This study explores the amplitude and phase transmission of audio-frequency sound through a waveguide side-loaded with a series of closely spaced and sequentially tuned Helmholtz resonators. This system exhibits a series of acoustic bandgaps due to the Helmholtz resonance and standing-wave cavity modes. The bandgaps are achieved in a physically compact manner in that the resonators are spaced b...

The Helmholtz equation for symmetric, traceless, second-rank tensor fields in three-dimensional flat space is solved in spherical and cylindrical coordinates by separation of variables making use of the corresponding spin-weighted harmonics. It is shown that any symmetric, traceless, divergenceless second-rank tensor field that satisfies the Helmholtz equation can be expressed in terms of two s...

Title: Influence of demographic changes on the impact of vaccination against varicella and herpes zoster in Germany a mathematical modelling study Authors: Johannes Horn ([email protected]) Oliver Damm ([email protected]) Wolfgang Greiner ([email protected]) Hartmut Hengel ([email protected]) Mirjam Kretzschmar ([email protected]) Anne...

Landscape Ecology Group, University of Oldenburg, D-26111 Oldenburg, Germany Institute of Geoecology, University of Potsdam, D-14415 Potsdam, Germany Helmholtz Centre for Environmental Research – UFZ, Department of Conservation Biology, Permoserstr. 15, 04318 Leipzig, Germany Field Station Fabrikschleichach, University of Würzburg, Glashuettenstrasse 5, 96181 Rauhenebrach, Germany Institute of ...

In this paper, we extend to the time-harmonic Maxwell equations the p–version analysis technique developed in [R. Hiptmair, A. Moiola and I. Perugia, Plane wave discontinuous Galerkin methods for the 2D Helmholtz equation: analysis of the p-version, SIAM J. Numer. Anal., 49 (2011), 264-284] for Trefftz-discontinuous Galerkin approximations of the Helmholtz problem. While error estimates in a me...

The ultra weak variational formulation (UWVF) approach has been proposed as an effective method for solving Helmholtz problems with high wave numbers. However, for coarse meshes the method can suffer from instability. In this paper we consider computational aspects of the ultra weak variational formulation for the inhomogeneous Helmholtz problem. We introduce a method to improve the UWVF scheme...

In this paper we extend the source transfer domain decomposition method (STDDM) introduced by the authors to solve the Helmholtz problems in two-layered media, the Helmholtz scattering problems with bounded scatterer, and Helmholtz problems in 3D unbounded domains. The STDDM is based on the decomposition of the domain into non-overlapping layers and the idea of source transfer which transfers t...

In this paper, the formulation of a new group explicit method with a fourth order accuracy is described in solving the two dimensional Helmholtz equation. The formulation is based on the nine-point fourth order compact finite difference approximation formula. The complexity analysis of the developed scheme is also presented. Several numerical experiments were conducted to test the feasibility o...

Pushed by the rising interest in high resolution requirements and high-dimensional applications, the diffusion term in the Laplacian equation drives the condition number of the associated discretized operator to undesirable sizes for standard iterative methods to converge rapidly. In addition, for realistic values of the wavenumber k(x) in (1), the Helmholtz operator H becomes indefinite, destr...

BACKGROUND Effects of electromagnetic fields on healing have been investigated for centuries. Substantial data indicate that exposure to electromagnetic field can lead to enhanced healing in both soft and hard tissues. Helmholtz coils are devices that generate pulsed electromagnetic fields (PEMF). Objective : In this work, a pair of Helmholtz coils for enhancing the healing process in periodont...