Browsing by Author "Silva, Daniel"
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- Adaptive predictive coding speech coding techniques applied to electrocardiogram signalsPublication . Silva, Daniel; Martins, Guilherme; Lourenço, André; Meneses, CarlosThis paper describes a lossy ECG signal coder with an adaptive predictive coding scheme initially proposed for speech coders. The predictors include linear predictive coding that takes advantage of the correlation between consecutive samples and long-term predictor that takes advantage of the signal quasi-periodicity. The prediction residue, with less dynamic range and therefore able to be encoded with less bits than the original, is transmitted sample by sample. The prediction coefficients and the amplitude of the residue are transmitted once for each heartbeat, with a negligible number of bits compared to the total bit rate. The long-term predictor is shown to obtain reliable performance when the heart rate does not change rapidly. Linear predictive coding, on the contrary, is more reliable and presents better prediction gain. The best developed coder uses double prediction and with 45% compression ratio allows a prediction gain of 24.8 dB.
- Assessing the stakeholders’ responses in public discussions of IPSASB standards from a cultural perspectivePublication . Albuquerque, Fábio; Gomes Dos Santos, Paula; Penha, Eugênia Paiva da; Silva, DanielThis article assesses the factors that may explain stakeholders’ responses in public due processes carried out by the IPSASB. Seven ongoing projects were assessed, comprising 328 comment letters sent to IPSASB from 47 countries. The authors present a new approach which takes into account cultural values in public sector accounting and financial reporting. This article shows that factors that can explain stakeholders’ responses in public discussions of the International Public Sector Accounting Standards Board’s (IPSASB) standards may differ according to underlying cultural values. Respondents’ affiliation, countries’ level of development and their accounting framework can explain underlying cultural values. The article will help standard setters, governments and regulatory bodies to understand the differences in stakeholders’ positions according to the cultural nature of issues proposed for public discussion.
- Modelling, monitoring and control of plasmid bioproduction in Escherichia coli culturesPublication . Lopes, Marta B.; Scholtz, Teresa; Silva, Daniel; Santos, Inês; Silva, Tito; Sampaio, Pedro; Couto, Andreia; Lopes, Vitor V.; Calado, CecíliaAn integrated approach for modelling, monitoring and control the plasmid bioproduction in Escherichia coli cultures is presented. In a first stage, by the implementation of a kinetic model for E. coli cultures, a better bioprocess understanding was reached, concerning the availability of nutrients and products along the bioprocess, and their effects on the plasmid production. Results presented may provide significant help for future modelling and monitoring implementation. In a second stage, FTIR spectroscopy coupled with chemometrics, namely PLS regression, shows its potential as a high-throughput technique for simultaneously estimating the key variables involved in the plasmid production process by E. coli cultures run under distinct conditions. Finally, owing to online monitoring and process control, an NIR fibre optic probe and chemometrics provided promising results concerning the control of biomass and carbon sources in E. coli cultures.