Palaniappan Ramu

In the present study, a multi-fidelity, multi-objective and multi-disciplinary design problem statement for aeroelastic optimization of an aircraft wing has been posed. The problem minimizes the twin objectives of transonic drag and the weight of the structure during cruise flight at Mach 0.8 at 10 km altitude. The wing geometry was parametrized using 11 design variables. A multi-fidelity-based co-kriging metamodel was used to replace the multi-disciplinary analysis routine in the optimization problem. Reynolds-averaged Navier–Stokes (RANS) and Euler solvers were used as high and low fidelity aerodynamic solvers while refined and coarse meshes were used with a default Finite Element (FEM) solver for multi-fidelity structural analysis. Latin hypercube sampling was used to generate 100 design points, out of which 30 were used to perform high fidelity simulations and the rest were used for low fidelity simulations. A high fidelity MDA routine run had a computational time of 4 h while the low fidelity runs were of 30 min. A successful and computationally inexpensive coupled aeroelastic optimization methodology has been demonstrated using MDF and co-kriging. The aerodynamic coefficients Cl and Cd showed improvement of 4.69% and 17.9%, respectively, compared to the baseline values. The structural weight of the optimized geometry was reduced by 355.7 Kg, and there was 14.54% reduction in the maximum von-Mises stress in the optimized structure.

Visualization techniques in design space exploration with high dimensional data are helpful in enhancing the decision making in the context of multiple objective optimization. Visualization of Pareto solutions obtained is crucial to understand the trade-off between the objectives as it enables intuitive decision making. However, such a task is not trivial beyond three dimensions. In this work, we propose using interpretable self-organizing map (iSOM), to visualize Pareto solutions for MOO problems involving n objectives (n> 3 ). iSOM enable simplified component plane plots that allow visual inspection of the Pareto fronts and also allow identifying clusters in the Pareto front and the corresponding design variables. Proposed approach is successfully demonstrated on 3 analytical examples.

ECG steganography hides patient data inside their ECG signal to ensure the protection of patient's identity. In this work, an attempt has been made to evaluate ECG Steganography where Quantization Index Modulation (QIM) method is used to embed patient data into the Contourlet transform coefficients of ECG image. Tompkins QRS detection algorithm is used to construct ECG image and which is decomposed into a series of multiscale, local and directional image expansion using contour segments. QIM scheme is applied on the appropriate coefficients of the selected frequency sub-bands. QIM divides the selected frequency sub-bands into non overlapping blocks of matrix size 2×2. Two quantizers are used to embed binary watermark 0 and 1. The reverse Contourlet transform provides the watermarked ECG image from which 1D stego-ECG signal is re-ordered. The proposed scheme retrieves the watermark without the need of cover image. The deterioration due to the modified coefficients are reduced using adaptive selection of a coefficient to hide watermark bit. The efficiency of ECG steganography is measured using imperceptibility of watermark and Bit Error Rate of the retrieved watermark. Similarity metrics such as Peak Signal to Noise ratio, Percentage Residual Difference and Kullback-Leibler distance are used to estimate the imperceptibility of watermark on the stego-ECG signal. It is demonstrated that the proposed approach provides higher imperceptibility and less Bit Error Rate in the retrieved watermark, which is closed to zero. ECG signals obtained from MITBIH normal sinus rhythm data base are used to evaluate the performance of the proposed ECG Steganography approach.

In teaching a product design laboratory course in an engineering design department, it is desirable for students to be able to build products to appreciate design theory, the need for requirement elicitation, concept ranking, functional and conceptual decomposition and other related concepts. This allows them to understand the design life cycle and also provides a sense of accomplishment when they develop a product hands-on. It also becomes eminent to appreciate adaptive design and design with constraints for an existing product. We experimented by inviting industry collaborators to share their design problems and let students brainstorm and come up with solutions for the same. This paper will discuss our experiences on such an experiment over multiple years.