The present study focuses on experimental techniques to understand the self-excited oscillation characteristics in low-density round for fully developed and turbulent flow conditions, as well as rectangular jets, and study the effects Reynolds number, momentum thickness, density ratio and aspect ratio on self-excited oscillation. Two global modes exist in low-density round jets. The results confirms that oscillations in low-density round jets are axisymmetric irrespective of S and D/θ, and turbulent jets can exhibit self-excited oscillations for S ≤ 0.53. Studies on rectangular low-density jet reveal that the jet transitions from a stable to a self-excited state through subcritical and supercritical Hopf bifurcation. Only supercritical bifurcations are observed during transition when AR ≥ 12. For lower aspect ratios, the type of Hopf bifurcation is dependent on the density ratio. SPOD analysis of low AR rectangular jets (AR ≤6) show that the spatial structure of the oscillation is a symmetric mode. SPOD analysis reveals that the spatial structure of the oscillation in high AR rectangular jets (AR ≥ 12) consists of three modes: a symmetric mode, a flapping mode in the major dimension and a complex mode similar to the ce2 mode in elliptic jets.

Selective Catalytic Reduction (SCR) is one of the most promising technologies for reducing after-exhaust NOx emissions. Cu zeolites generally provide high SCR conversion rates at temperatures ≤ 350◦C. The limitations associated with powdered catalysts, such as low mass diffusion and high pressure drop, can be minimized to a certain extent by replacing them with structured catalysts. The foam catalysts exhibit superior characteristics, such as a high surface-to-volume ratio, porosity, and tortuosity, which improve the mass diffusion and lower the pressure drop. In this study, α-alumina foam was prepared using a thermo-foaming technique. The procedure followed during this research for the preparation of the Cu-ZSM-5 zeolite coating over alumina foam through in situ hydrothermal and dip-coating methods is also presented in detail. A self-supporting foam catalyst of Cu-ZSM-5 is prepared using a freeze-casting emulsion method. A comprehensive experimental study was conducted to understand the mass transfer and pressure drop characteristics of the foam catalysts. Correlations for the mass transfer coefficient and friction factor were derived for the foam catalyst and validated against the available data in the literature reviewed. A detailed investigation of key SCR reactions, such as the standard SCR, fast SCR, slow SCR, NO oxidation, NH3 oxidation, and NO2 decomposition, was also carried out in this research. The inhibitory effects of the feed reactants were studied by varying the feed concentration. A detailed investigation of the impact of the inhibition effect of NO2 and NH3 on the SCR reaction at low temperatures is also presented.

Experiments probing correlations between spin-1/2 nuclei (I) and nuclear spins (S) with large anisotropic interactions (quadrupolar or chemical shift anisotropy ) often offer valuable access routes to molecular structures and dynamics. In such experiments, development of efficient correlation schemes is not trivial and constitutes an ever-evolving theme of research. As these experiments are performed routinely under MAS, interference between the RF filed and the large time- dependent quadrupolar or chemical shift anisotropic interaction leads to complex spin dynamics, often leading to poor and orientation-dependent transfer efficiency.

The current work proposes novel stochastic meshless methods for the analysis of linear and nonlinear problems in structural mechanics which can take care of uncertainties in material property and loading when they appear as random variables or homogeneous random fields. The study suggests an improved response function based stochastic meshless method for the analysis of linear elastic problems. Further, the study also proposes a simple and efficient stochastic meshless method for the analysis of linear eigenvalue problems in structural mechanics. A high dimensional model representation based stochastic meshless technique is proposed in the current study for the analysis of geometric nonlinear problems in solid mechanics. A few numerical examples are solved to validate the proposed method by comparing the results with the direct Monte Carlo simulation or other existing methods. Further, the computational efficiency of the proposed methods is also established.

Defect free machining of Fibre Reinforced Polymer (FRP) Composites, crossing the challenges posed by anisotropic non-homogenous fibre-matrix system, is one of the important material processing requirements with a wide scope in industrial applications. Eccentric Sleeve Grinding (ESG) projected in this research is a unique strategy with progressive-intermittent cutting scheme for achieving minimal damage machined surfaces on FRPs. Progressively varying depth of engagement for active abrasive grains in the cutting zone with an intermittent and periodically repeating cutting pattern, achieved through precisely controlled eccentric rotation of grinding wheel is the key highlight of ESG. Through this step-by-step cutting methodology, significant reduction in average grinding force, surface defects and surface roughness have been achieved on Carbon Fibre Reinforced Polymer (CFRP) composites under varying cutting conditions. The thesis covers the geometric configurations, kinematics, coordination of work feed and wheel rotation to achieve scallop free surfaces during intermittent cutting, theoretical and experimental studies on mechanics and micro-mechanics of ESG, thermal aspects and other miscellaneous findings (theoretical and experimental) on ESG.

The eco-cultural space Kavu (sacred groves) has been subjected to academic introspection from ecological, anthropological, historical and Folk Culture Studies perspectives. The thesis focuses on the representation of kavu in the popular discourse of Malayalam cinema. The primary objective of this thesis is to determine whether Malayalam films have addressed the heterogeneity of kavu, while considering its diverse systems of worship, caste dynamics, gender equations and ecological diversity.

We begin our work by studying the most general class of oscillators, called ‘f-deformed oscillators’ or ‘f-oscillators’. We define the quadrature operator for the f-deformed algebra and hence obtain the deformed quadrature operator eigenstates. We derived a new set of polynomials and derived the deformed oscillator wavefunctions in terms of them. The position probability distribution for three different types of deformations are plotted, and each is compared with the corresponding non-deformed counterpart. The newly obtained quadrature operator eigenstates will be helpful for those who are working in the field of quantum state reconstruction and quantum information processing of deformed states.

A systematic, extensive and in-depth study of channel characteristics for both static and dynamic human body model is reported in this thesis. The work involves design, fabrication and testing of various printed and dielectric antennas with very high gain for the proposed applications. A significant part of the thesis deals with human model which features the critical body segments such as head, shoulder, torso, upper arm, lower arm, thighs and calf for the study of double arm swing activity. Two cross-slot antennas (CSA) are designed and fabricated, for investigation of the double arm swing activity using the newly introduced twelve cylinder body model. The same CSA is used for creeping wave analysis on cylindrical single layered phantom. Simulations are done in CST Microwave studio suite and experiments are carried out using container filled with distilled water as phantom. The work reported in the thesis are published in very high quality journals such as IEEE Antennas and Wireless Propagation Letters, Wiley RFMICAE, Journal of Electronics Materials and so on.

This study is an earnest attempt to understand the role of mass media in the transition of Adivasis in the Wayanad District of Kerala. It was designed to address certain intriguing questions that emerged in the researcher’s mind, ranging from when the media technologies made inroads into the life of the Adivasi communities, what are the media artefacts that have got diffused, what are the different factors that have influenced the diffusion of mass media among Adivasis and how they have influenced the everyday life.

This dissertation is explored the photonics inter sub band transitions (ISBT) phenomenon in an electronics Gallium Nitride (GaN) high electron mobility transistor (HEMT) device. Conventional photonic devices are operated at cryogenic temperatures to minimize the thermal effect. The reported maximum operating temperature of THz quantum cascade laser (QCL) is in the range of 150-200 K which is too low for general applications. The conduction band tuning through external gate bias makes advantage of HEMT device for room temperature (RT) terahertz applications. The theoretical models for electrically tuneable plasmonic metamaterials assisted ISBT have been developed. Experimental demonstration of electrical tuning of ISBT in a GaN HEMT device at room temperature has not only provided a novel mechanism but also discriminates ISBT from other transitions induced by deep-level traps and defects in the 100 nm GaN HEMT device. It is possible to tune the subband energy level inside triangular quantum well of GaN HEMT by applying gate voltage. The GaN HEMT device responds toward incident terahertz radiation due to inherent advantage of conduction subband tuning through external bias. The presented novel approach for ISBT in GaN HEMT has the potential possibilities in the context of overcome the THz gap in the electromagnetic spectrum at ambient temperature.

Electrochemistry deals with the relation between electrical and chemical phenomena and has an ever-increasing impact on everybody's daily life. Out of the myriad applications of electrochemistry, considerable attention has been devoted to the fields of electrochemical (EC) sensing in recent decades because of its inherently fast, accurate, compact, portable, and cost-effective properties. In this scenario, the thesis work aims to address the challenges in the fields of EC sensing by using the rational design of nano-functional materials using graphene quantum dots (GQDs) and metal nanoclusters (MNC). The on-site monitoring of various analyte species in the environment by EC sensors requires enhanced sensitivity, specificity, and accuracy. Herein, we are trying to meet the aforementioned needs by developing various nano-functional materials based on GQDs and MNC. We have developed nitrogen (N-) and sulphur (S-) doped GQDs and gold (Au) and copper (Cu) -based NCs for the EC sensing of toxic heavy metal ions and biologically relevant molecules. The EC sensor materials exhibited excellent sensitivities and lowest detection limits reported hitherto, indicating the potentiality of the developed materials. In conclusion, this thesis presents an understanding of how the logical designing of nano-functional materials can meet the needs and conquer the challenges in the EC sensing of various analytes.

First phase of the research work focuses on dynamic modeling and ascent flight control of a highly unstable and flexible launch vehicle. Stabilizing adaptive PD/PID controllers are developed in MRAC framework using standard quadratic Lyapunov function to control the time varying rigid body dynamics during the atmospheric phase of flight. Further, Lyapunov stability and Barbalat’s Lemma are applied to prove the stability of the time-varying system. In the second phase of the research work proposes projection and barrier Lyapunov based adaptive controllers for the descent phase flight control of a winged re-entry vehicle. A rectangular projection operator is used in the adaptive control design to constrain the adapted gains within a maximum and minimum limit simultaneously.