IIT KanpurUP


IIT KanpurUP

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Das D.,IIT KanpurUP | Goswami D.,IIT KanpurUP
Optics InfoBase Conference Papers | Year: 2016

We show important applications of our imaging technique in visualizing the morphology as well as division of diatoms in aqueous solution. The technique involves the efficient detection of the auto-fluorescence from chloroplast and shell structure through laser scanning confocal microscopy. © OSA 2016.

Chandravanshi S.,IIT KanpurU.P. | Akhtar M.J.,IIT KanpurU.P.
Microwave and Optical Technology Letters | Year: 2017

An improved rectifier based on harmonic rejection filter with inter-digital capacitor for RF energy harvesting application is proposed. The designed circuit is fabricated on a low cost FR-4 substrate, and works at GSM/CDMA 900 MHz band. The measured maximum efficiency is 66.31% and maximum obtained power is 15.13 mW at 1.1 KΩ load value. The overall dimension of circuit is 80 × 45 × 1.6 mm3, which can be easily implemented in any device for energizing wireless sensor network. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:681–686, 2017. © 2017 Wiley Periodicals, Inc.

Raksharam,IIT KanpurUP | Dutta A.K.,IIT KanpurUP
Solid-State Electronics | Year: 2017

In this paper, a unified analytical model for the drain current of a symmetric Double-Gate Junctionless Field-Effect Transistor (DG-JLFET) is presented. The operation of the device has been classified into four modes: subthreshold, semi-depleted, accumulation, and hybrid; with the main focus of this work being on the accumulation mode, which has not been dealt with in detail so far in the literature. A physics-based model, using a simplified one-dimensional approach, has been developed for this mode, and it has been successfully integrated with the model for the hybrid mode. It also includes the effect of carrier mobility degradation due to the transverse electric field, which was hitherto missing in the earlier models reported in the literature. The piece-wise models have been unified using suitable interpolation functions. In addition, the model includes two most important short-channel effects pertaining to DG-JLFETs, namely the Drain Induced Barrier Lowering (DIBL) and the Subthreshold Swing (SS) degradation. The model is completely analytical, and is thus computationally highly efficient. The results of our model have shown an excellent match with those obtained from TCAD simulations for both long- and short-channel devices, as well as with the experimental data reported in the literature. © 2017 Elsevier Ltd

Guha A.,IIT KanpurUP | Udwadia F.E.,University of Southern California
Journal of Fluid Mechanics | Year: 2017

Using simple kinematics, we propose a general theory of linear wave interactions between the interfacial waves of a two-dimensional (2D), inviscid, multilayered fluid system. The strength of our formalism is that one does not have to specify the physics of the waves in advance. Wave interactions may lead to instabilities, which may or may not be of the familiar 'normal-mode' type. Contrary to intuition, the underlying dynamical system describing linear wave interactions is found to be nonlinear. Specifically, a saw-tooth jet profile with three interfaces possessing kinematic and geometric symmetry is explored. Fixed points of the system for different ranges of a Froude number like control parameter are derived, and their stability evaluated. Depending upon the initial condition and , the dynamical system may reveal transient growth, weakly positive Lyapunov exponents, as well as different nonlinear phenomena such as the formation of periodic and pseudo-periodic orbits. All these occur for those ranges of where normal-mode theory predicts neutral stability. Such rich nonlinear phenomena are not observed in a 2D dynamical system resulting from the two-wave problem, which reveals only stable and unstable nodes. © 2017 Cambridge University Press.

Ahmed N.,IIT KanpurUP | Dutta A.K.,IIT KanpurUP
Solid-State Electronics | Year: 2017

In this paper, we present a completely analytical model for the 2DEG concentration in AlGaN/GaN HEMTs as a function of gate bias, considering the donor-like trap states present at the metal/AlGaN interface to be the primary source of 2DEG carriers. To the best of our knowledge, this is a completely new contribution of this work. The electric field in the AlGaN layer is calculated using this model, which is further used to model the gate leakage current under reverse bias. We have modified the existing TTT (Thermionic Trap-Assisted Tunneling) current model, taking into account the effect of both metal/AlGaN interface traps as well as AlGaN bulk traps. The gate current under forward bias is also modeled using the existing thermionic emission model, approximating it by its Taylor series expansion. To take into account the effect of non-zero drain-source bias (VDS), an empirical fitting parameter is introduced in order to model the channel voltage in terms of VDS. The results of our models have been compared with the experimental data reported in the literature for three different devices, and the match is found to be excellent for both forward and reverse bias as well as for zero and non-zero VDS. © 2017 Elsevier Ltd

Sahoo S.K.,IIT KanpurU.P. | Katare K.K.,IIT KanpurU.P. | Biswas A.,IIT KanpurU.P.
Asia-Pacific Microwave Conference Proceedings, APMC | Year: 2017

In this paper, a planar dielectric phase correcting structure (PCS) along with partially reflecting surface (PRS) is used to enhance the gain of cylindrical dielectric resonator antenna (CDRA) up to 14.5 dBi at the design frequency of 10 GHz. PRS loaded CDRA forms electromagnetic bandgap resonator antenna (ERA). ERA gives high gain due to presence of multiple reflections between completely reflecting ground plane surface and partially reflecting dielectric surface. Non-uniform phase distribution of electric field over the ERA aperture generally degrades the radiation characteristics of antenna. In order to achieve further gain improvement, planar multi-dielectric PCS is used to transform non-uniform phase distribution to relatively uniform phase distribution over the ERA aperture. © 2016 IEEE.

Bhowmick S.,IIT KanpurUP | Mishra S.K.,IIT KanpurUP
Soil Dynamics and Earthquake Engineering | Year: 2017

A new variant of ferrous Shape Memory Alloy with Fe-Ni-Co-Al-Ta-B (FNCATB) composition have been proposed that shows huge superelasticity under a wide temperature range. This shows the potential as a much superior and economic alternative for seismic applications. With this as the eventual goal, the FNCATB wires are employed as restrainers in conjunction with the pure-friction bearing, referred as super-elastic Friction Base Isolator (S-FBI). The FNCATB based S-FBI shows superior performance over the conventional Frictional Pendulum System (FPS) and the Nitinol based S-FBI, with a much less (1/17-th) volume requirement, estimated from the pertinent isolator parameters, the optimal choice of which are obtained through ad hoc optimization. The performance assessment is based on nonlinear dynamic analysis under a suite of recorded near-fault ground motions. An experimental force-deformation dataset for the FNCATB are fitted in the existing Wilde's model to describe the super-elasticity. The FNCATB S-FBI offers considerable improvement, either in the isolation efficiency or reducing the base displacement with slight or no compromise in the other. The performances are also supported by a set of performance indices adopted from benchmark seismic control problem. An energetic assessment also corroborate to these findings. A Short Time Fourier Transform (STFT) based analysis of floor accelerations demonstrate the superior high frequency suppression characteristics of the FNCATB over the Friction Pendulum System (FPS) and Nitinol based S-FBI. The ferrous composition while coupled with less volume requirement implies to superior economic viability that can be studied through detailed cost-benefit analysis. © 2017 Elsevier Ltd

Kulkarni K.,IIT KanpurU.P. | Chauhan G.P.S.,IIT KanpurU.P.
AIP Advances | Year: 2015

Interdiffusion was investigated at 1000°C in a quaternary Fe-Ni-Co-Cr system, which is an essential constituent of many high-entropy alloys. The relative values of main and cross interdiffusion coefficients determined from concentrations and interdiffusion fluxes developed in a single diffusion couple indicate that significant diffusional interactions exist in this system. Thermodynamic interactions between the binary constituents were analyzed based on the activity coefficient relations and it is shown that the observed diffusional interactions of a component with others are consistent with relative thermodynamic interactions between them. © 2015 Author(s).

Chakraborty S.,IIT KanpurUP | Roy K.,IIT KanpurUP | Ray-Chaudhuri S.,IIT KanpurUP
Engineering Structures | Year: 2016

This study addresses the design of nonlinear elastic springs that render an effective re-centering mechanism for a flat sliding base isolation system. A nonlinear stiffening behavior of the elastic spring offers added advantage of re-centering mechanism. The proposed spring-sliding system works in a similar fashion as that of the flat sliding base isolation system supplemented with re-centering mechanism for small to medium level of shaking. For high intensity shaking, the proposed system minimizes the peak bearing displacement in addition to keeping the bearing residual displacement close to zero. To demonstrate the concept of the proposed isolation system, a numerical study is conducted with a steel moment-resisting frame when subjected to ground motions of varying hazard levels. It has been found from this study that the proposed spring-sliding device is effective in limiting the peak bearing displacement and making the residual bearing displacement negligible for varying hazard levels. It has also been observed that the presence of nonlinear spring is in general beneficial in reducing the horizontal peak floor acceleration in comparison to the sliding only for ground motion with moderate hazard levels (i.e., 10% in 50 years). © 2016 Elsevier Ltd

Khan A.,IIT KanpurUP | Dutt P.,IIT KanpurUP | Upadhyay C.S.,IIT KanpurUP
Computers and Mathematics with Applications | Year: 2015

Several methods have been proposed in the literature for solving the Black-Scholes equation for European Options. The method proposed in the current study achieves spectral accuracy in both space and time. The method is based on minimization of a functional given in terms of the sum of squares of the residuals in the partial differential equation and initial condition in different Sobolev norms, and a term which measures the jump in the function and its derivatives across inter-element boundaries in appropriate fractional Sobolev norms. To obtain values of the solution and its derivatives the initial condition is mollified and the computed solution is post processed. Error estimates are obtained for this method. Specific numerical examples are given to show the efficiency of this method. © 2015 Elsevier Ltd.

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