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Natural convection in a porous layer between two horizontal, concentric cylinders is investigated numerically by solving the 2‐D Darcy‐Boussinesq equations on a very fine grid. The parabolic‐elliptic system was solved by a second order finite difference scheme based on the implicit alternating direction method coupled with successive under relaxation. The calculations show that for radius ratios above 1.7, the functional relationship between the mean Nusselt number and the Rayleigh number exhibits a closed hysteresis loop associated with the transition from a two to a four cell flow pattern. For very small radius ratios, steady state regimes containing 2, 4, 6, and 8 cells are progressively obtained as the Rayleigh number is increased, but no hysteresis behaviour is observed. For a radius ratio of 2, the numerical results are in good agreement with the experimental data. Multi‐cellular regimes and hysteresis loops have also been reported in the literature for fluid annuli but some differences between the two cases exist and are fully explained below.

A finite difference solution for steady natural convective flow within the human eye, modelled as a sphere with a specified temperature distribution over its surface, has been obtained. The stream function—vorticity formulation of the equations of motion for the unsteady axisymmetric flow is used; interest lying in the final steady solution. Forward differences are used for the time derivatives and second‐order central differences for the space derivatives. The alternating direction implicit method is used for solution of the discretization equations. Local one‐dimensional grid adaptation is used to resolve the steep gradients in some regions of the flow at large Rayleigh numbers. The break‐up into multi‐cellular flow is found at high Rayleigh numbers. Results identify regions of stagnant fluid in locations similar to those of blind spots in the eye.

It is well known that the mixed convection process is the combined effect of the presence of both the forced and the free convection processes. In several applications such as environmental chambers, IC engines, etc. the forced convection is brought in by multiple suction/injection (S/I) effect. Study of mixed convection in a vertical square fluid saturated porous cavity with multiple S/I effect greatly contributes to such an understanding. So far, not much research work has reported in this direction. Hence, the purpose of this paper is to investigate such a mixed convection process in a fluid saturated vertical porous square cavity.

In this study, the authors numerically solved the couple partial differential equations governing the mixed convection process in a fluid saturated vertical square porous cavity by finite element method. The study is parametric in nature wherein the authors cover a large range of values for different parameters arising the mathematical model governing the problem under consideration.

The influence of multiple S/I effects on mixed convection is analyzed for a wide range of controlling parameters such as S/I flow velocities (a), S/I window size (D/H) and Rayleigh number (Ra). Both the flow and temperature fields are highly sensitive to magnitude of S/I velocity, S/I window slit size and “Ra”. While heat fluxes along the isothermal left vertical wall decrease with increasing S/I velocities they are formed to increase with increasing “(D/H)” and “Ra”. Nusselt numbers increase with increasing “Ra” and increasing size of S/I window slit size. Multi‐cellular circulation pattern and thermal boundary layers are seen to manifest in flow and temperature fields, respectively.

The study is based on 2D model, but the model is generic in nature; also it is fully numerical in nature. Due to lack of apt literature no experimental support is provided. The mathematical model used in the study is based on certain assumptions such as isotropic porous medium, fluid is viscous in nature and follows Newtonian laws and the porous structure is saturated with fluid, etc. Regarding future work, 3D modelling and simulation is in progress and attempts are also being made to collaborate with experimental groups on the problem under investigation.

The results from the work are relevant to the context of heat and fluid flow studies in IC engines, influence of mixed convection process on bacterial growth process in environmental chambers and cooling of electronic devices, etc.

The paper describes a mathematical model, especially the boundary treatment, for describing the influence of multiple S/I effects on mixed convection flow in a vertical square enclosure filled with a Darcian fluid saturated homogeneous porous medium. To understand the physics behind the mixed convection process in the proposed configuration, extensive numerical simulations have been carried out for the first time for different values of the important governing parameters arising from the model.

The purpose of this paper is to examine the association between information and boundaries. Life depends on boundaries; but in order to survive an organism needs to make decisions based on an interpretation of the environment beyond its boundaries: it therefore needs information.

The paper explores the evolution of physical, social and cultural boundaries and considers how they have shaped ways in which information is gathered and used.

Several evolutionary developments are reviewed. The paper argues that each one has generated an additional boundary and that each new boundary has affected the information needs within it. The paper argues that all living things use information to help address three fundamental concerns: “Where can the energy needed to stay alive be found?”, “How can it be stored?”, and “How can use of energy be reduced?” Because these questions are fundamental at a biological level they are also fundamental at a societal level. One way to increase energy efficiency was for organisms to grow larger. This brought risks which were alleviated by the evolution of better information gathering and processing tools. Amongst these tools were the means to communicate, which afforded the evolution of social boundaries.

This is a new perspective on a topic of growing interest in information science and demonstrates further the significance of information as a factor in the shaping of life.

This paper aims to reconceptualise the literature on learning organisations, fourth blueprint management and entrepreneurialism to develop the idea of a global learning network.

This notion is used to highlight successful leadership and management practices used by a transnational organisation to respond to change in a way that fosters entrepreneurial action.

The author has identified al‐Qaeda as a pertinent and timely example through which to examine this new perspective because of its unique culture and enabling structure that encourage members to act as both “environmental scanners” and agents of influence in affecting change.

The al‐Qaeda case study illustrates how the four elements of metastrategic design – namely: vision, identity, configuration, and action – can operate to sustain organisational learning and renewal for more conventional transnational organisations.

Presents a numerical study on heat transfer by natural convection in porous media in vertical enclosures with side wall heating. The model for porous media includes inertia terms and also the Brinkman extension in addition to the Darcy resistance term. A semi‐implicit finite element scheme based on operator splitting method is adopted for solving the time‐dependent system of equations. The first half of the investigations is confined to the low permeability regime where Darcy law holds good. Presents the results for annular and rectangular cavities and proposes correlations for two types of boundary conditions, namely constant wall temperature case and uniform wall heat flux case. In the second half of the investigations, the scheme is applied in a high permeability regime, where the validity of Darcy law becomes questionable. Employs plane rectangular cavities with the two types of boundary conditions mentioned earlier. Highlights the influence of Rayleigh number (Ra) and Darcy number (Da) as separate parameters and proposes correlations for a square cavity for the first time in terms of Ra and Da as separate parameters. Discusses a qualitative study of the effect of aspect ratio on heat transfer as the permeability changes.

A numerical simulation has been carried out to investigate the buoyancy induced flow and heat transfer characteristics inside a wavy walled enclosure. The enclosure consists of two parallel wavy and two straight walls. The top and the bottom walls are wavy and kept isothermal. Two straight‐vertical sidewalls are considered adiabatic. Governing equations are discretized using the control volume based finite‐volume method with collocated variable arrangement. Simulation was carried out for a range of surface waviness ratios, λ=0.00‐0.25; aspect ratios, A=0.25‐0.5; and Rayleigh numbers Ra=10⁰‐10⁷ for a fluid having Prandtl number equal to 1.0. Results are presented in the form of local and global Nusselt number distributions, streamlines, and isothermal lines for different values of surface waviness and aspect ratios. For a special case of λ=0 and A=1.0, the average Nusselt number distribution is compared with available reference. The results suggest that natural convection heat transfer is changed considerably when surface waviness changes and also depends on the aspect ratio of the domain. In addition to the heat transfer results, the heat transfer irreversibility in terms of Bejan number (Be) was measured. For a set of selected values of the parameters (λ, A, and Ra), a contour of the Bejan number is presented at the end of this paper.

Political economies evolve institutionally and technologically over time. This means that to understand evolutionary political economy one must understand the nature of the evolutionary process in its full complexity. From the time of Darwin and Spencer natural selection has been seen as the foundation of evolution. This view has remained even as views of how evolution operates more broadly have changed. An issue that some have viewed as an aspect of evolution that natural selection may not fully explain is that of emergence of higher order structures, with this aspect having been associated with the idea of emergence. In recent decades it has been argued that self-organization dynamics may explain such emergence, with this being argued to be constrained, if not overshadowed, by natural selection. Just as the balance between these aspects is debated within organic evolutionary theory, it also arises in the evolution of political economy, as between such examples of self-organizing emergence as the Mengerian analysis of the appearance of commodity money in primitive societies and the natural selection that operates in the competition between firms in markets.

Under this heading are published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Committee, Reports and Technical Notes of the U.S. National Advisory Committee for Aeronautics and publications of other similar research bodies as issued