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Consistent Framework (consistent + framework)
Selected AbstractsComparing Investments in New Transport Infrastructure: Roads versus Railways?FISCAL STUDIES, Issue 3 2003Luisa Affuso Abstract This paper contributes to the debate on investment in transport infrastructure and the allocation of public funds between road and railway projects. We model the two options and provide a consistent framework to appraise investment in typical new inter,urban road and rail projects. Our results suggest that road improvements have substantially higher returns than railway schemes. These findings cast doubt on the rationale of the new transport policy for the UK, which proposes to allocate more public funds to the (private) railways than total new investment in strategic roads. [source] A variationally consistent framework for the design of integrator and updates of generalized single step representations for structural dynamicsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 8 2003R. Kanapady Abstract A variationally consistent framework leading to the concise design of both the ,integrator' and the associated ,updates' as related to the single step representations encompassing the so-called LMS methods for structural dynamics is described. The present paper shows for the first time, a consistent treatment involving both the ,integrator' and ,updates' that are inherent in the general context of designing the time integration process. Furthermore, the framework encompasses not only all the existing time integration algorithms that are dissipative and non-dissipative within the scope of LMS methods but also contains new optimal algorithms useful for practical applications,in the sense of accuracy, stability, numerical dissipation and dispersion, and overshoot characteristics of computational algorithms for time dependent problems encountered in structural dynamics. Copyright © 2003 John Wiley & Sons, Ltd. [source] Thermodynamically consistent phase-field models of fracture: Variational principles and multi-field FE implementationsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 10 2010C. Miehe Abstract The computational modeling of failure mechanisms in solids due to fracture based on sharp crack discontinuities suffers in situations with complex crack topologies. This can be overcome by a diffusive crack modeling based on the introduction of a crack phase-field. In this paper, we outline a thermodynamically consistent framework for phase-field models of crack propagation in elastic solids, develop incremental variational principles and consider their numerical implementations by multi-field finite element methods. We start our investigation with an intuitive and descriptive derivation of a regularized crack surface functional that ,-converges for vanishing length-scale parameter to a sharp crack topology functional. This functional provides the basis for the definition of suitable convex dissipation functions that govern the evolution of the crack phase-field. Here, we propose alternative rate-independent and viscous over-force models that ensure the local growth of the phase-field. Next, we define an energy storage function whose positive tensile part degrades with increasing phase-field. With these constitutive functionals at hand, we derive the coupled balances of quasi-static stress equilibrium and gradient-type phase-field evolution in the solid from the argument of virtual power. Here, we consider a canonical two-field setting for rate-independent response and a time-regularized three-field formulation with viscous over-force response. It is then shown that these balances follow as the Euler equations of incremental variational principles that govern the multi-field problems. These principles make the proposed formulation extremely compact and provide a perfect base for the finite element implementation, including features such as the symmetry of the monolithic tangent matrices. We demonstrate the performance of the proposed phase-field formulations of fracture by means of representative numerical examples. Copyright © 2010 John Wiley & Sons, Ltd. [source] Geometry update driven by material forces for simulation of brittle crack growth in functionally graded materialsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 13 2009Rolf Mahnken Abstract Functionally graded materials (FGMs) are advanced materials that possess continuously graded properties, such that the growth of cracks is strongly dependent on the gradation of the material. In this work a thermodynamic consistent framework for crack propagation in FGMs is presented, by applying a dissipation inequality to a time-dependent migrating control volume. The direction of crack growth is obtained in terms of material forces as a result of the principle of maximum dissipation. In the numerical implementation a staggered algorithm,deformation update for fixed geometry followed by geometry update for fixed deformation,is employed within each time increment. The geometry update is a result of the incremental crack propagation, which is driven by material forces. The corresponding mesh is generated by combining Delaunay triangulation with local mesh refinement. Furthermore a Newton algorithm is proposed, taking into account mesh transfer of displacements for crack propagation in incremental elasticity. In two numerical examples brittle crack propagation in FGMs is investigated for various directions of strength gradation within the structures. Copyright © 2008 John Wiley & Sons, Ltd. [source] Survivor Derivatives: A Consistent Pricing FrameworkJOURNAL OF RISK AND INSURANCE, Issue 3 2010Paul Dawson Survivorship risk is a significant factor in the provision of retirement income. Survivor derivatives are in their early stages and offer potentially significant welfare benefits to society. This article applies the approach developed by Dowd et al. (2006), Olivier and Jeffery (2004), Smith (2005), and Cairns (2007) to derive a consistent framework for pricing a wide range of linear survivor derivatives, such as forwards, basis swaps, forward swaps, and futures. It then shows how a recent option pricing model set out by Dawson et al. (2009) can be used to price nonlinear survivor derivatives, such as survivor swaptions, caps, floors, and combined option products. It concludes by considering applications of these products to a pension fund that wishes to hedge its survivorship risks. [source] Why Are You Learning a Second Language?LANGUAGE LEARNING, Issue S1 2003Motivational Orientations, Self-Determination Theory The data for this study were collected in my first year of graduate school for a term paper for a course I was taking from Luc Pelletier. When I began graduate school, Luc also started at the University of Ottawa as a new faculty member, and he taught a course in motivation. I had worked with Richard Clément for a couple of years already as an honors student and as a research assistant and had conducted research on orientations and motivation under his supervision as part of my honors thesis project. Luc was very interested in self-determination theory (SDT) and had worked with Bob Vallerand on an instrument to assess academic motivation from this perspective. Luc and I decided to carry out a study on language learning orientations using SDT and enlisted Richard's and Bob's involvement in the project. As a bilingual institution where all students were required to demonstrate competence in their second language (L2), whether French or English, the University of Ottawa was an ideal setting for this type of research. The project was a first examination of SDT in the language learning context, and to the best of my knowledge it was the only, or at least one of the very few, empirical investigations of intrinsic and extrinsic motivation in the area. It involved the development of a valid and reliable instrument to assess the different subtypes of intrinsic and extrinsic motivation. It also explored the link between these motivational subtypes and various orientations to language learning that had been identified by Clément and Kruidenier (1983), including the travel, friendship, knowledge, and instrumental orientations. The results showed that the instrumental orientation and the SDT external regulation orientation were strongly correlated, and that the travel, friendship, and knowledge orientations were quite highly intercorrelated with identified regulation and intrinsic motivation. Moreover, the instrumental and external regulation orientation scales correlated in similar ways with the hypothesized antecedents of perceived autonomy and competence and the hypothesized consequences of intention to pursue L2 study and anxiety. In addition, the travel, friendship, and knowledge orientations were correlated with the hypothesized antecedents and consequences in a manner similar to intrinsic motivation and identified regulation. These results suggested that Clément and Kruidenier's 4 orientations may be tapping a similar construct as the SDT orientations. My only regret with this study is that I did not include a scale to measure the integrative orientation (Gardner, 1985) to determine its relation with the SDT subtypes. This issue would have to wait until a later study to be addressed. The results of this initial investigation encouraged me to pursue research integrating SDT with other theoretical frameworks of language learning motivation. I believe that the SDT framework has several advantages over some other formulations of learner orientations. SDT offers a parsimonious, internally consistent framework for systematically describing many different orientations in a comprehensive manner. It also offers considerable explanatory power for understanding why certain orientations are better predictors of relevant language learning variables (e.g., effort, persistence, attitudes) than others. Also, by invoking the psychological mechanisms of perceived autonomy, competence, and relatedness, it can account for why certain orientations are evident in some learners and not in others. Moreover, the framework is empirically testable and indeed has stood up well under empirical scrutiny in our studies. Its clear predictions may also be particularly valuable in applying the theory in language teaching and program development. [The present article first appeared in Language Learning, 50 (1), 2000, 57,85] [source] Modeling process flow using diagramsQUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 4 2010Benjamin Kemper Abstract In the practice of process improvement, tools such as the flowchart, the value-stream map (VSM), and a variety of ad hoc variants of such diagrams are commonly used. The purpose of this paper is to present a clear, precise, and consistent framework for the use of such flow diagrams in process improvement projects. The paper finds that traditional diagrams, such as the flowchart, the VSM, and OR-type of diagrams, have severe limitations, miss certain elements, or are based on implicit but consequential premises. These limitations restrict the applicability of traditional diagrams in non-manufacturing areas such as service and healthcare processes. We show that a rational reconstruction for the use of diagrams in various disciplines regarding process flow boils down to a generic framework of elements, definitions of generic process metrics, and three classes of applications, namely the ,as-is', ,could-be', and ,should-be' analysis. The goal is not to replace all currently used diagrams, but merely to discuss the role of diagram usage in process flow modeling. This paper provides an explicit framework that is unambiguous and flexible, and has the potential to serve as a guideline for the practitioner, in manufacturing as well as in service and healthcare. Besides, it may serve as a starting point to develop an ontology of business processes. Copyright © 2009 John Wiley & Sons, Ltd. [source] Phylogeny and phylogeography of squirrel monkeys (genus Saimiri) based on cytochrome b genetic analysisAMERICAN JOURNAL OF PRIMATOLOGY, Issue 3 2010Anne Lavergne Abstract Squirrel monkeys (genus Saimiri) are distributed over a wide area encompassing the Amazon Basin: French Guiana, Suriname, and Guyana, together with Western Panama and Western Costa Rica. The genus Saimiri includes a complex of species and subspecies displaying considerable morphological variation. Taxonomic and systematic studies have identified, in this genus, one to seven species comprising up to 16 subspecies. The phylogenetic relationships between these taxa are poorly understood. Molecular markers have yielded a consistent framework for the systematics of Central and South American Saimiri, identifying four distinct clades: S. oerstedii, S. sciureus, S. boliviensis, and S. ustus. Here, we reconsider the phylogenetic and biogeographic history of Saimiri on the basis of mitochondrial (mtDNA) sequence data, focusing mostly on individuals originating from the Amazon Basin. We studied 32 monkeys with well-defined geographic origins and inferred the phylogenetic relationships between them on the basis of full-length cytochrome b gene nucleotide sequences. The high level of gene diversity observed (0.966) is consistent with the high level of behavioral and morphological variation observed across the geographic range of the genus: 20 mtDNA haplotypes were identified with a maximum divergence of 4.81% between S. b. boliviensis and S. ustus. In addition to confirming the existence of the four clades previously identified on the basis of molecular characters, we suggest several new lineages, including S. s. macrodon, S. s. albigena, S. s. cassiquiarensis, and S. s. collinsi. We also propose new patterns of dispersion and diversification for the genus Saimiri, and discuss the contribution of certain rivers and forest refuges to its structuring. Am. J. Primatol. 72:242,253, 2010. © 2009 Wiley-Liss, Inc. [source] Mixtures of correlated bosons and fermions: Dynamical mean-field theory for normal and condensed phasesANNALEN DER PHYSIK, Issue 9 2009K. Byczuk Abstract We derive a dynamical mean-field theory for mixtures of interacting bosons and fermions on a lattice (BF-DMFT). The BF-DMFT is a comprehensive, thermodynamically consistent framework for the theoretical investigation of Bose-Fermi mixtures and is applicable for arbitrary values of the coupling parameters and temperatures. It becomes exact in the limit of high spatial dimensions d or coordination number Z of the lattice. In particular, the BF-DMFT treats normal and condensed bosons on equal footing and thus includes the effects caused by their dynamic coupling. Using the BF-DMFT we investigate two different interaction models of correlated lattice bosons and fermions, one where all particles are spinless (model I) and one where fermions carry a spin one-half (model II). In model I the local, repulsive interaction between bosons and fermions can give rise to an attractive effective interaction between the bosons. In model II it can also lead to an attraction between the fermions. [source] | |||||||||||||