The influence of losses in double-negative metamaterial slabs recently introduced by Graciá-Salgado et al. [Phys. Rev. B 88, 224305 (2013)] is comprehensively studied. Viscous and thermal losses are considered in the linearized Navier-Stokes equations with no flow. Despite the extremely low thicknesses of boundary layers associated with each type of losses, the double-negative behavior is totally suppressed for the rigid structures under analysis. In other words, almost 100% of the energy transmitted into the slab is dissipated by viscothermal effects, in agreement with experimental data. Simulations undertaken for larger structures, using scale factors of up to 20 times, show that double-negative behavior is never recovered. The huge dissipation obtained by these structures leads us to propose them as interesting alternatives to conventional absorbers for specific situations, e.g., when treating low frequencies or when the excitation is narrow banded.

A study was conducted on the use of a Moving Bed Heat Exchanger-Filter (MHEF) for removing fine dust particles from gases. The influence of a number of variables was examined, including gas velocities, solid velocities, gas temperatures and dust sizes. The collection efficiency was found to decrease with increasing temperature; the total collection efficiency decreases strongly when the solid velocity increases. A stable numerical model for filtration and heat exchange was developed that predicts the two dimensional transient response of both solid and fluid phases. The numerical model incorporates variation in void fraction, velocities and transport coefficient due to combined processes ot' filtration and heat exchange.

Published 26In recent years, boundary element method (BEM) and finite element method (FEM) implementa-

This is the final report for key comparison CCAUV.A-K3 on the sensitivity calibration of laboratory standard microphones in the frequency range from 31.5 Hz to 31.5 kHz. Fifteen national measurement laboratories took part in this key comparison and the Centro Nacional de Metrología (CENAM), Mexico, piloted the project with the assistance of the Danish Primary Laboratory for Acoustics (DPLA), Denmark. Four travelling standard microphones were circulated to the participants in two loops linked through the measurements of the CENAM and the DPLA. The participants' results in the form of sensitivity measurements (dB re 1 V/Pa) and full uncertainty budgets were collected throughout the project. Reference values for all four standard microphones have been calculated using a linear least squares minimization method. The differences between measurements and references have been averaged to obtain the degrees of equivalence per laboratory and interlaboratory. The deviations are all below 0.1 dB, except at 31.5 kHz. A frequency of 1000 Hz has been chosen to illustrate the degrees of equivalence. In all cases, the deviation is smaller than the associated uncertainty.Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCAUV, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).