Numerical methods are used to determine the improvement in the aerodynamic characteristics of a novel canard UAV fitted with electrically powered propellers by subjecting the aircraft to a constant freestream at varying angles of attack for several propeller configurations using different slipstream modelling techniques. The slipstream is simulated using a modified actuator disk model and rotating propeller profiles. The four propeller configurations being studied are, pushers only, tractors only, tractors with a tail rotor, and tractors with tail and tip rotors. The configuration with tractors and a tail rotor provides the highest increase in the lifting capacity of the aircraft for positive angles of attack while the offset tractors-only configuration has the highest lift-to-drag ratio, in the actuator disk studies. A hybrid RANS-LES numerical turbulence model called Detached Eddy Simulation is used for the unsteady cases. This results in outperformance of the pusher configuration as compared to the tractor configuration. The tractors deteriorate the aerodynamic efficiency of the UAV more than the pushers. Although the tractor configuration injects momentum directly into the boundary layer of the wing, at higher angles of attack at the given ambient conditions, it proves to be insufficient to avoid the separation of the boundary layer resulting in a separation bubble enlargement towards the trailing edge of the wing as the angle of attack increases. The better aerodynamic efficiency of the pusher configuration can be explained by the smoother flow over the suction surface as visualized by the velocity streamlines. The study also shows a trending decrease in the contribution of the viscous drag component for the two configurations for both numerical approaches.

Hybrid composites comprising glass and carbon fibres have significantly increased applications due to their synergetic effect. Fibre hybridisation generally overcomes the limitation of one fabric by the benefit offered by the other fabric. However, during the service life, a structure may undergo various damages because of mechanical load or environmental conditions, which reduces the component's strength. In this work, the carbon-glass hybrid composite was repaired using the adhesive patch repair technique. The post repair behaviour is investigated in high velocity impact, tensile static and fatigue loading environments. In the impact study, the stacking sequence of plies in a patch and the effect of different patches were studied. A 3D finite element model was also developed in ABQUS with the VUMAT subroutine and validated with the experimental results. It is observed that the placement of glass plies and the number of glass plies in the patch significantly enhance the impact resistance of the specimen. This 3D finite element model was further modified to incorporate the effect of resin fill in the hole area of a repaired specimen. With the help of the modified model, the effect of patch size and stacking sequence for a fixed parent specimen was studied. In the tensile study, the effect of the patch parent stacking sequence and the patch stiffness were analysed with the aid of digital image correlation (DIC) and acoustic emission (AE). The least stiff patch with parent laminate having glass ply as the exterior ply exhibited the highest strength recovery during the tensile loading. Furthermore, tensile-tensile fatigue tests were performed for the drilled and repaired specimens to understand the behaviour of parent stacking sequences. In the fatigue environment, the parent specimen with glass plies at the exterior layer performed better than the carbon plies at the exterior layer.

Distributed generation (DG) is a dynamic trend connecting renewable energy sources (RES) like solar and wind to the grid alongside conventional sources. The rapid adoption of RES and power electronics at industrial and residential levels cause power quality (PQ) issues. Custom power devices (CPD) emerged to enhance PQ due to strict DG regulations and consumer demand. One of the CPDs, distribution static compensator (DSTATCOM) addresses current related PQ issues, while dynamic voltage restorer (DVR) tackles voltage-related concerns. Unified power quality conditioner (UPQC) combines DSTATCOM and DVR using the conventional back-to-back (BTB) converter topology, yet DVR is underutilized due to rare voltage issues. To improve converter utilization factor, the BTB converter is replaced with a reduced switch count converter (dual-output converter, DOC) for UPQC operation. However, the DOC topology requires control schemes capable of managing converter neutral-point voltage (NPV) alongside current and voltage. Implementing the control scheme in the natural abc reference frame reduces computation and eliminates the errors due to signal transformations. While implementing conventional sliding mode control (SMC) in the abc frame, it experiences coupling issues among the phases which makes the controller difficult to generate switching pulses. Considering these points, an improved sliding mode control is proposed in abc frame, which incorporates control of converter NPV along with current or voltage control and also addresses the coupling issue. Simulation and experiments confirm the proposed control scheme's effectiveness for the four-leg DOC based DSTATCOM and DVR under diverse conditions. Finally, the performance of the proposed scheme for four-leg DOC based UPQC is verified through simulation studies.

Graphene nanoplatelets (GNPs) is a 2-dimensional crystalline allotrope of carbon that is SP2 hybridized and densely packed in a honeycomb crystal lattice. GNPs are the genesis of a range of disruptive technologies spread across many industrial sectors. The unique properties of graphene, strength, surface area, flexibility, and high thermal and electrical conductivity help graphene sense the environmental changes during structural health monitoring purposes. Here in the thesis, the GNP sensors provide a multifunctional approach in the context of (a) mechanical strain sensing for SHM applications, (b) improved thermal signature coatings for SHM applications, and (c) bio-mechanical sensing for human locomotion monitoring. The research reported in this thesis investigates the interaction of piezoresistivity and mechanical strain associated with realistic deformation in terms of monotonic, step and cyclic loading. Also, it has been aimed to monitor the delamination and crack during thermo-elastic behaviour by smart skin graphene nanoplatelet (GNPs) based strain sensor. In the analysis of smart sensing, the change in resistance was observed in cases of coating the structures and has been validated with commercial strain sensors. Sensors have shown good response and stability under dynamic and static loading. The scotch tape erosion method is used to tailor the initial resistance. A GF of 55 (±0.5), 70 (±2), and 77 (±1) were obtained for Ro of 1 kΩ, 7 kΩ and 21kΩ, respectively. The results show that the smart layers exhibit a significantly higher sensitivity than the commercial strain gauge. The GF is found to be dependent upon the GNP density on the surface. Also, it has helped in the investigation of thermal management in the case of composites and metals too by improving thermal signatures. The understanding of the interaction of smart strain sensors out from carbon allotrope called graphene nanoplatelets in metals, composites like GFRP and human health monitoring is further extended to natural frequency sensing in case of metals like SS304 during defect and without defect investigation. This has been validated with a commercial-based strain gauge whose sensitivity is less. Human disease monitoring in terms of flexibility has been validated with various resistance changes in healthy and unhealthy calf muscles and with Doppler ultrasonography. This GNPs-based sensor has also helped in sensing human locomotion in the neck, calf muscles and biceps. Also, novel research has been mentioned in this thesis on the context of a smart wearable sensor, called Lycra denim textile sensor which has helped in sensing human locomotion. Also, this sensor has helped in monitoring the natural frequency of SS304, with and without defect specimen in terms of piezoresistivity. In the case of metals like aluminium of grade 2024-T351, GNPs/PMMA sensor has helped in sensing mechanical strain at different zone of temperatures in pre-processing, during temperature and post-processing techniques. The basic goal is to study sensor performance under heating type during monitoring of cold and heat-treated aluminium specimens. The intelligent strategy for health monitoring potential ability opens new possibilities for implementing the sensor in future with graphene of high quality in a clean and straightforward way. Hence, GNP spray-coated sensors can be a potential candidate for structural health monitoring in near future.

Liquid-liquid interactions occur in many applications, such as solvent extraction, oil recovery plants, emulsification, and washing of organic phases. The exchanges may become more significant once the container experiences vibrations. In some cases, such as mixing, the requirement of instability between the immiscible liquids is appreciated, whereas, in the case of solvent extraction, the instabilities have to be avoided. There are primarily three types of vibrations studied in the literature: 1. Oscillation along the vertical axis, 2. Oscillation along the perpendicular to the interface, and 3. Oscillation along the tangential to the interface (Frozen wave instability). In the present work, the second and third types of oscillations are considered to investigate the volumetric effects of each liquid on their instability threshold and wave amplitude response.

Higher functionality electronics demand cooling devices that use boiling and condensation to dissipate large heat through latent heat. Thermosyphon is a cost-effective wickless heat pipe that can dissipate heat by boiling and condensing the working fluid. In the present study, novel configurations of flat thermosyphon heat sinks are developed, and their thermal performance is investigated. First, the thermal performance of a compact flat thermosyphon is experimentally and numerically investigated with different working fluids, filling ratios, and the number of heat sources. It is observed that the flat thermosyphon is more reliable in cooling multiple heat sources than a single-phase cold plate. The thermal performance of the flat thermosyphon is then experimentally investigated for different combinations of evaporator and condenser surface wettabilities. A novel integrated flat thermosyphon heat sink (IFTHS) is then developed from the insights gained through the studies on compact flat thermosyphon. The IFTHS has a condenser with integrated hollow fins wherein the inner surface of the hollow fins is used for condensation, and the outer surface is used for air-side convective cooling. The thermal performance of the IFTHS is enhanced further through an evaporator with minichannels and a superhydrophobic condenser. The IFTHS outperforms conventional heat sinks in thermal performance, weight reduction, and energy savings. The IFTHS developed in the present work is a promising, cost-effective, and energy-efficient thermal management solution.

One of the main challenges facing mankind in 21 st century is to supply the world’s population of sufficient energy to meet desired living standards. As the world faces growing concerns over climate change and the depletion of fossil fuel reserves, the need for sustainable and clean energy solutions has become critical. Hydrogen is a clean and versatile fuel with zero greenhouse gas emissions when consumed in fuel cells or hydrogen-based combustion engines. Being an energy carrier, it can store and deliver huge amount of energy. It’s only byproduct is water, making it an ideal replacement for fossil fuels that contribute to global warming and air pollution. Solar-driven photoelectrochemical catalysis is a promising pathway for producing hydrogen. This technique involves the use of solar energy to split water molecules into hydrogen and oxygen through a process called electrolysis. By utilizing solar power to generate hydrogen, we can ensure a truly sustainable and eco-friendly energy cycle. The development of efficient and stable photoelectrode materials is critical for enhancing the performance of phototelectrochemical cells. Identifying materials that can efficiently absorb sunlight, facilitate the necessary electrochemical reactions, and withstand harsh operating conditions remains a complex task. Metal oxide clusters such as polyoxometalates (POMs) and metal organic frameworks (MOFs) consist of a small number of metal oxide units, offer unique advantages over bulk materials, making them attractive candidates for enhancing photoelectrochemical efficiency. They can provide enhanced light absorption, efficient charge separation, redox catalysis, stability, durability and compatibility with semiconductors helps in developing better photoelectrochemical systems. The POMs offers unique redox properties which is beneficial for better catalytic activities. Similarly the MOFs also shows enhanced catalytic and electron transport properties along with better light harvesting capabilities. This helps to lower the energy barrier for the hydrogen evolution reaction (HER), making the process more favourable and stable. The current research focusing on the strategy of supporting POMs or MOFs into a specific substrate. The combination of POMs/MOFs and the substrates can benefit from the virtues of both materials while avoiding the drawbacks of them. These include the significant improvement in terms of mechanical stabilization, surface area, light absorption, electrical conductivity and charge transport. Specifically the integration ensures that the photogenerated electrons efficiently reach the POM/MOF sites for HER, leading to improved hydrogen production rates. Further optimization and exploration of such kind of hybrid systems are necessary to fully realize their potential in renewable hydrogen generation.

While entrepreneurship provides women the desired autonomy and flexibility, having a challenging career like entrepreneurship can impose additional workloads and mental strain, making it demanding for them to achieve a work-life balance. Boundary management is a crucial phenomenon that explains how women entrepreneurs create and manage their work and family boundaries to achieve work-family balance. The literature provides mixed evidence on individuals’ boundary preferences and boundary management strategies, which tend to differ across individuals and situations. With this background, the current study aims to explore the boundary preferences, boundary management strategies, and work-family interface of women entrepreneurs from Micro, Small, and Medium Enterprises using an exploratory sequential mixed-method approach (Phase I - qualitative research and Phase II - quantitative research). In the first phase, we explored how women entrepreneurs prioritized and managed the boundaries between work and family role domains. We also examined whether boundary management strategies varied based on motherhood and business stages. The in-depth qualitative investigation of twenty-five highly educated and financially successful women entrepreneurs from India (in two distinct phases over a gap of six months) helped us elucidate the nuances of work-family role management and identify the critical response strategies. We found that the mothers with younger children and entrepreneurs in the early stages of the business preferred to integrate the work and family roles rather than to set a clear boundary between the roles, using various boundary management tactics to achieve work-life balance. They attempted to minimize imbalance by creating a resource pool, flexible scheduling, working fewer hours, and preferring workplace proximity. Social support seemed to be essential to reconcile the multiple role demands. To delve deeper into the insights of phase I, this study collected data from 446 women entrepreneurs from various districts of Tamil Nadu employing temporally-lagged surveys: Survey I (Time 1) and Survey II (Time 2), with a 4-week interval in the second phase. This study tested the impact of boundary preference toward integration on subjective well-being through actual boundary enactment and work-to-family enrichment as mediators, moderated by the problem-focused coping strategy. Data were analysed using structural equation modelling. Results suggest that women entrepreneurs actively work towards their boundary preference. The normative expectations placed on women to perform traditional gender roles and work autonomy tend to impose integration as a boundary management strategy for women entrepreneurs in India. Since individuals have only finite resources, integrating multiple roles could invariably lead to role strain. However, based on the tenets of the work-home resource (W-HR) model and boundary theory, role integration provides access to one or more resources that can provide an enriching experience for women entrepreneurs, enhancing their subjective well-being. The findings reveal that the study participants do not see business and family demands as competing entities. Instead, they accept the role demands and prefer to integrate the boundaries. Women entrepreneurs utilize the resources gained through work to enrich their family role. Moreover, to organize themselves within the roles and to offset additive role burdens, they have mastered several problem-coping strategies, such as active operational planning, prioritizing, self-regulatory activities, etc., to achieve subjective well-being. This study concludes that boundary management is crucial for managing the role expectations imposed on women entrepreneurs and also to enhance their subjective well-being. This study contributes to the literature by i) investigating boundary preference and actual boundary enactment as two distinct constructs, ii) examining the moderated mediated mechanism in the boundary preference toward integration and subjective well-being, iii) considering actual boundary enactment and work-to-family enrichment as mediators; iv) demonstrating that individual strategies such as problem-focused coping positively moderate the indirect effects of boundary preference toward integration on subjective well-being through actual boundary enactment and work-to-family enrichment such that the relationship is stronger among women entrepreneurs employing higher levels of such coping strategies. The theoretical and practical implications for women entrepreneurs are discussed in detail.

Food can become unsafe or contaminated at any point from production to distribution. The stakeholders and customers are also ready to pay more to ensure food safety and timely delivery. This shows the importance of visibility and operational efficiency in a food supply chain (FSC). Traditional supply chains are primarily manual and won't involve technologies. There will be issues like low traceability, efficiency, data tampering, etc. Implementing new and developing data-acquiring technologies is a benefit to all the stakeholders, which helps them to make crucial decisions. It is necessary to trace the movement of products from origin to the consumers as supply chains that allow financial transactions between entities lack trust and credibility, So, it is evident that there is a need for a change in the traditional food supply chain by implementing technology systems. The purpose of this work is to study how blockchain is used in the FSC for visibility and operational efficiency. A content analysis-based systematic literature review is conducted to find the research gaps. Based on the research gaps found, our research proposes to answer the following research questions: RQ-1. How is blockchain impacting the food supply chain in terms of visibility and operational efficiency? RQ-2. How can technology costs be shared among various entities of the food supply chain? RQ-3. How the integration of two or more technologies with blockchain can improve the FSC? The proposed work can help the practitioners of FSC to redesign the existing supply chain. The number of food incidents can be reduced to a certain extent, and the coordination between the entities of the supply chain can be improved.