Albertian Institute of Science and Technology

India

Albertian Institute of Science and Technology

India
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Pulikkottil V.V.,Albertian Institute of Science and Technology | Sujith R.I.,Indian Institute of Technology Madras
Physics of Fluids | Year: 2017

A combustion chamber has a hydrodynamic field that convects the incoming fuel and oxidizer into the chamber, thereby causing the mixture to react and produce heat energy. This heat energy can, in turn, modify the hydrodynamic and acoustic fields by acting as a source and thereby, establish a positive feedback loop. Subsequent growth in the amplitude of the acoustic field variables and their eventual saturation to a limit cycle is generally known as thermo-acoustic instability. Mathematical representation of these phenomena, by a set of equations, is the subject of this paper. In contrast to the ad hoc models, an explanation of the flame-acoustic-hydrodynamic coupling, based on fundamental laws of conservation of mass, momentum, and energy, is presented in this paper. In this paper, we use a convection reaction diffusion equation, which, in turn, is derived from the fundamental laws of conservation to explain the flame-acoustic coupling. The advantage of this approach is that the physical variables such as hydrodynamic velocity and heat release rate are coupled based on the conservation of energy and not based on an ad hoc model. Our approach shows that the acoustic-hydrodynamic interaction arises from the convection of acoustic velocity fluctuations by the hydrodynamic field and vice versa. This is a linear mechanism, mathematically represented as a convection operator. This mechanism resembles the non-normal mechanism studied in hydrodynamic theory. We propose that this mechanism could relate the instability mechanisms of hydrodynamic and thermo-acoustic systems. Furthermore, the acoustic-hydrodynamic interaction is shown to be responsible for the convection of entropy disturbances from the inlet of the chamber. The theory proposed in this paper also unifies the observations in the fields of low Mach number flows and zero Mach number flows. In contrast to the previous findings, where compressibility is shown to be causing different physics for zero and low Mach number flows, we show that the heat release rate can also introduce the distinction between the zero and low Mach number flows. Therefore, during the thermo-acoustic interaction, we should consider the coupling of convection modes that arise from the interaction of acoustic and hydrodynamic fields with the entropy modes.


Joy A.,Albertian Institute of Science and Technology | Chakka V.K.,Shiv Nadar University
International Congress on Ultra Modern Telecommunications and Control Systems and Workshops | Year: 2015

In this paper we introduce an adaptive channel estimation scheme for two-way relay with node capability. The adaptive filter used is called Block Fast Array Multichannel 2D-Recursive Least Square (BFAM 2D-RLS). The modulation used is Orthogonal Frequency Division Multiplexing (OFDM) and channel estimation is done in the frequency domain. The proposed channel estimator considers correlation of channel frequency response in both time and frequency domain. The computational complexity is calculated and convergence performance of the adaptive channel estimator is studied. This paper also introduces an AOFDM scheme for two-way relay systems. The effect of channel estimation error on performance of Adaptive OFDM (AOFDM) is analyzed for pedestrian A (pedA) channel. All computer simulations are performed using MATLAB ®. © 2014 IEEE.


Joy A.,Albertian Institute of Science and Technology | Chakka V.K.,Shiv Nadar University
Proceedings - 2015 Advances in Wireless and Optical Communications, RTUWO 2015 | Year: 2015

In this paper we propose an adaptive channel estimation scheme for Amplify and Forward (AF) two-way relay systems with frequency selective and fast varying channels. The modulation used is Orthogonal Frequency Division Multiplexing (OFDM). This adaptive filter is called Block Fast Array Multichannel 2D Recursive Least Square (BFAM 2D-RLS) filter. The complexity of this adaptive filter is comparable to that of Least Mean Square (LMS) algorithm while maintaining similar convergence rate as that of the standard Recursive Least Mean Square (RLS) algorithm. Computer simulation using Matlab is performed to analyse the performance of BFAM 2D-RLS filter in estimating fast varying Vehicular-A (Veh-A) channel. The results obtained is compared with slow varying channels. © 2015 IEEE.


Krishnan A.K.,Cochin University of Science and Technology | George K.E.,Albertian Institute of Science and Technology
Polymers for Advanced Technologies | Year: 2014

Nanocomposites based on polypropylene/polystyrene blends were prepared by melt mixing in a Thermo Haake Rheochord mixer. The effect of mercapto silane modified kaolin clay on the properties of nanocomposites has been studied. The characterization of polypropylene/polystyrene/clay nanocomposites was made by dynamic mechanical analysis, scanning electron microscope, and transmission electron microscopic, and the thermal stability was determined by using Thermogravimetric analysis. The activation energy of degradation was determined using three mathematical models, namely Horowitz-Metzger, Coats-Redfern and Broido's methods, and the results were compared. TGA results show an improved thermal stability for nanocomposite than the pure blend. The improvement in thermal stability of nanocomposites was confirmed by increasing the activation energy. Transmission electron microscopic observations showed that nanoclay layers were intercalated on the polymer matrix and were located at the interface between the two polymers. © 2014 John Wiley & Sons, Ltd.


Nair P.P.,Government Engineering College at Thrissur | George K.E.,Albertian Institute of Science and Technology
International Journal of ChemTech Research | Year: 2014

This is the era of polymer nanocomposites which truly dominates the conventional composites with improved properties. High-Impact Poly Styrene/Vinylclay NanoComposites (HIPS/VNCs) are synthesized by in situ polymerization and by melt compounding. The effects of dispersion of the nanoclay on the morphology and material properties of HIPS/VNCs were compared for both the methods, and it is found that in-situ method gives better properties when compared to the other. Model equations were developed and Optimization of the properties was done by deploying Response Surface Methodology.


Krishnan K.A.,Cochin University of Science and Technology | Anjana R.,Cochin University of Science and Technology | George K.E.,Cochin University of Science and Technology | George K.E.,Albertian Institute of Science and Technology
Polymer Composites | Year: 2016

Alkali-resistant glass fiber (GF) reinforced polypropylene (PP)/polystyrene (PS) blends were prepared by melt mixing in a Thermo Haake Rheochord mixer. Variation in thermal and mechanical properties with the addition of glass fibers into the polypropylene/polystyrene blends was investigated. The characterization of PP/PS/GF composites was done by dynamic mechanical analysis (DMA), thermogravimetric analysis, scanning electron microscope, and transmission electron microscope. The experimentally observed tensile properties of glass fiber reinforced PP/PS blends were compared with various published models. It was found that the experimental results agree well with Hui- Shia and series models. DMA tests revealed an increase in storage modulus with fiber loading confirms the greater degree of stress transfer from the matrix to the fiber. TEM micrographs reveal that the glass fibers are located at the interface between the blend components. POLYM. COMPOS., 37:398-406, 2016. © 2014 Society of Plastics Engineers.


Joy A.,Albertian Institute of Science and Technology | Chakka V.K.,Dhirubhai Ambani Institute of ICT
Proceedings - 2013 3rd International Conference on Advances in Computing and Communications, ICACC 2013 | Year: 2013

This paper discusses a joint adaptive channel estimation and transceiver design scheme for MIMO two-way relay systems. In order to reduce the computational complexity at the transmitting nodes, the transceiver is implemented at the relay station. Adaptive transceiver consists of an adaptive postequalizer known as receive filter and an adaptive pre-equalizer known as transmit filter. The design of adaptive pre-equalizer requires the knowledge of Channel State Information (CSI) between nodes and relay station. So a channel tracking adaptive filter should be implemented at the relay. Due to the structure of a two-way relay system, the training signals used to train the receive filter can be used to train the channel tracking filter. Thus the adaptive channel estimator and receive filter work simultaneously. The channel estimate is then used to design the transmit filter. The adaptive filters are implemented using the NLMS algorithm. The performance of the proposed scheme is verified by making use of MATLAB simulations. © 2013 IEEE.


Joy A.,Albertian Institute of Science and Technology | Chakka V.K.,Dhirubhai Ambani Institute of ICT
International Conference on Next Generation Mobile Applications, Services, and Technologies | Year: 2013

This paper introduces a low complexity adaptive channel estimation technique for OFDM based two-way relay systems. The adaptive filter used is known as Group Fast Array Multichannel 2D-Recursive Least Square (GFAM 2DRLS) filter. It has a computational complexity comparable to that of 2D-Normalized Least Mean Square (2D-NLMS) algorithm while maintaining the same convergence rate as the classic 2D Recursive Least Square (2D-RLS) algorithm. It considers the correlation of the channel frequency response in both time and frequency, while estimating the channel. In order to reduce the number of training data for time varying channel, the channel estimation is carried out based on the Decision Directed (DD) principle. It is assumed that the relay is capable of performing complex signal processing tasks. Hence the channel estimation is performed at the relay. Since the Channel State Information (CSI) is available at the relay, it could perform Multiple Input Multiple Output (MIMO) precoding of the transmitted data. Hence CSI is not required at the transmitting nodes. The convergence rate of GFAM 2D-RLS is compared with the existing 2D-NLMS algorithm and the computational complexity at each iteration is tabulated. Simulations are performed using MATLAB. © 2013 IEEE.


George M.,Albertian Institute of Science and Technology | Kumar J.,Model Engineering College | Mini M.G.,Model Engineering College
2015 IEEE International Conference on Signal Processing, Informatics, Communication and Energy Systems, SPICES 2015 | Year: 2015

Electrical stimulation by means of a medical implant is used as a means of restoring the lost functionality of different physiological organs. An active implant which works on a battery or a passive implant which works on power wirelessly transferred to it, could be used for this purpose. The future developments and applications will be in passive implants because of their smaller size and greater implantability. At the moment Manchester encoding is utilized as the data encoding scheme in medical implants. But this work proposes an alternative encoding scheme called Pulse Interval Encoding(PIE) for application in a passive implant. PIE offers the advantage of a simpler decoding methodology and greater power transferred to the implant. A PIE decoder that is resilient to data jitter to the tune of 2.5 μs and that works with clock frequency between 1.52 MHz and 1.76 MHz is implemented in this work. The electrical stimulation patterns that the implant generate will vary according to the application. This work also presents the design of an universal digital stimulus generator which can be programmed to generate the stimuli patterns for a variety of applications like pain relief and bladder control. © 2015 IEEE.


Pai P.S.,Albertian Institute of Science and Technology | Beevi S.,RIT Government Engineering College
Proceedings of 2013 International Conference on Renewable Energy Research and Applications, ICRERA 2013 | Year: 2013

Solar energy utilization is gaining much importance these days owing to energy crisis and large power rating panels are used even for residential applications. The panels used in these medium power applications are usually fixed at a particular tilting angle. To extract power up to maximum by all possible ways, Dual Maximization Technique is proposed. Maximum Power Point Tracking and Mechanical Solar Tracking is used for Dual Maximization. Proposed system utilize active solar tracking to keep panel aligned to position of sun. The low power motors such as stepper motors and dc motors, which are usually used for tracking applications are not capable of handling torque requirement for tilting these heavy panels. This paper analyzes the use of induction motor for the tracking purpose. Induction motor used in this proposed system consumes only few watts of power which can be provided by the panel itself. For the proper control of induction motor at low speed, which is required for this application, a Variable Frequency Control is used. As no external input is required, except during initial implementation, it acts like a self supporting system. P&O algorithm is implemented as a part of dual maximization method. Simulation of the system is done in MATLAB-SIMULINK. © 2013 IEEE.

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