405 research outputs found
Adaptive Energy Preserving Methods for Partial Differential Equations
A method for constructing first integral preserving numerical schemes for
time-dependent partial differential equations on non-uniform grids is
presented. The method can be used with both finite difference and partition of
unity approaches, thereby also including finite element approaches. The schemes
are then extended to accommodate -, - and -adaptivity. The method is
applied to the Korteweg-de Vries equation and the Sine-Gordon equation and
results from numerical experiments are presented.Comment: 27 pages; some changes to notation and figure
Variational image regularization with Euler's elastica using a discrete gradient scheme
This paper concerns an optimization algorithm for unconstrained non-convex
problems where the objective function has sparse connections between the
unknowns. The algorithm is based on applying a dissipation preserving numerical
integrator, the Itoh--Abe discrete gradient scheme, to the gradient flow of an
objective function, guaranteeing energy decrease regardless of step size. We
introduce the algorithm, prove a convergence rate estimate for non-convex
problems with Lipschitz continuous gradients, and show an improved convergence
rate if the objective function has sparse connections between unknowns. The
algorithm is presented in serial and parallel versions. Numerical tests show
its use in Euler's elastica regularized imaging problems and its convergence
rate and compare the execution time of the method to that of the iPiano
algorithm and the gradient descent and Heavy-ball algorithms
Dissipative numerical schemes on Riemannian manifolds with applications to gradient flows
This paper concerns an extension of discrete gradient methods to
finite-dimensional Riemannian manifolds termed discrete Riemannian gradients,
and their application to dissipative ordinary differential equations. This
includes Riemannian gradient flow systems which occur naturally in optimization
problems. The Itoh--Abe discrete gradient is formulated and applied to gradient
systems, yielding a derivative-free optimization algorithm. The algorithm is
tested on two eigenvalue problems and two problems from manifold valued
imaging: InSAR denoising and DTI denoising.Comment: Post-revision version. To appear in SIAM Journal on Scientific
Computin
Complete analytic anharmonic hyper-Raman scattering spectra
We present the first computational treatment of the complete second-order vibrational perturbation
theory applied to hyper-Raman scattering spectroscopy. The required molecular properties are
calculated in a fully analytic manner using a recently developed program [Ringholm, Jonsson and
Ruud, J. Comp. Chem., 2014, 35, 622] that utilizes recursive routines. For some of the properties,
these calculations are the first analytic calculations of their kind at their respective levels of theory.
We apply this approach to the calculation of the hyper-Raman spectra of methane, ethane and
ethylene and compare these to available experimental data. We show that the anharmonic
corrections have a larger effect on the vibrational frequencies than on the spectral intensities, but
that the inclusion of combination and overtone bands in the anharmonic treatment can improve the
agreement with the experimental data, although the quality of available experimental data limits a
detailed comparison
Innovative forms of citizen participation at the fringe of the formal planning system
In the Nordic countries, we are witnessing a proliferation of novel and more experimental ways of citizen and authority interaction within the field of urban planning and governance. These formats are seen in urban regeneration projects and planning experiments that endorse more inclusive interactions between public authorities and local actors than in the traditional formal hearings. The intention of this article is to explore the potential of these forms of participation in contributing to social innovation particularly related to including citizens that are difficult to reach, and in creating new arenas for interaction and collaboration. Theoretically, the article is inspired by the concepts of social innovation, planning as experimentation (Hillier, 2007; Nyseth, Pløger, & Holm, 2010), and co-creation (Voorberg, Bekkers, & Tummers, 2013). Empirically, the article draws on three different cases from Norway and Denmark which entailed some novel ways of involving local citizens in urban planning. Finally, the article discusses how formal planning procedures can gain inspiration from such initiatives
When Innovative Ideas Encounter Institutions: An Analytical Model
This paper presents an analytical model for studying “encounters” that take place when ideas for innovation meet institutions (The IIE-model). Our model aims to expand the dichotomous barriers/driver approach in innovation research. Building on the theoretical contributions of studies on institutional logics and change, this model presents a dynamic, institution-based understanding of what happens when innovative ideas meet institutions. Four ideal types of encounters describe the mutual impact of institutions and innovative ideas. This paper aims to contribute to a wider and more nuanced understanding of the dynamics of innovation processes
Improved Pregnancy Outcome in Type 1 Diabetic Women With Microalbuminuria or Diabetic Nephropathy: Effect of intensified antihypertensive therapy?
OBJECTIVE—To describe pregnancy outcome in type 1 diabetic women with normoalbuminuria, microalbuminuria, or diabetic nephropathy after implementation of an intensified antihypertensive therapeutic strategy
Participation according to the law? The research-based knowledge on citizen participation in Norwegian municipal planning
Source at http://doi.org/10.30689/EJSD2018:67.1650-9544. Citizen participation is enshrined in the Norwegian Planning and Building Act
(PBA) 1985 and accentuated by the 2008 revision of the PBA. In this article,
we ask if the research on participation in municipal planning is sufficient to
draw conclusions on whether the Act is effective with regard to both the
spirit and the letter of the law. The guiding framework for the analysis is
based on the concepts of input and output legitimacy and the distinction
between ‘tidy’ and ‘untidy’ participation. The analysis is based on scientific
publications published after the 2008 revision of the PBA. We find that the
majority of the research concentrates on zoning plans and municipalityinitiated ‘tidy’ participation. As a result, there are gaps in the research with
regard to both the planning context and the interconnectedness of different
forms of participation. Therefore, the research reviewed can only partially
inform the law-makers on the functioning of the Act
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