IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

The evaluation of adhesively bonded structures has been a challenge over the several decades that these structures have been used. Applications within the aerospace industry often call for particularly high performance adhesive bonds. Several techniques have been proposed for the detection of disbonds and cohesive weakness but a reliable NDE method for detecting interfacial weakness (also sometimes called a kissing bond) has been elusive. Different techniques, including ultrasonic, thermal imaging and shearographic methods, have been proposed; all have had some degree of success. In particular, ultrasonic methods, including those based upon shear and guided waves, have been explored for the assessment of interfacial bond quality. Since 3-D guided shear horizontal (SH) waves in plates have predominantly shear displacement at the plate surfaces, we conjectured that SH guided waves should be influenced by interfacial conditions when they propagate between adhesively bonded plates of comparable thickness. This paper describes a new technique based on SH guided waves that propagate within and through a lap joint. Through mechanisms we have yet to fully understand, the propagation of an SH wave through a lap joint gives rise to a reverberation signal that is due to one or more reflections of an SH guided wave mode within that lap joint. Based upon a combination of numerical simulations and measurements, this method shows promise for detecting and classifying interfacial bonds. It is also apparent from our measurements that the SH wave modes can discriminate between adhesive and cohesive bond weakness in both Aluminum-Epoxy-Aluminum and Composite-Epoxy-Composite lap joints. All measurements reported here used periodic permanent magnet (PPM) Electro-Magnetic Acoustic Transducers (EMATs) to generate either or both of the two lowest order SH modes in the plates that comprise the lap joint. This exact configuration has been simulated using finite element (FE) models to describe the SH mode generation, propagation and reception. Of particular interest is that one SH guided wave mode (probably SH0) reverberates within the lap joint. Moreover, in both simulations and measurements, features of this so-called reverberation signal appear to be related to interfacial weakness between the plate (substrate) and the epoxy bond. The results of a hybrid numerical (FE) approach based on using COMSOL to calculate the driving forces within an elastic solid and ABAQUS to propagate the resulting elastic disturbances (waves) within the plates and lap joint are compared with measurements of SH wave generation and reception in lap joint specimens having different interfacial and cohesive bonding conditions. © 2012 American Institute of Physics.

Department of Management Studies

Department of Mechanical Engineering

GENERAL

Fulltext

AIP Conference Proceedings

An EMAT-based shear horizontal (SH) wave technique for adhesive bond inspection

We use information theoretic achievable rate formulas for the multi-relay channel to study the problem of optimal placement of relay nodes along the straight line joining a source node and a destination node. The achievable rate formulas that we utilize are for full-duplex radios at the relays and decode-and-forward relaying. For the single relay case, and individual power constraints at the source node and the relay node, we provide explicit formulas for the optimal relay location and the optimal power allocation to the source-relay channel, for the exponential and the power-law path-loss channel models. For the multiple relay case, we consider exponential path-loss and a total power constraint over the source and the relays, and derive an optimization problem, the solution of which provides the optimal relay locations. Numerical results suggest that at low attenuation the relays are mostly clustered close to the source in order to be able to cooperate among themselves, whereas at high attenuation they are uniformly placed and work as repeaters. We also prove that a constant rate independent of the attenuation in the network can be achieved by placing a large enough number of relay nodes uniformly between the source and the destination, under the exponential path-loss model with total power constraint. © 2012 IFIP.

Department of Electrical Engineering

World University root node

2012 10th International Symposium on Modeling and Optimization in Mobile, Ad Hoc and Wireless Networks, WiOpt 2012

Optimal capacity relay node placement in a multi-hop network on a line

In this paper we address the operator assignment/reassignment problem in incremental cell formation. In incremental cell formation, cells are created based on parts and products that have high contributions. When these are created, it is necessary to assign operators, both from existing cells and new operators to work in the new cells. We consider three scenarios, where in the first we consider the assignment of operators to the new cells only. In the other two scenarios, we consider reallocation of operators to the existing cells if some operators from these are allotted to new cells. We show integer programming and network formulation for the three scenarios. We also test the network problems using randomly generated large sized problem instances.

International Journal of Manufacturing Technology and Management

Operator assignment/reassignment problems in incremental cell formation

Purpose&colon; The purpose of this paper is to investigate empirically the difference in long run post issue performance of initial public offerings &lpar;IPOs&rpar; that tapped the Indian primary market through a fixed price offer and book building offer&semi; also to assess the persistence of underperformance between these two routes of offering. Design&sol;methodology&sol;approach&colon; The after market performance of the IPOs is empirically assessed based on their market prices and also taking into consideration the other factors associated with the after market performance such as the period of issue &lpar;boom&sol;slump&rpar;, sector in which the industry is operating, etc. Findings&colon; The results suggest that there is no difference in the direction of performance of the issues post listing in the short run, however in the long run the issues that tapped the market through the book building route seemed to perform far better than the ones that raised money through a fixed price offer. The results also suggested that the average return irrespective of the route of issue remains the same and this is because of the high initial return of issues that tapped the market with fixed price offers. Originality&sol;value&colon; The paper provides useful information about the IPO markets of India and abroad, related literature and theories or hypotheses concerning methods of issue. © 2008, Emerald Group Publishing Limited.

Journal of Advances in Management Research

Long run post issue performance of fixed price and book built IPOs&colon; an empirical study on Indian markets

This research work empirically investigates the differences in stock price reaction of target and acquiring companies due to merger announcements. The role of insider information before merger announcements is also empirically tested and explained to be the cause for observed pre-announcement price run-ups. The investigation has been carried out using traditional event study methodology. Various event windows have been considered and compared to find out the period where the price run-up initiates. The post-merger price variations have also been studied. This analysis is suggestive of an upward trend in cumulative abnormal returns for companies in the pre-announcement period which in turn is indicative of insider information or anticipation. In addition, the evidence also suggests that around the announcement period the returns for the acquiring companies are higher than those for the target companies. In the post amalgamation period there is a downward trend in the cumulative returns implying a negative result of the merger. © Arun Kumar Gopalaswamy, Debashis Acharya, Jaideep Malik, 2008.

Investment Management and Financial Innovations

Stock price reaction to merger announcements: An empirical note on Indian markets

This paper empirically examines the properties of a new weighted monetary aggregate, Currency equivalent monetary aggregate (CEMA) for India using the components of a broad monetary aggregate NM3 recommended by the working group on Money Supply, Analytics and Methodology of Compilation, Reserve Bank of India (RBI, 1998). The empirical properties of this aggregate via a money demand function are compared with its simple sum counterpart NM3. The results suggest the superiority of the CEMA over NM3. © 2007 Dietrich Schönwitz.