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- Publication1,2,4,5-Tetrazines(01-01-2021)
;Chaitanya, ManthenaSubstituted 1,2,4,5-tetrazine is one of the important heterocyclic compounds that found widespread application in biological, industrial applications and utilized as a ligand in the synthesis of various metal complexes and metal-organic frameworks. This article will describe the recent theoretical and experimental studies, developments in the synthesis of novel 1,2,4,5-tetrazine derivatives, and the applications of 1,2,4,5-tetrazines from 2008 to 2018. - Publication1-D mathematical modeling of a diesel oxidation catalyst for transient hot start drive cycle(11-09-2020)
;Nair, SreeharshThe need to obey with increasingly stringent emission regulations has amplified the importance of after treatment devices, and therefore, reliable tools need to be developed for the evolution of better aftertreatment devices. Even though the upcoming regulations paved the way for improved combustion engines, their high carbon monoxide and hydrocarbon emissions increased the load on catalytic converters. Numerical modeling is one such tool which is extremely useful in providing the basic information which helps in designing the reactor, understanding its operation, and predicting the performance. In this context, the utmost aim of the numerical modeling is to simulate the driving cycle where inlet conditions to the catalytic converter vary with respect to time. Such a simulation must include the calculations of transient temperature-field of the monolith substrate and converter-out mass emissions. In this paper, a one-dimensional mathematical modeling of an oxidation catalyst has been implemented to simulate a hot start New European Drive Cycle (NEDC). The transient engine data was taken from the literature, and the measured instantaneous traces at the outlet of the catalyst were compared with the model predictions. This model has been developed to investigate the CO conversion performance of the catalyst. The comparison between model predictions and experiments has shown a satisfactory agreement in terms of both substrate temperature and CO emission at the catalyst outlet, confirming the effectiveness of the methodology applied. The reliability of the 1-D model was also proved with the probability density function of the conversion efficiency. - Publication2D Immersed Boundary Solver for Compressible Laminar Flows(01-01-2021)
;Rangan, KasturiIn this paper, an immersed-boundary method developed for compressible viscous flows is further improved to account for better mass conservation and address numerical instabilities associated with the velocity reconstruction. The 2D embedded object is represented as a set of line segments along with their outward unit normal vectors. A forcing method that leverages the finite-volume approach is used, wherein the solution at cell interface that lie near the boundaries of the embedded solid is reconstructed. A cut-cell type approach is proposed to the determine the effective flow through area of a cell face that is intersected by the immersed boundary to improve mass conservation; however, the boundary of the embedded object is not reconstructed in its entirety. This method shall is validated for supersonic inviscid flow past a bump in a channel and a circular cylinder, transonic viscous flow past a NACA0012 airfoil and supersonic viscous flow past a circular cylinder. The results are compared with simulations from literature using contours of flow properties, surface pressure and show fair to good agreement. - Publication2D MoS2 for sweat based biosensor application(05-11-2020)
;Chithra Lekha, P. ;Satheeshkumar, E.Chandra, T. S.The MoS2 2D nanosheets prepared by the hydrothermal method are characterized for its structural and morphological features. The structural studies show the pure form of MoS2 with hexagonal phase. The morphological study done with Tunnelling Electron Microscope shows that there are 6 to 10 2D atomic layers of MoS2. The sensitivity of this 2D MoS2towards Sodium ion was done using Cyclic Voltammetry. The results confirm that 2D MoS2modified Carbon electrodes are good candidates for selective sensing of sodium ion in sweat. The sensing mechanism is explained. - Publication3D Computational Studies of Flapping Wing in Frontal Gusty Shear Flow(01-01-2021)
;De Manabendra, M. ;Mathur, J. S.The present paper reports findings of the 3D computational studies of the effect of frontal gusty shear flow on the force patterns of a flapping wing. A rigid wing with semi-elliptical wing planform with asymmetric 1 DoF flapping kinematics was exposed to a gusty shear flow. The shear gradient of the flow was varied from −10 to +10 in steps of 5. Computation studies were carried out for Re = 150 which lies in the typical flight Reynolds number range of natural flyers like a fruit fly and anthropogenic flyers like a Pico Aerial Vehicle. 3D, unsteady, laminar, and incompressible Navier-Stokes equations were solved using finite volume formulation based commercial code ANSYS Fluent. Wing kinematics and gusty inflow conditions were modelled into the solver by User Defined Functions (UDFs). Wing motion was simulated using the dynamic meshing technique. The effect due to variation in the frontal inflow condition was studied quantitatively and qualitatively. Comparisons of the instantaneous and gust cycle averaged forces and moment coefficients about the wing root mid chord point and 3D phase space projections of the forces and moment coefficients was carried out. Qualitative studies were carried out by comparing the static pressure over both the surfaces of the wing and the vortex patterns near the flapping wing using λ2–criteria. It was observed from these studies that negative shear gradient resulted in a rise in the vertical force and moment and a minor reduction in the horizontal force. Positive shear gradient resulted in a minor rise in horizontal force and a significant reduction in vertical force and moment. - Publication3D Crustal Velocity Model for Ground Motion Simulations in North-East India(01-01-2021)
;Sangeetha, S. ;Dhanya, J.The present study focuses on developing a 3D crustal velocity model and applying it to perform ground motion simulations for North East India. The study region encompasses area between 89°E to 97°E longitude and 22°N to 30°N latitude. The calibration of the material property is based on 48 shear wave profiles available for the region along with the geotectonic features reported in the literature. The 3D material model arrived from the study is implemented in a finite element framework for ground motion simulations. The developed model is validated using the strong motion data available for four events; 1988 Mw 7.2 India–Bangladesh earthquake, 2011 Mw 6.3 India–Myanmar earthquake, 2013 Mw 5.5 Assam earthquake and Mw 5.2 Bhutan earthquake. The simulations are able to capture the prominent features of the recorded data up to 2Hz. Hence, the developed model can be implemented for estimating ground motions (< 2Hz) in the north eastern region of India. The simulated results can be used to estimate region-specific hazard and the displacement-based design of structures. - Publication3D Ground Response Analysis of Simplified Kutch Basin by Spectral Element Method(01-02-2020)
;Vijaya, R.; Mazzieri, IlarioThe damage pattern observed during the 1819 Kutch earthquake and 2001 Bhuj earthquake of magnitude Mw>7.7 in India implied the significance of the effect of Kutch basin on seismic ground motion. In the present study, the Kutch rift basin is modeled as a simplified rectangular basin of size 150km × 90km × 1.5km. The shear wave velocity of the Kutch region varies from 300m/s at the surface to 800m/s at the depth of 60m. Three-dimensional ground response analysis is carried out for the simplified Kutch basin subjected to ricker wave, using the spectral element code SPEED. The soil medium is modeled through visco-elastic soil model, where the damping is represented by Quality factor. It is found out from the numerical analysis that maximum amplification of 3.6 times occurs at the corner of the basin where interference of waves reflected from multiple edges happen. The long period structures with fundamental period in the range of 1.5-2.5s located near the basin edge are found to be significantly affected by the basin effect. - Publication3D printing of human anatomical models for preoperative surgical planning(01-01-2020)
;Paramasivam, V. ;Sindhu, ;Singh, G.Rapid Prototyping (RP) is an emerging technology, especially in a Three-Dimensional Printing (3DP) application. 3DP is used in many fields such as aeronautical, automotive, architecture, medical, and many others. 3DP can be effectively used in anatomical education for medical students who are pursuing their undergraduate degrees.It can also be used for pre-operative surgical planning by experts before surgery. Some complex organs of the human body which cannot be seen visible even after dissection of the cadaver can be printed using a 3D printer which provides haptic studies on organs and bones to students. These 3D printed parts can be used in pre-operative planning such as analysis and diagnosis formulation of affected organs. Further, it can be used in explaining the operative procedures to patients which helps them to understand and co-operate with the medical procedures. Therefore, this project aims at 3DP of complex organs and bones for anatomical studies and pre-operative planning procedures. As a first step in the project, some of the human bones were printed and analyzed for its quality. - Publication3D seismic wave amplification in the Indo-Gangetic basin from spectral element simulations(01-02-2020)
;Jayalakshmi, S. ;Dhanya, J.; Martin Mai, P.This study investigates seismic wave amplification effects in the Indo-Gangetic (IG) basin for possible large earthquakes in the region using spectral-element simulations. The Indo-Gangetic basin is a large and deep sedimentary basin that covers the northern part of India, in which several mega-cities are located, including the capital city of New Delhi. The seismicity in the region due to presence of many active tectonic faults is an important matter of concern for engineers. The damage caused in a future large earthquake could affect a huge population and hinder the development of numerous large-scale industrial establishments. Due to local soil conditions and the structural complexity of the sedimentary basin, seismic wave amplification is expected. However, the absence of seismic data for large earthquakes and limited knowledge of the structure of the basin poses challenge in estimating shaking amplifications. Therefore, we model the 3D structure of the basin using Spectral Finite Element method (Specfem3D) including the topography of the Himalayan mountains, and compute synthetic seismograms for a suite of simulated rupture scenarios. First, we use two past earthquakes in the basin to calibrate our 3D model by comparing the simulated ground motions with the recorded data. Later, we consider realizations of potential future large earthquake (Mw 7.1), by generating different kinematic rupture models. We simulate earthquake scenarios for different source parameters to quantify the statistics of expected ground shaking levels. We then infer seismic wave amplification as a function of both frequency and basin depth for complex seismic sources. Our results indicate a maximum amplification of 16 in Peak Ground Velocity (PGV) and 19–35 in Spectral Accelerations (Sa) at long periods. The results presented in this study may be useful for engineers to predict ground motions for future large earthquakes in absence of any available seismicity data. - Publication3D Simulation of Wave Slamming on a Horizontal Deck Using WCSPH(01-01-2021)
;Sasikala, N.; Manasseh, RichardWave slamming induces extremely high loads to offshore structures and ships whether, due to wave impact on the deck of offshore structure or due to moving bodies such as ships and air crafts hitting the water surface. During slamming wave impact, a localized high pressure will generate at the point of incidence. This very high pressure experienced by the bottom of deck plate is difficult to predict. In this paper, numerical simulation of wave slamming on offshore platform deck structures in incident waves is carried out using weakly compressible smoothed particle hydrodynamics (WCSPH). Pressure values in SPH are very sensitive to errors in the treatment of boundary conditions. Hence, two types of boundary conditions are tried for this slamming problem: repulsive and dynamic boundary conditions. The pressure values on the center regions of the structure are observed from the SPH generated pressure contour lines, to be larger than the values on the surrounding parts. - Publication3d sph simulation of wave interaction between wave energy converters: Towards optimum wave power absorption in wave farms(01-01-2020)
;Sasikala, N.; Manasseh, RichardOcean waves are one of the sustainable resources of renewable energy for carbon-free electricity. For cost-effective commercial-scale projects, Wave Energy Converters (WECs) are deployed in arrays with optimum spacing as an alternative for a large (oscillatory) device in isolation. It has been found that when the wave excitation frequency is close to the resonant frequency of the WEC, the efficiency factor of energy farms, called q-factor, increases with the oscillation amplitude of the device. It has been found that the maximum absorbed energy of WECs depends directly on array configuration as that the radiated and incident wave fields interfere to direct the energy flux in the ocean towards the floating bodies. In this paper, the fully nonlinear interaction between two 3D floating bodies in close proximity and excited near its' resonance is studied using Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH). Apart from the calculations of q factor, hydrodynamic forces acting on the floating bodies and their dynamic responses are also calculated. An optimum array of WECs is proposed. - Publication4-E (Energy-Exergy-Environment-Economic) analyses of integrated solar powered jaggery production plant with different pan configurations(01-02-2020)
;Venkata Sai, P.Conventional jaggery making process utilizes the bagasse for boiling of sugar cane juice which releases pollutants into the atmosphere and high particulate matter from these emissions causes air pollution. In this article, solar powered jaggery industry with freeze pre-concentration is proposed with conventional and modified heating pans. The system performance, environmental impacts and economic feasibility were assessed by carrying out 4E (Energy-Exergy-Environment-Economic) analyses using the developed mathematical model. These systems were designed to produce 300 kg of jaggery per day when operated for 7.5 h in 3 batches with average solar direct normal irradation of 662 W/m2 and 343 °C. These systems are integrated with auxiliary heating for uninterrupted production in the absence of sunlight. These systems can mitigate nearly 2015.95 to 3062.15 tons of CO2 emission during its 25 years of lifespan under 300 clear days of operation each year. Jaggery produced by this technique is rich in its colour and completely safe for human consumption as no artificial clarificants are used. Amount invested in these systems can be recovered in a span of 12.03 to 13.45 years for jaggery selling price of USD.0.514/kg or INR.36/kg. - Publication67PIN-33PT relaxor ferroelectric as energy storage device for pulsed power technologies(05-11-2020)
;Ramesh, G.Chithra Lekha, P.The ferroelectrics with high efficiency and excellent energy storage density are good candidate for energy storage devices in pulsed power technologies. Single phase morphotrophic composition of 0.67PIN-0.33PT is prepared by solid state method. Structural analysis with Rietveld refinement indicates that both R3m and P4mm phases coexist in this system. The remnant polarization (Pr) decreases above depolarization temperature (Td) ~ 100oC. Above Td macro-ferroelectric domains breaks into micro domains. The efficiency and recoverable energy storage density (Wrec) increases linearly above Td, making 0.67PIN-0.33PT a suitable material for energy storage in pulsed power technologies. - PublicationA -Fractal Rational Functions and Their Positivity Aspects(01-01-2021)
;Katiyar, S. K.Coalescence hidden variable fractal interpolation function (CHFIF) proves more versatile than classical interpolant and fractal interpolation function (FIF). Using rational functions and CHFIF, a general construction of A-fractal rational functions is introduced for the first time in the literature. This construction of A-fractal rational function also allows us to insert shape parameters for positivity-preserving univariate interpolation. The convergence analysis of the proposed scheme is established. With suitably chosen numerical examples and graphs, the effectiveness of the positivity-preserving interpolation scheme is illustrated. - PublicationA 2.5-5GHz injection-locked clock multiplier with embedded phase interpolator in 65nm CMOS(01-01-2020)
;Gautam, R. ;Bandarupalli, Jaya DeepthiWe present a wide-range ring oscillator based injection-locked clock multiplier with an embedded phase interpolator. The pseudo-differential ring oscillator employs current-starved inverters with a tunable capacitor load. The inverter delays are controlled to change the output phase while retaining the output frequency and jitter. Designed in a 65nm CMOS process, the clock multiplier uses a 312.5MHz reference clock and generates a 2.5-5.0GHz output clock when simulated with RC-extracted parasitics. The output clock phase can be controlled with 1.5° - 2° accuracy. At 5GHz output, the clock multiplier achieves an integrated rms jitter of 450-550fs across phase interpolation codes. Operating from 1.2V supply, it consumes 9.4mW at 5GHz that scales down to 4.3mW at 2.5GHz. - PublicationA 20 MHz Bandwidth Continuous-Time Delta-Sigma ADC Achieving 82.1 dB SNDR and > 00 dB SFDR Using a Time-Interleaved Virtual-Ground-Switched FIR Feedback DAC(01-03-2020)
;Baluni, AlokPavan, ShanthiWe present a single-bit continuous-time delta-sigma ADC that achieves 82.1 dB peak SNDR and 101.2 dB SFDR in a 65 nm CMOS process. The modulator, which operates with a sampling rate of 2.56 GHz, uses a 2x time-interleaved single-bit ADC in the loop. The key technique that enables low distortion is the use of a virtual-ground-switched resistive FIR feedback DAC, which operates in a 4x time-interleaved manner to reduce power dissipation. Interleaving artifacts, caused by mismatch, are addressed by mixed-signal calibration. The decimator is realized using polyphase techniques. The modulator and decimator consume 11.4mW and 15mW from a 1.1 V supply respectively. The Schreier FoM is 174.1 dB. - PublicationA 28.5µW all-analog voice-activity detector(01-01-2021)
;Mukherjee, Udita ;Halder, Tanmay ;Kannan, Anand ;Ghosh, SovanPavan, ShanthiWe describe the design principles behind an all-analog, neural-network-based voice activity detector (VAD). Our architecture, which uses a neural engine with weights that only take on values -1,0 and 1, achieves high accuracy along with low latency. Implemented in a 130 nm CMOS process, the VAD consumes 28.5 µW from a 1.8 V supply and achieves a latency of only 10 ms. The measured hit rate for speech(non-speech) is 94.3%(94.1%). - PublicationA 28GHz Reflective-Type Transmission-Line-Based Phase Shifter(01-12-2020)
;Kadam, Madhavi ;Kumar, AbhishekThis work presents a 28GHz reflection type transmission-line (TL) based phase shifter. The proposed architecture employs a completely passive approach to double the phase shift achievable using a TL when compared to conventional architectures. The phase shifter, along with a preceding low noise amplifier and buffer, is implemented in a 65nm CMOS process. The fabricated chip achieves a measured phase resolution of 11.25° at 28GHz, with an rms error of 3° and a total phase shift of 180°. The insertion loss of the phase shifter alone is 17dB. The active area of the entire phase shifter, including LNA and buffer is 0.41mm2. - PublicationA 3D Kinetic Distribution that Yields Observed Plasma Density in the Inner Van Allen Belt(01-01-2021)
;Maiti, SnehanshuRamachandran, HarishankarA steady-state distribution is obtained that approximately yields the observed plasma density profile of the inner Van Allen radiation belt. The model assumes a collisionless, magnetized plasma with zero electric field present. The inner Van Allen belt consists of a plasma comprising high-energy protons and relativistic electrons. The particle trajectories are obtained from the collisionless Lorentz Force equation for different initial distributions. The resulting steady-state distributions obtained after particles lost to the loss cone are eliminated and are used to generate the density profile. The distribution’s dependence on energy E and magnetic moment μ is adjusted to make the density profile agree with observations. For a distribution that is a function of energy times a function of magnetic moment, the calculation leads to the desired type of density profile. The kinetic distribution and the type of density profile obtained are presented. - PublicationA 52dB spurious-free dynamic range Ku-band LNA-mixer in a 130nm SiGe BiCMOS process(01-01-2020)
;Bhatia, Apoorva ;Darwhekar, Yogesh ;Mukherjee, Subhashish ;Martin, SamuelThis work presents a high-linearity, low noise figure, Ku-band (12 to 18 GHz) LNA-Mixer front-end block in a 130 nm SiGe BiCMOS process. A tuned transformer converts the single-ended output of the LNA to a differential signal at its secondary which is coupled directly to the tail nodes of the switching pairs of the Gilbert mixer. The LNA output sees a low impedance, and hence a low output voltage swing. This along with the absence of the extra trans-conductance stage in the mixer enhances its linearity. The measured gain, noise figure, and IIP3 at 16 GHz input are 12 dB, 4 dB, and 4 dBm. This gives a spurious-free dynamic range of 52 dB in a 4 GHz bandwidth. The chip consumes 272 mW and occupies 1 mm2