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Hyderabad, India

Buragohain M.,Advanced Systems Laboratory | Velmurugan R.,Indian Institute of Technology Madras
Composite Structures | Year: 2011

Grid-stiffened composite structures are known for their very high efficiency under compressive loading environment. The grid of stiffening ribs is the primary feature in these structures and filament winding is employed as the most convenient manufacturing technique. Three different types of circular cylindrical structures - unstiffened shell (with skin only), lattice cylinder (with ribs only) and grid-stiffened shell (with skin and ribs) - are considered for experimental study and a series of these structures have been manufactured adopting a simplified and cheap manufacturing process. Different aspects of manufacturing that include tooling and other processing aspects are presented in this paper. Axial compression tests have been carried out and the results are compared with finite element analysis. Based on the test results and comparison with finite element analysis, conclusions are drawn on the efficacies of this relatively new class of structures. © 2010 Elsevier Ltd.

Verma O.P.,Delhi Technological University | Hanmandlu M.,Indian Institute of Technology Delhi | Kumar P.,Advanced Systems Laboratory | Chhabra S.,Delhi Technological University | Jindal A.,Delhi Technological University
Pattern Recognition Letters | Year: 2011

A new approach for edge detection using a combination of bacterial foraging algorithm (BFA) and probabilistic derivative technique derived from Ant Colony Systems, is presented in this paper. The foraging behavior of some species of bacteria like Escherichia coli can be hypothetically modeled as an optimization process. A group of bacteria search for nutrients in a way that maximizes the energy obtained per unit time spent during the foraging. The proposed approach aims at driving the bacteria through the edge pixels. The direction of movement of the bacteria is found using a direction probability matrix, computed using derivatives along the possible directions. Rules defining the derivatives are devised to ensure that the variation of intensity due to noise is discarded. Quantitative analysis of the feasibility of the proposed approach and its comparison with other standard edge detection operators in terms of kappa and entropy are given. The effect of initial values of parameters of BFA on the edge detection is discussed. © 2011 Elsevier B.V. All rights reserved.

Gunda J.B.,Advanced Systems Laboratory
ZAMM Zeitschrift fur Angewandte Mathematik und Mechanik | Year: 2013

Large amplitude free vibration behavior of thin, isotropic square plate configurations resting on Winkler type of elastic foundation are expressed in the form of simple closed-form solutions by using the Rayleigh-Ritz (R-R) method based on coupled displacement fields (CDF). Geometric non-linearity of von-Kármán type is taken into consideration. The in-plane displacement field variations used in the formulation of the R-R (CDF) method are derived by using the governing in-plane static differential equations of the plate which in turn simplifies the difficulty of assuming an in-plane displacement field variations of the plate. Accuracy and robustness of proposed closed-form solutions is compared to the available finite element formulation results. Proposed closed-form solutions are corrected for the simple harmonic motion (SHM) assumption using the well established harmonic balance method (HBM) which is applicable for the homogeneous form of cubic non-linear Duffing equation. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Verma O.P.,Delhi Technological University | Kumar P.,Advanced Systems Laboratory | Hanmandlu M.,Indian Institute of Technology Delhi | Chhabra S.,Delhi Technological University
Applied Soft Computing Journal | Year: 2012

This paper presents a novel approach for the enhancement of high dynamic range color images using fuzzy logic and modified Artificial Ant Colony System techniques. Two thresholds, the lower and the upper are defined to provide an estimate of the underexposed, mixed-exposed and overexposed regions in the image. The red, green and blue (RGB) color space is converted into Hue Saturation and Value (HSV) color space so as to preserve the chromatic information. Gaussian MFs suitable for the underexposed and overexposed regions of the image are used for the fuzzification. Parametric sigmoid functions are used for enhancing the luminance components of under and over-exposed regions. Mixed-exposed regions are left untouched throughout the process. An objective function comprising of Shannon entropy function as the information factor and visual appeal indicator is optimized using Artificial Ant Colony System to ascertain the parameters needed for the enhancement of a particular image. Visual appeal is preferred over the consideration of entropy so as to make the image human-eye-friendly. Separate power law operators are used for the saturation adjustment so as to restore the lost information. On comparison, this approach is found to be better than the bacterial foraging (BF)-based approach [1]. © 2011 Elsevier B.V. All rights reserved.

Gunda J.B.,Advanced Systems Laboratory | Gupta R.K.,Advanced Systems Laboratory | Ranga Janardhan G.,JNTUH College of Engineering | Venkateswara Rao G.,Sreenidhi Institute of Science and Technology
Composite Structures | Year: 2011

Large amplitude vibration analysis of laminated composite beam with axially immovable ends is investigated with symmetric and asymmetric layup orientations by using the Rayleigh-Ritz (R-R) method. The displacement fields used in the analytical formulation are coupled by using the homogeneous governing static axial equilibrium equation of the beam. Geometric nonlinearity of von-Karman type is considered which accounts for the membrane stretching action of the beam. The simple closed-form solutions are presented for the nonlinear harmonic radian frequency as function of central amplitude of the beam using the R-R method. The nonlinear harmonic radian frequency results obtained from the closed-form solutions of the R-R method in general show good agreement with the results obtained from simple iterative finite element formulation. Furthermore, the closed-form expressions are corrected for the harmonic motion assumption from the available literature results on the existence of quadratic and cubic nonlinearity. It is interesting to note that the composite beams can result in asymmetric frequency vs. amplitude curves depending upon the nature of direction of displacement in contrast to isotropic beams which exhibit cubic nonlinearity only and leads to symmetric frequency vs. amplitude curves with respect to sign of the amplitude. © 2010 Elsevier Ltd.

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