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In this study, the stationary flow of a polymeric fluid governed by the upper convected Maxwell law is computed in a 2‐D convergent geometry. A finite element method is…
In this study, the stationary flow of a polymeric fluid governed by the upper convected Maxwell law is computed in a 2‐D convergent geometry. A finite element method is used to obtain non‐linear discretized equations, solved by an iterative Picard (fixed point) algorithm. At each step, two sub‐systems are successively solved. The first one represents a Newtonian fluid flow (Stokes equations) perturbed by known pseudo‐body forces expressing fluid elasticity. It is solved by minimization of a functional of the velocity field, while the pressure is eliminated by penalization. The second sub‐system reduces to the tensorial differential evolution equation of the extra‐stress tensor for a given velocity field. It is solved by the so‐called ‘non‐consistent Petrov‐Galerkin streamline upwind’ method. As with other decoupled techniques applied to this problem, our simulation fails for relatively low values of the Weissenberg viscoelastic number. The value of the numerical limit point depends on the mesh refinement. When convergence is reached, the numerical solutions for velocity, pressure and stress fields are similar to those obtained by other authors with very costly mixed methods.
A technique for computing free surfaces by a steady state approach has been included in the hot rolling code ROLL3. It has been described in a previous paper, along with…
A technique for computing free surfaces by a steady state approach has been included in the hot rolling code ROLL3. It has been described in a previous paper, along with applications to some simple rolling passes. In the present text, new developments are included to deal with more complex geometries, in particular when several potentially free surfaces exist. The problem of contact with flanks of grooves is given special care. Application to dog bone formation and flattening is presented. Then a case with two free surfaces is computed and compared to experiments. An application is then performed to beam roughing passes.
A two‐grid iterative method for 3D linear elasticity problems,discretized using quadratic tetrahedral elements is proposed. Theconjugate‐gradient method is used as…
A two‐grid iterative method for 3D linear elasticity problems, discretized using quadratic tetrahedral elements is proposed. The conjugate‐gradient method is used as smoother. As compared to the conjugate‐gradient alone, it is shown, via numerical examples, that the method is much more efficient on the basis of computing time and memory allocation. The convergence property of the method is sensitive to the regularity of the problem.
The purpose of this paper is to investigate thermally and hydrodynamically fully developed convection in a duct of rectangular cross-section containing a porous medium and…
The purpose of this paper is to investigate thermally and hydrodynamically fully developed convection in a duct of rectangular cross-section containing a porous medium and fluid layer.
The Darcy–Brinkman–Forchheimer flow model is adopted. A finite difference method of second-order accuracy with the Southwell-over-relaxation method is deployed to solve the non-dimensional momentum and energy conservation equations under physically robust boundary conditions.
It is found that the presence of porous structure and different immiscible fluids exert a significant impact on controlling the flow. Graphical results for the influence of the governing parameters i.e. Grashof number, Darcy number, porous media inertia parameter, Brinkman number and ratios of viscosities, thermal expansion and thermal conductivity parameters on the velocity and temperature fields are presented. The volumetric flow rate, skin friction and rate of heat transfer at the left and right walls of the duct are also provided in tabular form. The numerical solutions obtained are validated with the published study and excellent agreement is attained.
To the author’s best knowledge this study original in developing the numerical code using FORTRAN to assess the fluid properties for immiscible fluids. The study is relevant to geothermal energy systems, thermal insulation systems, resin flow modeling for liquid composite molding processes and hybrid solar collectors.
To provide a selective bibliography for researchers working with bulk material forming (specifically the forging, rolling, extrusion and drawing processes) with sources…
To provide a selective bibliography for researchers working with bulk material forming (specifically the forging, rolling, extrusion and drawing processes) with sources which can help them to be up‐to‐date.
A range of published (1996‐2005) works, which aims to provide theoretical as well as practical information on the material processing namely bulk material forming. Bulk deformation processes used in practice change the shape of the workpiece by plastic deformations under forces applied by tools and dies.
Provides information about each source, indicating what can be found there. Listed references contain journal papers, conference proceedings and theses/dissertations on the subject.
It is an exhaustive list of papers (1,693 references are listed) but some papers may be omitted. The emphasis is to present papers written in English language. Sheet material forming processes are not included.
A very useful source of information for theoretical and practical researchers in computational material forming as well as in academia or for those who have recently obtained a position in this field.
There are not many bibliographies published in this field of engineering. This paper offers help to experts and individuals interested in computational analyses and simulations of material forming processes.
The purpose of this paper is to compute flow effects of the transition from adherence-to-slip in two-dimensional flows, for a polymer melt obeying a memory-integral…
The purpose of this paper is to compute flow effects of the transition from adherence-to-slip in two-dimensional flows, for a polymer melt obeying a memory-integral viscoelastic equation, in isothermal and non-isothermal cases.
Temperature dependence is expressed by Arrhenius and William-Landel-Ferry models. A coupling approach is defined. For the dynamic equations, the Stream-Tube Method (STM) is used with finite differences in a mapped rectangular domain of the real domain, where streamlines are parallel and straight. STM avoids particle-tracking problems and allows simple formulae to evaluate stresses resulting from the constitutive equation. For the temperature field, a finite-element method is carried out to solve the energy equation in the real domain.
The approach avoids numerical problems arising with classical formulations and proves to be robust and efficient. Large elasticity levels are attained without convergence and refinement difficulties that may arise close to the “stick-slip” transition section. The method highlights the role of temperature conditions and reveals interesting differences for the ducts considered.
The results of the study are of interest for polymer processing where slip at the wall can be encountered, in relation with the physical properties of the materials.
The paper presents a simple approach that limits considerably numerical problems coming from stick-slip boundary conditions and avoids particle-tracking. Results are obtained at flow rates encountered in industrial conditions.
Despite the existence of a variety of approaches to the understanding of behavioral and managerial ethics in organizations and business relationships generally, knowledge…
Despite the existence of a variety of approaches to the understanding of behavioral and managerial ethics in organizations and business relationships generally, knowledge of organizing systems for fidelity remains in its infancy. We use halakha, or Jewish law, as a model, together with the literature in sociology, economic anthropology, and economics on what it termed “middleman minorities,” and on what we have termed the Landa Problem, the problem of identifying a trustworthy economic exchange partner, to explore this issue.
The article contrasts the differing explanations for trustworthy behavior in these literatures, focusing on the widely referenced work of Avner Greif on the Jewish Maghribi merchants of the eleventh century. We challenge Greif’s argument that cheating among the Magribi was managed chiefly via a rational, self-interested reputational sanctioning system in the closed group of traders. Greif largely ignores a more compelling if potentially complementary argument, which we believe also finds support among the documentary evidence of the Cairo Geniza as reported by Goitein: that the behavior of the Maghribi reflected their deep beliefs and commitment to Jewish law, halakha.
Applying insights from this analysis, we present an explicit theory of heroic marginality, the production of extreme precautionary behaviors to ensure service to the principal.
Generalizing from the case of halakha, the article proposes the construct of a deep code, identifying five defining characteristics of such a code, and suggests that deep codes may act as facilitators of compliance. We also offer speculation on design features employing deep codes that may increase the likelihood of production of behaviors consistent with terminal values of the community.
We present a critical literature review debating Brazilian research on social and environmental accounting (SEA). The aim of this study is to understand the role of…
We present a critical literature review debating Brazilian research on social and environmental accounting (SEA). The aim of this study is to understand the role of politics in the construction of hegemonies in SEA research in Brazil. In particular, we examine the role of hegemony in relation to the co-option of SEA literature and sustainability in the Brazilian context by the logic of development for economic growth in emerging economies. The methodological approach adopts a post-structural perspective that reflects Laclau and Mouffe’s discourse theory. The study employs a hermeneutical, rhetorical approach to understand and classify 352 Brazilian research articles on SEA. We employ Brown and Fraser’s (2006) categorizations of SEA literature to help in our analysis: the business case, the stakeholder–accountability approach, and the critical case. We argue that the business case is prominent in Brazilian studies. Second-stage analysis suggests that the major themes under discussion include measurement, consulting, and descriptive approach. We argue that these themes illustrate the degree of influence of the hegemonic politics relevant to emerging economics, as these themes predominantly concern economic growth and a capitalist context. This paper discusses trends and practices in the Brazilian literature on SEA and argues that the focus means that SEA avoids critical debates of the role of capitalist logics in an emerging economy concerning sustainability. We urge the Brazilian academy to understand the implications of its reifying agenda and engage, counter-hegemonically, in a social and political agenda beyond the hegemonic support of a particular set of capitalist interests.
This chapter aims to reconstruct the trajectory of comparative education in Brazil using the timeline concept to identify structural elements in the emergence and…
This chapter aims to reconstruct the trajectory of comparative education in Brazil using the timeline concept to identify structural elements in the emergence and reconfiguration of this field of study. The timeline historical perspective allows us to use two additional features: (a) the reconstruction of the scenario in which emerge the intellectual productions; and simultaneously (b) identify how themes, issues, and research objects appears, whether in a homogeneous association or not. These elements allow us to associate comparative and historical methods to recognize the supranational and supraregional influence, determining the configuration of what is meant by comparative education in Brazil. The text distinguishes seven different moments for the Brazilian comparative educational area, which are: (1) the study of the structure and functioning of European and North American systems education; (2) the United Nations Educational, Scientific and Cultural Organization’s (UNESCO) pioneering influence on the production of annuals; (3) the prioritization of educational practices; (4) the influence of supranational relations; (5) the focus on educational public policies; (6) new cycle of supranational influence; and (7) (re)definition of the theoretical, methodological, and epistemological anchorage of comparative education. In the last quarter century, it can be said that there is a resurgence of Comparative Education in Brazil and the region, which may be associated with strong historical influences, here reconstructed by periodization.
This chapter deals with different perspectives and structural transformations between capitalist society and indigenous ways of life. I approach the A’uwẽ-Xavante myth of…
This chapter deals with different perspectives and structural transformations between capitalist society and indigenous ways of life. I approach the A’uwẽ-Xavante myth of the theft of the jaguar’s fire, one of many versions of the story of the bird-nester, which Lévi-Strauss interprets as the acquisition of culture through cooking technique. I compare it with Proudhon’s study on property as the theft of collective force which he treats as the groundwork of the manufacturing process in capitalist society. This highlights the difference between Proudhon’s ideal mutualism, based on free access to means of production and polytechnic education, and the A’uwẽ-Xavante’s acquisition of power and its technical reproduction. Proudhon’s mutualism envisages auto-organization of collective force in cooperative work favoring its collective appropriation by the workers; while in the A’uwẽ-Xavante way of life, there is an off-centered collective force from which technical acquisition is redistributed. In common with Proudhon’s ideal labor mutualism, A’uwẽ-Xavante’s ways welcome outsiders to their means of production of people; but unlike Proudhon’s, this welcome is not for free: they have to prove their generosity and personal commitment to the game.