Stability Condition Based Sliding Mode Modulators for Multilevel Power Converters

Sliding mode controllers for power converters usually employ hysteresis comparators to directly generate the power semiconductors switching states. This paper presents a new sliding mode modulator based on the direct implementation of the sliding mode stability condition, which for multilevel power converters shows advantages, as branch equalized switching frequencies and less distortion on the ac currents when operating near the rated converter power. The new sliding mode multilevel modulator is used to control a three-phase multilevel converter, operated as a reactive power compensator (STATCOM), implementing the stability condition in a digital signal processing system. The performance of this new sliding mode modulator is compared with a multilevel modulator based on hysteresis comparators. Simulation and experimental results are presented in order to highlight the system operation and control robustness

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

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

Portugal 2020 e a Integração de Energias Renováveis nos Edifícios

O elevado consumo de energia nos edifícios tem vindo a ser responsável pela publicação de legislação europeia que visa limitar esse consumo, por via da melhoria dos processos construtivos e da adopção de estratégias de redução do consumo em paralelo com a definição de esquemas de certificação energética que permitam ao mercado escolher e por essa via promover a disseminação das melhores práticas. Em Portugal é o RCCTE, actualmente em processo de revisão, que para além dos requisitos mínimos construtivos obriga a colocação de colectores solares térmicos, mas também valoriza a introdução de outras renováveis nos edifícios. Neste texto iremos percorrer de forma sucinta, as várias tecnologias e aspectos de desenho que já se apresentam no terreno ou se perfilam no horizonte próximo e que em conjunto permitem aproximar de zero, o balanço energético dos edifícios

An aviation safety risk model to close the gap between management and operational safety staff

The thesis probes the safety risk-management component of the complex Commercial Air Transport (CAT) industry. It argues that adoption of the ICAO (2018b) framework failed to address the challenges the industry faces, and suggests that the continuous reduction of risk exposure observed in the last couple of decades has been negatively impacted as a result. The document begins by outlining a conceptual framework based on a continuous cycle – safety boundaries, risk tools, safety protection, safety benchmarking, and safety culture – that represents a theoretical safety model as an alternative to the current risk-management vision. The research into these topics is based on an interpretivist stance, whereby 26 semi-structured interviews were performed across different segments within the CAT industry. The healthcare sector was also included in the research to enable benchmarking analysis. Opposed to the commonly established knowledge, the thesis argues that the industry defines and measures the acceptable risk exposure of each organization in a degraded fashion and, in doing this, restricts individual airlines’ contributions to industry safety figures. The literature around the subject restricts its research scope to specific topics and fails to address risk management holistically. Compounding the narrowness of the scope, safety-related linear risk models have failed to integrate concurrent events with undesirable states. In contrast, the models based on complexity and systems thinking theory develop a higher conceptual abstraction, but present challenges when airlines try to implement them. It is suggested that in failing to harness the explanatory power provided by clues concerning safety, an exposure uncertainty is developed, which, as this has the potential to produce a gap between management and operational staff, creates a barrier to investments in safety. Moreover, while the extant research and literature identifies safety culture as an important factor in the robustness of commercial aviation risk management, its explanatory power is weak – models fail to explain their impact on safety performance – that is, they fail in terms of operationalizing the concept. As a significant innovative approach to practice and consequently to the theory that supports it, the current research suggests a new risk model that transforms statistical data into meaningful and easily understandable safety figures. In contrast, the risk model put forward here conveys a proactive perspective when dealing with risk exposure and the drifting of safety systems

PREMIVM – improving grape quality with multiparametric field analysis of grapes and leaves in vineyards

European wine industry is a strategic economic sector that is nowadays facing a growing competition in the international market at the same time it as to deal with predictable lower support from the CAP. Taking into consideration that the use of ICT can support the development of new tools and devices that can reduce costs and increase final product quality/quantity an international consortium that comprises 3 technical companies and 3 winegrowers together with 3 research groups setup the EU Project PREMIVM. In this work will present the PREMIVM decision support system that was developed including the field device for data collection - WINEPEN, the web information management system for data storage, processing and information visualization, and the smartphone interface for information deliveryinfo:eu-repo/semantics/publishedVersio

Adensamentos periódicos do rebanho bovino de corte no Pantanal e seus reflexos na eficiência reprodutiva: um relato.

Os adensamentos consistem em promover, periodicamente, rodeios (agrupar o rebanho de cria), sob a hipótese de que a aproximação de touros e vacas conduz a um maior índice de prenhez. Este trabalho teve como objetivo relatar a experiência de um estudo realizado para averiguar se essa pratica tem, efetivamente, o efeito esperado, bem como relatar as dificuldades encontradas. Foi conduzido numa propriedade particular representativa do Pantanal de Rio Verde de Mato Grosso, MS, no período de 1987 a 1990. Utilizaram-se 766 vacas neloradas e 46 touros da raça Nelore, mantidos em duas invernadas (pastagem nativa) de, aproximadamente, 1.500 hectares cada, cuja lotação foi de 3 hectares/unidade animal e a relação touro/vaca foi de 1:16. O ensaio envolveu dois tratamentos (T1 e T2). O T1 obedeceu ao manejo tradicional da região (testemunha). No T2, o rebanho foi submetido a adensamentos a cada 21 dias, durante a estação de monta (setembro a março). O adensamento consistiu em levar todo o gado para um piquete a parte, com 19 hectares, mantendo-o por 48 horas. Os resultados obtidos não são conclusivos por falta de controle das condições experimentais. Discutem-se as dificuldades encontradas nesse ensaio, bem como são apresentadas sugestões para futuros trabalhos a serem conduzidos na região.bitstream/item/139369/1/cir-tec-28.pd

Adaptation to different salinities exposes functional specialization in the intestine of the sea bream (Sparus aurata L.)

The processing of intestinal fluid, in addition to a high drinking rate, is essential for osmoregulation in marine fish. This study analyzed the long-term response of the sea bream (Sparus aurata L.) to relevant changes of external salinity (12, 35 and 55p.p.t.), focusing on the anterior intestine and in the less-often studied rectum. Intestinal water absorption, epithelial HCO3– secretion and gene expression of the main molecular mechanisms (SLC26a6, SLC26a3, SLC4a4, atp6v1b, CFTR, NKCC1 and NKCC2) involved in Cl– and HCO3– movements were examined. The anion transporters SLC26a6 and SLC26a3 are expressed severalfold higher in the anterior intestine, while the expression of Atp6v1b (V-type H+-ATPase β-subunit) is severalfold higher in the rectum. Prolonged exposure to altered external salinity was without effect on water absorption but was associated with concomitant changes in intestinal fluid content, epithelial HCO3– secretion and salinity-dependent expression of SLC26a6, SLC26a3 and SLC4a4 in the anterior intestine. However, the most striking response to external salinity was obtained in the rectum, where a 4- to 5-fold increase in water absorption was paralleled by a 2- to 3-fold increase in HCO3– secretion in response to a salinity of 55p.p.t. In addition, the rectum of high salinity-acclimated fish shows a sustained (and enhanced) secretory current (Isc), identified in vitro in Ussing chambers and confirmed by the higher expression of CFTR and NKCC1 and by immunohistochemical protein localization. Taken together, the present results suggest a functional anterior–posterior specialization with regard to intestinal fluid processing and subsequently to salinity adaptation of the sea bream. The rectum becomes more active at higher salinities and functions as the final controller of intestinal function in osmoregulation