Conversor CC-CC para aplicação em filtro ativo paralelo do tipo fonte de corrente

Dissertação de mestrado em Engenharia Eletrónica Industrial e de ComputadoresAtualmente, a utilização de cargas não lineares é cada vez mais frequente. Estas, originam problemas de qualidade de energia elétrica (QEE), resultando em várias consequências, como falhas em equipamentos eletrónicos, podendo causar prejuízos elevados em diversos setores. Os filtros ativos de potência, que também podem fazer interface com fontes de energia renovável, apresentam-se como uma boa solução para mitigar estes problemas. Nesta dissertação de mestrado apresentam-se as topologias de filtros ativos de potência, tendo sido simulada uma topologia de Filtro Ativo Paralelo do Tipo Fonte de Corrente. Nesta simulação, para além do inversor fonte de corrente (Current-Source Inverter - CSI), implementou-se um algoritmo baseado na Teoria p-q, bem como a técnica de modulação vetorial (Space-Vector Modulation - SVM). Estas técnicas foram as escolhidas para efetuar o controlo e a modulação do Filtro Ativo Paralelo do Tipo Fonte de Corrente. Nesta dissertação é ainda efetuado um estudo sobre o estado da arte dos conversores CC-CC utilizados em sistemas solares fotovoltaicos, e sobre os sistemas de controlo aplicáveis aos mesmos. Tendo em conta as características do sistema, foi selecionado o conversor CC-CC push-pull, sendo o mesmo simulado e implementado. Nesta dissertação é realizado o dimensionamento e a construção do transformador de alta-frequência deste conversor CC-CC. São ainda apresentadas as placas do andar de potência e o sistema de controlo, desenvolvido no DSP TMS320F28335 da Texas Instruments. A presente dissertação de mestrado apresenta também os testes realizados ao transformador de alta-frequência e ao conversor CC-CC push-pull a operar isoladamente. São ainda apresentados resultados experimentais para a operação de todas as placas desenvolvidas.Nowadays, the use of no-linear loads in industry and by general consumers is increasingly common. This situation causes Power Quality problems, resulting in various consequences, such as flaws in electronic equipment, which may cause revenue losses in several sectors. Besides that, Power Quality problems contributes to the increase of efficiency losses in domestic and industrial equipment, and also in the electrical installations. The Active Power Filters, which can be incorporated with Renewable Energy solutions, are a good solution to mitigate these problems. In this Master Thesis are presented the main topologies of Active Power Filters, with Current-Source Shunt Active Power Filter being simulated. In this simulation, in addition to the Current-Source Inverter, an algorithm based on the p-q Theory and the Space Vector Modulation technique was implemented. These techniques were chosen to control and modulate the Current-Source Shunt Active Power Filter. In this work, it is also made a study about the state of the art of DC-DC Converters used in Photovoltaic Solar Systems, and the control systems that can be applied to them. Considering the characteristics of the system, the DC-DC Push Pull Converter has been selected, where it is simulated and implemented. In this Master Thesis the design and construction of the high-frequency transformer of this converter was developed. The power stage boards and the control system, implemented in the Texas Instruments microcontroller DSP TMS320F28335, are also developed and presented. This work also presents the tests performed for the developed high-frequency transformer and DC-DC Push Pull Converter. Experimental results of all developed circuits are presented

Portal universitário: validação de modelo de satisfação de usuário com utilização de modelagem de equações estruturais University portal: user satisfaction model validation with structural equation modeling use

Atualmente, sistemas de informação são utilizados e têm fundamental importância em todo tipo de organização, e a satisfação do usuário tem sido utilizada como fator chave para a avaliação desses sistemas. As instituições de ensino superior, assim como qualquer organização, também necessitam de tais sistemas para o gerenciamento de informações necessárias à gestão. Desta forma, a presente pesquisa teve como objetivo verificar se as dimensões “qualidade do sistema”, “qualidade da informação”, “qualidade do serviço” e “utilidade percebida” exercem impacto sobre a satisfação do usuário de sistema de informação acadêmica. O estudo teve abordagem quantitativa e foi realizado em uma instituição de ensino superior sediada no município de Duque de Caxias, no estado do Rio de Janeiro. Para tanto, foi conduzida pesquisa de survey, sendo utilizado questionário estruturado com cinco opções de resposta do tipo Likert, aplicado em alunos de graduação da referida instituição, selecionados por conveniência. Os dados foram tratados com a técnica de modelagem de equações estruturais com base em modelo de avaliação de sistema de informação encontrado na literatura. Como resultado, as hipóteses do estudo não foram confirmadas, pois apesar das estimativas dos parâmetros dos caminhos de cada construto em relação à satisfação do usuário apresentaram significância estatística, o ajustamento global do modelo não apresentou índices aceitáveis

Boosting cultural heritage in rural communities through an ICT platform: the Viv@vó project

Rural regions concentrate on themselves a very rich set of ancestral traditions. The perpetuation of such traditions has been achieved through transmission between generations. Unfortunately, all this knowledge is typically elders-centered and it lacks effective processes of digitalization, storage and providing-systems for that all this heritage can effectively be perpetuated through future generations that are digital-born. From this base, it was created a project case study limited to the Portuguese Northeast region, named Viv@vó – living in the grandma's house. This paper presents the ICT platform that was created in this project and some main achievements during the project development process. Tourism and mainly experience and cultural heritage tourism are growing in tourist’s interests. Rural regions have an untapped potential for this slice of tourism industry. Rural regions have an enormous collection of ancestral knowledge that we are responsible to deliver to future generations as an inheritance to which they are entitled.The present work was developed under the Viv@vó Project: "Living in the Grandma's House", with the reference NORTE-01- 0145-FEDER-023637, financed by the Regional Operational Program of the North, Notice 02/SAICT/2016.info:eu-repo/semantics/publishedVersio

Serological and Molecular Survey of Leishmania infantum in a Population of Iberian Lynxes (Lynx pardinus)

This article belongs to the Special Issue Advances in Leishmania Research: From Basic Parasite Biology to Disease Control.Leishmania infantum, the sand fly-transmitted protozoan parasite responsible for leishmaniasis in humans, dogs, and cats, is endemic in the Iberian Peninsula. However, the impact of L. infantum infection on the conservation of the endangered Iberian lynx (Lynx pardinus) is unknown. Herein, we describe for the first time the occurrence of L. infantum infection among a population of reintroduced and wild-born L. pardinus living in the Portuguese Guadiana Valley Park. The presence of infection was addressed by molecular detection of Leishmania kinetoplast DNA (kDNA) in 35 lynxes, with further confirmation of L. infantum species performed by an internally transcribed spacer (ITS)-1 sequencing. Eight blood samples were positive for kDNA, and ITS-1 sequencing confirmed the presence of L. infantum in two of those samples. Exposure to Leishmania was screened in a group of 36 lynxes using an immunofluorescence antibody test (IFAT) and a multi-antigen enzyme-linked immunosorbent assay (ELISA), using SPLA, rK39, and CPX as Leishmania-specific antigens. Four animals presented a positive IFAT at a dilution of 1:40. Eight samples were considered seropositive to all ELISA Leishmania-specific antigens. Agreement between PCR, IFAT, and all ELISA antigens was found for 1 in 27 samples. These results highlight the susceptibility of autochthonous L. pardinus to L. infantum infection. Further investigation is required to assess the impact of L. infantum infection on this wild species conservation.This research was funded by the Parasite Disease Group at i3S, Porto, Portugal, and the Portuguese Foundation for Science and Technology (FCT) under the PhD scholarship number 2020.07306.BD and the project PTDC/CVT-CVT/6798/2020.info:eu-repo/semantics/publishedVersio

Pre-heating mitigates composite degradation

Dental composites cured at high temperatures show improved properties and higher degrees of conversion; however, there is no information available about the effect of pre-heating on material degradation. Objectives This study evaluated the effect of pre-heating on the degradation of composites, based on the analysis of radiopacity and silver penetration using scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS). Material and Methods Thirty specimens were fabricated using a metallic matrix (2x8 mm) and the composites Durafill VS (Heraeus Kulzer), Z-250 (3M/ESPE), and Z-350 (3M/ESPE), cured at 25°C (no pre-heating) or 60°C (pre-heating). Specimens were stored sequentially in the following solutions: 1) water for 7 days (60°C), plus 0.1 N sodium hydroxide (NaOH) for 14 days (60°C); 2) 50% silver nitrate (AgNO3) for 10 days (60°C). Specimens were radiographed at baseline and after each storage time, and the images were evaluated in gray scale. After the storage protocol, samples were analyzed using SEM/EDS to check the depth of silver penetration. Radiopacity and silver penetration data were analyzed using ANOVA and Tukey’s tests (α=5%). Results Radiopacity levels were as follows: Durafill V

Zeolites: A Theoretical and Practical Approach with Uses in (Bio)Chemical Processes

This review provides a state-of-the-art summary of distributed zeolite technology, as well as identifying strategies to further promote the absorption of these materials in various areas of study. Zeolites are materials that can be synthesized or found in natural rock deposits a with a basic composition consisting in Al, Si, and O. Zeolite’s consideration as a future material is due to many facile synthesis methods to obtain different structures with variations in pore size, surface area, pore volume and physical properties. These methods are developed using the control of relevant synthesis parameters that influences structure formation, such as crystallization temperature, time of aging and/or crystallization, stoichiometric relationships between components of synthesis gel, pH of the medium, and in some cases the type of structure-directing agent. Each method will lead to geometric changes in the framework formation, making possible the formation of typical chemical bonds that are the fingerprint of any zeolitic structure (O-Si-O and Al-O-Si), forming typical acid sites that give specificity in zeolite and allows it to act as a nanoreactor. The specificity is a characteristic that in some cases depends on selectivity, a fundamental property derived of the porosity, mostly in processes that occur inside the zeolite. In processes outside the structure, the surface area is the main factor influencing this property. Moreover, there are many natural sources with adequate chemical composition to be used as precursors. Some of these sources are waste, minimizing the deposition of potential hazardous materials that can be recalcitrant pollutants depending on the environment. Besides its uses as a catalyst, zeolite serves as a support for many bioprocesses; therefore, this review aims to explain relevant aspects in chemical nature, physical properties, main methods of synthesis, main precursors used for synthesis, and relevant applications of zeolites in chemical catalysis and biological processes

Root causes and outcomes of postoperative pulmonary complications after abdominal surgery: A retrospective observational cohort study

FCT project IPOscore (DSAIPA/DS/0042/2018).Background: Postoperative pulmonary complications (PPCs) contribute significantly to overall postoperative morbidity and mortality. In abdominal surgery, PPCs remain frequent. The study aimed to analyze the profile and outcomes of PPCs in patients submitted to abdominal surgery and admitted in a Portuguese polyvalent intensive care unit. Methods: From January to December 2017 in the polyvalent intensive care unit of Hospital Garcia de Orta, Almada, Portugal, we conducted a retrospective, observational study of inpatients submitted to urgent or elective abdominal surgery who had severe PPCs. We evaluated the perioperative risk factors and associated mortality. Logistic regression was performed to find which perioperative risk factors were most important in the occurrence of PPCs. Results: Sixty patients (75% male) with a median age of 64.5 [47-81] years who were submitted to urgent or elective abdominal surgery were included in the analysis. Thirty-six patients (60%) developed PPCs within 48 h and twenty-four developed PPCs after 48 h. Pneumonia was the most frequent PPC in this sample. In this cohort, 48 patients developed acute respiratory failure and needed mechanical ventilation. In the emergency setting, peritonitis had the highest rate of PPCs. Electively operated patients who developed PPCs were mostly carriers of digestive malignancies. Thirty-day mortality was 21.7%. The risk of PPCs development in the first 48 h was related to the need for neuromuscular blocking drugs several times during surgery and preoperative abnormal arterial blood gases. Median abdominal surgical incision, long surgery duration, and high body mass index were associated with PPCs that occurred more than 48 h after surgery. The American Society of Anesthesiologists physical status score 4 and COPD/Asthma determined less mechanical ventilation needs since they were preoperatively optimized. Malnutrition (low albumin) before surgery was associated with 30-day mortality. Conclusion: PPCs after abdominal surgery are still a major problem since they have profound effects on outcomes. Our results suggest that programs before surgery, involve preoperative lifestyle changes, such as nutritional supplementation, exercise, stress reduction, and smoking cessation, were an effective strategy in mitigating postoperative complications by decreasing mortality.publishersversionpublishe

Selection of Bacillus thuringiensis Berliner strains to control Aedes aegypti Linnaeus

The present study aimed to select strains of Bacillus thuringiensis with insecticidal activity against Aedes aegypti. It was tested sixteen strains of bacteria, isolated from Paraná state, Brazil, that were used in laboratory assays with mosquito larvae. Tests were carried out in two stages, first one to select the most efficient strains (screening) and second to estimate LC50. The protein profile of the highest toxicity of strain was obtained by SDS-PAGE (sodium dodecyl sulfate polyacrylamide gel electrophoresis). The best performance of larval mortality was produced by BR-01 strain, which 96.7% mortality rate, significantly higher than others. In the second part, there was obtained a LC50 of 9.07 µL.L-1 fermented extract. The protein profile revealed many peptides between 15 and 140kDa, similar to that reported in Bacillus thuringiensis ser. israelensis strains which high toxicity to mosquito species.O presente trabalho buscou selecionar cepas de Bacillus thuringiensis com atividade inseticida contra Aedes aegypti. Foram testadas 16 estirpes da bactéria provenientes do estado do Paraná, Brasil, que foram utilizadas em ensaios laboratoriais com larvas do culicídeos. Os testes foram realizados em duas etapas, a primeira com a seleção de cepas e a segunda para estimar a CL 50 das cepas com melhores resultados. O perfil protéico do isolado de maior toxicidade foi obtido por SDS-PAGE (dodecil sulfato de sódio –eletroforese em gel de poliacrilamida). O melhor resultado de mortalidade foi produzido com a cepa BR-01, que produziu 96,7% de mortalidade de A. aegypti, valor significativamente superior aos demais. Na segunda fase, obteve-se CL50 de 9,07 μL.L -1 de extrato fermentado. O perfil protéico revelou peptídeos entre 15 e 140 kDa, resultado semelhante ao relatado nas cepas de Bacillus thuringiensis var. israelensis de maior toxicidade às espécies de culicídeo

Reflexão sobre a usabilidade dos aplicativos winplot, geogebra e desmos no ensino de matemática / Reflection on the usability of winplot, geogebra and desmos in mathematics education

O presente artigo tem por objetivo analisar a usabilidade dos aplicativos WINPLOT, GEOGEBRA e DESMOS  no ensino de matemática. A análise demonstra que a definição e escolha de aplicativos para uso no ensino de matemática não tem sido fácil, visto que boa parte dos  Materiais Didáticos Digitais - MDDs tendem a resumir o conteúdo a uma dinâmica de pergunta e resposta, em que o aluno simplesmente insere a fórmula e obtém o resultado, sem compreender o raciocínio lógico necessário à operação. Para melhor compreensão da aplicação desses materiais e seus possíveis problemas foi feita uma análise desses aplicativos e também quanto requisitos necessários à aplicação dos MDDs para melhorar a aprendizagem.  Pode-se concluir por meio desse estudo que a aplicação dos MDDs pode ser uma ferramenta de apoio em sala de aula e fora dela, porém seu uso deve estar vinculado ao papel do professor como gestor da sala de aula dando suporte a esta aplicação