2,147 research outputs found
Viewing the Steklov eigenvalues of the Laplace operator as critical Neumann eigenvalues
We consider the Steklov eigenvalues of the Laplace operator as limiting
Neumann eigenvalues in a problem of boundary mass concentration. We discuss the
asymptotic behavior of the Neumann eigenvalues in a ball and we deduce that the
Steklov eigenvalues minimize the Neumann eigenvalues. Moreover, we study the
dependence of the eigenvalues of the Steklov problem upon perturbation of the
mass density and show that the Steklov eigenvalues violates a maximum principle
in spectral optimization problems.Comment: This is a preprint version of a paper that will appear in the
Proceedings of the 9th ISAAC Congress, Krak\'ow 201
Wave simulation for the design of an innovative quay wall: the case of Vlorë Harbour
Sea states and environmental conditions are basic data for the
design of marine structures. Hindcasted wave data have been applied here
with the aim of identifying the proper design conditions for an innovative
quay wall concept.
In this paper, the results of a computational fluid dynamics model are used to
optimise the new absorbing quay wall of Vlorë Harbour (Republic of
Albania) and define the design loads under extreme wave
conditions. The design wave states at the harbour entrance have been
estimated analysing 31Â years of hindcasted wave data simulated through the
application of WaveWatch III. Due to the particular geography and topography
of the Bay of Vlorë, wave conditions generated from the north-west are
transferred to the harbour entrance with the application of a 2-D spectral wave
module, whereas southern wave states, which are also the most critical for
the port structures, are defined by means of a wave generation model,
according to the available wind measurements. Finally, the identified extreme
events have been used, through the NewWave approach, as boundary conditions
for the numerical analysis of the interaction between the quay wall and the
extreme events. The results show that the proposed method, based on
numerical modelling at different scales from macro to meso and to micro,
allows for the identification of the best site-specific solutions, also for a
location devoid of any wave measurement. In this light, the objectives of
the paper are two-fold. First, they show the application of sea condition
estimations through the use of wave hindcasted data in order to properly
define the design wave conditions for a new harbour structure. Second, they
present a new approach for investigating an innovative absorbing quay wall based
on CFD modelling and the NewWave theory
Gradient based sequential Markov chain Monte Carlo for multitarget tracking with correlated measurements
Measurements in wireless sensor networks (WSNs) are often correlated both in space and in time. This paper focuses on tracking multiple targets in WSNs by taking into consideration these measurement correlations. A sequential Markov Chain Monte Carlo (SMCMC) approach is proposed in which a Metropolis within Gibbs refinement step and a likelihood gradient proposal are introduced. This SMCMC filter is applied to case studies with cellular network received signal strength data in which the shadowing component correlations in space and time are estimated. The efficiency of the SMCMC approach compared to particle filtering, as well as the gradient proposal compared to a basic prior proposal, are demonstrated through numerical simulations. The accuracy improvement with the gradient-based SMCMC is above 90% when using a low number of particles. Thanks to its sequential nature, the proposed approach can be applied to various WSN applications, including traffic mobility monitoring and prediction
Sequential Markov Chain Monte Carlo for multi-target tracking with correlated RSS measurements
In this paper, we present a Bayesian approach to accurately track multiple objects based on Received Signal Strength (RSS) measurements. This work shows that taking into account the spatial correlations of the observations caused by the random shadowing effect can induce significant tracking performance improvements, especially in very noisy scenarios. Additionally, the superiority of the proposed Sequential Markov Chain Monte Carlo (SMCMC) method over the more common Sequential Importance Resampling (SIR) technique is empirically demonstrated through numerical simulations in which multiple targets have to be tracked
Spectral analysis of the biharmonic operator subject to Neumann boundary conditions on dumbbell domains
We consider the biharmonic operator subject to homogeneous boundary
conditions of Neumann type on a planar dumbbell domain which consists of two
disjoint domains connected by a thin channel. We analyse the spectral behaviour
of the operator, characterizing the limit of the eigenvalues and of the
eigenprojections as the thickness of the channel goes to zero. In applications
to linear elasticity, the fourth order operator under consideration is related
to the deformation of a free elastic plate, a part of which shrinks to a
segment. In contrast to what happens with the classical second order case, it
turns out that the limiting equation is here distorted by a strange factor
depending on a parameter which plays the role of the Poisson coefficient of the
represented plate.Comment: To appear in "Integral Equations and Operator Theory
High-Voltage Energy Harvesting and Storage System for Internet of Things Indoor Application
On the path toward independence from fossil fuels, solar energy is the mostpromising solution, but it needs a robust and reliable storage system to face itsintrinsicfluctuations due to location, day cycle, and weather. The integrationbetween energy harvesting and storage (H&S) technologies is a must toward cleanenergy production, and it becomes even more appealing considering the possi-bility of producing electricity not only from direct sunlight but also from diffuselight and indoor illumination. Herein, a dye-sensitized solar module (DSSM)developed to harvest indoor illumination and directly store it into an electricaldouble-layer capacitor (EDLC) is presented. Five series-connected dye-sensitizedsolar cells are fabricated on the same substrate and the module is integrated with ahigh-voltage EDLC. The integrated device is characterized under indoor lightsources such as light emitting diodes andfluorescent lamps. The results show oneof the highest efficiencies ever reported for a high-voltage DSSM under indoorillumination (16.27%), the largest voltage window ever reported for an indoor H&Sdevice based on DSSM and EDLC—up to 3 V—and an overall photoelectricconversion and storage efficiency of 9.73% under indoor illumination
CFD investigations of OXYFLUX device, an innovative wave pump technology for artificial downwelling of surface water
publisher: Elsevier articletitle: CFD investigations of OXYFLUX device, an innovative wave pump technology for artificial downwelling of surface water journaltitle: Applied Ocean Research articlelink: http://dx.doi.org/10.1016/j.apor.2016.10.002 content_type: article copyright: © 2016 Elsevier Ltd. All rights reserved
Steklov-type eigenvalues associated with best Sobolev trace constants: domain perturbation and overdetermined systems
We consider a variant of the classic Steklov eigenvalue problem, which arises
in the study of the best trace constant for functions in Sobolev space. We
prove that the elementary symmetric functions of the eigenvalues depend
real-analytically upon variation of the underlying domain and we compute the
corresponding Hadamard-type formulas for the shape derivatives. We also
consider isovolumetric and isoperimetric domain perturbations and we
characterize the corresponding critical domains in terms of appropriate
overdetermined systems. Finally, we prove that balls are critical domains for
the elementary symmetric functions of the eigenvalues subject to volume or
perimeter constraint
3D Reconstruction and Presentation of Cultural Heritage: AR and VR Experiences at the Museo d’Arte Orientale di Torino
For years, virtual reconstruction in the figurative arts, and sculpture, in particular, has been developing and consolidating. The
workflow from the acquisition to three-dimensional modelling and to the integration of missing parts, has been optimized through
processes entirely implemented in the digital dimension. The most recent developments in augmented reality and virtual reality
technologies, together with the possibility of using low-cost and widely available devices, have made it possible to establish new
links between the real and the virtual. The experiences presented in this paper comes up within the agreement between the
Politecnico di Torino and the Museo d’Arte Orientale (MAO). The workflow set up for this research involves: structure from motion
(SfM) survey, 3D modelling, and 3D philological reconstruction, then develops a proposal to implement augmented and virtual
reality experiences aimed at the communication and fruition of the exhibits. The case study concerns two Japanese statues, and
proposes their visualisation with the respective weapons virtually reconstructed, and through VR, involving the reconstruction of the
interior space of a temple recognised as philologically compatible with the location of the statues within a statuary complex
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