Modeling Broadband Microwave Structures by Artificial Neural Networks

The paper describes the exploitation of feed-forward neural networks and recurrent neural networks for replacing full-wave numerical models of microwave structures in complex microwave design tools. Building a neural model, attention is turned to the modeling accuracy and to the efficiency of building a model. Dealing with the accuracy, we describe a method of increasing it by successive completing a training set. Neural models are mutually compared in order to highlight their advantages and disadvantages. As a reference model for comparisons, approximations based on standard cubic splines are used. Neural models are used to replace both the time-domain numeric models and the frequency-domain ones

Modeling flows in periodically heterogeneous porous media with deformation-dependent permeability

The paper proposes a non-linear model of the Biot continuum. The nonlienarity is introduced in terms of the material coefficients which are expressed as linear functions of the macroscopic response. These functions are obtained by the sensitivity analysis of the homogenized coefficients computed for a given geometry of the porous structure which transforms due to the local deformation. Linear kinematics is assumed, however, the approach can be extended to large deforming porous materials

How to observe a non-Kerr spacetime

We present a generic criterion which can be used in gravitational-wave data analysis to distinguish an extreme-mass-ratio inspiral into a Kerr background spacetime from one into a non-Kerr background spacetime. The criterion exploits the fact that when an integrable system, such as the system that describes geodesic orbits in a Kerr spacetime, is perturbed, the tori in phase space which initially corresponded to resonances disintegrate so as to form the so called Birkhoff chains on a surface of section, according to the Poincar\'{e}-Birkhoff theorem. The KAM curves of these islands in such a chain share the same ratio of frequencies, even though the frequencies themselves vary from one KAM curve to another inside an island. On the other hand, the KAM curves, which do not lie in a Birkhoff chain, do not share this characteristic property. Such a temporal constancy of the ratio of frequencies during the evolution of the gravitational-wave signal will signal a non-Kerr spacetime which could then be further explored.Comment: 4 pages, 2 figure

The non-integrability of the Zipoy-Voorhees metric

The low frequency gravitational wave detectors like eLISA/NGO will give us the opportunity to test whether the supermassive compact objects lying at the centers of galaxies are indeed Kerr black holes. A way to do such a test is to compare the gravitational wave signals with templates of perturbed black hole spacetimes, the so-called bumpy black hole spacetimes. The Zipoy-Voorhees (ZV) spacetime (known also as the $\gamma$ spacetime) can be included in the bumpy black hole family, because it can be considered as a perturbation of the Schwarzschild spacetime background. Several authors have suggested that the ZV metric corresponds to an integrable system. Contrary to this integrability conjecture, in the present article it is shown by numerical examples that in general ZV belongs to the family of non-integrable systems.Comment: 10 pages, 13 figure

Dynamics and constraints of the Unified Dark Matter flat cosmologies

We study the dynamics of the scalar field FLRW flat cosmological models within the framework of the Unified Dark Matter (UDM) scenario. In this model we find that the main cosmological functions such as the scale factor of the Universe, the scalar field, the Hubble flow and the equation of state parameter are defined in terms of hyperbolic functions. These analytical solutions can accommodate an accelerated expansion, equivalent to either the dark energy or the standard $\Lambda$ models. Performing a joint likelihood analysis of the recent supernovae type Ia data and the Baryonic Acoustic Oscillations traced by the SDSS galaxies, we place tight constraints on the main cosmological parameters of the UDM cosmological scenario. Finally, we compare the UDM scenario with various dark energy models namely $\Lambda$ cosmology, parametric dark energy model and variable Chaplygin gas. We find that the UDM scalar field model provides a large and small scale dynamics which are in fair agreement with the predictions by the above dark energy models although there are some differences especially at high redshifts.Comment: 11 pages, 7 figures, published in Physical Review D, 78, 083509, (2008

Asymptotic gravitational-wave fluxes from a spinning test body on generic orbits around a Kerr black hole

This work provides gravitational wave energy and angular momentum asymptotic fluxes from a spinning body moving on generic orbits in a Kerr spacetime up to linear in spin approximation. To achieve this, we have developed a new frequency domain Teukolsky equation solver that calculates asymptotic amplitudes from generic orbits of spinning bodies with their spin aligned with the total orbital angular momentum. However, the energy and angular momentum fluxes from these orbits in the linear in spin approximation are appropriate for adiabatic models of extreme mass ratio inspirals even for spins non-aligned to the orbital angular momentum. To check the newly obtained fluxes, they were compared with already known frequency domain results for equatorial orbits and with results from a time domain Teukolsky equation solver called Teukode for off-equatorial orbits. The spinning body framework of our work is based on the Mathisson-Papapetrou-Dixon equations under the Tulczyjew-Dixon spin supplementary condition.Comment: 19 pages, 8 figure

Non-Linear Effects in Non-Kerr spacetimes

There is a chance that the spacetime around massive compact objects which are expected to be black holes is not described by the Kerr metric, but by a metric which can be considered as a perturbation of the Kerr metric. These non-Kerr spacetimes are also known as bumpy black hole spacetimes. We expect that, if some kind of a bumpy black hole exists, the spacetime around it should possess some features which will make the divergence from a Kerr spacetime detectable. One of the differences is that these non-Kerr spacetimes do not posses all the symmetries needed to make them integrable. We discuss how we can take advantage of this fact by examining EMRIs into the Manko-Novikov spacetime.Comment: 8 pages, 3 Figures; to appear in the proceedings of the conference "Relativity and Gravitation: 100 Years after Einstein in Prague" (2012

Developing a framework for the analysis of power through depotentia

Stakeholder participation in tourism policy-making is usually perceived as providing a means of empowerment. However participatory processes drawing upon stakeholders from traditionally empowered backgrounds may provide the means of removing empowerment from stakeholders. Such an outcome would be in contradiction to the claims that participatory processes improve both inclusivity and sustainability. In order to form an understanding of the sources through which empowerment may be removed, an analytical perspective has been developed deriving from Lukes�s views of power dating from 1974. This perspective considers the concept of depotentia as the removal of �power to� without speculating upon the underlying intent and also provides for the multidimensionality of power to be examined within a single study. The application of this analytical perspective has been tested upon findings of the government-commissioned report of the Countryside and Community Research Unit in 2005. The survey and report investigated the progress of Local Access Forums in England created in response to the Countryside and Rights of Way Act 2000. Consideration of the data from this perspective permits the classification of individual sources of depotentia which can each be addressed and potentially enable stakeholder groups to reverse loss of empowerment where it has occurred

Sustainable flood risk and stormwater management in blue‐green cities; an interdisciplinary case study in Portland, Oregon

Blue-Green Infrastructure (BGI) is recognized as a viable strategy to manage stormwater and flood risk, and its multifunctionality may further enrich society through the provision of multiple cobenefits that extend far beyond the hydrosphere. Portland, Oregon, is an internationally renowned leader in the implementation of BGI and showcases many best practice examples. Nonetheless, a range of interdisciplinary barriers and uncertainties continue to cloud decision making and impede wider implementation of BGI. In this paper, we synthesize research conducted by the “Clean Water for All” (CWfA) research project and demonstrate that interdisciplinary evaluation of the benefits of Portland’s BGI, focusing on green street bioswales and the East Lents Floodplain Restoration Project, is essential to address biophysical and sociopolitical barriers. Effective interdisciplinary approaches require sustained interaction and collaboration to integrate disciplinary expertise toward a common problem-solving purpose, and strong leadership from researchers adapt at spanning disciplinary boundaries. While the disciplinary differences in methodologies were embraced in the CWfA project, and pivotal to providing evidence of the disparate benefits of multifunctional BGI, cross-disciplinary engagement, knowledge coproduction, and data exchanges during the research process were of paramount importance to reduce the potential for fragmentation and ensure research remained integrated. © 2020 The Authors. Journal of the American Water Resources Association published by Wiley Periodicals LLC on behalf of American Water Resources Associatio