Bulletin of Environmental Contamination and Toxicology, Jan 3, 2013
Identifying the sources of volatile organic compounds (VOCs) is key issue to reducing ground-leve... more Identifying the sources of volatile organic compounds (VOCs) is key issue to reducing ground-level ozone and PAN. A multivariate receptor model (Unmix) was used for the determination of the contributions of VOCs sources in Tehran-Iran. Concentrations of ambient C2-C10 VOCs were measured continuously and online at the center of Tehran city during the winter of 2012. A high correlation coefficient existed between measured and predicted values (R (2) = 0.99), indicating that the data were well modeled. Five possible VOCs source categories were identified and mobile sources such as vehicle exhaust (61 %) and fuel evaporation (12 %) more than half of the total VOC concentration. City gas and CNG sources, biogenic source, and industrial solvent source categories accounted for 17 %, 8 % and 2 % of the total VOC, respectively. Result showed Unmix for VOCs source apportionment can be used to analyze and generate air pollution control strategies and policies.
This paper applies the discrete wavelet transform to decompose the instantaneous unit hydrograph ... more This paper applies the discrete wavelet transform to decompose the instantaneous unit hydrograph (IUH) into low and high frequency bands. The fast Fourier transform exploits to extract IUH from observed rainfall - runoff data. It is estimated the oscillations of IUH by wavelet coefficients and coefficients that are close to zero are set to zero. The obtained result is a hydrograph with the information of low frequency that approximates the real IUH. Calibration criteria between observed and calculated hydrographs are used to select the best filter length in wavelet. In this research, it is demonstrated that wavelets introduced by Daubechies (1992) with filter length 6 is the best alternative in this study. The results have shown that the methodology is acceptable for the system identification of rainfall - runoff for small catchments.
This paper deals with the problem of the presence of noise in the calculated instantaneous unit h... more This paper deals with the problem of the presence of noise in the calculated instantaneous unit hydrograph (IUH). Daubechies wavelets are used to decompose and smooth the derived IUH by way of fast Fourier transform. The results reveal the effectiveness of wavelet analysis in obtaining a fine separation of the noise frequencies from the main frequencies relating to IUHs. Choosing a representative IUH through the smoothed IUHs by a cross-validation technique, it can be applied to predict other flood events or as a design tool in hydrology.
Bulletin of Environmental Contamination and Toxicology, Jan 3, 2013
Identifying the sources of volatile organic compounds (VOCs) is key issue to reducing ground-leve... more Identifying the sources of volatile organic compounds (VOCs) is key issue to reducing ground-level ozone and PAN. A multivariate receptor model (Unmix) was used for the determination of the contributions of VOCs sources in Tehran-Iran. Concentrations of ambient C2-C10 VOCs were measured continuously and online at the center of Tehran city during the winter of 2012. A high correlation coefficient existed between measured and predicted values (R (2) = 0.99), indicating that the data were well modeled. Five possible VOCs source categories were identified and mobile sources such as vehicle exhaust (61 %) and fuel evaporation (12 %) more than half of the total VOC concentration. City gas and CNG sources, biogenic source, and industrial solvent source categories accounted for 17 %, 8 % and 2 % of the total VOC, respectively. Result showed Unmix for VOCs source apportionment can be used to analyze and generate air pollution control strategies and policies.
This paper applies the discrete wavelet transform to decompose the instantaneous unit hydrograph ... more This paper applies the discrete wavelet transform to decompose the instantaneous unit hydrograph (IUH) into low and high frequency bands. The fast Fourier transform exploits to extract IUH from observed rainfall - runoff data. It is estimated the oscillations of IUH by wavelet coefficients and coefficients that are close to zero are set to zero. The obtained result is a hydrograph with the information of low frequency that approximates the real IUH. Calibration criteria between observed and calculated hydrographs are used to select the best filter length in wavelet. In this research, it is demonstrated that wavelets introduced by Daubechies (1992) with filter length 6 is the best alternative in this study. The results have shown that the methodology is acceptable for the system identification of rainfall - runoff for small catchments.
This paper deals with the problem of the presence of noise in the calculated instantaneous unit h... more This paper deals with the problem of the presence of noise in the calculated instantaneous unit hydrograph (IUH). Daubechies wavelets are used to decompose and smooth the derived IUH by way of fast Fourier transform. The results reveal the effectiveness of wavelet analysis in obtaining a fine separation of the noise frequencies from the main frequencies relating to IUHs. Choosing a representative IUH through the smoothed IUHs by a cross-validation technique, it can be applied to predict other flood events or as a design tool in hydrology.
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Papers by Ali Ghiami Bajgirani