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In this paper, an effort is made to determine the optimized parameters in laser welding of Hastelloy C-276 using Artificial Neural Network (ANN) and Genetic Algorithm (GA). CO2 Laser welding was performed on a sheet of thickness 1.6[Formula: see text]mm based on Taguchi L27 orthogonal array. Laser power, welding speed and shielding gas flow rate were chosen as input parameters and Bead width, depth of Penetration and Microhardness were measured for assessing the weld quality. ANN was applied for modeling the welding process parameters i.e. heat input, welding speed and gas flow rate. Various learning algorithms such as Batch Back Propagation (BBP), Incremental Back Propagation (IBP), Quick Propagation (QP) and Levenberg–Marquardt (LM) were comprehensively tested for estimating the output parameters and a comparison was also made among them, with respect to prediction accuracy. BBP method was found to be the best learning algorithm. Experimental validation test was performed based on the ANN and GA predicted optimized responses and this welding input parameters provided satisfactory weld metal characteristics in terms of penetration depth, bead width and microhardness.

Flooding of the cathode flow channel is a major hindrance in achieving maximum performance from Proton Exchange Membrane Fuel Cells (PEMFC) during the scaling up process. Water accumulated between the interface region of Gas Diffusion Layer (GDL) and rib of the cathode flow field can be removed by the use of Porous Sponge Inserts (PSI) on the ribs. In the present work, the experimental investigations are carried out on PEMFC for the various reaction areas, namely 25, 50 and 100 cm2. Stoichiometry value of 2 is maintained for all experiments to avoid variations in power density obtained due to differences in fuel utilization. The experiments include two flow fields, namely Serpentine Flow Field (SFF) and Modified Serpentine with Staggered provisions of 4 mm PSI (4 mm × 2 mm × 2 mm) Flow Field (MSSFF). The peak power densities obtained on MSSFF are 0.420 W/cm2, 0.298 W/cm2 and 0.232 W/cm2 compared to SFF which yields 0.242 W/cm2, 0.213 W/cm2 and 0.171 W/cm2 for reaction areas of 25, 50 and 100 cm2 respectively. Further, the reliability of experimental results is verified for SFF and MSSFF on 25 cm2 PEMFC by using Electrochemical Impedance Spectroscopy (EIS). The use of 4 mm PSI is found to improve the performance of PEMFC through the better water management.

Wire drawing is the most widely employed process for manufacturing the micrometer sized gold wire (φ10 − φ50 µm) used for electronic interconnects. Currently, gold wire is applied in the bonding pad and miniaturization has resulted in need of higher quality of wire; wire quality is dependent on mechanical properties. The mechanical properties are based on microstructural behavior. This work was performed during my Ph.D candidature at Nanyang Technological University, Singapore. This thesis would not have been possible without the cooperation and time of many people, whom I owe my deepest gratitude to. • My greatest thanks are reserved for my supervisor Associate Professor Sridhar Idapalapati whose help shall remain understated. His enthusiasm, inspiration and encouragement rubs off on students motivating us to perform better. His sound advice, constructive criticisms and his ability to explain things in a lucid manner shall always be remembered. • I would also like to thank Assistant Professor Sathyan Subbiah for co-advising this thesis. His efforts in guiding the thesis was amazing. It was an exorbitant privilege working with him. • My committee members Associate Professors Liu Er Jia, Tang Ming Jen and Assistant Professor Castagne Sylvie for overlooking my thesis work. • My special thanks to our subject librarian Mr. Ramaravikumar Ramakrishnan for providing me all the necessary resources for doing this Ph.D research. The library walk thru and ENDNOTE workshops were extremely helpful. His affable and risible attitude will always be remembered. • Thanks to Ms. Yong Mei Yoke for helping me with the SEM, Mr. Leong Kwok Phui for assisting me with the XRD and Dr. Zviad of the MSE school with the pole figure measurements. Mr. Teo Hai Beng for setting my LINUX cluster without which my simulations would never have happened.