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Some Control Problems on Lie Groups and Symmetric Spaces
No full textThe matrix Lie groups appears naturally in physics, typically as the configuration space of some concrete mechanical problems and their corresponding dynamics leads naturally to a set of differential equations on the ambient matrix Lie group. Many authors have studied various mechanical and non-mechanical problems whose configuration space is some matrix Lie group, still there is scope for further studies. Adding to these studies, in this dissertation, we have defined control systems on some mechanical problems, on Lie groups which play important role in physics and control systems defined on the groups associated with the Black-Scholes equation, which is an integral part of finance. This dissertation presents an introduction to nonlinear control systems, with main emphasis on controllability properties of such systems. We have analyzed the controllability of the systems, using certain Lie algebras of the vector fields defined by the system.
This dissertation studies the system dynamics and optimal control problems by providing theoretical analyses while considering the fundamental geometric properties and by using computational algorithms that preserve those geometric properties. The optimal control problems of systems like, kinematic car and kinematic unicycle model, with a Lie group configuration manifold is discussed. Optimal control problems for systems defined on matrix Lie groups SU(2), S0(3; 1) and a group associated with the conformal coordinate transformations of Black-Scholes equation is also considered. Further more, two unconventional integrators are applied to the system dynamics and some geometric properties are discussed. The trajectories for both the unconventional integrators and conventional Runge-Kutta integrator, for each of the control systems is shown.
In this dissertation, the study of mathematical control theory on a manifold which is simultaneously a symmetric space is discussed from a geometric viewpoint. There has been many studies and theories developed in a manifold, i.e., Lie groups. But in recent times, many new kinetic models have been developed with the help of exponential submanifolds in the areas of robotics, control, etc. It thus becomes necessary to study the behavior of the control system defined on the exponential submanifolds, also known as symmetric spaces. There are many parallel similarities between the theory of Lie groups and symmetric spaces. Lie triple system and symmetric spaces are related by exponential mapping similar to Lie groups and Lie algebras. As a result, parallel theories and calculations of control theory on Lie groups and Lie algebras can be extended to the case of symmetric spaces and Lie triple systems. The first natural problem to study in control theory is the controllability problem,i.e., to characterize the states reachable from a given initial state. So global controllability condition for system defined on symmetric spaces is established and illustrated by few examples of controllable systems of exponential submanifolds of SE ( 3) and random matrix ensemble
Roles of Uniaxial, Shear and Cyclic Loading on the Microstructure and Texture Evolution during Plastic Deformation of Ti6Al4V Alloy
No full textThe objective of the present research was to investigate the effects of uniaxial, shear, and cyclic loading on the microstructure and texture evolution of Ti6Al4V (Ti64) alloy during plastic deformation. Ti64 alloy samples were subjected to both uniaxial tension and compression in the temperature range of 298 873 K for different degrees of deformation. During uniaxial tension, refinement of both and grains was observed during deformation at all temperatures. This has been attributed to the continuous dynamic recovery and recrystallization (CDRR) mechanism. A Burgers orientation relationship (BOR) between and grains was also observed in the alloy. The co-linearity of BOR between and grains was found to refine the grains, and that of non-BOR refined the grains. The crystallographic texture of the samples was observed to be along the off-basal orientation after deformation. The Schmid factor value for pyramidal slip was found to be the highest among all the slip systems during the uniaxial tension of the alloy. Stage III hardening was observed in the samples during deformation at all the studied temperatures, and an athermal hardening rate was found up to 4 % deformation of the samples. During uniaxial compression, a significant amount of deformation twins were observed in the samples beyond 20 % reductions at temperatures of 298 K and 673 K only. Such twins were further found to be of non-Schmid type and were confirmed through VPSC (Visco-plastic self-consistent) simulation. It was further found that the deformation bands formed during deformation facilitated the twin’s formation inside the grains. The texture strength of (0001) pole increased up to a 30 % reduction at all temperatures of deformation. However, the dominant texture strength remained along (1 2 10) pole, which was also the starting texture of the sample before being subjected to uniaxial compression. An initial decrease and subsequent increase in hardening rate was observed in the samples deformed at room temperature. The maximum decrease in the rate of hardening was observed at a temperature of 673 K up to 18 % strain, followed by a relative increase thereafter. Further, the observed decrease in the rate of hardening was found to be relatively lower at a temperature of 873 K compared to that at 673 K. Similarly, free-end torsion tests were conducted to understand the microstructure and texture evolution in the alloy during shear deformation. Torsion tests were conducted at temperatures of 298 K, 673 K, and 873 K for different strains ranging from 0.22 to 0.99. A nearequiaxed homogeneous microstructure was observed after deformation at all temperatures. Dynamically recrystallized (DRX) grains were observed in the samples at higher deformation temperatures, and these were found to be significant at 873 K for strains > 0.66. Dynamic transformation from → was also observed at a deformation temperature of 873 K. The initial fiber texture got rotated towards the ideal B fiber orientation and reached at the ideal C2 fiber orientation after deformation for a maximum strain of 0.99. The deformation texture was further simulated through the Visco plastic self-consistent (VPSC) method, and it was found that the basal slip was the dominant deformation mode, followed by prismatic and both pyramidal I and II slip systems. Ti64 alloy was also subjected to low cycle fatigue (LCF) to examine the role of cyclic deformation on the microstructure and texture evolution in the alloy. The LCF tests were carried out at room temperature for different strain amplitudes ranging from 0.5 % to 2 %. Cyclic softening behavior was observed at all strain amplitudes, and it was found to increase with increasing the strain amplitude. It was observed that softening behavior at low strain amplitudes (a ≤ 1 %) was due to the combined effect of both back stress and friction stress. However, at higher strain amplitudes (a > 1 %), it was attributed to the significant decrement in friction stress, which was further related to the sub-grain formation. Only (1012) type tensile twins were formed during the deformation, and this was found to be significant at a higher strain amplitude of 2 %. The [1010] grains were further found to have substantial cyclic deformation than the other grains, such as [2110] and [0001]. The dominant texture was found along [1010] during the LCF tests. However, the sample at a higher strain amplitude of 2 % also had prominent [0001] texture along with [1010] texture. Fractographic examination revealed a dimple fracture surface at lower strain amplitude (0.5 %), whereas a quasi-cleavage type fracture was observed at higher strain amplitudes (1 % & 2 %)
Study on Generation and Transfer of Non-classical States for Application in Quantum Communication
No full textThis thesis is devoted to the study of optical waveguide arrays for their applications in quantum information processing tasks. Using integrated waveguide structures, generation and non-locality study of multiqubit entangled states have been presented. Further using specially engineered waveguide structures, perfect transfer of important non-classical states have been studied. In addition, the non-locality of entangled states was first studied using Mermin’s and Svetlichny’s inequalities and then was verified on IBMQ quantum computing device. Integrated optical waveguide structures are stable, scalable, precisely fabricated and offers low photon propagation losses and hence have gained interest for their applications in diverse areas of science. In this thesis focus has been made on utilization of optical waveguide arrays for the use in quantum information processing tasks. In the first part of this work using single photon propagation through weakly coupled waveguide structures an approach have been made to generate important entangled states. These entangled states are useful for quantum information processing tasks such as perfect quantum teleportation and superdense coding. Next the non-locality of entangled states has been studied using Mermin’s and Svetlichny’s inequality and later was verified on IBM’s quantum computing platform, IBMQ. In the next part of the work using integrated waveguide structure with parabolic coupling maintained between individual waveguides, perfect state transfer of important non-classical light has been explored. In the last part of the work both ID and 2D integrated waveguide structures were utilized for the generation and entanglement study of multiqubit entangled states suitable for perfect teleportation and superdense coding. The findings of the work are important for the utilization of photonic system in quantum information processing tasks. The results are significant in the study of important entangled states
Study on Micro-Drilling Characteristics of a Ni Based Superalloy
No full textAccomplishment of good dimensional accuracy in micro drilling of Ni-based superalloys has always been a challenge. Hence, ample research, especially on the micro machinability of the superalloy, is required for the low cost, large scale utilisation of the material in different industrial fields. At the very outset, the FEM simulation of micro-drilling of Incoloy 825 using a 0.4 mm drill made up of cemented carbide (WC-Co) was carried out. The aim of this initial phase of work was to explore fundamental insights into various micro-drilling characteristics of the same workpiece material. The effect of feed was simulated on various cutting forces, dynamic fluctuations and specific cutting energy under dry environment. Thrust force and radial forces along with their dynamic components obtained during experimentation were in close agreement with the results of simulation with a deviation in the range of 7 to 8 %. Moreover, efforts were also made to experimentally study the various features of the micro holes including oversize error and circumferential deformation layer under the same condition. A comparative study of micro-drilling of Incoloy 825 with pilot and without prior pilot under minimum quantity lubrication (MQL) condition was carried out to understand the effect of pilot hole. The next phase of study sought to explore the mechanism of physical vapour deposition (PVD)-based TiAlN coating in micro-drilling of Ni-based superalloy. Results indicated that increase in edge radius due to coating hindered the performance of coated micro-drill while machining under very low feed (1 μm/rev). This was attributed to ‗size effect‘. However, elevation of feed, cutting speed and also machining duration (number of holes drilled) was found to be effective for TiAlN coated micro-drill. Furthermore, a comparative study of different cooling techniques was undertaken to investigate their influences on thrust force, tool wear, oversize error and circumferential deformation layer under constant cutting parameters (spindle speed of 20000 rpm and feed of 2.5 μm/rev). The experimental results demonstrated remarkable improvement in micro-machining characteristics under MQL which caused significant reduction in thrust force of around 8 % and average flank wear of 60 % compared to flood cooling. Therefore, MQL may successfully replace conventional flood cooling process during micro-drilling difficult-to-cut materials like Ni-based superalloys. The final phase of experiment aimed at investigating the effects of CrAlN and TiAlN coatings deposited using high power impulse magnetron sputtering (HiPIMS). Influence of feed which plays a major role on size effect was studied for the uncoated and coated micro-drills in terms of thrust force along with its bandwidth, oversize error and average flank wear. Particular emphasis was placed on the exploration of the mechanism of wear of the coated micro-drills in comparison with their uncoated counterpart. HiPIMS coated micro-drills were successful in mitigating thrust force, bandwidth and rate of progression of wear. However, TiAlN consistently outperformed the CrAlN coating in micro drilling of Incoloy 825 owing to the superior hardness, coating adhesion and chemical inertness of TiAlN towards Ni based superalloys
Characterization of Arsenic (As) Transforming Bacteria and Red Mud to Construct a two-step Bio-filter Column for total as Removal from Groundwater
No full textGroundwater arsenic (As) contamination inherently affects millions of people worldwide through drinking water, food materials, irrigation water, and soil. Arsenic is a toxic metalloid, designated as category – I human carcinogen causing potential threat to individuals exposed to concentrations of 10 ppb from ingested water for a prolonged period of time. Severe carcinogenic and non-carcinogenic illnesses can occur over prolonged As exposure such as keratosis, melanosis, neurological disorders, skin lesions, respiratory complications, hepatic damage, and various form of cancers. The two major countries extensively affected by groundwater As-contamination are India and Bangladesh. In India, the middle Gangetic plains, covering particularly 89% geographical area in the state of Bihar is severely affected which holds prospective alluvial aquifers. The Bhojpur district in Bihar, located in the middle Gangetic plains, amidst the flood-prone belt of the Sone-Ganga interfluvial region is one of the worst affected areas from geogenic As. The present investigation begins with a microcosm based bio-stimulation study and substrate amendments over 45 days to analyze the bacterial community structure and distribution to indicate the possible in-situ bioremediation strategy in six severely As contaminated groundwater sites of the middle Gangetic plains in Bhojpur district of Bihar, India. Proteobacteria was primarily the dominant bacterial phylum in all the samples, followed by Actinobacteria, Bacteroidetes, Firmicutes, and Cyanobacteria. The major groups in the genus level were Delftia, Acinetobacter, Lysobacter, Bacillus, and Pseudomonas in the As-rich aquifer system. The bio-stimulated samples showed a change in the community structure with the dominance of Planctomycetes, with a minute portion of Proteobacteria. The species richness was determined using the Alpha diversity and Chaol curve with an As tolerant capacity of 152.28 ppb. The supremacy of γ- proteobacteria and α- proteobacterial members in the high and low As-containing water samples indicated their role in As mobilization and detoxification. The extensive role of arsenite [As (III)] oxidizing microbial communities within different levels of As-contaminated areas in Bihar was studied due to complete change in microbial community structure within the bio-stimulated conditions, deciphering the considerable role of these microbial communities in the As-biogeochemical cycle.
From the previous study, it was learned that several As (III) oxidizing groups dominated the predominant aquifers in the region. Several superior As (III) oxidizing strains were isolated by enrichment technique from six shallow aquifers of Bhojpur district. The isolates were screened using silver nitrate assay for As (III), and arsenate [As (V)] tolerance up to 100 mM of As (III) and 1000 mM of As (V). The isolates were also tested for their multi-metal resistance and utilization of various carbon sources. The molecular identification of the four highly efficient As (III) oxidizing strains showed their relatedness with different Delftia sp. Finally, a gram-negative rod-shaped strain of Delftia sp. BAs29 was characterized thoroughly based on its superior As (III) oxidation potential for its growth and effective As (III) oxidation ability. A mixed growth associated, facultative chemolithotrophic As (III) oxidation process was revealed by the strain, with a Km and Vmax value of 21.97 μM and 0.657μM/min. Further, testing of natural and cost-effective bio-sorbents showed efficient As (V) removal from the contaminated water. Moringa oleifera showed the maximum As (V) removal capacity of 57.89% among the tested bio-sorbents, followed by sawdust and riverside red mud. The process of As (III) biooxidation was optimized using Response Surface Methodology by considering four factors such as temperature (30 °C – 37 °C), inoculum percentage (1% – 5%), initial As (III) concentration (80 μM –120 μM), and time (10 h –16 h). Hence, this study deciphered a proficient process of As removal by combining an indigenous As (III) oxidizing strain and a natural bio-sorbent. The next study aimed at utilizing powdered neutralized red mud as a natural adsorbent for As removal as it is a waste from the alumina industry. Its enormous volume production and difficulty of disposal makes it a cost-effective adsorbent. The mineralogical composition of red mud consists of iron, aluminium, silicon, and titanium oxides which cause elemental species transformation and precipitation during bio-oxidation of complexes such as arsenopyrites by inherent microbial organisms. The iron bearing minerals significantly affect the solution chemistry of As, making it a valuable adsorbent for effective As removal. The previously used Moringa oleifera is a seasonal adsorbent and its production may be expensive. Hence microbial transformation of As (III) seems to be a favorable approach, coupled with several adsorption techniques such as powdered neutralized red mud without producing lethal by-products or demanding chemical addition. This study highlighted the potential contribution of the previously isolated highly efficient As (III) transforming bacteria Delftia sp. BAs29 and the adsorption of transformed As (V) using powdered neutralized red mud under suitable treatment conditions. The rate and oxidation efficiency elucidated diverse experimental conditions for the process. The neutralized red mud was characterized using X-Ray diffraction (XRD) microanalysis, Scanning electron microscopy – Energy dispersive X-Ray spectroscopy (SEM-EDX), and Fourier – Transform infrared spectroscopy (FTIR). The adsorption of As (V) using powdered neutralized red mud was also studied as a function of time and pH, initial As (V) concentration and adsorbent dosage. The decrease in solution pH significantly increased the adsorption efficiency. The maximum monolayer capacity for adsorption of 274.1 mg/g As (V) was found at optimum conditions of pH 4.0, a contact time of 30 min at a temperature of 30 °C respectively. Hence, various strategic methods of As bioremediation could be developed using this process to remove the inherent groundwater As. The final objective aimed at developing a two-step approach to combat the toxic metalloid As by combining the previously isolated, highly efficient As (III) oxidizing bacteria; Delftia sp. BAs29 and porous red mud pellets to remove the total As from groundwater including both As (III) and As (V) ions. For the first step, the maximum capacity of As (III) oxidation by Delftia sp. BAs29 was seen to be 95.65% for 500 ml of As contaminated groundwater using an optimized As (III) concentration of 300 ppb and 6.5 g of bacterial cell mass for 7 days. The second step indicated the maximum As (V) adsorption capacity by the stacked red mud pellets to be 97.91% for 500 ml of As contaminated groundwater using an optimized pore size of 106 μ - 125 μ for 7 days. The total As removal efficiency increased to 98.76% at a flow rate of 50 ml/h on combination of both the steps. Further, the chemical composition, morphological properties, and crystal structure of the As (V) adsorbed red mud pellets were characterized by Fourier – Transform infrared spectroscopy (FTIR), Scanning electron microscopy – Energy dispersive X-Ray spectroscopy (SEM-EDX), and X-Ray diffraction (XRD) microanalysis. The techno economic feasibility of this entire unit was studied using SuperPro 10 software to estimate its optimal demand and potential. Hence, in the near future the scaling up of this two-step bio-filter column can serve as a cost-effective and efficient filtration unit to eradicate the total As from drinking water, both at household and industrial levels
Co-pyrolysis of Sugarcane Bagasse and Thermocol Waste to Obtain an Upgraded Product
No full textThe co-pyrolysis of sugarcane bagasse and thermocol waste is investigated at different temperatures, and blending ratios to establish the optimum conditions for maximum liquid product yield. In the initial section characterization of the precursors, followed by the thermogravimetric analysis of the blend of sugarcane bagasse and thermocol waste at a 1:1 ratio, sued by optimizing the process parameters using response surface methodology, kinetics study of 1:1, and in the utmost section of thesis, the engine studies of the co-pyrolysis liquid blend with diesel in various proportions are performed. The experimental results showed a maximum liquid yield of 66.75 wt. “%” at 550 C, 1:3 ratio of mixture, and 20C min-1 rate of heating respectively. The optimization results showed an optimum co-pyrolytic liquid yield of 66.94 “%”, at sugarcane bagasse blending ratio of 47.09 “%”, 18.66 °C min-1 rates of heating, and 563.2 °C optimum temperature. The characterization studies indicated some properties of the co- pyrolytic liquid namely, higher heating value (41.05 MJ kg-1), and kinematic viscosity (3.70 cSt) either within the range or in the nearby range of diesel and gasoline fuels. The Fourier Transform Infrared Spectroscopy and Gas-chromatography Mass-spectrometry analysis results presented the presence of aromatic compounds in abundance. The activation energy (Ea) for sugarcane bagasse and thermocol waste (1:1) blend was determined using Kissinger, Kissinger Akahira Sunose, and Ottawa Flynn Wall methods. Furthermore, the thermodynamic parameters were assessed, and the CR method was used to estimate the pre-exponential factors for sugarcane bagasse and thermocol waste blend. The Ea for co-pyrolysis of sugarcane bagasse, and thermocol waste obtained by the Kissinger method was 145.94 kJ mol‒1, while the average value of Ea by Kissinger Akahira Sunose and Ottawa Flynn Wall methods was 160.34 and 170.47 kJ mol‒1 respectively. The kinetics analysis results suggest that the sugarcane bagasse, and thermocol waste blend has the potential to be used as a precursor for pyrolysis. Under full load conditions, the optimum values for brake power, brake thermal efficiency, brake-specific fuel consumption, and torque was determined to be 3.62 kW, 31.24 “%”, 0.2 kg/kWh, and 21.56 Nm for 5 “%” blend
Energy Harvesting from Beam like Structures
No full textIn this era, energy harvesting from an external source is a new field of research. The main purpose of energy harvesters is to drive low-energy devices without battery support. Considering different environmental concerns of the energy sources, vibration is found to be favorable to generate environmental friendly energy having prospects of technological development. In the environment, a lot of residual energy is presented as wasted energy which can be extracted using different energy harvesters. This can be achieved by implementing the concept of smart materials and other different techniques of energy harvesting. This energy source is exploited from the environment through the application of a moving body. In our day-to-day life, these applications are found in various fields such as civil constructions, aerospace, mechanical shop and in the field of transportation, etc. Keeping eye on the environmental concern, piezoelectric is the newest self-sustained material for the extraction of energy to empower small-scale devices. In all the mentioned cases due to vibration of structures, residual energies discharged into the surroundings as wasted energy can be extracted using various energy harvesters. The present work focuses on the modeling of piezoelectric energy harvester having different structures excited by a moving body. The thesis covers both analytical and finite element analysis of different models as per requirement. Different electromechanically coupled mathematical models of various systems are derived by using Hamilton’s principle, Galerkin’s method, and Newmark’s integration method to obtain the dynamic response of beam under given boundary conditions. To make the solution more practical, the analysis is carried out by considering different nonlinearities like kinematic and geometrical nonlinearity to the system model. A piezoelectric patch is attached to the beam-mass system to extract electrical energy and store it using an electrical circuit. Different mechanical structures are modeled for vibration analysis and energy harvesting. Finally, an optimization technique is implemented to get optimal energy harvesting from the structures
Mechanical, Tribological and Hydrophobic Properties Evaluation of Atmospheric Plasma Sprayed NiTi Coating
No full textIn the current investigation, the atmospheric plasma spray technique was implemented to develop a protective coating of NiTi alloy on the mild steel substrate using different primary gas flow rates and plasma arc currents. For this purpose, an elemental mixture of equiatomic Ni and Ti powder was considered as the feedstock material. After successful deposition, the coatings were characterized using various characterization methods. The physical, mechanical, and tribological properties of the coatings were determined. Furthermore, the plasma spray process parameters were optimized using different optimization tools to achieve the best product. The physical and mechanical properties include the investigation of phase, microstructure, porosity, deposition efficiency, surface roughness, microhardness, adhesion strength, and correlation. The phase analysis revealed the presence of various phases in the coatings, such as NiTi-B2, Ni3Ti, Ti2Ni, Ni, Ti, NiO, TiO, and Ni4Ti3. From the microstructural analysis, various surface and interface defects such as surface microcracks, unmelted/partially melted particles, surface pores, splat fracture, interface porosity, inter-lamellar cracks, vertical cracks, inter-splat cracks, etc. were observed in the coatings developed at lower primary gas flow rates and plasma arc currents. Furthermore, the molten fraction of the powders, thermal pinching effect, enthalpy effect, and air diffusion into the plasma plume influenced the microhardness values of the plasma sprayed NiTi coating. The mechanical interlocking phenomenon of the coating is mainly responsible for the adhesion strength variation of the coatings. The adhesion strength analysis of the coatings depicted various failure modes such as adhesive failure, cohesive failure, mixed-mode failure, glue joint failure, etc. The tribological behavior of the NiTi plasma sprayed coatings was analyzed by the solid particle erosion test performed at two different erodent impingement angles, i.e., 45˚ and 90˚. The results revealed that with the increase in primary gas flow rate and plasma arc current, the erosion rate of the samples eroded with 90˚ erodent impingement angle increase due to the rise in brittle nature of the surface. The lack of edge strength and increase in stress concentration of the coatings having more porosity percentage lead to more damage by the erodents at both the angles of impingements. Furthermore, the surface area of the roughness peaks and the gap between the roughness peaks also influenced the erosion rate of the coatings. Again, due to the difficulty in penetration of the erodent in the surface of the coatings having a higher hardness, the erosion rate is less in those samples. Various wear mechanisms have been observed in the eroded samples, such as plastic deformation, ploughing, microcutting, lip formation, scratches, groove formation, splat fracture, splat fragmentation, splat delamination, pit formation, etc. To optimize the process parameters of the plasma spray coating, in the current work, two optimization techniques were considered. Initially, using the genetic algorithm technique, the process parameters were optimized, and then to validate the obtained result the fuzzy-TOPSIS technique was adopted. From the genetic algorithm, the obtained results revealed the optimized parameters as plasma arc current 550 A and primary gas flow rate as 45 lpm, and the fuzzy-TOPSIS technique also confirmed the same. Also, the primary gas flow rate was the major contributing factor proved by the ANOVA technique. The coating developed at optimized process parameters revealed the superhydrophobic characteristic ensured by the water contact angle 165º and sliding angles 8±10. The surface profile of the coating supports the theory. The coating loses its superhydrophobic characteristics after 90 passes of abrasion in sandpaper. Furthermore, from the annealing, it was observed that the coating retained its superhydrophobic characteristics up to 400 ˚C. The pH test disclosed the sensitiveness of the coatings in an acidic (pH=10) and basic (pH=2) environment. The dropwise evaporation analysis ensured the lower heat absorption of the coating. The coating also has interchanging characteristics in the presence of an electric field
Simulation and Experimental Verification for Acoustic Attenuation of Intuitive Designs of Periodic Scatterers and Combination with Acoustic Panels
No full textThis thesis endeavors design, simulation, and experimental verification of periodic scatterers with an aim to attain elevated acoustic attenuation in broadband by suggesting intuitive designs such as shells having the helical slit, multi-resonant scatterers such as coaxial combinations of resonant shells, and hybrid configurations by installing acoustic panels within the rows of periodic scatterers followed by a time-domain pulse separation based measurement technique to calculate the free-field insertion loss (IL) and echo reduction (ER) in the room environment. As the estimating acoustic performance of periodic scatterers during the design phase has been observed indispensable, the finite element method (FEM) based simulation having appropriate boundary conditions has been shown reliable enough to calculate the insertion loss (IL) with corroboration to the corresponding band structure. The calculated IL for periodic cylindrical and C-shaped scatterers have been presented which agree adequately with the experimental measurements, carried out in an anechoic chamber. With the parametric study of periodic C-shaped scatterers, it has been shown that on increasing the slit width, the IL around the Bragg band is getting reduced which has been addressed by an intuitive design modification such as altering the vertical slit of the shell to a helical shape. The associated tunable parameters of local resonance have been studied and the elevated IL has been demonstrated via simulations accompanied by a comparative study with periodic C-shaped scatterers. After achieving elevated IL with periodic locally resonant scatterer, the multi-resonant scatterers have been designed intuitively by combining two resonant shells such as C-shaped scatterer (C) and perforated scatterer (P). Three decoupled bandgaps other than the Bragg band have been discovered with suggested multi resonant scatterers which are CC, PP, CP, and PC scatterers, which is more than the combination of the resonance peak of participant resonant shells. Via simulation, it has been shown that the first two peaks are corresponding to the participant resonant shells, and the third peak is in the direction of wave propagation due to the dipolar resonance of the hollow cavity within, which is also supported by experimental observations. Next, the hybrid periodic scatterers have been explored where the porous acoustic panels have been installed within the rows of scatterers and the elevated IL in broadband has been shown to be achieved. On installing the porous panels, the IL is getting elevated in post Bragg band which is even if more than the summation of IL corresponding to the individual participants such as periodic scatterers and parallel porous panels. Further enhancements in IL also have been achieved with hybrid resonant and multi-resonant scatterers. The additional observation with hybrid resonant and multi-resonant scatterers is that the passbands present on both sides of the resonance peak are getting converted to stopbands with elevated IL which also has been authenticated via experimentations. In the aforementioned investigations, the experimentations have been conducted in the free field which is an anechoic environment to substantiate the observations made from simulations. To make it possible with a room environment, next, the time domain pulse separation technique has been demonstrated to calculate the IL and ER of periodic scatterers via simulation first. Next, the techniques used for experimentations in the room environment, and the good agreement with results obtained from the simulations have been presented
Studies on Microbial Production and Extraction of poly β-hydroxybutyrate using Bacillus Subtilis
No full textPoly-β-hydroxybutyrate (PHB) has wide applications in industry as it has properties similar to that of conventional plastics. Most important properties of PHB are its biodegradable nature, thermo-stability, and biocompatibility, durability, non-toxicity and water insolubility. Bacillus subtilis is a well-known bacterium that has been used for the industrial production of several proteins and biochemicals. Bacillus subtilis (ATCC®6051™) was used for PHB production. PHB was quantified using UV-VIS spectrophotometer and High-Pressure Liquid Chromatography (HPLC). The PHB yield of B. subtilis (ATCC®6051™) was estimated in batch cultivation by HPLC and GC methods. In this study, B. subtilis was employed for intracellular PHB Production in batch and fed-batch cultivation. The batch kinetic study of B. subtilis culture was conducted in an optimized medium in stirred tank bioreactor. The B. subtilis culture showed maximum biomass formation (1.78±0.1 g/l) and PHB accumulation (1.18±0.04 g/l) with 66.29 % PHB content of dry cell weight (DCW) at 28 h in optimized media using shake flask cultivation. The overall productivity was found to be 0.039 g/l/h. B. subtilis culture showed maximum biomass (1.79±0.026 g/l) and PHB accumulation (1.23±0.024 g/l) with the PHB content of 68.72% of DCW after 24 h in a bioreactor. The overall productivity was found to be 0.051 g/l/h. Substrate inhibition reduces the overall production in microbial production of PHB. Therefore, substrate (glucose, phosphate, and ammonium) inhibition studies were performed in shake flask conditions. The complete inhibition of growth of bacterial culture was seen at glucose, phosphate, and ammonium concentration of 120 g/l, 80 g/l, and 100 g/l, respectively. The optimum value of kinetic parameters was estimated to be: 0.376 h-1 for μm, 4.162 g/l for KSG, 1.611 g/l for KSN, 0.427 g/l for KSP, 123.6 g/l for KIG, 103 g/l for KIN, 82.4 g/l for KIP, 1.646 g/g for 1/Y(x/SG), 0.0923 g/g/h for mSG, 0.688 g/g for k1, 0.0041 for k2 and 9.671 for n. Initial values of biomass (=0.05 /), substrate (=7.3 /,) and PHB concentration (P = 0.012 g/l) and optimum parameters values were utilized to get a modified Monod model for PHB production. Inhibition kinetics data was also utilized for the prediction of inhibition kinetics parameters in the batch model. The productivity was found to be 0.041 g/l/h. The batch model was utilized for the prediction of the best fed-batch strategy. In constant feed rate fed-batch cultivation in shake flask, B. subtilis culture showed maximum biomass (1.91±0.05 g/l) and PHB production (1.37±0.08 g/l) with PHB content of 71.73% of dry cell weight at 30 h. The productivity was found to be 0.046 g/l/h. PHB production was enhanced 1.16 folds in constant feed rate fed-batch conditions, as compared to batch cultivation of B. subtilis. In this study, batch kinetic parameters for biomass production, substrate utilization and PHB production were estimated for B. subtilis culture. The resulting data was utilized for the development of mathematical model for production of biomass and PHB. This constant feed rate fed-batch cultivation was performed in a bioreactor using statistically optimized media. The maximum biomass obtained was 1.66±0.050 g/l and PHB was 1.42±0.05 g/l with the PHB content of 85.54% of DCW at 30 h cultivation. Two-stage cultivation of B. subtilis was performed using two medium of different composition for growth and production in bioreactor using constant fed-batch strategy. In bioreactor, in which maximum biomass (1.95±0.045 g/l) and PHB production (1.396±0.017 g/l) were obtained in 8th h of production with a PHB content of 93.33% of DCW. This is the highest reported PHB yield by fermentation to the best of our knowledge. The maximum biomass (1.953±0.045 g/l) at 4 h and PHB production (1.396±0.017 g/l) at 8 h were obtained during mass production of PHB in a bioreactor. In this study, several off-line feeding strategies were examined for enhanced biomass and PHB production by B. subtilis. After shake flask trials it was established that enhanced PHB production took place by constant feed rate fed-batch cultivation strategy. The successful model based feeding strategy can be applied for the production of PHB on commercial scale. A new extraction process with non-toxic and cheaper solvent was developed. In this study, different parameters like acetone percentage, and solvent pH, temperature, and incubation period were optimized using statistical tools such as Plackett-Burman (PB) design and Response Surface Methodology (RSM). An attempt was made to develop a robust process for the extraction of PHB from cells by liquid-liquid extraction. Different parameters like acetone percentage (30 % to 70 %), and pH (5 to 9), temperature (30 °C to 70 °C), and incubation periods (30 to 70 min) were chosen for optimization using Central Composite Design (CCD). The most effective factors predicted by PB design were cell biomass (t-value of 0.0404), incubation temperature (t-value of 0.0057), solvent pH (t-value of 0.0039), solvent percentage (t-value of 0.0023), incubation period (t-value of 0.0009). The agitation speed (t-value of -0.0094) did not show a significant effect on PHB recovery. The optimum conditions for the enhanced PHB recovery and purity were found to be solvent pH 7, extraction temperature - 43 °C, incubation time - 70 min, and percentage acetone – 30 % by Central Composite Design (CCD). The experimentaly recovered PHB was 0.87 g/g with a purity of 95.02% which is higher than the model predicted value of PHB recovery of 0.84 g/g of biomass with a purity of 97.23 %. In this study, PHB extraction process parameters were optimized for PHB recovery (g/g) and purity (%) using PB design and RSM statistical tools. The cheaper and green solvent acetone was employed for extraction of PHB. PHB extracted from this process is less toxic as compared to the PHB extracted using the halogenated solvents (chloroform, di-chloromethane, dichloroethane and sodium hypochlorite). The extracted PHB can be utilized in food industries, pharmaceutical and tissue engineering applications