The value of switching costs

We study the consequences of heterogeneity of switching costs in a dynamic model with free entry and an incumbent monopolist. We identify the equilibrium strategies of the incumbent and of the entrants and show that the strategic interactions are more complex and more interesting than either in static models or in models where all consumers have the same switching costs. In particular, we prove that even low switching cost customers have value for the incumbent: when there are more of them its profits increase. Indeed, their presence hinders entrants who find it more costly to attract high switching cost customers. This leads to different comparative statics: for instance, an increase in the switching costs of all consumers can lead to a decrease in the profits of the incumbent.

The Value of Incumbency in Heterogeneous Platforms

We study the dynamics of competition in a model with network effects, an incumbent and entry. We propose a new way of representing the strategic advantages of incumbency in a static model. We then embed this static analysis in a dynamic framework with heterogeneous consumers. We completely identify the conditions under which inefficient equilibria with two platforms will emerge at equilibrium; explore the reasons why these inefficient equilibria arise; and compute the profits of the incumbent when there is only one platform at equilibrium

Supersonic propulsion simulation by incorporating component models in the large perturbation inlet (LAPIN) computer code

An approach to simulating the internal flows of supersonic propulsion systems is presented. The approach is based on a fairly simple modification of the Large Perturbation Inlet (LAPIN) computer code. LAPIN uses a quasi-one dimensional, inviscid, unsteady formulation of the continuity, momentum, and energy equations. The equations are solved using a shock capturing, finite difference algorithm. The original code, developed for simulating supersonic inlets, includes engineering models of unstart/restart, bleed, bypass, and variable duct geometry, by means of source terms in the equations. The source terms also provide a mechanism for incorporating, with the inlet, propulsion system components such as compressor stages, combustors, and turbine stages. This requires each component to be distributed axially over a number of grid points. Because of the distributed nature of such components, this representation should be more accurate than a lumped parameter model. Components can be modeled by performance map(s), which in turn are used to compute the source terms. The general approach is described. Then, simulation of a compressor/fan stage is discussed to show the approach in detail

Review of The Birth of the Gods and the Origins of Agriculture by Jacques Cauvin, translated by Trevor Watkins (New Studies in Archaeology).

When, almost a century ago, Raphael Pumpelly put forward the ‘oasis theory’ for the origins of farming in the Near East, his was one of the first in a long series of explanations which looked to environment and ecology as the cause of the shift from hunting and gathering to cultivation and animal husbandry. Pumpelly envisaged climatic desiccation at the end of the last Ice Age as the primary factor, forcing humans, plants and animals into ever closer proximity as the arid zones expanded around them. Subsequent fieldworkers took the closer investigation of environmental changes as a key aim of their research, both in the Near East and elsewhere, and this has remained a fundamental theme in theories for the emergence of agriculture. More recent advances in our understanding of environmental change have placed particular emphasis on the cold Younger Dryas episode, at the end of the last Ice Age. The impact of this sudden reversal of climate warming on the complex Natufian hunter-gatherers of the Levant may, it is argued, have forced or encouraged these communities to explore novel subsistence modes. Not everybody accepts such a chain of reasoning, however, and in The Birth of Gods and the Origins of Agriculture, French archaeologist Jacques Cauvin rejects this emphasis on ecology and environment as the cause of change. Instead, he argues that primacy should be accorded to a restructuring of human mentality from the thirteenth to the tenth millennium BC, expressed in terms of new religious ideas and symbols. Cauvin's book, originally published in French in 1994 under the title Naissance des divinités, naissance de l'agriculture, adopts an ideological approach to explaining the Neolithic which is at odds with many traditional understandings, but which resonates closely with the idea that the Neolithic is much more than an economic transition, and coincided with a transformation in the world view of the prehistoric societies concerned. The present English translation appeared in 2000, and is based on the second French edition (1997) with the addition of a postscript summarizing relevant discoveries made since that date. Owing to illness, Jacques Cauvin has been unable to contribute to this Review Feature as had been hoped, but we are fortunate that his translator, Trevor Watkins, has agreed to draft a response to the comments made by our invited reviewers. These include Ian Hodder, whose own work on the Neolithic transition has been influenced by Cauvin's research, and Ofer Bar-Yosef and Gary Rollefson, both specialists in the prehistory of the Levant. At Dr Watkins' suggestion, the introductory piece which opens the Review Feature is a translated extract from Jacques Cauvin's contribution to a similar review treatment in Les Nouvelles de l'Archéologie (No. 79, 2000, 49–53). As our reviewers make clear, the significance of the book, and the debate which it has initiated, will make it akey text for many years to come.Anthropolog

Primary and secondary yield losses caused by pests and diseases: Assessment and modeling in coffee

The assessment of crop yield losses is needed for the improvement of production systems that contribute to the incomes of rural families and food security worldwide. However, efforts to quantify yield losses and identify their causes are still limited, especially for perennial crops. Our objectives were to quantify primary yield losses (incurred in the current year of production) and secondary yield losses (resulting from negative impacts of the previous year) of coffee due to pests and diseases, and to identify the most important predictors of coffee yields and yield losses. We established an experimental coffee parcel with full-sun exposure that consisted of six treatments, which were defined as different sequences of pesticide applications. The trial lasted three years (2013–2015) and yield components, dead productive branches, and foliar pests and diseases were assessed as predictors of yield. First, we calculated yield losses by comparing actual yields of specific treatments with the estimated attainable yield obtained in plots which always had chemical protection. Second, we used structural equation modeling to identify the most important predictors. Results showed that pests and diseases led to high primary yield losses (26%) and even higher secondary yield losses (38%). We identified the fruiting nodes and the dead productive branches as the most important and useful predictors of yields and yield losses. These predictors could be added in existing mechanistic models of coffee, or can be used to develop new linear mixed models to estimate yield losses. Estimated yield losses can then be related to production factors to identify corrective actions that farmers can implement to reduce losses. The experimental and modeling approaches of this study could also be applied in other perennial crops to assess yield losses. (Résumé d'auteur

Towards an agroecological viticulture: advances and challenges

To improve its sustainability, viticulture should increase the provision of ecosystem services to decrease its use of inputs and the resulting environmental impact while maintaining high socio-economic performance. Soil functions in relation with their physical, chemical and biological properties can be regulated by proper soil surface management. Cover crops deliver ecosystem services such as protection of soils, better water infiltration and nitrogen fixation. Yet to avoid trade-off between provision of services and production of grapes, the management of cover crops should adapt to climate variations and to the yield objective. Pest and diseases can be regulated by various technical levers, including the control of the grape vegetative development. The assessment of damages due to pests and disease and of their consequences on yield losses is a key component of the design of alternative strategies of crop protection. This knowledge provides clues for designing management strategies with low pesticide use and high agro-ecological performance. A French national network of experiments has quantified the reduction of pesticide use with decision support systems, biocontrol or resistant varieties. To go further the challenge is now to design agroecological vineyards that combine innovations in management, and also in spatial organization at field, farm and landscape scales

The fables of pity: Rousseau, Mandeville and the animal-fable

Copyright @ 2012 Edinburgh University PressPrompted by Derrida’s work on the animal-fable in eighteenth-century debates about political power, this article examines the role played by the fiction of the animal in thinking of pity as either a natural virtue (in Rousseau’s Second Discourse) or as a natural passion (in Mandeville’s The Fable of the Bees). The war of fables between Rousseau and Mandeville – and their hostile reception by Samuel Johnson and Adam Smith – reinforce that the animal-fable illustrates not so much the proper of man as the possibilities and limitations of a moral philosophy that is unable to address the political realities of the state

Library of model components for process simulation relevant to production activities, Prototype 1 versions

Production Economics,

Fruit-trees in agroforestry systems - review and prospects for the temperate and Mediterranean zones. Abstract number 33

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