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Wyświetlanie 1-2 z 2
Tytuł:
Research on Airflow Background Noise Suppression for Aeroacoustic Wind Tunnel Testing
Autorzy:
Li, Yuanwen
Li, Min
Feng, Daofang
Yang, Debin
Wei, Long
Powiązania:
https://bibliotekanauki.pl/articles/2141671.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
aeroacoustic measurement
acoustic source localization
EEMD; background noise suppression
wind tunnel test.
Opis:
The microphone data collected in aeroacoustic wind tunnel test contains not only desired aeroacoustic signal but also background noise generated by the jet or the valve of the wind tunnel, so the desired aeroacoustic characteristics is difficult to be highlighted due to the low Signal-to-Noise Ratio (SNR). Classical cross spectral matrix removal can only reduce the microphone self-noise, but its effect is limited for jet noise. Therefore, an Airflow Background Noise Suppression method based on the Ensemble Empirical Mode Decomposition (ABNSEEMD) is proposed to eliminate the influence of background noise on aeroacoustic field reconstruction. The new method uses EEMD to adaptively separate the background noise in microphone data, which has good practicability for increasing SNR of aeroacoustic signal. A localization experiment was conducted by using two loudspeakers in wind tunnel with 80 m/s velocity. Results show that proposed method can filter out the background noise more effectively and improve the SNR of the loudspeakers signal compared with spectral subtraction and cepstrum methods. Moreover, the aeroacoustic field produced by a NACA EPPLER 862 STRUT airfoil model was also measured and reconstructed. Delay-and-sum beamforming maps of aeroacoustic source were displayed after the background noise was suppressed, which further demonstrates the proposed method’s advantage.
Źródło:
Archives of Acoustics; 2022, 47, 2; 241-257
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Chemical Information of Chitosan-Based Complex Extracted from Coincidence Doppler Broadening Spectra
Autorzy:
Cao, Xingzhong
Xia, Rui
Yang, Jing
Zeng, Minfeng
Wang, Baoyi
Yu, Runsheng
Wei, Long
Powiązania:
https://bibliotekanauki.pl/articles/1033908.pdf
Data publikacji:
2017-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
64.70.km
82.30.Gg
Opis:
In recent years, coincidence Doppler broadening (CDB) of annihilation radiation measurement on polymeric system has been attracting special attention because of its unique elemental sensitivities in comparison to the traditional Doppler broadening measurement. In the present study, chitosan-Fe₃O₄ nanocomposite (CS-Fe₃O₄) and copper-chitosan (Cu-CS) complexes were prepared through a simple casting method from aqueous solution. The inclusion of Fe₃O₄ nanoparticles in the chitosan matrix is confirmed by X-ray diffraction. In order to obtain data about atomic composition of the annihilation site in the CS composites, CDB measurements were carried out. The normalized CDB ratio curve, which is related to the ratio between the momentum density distribution for the studied samples and pure CS, was displayed to illustrate the variation of ion cores of different elements present in the chitosan matrix. Our result confirms a contribution of active group available in chitosan molecules to the features in the high-momentum region of the CDB ratio curve. The findings show that the local chemical environment of the annihilation site in chitosan-based complexes could be estimated by such positron annihilation spectroscopic investigation.
Źródło:
Acta Physica Polonica A; 2017, 132, 5; 1535-1537
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-2 z 2

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