(SoE) School of Engineering

<p>Shiv Nadar University is a comprehensive, multidisciplinary, research-focused, and student-centric University offering a full range of academic programs at the undergraduate, postgraduate and doctoral level. With state-of-the-art infrastructure, the University comprises of academic wings, sophisticated labs, international standard sports facilities, amphitheaters, auditorium, conference rooms and smart classrooms. The University&rsquo;s goal is to become internationally recognized for the quality of its research and creative endeavors and their applicability to improving quality of life, generating new insights and expanding the boundaries of human knowledge creativity. Committed to excellence in teaching, research and service, the University aims to serve the higher education needs of India and the world beyond.</p>

Shiv Nadar University

Epoxy matrix reinforced with conventional microscale short carbon fibers (SCFs) and carbon nanotubes (CNTs) form a hybrid material system where the characteristic length scales of SCFs and CNTs differ by multiple orders of magnitude. Several recent studies show that the addition of CNTs into a non-conducting polymer matrix improves both structural performance such as modulus, strength and fracture toughness and functional response such as electrical and thermal conductivities of the resulting nano-composite. In this study, a physics-based hierarchical multiscale modeling approach is presented to calculate the effective electrical conductivity of SCF-CNT-polymer hybrid composites. A dual step procedure is adopted to couple the effects of nano- and micro-scale so as to estimate the effective electrical properties of the composite. First, CNTs are dispersed into the non-conducting polymer matrix to obtain an electrically conductive CNT-epoxy composite. The effective electrical conductivity of CNT-epoxy composite is modeled using a physics-based formulation for both randomly distributed and vertically aligned cases of CNTs and the results are verified with the measured data available in the literature. In the second step, SCFs are randomly distributed in the CNT-epoxy composite and the effective electrical conductivity of the resulting SCF-CNT-epoxy hybrid composite is estimated using a micromechanics based self-consistent approach considering SCFs as microscopic inhomogeneities.

Civil Engineering

World University root node

Materials and Design

Multiscale modeling of effective electrical conductivity of short carbon fiber-carbon nanotube-polymer matrix hybrid composites

Design of high-performance power lines with advanced materials is indispensable to effectively eliminate losses in electrical power transmission and distribution (T&D) lines. In this study, aluminum conductor composite core with carbon nanostructure (ACCC-CNS) coating in a multilayered architecture is considered as a novel design alternative to conventional aluminum conductor steel-reinforced (ACSR) transmission line. In the multiphysics approach presented herein, first, electrothermal finite element analysis (FEA) of the ACSR line is performed to obtain its steady-state temperature for a given current. Subsequently, the sag of the ACSR line due to self-weight and thermal expansion is determined by performing thermostructural analysis employing an analytical model. The results are then verified with those obtained from the FEA of the ACSR line. The electrothermal finite element (FE) model and the thermostructural analytical model are then extended to the ACCC-CNS line. The results indicate that the ACCC-CNS line has higher current-carrying capacity (CCC) and lower sag compared to those of the ACSR line. Motivated by the improved performance of the ACCC-CNS line, a systematic parametric study is conducted in order to determine the optimum ampacity, core diameter and span length. The findings of this study would provide insights into the optimal design of high-performance overhead power lines.

Journal of Engineering Materials and Technology, Transactions of the ASME

High-Ampacity Overhead Power Lines with Carbon Nanostructure-Epoxy Composites

Degradation of organic light emitting diodes (OLEDs) is the most serious obstacle towards their commercialization. OLED degrades due to various internal and external mechanisms. External degradation is mainly caused due to the instability of low work function cathode, pin-hole formation during fabrication which provides a path for oxygen and moisture infiltration. Operation of OLED also leads to degradation with major causes being morphological instability of organic layers, trap formation, indium or oxygen diffusion from anode, interface deterioration etc. Heat generation in the OLED also acts as a source of degradation. Most of the heat is generated instantaneously upon biasing of OLED due to resistive or Joule heating as a consequence of high resistance of organic layers and non-radiative recombination. Generated heat can be reduced by reducing the effects of the generation sources such as improving conductivity of organic layers by doping, using additional layers to improve charge injection, employing emissive layers with low recombination losses etc. However, these ways can only reduce the heat up to a certain amount. To further improve the lifetime of OLED, the generated heat can be dissipated by employing heat sinks using either thermally conducting substrate or encapsulation etc. We present a review on OLED degradation with a particular focus on heat generation, its consequences and ways of reduction. © 2015 Elsevier B.V. All rights reserved.

Electrical Engineering

Synthetic Metals

Degradation of organic light emitting diode: Heat related issues and solutions

Detection of polarisation of microwave signals using infrared thermography is described in this paper. A metal grating consisting of parallel, equally spaced metallic strips is placed in between a microwave source (antenna) and a microwave absorption screen for permitting the determination of direction of electric field vector (polarisation). Very low frequency modulation of the microwave source is added to permit lock-in thermography which enhances thermal resolution.In case of linear polarisation when the metallic strips of the grating are parallel to the direction of electric field vector, the temperature rise on the screen as observed by an infrared camera, is minimum. On the other hand if the metallic strips are perpendicular to the electric field vector the temperature rise observed on the screen is maximum. The orientation of the grid is changed by rotating the grid about a central axis perpendicular to its plane. With each different orientation of the grid a change in temperature rise is observed on the screen.In case of circular polarisation the temperature rise on the absorption screen is almost independent of the grid orientation i.e. there is negligible change in temperature rise with each different orientation of the grid, as the electric field strength perpendicular to grid strips is almost constant for all grid orientations, corresponding to an axial ratio of unity. While in case of elliptical polarisation the temperature change is appreciable depending on the axial ratio.The proposed method is validated on linearly, circularly and elliptically polarised patch antennas radiating at 8 GHz. Simulation is carried out in CST MICROWAVE STUDIO (CST MWS2013) and a good agreement between simulated and experimental (thermographic) results is observed. © 2016 IETE.

IETE Journal of Research

Determination of Polarisation of Microwave Signals by Lock-in Infrared Thermography

Radio Frequency (RF) Microelectromechanical system (MEMS) switches are becoming more and more popular in the electronics industry. The main concern in using RF MEMS switch is its high actuation voltage. Thus the main focus in this paper is to obtain low actuation voltage. This paper presents the simulation and analysis of RF MEMS cantilever beam and Fixed - Fixed beam switches. RF MEMS switches simulated in this paper use electrostatic actuation method. Simulations were done using finite element modeling. Different designs and parameters such as gap between electrodes, beam thickness, beam length, and relative permittivity values of medium between electrodes were chosen for analyzing the deflection of beams for various actuation voltages. Perforations of different dimensions were made on both type of beams and the resulted deflections were studied. The simulation results show that the Cantilever and Fixed - Fixed beams follow approximately similar deflection pattern with Cantilever beam deflecting more for applied actuation voltage in all the studies. © 2016 IEEE.

Proceedings - 2016 International Conference on Micro-Electronics and Telecommunication Engineering, ICMETE 2016

Simulation and analysis of actuation voltage of electrostatically actuated RF MEMS cantilever and fixed - Fixed switches with variable beam parameters

The tape helix slow wave structures used in travelling wave tube (TWT) amplifiers are exploited for use as radiating devices through the fast wave analysis. The dispersion equation is derived from accurate boundary conditions that neither involve assumptions on the current density distribution, nor considers a defined distribution function for a dielectric loaded tape helix slow wave structure surrounded by a conductor or a conductor placed inside the tape helix. Analytical computation of the dispersion characteristics of both the structures revealed the presence of fast wave modes usable for applications such as antennas. © 2016 IEEE.

Fast wave propagation characteristics of dielectric loaded tape helix structures placed around and within a cylindrical core

The next generation sub1GHz Wireless local area network (WLAN) IEEE802.11ah is being standardized to operate around 1GHz ISM band. It is currently much less congested and enable the WLAN devices to access the network to send burst data. It penetrates easily the obstacles and is less affected by frequency fading and thus offers a long range. It offers simple architecture, high energy efficiency, long life of sensor nodes, improvement in range capability with better data rates in comparison with present IEEE802.15.x WPAN (ZigBee, Bluetooth) which works at 2.4GHz for short ranges and due to high power consumption in Bluetooth sensor nodes life is very short. The ZigBee provides data rates up to 250kbps. The 802.11 ah based on Wi-Fi sensor nodes combines the sensors and communication applications together to obtain high data rates from 100kbps to several Mbps. In Internet of Things (IoT) the smart objects are coverted from physical to virtual world to connect with Internet. The Internet of Things enables smart objects to observe, identify, and understand the world without intervention of human-being. The 802.11 ah has architecture similar to IEEE802.11 WLAN to operate on existing infrastructure, which will commercially empower the future of technology to develop and deploy many applications in IoT era and WSN world. © 2015 IEEE.

Proceedings of the 2015 39th National Systems Conference, NSC 2015

Recent trends in next generation sub1GHz wireless local area network for Internet of Things

Metallic glasses show a unique combination of high strength, excellent corrosion, and wear resistances because of their amorphous structure having a short-range order. In spite of excellent properties, the application of metallic glasses is restricted because of their inherent limitations in the bulk form, including limited tensile ductility. Using metallic glasses as the coatings for structural applications is an attractive way of taking advantage of their superior properties. Additionally, metallic glass-based composites having crystalline phases embedded in a amorphous matrix have also shown improved properties. Thus, metallic glasses can be synthesized as the coatings or subjected to surface modification to provide functionally superior surfaces. This article is a review of metallic glass-based coatings and surface modification of metallic glasses to achieve functionally superior surfaces for structural applications. Essential theoretical concepts were discussed which influence the processing. Common ways of processing along with the influence of various processing parameters were explored. Some non-conventional techniques which emerged as a result of continued efforts were also taken into account. Corrosion and wear properties of these materials along with the underlying mechanisms were discussed in detail. Focus was given to the recent product level applications explored in the open literature. Current challenges in the field were reviewed and guidelines for the future developments were provided. Copyright © Taylor & Francis Group, LLC.

Mechanical Engineering

Critical Reviews in Solid State and Materials Sciences

Amorphous Coatings and Surfaces on Structural Materials

This book explores the domain of reliability engineering in the context of machine tools. Failures of machine tools not only jeopardize users' ability to meet their due date commitments but also lead to poor quality of products, slower production, down time losses etc. Poor reliability and improper maintenance of a machine tool greatly increases the life cycle cost to the user. Thus, the application area of the present book, i.e. machine tools, will be equally appealing to machine tool designers, production engineers and maintenance managers. The book will serve as a consolidated volume on various dimensions of machine tool reliability and its implications from manufacturers and users point of view. From the manufacturers' point of view, it discusses various approaches for reliability and maintenance based design of machine tools. In specific, it discusses simultaneous selection of optimal reliability configuration and maintenance schedules, maintenance optimization under various maintenance scenarios and cost based FMEA. From the users' point of view, it explores the role of machine tool reliability in shop floor level decision- making. In specific, it shows how to model the interactions of machine tool reliability with production scheduling, maintenance scheduling and process quality control. © 2016 Scrivener Publishing LLC. All rights reserved.

Machine Tool Reliability

The homogeneous boundary value problem existing in the electromagnetic wave propagation in a dielectricloaded perfectly conducting tape helix with infinitesimal tape thickness is investigated in this study. The ill-posed boundary value problem is regularised using the mollification method. The homogeneous boundary value problem is solved for the dielectric loaded perfectly conducting tape helix taking into account the exact boundary conditions for the perfectly conducting dielectric loaded tape helix. The solved approximate dispersion equation takes the form of the solvability condition for an infinite system of linear homogeneous equations namely, the determinant of the infinite order coefficient matrix is zero. For the numerical computation of the dispersion equation, all the entries of the symmetrically truncated version of the coefficient matrix are estimated by summing an adequate number of the rapidly converging series for them. The tape-current distribution is estimated from the null-space vector of the truncated coefficient matrix corresponding to a specified root of the dispersion equation. The numerical results suggest that the propagation characteristic computed by the anisotropically conducting model (that neglects the component of the tape-current density perpendicular to the winding direction) is only an abstinent approximation to consider for moderately wide tapes. © The Institution of Engineering and Technology 2016.