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Digitally controlled oscillator design with a variable capacitance XOR gate

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Journal of Semiconductors 2011年第10期32卷 86-92页

作者： Manoj kumar Sandeep k.Arya Sujata Pandey Department of Electronics and Communication Engineering Guru Jambheshwar University of Science and TechnologyHisarIndia Amity University NoidaIndia

A digitally controlled oscillator（DCO） using a three-transistor XOR gate as the variable load has been presented.A delay cell using an inverter and a three-transistor XOR gate as the variable capacitance is also proposed. Three-,five- and seven-stage DCO circuits have been designed using the proposed delay *** output frequency is controlled digitally with bits applied to the delay *** three-bit DCO shows output frequency and power consumption variation in the range of 3.2486-4.0267 GHz and 0.6121-0.3901 mW,respectively,with a change in the control word *** five-bit DCO achieves frequency and power of 1.8553-2.3506 GHz and 1.0202-0.6501 mW,respectively,with a change in the control word ***,the seven-bit DCO shows a frequency and power consumption variation of 1.3239-1.6817 GHz and 1.4282-0.9102 mW,respectively, with a varying control word *** power consumption and output frequency of the proposed circuits have been compared with earlier reported circuits and the present approaches show significant improvements.

关键词： digital control oscillator delay cell power consumption variable capacitance voltage controlled oscillators XOR gate

Lie group analysis, numerical and non-traveling wave solutions for the (2+1)-dimensional diffusion–advection equation with variable coefficients

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Chinese Physics B 2014年第3期23卷 71-76页

作者： Vikas kumar R.k.Gupta Ram Jiwari Department of Mathematics D.A.V.College Pundari School of Mathematics and Computer Applications Thapar University

In this paper, the variable-coefficient diffusion-advection （DA） equation, which arises in modeling various physical phenomena, is studied by the Lie symmetry approach. The similarity reductions are derived by determining the complete sets of point symmetries of this equation, and then exact and numerical solutions are reported for the reduced second-order nonlinear ordinary differential equations. Further, an extended （Gl/G）-expansion method is applied to the DA equation to construct some new non-traveling wave solutions.

关键词： diffusion-advection equation Lie group analysis numerical solutions extended (G'/G)-expansion method

Corrosion Protective Conversion Coatings on Magnesium Disks Using a Hydrothermal Technique

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Journal of Materials Science & Technology 2014年第1期30卷 47-53页

作者： R.k.Gupta k.Mensah-Darkwa D.kumar Department of Chemistry Pittsburg State University Engineering Research Center for Revolutionizing Metallic Biomaterials(ERC-RMB) Department of Mechanical EngineeringNorth Carolina A&T State University

A uniform, compact, and well adherent conversion coating of magnesium hydroxide has been formed on bioresorbable magnesium disks by means of a hydrothermal technique. Electrochemical results indicate that the coating brings about a significant reduction in magnesium corrosion in phosphate buffered saline （PBS） solution. It is also observed that corrosion resistance of the coating increases with an increase in treatment time, which in turn, increases the coating thickness. The protective behavior of magnesium hydroxide coating is attributed to its chemical inertness in PBS solution. The coatings are found to be free from pores that reduce the direct contact between corroding media and underlying magnesium.

关键词： Magnesium Polarization Electrochemical impedance spectroscopy (EIS) Scanning electron microscopy (SEM) Conversioncoating Corrosion

Enabling intercalation-type TiNb_(24)O_(62)anode for sodiumand potassium-ion batteries via a synergetic strategy of oxygen vacancy and carbon incorporation

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SusMat 2023年第2期3卷 222-234页

作者： Ajay Piriya vijaya kumar Saroja Zhipeng Wang Henry R.Tinker Feng RyanWang Paul R.Shearing Yang Xu Department of Chemistry University College LondonLondonUK Materials and Catalysis Laboratory Department of Chemical EngineeringUniversity College LondonLondonUK Electrochemical Innovation Lab Department of Chemical EngineeringUniversity College LondonLondonUK

The key to develop earth-abundant energy storage technologies sodium-and potassium-ion batteries(SIBs and PIBs)is to identify low-cost electrode materials that allow fast and reversible Na^(+)/k^(+)***,we report an intercalation-type material TiNb_(24)O_(62)as a versatile anode for SIBs and PIBs,via a synergistic strategy of oxygen vacancy and carbon incorporation to enhance ion and electron *** TiNb_(24)O_(62-x)/reduced graphene oxide(rGO)composite anode delivers high reversible capacities(130 mA h g^(-1)for SIBs and 178 mA h g^(-1)for PIBs),great rate performance(54 mA h g^(-1)for SIBs and 37 mA h g^(-1)for PIBs at 1 A g^(-1)),and superior cycle stability(73.7%after 500 cycles for SIBs and 84%after 300 cycles for PIBs).The performance is among the best results of intercalation-typemetal oxide anodes for SIBs and *** better performance of TiNb_(24)O_(62-x)/rGO in SIBs than PIBs is due to the better reaction kinetics of the ***,mechanistic study confirms that the redox activity of Nb4+/5+is responsible for the reversible intercalation of Na^(+)/k^(+).Our results suggest that TiNb_(24)O_(62-x)/rGO is a promising anode for SIBs and PIBs and may stimulate further research on intercalation-type compounds as candidate anodes for large ion batteries.

关键词： anode defects intercalation potassium-ion battery sodium-ion battery sustainability

Synthesis of Aligned ZnO Nanorod Array on Silicon and Sapphire Substrates by Thermal Evaporation Technique

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Journal of Materials Science & Technology 2011年第8期27卷 701-706页

作者： k.M.k. Srivatsa Deepak Chhikara M. Senthil kumar Materials Physics and Engineering Division National Physical Laboratory Council of Scientific & Industrial Research (CSIR) Physics of Energy Harvesting Division National Physical Laboratory Council of Scientific & Industrial Research (CSIR)

High density ZnO nanorods were grown by thermal evaporation of Zn powder at 700℃ on Si （100） and sapphire （0001） substrates at atmospheric pressure without adding any catalyst. The nanorods were characterizated in terms of their structural and optical properties. The nanorods grown on Si have a diameter of 350-400 nm and a length of 1.2 μm while those on sapphire have a diameter of 600-800 nm and a length of 2.5 μm. During the structural characterization, it is noticed that the rods grow along the （0002） plane with perfect hexagonal facet. The room temperature photoluminescence spectrum showed a strong UV emission peak at 385 nm with a weak green band emission, which confirms that nanorods have good optical properties. It is observed that the oxygen partial pressure plays an important role to control the shape and size of the nanorods in thermal evaporation growth technique.

关键词： Thermal evaporation technique ZnO nanorods X-ray diffraction Photoluminescence

Mechanical and Corrosion Properties of Magnesiume-Hydroxyapatite (MgeHA) Composite Thin Films

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Journal of Materials Science & Technology 2013年第9期29卷 788-794页

作者： k.Mensah-Darkwa R.k.Gupta D.kumar Engineering Research Center of Revolutionizing Metallic Biomaterials Department of Mechanical Engineering North Carolina A & T State University Department of Chemistry Pittsburg State University

Magnesium(Mg)-hydroxyapatite(Ca10(PO4)6(OH)2,abbreviated as HA) composite films have been grown on Mg plates using a pulsed laser deposition *** property measurements and analysis have indicated that hardness and Young’s modulus of nMge(100e n)HA composite coatings increase with Mg content in the coatings and reach a maximum at a 70Mge 30HA composition.n and 100e n in the nMge(100e n)HA represent the relative number of laser pulses impinging on Mg and HA targets,*** current potentiodynamic polarization studies have shown that the corrosion of Mg plate(control) decreases with an increase in the HA ratio in the composite *** example,the corrosion current density of Mg plate reduces by w350 times after coating the Mg plate with 10Mge 90HA composite *** reduction in corrosion current density of Mg plates was also accompanied by a positive shift in the corrosion potential(w6%) due to this *** mechanism behind the reduction in corrosion behavior of Mg plates due to nMge(100e n) HA composite coatings has been understood by electrochemical impedance spectroscopy.

关键词： Magnesium Hydroxyapatite Scanning electron microscopy Pulsed laser deposition Corrosion Impedance spectroscopy

Mechanics of granular column collapse in fluid at varying slope angles

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Journal of Hydrodynamics 2017年第4期29卷 529-541页

作者： k.kumar J.-Y.Delenne k.Soga Computational Geomechanics Research Group Department of Engineering University of Cambridge IATE UMR 1208 INRA-CIRAD-Montpellier Supagro-UM2 University of Montpellier 2 Department of Civil and Environmental Engineering University of California

This paper investigates the effect of initial volume fraction on the runout characteristics of collapse of granular columns on slopes in fluid. 2-D sub-grain scale numerical simulations are performed to understand the flow dynamics of granular collapse in fluid. The discrete element method（DEM） technique is coupled with the lattice Boltzmann method（LBM）, for fluid-grain interactions, to understand the evolution of submerged granular flows. The fluid phase is simulated using multiple-relaxation-time LBM（LBM-MRT） for numerical stability. In order to simulate interconnected pore space in 2-D, a reduction in the radius of the grains（hydrodynamic radius） is assumed during LBM computations. The collapse of granular column in fluid is compared with the dry cases to understand the effect of fluid on the runout behaviour. A parametric analysis is performed to assess the influence of the granular characteristics（initial packing） on the evolution of flow and run-out distances for slope angles of 0 °, 2.5°, 5 ° and 7.5 °. The granular flow dynamics is investigated by analysing the effect of hydroplaning, water entrainment and viscous drag on the granular mass. The mechanism of energy dissipation, shape of the flow front, water entrainment and evolution of packing density is used to explain the difference in the flow characteristics of loose and dense granular column collapse in fluid.

关键词： Lattice Boltzmann method(LBM) discrete element method(DEM) granular column collapse granular flows hydroplaning water entrainment viscous drag

Effect of Ba Substitution on the Structural and Magnetic Properties of BiFeO₃

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World Journal of Nano Science and Engineering 2016年第1期6卷 38-44页

作者： V. Srinivas A. T. Raghavender k. vijaya kumar Department of Physics Government Institute of Electronics Secunderabad TS India Department of Electronics and Communication Engineering Nishitha College of Engineering and Technology Hyderabad TS India Department of Physics JNTUH College of Engineering Jagtial Nachupally (Kondagattu) Karimnagar-Dist. TS India

Bi1-xBaxFeO3 (0 ≤ x ≤ 0.3) nanopowders were synthesized using sol-gel technique. The structural and magnetic properties were investigated using X-ray diffraction, SEM and VSM. As Ba2+ doping concentration was increased, the structure of the samples changed from rhombohedral to tetragonal or monoclinic. The structural change might be an important factor for achieving the ferroelectric properties in this material. The lattice parameters were observed to increase with increase in Ba2+ concentration. All the M-H loops showed the ferromagnetic behavior. Magnetization was observed to enhance with increase in Ba concentration. The enhancement in the magnetization due to Ba2+ doping may be due to the replacement of Bi3+ ions by Ba2+ which might have resulted in the suppression of spiral spin structure.

关键词： Multiferroic Material Structural Magnetic Properties

Geochemistry and geochronology of A-type basement granitoids in the north-central Aravalli Craton: Implications on Paleoproterozoic geodynamics of NW Indian Block

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Geoscience Frontiers 2021年第4期12卷 138-150页

作者： Manoj k.Pandit Hitesh kumar WeiWang Department of Geology University of RajasthanJaipur 302004India Department of Mines and Geology Government of RajasthanJaipurRajasthanIndia State key Laboratory of Geological Processes and Mineral Resources School of Earth Sciences and ResourcesChina University of GeosciencesWuhan 430074China

The basement granite gneisses from the north-central Aravalli Craton in NW India were investigated for geochemistry and *** a peneplain terrain,the granite gneiss outcrops are scanty and samples were collected mainly from two small hills and several ground-level exposures in the Sakhun–Ladera *** granite gneiss is the dominant lithology that also hosts dark,lenticular enclaves,and is in turn,intruded by mafic *** granite gneiss has silica content ranging from 61.37 wt.%to 68.27 wt.%that marks a slight overlap with the enclaves(54.32wt.%to 62.17wt.%).Both groups have a highk2O/Na2O(~2 or higher)***,the granite gneiss classify as granite–granodiorite,and enclaves as *** In-situ LA-ICP-MS zircon U–Pb geochronology of granite gneiss has yielded a statistically valid 1721±9 Ma age that we interpret as the emplacement age for the granitic *** characteristics of granite gneiss underline fractional crystallization of an I-type melt as themain process,and continuity of trends in enclaves underlines their mutual genetic *** genetic association is further verified by a consistency in the trace element characteristics and REE *** Nd-isotope signatures define a single grouping for both granite gneiss and enclaves,withεNd(t)values ranging from−6.38 to−6.61,further substantiating a common *** geochemical tectonic discrimination schemes consistently point toward an extensional setting and A-type characteristics for granite gneiss and *** are analogous to the coeval(1.72–1.75 Ga),A-type granitoids from the khetri and Alwar basin in the North Delhi Fold Belt,implying a much larger areal extent for the Paleoproterozoic anorogenic magmatism in the northern segment of the Aravalli *** Paleoproterozoic age for the presumed‘Archean’basement in this region offers tacit evidence that the BGC–II is a stratigraphically younger terrane as compared to the Archean age,

关键词： Basement granite Geochemistry Zircon U–Pb geochronology A-type granites Aravalli Craton NWIndian Block