National postgraduate system (SNPG) and chemistry area at the brazilian federal agency for post-graduate education (CAPES)

The Coordination for the Improvement of High Education Personnel (CAPES), the Brazilian federal agency for graduate programs, plays a fundamental role for the expansion and consolidation of the National Postgraduate System (SNPG) and the execution of the National Graduate Plan (PNPG) 2011-2020. In this paper, we discuss the evolution of the Brazilian graduate program in chemistry and its role in the formation of highly qualified professionals in chemistry (academic master’s degree, professional master’s degree and doctoral degree) for the academy, teachers and lecturers for all levels of the education system, as well for the non-academic market

Experiments with embedded system design at UMinho and AIT

Nowadays, embedded systems are central to modern life, mainly due to the scientific and technological advances of the last decades that started a new reality in which the embedded systems market has been growing steadily, along with a monthly or even weekly emergence of new products with different applications across several domains. This embedded system ubiquity was the drive for the following question ”Why should we focus on embedded systems design?” that was answered in [1, 2] with the following points: (1) high and fast penetration in products and services due to the integration of networking, operating system and database capabilities, (2) very strategic field economically and (3) a new and relatively undefined subject in academic environment. Other adja- cent questions have been raised such as ”Why is the design of embedded systems special?”. The answer for this last question is based mainly on several problems raised by the new technologies, such as the need for more human resources in specialized areas and high learning curve for system designers. As pointed in [1], these problems can prevent many companies from adopting these new technologies or force them not to respond timely in mastering these technological and market challenges. In this paper, it is described how staff at ESRG-UMinho 1 and ISE-AIT 2 faced the embedded systems challenges at several levels. It starts to de- scribe the development of the educational context for the new technolo- gies and show how our Integrated Master Curriculum in Industrial Elec- tronics and Computer Engineering has been adapted to satisfy the needs of the major university customers, the industry

A modeling domain-specific language for IoT-enabled operating systems

With the increased complexity of low-end devices in the Internet of Things (IoT), mainly due to the connectivity and interoperability requirements, the development and configuration of embedded operating systems (OSes) for such devices is not straight forward. The complexity of the communication requirements is usually mitigated by the OS, e.g., the Contiki-OS, as it already incorporates an IoT-compliant network stack. Yet, the configuration of such stack requires major knowledge on the code structure, leading to additional development time, particularly when the network comprises several wireless nodes and individual configurations with subsequent firmware that needs to be generated. Based on a developed software modeling domain-specific language, this paper presents the EL4IoT framework. It aims to reduce and ease the development time by promoting a design automation tool that can configure, and automatically generate code (ready to compile) for low-end IoT devices running the Contiki-OS. Although leveraging the whole Contiki-OS modeling, this work only refactored and modeled the network stack while approaching the OS itself as one big building block or component. The proposed approach can be extended to other IoT-enabled OSes as well as integrated in other design automation tools.This work has been supported by COMPETE: POCI-01-0145-FEDER-007043 and FCT - Fundação para a Ciência e Tecnologia within the Project Scope: UID/CEC/00319/2013. Tiago Gomes is supported by FCT PhD grant SFRH/BD/90162/2012

Cost estimation of rail power conditioner topologies based on indirect modular multilevel converter in v/v and scott power transformers

This paper presents a cost estimation study for several rail power conditioner (RPC) topologies based on an indirect modular multilevel converter (MMC), in which these topologies are combined with V/V or Scott power transformers. The RPC topologies under interest in this paper are: the RPC based on a full-bridge MMC (RPC based on MMC4), the RPC based on two-phase three-wire MMC (RPC based on MMC3), and the RPC based on a half-bridge MMC (RPC based on MMC2). These RPC systems operate at medium voltage levels in the interconnection to 25 kV-50 Hz catenary sections to solve power quality problems, such as the current harmonics and the negative sequence components (NSCs) of currents. Along the paper are described the V/V and the Scott power transformers, the RPC main architectures, and the estimated cost of implementation for each RPC topology considering V/V or Scott implementations. As main contribution, the presented results could help in the selection procedure of the RPC topology, giving the best economical solution according to the used power transformer (V/V or Scott).This work has been supported by FCT – Fundação para a Ciência e Tecnologia within the Project Scope: UID/CEC/00319/2019. This work has been supported by FCT within the Project Scope DAIPESEV – Development of Advanced Integrated Power Electronic Systems for Electric Vehicles: PTDC/EEI-EEE/30382/2017. Mohamed Tanta is supported by the doctoral scholarship with a reference PD/BD/127815/2016 granted by the Portuguese FCT agency

Efficiency and cost estimation for a static frequency converter and a rail power conditioner based on an indirect modular multilevel converter in railways applications

This paper presents a comparative study between two different power electronics solutions for electrified railway substations to overcome some drawbacks which could appear on the public grid side. These drawbacks or troubles on the public grid side are mainly the harmonics and the negative sequence components (NSCs) of currents, which could become clear in the case of feeding single-phase locomotives or unbalanced loads. The static frequency converters (SFCs) and the rail power conditioners (RPCs) based on an indirect AC/DC/AC modular multilevel converter (MMC) are the main area of interest in this study, taking into consideration the costs estimation analysis between solutions, the efficiency and the power quality on the public grid side. Both systems of SFC and RPC based on an indirect MMC operate on medium voltage levels to feed the catenary line and to solve the problems of harmonics and NSCs. Along the paper are described the system architecture, the control algorithm, the inherent benefits, the estimated cost of implementation, and the operation efficiency based on computational simulation results for each system.This work has been supported by COMPETE: POCI-01-0145-FEDER-007043 and FCT – Fundação para a Ciência e Tecnologia within the Project Scope: UID/CEC/00319/2013. Mohamed Tanta is supported by FCT doctoral scholarship with a reference PD/BD/127815/2016.info:eu-repo/semantics/acceptedVersio

Deadbeat predictive current control for circulating currents reduction in a modular multilevel converter based rail power conditioner

This paper presents a deadbeat predictive current control methodology to reduce the circulating currents in a modular multilevel converter (MMC) when it operates as a rail power conditioner (RPC) in a conventional railway system-based V/V connection. For this purpose, a half-bridge MMC based on half-bridge submodules, operating as an RPC is explained, and the total system is denominated as a simplified rail power conditioner (SRPC). The SRPC in this study is used to compensate harmonics, reactive power, and the negative sequence component of currents. This paper explains the SRPC system architecture, the key control algorithms, and the deadbeat predictive current control methodology. Mathematical analysis, based on the MMC equivalent circuit, is described and the reference equations are presented. Moreover, simulation results of the deadbeat predictive current control methodology are compared with the results of the conventional proportional-integral (PI) controller. This comparison is to verify the effectiveness of the proposed control strategy. Simulation results of the SRPC show reduced circulating currents in the MMC phases when using the predictive control approach, besides accomplishing power quality improvement at the three-phase power grid side.This work has been supported by the Portuguese Foundation of Science and Technology (FCT), in Portuguese, Fundação para a Ciência e Tecnologia within the R&D Units Project Scope: UIDB/00319/2020 and PTDC/EEI-EEE/28813/2017. The first author Mohamed Tanta is supported by FCT Ph.D. grant with a reference PD/BD/127815/2016

A comprehensive comparison of rail power conditioners based on two-level converters and a V/V power transformer in railway traction power systems

Electric locomotives in the traction power systems represent huge nonlinear single phase loads and they affect adversely the public electrical grid stability and the power quality. Some of such problems are related to the harmonic distortion and the Negative Sequence Components (NSCs). The Rail Power Conditioners (RPCs) are widely used to accomplish harmonics mitigation, besides NSCs compensation, then, maintaining balanced and sinusoidal public electrical grid currents. This paper presents a comprehensive comparison study between three different RPCs based on the two level converters and a V/V power transformer. The Four Wire Rail Power Conditioner (FW RPC), the Three Wire Rail Power Conditioner (TW RPC) and the Half Bridge Rail Power Conditioner (HB RPC) are the main conditioners of interest. The main contribution of this paper is to perform a comprehensive comparison between the aforementioned RPCs, including the control algorithms and the compensating performance regarding the power quality problems. Simulation results with different operation scenarios are presented to establish an appropriate comparison between the aforementioned RPCs topologies.Mohamed Tanta was supported by FCT (Fundação para a Ciência e Tecnologia) PhD grant with a reference PD/BD/127815/2016. This work has been supported by COMPETE: POCI-01-0145–FEDER–007043 and FCT within the Project Scope: UID/CEC/00319/2013.info:eu-repo/semantics/publishedVersio

Topologies and operation modes of rail power conditioners in AC traction grids: review and comprehensive comparison

Electric locomotives in AC traction power systems represent a huge single-phase non-linear load and, detrimentally, affect the power quality and the efficiency of the three-phase power grid. Nevertheless, along the last decades, power electronics are being used to mitigate power quality problems in the three-phase power grid. In particular, Rail Power Conditioner (RPC) helps to increase the loading capacity of traction substations and improve the power quality of three-phase power grids. As the main characteristics, an RPC can supply reactive power, suppress current harmonics and overcome currents imbalance of the three-phase power grid. On the other hand, the traction substations may be constituted by different types of power transformers. For instance, single-phase power transformers and open-delta (V/V) power transformers are widely used, while Scott power transformers are less frequently used, since they are more complex and expensive. In this framework, this work presents a review study of RPC topologies, including their operation modes, and a comprehensive comparison between the characteristics of the RPC topologies when using different types of AC traction substations and power transformers. This helps to ensure the correct selection of the RPC topology for a specific application, according to the main structure of the traction substation. Consequently, and based on the established review, it is possible to sort and allocate each RPC topology for limited or wider applications.This work was supported by the Portuguese Foundation of Science and Technology (FCT) (in Portuguese, Fundação para a Ciência e Tecnologia, within the R&D Units Project Scope: UIDB/00319/2020). The first author Mohamed Tanta is supported by FCT Ph.D. grant with a reference PD/BD/127815/2016

Acid-base and biochemical stabilization and quality of recovery in male cats with urethral obstruction and anesthetized with propofol or a combination of ketamine and diazepam

This study compared acid-base and biochemical changes and quality of recovery in male cats with experimentally induced urethral obstruction and anesthetized with either propofol or a combination of ketamine and diazepam for urethral catheterization. Ten male cats with urethral obstruction were enrolled for urethral catheterization and anesthetized with either ketamine-diazepam (KD) or propofol (P). Lactated Ringer's solution was administered by intravenous (IV) beginning 15 min before and continuing for 48 h after relief of urethral obstruction. Quality of recovery and time to standing were evaluated. The urethral catheter was maintained to measure urinary output. Hematocrit (Hct), total plasma protein (TPP), albumin, total protein (TP), blood urea nitrogen (BUN), creatinine, pH, bicarbonate (HCO3-), chloride, base excess, anion gap, sodium, potassium, and partial pressure of carbon dioxide in mixed venous blood (pvCO(2)) were measured before urethral obstruction, at start of fluid therapy (0 h), and at subsequent intervals. The quality of recovery and time to standing were respectively 4 and 75 min in the KD group and 5 and 16 min in the P group. The blood urea nitrogen values were increased at 0, 2, and 8 h in both groups. Serum creatinine increased at 0 and 2 h in cats administered KD and at 0, 2, and 8 h in cats receiving P, although the values were above the reference range in both groups until 8 h. Acidosis occurred for up to 2 h in both groups. Acid-base and biochemical stabilization were similar in cats anesthetized with propofol or with ketamine-diazepam. Cats that received propofol recovered much faster, but the ketamine-diazepam combination was shown to be more advantageous when treating uncooperative cats as it can be administered by intramuscular (IM) injection.Cette étude visait à comparer les changements biochimiques et acide-base ainsi que la qualité de la convalescence chez des chats mâles avec une\ud obstruction urétrale induite expérimentalement et anesthésiés avec soit du propofol ou une combinaison de kétamine et diazépam pour une\ud cathétérisation urétrale. Dix chats mâles avec une obstruction urétrale ont été recrutés pour cathétérisation urétrale et anesthésiés avec soit\ud une combinaison kétamine-diazépam (KD) ou du propofol (P). Une solution de lactate de Ringer a été administrée par voie intraveineuse (IV)\ud débutant 15 min avant et continuant 48 h après l’élimination de l’obstruction urétrale. La qualité de la convalescence et le délai avant de se\ud tenir debout ont été évalués. Le cathéter urinaire était laissé en place pour mesurer l’excrétion urinaire. Les valeurs des paramètres suivants\ud ont été mesurées avant l’obstruction urétrale, au début de la fluidothérapie (0 h) et à des intervalles subséquents : hématocrite (Hct), protéines\ud plasmatiques totales (TPP), albumine, protéines totales (TP), azotémie (BUN), créatinine, pH, bicarbonate (HCO3\ud 2), chlorure, excès de base,\ud trou anionique, sodium, potassium, pression partielle de dioxide de carbone dans le sang veineux (pvCO2). La qualité de la convalescence et\ud le temps avant de se tenir debout étaient respectivement de 4 et 75 minutes dans le groupe KD et de 5 et 16 minutes dans le groupe P. Les\ud valeurs de BUN étaient augmentées à 0, 2 et 8 h dans les deux groupes. La créatinine sérique augmenta à 0 et 2 h chez les chats recevant KD\ud et à 0, 2 et 8 h chez les chats recevant P, bien que les valeurs étaient supérieures à l’écart de référence dans les deux groupes jusqu’à 8 h. Une\ud acidose s’est produite pendant 2 h dans les deux groupes. L’équilibre acide-base et la stabilisation biochimique étaient similaires chez les chats\ud anesthésiés avec du propofol ou avec KD. Les chats qui ont reçu du propofol ont récupéré beaucoup plus rapidement, mais la combinaison KD\ud s’est avérée plus avantageuse pour traiter des chats non-coopératifs étant donné la possibilité d’administration par voie intra-musculaire

Power quality phenomena in electrified railways: Conventional and new trends in power quality improvement toward public power systems

Nowadays, railway electrification is the most efficient way to power the trains. However, power quality (PQ) phenomena toward public power systems (PPSs) have always a main concern to the railway operators, especially when the single phase traction power system is interconnected to the three phase PPS. The last decades have witnessed an on going evolution of PQ improvement and traction power supply systems, contributing to diminish the negative impacts of AC railway networks on PQ of the three phase PPS. In this context, this paper presents a global overview of the PQ phenomena in AC railway electrification, as well as the impacts of the potential hazards on the safe operation of electrified railways. The paper also reviews PQ improvement methods from the early use of AC railway electrification until the emergence of the new power electronics devices in railways industry.Mohamed Tanta was supported by FCT (Fundação para a Ciência e Tecnologia) PhD grant with a reference PD/BD/127815/2016. This work has been supported by COMPETE: POCI-01-0145–FEDER–007043 and FCT within the Project Scope: UID/CEC/00319/2013.info:eu-repo/semantics/publishedVersio