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Search Results: 1 - 10 of 222 matches for " Chaitanya Poolla "
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Temporal Prediction of Aircraft Loss-of-Control: A Dynamic Optimization Approach  [PDF]
Chaitanya Poolla, Abraham K. Ishihara
Intelligent Control and Automation (ICA) , 2015, DOI: 10.4236/ica.2015.64023
Abstract: Loss of Control (LOC) is the primary factor responsible for the majority of fatal air accidents during past decade. LOC is characterized by the pilot’s inability to control the aircraft and is typically associated with unpredictable behavior, potentially leading to loss of the aircraft and life. In this work, the minimum time dynamic optimization problem to LOC is treated using Pontryagin’s Maximum Principle (PMP). The resulting two point boundary value problem is solved using stochastic shooting point methods via a differential evolution scheme (DE). The minimum time until LOC metric is computed for corresponding spatial control limits. Simulations are performed using a linearized longitudinal aircraft model to illustrate the concept.
Monte Carlo cell simulations
Chaitanya Athale
Genome Biology , 2001, DOI: 10.1186/gb-2001-3-1-reports2001
Abstract: The general Monte Carlo simulator of cellular microphysiology (MCell) on this site is a program that allows three-dimensional dynamic simulations of subcellular architecture and physiology. In addition to an introduction to the modeling of cellular physiology, details of probability and random-event-based methods and complex geometry generation are discussed. The MCell program can be downloaded after registration (free to academic users). The site provides a good introduction to researchers interested in using Monte Carlo Simulations (a random number based simulation method, with the physical process simulated directly by sampling a probability distribution function) to answer questions in cellular physiology and structure, as well as having much to offer for users of the MCell tool. There are links to other simulation tools such as NEURON and GENESIS and visualization tool sites such as Open Visualization Data Explorer and POV-Ray. The minimal nature of the site and the clear introduction to the simulation of microphysiology are its most striking features.Most parts of the site can be found easily and there are tutorials for its use. There are some ambiguous links, including example images. Once in any of the internal pages, there are no links to other pages, which makes moving around a bit tedious. Browsing is easy but customization is not possible. The site has a lot of large images, and on a low-bandwidth connection this might slow access down. Printing pages is not ideal, as text and images do not fit on standard pages, but text and images can be easily downloaded. The response to feedback is excellent and useful answers were obtained within a working day.There is no mention of when the site was last updated, but the new downloading facility for the program was added in October 2001.Monte Carlo simulation methods are not widely represented in cell-simulation websites, so the good overview of modeling in cell biology and the relevance of the Monte Carlo approach
Cell-simulations portal
Chaitanya Athale
Genome Biology , 2001, DOI: 10.1186/gb-2001-3-1-reports2002
Abstract: Navigation is reasonably straightforward and finding the different parts of the site is easy, although there is no dedicated search engine. The links back and forth are not uniform, however: good in some places but absent from others. Customization is possible in the modeling, simulation and image framework. Most pages print as they are seen on-screen, including the figures. No special software, other than a JAVA-enabled browser, is needed to access the site.The last update at the time of writing was 13 June 2001 with Version 3.0 of Virtual Cell.The availability of a modeling platform that frees biologists from having to invest in local computing resources is great. It realizes the vision of remote computing with bare-bones computers logged into central high-performance machines over the internet.At the moment, even small simulations take a very long time to run, without any indication of how long it will take. The response to feedback is poor, having taken over a working week for meBetter performance from the program and a fitting and optimization module added to the virtual cell software would certainly add to the attractiveness of the resources.Tools for similar simulations in cell biology are commercially available for work offline from Berkeley Madonna and the ordinary differential equations (ODE) and partial differential equations (PDE) solvers of MATLAB. Image libraries of cells are available at, for example, the Virtual Cell for plant cells. Data standards in computational cell biology are available at CellML and Systems Workbench Development Group.The National Resource for Cell Analysis and ModelingBerkeley MadonnaMATLABVirtual CellCellMLSystems Workbench Development Group
Software for cell simulation
Chaitanya Athale
Genome Biology , 2002, DOI: 10.1186/gb-2002-3-3-reports2011
Abstract: Access was good at all times tested, and searching and browsing is not problematic. The site is mainly organized into three modules (for the developer, user and general audience), and each module has a clear but different structure. As the design of the modules differs, moving within a module is convenient, but once one has crossed over from one to another, getting back can be inconvenient. The section devoted to the E-CELL development and user forums is full of dynamic sections where comments can be directly added to the online material. Other parts of the user forums are also convenient to search because of the use of the MoinMoin-based script with features like indices based on title, words and recent change, full search facilities and page views showing deletions and additions. The literature on the site can be downloaded in HTML and postscript formats. E-CELL software versions 1.x and 2.x are available for download under a General Public License (GPL), with source code as well as the model descriptions.The site was last updated on 11 November 2001.The multitude of features on offer for collaboration and exchanges between and within the developer and user communities is by far the best aspect of the site.A lack of discussion about results obtained with the stable E-CELL version (version 1.x ) is the biggest deficiency.Discussions about results obtained with E-CELL and a list of related and similar sites.The older E-CELL site hosts a user manual, literature, models, a user mailing-list and information about Masaru Tomita's group, who created E-CELL. This site has links to the lab in which the E-CELL project started - the Bioinformatics Laboratory at Keio University - and the Institute for Advanced Biosciences, Keio University, where further work on the project, including the application of E-CELL to optimal industrial-microbe design, is planned. Tools similar to E-CELL are also available at the websites for GEPASI, a biochemical network simulator, and GENESIS, a
Research on preserving User Confidentiality in Cloud Computing – Design of a Confidentiality Framework
Chaitanya Dwivedula
International Journal of Engineering Research and Applications , 2013,
Abstract: Cloud Computing creates a dynamicresource sharing platform that provides dataanalytically to the proficient users who are atdemand to access data present in the cloud. Asthis data is stored outside the data owner's boundaries, they are skeptical for utilizingcloud technology in order to store or accesstheir data from those external cloudproviders who are outside their own controlenvironment. There are many issues for theseactive clients (companies or individuals) to bepetrified at the thought of using cloudcomputing paradigm. Some of the main issuesthat make the clients swear against Cloud Computing are generated from threeimportant security aspects: Confidentiality, Integrity, and Availability.In this Research, we focused only on securitymodels that relate Confidentiality issues. We performed a literature Review foranalyzing the existing confidentialityframeworks and security models. We thendesigned a new theoretical framework forconfidentiality in Cloud computing byextracting this literature. We expect this Framework when implemented practically inthe cloud computing paradigm, may generatehuge successful results that motivate the clients to transform their businesses on to Cloud.
Social Utility of Academic Research
Chaitanya Mishra
Himalayan Journal of Sociology and Anthropology , 2010, DOI: 10.3126/hjsa.v4i0.4678
Abstract: The Nepal Intellectual Forum (NepIf), Pokhara, had invited Professor Chaitanya Mishra to deliver a lecture on ‘Social Utility of Academic Research’ on May 22, 2010. We thank Prof Mishra and the NepIf for providing extracts from the lecture to this publication. -Editors DOI: http://dx.doi.org/10.3126/hjsa.v4i0.4678 Himalayan Journal of Sociology and Anthropology Vol.IV (2010) 241-253
Theorems of Barth-Lefschetz type and Morse Theory on the space of paths in Homogeneous spaces
Chaitanya Senapathi
Mathematics , 2014,
Abstract: Homotopy connectedness theorems for complex submanifolds of homogeneous spaces (sometimes referred to as theorems of Barth-Lefshetz type) have been established by a number of authors. Morse Theory on the space of paths lead to an elegant proof of homotopy connectedness theorems for complex submanifolds of Hermitian symmetric spaces. In this work we extend this proof to a larger class of compact complex homogeneous spaces.
Improved Approximation Algorithms for Matroid and Knapsack Median Problems and Applications
Chaitanya Swamy
Computer Science , 2013,
Abstract: We consider the {\em matroid median} problem \cite{KrishnaswamyKNSS11}, wherein we are given a set of facilities with opening costs and a matroid on the facility-set, and clients with demands and connection costs, and we seek to open an independent set of facilities and assign clients to open facilities so as to minimize the sum of the facility-opening and client-connection costs. We give a simple 8-approximation algorithm for this problem based on LP-rounding, which improves upon the 16-approximation in \cite{KrishnaswamyKNSS11}. Our techniques illustrate that much of the work involved in the rounding algorithm of in \cite{KrishnaswamyKNSS11} can be avoided by first converting the LP solution to a half-integral solution, which can then be rounded to an integer solution using a simple uncapacitated-facility-location (UFL) style clustering step. We illustrate the power of these ideas by deriving: (a) a 24-approximation algorithm for matroid median with penalties, which is a vast improvement over the 360-approximation obtained in \cite{KrishnaswamyKNSS11}; and (b) an 8-approximation for the {\em two-matroid median} problem, a generalization of matroid median that we introduce involving two matroids. We show that a variety of seemingly disparate facility-location problems considered in the literature---data placement problem, mobile facility location, $k$-median forest, metric uniform minimum-latency UFL---in fact reduce to the matroid median or two-matroid median problems, and thus obtain improved approximation guarantees for all these problems. Our techniques also yield an improvement for the knapsack median problem.
Algorithms for Probabilistically-Constrained Models of Risk-Averse Stochastic Optimization with Black-Box Distributions
Chaitanya Swamy
Computer Science , 2008,
Abstract: We consider various stochastic models that incorporate the notion of risk-averseness into the standard 2-stage recourse model, and develop novel techniques for solving the algorithmic problems arising in these models. A key notable feature of our work that distinguishes it from work in some other related models, such as the (standard) budget model and the (demand-) robust model, is that we obtain results in the black-box setting, that is, where one is given only sampling access to the underlying distribution. Our first model, which we call the risk-averse budget model, incorporates the notion of risk-averseness via a probabilistic constraint that restricts the probability (according to the underlying distribution) with which the second-stage cost may exceed a given budget B to at most a given input threshold \rho. We also a consider a closely-related model that we call the risk-averse robust model, where we seek to minimize the first-stage cost and the (1-\rho)-quantile of the second-stage cost. We obtain approximation algorithms for a variety of combinatorial optimization problems including the set cover, vertex cover, multicut on trees, min cut, and facility location problems, in the risk-averse budget and robust models with black-box distributions. We obtain near-optimal solutions that preserve the budget approximately and incur a small blow-up of the probability threshold (both of which are unavoidable). To the best of our knowledge, these are the first approximation results for problems involving probabilistic constraints and black-box distributions. A major component of our results is a fully polynomial approximation scheme for solving the LP-relaxation of the risk-averse problem.
Advancement in Nanoscale CMOS Device Design En Route to Ultra-Low-Power Applications
Subhra Dhar,Manisha Pattanaik,Poolla Rajaram
VLSI Design , 2011, DOI: 10.1155/2011/178516
Abstract: In recent years, the demand for power sensitive designs has grown significantly due to the fast growth of battery-operated portable applications. As the technology scaling continues unabated, subthreshold device design has gained a lot of attention due to the low-power and ultra-low-power consumption in various applications. Design of low-power high-performance submicron and deep submicron CMOS devices and circuits is a big challenge. Short-channel effect is a major challenge for scaling the gate length down and below 0.1 μm. Detailed review and potential solutions for prolonging CMOS as the leading information technology proposed by various researchers in the past two decades are presented in this paper. This paper attempts to categorize the challenges and solutions for low-power and low-voltage application and thus provides a roadmap for device designers working in the submicron and deep submicron region of CMOS devices separately.
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