Is UK agriculture sustainable? Environmentally adjusted economic accounts for UK agriculture

Agricultural sectors in most advanced economies have come under severe criticism for lacking the characteristics of 'sustainability'. What is usually meant is that a combination of subsidies and modern farming methods is producing an economically and environmentally non-viable agricultural sector. Using economic valuation techniques, and adjusting for prevailing subsidies, we seek to re-estimate the contribution that the agricultural sector made to the UK economy in the year 1998. The sector is markedly smaller if adjustments are made for subsidies. But these subsidies allow the sector to be a generator of both substantial environmental benefits, and also of extensive environmental damages

Three-Dimensional Navier-Stokes Simulation of Space Shuttle Main Propulsion 17-inch Disconnect Valves

A steady incompressible three-dimensional viscous flow analysis has been conducted for the Space Shuttle external tank/orbiter propellant feed line disconnect flapper valves with upstream elbows. The Navier-Stokes code, INS3D, is modified to handle interior obstacles and a simple turbulence model. The flow solver is tested for stability and convergence in the presence of interior flappers. An under-relaxation scheme has been incorporated to improve the solution stability. Important flow characteristics such as secondary flows, recirculation, vortex and wake regions, and separated flows are observed. Computed values for forces, moments, and pressure drop are in satisfactory agreement with water flow test data covering a maximum tube Reynolds number of 3.5 million. The predicted hydrodynamical stability of the flappers correlates well with the measurements

Advancing subsidy reforms: towards a viable policy package

Executive Summary: World subsidies may total some $800 billion, of which perhaps two-thirds occur in the developed economies of the OECD. Reforming subsidy regimes that damage the prospects for sustainable development is immensely complex. Simply calling for subsidy removal is unlikely to succeed. The complexity arises from the fact that subsidies are manifestations of rent-seeking, which, in turn is part of a wider category of unproductive activity in economic systems. Rentseeking involves redirecting economic resources to special interest groups rather than using resources productively. Interest groups then use those resources to reinforce their privleged positions. Subsidy reform will inevitably conflict with those special interests. The idea that subsidy reform is a ‘win-win’ policy is therefore misleading – there will always be losers, even if they are undeserving losers. In many cases, the most harmful subsidies will be those that are least easy to remove. Subsidy reform is therefore about dissipating rents, has to be part of a wider programme of macroeconomic and political reform. Subsidies are often linked to corruption, thus emphasising the difficulty of securing the political changes that are needed. Moreover, instituting democratic reform is not sufficient either: democratic societies have even larger subsidy regimes than less democratic societies. Political change has to be combined with economic reform. Some have advocated ‘sudden shocks’ whereby dramatic events are seized as an opportunity to institute reform. There is some evidence to suggest that if a crisis does occur, it may be best to implement subsidy reform along with other transitional measures in one large package. An alternative is to let the almost inevitable growth of subsidies produce economic bankruptcy, and then institute reform. But many societies have proved surprisingly resilient whilst sustaining extensive subsidy regimes, and the costs of waiting may not be acceptable anyway. In the absence of crisis, a gradual approach is best. Policies need to be pre-announced and gradual subsidy reduction needs to be combined with careful public awareness campaigns and efforts at political transparency and accountability. Bilateral and multilateral lenders have a strong role to play, even though reforming subsidies as part of a conditionality package is still controversial. Reform almost inevitably involves privatisation since exposure to market forces is essential for rent dissipation. Nonetheless, reform is complex and its success if difficult to guarantee: for example, privatisation may simply shift rents from the public to the private sector. Subsidy regimes seem peculiarly resilient to change

Linear response to leadership, effective temperature and decision making in flocks

Large collections of autonomously moving agents, such as animals or micro-organisms, are able to 'flock' coherently in space even in the absence of a central control mechanism. While the direction of the flock resulting from this critical behavior is random, this can be controlled by a small subset of informed individuals acting as leaders of the group. In this article we use the Vicsek model to investigate how flocks respond to leadership and make decisions. Using a combination of numerical simulations and continuous modeling we demonstrate that flocks display a linear response to leadership that can be cast in the framework of the fluctuation-dissipation theorem, identifying an 'effective temperature' reflecting how promptly the flock reacts to the initiative of the leaders. The linear response to leadership also holds in the presence of two groups of informed individuals with competing interests, indicating that the flock's behavioral decision is determined by both the number of leaders and their degree of influence.Comment: 8 pages (incl. supplementary information), 8 figures, Supplementary movies can be found at http://wwwhome.lorentz.leidenuniv.nl/~giomi/sup_mat/20151108