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Author

Palaniappan Ramu

Other affiliations: University of Florida
Bio: Palaniappan Ramu is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Computer science & Steganography. The author has an hindex of 13, co-authored 41 publications receiving 847 citations. Previous affiliations of Palaniappan Ramu include University of Florida.


Papers
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Journal ArticleDOI
TL;DR: An efficient approximation-based generalized RDO framework that allows transformation of the RDO problem to an equivalent deterministic one and yields desirable results in significantly less number of functional evaluations is proposed.
Abstract: Robust design optimization (RDO) has been eminent in determining the optimal design of real-time complex systems under stochastic environment. Unlike conventional optimization, RDO involves uncertainty quantification which may render the procedure to be computationally intensive, if not prohibitive. In order to deal with such issues, an efficient approximation-based generalized RDO framework has been proposed. Since RDO formulation comprises of statistical terms of the performance functions, the proposed framework deals with approximation of those statistical quantities, rather than the performance functions. Consequently, the proposed framework allows transformation of the RDO problem to an equivalent deterministic one. As a result, unlike traditional surrogate-assisted RDO, the proposed framework yields desirable results in significantly less number of functional evaluations. For performing such response statistical approximation, two adaptive sparse refined Kriging-based computational models have been proposed. However, the generality of the proposed methodology allows any surrogate models to be employed within this framework, provided it is capable of capturing the functional non-linearity. Implementation of the proposed framework in three test examples and two finite element-based practical problems clearly illustrates its potential for further complicated applications.

12 citations

Journal ArticleDOI
TL;DR: This work proposes a modified SOM algorithm whose maps are interpretable and that does not fold and allows smoother input and performance space visualization and shows that the proposed approach is highly efficient in identifying the RoI and in obtaining the optima with less samples.
Abstract: Identifying regions of interest (RoI) in the design space is extremely useful while building metamodels with limited computational budget. Self-organizing maps (SOM) are used as a visualization technique for design space exploration that permits identifying RoI. Conventional implementation of SOM is susceptible to folds or intersections that hinder visualizing the design space. This work proposes a modified SOM algorithm whose maps are interpretable and that does not fold and allows smoother input and performance space visualization. The modified algorithm enables identification of RoI and additional sampling in the identified RoI allows building accurate Kriging metamodel, which is then used for optimization. The proposed approach is demonstrated on benchmark nonlinear analytical examples and two practical engineering design examples. Results show that the proposed approach is highly efficient in identifying the RoI and in obtaining the optima with less samples.

12 citations

Proceedings ArticleDOI
16 Apr 2007
TL;DR: In this article, the authors investigated the error in the failure probability estimated using a response surface approximation and found that small errors in the response surface may amplify to large errors in failure probability, and the amplification occurs when the failure surface is far away from the response mean and the DOE has more points near the mean.
Abstract: Response surface methods which approximate the actual performance function using simple algebraic equations are widely used in structural reliability studies. The response surface approximations are often used to estimate the reliability of a structure. Errors in the response surface approximation affect the results of reliability analysis. This work investigates the error in the failure probability estimated using a response surface approximation. It is observed that small errors in the response surface may amplify to large errors in the failure probability. It is observed that the amplification occurs when the failure surface is far away from the response mean and the DOE has more points near the mean. Another situation is when the failure region is a small island encompassed within the safe region, and the points in the DOE fail to capture the failure region. Analytical and engineering application examples are investigated to understand the amplification of error in the failure probability.

10 citations

Journal ArticleDOI
TL;DR: An easy-to-use mobile and web based, free and open source PP-GIS solution, Watershed GIS, was developed and scored better than the three existing solutions and its usage resulted in substantial reduction of variability in criteria values and thus better ranking of alternatives.
Abstract: Participatory approaches elicit information from multiple stakeholders while planning and implementing resource management systems. Such elicited information is often associated with significant variability. Public participation geographical information science GIS PP-GIS solutions can reduce this variability by helping stakeholders to measure the factors involved and provide the elicited information. We propose a ‘Quality Function Deployment’-based participatory framework for developing such PP-GIS solutions. It is demonstrated using a case study to enhance an existing PP-GIS into a solution for rainwater harvesting systems in Indian villages. The novelty of the proposed framework is that it identifies metrics and carries out comparative analysis of three existing solutions: participatory rural appraisal, participatory mapping and PP-GIS. In the case study, PP-GIS scored less than participatory mapping as it scored less on usability and affordability. To improve PP-GIS in these aspects, an easy-to-use mobile and web based, free and open source PP-GIS solution, Watershed GIS, was developed. It scored better than the three existing solutions and its usage resulted in substantial reduction of variability in criteria values and thus better ranking of alternatives, with the average coefficient of variation decreasing from 0.12 to 0.05.

9 citations

Journal ArticleDOI
TL;DR: In this article, the authors proposed Alpha shapes, a computational geometry technique to approximate the boundaries of the failure domain to estimate reliability and perform optimization of a tube impacting a rigid wall and a tuned mass damper.
Abstract: Treatment of uncertainties in structural design involves identifying the boundaries of the failure domain to estimate reliability. When the structural responses are discontinuous or highly nonlinear, the failure regions tend to be an island in the design space. The boundaries of these islands are to be approximated to estimate reliability and perform optimization. This work proposes Alpha (?) shapes, a computational geometry technique to approximate such boundaries. The ? shapes are simple to construct and only require Delaunay Tessellation. Once the boundaries are approximated based on responses sampled in a design space, a computationally efficient ray shooting algorithm is used to estimate the reliability without any additional simulations. The proposed approach is successfully used to decompose the design space and perform Reliability based Design Optimization of a tube impacting a rigid wall and a tuned mass damper.

9 citations


Cited by
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Book ChapterDOI
17 Jul 2002

1,123 citations

Journal ArticleDOI
TL;DR: In this article, the authors present a brief survey on some of the most relevant developments in the field of optimization under uncertainty, including reliability-based optimization, robust design optimization and model updating.

487 citations

Journal ArticleDOI
TL;DR: A comprehensive review of Uncertainty-Based Multidisciplinary Design Optimization (UMDO) theory and the state of the art in UMDO methods for aerospace vehicles is presented.

426 citations