Job crafting and job performance: the mediating effect of engagement

The main purpose of this study was to investigate whether work engagement mediates the relationship between job crafting and job performance. To this end, the following hypotheses were formulated: (1) job crafting establishes a positive and significant association with job performance; (2) job establishes a positive and significant association with work engagement; (3) work engagement establishes a positive and significant association with job performance; (4) work engagement mediates the association between job crafting and job performance. The sample was composed of 453 participants working in organisations based in Portugal. The hypotheses formulated in this study were tested by performing simple and multiple linear regressions. The results indicated that only increasing structural job resources and increasing challenging job demands established a positive and significant association with task performance. Increasing structural job resources, increasing social job resources, and increasing challenging job demands established a positive and significant association with citizenship performance and work engagement. Work engagement established a positive and significant association with task performance and citizenship performance. Only a partial mediating effect, through work engagement, was observed on the association between increasing challenging job demands and task performance, and between increasing social job resources and citizenship performance.info:eu-repo/semantics/publishedVersio

Comparative Study of the Response of Kinematical Variables from the Hip and the Center of Mass in Butterfliers

The aim of this study was to compare the intracyclic variation of kinematical variables from the hip and the center of mass (CM) with the purpose to assess if the analysis of kinematical variables of the hip might replace the study of the kinematical variables of the CM. Seven Portuguese male swimmers of national and intemational levei were studied. Each swimmer performed 3 sets of3x25 meters, at a constant velocity and as close as possible to the maximum, using exclusively frontal inspiration cycles, lateral inspiration cycles and non-inspiratory cycles in each set. Two pairs of cameras were used to create "dual media" images. Another cam era was set behind an underwater window in the endwall. One last camera was placed above the water surface. The study comprised the analysis of complete stroke cycles in buttert1y using the "Ariel Performance Analysis System" from Ariel Dynamics Inc. Some of the correlations between the maximal vertical amplitude of displacement of the hip and the CM didn't present significant values. AlI the correlations between the horizontal velocity and horizontal acceleration of the hip and the CM were significant in all breathing models. However, only one swimmer presented in both cases r>=O.95. So, apparently, the hip does not represent properly the intracyclic variations ofthe kinematical variables ofthe CM.info:eu-repo/semantics/publishedVersio

Traction system for electric vehicles based on synchronous reluctance permanent magnet machine

Electric vehicles (EVs) integrate two main power electronics systems, namely, the battery charging system and the traction system. In this study, we aimed to complement and deepen the study of the latter, more specifically, focusing on a traction system based on a synchronous reluctance permanent magnet (SRPM) machine, since this is an emerging electric machine in the EV paradigm. The developed prototype integrates bidirectional ac-dc and dc-dc converters, allowing for regenerative braking, and the SRPM machine is controlled using a maximum torque per ampere (MTPA) algorithm. Computer simulations and the experimental results for the traction system are presented in this paper. The dynamic characteristics of the SRPM machine proved to be relevant for EV applications, with effective results obtained during load and speed changes. The effective behavior of the SRPM machine was partially rooted in the use of the MTPA algorithm, which has proven itself to be an effective algorithm for the electric machines of EVs.This work has been supported by FCT—Fundação para a Ciência e Tecnologia within the R&D Units Project Scope: UIDB/00319/2020

MEASUREMENT OF BUTTERFLY AVERAGE RESULTANT IMPULSE PER PHASE

The aim of this study was to measure the average resultant impulse (ARI) per phase of the stroke cycle in butterfly and to analyse the variability of ARI according to the adopted breathing technique. The sample was composed of 6 male Portuguese swimmers at national and international level. 6 cameras were set, obtaining non coplanar images (2 "dual media" images included). The study comprised the kinematical analysis of stroke cycles of the butterfly stroke using the "Ariel Performance Analysis System" from Ariel Dynamics Inc. and a VCR at a frequency of 50 Hz. The ARI was calculated using the mean horizontal acceleration of the cenler of mass in each phase, the absolute duration of each phase and the body mass of the swimmer. Comparing the ARI according to the breathing technique adopted in each phase of the stroke cycle, we only observed significant differences in the outsweep. Comparing the intra-cyclic variations of the ARI in the different breathing techniques adopted, the arm's recovery when compared with the remained phases presented a significantly lower ARI

A novel front-end multilevel converter for renewable energy systems in smart grids

The integration of renewable energy systems into smart grids requires dc-to-ac power electronics converters for adapting the voltage levels of both sides. In this context, a novel topology of front-end multilevel dc-to-ac converter is proposed in order to enhance the integration of renewable energy systems into smart grids, preventing power quality problems. The proposed converter is designed to operate as a grid-tied inverter, imposing controlled sinusoidal grid currents in phase opposition with the power grid voltage, and establishing five distinct voltage levels to improve the current waveform. The dc side is suitable to be connected directly to a set of photovoltaic solar panels with an appropriated voltage level, or to an external dc-to-dc intermediary converter used to interface other renewable energy sources. An entire analysis of the hardware design and the operation principle is presented, including the adopted control strategy for the proposed front-end converter in conditions of current control. An accurate computational validation under realistic operating conditions for a significant operating power range is presented using a dedicated power electronics simulation software, where the obtained results show the advantages and the convenience of the proposed front-end converter in detriment of the classical solutions.Fundação para a Ciência e Tecnologia (FCT); COMPETE: POCI-01-0145 –FEDER–007043 and FCT – Fundação para a Ciência e Tecnologia within the Project Scope: UID/CEC/00319/2013. This work is financed by the ERDF – European Regional Development Fund through the Operational Programme for Competitiveness and Internationalisation – COMPETE 2020 Programme, and by National Funds through the Portuguese funding agency, FCT – Fundação para a Ciência e a Tecnologia, within project SAICTPAC/0004/2015 – POCI – 01–0145– FEDER–016434info:eu-repo/semantics/publishedVersio

Performance comparison of a typical nonlinear load connected to Ac and Dc power grids

This paper presents a performance comparison of a typical nonlinear load used in domestic appliances (electronic load), when supplied by an ac and a dc voltage of the same rms value. The performance of the nonlinear load towards its connection to ac and dc power grids is accomplished in terms of the waveforms which are registered in the consumed current, internal dc-link voltage and output voltage. A simulation model was developed using realistic database models of the power semiconductors comprising a nonlinear load with input ac-dc converter, so that the efficiency can be calculated and compared for three distinct cases: (1) load supplied by an ac voltage; (2) load supplied by a dc voltage; (3) load without the input ac-dc converter supplied by a dc voltage. Thus, besides the comparison between the ac and dc power grids supplying the same nonlinear load (cases 1 and 2), a third case is considered, which consists of removing the input ac-dc converter (eliminating needless components of the nonlinear load when supplied by a dc voltage). The obtained results show that supplying nonlinear loads with dc power grids is advantageous in relation to the ac power grid, and therefore it can be beneficial to adapt nonlinear loads to be powered by dc power grids.This work has been supported by COMPETE: POCI-01-0145–FEDER–007043 and FCT –Fundação para a Ciência eTecnologia within the Project Scope: UID/CEC/00319/2013. This work is financed by the ERDF –European Regional De-velopment Fund through the Operational Programme for Competitiveness and Interna-tionalisation –COMPETE 2020 Programme, and by National Funds through the Por-tuguese funding agency, FCT –Fundação para a Ciência e a Tecnologia,within project SAICTPAC/0004/2015 –POCI –01–0145–FEDER–016434. Mr. Tiago Sousa is sup-ported by the doctoral scholarship SFRH/BD/134353/2017 granted by the Portuguese FCT agency

Performance comparison of a typical nonlinear load supplied by ac and dc voltages

This paper presents a performance comparison of a typical nonlinear load when supplied by ac or dc voltages with the same rms value. The performance of the nonlinear load towards its connection to ac and dc power grids is accomplished in terms of the waveforms and efficiency. A simulation model was developed using realistic database models of the power semiconductors comprising the load, and an experimental setup was assembled, so that the efficiency can be determined and compared for simulation and real operating conditions. Three distinct cases were considered for this study: (1) Load supplied by ac voltage; (2) Load supplied by dc voltage; and (3) Load without the input ac-dc converter supplied by dc voltage. The obtained results show that supplying nonlinear loads with dc power grids is advantageous in relation to the ac power grid, and therefore it can be beneficial to adapt nonlinear loads to be powered by dc power grids.This work has been supported by COMPETE: POCI-01-0145–FEDER–007043 and FCT –Fundação para a Ciência e Tecnologiawithin the Project Scope: UID/CEC/00319/2013. This work is financed by the ERDF –European Regional Development Fund through the Operational Programme for Competitiveness and Internationalisation –COMPETE 2020 Programme, and by National Funds through thePortuguese funding agency, FCT –Fundação para a Ciência e a Tecnologia, within project SAICTPAC/0004/2015 –POCI –01–0145–FEDER–016434. Mr. Tiago Sousa is supported by the doctoral scholarship SFRH/BD/134353/2017 granted by the Portuguese FCT agenc

Magnetic resonance imaging and Ménière’s disease : unavoidable alliance

Copyright © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer NatureMénière’s disease (MD) is a clinical syndrome characterized by recurrent episodes of spontaneous vertigo, unilateral fluctuating sensorineural hearing loss, tinnitus, and aural fullness. Endolymphatic hydrops is recognized as the pathophysiological substrate of the disease, having been demonstrated in anatomical pathological studies and more recently by magnetic resonance imaging (MRI). The current criteria of the disease, however, remain symptom based and do not include the demonstration of endolymphatic hydrops. The authors review MRI techniques and diagnostic criteria of endolymphatic hydrops and the role of MRI in MD is discussed.info:eu-repo/semantics/publishedVersio

Unified architecture of single-phase active power filter with battery interface for UPS operation

This paper presents a shunt active power filter with battery interface for uninterruptible power supply (UPS) operation. The proposed unified architecture is composed by a single-phase ac-dc converter from the power grid side and by a bidirectional isolated dc-dc converter to interface the batteries, allowing the operation in three distinct modes: (1) Shunt active power filter; (2) Off-line UPS to supply a set of priority loads during power outages; (3) Energy storage system to support the power grid. The proposed architecture and the developed control algorithms were validated with a reduced-scale laboratorial prototype in all the three different operation modes. The presented experimental results highlight the benefits of the proposed architecture.Fundação para a Ciência e Tecnologia (FCT)info:eu-repo/semantics/publishedVersio