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- Davidsson, Peter, et al.
(author)
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Analysis of sound transmission loss of double-leaf walls in the low-frequency range using the finite element method
- 2004
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In: Building Acoustics. - : SAGE Publications. - 1351-010X .- 2059-8025. ; 11:4, s. 239-257
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Journal article (peer-reviewed)abstract
- The sound transmission loss of double walls in the low-frequency range is studied by means of structure-acoustic finite element analysis. The analysis simulates standard experiments to determine sound transmission loss of walls. The model is a detailed description of the geometry of the system, including both the double wall and the rooms acoustically coupled to the wall. The frequency range studied is in the 1/3-octave bands between 40 Hz and 200 Hz. A parametric study is performed to investigate the influence on the sound transmission loss of various material and geometric properties of the wall and the dimensions of the connecting rooms. The model confirms the importance of primary structural resonance and the size of the connecting rooms in determining the degree of sound transmission loss. The primary structural resonance is mainly determined by the distance between the wall studs and the properties of the sheeting material. Wall length is also important; if the length is such that the wall studs of the last wall cavity are closer together than those of the other wall cavities, the primary structural resonance will be at a higher frequency, thereby decreasing sound transmission loss over a broader frequency range. Similar dimensions of the connecting rooms results in poor transmission loss, mainly at frequencies below 100 Hz (for the wall and room dimensions studied here).
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2. |
- Brackmann, Christian, et al.
(author)
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Optical and mass spectrometric study of the pyrolysis gas of wood particles
- 2003
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In: Applied Spectroscopy. - : SAGE Publications. - 1943-3530 .- 0003-7028. ; 57:2, s. 216-222
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Journal article (peer-reviewed)abstract
- A detailed experimental investigation has been made of the pyrolysis-the first step in biomass combustion-of single birchwood particles. In addition to mass spectrometric and gravimetric analysis, the pyrolysis volatiles were characterized by different optical techniques. Absorption measurements showed a nearly featureless absorption in the ultraviolet spectral region with a continuously stronger absorption for shorter wavelengths. Using different excitation wavelengths, laser-induced fluorescence measurements revealed generally broad spectra in the spectral region from 300-500 nm, which are characteristic spectral signatures for larger hydrocarbons. The optical data were monitored at different times in the pyrolysis process of the particles and compared with the results from the mass spectrometric and gravimetric analysis. The sensitivity of the optical techniques for differentiation between specific molecules was rather low, although formaldehyde could be observed both in absorption and fluorescence spectra. Laser-induced fluorescence measurements were also made for two-dimensional visualization of the pyrolysis volatiles; emitted from heated birchwood particles, indicating much higher flows along the fiber direction than across.
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- Davidsson, Hans, 1958, et al.
(author)
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Organs in Göteborg
- 2002
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In: Jaud, R (ed). European cities of historical organs : Alkmaar, Freiberg, Göteborg, Innsbruck, Lisboa, Roskilde, Toulouse, Treviso, Zaragoza = Europae civitates historicorum organorum [ECHO]. - Innsbruck, Austria : ECHO.
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Book chapter (other academic/artistic)
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