973 research outputs found
The Power of Proximity: Strategic Decisions in African Party Politics
No full textRecent publications suggest that exclusively ethnoregional parties are as rare in sub- Saharan Africa as elsewhere. At the same time, the idea that ethnicity is a very special feature of African party politics persists. The paper acknowledges the general relevance of ethnicity in party competition but emphasizes the level on which it becomes important. It develops a microbehavioral approach which pays particular attention to the strategic choices of party elites in order to supplement the dominant structuralist thinking in party research on Africa. An in-depth evaluation of detailed election data from Burkina Faso shows that strategies which rely on personal proximity between the voter and the candidates influence the parties’ success to a great extent. Parties maximize their chances of winning seats if they concentrate their limited resources on the home localities of leading party members. Hence, African party politics are less dependent on ethnic demography than is often implied but more open to change through elite behavior.political parties, Burkina Faso, elections, local mobilization, resource efficiency, son of the soil
Treatment of unruptured intracranial aneurysms : a surgical long-term evaluation for preoperative predictive analytics
No full textAuthor Dr.med.univ. Nico Henrique Stroh-HollyDissertation Johannes Kepler Universität Linz 202
Are habitat types compatible with floristically‐derived associations?
No full textThe habitat type system developed by R. Daubenmire has been widely adopted throughout the western United States. Habitat types result from a site classification derived from the classification of late seral plant communities using selected indicator species. It has been suggested that the classification of late successional vegetation used to derive habitat types does not substantially differ from phytosociological classification in the sense of Braun-Blanquet approach, and that habitat types can be adopted in their present form into floristically-based vegetation classifications. Despite the many commonalities between the two systems, however, the classification methods, and specifically the use of indicator species in the habitat type system, yield a significantly different classification than the phytosociological approach. This is demonstrated in the comparison of a habitat type classification with the results of a recent phytosociological classification of forest vegetation in the northern Salish Mountains of Montana
Electroelastic plate instabilities based on the Stroh method in terms of the energy function Ω*(F, DL)
No full textThe stability of an electroelastic dielectric elastomer plate with compliant electrodes on its major surfaces under an applied potential difference is examined on the basis of the incremental theory of electroelastic fields. The Stroh method of analysis of the governing equations is used with the material constitutive law given in terms of the energy function Ω*(F, DL), where F is the deformation gradient and DL is the Lagrangian electric displacement field. For a particular class of energy functions, explicit bifurcation equations are obtained for antisymmetric and symmetric modes of instability and the results are illustrated for a Gent electroelastic material model with different values of the Gent parameter. This work confirms previous results obtained in terms of the energy function Ω(F, EL), where EL is the Lagrangian electric field
Elastodynamics of radially inhomogeneous spherically anisotropic elastic materials in the Stroh formalism
No full textA method is presented for solving elastodynamic problems in radially inhomogeneous elastic materials with spherical anisotropy, i.e. materials such that cijkl = cijkl(r) in a spherical coordinate system. The time harmonic displacement field u is expanded in a separation of variables form with dependence on described by vector spherical harmonics with r-dependent amplitudes. It is proved that such separation of variables solution is generally possible only if the spherical anisotropy is restricted to transverse isotropy with the principal axis in the radial direction, in which case the amplitudes are determined by a first-order ordinary differential system. Restricted forms of the displacement field, such as u admit this type of separation of variables solutions for certain lower material symmetries. These results extend the Stroh formalism of elastodynamics in rectangular and cylindrical systems to spherical coordinates.Peer reviewedReceived July 29, 2011; accepted September 16, 2011; published online December 23, 2011. Print publication date February 2012. Manuscript dated September 14, 2011
Stroh formalism in analysis of skew-symmetric and symmetric weight functions for interfacial cracks
No full textThe focus of the paper is on the analysis of skew-symmetric weight functions for interfacial cracks in two-dimensional anisotropic solids. It is shown that the Stroh formalism proves to be an efficient tool for this challenging task. Conventionally, the weight functions, both symmetric and skew-symmetric, can be identified as non-trivial singular solutions of a homogeneous boundary-value problem for a solid with a crack. For a semi-infinite crack, the problem can be reduced to solving a matrix Wiener-Hopf functional equation. Instead, the Stroh matrix representation of displacements and tractions, combined with a Riemann-Hilbert formulation, is used to obtain an algebraic eigenvalue problem, which is solved in a closed form. The proposed general method is applied to the case of a quasi-static semi-infinite crack propagating between two dissimilar orthotropic media: explicit expressions for the weight functions are evaluated and then used in the computation of the complex stress intensity factor corresponding to a general distribution of forces acting on the crack faces. © The Author(s) 2012
The Stroh formalism for acoustic waves in 1D-inhomogeneous media: unified background and some applications
No full textThe aim of the review is to consolidate the core aspects of the Stroh formalism, trace the development of the impedance matrix concept, and outline the range of acoustic problems that have been treated by these methods over the last two and a half decades
The Stroh formalism for acoustic waves in 1D-inhomogeneous media: unified background and some applications
No full textThe aim of the review is to consolidate the core aspects of the Stroh formalism, trace the development of the impedance matrix concept, and outline the range of acoustic problems that have been treated by these methods over the last two and a half decades
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