Doctor of Philosophy

dissertationFroth flotation is a highly complex, multiphase, and multiscale process that is usually performed in large tanks called mechanical flotation cells. The aim of this research is to investigate the single and multiphase flow hydrodynamics in lab scale flotation cells by decoupling the hydrodynamics from physicochemical effects. Both experimental and numerical approaches are used to study the behavior of flows in lab and pilot scale flotation cells. Nonintrusive experimental techniques such as particle image velocity (PIV) and electrical resistance tomography (ERT) techniques are used to measure flow velocities, solids holdup, mixing efficiency, and to interpret flow pattern. Eulerian-Eulerian computational fluid dynamics (CFD) models are developed and tested for solid-liquid (slurry) and gas-liquid flows in stirred tanks and flotation cells. Using single phase CFD simulations, the effect of flotation specific impeller blade shape and impeller size on mean flow and pumping behavior is tested in lab scale flotation cells for the first time. In the absence of a stator, the mean flow is found to transition from radial to axial type flow when the off-bottom clearance is below the critical value. This prediction is experimentally verified using time averaged PIV data. Based on the analysis of pumping and power number data, the rectangular shaped blade design is found to be the most efficient. The impeller blade shape is found to critically affect the flow in the vicinity of the impeller and a design with the largest surface area is needed to create an intense turbulence zone, needed for mixing and dispersion of incoming air. Eulerian-Eulerian CFD model is used to study the solid phase suspension and mixing characteristics for monosized silica particles. Experimental comparison with the results from the literature for stirred tanks and in-house ERT measurements suggest that the model performs reasonably well. Population balance equation model (PBM) is coupled with CFD to study gas dispersion, mixing, and local bubble size distribution in the stirred tank and flotation cell using quadrature method of moments (QMOM) approach in ANSYS Fluent solver. The default QMOM model in Fluent is found to be inaccurate due to independent solution of moment transport equations and therefore is supplied with a moment correction algorithm from the literature to successfully identify and correct the invalid moment sequence during the CFD simulation. The new model is found to be superior to the current models in its ability to satisfactorily predict the overall gas holdup and local bubble size distribution for stirred tanks under moderate aeration and agitation rates. This model is extended to study the development of flow regimes based on the gas dispersion pattern in a generic flotation cell. Though highly useful, the coupled CFD-PBM approach is computationally intensive and requires considerable effort to achieve an accurate solution. This motivated us to develop a PBM based on the high-order moment conserving method of classes (HMMC) approach for a pilot scale XCELL flotation cell for frother concentration over critical coalescence concentration, thus, only considering breakage of bubbles. Nonlinear optimization solvers in Matlab are used to calculate the point estimates of adjustable parameters in breakage models. The 95% bootstrap calculated using empirical bootstrap indicates very high confidence in estimated parameters. The HMMC model provides an accurate description of steady state bubble size distribution and the mean number diameters only using overall gas holdup and specific energy as inputs

Surface dissolution and degradation of dental resin-based materials with special emphasis by the effects of solvent ethanol, dimethacrylate monomer resin and catalyst solution of ethylene glycol

In today’s modern dentistry, various synthetic materials are used for the replacement or restoration of the missing teeth or parts of teeth structures. These are primarily either polymers or composite materials. The evolution of the synthetic polymers dates back to the use of natural rubbers to poly(methylmethacrylate), (PMMA) to the present-day use of cross-linked copolymers and interpenetrating polymer network (IPN). One commonly used polymer is the group of denture base polymers where polymer beads of poly(methylmethacrylate) and the monomer of methylmethacrylate (MMA) form multiphase polymer system. During the phase of polymerization, some residual MMA monomers are left unconverted and heat-cured however, auto polymerized denture base polymers differ in this respect. In crosslinked dental resins, monomers are typically bis-phenol A-glycidyl methacrylate (bis-GMA) and triethylene glycol dimethacrylate (TEGDMA) or epoxies and they on combination with PMMA form IPN polymer. This study aimed to investigate surface crazing and surface dissolving of dental polymer with solvent and disinfectant ethanol by chemical reaction of transesterification. Scanning electron microscopy, infrared spectroscopy, and Nanoindentation were used as the research methods. The outcomes of the study on various dental polymers suggested that ethanol had a significant influence on affecting the surface roughness, and nanomechanical properties with surface topographical changes of denture base polymers. The effect of ethanol was dependent on time and concentration. Transesterification of the crosslinked bis-GMA based substrate was seen on contrary to the epoxy resin, which did not show signs of transesterification. This was explained by the lack of the ester group in the mainly studied epoxy polymer

IMPROVED INFECTIOUS LARYNGOTRACHEITIS VIRUS VACCINES USING NEWCASTLE DISEASE VIRUS VECTOR

Infectious laryngotracheitis (ILT) is a highly contagious acute respiratory disease of chickens for which safe and efficacious vaccines are not available currently. In the present study, we have generated three recombinant Newcastle disease viruses (rNDV's) expressing three major envelope glycoproteins gB, gC and gD of ILTV individually. A single oculonasal inoculation of chickens with rNDV's elicited detectable level of systemic antibodies specific to ILTV. Following challenge with virulent strain of ILTV, chickens immunized with the rNDV's displayed partial protection with reduced clinical signs and shorter duration of disease compared to the control group. Our data suggested that NDV vectored ILTV vaccines are useful against ILTV infection, but might require augmentation by a second dose or require modification of ILTV glycoproteins which allow them to incorporate into the mature rNDV virions for better induction of humoral and cell mediated immune responses

Study of flow of Buongiorno nanofluid in a conical gap between a cone and a disk

The cone–disk apparatus consists of a cone that touches the disk at its apex and is used in medical evices, viscosimeters, conical diffusers, etc. Theoretically, a three-dimensional flow of a nanofluid in a conical gap of a cone–disk apparatus is studied for four different physical configurations. Buongiorno nanofluid model, consisting of thermophoresis and Brownian diffusion mechanisms, is used to describe the convective heat transport of the nanofluid. The continuity equation, the Navier–Stokes momentum equation, the heat equation, and the conservation of nanoparticle volume fraction equation constitute the governing system for the flow of nanofluids. The Lie group approach is used to obtain self-similar equations. Solutions are computed for an appropriate rotational Reynolds number and four different gap angles to examine flow, mass, and heat transport features. The skin friction coefficients and torque are computed and analyzed. Multivariate nonlinear regression analysis is also performed. A co-rotating disk and cone configuration has been shown to produce less torque due to the increased centrifugal force. Of the four cone–disk apparatus configurations, the maximum heat/mass transport occurs for a rotating disk with a static cone for all selected gap angles, and the least drag in the radial direction is attained for a rotating cone with a static disk. In addition, there is a minimal drag along the tangential direction for the counter-rotating disk and cone configuration. Brownian diffusion and thermophoresis of the nanoparticles lead to a higher fluid temperature and, thus, lower Nusselt numbers are obtained

Non-Timber Forest Products (NTFPs) for Food and Livelihood Security: An Economic Study of Tribal Economy in Western Ghats of Karnataka, India

Thesis submitted in partial fulfilment of the requirements for the joint academic degree of International Master of Science in Rural Development from Ghent University (Belgium), Agrocampus Rennes (France), Humboldt University of Berlin (Germany) and University of Cordoba (Spain) in collaboration with Wageningen University (The Netherlands), Slovak University of Agriculture in Nitra (Slovakia) and the University of Pisa (Italy).Crop Production/Industries, Farm Management,

Study of Multilayer Flow of a Bi-Viscous Bingham Fluid Sandwiched Between Hybrid Nanofluid in a Vertical Slab with Nonlinear Boussinesq Approximation

Bi-Viscosity Bingham plastic fluids are used to understand the rheological characteristics of pigment-oil suspensions, polymeric gels, emulsions, heavy oil, etc. High-temperature applications in many industrial and engineering problems, linear density-temperature variation is inadequate to describe convective heat transport. Therefore, the characteristics of the nonlinear convective flow of a Bi-Viscosity Bingham Fluid (BVBF) through three layers in a vertical slab are studied. The two outer layers of the oil-based hybrid nanofluid and the intermediate layer of BVBF are considered. The thermal buoyancy force is governed by the nonlinear Boussinesq approximation. Continuity of heat flux, velocity, shear stress, and temperature are imposed on the interfaces. The governing equations are derived from the Navier-Stokes equation, conservation of energy, and conservation of mass for three layers. The nonlinear multipoint (four-point) boundary value problem (NMBVP) is solved using the differential transform method (DTM). Converging DTM solutions are obtained, and they are validated. The entropy equation and Bejan number were also derived and analyzed. It is established that the nonlinear density-temperature variation leads to a significant improvement in the magnitude of the velocity and temperature profiles due to the increased buoyancy force and as a result, the drag force on the walls is reduced. The drag force on the slab gets reduced by decreasing the volume of nanoparticles. Furthermore, nonlinear convection and mixed convection give rise to an advanced rate of heat transport on the walls and thereby to an enhanced heat transport situation

An optimal artificial neural network controller for load frequency control of a four-area interconnected power system

In this paper, an optimal artificial neural network (ANN) controller for load frequency control (LFC) of a four-area interconnected power system with non-linearity is presented. A feed forward neural network with multi-layers and Bayesian regularization backpropagation (BRB) training function is used. This controller is designed on the basis of optimal control theory to overcome the problem of load frequency control as load changes in the power system. The system comprised of transfer function models of twothermal units, one nuclear unit and one hydro unit. The controller model is developed by considering generation rate constraint (GRC) of different units as a non-linearity. The typical system parameters obtained from IEEE press power engineering series and EPRI books. The robustness, effectiveness, and performance of the proposed optimal ANN controller for a step load change and random load change in the system is simulated through using MATLAB-Simulink. The time response characteristics are compared with that obtained from the proportional, integral and derivative (PID) controller and non-linear autoregressive-moving average (NARMA-L2) controller. The results show that the algorithm developed for proposed controller has a superiority in accuracy as compared to other two controllers

Ion—modified optimization of smart scaffolds in bone tissue regeneration

Bioactive glasses and Calcium Phosphate bioceramics have emerged as promising scaffold biomaterials for bone tissue engineering. These materials possess inherent osteoinductive properties that work to create a more suitable environment for bone tissue formation. Additionally, these scaffolds exhibit dissolution properties when submerged in physiological fluids in vivo and therefore can release different ions. Incorporating therapeutic ion-modifiers that have independently demonstrated their osteogenic favorability to these scaffolds can further increase environmental suitability. This review discusses the favorable properties of bioactive glasses and Calcium Phosphate bioceramics in the context of Bone Tissue Engineering as well as potential incorporable metal ion-modifiers