Abstract A two non-linear dynamic models, first one in two state variables and one control and the second one with three state variables and one control, are presented for the purpose of finding the optimal combination of exploitation, capital investment and price variation in the commercial fishing industry. This optimal combination is determined in terms of management policies. Exploitation, capital and price variation are controlled through the utilization rate of available capital. A novel feature in this model is that the (...) variation of the capital depends on the income. Content Type Journal Article Category Regular Article Pages 1-15 DOI 10.1007/s10441-012-9152-6 Authors Chakib Jerry, Département de Mathématiques, Faculté des Sciences, Equipe d’ingénieurie mathématiques EIMA, Université Ibn Tofail, B.P. 133, Kenitra, Morocco Nadia Raissi, Département de Mathématiques, Faculté des Sciences, Université Mohamed V-Rabat AGDAL, Rabat, Morocco Journal Acta Biotheoretica Online ISSN 1572-8358 Print ISSN 0001-5342. (shrink)
We study the effects of density dependent migrations on the stability of a predator-prey model in a patchy environment which is composed with two sites connected by migration. The two patches are different. On the first patch, preys can find resource but can be captured by predators. The second patch is a refuge for the prey and thus predators do not have access to this patch. We assume a repulsive effect of predator on prey on the resource patch. Therefore, when (...) the predator density is large on that patch, preys are more likely to leave it to return to the refuge. We consider two models. In the first model, preys leave the refuge to go to the resource patch at constant migration rates. In the second model, preys are assumed to be in competition for the resource and leave the refuge to the resource patch according to the prey density. We assume two different time scales, a fast time scale for migration and a slow time scale for population growth, mortality and predation. We take advantage of the two time scales to apply aggregation of variables methods and to obtain a reduced model governing the total prey and predator densities. In the case of the first model, we show that the repulsive effect of predator on prey has a stabilizing effect on the predator-prey community. In the case of the second model, we show that there exists a window for the prey proportion on the resource patch to ensure stability. (shrink)
Abstract This work is about the viability domain corresponding to a model of fisheries management. The dynamic is subject of two constraints. The biological constraint ensures the stock perennity where as the economic one ensures a minimum income for the fleets. Using the mathematical concept of viability kernel, we find out a viability domain which simultaneously enables the fleets to exploit the resource, to ensure a minimum income and stock perennity. Content Type Journal Article Category Regular Article Pages 1-19 DOI (...) 10.1007/s10441-012-9153-5 Authors C. Sanogo, LIRNE, Mathmatics Engineering Team, Ibn Tofail University, Kenitra, Morocco S. Ben Miled, ENIT-LAMSIN, Tunis el Manar University, Tunis, Tunisia N. Raissi, LAA, Mohamed V University, Rabat, Morocco Journal Acta Biotheoretica Online ISSN 1572-8358 Print ISSN 0001-5342. (shrink)
This work presents a specific stock-effort dynamical model. The stocks correspond to two populations of fish moving and growing between two fishery zones. They are harvested by two different fleets. The effort represents the number of fishing boats of the two fleets that operate in the two fishing zones. The bioeconomical model is a set of four ODE's governing the fishing efforts and the stocks in the two fishing areas. Furthermore, the migration of the fish between the two patches is (...) assumed to be faster than the growth of the harvested stock. The displacement of the fleets is also faster than the variation in the number of fishing boats resulting from the investment of the fishing income. So, there are two time scales: a fast one corresponding to the migration between the two patches, and a slow time scale corresponding to growth. We use aggregation methods that allow us to reduce the dimension of the model and to obtain an aggregated model for the total fishing effort and fish stock of the two fishing zones. The mathematical analysis of the model is shown. Under some conditions, we obtain a stable equilibrium, which is a desired situation, as it leads to a sustainable harvesting equilibrium, keeping the stock at exploitable densities. (shrink)
The emergence of cave art in Europe about 30,000 years ago is widely believed to be evidence that by this time human beings had developed sophisticated capacities for sym- bolization and communication. However, comparison of the cave art with the drawings made by a young autistic girl, Nadia, reveals surprising similarities in content and style. Nadia, despite her graphic skills, was mentally defective and had virtually no language. I argue in the light of this comparison that the existence (...) of the cave art cannot be the proof which it is usually assumed to be that the humans of the Upper Palaeolithic had essentially.. (shrink)
This article traces the development of the theory and practice of what is known as ‘community of inquiry’ as an ideal of classroom praxis. The concept has ancient and uncertain origins, but was seized upon as a form of pedagogy by the originators of the Philosophy for Children program in the 1970s. Its location at the intersection of the discourses of argumentation theory, communications theory, semiotics, systems theory, dialogue theory, learning theory and group psychodynamics makes of it a rich site (...) for the dialogue between theory and practice in education. This article is an exploration of those intersections, and a prospectus of its possible role in the formation and reformulation of school curriculum. It will be argued here that, when formulated as community of philosophical inquiry in particular, it offers the possibility of ‘philosophising’ the school curriculum in general, by extending the concept-work that doing philosophy entails to all of the disciplines. The article begins with an attempt at an operational definition of the term as, move to an analysis of its dynamics, offers an example of its use in a mathematics classroom, and finishes with a schematic view of its whole-curriculum and whole-school possibilities. (shrink)
The year 2006 marked the two hundredth anniversary of John Stuart Mill's birth. Though his philosophical reputation has varied greatly, it is now clear that Mill ranks among the most influential modern political thinkers. Despite his enduring influence, the breadth and complexity of Mill's political thought is often underappreciated. While his writings remain a touchstone for debates over liberty and liberalism, many other important dimensions of his political philosophy have until recently been ignored. This book aims to correct such neglect, (...) by illustrating the breadth and depth of Mill's political writings, by drawing together a collection of essays whose authors explore underappreciated elements of Mill's political philosophy. The book shows how Mill's thinking remains pertinent to our own political life in three broad areas - democratic institutions and culture, liberalism, and international politics - and offers a critical reassessment of Mill's political philosophy in light of recent political developments and transformations. (shrink)
One of John Dewey's major contributions to the reconstruction of the educational process was in his understanding that education needed to develop a working relationship between the refined end-products of inquiry that are codified and sedimented in textbooks, and the raw subject matter inquiry that is natural to the young. Such inquiry, he was convinced, should be shaped and fashioned to the well-known model of scientific inquiry which he set forth in How We Think (Dewey, 1933). In that same book, (...) he describes "reflective thinking" as a special kind of ratiocination that is aware of its means and consequences, and thus is a major instrument in discipline-based inquiry. Dewey's "scientific method" became a .. (shrink)
Besides Dracula, Ceau?escu, and Nadia Com?neci, monasteries constitute a permanent Romanian brand, inextricably linked in every foreign visitor's mind to Romanianness. Specific to Moldavia and Bucovina?the Eastern and Northern parts of Romania?these monasteries have attracted visitors for the past 500 years. The person visiting a sacred site is transformed from being merely a tourist into a pilgrim. The painting ?The Ladder towards Heaven? at the Pâng?ra?i Monastery, for example, highlights the importance of the mental and physical involvement of the (...) tourist-pilgrim as an interactive participant in the process of self-discovery. (shrink)
The 'Art of Life' is John Stuart Mill's name for his account of practical reason. In this volume, eleven leading scholars elucidate this fundamental, but widely neglected, element of Mill's thought. Mill divides the Art of Life into three 'departments': 'Morality, Prudence or Policy, and Æsthetics'. In the volume's first section, Rex Martin, David Weinstein, Ben Eggleston, and Dale E. Miller investigate the relation between the departments of morality and prudence. Their papers ask whether Mill is a rule utilitarian and, (...) if so, whether his practical philosophy must be incoherent. The second section contains papers by Jonathan Riley and Wendy Donner, who explore the relation between the departments of morality and aesthetics. They discuss issues ranging from supererogation to aesthetic pleasure and humanity's relationship with nature. -/- The papers in the third section consider the Art of Life's axiological first principle, the principle of utility. Elijah Millgram contends that Mill's own life refutes his claim that the Art of Life has a single axiological first principle. Philip Kitcher maintains that Mill has a dynamic axiology requiring us to continually refine our conception of the good. In the final section, three papers address what it means to put the Art of Life into practice. Robert Haraldsson locates an 'Art of Ethics' in On Liberty that is in tension with the Art of Life. Nadia Urbinati plumbs the classical roots of Mill's view of the good life. Finally, Colin Heydt develops Mill's suggestion that we regard our own lives as works of art. (shrink)
Many proposals for logic-based formalisations of argumentation consider an argument as a pair (Φ,α), where the support Φ is understood as a minimal consistent subset of a given knowledge base which has to entail the claim α. In case the arguments are given in the full language of classical propositional logic reasoning in such frameworks becomes a computationally costly task. For instance, the problem of deciding whether there exists a support for a given claim has been shown to be -complete. (...) In order to better understand the sources of complexity (and to identify tractable fragments), we focus on arguments given over formulæ in which the allowed connectives are taken from certain sets of Boolean functions. We provide a complexity classification for four different decision problems (existence of a support, checking the validity of an argument, relevance and dispensability) with respect to all possible sets of Boolean functions. Moreover, we make use of a general schema to enumerate all arguments to show that certain restricted fragments permit polynomial delay. Finally, we give a classification also in terms of counting complexity. (shrink)
The poetic image results from the effort undertaken by affectivity to express itself in a language that is not originally its very own, but that holds the advantage of being communicable not only at the level of representation, but at the level of feeling as well. The image is not considered, therefore, to be a synthesis of true and false. In the process of creation, the affect is the material principle of the image as an ideal unity of syntheses. It (...) is implied here that poetic writing is not about a content of internal aiming, previously possessed by consciousness, that is made to correspond with an element of the world, eventually represented by means of sensible intuition. In order to illustrate this, the author interprets a poem by Nadia Tueni, showing that it is essentially about its own production. (shrink)
Recent work has shown that preschool-aged children and adults understand freedom of choice regardless of culture, but that adults across cultures differ in perceiving social obligations as constraints on action. To investigate the development of these cultural differences and universalities, we interviewed school-aged children (4–11) in Nepal and the United States regarding beliefs about people's freedom of choice and constraint to follow preferences, perform impossible acts, and break social obligations. Children across cultures and ages universally endorsed the choice to follow (...) preferences but not to perform impossible acts. Age and culture effects also emerged: Young children in both cultures viewed social obligations as constraints on action, but American children did so less as they aged. These findings suggest that while basic notions of free choice are universal, recognitions of social obligations as constraints on action may be culturally learned. (shrink)
In this paper, I discuss the social philosopher Pierre Bourdieu’s concept of habitus, and use it to locate and examine dispositions in a larger constellation of related concepts, exploring their dynamic relationship within the social context, and their construction, manifestation, and function in relation to classroom mathematics practices. I describe the main characteristics of habitus that account for its invisible effects: its embodiment, its deep and pre-reflective internalization as schemata, orientation, and taste that are learned and yet unthought, and are (...) subsumed by our practices, which we understand as something that “goes without saying.” I also propose that, similarly to Bourdieu’s concept of linguistic habitus, a math habitus is made up of a complex intertwining of collective and individual histories that turn into “nature,” which structure all individual and collective action and inform mathematical classroom practice. I suggest that individual math dispositions may be liable to reconstruction through the reconstruction of the collective math habitus, which follows from opening spaces for dialogue, problematization and reconstruction of the unthought categories of the doxa. This requires that students acquire new concrete and symbolic means with which to challenge their current sense of mathematics as a discipline, and mathematical practice tout court. Finally, I argue that community of inquiry, employed as a pedagogical model, provides an avenue for both: for opening those spaces for reflective dialogical inquiry into concepts and questions whose meanings and references have so far been taken for granted, and for acquiring critical thinking and dialogical skills and dispositions that are a necessary means for participating in such reflective inquiry that offers significant promise for reconstructing individual and collective habitus in school settings. (shrink)
