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Interaction of Extracellular Polymeric Substances of Biofilm forming Marine Bacteria with Petroleum Hydrocarbons for the Emulsification and Biodegradation
No full textThis thesis illustrates the biofilm-forming potential and petroleum hydrocarbons (PHs) degradation efficiency of marine bacteria. Sediment samples were collected from the Paradip and Gopalpur ports of coastal regions of Odisha, India. A total of 50 marine bacterial strains were isolated following selective enrichment with 2% (v/v) crude oil. Biofilm-forming potential was observed in 45 marine bacterial isolates, of which 12 were strong, 9 were moderate, and 24 were weak biofilm formers. Further biofilm screening in the presence of crude oil resulted in the selection of 10 marine bacterial isolates having the potential to form biofilm at the oil-water interface. 16S rRNA gene sequencing revealed that all the potent biofilm-forming marine bacterial isolates belonged to Gammaproteobacteria class, out of which 6 isolates were Pseudomonas, 3 isolates were Acinetobacter, and 1 isolate was from Zobellella genera. Scanning electron micrographs (SEM) analysis revealed that isolates belonging to Pseudomonas genus were short rods clustered together in a thick layer of extracellular polymeric substances (EPS). However, isolates under the Acinetobacter genus appeared as coccobacilli in shape with compact aggregation, while the isolate under Zobellella genus appeared as long rods scattered in the EPS matrix. Confocal laser scanning micrographs (CLSM) revealed different biofilm components, and community statistics (COMSTAT) analysis revealed different biofilm parameters. A. junii PPS-3, P. mendocina PPS-8, P. guguanensis PPS-12, A. junii PPS-16, and P. furukawaii PPS-19 showed high specific growth rate and yield coefficient in the presence of crude oil. Biofilm-forming marine bacterial isolates showed significantly higher utilization of crude oil in the biofilm than in the planktonic mode of growth (P<0.05). P. furukawaii PPS-19 showed the highest utilization of crude oil and significantly reduced 38% (v/v) crude oil in the biofilm than planktonic mode of growth (61.3%) (P<0.001). Colorimetric analysis revealed polysaccharides were the major components of EPS of P. furukawaii PPS-19. The architecture of purifed EPS was studied through field emission scanning electron microscopy (FESEM), which exposed its porous and three-dimensional flakes-like structure. The structural characterization by Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) revealed that EPS was composed of primary alkane, amines, halide, hydroxyl groups, uronic acid, and saccharides. The X-ray diffractogram (XRD) profile exhibited an amorphous phase of the EPS with a crystallinity index of 0.336. The EPSa showed three-step thermal decomposition and thermal stability up to 600°C, as confirmed by thermogravimetric analysis (TGA). Differential scanning calorimetry (DSC) thermogram revealed one crystallization temperature at 69.18°C with 343.15 mJ latent energy and two melting temperatures at 424.76°C and 556.90°C with 211.73 mJ and 2030.44 mJ latent energies, respectively. EPS produced by the marine bacterium P. furukawaii PPS-19 was good bioemulsifer and showed the highest emulsifying activity of 66.23% on petrol. The emulsifying ability of the EPS was superior to the commercial polymer xanthan. The emulsion also showed high stability with time and temperature exposure. EPS interaction with crude oil and pyrene showed n→π* and π→π* transition in UV-Vis spectra, reflecting the change in energy of bond orbital of aromatic groups in EPS. Shifting of polysaccharides and protein-associated bonds after interaction with PHs was observed. Circular dichroism (CD) spectra presented conformational changes in the protein secondary structure of EPS treated with PHs. X-ray photoelectron spectroscopy (XPS) spectra exhibited changes in major element composition and percentage of different functionalities of EPS. X-ray diffraction (XRD) profile showed complete disruption of crystalline peaks in EPS treated with crude oil and n-Dodecane, while with pyrene, CIXRD changed from 0.3 to 0.8. Pore size of the purified EPS increased considerably after treatment with crude oil and n-Dodecane. Surface electronegativity and hydrodynamic diameter of EPS were increased, indicating the formation of the conglomerate. EPS was quenched in the presence of PHs, establishing a static mechanism, and the maximum binding was obtained with n-Dodecane (1.88 L/mol, - 1.57 kJ/K/mol). alg8 gene was identified in the bacterium, and it showed significantly increased expression in the presence of n-Dodecane (6.31 fold) (P<0.05). The n-Dodecane and pyrene bioadsorption capacity of EPS-alginate was significantly higher (356.5 and 338.2 mg/g, respectively) (P<0.001) than calcium-alginate. EPS-alginate also showed high n- Dodecane and pyrene bioadsorption capacity under various pH and salinity stress. The n- Dodecane and pyrene bioadsorption rate by the developed bioadsorbents fits into the pseudo- second-order kinetic model. P. furukawaii PPS-19 showed strong cell surface hydrophobicity (CSH) under different physicochemical stressors, such as pH and salinity. Strong aggregation of P. furukawaii PPS-19 was observed at hydrophobic interfaces of n-Dodecane and crude oil, while uptake of pyrene resulted in blue fluorescence of the bacterium. Changes in biofilm microcolonies were observed under different physicochemical stressors with maximum biofilm thickness of 15.15 μm and 15.77 μm at pH 7% and 1% salinity, respectively. Relative expression analysis of alkB2 gene revealed the maximum expression in n-Dodecane (10.5 fold) at pH 7 (1 fold) and 1% salinity (8.3 fold). 3D homology modeling followed by validation revealed a high-quality model with 93.7% residues in the favored zone of Ramachandran plot. Molecular docking study displayed a substantial binding affinity of n- Dodecane (-8.050 kcal/mol) with amino acid residues at the active binding site of AlkB2, indicating a strong interaction. During the degradation process, a significant drop in surface tension resulted in increased emulsification activity. P. furukawaii PPS-19 showed the respective n-Dodecane and pyrene degradation of 94.3% and 81.5% at pH 7% and 94.5% and 83% at 1% salinity. A significant positive correlation was obtained between CSH, biofilm formation, and PHs degradation (P<0.05) under all the physicochemical stressors, with the highest value at pH 7% and 1% salinity. Analysis of metabolites indicated that mono-terminal oxidation and multiple pathways were followed for n-Dodecane and pyrene biodegradation, respectively. Thus, P. furukawaii PPS-19 is an efficient hydrocarbonoclastic bacterium that may be exploited for large-scale oil pollution abatement. Moreover, EPS of P. furukawaii PPS-19 could also be used as a bioadsorbent material for biodegradation of PHs
Metal Additive Manufacturing Using Non-transferred and Transferred Type Electric Arc: Microstructural, Mechanical and Biomedical Investigations
No full textRecent developments in the additive manufacturing (AM) field require a process with maximum deposition rate and superior build quality while reducing the cost of production, porosity and contaminations. In such situations, wire arc additive manufacturing (WAAM) found beneficial compared to the laser and electron beam melting-based AM systems. Additionally, the WAAM system relies on wire feedstock, which makes it more advantageous to achieve high deposition at low feedstock cost and improvement in part density and mechanical characteristics. However, geometrical undulation, spatter, molten metal overflow, thermal distortions, anisotropy, and wastage of substrate material are the key points to consider during WAAM. Based on these issues, the objectives of this experimental investigation are ormulated. Initially, a non-transferred type electric arc (NTA) has been developed between tungsten and wire electrodes, which facilitates deposition even on the non-conductive substrate. The unavailability of electric arc connection with substrate, makes minimal heat input to the substrate and maximises the developed heat for wire melting. It also minimized the impingement of filler wire and molten droplets into the melt pool, enhancing the deposition efficiency while reducing the spatter. No arc connection also limits the generation of oversized molten pool on the substrate surface and later on minimises the molten metal overflow during thin-layered fabrication. The developed NTA system is also applicable in small-scale castings via drop-by- drop transfer of molten metal into a mould cavity under the plasma shielding (helps in reducing the porosity chances). It also culminates the requirement of melt furnace, sprue and risers that make the process advantageous from the cost point of view (reduction in initial setup and production cost). Moreover, the casted part shows improvements in ultimate tensile strength (UTS) compared to its wrought part. Geometrical undulations and anisotropy are primarily caused by improper thermal energy management, as most of the commercially available GMAW machines have current controlled wire feeding mechanisms. So, adequate control over arc current generation and wire feed speed (WFS) is not achieved. To mitigate such issue, an autonomous wire feeding system (AWFS) has been designed and integrated into the GMAW-WAAM, which independently controls the WFS of filler wire irrespective of the welding current values. The availability of fine-tuning options for WFS meticulously controls the flow of arc current that in turn, maintains and manages the thermal energy distributions during the deposition process. The thin-layered structures (using ER70S-6 and 316 and filer wire) fabricated through this approach depict mechanical anisotropy of <5%, indicating the isotropic nature of deposit. Moreover, the bulk texture evolution depicts similar fiber texture evolutions with limited variations in the texture intensity, which also highlights the isotropic nature of the deposit. Further, the deposited structures of 316LL SS (via AWFS-WAAM) evolve δ-ferrite structure, which is tunable with the interlayer dwell time (IDT). Its occurrences improved the corrosion resistance, preventing the release of toxic ions into the bloodstream (reduces the hemolysis rate <0.3%) and unaltered the CD spectra of plasma protein, reflecting high hemocompatibility for the WAAMed 316L SS. Also, less adherence and activation of platelets on the WAAMed deposits indicates high biocompatibility. Moreover, the reduction in contact angle (highly hydrophilic) promotes the adsorption of body fluid and proteinaceous materials that boost the adhesion, viability, proliferation, and spreading of MG63 cells (in-vitro). It also allows the growth of osteoblast cells, marrow spaces and collagen fibers (from in-vivo studies) on the WAAMed deposits. The WAAMed implant does not show any acute toxicity in the blood profiles and vital organs like liver and kidney after long-term toxicology analysis in WISTAR rats. Moreover, a double-wire WAAM (after integrating AWFS) system has been developed to fabricate Fe-based alloy fabrication, especially advanced high-strength steel (AHSS). It aims to tune the chemical composition and mechanical performance of the as-built alloy. The fabricated thin-layered alloys exhibit anisotropy within 5%, indicating the process’s effectiveness in maintaining the isotropicity. While compared to different AHSS standards, the as-built alloys exhibit superior mechanical performances in terms of strength and ductility
Numerous Novel Analytical Techniques for Solving Nonlinear Partial Differential Equations Arising in Physical Systems
No full textPartial differential equations (PDEs) are widely used to model a wide range of physical phenomena and are of crucial significance in numerous scientific and engineering fields. In recent years, fractional-order differential equations, being powerful generalizations of ordinary and PDEs to non-integer orders, have received significant attention for their remarkable effectiveness in modelling diverse real-world phenomena in numerous scientific and engineering disciplines. The fractional partial differential equation has been occurring gradationally in several study fields over the past two decades. Numerous critical phenomena in bioengineering, viscoelasticity, cosmology, biomathematics, signal analysis, traffic flow, biomedicine, electrochemistry, financial systems, and many others may be better understood using this fractional differential equation. The fractional calculus is a non-integer order extension of classical differentiation and integration. The tools and approaches of fractional calculus are utilized in almost every modern science and engineering field. One of the foremost significant nonlinear evolution equations in nonlinear optics is the nonlinear Schrödinger equation (NLSE), and numerous exact soliton solutions can be obtained by using various approaches. The NLSE is a nonlinear partial differential equation that is found in several chemistry, physics, and engineering fields. A significant aspect of this NLSE in a nonlinear dispersive medium is that it interprets wave propagation. The NLSE is widely used in a variety of domains, including plasma physics, semiconductor materials, fluids, and many more. Obtaining the exact solution to nonlinear equations is one of the most challenging tasks in engineering, applied mathematics, and physics. Exact solutions consistently provide an excellent description of the behavior of the phenomenon being investigated. Although, for some equations, obtaining these solutions is extremely challenging and, in some instances, impossible. Consequently, numerous analytical methods have been suggested for finding the exact solutions to nonlinear problems. By employing numerous strategies, various types of exact soliton and solitary wave solutions for a variety of nonlinear problems have been obtained in this study, such as kink singular, singular, bright, dark, combined dark-bright, the double periodic singular, the periodic singular, the dark singular, the dark kink singular, the periodic solitary singular, breather, W -shaped, bell-shaped, anti-kink, and kink-shaped solitons. In order to illustrate the physical significance of the acquired solutions and by giving particular values to undefined parameters, the graphical representation of certain derived solutions has been shown
Broadband Spectral Study of Blazars
No full textBlazars belong to a subclass of radio-loud active galactic nuclei (AGN) with a relativistic jet directed towards the observer. The spectral energy distribution (SED) of a blazar extends from radio to -ray energies and is generally characterized by a double hump structure. The low energy hump peaking in the optical to X-ray energies and is explained by synchrotron process whereas the high energy hump with a peak located in γ-ray band and is mainly explained by inverse-Compton (IC) scattering of low-energy photons. The X-ray spectrum in most of the high enegy peaked blazars (HBLs) exhibits mild/strong curvature which can be well-fitted with a log-parabola function. However, for a better understanding of the intrinsic curvature and its evolution, a physically motivated synchrotron emission model is required. The main contribution of this thesis is to develop synchrotron and synchrotron self-Compton (SSC) emission models with different particle distribution of blazar-jets and their validation attributing to the unique curved spectral features observed in blazars. We have made multi-wavelength study of high-energy peaked blazar (HBL), Mkn 421 and extreme HBL (EHBL) source, 1ES 0229+200 using observations with various instruments including AstroSat−LAXPC, SXT, UVIT, Swift−UVOT, XRT, Fermi-LAT, and MAGIC. We present a time-resolved X-ray spectral study of the high peak blazar (HBL) source, Mkn 421, utilizing the simultaneous observations from LAXPC and SXT instruments onboard AstroSat during its flaring state. We fitted the observed X-ray spectrum with the synchrotron emission from various particle energy distributions, viz. max , EDD, EDA, and log parabola models. We found that although all these models fit the spectra, the EDD and EDA models were marginally better. The time-resolved spectral analysis allowed us to study the correlations between the spectral parameters of different models. In the simplest and direct approach, the observed correlations are not compatible with the predictions of the max model. While the EDD and EDA models do predict the correlations, the values of the inferred physical parameters are not compatible with the model assumptions. Thus, we show that the spectrally degenerate models can be distinguished based on their spectral parameter correlations (especially those between the model normalization and spectral shape) making time-resolved spectroscopy a powerful tool to probe the nature of such systems. Further, to test whether the correlation results from the long-term observations are consistent with the one obtained from short-term flare, we have performed a detailed analysis of the X-ray spectra of the blazar Mkn 421 using Swift-XRT observations and quantified the correlations between spectral parameters for different models. We show that the results from the long-term spectral-parameter correlations are consistent with those obtained from the single flare. The consistency of the results obtained from the long and short-term evolution of the source underlines the reliability of the technique to use the spectral-parameter correlations to distinguish various physical models of the blazar-jet emission. We have also studied broadband SED of an EHBL source, 1ES 0229+200, using quasi-simultaneous observations with various instruments including MAGIC, Fermi-LAT, AstroSatLAXPC, SXT, UVIT, and SwiftUVOT. We investigate the one-zone synchrotron and synchrotron self-Compton (SSC) model, employing diverse particle distributions such as the log parabola, broken power law, max , EDD, and EDA models to fit the broadband SED of the source. Our findings indicate that both peaks in the SED are well described by the one-zone SSC model across all particle distribution models. We estimate the jet power for different particle distributions. The estimated jet power for broken power law particle distributions is found to be on the order of 1047 (1044) erg s1 for a minimum electron energy min 10 (104). However, for intrinsically curved particle energy distributions (e.g., log parabola, EDD, and EDA models), the estimated jet power is 1044 erg s1. The SED fitting at five epochs enables us to explore the correlation between the derived spectral parameters of various particle distribution models. Notably, the observed correlations are inconsistent with the predictions in the max model, although the EDD and EDA models yield the correlations as expected. Moreover, the estimated physical parameter values are consistent with the model assumptions
Design and Development of Novel Desiccant Coated Fin Tube Heat Exchanger for Air Conditioning Application
No full textTo improve indoor air quality, enhance the energy exchange capabilities, and minimize the spread of microbial pollutants, desiccant coated fin tube heat exchanger (DCFTHE) seem a promising alternative to conventional heat exchangers such as rotary wheel and adsorber beds due to their capability of decoupling the sensible and latent loads and utilizing low-grade thermal energy. The concept of desiccant coated fin tube heat exchangers can be employed in various heat exchange/transport systems like heat pumps, atmospheric water harvesters, adsorption chillers, and air conditioners. Thus, precise prediction of the design and performance characteristics of DCFTHE is vital for improving the overall performance of the air conditioning system. Therefore, two dynamic models based on the Laplace transform and finite difference approach are developed to assess the adsorption/desorption kinetics and thermal effects of DCFTHE. Lewis and Stanton numbers are chosen as the research parameters because they are significant in characterizing the coupled heat and mass transfer processes occurring across the air-desiccant interface. The interactive effect of the Lewis number and Stanton number on the performance parameters has been examined judiciously. Four different artificial intelligence/machine learning (AI/ML) models, namely adaptive neuro-fuzzy inference system (ANFIS), k-nearest neighbor (KNN), artificial neural network (ANN), and principal component analysis (PCA) have been developed to predict the exit parameters of DCFTHE and a physics-informed neural network (PINNs) based deep learning model has been established by integrating the underlying physical laws governing the energy and mass transport with the neural network. The optimal design/inlet conditions for the given operating and design parametric range of DCFTHE are obtained by employing the AI/ML approaches. A novel DCFTHE has been proposed, designed, and fabricated. Silica gel is used as the solid desiccant material. Experiments have been carried out to assess the moisture adsorption/desorption kinetics of the novel DCFTHE and evaluate the moisture uptake capability of the coated desiccant. The conjugate heat and mass transfer characteristics of the DCFTHE are experimentally examined. Phase change material (PCM) based thermal energy storage systems have evolved as a promising answer for effective thermal energy storage applications. Hence, the practicality of integrating PCM with DCFTHE for air conditioning and thermal energy storage necessitates experimental investigation. Thus, phase change material (paraffin wax) has been integrated with the novel DCFTHE to evaluate its dehumidification characteristics and the performance for thermal energy storage in its latent and sensible form. One of the key emphases of this research is the employment of PCM-Silica gel as a working pair instead of conventional Water-Silica gel. Two case studies have been carried out: first, a dehumidifier is integrated with an M-cooler/solar heater to evaluate the cooling/drying performance during dehumidification. Second, a thermal energy module is integrated with an industrial waste heat-driven DCFTHE during the regeneration process to assess the performance potentiality and energy storage capability of five different PCMs such as Climsel C48, Stearic acid, Myristic acid, n-hexadecane, and Palmitic acid, respectively. The influence of heating the regeneration heat transfer fluid via renewable energy sources on the performance of heat exchanger is examined. Silica gel's adsorption kinetics revealed that the maximum water uptake capability for the given operating range is 0.345 g.g-1. The case study shows that inlet cooling water temperature and inlet air temperature are the most significant parameters for the M-cooler and solar heater, which produce the lowest/highest temperature at the M-cooler/solar heater outlet, respectively. The effectiveness of thermal energy storage and the sensible energy efficacy ratio are maximum for Palmitic acid and minimum for Climsel C48, having corresponding values of 0.73/5.489 and 0.37/2.89, respectively. The significant findings of this research show that the developed dynamic models simplify the approach for assessing the DCFTHE transient performance and adsorption kinetics. The AI/ML approaches comprehended can be used for the design and performance prediction, analysis, and optimization of any heat exchanger. The proposed novel circular fin tube desiccant coated heat exchanger paves the way for the new design configuration of the desiccant coated fin tube heat exchangers
Processing and Characterization of Basalt Fiber Reinforced Polymer Composites Modified with CaCO3 Nanoparticles
No full textNowadays, the fiber reinforced polymer (FRP) composites are increasingly being used in wide range of applications as they have the ability to replace the conventional materials. In past few years, the natural fibers have gained widespread attention due to their low cost, negligible toxicity, easy availability and good specific properties. Basalt fiber, also known as green industrial fiber, is a fantastic alternative to traditional glass and carbon fibers. Basalt fibers are environmentally beneficial since they are made from readily available volcanic rocks. Recently, the hybridization of the FRP composites with nanofillers has been done by various researchers to improve the properties of composite materials. When two reinforcements are jointly used in a matrix, they provide the synergistic effect that improves the properties of the material. Among the various nanofillers used, calcium carbonate (CaCO3) nanoparticles are being used as fillers in various FRP composites. They are highly economical in comparison to other nanoparticles and provide excellent impact and fire-retardant properties. Hence, the proper selection of matrix material and reinforcement can give a composite with properties even superior to those of the conventional materials. The objective of the present research work is to study the mechanical, flammability and wear properties of nano CaCO3 reinforced basalt fiber/epoxy composites. The mechanical properties such as tensile strength, flexural strength, inter-laminar shear strength (ILSS), impact strength and hardness of the composites are analyzed. The moisture absorption behavior of the composites is also studied. Further, the surface properties of the composites are analyzed through drop contact angle measurements. The fire performance of the composites is analyzed through UL 94 horizontal and vertical burning tests, limited oxygen index study and smoke density study. A ball-on-disk tribometer is used for the wear analysis of the composites. Surface morphology study of the fracture surfaces of the composites is made using SEM analysis
Development of Attention based Large-Scale Person Re Identification Systems
No full textPerson re-identification (PRId) is critical in computer vision with significant surveillance, security, and public safety applications. This thesis explores the latest advancements in person re-identification techniques to address the challenges of matching individuals across different camera views and under varying conditions. The primary goal of this research is to enhance the accuracy and efficiency of PRId systems, ultimately contributing to improving security and surveillance systems. The thesis begins by providing an in-depth review of existing PRId methodologies, highlighting their strengths and limitations. It delves into the importance of feature extraction, metric learning, and deep neural networks in Re-ID systems. Furthermore, it discusses the challenges posed by variations in lighting, pose, occlusions, and camera viewpoints, which are inherent to real-world surveillance scenarios. A person-identification framework is proposed to highlight the within-part inconsistency problems that exist in the part-based PRId system, which assumes all the pixels in each part partition are homogeneous. Traditionally, hard and soft partition strategies were used to partition the body parts. However, the proposed method focuses on a recent convolutional part partition strategy. The proposed method demonstrates the effectiveness of convolutional part-partition over the hard and soft partition of body parts over three publicly available benchmark datasets. A graph-based PRId system is developed, which concentrates on two aspects: an explainable approach to attention selection and graph convolution methods. The proposed multi-channel framework utilizes visual features and attribute labels to represent each person uniquely. The proposed approach integrates an attention-based approach to evaluate the importance of different features by estimating the distance between the nodes. The research presents novel feature extraction and representation learning approaches to address these challenges, emphasizing deep convolutional neural networks (CNNs) and attention mechanisms. These techniques aim to capture discriminative information from images and encode it into compact and informative feature representations. Additionally, the thesis investigates the incorporation of domain adaptation and transfer learning to improve model generalization across different surveillance environments. Moreover, the thesis explores the utilization of large-scale PRId datasets and benchmark evaluation metrics to assess the performance of the proposed methods rigorously. It also discusses the ethical considerations and privacy implications associated with PRId technology, emphasizing the importance of responsible deployment. The experimental results demonstrate significant improvements in person re-identification accuracy and robustness compared to state-of-the-art techniques, validating the effectiveness of the proposed methodologies. Furthermore, the research discusses potential real-world applications of these advancements, including enhanced security in public spaces, more efficient search and retrieval in video archives, and improved human tracking in autonomous systems. In conclusion, this thesis contributes to the ongoing development of the PRId system by presenting innovative approaches to address its challenges. The research outcomes have the potential to reshape the landscape of security and surveillance systems, making them more reliable and capable of safeguarding public spaces effectively while respecting privacy concerns
Synthetic Attempts with Visible Light Catalysis and Metal Catalysis Towards Dearomatization and Related Intrigues
No full textChapter-I: Photo-redox Catalytic Radical Relay for para-Selective Amination and Aminative Dearomatization of Phenols and Anilines An efficient organic photocatalytic para-selective amination and aminative dearomatization of phenols and anilines with azodicarboxylates is developed. The formation of para-amino pheno or aniline and para- amino cyclohexadinone depends on whether it has a para- substitution or not. Organic photocatalyst riboflavin tetraacetate (RFTA) is successfully demonstrated to avoid metal contamination. The reaction condition is simple and mild, giving high selectivity with good to excellent yield. A broad substrate scope and nice functional group tolerance, with scalability and post functionalization, make the protocol worthy. Chapter-II: Photocatalytic ortho-Selective Amination and Aminative Dearomatization of Phenols and Naphthols via Synergistic use of Phase Transfer Catalysis in Water An organo-photocatalytic ortho-selective amination and aminative dearomatization of phenols and naphthols is developed using azodicarboxylates as aminating reagent. The key achievement of this protocol is the use of phase transfer catalysts (PTC) such as ammonium bromide salts, which not only made the reaction medium completely aqueous but also induced ortho-selectivity. The formation of ortho-amino phenol or naphthol and ortho-amino cyclohexadinone depends on whether it has an ortho-substitution or not. The reaction condition is simple and mild, giving high regioselectivity with moderate to good yield. A broad range of substrate variation with good functional group tolerance and the application of the protocol for scale-up reactions along with post functionalization make the protocol worthy. Chapter-III: Access to z-Enynoate Equipped Coumarin Employing Organic Photocatalysis A photocatalytic protocol for the synthesis of 3-ester-4-alkynyl (z-enynoate) coumarin is reported using eosin Y as a suitable organic photocatalyst. The protocol was executed under mild conditions like room temperature, organic photocatalysis, less reaction time, and visible light irradiadtion. The exemplary functional group tolerance and concerted activation of the dual mode of catalyst eosin Y make this protocol useful. Again, the product formed bears the scope for broad synthetic applications such as the hydrogenation gave 3,4- dihydro coumarin, an important motif in organic synthesis. Chapter-IV: Ruthenium (VIII) Catalyzed Dearomative Pyridyl C-X Activation: Direct Synthesis of N- Alkyl-2- pyridinones An efficient synthetic strategy employing pyridyl C-X activation for the generation of N-alkyl- 2-pyridinones from N-alkyl-2-halopyridinium salts is described. As pyridinones are dearomatized synthetic derivatives of pyridines, a versatile scope exists for pyridyl C-H functionalization. The present strategy exemplifies a straightforward in situ generation of Ru(VIII), leading catalytic dearomative synthesis of pyridinones. The N-alkyl-2-pyridinones, are further reduced to N-alkyl-2-piperidinones and a plausible mechanism is also drawn, supported by some controlled reactions. Chapter-V: Trials Towards Photocatalyst Free Visible Light Catalyzed Synthesis of [3]Cumulene-1-ol via Encouraged Boron-Catalysis The synthesis of tetra-substituted [3]cumulene-1-ol via photocatalysis with boron co-catalysis has been reported. The beauty of this protocol is the use of simple and normal conditions like room temperature, metal and catalyst free, visible light as activation source and molecular oxygen as oxidant. The post-modification of the obtained [3]cumulene-1-ol resulted in an important organic precursor, allenic ketone
Design And Development Of Various Adaptive Filtering-based Control Schemes For A Grid-tied Multifunctional Photovoltaic System
No full textIn view of the rising demand for electricity and fossil fuel pollution, environmentally acceptable alternatives to traditional electrical energy generation are essential. Using renewable energy sources (RES) to generate electrical energy reduces environmental impacts. Solar photovoltaic (PV)-based power generation is popular among RES due to its decentralized nature, reduced transmission losses, improved efficiency, minimal maintenance, increased safety, and lower solar panel costs due to technological advancements. This research work is on a single-stage configured grid-tied multifunctional PV system (GTPVS). On the other side, as the nature of various loads in the distribution grid (DG) degrades power quality (PQ), and due to the intermittent nature of PV power, the synchronization of PV power to the grid at enhanced PQ is a challenging task. Thus, to enhance PQ while handling the dynamic conditions associated with the environment and loads, this thesis focuses on the development of multifunctional control schemes based on various adaptive filters to operate the three-phase single-stage GTPVS. Firstly, this thesis considers ideal grid conditions where there are no distortions in the grid voltages and with nonlinear loads drawing harmonic currents, where there is a necessity to develop control schemes that filter only nonlinear load currents to estimate their fundamental components for enhancing grid PQ. Secondly, in general, as the interconnection of the PV system to the distribution grid faces challenges like non-ideal grid conditions such as voltage distortions, voltage swell, grid voltage sag, unbalanced voltages, and DC offset along with problems related to currents, the control schemes are developed to filter both distorted voltages and nonlinear load currents to estimate their fundamental components to enhance grid PQ. The selective harmonics and DC offset rejection capabilities are also considered further. The control schemes were developed by including various adaptive filtering algorithms that work with fixed step size and variable step size strategies for a GTPVS to improve PQ while extracting maximum PV power to synchronize the PV system to the grid. Further, the need for separate controllers to filter non-ideal voltages and distorted currents is eliminated by developing a control scheme that utilizes a single controller to achieve the desired functionalities of GTPVS. All the proposed control schemes mitigate harmonics, compensate load unbalances, achieve a unity power factor (UPF), and compensate load reactive power, thus inculcating multifunctional capabilities into GTPVS to deliver balanced sinusoidal currents with the UPF at the grid side and achieving effective power management between the PV system, grid, and loads to ensure THD of the grid current as specified by IEEE 519-2022 standard. Further, a comparative assessment between the proposed and the existing adaptive filtering algorithms is provided in terms of convergence, oscillations, mean square deviation (MSD), computational complexity, and grid current THD to confirm the superiority of the proposed control schemes. The GTPVS, along with all the proposed control schemes, are modeled in MATLAB/Simulink. The behavior of GTPVS is observed and analyzed under steady-state and dynamic conditions. Further, a laboratory-developed prototype of GTPVS is used to carry out the experimental validation of the proposed control schemes
Experimental Studies on Wire Arc Additive Manufacture of SS 308L and Inconel 718 Part
No full textWire Arc Additive Manufacturing (WAAM) belongs to the category of Direct Energy Deposition (DED)-based Additive Manufacturing (AM) in which the feedstock material is in the form of metallic wire. The wire melts under the action of a welding arc; the molten material is deposited on a substrate. Successive bead deposition in a layer-upon-layer manner (along the build direction) develops the final 3D part. In order to build a cross-section/ layer, multiple beads need to be deposited one-after- another onto the horizontal plane in accordance with a given pattern. WAAM is characterized by its high material deposition rate (when compared to the powder- based AM techniques) and is suitable towards fabricating parts which are medium- to-large sized, possessing low-to-medium level of design intricacy. The present dissertation focuses on microstructure and mechanical property characterization of Cold Metal Transfer (CMT) + Metal Inert Gas (MIG) welding based WAAMed SS 308L and Inconel 718 parts. The complex heat interaction phenomena that take place during execution of WAAM process is also studied herein. In the first part of the dissertation work, the SS 308L-T1 wire is utilized to fabricate a 3D slab (149 22 125 mm3). Evolution of location-dependent microstructure and thereby anisotropic static mechanical properties (tensile properties and microhardness) is witnessed. WAAMed SS 308L as fabricated microstructure is composed of grain boundary ferrite of varied morphologies (vermicular/ skeletal and lathy) within the inter-dendritic regions of austenite. The average value of the Ultimate Tensile Strength (UTS) of the horizontally-cut specimens (~ 542 MPa) exceeds to that of the vertically-cut specimens (~ 520 MPa). Post-heat treatment (at 1200 °C, 4 h + furnace cooling) causes significant grain growth; therefore, reduction in the microhardness value from 178 HV0.1 to 143 HV0.1 is witnessed. It is also experienced that the proportion of ferrite phase gets reduced considerably upon the said post-heat treatment. In the second part of the dissertation, an attempt is made to fabricate a 3D slab (15 25 18 mm3) of Inconel 718 through CMT + MIG based WAAM. WAAMed Inconel 718 exhibits dendritic microstructure decorated with Laves phase, phase and MC- type carbides. In the as fabricated condition, the average value of the UTS along horizontal direction obtained is ~ 824 MPa. Post-heat treatment cycle attempted herein consists of homogenization (at 1080 °C, 1.5 h + air cooling) followed by solution treatment (at 980 °C, 1 h + air cooling) and finally, double stage ageing – the first stage ageing is at 720 °C, 8 h + furnace cooling and the second stage ageing is at 620 °C, 8 h + air cooling. It is experienced that detrimental Laves phase is completely dissolved during homogenization treatment although residues of phase is witnessed after the solution treatment. Ageing treatment causes precipitation of the strengthening phase ′′ (Ni3Nb). Thus, post-heat treatment imparts 50 % improvement in the UTS and 85 % increment in the microhardness value when compared to the as fabricated condition. However, post-heat treatment lowers ductility. In comparison with the as fabricated specimen, better wear resistance is attributed to the post-heat treated specimen as evidenced through the dry sliding wear test (at room temperature). The wear rate of the as fabricated specimen obtained is ~ 0.0035 mm3/Nm; on the other hand, the post-heat treated specimen corresponds to the wear rate of ~ 0.0025 mm3/Nm