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Molecular Engineering of Organic Fluorophores for Blue Organic Light Emitting Diodes: Synthesis, Photophysical and Electroluminescence Investigation
No full textThe current thesis investigates the molecular engineering and synthesis of a novel class of blue organic fluorophores with the goal of employing them in blue and white organic light emitting diodes (OLEDs). In chapter 1, a general overview of the development of the new generation and several molecular design strategies, fundamental principles used to achieve high efficiency, a literature survey of recent trends, and brief objectives of the present thesis work were discussed. The design and synthesis of imidazole-based blue fluorescent materials, as well as their applications in blue OLEDs, were highlighted in the introduction. The main aim and importance of the proposed work of the thesis were summarized in this chapter. In chapter 2, two sets of new deep-blue phenanthroimidazole (PI)/benzilimidazole(BI) (A) and triphenylamine (TPA) (D) based fluorophores were designed and synthesized. In the first set of fluorophores, two phenanthroimidazole linearly connected with the hole transporting TPA with the aromatic ring as a spacer and different functional groups at N1 position and of the PI (p-tolyl benzene and p-triflurobenzene) moiety (4-PIPCFTPA and 4-PIPTPA). In the second set of fluorophores, the hole transporting TPA unit linearly connected with electron-transporting PI and BI through the aromatic ring as spacer linearly between D-A with m-triflurobenzene moiety at the N1 position of both imidazole (4- PIMCFTPA and 4-BICFTPA). The synthesized fluorophores were structurally characterized by spectroscopic methods. These fluorophores are thermally stable with the thermal decomposition temperature (Td) of ~446 C. The photophysical, electronic (theoretical), electrochemical (CV), and electroluminescence properties of all the fluorophores were thoroughly investigated, and the N1 substituted moieties play a vital role as it affects the photophysical as well as electronic properties of the synthesized fluorophores. These fluorophores showed deep-blue photoluminescence (PL) emission and high photoluminescence quantum yield (PLQY) in the solution as well as in the solid phase. The HOMO-LUMO energy level of the fluorophores was calculated using electrochemical studies and the same was compared with the theoretical calculation density-functional-theory (DFT). OLED devices were fabricated using solution processes to demonstrate these materials as emissive materials. Fabricated doped devices in the first set, with 4-PIPCFTPA demonstrated superior performance as compared to that of 4-PIPTPA. The best electroluminescence (EL) performance is displayed by the device fabricated with 4-PIPCFTPA (1 wt% in the CBP host) and (3 wt% in the CBP host) with a maximum external quantum efficiency (EQEmax) of 2.7 and 2.9%, respectively and CIE coordinates of (0.17, 0.07) and (0.18, 0.12) were observed, respectively. In the second set of fluorophores, doped devices fabricated with 4-PIMCFTPA demonstrated good EL performance as compared with BI–based emitter. The EL performance based on 4-PIMCFTPA (1 wt% in the CBP host) with an EQEmax of 1.7% CIE coordinates of (0.17, 0.06). The observed EL properties of these emitters reveal their potential as efficient deep-blue emitters for display applications. In chapter-3, two sets of novel NUV and deep-blue light emitting fluorophores based on phenanthroimidazole (PI)/benzilimidazole(BI) (A) integrating with triphenylamine (TPA) (D) emitters were designed and synthesized with meta linking between PI/BI and TPA D--A design strategy which efficiently shortens the -conjugation length, which results in emission in the higher energy end of the emitters. In the first set of compounds three deep blue 4-BIPTPA (para-linked), 3-BIPTPA, and 3-PIPTPA (meta-linked) by integrating a TPA moiety with BI/PI with the different linking arrangement between donor-acceptor and functionalization at the N1 position of the imidazole with electron-donating (p-tolyl benzene) moiety has been successfully designed and synthesized and in the second set of compounds two efficient NUV/deep-blue fluorophores with electron-transporting PI/BI and the hole transporting TPA unit through meta linking D--A design strategy with m-triflurobenzene moiety at the N1 position of both imidazole moiety (3-PIMCFTPA and 3-BICFTPA). Experimental and theoretical investigation reveals materials with efficient NUV/deep-blue emission and good bipolar carrier transporting properties. In addition, doped and non-doped OLEDs were fabricated using the solution processes technique to demonstrate these materials as emissive materials. In the first set of fluorophores, the doped OLED devices based on 4-BIPTPA emitter as dopant showed deep blue emissions with excellent device performance of EQEmax of 6.2%, and CIE coordinates of (0.17, 0.14) at 5 wt% doping concentration and doped device based on 3-PIPTPA shows deep blue emission with EQEmax of 6.0%, and CIE coordinates of (0.17, 0.09) at 1 wt%. In the second set of fluorophores, the 3-PIMCFTPA showed the best EL performance with EQEmax of 5.7% and 3.4% with Commission Internationale d’Énclairage (CIE) coordinates of (0.17, 0.10) and (0.17, 0.02) respectively. Moreover, the 3-PIMCFTPA possesses pure violet emission (385 nm) with high performance allowing the emitter to be used to realize high-performance hybrid white OLEDs. The 1wt% yellow emitter-based device displayed pure white light with an EQEmax of 12.0% with a CIE coordinate (0.33, 0.37) at 1000 cd m–2 . These results of emitters make them potential for smart displays and lighting applications. In chapter-4, A series of deep blue fluorophores (PTPIBI and m-CF3PIBI) based on the hybridized local and charge transfer (HLCT) characteristics were designed and synthesized by incorporating weak donor phenanthroimidazole (PI) and weak acceptor benzimidazole (BI) to study their potential application in deep-blue organic electronic devices. The systematic investigation of photophysical and theoretical properties of both the fluorophores indicates that the materials possess locally excited (LE) and charge transfer (CT) excited states character. The synthesized emitters showed high thermal stability and intense blue emission with high quantum yields. fabricated solution-processed undoped and doped OLED devices with newly synthesized emitters and observed that the PTPIBI demonstrated superior performance as compared to that of m-CF3PIBI. The best electroluminescent (EL) performance is displayed by the device fabricated with PTPIBI (5 wt% in the TCTA host), showing an EQEmax of 2.4%, CIE coordinates of (0.15, 0.08), and maximum luminance of 2,507 cd m–2 . In addition, deep blue pure organic light-emitting material based on donor--acceptor weak donor benzilimidazole and weak acceptor BI(m-CNBIBI) has been designed and synthesized. The synthesized m-CNBIBI was well characterized by spectroscopic techniques and theoretical, optical, thermal stability, redox, and EL characteristics were systematically explored. The fully twisted m-CNBIBI emitter can emit pure blue emission in the solution and solid phase having good PLQY. The new deep blue emissive material displays a positive solvatochromism effect indicating material with charge transfer properties in the excited state. Moreover, a deep blue organic light-emitting device (OLED) was fabricated by using a low-cost solution-processed technique. The doped device shows good EL performance with EL emission in the deep blue region with color purity Commission International de l’Eclairage (CIE) of (0.16, 0.08) which is close to the National Television Standard Committee (NTSC) standard (0.14, 0.08). In chapter-5, a series of pure deep-blue organic fluorescence light-emitting materials which are thermally stable and have improved photophysical properties and with hybrid local and charge-transfer (HLCT) states were designed and synthesized by using weak donor and weak acceptor designed strategy (PTBIBI and MCFBIBI). Additionally, a thermally stable deep blue emissive material (MCNPIBI) by integrating moderate donor and acceptor namely phenanthroimidazole (PI) and benzimidazole with cyanophenyl (-CN) group at the N1 position of the PI to tune the CT component in the excited states. Systematic theoretical and photophysical study reveals the MCNPIBI with HLCT excited states. Time dependent density functional theory (TD–DFT) calculation suggests that the reverse intersystem crossing (RISC) process in MCNPIBI occurs from high-lying triplet states to singlet states. Furthermore, the synthesized deep blue emissive materials were employed as dopants in multilayer organic light-emitting diode (OLED) devices resulting in deep-blue EL with emission wavelength of 447 nm and CIE coordinates of (0.15, 0.08) which are close to standard values for blue emitters as suggested by NTSC (0.14, 0.08). The doped devices based on PTBIBI and MCFBIBI display a reasonably good device performance having the CIE coordinate of (0.15, 0.06) in the deep blue region and maximum luminance of 6599 cd m−2 and 3305 cd m−2 , maximum current efficiency (CEmax) of 1.95 and 1.54 cd A–1 , maximum power efficiency (PEmax) of 1.59 and 1.39 lm W–1 , and EQEmax of 3.59 and 2.67 %, respectively. The OLED device based on MCNPIBI displays CEmax of 2.78 cd A–1 , PEmax of 1.94 lm W–1 , and EQEmax of 3.69% respectively. In addition, the OLED device has low turn in voltage of 3.8 V. In chapter-6, two sets of D--A novel deep-blue light-emitting fluorophores based on benzothiazole as acceptor core and phenanthroimidazole (PI)/benzilimidazole(BI) as donor cores were designed and synthesized. In the first set of fluorophores three blue-light emitting materials by integrating BI as a weak donor and benzothiazole as a weak acceptor moiety (PHBISN, PTBISN, and m-CFBISN) with different functionalization at the N1 position of imidazole (benzene, p-tertbutyl benzene, and m triflurobenzene) to tune the electrical and photophysical properties and in the second set of fluorophores, three blue emissive materials with electron-donating and stable PI as weak donor integrated with electron accepting benzothiazole as a weak acceptor (PTPISN, m-CFBISN, and m-CNBISN) with varying substituents at the N1 position of imidazole (p-tertbutyl benzene, m-triflurobenzene, and m-cyanobenzene) to tune the properties of the materials have been designed and synthesized. All the synthesized fluorophores were structurally confirmed by spectroscopic techniques. All the fluorophores exhibited good thermal properties with high thermal degradation temperatures. An optical study reveals that the fluorophores are capable of emitting in the blue spectral region in solution and solid. The quantum chemical investigations were also performed with the aim to understand the electronic structures of the fluorophores. In addition, doped and non-doped OLEDs were fabricated using the solution processes technique to demonstrate these materials as emissive materials. The solution-processed OLED device was fabricated by using these fluorophores as emissive dopants shown good device performance with bright deep-blue electroluminescence with CIEy of (~0.08), which is near to the blue standard (0.14, 0.08) of the National Television System Committee (NTSC). The obtained results suggest that the introduction of benzothiazole moiety is a promising design strategy for obtaining new deep-blue emitters. In chapter-7, a series of three sky-blue fluorophores based on Imidazo[1,5-a]pyridine (ImPy) decorated with aromatic π-system (C3 position of ImPy is decorated with naphthalene, methoxy naphthalene, and pyrene) was designed and synthesized by the one-pot synthesis method. The fluorophores were structurally characterized by spectroscopic techniques. The density functional theory (DFT) calculations were carried out to understand the HOMO-LUMO energy level as well as excited energy level (singlet and triplet) of the molecules, detailed computational study reveals that the compounds showed a wide energy gap (>3 eV). Their photophysical and electrochemical properties, including UV-Vis, photoluminescence, and cyclic voltammetry were systematically studied. The presently studied fluorophores exhibited good thermal and electrochemical stability. The systematic photophysical study reveals that the compounds showed sky-blue emission with CIE color coordinates (x = 0.16/0.20, y = 0.22/0.32). ImPy derivatives were used as an emitter to fabricate the sky-blue emission OLED. Novel synthesized Impy derivatives demonstrate a good performance for sky blue emission OLED. Among the three emitters, the highest performance was observed with ImPy-3 demonstrating the maximum EQEmax of 4.3%, PEmax of 4.7 lm W–1 , and CEmax of 8.4 cd A–1 at 100 cd m–2 . Chapter 8 deals with the summary and conclusion as well as the future prospects of the work. The present thesis works deals with molecular engineering and synthesis of novel/new class of bipolar strong D-A and weak D-A blue organic fluorophores, with the aim of exploring their potential application in blue and white OLED. The observations and the conclusions derived from the present investigations are summarized in this chapter
Redesigning Smart Healthcare Supply Chain: Value Creation in the Era of Industry 4.0
No full textIndian healthcare (HC) sector has faced severe challenges of increased cost and quality over the past few decades. On the same front, the value chain environment as a challenge is exerting a strong thrust on HCFs to search for opportunities to enhance quality, reduce costs and excel in operational efficiencies. Supply chain management in the HC sector is more complex as compared to other industries. This is due to the fact of repetitive sudden health outbreaks and the level of HC services and product delivery required to the patients covering the vast geographical areas. In pursuance of this, the present research aims to take into account smartening the healthcare supply chain (HCSC) from the perspective of Industry 4.0 implementation. To achieve smart HCSC performance, the decision-making variables and other related dimensions of HCSC are identified and analyzed to present a holistic model of HC services delivery. The decision-making variables are identified through an extensive literature survey and consultation with both industry and academic experts. The present study has used various multi criteria decision making (MCDM) tools like: grey theory, fuzzy theory, analytic hierarchy process (AHP), decision making trial and evaluation laboratory (DEMAEL), total interpretive structural modelling (TISM) to explore and analyse their overall contribution for developing the smart HCSC. Further, the study proposes the hypothetical model on redesigning the smart HCSC and empirically validates it using structural equation modelling (SEM) to bring into light the possible areas of enhancing the smart HCSC performance through the implementation of Industry 4.0. The findings of the study suggests that healthcare logistic management, integrated HCSC and sustainable HCSC are the most prioritized factors implementing industry 4.0 in the HCSC hierarchical model. The theoretical model based on TISM has structured the enablers of emergency HCSC into seven interpretive levels to be used for policy and decision making by managers. The analysis of sustainability in the HCSC has resulted in ‘HC bye-product management system’ coordinating and Facilitating Green suppliers in the HCSC’, ‘green packaging of pharmaceutical’, ‘eco-friendly designed HC products and services’ and ‘complying with the ISO 14000 certification’ as the most important drivers. The empirical study conducted in the present research, validated the proposed model on smart HCSC performance and resulted in confirming the effect of HCSC responsiveness (mediator) between independent variables (like: ‘HCSC dynamic capability’, ‘HCSC integration and collaboration’, ‘HCSC technological innovations’ and ‘HCSC risks mitigation’) and the outcome variable ‘smart HCSC performance’. Additionally, the moderation effect through ‘industry 4.0’ is tested positively between the independent variables and HCSC responsiveness. The study has developed theoretical, managerial and administrative implications for practitioners and policy makers in the hope to redesign and achieve smart HCSC performance to be highly responsive to the constant turmoil of demand for HC products and services
Structural, Spectroscopic and Photophysical Properties of Rare-earth Activated CaXO4 (X = W, Mo) Phosphors
No full textPhotonics is predominantly elucidated as the physical science and technology for realizing, controlling and manipulating the interaction between light and matter which furnishes technological base for solar-cell devices, lighting displays, medical science, solid state lighting (WLEDs), bio-imaging, biotechnology, etc. The energy efficiency needs to be an important criterion for all such applications. In this framework, lanthanide ions hold a special place in photonics owing to their unique photo-physical properties favouring the generation and amplification of light. To accomplish the above requirements this thesis work tries to study various photo-physical processes involved in a self-activated Scheelite family like down-conversion and up-conversion. Different approaches are made including incorporation of activators, sensitizers, charge compensators and surface treatment in order to enhance the luminescence properties. The detailed synthesis procedure and the characterization of the phosphors along with the results based on the structural, morphological, vibrational and photo-physical properties of synthesized phosphors are investigated and are systematically documented. Some possible field of applications are also explored and discussed in this work. The Scheelite family with chemical formula CaXO4(X = W and Mo) have emerged as the technologically interesting materials owing to their excellent thermal and chemical stability, interesting luminescence behaviour, self-activated nature, wide emission spectra in the visible region, low afterglow to luminescence, and attractive structural properties. In this context, a series of CaWO4:0.03Eu3+:xBi3+ (x = 0.02,0.05,0.07 and 0.10) nanophosphors are studied in detail. The phosphors are synthesized through the efficient low temperature ethylene glycol route. X-ray diffraction analysis and XPS survey proves that the Bi3+ and Eu3+ ions are perfectly incorporated into Ca2+ without disturbing the lattice. The nanophosphors show orange-red luminescence which is further tuned to red via incorporation of sensitizers Bi3+ ions. This color tuning of the nanoparticles is described in the frame work of energy transfer processes from WO4 2- group and sensitizer Bi3+ ions to the activator Eu3+ ions. The energy transfer efficiency and the quenching phenomenon are discussed in detail. The CIE diagram supports this color tenability which evident the application of the phosphor in solid state lighting applications. A series of un-doped and Li+ co-doped CaMoO4:Dy3+ nanoparticles are synthesized via. modified reflux method. The host shows broad dual band emission centered in blue and green regions endowed by charge transfer and defects. Upon Dy3+ doping, the host to dopant energy transfer (hdet) cause the CaMoO4:Dy3+ nanoparticles to exhibit characteristic emission lines from Dy3+. The CIE 1931 chromaticity coordinates for the prepared phosphors are found to lie in the nearly white region of color space. The light output as well as excited state lifetimes are successfully improved by lithium co-doping by virtue of reduced charge compensating defects and sensitization via. oxygen related defects. The positron annihilation studies show that all the lithium concentration co-doped for charge compensation is merely helping in removal of cations. An attempt is made to synthesize core nanoparticles (NPs) and core-shell particles using the reflux method. The structural and photo-physical properties of the developed phosphors have been investigated through various analytical techniques. The transmission electron microscopy (TEM) analysis evidences the formation of the shell on the core NPs. An 8-fold enhancement of emission intensity is observed in the core-shell particles as compared to that of core, due to the reduced surface quenchers after silica coating. The tunable red emission on formation of core-shell structures is confirmed from the CIE diagram. These results are ascribed to the formation of the chemical bonds between CaWO4@ CaWO4:0.03Eu:0.05Bi (core) and amorphous SiO2 shell via W – O – Si bridges. Better hydrophilicity developing from active functional groups in solutions and intense luminescence behavior with a quantum efficiency of 91% allow the developed phosphors for various potential applications such as solid state lighting, bio-labelling agent for the visualization of latent fingerprints (LFPs) and anti-counterfeiting, etc. Upconversion emission in CaWO4:Er3+/Yb3+/Mn2+ phosphor synthesized via ethylene glycol route has been analyzed on excitation under 980 nm diode laser. The structural information and morphology have been widely studied through different experimental techniques. The Yb-Mn dimer is established to explicate the energy transfer mechanism which brings about two-fold enhancement in the green emission. The optical thermometric performance of the developed phosphor based on the thermally coupled green levels of Er3+ (2H11/2 and 4S3/2) ions in the range of 303-623 K has been explored using the fluorescence intensity ratio (FIR) technique. The maximum sensitivity of 1.04 % K-1 at 303 K is obtained for the optimized phosphor with a thermal resolution of 0.4 K. Additionally, the internal heating characteristics of the said phosphor developed by the variation in excitation laser power is also studied which is found to raise from 265 to 563 K. Under 980 nm excitation the prepared phosphors exhibit strong green emission with a color purity of 98%. The energy transfer mechanism, population redistribution ability and thermal stability have been discussed in detail and the possible field of applications have been explored
Assessing Multidimensional Child Poverty in India: A Decomposition Analysis
No full textChildren are universally recognised as one of the most vulnerable groups in society, as they depend on adults for fulfilling their basic needs and rights. Importantly, they experience deprivations and poverty differently from adults. In this regard, the Sustainable Development Goals (SDGs) Target 1.2 is significant because, for the first time, children are being explicitly included in the global poverty goal and recognizing the multidimensional nature of poverty. According to the global multidimensional poverty index report, 2022, approximately half of the 1.2 billion multidimensional poor people are children under 18, amounting to 593 million children globally. Data on child poverty shows that one in three children is multidimensionally poor, whereas the ratio is one in seven for adults. These statistics highlight that child poverty is a matter of global concern, not only due to its alarming prevalence among children but also it poses a significant threat to their present and future well-being. Although poverty among children fell faster in India, the country still has the highest number of poor children in the world, that is, 97 million. Nevertheless, there is a lack of in-depth research on the extent and nature of multidimensional child poverty (MCP) in the Indian context. In this regard, this study aims to fill this gap and uses data from two rounds of the National Family and Health Survey: 4th (2015-16) and 5th (2019-21). The study objectives are to examine the changes in MCP between 2015-16 and 2019-21 across all States/UTs and various population subgroups; decompose the MCP by various population subgroups and geographic locations; investigate the determinants of MCP in India and across its regions; and examine the multidimensional household poverty and intra-household inequality in child deprivation in India. The study uses the Alkire-Foster counting approach for measuring and decomposing MCP across dimensions, indicators and social groups. Further, Shapley decomposition and Alkire, Haq & Alim’s methods were employed to decompose the reduction in MCP by the within-group and demographic effects. The study employed various statistical models such as logistic regression, tetrachoric correlation and first order stochastic dominance approach to examine the above objectives. The results show that in India, the incidence of child poverty reduced by over 40% between 2015-16 and 2019-21 (46.6% to 27.4%) and the MCP Index reduced by half (0.242 to 0.126). Notably, the decline in MCP has been most significant in urban areas, northern regions, OBCs and Hindus. Children from rural areas, SCs, STs, and Muslim households are the poor performers. When focusing the deprivation status of poor child, the study found significant improvements in indicators such as access to electricity, birth registration, clean drinking water, assisted delivery during childbirth, sanitation facilities, and cooking fuel between 2015-16 and 2019-21 across population subgroups and geographic locations. The results also highlight that among the 15 indicators considered, sanitation had the largest contribution to the MCPI, followed by the mother’s education, cooking fuel, housing condition, and hand hygiene. These contributions varied significantly across population subgroups and geographical locations. Various factors were found to significantly influence child poverty in India, including the child’s sex, mother’s education, education level of the household head, age and sex of household headship, child’s birth order, caste, religion, household structure, and size. The study also found intriguing results in intra-household inequality in child deprivation in their nutritional and school attendance status. Specifically, it was observed that intra-household inequality in nutrition and school attendance is more prevalent in the multidimensional poor household. Both SCs and OBCs show higher levels of intra-household inequality in the nutritional status of children. Whereas, in school attendance, it is the ST households where intra-household inequality is more prevalent. Moreover, the country's central and eastern regions were particularly vulnerable to multidimensional household poverty and intra-household inequality. The findings suggest this analysis assists in ensuring the commitment to “Leave No One Behind” by identifying and addressing the specific deprivations faced by children from diverse subgroups within the Indian population
Structural Behaviour of Lightweight Concrete Block Masonry
No full textLightweight concrete (LWC), an emerging masonry material, is produced by replacing natural sand with industrial waste, resulting in the conservation of natural resources and better waste management in addition to reducing production costs. LWC is accepted as an alternative to conventional masonry materials due to various advantages such as lower thermal conductivity, sound insulation properties besides its lighter weight, cost effectiveness and environmental friendliness. Consequently, considerable research effort has been made in this direction, as is apparent from the published literature. However, to build confidence for this masonry material among stakeholders, comprehensive research outputs are needed in all possible directions. The detailed literature review revealed that the strain rate sensitivity of different mechanical properties of LWC masonry and the effect of pre-compression on the shear bond behavior of LWC masonry are the two important aspects that have not received the attention of the research community. Therefore, the work presented in this thesis attempted to address the above two major research gaps through a systematic laboratory experimental program and numerical analysis through finite element modeling. This research work was carried out in three parts (a) evaluation of physical and mechanical properties of LWC masonry units with special attention to strain rate sensitivity, (b) evaluation of compressive strength properties of LWC masonry assemblies with special attention on strain-rate sensitivity and (c) evaluation of bond shear strength properties of LWC masonry assemblies with special attention to the effect of precompression in addition to strain rate sensitivity. The first part of the research is carried out with experimental investigations to determine the selected physical properties, such as density, moisture content, water absorption, initial absorption rate, and sorptivity of autoclave aerated concrete (AAC) and cellular lightweight concrete (CLC) masonry units. In addition, microstructure analyses (such as XRD and SEM) are also performed to understand material properties that affect strength properties in LWC. It also evaluates the mechanical parameters such as compressive strength, splitting tensile strength, and flexural strength of LWC units under varying strain rates. Along with that, the finite element model using Abaqus is proposed to predict the strength parameters of the LWC unit at different levels of strain rate. The proposed model seems to correctly capture both the maximum load and the crack patterns obtained from the laboratory experiments. An empirical relationship is established using the experimental results to find the strength properties of the LWC unit. Next, the present study evaluates the uniaxial compressive strength of the LWC masonry assembly through systematic laboratory tests under varying strain rate conditions followed by a numerical study. The results showed that the compressive strength of LWC masonry assemblage is considerably dependent on strain rate. It is found that the increase in the strength and elasticity parameter maintains a logarithmic relationship with the strain rates. The experimental procedure is always expensive and time-consuming, while numerical modeling can be an efficient way to study the behavior of any structure. Therefore, the numerical models are developed in this study using the finite element software (Abaqus). The proposed models can predict the strength of LWC masonry assemblage under different strain rates with significant accuracy but with less time and effort. The compressive strength of LWC masonry assemblages increases with the increase of strain rates. When the strain rate increases from 0.1 mm/min to 10 mm/min, the modulus of elasticity and uniaxial compressive strength increases by about 100% and 200% respectively, which is quite significant. In the last part of this study, both experimental and numerical strategies have been developed to study the shear response of LWC masonry assemblages under different levels of pre-compression considering low to high load rates. The peak shear strength observed during monotonic shear tests increased with increasing levels of precompression pressure and load rates. The experimental and numerical failure modes of the masonry triplets showed a reasonably good agreement. Particularly, failure modes were influenced by the pre-compression level, i.e., slipping occurred along with the brick-to-mortar interface for lower, while diagonal cracks developed in the mortar layers for higher compression levels. Therefore, the level of precompression was found to significantly affect the shear response and failure mode of the LWC masonry triplet
NZVI and Fe3O4 Based Composites for the Treatment of Dairy Wastewater and Heavy Metal Removal by Adsorption using Digested Sludge
No full textDevelopmental and industrial activities have caused extensive environmental impacts worldwide. Many proactive ‘clean-environment’ strategies have been proposed and implemented with the support of UNEP. The peer pressure on the government has assured more stringent regulations to reduce the burgeoning effect of atmospheric pollution and improve environmental performance. To comply with environmental regulations, the stakeholders may need to depend on more efficient and competitive waste treatment methodologies. Researches on sustainable wastewater treatment technologies are on an increasing trend. Studies help to develop processes with eco-friendly reactants, less energy requirement, easy residue management, and high efficiency. Incorporating nanosystems into wastewater treatment methodologies has been observed to be highly efficient due to the superior physicochemical properties of nanoparticles. Iron nanoparticles (INPs) are preferred among the studied nanoparticles because iron is highly abundant, low cost, has no secondary pollution, and has easy separation from aqueous media. But, INPs show a high tendency for aggregate formation and scavenging effects when used alone. Composites of INPs have been employed to alleviate these problems. This study analyzed the impact of composites of nano zerovalent iron (NZVI) and nano Fe3O4 for wastewater treatment. A composite was developed with NZVI and reduced graphene oxide (RGO) and studied the effect on the anaerobic digestion of dairy wastewater. There was 86.27 ± 2.8% more CH4 production and 47.37 ± 1.3% improved COD removal. Comparing different ratios of RGO-NZVI revealed that a proportion of 2:1 was beneficial for maximum CH4 generation. Further, the higher concentrations of the conductive additives could be fatal for microbial metabolism. The metagenomic analysis showed that the diversification of the microbial community and switching to direct interspecies electron transfer caused higher CH4 generation. The effect of pretreatment on dairy wastewater digestion was also evaluated. Ammonium persulfate (APS) assisted photocatalytic pretreatment using RGO-NZVI catalyst and anaerobic digestion were integrated and assessed at different operational parameters. The maximum solubilization was found at an initial pH 5 until 4 h of pretreatment with an increase of 38.77±0.85% SCOD and 39.05±1.3% dissolved organic carbon (DOC). Digestion with pretreatment and fresh composite addition showed 81.01±3.24% more CH4 production and 72.99±2.84% more SCOD removal. The anaerobic digestion of pretreated wastewater containing spent catalyst was also producing a better volume of CH4. Another experiment incorporated the composite made of NZVI, polypyrrole (PPy), and carbon black (CB) in biogas production. A dosage of 0-0.8 g L-1 of Ppy-CB was chosen. The maximum cumulative biogas production and SCOD removal efficiency were 2185 ± 76 mL and 74.69%, respectively. A Ppy-CB-NZVI dosage of 0.4 g L-1 (D3) caused 43.27% more biogas than the control digester. Similarly, the total CH4 production in D3 was about 1.79 times higher. The results of residual VFA analysis and corresponding CH4 generation illustrated that the ternary additive significantly influenced hydrolysis, fatty acid metabolism and acetogenesis, leading to higher gas production. After anaerobic digestion, the active functionality of sludge was utilized to develop a low-cost adsorbent by magnetic modification of pretreated biogas slurry solids (BSS) to remove heavy metals such as Cu2+, Cd2+ and Pb2+. The temperature (423 K) and time (1.5 h) of pretreatment, BSS to KOH ratio (1:10 w/v) and the ratio of magnetic iron nanoparticle (MIN) to pretreated BSS (PSS) (1:2 w/w) were optimized for the preparation of adsorbent. The optimum conditions for the adsorption of heavy metals were obtained from response surface methodology (RSM) incorporating Central Composite Design (CCD). Model validation experiments for optimization of the adsorption process showed comparable results with predicted values. The adsorption capacity at optimum conditions from RSM analysis was 29.721 mg L-1, 28.551 mg L-1 and 28.601 mg L-1 for Cu2+, Cd2+and Pb2+, respectively. The adsorption kinetics followed a pseudo-second-order model with an R2 value above 0.9 for all metals with a well-approaching equilibrium pattern. The excellent fit of experimental data by the Langmuir isotherm model implied monolayer adsorption. By this, the effluents containing heavy metal, which causes contamination of water resources, may be remediated effectively
Impact of Crowding Environment on the Stability, Conformation and Kinetics of CRABP I
No full textThe importance of macromolecules paves the way towards a detailed molecular level investigation as all most all cellular processes occurring at the interior of cells in the form of proteins, enzymes, nd other biological molecules are significantly affected because of their crowding. Thus, exploring the role of crowding environment on the conformation, stability and denaturation/renaturation kinetics of protein molecules is of great importance. Here, CRABP I (cellular retinoic acid binding protein I) is employed as a model protein along with different molecular weights of polyethylene glycol (PEG 400, PEG 1000, PEG 2000, PEG 4000, PEG 6000, and PEG 8000) as molecular crowders. The experimental evaluations are done by accessing the protein secondary structure analysis using circular dichroism (CD) spectroscopy and unfolding/refolding kinetics using intrinsic fluorescence of CRABP I at 37 °C to mimic the in vivo crowding environment. Experimental results show that both conformation and stability of the native state of the protein is not significantly affected by the presence of crowding agents in the solution, whereas the crowding environment has a great impact on the unfolding/refolding kinetics of CRABP I. However, our findings show that not only the type of crowder but also the crowder size played a key role in the effects of excluded volume. In case of lower molecular weight of PEG (MW 400), even at 200 g/L concentration only the viscosity effect is observed whereas, for higher molecular weight of PEG (MW 1000), along with viscosity effect, excluded volume effect is noticed and, even at more higher concentration (200 g/L) of PEG 1000, excluded volume predominates over the viscosity effect. Using the transition state theory, we were also able to determine the free energies of activation for the unfolding and refolding studies from their respective rate constants. Furthermore, m, Cm and ΔG° of CRABP I are affected by crowding via urea-induced unfolding with increase in the size of PEG. Kinetic and stability outcomes presented the importance of crowding environment on the stability, conformation and unfolding/refolding kinetics of CRABP I
Macromolecular Structure of Sunn Hemp Fiber and its Influence on Properties of the Fiber Reinforced Epoxy Composites
No full textThe present dissertation entitled “Macromolecular Structure of Sunn Hemp Fiber and its Influence on Properties of the Fiber Reinforced Epoxy Composites” is the amalgamation of the investigation aimed at the structural modification of sunn hemp fiber and using those modified fibers as a reinforcement for composites fabrication. Various characterization tools have been adopted for both the fiber and composites. The whole thesis has been classified into seven chapters. Due to high resistance to root-knot nematodes and wide application in cordage, fishing nets, ropes and canvas industries, sunn Hemp holds a potential emerging fiber crop. Unsheathing from the stem region, sunn Hemp exhibits 70-78% of cellulose, about 12.5 MPa flexural strength, low density (1.5 g/ cm3) with a high aspect ratio (450-600). All these properties make sunn Hemp fiber a target material for automobiles, domestic appliances, sports industries, etc. However, the inherent hydrophilic character of sunn hemp fiber due to intramolecular hydrogen bonds causes it to be incompatible with hydrophobic matrix resin. In such a series, various modification techniques are proposed to enhance the functionalization process between fiber-matrix, aiming to improve the various physical properties of the end-use composite products. In the recent study, treatment strategies, including the dewaxing process, potassium hydroxide (KOH) and microwave irradiation treatment, are addressed to modify the sunn hemp fiber structurally. Before any treatment, the fiber loading is optimized for composites fabrication. The hand layup technique is adopted to process composite specimens. Among 5, 10, 15, 20, 25, and 30 vol% of loading, 20 vol% loading fiber in composites yields better mechanical strength and a low dielectric loss and is subsequently optimized for further composite fabrication. The hydrophilic sunn hemp fiber is functionalized using the dewaxing process, where fiber is soaked in an ethanol and benzene solution in a ratio of 1:2, followed by 12 hours of consecutive heating and cooling. The second chemical way of treating the fiber is the alkalization process, where fiber is immersed in 5, 10, 15 and 20wt% of KOH solution for 2, 4,6, 8 and 10h. In physical treatment, the fiber is exposed to microwave irradiation at 160, 320, 480, 640 and 800 watts for 2, 6 and 10 min exposure time. The effect of treatment on the fiber as well as on the composites is investigated. The fine structure of untreated and treated fiber is studied by SAXS and XRD analysis. The macromolecular parameters like average periodicity to layers, volume fraction in the matter and void phase, range of inhomogeneity, heterogeneity, etc., are computed and found to be enhanced in all treated fiber for a specific combination of concentration-soaking and irradiation power-exposure time. The XRD study revealed the crystallographic parameters like crystalline index and cellulose crystallites and observed to be higher in dewaxed fiber, fiber treated with 10% alkali concentration for 6 h (10K6) and fiber irradiated at 320 watts for 2 min. FTIR peaks show specific bond removal in treated fiber, which justifies the removal of non-cellulosic components from fiber structure. The increased roughness and fibrillation are visible on the treated fiber surface, but beyond optimization, it shows the degradation as confirmed by FESEM images. The single fiber tensile strength of the sunn hemp fiber is evaluated using Weibull analysis and a statistical average on the fiber strength is reported. The effect of pre-treatment on the fibers can be legitimate as the composites's overall mechanical and dielectric properties are compared to the untreated ones. The crosslinking density of the composites is determined by the Flory-Rehner equilibrium theory and correlated with the mechanical properties of composites. The 3-point bending and tensile test of the composites are higher in dewaxed, 10K6 and 800W6M fiber. The improvement in mechanical behavior indicates an excellent interfacial adhesion between fiber-matrix. However, the decrease in mechanical properties is the consequence of weak adhesion and compatibility between fiber and matrix. Such a scene may also arise due to low crosslinking between fiber and matrix resulting from the void formation at the interface region. The dielectric study of the composites is carried out by an LCR impedance meter and notices that the treated fiber results in a lower dielectric constant (′) and lower dielectric loss (tanδ). However, after an optimal controlling parameter, the ′ and tanδ are observed to be increasing. It can be attributed to the loss of the polar hydroxyl (-OH) group from the fiber structure upon treatment, which led to a decrease ′ and tanδ. Other electrical parameters like ac conductivity, modulus and impedance of the composites are also studied and reported in the subsequent chapters
An Investigation on Robust Control of Isolated DC-DC Dual Active Bridge Converter
No full textIn recent years, DC-DC power converters are comprehensively used for numerous applications such as in dc-microgrids, energy storage systems, distributed generating systems, power filters, electric vehicles, etc. With the increase in usage of renewable energy sources and electric vehicles, the DC-DC converter finds larger application area in nearby future. The dual active bridge (DAB) converter is an isolated DC-DC converter which has risen in popularity for its notable advantages such as ohmic isolation, higher efficiency, bidirectional power flow, high voltage gains and smaller size and weight, makes it a preferable option for various applications. The control of DAB converter is an important research area to achieve an efficient and robust system. With various control methods proposed earlier, the converter provides satisfactory performance, however, the robustness, voltage regulation and stability need to be improved further. This thesis provides sliding mode-based control methods for the DAB converter to obtain a robust and stable system. The frequent disturbances including load change and input voltage change is handled to obtain a fix output voltage. The parameters of the converter deteriorate over the period of time and changes the converter overall performance. Therefore, the robust controller presented in this thesis, handle the parametric uncertainties and provide better performance. The sliding mode based direct power control (SM-DPC) is proposed and the experimental results are compared with feedback linearization control (FLC), sliding mode control with harmonic modelling (SM-DPC) and virtual direct power control (VDPC). The SM-DPC shows the improved in voltage regulations and handles disturbances and uncertainties. With several advantage over classical sliding mode control, super-twisting sliding mode control (ST-SMC) provides better performance under large disturbance and uncertainties. Thus, the ST-SMC control for DAB is proposed in this thesis. The experimental results are shown and compared with conventional SMC and proportional-integral (PI) method, which conforms the improvement in the overall performance of DAB converter system and eliminates the problems of chattering in the classical sliding mode control. As the major applications of DAB are in electric vehicles, dc-microgrid, renewable energy systems, solid-state transformers (SST), and energy storage systems. These systems are multi-converter systems with back-to-back connections of power electronics converters. In multi converter systems, the power electronics converter acts as feeding converters as well as loads to other converters. The tightly regulated power converters act as constant power load (CPL) and has destabilizing effect on the connected system. The sliding mode and current observer based direct power control (SMC+O) is proposed in this thesis, which make the DAB converter stable while feeding CPL. The current observer eliminates the requirement of current sensor from the system and help in minimizing the chattering phenomenon. The SMC+O method is compared with PI and SMC methods in experimentation and the results shows the improvement in transient and steady state performance of the system with CPL. Thus, the methods proposed in this thesis can be adapted for various DAB applications as the proposed robust control of the converter makes the system efficient and reliable
Web based Application and Collaborative Machine Learning Approaches for Credit Card Fraud Detection
No full textWith advancement of growing technology, the financial transactions linked to credit card are augmented across online mode. The convenience and popularity of credit card usage leads to the anticipation of fraudulent activities cunningly plotted by the fraudsters. It is a matter of great concern for credit card users as well as financial institutions, to provide credit card facilities for making the transactions free from possible frauds being carried out by fraudsters. To sort out the issue on fraud detection, number of researchers and professionals have applied various strategies including computer algorithms and automation technology. Even though a good number of researchers and analysts have extended their studies in detection of fraudulent transactions by applying various methodologies, still the research track is not so proficient enough due to the privacy concern in research data and variable strategies adopted by fraudsters. Hence, developing a fraud detection system to identify the fraudulent activities is an important area of research to improve the credibility of credit card-based digital transactions. Various model-based approaches have been proposed based on the application of machine learning techniques, deep learning techniques, web service based approach and graph-based algorithms. Critical assessment on performance of various methodologies have been carried out based on the evaluation metrics considered for analysis. Developing a fraud detection model based on machine learning algorithms and ensemble method has been carried out in this study as the first contribution to this thesis. In this study, the application of various classification models has been proposed by implementing machine learning techniques and their performance parameters are critically assessed for detecting fraudulent transactions. Five classification algorithms such as k-nearest neighbor (K-NN), extreme learning machine (ELM), random forest (RF), multilayer perceptron (MLP) and bagging classifier have been implemented because of their improved performance with the considered BankSim and PaySim datasets. We have proposed a predictive classification model by ensemble of five individual machine learning algorithms, as it provides improved predictive performance on different metrics. Second contribution to this thesis highlights on the detection of fraudulent transactions, performed using various deep learning techniques to improve the performance of different measures. For this study, the deep learning techniques such as convolutional neural network (CNN), recurrent neural network (RNN), long short-term memory (LSTM) and autoencoder have been studied on the transactional data BankSim and PaySim to predict the class label as fraudulent or normal. These models are effective enough to identify the high level features vii and the hidden patterns on the data. Each of the four models have been trained with efficient Adam optimizer and the loss function has been used for fitting the binary cross-entropy loss function. Four models are critically assessed to evaluate the parameters such as accuracy, precision, recall, F-measure, AUPR measure and ROC-AUC score for analysis of each model. The third contribution indicates a fraud detection system based on web services by considering two different protocols for the web-based services such as simple object access protocol (SOAP) and representational state transfer (REST). Further, for detecting the fraudulent transactions, these services are associated with five different machine learning techniques such as support vector machine (SVM), multilayer perceptron (MLP), random forest regression, autoencoder and isolation forest due to their improved performance. The performance analysis of each machine learning algorithm associated with SOAP and REST services are critically assessed. The web services have been designed based on concepts of service oriented architecture (SOA) by considering a middleware family of software products i.e., Oracle SOA suite which is very often used by the software architects. Various performance metrics have been evaluated for five machine learning techniques with and without incorporation of the web services. In the fourth contribution, the fraud detection system has been proposed based on the application of graph database model. From the transactional data, a graph model has been developed by applying Neo4j tool and important graph features are extracted from the graph model using different graph algorithms. Subsequently various supervised and unsupervised machine learning algorithms have been applied to detect the fraudulent transactions explicitly with and without the incorporation of graph features in the BankSim and PaySim datasets. Features extracted using different graph algorithms such as degree centrality algorithm (DCA), closeness centrality algorithm (CCA), betweenness centrality algorithm (BCA), PageRank algorithm, label propagation algorithm (LPA) and node clustering coefficient (NCC) are applied with various supervised and unsupervised machine learning techniques individually as well as in combined approach to classify the fraudulent and normal transactions. Graph based methods such as combined graph based approach with machine learning techniques, CGB-GMM and GB-LOF have been proposed to improve the fraud detection by considering the features obtained from the transactional data. With the above contributions, it is intended to develop the fraud detection model with different approaches for identifying the fraud patterns in the transactional data and to study various performance metrics for analysis purpose