National Institute of Technology, Meghalaya

About: National Institute of Technology, Meghalaya is a education organization based out in Shillong, India. It is known for research contribution in the topics: Control theory & Computer science. The organization has 503 authors who have published 1062 publications receiving 6818 citations. The organization is also known as: NIT Meghalaya & NITM.

An Empirical Seed Initialization Idea for K-Means Algorithm Inspired by CLIQUE Algorithm

Abstract: The K-means clustering algorithm gives good clustering results when the initial centroids or seeds are chosen close to actual cluster centers. In this paper an empirical centroid initialization technique has been presented for the K-means clustering algorithm. The technique is inspired by a well-known grid-based clustering algorithm called 'CLIQUE.' The technique evaluates the initial centroids by evaluating validity indices to check their vicinity from actual cluster centers. Experiments on datasets show that the technique obtains good initial centroids for the datasets compared to state-of-the-art K-means++ clustering algorithm.

Analysis of Different Types of Micro Grains in Stick Welded Mild Steel Plates

Abstract: Nowadays, arc welding is the most essential thing in every field. Therefore, researchers are focusing on the improvement of the quality of the arc welding. For that microstructure plays a major role in this work, mild steel plates were taken as workpiece material to do welding operation in stick welding. V-edge was prepared to conduct butt welding between the plates which has to be joined by application of 120 A current. After cooling, the microstructure of the welded specimen was observed. Importantly, two main constituents’ ferrite and pearlite were found mostly. Eight varieties of ferrite were analyzed in fusion zone and heat-affected zone. The primary ferrites were distinguished in the heat-affected zone and the Widmanstatten ferrites in fusion zone in between the dendritic structures. The primary ferrites have been more circular in nature and the Widmanstatten ferrites were columnar. The mechanical properties also vary due to the variation of ferrite structures. Pearlites were observed in between the ferrites with more percentage of carbon content which is the most distinguished feature of pearlite grains.

Application of Taguchi’s Orthogonal Array and Overall Evaluation Criteria in Turning of AISI D2 Steel in Dry and Forced Air-Cooled Environment

Abstract: Optimization of process parameters is an important technique in machining sector. In the present work, an experimental study has been performed in turning of AISI D2 steel using coated carbide tool in dry and forced air-cooled environment. Taguchi’s orthogonal array L9 has been used for running the experiments considering cutting speed, feed rate and depth of cut as process parameters and surface roughness, flank wear and cutting force as performance parameters. To optimize the performance parameters together in a single setting, an overall evaluation criterion (OEC) has been used. Analysis of variance (ANOVA) and average performance value of OEC is also analyzed. It is found that from the predicted setting of the average performance value of OEC, the surface roughness, flank wear and cutting force is reduced in both dry turning (DT) and forced air-cooled turning (ACT) as compared to the optimum value obtained from the experimental run.

Understanding the Flashover Characteristics across Stay Arm Insulator due to Lightning Stroke

Abstract: The lightning strike on any electrical system hampers reliability of the system. In this work, the effect of lightning stroke on the flashover characteristics of stay arm insulator of a traction mast is studied. To understand the flashover characteristics across stay arm insulator, firstly the effect of lightning stroke with different peak magnitude and steepness is studied. Secondly the effect of lighting striking at different polarity of sinusoid conductor voltage is studied. It is observed that lightning stroke parameters affects the overvoltage characteristics across stay arm insulator. However flashover behavior largely depends on leader propagation and ionization of soil. The polarity of conductor voltage also affects overvoltage and flashover behavior. It is seen in either case, soil ionization and leader propagation behavior may explain the occurrence of flashover.

Automated Vehicles Path Modification for Designated Via-Point Using Nonlinear Simplex Optimizer

Abstract: Path generation and modification are very important issues in the operation of automated vehicles. The pertaining processing time and accuracy in real time often depend on the type of solution algorithm. In this paper, a gradient-free optimization algorithm has been used for Bezier curve-based base path modification for passing through the designated via-point. The strength of nonlinear simplex optimizer in the limited three-dimensional solution space is added with the features of no requirement of computing derivatives and smooth objective function. The performance of the proposed method is compared with that of the method using gradient-based optimizer through computer simulation results.