Browsing by Author "Andrade, P."
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- Comparative study of the whisky aroma profile based on headspace solid phase microextraction using different fibre coatingsPublication . Câmara, J. S.; Marques, J. C.; Perestrelo, Rosa Maria de Sá; Rodrigues, F.; Oliveira, L.; Andrade, P.; Caldeira, M.A dynamic headspace solid-phase microextraction (HS-SPME) and gas chromatography coupled to ion trap mass spectrometry (GC–ITMS) method was developed and applied for the qualitative determination of the volatile compounds present in commercial whisky samples which alcoholic content was previously adjusted to 13% (v/v). Headspace SPME experimental conditions, such as fibre coating, extraction temperature and extraction time, were optimized in order to improve the extraction process. Five different SPME fibres were used in this study, namely, poly(dimethylsiloxane)(PDMS),poly(acrylate)(PA),Carboxen-poly(dimethylsiloxane)(CAR/PDMS),Carbowax-divinylbenzene(CW/DVB)and Carboxen-poly(dimethylsiloxane)-divinylbenzene (CAR/PDMS/DVB). The best results were obtained using a 75 m CAR/PDMS fibre during headspace extraction at 40◦C with stirring at 750rpm for 60min, after saturating the samples with salt. The optimised methodology was then appliedtoinvestigatethevolatilecompositionprofileofthreeScotchwhiskysamples—BlackLabel,BallantinesandHighlandClan.Approximately seventy volatile compounds were identified in the these samples, pertaining at several chemical groups, mainly fatty acids ethyl esters, higher alcohols, fatty acids, carbonyl compounds, monoterpenols, C13 norisoprenoids and some volatile phenols. The ethyl esters form an essential group of aroma components in whisky, to which they confer a pleasant aroma, with “fruity” odours. Qualitatively, the isoamyl acetate, with “banana” aroma,wasthemostinteresting.Quantitatively,significantcomponentsareethylestersofcaprilic,capricandlauricacids.Thehighestconcentration of fatty acids, were observed for caprilic and capric acids. From the higher alcohols the fusel oils (3-methylbutan-1-ol and 2.phenyletanol) are the most important ones.
- Numerical methods to predict vibration serviceability on high frequency stairsPublication . Andrade, P.; Santos, José; Escórcio, P.With the increasingly deepen knowledge on structural dynamic behaviour, nowadays, monumental staircases and their steps are usually designed with high stiffness and low mass, obtaining high fundamental frequencies, out of the interval of step frequencies excitable by the human walking. However, neglecting the structure's mass can also result in with high levels of impulsive responses. Furthermore, often the connection between the staircase and its steps experience an almost null rotational stiffness, which can cause local vibrations in steps, where the structural behaviour of two elements is nearly independent from each other. In this scenario, steps will most likely exhibit undesirable vibrations. Hence, intending to improve future designs, this paper compares different numerical methods that can be used to predict human induced vibrations in this type of structures, applying them to a real staircase with a high local liveness. The results showed that the footfall force time histories method could realistically predict the vibrations for almost all tested step frequencies, while the effective impulse could accurately estimate the vibrations for descents at different step frequencies. The walking models defined by Fourier coefficients only generated close vibrations for descents at 3.3 Hz.