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Heat transfer in boundary layer stagnation-point flow towards a shrinking sheet with non-uniform heat flux

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Chinese Physics B 2013年第7期22卷 328-333页

作者： Krishnendu bhattacharyya Department of Mathematics The University of Burdwan

In this paper, the effect of non-uniform heat flux on heat transfer in boundary layer stagnation-point flow over a shrinking sheet is studied. The variable boundary heat fluxes are considered of two types： direct power-law variation with the distance along the sheet and inverse power-law variation with the distance. The governing partial differential equations （PDEs） are transformed into non linear self-similar ordinary differential equations （ODEs） by similarity transformations, and then those are solved using very efficient shooting method. The direct variation and inverse variation of heat flux along the sheet have completely different effects on the temperature distribution. Moreover, the heat transfer characteristics in the presence of non-uniform heat flux for several values of physical parameters are also found to be interesting.

关键词： non-uniform heat flux heat transfer stagnation-point flow shrinking sheet

Boundary Layer Flow and Heat Transfer over an Exponentially Shrinking Sheet

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Chinese Physics Letters 2011年第7期28卷 198-201页

作者： Krishnendu bhattacharyya Department of Mathematics the University of BurdwanBurdwan-713104West BengalIndia

An analysis is made to study boundary layer flow and heat transfer over an exponentially shrinking *** similarity transformations in exponential form,the governing boundary layer equations are transformed into self-similar nonlinear ordinary differential equations,which are then solved numerically using a very efficient shooting *** analysis reveals the conditions for the existence of steady boundary layer flow due to exponential shrinking of the sheet and it is found that when the mass suction parameter exceeds a certain critical value,steady flow is *** dual solutions for velocity and temperature distributions are *** increasing values of the mass suction parameter,the skin friction coefficient increases for the first solution and decreases for the second solution.

关键词： solution method exponential

Dual Solutions in Unsteady Stagnation-Point Flow over a Shrinking Sheet

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Chinese Physics Letters 2011年第8期28卷 165-168页

作者： Krishnendu bhattacharyya Department of Mathematics The University of BurdwanBurdwan-713104West BengalIndia

An analysis is made to study the dual nature of solution of unsteady stagnation-point flow due to a shrinking *** similarity transformations,the governing boundary layer equations are transformed into the self-similar nonlinear ordinary differential *** transformed equations are solved numerically using a very efficient shooting *** study reveals the conditions of existence,uniqueness and non-existence of unsteady similarity *** dual solutions for velocity distribution exist for certain values of velocity ratio parameter(c/a),and the increment in the unsteadiness parameter A increases the range of c/a where solution ***,with increasing A,the skin friction coefficient increases for the first solution and decreases for the second.

关键词： solution method unsteady

Simultaneous observations of a pair of kilohertz QPOs and a plausible 1860Hz QPO from an accreting neutron star system

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Research in Astronomy and Astrophysics 2010年第3期10卷 227-234页

作者： Sudip bhattacharyya Department of Astronomy and Astrophysics Tata Institute of Fundamental Research

We report an indication （3.22 or） of ≈ 1860 Hz quasi-periodic oscillations from a neutron star low-mass X-ray binary 4U 1636-536. If confirmed, this will be by far the highest frequency feature observed from an accreting neutron star system, and hence could be very useful in understanding such systems. This plausible timing feature was observed simultaneously with lower （≈ 585 Hz） and upper （≈ 904 Hz） kilohertz quasi-periodic oscillations. The two kilohertz quasi-periodic oscillation frequencies had a ratio of ≈ 1.5, and the frequency of the alleged ≈ 1860 Hz feature was close to the triple and the double values of these frequencies. This can be useful for constraining the models of all the three features. In particular, the ≈ 1860Hz feature could be （1） from a new and heretofore unknown class of quasi-periodic oscillations, or （2） the first observed overtone of lower or upper kilohertz quasi-periodic oscillations. Finally, we note that, although the relatively low significance of the ≈ 1860 Hz feature argues for caution, even a 3.22 σ feature at such a uniquely high frequency should be interesting enough to spur a systematic search in the archival data, as well as to scientifically motivate sufficiently large timing instruments for the next generation X-ray missions.

关键词： accretion accretion disks -- methods: data analysis -- relativity -- stars: neutron -- X-rays: binaries -- X-rays: individual (4U 1636-536)

Heat transfer for boundary layers with cross flow

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Chinese Physics B 2014年第2期23卷 327-332页

作者： Krishnendu bhattacharyya Ioan Pop Department of Mathematics The University of Burdwan Faculty of Mathematics Babes-Bolyai University

An analysis is presented to study the dual nature of solutions for the forced convective boundary layer flow and heat transfer in a cross flow with viscous dissipation terms in the energy equation. The governing equations are transformed into a set of three self-similar ordinary differential equations by similarity transformations. These equations are solved numerically using the very efficient shooting method. This study reveals that the dual solutions of the transformed similarity equations for velocity and temperature distributions exist for certain values of the moving parameter, Prandtl number, and Eckert numbers. The reverse heat flux is observed for larger Eckert numbers; that is, heat absorption at the wall occurs.

关键词： heat transfer boundary layer cross flow viscous dissipation dual solutions

Stress distribution variations during nanoindentation failure of hard coatings on silicon substrates

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Nanotechnology and Precision Engineering 2023年第4期6卷 1-10页

作者： Ritambhara Dash Kushal bhattacharyya Arnab S.bhattacharyya Department of Metallurgical and Materials Engineering Central University of JharkhandRanchi 835205India Department of Mechanical Engineering Netaji Subhash Engineering CollegeKolkata 700152India Centre of Excellence in Green and Efficient Energy Technology(CoE GEET) Central University of JharkhandRanchi 835205India

Regarding quality inspection of technologically important nanocomposite hard coatings based on Ti,B,Si,C,and N and bioceramics such as hydroxyapatite that are used in small-scale high-precision devices and bio-implants,it is essential to study the failure mechanisms associated with nanoindentation,such as fracture,delamination,and *** stress imposed by the indenter can affect the fracture morphology and the interfacial fracture energy,depending on indenter shape,substrate type,crystallographic properties,pre-existing flaws,internal microcracks,and *** here are finite-element-based fracture studies that provide insights into the different cracking mechanisms related to the aforementioned failure process,showing that the fracture morphology is affected by the interaction of different cracking *** interfacial fracture energy,toughness,and residual stress are calculated using existing models with minor adjustments,and it is found that increasing the indenter sharpness improves the shear stress distribution,making the coating more prone to *** on the prevailing type of stress,the stress distribution beneath the depression results in either crack formation or a dislocation pile-up leading to strain *** forms of resistances resulting from the indentation process are found to affect the tip–sample conduction,and because of its stronger induced plasticity than that of a Berkovich indenter tip,a sharper cube-corner tip produces more resistance.

关键词： Nanoindentation Hard film Finite-element analysis(FEA) Cracking mechanism Stress

Neutrino Mass Generation in SO(4) Model

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Communications in Theoretical Physics 2010年第8期54卷 305-307页

作者： Indranath bhattacharyya Department of Mathematics Govt.College of Engineering and Ceramic Technology

Generation of neutrino mass in SO（4） model is proposed here. The algebraic structure of SO （4） is same as to that ofSU（2）L x SU（2）R. It is shown that the spontaneous symmetry breaking results three massive as well as three massless gauge bosons. The standard model theory according to which there exist three massive gauge bosons and a massless one is emerged from this model. In the framework ofSU（2）L x SU（2）R a small Dirac neutrino mass is derived. It is also shown that such mass term may vanish with a special choice. The Majorana mass term is not considered here and thus in this model the neutrino mass does not follow seesaw structure.

关键词： left right symmetry S0(4) modei extension of electroweak gauge sectors neutrino mass generation Dirac neutrino mass

A Kenmotsu Metric as a *-conformal Yamabe Soliton with Torse Forming Potential Vector Field

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Acta Mathematica Sinica,English Series 2021年第12期37卷 1896-1908页

作者： Soumendu ROY Arindam bhattacharyya Department of Mathematics Jadavpur UniversityKolkata 700032India

The purpose of the present paper is to deliberate *-conformal Yamabe soliton,whose potential vector field is torse-forming on Kenmotsu ***,we have shown the nature of the soliton and find the scalar curvature when the manifold admitting *-conformal Yamabe soliton on Kenmotsu ***,we have evolved the characterization of the vector field when the manifold satisfies *-conformal Yamabe *** we have embellished some applications of vector field as torse-forming in terms of *-conformal Yamabe soliton on Kenmotsu *** have developed an example of *-conformal Yamabe soliton on 3-dimensional Kenmotsu manifold to prove our findings.

关键词： *-conformal Yamabe soliton torse forming vector field conformal Killing vector field Kenmotsu manifold

Electrical conductivity of the graphene nanoplatelets coated natural and synthetic fibres using electrophoretic deposition technique

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International Journal of Smart and Nano Materials 2018年第3期9卷 167-183,I0002页

作者： Hamid Souri Debes bhattacharyya Centre for Advanced Composite Materials Department of Mechanical EngineeringThe University of AucklandAucklandNew Zealand

Herein,electrically conductive natural and synthetic yarns through electrophoretic deposition(EPD)technique were fabricated.A parametric study on the conductivity enhancement of the yarns is carried out by Taguchi *** this method,the desirable conditions are determined by studying the effects of important parameters on the electrical conductivity of the yarns in the EPD coating *** on the L18 design of experiments table,the preferred combination of factors to obtain the highest electrical conductivity of the yarns is found by Taguchi *** addition,the Pareto ANOVA analysis is conducted to identify the major contributing factors on the electrical conductivity of the *** techniques,such as scanning electron microscopy(SEM),Fourier transformed infrared spectroscopy(FTIR)in attenuated total reflectance(ATR)mode,and thermogravimetric analysis(TGA)are utilised for better understanding the microstructure and physical *** powered by only 3 V,the maximum temperature of a Joule heated conductive sample based on natural fibre yarns reached 102°C in less than 25 s.

关键词： Graphene nanoplatelets electrical conductivity natural fibres electrothermal behaviour Taguchi method