(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

We consider the following one- and two-dimensional bucketing problems: Given a set S of n points in ℝ1 or ℝ2 and a positive integer b, distribute the points of S into b equal-size buckets so that the maximum number of points in a bucket is minimized. Suppose at most (n/b) + △ points lies in each bucket in an optimal solution. We present algorithms whose time complexities depend on b and △. No prior knowledge of △ is necessary for our algorithms. For the one-dimensional problem, we give a deterministic algorithm that achieves a running time of 0(b4△2 log n + n). For the two-dimensional problem, we present a Monte-Carlo algorithm that runs in sub-quadratic time for certain values of b and △. The previous algorithms, by Asano and Tokuyama [1], searched the entire parameterized space and required Ω(n2) time in the worst case even for constant values of b and △. © Springer-Verlag Berlin Heidelberg 1999.

World University root node

Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)

Output-sensitive algorithms for uniform partitions of points

The effect of drag-reducing agent (DRA) on multiphase flow in upward and downward inclined pipes has been studied. The effect of DRA on pressure drop and slug characteristics such as slug translational velocity, the height of the liquid film, slug frequency, and Froude number have been determined. Experiments were performed in 10-cm i.d., 18-m long plexiglass pipes at inclinations of 2 and 15 degfor 50 percent oil-50 percent water-gas. The DRA effect was examined for concentrations ranging from 0 to 50 ppm. Studies were done for superficial liquid velocities between 0.5 and 3 mJs and superficial gas velocities between 2 and 10 m/s. The results indicate that the DRA was effective in reducing the pressure drop for both upflow and downflow in inclined pipes. Pressure gradient reduction of up to 92 percent for stratified flow with a concentration of 50 ppm DRA was achieved in 2 deg downward inclined flow. The effectiveness of DRA for slug flow was 67 percent at a superficial liquid velocity of 0.5 m/s and superficial gas velocity of 2 m/s in 15 deg upward inclined pipes. Slug translational velocity does not change with DRA concentrations. The slug frequency decreases from 68 to 54 slugs/min at superficial liquid velocity of 1 m/s and superficial gas velocity of 4 m/s in 15 deg upward inclined pipes as the concentration of 50 ppm was added. The height of the liquid film decreased with the addition of DRA, which leads to an increase in Froude number. © 1999 by ASME.

Electrical Engineering

Journal of Energy Resources Technology, Transactions of the ASME

Effect of drag-reducing agent on slug characteristics in multiphase flow in inclined pipes

This paper presents a family of circuits for single phase diode rectifiers capable of drawing approximately sinusoidal current waveforms at unity power factor with high efficiency and minimum voltage stress across the switches. Moreover, they are suitable to work as boost and flyback converters. These topologies use coupled inductors with capacitor for resonance to achieve zero voltage switching (ZVS) of the converters. The circuits consist of a single-phase diode bridge rectifier, followed by a boost stage containing two switches-the main switch for controlling the output DC voltage and the auxiliary switch for achieving ZVS. The output voltage is regulated by employing fixed frequency control. The paper explains the principle of operation and describes the analysis of each mode of operation for both boost and flyback converters. It also gives design criteria, derived from the mathematical analysis carried out, for achieving ZVS under all loading conditions from no load to full load. The simulation results obtained using PSPICE demonstrate the validity of the proposed converter.

IECON Proceedings (Industrial Electronics Conference)

Fixed-frequency zero-voltage switched low-cost single phase high quality rectifier circuits with minimum voltage stress across the switches

This paper presents some novel synchronized quasi-resonant circuits for achieving soft-switching DC/DC boost and flyback power converters. These topologies use coupled inductors with capacitor for resonating the circuit to achieve zero voltage switching of the power converters. The circuits have minimum voltage stress across the switches. Moreover, they have reduced commutation losses and increased switching frequency. The paper explains the principle of operation of the circuit and describes the analysis of each mode of operation for both boost as well as flyback power converters. It also gives design criteria, derived from the mathematical analysis carried out, for achieving zero voltage switching under all loading conditions from no load to full load. The feasibility of the proposed circuits has been verified by PSPICE simulation. © 1998 IEEE.

PESC Record - IEEE Annual Power Electronics Specialists Conference

Certain novel synchronized quasi-resonant topologies for achieving soft-switching DC/DC boost and flyback converters with minimum voltage stress across the switches

A non-contact, non-destructive technique for the depth profiling of micromachined structures is presented. Based on the mirage or optical-beam deflection method of photothermal spectroscopy, an experimental measurement of a 8 μm step in silicon is given by way of illustration. © 1998 Elsevier Science S.A.

Sensors and Actuators, A: Physical

Mirage-effect-based depth profiling of micromachined silicon structures

We investigate a new paradigm of algorithm design for geometric problems that can be termed distribution-sensitive. Our notion of distribution is more combinatorial in nature than spatial. We illustrate this on problems like planar-hulls and 2D-maxima where some of the previously known output-sensitive algorithms are recast in this setting. In a number of cases, the distribution-sensitive analysis yields superior results for the above problems. Moreover these bounds are shown to be tight for a certain class of algorithms. Our approach owes its spirit to the results known for sorting multisets and we exploit this relationship further to derive fast and efficient parallel algorithms for sorting multisets along with the geometric problems. © 1998, Springer-Verlag. All rights reserved.

Distribution-sensitive algorithms

We describe an efficient parallel algorithm for hidden-surface removal for terrain maps. The algorithm runs in O(log4 n) steps on the CREW PRAM model with a work bound of O((n+k)polylog(n)) where n and k are the input and output sizes respectively. In order to achieve the work bound we use a number of techniques, among which our use of persistent data-structures is somewhat novel in the context of parallel algorithms. To the best of our knowledge this is the most efficient parallel algorithm for hidden-surface removal for an important class of 3-D scenes. © 1998 IEEE.

Proceedings of the 1st Merged International Parallel Processing Symposium and Symposium on Parallel and Distributed Processing, IPPS/SPDP 1998

An improved output-size sensitive parallel algorithm for hidden-surface removal for terrains

This paper summarizes the results of mass transfer mechanisms under disturbed liquid-gas flow in 10 cm diameter pipe using electrochemical limiting current density and potentiostatic noise technique. The solution used is potassium ferro/ferricyanide dissolve in 1.3 N sodium hydroxide system. Mass transfer coefficients in full pipe flow and slug flow are obtained. The relationship between mass transfer coefficient with full pipe flow velocities and with slug flow Froude numbers are studied. The impact of bubbles in slugs on the mass transfer coefficient is revealed. The impact of flow disturbance, including weld beads and pits, are discussed for both full pipe flow and slug flow. © 1998 by NACE International.

NACE - International Corrosion Conference Series

Calculation of mass transfer in multiphase flow

Previous work has demonstrated the mechanism of enhanced corrosion in slug flow due to entrained pulses of gas bubbles (Gopal et al, 1997). Corrosion rate measurements have been made at pressures up to 0.79 MPa and temperatures up to 90°C, and it has been shown that the effect of these pulses of bubbles increases with pressure and Froude number. This paper describes mass transfer measurements under multiphase slug and annular flows using the limiting current density technique. The experimentsare carried out in a 10-cm-dia pipe using a 0.01-Mpotassium ferro/ferricyanide solution in 1.3 N sodium hydroxide for the liquid phase and nitrogen in the gas phase. Froude numbers of 4, 6, and 9 in slug flow have been studied, while gas velocities up to 10 m/s are investigated in annular flows. The remits show instantaneous peaks in the mass transfer rates corresponding to the pulses of bubbles in slug flow. Instantaneous increases of 10-100 times the average values in multiphase flow are seen. Peaks are also seen in instantaneous mass transfer rates in some annular flows. © 1998 by ASME.

Multiphase flow-enhanced corrosion mechanisms in horizontal pipelines

A mechanistic model was developed for predicting carbon dioxide corrosion rates of carbon steel pipes in multiphase flow conditions. The model incorporates the chemistry, thermodynamics of carbon dioxide dissolution, multiphase mass transfer, electrochemical kinetics on the metal surface and the presence of a corrosion product film. The predicted corrosion rates show good agreement with the experimental results. © 1998 by NACE International.