is presented in this paper.

关键词： Micro-electrochemical discharge machining C103 niobium alloy surface integrity Material removal rate Hybrid powder mixed ECDM

Electron-phonon coupling and spin fluctuations in the Ising superconductor Nbse_(2)

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npj Computational Materials 2023年第1期9卷 1686-1694页

作者： s.das H.Paudyal E.R.Margine D.F.Agterberg I.I.Mazin Department of Physics and Astronomy George Mason UniversityFairfaxVA 22030USA Quantum science and Engineering Center George Mason UniversityFairfaxVA 22030USA Department of Physics Applied Physicsand AstronomyBinghamton University-SUNYBinghamtonNY 13902USA Department of Physics University of WisconsinMilwaukeeWI 53201USA

Ising superconductivity,observed in Nbse2 and similar materials,has generated tremendous ***,attention was called to the possible role that spin fluctuations(sF)play in this phenomenon,in addition to the dominant electron–phonon coupling(EPC);the possibility of a predominantly triplet state was discussed and led to a conjecture of viable singlet–triplet Leggett ***,these hypotheses have not been put to a quantitative *** this paper,we report first principle calculations of the EPC and also estimate coupling with sF,including full momentum *** find that:(1)EPC is strongly anisotropic,largely coming from the K-K0 scattering,and therefore excludes triplet symmetry even as an excited state;(2)superconductivity is substantially weakened by sF,but anisotropy remains as above;and,(3)we do find the possibility of a Leggett mode,not in a singlet–triplet but in an s_(++)–s_(±)channel.

关键词： coupling phonon superconductivity

A comparative corrosion behavior of Mg,AZ31 and AZ91 alloys in 3.5%NaCl solution

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Journal of Magnesium and Alloys 2015年第2期3卷 142-148页

作者： I.B.singh M.singh s.das CsIR-Advanced Materials and Processes Research Institute Bhopal 462026M.P.India

The corrosion behavior of Mg,AZ31 and AZ91 has been evaluated in 3.5%NaCl solution using weight loss,electrochemical polarization and impedance *** rate derived from the weight losses demonstrated the occurrence of steeply fast corrosion reaction on AZ91 alloy after three hours of immersion,indicating the start of galvanic *** increase of corrosion rate with immersion time was also observed for AZ31 but with lesser extent than AZ91 *** Mg metals showed a decrease of corrosion rate with immersion time,suggesting the formation of a protective layer on their *** contrast,the corrosion current density(I_(corr))derived from the Tafel plots,exhibited their corrosion resistances in order of Mg>AZ91>*** charge transfer resistance(R_(ct))and double layer capacitance measured by electrochemical impedance spectroscopy(EIs),are well in accordance with the measured I_(corr).EIs measurements with time and microstructural examination of the corroded and uncorroded samples are helpful in elucidation of results measured by electrochemical polarization.

关键词： Mg and alloys Weight loss Electrochemical measurements sEM

Experimental Observation of Bright and Dark solitons Mode-Locked with Zirconia-Based Erbium-Doped Fiber Laser

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Chinese Physics Letters 2018年第2期35卷 25-28页

作者： A.M.Markom s.J.Tan H.Haris M.C.Paul A.Dhar s.das s.W.Harun Faculty of Electrical Engineering Universiti Teknologi MARAMasai 81750Malaysia school of Engineering KDU University CollegeUtropolis GlenmarieShah Alam 40150Malaysia Department of Electrical Engineering University of MalayaKuala Lumpur 50603Malaysia Fiber Optics and Photonics Division CSIR-Central Glass and Ceramic Research InstituteKolkata 700032India

We demonstrate the generation of dark and bright solitons with our homemade zirconia-based erbium-doped fiber and graphene oxide（GO） saturable absorber in anomalous dispersion *** GO is fabricated using an abridged Hummer＇s method,which is combined with polyethylene oxide to produce a composite *** film is sandwiched between two optical ferrules and embedded in the laser cavity to enhance its birefringence and *** self-starting bright soliton is easily generated at pump power of 78 mW with the whole length cavity of 14.7 *** laser produces the bright pulse train with repetition rate,pulse width,pulse energy and central wavelength being 13.9 MHz,0.6 ps,2.74 p J and 1577.46 nm,***,by adding the 10 m of single mode fiber into the laser cavity,dark soliton pulse is *** the formation of dark pulse train,the measured repetition rate,pulse width,pulse energy and central wavelength are 8.3 MHz,20 ns and 4.98 p J and1596.82 nm,*** pulses operate in the anomalous region.

关键词： Zr EDF Experimental Observation of Bright and Dark solitons Mode-Locked with Zirconia-Based Erbium-Doped Fiber Laser

Dual-Wavelength Holmium-Doped Fiber Laser Pumped by Thulium-Ytterbium Co-Doped Fiber Laser

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Chinese Physics Letters 2016年第5期33卷 39-42页

作者： A.A.Latiff A.Dhar s.W.Harun I.M.Babar s.das M.C.Paul H.Ahmad Photonics Research Center University of Malaya Faculty of Electronics & Computer Engineering Universiti Teknikal Malaysia Melaka CsIR-Central Glass and Ceramic Research Institute Department of Electrical Engineering University of Malaya

We present an all-fiber dual-wavelength holmium-doped veloped holmium-doped fiber （HDF） as a gain medium fiber laser operating in 2 #m region using a newly de- The proposed fiber laser is constructed by using a hybrid gain medium, i.e., a thulium ytterbium co-doped fiber （TYDF） and an HDF in conjunction with a simple half-opened linear cavity, which is formed by a broadband mirror and an output coupler reflector. Without the HDF, the TYDF laser operates at wavelengths of 1991 and 1999nm with a signal-to-noise ratio of more than 34dB and the slope efficiency of 26.16 %. With the HDF, dual-wavelength output lines are obtained at 2075 and 2083nm with signal-to-noise ratios of more than difference between the two peaks of less than 1 dB at 17dB, 3dB bandwidth of less than 0.2nm and the power the TYDF laser pump power of 320roW.

关键词： by in is as nm of Dual-Wavelength Holmium-Doped Fiber Laser Pumped by Thulium-Ytterbium Co-Doped Fiber Laser HDF

Effect of Al-TiB master alloy addition on microstructure, wear and compressive deformation behaviour of aluminum alloys

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Transactions of Nonferrous Metals society of China 2012年第5期22卷 1001-1011页

作者： D.P.MONDAL Nidhi JHA Anshul BADKUL s.das Advanced Materials and Processes Research Institute(CsIR LAB) Bhopal 462064India

Aluminum-10% TiB master alloy was added in various proportions in 7178 Al alloy in order to examine the effect of TiB on grain refinement, wear and compressive deformation of the later one. Microstructural characterization reveals that TiB particles act as grain refiners for primary base alloy and result in globular dendrites. It was observed that the wear resistance and strength of the alloy decreased when the master alloy addition increased beyond 20%, even though the dendrites become much finer and almost spherical in nature.

关键词： aluminum alloys grain refinement Al-TiB master alloy compressive deformation sliding wear