The aerial parts of Gutierrezia resinosa afforded two highly oxygenated flavones 5,4′-dihydroxy-3... more The aerial parts of Gutierrezia resinosa afforded two highly oxygenated flavones 5,4′-dihydroxy-3,6,7,8,3′-pentamethoxyflavone and 5,3′,4′-trihydroxy-3,6,7,8-tetramethoxyflavone . The structures were elucidated by spectroscopic methods and confirmed by X-ray ...
An adaptive technique for the estimation and tracking of the direction of arrival of multiple non... more An adaptive technique for the estimation and tracking of the direction of arrival of multiple nonstationary plane waves from the outputs of a uniform linear array of sensors is presented. This task is performed by using a decomposed filtering structure to spatially isolate each signal component while ...
In this paper adaptive predictors structured in cascade form are used to analyse superimposed exp... more In this paper adaptive predictors structured in cascade form are used to analyse superimposed exponential signals with time-varying parameters. On-line optimisation of the filters parameters is achieved using gradient descent techniques focused on the direct estimation of ...
IEEE Transactions on Audio, Speech & Language Processing, 2008
AbstractIn this paper, a simple and reliable technique is pro-posed to track vocal tract resonan... more AbstractIn this paper, a simple and reliable technique is pro-posed to track vocal tract resonances in continuous speech. The ap-proach is based on the use of predictor filters with adaptive zeros whose constrained trajectories guarantee the successful tracking of the frequency and the ...
Bioethanol, obtained by biomass fermentation, could be an important hydrogen supplier as a renewa... more Bioethanol, obtained by biomass fermentation, could be an important hydrogen supplier as a renewable source. The development of active, selective and stable catalysts for bioethanol steam reforming is a key point.
Ethanol steam reforming has been studied over Ni/SiO 2 catalysts under a wide range of operating ... more Ethanol steam reforming has been studied over Ni/SiO 2 catalysts under a wide range of operating conditions, and the effect of Ni loading on catalyst properties and H 2 yield and selectivity has been analyzed. Surface area and pore volume significantly decrease with nickel content, but there is only a slight decrease in mean pore diameter. XRD patterns show peaks corresponding to NiO but no evidence of nickel silicate species has been found. Ni/SiO 2 catalysts are active for H 2 production by ethanol steam reforming over 400 ºC. Ethanol conversion and H 2 yield considerably increase with temperature and Ni loading. Up to 3.9 mol H2 /mol EtOH is obtained at 600 ºC and 8.3 g catalyst min/g EtOH , although lower temperatures (500 ºC) are more suitable for minimizing CO selectivity. An improvement in catalyst performance is observed for high values of time-on-stream, which is explained by coke deposition in the form of carbon fibers.
The aerial parts of Gutierrezia resinosa afforded two highly oxygenated flavones 5,4′-dihydroxy-3... more The aerial parts of Gutierrezia resinosa afforded two highly oxygenated flavones 5,4′-dihydroxy-3,6,7,8,3′-pentamethoxyflavone and 5,3′,4′-trihydroxy-3,6,7,8-tetramethoxyflavone . The structures were elucidated by spectroscopic methods and confirmed by X-ray ...
An adaptive technique for the estimation and tracking of the direction of arrival of multiple non... more An adaptive technique for the estimation and tracking of the direction of arrival of multiple nonstationary plane waves from the outputs of a uniform linear array of sensors is presented. This task is performed by using a decomposed filtering structure to spatially isolate each signal component while ...
In this paper adaptive predictors structured in cascade form are used to analyse superimposed exp... more In this paper adaptive predictors structured in cascade form are used to analyse superimposed exponential signals with time-varying parameters. On-line optimisation of the filters parameters is achieved using gradient descent techniques focused on the direct estimation of ...
IEEE Transactions on Audio, Speech & Language Processing, 2008
AbstractIn this paper, a simple and reliable technique is pro-posed to track vocal tract resonan... more AbstractIn this paper, a simple and reliable technique is pro-posed to track vocal tract resonances in continuous speech. The ap-proach is based on the use of predictor filters with adaptive zeros whose constrained trajectories guarantee the successful tracking of the frequency and the ...
Bioethanol, obtained by biomass fermentation, could be an important hydrogen supplier as a renewa... more Bioethanol, obtained by biomass fermentation, could be an important hydrogen supplier as a renewable source. The development of active, selective and stable catalysts for bioethanol steam reforming is a key point.
Ethanol steam reforming has been studied over Ni/SiO 2 catalysts under a wide range of operating ... more Ethanol steam reforming has been studied over Ni/SiO 2 catalysts under a wide range of operating conditions, and the effect of Ni loading on catalyst properties and H 2 yield and selectivity has been analyzed. Surface area and pore volume significantly decrease with nickel content, but there is only a slight decrease in mean pore diameter. XRD patterns show peaks corresponding to NiO but no evidence of nickel silicate species has been found. Ni/SiO 2 catalysts are active for H 2 production by ethanol steam reforming over 400 ºC. Ethanol conversion and H 2 yield considerably increase with temperature and Ni loading. Up to 3.9 mol H2 /mol EtOH is obtained at 600 ºC and 8.3 g catalyst min/g EtOH , although lower temperatures (500 ºC) are more suitable for minimizing CO selectivity. An improvement in catalyst performance is observed for high values of time-on-stream, which is explained by coke deposition in the form of carbon fibers.
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Papers by Julio Vargas