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Transactions of Nonferrous Metals Society of China 2010年第10期20卷 1822-1828页

作者： P.VENKATACHALAM S.RAMESH kumar.b.RAVISANKAR V.THOMAS PAUL M.VIJAYALAKSHMI Department of Metallurgical and Materials Engineering National Institute of Technology Physical Metallurgy Division IGCAR

Al-Cu alloy was deformed through equal channel angular pressing(ECAP) by routes A,ba,bc and C up to 5 *** was done using a 90° die for three different conditions,namely 1) as received,2) solutionised at 768 K for 1 h and 3) solutionised at 768 K for 1 h + aged at 468 K for 5 *** microstructure,microhardness and tensile strength were studied for all the three conditions and four *** improvement in hardness(HV 184 after five passes) and strength(602 MPa after three passes) was observed in solutionised and aged 2014 Al alloy deformed through route *** evolution was reasonably equiaxed in route bc with aspect ratio of *** and aged 2014 Al alloy deformed through route bc was identified to have better microstructure and mechanical property than the other processing routes and conditions.

关键词： ECAP processing route 2014 aluminium alloy

STAbILITY AND bIFURCATION ANALYSIS OF A DELAYED INNOVATION DIFFUSION MODEL

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Acta Mathematica Scientia 2018年第2期38卷 709-732页

作者： Rakesh kumar Anuj kumar SHARMA Kulbhushan A GNIHOTRI Department of Applied Sciences S.B.S. State Technical Campus Ferozepur Punjab 152004 India Research Scholar with I.K.G. Punjab Technical University Kapurthala Punjab 144603 India Department of Mathematics L.R.D.A. V. College Jagraon Ludhiana Punjab 142026 India

In this article, a nonlinear mathematical model for innovation diffusion with stage structure which incorporates the evaluation stage （time delay） is proposed. The model is analyzed by considering the effects of external as well as internal influences and other demographic processes such as emigration, intrinsic growth rate, death rate, etc. The asymptotical stability of the various equilibria is investigated. by analyzing the exponential characteristic equation with delay-dependent coefficients obtained through the variational matrix, it is found that Hopf bifurcation occurs when the evaluation period （time delay, T） passes through a critical value. Applying the normal form theory and the center manifold argument, we de- rive the explicit formulas determining the properties of the bifurcating periodic solutions. To illustrate our theoretical analysis, some numerical simulations are also included.

关键词： Innovation diffusion model stability analysis Hopf-bifurcation normal form theory center manifold theorem

Effect of pressure on electronic and thermoelectric properties of magnesium silicide: A density functional theory study

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Chinese Physics b 2016年第5期25卷 246-252页

作者： Kulwinder Kaur Ranjan kumar Department of Physics Panjab University

We study the effect of pressure on electronic and thermoelectric properties of Mg_2Si using the density functional theory and boltzmann transport equations. The variation of lattice constant, band gap, bulk modulus with pressure is also analyzed. Further, the thermoelectric properties（Seebeck coefficient, electrical conductivity, electronic thermal conductivity） have been studied as a function of temperature and pressure up to 1200 K. The results show that Mg_2Si is an n-type semiconductor with a band gap of 0.21 eV. The negative value of the Seebeck coefficient at all pressures indicates that the conduction is due to electrons. With the increase in pressure, the Seebeck coefficient decreases and electrical conductivity increases. It is also seen that, there is practically no effect of pressure on the electronic contribution of thermal *** paper describes the calculation of the lattice thermal conductivity and figure of merit of Mg_2Si at zero pressure. The maximum value of figure of merit is attained 1.83 × 10^（-3） at 1000 K. The obtained results are in good agreement with the available experimental and theoretical results.

关键词： semiconductors effects of pressure electric and thermal conductivity density functional theory

Wildland fires and moist deciduous forests of Chhattisgarh, India: divergent component assessment

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Journal of Forestry Research 2014年第4期25卷 857-866页

作者： b.H.Kittur S.L.Swamy S.S.bargali Manoj kumar Jhariya Department of Silviculture & Agroforestry College of Forestry Kerala Agriculture University Vellanikara Thrissure Kerala India Department of Forestry College of Agriculture Indira Gandhi Krishi Vishwavidyalaya Raipur (C.G.) 492006 India Department of botany DSB Campus Kumaun University Nainital–263001 (Uttarakhand) India

We studied moist deciduous forests of Chhattisgarh, India （1） to assess the effect of four levels of historic wildland fire frequency （high, medium, low, and no-fire） on regeneration of seedlings in fire affected areas during pre and post-fire seasons, （2） to evaluate vegetation struc- ture and diversity by layer in the four fire frequency zones, （3） to evalu- ate the impact of fire frequency on the structure of economically impor- tant tree species of the region, and （4） to quantify fuel loads by fire fre- quency level. We classified fire-affected areas into high, medium, low, and no-fire frequency classes based on government records. Tree species were unevenly distributed across fire frequency categories. Shrub density was maximum in zones of high fire frequency and minimum in low- frequency and no-fire zones. Lower tree density after fires indicated that regeneration of seedlings was reduced by fire. The population structure in the high-frequency zone was comprised of seedlings of size class （A） and saplings of size class （b）, represented by Diospyros melanoxylon, Dalbergia sissoo, Shorea robusta and Tectona grandis. Younger and older trees were more abundant for Tectona grandis and Dalbargia sis- soo after fire, whereas intermediate-aged trees were more abundant pre- fire, indicating that the latter age-class was thinned by the catastrophic effect of fire. The major contributing components of fuel load included duff litter and small woody branches and twigs on the forest floor. Total fuel load on the forest floor ranged from 2.2 to 3.38 Mg/ha. The netchange in fuel load was positive in high- and medium-frequency fire zones and negative under low- and no-fire zones. Repeated fires, how- ever, slowly reduced stand stability. An ecological approach is needed for fire management to restore the no-fire spatial and temporal structure of moist deciduous forests, their species composition and fuel loads. The management approach should incorporate participatory forest ma

关键词： forest fire diversity fuel load vegetation structure

Multi-Objective Grey Wolf Optimization Algorithm for Solving Real-World bLDC Motor Design Problem

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Computers, Materials & Continua 2022年第2期70卷 2435-2452页

作者： M.Premkumar Pradeep Jangir b.Santhosh kumar Mohammad A.Alqudah Kottakkaran Sooppy Nisar Department of Electrical and Electronics Engineering GMR Institute of TechnologyRajam532127Andhra PradeshIndia Rajasthan Rajya Vidyut Prasaran Nigam Sikar332025RajasthanIndia Department of Computer Science and Engineering GMR Institute of TechnologyRajam532127Andhra PradeshIndia German Jordanian University Amman11180Jordan Department of Mathematics College of Arts and SciencesPrince Sattam Bin Abdulaziz UniversityWadi Aldawaser11991Saudi Arabia

The first step in the design phase of the brushless Direct Current(bLDC)motor is the formulation of the mathematical framework and is often used due to its analytical ***,the bLDC motor design problem is considered to be an optimization *** this paper,the analytical model of the bLDC motor is presented,and it is considered to be a basis for emphasizing the optimization *** analytical model used for the experimentation has 78 non-linear equations,two objective functions,five design variables,and six non-linear constraints,so the bLDC motor design problem is considered as highly non-linear in electromagnetic ***-objective optimization becomes the forefront of the current research to obtain the global best solution using metaheuristic *** bio-inspired multi-objective grey wolf optimizer(MOGWO)is presented in this paper,and it is formulated based on Pareto optimality,dominance,and archiving *** performance of theMOGWO is verified on standard multi-objective unconstraint benchmark functions and applied to the bLDC motor design *** results proved that the proposedMOGWO algorithm could handle nonlinear constraints in electromagnetic optimization *** performance comparison in terms of Generational Distance,inversion GD,Hypervolume-matrix,scattered-matrix,and coverage metrics proves that the MOGWO algorithm can provide the best solution compared to other selected *** source code of this paper is backed up with extra online support at https://***/mysite and https://***/matlabcentral/fileexchange/75259-multiobjective-non-sorted-grey-wolf-mogwo-nsgwo.

关键词： bLDC motor electromagnetics metaheuristic multi-objective grey wolf optimizer

Uniqueness,reciprocity theorem,and plane waves in thermoelastic diffusion with a fractional order derivative

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Chinese Physics b 2013年第7期22卷 286-297页

作者： Rajneesh kumar Vandana Gupta Department of Mathematics Kurukshetra University

In this work, a theory of thermoelasticity with diffusion is taken into consideration by using the methodology of fractional calculus. The governing equations for particle motion in a homogeneous anisotropic fractional order generalized thermoelastic diffusive medium are presented. Uniqueness and reciprocity theorems are proved. The plane wave propagation in the homogeneous transversely isotropic thermoelastic diffusive medium with fractional order derivative is studied. For the two-dimensional problem, there exist a quasi-longitudinal wave, a quasi-transverse wave, a quasi-mass diffusion wave, and a quasi-thermal wave. From the obtained results, the different characteristics of waves, like phase velocity, attenuation coefficient, specific loss, and penetration depth, are computed numerically and presented graphically. Some special cases are also discussed.

关键词： thermoelastic diffusion fractional calculus uniqueness theorem reciprocity theorem

Computational study of different venturi and orifice type hydrodynamic cavitating devices

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Journal of Hydrodynamics 2016年第2期28卷 293-305页

作者： Kuldeep Virendra kumar SAHARAN Chemical Engineering Department Malaviya National Institute of Technology

This paper reports optimization of various geometrical parameters of two types of hydrodynamic cavitation reactors （HC） such as venturi type and orifice type. Mostly orifice and venturi nozzles are used as HC reactor, a simple valve can also be used to cause cavitation which depends on geometry and area of opening. Different operating and geometrical parameters such as divergence angle, throat height/diameter to length ratio, number of holes and inlet pressure to the cavitating device were selected to study the inception, growth and dynamics of cavities. In this work, a comprehensive computational fluid dynamics simulation is performed to numerically investigate the 3-D flow behaviors within HC reactors using cavitational model with standard κ - ε Turbulence model. The study of different geometries of venturi type HC reactor （like slit, circular and elliptical） shows that 1：1 of the ratio of throat height/diameter to length and 6.5% of divergence angle is an optimum geometry for best cavitational activity. In case of orifice, 1：3 of the ratio of diameter to length is best for cavitation and an increase in the total flow area increases the cavitational yield.

关键词： hydrodynamic cavitation (HC) computational fluid dynamics (CFD) cavitation number (CN) venture orifice

Unraveling the effect of uniaxial strain on thermoelectric properties of Mg2Si:A density functional theory study

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Chinese Physics b 2017年第6期26卷 301-306页

作者： Kulwinder Kaur Ranjan kumar Department of Physics Pan jab University Chandigarh-160014 India

In this work, the effect of uniaxial strain on electronic and thermoelectric properties of magnesium silicide using density functional theory（DFT） and boltzmann transport equations has been studied. We have found that the value of band gap increases with tensile strain and decreases with compressive strain. The variations of electrical conductivity,Seebeck coefficient, electronic thermal conductivity, and power factor with temperatures have been calculated. The Seebeck coefficient and power factor are observed to be modified strongly with strain. The value of power factor is found to be higher in comparison with the unstrained structure at 2% tensile strain. We have also calculated phonon dispersion, phonon density of states, specific heat at constant volume, and lattice thermal conductivity of material under uniaxial strain. The phonon properties and lattice thermal conductivity of Mg2Si under uniaxial strain have been explored first time in this report.

关键词： semiconductors thermoelectric and thermo magnetic effects electric and thermal conductivity density functional theory

DYNAMICAL bEHAVIOR OF AN INNOVATION DIFFUSION MODEL WITH INTRA-SPECIFIC COMPETITION bETWEEN COMPETING ADOPTERS

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Acta Mathematica Scientia 2022年第1期42卷 364-386页

作者： Rakesh kumar Anuj kumar SHARMA Govind Prasad SAHU Department of Applied Sciences Shaheed Bhagat Singh State UniversityFerozepurPunjab 152004India Department of Mathematics L.R.D.A.V.CollegeJagraonLudhianaPunjab 142026India Center for basic Sciences Pt Ravishankar Shukla UniversityRaipur(Chhattisgarh).India

In this paper,we proposed an innovation diffusion model with three compartments to investigate the diffusion of an innovation(product)in a particular *** model exhibits two equilibria,namely,the adopter-free and an interior *** existence and local stability of the adopter-free and interior equilibria are explored in terms of the effective basic Influence Number(bIN)R_(A).It is investigated that the adopter free steady-state is stable if R_(A)bifurcation parameter,we have been able to obtain the critical value ofτresponsible for the periodic solutions due to Hopf *** direction and stability analysis of bifurcating periodic solutions has been performed by using the arguments of normal form theory and the center manifold *** numerical simulations in the support of analytical results have been presented.

关键词： intra-specific competition basic influence number local stability Hopf-bifurcation normal form theory center manifold theorem

Magnesium based surface metal matrix composites by friction stir processing

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Journal of Magnesium and Alloys 2016年第1期4卷 52-61页

作者： b.Ratna Sunil G.Pradeep kumar Reddy Hemendra Patle Ravikumar Dumpala Department of Mechanical Engineering Rajiv Gandhi University of Knowledge Technologies(AP-IIIT)Nuzvid 520202India Department of Mechanical Engineering Vignana Bharathi Institute of TechnologyHyderabad 501301India Department of Mechanical Engineering Visvesvaraya National Institute of TechnologyNagpur 440010India

Surface metal matrix composites(MMCs)are a group of modern engineered materials where the surface of the material is modified by dispersing secondary phase in the form of particles or fibers and the core of the material experience no change in chemical composition and *** potential applications of the surface MMCs can be found in automotive,aerospace,biomedical and power ***,friction stir processing(FSP)technique has been gaining wide popularity in producing surface composites in solid state *** and its alloys being difficult to process metals also have been successfully processed by FSP to fabricate surface *** aim of the present paper is to provide a comprehensive summary of state-of-the-art in fabricating magnesium based composites by *** of the secondary phase particles and grain refinement resulted from FSP on the properties of these composites is also discussed.

关键词： Surface composites Friction stir processing Hardness Light weight Magnesium alloys biomedical implants