Sandip Roy - Academia.edu (original) (raw)

Papers by Sandip Roy

Polar Science, 2012

The scientific study of quartz grains is a powerful tool in deciphering the depositional environm... more The scientific study of quartz grains is a powerful tool in deciphering the depositional environment and mode of transportation of sediments, and ultimately the origin and classification of sediments. Surface microfeatures, angularity, chemical features, and grain-size analysis of quartz grains, collectively reveal the sedimentary and physicochemical processes that acted on the grains during different stages of their geological history. Here, we apply scanning electron microscopic (SEM) analysis to evaluating the sedimentary provenance, modes of transport, weathering characteristics, alteration, and sedimentary environment of selected detrital quartz grains from the peripheral part of two epi-shelf lakes (ESL-1 and ESL-2) of the Schirmacher Oasis of East Antarctica. Our study reveals that different styles of physical weathering, erosive signatures, and chemical precipitation variably affected these quartz grains before final deposition as lake sediments. Statistical analysis (central tendencies, sorting, skewness, and kurtosis) indicates that these quartz-bearing sediments are poorly sorted glaciofluvial sediments. Saltation and suspension seem to have been the two dominant modes of transportation, and chemical analysis of these sediments indicates a gneissic provenance.

Journal of the Geological Society of …, 2011

Page 1. 0016-7622/2011-78-2-117/$ 1.00 © GEOL. SOC. INDIA JOURNAL GEOLOGICAL SOCIETY OF INDIA Vol... more Page 1. 0016-7622/2011-78-2-117/$ 1.00 © GEOL. SOC. INDIA JOURNAL GEOLOGICAL SOCIETY OF INDIA Vol.78, August 2011, pp.117-123 The Ice Sheet Dynamics around Dakshin Gangotri Glacier, Schirmacher Oasis, East Antarctica vis-à-vis Topography ...

Int J Robust Nonlinear Contr, 2010

We use a high-gain methodology to construct linear decentralized controllers for consensus, in ne... more We use a high-gain methodology to construct linear decentralized controllers for consensus, in networks with identical but general multi-input multi-output (MIMO) linear time-invariant (LTI) agents and quitegeneral observation topology, including numerous time-invariant and time-varying ones.

2015 49th Annual Conference on Information Sciences and Systems, Mar 1, 2015

2009 European Control Conference, Aug 1, 2009

Abstract We study approximation of multiple-derivative output feedback for linear timeinvariant (... more Abstract We study approximation of multiple-derivative output feedback for linear timeinvariant (LTI) plants using multiple-delay approximations. We obtain a condition on the plant and feedback that yields an equivalence between the closed-loop spectra for the ...

Proceedings of the 48h Ieee Conference on Decision and Control Held Jointly With 2009 28th Chinese Control Conference, 2009

Motivated by both distributed-computation and decentralized-control applications, we study distri... more Motivated by both distributed-computation and decentralized-control applications, we study distributed linear iterative algorithms with memory. Specifically, we show that the system of linear equations Gx = b can be solved through a distributed linear iteration for arbitrary invertible G, using only a single memory element at each processor. Further, we demonstrate that the memoried distributed algorithm can be designed to achieve much faster convergence than a memoryless distributed algorithm. A small simulation example is included to illustrate the results.

Ieee Transactions on Automatic Control, Feb 1, 2010

We demonstrate that some delay-differential equations of neutral type are, up to basis transforma... more We demonstrate that some delay-differential equations of neutral type are, up to basis transformation, equivalent to retarded delay differential equations. In particular, for two classes of neutral delay differential equation models, we use state transformations to show that delayed derivatives can in some cases be expressed in terms of the model's state. Hence, we obtain conditions when neutral delay differential equations can be transformed into retarded delay differential equations.

We study decentralized controller design for stabilization and pole-placement, in a network of au... more We study decentralized controller design for stabilization and pole-placement, in a network of autonomous agents with double-integrator internal dynamics and arbitrary observation topology. We show that a simple multi-lead-compensator architecture, in particular one in which each agent uses a derivative-approximation compensator with three memory elements, can achieve both stabilization and effective pole placement while subdividing complexity/actuation among the agents. Through a scaling argument, we also demonstrate that the multi-lead-compensator can stabilize the double-integrator network under actuator saturation constraints.

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We explicitly construct a precompensator that cancels all open left half plane finite invariant z... more We explicitly construct a precompensator that cancels all open left half plane finite invariant zeros of a general MIMO LTI plant, by exploiting the special coordinate basis for linear systems. This approach to cancellation avoids the inclarity inherent in defining ...

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We motivate the problem of designing a subset of the edge weights in a graph, to shape the spectr... more We motivate the problem of designing a subset of the edge weights in a graph, to shape the spectrum of an associated linear time-invariant dynamics. We address a canonical design problem of this form by applying time-scale assignment methods, and give graph-theoretic characterizations of the designed dynamics.

Motivated by needs in strategic traffic flow management, we study the problem of forecasting airp... more Motivated by needs in strategic traffic flow management, we study the problem of forecasting airport capacity profiles over a full-day time horizon. Specifically, we present a case study of Atlanta's Hartsfield-Jackson International Airport (KATL), which explores use of 1) convective weather presence/absence near the terminal, 2) cloud ceiling height, and 3) wind speed as predictors of the total airport capacity. It is shown that terminal-area convective weather is a primary cause of capacity reduction, and also that low ceilings are a sensitive and specific predictor of reduced capacity. Wind speeds are shown to be less specific predictors, but nevertheless modulate capacity.

International Journal of Distributed Sensor Networks, 2008

This article proposes a flexible and distributed stochastic automaton-based network partitioning ... more This article proposes a flexible and distributed stochastic automaton-based network partitioning algorithm that is capable of finding the optimal k-way partition with respect to a broad range of cost functions, and given various constraints, in directed and weighted graphs. Specifically, we motivate the distributed partitioning (self-partitioning) problem, introduce the stochastic automaton-based partitioning algorithm, and show that the algorithm finds the optimal partition with probability 1 for a large class of partitioning tasks. Also, a discussion of why the algorithm can be expected to find good partitions quickly is included, and its performance is further illustrated through examples. Finally, applications to mobile/sensor classification in ad hoc networks, fault-isolation in electric power systems, and control of autonomous vehicle teams are pursued in detail.

2007 Ieee International Conference on Communications, 2007

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