Electrothermoconvective instability in a heat generating dielectric fluid layer

The combined effects of vertical d.c. electric field and uniform internal heat generation on the onset of convection in a horizontal poorly conducting dielectric fluid layer heated uniformly from below are investigated. The Galerkin method is used to solve the resulting eigenvalue problem. Parametric study is conducted to know the effects of varying electric Rayleigh number, Re and dimensionless heat source strength, Ns. It is found that these two parameters exhibit a dual effect on the onset of natural convection; a result noticed in contrast to their effects when they are acting in isolation. © 2007 Elsevier Ltd. All rights reserved

Effect of mfd viscosity on the onset of ferromagnetic fluid layer heated from below and cooled from above with constant heat flux

The effect of magnetic field dependent (MFD) viscosity on the onset of convection in a ferromagnetic fluid layer heated from below and cooled from above in the presence of vertical magnetic field is investigated theoretically. The bounding surfaces are considered to be either rigid-ferromagnetic or stress free with constant heat flux conditions. The resulting eigenvalue problem is solved using the Galerkin technique and also by regular perturbation technique. It is found that increase in MFD viscosity and decrease in magnetic number is to delay the onset of ferroconvection, while the nonlinearity of fluid magnetization has no influence on the stability of the system

Effect of Cross-Diffusion on the Stability of a Triple-Diffusive Oldroyd-B Fluid Layer

The onset and stability of a triple cross-diffusive viscoelastic fluid layer is investigated. The rheology of viscoelastic fluid is approximated by the nonlinear Oldroyd-B constitutive equation which encompasses Maxwell and Newtonian fluid models as special cases. By performing the linear instability analysis, analytical expression for the occurrence of stationary and oscillatory convection is obtained. The numerical results show that the elasticity and cross-diffusion effects reinforce together in displaying complex dynamical behavior on the system. The presence of cross-diffusion is found to either stabilize or destabilize the system depending on the strength of species concentration as well as elasticity of the fluid and also alters the nature of convective instability. The disconnected closed oscillatory neutral curve lying well below the stationary neutral curve is observed to be convex in its shape in contrast to quasiperiodic bifurcation from the quiescent basic state noted in the case of Newtonian fluids. This striking feature is attributed to the viscoelasticity of the fluid. By performing a weakly nonlinear stability analysis, the stability of bifurcating solution is discussed. It is worth reporting that the viscoelastic parameters significantly influence the stability of stationary bifurcation though the stationary onset is unaffected by viscoelasticity. Besides, subcritical instability is occurs and the critical Rayleigh number at which such an instability is possible decreases in the presence of cross-diffusion terms. The results of Maxwell and Newtonian fluids are delineated as particular cases from the present study

Effects of thermal nonequilibrium and non-uniform temperature gradients on the onset of convection in a heterogeneous porous medium

The simultaneous effect of local thermal nonequilibrium (LTNE), vertical heterogeneity of permeability, and non-uniform basic temperature gradient on the criterion for the onset of Darcy-Benard convection is studied. The eigenvalue problem is solved numerically using the Galerkin method. The interaction of various types of permeability heterogeneity and non-uniform basic temperature gradient functions on the stability characteristics of the system is analyzed. It is observed that the linear variation (about the mean) of the permeability and the basic temperature gradient with depth has no added effect on the criterion for the onset of convection. However, the concurrent variation in heterogeneous permeability and non-uniform basic temperature gradient functions has more stabilizing effect on the system, while opposite is the trend when the effect of non-uniform basic temperature gradient alone is present. (C) 2011 Elsevier Ltd. All rights reserved

Dynamics and ‘normal stress’ evaluation of dilute suspensions of periodically forced prolate spheroids in a quiescent Newtonian fluid at low Reynolds numbers

The problem of determining the force acting on a particle in a fluid where the motion of the fluid and the particle is given has been considered in some detail in the literature. In this work, we propose an example of a new class of problems where, the fluid is quiescent and the effect of an external periodic force on the motion of the particle is determined at low non-zero Reynolds numbers. We present an analysis of the dynamics of dilute suspensions of periodically forced prolate spheroids in a quiescent Newtonian fluid at low Reynolds numbers including the effects of both convective and unsteady inertia. The inclusion of both forms of inertia leads to a nonlinear integro — differential equation which is solved numerically for the velocity and displacement of the individual particle. We show that a ‘normal stress’ like parameter can be evaluated using standard techniques of Batchelor. Hence this system allows for an experimentally accessible measurable macroscopic parameter, analogous to the ‘normal stress’, which can be related to the dynamics of individual particles. We note that this ‘normal stress’ arises from the internal fluctuations induced by the periodic force. In addition, a preliminary analysis leading to a possible application of separating particles by shape is presented. We feel that our results show possibilities of being technologically important since the ‘normal stress’ depends strongly on the controllable parameters and our results may lead to insights in the development of active dampeners and smart fluids. Since we see complex behaviour even in this simple system, it is expected that the macroscopic behaviour of such suspensions may be much more complex in more complex flows

Effect of Gender on Environmental Awareness of Post-Graduate Students

Aims: It was aimed in the present study to explore the effect of gender on environmental awareness of the post-graduate students. When education diversity was controlled to be science and social-science the environmental awareness was expected to be influenced by the gender of individuals. Study Design: In order to test the above objective the present study used comparative analyses in respect of the gender taking the subjects from science and social-science discipline represented from different areas. Place and Duration of Study: Place of the study was the post-graduate students selected from Karnatak and Bangalore Universities of Karnataka State, duration of the study was between February 2011 to July 2012. Methodology: The students of science discipline pursuing their 3rd semester of course in Botany, Chemistry, Geography, Geology, Applied Genetics, Physics and Zoology in Karnatak and Bangalore Universities were included in the study. However, in the Bangalore University the environmental science students were added to the science discipline as the course is offered in the university. The students included for the social-science discipline were from 3rd semester courses of Economics, History, Political Science, Social Work and Sociology. On the subjects the environmental awareness test developed by Jha (1998) was administered in group and the responses were obtained by the subjects. Sample: The included total subjects for the study were 605 post-graduate students comprising from science and social-science discipline. The age range of the students was between 22 to 24 years. For the obtained data after calculating mean and SD for the groups, ‘t’ analyses was carried out to find significant difference between the groups. Results: Statistical results using the ‘t’ test revealed no significant difference between the male and the female students of both science and social-science students of Karnatak University (Dharwad Science Male mean 50.54 (SD 11.15)/Female mean 51.41 (SD 08.15), ‘t’ 0.54, p>0.05. Dharwad Social-Science Male mean 51.02 (SD 09.07)/Female mean 51.68 (SD 07.34),‘t’ 0.51, p>0.05). The study also did not find significant difference between the male and the female science students of Bangalore university. However, there was difference between the social-science students in relation to their gender, the awareness results favouring the females (Bangalore Science Male mean 49.75 (SD 11.73)/Female mean 53.97, (SD 07.37), ‘t’ 2.26, p0.05). Conclusion: It was evidenced in the present study that gender has no significant effect on environmental awareness of the post-graduate students. Out of the four comparative analyses, in three the results are in accordance with the hypothesis and in one comparative analysis it was found that the females have higher environmental awareness. This implies that gender significance study on effect of environmental awareness needs further careful verification with control of other variables

Enhanced photoluminescence of Gd 2O 3:Eu 3+ nanophosphors with alkali (M = Li +, Na +, K +) metal ion co-doping

Gd 1.95Eu 0.04M 0.01O 3 (M = Li +, Na +, K +) nanophosphors have been synthesized by a low temperature solution combustion (LSC) method. Powder X-ray diffraction pattern (PXRD), scanning electron microscopy (SEM), UV-vis and photoluminescence (PL) measurements were carried out to characterize their structural and luminescent properties. The excitation and emission spectra indicated that the phosphor could be well excited by UV light (243 nm) and emit red light about 612 nm. The effect of alkali co-dopant on PL properties has been examined. The results showed that incorporation of Li +, Na + and K + in to Gd 2O 3:Eu 3+ phosphor would lead to a remarkable increase of photoluminescence. The PL intensity of Gd 2O 3:Eu 3+ phosphor was improved evidently by co-doping with Li + ions whose radius is less than that of Gd 3+ and hardly with Na +, K + whose radius is larger than that of Gd 3+. The effect of co-dopants on enhanced luminescence was mainly regarded as the result of a suitable local distortion of crystal field surrounding the Eu 3+ activator. These results will play an important role in seeking some more effective co-dopants. © 2011 Elsevier B.V. All rights reserved

Pheromone Trapping Protocols for Brinjal Shoot and Fruit Borer, Leucinodes orbonalis Guenee (Lepidoptera: Pyralidae): Evaluation of Trap Design, Quantity and Dispenser

Studies were conducted at the Indian Institute of Horticultural Research, Bangalore, and Central Horticultural Experiment Station, Bhubaneshwar, India, to evaluate trap design, quantity of pheromone loading and dispensers for attracting brinjal shoot and fruit borer, Leucinodes orbonalis Guenee (Lepidoptera: Pyralidae) using indigenously synthesized pheromone lure [synthesized by Indian Institute of Chemical Technology (IICT), Hyderabad], during 2003 and 2004. A water trap consisting of plastic container (20 cm dia. and 7.5 cm depth) with a facility to place the pheromone septum was designed. Pheromone load of 4 mg in both water trap and Pest Control India (PCI®) delta trap was observed to catch higher number of male moths compared to dispensers with lesser loading. When trap designs were compared, water trap with pheromone lure was observed to attract higher number of males than Pest Control India (PCI®) delta trap. Among the different pheromone dispensers tested, rubber septum was superior to plastic vial or plastic septum. Rubber septum supplied by Bio Pest Management® captured significantly higher number of moths compared to rubber and plastic septum supplied by difTerent firms. A comparison of IICT synthesized lures along with some commercially available lures indicated that Bio Pest Management® lure dispensed in rubber outperformed PCI® and IICT lures