Model-based estimation of reaction rates in stirred tank bioreactors

In this paper an adaptive model-based algorithm is proposed for the on-line estimation of reaction rates in stirred tank bioreactors. The main design condition imposes that the observation errors reflecting the mismatch between the estimated parameters and the 'true' values follow second-order dynamics of convergence. The gain matrices are shown to be functions of the state and of user-defined damping coefficients and natural periods of oscillation for second-order trajectories. The application of the algorithm is illustrated with a simple case-study involving the estimation of the specific reaction rate for a single substrate, single product scheme.Junta Nacional de Investigação Científica e Tecnológica (JNICT)

Stability, dynamics of convergence and tuning of observer-based kinetics estimators

This work discusses issues concerning stability, tuning and dynamics of convergence of observer-based kinetics estimators. The analysis focuses on both continuous and discrete time formulations of the estimation algorithms. Concerning the former, it is shown that, with proper tuning, stability can be guaranteed, while simultaneously imposing a desired quasi-time invariant second order time response for the convergence of estimates to true values. Concerning the latter, an algorithm is presented, based on a forward Euler discretisation, whose error system is shown to be linear time-invariant. Furthermore, stability conditions were derived, which define the stable domain for the discretisation period as function of the tuning parameters. The theory is illustrated with a case-study of Baker’s yeast fermentation. Results clearly confirm the theoretical developments. In particular, results concerning the stability domain for the Euler-based discrete formulation of the estimator are shown to have relevant practical implications

A study on the convergence of observer-based kinetics estimators in stirred tank bioreactors

This paper is devoted to the tuning problem of the "observer-based kinetics estimator" in stirred tank bioreactors. This algorithm estimates the reaction kinetics from the on-line knowledge of the state variables (either from measurement or by means of state observer), when the yield coefficients are known. The relation between the dynamics of convergence and the tuning procedure is explored. The method proposed imposes a second-order dynamics to the convergence of the estimator. This approach will be shown to compare favourably with a pole placement based technique, in an application to a baker's yeast fed-batch fermentation.Junta Nacional de Investigação Científica e Tecnológica (JNICT) - contract numbers BIC/636/92, BD/224/90-IF, BD/1476/91-RM

O epitélio respiratório em ratos Wistar após 48 horas de exposição contínua ao ruído de baixa frequência

ABSTRACTPrevious studies show that exposure to low frequency noise (LFN) (≤500Hz, including infrasound) produces irreversible lesions in Wistar rat respiratory epithelia. Recovery periods for LFN-induced lesions have thus become an object of interest. Changes in the respiratory epithelia of Wistar rats after continuous short-term exposure to LFN are described. Twelve rats were exposed to continuous LFN for 48hrs, and 10 age-matched rats were kept in silence. Animals were treated in accordance with 86/609/CE. After exposure ceased, two rodents were sacrificed immediately, and another two after 6, 12, 24, 48hrs, and 7 days of post-exposure silence. Respiratory epithelial fragments were prepared for light and scanning/ transmission electron microscopy. Six hours after exposure, intense and irregular cellular tumefaction was visible and rosetta structures, formed by secretory cells (SC) centered on a brush cell (BC), were identifiable. Cilia were shorter and shaggy. BC microvilli tended to group, losing the uniform distribution seen in controls. Twelve hours after exposure, cell balooning was still present, BC shape was highly irregular and microvilli were grouped. SC microvilli were still shorter than controls. Seven days after exposure, controls and exposed were indistinguishable. LFN-induced epithelial lesions seem to be reversible if recovery periods are respected.REV PORT PNEUMOL 2003; IX (6): 473-47

Infill masonry: simple analytical methods for seismic design

The latest earthquake codes in Europe require the safety assessment of no-structural elements (parapets, masonry wall’s veneer, infill walls, etc.), as their collapse entails risks for people or for the main structure stability. This work made possible th e development of a design method, supported by previous experimental researches by applying cyclic out-of-plane loads to damaged masonry infill in RC frames. Panels tested reproduce Portuguese traditional RC structure construction system and two reinforced solutions were created as innovative solutions. The experimental campaign was carried out in order to determine: masonry properties; out-of-plane panel behaviour with previous in-plane damage; building behaviour subjected to dynamic tests performed in shaking table. Using finite element method to reproduce experimental tests and to broaden the range of samples it was possible to figure out equations according to parametric analysis which was able to reproduce in-plane and out-plane behaviour leading to an estimated load bearing capacity of each model and to determine frame strength and its stiffness. Those equations permit to design or verify the masonry infill panels in RC frames subjected to seismic loads

Behavior of masonry infill panels in RC frames subjected to in plane and out of plane loads

The building envelope in Europe is usually made of masonry walls, with enclosure and infill functions. Masonry walls have a major economical importance and contribute significantly to the building performance. Even if infill walls have no load-bearing function, they contribute significantly to the seismic behavior of buildings. Therefore, their adequate structural performance is needed, avoiding the occurrence of severe in-plane damage, with very large economical losses, and the out-of-plane expulsion, which additionally represents a large risk for human life. Recent earthquake codes in Europe require the safety assessment of non-structural elements (parapets, veneer masonry walls, infill walls, etc.), when their collapse entails risks for people or for the main structure. The Eurocode standards, entering the mandatory stage now, incorporate new requirements to be fulfilled by buildings or their parts. Such is the case of masonry infilled RC frames whose panels, according to Eurocode 8, are explicitly required to withstand the out-of-plane movement induced by earthquakes. Appropriate measures should be taken to avoid brittle failure and premature disintegration of the infill walls, as well as the partial or total out-of-plane collapse of slender masonry panels. This paper presents the experimental work and results achieved by applying cyclic out-ofplane loads to damaged masonry infilled RC frames. The masonry panels were previously damaged by applying an in-plane cyclic load after which the cyclic out-of- plane loads were applied. The frames and panels tested follow the traditional Portuguese RC structure construction system to which different types of reinforcement have been introduced in the panels

Presidential elections in Bulgaria

Polis. - ISSN 0872-8208. - S. 2, n. 4 (Julho-Dezembro 2021). - p. 251-254.On the 21st of November 2021, the Bulgarian electorate was again called to the polls it what may be defined as a moment of consolidation of the winds of change blowing over the Bulgarian electoral scene. With the victory of the new party “We Continue the Change” (Продължаваме промяната - Prodalzhavame promyanata) 4 in the legislative elections – the third in a row – scheduled for the same day as the presidential elections, with the GERB (ГЕРБ) party being defeated, president Rumen Radev (Румен Радев) which ran as an independent although supported by “We Continue the Change” was reelected, being able to ensure, on the presidential side of power, the stability won by this party. In the second round of the elections, the “new opposition” GERB and the Union of Democratic Forces (Съюз на демократичните сили - Sayuz na demokratichnite sili) supported the independent candidate Anastas Gerdjikov (Анастас Герджиков), a professor at the University of Sofia. This brief analysis of the presidential electoral system and the following election results is relevant as Radev’s victory granted the president a second and last presidential mandate, while a hypothetic victory of Gerdjikov would potentially moderate the reformist impulses of the new government

Effects of supervised practice on the accuracy of observers for manual segmentation of simulated electromyograms

Visual interpretation of electromyograms is common, but its accuracy is unknown. This study compared the accuracy curves of inexperienced observers in detecting muscular contractions from variable, simulated surface electromyogram signals. Accuracy was assessed both without feedback (unsupervised practice) and with feedback (supervised practice) to determine whether a training effect existed. Six observers performed manual segmentation in 300 simulated waveforms using a phenomenological model with a variable number of contractions (n=1, 2 or 3), smooth changes in amplitude, marked on-off timing, and a variable signal-to-noise ratio (0-39 dB). Segmentation was organized in two one-day sessions with 15 blocks of 20 signals each for the unsupervised and supervised practices, respectively. Supervised practice was provided by an immediate visual feedback on the manual segmentation. The accuracy curve showed no significant linear regressions for either unsupervised (R2=.104, p=.241) or supervised practices (R2=.153, p=.150). No significant difference in accuracy was observed between the unsupervised and supervised practices (85% [77; 99] and 88% [73; 97], respectively; p=.295). Unsupervised practice yielded low accuracy for one muscular contraction (AUC=.43; cut-off=12.8 dB) and increased with supervised practice (AUC=.63; cut-off=9.5 dB). Unsupervised practice resulted in high accuracy for two contractions (AUC=.88; cut-off=6.9 dB) and was similar to the supervised practice (AUC=.81; cut-off=6.3 dB). Supervised practice using visual feedback improved the accuracy of inexperienced observers in the segmentation of one muscular contraction in simulated electromyograms and did not influence the accuracy of two muscular contractions

Computer-aided teaching of process engineering : VI - studies on bioprocess identification and control through a process simulator

In this paper we present a simple computer-based laboratory set-up for experiments concerning real-time system identification. The set-up is constituted by a 'Process Simulator' computer and a 'Control' computer, communicating via serial RS-232 protocol. The former can simulate multivariable non-linear systems in real-time, in this specific experiment the fed-batch fermentation of baker's yeast. The latter performs the tasks of system identification and control, viz - (i) identification is performed employing a methodology based on a general non-linear deterministic model representation of fed-batch fermentations; (ii) control is performed employing an adaptive linearizing scheme.Junta Nacional de Investigação Científica e Tecnológica (JNICT) - contract nr. B/D 224/90-IF