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High Strain-Rate Compressive Behaviour of Plain Weave Fiber/Epoxy Composites: Numerical Simulation and Experimentation
No full textNowadays, fiber-reinforced polymer (FRP) composites often penetrate into various critical and supercritical applications because of their inherent superior properties and performances, which are most often easily engineered to meet the design criteria. It is critical to ascertain the complexity of strain rate implications in FRP composites during static and dynamic modes. Since the split Hopkinson pressure bar (SHPB) testing has been extensively used to examine the dynamic behavior of various materials, the data processing techniques and relevant theories for the SHPB evolution are discussed. In the compressive SHPB experiments, the striker bar's velocity (SV) and the incident bar's impact surface are widely recognized for having a substantial influence in obtaining a clean signal. The beginning of this study includes a parametric investigation of such understudied instances utilizing Abaqus software for finite element analysis (FEA). Symmetrically non-parallel plane impact surface, and the filleted impact surface was also studied. It was found that the absolute value of incidence strain at peak increases with an increase in striker velocity, keeping the rise time almost constant. The peak strain, in contrast, remains the same, but the rise time increases with an increase in symmetrically non-parallel plane surface angle and fillet radius. Before finding the polymer composites' dynamic strength, the effect of specimen geometry was essential to understand. Specimen geometry is one of the essential parameters that can ease sample fabrication and help in-situ analysis when altered as per convenience. As part of the current study, high strain rate tests using a compressive SHPB setup were conducted on plain weave glass/epoxy (GE) laminated composite samples of both square prismatic and cylindrical shapes along the through-thickness direction experimentally. Negligible differences were observed due to the change in specimen geometry. Furthermore, developing a computationally accurate model would reduce the need for multiple experimental iterations, thus saving cost and time. The effect of strain-rate dependency of the yarn was analyzed numerically on Abaqus software using a square prismatic-shaped yarn-level finite element composite model. The bulk epoxy's and yarn's material properties were defined using the Johnson-Cook (JC) constitutive model, and the failure mechanism was defined using the JC damage model. One of the primary reasons for using this model is its availability and ease of implementation in almost every FEA simulation software. It was observed that the completely strain-rate-dependent model showed comparable peak stress and strain values with the experimental result to that of other models. Afterward, the high strain rate (HSR) compressive behavior of GE composite embedded with randomly oriented discontinuous carbon fibers (RODCF) was investigated along the through thickness direction using a compressive SHPB setup. The amount of RODCF dispersion in the sample tested was 0.25% and 0.5% by weight of epoxy. The mean compressive strength of the glass/epoxy (GE) sample was observed to increase by 7.4% and 5.8%, with RODCF addition of 0.25% and 0.5% by weight of epoxy, respectively. Finally, the HSR behavior of hybrid composites of symmetrical epoxy-based carbon/glass (CGE) and carbon/Kevlar (CKE) were analyzed along the through-thickness direction. The stacking sequence used for the hybrid composites was [C5/G5]S and [C5/K5]S. An initial striker velocity of about 25 m/s was used for all experiments. The mean reference strain rate observed for CGE and CKE hybrid composites was 2293 and 2333 s-1 , respectively, with a negligible difference in mean compressive strength. The mean strain to failure of [C5/K5]S was almost 17% higher than [C5/G5]S, and proper stress equilibrium was observed. Finally, conclusions and prospects are presented to emphasize the possible promising polymer composites that may be employed in various applications involving high strain rate loading conditions
Investigation of Biological and Magnetic Properties of Vanadium(IV/V) and Cobalt(II) Complexes Incorporating Mono and Dibasic Ligands
No full textTransition metals play a significant role in bio-inorganic chemistry. Transition metals can interact with several molecules that are negatively charged and display various oxidation states. Because of this activity, transition metal-based medicines have recently been developed and are being explored as good candidates for pharmacological and therapeutic uses. Among the transition metals, vanadium complexes have shown promising candidates as an alternative for the treatment of cancer. It is because these complexes exhibit a wide range of chemical properties and structures, which allows for the design of specific complexes tailored to target specific cancer cells. This versatility can potentially lead to more effective and targeted cancer therapies. Furthermore, targeting these particular metal ions is also justified by the fact that they are less toxic, and their toxicity can be further decreased when combined with ligands. Even though there are several ligands available, the chosen arylazo, aroylhydrazone, Schiff base, and N-heterocycles (1,10- phenanthroline, bipyridine) each offer a distinct advantage that is very helpful in designing an ideal drug. Additionally, the N-heterocycles' role as ligands alters the environment of the complex in a way that promotes their lipophilicity, which is a crucial aspect of drug design. Therefore, the emphasis of this dissertation is mostly on the study of a few pharmacological actions of the more accessible and less expensive first-row transition metal V(IV/V) complexes. To assess the biological activity of complexes, various analytical techniques are used to study the interactions of complexes with CT-DNA and a variety of proteins (HSA, BSA, and lysozyme). The findings of the investigations indicated that the test complexes were good DNA and protein binders. Additionally, the in vitro antiproliferative activity of the synthesized complexes were investigated against different cancer [human cervical cancer (HeLa), human colorectal adenocarcinoma (HT-29)], and noncancerous cell lines [human epidermal keratinocyte cells (HaCaT) and mouse embryonic fibroblast cell line (NIH-3T3)]. The complexes examined here showed noticeable in vitro cytotoxicity when compared to numerous clinically reported chemotherapeutic drugs which could provide the basis for the design of potentially effective target-specific drugs for the treatment of cancer. In addition to the pharmacological activity, the temperature-dependent magnetic susceptibility of di-nuclear oxidovanadium(IV) and mono-nuclear cobalt(II) complexes have been investigated to understand the structural influence on magnetic behavior. Further, I have explored their solid and solution state EPR spectra, FD-FT THz-EPR spectra, magnetization, dynamic magnetic behavior, slow magnetic relaxation behavior, and ab initio computational studies. For di-nuclear oxidovanadium(IV) complexes the temperature-dependent magnetic susceptibility measurements of 1 and 2 revealed the exchange between the two vanadium centres to be weak and antiferromagnetic. Theoretical calculations of 1 and 2 were carried out using broken-symmetry DFT, which shows good agreement with the experimental results. For cobalt(II) complexes the magnetic susceptibility and FD-FT THz-EPR measurements together with ab initio calculations reveal an easy-axis type of anisotropy for both 1 and 2, with a spin-reversal barrier of 58.9 and 60.5 cm–1 , respectively. For both compounds, frequency-dependent ac susceptibility measurements show an out-of-phase susceptibility under applied static fields of 40 and 100 mT, which can be analyzed in terms of Orbach and Raman processes within the observed temperature range. Finally, a detail of the structural influence on magnetic studies has also been discussed in detail. Keeping all these things in mind, in this dissertation the chemistry of a wide variety of new versatile oxido/dioxido vanadium(IV/V), dinuclear oxidovanadium(IV), and mononuclear cobalt(II) complexes of some bidentate uni-negative ON and tridentate bi-negative ONO donor arylazo, aroyl hydrazone, and Schiff base as main and an ancillary ligand (bipy and phen) as co-ligand are reported, with special emphasis on their solution behavior, pharmacological activity, and magnetic studies. A variety of physicochemical techniques, including elemental analysis (CHNS), spectroscopic (UV-vis, IR, NMR, and EPR), spectrometric (ESI-MS), and electrochemical (cyclic voltammetry), have been used to characterize all the synthesized ligands and their corresponding metal complexes. The structure of all the complexes was further confirmed by single-crystal X-ray diffraction analysis. Molecular structure and spectroscopic characteristics like EPR and magnetic data of some of the aforesaid compounds were simulated using DFT (density functional theory) methods to obtain more information. In summary, these findings have helped us to figure out the active species that are responsible for cytotoxic activity, which often remains elusive. The limited understanding of the active species' identification is an important aspect of the progress of clinical studies with vanadium-based drugs and industrial experimentation. So, these findings of the current investigation on the capabilities of recently synthesized vanadium(IV/V) complexes serve as a source of motivation for us to persist in the advancement of metal-based compounds for anti-cancer research. Further, the knowledge acquired from the examination of the magnetic properties of vanadium and cobalt complexes serves as a basis for visualizing a prospective scenario in which these elements assume a crucial function in the advancement of medical science. The range of prospective applications encompasses a wide spectrum, ranging from enhanced imaging diagnostics to novel cancer therapies and tailored drug delivery systems. This approach must take into consideration both the magnetic characteristics of the complexes as well as their interactions with biological systems
A Vehicle Detection Scheme for Heterogeneous and Lane-Less Traffic
No full textA traffic management system (TMS) is essential to manage traffic congestion, save fuel, save travel time, and enhance user safety. A vehicle detector is a vital component for building such TMS. Different types of vehicle detectors are developed for homogeneous and disciplined traffic, but they are not suitable for heterogeneous and lane-less traffic conditions, which is common in developing countries. The proposed work presents a dimension based vehicle classification technique. At first performance of vehicle classification based on dimensions is verified analytically. Thereafter, a vehicle detection scheme for heterogeneous and lane-less traffic by extracting a binary image from the sensor nodes is proposed. The binary image is recorded based on the occupancy status at respective sensor zone as logic 1 or 0. Vehicle classification and its corresponding speed is estimated from the obtained binary images. Initially, the proposed work is validated by a photodetector based set-up. Then, with the help of scaled-down 2D vehicle models, a binary image is obtained. Photo-detector based set-up serves dual purpose, i.e., it can be used for vehicle to infrastructure (V2I) communication using visible light and vehicle detection. Moreover, in the real scenario, proposed method is validated by generating a binary image from virtual loops in a video recording. To enhance its effectiveness a convolutional neural network (CNN) based foreground detection method is applied. But, camera based systems efficiency reduces by environment conditions. To overcome this issue, an array of micro-LiDARs is designed and implemented. The proposed method requires less storage, less bandwidth, less computation complexity, and easily can be implemented. The detection accuracy of 98% is observed while extracting data from video and 91.3% while using micro-LiDARs. The proposed works are compared with existing techniques. Finally, the obtained data is recorded remotely and displayed it on customized web map. A traffic management system (TMS) is essential to manage traffic congestion, save fuel, save travel time, and enhance user safety. A vehicle detector is a vital component for building such TMS. Different types of vehicle detectors are developed for homogeneous and disciplined traffic, but they are not suitable for heterogeneous and lane-less traffic conditions, which is common in developing countries. The proposed work presents a dimension based vehicle classification technique. At first performance of vehicle classification based on dimensions is verified analytically. Thereafter, a vehicle detection scheme for heterogeneous and lane-less traffic by extracting a binary image from the sensor nodes is proposed. The binary image is recorded based on the occupancy status at respective sensor zone as logic 1 or 0. Vehicle classification and its corresponding speed is estimated from the obtained binary images. Initially, the proposed work is validated by a photodetector based set-up. Then, with the help of scaled-down 2D vehicle models, a binary image is obtained. Photo-detector based set-up serves dual purpose, i.e., it can be used for vehicle to infrastructure (V2I) communication using visible light and vehicle detection. Moreover, in the real scenario, proposed method is validated by generating a binary image from virtual loops in a video recording. To enhance its effectiveness a convolutional neural network (CNN) based foreground detection method is applied. But, camera based systems efficiency reduces by environment conditions. To overcome this issue, an array of micro-LiDARs is designed and implemented. The proposed method requires less storage, less bandwidth, less computation complexity, and easily can be implemented. The detection accuracy of 98% is observed while extracting data from video and 91.3% while using micro-LiDARs. The proposed works are compared with existing techniques. Finally, the obtained data is recorded remotely and displayed it on customized web map
A Study On Nonconvex Feasibility Problems Using Douglas Rachford Operator Splitting Method
No full textThis thesis studies the splitting algorithms for solving feasibility problems involving one or more nonconvex sets. The Douglas-Rachford algorithm and the method of alternating projection are the two projection algorithms frequently used for solving the feasibility problems. The method of alternating projection is the simplest projection algorithm to find a feasibility point involving two or more nonempty, closed sets. It involves finding orthogonal projection alternatingly onto two or more closed sets in a Hilbert space. Weak convergence of the method is established in a convex setting for periodic or quasiperiodic projection provided the intersection of the sets is nonempty. The Douglas-Rachford splitting algorithm is successfully implemented in the convex feasibility problems. When one or more set is nonconvex, the algorithm is used to solve different types of feasibility problems, but the convergence of the algorithm is still not thoroughly investigated. The behavior of the Douglas-Rachford method in both consistent and inconsistent settings are studied. Interestingly, here, the Douglas-Rachford operator is not a nonexpansive map which is an essential requirement for studying the convergence of the Douglas-Rachford algorithm. In the consistent setting, it has been shown that the Douglas Rachford sequence converges and the corresponding shadow sequence converges to the intersection of sets. In the inconsistent setting, it is observed that the Douglas Rachford sequence diverges, and the corresponding shadow sequence has a weak cluster point. The convergence of both the algorithms is still not fully clear when one or more set is nonconvex. Here, behavior of both the algorithms involving one set as convex and the other set being nonconvex are analyzed
Biofilm Modulation and Catabolic Gene Expression in Marine Bacteria for Biodegradation of Polycyclic Aromatic Hydrocarbon
No full textThis thesis illustrates the biofilm formation of marine bacteria and biofilm-mediated degradation of phenanthrene. Sediment samples were collected from Paradip Port and Chilika Lake, Odisha coast, India. A total of 132 marine bacterial strains were isolated by selective enrichment with 100 mg/L phenanthrene. Biofilm formation was observed in 69 marine bacterial isolates, out of which 41 formed weak biofilms, 23 formed moderate biofilms, and 5 isolates formed strong biofilms. Among the 28 moderate to strong biofilm formers, 8 strains harbored the nahAc gene responsible for the catabolism of phenanthrene. Biochemical and molecular identification grouped the isolates into Pseudomonas and Brucella genera. Scanning electron micrographs (SEM) analysis of the bacterial biofilms revealed rod-shaped cells glued together within a slimy matrix of extracellular polymeric substances (EPS). Chemotaxis movement towards phenanthrene was observed in 4 marine bacterial isolates, Pseudomonas mendocina AS2-P3, Pseudomonas aeruginosa AS2-P13, Pseudomonas guguanensis OS-P8, and Pseudomonas aeruginosa PFL-P1. The degradation of phenanthrene was significantly higher in the biofilm mode of growth than in the planktonic counterparts (p<0.05). The highest degradation of ~74% phenanthrene (100 mg/L) was achieve within 5 d using biofilm cultures of P. aeruginosa PFL-P1 grown on glass beads. The biofilm-EPS of P. aeruginosa PFL-P1 exhibited high emulsification activity against different hydrophobic compounds. Fluorescence spectroscopy analysis revealed the presence of two protein-like fluorophores at (Ex/Em) wavelengths of 280/351 nm and 220/350 nm. The fluorescence intensity of the fluorophore gradually decreased with the increasing concentration of phenanthrene. The high binding constant (4.42 L/mol) and binding site number (1.38) indicated strong interaction between EPS and phenanthrene. Biofilm formation in P. aeruginosa PFL-P1 evaluated on glass, polystyrene, steel, ceramic and rubber substrata revealed maximum arithmetic mean biofilm height of 611 nm on the ceramic substratum. Analysis of the bare substratum indicated the highest surface roughness of 545 nm on the ceramic substratum. The increased roughness promoted biofilm growth, and the biofilm biomass increased to ~18 μm3/μm2 on ceramic substratum with a maximum biofilm thickness of ~50 μm in the aqueous state. Molecular docking studies revealed that 3OC8-HSL interacted with LasR with a binding energy of -10.19 kcal/mol, and C6-HSL bound to RhlR with a binding energy of -8.59 kcal/mol. Exogenous addition of 10 μM C6-HSL and 3OC8-HSL improved the biofilm formation ability in P. aeruginosa PFL-P1. Significant improvement in cell surface hydrophobicity, auto-aggregation ability, swimming, and swarming motility was observed in the presence of AHLs (p<0.05). The biofilm cultures of P. aeruginosa PFL-P1 grown over ceramic beads achieved 85% degradation of 100 mg/L phenanthrene within 5 d. The phenanthrene degradation ability of the bacterium increased to 97% in the presence of 10 μM 3OC8-HSL with a degradation rate constant of 0.7027/d and t1/2 of 0.986 d. Exogenously supplemented AHLs significantly improved the relative expression of nahAc, pslB, lasI, and rhlI genes in P. aeruginosa PFL-P1 (p<0.05). Further, next-generation sequencing of P. aeruginosa PFL-P1 revealed the presence of 145 genes involved in xenobiotics biodegradation and metabolism. Common gene clusters, benABCD, xylXYZ, and catAB, playing crucial roles in the degradation of toxic aromatic compounds, were present in the genome. Metabolic pathway analysis revealed P. aeruginosa PFL-P1 utilized both the naphthalene route as well as the phthalic acid route for the degradation of phenanthrene. It also encodes several catabolic genes for the degradation of naphthalene, benzoate, aminobenzoate, fluorobenzoate, toluene, xylene, styrene, atrazine, caprolactam, etc., which indicate that this biofilm-forming marine bacterial strain can adapt to heavily contaminated environments and is a potential organism to be used for bioremediation purposes
E-Connect: Connecting People Through Apps in Post Disaster Situation
No full textMost of the communication facility gets uprooted in the area affected by the disaster. In such a scenario communicating with people in the area affected by disaster is a challenging task. Existing technology can be used to establish communication within a certain range without connectivity to any network or access point one such technology is Wi-Fi direct, which can enable D2D user communication, single-group communication, or multi-group communication with each other device without any access point or without any internet access point. It is reported that approximately 81.7% of people currently use Android phones. To establish communication, in post-disaster an Android application has been developed that allows users to connect with one, a batch of users, or a selected batch of users without the use of an access point. In the absence of a fixed access point, this program establishes a connection using the Wi-Fi P2P connectivity concept via Wi-Fi-Direct. The user must turn on his Wi-Fi before opening the app, and after that, the app will look for devices that are currently active within a 200-foot radius. Without the necessity for a pre-existing network, a chat can be held with those users once a link has been made. Some specific linked users serve as a hotspot or soft access point throughout this process, and the other connected devices first function as clients looking for new clients before transitioning to the server. The purpose of this Android application is to assist disaster management activities by enabling users to report critical information during the critical period of a disaster, such as the number of affected individuals, information regarding affected zones (such as the location of trapped individuals, food and medicine requirements, etc.), and so on. By using this software, impacted individuals can be helped promptly and effectively, ensuring a quick reaction to the crisis. For supporting single-group or multi-group communication between each Wi-Fi direct supported device a gateway layer and routing layer are proposed. The selection of random group owners through Wi-Fi direct and message prioritization among the nodes is also discussed
Chemistry of Vanadium(IV/V) and Ruthenium(II) Complexes with O- and/or N- and/or S- Donor Ligands Incorporating Bio-Active Molecules in Relation to their Anticancer Activity
No full textThe history of transition metal complexes in anticancer research is a fascinating journey that in progress for the last several decades. In the 1960s, with the discovery of cisplatin as a potential anticancer drug, the investigation of non-platinum-based transition metal complexes marked the beginning of the field's exploration of cancer therapy. Transition metal complexes have significant attention due to their potential to serve as innovative and effective agents in the treatment of cancer. In addition, the adaptability in oxidation states allows the transition metals to form various coordination complexes with different types of organic ligands or molecules and exhibit different chemical and biological behaviors. Thus, designing new ligands through thoughtful substitution and tuning of metal-binding sites could be a great area of research on advancement of the metal-based compounds as promising anticancer drugs. Several reports of metal complexes encourage further studies for the exploration of new metallodrugs with attractive properties like biological potency, easy accessibility, least toxicity, and improved physical profile. However, few transition metal complexes already have progressed into human and clinical testing. Keeping these factors in mind, in this dissertation the chemistry of vanadium(IV/V) and ruthenium(II)-based transition metal complexes with O- and/or N- and/or S- donating Schiff base, aroylhydrazones, and dithocarbazates ligands are described, with special addressing to their aqueous/solution behavior and pharmacological activity. All the synthesized ligands and their respective metal complexes have been successfully characterized by elemental analysis, spectroscopic (UV-vis, IR, and NMR), spectrometric (HR‒ESI‒MS), and electrochemical methods. The structures of the complexes were further confirmed by single- crystal X-ray diffraction analysis. The solution behavior of all the complexes has been studied in order to understand their stability, transformation, interconversion, changes in coordination geometry, and nuclearity taking place in the aqueous/cell culture medium. Further, the biomolecular interactions of the investigated complexes were studied with DNA (Calf thymus DNA, CT‒DNA) and proteins (Bovine serum albumin, BSA) through various analytical techniques (absorption, fluorescence, and circular dichroism studies). The in vitro anticancer activity of the synthesized complexes was studied against different cancerous cell lines such as human cervical cancer (HeLa), human breast adenocarcinoma, (MCF-7), human colorectal adenocarcinoma (HT-29), human lung adenocarcinoma (A549) and noncancerous cell lines mouse embryonic fibroblast cell line (NIH-3T3)]. Results of the aforementioned experiments showed that the tested complexes bind DNA and proteins more effectively. Furthermore, the in vitro anticancer activity of the complexes implies that they are potentially useful as lead compounds for drug development. Further interest in the investigation of the mechanism of action of these metallodrugs for which various experiments were conducted such as apoptosis analysis, reactive oxygen species (ROS) generation, mitochondria membrane potential (MMP), etc. by live cell confocal microscopy and flow cytometer techniques. Apart from that, as few compounds of the series are found fluorescence active, their intracellular colocalization studies were performed and resulted in targeting the mitochondria of the cell
Multiwavelet Sets, Multiframelet Sets and Related Systems on Qp
No full textThe work done in this dissertation revolves around wavelets, MRAs and frames on the p-adic field Qp. It is well known that every element of a separable Hilbert space can be represented in terms of its orthonormal basis by using the respective Fourier coefficients. Multiwavelets serve this purpose in wavelet theory. Multiwavelet is a collection of finitely many functions whose dilates followed by translates give an orthonormal basis. Multiframelets are generalization of multiwavelets. Multiframelets provide more flexibility in the representation of an element of the space under consideration. These concepts were initially studied for the Euclidean space Rn (n ≥ 1) and later on this study was extended to more general spaces like local fields of positive characteristic. In the same spirit, here we have established results related to muliwavelets/multiframelets for Qp. Multiwavelet sets/multiframelet sets provide a special class of muliwavelets/multiframelets. Multiwavelet and multiframelet sets can be constructed by using scaling sets, generalized scaling sets and frame scaling sets. These sets are not studied in Qp. MRAs also generate wavelets and a generalization of MRA is FMRA. Results related to MRA in L2(Qp) are available in literature but as per our knowledge FMRAs in L2(Qp) are not studied. The dissertation is divided into nine chapters. First two chapters contain basic definitions and results. Next six chapters are devoted to the study of above mentioned concepts in L2(Qp) and contain their properties, some characterizations and related examples. Finally, some problems for future work are given in Chapter 9
Geo-engineering Properties of Expansive Soil Treated with Geopolymer and Conventional Stabilizers
No full textExpansive soils occur worldwide and are also abundant in the Indian subcontinent. The shrink-swell mainly influences lightly loaded structures like road and railway pavements, developing surface heave and crack, and everlasting sealing problems during the impact of loading. Of the various techniques used for improving the properties of the expansive soils, the calcium-based additives have been effectively applied to improve the strength and control the volume change behavior of expansive soils both efficiently and economically. However, despite the benefits and multi-faceted utilization of lime and cement, high carbon emission and high-energy requirements associated with these binders represent environmental constraints. Hence, research is being focused on developing substitute chemical additives to cut the use of conventional cement. Consequently, waste products in industries have received the top most attention due to their low carbon footprints and alternative waste utilization advantages. Geopolymer produced from aluminosilicate-rich industrial wastes has been found suitable as an alternate binding material to conventional binders like cement and lime. Considering this in the present research, the geo-engineering properties of a locally available expansive soil treated with slag-geopolymer, cement, and lime are evaluated through laboratory tests. The whole work is divided into three phases. In the 1st phase, the compaction characteristics and unconfined compressive strength (UCS) of a large combination of soil and additive are used. For geopolymer stabilization, the proportions of slag in the mixture were varied as 0%, 5%, 10%, 15%, and 20% by weight of the dry soil, with the concentration of NaOH solution varying from 0 M, 0.5 M, 1 M, 2 M, 4 M, 6 M, and 8 M. Thus, altogether 35 soil-geopolymer combinations were tested. Similarly, for lime and cement treatments, the mixture's proportions of lime or cement were varied as 0, 1%, 2%, 4%, 8%, 12%, and 15% of the dry soil mass. The UCS value was used to measure the degree of reactivity of various components of the geopolymer in the treated expansive soil, and the results were evaluated at curing periods of 7 and 30 days. Based on the 30-day UCS value, three mixed proportions of geopolymer, cement, and lime were selected to evaluate their comprehensive geo-engineering properties. In the 2nd phase of the investigation, the effects of stabilizer content and curing period were explored for consistency limits, compaction parameters, hydraulic conductivity, swell-shrink properties, California bearing ratio value, strength properties, and durability performance of expansive soil. Finally, in 3rd phase of the investigation, the effects of delay time on geo-engineering properties are evaluated. A detailed examination of the geo-engineering properties of expansive soil treated with slag-geopolymer, cement, and lime, concerning strength, durability, and influence of delay period, is made. The underneath conclusions are drawn from this research: • The plasticity properties of expansive soil are reduced with an increase in the additive content. The plasticity properties such as LL and PI of geopolymer added soil are related to slag content, alkali solution concentration, and delay period. In the case of lime and cement, the reduction is due to these additives' non-plastic character and the flocculation effects. It is mainly due to the depression of the thickness of adsorbed layer of water and the microstructural changes of the clay particles. The virgin clay classified as CH type is changed to CI, CL, MI, and non-plastic with different proportions of additives. • Soil treated with different stabilizers exhibits different compaction characteristics. The MDU increased with the stabilizer content for cement and geopolymer treated soil. However, MDU reduces with an increase in lime content for lime-treated soil. The OMC soil-geopolymer mixes decrease with increased geopolymer content, while it increases for lime and cement-treated soils. With an increase in the delay time, the mechanical characteristics such as dry density and UCS of the stabilized soil are reduced. It is due to the formation of strong flocs, which leads to the loose packing of stabilized material with the increase in void ratio. It is identified that with the addition of chemicals, the grain size distribution (GSD) curve of the treated soils shifted towards a larger grain size. Overall, geopolymer stabilized material attains higher compacted density and mechanical strength than conventional stabilizers. • Slag-based geopolymer improves the strength and stiffness of the treated soil, but the ductility of the virgin soil reduces. This is more prominent as either the amount of slag, the concentration of NaOH activator, or the curing time increases. There is no optimum dose for slag content or NaOH concentration in geopolymer-treated soil mixtures. The UCS of soil-slag mixes increases with the amount of slag and strength of NaOH solution. Similarly, no optimum dose of cement or lime was observed in the present investigation, where a maximum of 15% of cement/lime is used. Geopolymer and cement-treated soil achieve higher early strength than lime-treated soil. At 30 days of curing, geopolymer stabilized soil (S20M8) developed a strong structural bond and had a peak strength of 5.11 MPa. • Chemical additives significantly control the swelling behavior of the treated expansive soil. At low additive contents, lime significantly decreases the free swell index value and swell pressure of the treated soil. However, as the additive content increased, all three stabilizers developed strong resistance toward swell pressure. The permeability coefficient reduces, whereas the California bearing value significantly improves with the addition of chemicals and the curing period. • The durability of geopolymer-treated soil under slake durability test (SDT) is superior to conventional stabilizers. The geopolymer treated soil retained its integrity even after four cycles of slacking. Based on the slaked durability indices, soil treated with 20% geopolymer, 15% cement, and 15% lime are categorized as a medium, low, and very low durable materials. Freeze-thaw (F-T) cycles have a significant influence on stabilized soil. The strength and mass loss are more at initial F-T cycles. However, stability is attained after the sixth cycle. The loss in strength of geopolymer, cement, and lime stabilized soil after 12 F-T cycles are 48%, 54%, and 60%, respectively. Water immersion and modified durability tests (MDT) demonstrate that the geopolymer treated soil has substantial resistance, followed by cement and lime treated soil. • The evolution of the mineralogy and microstructure results in the strength gain. It is assumed that the cementitious products formed by the alkaline activation of slag particles serve as nucleation sites on the clay surface. These reaction products bind clay plates to form clay clusters, strengthening the soil structure and thus enhancing its strength. Both hydration and geopolymeric compounds were detected in the geopolymer treated soil, whereas only calcium-based hydration products were found in both lime and cement treated soil. Therefore, geopolymer treated soil achieves higher strength gain. The massive and dense structure with the formation of rich hydration and geopolymeric compounds was identified from the SEM images of geopolymer-treated soil. In contrast, micro-pores were observed in the lime-stabilized soil due to the development of lesser reactive products. No such micro-pores were noticed in the cement, and geopolymer treated soil. Geopolymer treated clay has a dense and compacted microstructure compared to conventional stabilizers. It develops high early strength, higher ultimate strength, and better durability response compared to cement and lime-treated soil. Hence, geopolymer can be considered an effective cementing material to stabilize expansive soil than conventional stabilizers
Numerical Solutions of Nanofluid Flow Problems in Crisp and Uncertain Environments
No full textFluids are often used as heat carriers in heat transfer equipments. Examples of important uses of heat transfer fluids include cooling systems in the transportation industry, hydronic heating, and cooling systems in buildings, industrial process heating and cooling systems in the petrochemical, textile, etc. In all these applications, the thermal conductivity of fluid plays an important role in the development of energy-efficient heat transfer equipment. However, the existing heat transfer fluids, viz. water, oil, ethylene glycol mixture, etc., have poor thermal conductivity, which is a limitation in improving the performance of many heat transfer equipments. But nowadays, due to various recent applications, industries have a strong need to develop advanced heat transfer fluids with a higher thermal conductivity compared to the thermal conductivity of existing heat transfer fluids. As such, a new class of fluid has been introduced by researchers, called nanofluid, which is a fluid with suspended nanoparticles. The introduction of nanofluid made researchers to think beyond the traditional fluid flow problems for handling the challenging nanofluid dynamics problems. As such, this dissertation addresses the nanofluid flow between two plates, viz. vertical parallel plates, horizontal parallel plates, and inclined plates. These problems are usually governed by nonlinear partial differential equations, which may be converted into nonlinear ordinary differential equations with the aid of appropriate similarity variables. It may not always be possible to get analytical solutions to these nonlinear differential equations. Accordingly, different semi-analytical and numerical methods such as homotopy perturbation method, optimal homotopy analysis method, Adomian decomposition method, Galerkin’s method, and least square method are applied here to handle the corresponding governing differential equations. Convergence for each method is discussed numerically, and residual errors have been computed to see the efficacy of the mentioned methods. Effects of the involved parameters on velocity and/or temperature profiles have been illustrated graphically for all the considered models, and the results are discussed in detail. Generally, the physical parameters used in different nanofluid dynamics models are assigned crisp values. But in practical scenarios, these parameters may be uncertain in nature due to errors in the measurements, observations, or experiments. The involvement of uncertain parameters mimics the actual practical problems and leads to uncertain differential equations. For example, nanoparticle volume fraction plays an important role in many nanofluid flow problems. A small change in the value of nanoparticle volume fraction or any other parameter may affect the velocity and/or temperature profiles of nanofluid. As such, it will be important and challenging to study nanofluid flow problems by considering nanoparticle volume fraction as an uncertain parameter. In this regard, this thesis also aims to investigate the above-mentioned nanofluid problems in uncertain environment. The uncertain parameter(s) may be considered in terms of interval or fuzzy number. Accordingly, fuzzy number has been used here to express the impreciseness in the value of parameters such as the volume fraction. Further, homotopy perturbation and Adomian decomposition methods have been extended with the aid of the double parametric concept of fuzzy numbers to handle uncertain differential equations. Further, one may have recorded the velocity and/or temperature profile from experiments, but they may demand the value of one or more parameters involved in the models. In such cases, it will be helpful to compute the values of the unknown parameters from the recorded velocity and/or temperature profiles, which is known as the inverse problem. In this regard, this dissertation introduces the inverse problem related to nanofluid flow model also. Here, the desired inclined angle between two plates has been computed using the given velocity profile of nanofluid flow between the channel. It is worth mentioning that the inverse problem in uncertain environment may be more challenging. Accordingly, desired fuzzy volume fraction has been computed here for a given fuzzy velocity profile of nanofluid flow in an inclined channel. The homotopy perturbation method has been used here to study the inverse case for both crisp and uncertain environments