A high accuracy Leray-deconvolution model of turbulence and its limiting behavior

In 1934 J. Leray proposed a regularization of the Navier-Stokes equations whose limits were weak solutions of the NSE. Recently, a modification of the Leray model, called the Leray-alpha model, has atracted study for turbulent flow simulation. One common drawback of Leray type regularizations is their low accuracy. Increasing the accuracy of a simulation based on a Leray regularization requires cutting the averaging radius, i.e., remeshing and resolving on finer meshes. This report analyzes a family of Leray type models of arbitrarily high orders of accuracy for fixed averaging radius. We establish the basic theory of the entire family including limiting behavior as the averaging radius decreases to zero, (a simple extension of results known for the Leray model). We also give a more technically interesting result on the limit as the order of the models increases with fixed averaging radius. Because of this property, increasing accuracy of the model is potentially cheaper than decreasing the averaging radius (or meshwidth) and high order models are doubly interesting

Cross-border activity in the Kent - Nord-Pas de Calais - Belgium Euroregion: some comparative evidence on the location and recruitment decisions of internationally mobile firms

Border regions and the implications for their development have become a subject of considerable interest in the ongoing process of European integration. The removal of national barriers and the development of greater economic and political transborder co-operation has led to a reconsideration of spatial identity and the definition of regional economies or markets. Much of the interest has focussed on the implications for labour mobility, especially within the context of the perceived need for greater mobility to provide the necessary adjustment process within the Eurozone. However, not only has international labour migration remained quite low within the EU, so has the level of cross-border commuting. There has, however, been considerable interest in the growth of cross-border capital flows. In this paper we explore the nature of this cross-border movement of firms in the context of the Kent - Nord-Pas de Calais - Belgium Euroregion. This transnational region is a large region of over 15 million people, close to a number of national borders. The original focus was the Transmanche region between Kent and Nord-Pas de Calais, established in relation to the construction of the Channel Tunnel in1987 in order to identify common problems, minimise the competition for the same resources between the regions and emphasise complementarity in their economic structures. The region was later extended to include the three Belgian regions in 1991 when it was renamed the Euroregion, and there have been suggestions that it should extend even more widely to include most or all of the Central Capitals Region of the EU. This paper brings together some findings from a survey of French firms which have located in Kent and a parallel survey of Belgian firms which have located in the Dunkerque employment area of Nord-Pas de Calais (Boutillier et al, 2001). In this analysis we seek to discover whether the same general set of principles govern cross-border movements, or whether there are individual circumstances in each region to which specific types of firm respond. Despite similarities, it is difficult to conclude that there is a consistent pattern of cross-border investment activity. As with all investment activity, cross-border investment seeks to exploit differentials which exist and opportunities which arise; these are different in different cases. Belgian activity in the Dunkerque region is responding to clear advantages which are offered through location in an area where incentives are strong and where there are specific skills which can be used to advantage. French investment in Kent seems to be responding to wider national opportunities available in the UK, but using a location which has certain advantages of proximity. It would seem unwise to rely on either of these factors as being likely to persist indefinitely. By definition firms which have been willing to move in will also find it relatively easy to move on to other locations, possibly to other regions within the host country. In this sense border regions continue to act as staging posts for mobile factors and thus have to recognise the need for continuing activity to attract new firms and retain existing ones.

Dynamic Enfranchisement

Why would a political elite voluntarily dilute its political power by extending the voting franchise? This paper develops a dynamic recursive framework for studying voter enfranchisement. We specify a class of dynamic games in which political rights evolve over time. Each period, private decisions of citizens co-mingle with government policies to act upon a state variable such as a capital stock, a public good, or the likelihood of an insurrection. Policies are determined by a pivotal decision maker in a potentially restricted franchise. The pivotal decision maker can also delegate decision authority to a new decision maker in the subsequent period. We describe conditions under which an equilibrium of this "dictator delegation game" corresponds to a majority vote decision by the enfranchised group to expand the set of citizens with voting rights. Under these conditions, each period's pivotal decision maker is a median voter who can designate authority to a new median of a larger voting franchise in the next period. We characterize the equilibria by their Euler equations. In certain games, the equilibria generate paths that display a gradual, sometimes uneven history of enfranchisement that is roughly consistent with observed patterns of extensions. Our main result shows that extensions of the franchise occur in a given period if and only if the private decisions of the citizenry have a net positive spillover to the dynamic payoff of the current median voter. The size of the extension depends on the size of the spillover. Since the class of games we study can accommodate a number of proposed explanations for franchise extension (e.g., the threat of insurrection, or ideological or class conflict within the elite, etc), the result suggests a common causal mechanism for these seemingly different explanations. We describe a number of parametric environments that correspond to the various explanations, and show how the mechanism works in eachDynamic games, voter enfranchisement, franchise extension, dictator delegation game

Dynamic Enfranchisement

Why would a political elite voluntarily dilute its political power by extending the voting franchise? This paper develops a dynamic recursive framework for studying voter enfranchisement. We specify a class of dynamic games in which political rights evolve over time. Each period, private decisions of citizens co-mingle with government policies to act upon a state variable such as a capital stock, a public good, or the likelihood of an insurrection. Policies are determined by a pivotal decision maker in a potentially restricted franchise. The pivotal decision maker can also delegate decision authority to a new decision maker in the subsequent period. We describe conditions under which an equilibrium of this "dictator delegation game" corresponds to a majority vote decision by the enfranchised group to expand the set of citizens with voting rights. Under these conditions, each period's pivotal decision maker is a median voter who can designate authority to a new median of a larger voting franchise in the next period. We characterize the equilibria by their Euler equations. In certain games, the equilibria generate paths that display a gradual, sometimes uneven history of enfranchisement that is roughly consistent with observed patterns of extensions. Our main result shows that extensions of the franchise occur in a given period \emph{if and only if} the private decisions of the citizenry have a net positive spillover to the dynamic payoff of the current median voter. The size of the extension depends on the size of the spillover. Since the class of games we study can accommodate a number of proposed explanations for franchise extension (e.g., the threat of insurrection, or ideological or class conflict within the elite, etc), the result suggests a common causal mechanism for these seemingly different explanations. We describe a number of parametric environments that correspond to the various explanations, and show how the mechanism works in each.Dynamic games, voter enfranchisement, franchise extension equilibria, dictator delegation game

Dynamic Enfrachisement

Why would a political elite voluntarily dilute its political power by extending the franchise? This paper develops a dynamic recursive framework for studying voter enfranchisement. We study properties of dynamic enfranchisement games, dynamic games in which political rights evolve over time. Each period, private decisions of citizens co-mingle with government policies to act upon a state variable such as capital stock, a public good, or the likelihood of an insurrection. Policies are determined by the median voter of a potentially restricted franchise. The enfranchised group can choose, through its median voter, to expand the set of citizens with voting rights. In this way, each period's median voter can e.ectively delegate decision authority to a new median in the next period. We characterize the equilibria of a dynamic enfranchisement game by its Euler equations. In certain games, the equilibria generate paths that display a gradual, sometimes uneven history of enfranchisement that is roughly consistent with observed patterns of extensions. Our main result shows that extensions of the franchise occur in a given period if and only if the private decisions of the citizenry have a net positive spillover to the dynamic payo. of the current median voter. The size of the extension depends on the size of the spillover. Since the class of games we study can accommodate a number of proposed explanations for franchise extension (e.g., the threat of insurrection, or ideological or class conflict within the elite, etc), the result suggests a common causal mechanism for these seemingly di.erent explanations. We describe a number of parametric environments that correspond to the various explanations, and show how the mechanism works in each.Dynamic games, voter enfranchisement, franchise extension equilibria

Resource allocation, hyperphagia and compensatory growth

Organisms often shown enhanced growth during recovery from starvation, and can even overtake continuously fed conspecifics (overcompensation). In an earlier paper (Ecology 84, 2777-2787), we studied the relative role played by hyperphagia and resource allocation in producing overcompensation in juvenile (non-reproductive) animals. We found that, although hyperphagia always produces growth compensation, overcompensation additionally requires protein allocation control which routes assimilate preferentially to structure during recovery. In this paper we extend our model to cover reproductively active individuals and demonstrate that growth rate overcompensation requires a similar combination of hyperphagia and allocation control which routes the part of enhanced assimilation not used for reproduction preferentially towards structural growth. We compare the properties of our dynamic energy budget model with an earlier proposal, due to Kooijman, which we extend to include hyperphagia. This formulation assumes that the rate of allocation to reserves is controlled by instantaneous feeding rate, and one would thus expect that an extension to include hyperphagia would not predict growth overcompensation. However, we show that a self-consistent representation of the hyperphagic response in Kooijman's model overrides its fundamental dynamics, leading to preferential allocation to structural growth during recovery and hence to growth overcompensation

El Niño, Ice Storms, and the Market for Residential Fuelwood in Eastern Canada and the Northeastern U.S.

Extreme weather events such as the ice storm that affected eastern Canada and the Northeastern US in January of 1998 have significant impacts on both human populations and forests. One of the questions currently facing climate scientists is whether or not better forecasting of such events would lessen the economic impacts borne by households, industry, agricultural producers and the public sector when such weather events occur. This case study examines the economic impacts of the ice storm on the residential market for fuelwood. It is hypothesized that demand for fuelwood will increase due to the failure of non-wood heating sources during the ice storm. In addition, damage to trees in the region should increase the supply of fuelwood; the net effect of these outward shifts of supply and demand on price is not known. A household level survey administered to over one thousand households indicates that less than half of the households in the affected region currently rely on wood burning technologies as a source of heat for their homes. However, those households with wood burning technologies were better able to manage during the ice storm. The main policy implication of better forecasting of extreme weather events is the ability of households to alter or substitute home heating strategies and technologies in addition to other mitigative strategies such as storing food etc. In addition, forest managers or forest product producers who have information regarding extreme weather events have the option to undertake various management strategies to lessen the economic and biophysical impacts of ice storms on forests. Forest managers and woodlot owners may also enter or expand into the market for residential fuelwood when the production of other forest produce such as maple syrup and veneer are hindered by ice storm damage.

SUGGESTED PROCEDURES FOR ESTIMATING FARM MACHINERY COSTS FOR EXTENSION AUDIENCES

North Central Farm Machinery Task Force is a group of extension economists who evaluated alternative methods for estimating farm machinery costs and made recommendations for the development of extension materials. This paper describes the procedures agreed upon, and explains the rationale for the procedures chosen. The focus is on "typical" machinery costs for use in extension budgets and other analyses and examples. This paper also provides detailed documentation of the methods used in recent versions of the widely used Minnesota Farm Machinery Economic Cost Estimates publication (referred to below as "the Minnesota fact sheet"), focusing mainly on the 2000 version.Agricultural Finance, Farm Management,

Thermal stress analysis of space shuttle orbiter subjected to reentry aerodynamic heating

A structural performance and resizing (SPAR) finite-element computer program and NASA structural analysis (NASTRAN) finite-element computer programs were used in the thermal stress analysis of the space shuttle orbiter subjected to reentry aerodynamic heating. A SPAR structural model was set up for the entire left wing of the orbiter, and NASTRAN structural models were set up for: (1) a wing segment located at midspan of the orbiter left wing, and (2) a fuselage segment located at midfuselage. The thermal stress distributions in the orbiter structure were obtained and the critical high thermal stress regions were identified. It was found that the thermal stresses induced in the orbiter structure during reentry were relatively low. The thermal stress predictions from the whole wing model were considered to be more accurate than those from the wing segment model because the former accounts for temperature and stress effects throughout the entire wing