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Steady Quadratic Stokes Flow Past Deformed Sphere: A Novel Perturbation Technique
Get PDFIn this paper, the problem of steady quadratic Stokes flow past a deformed sphere has been tackled with the use of a novel perturbation technique in both situations when a uniform stream is along the axis of symmetry (axial flow) and when it is perpendicular to the axis of symmetry (transverse flow). The most general form of the deformed sphere, governed by polar equation, is considered here for the study. The general expressions for axial and transverse Stokes drag for deformed sphere has been derived up to the second order of deformation parameter for parabolic and stagnation like parabolic flow. The class of prolate, oblate and egg-shaped axisymmetric bodies is considered for the validation and further numerical discussions. The numerical values of the drag coefficients and their ratio have been evaluated for the various values of deformation parameters, eccentricity and aspect ratio and corresponding variations are depicted via graphs
Effects of Radiation Absorption and Thermo-diffusion on MHD Heat and Mass Transfer Flow of a Micro-polar Fluid in the Presence of Heat Source
Get PDFAn analysis of the heat and mass transfer effects on an unsteady flow of a micro-polar fluid over an infinite moving permeable plate in a saturated porous medium in the presence of a transverse magnetic field, radiation absorption and thermo-diffusion were studied. The governing system of partial differential equations was transformed to dimensionless equations using suitable dimensionless variables. The dimensionless equations were then solved analytically using perturbation technique to obtain the expressions for the velocity, micro-rotation, temperature and concentration. With the help of graphs, the effects of the various important parameters such as the translational velocity, micro-rotational velocity, temperature and concentration fields within the boundary layer entering into the problem were discussed. Also the effects of the pertinent parameters on the skin friction coefficient, couple stress coefficient and rates of heat and mass transfer in terms of the Nusselt number and Sherwood numbers were presented numerically in tabular form. The results showed that the observed parameters have a significant influence on the flow, heat and mass transfer
Acidic Ionic Liquid Catalyzed One-Pot Conversion of Cellulose to Ethyl Levulinate and Levulinic Acid in Ethanol-Water Solvent System
No full textCellulose can be converted to a mixture of ethyl levulinate and levulinic acid by heating with a Brönsted acidic ionic liquid catalyst in aqueous ethanol medium in a one-pot operation under mild conditions. The highest ethyl levulinate yield of 19.0 % was obtained for a reaction carried out at 170 °C for 12 h in water-ethanol medium containing 38.5 % water and using 1-(1-propylsulfonic)-3-methylimidazolium chloride as the catalyst. The levulinic acid yields continue to increase with increasing water content up to about 54 % water in aqueous ethanol for reactions carried out at 150 °C for 48 h, and the highest levulinic acid yield was 23.7 %. The acidic, ionic liquid catalyst used can be efficiently recovered (96 %) from the water phase with negligible contamination, and the stability of the catalyst was confirmed by comparison of the 1H NMR spectrum of the recovered catalyst with fresh catalyst
Trends and variability of climate and river flow in context of run-of-river hydropower schemes: A case study of sunkoshi river basin, Nepal
No full textThe increasing trend of glacier retreat and climate change/variability has direct impact on run-of-river hydropower schemes. This study analyses climate change risk in a Himalayan Sunkoshi river basin which consists of several existing/under-construction run-of-river hydropower schemes. Climate change impact has been examined by comparing observed and projected hydro-climatic trends. Projected monthly climatology (based on A1B emission scenario) of Meteorological Research Institute, Japan has been employed for the analysis. Observed annual minimum and lean season (January, February, March and April) discharges, which have larger significance for run-of-river schemes were analysed to identify any significant trend. The annual minimum and lean season monthly discharges were found with decreasing trend. Comparison of present and future precipitation pointed out that there will be 4.3% increase in monsoon (June, July, August and September) precipitation and 10.4% decrease in remaining months. Similarly, the study revealed that monthly temperature will be increased by 1.5 to 4.6°C
Finite Thermal Wave Propagation in a Half-Space Due to Variable Thermal Loading
Get PDFThe thermoelastic interaction for the dual-phase-lag (DP) heat conduction in a thermoelastic half space is studied in the light of two-temperature generalized thermoelasticity theory (2TT). The medium is assumed to be initially quiescent. Using Laplace transform, the fundamental equations are expressed in the form of a vector-matrix differential equation which is then solved by statespace approach. The obtained general solution is then applied to the mechanical loading and various types of thermal loading (the thermal shock and the ramp-type heating). The numerical inversion of the Laplace transforms are carried out by the method of Fourier series expansion technique. The numerical results are computed for copper like material. Significant dissimilarities between two models (the two-temperature Lord-Shulman (2TLS) and the two temperature Dual-phase-lag model (2TDP)) are shown graphically. Because of the short duration of the second sound effect, the small-time solutions are analyzed and the discontinuities that occur at the wave fronts are also discussed. The effects of two-temperature and ramping parameters are studied
Modeling the Transmission Dynamics of Typhoid in Malaria Endemic Settings
Get PDFTyphoid and malaria co-infection is a major public health problem in many developing countries. In this paper, a deterministic model for malaria and typhoid co-infection is proposed and analyzed. It has been established that the model exhibits a backward bifurcation phenomenon. Overall, the study reveals that a typhoid outbreak in malaria endemic settings may lead to higher cumulative cases of dually-infected individuals displaying clinical symptoms of both infections than singly-infected individuals displaying clinical symptoms of either malaria or typhoid
Existence of Mild Solutions for Semilinear Impulsive Functional Mixed Integro-differential Equations with Nonlocal Conditions
Get PDFIn this paper, we prove the existence, uniqueness and continuous dependence of initial data on mild solutions of first order semilinear functional impulsive mixed integro-differential equations with nonlocal condition in general Banach spaces. The results are obtained by using the semigroup theory and Banach contraction theorem
Zero-stabilization for some diffusive models with state constraints
No full textWe discuss the zero-controllability and the zero-stabilizability for the nonnegative solutions to some Fisher-like models with nonlocal terms describing the dynamics of biological populations with diffusion, logistic term and migration. A necessary and sufficient condition for the nonnegative zero-stabilizabiity for a linear integro-partial differential equation is obtained in terms of the sign of the principal eigenvalue to a certain non-selfadjoint operator. For a related semilinear problem a necessary condition and a sufficient condition for the local nonnegative zero-stabilizability are also derived in terms of the magnitude of the above mentioned principal eigenvalue. The rate of stabilization corresponding to a simple feedback stabilizing control is dictated by the principal eigenvalue. A large principal eigenvalue leads to a fast stabilization to zero. A necessary condition and a sufficient condition for the stabilization to zero of the predator population in a predator-prey system is also investigated. Finally, a method to approximate the above mentioned principal eigenvalues is indicated. © EDP Sciences, 2014
Optimal sustainable policies under pollution ceiling: The demographic side
No full textWe study optimal sustainable policies in a benchmark logistic world (where both population and technological progress follow logistic laws of motion) subject to a pollution ceiling. The main policy in the hands of the benevolent planner is pollution abatement, ultimately leading to the control of a dirtiness index as in the early literature of the limits to growth literature. Besides inclusion of demographic dynamics, we also hypothesize that population size affects negatively the natural regeneration or assimilation rate, as a side product of human activities (like increasing pollution, deforestation, ⋯). We first characterize optimal sustainable policies. Under certain conditions, the planner goes to the pollution ceiling value and stays on, involving a more stringent environmental policy and a sacrifice in terms of consumption per capita. Second, we study how the sustainable problem is altered when we depart from the logistic world by considering exponential technical progress (keeping population growth logistic). It\u27s shown that, as expected, introducing such an asymmetry widens the margins of optimal policies as sustainable environmental policies are clearly less stringent under exponential technical progress. Third, we connect our model to the data, using in particular UN population projections. © EDP Sciences, 2014