Challenging reductionism in analyses of EU-Russia energy relations

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Learning Dictionaries with Bounded Self-Coherence

Sparse coding in learned dictionaries has been established as a successful approach for signal denoising, source separation and solving inverse problems in general. A dictionary learning method adapts an initial dictionary to a particular signal class by iteratively computing an approximate factorization of a training data matrix into a dictionary and a sparse coding matrix. The learned dictionary is characterized by two properties: the coherence of the dictionary to observations of the signal class, and the self-coherence of the dictionary atoms. A high coherence to the signal class enables the sparse coding of signal observations with a small approximation error, while a low self-coherence of the atoms guarantees atom recovery and a more rapid residual error decay rate for the sparse coding algorithm. The two goals of high signal coherence and low self-coherence are typically in conflict, therefore one seeks a trade-off between them, depending on the application. We present a dictionary learning method with an effective control over the self-coherence of the trained dictionary, enabling a trade-off between maximizing the sparsity of codings and approximating an equiangular tight frame.Comment: 4 pages, 2 figures; IEEE Signal Processing Letters, vol. 19, no. 12, 201

pde2path - version 2.0: faster FEM, multi-parameter continuation, nonlinear boundary conditions, and periodic domains - a short manual

pdepath 2.0 is an upgrade of the continuation/bifurcation package pde2path for elliptic systems of PDEs over bounded 2D domains, based on the Matlab pdetoolbox. The new features include a more efficient use of FEM, easier switching between different single parameter continuations, genuine multi-parameter continuation (e.g., fold continuation), more efficient implementation of nonlinear boundary conditions, cylinder and torus geometries (i.e., periodic boundary conditions), and a general interface for adding auxiliary equations like mass conservation or phase equations for continuation of traveling waves. The package (library, demos, manuals) can be downloaded at www.staff.uni-oldenburg.de/hannes.uecker/pde2pat

Price Pooling and the Gains from Hedging: Application to a Swedish Grain Cooperative

Optimal hedging strategies are analyzed for a cooperative operating a price pooling system in the presence of price and quantity risk. A three-period model, accounting for default risk and storage, is developed. Hedging allows the cooperative to increase the pool price offered to farmers by 2.8 - 4% for moderate risk parameters.Agribusiness, Marketing,

No approximate complex fermion coherent states

Whereas boson coherent states with complex parametrization provide an elegant, and intuitive representation, there is no counterpart for fermions using complex parametrization. However, a complex parametrization provides a valuable way to describe amplitude and phase of a coherent beam. Thus we pose the question of whether a fermionic beam can be described, even approximately, by a complex-parametrized coherent state and define, in a natural way, approximate complex-parametrized fermion coherent states. Then we identify four appealing properties of boson coherent states (eigenstate of annihilation operator, displaced vacuum state, preservation of product states under linear coupling, and factorization of correlators) and show that these approximate complex fermion coherent states fail all four criteria. The inapplicability of complex parametrization supports the use of Grassman algebras as an appropriate alternative.Comment: Argumentation made cleare

Low-Temperature Thermal Conductivity of Superconductors With Gap Nodes

We report a detailed analytic and numerical study of electronic thermal conductivity in d-wave superconductors. We compare theory of the cross over at low temperatures from T-dependence to T^3-dependence for increasing temperature with recent experiments on YBCO in zero magnetic field for temperatures from 0.04K to 0.4K by Hill et al., Phys. Rev. Lett. 92, 027001 (2004). Transport theory, including impurity scattering and inelastic scattering within strong coupling superconductivity, can consistently fit the temperature dependence of the data in the lower half of the temperature regime. We discuss the conditions under which we expect power-law dependences over wide temperature intervals.Comment: 4 pages, 3 figure

Structural Change in Transition: A Role for Organizational Legitimacy? Evidence from Czech Agriculture

Market liberalization in Central and Eastern Europe was targeted at establishing incentives that would improve economic performance. While substantial reorganization of enterprises is observed, firms can also be observed which devote resources towards establishing organizational legitimacy. Motivations for such behavior are considered and empirical evidence of its relationship with technical efficiency using a distance function approach is analyzed for the case of Czech agriculture. Contrary to the expectation that such behavior would be inefficient, we find that firms reap private economic gains from legitimacy efforts through improved access to agricultural land, investment subsidies and firm internal social capital. However, its effect on technical efficiency depends on whether such legitimacy efforts are valued by stakeholders or understood as a norm. Evidence of the trade-off between gains or sustainability from legitimacy and reorganization thus brings a new perspective to the understanding of structural changes in transition.organizational legitimacy, efficiency, structural change, transition, agriculture, Industrial Organization, D21, D23, D24,

Densidade de Rhea americana em três paisagens diferentes no Pantanal da Nhecolândia.

Pecuária em campos nativos constitui uma atividade tradicional no Pantanal brasileiro. Contudo, tem um aumento na substituição de vegetação nativa por pastagens cultivadas de espécies exóticas. As respostas da fauna local em relação a essas transformações ainda são pouco conhecidas. O objetivo do trabalho foi estimar a densidade de ema, Rhea americana, em três diferentes paisagens, para verificar como as densidades de ema respondem a estas diferenças. Cattle ranching on native grasslands is a traditional activity in the Brazilian Pantanal. However, recently there is an increase in the replacement of the native vegetation by cultivated pastures with exotic species. The responses of the local fauna in relation to these changes are still poorly known. The objective of this study was to estimate the density of rhea, Rhea americana, in three landscapes in order to assess the response population density to these differences