Numerical Comparison of the Drag Models of Granular Flows Applied to the Fast Pyrolysis of Biomass

The paper presents a comparison between the different drag models for granular flows developed in the literature and the effect of each one of them on the fast pyrolysis of wood. The process takes place on an 100 g/h lab scale bubbling fluidized bed reactor located at Aston University. FLUENT 6.3 is used as the modeling framework of the fluidized bed hydrodynamics, while the fast pyrolysis of the discrete wood particles is incorporated as an external user defined function (UDF) hooked to FLUENT’s main code structure. Three different drag models for granular flows are compared, namely the Gidaspow, Syamlal O’Brien, and Wen-Yu, already incorporated in FLUENT’s main code, and their impact on particle trajectory, heat transfer, degradation rate, product yields, and char residence time is quantified. The Eulerian approach is used to model the bubbling behavior of the sand, which is treated as a continuum. Biomass reaction kinetics is modeled according to the literature using a two-stage, semiglobal model that takes into account secondary reactions.

Symmetry of coherent vortices in plane couette flow

A numerical continuation method is carried out in a homotopy space connecting two different flows, the Plane Couette Flow (PCF) and the Laterally Heated Flow in a vertical slot (LHF). This numerical continuation method enables us to obtain an exact steady solution in PCF. The new solution has the shape of hairpin vortices (HVS: hairpin vortex solution), which is observed ubiquitously in turbulent shear flows.

The development of a market orientation in a turbulent, transitional environment:the case of Ukraine

This research is concerned with the case of Ukraine where there has been a fundamental change in the economic environment engendered by the transition from a centrally planned to a market economy and the resulting conditions of economic crisis. The way that Ukrainian marketers and consumers are reacting to this environmental change is the principal concern of the research together with the basic linkages between critical environmental elements and strategic marketing decisions. This research analyses the way in which marketing evolves in a turbulent, transitional environment. The study is based on eight case analyses within the retail sector of the Ukrainian market. The process of transition to a free market economy leads a researcher to question the validity of existing theories that have been based on empirical data that has been collected in the stable marketing environment of the West. For this reason an in-depth, theory building methodology is preferred. A number of broad research objectives were set. Firstly, to establish whether the sales - production - marketing stages model of marketing evolution, derived from empirical data collected in stable Western environments, is relevant in the context of the turbulent, transitional environment of Ukraine. Secondly, to establish if, in this turbulent, transitional environment, idiosyncratic approaches to marketing are emerging and thirdly to assess the development of attitudes to marketing, organisation for marketing and the development of marketing strategy in Ukraine. The main conclusions of this thesis are firstly, that the stages model of marketing orientation is not relevant in the context of Ukraine, secondly that there are idiosyncratic approaches to marketing emerging in the turbulent, transitional environment of Ukraine and finally that the above developments have a profound impact on the development of attitudes to marketing, organisation for marketing and the development of marketing strategy in Ukraine.

Transition in convective flows heated internally

The stability of internally heated convective flows in a vertical channel under the influence of a pressure gradient and in the limit of small Prandtl number is examined numerically. In each of the cases studied the basic flow, which can have two inflection points, loses stability at the critical point identified by the corresponding linear analysis to two-dimensional states in a Hopf bifurcation. These marginal points determine the linear stability curve that identifies the minimum Grashof number (based on the strength of the homogeneous heat source), at which the two-dimensional periodic flow can bifurcate. The range of stability of the finite amplitude secondary flow is determined by its (linear) stability against three-dimensional infinitesimal disturbances. By first examining the behavior of the eigenvalues as functions of the Floquet parameters in the streamwise and spanwise directions we show that the secondary flow loses stability also in a Hopf bifurcation as the Grashof number increases, indicating that the tertiary flow is quasi-periodic. Secondly the Eckhaus marginal stability curve, that bounds the domain of stable transverse vortices towards smaller and larger wavenumbers, but does not cause a transition as the Grashof number increases, is also given for the cases studied in this work.

Transition in plane parallel shear flows heated internally

The stability of internally heated inclined plane parallel shear flows is examined numerically for the case of finite value of the Prandtl number, Pr. The transition in a vertical channel has already been studied for 0≤Pr≤100 with or without the application of an external pressure gradient, where the secondary flow takes the form of travelling waves (TWs) that are spanwise-independent (see works of Nagata and Generalis). In this work, in contrast to work already reported (J. Heat Trans. T. ASME 124 (2002) 635-642), we examine transition where the secondary flow takes the form of longitudinal rolls (LRs), which are independent of the steamwise direction, for Pr=7 and for a specific value of the angle of inclination of the fluid layer without the application of an external pressure gradient. We find possible bifurcation points of the secondary flow by performing a linear stability analysis that determines the neutral curve, where the basic flow, which can have two inflection points, loses stability. The linear stability of the secondary flow against three-dimensional perturbations is also examined numerically for the same value of the angle of inclination by employing Floquet theory. We identify possible bifurcation points for the tertiary flow and show that the bifurcation can be either monotone or oscillatory. © 2003 Académie des sciences. Published by Elsevier SAS. All rights reserved.

Social network theory and the sales manager role:engineering the right relationship flows

Sales leadership research has typically taken a leader-focused approach, investigating key questions from a top-down perspective. Yet considerable research outside sales has advocated a view of leadership that takes into account the fact that employees look beyond a single designated individual for leadership. In particular, the social networks of leaders have been a popular topic of investigation in the management literature, although coverage in the sales literature remains rare. The present paper conceptualizes the sales leadership role as one in which the leader must manage a network of simultaneous relationships; several types of sales manager relationships, such as the sales-manager-to-top-manager and the sales-manager-to-sales manager relationships, have received limited attention in the sales literature to date. Taking an approach based on social network theory, we develop a conceptualization of the sales manager as a "network engineer," who must manage multiple relationships, and the flows between them. Drawing from this model, we propose a detailed agenda for future sales research. © 2012 PSE National Educational Foundation. All rights reserved.

Technology flows, outsourcing and productivity:an analysis of UK trade and FDI

The literature on technology spillovers from trade and FDI is ambiguous in its findings. This may in part be because of the assumption in much of the work that trade and FDI flows are homogeneous in their determinants and thus in their effects. We develop a taxonomy of trade and FDI determinants based on R&D intensity and unit labour cost differentials, and test for the presence of spillovers from inward investment and imports on an extensive sample of UK manufacturing plants. We find that both trade and FDI have measurable spillover effects, but the sign and extent of these effects varies depending on the technological and factor cost differentials between the recipient and host economies. There is therefore an identifiable link between the determinants and effects of trade and FDI which the previous literature has not explored.

Technology flows, outsourcing and productivity:an analysis of UK trade and FDI

The literature on technology spillovers from trade and FDI is ambiguous in its findings. This may in part be because of the assumption in much of the work that trade and FDI flows are homogeneous in their determinants and thus in their effects. We develop a taxonomy of trade and FDI determinants based on R&D intensity and unit labour cost differentials, and test for the presence of spillovers from inward investment and imports on an extensive sample of UK manufacturing plants. We find that both trade and FDI have measurable spillover effects, but the sign and extent of these effects varies depending on the technological and factor cost differentials between the recipient and host economies. There is therefore an identifiable link between the determinants and effects of trade and FDI which the previous literature has not explored.

Editorial:knowledge flows, learning and development in an international context

In the editorial of this special issue we argue that knowledge flows, learning and development are becoming increasingly important in all organisations operating in an international context. The possession of capabilities relating to acquisition, configuration and transfer of relevant knowledge effectively within and across different organisational units, teams, and countries is integrally related to superior organisational performance. In mastering such capabilities, internationalised organisations need to grapple with the inherent challenges relating to contextual variation and different work modes between subsidiaries, partners or team members. The papers in this special issue cast light on crucial aspects of knowledge flows, learning and development in internationalised organisations. Their contribution varies from the provision of frameworks to systematise investigation of these issues, to empirical evidence about effective mechanisms, as well as enabling and constraining forces, in facilitating knowledge transfer, learning and human capital development. © 2012 Inderscience Enterprises Ltd.

Mean zonal flows generated by librations of a rotating spherical cavity

Longitudinal librations represent oscillations about the axis of a rotating axisymmetric fluid-filled cavity. An analytical theory is developed for the case of a spherical cavity in the limit when the libration frequency is small in comparison with the rotation rate, but large in comparison with the inverse of the spin-up time. It is shown that longitudinal librations create a steady zonal flow through the nonlinear advection in the Ekman layers. The theory can be applied to laboratory experiments as well as to solid planets and satellites with a liquid core. Copyright © Cambridge University Press 2010.

Bistability and hysteresis of dipolar dynamos generated by turbulent convection in rotating spherical shells

Bistability and hysteresis of magnetohydrodynamic dipolar dynamos generated by turbulent convection in rotating spherical fluid shells is demonstrated. Hysteresis appears as a transition between two distinct regimes of dipolar dynamos with rather different properties including a pronounced difference in the amplitude of the axisymmetric poloidal field component and in the form of the differential rotation. The bistability occurs from the onset of dynamo action up to about 9 times the critical value of the Rayleigh number for onset of convection and over a wide range of values of the ordinary and the magnetic Prandtl numbers including the value unity. Copyright © EPLA, 2009.