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Applied Mathematics and Mechanics(English Edition) 2017年第9期38卷 1313-1328页

作者： P.ALAM s.KUNDU s.gupta Department of Applied Mathematics Indian Institute of Technology(Indian School of Mines)Dhanbad 826004JhrkhandIndia

Propagation of a torsional wave in a doubly-layered half-space structure of an initially stressed heterogeneous viscoelastic layer sandwiched between a layer and a half-space of heterogeneous dry sandy media is studied. A closed form complex expression for the velocity profile is obtained under effective boundary conditions. The real part of the complex expression provides a dispersion equation, and the imaginary part yields a damping equation. The derived dispersion and damped equations are in well agreement with the classical Love wave condition. In addition, to study the effect of the dissipation factor, the attenuation coefficient, the sandy parameters, the initial stress, the hetero- geneity parameters, and the thickness ratio parameter, some noteworthy contemplations are made by numerical calculations and graphical visuals. The results of this paper may present a deeper insight into the behaviour of propagation phenomena in heterogeneous viscoelastic and heterogeneous dry sandy materials that can provide a theoretical guide for the design and optimization in the field of earthquake engineering. The study also reveals that the presence of a damping part due to viscoelasticity affects the torsional wave propagation significantly.

关键词： attenuation dissipation viscoelastic sandy heterogeneous initial stress,phase damping

Propagation of P-and s-waves in initially stressed gravitating half space

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Applied Mathematics and Mechanics(English Edition) 2013年第7期34卷 847-860页

作者： s. gupta s. K. VIsHWAKARMA Department of Applied Mathematics Indian School of Mines

The present paper contributes in studying the phase velocities of P- and s-waves in a half space subjected to a compressive initial stress and gravity field. The density and acceleration due to gravity vary quadratically along the depth. The dispersion equation is derived in a closed form. It is shown that the phase velocities depend not only on the initial stress, gravity, and direction of propagation but also on the inhomogeneity parameter associated with the density and acceleration due to gravity. Various particular cases are obtained, and the results match with the classical results. Numerical investigations on the phase velocities of P- and s-waves against the wave number are made for various sets of values of the material parameters, and the results are illustrated graphically. The graphical user interface model is developed to generalize the effect.

关键词： P-wave s-wave initial stress gravity half space graphical user interface

Microstructural image based convolutional neural networks for efficient prediction of full-field stress maps in short fiber polymer composites

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Defence Technology（防务技术） 2023年第6期24卷 58-82页

作者： s.gupta T.Mukhopadhyay V.Kushvaha Department of Civil Engineering Indian Institute of Technology JammuJ&KIndia Department of Aerospace Engineering Indian Institute of Technology KanpurUPIndia

The increased demand for superior materials has highlighted the need of investigating the mechanical properties of composites to achieve enhanced constitutive ***-reinforced polymer composites have emerged as an integral part of materials development with tailored mechanical ***,the complexity and heterogeneity of such composites make it considerably more challenging to have precise quantification of properties and attain an optimal design of structures through experimental and computational *** order to avoid the complex,cumbersome,and labor-intensive experimental and numerical modeling approaches,a machine learning(ML)model is proposed here such that it takes the microstructural image as input with a different range of Young’s modulus of carbon fibers and neat epoxy,and obtains output as visualization of the stress component s11(principal stress in the x-direction).For obtaining the training data of the ML model,a short carbon fiberfilled specimen under quasi-static tension is modeled based on 2D Representative Area Element(RAE)using finite element *** composite is inclusive of short carbon fibers with an aspect ratio of 7.5that are infilled in the epoxy systems at various random orientations and positions generated using the simple sequential Inhibition(ssI)*** study reveals that the pix2pix deep learning Convolutional Neural Network(CNN)model is robust enough to predict the stress fields in the composite for a given arrangement of short fibers filled in epoxy over the specified range of Young’s modulus with high *** CNN model achieves a correlation score of about 0.999 and L2 norm of less than 0.005 for a majority of the samples in the design spectrum,indicating excellent prediction *** this paper,we have focused on the stage-wise chronological development of the CNN model with optimized performance for predicting the full-field stress maps of the fiber-reinforced composite ***

关键词： Micromechanics of fiber-reinforced composites Machine learning assisted stress prediction Microstructural image-based machine learning CNN based stress analysis

Dispersion equation of magnetoelastic shear waves in irregular monoclinic layer

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Applied Mathematics and Mechanics(English Edition) 2011年第5期32卷 571-586页

作者： A.CHATTOPADHYAY s.gupta s.A.sAHU A.K.sINGH Department of Applied Mathematics Indian school of Mines

This paper studies the propagation of horizontally polarized shear waves in an internal magnetoelastic monoclinic stratum with irregularity in lower interface. The stratum is sandwiched between two magnetoelastic monoclinic semi-infinite media. Dispersion equation is obtained in a closed form. In the absence of magnetic field and irregularity of the medium, the dispersion equation agrees with the equation of classical case in three layered media. The effects of magnetic field and size of irregularity on the phase velocity are depicted by means of graphs.

关键词： shear wave magnetoelastic monoclinic irregularity dispersion equation perturbation

Influence of linearly varying density and rigidity on torsional surface waves in inhomogeneous crustal layer

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Applied Mathematics and Mechanics(English Edition) 2012年第10期33卷 1239-1252页

作者： s.gupta s.KVIsHWAKARMA D.K.MAJHI s.KUNDU Department of Applied Mathematics Indian School of Mines

The present work deals with the possibility of propagation of torsional surface wave in an inhomogeneous crustal layer over an inhomogeneous half space. The layer has inhomogeneity which varies linearly with depth whereas the inhomogeneous half space exhibits inhomogeneity of three types, namely, exponential, quadratic, and hyperbolic discussed separately. The dispersion equation is deduced for each case in a closed form. For a layer over a homogeneous half space, the dispersion equation agrees with the equa- tion of the classical case. It is observed that the inhomogeneity factor due to linear variation in density in the inhomogeneous crustal layer decreases as the phase velocity increases, while the inhomogeneity factor in rigidity has the reverse effect on the phase velocity.

关键词： torsional wave phase velocity crustal layer exponential quadratic,hyperbolic

Effect of irregularity on the propagation of torsional surface waves in an initially stressed anisotropic poro-elastic layer

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Applied Mathematics and Mechanics(English Edition) 2010年第4期31卷 481-492页

作者： s.gupta A.CHATTOPADHYAY D.K.MAJHI Department of Applied Mathematics Indian School of Mines University

The paper studies the propagation of torsional surface waves in an initially stressed anisotropic poro-elastic layer over a semi-infinite heterogeneous half space with linearly varying rigidity and density due to irregularity at the interface. The irregularity is taken in the half space in the form of a rectangle. It is observed that torsional surface waves propagate in this assumed medium. In the absence of the irregularity, the velocity equation of the torsional surface wave is also obtained. For a layer over a homogeneous half space, the velocity of torsional surface waves coincides with that of the Love waves.

关键词： irregularity torsional surface waves anisotropic initial stress

Propagation of Love waves in non-homogeneous substratum over initially stressed heterogeneous half-space

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Applied Mathematics and Mechanics(English Edition) 2013年第2期34卷 249-258页

作者： s.gupta D.K.MAJHI s.KUNDU s.K.VIsHWAKARMA Department of Applied Mathematics Indian School of Mines

The paper studies the propagation of Love waves in a non-homogeneous substratum over an initially stressed heterogeneous half-space. The dispersion equation of phase velocity is derived. The velocities of Love waves are calculated numerically as a function of kH and presented in a number of graphs, where k is the wave number, and H is the thickness of the layer. The case of Gibson＇s half-space is also considered. It is observed that the speed of Love waves is finite in the vicinity of the surface of the half-space and vanishes as the depth increases for a particular wave number. It is also observed that an increase in compressive initial stresses causes decreases of Love waves velocity for the same frequency, and the tensile initial stress of small magnitude in the half-space causes increase of the velocity.

关键词： Love waves initial stress heterogeneous half-space Gibson's half-space,dispersion equation phase velocity

An Interacting Gauge Field Theoretic Model for Hodge Theory: Basic Canonical Brackets

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Communications in Theoretical Physics 2014年第6期61卷 715-728页

作者： R.Kumar s.gupta R.P.Malik Department of Physics Centre of Advanced Studies Banaras Hindu University DsT Centre for Interdisciplinary Mathematical sciences Faculty of Science Banaras Hindu University

We derive the basic canonical brackets amongst the creation and annihilation operators for a two(1 + 1)-dimensional(2D) gauge field theoretic model of an interacting Hodge theory where a U(1) gauge field(Aμ) is coupled with the fermionic Dirac fields(ψ andˉψ). In this derivation, we exploit the spin-statistics theorem, normal ordering and the strength of the underlying six infinitesimal continuous symmetries(and the concept of their generators) that are present in the theory. We do not use the definition of the canonical conjugate momenta(corresponding to the basic fields of the theory) anywhere in our whole discussion. Thus, we conjecture that our present approach provides an alternative to the canonical method of quantization for a class of gauge field theories that are physical examples of Hodge theory where the continuous symmetries(and corresponding generators) provide the physical realizations of the de Rham cohomological operators of differential geometry at the algebraic level.

关键词： continuous symmetries 2D QED with fermionic Dirac fields symmetry principles basic canoni-cal (anti)commutators creation and annihilation operators conserved charges as generators deRham cohomological operators Hodge theory

Effect of rigid boundary on propagation of torsional surface waves inporous elastic layer

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Applied Mathematics and Mechanics(English Edition) 2011年第3期32卷 327-338页

作者： s. gupta A. CHATTOPADHYAY D. K. MAJHI Department of Applied Mathematics Indian School of Mines

The paper presents the effect of a rigid boundary on the propagation of torsional surface waves in a porous elastic layer over a porous elastic half-space using the mechanics of the medium derived by Cowin and Nunziato （Cowin, s. C. and Nunziato, J. W. Linear elastic materials with voids. Journal of Elasticity, 13（2）, 125-147 （1983））. The velocity equation is derived, and the results are discussed. It is observed that there may be two torsional surface wave fronts in the medium whereas three wave fronts of torsional surface waves in the absence of the rigid boundary plane given by Dey et al. （Dey, s., gupta, s., gupta, A. K., Kar, s. K., and De, P. K. Propagation of torsional surface waves in an elastic layer with void pores over an elastic half-space with void pores. Tamkang Journal of science and Engineering, 6（4）, 241-249 （2003））. The results also reveal that in the porous layer, the Love wave is also available along with the torsional surface waves. It is remarkable that the phase speed of the Love wave in a porous layer with a rigid surface is different from that in a porous layer with a free surface. The torsional waves are observed to be dispersive in nature, and the velocity decreases as the oscillation frequency increases.

关键词： torsional surface wave Love wave rigid boundary porous wave front

Cylindrical gate all around schottky barrier MOsFET with insulated shallow extensions at source/drain for removal of ambipolarity:a novel approach

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Journal of semiconductors 2017年第12期38卷 42-47页

作者： Manoj Kumar Yogesh Pratap subhasis Haldar Mridula gupta R.s.gupta semiconductor Device Research Laboratory Department of Electronic ScienceUniversity of Delhi South CampusNew Delhi 110021India Department of Electronics shaheed Rajguru College for Applied sciences for Women University of DelhiNew Delhi 110021India Department of Physics Motilal Nehru CollegeUniversity of DelhiNew Delhi 110021India Department of Electronics and Communication Engineering Maharaja Agrasen Institute of TechnologyNew Delhi 110086India

In this paper TCAD-based simulation of a novel insulated shallow extension （IsE） cylindrical gate all around （CGAA） schottky barrier （sB） MOsFET has been reported, to eliminate the suicidal ambipolar behavior （bias-dependent OFF state leakage current） of conventional sB-CGAA MOsFET by blocking the metal-induced gap states as well as unwanted charge sharing between source/channel and drain/channel regions. This novel structure offers low barrier height at the source and offers high ON-state current. The IoN/Iovr： of IsE-CGAA-sB-MOs- FET increases by 1177 times and offers steeper subthreshold slope （-60 mV/decade）. However a little reduction in peak cut off frequency is observed and to further improve the cut-off frequency dual metal gate architecture has been employed and a comparative assessment of single metal gate, dual metal gate, single metal gate with IsE, and dual metal gate with IsE has been presented. The improved performance of schottky barrier CGAA MOsFET by the incorporation of IsE makes it an attractive candidate for CMOs digital circuit design. The numerical simulation is performed using the ATLAs-3D device simulator.

关键词： ATLAs-3D cylindrical gate all around dual metal gate insulated shallow extension schottky barrier