Stefan blowing, navier slip and radiation effects on thermo-solutal convection from a spinning cone in an anisotropic porous medium

Thermal radiation features in many high temperature materials processing operations. To evaluate the influence of radiative flux on spin coating systems, we consider herein the thermo-solutal (coupled heat and mass transfer) in steady laminar boundary layer natural convection flow from a rotating permeable vertical cone to an anisotropic Darcian porous medium. Surface slip effects are also included in the model presented. The conservation equations are rendered into self-similar form and solved as an ordinary differential two-point boundary value problem with surface and free stream boundary conditions using MAPLE 17 software. The transport phenomena are observed to be controlled by ten parameters, viz primary and secondary Darcy numbers (Dax and Da), rotational (spin) parameter (NR), velocity slip parameter (a), suction/injection parameter (S), thermal slip parameter (b), mass slip parameter (c) buoyancy ratio parameter (N), and conduction-radiation parameter (Rc). Tangential velocity and temperature are observed to be enhanced with greater momentum slip whereas swirl velocity and concentration are reduced. Increasing swirl Darcy number strongly accelerates both the tangential and swirl flow and also heats the regime whereas it decreases concentrations. Conversely a rise in tangential Darcy number accelerates only the tangential flow and decelerates swirl flow, simultaneously depressing temperatures and concentrations. Increasing thermal slip accelerates the swirl flow and boosts concentration but serves to retard the tangential flow and decrease temperatures. With higher radiation contribution (lower Rc values) temperatures are elevated and concentrations are reduced. Verification of the MAPLE 17 solutions is achieved using a Keller-box finite difference method (KBM). A number of interesting features in the thermo-fluid and species diffusion characteristics are addressed. Key words: Stefan blowing; Spinning cone; MAPLE 17; Anisotropi

An adaptive preconditioner for steady incompressible flows

This paper describes an adaptive preconditioner for numerical continuation of incompressible Navier--Stokes flows. The preconditioner maps the identity (no preconditioner) to the Stokes preconditioner (preconditioning by Laplacian) through a continuous parameter and is built on a first order Euler time-discretization scheme. The preconditioner is tested onto two fluid configurations: three-dimensional doubly diffusive convection and a reduced model of shear flows. In the former case, Stokes preconditioning works but a mixed preconditioner is preferred. In the latter case, the system of equation is split and solved simultaneously using two different preconditioners, one of which is parameter dependent. Due to the nature of these applications, this preconditioner is expected to help a wide range of studies

A COMPARATIVE STUDY OF LAND TENURE, PROPERTY BOUNDARIES, AND DISPUTE RESOLUTION: EXAMPLES FROM BOLIVIA AND NORWAY

This paper compares and contrasts patterns of land tenure, property boundaries, and dispute resolution regarding property using examples from two diverse social and economic regions: Bolivia and Norway. The goal of the paper is essentially a comparative one. By placing the examples of Bolivia and Norway side by side, the authors hope to shed light on common strategies while recognizing the diversity to be found in the ways that people relate to land. It is hoped that readers will be able to compare the material here with examples from other regions. By using data based on field research and related methods from two regions starkly distinguished from each other by language, socioeconomic levels, political histories, and extent of integration into world markets, the authors present a picture of how people interact with their bounded environments and the various meanings that they construct through such environments. Norway has one of the highest standards of living in the world and is in many ways a model of economic and social efficiency; Bolivia, by contrast, is characterized by extreme ecological zones and has struggled for most of its 170 years of independence to both maintain its population at the most basic of levels and to achieve social stability. Yet, despite these significant historical and contemporary differences, the ways in which people relate to land in both countries are often remarkably similar, particularly in rural areas.Land tenure -- Bolivia, Land tenure -- Norway, Dispute resolution -- Bolivia, Dispute resolution -- Norway, Land conflicts -- Bolivia, Land conflicts -- Norway, Land Economics/Use,

The biology and behaviour of a free-living population of black rats (Rattus rattus)

A population of wild Rattus rattus living in the roofs of the laboratory buildings was studied by supplying food every evening and watching the behaviour of the animals at the feeding place. Some observations were also made on caged animals. The rats were predominantly of the black rattus variety but white-bellied greys appeared now and then. In breeding tests the grey colour behaved as though determined by a single recessive gene. The study covered two periods of approximately 9 months each, separated by an interval of 3 months during which a reduced quantity of food was provided and the rat population underwent a major decline. During the two periods of richer feeding the population first increased and then stabilized at a level where the animals remained in good condition and there was no starvation. In the first 9-month period, stabilization was achieved by emigration of young adults who colonized neighbouring buildings. Towards the end of the second period, stabilization was achieved by limitation of breeding. The rats accepted a wide variety of foods, including meat, and a number of instances of predation were seen. Small vertebrates as well as insects were killed and eaten. Small pieces of food were usually eaten in situ but large bits were taken up to the nests in the roof. Such differential treatment in relation to size may be a factor of some importance in the evolution of hoarding. The rats visiting the feeding place formed a unit with a definite social structure. A single dominant male and never more than one, was always present and in certain circumstances a linear male hierarchy was formed. There were usually two or three mutually tolerant top ranking females who were subordinate to the top male but dominant to all other members of the group. Within the group attacks were directed downwards in the social scale. An attacked subordinate either fled or appeased and serious fights therefore did not develop. The most essential component of the appease. ment appeared to be a mouth to mouth contact which may be derived from the infantile pattern of 'mouth suckling'. Appeasement permitted superior rats to maintain their status without the necessity of carrying attacks on subordinates to the point where actual hurt was inflicted. A group territory round the feeding place was defended against interlopers. Both sexes took part in chasing out intruders but since males showed inhibition in attacking females, the exclusion of strange females was due principally to the activities of the home females. The point at which pursuit of an intruder stopped was regarded as the territorial boundary. This was also the limit beyond which a group member would not allow himself to be chased but it was not a prison wall. When agonistic tendencies were not aroused the animals no longer always I turned back at the boundary and foraging beyond its limits allowed them to become familiar with an area larger than the territory. Although intruders were normally driven out, it was occasionally possible for a particularly determined animal of either sex to force its way in and ultimately become a member of the group. The patterns of behaviour seen are described, particularly those concerned with hostile encounters and with mating. Scent marking with urine drip trails was not seen but adults of both sexes marked by rubbing the cheeks and ventral surface on branches. The circumstances in which tooth gnashing was heard suggest that this behaviour is not a form of threat but a response to unfamiliar auditory or visual stimuli. There was some evidence that it functioned as an alarm signal within the group. Pilo-erection and a gait or posture with the hind legs much extended ('stegosauring') are considered to function as threats. Pilo-erection occurred in situations where there was little to suggest conflict and is considered to represent a form of threat which has undergone emancipation. Various forms of displacement and ambivalent behaviour were seen. Rapid vibration of the tail occurred in thwarting situations, either during mating or when a defeated opponent suddenly vanished. There was no evidence that it acted as a signal. The common form of amicable behaviour was social grooming. Another amicable action was sitting together with the bodies in contact. Animals reared in cages remained shy and wary and even hand reared young developed the usual alarm responses to movement and noises. Females had their first litters at ages of 3 to 5 months. For first litters gestation periods were 21 to 22 days but in females that were simultaneously lactating they ranged from 23 to 29 days. Eight was the commonest litter number and ten the highest recorded. At birth the tail is very much shorter than the body but has outstripped it by the time the youngster emerges from the nest. This was found to be the result of a period of extremely rapid tail growth immediately preceding emergence. In Rattus norvegicus the peak in tail growth rate was found to be later and less striking. The difference is interpreted as related to the importance of the tail in climbing in the more arboreal R. rattus. During the second week of life an edge response (retreat from a declivity) and a clinging response made their appearance: these have the function of preventing accidental falls from a nest situated above ground level. Mouth suckling was seen only during a period of a few days towards the end of lactation. Play developed within a few days of emergence from the nest: locomotor and fighting play were the common types. Older animals occasionally joined in play with the young. In problem solving tests, first solutions were not insightful but once a solution had been found, the successful technique was at once adopted and subsequently perfected. There was no evidence of learning by imitation but the rats did learn from each other's behaviour that food could be obtained at a certain location and thus the solution of a problem by one rat accelerated its independent solution by others. The reasons for the differences between the behaviour of the free living population and the caged animals studied by other authors are discussed

Stabilized finite element methods for natural and forced convection-radiation heat transfer

Thermal radiation in forced and natural convection can be an important mode of heat transfer in high temperature chambers, such as industrial furnaces and boilers, even under non-soot conditions. Growing concern with high temperature processes has emphasized the need for an evaluation of the eect of radiative heat transfer. Nevertheless, the modelling of radiation is often neglected in combustion analysis, mainly because it involves tedious mathematics, which increase the computation time, and also because of the lack of detailed information on the optical properties of the participating media and surfaces. Ignoring radiative transfer may introduce signicant errors in the overall predictions. The most accurate procedures available for computing radiation transfer in furnaces are the Zonal and Monte Carlo methods. However, these methods are not widely applied in comprehensive combustion calculations due to their large computational time and storage requirements. Also, the equations of the radiation transfer are in non-dierential form, a signicant inconvenience when solved in conjunction with the dierential equations of ow and combustion. For this reason, numerous investigations are currently being carried out worldwide to assess computationally ecient methods. In addition ecient modelling of forced and natural convection-radiation would help to simulate and understand heat transfer appearing in various engineering applications, especially in the case of the heat treatment of high-alloy steel or glass by a continuously heating process inside industrial furnaces, ovens or even smaller applications like microwaves. This thesis deals with the design of such methods and shows that a class of simplied approximations provides advantages that should be utilized in treating radiative transfer problems with or without ow convection. Much of the current work on modelling energy transport in high-temperature gas furnaces or chemically reacting ows, uses computational uid dynamics (CFD) codes. Therefore, the models for solving the radiative transfer equations must be compatible with the numerical methods employed to solve the transport equations. The Zonal and Monte Carlo methods for solving the radiative transfer problem are incompatible with the mathematical formulations used in CFD codes, and require prohibitive computational times for spatial resolution desired. The main objectives of this thesis is then to understand and better model the heat treatment at the same time in the furnace/oven chamber and within the workpieces under specied furnace geometry, thermal schedule, parts loading design, initial operation conditions, and performance requirements. Nowadays, there is a strong need either for appropriate fast and accurate algorithms for the mixed and natural convection-radiation or for reduced models which still incorporate its main radiative transfer physics. During the last decade, a lot of research was focused on the derivation of approximate models allowing for an accurate description of the important physical phenomena at reasonable numerical costs. Hence, a whole hierarchy of approximative equations is available, ranging from half-space moment approximations over full-space moment systems to the diusion-type simplied PN approximations. The latter were developed and extensively tested for various radiative transfer problems, where they proved to be suciently accurate. Although they were derived in the asymptotic regime for a large optical thickness of the material, these approximations yield encouraging even results in the optically thin regime. The main advantage of considering simplied PN approximations is the fact that the integro-dierential radiative transfer equation is transformed into a set of elliptic equations independent of the angular direction which are easy to solve. The simplied PN models are proposed in this thesis for modelling radiative heat transfer for both forced and natural convection-radiation applications. There exists a variety of computational methods available in the literature for solving coupled convection-radiation problems. For instance, applied to convection-dominated ows, Eulerian methods incorporate some upstream weighting in their formulations to stabilize the numerical procedure. The most popular Eulerian methods, in nite element framework, are the streamline upwind Petrov-Galerkin, Galerkin/least-squares and Taylor-Galerkin methods. All these Eulerian methods are easy to formulate and implement. However, time truncation errors dominate their solutions and are subjected to Courant-Friedrichs-Lewy (CFL) stability conditions, which put a restriction on the size of time steps taken in numerical simulations. Galerkin-characteristic methods (also known by semi-Lagrangian methods in meteorological community) on the other hand, make use of the transport nature of the governing equations. The idea in these methods is to rewrite the governing equations in term of Lagrangian co-ordinates as dened by the particle trajectories (or characteristics) associated with the problem. Then, the Lagrangian total derivative is approximated, thanks to a divided dierence operator. The Lagrangian treatment in these methods greatly reduces the time truncation errors in the Eulerian methods. In addition, these methods are known to be unconditionally stable, independent of the diusion coecient, and optimally accurate at least when the inner products in the Galerkin procedure are calculated exactly. In Galerkin-characteristic methods, the time derivative and the advection term are combined as a directional derivative along the characteristics, leading to a characteristic time-stepping procedure. Consequently, the Galerkin-characteristic methods symmetrize and stabilize the governing equations, allow for large time steps in a simulation without loss of accuracy, and eliminate the excessive numerical dispersion and grid orientation eects present in many upwind methods. This class of numerical methods have been implemented in this thesis to solve the developed models for mixed and natural convection-radiation applications. Extensive validations for the numerical simulations have been carried out and full comparisons with other published numerical results (obtained using commercial softwares) and experimental results are illustrated for natural and forced radiative heat transfer. The obtained convectionradiation results have been studied under the eect of dierent heat transfer characteristics to improve the existing applications and to help in the furnace designs

Access to common property resource and poverty reduction: inland open-water fisheries in Bangladesh

In Bangladesh, experiences from good practices for a Common Property Resources (CPR) identified that it is necessary to choose CPR members from the resource users with clearly defined rights to use the resource with defined physical boundary. The long-term security of tenure is a precondition for establishment of common property resources in the water bodies by the users (mainly fishers and adjoining agriculturists of the water body) themselves. The sustainability of such CPRs depends on the equity in sharing expenses and income; monitoring by the users themselves; graduated sanctions for violations of CPR rules; and development of local forums for resolving conflicts.Resource management

Numerical study of heat source/sink effects on dissipative magnetic nanofluid flow from a non-linear inclined stretching/shrinking sheet

This paper numerically investigates radiative magnetohydrodynamic mixed convection boundary layer flow of nanofluids over a nonlinear inclined stretching/shrinking sheet in the presence of heat source/sink and viscous dissipation. The Rosseland approximation is adopted for thermal radiation effects and the Maxwell-Garnetts and Brinkman models are used for the effective thermal conductivity and dynamic viscosity of the nanofluids respectively. The governing coupled nonlinear momentum and thermal boundary layer equations are rendered into a system of ordinary differential equations via local similarity transformations with appropriate boundary conditions. The non-dimensional, nonlinear, well-posed boundary value problem is then solved with the Keller box implicit finite difference scheme. The emerging thermo-physical dimensionless parameters governing the flow are the magnetic field parameter, volume fraction parameter, power-law stretching parameter, Richardson number, suction/injection parameter, Eckert number and heat source/sink parameter. A detailed study of the influence of these parameters on velocity and temperature distributions is conducted. Additionally the evolution of skin friction coefficient and Nusselt number values with selected parameters is presented. Verification of numerical solutions is achieved via benchmarking with some limiting cases documented in previously reported results, and generally very good correlation is demonstrated. This investigation is relevant to fabrication of magnetic nanomaterials and high temperature treatment of magnetic nano-polymers

Determination of physical and chemical states of lubricants in concentrated contacts, part 3

Solid and liquid thin films were analyzed by infrared emission Fourier microspectrophotometry. The apparatus used is a commercial absorption instrument modified to an emission instrument, comprising a rotating polarizing device, a miniature blackbody temperature reference adjustable in temperature and radiant flux and a microscope lens with a high numerical aperture in the entrance system for increased sensitivity and resolution. Studies of lubricant behavior in a simulated ball bearing showed the alignment of the fluid molecules in the Hertzian area. Polyphenyl ether plus 1% 1,1,2-trichloroethane (TCE) required lower shear rates for the same degree of alignment than without TCE. The experiment was run with 440 C stainless steel balls coated with TiN, a chemically inert material. In both cases, the alignment was strongly influenced by the presence of TCE. The results showed (1) the dependence of alignment of fluid molecules on flow and not on adsorption at metallic surfaces, (2) phase separation between lubricant and additive under high pressure which results in two phase flow and (3) reduction in traction of torque transmitting (traction) fluids