(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

Cavitation erosion (CE) of various components in hydroturbines is a critical issue. Several attempts have been made in the past to counter CE through various surface modification techniques. In this study, a novel attempt has been made to modify the surface properties of hydroturbine steel with the aid of friction stir processing (FSP). Metallurgical characterization of the processed steel was undertaken with the help of XRD, SEM/EDS, EBSD and optical microscopy. For mechanical characterization micro-hardness and cavitation erosion studies were conducted. EBSD results confirmed the presence of grains in nano range. Processed steel showed gain in hardness of the order of 160 % in comparison to unprocessed steel. XRD results show a significant variation in the type and quantity of various phases in pre-and post processed steel. It was observed that FSPed steel showed a significant improvement in the erosion resistance in contrast to the unprocessed steel.

Mechanical Engineering

World University root node

Transactions of the Indian Institute of Metals

Cavitation erosion studies on friction stir processed hydroturbine steel

We present a fully dynamic algorithm for maintaining approximate maximum weight matching in general weighted graphs. The algorithm maintains a matching M whose weight is at least 1/8M* where M* is the weight of the maximum weight matching. The algorithm achieves an expected amortized O(log n log C) time per edge insertion or deletion, where C is the ratio of the weights of the highest weight edge to the smallest weight edge in the given graph. © A. Anand, S. Baswana, M. Gupta and S. Sen.

Leibniz International Proceedings in Informatics, LIPIcs

Maintaining approximate maximum weighted matching in fully dynamic graphs

Purpose - The purpose of this paper is to give a comprehensive description of various safety factors that need to be determined while assessing the short-circuit strength of transformers. Design/methodology/approach - Factors of safety are divided into two categories: radial and axial. Some of the latest approaches in assessing the strength are elaborated. Findings - Six major sets of calculations are identified: three each for radial and axial electromagnetic forces. Corresponding factors of safety are defined and calculated for practical transformers. These factors are related to the strength and stability aspects of windings. Research limitations/implications - The work gives pointers for further research at appropriate places while highlighting the challenges involved in the assessment of the short-circuit strength. Practical implications - The presented overview of the factors of safety can be a useful guide for the practicing transformer engineers. Originality/value - The main contribution of the reported work is in highlighting the intricacies associated with the subject of short-circuit strength of power transformers. It can serve as a reference document for future research works in the area since the procedures are outlined for calculating the factors of safety through six case studies. © 2012 Emerald Group Publishing Limited. All rights reserved.

Electrical Engineering

COMPEL - The International Journal for Computation and Mathematics in Electrical and Electronic Engineering

Towards short-circuit proof design of power transformers

In the present study a novel modeling approach is presented to solve the combined internal sloshing and sea-keeping problem. The model deals with interesting effects arising due to the coupled interaction between the sloshing in partially filled containers of several geometries and the ship motion. The study is very important for the liquid cargo carrier operating in rough sea or under different environmental conditions. The resulting slosh characteristics that include transient pressure variation, free surface profiles and hydrodynamic pressure over the container walls have been reported in this study. In addition, the effects of coupled ship response and sloshing on ship motion parameters have also been investigated. The equations of motion of fluid, considered inviscid, irrota-tional, and partially compressible, are expressed in terms of the pressure variable alone. A finite difference-based iterative time-stepping technique is employed to advance the coupled solution in the time domain. Several parameters of interest, including the container parameters, level of liquid, thrusters modeling and some important environmental factors are investigated. © 2012 JASNAOE.

Journal of Marine Science and Technology (Japan)

A fully coupled ship motion and sloshing analysis in various container geometries

The impact of micromixers on copolymers ' characteristics in a continuous-flow microprocess was studied. A stainless steel coiled tube was used as the microreactor. Several micromixers with different working principles, like bilamination, multilamination and impact jet, were used to mix the reactants ' streams before entering the reactor. (Co)polymers of 2-dimethyl amino ethyl methacrylate (DMAEMA) and benzyl methacrylate (BzMA) were synthesized by the atom transfer radical polymerization (ATRP) technique, with two different compositions of BzMA (20% and 40%). A faster polymerization rate was observed in case of microprocess, as compared to batch process, highlighting the inherent intensification nature of microfluidic-assisted processes. Despite equal conversion for the three micromixers, a remarkable difference in molecular weight was observed. The highest molecular weights with lowest polydispersity indices (PDIs) were obtained when the multilamination micromixer was used, while the bilamination gave polymers with high PDIs and low molecular weights. Diffusion constraints arising from the increase in viscosity was clearly visible for highest residence times in the microreactor, resulting in a deviation of molecular weight from the theoretical value.

Chemical Engineering

Fulltext

Green Processing and Synthesis

Intensifying the ATRP synthesis of statistical copolymers by continuous micromixing flow techniques

This article deals with the effect of adhesive bond on piezoelectric ceramic (PZT) patch-structure interaction system and the resulting effect on admittance signature, which has a major impact on the electromechanical coupled phenomena pertinent for the electro-mechanical impedance technique. The adhesive bond acts as an elastic medium which facilitates the transfer of stresses and strains developed due to piezo displacement and also couples the impedance of PZT patch with that of the host structure. In this work, the force transfer mechanism is studied along the length of the PZT patch as also the variation of the shear stress and strain along the bond. This article presents a numerical approach to study the inclusion of shear lag in the electro-mechanical impedance model through commercially available finite element (FE) simulation software. The results are compared with existing analytical as well as experimental data. Parametric study of the FE shear lag model is carried out to examine the effect of piezo-mechanical parameters on the admittance signature.

Civil Engineering

Current Science

Numerical investigations of shear lag effect on PZT-structure interaction: Review and application

The pseudospark (PS) discharge is, however, more recently recognized as a different type of discharge which is capable of generating electron beams with the highest combined current density and brightness of any known type of electron source. PS discharge is a specific type of gas discharge, which operates on the left-hand side of the hollow cathode analogy to the Paschen curve with axially symmetric parallel electrodes and central holes on the electrodes. The PS discharge generated electron beam has tremendous applications in plasma filled microwave sources where normal material cathode cannot be used. Analysis of the electron beam profile has been carried out experimentally for different applied voltages. The investigation has been done at different axial and radial location inside the drift tube in argon atmosphere. This paper represents experimentally derived axial and radial variation of the beam current inside the plasma filled drift tube of PS discharge based plasma cathode electron (PCE) gun. With the help of current density estimation the focusing and defocusing point of electron beam in axial direction can be analyzed. It has been further confirmed the successful propagation of electron beam in confined manner without any assistance of external magnetic field.

Journal of Physics: Conference Series

Experimental investigation of pseudospark generated electron beam

Scheduling a meeting is a difficult task for people who have overbooked calendars and many constraints. The complexity increases when the meeting is to be scheduled between parties who are situated in geographically distant locations of a city and have varying travel patterns. In this paper, we present a solution that identifies a common meeting point for a group of users who have temporal and spatial locality constraints that vary over time. The problem entails answering an Optimal Meeting Point (OMP) query in spatial databases. Under Euclidean space OMP query solution identification gets reduced to the problem of determining the geometric median of a set of points, a problem for which no exact solution exists. The OMP problem does not consider any constraints as far as availability of users is concerned whereas that is a key constraint in our setting. We there- fore focus on finding a solution that uses daily movements information obtained from GPS traces for each user to compute stay points during various times of the day. We then determine interesting locations by analyzing the stay points across multiple users. The novelty of our solution is that the computations are done within the database by using various relational algebra operations in combination with statistical operations on the GPS trajectory data. This makes our solution scalable to larger groups of users and for multiple such requests. Once this list of stay points and interesting locations are obtained, we show that this data can be utilized to construct spatiotemporal graphs for the users that allow us eficiently decide a meeting place. We perform experiments on a real-world dataset and show that our method is effective in finding an optimal meeting point between two users. Copyright © 2012 ACM.

Computer Science and Engineering

ACM International Conference Proceeding Series

Mining GPS traces to recommend common meeting points

We propose a new way to estimate the sparse multipath channel of an Amplify and Forward Two Way Relay Network (AF-TWRN) based on Compressive Sensing (CS), using Compressive Sampling Matching Pursuit (CoSaMP). MSE based performance of CoSaMP and OMP methods and corresponding BPSK based BER performance of the system using the estimated channels are plotted. CoSaMP based channel estimation is performing similar to OMP based channel estimation, with lesser time complexity, in both MSE and BER measures of the system, when the sparsity/worst case sparsity of the channel is known. © 2012 IEEE.

Proceedings of the 2012 3rd International Conference on Computer and Communication Technology, ICCCT 2012

Performance comparison of OMP and CoSaMP based channel estimation in AF-TWRN scenario

We report structural and optical properties of aluminum nitride (AlN) thin films prepared by RF magnetron sputtering. A ceramic AlN target was used to sputter deposit AlN films without external substrate heating in Ar-N 2 (1:1) ambient. The X-ray diffraction and high resolution transmission electron microscopy results revealed that the films were preferentially oriented along c-axis. Cross-sectional imaging revealed columnar growth perpendicular to the substrate. The secondary ion mass spectroscopy analysis confirmed that aluminum and nitrogen distribution was uniform within the thickness of the film. The optical band gap of 5.3 eV was evaluated by UV-vis spectroscopy. Photo-luminescence broad band was observed in the range of 420-600 nm with two maxima, centered at 433 nm and 466 nm wavelengths related to the energy states originated during the film growth. A structural property correlation has been carried out to explore the possible application of such important well oriented nano-structured two-dimensional semiconducting objects. © 2011 Elsevier B.V. All rights reserved.