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1

Failure analysis of laminated composite plate under hygro-thermo mechanical load and optimisation

Choudhury A., Mondal S. C., Sarkar S.

International Journal of Applied Mechanics and Engineering

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2019

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Vol. 24, no. 3

509--526

EN

Failure analysis of laminated composite plates for different mechanical, thermo mechanical and hygro-thermo mechanical loads for different ply thicknesses, stacking sequences, fiber orientation angles and composite material systems is presented in the paper. A comparative study of different failure theories is also presented in the paper. The effect of fiber orientation angles on the first ply failure load is also studied. A hybrid composite laminate is developed based on the first ply failure load which minimizes weight and cost. The last ply failure load based on fully discounted method is calculated for different stacking sequences. An optimum composite material system and laminate layup is studied for a targeted strength ratio which minimizes weight.

2

Study of memory effect in an economic order quantity model with quadratic type demand rate

Pakhira R., Ghosh U., Sarkar S.

Computational Methods in Science and Technology

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2019

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Vol. 25, No. 2

71--80

EN

The study of memory effect in an economic order quantity model has a great impact on the inventory system. Although business policy almost depends on the past experiences of the system, usually the classical inventory model does not include the past experience or memory effect, i.e. one important part of the system is ignored. Our purpose is to include memory or past experience in the inventory model. The purpose of this paper is to incorporate the existence of dynamic memory in an inventory model with shortage via fractional calculus. To derive the memory dependent inventory model associated with inventory holding cost, shortage cost has been developed. Analytical solution of the proposed inventory model has been solved via primal geometric programming method. Numerically long memory effect or short memory effect of the inventory system has been established. In this paper, an effort has also been made to compare the memory effect on the minimized total average cost and the optimal ordering interval using different numerical examples.

3

Reservoir's impact on the water chemistry of the Teesta River mountain course (Darjeeling Himalaya)

Wiejaczka Ł., Prokop P., Kozłowski R., Sarkar S.

Ecological Chemistry and Engineering. S

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2018

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Vol. 25, nr 1

73--88

EN

The article presents the role of the newly built reservoir in the formation of the hydrochemistry of water of the Teesta River (a tributary of the Brahmaputra) in its Himalayan course. Field research were performed in the post-monsoon season of the period 2013-2015. Sampling and measuring points were located in five points over 43 km of the Teesta River in the Darjeeling Himalaya. Analysis of water along of river longitudinal profile above and below the reservoir suggest that the reservoir caused decrease most of the basic ions concentrations (Cl−, K+, Na+, Mg2+, NO3− and PO43−). An inverse trend was observed only with respect to Ca2+, SO42− and NH4+. The dam does not influent on the F− concentration. The reservoir causes minor enrichment most of the heavy metals such Cu, Ni, Zn, Cr, Cd and Sr. The lower enrichment of Teesta water below the dam indicates the water self-purification processes for metals by the Teesta Reservoir. The changes of physicochemical properties and concentrations of ions caused by the reservoir are usually normalised by environmental factors before the Teesta River outlet from the Himalayas (within 15 km of the river).

4

Qualitative Analysis of Both Hyperbolic and Non-hyperbolic Equilibria of a SIRS Model with Logistic Growth Rate of Susceptibles and Inhibitory Effect in the Infection

Ghosh J. K., Ghosh U., Sarkar S.

Computational Methods in Science and Technology

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2018

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Vol. 24, No. 4

285--300

EN

This paper describes a SIRS model with the logistic growth rate of susceptible class. The effect of an inhibitory factor in the infection is also taken into consideration. We have analysed local as well as global stabilities of the equilibrium points (both hyperbolic and non-hyperbolic) of the system and investigated the Transcritical bifurcation at the disease free equilibrium point with respect to the inhibitory factor. The occurrence of Hopf bifurcation of the system is examined and it was observed that this Hopf bifurcation is either supercritical or subcritical depending on parameters. Some numerical simulations are carried out for the validity of theoretical results.

5

Global Stability Analysis of Logistically Grown SIR Model with Loss of Immunity, Inhibitory Effect, Crowding Effect and its Protection Measure

Ghosh U., Sarkar S.

Computational Methods in Science and Technology

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2018

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Vol. 24, No. 2

125--141

EN

In this paper we have considered an SIR model with logistically grown susceptible in which the rate of incidence is directly affected by the inhibitory factors of both susceptible and infected populations and the protection measure for the infected class. Permanence of the solutions, global stability and bifurcation analysis in the neighborhood of equilibrium points has been investigated here. The Center manifold theory is used to find the direction of bifurcations. Finally numerical simulation is carried out to justify the theoretical findings.

6

Effects of Hall current on unsteady hydromagnetic free convection flow past an impulsively moving vertical plate with Newtonian heating

Seth G. S., Sarkar S., Sharma R.

International Journal of Applied Mechanics and Engineering

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2016

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Vol. 21, no. 1

187--203

EN

An investigation of unsteady hydromagnetic free convection flow of a viscous, incompressible and electrically conducting fluid past an impulsively moving vertical plate with Newtonian surface heating embedded in a porous medium taking into account the effects of Hall current is carried out. The governing partial differential equations are first subjected to the Laplace transformation and then inverted numerically using INVLAP routine of Matlab. The governing partial differential equations are also solved numerically by the Crank-Nicolson implicit finite difference scheme and a comparison has been provided between the two solutions. The numerical solutions for velocity and temperature are plotted graphically whereas the numerical results of skin friction and the Nusselt number are presented in tabular form for various parameters of interest. The present solution in special case is compared with a previously obtained solution and is found to be in excellent agreement.

7

Analytical Solutions of Classical and Fractional KP-Burger Equation and Coupled KdV Equation

Ghosh U., Sarkar S., Das S.

Computational Methods in Science and Technology

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2016

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Vol. 22, No. 3

143--152

EN

Development of new analytical and numerical methods and their applications for solving non-linear partial differential equations (both classical and fractional) is a rising field of Applied Mathematical research because of its applications in Physical, Biological and Social Sciences. In this paper we have used a generalized Tanh method to find the exact solution of KP-Burger equation and coupled KdV equation. The fractional Sub-equation method has been used to find the solution of fractional KP-Burger equation and fractional coupled KdV equations. The exact solution obtained by the fractional sub-equation method reduces to classical solution when the order of fractional derivative tends to one. Finally numerical simulation has been done. The numerical simulation justifies that the solutions of two fractional differential equations reduce to shock solution for KP-Burger equation and soliton solution for coupled KdV equations when the order of derivative tends to one.

8

Time-averaged Turbulent Flow Characteristics over a Highly Spatially Heterogeneous Gravel-Bed

Sarkar S.

Acta Geophysica

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2016

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Vol. 64, no. 5

1797--1824

EN

The present study focuses on the time-averaged turbulence characteristics over a highly spatially-heterogeneous gravel-bed. The timeaveraged streamwise velocity, Reynolds shear and normal stresses, turbulent kinetic energy, higher-order moments of velocity fluctuations, length scales, and the turbulent bursting were measured over a gravel-bed with an array of larger gravels. It was observed that the turbulence characteristics do not vary significantly above the crest level of the array as compared to those below the array. The nondimensional streamwise velocity decreases considerably with a decrease in depth below the array. Below the array, the Reynolds shear stress (RSS) deviates from the gravity-law of RSS distributions. Turbulence intensities reduce below the crest level of the gravel-bed. The third-order moments of velocity fluctuations increase below the crest level of the gravel-bed and give a clear indication of sweeps as the predominating event which were further verified with the quadrant analysis plots. The turbulent length scales values change significantly below the crest level of the gravel-bed.

9

Seismic and non-seismic soft-sediment deformation structures in the Proterozoic Bhander Limestone, central India

Sarkar S., Choudhuri A., Banerjee S., Van Loon A. J., Bose P. K.

Geologos

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2014

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Vol. 20, No. 2

89--103

EN

Numerous soft-sediment deformation structures occur within the Proterozoic Bhander Limestone of an intracratonic sag basin in a 750 m long section along the Thomas River, near Maihar, central India. Part of these deformation structures have most probably a non-seismic origin, but other structures are interpreted as resulting from earthquake-induced shocks. These seismic structures are concentrated in a 60 cm thick interval, which is interpreted as three stacked seismites. These three seismites are traceable over the entire length of the section. They divide the sedimentary succession in a lower part (including the seismites) deposited in a hypersaline lagoon, and an upper open-marine (shelf) part. Most of the soft-sediment deformations outside the seismite interval occur in a lagoonal intraclastic and muddy facies association. The SSDS within the seismite interval show a lateral continuity. They record simultaneous fluidisation and liquefaction. The bases of each of the three composing seismite bands are defined by small-scale shear folds, probably recording an earthquake and aftershocks. The presence of the three seismite bands at the boundary between the lagoonal and the overlying open-marine oolitic facies association suggests that the seismic event also triggered basin subsidence.

10

MHD natural convection flow with radiative heat transfer past an impulsively moving vertical plate with ramped temperature in the presence of hall current and thermal diffusion

Seth G. S., Mahato G. K., Sarkar S.

International Journal of Applied Mechanics and Engineering

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2013

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Vol. 18, no. 4

1201--1220

EN

An investigation on an unsteady MHD natural convection flow with radiative heat transfer of a viscous, incompressible, electrically conducting and optically thick fluid past an impulsively moving vertical plate with ramped temperature in a porous medium in the presence of a Hall current and thermal diffusion is carried out. An exact solution of momentum and energy equations, under Boussinesq and Rosseland approximations, is obtained in a closed form by the Laplace transform technique for both ramped temperature and isothermal plates. Expressions for the skin friction and Nusselt number for both ramped temperature and isothermal plates are also derived. The numerical values of fluid velocity and fluid temperature are displayed graphically versus the boundary layer coordinate y for various values of pertinent flow parameters for both ramped temperature and isothermal plates. The numerical values of the skin friction due to primary and secondary flows are presented in tabular form for various values of pertinent flow parameters.