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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

Sarkar D.,IIT KanpurUP | Saurav K.,IIT KanpurUP | Srivastava K.V.,IIT KanpurUP
European Microwave Week 2016: "Microwaves Everywhere", EuMW 2016 - Conference Proceedings; 46th European Microwave Conference, EuMC 2016 | Year: 2016

In this paper, a four element compact MIMO antenna system is proposed for dual-band (GSM/WLAN/WiFi/LTE) applications. Dual-band antenna characteristics is obtained by loading L-shaped monopoles with complementary split ring resonators (CSRR), which produce an antenna resonance in addition to the reference monopole mode. Inter-element isolation of more than 15 dB is achieved in both the operating bands. The four element MIMO configuration exhibits pattern diversity in both the bands due to the directional radiation characteristics of the dual-band antenna element. The proposed antenna has satisfactory performance in terms of MIMO parameters as envelope correlation coefficient (ECC) < 0.5, mean effective gain (MEG) ratio (MEGi/MEGj) ≈ 1, total active reflection coefficient (TARC) < -10 dB and average channel capacity loss (CCL) < 0.5 bits/s/Hz are obtained in both the working bands. Experimental results on the fabricated MIMO antenna prototype confirms the validity of the proposed design concept. © 2016 EuMA.

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

Mondal D.,IIT KanpurUP | Roy D.,IIT KanpurUP | Goswami D.,IIT KanpurUP
YSF 2015 - International Young Scientists Forum on Applied Physics | Year: 2015

We demonstrate control over two photon fluorescence (TPF) resonance energy transfer under femtosecond optically tweezed condition. We also extract information about the structure and dynamics of the trapped particles and their clusters as observed from the TPF decay times of the trapped multiple microspheres (0.50 μm size) by varying the polarization of the trapping laser. This micron to nano regime of the energy transfer process has provided us the necessary control over the molecular level energy transfer rate due to the different overlap integral of excitation and emission spectra of the dye that is coated on the surface of 1.0 μm polystyrene particles. Our background free detection method thus provides additional structural information about multiple trapping events. © 2015 IEEE.

Muthuchamy A.,Vellore Institute of Technology | Raja Annamalai A.,Vellore Institute of Technology | Agrawal D.K.,Pennsylvania State University | Upadhyaya A.,IIT KanpurUP
Materials Characterization | Year: 2016

The present study examines the effect of sintering temperature and heating mode on densification, microstructure and mechanical properties of Fe-P alloys. The green compacts were heated conventionally and in microwave under 95%N2-5%H2 (forming gas) at 1120 °C and 1250 °C for 60 min. Both the compositions (Fe-1.5P and Fe-3P in wt%) were found to couple well in microwave field with rapid heating (∼ 40 °C min-1) and resulted in reduction of overall processing time by about 90% in comparison of conventional heating. Microwave sintering resulted in higher densification in case of Fe-P alloys. Moreover, an important feature of microwave and conventionally sintered samples was that their microstructures exhibited distinctly rounded pores. This resulted into improved corrosion and mechanical properties in general. © 2016 Elsevier Inc. All rights reserved.

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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