Department of Applied Mechanics

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Multiple cores in a tiled multi-core processor are connected using a network-on-chip mechanism. All these cores share the last-level cache (LLC). For large-sized LLCs, generally, non-uniform cache architecture design is considered, where the LLC is split into multiple slices. Accessing highly shared cache blocks from an LLC slice by several cores simultaneously results in congestion at the LLC, which in turn increases the access latency. To deal with this issue, we propose a congestion management technique in the LLC that equips the NoC router with small storage to keep a copy of heavily shared cache blocks. To identify highly shared cache blocks, we also propose a prediction classifier in the LLC controller. We implement our technique in Sniper, an architectural simulator for multi-core systems, and evaluate its effectiveness by running a set of parallel benchmarks. Our experimental results show that the proposed technique is effective in reducing the LLC access time. © 2020 IEEE.

Department of Computer Science and Engineering

World University root node

Proceedings - IEEE International Conference on Computer Design: VLSI in Computers and Processors

Router Buffer Caching for Managing Shared Cache Blocks in Tiled Multi-Core Processors

Conventional text-to-speech (TTS) synthesis requires extensive linguistic processing for producing quality output. The advent of end-to-end (E2E) systems has caused a relocation in the paradigm with better synthesized voices. However, hidden Markov model (HMM) based systems are still popular due to their fast synthesis time, robustness to less training data, and flexible adaptation of voice characteristics, speaking styles, and emotions. This paper proposes a technique that combines the classical parametric HMM-based TTS framework (HTS) with the neural-network-based Waveglow vocoder using histogram equalization (HEQ) in a low resource environment. The two paradigms are combined by performing HEQ across mel-spectrograms extracted from HTS generated audio and source spectra of training data. During testing, the synthesized mel-spectrograms are mapped to the source spectrograms using the learned HEQ. Experiments are carried out on Hindi male and female dataset of the Indic TTS database. Systems are evaluated based on degradation mean opinion scores (DMOS). Results indicate that the synthesis quality of the hybrid system is better than that of the conventional HTS system. These results are quite promising as they pave way to good quality TTS systems with less data compared to E2E systems. Copyright © 2020 ISCA

Department of Aerospace Engineering

Department Of Biotechnology

Proceedings of the Annual Conference of the International Speech Communication Association, INTERSPEECH

A hybrid HMM-Waveglow based text-to-speech synthesizer using histogram equalization for low resource Indian languages

Camber morphing is an effective way to control the lift generated in any airfoil and potentially improve airfoil efficiency (lift-drag ratio). This can be especially useful for fixed wing UAVs undergoing different flying manoeuvres and flight phases. This work investigates the aerodynamic characteristics of NACA0012 airfoil morphed by the Single Corrugated Variable Camber (SCVC) morphing and Double Corrugated Variable Camber (DCVC) morphing approach. The airfoil is reconstructed from the camber line using a Radial Basis Function (RBF) based interpolation method (J. H. S. Fincham and M. I. Friswell, “Aerodynamic optimisation of a camber morphing aerofoil,” Aerosp. Sci. Technol., 2015). The aerodynamic analysis is done by employing two different finite volume solvers: OpenFOAM and ANSYS-Fluent, and a panel method code (XFoil). Results reveal that the aerodynamic coefficients predicted by the two finite-volume solvers using a fully turbulent flow assumption are similar but differ from those predicted by XFoil. The aerodynamic performance of morphed airfoils are nearly equal or lower than that of the baseline airfoil at lower values of coefficient of lift whilst at large values of the morphed airfoils display superior aerodynamic performance. At identical morphing angles, the aerodynamic characteristics of SCVC and DCVC airfoils are almost identical. Finally, it is observed for a fixed angle of attack, that an optimum morphing angle exists for which the aerodynamic efficiency becomes maximum. © 2020, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

Department of Ocean Engineering

AIAA AVIATION 2020 FORUM

Numerical study of camber morphing in naca0012 airfoil

Multiphase materials, such as composite materials, exhibit multiple competing failure mechanisms during the growth of a macroscopic defect. For the simulation of the overall fracture process in such materials, we develop a two-phase spring network model that accounts for the architecture between the different components as well as the respective disorders in their failure characteristics. In the specific case of a plain weave architecture, we show that any offset between the layers reduces the delocalization of the stresses at the crack tip and thereby substantially lowers the strength and fracture toughness of the overall laminate. The avalanche statistics of the broken springs do not show a distinguishable dependence on the offsets between layers. The power-law exponents are found to be much smaller than that of disordered spring network models in the absence of a crack. A discussion is developed on the possibility of the avalanche statistics being those near breakdown. © 2020 American Physical Society.

Department of Mechanical Engineering

Fulltext

Physical Review E

Role of spatial patterns in fracture of disordered multiphase materials

Fluid–elastic systems nearing dynamic instabilities are known to be sensitive to fluctuations in fluid flow. A cantilever plate in axial flow with random temporal fluctuations, is examined numerically for its dynamical behaviour. The numerical model comprises of a nonlinear structural model for the flexible plate, coupled with unsteady lumped vortex model for the fluid forces. As the mean flow velocity is increased, the system transitions to limit cycle oscillations from a state of rest, through a regime of intermittent oscillations. The conditions for onset and disappearance of intermittency are discussed and are interpreted using stochastic bifurcation theories. While the onset of intermittency is found to be unaffected by the time scales of the flow fluctuations, they are observed to affect the length of the intermittency regime. The effect of plate flexibility on intermittency is also discussed. © 2019 Elsevier Ltd

GENERAL

Journal of Fluids and Structures

Intermittency in a cantilever plate in a randomly fluctuating fluid flow

The detrimental effect of porosity in cast turbine and compressor blades has been a major issue since long. Though there has been extensive development in casting technology and the incorporation of advanced strategies to reduce the defects, the complete preclusion of porosity in the cast products has not been achieved. The influence of porosity on the path of propagation of a crack has been studied in this work. Quasi-static tensile simulation was performed on polymethyl methacrylate specimens, using Extended Finite Element Method (XFEM). This was done to observe the changes in the crack propagation path due to the presence of macro porosity. The XFEM results were validated by experimental tensile testing on the same specimens. This serves as a pilot study to understand and predict the path of crack propagation in cast components such as turbine/compressor blades with inherent porosity. Â© 2019 Elsevier Ltd.

Materials Today: Proceedings

Study on the effect of porosity on crack propagation

Colour adaptation techniques are useful in extending the method of Twelve fringe photoelasticity (TFP) to solve problems in industries as one can minimise the generation of specific calibration tables for each experiment. Image artefacts affect the functioning of existing colour adaptation techniques affecting the fringe order demodulation. Colour transfer is a popular technique in the field of image processing to tackle colour mismatch between images. In this paper, the applicability of two colour transfer strategies in the context of TFP is explored, of which one is selected for implementation. A comparative study on the performance of the novel colour transfer method with the existing colour adaptation techniques is carried out. © 2019 Elsevier Ltd

Optics and Lasers in Engineering

Applicability of colour transfer techniques in Twelve fringe photoelasticity (TFP)

In this article, the effect of charge partitioning in a silicon-on-insulator lateral double-diffused metal-oxide-semiconductor (LDMOS) transistor on its nonlinearity model is investigated. It is found that the prediction of the third-order intermodulation distortion (IM3) depends on the model equivalent circuit (EC) and appropriate charge assignments at various nodes therein. The investigation is carried out using a highly accurate static model of LDMOS along with a couple of different charge-partitioning schemes in order to single out their effects on the nonlinearity model behavior. We observe that charge partitioning in a more flexible EC framework yields an improved IM3 prediction when compared with the TCAD simulated results. © 1963-2012 IEEE.

Department of Electrical Engineering

IEEE Transactions on Electron Devices

Effect of Charge Partitioning on IM3 Prediction in SOI-LDMOS Transistors

This study investigates the behavior of a damped, inelastic, sinusoidally forced impact oscillator which has its barrier placed such that the oscillator always vibrates under compression about its subharmonic resonant frequencies. The Poincaré sections at near subharmonic resonance conditions exhibit finger-shaped chaotic attractors, similar to the strange attractor mapping of Hénon and the ones found by Holmes in his study of chaotic resonances of a buckled beam. The number of such fingers are observed to increase as the barrier distance from the equilibrium is decreased. These chaotic states are interspersed with regimes of periodic behavior, with the periodicity being in accordance with well defined period adding laws. This study also focuses on the ordered behavior of the one-impact period-p orbits around the higher subharmonics of the oscillator. © 2020 World Scientific Publishing Company.

International Journal of Bifurcation and Chaos

Bifurcations in a Pre-Stressed, Harmonically Excited, Vibro-Impact Oscillator at Subharmonic Resonances

Crack growth kinetics in crystalline materials is examined both from the point of continuum mechanics and discrete dislocation dynamics. Kinetics ranging from the Griffith crack to continuous elastic-plastic cracks are analyzed. Initiation and propagation of incipient cracks require very high stresses and appropriate stress gradients. These can be obtained either by pre-existing notches, as is done in a typical American Society of Testing and Materials (ASTM) fatigue and fracture tests, or by in situ generated stress concentrations via dislocation pile-ups. Crack growth kinetics are also examined using the modified Kitagawa–Takahashi diagram to show the role of internal stresses and their gradients needed to sustain continuous crack growth. Incipient crack initiation and growth are also examined using discrete dislocation modeling. The analysis is supported by the experimental data available in the literature. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.