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The present article deals with the influence of the local thermal nonequilibrium (LTNE) state on natural convection in an enclosure filled with nanofluid-saturated porous medium. The flow is induced due to the maintenance of constant heat flux on the vertical walls and insulation of horizontal walls. The Darcy model has been adopted to describe the flow governing equations. These equations are solved numerically by using the alternate direction implicit method and analytically by applying parallel flow assumptions valid for large aspect ratios. Boundary layer analysis is performed to report the boundary layer thickness (δ x ∼ 2 1 / 2 (k nf / k f) 1 / 10 (R a T) − 1 / 5) as well as the heat transfer rate of nanofluid ( N u nf ∼ (k nf / k f) − 1 / 5 R a T 2 / 5). The combined effect of LTNE state parameters (interface heat transfer coefficient (H), porosity scaled thermal conductivity ratio (γ)) and volume fraction of nanoparticle ( ϕ ) is addressed on the flow dynamics and heat transfer mechanism. Rigorous analysis, indicates that the average heat transfer rate of nanofluid and solid porous matrix are increasing function of H and γ, however, the role of γ is accelerated for a relatively high value of H. For increasing the value of γ from 1 to 10, the enhancement in the heat transfer rate of nanofluid is reported to be up to 27% at 10% volume fraction of nanoparticles. The average Nusselt number of nanofluid, as well as solid phase, are reduced when the value of ϕ is increased under the LTNE circumstances. Furthermore, the flow structure is controlled by unicellular structure with rotating anticlockwise direction in the entire study. For the very small value of H the temperature distribution in the solid porous matrix is mainly by conduction mode and distribution is linear, however, for a relatively high value of H the distribution in the same is controlled by both conduction as well as convection, and it will be more pronounced for the higher value of γ. [ABSTRACT FROM AUTHOR]

AbstractThe influence of the local thermal nonequilibrium (LTNE) state on steady-state natural convection due to the heating and cooling of the side walls of the slender porous cavity has been addressed analytically and numerically. The porous medium is assumed to be hydrodynamically anisotropic. The Darcy model has been adopted. A closed-form solution, based on a parallel hypothesis, is reported for a slender cavity. The combined impact of media anisotropy and LTNE state on the heat transfer rate, as well as flow dynamics, have been analyzed. The help of boundary layer analysis is taken to report the boundary layer thickness and heat transfer rate of fluid flow analytically. It has been found that the maximum (minimum) heat transfer rate of the fluid phase as well as solid phase takes place at orientation angle, ϕ, equal to π/2 when permeability along the horizontal (vertical) direction is higher than the same along vertical (horizontal) direction. [ABSTRACT FROM AUTHOR]

In the present article, a comprehensive numerical investigation of the magneto-convection in an electrically conducting isotropic, and hydro-dynamically as well as a thermally anisotropic porous cavity, is presented. The motion of the flow is due to the applied nonuniform heat flux on the bottom wall of the cavity and the insulation of other walls. The non-Darcy model has been adopted that includes Darcy and Brinkman terms in the momentum equations. The coupled governing equations are solved numerically by using the finite volume method (FVM). The impact of periodicity parameter (N), Hartmann number (Ha), and anisotropy parameters (K * , ϕ , and k *) on the dynamics of flow as well as heat transfer rate have been investigated. From rigorous numerical experiments, it has been found that the structure of streamlines is unicellular except for the inner kernel in some situations. In general, the profile of local heat transfer rate possesses (N − 1) points of singularity for sinusoidal heat flux with periodicity parameter (N), and the profile of local Nusselt number is not symmetric for even values of N. The heat transfer rate is highly affected by a relatively large value of thermal conductivity ratio ( k * ) as well as Ha, and the absolute difference between the maximum and minimum temperature of the system increases as a function of k * as well as Ha, whereas the strength of flow decreases gradually with increasing Ha. [ABSTRACT FROM AUTHOR]

The study examines the stability of parallel airflow within a tall vertical coaxial circular annulus filled with a highly permeable porous medium under stable stratification. The linear stability theory predicts that the least unstable mode can be either axisymmetric or non-axisymmetric, depending on the values of the governing parameters. The curvature parameter, defined as the gap between coaxial circular cylinders, contributes to the stabilization of the flow. Depending on various controlling parameter values, the stably stratified non-isothermal annular parallel flow (SNAPF) can manifest three instability modes: thermal-shear, thermal-buoyant, and mixed or interactive. The instability type can change abruptly with Reynolds number, curvature parameter, and media permeability. A finite-amplitude instability analysis is examined using weakly nonlinear stability theory. The analysis demonstrates both subcritical and supercritical bifurcations near the instability boundary. The range of Reynolds numbers for subcritical bifurcation expands when switching from axisymmetric to non-axisymmetric disturbance. Bifurcation transitions between supercritical and subcritical occur due to changes in the least stable azimuthal mode. The study also investigates the equilibrium/threshold amplitude within the supercritical/subcritical instability regime, and it verifies the existence of subcritical/supercritical bifurcation through nonlinear kinetic energy balance. Furthermore, the finite-amplitude analysis anticipates that the lower critical Rayleigh number increases as the Reynolds number, curvature parameter, or media permeability decreases. An increase in the Reynolds number shifts the point of inflection in the velocity profile toward the inner cylinder, which subsequently leads to a reduction in the size of the core vortex region. In the subcritical instability regime, the radius of the primary vortex cell decreased significantly as the Rayleigh number increased. When the curvature is altered, a structural transition occurs in the isotherms from multicellular to unicellular. • Stability analysis of mixed convection flow through an annular domain filled with a porous medium was studied. • The impact of the curvature parameter, media permeability, and form drag coefficient on the flow instability and bifurcation has been explored. • Instability mechanism was explored with the help of the kinetic energy budget. • Secondary flow pattern, both near and away from the instability boundary, was analyzed by examining vorticity and temperature distribution. • A range of Reynolds numbers and Rayleigh numbers corresponding to a subcritical bifurcation has been reported. [ABSTRACT FROM AUTHOR]

The relative influence of momentum diffusivity and thermal diffusivity, in terms of the Prandtl number (Pr), on the finite-amplitude instability of a non-isothermal annular Poiseuille flow (NAPF) is analyzed. The limiting value of the growth of instabilities under nonlinear effects is studied by deriving a cubic Landau equation. Emphasis is given especially on studying the impact of the low Prandtl number and the curvature parameter (C) on the bifurcation and the pattern variation of the secondary flow for both axisymmetric and non-axisymmetric disturbances. The finite-amplitude analysis predicts that in contrast to NAPF of water or fluid with Pr ≥ O(1) where the flow is supercritically unstable, the NAPF of low Pr fluids, particularly liquid metals, has shown both supercritical and subcritical bifurcation in the vicinity as well as away from the critical point. The nonlinear interaction of different harmonics for the liquid metal predicts a lower heat transfer rate than those by the laminar flow model, whereas for a fluid with Pr > 2, it is the other way. The maximum heat transfer takes place for the considered minimum value of C. For fluids with low Pr, a probable lower critical Rayleigh number is obtained. The corresponding variation in neutral stability curves as a function of wavenumber reveals that the instability that is supercritical for some wavenumber may be subcritical or vice versa at other nearby wavenumbers. The structural feature of the pattern of the secondary flow under the linear theory differs significantly from those of the secondary flow under nonlinear theory away from the bifurcation point. This is a consequence of the intrinsic interaction of different harmonics that are responsible for the stabilizing or the destabilizing nature of different components in the disturbance kinetic energy balance. [ABSTRACT FROM AUTHOR]

In this article, a comprehensive numerical investigation of the natural convection in a hydro-dynamically as well as thermally anisotropic porous enclosure with insulated side walls is presented. The two different cases, (I) same heat flux on the top as well as bottom walls and (II) heat flux on the top wall being negative of the heat flux on the bottom wall, are considered. A non-Darcy model that includes Darcy and Brinkman terms have been adopted and the coupled governing equations are solved numerically by SIMPLER algorithm. The influence of periodicity parameter and anisotropy parameters on the flow dynamics as well as heat transfer rate has been addressed. It has been found from our rigorous numerical experiments that the structure of streamlines and isotherms for Case I is multicellular and depends on the value of periodicity parameter (N) as well as media permeability, whereas the same for Case II is unicellular. In general, the profile of local heat transfer rate under Case I possesses (N − 1) points of singularity inducing hyperbolic temperature contour. In contrast to Case I, the profile of local heat transfer rate under Case II is found to be free from points of singularity. [ABSTRACT FROM AUTHOR]

The bifurcation and instability of nonisothermal annular Poiseuille flow (NAPF) of air as well as water is studied. We have emphasized the impact of a gap between cylinders in terms of curvature parameter (C) for axisymmetric as well as nonaxisymmetric disturbances. The results from the linear stability analysis reveal that the first azimuthal mode acts as a least stable mode of the NAPF of air for relatively small values of C. In this situation, even though for some values of C, the NAPF has supercritical bifurcation, but the same flow may experience subcritical bifurcation under zero azimuthal mode. It has also been observed that for relatively larger values of the Reynolds number (Re) and lower values of C, the NAPF under axisymmetric disturbance always exhibits subcritical bifurcation. However, for small values of Re, the NAPF exhibits only supercritical bifurcation. The finite amplitude analysis predicts only supercritical bifurcation of NAPF of water. The influence of nonlinear interaction of different harmonics on the amplitude profile as well as kinetic energy spectrum is investigated. The amplitude profile possesses a jump in the vicinity of a point where the type of bifurcation is changed. In the subcritical regime, the induced shear production due to modification of the gradient production acts as a main destabilizing factor balanced by the gradient production of kinetic energy. [ABSTRACT FROM AUTHOR]

Shear and density stratification strongly affect the flow mechanism of the different atmospheric and ocean flows. In this paper, we investigate the stability characteristics of plane Couette–Poiseuille (CP) flow with stable density stratification in the vertical direction. A modal stability analysis is carried out to examine the exponentially growing instability of stratified plane CP flow under different controlling parameters. The domain of the flow is periodic in streamwise and vertical directions. The stability problem is solved numerically using the spectral collocation method. The present analysis is carried out for Reynolds number R e = 10 4 with different speeds of moving wall and different strengths of stratification. The results show that the mass diffusivity impact on the flow instability mechanism is almost negligible beyond the Schmidt number S c ≥ 20. The three-dimensional mode is generally the most unstable mode for density-stratified CP flow. However, the most unstable mode in unstratified CP flow is always two-dimensional. In contrast to unstratified CP flow, the density-stratified CP flow is unstable even moving wall velocity exceeds 70% of the center velocity of the plane Poiseuille flow component. It is also observed that the moving wall velocity and density stratification simultaneously affect the stability of the flow, which shows the importance of the shear and stratification in the flow. [ABSTRACT FROM AUTHOR]

A weakly nonlinear stability analysis of isothermal Poiseuille flow in a fluid overlying porous domain is proposed and investigated in this article. The nonlinear interactions are studied by imposing finite amplitude disturbances to the classical model deliberated in Chang, Chen, and Straughan [J. Fluid Mech., 564 (2006), pp. 287-303]. The order parameter theory is used to ascertain the cubic Landau equation, and the regimes of instability for the bifurcations are determined henceforth. The well-established controlling parameters viz. the depth ratio ( ... = depth of fluid domain/depth of porous domain), the Beavers--Joseph constant (α), and the Darcy number (δ ) are inquired upon for the bifurcation phenomena. The imposed finite amplitude disturbances are viewed for bifurcations along the neutral stability curves and away from the critical point as a function of the wave number (a) and the Reynolds number (Re). The even-fluid-layer (porous) mode along the neutral stability curves correlates to the subcritical (supercritical) bifurcation phenomena. On perceiving the bifurcations as a function of a and Re by moving away from the bifurcation/critical point, subcritical bifurcation is observed for increasing ..., α and decreasing δ. In contrast to only fluid flow through a channel, it is found that the inclusion of porous domain aids in the early appearance of subcritical bifurcation when α = 0.2, ... δ = 0.13, δ = 0.003. A considerable difference between the computed skin friction coefficient for the base and the distorted state is observed for small (large) values of ... (α). In addition, an intrinsic relation among the mode of instability, bifurcation phenomena, and secondary flow pattern is also observed. [ABSTRACT FROM AUTHOR]

The linear stability analysis of fluid flow, driven by an axial pressure gradient, inside the annular region partially filled with porous medium is investigated. The porous layer is attached to the inner cylinder. The flow is governed by the unsteady Darcy model in the porous region and the Navier–Stokes equation in the viscous region. The effect of the curvature parameter C (ratio of the inner cylinder radius to the gap between cylinders), the ratio of the fluid to the porous layer thickness (t ̂) , and the Darcy number (Da) on the stability characteristics are explored. In addition, the help of the radial velocity contours and the kinetic energy balance is taken to get an insight into the mode and the cause of instability, respectively. The results show that depending upon the value of t ̂ , a decrease in the value of C causes a shift in the neutral stability curve from bimodal to trimodal. For low values of t ̂ , when the onset of instability is dominated by a porous mode, C destabilizes the flow, whereas it has a stabilizing impact on the flow stability for the odd-fluid mode and the even-fluid mode. At high values of t ̂ , C has again destabilizing characteristics and instability is dominated by even-fluid mode. When axisymmetric disturbances are dominant, it is observed that the value of t ̂ for which similar instability characteristics are found varies directly as the square root of Da. However, the correlation between t ̂ and Da does not hold when the non-axisymmetric disturbances are least stable. Contrary to the unconditional stability of the annular Poiseuille flow under non-axisymmetric disturbances for C < 0.1325, the present system is unstable even for C = 0.005 and t ̂ ≤ 1. This shows the significant impact of the curved fluid–porous interface on the stability characteristics. [ABSTRACT FROM AUTHOR]

Highlights • A thermal non-equilibrium approach has been considered to investigate the double-diffusive natural convection in a square as well as slender enclosure for both buoyancy aided and opposed cases. • Both analytical (valid for slender enclosure) and numerical studies are made. • Influence of LTNE state on the existence of multiple solution (by analytically) and oscillation (by numerically) for buoyancy opposed flow is investigated. • The interval of buoyancy ratio in which multiple solution exists increases on increasing the value of interface heat transfer coefficient. • Significant impact of thermal non-equilibrium parameters on Nusselt numbers as well as Sherwood number has been illustrated. Abstract In this paper, we address the influence of the thermal non-equilibrium state on double-diffusive convection in a porous enclosure, subject to constant heat and solute fluxes at the vertical walls, while other walls of the enclosure are adiabatic. For this, Darcy model has been adopted. The governing equations are solved numerically by the ADI method and analytically by using parallel flow assumption valid for the slender enclosure. A comparative study has been made in between buoyancy aiding flow(i.e., buoyancy ratio, N > 0) and buoyancy opposed flow(i.e., buoyancy ratio, N < 0). It was found that same as LTE (local thermal equilibrium) state particular oscillations and multiple solutions have also been observed on considering local thermal non-equilibrium (LTNE) state between the fluid and solid phase, for a certain range of interphase heat transfer coefficient (H) and conductivity ratio of fluid and solid (γ), when both buoyancy forces are opposite in nature (buoyancy ratio, N < 0). The range of the interval for buoyancy ratio, I NM , (in which multiple solutions exists) increases on increasing the value of H as well as γ , while the range of the interval for buoyancy ratio, I NO , (in which oscillation exits) vary in a subtle way. In general, same as LTE state, here also I NO is found to be a subset of I NM for most of the values of H as well as γ considered in this study. Apart from this, in case of buoyancy aiding flow, the enhancement of aspect ratio (A) enhances the heat transfer rate for both the phases, up to a threshold value A 0 of A , beyond that threshold value the impact of the same is negligible, while Sh acts in other way. [ABSTRACT FROM AUTHOR]

Abstract Linear stability analysis is used to analyze the stability of parallel flow induced by an external pressure gradient and buoyancy force in a differentially heated vertical channel filled with a fluid-saturated high permeable porous medium. The non-Darcy model which gives rise to the volume averaged Navier-Stokes (VANS) equation is used except for some comparative study where Darcy model is also used. The investigation is made for a wide range of Prandtl numbers (P r) that includes mercury, air, water and heavy oils. The spectral method has been adopted to solve the governing equations of the problem. In the entire considered range of Reynolds number (R e) the linear stability results show that the type of instability for mercury is thermal-shear (i.e., the instability is hydrodynamic in origin, resulting from an unstable velocity distribution, and obtains most of its kinetic energy (KE) through shear source), for water as well as heavy oil it is thermal-buoyant (i.e., most of the KE for this instability is obtained through work done by fluctuating buoyant force), whereas for air it is interactive (i.e., KE for this instability is obtained from both shear as well as buoyant sources). When R e is fixed at 1000, the appearance of point of inflection in the basic flow velocity for a fluid with P r less than 30 acts as a necessary condition for instability for all considered values of Darcy number. Furthermore, the form drag stabilizes the fluid flow with P r ≥ 7, however, it acts other way up to a threshold value for fluid flow with P r < 1. Finally, scale analysis reveals that for thermal-shear or interactive instability the minimum critical Δ T for parallel mixed convection flow is less than the same for parallel natural convective flow and it is other way for thermal-buoyant instability. As an example of thermal-buoyant instability, when the channel is filled with a porous medium having permeability 2.5 × 10 − 6 m2 and half-width 5 cm, the mixed convective flow of water remains stable up to a temperature difference of 13.3 o C between the walls, whereas the natural convective flow of water remains stable up to a temperature difference of 8.58 o C between the walls. [ABSTRACT FROM AUTHOR]

We examine the influence of local thermal non-equilibrium state (LTNE) on the instability mechanism of non-isothermal Poiseuille flow in a vertical channel filled with porous medium. The temperature field of the solid porous matrix and the saturating fluid are governed by separate, but coupled, energy equations supplemented with three dimensionless LTNE parameters: inter-phase heat transfer coefficient ( H ), porosity scaled conductivity ratio (γ) and diffusivity ratio (Γ). The linear stability results show that the critical Rayleigh number ( Ra c ) increases (decreases) with H ( γ ), which indicates that the effect of H ( γ ) is to stabilize (destabilize) the flow. The stabilizing impact of H for fluid with low Prandtl number ( Pr ) becomes high when kinetic energy due to non-isothermal effect is lost to the basic flow. The energy loss to the basic flow increases on increasing (decreasing) H (γ). Depending on the magnitude of all the studied parameters, three types of instabilities, namely: shear, mixed and buoyant have been observed. For relatively low permeable medium buoyant instability becomes the most dominant instability in the range of Prandtl number considered in this study. [ABSTRACT FROM AUTHOR]

A field experiment was conducted during boro seasons of 2004-05 and 2005-06 to find out the effects of four different date of sowing and three non-chemical weed control methods and also their interaction effects on weed flora, yield and economics of drum seeded bororice at BCKV, Mohanpur, Nadia, West Bengal, India in a split plot design. The sowing of rice was done under puddled condition by using drum-seeder, which is an upgraded device for rice sowing. Sowing of rice on 15th December produced minimum weed density and biomass at both of the observations, maximum % of effective tillersand B:C ratiocompared to other dates of sowing. Though the highest grain (5.19 t ha-1) and straw (5.65 t ha-1) yields obtained from 1st December sowing, but itwas closely followed by 15th December sowing. Amongst non-chemical weed control methods, hand-weeding gave lowest weed population and dry matter m-2 at 30 and 60 DAS, which were statistically comparable with mechanical-weeding with Japanese paddy weeder. On the other hand, mechanical-weeding produced highest grain and straw yield as well as B:C ratio. In case of interaction effects of the treatments, 15th December sowing coupled with hand weeding gave minimum weed population m-2 followed by 1st December sowing with hand weeding treatments at both 30 and 60 DAS. Sowing of drum-seeded rice on 1st December along with weeding by using Japanese Paddy Weeder produced higher grain yields (6.07 t ha-1), net return (₹29265) and B:C ratio (1.41) ascompared to other treatment combinations under the experiment. [ABSTRACT FROM AUTHOR]

In this article, the non-isothermal Poiseuille flow and its stability in a vertical annulus filled with porous medium are investigated. The flow is induced by external pressure gradient and buoyancy force due to linearly varying inner wall temperature. The non-Darcy model along with Boussinesq approximation has been used. The Chebyshev spectral-collocation method has been adopted to solve the governing equations related to basic flow as well as its stability. Special attention is given to understand the effect of curvature parameter of the annular geometry on the flow, heat transfer rate and stability of the stably stratified flow. A comprehensive numerical experiment indicates that reducing gap between two concentric cylinders decreases the heat transfer rate as well as the maximum magnitude of the flow velocity. It stabilizes the flow which has been shown through stability analysis. Furthermore, appropriateness of the Forchheimer term in the momentum equation has been examined by investigating the flow regime as well as its stability in the presence and absence of Forchheimer term. Finally, it has been found from the energy analysis at critical point that the thermal-buoyant instability is the only mode of instability for the considered range of different parameters. [ABSTRACT FROM AUTHOR]

A field experiment was conducted in the summer seasons of 2010 and 2011 on four mungbean varieties (V1 -Pant Mung-5, V2-Bireswar, V3-RMG-62 and V4-Sukumar) sown on three different dates (D1-15th February, D2 -1st March and D3-15th March) at the university research farm under Sub-humid tropical environment. The experiment was laid out in a split plot design where the sowing dates and the varieties were considered as main plot and sub plot treatments respectively. The objective of this study was to identify the stress period in mungbean crop through canopy temperature measurement. The canopy temperatures were measured at 7:30, 11:30 and 15:30 hour during 25 to 46 days after emergence (DAE) at seven days interval. Canopy temperature increased from 7:30 to 11:30 hr, followed by a decline at 15:30 hr with a few aberrations. The mean canopy temperature under D2 was lower than D1 and D3 in both the year which indicated no moisture stress suffered by the crop during that period. The SDDI was more at 11.30 hr which indicated moisture stress at that period. Overall, the moisture adequacy was better under D2 sowing giving the probability of good yield under this sowing and was closely followed by D3 sown crops. The variety V1 suffered less moisture stress in comparison to the other varieties. [ABSTRACT FROM AUTHOR]

In this manuscript the influence of local thermal non-equilibrium state on double-diffusive natural convection in a square cavity filled with fluid-saturated porous medium has been addressed numerically. The two dimensional steady state flow is induced due to maintenance of constant temperature and concentration on the vertical walls and insulation of both horizontal walls of the cavity. Non-Darcy (Darcy–Brinkman–Forchheimer) model has been taken and the complete governing equations are solved by standard SIMPLER algorithm. A comparative study of the effect of the presence of Brinkman term in the momentum equation showed that results under the Darcy model are very close to those for the non-Darcy Brinkman model for relatively low permeable medium (e.g., in this study Da = 10 - 4 ). From our experiments it has been found that the impact of Lewis number ( Le ) on the average heat transfer rate of fluid ( Nu f ) and solid ( Nu s ) as well as on the thermal distribution of fluid and solid is not straightforward. It depends on the buoyancy ratio ( N ) and the value of inter-phase heat transfer coefficient ( H ) . However, Le increases the average mass transfer rate ( Sh ) . Also, for each Le there exist a point in the domain of N where Nu f is minimum. Similar points also exist for Nu s and Sh . In general, these points are different and depend on the LTNE state parameters, except at Le = 1 . For any relatively large value of H , when almost thermal equilibrium state is achieved, the point at which Nu f and Nu s are minimum is same due to similar thermal distribution of fluid and solid. Also, it has been found that, for the buoyancy aided flow ( N > 0 ) , the increase in H up to a threshold value ( H 0 ) decreases Sh as well as Nu f but increases Nu s . The H 0 is found to be a decreasing function of the porosity scaled thermal conductivity ratio ( γ ) of fluid and solid phases. Overall, the impact of LTNE state on the heat transfer rate and thermal distribution is significant but it is negligible on the mass transfer rate and solute distribution. [ABSTRACT FROM AUTHOR]

A two year (2010 and 2011) experiment was conducted on four mungbean varieties (V1-Pant Mung-5, V2-Bireswar, V3-RMG-62 and V4-Sukumar) sown on three different dates (D1-15th February, D2-1st March, D3-15th March) in a split plot design (Main plot-dates of sowing and Sub plot-variety) in the Student's Instructional Farm, BCKV, West Bengal. The reproductive components such as bud, flower and pod numbers plant-1 and pod:flower ratio were recorded from 25 to 46 days after emergence (DAE). The relationship between the mean air temperature and different reproductive components were computed. Bud number per plant was maximum on 34 DAE when sown on D2, while it was maximum on 37 DAE under D1 and D3 sown crops. Highest number of flower per plant was observed on 37 DAE irrespective of dates of sowing, whereas, the maximum number of pods per plant was observed on 46 DAE. Among the dates of sowing, the D2 sown crop recorded significantly higher number of bud, flower and pod. Among the four varieties, Pant Mung-5 recorded the maximum number of bud, flower and pod per plant. Pod: flower ratio under 1st March sowing was highest under 37 to 40 DAE. With the advancement of age, the D3 sown crop recorded highest pod:flower ratio. Number of buds per plant was found to be significantly related to the mean air temperature in 2010 under different varieties, but in 2011, it was insignificant. However, the number of flower and pod per plant were significantly related to the mean air temperature in both the year. Increased temperature increased the number of flower plant-1 but the reverse was true in case of pod. Increased temperature under delayed sowing significantly reduced the pod number plant-1. A temperature range of 27 to 32°C was found to be congenial for the reproductive development in mungbean. [ABSTRACT FROM AUTHOR]

In this article, the eigenvalues for the three-body interactions on the line and the Landau levels in the presence of topological defects have been regenerated by the Nikiforov-Uvarov (NU) method. Two exhaustive lists of such exactly solvable potentials are given. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports the influence of local thermal non-equilibrium state between solid porous matrix and saturated fluid on natural convection in enclosure. The two dimensional steady flow is induced by constant heat flux on side walls of the enclosure, when both horizontal walls are insulated. The governing equations are solved numerically by ADI method and analytically by using parallel flow assumption valid for slender enclosure. A comparative study has been made between convection in square cavity and the same in slender enclosure. Numerical experiments indicate that in comparison with square cavity, where a sharp decrease of local heat transfer rate for fluid (Nu f ) takes place up to a certain small value of interface heat transfer coefficient (H), in slender enclosure a smooth decrease of Nu f has been observed in the entire range of H when conductivity ratio (γ) is very small. However, for relatively high values of γ (e.g., γ =10), Nu f is almost independent of H in both geometries. For a given γ, when the value of H is relatively very high, up to a certain value of Ra the difference between both solid as well as fluid temperature rates is negligible. Corresponding temperature contours of two phases becomes almost identical in magnitude as well as patterns point of view, which indicates that equilibrium state between two phases is achieved. Finally, in equilibrium state maximum heat transfer rate used to take place at a certain value (A o ) of aspect ratio, lying in between 1 and 1.5, and is almost independent of all equilibrium parameters. In case of non-equilibrium state, A o acts as an increasing function of γ. [Copyright &y& Elsevier]

In this work, an alternative treatment known as Nikiforov-Uvarov (NU) method is proposed to find the exact solutions of the Feinberg-Horodecki equation for the time-dependent potentials. The present procedure is illustrated with two examples: (1) time-dependent Wei Hua oscillator, (2) time-dependent Manning-Rosen potential. [ABSTRACT FROM AUTHOR]

Abstract: In this article, double-diffusive mixed convection in a vertical pipe under local thermal non-equilibrium state has been investigated. The non-Darcy Brinkman–Forchheimer-extended model has been used and solved numerically by spectral collocation method. Special attention is given to understand the effect of buoyancy ratio (N) and thermal non-equilibrium parameters: inter phase heat transfer coefficient (H) as well as porosity scaled thermal conductivity ratio (γ) on the flow profiles as well as on rates of heat and solute transfer. Judged from the influence of buoyancy ratio on velocity profile, when both the buoyancy forces: thermal as well as solutal are in favor of each other and for given any value of H considered in this study, it has been found that for N equal to 10 as well as 100, the basic velocity profile shows back flow for small subdomain of the domain of the flow. When two buoyancy forces are opposing to each other (Ra T =−1000), velocity profile possesses a kind of distortion, in which the number of zeroes increases on increasing N. Corresponding variation of heat transfer rate in the (N, Nu f )-plane shows a sinusoidal pattern. The flow separation on the flow profile dies out on increasing H for N =0. It has been also found that for each N, when N <0.7, there exists a minimum value of H such that the velocity profile becomes free from flow separation. Influence of H on the profiles of solid temperature as well as solute, in both situations are similar. Overall, the impact of LTNE parameters, specially γ, on heat transfer rate of double-diffusive convection is not straight forward. [Copyright &y& Elsevier]

Abstract: This paper addresses the influence of thermal non-equilibrium state on fully developed mixed convection in a vertical channel filled with porous medium. The non-Darcy-Brinkman-Forchheimer extended model has been considered. The governing equations are solved numerically by spectral collocation method and analytically for a special case (form drag equal to zero). The governing parameters for this problem are Rayleigh number (Ra), Darcy number (Da), Forchheimer number (F), inter-phase heat transfer coefficient (H), and porosity-scaled thermal conductivity ratio (γ). Special attention is given to understand the effect of thermal non-equilibrium parameters: H and γ on the rates of heat transfer and fluid flow profiles, for both buoyancy assisted as well as opposed cases. A comprehensive investigation indicates that, in case of buoyancy assisted flow, for each Ra considered in this study and when γ ≤ 1, there exists a minimum value Ho of H such that the heat transfer rate of fluid (Nuf ) at the wall is an increasing function in [0, Ho ]. Furthermore, as H is varied beyond Ho , Nuf decreases. Initially the decay of Nuf is fast, but later on it becomes smooth and slow. Similar results are also observed in buoyancy opposed case for very small values of γ. Variation of velocity profile as a function of γ indicates that change in velocity profile is sudden and abrupt. For H > 6, when γ = 0.01, Da = 10−2, |Ra| = 103 and F = 102, flow separation and point of inflection are completely died out from the profile. Overall, for both the cases, on increasing H makes the flow profile smooth (stabilizes the flow) and recovers the system equivalent to equilibrium state, whereas, γ destabilizes the flow by inviting point of inflection or flow separation on the velocity profile. [Copyright &y& Elsevier]

Abstract: In this paper, natural convective flow within a rectangular enclosure has been investigated numerically. All the walls of the enclosure are adiabatic except the bottom wall, which is partially heated and cooled by sinusoidal temperature profile. Both situations: medium is hydro-dynamically isotropic and anisotropic are considered. The governing equations are written under assumption of Brinkman-extended non-Darcy model, including material derivative, and then solved by numerically using spectral element method (SEM). Main emphasize is given on effect of periodicity parameter (N) on local heat transfer rate (Nu x ) as well as flow mechanism in the enclosure. The result shows that, as the periodicity is decreased on increasing N, the absolute value of Nu x at the bottom left corner point increases in both situations. For odd values of N, the local heat transfer profile is symmetric about the line X =0.5. The entire flow is governed by two type convective cells: (i) rotating clockwise (ii) rotating anticlockwise. Furthermore, increasing of N increases the multiple cellular structures in the form of N +1. The relative impact of media permeability on Nu x at (0,0) shows that enhancement of media permeability along Y-direction is much more effective than the same along X-direction. In contrast to isotropic porous media, the effect of the permeability and permeability orientation angle on the flow is complex and often non intuitive. In particular the present analysis shows that, different periodicity of temperature boundary condition has significant effect on the flow mechanism and consequently on the heat transfer rate for both situations. [Copyright &y& Elsevier]

The exact solutions for the two- and N-dimensional Schrödinger equation have been rederived for the potential V( r) = αr − βr by Nikiforov-Uvarov method. Specific results are presented for (i) the hydrogen atom and (ii) an isotropic harmonic oscillator. The dimensionality of the problem is seen to enter into these relations in such a way that one can immediately verify the corresponding three-dimensional results. The local accidental degeneracies are also explained for the two- and N-dimensional problems. [ABSTRACT FROM AUTHOR]

Abstract: Two catalysts combining Cu–Ni with CeO2 and Gd-doped CeO2, respectively, are comparatively examined with respect to redox and catalytic properties towards interaction with CH4. For this, catalysts in oxidised starting states are explored by means of CH4-TPR tests up to 973K. Characterization of initial and final states of the catalysts is accomplished by means of XRD, Raman spectroscopy and EXAFS while carbon deposits formed during interaction with CH4 are examined by TPO, Raman spectroscopy and SEM–EDX. Oxygen handling characteristics of the catalysts are examined by means of oxygen isotopic exchange experiments. In turn, redox changes produced during the course of CH4-TPR tests are explored by operando-XANES. Methane oxidation or decomposition processes are observed as a function of redox state of the catalysts and sites involved in each of the processes are identified on the basis of the multitechnique approach employed. [Copyright &y& Elsevier]

The approximate analytical bound-state solutions of the Schrödinger equation for the Wei Hua oscillator are carried out in N-dimensional space by taking Pekeris approximation scheme to the orbital centrifugal term. Solutions of the corresponding hyper-radial equation are obtained using the conventional Nikiforov-Uvarov (NU) method. [ABSTRACT FROM AUTHOR]

Abstract: In many natural environments, such as in underwater hot springs and hydrothermal vents, thermal gradients are accompanied with changes in the concentration of chemical compounds transported to the seawater, causing the so-called double-diffusive, mixed convection. To study the physical scenarios in such systems, a vertical channel filled with a porous medium saturated with saline water is considered. The motion in the sediment-filled channel is induced by two buoyancy forces and an external pressure gradient, similar to the situation in a vent with an upward flow direction. The fluid flow has been modeled by an extended Darcy model, and the flow instability mechanisms have been studied numerically. The linear stability analysis is performed considering a wide range of Darcy number (Da=10−5 –10−8). The instability boundary curve showed three distinct dynamic regimes: (i) Rayleigh–Taylor (R–T), (ii) log–log non-linear variation, and (iii) log–log linear variation. The domain of different regimes were sensitive to external pressure gradient as well as permeability. Similar to cross-diffusive natural convection in pure viscous fluids, a linear relationship between logarithmic absolute values of critical thermal Rayleigh number (∣Ra T ∣) and solute Rayleigh number (Ra C ) is found in the third regime. Based on the permeability, for any solute Rayleigh number (Ra C ), there existed a minimum value of Reynolds number (Re), below which R–T type of instability appeared. Above this minimum value, the instability was due to two buoyancy forces, known as buoyant instability. Simulations of secondary flow via energy analysis demonstrated the development of complex dynamics at the critical state in all three regimes characterized by transition of multi to uni-cellular structures and vice verse. [Copyright &y& Elsevier]

Abstract: The present paper reports an analytical as well as numerical investigation of fully developed mixed convective flow in a vertical pipe filled with porous medium. The motion in the pipe is induced by external pressure gradient and buoyancy force. The non-Darcy Brinkman–Forchheimer-extended model has been considered. The Chebyshev spectral-collocation method has been used to solve the coupled differential equations numerically. A comprehensive investigation on the dependency of mixed convective flow on governing parameters indicates that depending on the values of other parameters the velocity profile possess point of inflection beyond a threshold value of Rayleigh number (Ra). In the case of buoyancy-opposed flow, the velocity profile may contain point of inflection in the center zone and point of separation at the vicinity of the wall. The appearance of point of separation causes the back flow near the wall. In contrast to buoyancy-opposed case, where enhancement of Ra increases the magnitude of the center velocity as well as temperature till the distortion appears on both profiles, in buoyancy-assisted case both velocity as well as temperature decrease on increasing Ra at the center. The points of separation as well as inflection die out on reducing the media permeability or increasing magnitude of the form drag coefficient. Further, it was observed that for buoyancy-opposed flow the velocity as well as temperature profiles have a kind of distortion beyond a threshold value of Ra, which is also a function of other governing parameters. In this situation, the heat transfer rate varies abruptly as a function of Ra. [Copyright &y& Elsevier]

n approximation method based on the iterative technique is developed within the framework of linear delta expansion (LDE) technique for the eigenvalues and eigenfunctions of the one-dimensional and three-dimensional realistic physical problems. This technique allows us to obtain the coefficient in the perturbation series for the eigenfunctions and the eigenvalues directly by knowing the eigenfunctions and the eigenvalues of the unperturbed problems in quantum mechanics. Examples are presented to support this. Hence, the LDE technique can be used for nonperturbative as well as perturbative systems to find approximate solutions of eigenvalue problems. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we report the influence of different terms appearing in the momentum equation on the stability of buoyancy-assisted mixed convection in a vertical channel filled with a porous medium. Four different models: (i) Darcy–Brinkman (DB), (ii) Darcy–Brinkman–Forchheimer (DBF), (iii) Darcy–Brinkman–Wooding (DBW), and (iv) Darcy–Brinkman–Forchheimer–Wooding (DBFW) are considered and a comparative study is made based on a linear stability analysis. We consider a Prandtl number range of Pr=0.1–10, which corresponds to water and gases. Judged from the instability boundary curves, it is found that with reduction of Darcy number there exists an equivalence of DB with DBF model from one side, and an equivalence of DBW with DBFW model from the other side. When the medium is a gas, a significant difference between DB and DBW (or DBF and DBFW) is visible, which is not the case for water. Furthermore, it is found that in case of a gas, inertia force destabilizes the flow, whereas, form drag stabilizes it. In contrast to a fluid-filled channel (where inertia term always destabilizes the buoyancy-assisted flow), here this destabilizing property might turn into a stabilizing one when fluid viscosity and permeability of the medium are changed. In the case of water, for Da=10−2, the inertia term stabilizes the flow beyond Re=25. When Da is reduced by one order of magnitude, the destabilizing effect continued up to Re=220. The combined effect of form drag (Forchheimer term) and inertia (Wooding term) on the stability of the flow is more intensive than their individual effects provided the medium is highly permeable. In most cases studied here, the disturbance flow patterns are similar for DB and DBF from one side, and DBW and DBFW from the other side. [ABSTRACT FROM AUTHOR]

Abstract: Non-Darcy mixed convective flow of water due to external pressure gradient and buoyancy opposed forces are considered in a vertical channel filled with porous medium, which can be either isotropic or anisotropic. The linear theory of stability analysis has been used to numerically investigate the dependence of the transition behavior of the fully developed basic flow on the permeability of the medium. Numerical experiments indicate that mainly two main instability modes appear: Rayleigh–Taylor (R–T) and buoyant instability. For Darcy numbers (Da) ⩽10−9, R–T instability dominates within the entire Reynolds number (Re) range considered here. It was also found that for the same Re, the fully developed base flow is highly unstable (stable) for porous media with high (low) permeability. Further, it was seen that the disturbance isotherm cells migrate from the channel walls toward the centerline when permeability is reduced. Reducing the permeability by one order of magnitude (corresponding to a decrease of Darcy number from 10−6 to 10−7) increases base flow stability approximately 20-fold. For higher Reynolds numbers, buoyant, mixed and shear instability of the basic flow were found when Da was increased from 10−7 to 10−3. However, for cases in which permeability and porosity behaved as suggested by Carman–Kozeny relation (CKR), buoyant stability was the only mode of instability. Critical values of the Rayleigh (Ra) and Darcy (Da) numbers in the R–T mode of instability were related to each other by the hyperbolic function RaDa =−2.465. [Copyright &y& Elsevier]

A unified approach in the light of supersymmetric quantum mechanics (SSQM) has been suggested for generating multidimensional quasi-exactly solvable (QES) potentials. This method provides a convenient means to construct isospectral potentials of derived potentials. [ABSTRACT FROM AUTHOR]

The linear delta expansion technique has been developed for solving the differential equation of motion for symmetric and asymmetric anharmonic oscillators. We have also demonstrated the sophistication and simplicity of this new perturbation technique. [ABSTRACT FROM AUTHOR]

Buoyancy opposed mixed convection is considered in a vertical channel filled with an isotropic, porous medium, in which the motion of an incompressible fluid is induced by external pressure gradients and buoyancy forces. The Brinkman-Wooding-extended Darcy model has been used to study the instability mechanisms of the basic flow and its dependence on the Prandtl number (Pr) of the fluid. The stability analysis indicated that for the same Reynolds number (Re), the fully developed base flow was highly unstable for a fluid with high Pr. For a porous medium with a Darcy number (Da) of 10-6 and Pr>=0.7, two different types of instability, Rayleigh-Taylor (R-T) and buoyant instability, are observed. The R-T instability mode is observed for relatively small values of Re. Further, the results show that for Da=10-5 and Pr<1, the spectrum of the energy profile is abrupt and sudden, whereas the same is smooth when Da=10-6. In the case of R-T instability, the critical value of Ra at low Re is given by -2.47/Da. Though the R-T mode of instability is independent of Pr, the range of Re that sustains the R-T mode is a function of Pr. It has been found that enhancement of Pr reduces the Re range mentioned above. In contrast to the case of a purely viscous fluid, where the effect of Pr is not significant, in isotropic porous media Pr plays a significant role in characterizing the flow stability. The instability characteristics of zero temperature flux perturbation (BC-I) and zero heat flux perturbation (BC-II) on the boundaries differ significantly in the case of the R-T stability mode. However, both conditions lead to similar results for buoyant stability, except at small values of Re. [ABSTRACT FROM AUTHOR]

The supersymmetric quantization condition is used to study the wave functions of SWKB equivalent q-deformed harmonic oscillator which are obtained by using only the knowledge of bound-state spectra of q-deformed harmonic oscillator. We have also studied the nonuniqueness of the obtained interactions by this spectral inverse method. [ABSTRACT FROM AUTHOR]

This paper addresses the stability of mixed convective buoyancy assisted flow due to external pressure gradient and buoyancy force in a vertical fluid saturated porous channel with linearly varying wall temperature. The porous medium is assumed to be both hydrodynamically and thermally anisotropic. Two different types of temperature perturbations, (i) zero temperature and (ii) zero heat flux, have been considered to study the effect of anisotropic permeability and thermal diffusivity on the flow stability. The stability analysis indicated that the least stable mode is two-dimensional. Furthermore, the results show that for the same Reynolds number, the fully developed base flow is highly unstable (stable) for high (low) permeable porous media as well as for a porous medium with small (large) thermal diffusivity ratio. Depending on the magnitude of all parameters studied, three types of instabilities (shear, thermal, and mixed instability) occurred. The transition of instability from one type to another took place smoothly, except when the permeability ratio exceeded 6. Based on the value of the permeability ratio, the flow in an anisotropic medium for a specific Reynolds number may be either more or less stable than the flow in an isotropic medium. In addition, the fully developed flow is more stable for relatively small values of the modified Darcy number than for larger values. The effect of Brinkman as well as Forchheimer terms are negligible for the set of other parameters studied here. In contrast to a pure viscous fluid or an isotropic porous medium, which are characterized by unicellular convective cells, in anisotropic porous media convective cells may be unicellular or bicellular. The stability analysis of mixed convection in channels filled either with a viscous fluid or with an isotropic saturated porous medium may be obtained as special cases of the general study presented here. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Focuses on the numerical analysis of heat and mass transfer in an anisotropic porous enclosure. Direction of the permeability tensor; Effects of permeability orientation angle on the flow rate of heat and mass transfer; Estimation of buoyancy ratio.

By dealing with a new integral representation for the irregular s-wave Coulomb function, exact analytical expressions for the corresponding Jost states in momentum space are constructed, and their usefulness in studying the Coulomb half-shell scattering is demonstrated. A supersymmetry-inspired ladder-operator relation is employed to derive higher partial-wave generalization of the results presented. Some applications of the integral representation for the associated regular solution are also sought. [ABSTRACT FROM AUTHOR]

• Linear stability analysis of stably stratified annular Poiseuille flow is carried out for a wide range of curvature parameter and the Prandtl number. • Instability of the pipe flow with a thin rod placed at the center even for a very small value of heat source intensity has been found. • Three types of instability have been observed through kinetic energy analysis. • For a large value of curvature parameter, the least stable azimuthal number may vary as large as 40. The stability of non-isothermal Poiseuille flow in a coaxial annular domain is studied using normal mode analysis. The stably stratified flow (i.e., when buoyant force is in the direction of forced flow) is induced due to external pressure gradient and maintenance of linear variation of the temperature of the inner cylinder. We have emphasized the impact of the gap between cylinders in terms of curvature parameter (C) and Prandtl number (Pr) on the instability of the flow under axisymmetric as well as non-axisymmetric disturbances. In general, it has been found that the flow of low Pr fluids under axisymmetric disturbance is more stable in comparison with the flow under non-axisymmetric disturbance. When the gap between cylinders is relatively small (i.e. C is large), the flow under non-axisymmetric is most stable for the fluids having high Pr. It is known that the Newtonian pipe flow is linearly stable for all values of Reynolds number (Re). However, in the present study, we have seen the instability of the pipe flow with a thin rod placed at the center even for a very small value of heat source intensity (in terms of Rayleigh number) at R e = 2000. Here the disturbance velocity is concentrated in the vicinity of the inner wall and instability is due to transfer of kinetic energy from the basic flow through Reynold's stress. Depending on the value of controlling parameters, three types of instability: thermal-shear, interactive, thermal-buoyant have been observed. In general, for a fixed value of Pr , the type of instability is not affected by C and Re. The non-isothermal Poiseuille flow of low Pr (including mercury and gases) is governed by thermal-shear instability and the same of high Pr (including liquid and oil) is governed by thermal-buoyant instability. [ABSTRACT FROM AUTHOR]

This paper reports the instability mechanism of parallel mixed convection flow in a differentially heated vertical channel filled with a highly permeable porous medium. Linear and weakly nonlinear stability analysis involving the finite-amplitude expansion method is considered to investigate the instability mechanism of the flow. Darcy–Brinkman's model is considered. The results are presented for both water-saturated and oil-saturated porous medium flows. The linear stability results show that the stability of the flow decreases on increasing the Reynolds number as well as the Darcy number, and the contribution of viscous dissipation in the kinetic energy balance is not negligible for highly permeable porous medium flows. The results from the weakly nonlinear analysis show only supercritical bifurcation in the vicinity of the critical or bifurcation point for both the fluids; however, for water, the parallel flow may experience subcritical bifurcation away from the critical point, which depends on the value of the Darcy number. The variation of neutral stability curves of the parallel flow of water reveals that a bifurcation that is supercritical for some wavenumber may be subcritical at other nearby wavenumbers. The nonlinear interaction of different harmonics enhances the heat transfer rate as well as the friction coefficient in the linearly unstable regime. A comparison with the results using a model based on volume averaged Navier–Stokes equation reveals the possibility of subcritical bifurcation even in the vicinity of the critical point. [ABSTRACT FROM AUTHOR]

Single layer coatings of hafnium carbide were deposited on stainless steel, copper and silicon substrates by means of reactive sputtering. The deposition process was optimized for maximum solar absorptance by varying the process parameters. In the case of coated stainless steel substrates, we obtained a maximum solar absorptance of 0.925 along with a thermal emittance of 0.13. For coated copper substrates we obtained a maximum solar absorptance of 0.948 along with a thermal emittance of 0.03. Reflectance spectra of SS and Cu substrates coated at optimized parameters were measured in the wavelength range 250 nm to 20 µm. Detailed x-ray photoelectron spectroscopy (XPS) studies were carried out to investigate the chemical composition of the coatings. XPS analysis of coated samples showed that because of the tendency of HfC to oxidize, the coating had a surface consisting mostly of HfO 2 but the extent of oxidation reduced with depth and partially oxidized HfC was present on the subsurface layers of the coatings. Along with the absorbing nature of HfC and appropriate coating thickness, the high solar absorptance of the coating can be partially attributed to the presence of HfO 2 near the surface which acts similar to an antireflection layer. Assuming a two-layer model of the coating, an upper HfO 2 layer and a HfC layer underneath it, reflectance spectra of the coated samples were simulated using SCOUT software and compared to the experimentally obtained spectra. For all the samples, best fit values of coating thicknesses were in the range 120–130 nm. [ABSTRACT FROM AUTHOR]

A comprehensive numerical investigation on the natural convection in a hydrodynamically anisotropic porous enclosure is presented. The flow is due to nonuniformly heated bottom wall and maintenance of constant temperature at cold vertical walls along with adiabatic top wall. Brinkman-extended non-Darcy model, including material derivative, is considered. The principal direction of the permeability tensor has been taken oblique to the gravity vector. The spectral element method has been adopted to solve numerically the governing conservative equations of mass, momentum, and energy by using a stream-function vorticity formulation. Special attention is given to understand the effect of anisotropic parameters on the heat transfer rate as well as flow configurations. The numerical experiments show that in the case of isotropic porous enclosure, the maximum rates of bottom as well as side heat transfers (Nub and Nus) take place at the aspect ratio, A, of the enclosure equal to 1, which is, in general, not true in the case of anisotropic porous enclosures. The flow in the enclosure is governed by two different types of convective cells: rotating (i) clockwise and (ii) anticlockwise. Based on the value of media permeability as well as orientation angle, in the anisotropic case, one of the cells will dominate the other. In contrast to isotropic porous media, enhancement of flow convection in the anisotropic porous enclosure does not mean increasing the side heat transfer rate always. Furthermore, the results show that anisotropy causes significant changes in the bottom as well as side average Nusselt numbers. In particular, the present analysis shows that permeability orientation angle has a significant effect on the flow dynamics and temperature profile and consequently on the heat transfer rates. [ABSTRACT FROM AUTHOR]

A Co continuous finite element model is developed to model the refined higher order shear deformation theory. The proposed element is an upgraded version of an element based on higher order shear deformation theory. The Co continuity of the present element is compensated in the stiffness matrix calculations. The computational efficiency is achieved by the Co continuous finite element model by satisfying the inter-laminar shear stress continuity at the interfaces and zero transverse shear stress conditions at plate top and bottom. The performance of the upgraded element is illustrated with many numerical examples. [ABSTRACT FROM AUTHOR]

Abstract: The International Atomic Energy Agency (IAEA) and the World Health Organisation (WHO) operate the IAEA/WHO TLD postal dose audit programme. Thermoluminescence dosimeters (TLDs) are used as transfer devices in this programme. In the present work the uncertainties in the dose determination from TLD measurements have been evaluated. The analysis of uncertainties comprises uncertainties in the calibration coefficient of the TLD system and uncertainties in factors correcting for dose response non-linearity, fading of TL signal, energy response and influence of TLD holder. The individual uncertainties have been combined to estimate the total uncertainty in the dose evaluated from TLD measurements. The combined relative standard uncertainty in the dose determined from TLD measurements has been estimated to be 1.2% for irradiations with Co-60 -rays and 1.6% for irradiations with high-energy X-rays. Results from irradiations by the Bureau international des poids et mesures (BIPM), Primary Standard Dosimetry Laboratories (PSDLs) and Secondary Standards Dosimetry Laboratories (SSDLs) compare favourably with the estimated uncertainties, whereas TLD results of radiotherapy centres show higher standard deviations than those derived theoretically. [Copyright &y& Elsevier]

The article presents a study on the use of inverse configurations of copper oxide (CuO) and cerium oxides (CeO2) catalyst for preferential oxidation of carbon monoxide (CO-PROX) in hydrogen-rich stream. It mentions that inverse catalyst configurations can be used as an alternative to traditional direct configurations in the enhancement of catalytic properties. It reveals that CO conversion under CO-PROX conditions for the inverse catalyst shows the highest oxidation activity of CO.

Abstract: The present work analyses bimetallic Cu–Ni formulations, in comparison to monometallic Cu ones, combined with CeO2 or other structurally related mixed oxides resulting from doping of the former with Gd or Tb, focusing to its possible use as anodes of solid oxide fuel cells (SOFC) for direct oxidation of methane. The main objective is the characterization of the various formulations at structural level as well as with regards to the redox changes taking place in the systems upon interaction with methane, in order to evaluate the effects induced by the presence of dopants. In the same sense, an analysis of thermal expansion and electrical properties of the systems is performed, considering its possible implantation in SOFC single cells. For the mentioned purposes, the systems have been analysed by means of CH4-TPR tests subsequently followed by TPO tests, as well as by XRD, Raman and XPS, with the aim of exploring structural and redox changes produced in the systems and the formation of carbon deposits during such interactions. The results reveal significant modifications in the structural, catalytic/redox and electrical properties of the systems as a function of the presence of Ni and/or Gd and Tb dopants in the formulation. [Copyright &y& Elsevier]