Compensation of Voltage disturbances in hybrid AC/DC Microgrids using series converter

In this paper a series power electronic converter is proposed to improve power quality of AC/DC hybrid microgrids. An injection transformer which is series with AC microgrid is used beside the series converter to inject voltage for the purpose of voltage disturbances compensation. The series converter by using a simple and effective control system in stationary reference framework of d-q-0 is proposed to compensate voltage sag and swell, source unbalanced voltages, voltage harmonics of the utility. In these types of micrigrids a lot of voltage disturbances have occurred due to large number of converters. Moreover, it is not required to use a storage energy system like battery; the required power is supplied by DC microgird, so the proposed system is very efficient. Simulation results in the MATLAB/Simulink environment have verified the appropriate performance of the proposed method

A Practical Investigation into Achieving Bio-Plausibility in Evo-Devo Neural Microcircuits Feasible in an FPGA

Many researchers has conjectured, argued, or in some cases demonstrated, that bio-plausibility can bring about emergent properties such as adaptability, scalability, fault-tolerance, self-repair, reliability, and autonomy to bio-inspired intelligent systems. Evolutionary-developmental (evo-devo) spiking neural networks are a very bio-plausible mixture of such bio-inspired intelligent systems that have been proposed and studied by a few researchers. However, the general trend is that the complexity and thus the computational cost grow with the bio-plausibility of the system. FPGAs (Field- Programmable Gate Arrays) have been used and proved to be one of the flexible and cost efficient hardware platforms for research' and development of such evo-devo systems. However, mapping a bio-plausible evo-devo spiking neural network to an FPGA is a daunting task full of different constraints and trade-offs that makes it, if not infeasible, very challenging. This thesis explores the challenges, trade-offs, constraints, practical issues, and some possible approaches in achieving bio-plausibility in creating evolutionary developmental spiking neural microcircuits in an FPGA through a practical investigation along with a series of case studies. In this study, the system performance, cost, reliability, scalability, availability, and design and testing time and complexity are defined as measures for feasibility of a system and structural accuracy and consistency with the current knowledge in biology as measures for bio-plausibility. Investigation of the challenges starts with the hardware platform selection and then neuron, cortex, and evo-devo models and integration of these models into a whole bio-inspired intelligent system are examined one by one. For further practical investigation, a new PLAQIF Digital Neuron model, a novel Cortex model, and a new multicellular LGRN evo-devo model are designed, implemented and tested as case studies. Results and their implications for the researchers, designers of such systems, and FPGA manufacturers are discussed and concluded in form of general trends, trade-offs, suggestions, and recommendations

Análise da função autonômica cardíaca em recém-nascidos saudáveis e com taquipnéia transitória que necessitaram ou não de CPAP nasal

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Educação Física, Programa de Pós-Graduação em Educação Física, 2019.Introdução: As adaptações autonômicas são fundamentais para os ajustes fisiológicos, em especial no coração, após a passagem da vida fetal para a pós-natal em recém-nascidos (RN). Ainda, na transição da vida intra-uterina para extra-uterina os RN apresentam diferentes ajustes pulmonares. Nesse cenário, destaca-se a Taquipnéia Transitória do RN (TTRN) uma disfunção frequentemente observada em RN, onde uma parcela de RN evolui com melhora sem a necessidade do auxílio do dispositivo CPAP nasal. Objetivo: Descrever e comparar o grau de modulação da função autonômica cardíaca, por meio da variabilidade da frequência cardíaca (VFC), em pacientes clinicamente saudáveis com pacientes com taquipnéia transitória do recém-nascido submetidos ou não a utilização da ventilação mecânica não invasiva, por meio do dispositivo, CPAP nasal, nas primeiras horas de vida. Método: Trata-se de um estudo transversal e observacional, composto por 94 RN que foram divididos em 3 grupos, a saber: Grupo Controle (n=27) com RN clinicamente saudáveis; Grupo S/CPAP (n=20) com RN com TTRN que não necessitaram de CPAP e o Grupo C/CPAP (n=17) com RN com TTRN que necessitaram de CPAP nasal, todos do sexo masculino, a termo com IG ≥37 semanas que nasceram de parto cesariano. A medida curta (5min) dos intervalos RR foram registradas com 2 horas e 14 horas pós-parto. Na sequência, os intervalos RR foram processados e analisados por meio do software Kubios® nos domínios do tempo (iRR, SDNN, pNN50 e rMSSD) e da frequência (TP, LF, HF e LF/HF). No presente estudo, após análise da distribuição amostral utilizou-se a estatística não-paramétrica, por meio dos testes de Wilcoxon e Kruskal-Wallis com post-hoc de Dull com valor de p bicaudal adotado em 5%. Resultados: Após 14 horas de vida extra-uterina verificou-se redução da frequência cardíaca e respiratória em todos os grupos (p<0,05). A função autonômica cardíaca (modulação global, atividade parassimpática, atividade simpato-vagal e balanço autonômico cardíaco) no grupo controle apresentou maior variação absoluta/relativa comparativamente aos outro grupos, com destaque para os índices vagais (rMSSD: Δ% = 32.6; p <0.03; HF: Δ% = 43.6; p <0.00). Os RN do grupo S/CPAP apresentaram maior magnitude absoluta/relativa com o aumento do grau de modulação global (CV: Δ% = 57,9% ; p <0.00 e AT Δ% = 199,7%; p <0.00) comparativamente aos grupos controle e C/CPAP. Por outro lado, os RN que necessitaram do suporte ventilatório (grupo C/CPAP) apresentaram similar ajuste autonômico em relação aos outros 2 grupos, entretanto com menor variação absoluta/relativa na atividade dos índices autonômicos parassimpáticos e de modulação global. A exceção observada no grupo C/CPAP em relação aos grupos controle e S/CPAP foi o aumento da atividade simpato-vagal ( p<0,05) com 14 horas de vida extra-uterina quando comparados com os outros grupos estudados (saudáveis e sem CPAP). Conclusão: nas primeiras 14 horas de vida foi observado o aumento da atividade autonômica cardíaca nos 3 grupos estudados (principalmente no grupo saudável), com dependência/predominância direta do aumento da atividade vagal.Introduction: Autonomic adaptations are fundamental for the physiological adjustments, especially at newborns’ (NB) heart, after the transition from fetal to postnatal life. Still, in the transition from intrauterine to extrauterine life the newborns present different pulmonary adjustments. In this scenario, we highlight the Transient Tachypnea of the newborn (TTN), a dysfunction frequently observed in NB, where a portion of NB progresses with improvement without the need of the nasal CPAP device. Objective: To describe and compare the degree of modulation of cardiac autonomic function through heart rate variability (HRV) in: clinically healthy patients, and patients with TTN that needed or not non-invasive mechanical ventilation (nasal CPAP), in the first hours of life. Method: This is a cross-sectional, observational study, composed of 94 newborns divided into 3 groups: Control Group (n=27) with clinically healthy NB; Group (n=20) with NB with TTN who did not require CPAP, and Group (n=17) with NB with TTN who required nasal CPAP. They are all males, term with gestational age ≥37 weeks after Cesarean delivery. The short (5 min) RR intervals were recorded at 2 hours and 14 hours postpartum. Afterwards, the RR intervals were processed and analyzed using the Kubios® software in the time domain (iRR, SDNN, pNN50 and rMSSD) and frequency domain (Total Power, LF, HF and LF/HF). In the present study, non-parametric statistics were used after analysis of the sample distribution, using Wilcoxon and Kruskal-Wallis tests with Dull post-hoc with a two-tailed p value adopted at 5%. Results: After 14 hours of extrauterine life, Cardiac and Respiratory Frequency were reduced in all groups (p<0.05). The autonomic cardiac function (overall modulation, parasympathetic activity, sympatho-vagal activity and cardiac autonomic balance) in the control group presented greater absolute/relative variation compared to the other groups, with emphasis on vagal indexes (rMSSD: Δ%=32.6, p<0.03, HF: Δ%=43.6, p<0.00). The NB group without CPAP, when compared with other groups, presented a greater absolute/relative magnitude with the increase of the degree of global modulation (coefficient of variation: Δ%=57.9%, p<0.00 and AT Δ%=199.7%, p<0.00). On the other hand, the infants who needed ventilatory support (group with CPAP) presented a similar autonomic adjustment in relation to the other groups, however with a lower absolute/relative variation in the activity of parasympathetic autonomic indexes and global modulation. The exception observed in the group with CPAP was the increase in the sympatho-vagal activity (p <0.05) with 14 hours of extrauterine life when compared to the other groups studied (healthy and without CPAP). Conclusion: in the first 14 hours of life, cardiac autonomic activity was observed in the 3 groups studied (mainly in the healthy group), with direct dependence/predominance of increased vagal activity

Pitting Corrosion Behavior of CUSTOM 450 Stainless Steel Using Electrochemical Characterization

In this study, the electrochemical polarization tests were performed on tensioned and non-tensioned CUSTOM 450 specimens in a 3.5 wt% NaCl solution to investigate pitting potential and stable pit initiation time. A potentiodynamic test was conducted to determine the exact amount of pitting potentials. According to the potentiostatic tests, a relation between applied potential and the stable pit initiation time was obtained. Concerning this relation, stable pitting time can be predicted without experimental works. Optical microscopy was used to evaluate the shape of the pits. Tensile stress led the pit to experience the “pit to crack” step. The corrosion rate of samples was studied by the determination of mass loss. Mass loss measurements and current density–time curve in potentiostatic tests demonstrated the rate of pitting corrosion decreased as time passed. Finally, the depth of the pits was measured by the eddy current technique. The results showed that tensile stress facilitated deeper pit development