Innovative contributions on calibration methodologies towards reliable microflow measurements

Flow measurement is critical in healthcare, chemistry and pharmaceutics, to mention a few. In fact, there are several applications in the microflow and nanoflow range, such as scaled-down process technology, drug development, and special health-care applications, as organ-on-a- chip technology. Nevertheless, the majority of the instruments used for the specified applica- tions are not sufficiently studied regarding their flow accuracy and traceability. Hence these fluid applications at the micro and nanoscale still lack well defined calibration methodologies for the devices working at the mentioned flow range with adequate uncertainty values. The work presented in this thesis focuses on the development and improvement of in- novative applications of calibration methodologies for microflow measuring instruments. The gravimetric method already implemented at IPQ from 120 L/h to 2000 mL/h was used and improved for low flow rates down to 10 L/h. Additionally, other 4 methods were developed to enable the calibration of micro/nano flows in a non-intrusive way. They are interferometry, pending drop, front track and comparison method (where a calibrated flow generator is used as the reference standard). The methodology that is best suited for each specific instrument and each measurement range, with the lowest uncertainty, was successfully identified along with the relevant influence factors in microflow measurements. A specific objective of this work was to increase the measuring range of IPQ-LVC down to 5 nL/min (0.3 L/h) with a 3% target uncertainty (k=2). This objective was possible to achieve and even surpass with the use of the interferometric method, where measurements were per- formed down to 1.6 nL/min (0.1 L/h) with 2 % uncertainty(k=2). This method was internally validated by comparison with the gravimetric method and is now in the process of external validation by EURAMET project 1508.A medição de caudal é extremamente importante em áreas como a saúde, a indústria química ou farmacêutica. Caudais à escala micro/nanométrica são já utilizados em várias aplicações, nomeadamente, processos tecnológicos de redução de escala, desenvolvimento de fármacos e especialmente em novas aplicações na área da saúde, tais como a tecnologia de órgãos-em- chip. Os sistemas de medição utilizados nas aplicações indicadas, por serem relativamente recentes, não estão ainda suficientemente estudados quanto a sua exatidão e rastreabilidade. É, assim, necessário desenvolver metodologias de calibração específicas para os referidos cau- dais com incertezas de medição adequadas. Este trabalho irá focar-se no desenvolvimento e melhoramento de metodologias de cali- bração de instrumentos utilizados na medição de micro/nanocaudal de fluidos. O método gra- vimétrico já implementado no IPQ numa gama de medição de 120 L/h a 2000 mL/h foi me- lhorado de forma se realizarem calibrações até 10 L/h. Foram ainda desenvolvidos 4 novos métodos, a interferometria, o método da gota pendente, o método do deslocamento de me- nisco e o método comparativo (onde um gerador de caudal é utilizado como referência). A metodologia que melhor se aplica a cada instrumento e a gama de medição, com a melhor incerteza foi identificada, assim como fatores de influência na medição de microcaudal. Um objetivo específico deste trabalho foi aumentar o intervalo de medição do IPQ-LVC para 5 nL/min (0.3 L/h) com uma incerteza de (k=2). Isso foi possível e até ultrapassável com a utilização do método interferométrico, em que as foram realizadas medições até 1.6 nL/min (0.1 L/h) com 2% de incerteza (k=2). Este método foi validado internamente por comparação com o método gravimétrico e está agora em processo de validação externa através do projeto EURAMET 1508

Probabilistic constraint reasoning

Dissertação apresentada para obtenção do Grau de Doutor em Engenharia Informática, pela Universidade Nova de Lisboa, Faculdade de Ciências e TecnologiaThe continuous constraint paradigm has been often used to model safe reasoning in applications where uncertainty arises. Constraint propagation propagates intervals of uncertainty among the variables of the problem, eliminating values that do not belong to any solution. However, constraint programming is very conservative: if initial intervals are wide (reflecting large uncertainty), the obtained safe enclosure of all consistent scenarios may be inadequately wide for decision support. Since all scenarios are considered equally likely, insufficient pruning leads to great inefficiency if some costly decisions may be justified by very unlikely scenarios. Even when probabilistic information is available for the variables of the problem, the continuous constraint paradigm is unable to incorporate and reason with such information. Therefore, it is incapable of distinguishing between different scenarios, based on their likelihoods. This thesis presents a probabilistic continuous constraint paradigm that associates a probabilistic space to the variables of the problem, enabling probabilistic reasoning to complement the underlying constraint reasoning. Such reasoning is used to address probabilistic queries and requires the computation of multi-dimensional integrals on possibly non linear integration regions. Suitable algorithms for such queries are developed, using safe or approximate integration techniques and relying on methods from continuous constraint programming in order to compute safe covers of the integration region. The thesis illustrates the adequacy of the probabilistic continuous constraint framework for decision support in nonlinear continuous problems with uncertain information, namely on inverse and reliability problems, two different types of engineering problems where the developed framework is particularly adequate to support decision makers

O conceito de justo valor e a sua aplicação nas empresas cotadas em Portugal

Esta investigação teve como principal objetivo analisar o conceito de justo valor, assim como a sua aplicação, enquanto método de mensuração. Pretendeu-se ainda apurar os fatores explicativos que influenciam a sua escolha como base de mensuração, analisando em particular a influência da implementação da IFRS 13. A amostra estudada é constituída por empresas pertencentes ao Portuguese Stock Index – 20 PSI-20, e os dados referentes ao período de 2010 a 2016. Os resultados obtidos revelam que a base de mensuração do justo valor é utilizada, em alguns ativos, verificando-se que o método do justo valor é utilizado nos ativos fixos tangíveis, sendo que na sua maioria é utilizado o método do custo histórico. Já os ativos intangíveis utilizam sempre o método do custo histórico. Os resultados revelam que entidades com maior número de trabalhadores e um maior nível de internacionalização estarão mais predisposta a escolher o justo valor como base de mensuração para os ativos fixos tangíveis. Esta investigação contribuiu para aprofundar conhecimento acerca do justo valor e da aplicação desta base de mensuração por parte das empresas do PSI – 20. Permitiu ainda analisar quais os fatores que influenciam a utilização ou não do mesmo. Apesar de esta investigação possuir algumas limitações, nomeadamente a reduzida dimensão da amostra, dada a pertinência desta temática sugere-se o seu aprofundamento através de uma amostra de maior dimensão, assim como a análise de outros fatores condicionantes à sua utilização

Application of the front tracking method in micro flow measuring devices

18HLT08This work has the main objective to develop a calibration method for micro flow measuring devices based on the front tracking principle, in the Volume and Flow Laboratory (LVC) of the Portuguese Institute of Quality (IPQ), in a partnership with and the Department of Mechanical and Industrial Engineering (DEMI) of The New University of Lisbon under the project MeDD II – Metrology for Drug Delivery. The experimental setup consists of using a camera and Python software to track the distance traveled by the meniscus of a liquid inside a capillary tube and calculate the flow rate according to appropriated equations. Experimental tests using a flow generator and a flow meter were carried out for different flow rates. Two different setups with cameras of different specifications were tested. To validate the developed front tracking method, internal comparisons using a Nexus pump and a Sensirion meter were performed with the gravimetric and interferometric methods already implemented at LVC. The results obtained by these two comparisons were consistent. This new developed method can therefore be used to calibrate flow devices from 1000 μL/h down to 1 μL/h with an uncertainty value from 2% to 7% (k = 2). The calibration procedure is easy to apply and can be used for both syringe and flow meters. This method is simple to implement in a laboratory and the setup is relatively cheap compared to the gravimetric or interferometric method. Finally, the front tracking method was applied to the calibration of an implantable insulin pump used by diabetic patients.publishersversionpublishe

Development of an experimental setup for micro flow measurement using the front tracking method

Funding Information: This work performed under 18HLT08 MeDDII project has received funding from the EMPIR programme co-financed by the Participating States and from the European Union's Horizon 2020 research and innovation programme .This work has the main objective to develop a method for microflow measurement using the front tracking principle under the project MeDD II – Metrology for Drug Delivery. The experimental setup uses a high-resolution camera and an image processing software to track the distance travelled by the meniscus of a liquid in a capillary tube and calculate the flow rate. Experimental tests using a flow generator were carried out for different flow rates using two different cameras. To validate the developed front tracking method, an internal comparison was made with the gravimetric method in LVC. The results obtained by this comparison were consistent. This developed method can be used to calibrate flow devices down to 1 μL/h with an uncertainty value of 7% (k = 2).publishersversionpublishe

Measurement of internal diameters of capillaries and glass syringes using gravimetric and optical methods for microflow applications

This work performed under 18HLT08 MeDDII project has received funding from the EMPIR programme co-financed by the Participating States and from the European Union’s Horizon 2020 research and innovation programme. The Authors would like to acknowledge Abir Wissam Boudaoud for her help in CETIAT inner diameter measurements and Václav Duchoň and Petr Grolich from CMI for their work on the glass syringe diameter calibration. © 2022 the author(s), published by De Gruyter, Berlin/Boston.OBJECTIVES: Microflow measurement devices are used in several science and health applications, mainly drug delivery. In the last decade, several new methods based on optical technology were developed, namely the front tracking and interferometric method, in which the knowledge of the inner diameter of the syringe or the capillary used is critical. Only a few National Metrology Institutes (NMIs) can perform inner diameter measurements below 1 mm, which requires expensive technology. Therefore, IPQ, in cooperation with CETIAT, CMI and UNIDEMI, under the EMPIR project 18HLT08 MeDDII - Metrology for Drug Delivery, developed new measurement methods for small inner diameter tubes based on the gravimetric principle and optical methods in order to simplify the apparatus used for this type of measurements without increasing uncertainty. METHODS: The gravimetric experimental setup consists of measuring the liquid volume on a specific length of the glass tube. The optical method used is based on the front track principle that uses a high-resolution camera and ImageJ software, to determine the diameter at both ends of each capillary. RESULTS: To validate the developed methods, a comparison was performed between CETIAT, CMI and IPQ and the results obtained were all consistent. CONCLUSIONS: This work allowed the determination of inner diameter of syringes or capillaries using two different methods with relative expanded uncertainties from 0.1 to 0.5% ( k=2), that can be applied for flow measurements using optical technology.publishersversionepub_ahead_of_prin

Unlocking the power of Twitter communities for startups

Peixoto, A. R., Almeida, A. D., António, N., Batista, F., Ribeiro, R., & Cardoso, E. (2023). Unlocking the power of Twitter communities for startups. Applied Network Science, 8, 1-21. [66]. https://doi.org/10.21203/rs.3.rs-3062630/v1, https://doi.org/10.1007/s41109-023-00593-0 --- This work was partially supported by Fundação para a Ciência e a Tecnologia, I.P. (FCT) namely by UIDB/04466/2020 and UIDP/04466/2020 (ISTAR_Iscte); UIDB/04152/2020 (MagIC/NOVA IMS); UIDB/50021/2020 (INESC-ID); and UIDB/03126/2020 (CIES_Iscte).Social media platforms offer cost-effective digital marketing opportunities to monitor the market, create user communities, and spread positive opinions. They allow companies with fewer budgets, like startups, to achieve their goals and grow. In fact, studies found that startups with active engagement on those platforms have a higher chance of succeeding and receiving funding from venture capitalists. Our study explores how startups utilize social media platforms to foster social communities. We also aim to characterize the individuals within these communities. The findings from this study underscore the importance of social media for startups. We used network analysis and visualization techniques to investigate the communities of Portuguese IT startups through their Twitter data. For that, a social digraph has been created, and its visualization shows that each startup created a community with a degree of intersecting followers and following users. We characterized those users using user node-level measures. The results indicate that users who are followed by or follow Portuguese IT startups are of these types: “Person”, “Company,” “Blog,” “Venture Capital/Investor,” “IT Event,” “Incubators/Accelerators,” “Startup,” and “University.” Furthermore, startups follow users who post high volumes of tweets and have high popularity levels, while those who follow them have low activity and are unpopular. The attained results reveal the power of Twitter communities and offer essential insights for startups to consider when building their social media strategies. Lastly, this study proposes a methodological process for social media community analysis on platforms like Twitter.publishersversionpublishe

Calibration of infusion pumps using liquids whose physical properties differ from those of water

Infusion medical devices are used in field applications, namely in clinical environments, here are used several types of liquids, according to the therapeutic to be administrated into the patient. In order to determine the influence of the fluids physical properties, such as viscosity and density and to produce an adequate reference liquid, tests were performed with a syringe pump, using the gravimetric method as reference calibration method.publishersversionpublishe