(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

Experiments have been performed in a 10 cm ID horizontal pipeline to observe the effect of temperature, carbon dioxide partial pressure, flow, and oil/water composition, on corrosion in horizontal multiphase slug flow, using a low viscosity (2 cp) oil. Corrosion rates have been measured for water cuts ranging form 20 to 100%, carbon dioxide partial pressures of 0. 27, 0. 45 and 0. 79 MPa, temperatures of 40. 60, 70. 80 and 90 C and Froude numbers of 6, 9 and 12. The corrosion rates are found to increase with an increase in temperature, Froude number and carbon dioxide partial pressure. The corrosion rates are found to decrease with increase in oil composition. The average void fraction as well as the pressure drop across the slug is found to increase with an increase in Froude number and carbon dioxide partial pressure. A model to predict corrosion rates for low viscosity oils has been established which relates the corrosion rate to the pressure gradient, temperature, carbon dioxide partial pressure and water cut. © 1996 by NACE International.

World University root node

Electrical Engineering

NACE - International Corrosion Conference Series

Predictive model for sweet corrosion in horizontal multiphase slug flow

Mathematical models are developed tor the prediction of corrosion rates in large diameter, high pressure, horizontal multiphase oil/water/gas pipelines. The models quantify the effects of multiphase flow characteristics, such as phase distribution, turbulent intensity, wall shear stress, and pressure drop, on the corrosion processes at the metal surface. Mechanisms are presented for both full pipe flow and slug flow. The models incorporate the effects of fluid properties, pressure, temperature, and pipe diameter, on corrosion rate. In full pipe oil/water flows, the corrosion rate can be predicted as a function of the total wall shear stress for a given carbon dioxide partial pressure and temperature. In slug flow, the effect of the liquid composition becomes significant, and the total shear stress is difficult to calculate. In this case, the pressure gradient across the slug can be correlated with the corrosion rate for a given liquid composition, at a particular carbon dioxide partial pressure and system temperature.

American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FED

Modeling of corrosion in high pressure horizontal multiphase flow pipelines

Surface Acoustic Wave (SAW) devices, are not normally amenable to simulation through circuit simulators. In this letter, an electrical macromodel of Mason's Equivalent Circuit for an interdigital transducer (IDT) is proposed which is compatible to a widely used general purpose circuit simulator SPICE endowed with the capability to handle negative capacitances and inductances. Illustrations have been given to demonstrate the simplicity of ascertaining the frequency and time domain characteristics of IDT and amenability to simulate the IDT along with other external circuit elements. © 1995 IEEE.

IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control

SPICE Simulation of Surface Acoustic Wave Interdigital Transducers

We present an alternative implementation of the fractional cascading data structure of Chazelle and Guibas (Algorithmica1 (1986), 133-162) that performs iterative search for a key in multiple ordered lists. The construction of our data structure uses randomization and simplifies the algorithm of Chazelle and Guibas, vastly making it practical to implement. Although our bounds are asymptotically similar to the earlier ones, there are improvements in the constant factors. Our analysis is novel and captures some of the inherent difficulties associated with the fractional cascading data structure. In particular, we use tools from branching process theory and derive some useful asymptotic bounds. The probability of deviation from the expected performance bounds decreases exponentially with number of keys. Also, under a restricted model, we obtain efficient bounds for updates in the data structure. © 1995 Academic Press, Inc.

Journal of Algorithms

Fractional cascading revisited

In this paper, we present an algorithm for hidden surface removal for a class of polyhedral surfaces which have a property that they can be ordered relatively quickly. For example, our results apply directly to terrain maps. A distinguishing feature of our algorithm is that its running time is sensitive to the actual size of the visible image, rather than the total number of intersections in the image plane which can be much larger than the visible image. The time complexity of this algorithm is O((k + n) log2n) where n and k are, respectively, the input and the output sizes. Thus, in a significant number of situations this will be faster than the worst case optimal algorithms which have running time of Ω(n2) irrespective of the output size. © 1995.

Mathematical and Computer Modelling

An efficient output-sensitive hidden-surface removal algorithm for polyhedral terrains

The paper investigates the application of inversion of a radial basis function network (RBFN) to nonlinear control problems for which the structure of the nonlinearity is unknown. Initially, the RBF network is trained to learn the forward dynamics of the plant. Two different controller structures are then proposed based on this identified RBFN model. In one scheme, a feedback control law is derived based on the input prediction by inversion of the RBFN model so that the system is Lyapunov stable. The second kind of controller structure predicts the feedforward control action, while the fixed controller actuates the feedback stabilizing signal. An extended Kalman filtering based algorithm is employed to carry out the network inversion during each sampling interval. Two examples are presented to verify the proposed scheme. Simulation results show that the performance of the controller based on the proposed network inversion scheme is efficient.

IEE Proceedings: Control Theory and Applications

Inversion of RBF networks and applications to adaptive control of nonlinear systems

Fast and accurate trajectory tracking of a robot arm primarily depends on the knowledge of its explicit inverse dynamics model. On line learning of inverse dynamics using supervised learning algorithm is difficult in the absence of a priori knowledge of command error. On the other hand, self-organizing neural network employing unsupervised learning scheme does not depend on the command error. These networks are suitable for both off-line and on-line schemes of learning the inverse dynamics. The present paper proposes both the schemes based on two unsupervised learning algorithms, namely, Kohonen's self-organizing topology conserving feature map and 'neural gas' algorithm. Simulation results on a single link manipulator confirms the efficacy of the proposed schemes.

IEEE/IAS International Conference on Industrial Automation and Control, Proceedings

Self-organizing neural networks for learning inverse dynamics of robot manipulator

The paper presents a new thyristorised inverter without the necessity of external commutation circuits for 3 phase induction motor control. The dc input is fed to the inverter through a fast acting load-commutated dc to dc thyristor chopper without any filter in between. The chopper output consists of a series of high frequency (1 to 3 kHz) saw-tooth shaped voltage pulses which are appropriately transferred to the three phase load by the inverter. Barring the high frequency capacitor used in the chopper, there are no other force-commutation elements. Only one snubber circuit at the input end of the inverter is sufficient. The turn-on and turn-off losses are small since the switchings are mostly soft. The paper explains the operation of the inverter with its control circuits and presents experimental results regarding voltage and current waveforms when used to drive a laboratory size induction motor.

Proceedings of the International Conference on Power Electronics and Drive Systems

New thyristor inverter without external commutation for AC motor control

The paper presents a comparative assessment of the static var system (SVS) bus frequency and line reactive power auxiliary controllers for the transient performance enhancement of series compensated long transmission lines. A new controller, namely, the combined reactive power and frequency (CRPF) auxiliary controller, has been developed and incorporated in the static var control system located at the middle of the transmission line. The series compensation is provided at the sending end of the line. The application of the auxiliary controllers considerably enhances the system damping and the unstable system modes are stabilized. A digital computer simulation study has been performed to compare the effectiveness of the auxiliary controllers under disturbance conditions and the superiority of the (CRPF) auxiliary controller has been established over the other auxiliary controllers. © 1995.

Electric Power Systems Research

Application of static var system auxiliary controllers to improve the transient performance of series compensated long transmission lines

A static VAR system has been considered located at the middle of a long transmission line, and the effect of the SVS auxiliary controllers on the system dynamic performances has been examined over a wide range of operating conditions. The performance of auxiliary controllers has been studied when a reduced order network model, represented by a lumped parameter T-circuit, is used. The performance is compared with a system having a network model represented by single lumped parameter π-circuit on either side of SVS. It is observed that the size of the system matrix reduces significantly when the reduced order model is used. Also The accuracy of the eigenvalues of the system Is not much affected. The application of the auxiliary controllers, considerably, increases the system damping and unstable system modes are stabilized. © 1995 Taylor & Francis Group, LLC.