2. Thesis and Dissertations
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Item Kinetics/Kinematics of Intact and Arthritic Knee Cartilages and A Novel Approach to Enhance Wear Characteristics of Uhmwpe Tibial Inserts for Prosthetic Knee(National Institute Of Technology Karnataka Surathkal, 2023) R, Vaishakh; Koorata, Poornesh KumarOsteoarthritis is a severe and progressive disorder that affects the knee joint due to cartilage degradation from daily rigours activities. Articular cartilage is more susceptible to knee arthritis compared with other soft tissues. Hence, understanding degradation phenomena are more critical and require understanding the tissue's stress fields. Experimental methods have limitations, such as inaccessible cadaveric knees and obtaining in-vivo data from intact and arthritic knees is difficult and imprecise. Hence the numerical method is the most effective technique for understanding the cartilage’s mechanical behaviours under different conditions. The cartilage constituents make the cartilage geometrically and mechanically heterogeneous. A 3D finite element knee joint model is used to compute the articular cartilage response during multiple activities. Various material models are available to model the heterogeneity of articular cartilage. Multiple constitutive models are compared for the prediction of mechanical response. In addition, the influence of the inhomogeneous distribution of collagen fiber in cartilage is investigated for intact and arthritic knee kinematics cases. In reality, the cartilage structure is heterogeneous, and the computational study shows the importance of heterogeneity in the mechanical response of the knee joint. Conventionally the knee implant-bearing material (UHMWPE) is homogeneous. Incorporating the heterogeneous characteristics in the bearing material may help enhance the implant's mechanical characteristics. The proposed model generates property-modulated characteristics in the bearing material using gamma irradiation, and the heterogeneous characteristics are incorporated into the knee implant. UHMWPE's tribological and chemical characteristics are analysed experimentally, and the wear rate and volume are calculated. The wear rate decreases as the radiation dose increase to a particular level and then increases as the dose increases further. Compared with the conventional technique, a reduction in wear rate for the material is observed for the proposed technique. Also, the hardness of the UHMWPE is measured, and its value increases as the irradiation dose increases.Item Assessing the Suitability of Thermally Sprayed Fly ASH Coatings For Marine Structures(National Institute Of Technology Karnataka Surathkal, 2023) F, Vishwanath Bhajantri; Jambagi, Sudhakar C.The current study assesses the suitability of fly ash in both powder and coating forms to cater to marine applications. Due to its rich mineralogy, fly ash (FA), an industrial waste, has been used to combat erosive, corrosive environments. Powder flowability dictates coating properties. In this investigation, firstly, raw FA powder was obtained from a thermal power plant and sieved in various sizes to assess their flowability. Powder’s physical characteristics, such as specific surface area, Blaine’s fineness number, and bulk density, were determined, and their influence on powder flowability was analysed. Of these properties, bulk density affects more. Rietveld refinement was performed on the powder to quantify the phases. The powders had 45.08 ± 11.38% amorphous and 11.00 ± 2.76% of mullite phases. Later, alumina was added between 10 and 50 wt% to FA, and samples were subjected to in situ high-temperature X-ray diffraction at 1150 ℃. A ⁓32.27% rise in Mullite content was observed for 50 wt% alumina, with a ⁓119% decrease in the amorphous phase. Finally, one set of FA without additives coating was plasma sprayed onto a marine-grade steel substrate. The coating showed ⁓17.31 ± 0.6% of mullite and ⁓69.43 ± 0.6% of the amorphous phase, with decent Mechanical properties. Therefore, 50 wt% alumina in FA powder has improved the mullite phase, bulk density (43%), and flowability by decreasing the amorphous phase content. Secondly, fly ash powders were doped with carbon nanotube (CNT) (1 or 2 wt%) powder feedstock produced using four routes: sonication, ball milling without crushing media and ball milling in the presence of ethanol (wet mixing), and spray drying. From the X-ray dot map, wet mixing and spray drying showed a homogenous dispersion of CNT in the FA powder. The flowability of all these powders was quantified with the help of a standard powder feeder. The wet-mixed and spray- dried powders exhibited better flowability. Finally, as-received FA from the power plant was deposited on a Marine grade steel substrate using the plasma-spraying technique to assess the performance of such coatings for erosion and corrosion properties. The coating has exhibited more than 100 % improvement in microhardness. The erosion resistance was improved by ∼11% compared to that of the uncoated sample, which is attributed to the hardness to elastic modulus ratio (H/E) and its unique mineralogy. The minor improvement in erosion resistance was attributed to the icoating’s poor fracture toughness. The erosion study shows that slurry concentration and rotational speeds were the most influential parameters. The scar depth was significantly shallower for FA-coated samples. The corrosion resistance has improved by ∼13.49%, owing to the porous nature of the coating. Therefore, such coatings with appropriate improvements in their properties are expected to alleviate both environmental and industrial challenges.Item solated Bidirectional DC-DO Converters to Integrate PVwith Energy Storage Systems for High Power Density Applications(National Institute Of Technology Karnataka Surathkal, 2023) Bathala, Kiran; H., NagendrappaAn isolated bidirectional DC-DC converter is a solution to integrate renewable energy-generating units with energy storage systems. This concept can overcome the drawback of intermittency or non-availability of renewable energy sources throughout the day, e.g., solar energy, by supplying the energy to loads through battery storage units. This research is to find a suitable isolated bidirectional dual active bridge (DAB) resonant DC-DC converter for high power density applications and investigate its performance. Therefore, in this work, the literature survey on isolated bidirectional dual active bridge converter topologies, their switching and power control schemes, and analysis methods are presented. Single phase-shift control technique a fixed-frequency control scheme makes the design of isolation transformer, inductive and capacitive filters easy for better filtering. The modeling, steady-state analysis and design of the converter have been presented. The detailed performance analysis of the proposed converter during various intervals of operation for both forward and reverse mode operation is presented. It has been found that the use of a single phase-shift control scheme, leads to continuous conduction mode operation of the converter without loss of duty cycle. This switching scheme successfully maintains constant output voltage with a small change in pulse width for wide variations in input voltage and load conditions. A 135 W, 48V converter has been proposed and its performance has been studied through theoretical calculations, simulations and experiment in the laboratory. The boundary condition of the soft-switching of the converter is studied by establishing an expression for instantaneous switch current and dead time in terms of the parasitic capacitance of the switching device i.e., MOSFET.Item Surface Modification of Mg-Zn-Dy Alloy Using Plasma Spray and Friction Stir Processing for Biomedical Applications(National Institute of Technology Karnataka, Surathkal, 2022) Rokkala, Uzwalkiran; Bontha, Srikanth; M.R, RameshMagnesium (Mg) and its alloys are currently under consideration for use as temporary implants. However, early degradation and maintaining mechanical integrity are causes of concern for the use of Mg alloys as materials for temporary implants. Also, failure due to bacterial infection limits their applications. To this end, surface modification techniques are being used to improve the mechanical, corrosion, biocompatibility and antibacterial properties of Mg-based alloys. In the present work, friction stir processing (FSP) and plasma spray coating techniques were used to tailor the surface characteristics of Mg-1Zn-2Dy (wt.%) alloy. Initially, as-cast (AC) Mg-1Zn-2Dy alloy was subjected to FSP to improve the surface properties. Further, to enhance biocompatibility and antibacterial properties, AC sample was coated with two different coating combinations: hydroxyapatite (HA)/silver (Ag) (C-HAg) and aluminium oxide (Al2O3)/HA (C-AHa). Later, FSP was carried out on coated plates to fabricate composite surface (F-HAg & F-AHa). The FSPed samples were characterized using EBSD to understand the influence of FSP on crystallographic texture, grain size, grain boundaries and thereby their effect on mechanical properties and corrosion behaviour. Microstructural and phase analysis of all samples (AC, FSP, C-HAg, C-AHa, F-HAg & F-AHa) were carried out using SEM, FESEM & XRD. Cytotoxicity and corrosion studies were performed on all samples. In addition, for coated and composite surface samples, antibacterial properties were investigated using Escherichia coli (E. Coli) and Staphylococcus aureus (S. aureus) bacteria. Results showed that the grain size of stir zone (SZ) in the FSP sample was refined to less than 3 μm due to dynamic recrystallization (DRX) during FSP. Further, the FSP sample exhibited better mechanical properties and corrosion behavior when compared to the AC sample. This improvement in mechanical properties and corrosion behavior of the FSP sample compared to the AC sample can be attributed to grain refinement, uniform distribution of secondary precipitates and strong basal texture. The degradation of the FSP sample resulted in the deposition of calcium phosphate-rich minerals, and thereby helping to improve apatite formation on the surface. Cytotoxicity studies using ii MTT assay showed more than 80 % cell viability for both AC and FSP samples suggesting non-toxic nature. Antibacterial studies reveal that both C-HAg and F-HAg samples inhibit Escherichia coli and Staphylococcus aureus bacteria. In comparison, AC, FSP, C-AHa and F-AHa samples exhibit bacterial adhesion on the surfaces. In-vitro cytotoxicity studies reveal that C-HAg, F-HAg & F-AHa samples are non-toxic in nature, while the C-AHa sample alone exhibited toxicity. Results of in-vitro corrosion studies reveal a significant reduction in the corrosion rate for the composite surface samples when compared to the coated samples. In particular, the F-HAg samples showed simultaneous improvement in corrosion resistance and antibacterial properties with good biocompatibility. Overall, the hardness, corrosion resistance, cytotoxicity, and antibacterial properties of F-HAg samples have improved significantly. Results indicate that the F-HAg sample has the potential to be used as material for temporary implant applications.Item Effect of High Temperature Biodiesel Injection In Compression Ignition Engines(National Institute of Technology Karnataka, Surathkal, 2022) Kodate, Shankar; Yadav, Ajay Kumar; G. N., KumarExtensive research is being done to produce and utilise a variety of renewable fuels to meet the growing global energy demand and combat many issues such as environmental pollution, high costs of fossil fuels, and dependence on foreign energy sources. The current research aimed to extract and characterize Vateria indica and Karanja biodiesels through the transesterification process. The use of extracted biodiesels in a diesel engine leads to lesser brake thermal efficiency (BTE) and increased brake specific energy consumption (BSEC) due to higher viscosity and lower calorific value of biodiesels. This problem of higher viscosity is resolved by fuel preheating before injecting into the engine cylinder. The current research aims to evaluate the engine performance, emission, and combustion characteristics of Karanja oil methyl ester (KOME) and Vateria indica methyl ester (VIME) biodiesels blended with diesel at elevated fuel inlet temperatures ranging from 35 °C to 95 °C. The tests are carried out using two different engines, mainly the conventional DI engine (low-pressure injection at 180 bar) and CRDI engine (high-pressure injection at 1000 bar). In the CRDI engine, the effects of fuel injection timings and exhaust gas recirculation (EGR) rates on the engine parameters are also investigated. Results are obtained in terms of brake thermal efficiency, brake specific energy consumption, in-cylinder pressure, heat release rate, exhaust emissions of carbon monoxide (CO), hydrocarbon (HC), nitrogen oxide (NOX), carbon dioxide (CO2), and smoke opacity. It is observed from the findings of both the engines that the preheating of blends decreases viscosity which enhances engine performance, lower CO, HC, and soot emissions with a slight increase in NOX emissions. It is found that advancing the injection timing to 15° bTDC in a CRDI engine improves engine performance and reduces CO, and HC emissions with an increase in NOX emission compared to standard injection timing of 12° bTDC and retarded injection timing of 9° bTDC. As the EGR rate increases, engine performance decreases, and exhaust emissions like CO and HC increase with a reduction in NOX emission.Item Investigation of Control Algorithms For Pv System Under Partial Shading Conditions and Their Effect on The Efficiency of Dc-Dc Converter(National Institute of Technology Karnataka, Surathkal, 2022) P, Raghavendra Rao; B, Venkatesaperuma; Vethanayagam, ignesh KumarGenerally, conventional energy resources such as fossil fuels are used to meet our electrical energy demand. But the fact is that they are being depleted at a more rapid rate besides creating environmental pollution. In order to mitigate this prob- lem, renewable energy sources such as wind, solar, biomass, hydropower, etc., are used as alternative to produce electricity. Among the renewable energy resources, solar energy has become increasingly popular for many reasons such as low oper- ating cost, no harmful emissions, long operational life, and a clean source. Pho- tovoltaic (PV) panels exhibit non-linear characteristics. Under uniform shading conditions, only one operating point exists where the power is maximum. Under mismatching or partial shading conditions, there exist multiple power peaks. The maximum power point tracking (MPPT) process extracts the maximum available power from the PV panel by fixing the panel voltage corresponding to the maxi- mum power point. A DC-DC converter usually accomplishes this by the impedance matching principle. There are different types of DC-DC converters that are used in between PV panel and the load depending on the applications. This thesis presents a brief literature review on different MPPT methods and losses in the DC-DC converters. The MPPT methods discussed in the literature vary in tracking speed, the number of sensors used, implementation complexity, and their dependence on the PV panels. In addition to different MPPT methods, the literature also presents the loss analysis of the boost converter employed for PV systems. The research gaps were identified based on literature survey, and three objectives have been defined in this thesis. As a first objective, a novel modified current control algorithm is proposed to track the global peak under fast-changing partial shading conditions. The algo- rithm perturbs the operating current in the forward and backward directions. If the irradiance changes during the tracking phase of any irradiance pattern, the proposed algorithm detects the irradiance change and tracks the global peak cor- responding to the new irradiance pattern. The proposed technique uses operating current as a parameter to detect the irradiance change during the tracking process of an existing irradiance pattern. The second objective proposes a global maximum power point tracking (GMPPT) algorithm by perturbing voltage and current. The algorithm perturbs panel volt- age or current based on the value of a control variable. Initially, the operating point is moved to the lowest possible voltage below which there is no global peak. iii Then the perturbation is carried out in the forward direction till the termination criterion is detected. The maximum power is updated during each perturbation so that the global peak is tracked accurately. The proposed technique is compared with two recently published modified GMPPT algorithms with respect to tracking speed and energy efficiency. The third objective compares the losses in the three-level and conventional boost converter for PV applications. Under partial shading conditions, there will be multiple power peaks in power versus voltage (P − V ) characteristics. The location of the global power peak varies over a wide range in the P − V char- acteristics. If the global peak lies to the left side of the P − V curve, the duty cycle required to fix the GMPP would be high. In such cases, the efficiency of the DC-DC converters decreases at higher duty ratios. The study investigates the conduction and switching losses in the conventional boost converter and three- level boost converter through precise mathematical equations. The variation of the losses with respect to the switching frequency is also investigated here. The simulations of all the algorithms and the converters’ loss analysis are performed using MATLAB/Simulink. The two algorithms proposed are compared with recent GMPPT algorithms. The simulations are experimentally validated using an experimental setup. The losses in the three-level boost converter are compared with the conventional boost converter, and the variation of the losses against the switching frequency is plotted and investigated.Item Investigation on Control of Voltage Source Inverter Interfacing Domestic PV System to The Grid(National Institute of Technology Karnataka, Surathkal, 2022) Kumar, Nisha B; U, VinathaThe integration of renewable energy like the clean solar energy into the grid has become increasingly relevant in the recent epoch due to the current energy demand, the depletion of fossil fuel reserves and their environmental impacts. The responsibility of providing adequate harmonic current compensation to the non-linear loads connected at the point of common coupling(PCC) and achieving the power flow balance in the sys- tem lies solely with the interfacing converter that forms the heart of the grid integrated photovoltaic system (PV). The above tasks can be accomplished by incorporating suit- able control strategies to the interfacing converter, preferably inverter. This thesis is an attempt to provide an insight into the various control strategies adopted for adding shunt active filtering feature to the inverter used to interface a domestic PV system to the grid. To regulate the power exchange between the grid and the PV system, a robust DC- link voltage controller capable of withstanding the intermittent nature of solar energy and sudden variations in load is required. A proportional integral controller (PI) used for DC-link voltage control, exhibits oscillations during steady-state and overshoot dur- ing transients. The conventional sliding mode controller reduces the overshoot at the expense of increased steady-state error. A robust sliding mode controller for the control of DC-link voltage to reduce steady-state error by incorporating integral action to the conventional sliding mode controller is proposed. The harmful effect of the chattering phenomenon seen in the conventional sliding mode controller is minimised by limit- ing the error in the control variable using a signum function. The results of numerical simulations carried out in MATLAB/Simulink platform for various system conditions illustrate that the proposed controller provides superior performance compared to PI controller and conventional sliding mode controller in terms of power flow balance and speed of response at all system conditions. The proliferation of power electronic devices and non-linear loads in grid inte- grated photovoltaic (PV) systems have caused power quality issues to originate in the system. The harmonic current requirement of the non-linear load has to be met to im- prove the system’s performance. A fast, simple and effective algorithm for harmonic current compensation that enhances the dynamic performance of the shunt active power filter under various system conditions for the grid is proposed. The proposed dual non- adaptive concatenated delayed signal cancellation (NACDSC) based algorithm extracts the fundamental component of grid voltage and load current that is used to generate ref- erence current required for the harmonic compensation of non-linear load. Moreover, the control algorithm does not require any tuning of controller parameters to eliminate higher-order harmonic components. The simulation results for various system con- ditions demonstrate that the proposed control algorithm offers enhanced performance compared to existing traditional self-tuning filter (STF) and low pass filter-based meth- ods in terms of speed of response and harmonic current compensation. A laboratory prototype of the shunt active power filter is implemented in which the control algorithm is realised in dSPACE 1202 RTI platform. From the hardware results presented under different operating conditions, it is observed that the control scheme provides a good response in terms of power quality and powe control.Item Investigation and Control of Magnetically Coupled Impedance Source Inverters For Pv Applications(National Institute of Technology Karnataka, Surathkal, 2022) Reddivari, Reddiprasad; Jen, DebashishaIndian power sectors expect to use more rooftop photovoltaic (PV) inte- gration to the power grid in the near future. However, the produced power from PV is highly dependent on solar irradiation and temperature, which are irregular and hard to monitor. Therefore, power electronic converters are expected to harvest the maximum available power from PV panels and then export it to the grid based on their requirements. The commercial two-stage grid-connected PV inverters are limited to narrow range MPP voltage, which requires higher starting or wake-up voltages to start the inverters. When the PV fails to maintain the inverter’s minimum oper- ating voltage, it shuts down. A shutdown inverter must now undergo a start-up process upon the cloud clearing, at which it must monitor both grid voltage and frequency for a given period before going online. Also, these inverters cannot function in the early morning and late evening due to low string voltages. In particular, the parallel configured PV mod- ules become an ideal solution for a rooftop generation system that does not suffer from shading problems. But this design requires a power con- version with high voltage gain to match the grid voltages. Single-stage impedance source inverters (ZSI) are preferable for producing high volt- age gains over two-stage converters due to their outstanding features such as single-stage buck-boost and inversion ability, high voltage gain, and inherent short-circuit/open-circuit protections. However, the ZSIs exhibit non-minimum phase behaviour due to the right half-plane (RHP) zero in the converter transfer functions that impose a constraint on the controller design. A detailed mathematical model of the converter plays a crucial role in designing an efficient control strategy. This thesis initially develops a detailed mathematical model of non-ideal ZSIs using averaged modelling approaches. Small-signal models are used to estimate the ZSIs steady-state and dynamic performance, which are used to tune the controller’s gains for closed-loop operation. The devel- oped mathematical models are verified through simulation/experimentation in open-loop/closed-loop operations. However, the developed prototype posses low conversion efficiency due to the usage of snubber and limited iii voltage gain due to internal resistive drops of selected components. This problem could be addressed with magnetically coupled impedance source inverters (MCIS), increasing the voltage gain by increasing the turn’s ra- tio while maintaining the duty ratio minimal. However, the transformer’s magnetic flux leakage generates high switching voltage spikes leading to unwanted switch failures. Therefore, the effect of leakage inductance on converter performance must be understood before mitigation techniques are proposed. This thesis investigates different MCISs for mitigating voltage spikes and utilizes the energy stored in leakage inductance to enhance the voltage gain. Firstly, a novel active clamped Y-source impedance network and its family to limit switching voltage spikes is proposed. One additional clamping diode is added to the type-I improved Y-source network to yield the proposed active clamped Y-source converter. The proposed converter absorbs the energy stored in leakage inductance and re-utilizes the ab- sorbed energy to enhance the voltage gain for loosely coupled inductors. The thesis further investigates potential improvements in coupled inductor design and winding orientation to avoid switching voltage spikes at their origin. A family of ferrite core-based differential mode MCZSI topologies is developed by adopting the inverse coupling theory, which mitigates the switching voltage spikes without increasing the components. The ability of the proposed converters to reduce switching voltage spikes is demon- strated using simulation and experimental results. Small-signal, loss anal- ysis, and reliability studies are performed to prove the practical feasibility of designed converters. Finally, a negative embedded impedance source inverter (NEZSI) is ver- ified for low voltage harvesting in PV applications. Furthermore, an im- proved Γ-type Y-source inverter with integrated EV has been validated for PV-applications for better return of investments (ROI).Item An Efficient Low-Power Rectifier Integrated Antennas for Rf Energy Harvesting and Autonomous Frequency Reconfiguration(National Institute of Technology Karnataka, Surathkal, 2022) Polaiah, Geriki; K, KrishnamoorthyVarious rectifier integrated antenna (RIA) structures are investigated in a search for new RF energy harvesting devices which might be useful for state-of-the-art multi-purpose energy harvesting and autonomous frequency reconfiguration applications. Starting from intuitive concepts to novel RIA device designs, their fabrication procedure, op- timization, and characterizations of these device structures have been carried out within the scope of this thesis. Modern wireless power transmission and energy harvesting technology demand low power, adaptive switching, and high RF to DC conversion ef- ficiency rectifier integrated antennas. To achieve these requirements, various rectify- ing antenna designs like open-loop slot line resonators, monopole, symmetrical slot, and variable feed length-based modified geometrical structures are demonstrated, fab- ricated, and compared the various results with similar kinds of structures reported in the literature. In addition, periodic metamaterial array-based metasurface is utilized as receiving antenna for maximum capture of ambient electromagnetic energy which provides high absorption efficiency, polarization-insensitive, and wide-angle reception. This thesis focuses on high efficient low power RIA designs, which give stable out- put DC voltage for continuous supply to electronic devices. We first demonstrated the rectifier integrated wideband monopole antenna and rectifier integrated dual-band mod- ern Aztec quatrefoil geometrical slotted structure for energy harvesting. The symmetri- cal geometry single band with harmonic suppression and multiband slotline structures are introduced with optimum feed length backed by different reflector structures for consistent unidirectional radiation performance and enhanced gain. In general, a full copper patch reflector is placed behind the antenna at a distance of λ/4, where λ is the free space wavelength at the lowest frequency. Instead of a full copper patch reflec- tor, an artificial magnetic conductor (AMC) and defected reflector structure (DRS) are introduced to reduce the profile of the antenna and enhanced gain. These designs ef- iii fectively capture the ambient electromagnetic energy from low input power levels and transferring to rectifying circuit for further conversion into DC. After successful demonstration of wideband/dual-band rectifier integrated antennas and multiband rectifier integrated antennas with enhanced gain, novel designs of fre- quency reconfigurable rectifier integrated antennas with differential configuration for receiving and rectifying the differential (two signals with equal amplitude and 1800 phase difference) radio frequency signals and a slotline open-loop resonators based fre- quency reconfigurable antenna with autonomous switching of frequency bands have been demonstrated. In addition, an ultra-wideband (UWB) crescent moon shape slotted monopole an- tenna with diplexer and rectifier has been demonstrated for simultaneous microwave energy harvesting and data communication applications. The antenna is composed of four symmetrical circularly slotted patches, a feed line, and a ground plane. A slotline open-loop resonator-based diplexer is implemented to separate the required signal from the antenna without an extra matching circuit. A microwave rectifier based on the volt- age doubler topology is designed for RF energy harvesting. The overall performance of the antenna with a diplexer and rectifier is also studied, and it is found to be suitable for SWIPT applications. Finally, a tri-band metamaterial periodic unit-cell array-based rectifying metasur- face has been investigated for receiving and rectifying the electromagnetic energy from wide-angle and all polarizations. The configurations of antenna design and simula- tion of various parameters are carried out by using Computer Simulation Technologies (CST) Microwave Studio, fabricated using the S103 Proto Mat LPKF PCB machine, and measured using the Agilent Technologies E8363C PNA network analyzer. Simi- larly, the rectifier design and simulations are carried out by using Keysight Technologies Advanced Design System (ADS) high-frequency RF simulator.Item Correlation Analysis and Tensor Data Modeling In Multimodal Environmental Wireless Sensor Networks(National Institute of Technology Karnataka, Surathkal, 2022) G, Rajesh; Chaturvedi, AshviniThe major challenges during the data acquisition process in an environment wireless sensor network (EWSN) architecture are the presence of outliers and missing data. The outliers are ubiquitous in the data acquired by the EWSN due to sensor failures, aging effects, power dwindling, external noise, etc. Missing data at the sink node owes to the communication failures, sensor node malfunction, inadequate sampling frequency and switching of sensor nodes into sleep mode, etc. as prominent rationales. Since the data acquired by the sensor nodes in a multimodal EWSN are spatially, temporally and attribute-wise correlated, these correlations play a pivotal role in missing data recovery and data prediction mechanisms. The thesis proposes an analytical framework to characterize the (multi-attribute) correlation between different pairs of modalities in a real-world EWSN. Monte Carlo simulation is performed to approximately model sensed environmental data character- istics. Three classical estimates and four robust estimates of correlation coefficients are used to establish the correlation between two typically correlated distinct pairs of sensed modalities in the obtained data. Stationarity analysis among the acquired envi- ronmental variables sheds light upon the best estimates of the correlation coefficient, which could be used for the prediction of missing/outlier corrupted data in a known region of slope/stationarity in the data characteristics. A novel outlier modeling scheme using Chebyshev’s inequality is developed for the addition of gross sparse outliers in the correlated data. The multi-dimensional nature of the acquired data in EWSNs (spatial, temporal and attribute dimensions) leads to tensors as a natural choice of data representation. The inherent correlations in the acquired data cause redundancy and hence, low-rankness of the acquired data tensor. Robust tensor principal component analysis (RTPCA) de- composes a noisy data tensor into a low-rank tensor and a sparse tensor, which can be v exploited in the data recovery process of multi-attribute EWSNs, where the low-rank component represents the intrinsic data tensor and the sparse component represents the gross outlier tensor. A novel probabilistic outlier modeling scheme using multivariate Chebyshev’s inequality hypothesis is introduced, which maps the sample population and the associated magnitudes of outliers with the spatio-temporal correlations inher- ently present in the acquired heterogeneous sensory data. The intrinsic data recovery in EWSNs is investigated in the presence of a varying population of sparse outliers and missing sample values. A robust incremental tensor decomposition (ITD) framework is also proposed in this thesis, which processes the tensor data sequentially and performs low-rank and sparse decomposition of tensor data in a faster way compared to batch processing methods and having comparable recovery accuracy. The ITD mechanism can be of greater interest, especially in scenarios where data processing demands real-time execution.