7,083 research outputs found

    A simple sufficient condition for the quasiconvexity of elastic stored-energy functions in spaces which allow for cavitation

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    In this note we formulate a sufficient condition for the quasiconvexity at x↊λxx \mapsto \lambda x of certain functionals I(u)I(u) which model the stored-energy of elastic materials subject to a deformation uu. The materials we consider may cavitate, and so we impose the well-known technical condition (INV), due to M\"{u}ller and Spector, on admissible deformations. Deformations obey the condition u(x)=λxu(x)= \lambda x whenever xx belongs to the boundary of the domain initially occupied by the material. In terms of the parameters of the models, our analysis provides an explicit upper bound on those λ>0\lambda>0 such that I(u)≄I(uλ)I(u) \geq I(u_{\lambda}) for all admissible uu, where uλu_{\lambda} is the linear map x↊λxx \mapsto \lambda x applied across the entire domain. This is the quasiconvexity condition referred to above

    Saturated torque formula for planetary migration in viscous disks with thermal diffusion: recipe for protoplanet population synthesis

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    We provide torque formulae for low mass planets undergoing type I migration in gaseous disks. These torque formulae put special emphasis on the horseshoe drag, which is prone to saturation: the asymptotic value reached by the horseshoe drag depends on a balance between coorbital dynamics (which tends to cancel out or saturate the torque) and diffusive processes (which tend to restore the unperturbed disk profiles, thereby desaturating the torque). We entertain here the question of this asymptotic value, and we derive torque formulae which give the total torque as a function of the disk's viscosity and thermal diffusivity. The horseshoe drag features two components: one which scales with the vortensity gradient, and one which scales with the entropy gradient, and which constitutes the most promising candidate for halting inward type I migration. Our analysis, which is complemented by numerical simulations, recovers characteristics already noted by numericists, namely that the viscous timescale across the horseshoe region must be shorter than the libration time in order to avoid saturation, and that, provided this condition is satisfied, the entropy related part of the horseshoe drag remains large if the thermal timescale is shorter than the libration time. Side results include a study of the Lindblad torque as a function of thermal diffusivity, and a contribution to the corotation torque arising from vortensity viscously created at the contact discontinuities that appear at the horseshoe separatrices. For the convenience of the reader mostly interested in the torque formulae, section 8 is self-contained.Comment: Affiliation details changed. Fixed equation numbering issue. Biblio info adde

    Exploring the perspectives of a mixed case study approach for the evaluation of the EU Rural Development Policy 2007-2013

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    For the evaluation of the EU Rural Development Policy in the programming period 2007-2013, the European Commission has designed a Common Monitoring and Evaluation Framework (CMEF). Given a widespread lack of enthusiasm and the complexity of the CMEF, in this paper a comparative analysis of 22 evaluation methods of rural development policy is conducted in order to explore whether an alternative approach for the evaluation of the EU Rural Development Policy exists. The mixed case study approach is identified as potential alternative. This approach combines the analysis of data on input and output with in-depth interviews. First results of testing this method in the mid-term evaluation of the EU Rural Development Policy 2007-2009 in the Dutch NUTS2 region of Zeeland indicate that this approach might be a promising alternative to the CMEF. It is easier to implement and renders useful insight into the question why measures have been effective.Evaluation methods, EU Rural Development Policy, mixed case-study approach, Agricultural and Food Policy, R500, R580,

    A Semicoarsening Multigrid Algorithm for SIMD Machines

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    A semicoarsening multigrid algorithm suitable for use on single instruction multiple data (SIMD) architectures has been implemented on the CM-2. The method performs well for strongly anisotropic problems and for problems with coefficients jumping by orders of magnitude across internal interfaces. The parallel efficiency of this method is analyzed, and its actual performance is compared with its performance on some other machines, both parallel and nonparallel

    TOWARDS REGIONAL DIFFERENTIATION OF RURAL DEVELOPMENT POLICY IN THE EU

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    In this study a comparative analysis of the Rural Development Plans (RDPs) in four intermediate rural regions (Northern Netherlands, Lower Saxony, Wales and Emilia Romagna) and four most urban regions (Southern Netherlands, North Rhine-Westphalia, Flanders and Lombardia) is made. Such plans are designed in the scope of the second pillar of the Common Agricultural Policy (CAP). In particular, the focus was on the question whether the menu approach of the second pillar enables EU member states and regions to design Rural Development Plans with a tailor-made set of measures which address their specific rural development needs. The findings of this study suggest that the current menu of rural development measures is sufficient to suit the wide range of socio-economic, ecological and physical circumstances in the EU regions. The analysis also revealed that there is some overlap between the three rural development priorities of the second pillar. Therefore, an outline of future rural development priorities and measures in the EU is designed, in which it is attempted to avoid overlap between the various rural development priorities and in which each measure contributes to the achievement of one development priority only. In addition, it is proposed that regions would select only those measures in their Rural Development Plan which really address the rural development needs in their region, even if this results in a Rural Development Plan with only one or two rural development measures. Such an approach of selecting rural development measures according to regional needs will result in a large variation in rural development measures implemented and may be considered regional differentiation of EU rural development policy.Agricultural and Food Policy,

    ALTERNATIVE FUTURES OF RURAL AREAS IN THE EU: A COMPARATIVE ANALYSIS OF SCENARIO STUDIES

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    What does rural Europe look like in 2030? Is agriculture still the main land user? In recent years, studies such as ESPON, Eururalis, SCENAR2020, SENSOR, SEAMLESS and PRELUDE have tried to address these questions. These studies resulted in a number of alternative futures of rural areas in the EU. In this paper a comparative analysis of these scenario studies is made in order to explore differences and similarities in the scenarios and alternative futures of rural areas in the EU. For this purpose, we designed a scheme for assessing the properties of the various scenarios and a scheme for a systematic description of the rural futures according to the scenarios. It appears that most scenario studies use a baseline scenario and a set of alternative scenarios with different degrees of policy regulation. Agriculture will continue to be a main land user in 2030, although some land abandonment will take place.Rural Europe, scenario studies, alternative futures, land-use, territorial disparities, Agribusiness, Community/Rural/Urban Development, Research Methods/ Statistical Methods,
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